Special Chapter for Project analysis
Shandong Minhe Animal Husbandry Co., Ltd.
Biogas Engineering Project for Excrement and Sewage Treatment and
Resource Utilization
Supplemental Environmental Impact
Assessment Chapter One Project Analysis
Chapter Two Alternative Proposal Evaluation
Chapter Three Environmental Management Program
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE
Jinan, Shandong Province
August 2007
Shandong Academy of Environmental Science
E1717 v2
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Special Chapter for Project analysis
Chapter One Project Analysis
Shandong Academy of Environmental Science 1
Special Chapter for Project analysis
I. About the Project
1.1 Nature and basic content
It is a new project to treat the high-concentration excrement, about 500t per day, of the 5
million chickens of Shandong Minhe Animal Husbandry Co., Ltd. (Minhe hereafter) and the
daily 1000t of cleaning sewage (after screening), with an annual processing capacity of
182,500t excrement and 365,000t sewage. It adopts the combined heat and power (CHP)
biogas generating set for power generation. The electric power is to be integrated into the
external power grid and sold. The residual heat produced by the generating set is to be used as
heat source to heat the anaerobic feed and preserve the temperature of anaerobic jar in winter.
It generates 30,000 m3 biogas per day, which can be used to generate 54,000kWh power per
day. Assuming the electricity rate is 0.594Yuan/kWh, it can bring a revenue of 11.70774
million Yuan every year. The daily power generation is 30,000×1.8=54,000 kWh; annual
power generation 19.71 million kWh. After the anaerobic fermentation of chicken excrement,
it can produce 10,376t biogas dregs (TS 75%; the moisture content decreases by less than 25%
through further dehydration in Phase Two project) and 490,000t biogas liquid every year,
which can be used as high-analysis organic fertilizer. And it can reduce the discharge of CO2
by an equivalent weight of 104,682 tons every year. The total investment of the project is
63.6785 million Yuan RMB. It needs 15 workers working 365 days every year, with each day
divided into three shifts. See Table 1 and Table 2 for the project contents and main
technological and economic indices:
Table 1 Project Contents
S/N Project
title Construction contents Note
1 Biogas
project
Pretreatment system, anaerobic digestion system, and
biogas liquid and biogas dregs separating system
2
Power
generation
project
Biogas purification and storage system, power generation
and residual heat utilization system etc.
3 Auxiliary Management house and blower house etc.
Shandong Academy of Environmental Science 2
Special Chapter for Project analysis
facility
Table 2 Main Technological and Economic Indices
S/N Title Unit Data Note
1 Processing scale Ton 1500 Process 500t fresh chicken
excrement and 1000t sewage.
2 Power generation 10,000k
Wh/year 1971
Biogas dregs Ton/year 11376
3
Organic
fertilize
r Biogas liquid
10,000
tons/year 49.0
In the preliminary period after the
project is completed, the biogas
liquid is provided free of charge.
4 Fixed number of workers 15
5 Working days per year Day 365 Four groups for three shifts, with
each shift being 8 hours
6 Fixed assets investment 10,000
Yuan 5095.9
Annual revenue 10,000
Yuan 1378.29
Annual profit 10,000
Yuan 384.74
1.2 Project Location
The project is to be located in the broiler chicken breeding base of Minhe, which lies in
Qujiagou Village, Beigou Township, Penglai City, Shandong Province. Lying in the hilly
terrain, the base is established through leveling up the mountainous terrain. The project to be
established is about 7.5km to the southwest of Penglai City. Around the project is farmland
and fruit tree land with villages such as Hanwang Village and Wujia Village in the vicinity.
1.3 General layout
This project is arranged compactly, and the technological process is smooth, which meets the
fire protection requirements of biogas engineering. The biogas generating set is laid on the
northern end of the production area, at some distance from the factory boundary and methane
storing tank, which effectively reduces the influence brought about by the methane risk
Shandong Academy of Environmental Science 3
Special Chapter for Project analysis
possibly. The finished biogas dregs and biogas liquid are stored in the south of the plant site.
There is a main gate in the southwest of the plant site to facilitate transportation. The greening
of the plant site is well and reasonably arranged, which helps reduce the influence of malodor
and noise on the environment. Generally speaking, the general arrangement of the plant is
reasonable. The project occupies an area of 19,998m2, with the building area being 12,312m2.
The buildings of the whole plant site are classified according to production type and fire
protection rating of civil architecture, and strictly comply with the relevant regulations of
Code for Design of Building Fire Protection (revision 2001).
All clear places in the plant site are covered with Chinese pine and other evergreen plants,
appropriately studded with parergon. The green belt is laid along the bounding wall, where the
grass and flower, evergreen broad-leaved shrub and arbor are planted to form the greening
screen. The evergreen shrub brush hurdle and broad-leaved arbor and flower and grass are
planted around the buildings and on both sides of roads. Through implementing these greening
measures, it will reduce the influence of stench on the ambient environment as much as
possible to provide good working and living environment for the site and facilitate the wind
resistance, noise resistance and dust resistance of the plant site. The green area is 6,900m2,
with the greening coefficient being 35%.
See Table 3 for the details of the main data for the general arrangement.
Table 3 Schedule of Main Data for the General Arrangement
S/N Item Unit Amount
1 Area of plant site m2 19,998
2 Area of buildings and constructions m2 1,960
3 Green area m2 6,900
4 Greening coefficient % 35
II. Technological Flow and Material Balance
2.1 Technological flow With “clean production, cyclic utilization of resource, and reducing discharging of pollutant”
as principle, this project adopts the anaerobic digestion as the core of technology and
combines with the cyclic economy mode of other process engineering to turn the excrement
into biogas and realize the goal of biogas combined heat and power, pluralistic utilization and
innocent treatment of biogas dregs and biogas liquid. Minhe processes the high-analysis
Shandong Academy of Environmental Science 4
Special Chapter for Project analysis
Shandong Academy of Environmental Science 5
organic wastewater to produce renewable energy source (biogas, electric power, and heat
energy) and (solid or liquid) organic fertilizer. With anaerobic digestion as the core of
technology, the whole scheme combines with the “cyclic economy” mode of other process
engineering, whose contents mainly include: (1) pretreatment system, (2) high-analysis
efficient anaerobic digestion system, (3) biogas liquid and biogas dregs after-treatment system,
(4) biogas purification and storage system, (5) biogas power generation and residual heat
utilization system, and (6) auxiliary buildings and constructions etc. See Diagram 1 for the
technological flow.
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Special Chapter for Project analysis
Note:
According to the experience of Denmark, for the biogas production with chicken
excrement, there are four key matters to be solved:
The first one is to remove sand. The sand ratio of excrement is commonly required to
be less than 1%. The sand ratio of chicken excrement TS of Minhe is 3%. During the
pretreatment process, it mainly removes sand grain through sand basin. In order to
remove the sand grain, the sand in the excrement sand basin should be cleared once
every year.
The second one lies in the chicken feather. The influence of chicken feather can be
reduced through the shear pump.
The third one is about ammonia. If the ammonia content of excrement is excessively
high, the operating efficiency of the system will be reduced. The ammonia content
contained in every ton of fermentation liquor in the biogas jar is generally required to
be no more than 3.8 kg/m3, and the total nitrogen contained is required to be no more
than 5 kg/m3 (because 25% of the total nitrogen can be converted into ammonia
nitrogen).
The fourth one is to desulfurate. The H2S contents of chicken excrement reach
1500-2000 mg/m3, which may seriously erode the equipment and generating set, so
the biological desulfurization technology must be adopted to purify the biogas.
2.1.1 Pretreatment technique
(1) Collection and transportation of chicken excrement
The broiler chicken excrement in the raising base is transported through pipeline. The
breeding chicken excrement in the raising base is transported to the biogas station
through vehicle. And it adopts the 8-hour working system.
(2) Homogenate sand basin
Put the collected chicken excrement into homogenate sand basin, and with rinsing
water, prepare it into the mixing chicken excrement sewage whose TS is 12%. The
sediment on the bottom of the basin is cleared periodically, and transported to be
buried in Penglai innocent garbage disposal plant.
2.1.2 Anaerobic digestion technique
(1) Anaerobic digestion reactor type
This project adopts continuous stirred tank reactor (CSTR), which is applicable to Shandong Academy of Environmental Science
Project Analysis
domestic animal excrement fermentation technique. It adopts the stirring and heating
technology in the biogas fermentation jar, which is a major breakthrough for the
biogas fermentation technique. The stirring facilitates the full contact between
fermentation material and microorganism in the jar and promotes the biogas yield
ratio of the equipment. The heating measure maintains the temperature inside the
anaerobic jar at the appropriate temperature for microorganism so as to ensure the
anaerobic jar can operate normally and stably in winter. The stirring and heating
greatly increase the biogas fermentation rate, so CSTR is also called high-velocity
biogas fermentation jar, which is characterized by high solid concentration, with TS
being 8-12%, enabling the biogas fermentation treatment for all domestic animal
excrement. Its merits include large processing capacity, large biogas output,
convenience for management, easy startup, and low transportation fees. It is generally
suitable for the area that mainly produces biogas and near which there are vegetable,
orchard, and farmland digesting and using the liquid organic fertilizer.
(2) Selection of anaerobic fermentation temperature
This project adopts the middle-temperature anaerobic digestion technique to treat the
chicken excrement, mainly considering the following two aspects:
a. The middle-temperature (35-38 ℃ ) fermentation can keep the anaerobic
fermentation biogas yield rate at a high level, and needs little heat to increase
temperature so as to reduce the heat consumption of the biogas engineering and save
the residual heat of generating set.
b. As the raw material of the biogas engineering of this project, the chicken excrement
contains high contents of ammonia. The free ammonia checks the anaerobic
fermentation. With the same total ammonia nitrogen concentration, the free ammonia
concentration in middle-temperature fermentation is lower than that in
high-temperature fermentation.
Therefore, this project adopts the middle-temperature fermentation technique to
reduce the check by anaerobic ammonia. And it doesn’t adopt the reutilization of
biogas liquid to ensure the stable and reliable anaerobic fermentation. The
high-temperature fermentation, if not managed appropriately, tends to bring about the
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 1
Project Analysis
ammonia check and abnormal fermentation etc.
The reasonable C/N for anaerobic fermentation is 15:1. The C/N ratio of fed material
of this project is 10~12:1. The ammonia content is a little higher. In general, it doesn’t
need to be adjusted, but the accumulation of ammonia nitrogen should be avoided in
the actual operation. For example, adopt the middle-temperature fermentation
technique to reduce the ammonia nitrogen concentration in the fermentation feed
liquid, and avoid the accumulation of ammonia nitrogen resulting from backflow of
biogas liquid.
(3) Anaerobic reactor structure
The anaerobic reactor of this project adopts the Lipp structure. Lipp jar-making
technology is to make use of work hardening theory and shell structure theory in the
plastic working of metals to make circular basin and jar with steel plate of certain
specifications through special technology and equipment and “spiral, double-fold, and
occluding” technique. Thanks to the mechanized and automated production and
adopting steel plate as construction material, Lipp technology has the merits of short
construction period, low price, and high quality etc. For the same construction scale,
its construction period is over 60% shorter than that of traditional production method.
The self-weight is only about 10% of the reinforced concrete tank, and about 50% of
the traditional carbon steel sheet welding tank. In this project, the part contacting
biogas, including cover of anaerobic jar, 1.5m high and above part of the jar wall, and
the part above liquid surface, is made of stainless steel. The other part is made of
galvanized sheet steel plus internal corrosion prevention. According to the experience
of biogas engineering of Denmark, the service life of anaerobic jar of this structure
can exceed 20 years.
(4) Stirring mode of anaerobic
This project adopts the central top stirring, which features: saving electric power, even
mixing of fermentation liquid, and preventing incrustation. The six anaerobic
fermentation jars of this project adopt the intermittent batch feed.
2.1.3 Solid-liquid separation and biogas dregs treatment technique
Put the anaerobic fermentation liquid in the biogas liquid after-fermentation basin for
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 2
Project Analysis
after-fermentation, collect the biogas, and then separate the liquid from the solid.
After the separation, the biogas dregs are further dehydrated in Phase Two project.
When the moisture content is reduced to less than 25%, it can be sold as organic
fertilizer. And the biogas liquid is discharged to the original 50,000m3 biogas basin to
be stored as the liquid organic fertilizer for the neighboring grapery, orchard, and
farmland etc.
2.1.4 Biogas purification and storage technique
The biogas coming from anaerobic fermentation jar is the mixed gas containing moist
steam. Apart from such gaseous fuel as CH4 and CO2, it contains H2S and suspended
granular impurity. H2S is not only toxic, but also very corrosive. The excessive H2S
and impurity will endanger the service life of generating set, so such purification
treatments as desulfurization and gas-water separation are required, among which the
desulfurization of biogas is the main issue.
The H2S content of biogas produced from chicken excrement wastewater is very high,
reaching 1500-2000 mg/m3, so the desulfurization is necessary. In this project, the
biological desulfurization measure will be adopted to desulfurize the biogas. The
biological desulfurization is to oxidize H2S into sulfur or sulfurous acid in the
micro-Aeration condition with colorless sulfur bacteria, such as sulfur oxide
thiobacilli and ferrous oxide thiobacilli etc. This desulfurization measure has been
widely used in Europe, and has been adopted in some projects in China. Its merits
include: not needing catalyst, not needing to treat chemical sludge, producing little
biological sludge, low energy consumption, and sulfur recoverable, and high
removing efficiency. Over 90% of H2S can be removed. After treatment, the H2S
content of biogas is lower than 200 mg/m3, which can meet the requirement of
generating set for the biogas.
According to the different oxygen supply amount, the biological desulfurization can
bring different products. The detailed reaction process is as follows:
H2S + 1/2O2 → S + H2O
H2S + 3/2O2 → H2SO3
The sulfur can be recovered and sold. And the sulfurous acid and very a little
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 3
Project Analysis
biological sludge can be returned to the biogas liquid to keep the nutritive equilibrium
of biogas liquid as organic fertilizer.
The biogas containing moist steam that is sent from anaerobic jar is stored in the gas
storing tank after the purification treatment of special equipment, such as biological
desulfurization tower, gas-water separator, and water condenser etc.
This project adopts the double-membrane dry-type gas storing tank to store the biogas.
It is composed of external membrane and internal membrane. The external membrane
constitutes the external ball shape of the gas storing tank. And the internal membrane
and bottom constitute the cavity to store biogas. The tank has an explosion prevention
blower fan, which automatically adjusts the amount of gas sent to biogas generator
according to the requirement to keep stable the internal gas pressure of the tank. The
external membrane has an upright hose, through which the explosion prevention
blower fan above-mentioned conveys the external air to the space between external
membrane and internal membrane so as to keep the external membrane spherical and
send the biogas out. In addition, it is equipped with ultrasonic range finder to
automatically adjust and control the biogas storing amount.
2.1.5 CHP generator allocation plan
This project adopts the CHP technology to make comprehensive use of the biogas
produced from chicken excrement waste and sewage of Minhe. It can be used for
power generation and heating to create considerable economic benefit, but also reduce
the drainage of greenhouse gasses, then control the pollution and improve the
environment.
The biogas is used to generate power through generating set. The generated electricity
power is integrated into the power grid to be sold, with remarkable economic benefit.
The exhaust heat produced by generating set produces 130℃ hot water through
needle tube heat exchanger. In winter, the hot water is mainly used to heat the
anaerobic feed, and the remaining is used as the heat source for the hencoop of the
chicken farm. In summer, the residual heat can be used to refrigerate the hencoop
through lithium bromide generating set and fan coil system (late phase project).
1) Generating set scale selection
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 4
Project Analysis
The generating set scale is decided according to the principle of “deciding energy
output through biogas amount”. The project produces 30,000 m3 biogas per day. The
heat value of 1m3 biogas is about 5,119 kcal, or 21.5MJ (the methane content of
biogas is 60%). The heat rate of 500GF1-1RZ biogas generating set is 12MJ/kWh.
Therefore, 1m3 biogas can be used to generate 21.5 MJ ÷12 MJ/kWh =1.8 kWh
electric power, then the generated power per day: 30,000×1.8=54,000 kWh (i.e.
generated power per hour: 2,250 kWh), and then the generated power every year:
54,000×365=19,710,000 kWh.
It plans to adopt the 500GF1-1RZ generating set. Based on the continuous power of
the generating set being 420kW and annual operating time being 7,200h, the number
of generating sets should be n=19710000/(7200×420)≈6.5. Therefore, it can install
7 generating sets.
According to the calculation based on biogas yield being 30,000m3/d or 1,250m3/h,
methane concentration being 60%, and unit power being 420kW, the number of
generating sets to which sufficient biogas can be supplied: 1250×1.8÷420=5.36,
and based on the operating time being 8,760h, the average operating power of 6
normally operated generating sets is 375kW.
To sum up, it can establish a CHP biogas power station with seven 500GF1-1RZ
generating sets (6 in service and 1 standby), which is equipped with cooling
circulating system, power distribution system, gas feed system, residual heat
utilization system, and other auxiliary production systems.
Technological Parameters of 500GF1-1RZ Generating Set
Model of generating set 500GF1-1RZ
Model of engine Z12V190ZLDK-2A
Generator mark TF454-6 / 1FC6 454-6LA42-Z
Model of control panel PCK1-RB500 (optional: PCK1-RZ500)
Rated power (kW) 500
Rated current (A) 901
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Project Analysis
Rated voltage (V) 400
Rated power factor, COSΦ 0.8 (hysteretic)
Rated frequency (Hz) 50
Gas heat rate, (MJ/kW·h) 12
Generating efficiency (%) 32
Startup manner 24V DC startup
Startup control mode Manual
Voltage adjustment mode Automatic
Mode of speed regulation Electronic
Excitation mode Brushless
Mode of connection Three-phase four-wire system
Circulated water cooling mode Open type (with heat exchanger)
Mode connection between
engine and generator Resilient coupling
Volume of oil sump (L) 180
Overall dimension (L×B×H)
mm 5,500×1,970×2,278
Mass of generating set (kg) 12,500
Main Technological and Economic Indices
S/N Item Unit Installation plan: 7×500kW (6 in
service and 1 standby)
1 Installed capacity kW 3,500
2 Continuous power kW 2,250
3 Annual operating time H 8,760
4 Comprehensive rate of
electricity use by
factory
% 2.5
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 6
Project Analysis
5 Annual average heat
loss from power
generation
MJ/kWh 12
6 Annual energy output kWh/ye
ar
1.971×107
7 Available exhaust heat kcal/yea
r
1.508×1010
8 Savable standard coal t/year 7.629×104
2.1.6 Main structure of CHP generating set
1. Cooling and circulating system: The seven 500GF1-1RZ generating sets (6 in
service and 1 standby) of the power station share one cooling and circulating system.
According to the performance requirement of 500GF1-1RZ, the cooling system of gas
generating set is divided into internal circulating system and external circulating
system. The two circulating systems exchange heat through the heat exchanger of the
generating set. The internal circulating system and external circulating system are
high-temperature cooling and circulating system and low-temperature cooling and
circulating system respectively. The temperature of influent water of high-temperature
cooling and circulating system is 35℃, and the return water temperature is 45℃. The
temperature of influent water of low-temperature cooling and circulating system is 25
℃, and the return water temperature is 35℃.
The high-temperature cooling and internal circulating is mainly used to cool engine
body and cylinder cover, while the low-temperature cooling and internal circulating is
mainly used to cool engine oil and air.
The internal circulating adopts the softened water. The consumption of each
generating set is about 5kg/d, and that of 6 generating sets is about 30kg/d. The
external circulating adopts the tap water. According to the calculation based on the
consumption of high-temperature and low-temperature cooling water of each
generating set being 40 m3/h, the total high-temperature and low-temperature
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 7
Project Analysis
circulating water consumption of 6 generating sets is 240m3/h. For the external
circulating, about 1,000kg-2,000kg water needs to be supplemented for each
generating set every day. If the multi-fan water tank cooling system is adopted, almost
no water will be lost, and then it almost doesn’t need to supplement water.
Flow of cooling and circulating system: circulating water basin→Y-shaped dirt
separator→circulating water pump→check valve→ influent water main pipe→
intelligent de-scaling electronic water treatment device→influent water branch pipe→
heat exchanger→return water branch pipe→return water main pipe→cooling tower→
circulating water basin
2. Power distribution system
1) Connect-in system: 3 of the 7 500GF1-1RZ generating sets constitute one group,
the other 4 generating sets constitute another group, which form unit connection with
a 2000kVA, 0.4/10.5kV, 2500kVA, and 0.4/10.5kV step-up transformer respectively,
and are integrated into the 10kV section of Qingou transformer station through
one-circuit overhead line.
Before the generating system is connected with the 10kV system, the electricity of
10kV system of Qingou transformer station is transmitted to the low-voltage side of
the power station through the step-up transformer to supply power for the auxiliary
system of the generating set. After the auxiliary system works normally, start the
generating set and check the synchronization at the 0.4kV side. The generating set
operates in parallel with user transformer station power source at the low-voltage side,
and is connected with the bus of 10kV system of Qingou transformer station.
2) Main electrical connection: 3 of the 7 500GF1-1RZ generating sets constitute one
group, the other 4 generating sets constitute another group, which form unit
connection with 2000kVA, 0.4/10.5kV, 2500kVA, and 0.4/10.5kV step-up transformer
respectively. The high-voltage connection adopts the single-bus desectorizing type,
and is connected with the bus of 10kV system of Qingou transformer station through
one-circuit high-voltage cable.
3) System of electricity for power station use: The low-voltage switch cabinet coil-in
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 8
Project Analysis
power source for the electricity for power station use adopts the double-power source
automatic switching device. The power sources are led from the 0.4kV bus of step-up
transformer station and local power grid respectively. The distribution voltage is
220/380V. The power distribution adopts the emanatory type. The AC contactor or
circuit breaker is controlled in site or in the switching room. As to the laying type, the
cable is laid along cable trench or through protecting tube under ground.
4) 10kV power distribution device: The KYN28A-12 moveable metal-enclosed switch
cabinet with five-protection function is adopted as the 10kV high-voltage switch
cabinet of the power station. And it is equipped with vacuum breaker and spring
operation mechanism. All coils in and coils out are ingoing cable and outgoing cable.
In Qingou transformer station, one GG-1A (F) high-voltage switch cabinet is
installed.
5) Integrated automation of power station
a. The generating set adopts 4 one-controlling-two TEM control systems (one TEM
controller controls two generating sets).
b. The generating set operating status is monitored in the generating set control panel
and TEM controller.
Synchronized system: every generating set has one control panel, in which the
synchronized device is installed to realize the low-voltage synchronized and parallel
operation.
3. Gas feed system
1) Feed system: One main DN300 biogas transmission pipeline is laid to transmit
biogas for six working generating sets. In order to ensure the normal operation of the
generating sets, silk screen filter and special flame arrester for pipeline are installed in
the biogas transmission pipeline. The above-ground aerial laying manner is adopted
for the main biogas transmission pipeline to transmit the biogas to the power station.
The diameter of biogas intake branch pipe of every 500GF1-1RZ generating set is
DN100. In order to be able to measure the biogas consumption by the power station,
one gas vortex shedding flow meter is installed in the DN300 main pipe for biogas
transmission. The flow meter is installed beside the generator room.
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Project Analysis
2) Technological process of biogas feed
A → B → C → D→E → F→ G → G
A: double-membrane dry-type gas storing tank B: gate valve C: silk screen filter D:
special flame arrester for pipeline E: gas vortex shedding flow meter F: biogas intake
branch pipe G: manual butterfly valve H: generating set
4. Residual heat utilization system
Seven 500GF1-1RZ gas generating sets (6 in service and 1 standby) are adopted. The
tail gas of the generating sets carries a large amount of heat while it is discharged
from the inside of the generating sets. The temperature of such tail gas is about 550℃.
The tail gas discharged from the generating sets is directly led to needle tube heat
exchanger to generate 130℃ water with the residual heat. In winter, the 90℃ water
produced from water-water heat exchanger is mainly used to heat the material in
anaerobic jar and maintain the temperature needed for middle-temperature
fermentation in anaerobic jar, and the remaining hot water is used to heat some
hencoops. The softened water of the power station is made through the full automatic
water softener installed in residual heat pump house. The water used to supplement
the residual heat utilization system comes from the water supply pipeline network of
the chicken farm.
5. Other auxiliary production system
1) Ventilation: The ventilation design of generator room is mainly on the principle of
ventilation, with heat elimination into consideration. According to the dimension of
generator size and the calculation based on at least 30 times of ventilation volume per
hour, the ventilation louver is installed in the roof of the generator room. The
explosion-proof axial flow fan in the generator room is interlock-controlled by gas
alarm system, and it can also be controlled manually.
2) Fire protection: The fire protection targets include generator room, high-voltage
switch room, low-voltage switch room, outdoor transformer, and residual heat pump
room etc. The fire protection follows the principle of “being based on prevention and
combining prevention and fighting” and the requirement of GB50016-2006 Code for
Design of Building Fire Protection. It mainly depends on the mobile fire extinguisher.
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Besides, the power station is equipped with hydrants to conduct the security
protection.
3) Lightning grounding: Apart from the generator room designed on the basis of
second-class lightning-protection building, other constructions of the power station
are designed on the basis of third-class lightning-protection building. All equipment
whose metal case is not electrified, such as generator room, high-voltage switch room
and low-voltage switch room and generating set, control panel, TEM control cabinet,
and transformer, is reliably connected with the down lead. The down lead is evenly
laid around the construction, whose spacing is no more than 25m. The impulse ground
resistance each down lead is no more than 10Ω. The integrated grounding network is
set in the power station. In order to ensure the reliable operation of microcomputer
system in the power station, the grounding resistance is no more than 1Ω.
4) Gas alarm: The combustible gas concentration detector is set in the generator room
to detect the gas concentration and give alarm and interlock the explosion-proof axial
flow fan in the generator room to initiate it for ventilation.
2.2 Engineering unit design and equipment type selection 2.2.1 Pretreatment system
1. Grille water collection basin
Function: collect the rinsing water of the hencoop, and remove the impurity in
the sewage.
Volume: 500 m3
Size: Φ13 m × 4.5 m
Residence time: 12h
Structure: underground reinforced concrete structure, with cover.
The mechanical grille is set before the basin. Model: GSHZ-600 Width of equipment: 600 mm Overall width of grille: 820 mm Speed of passing grille: 0.5~1.0 m/s Depth of water before grille: 1 m Motor power: 1.1 kW
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Number: 1 The submersible sewage pump is set in the basin.
Function: convey the sewage in the water collection basin to the homogenate sand basin or biogas after-fermentation basin. Model: WQ40-10-2.2 Flow rate: 40 m3/d Head: 10 m Power: 2.2 kW Number: 2 (1 in service and 1 standby) Model: WQ40-15-4 Flow rate: 40 m3/d Head: 15 m Power: 4 kW Number: 2 (1 in service and 1 standby)
2. Homogenate sand basin Function: dilute the chicken excrement until the TS concentration is 12%, blend it evenly and remove the sand. Volume: 1680 m3 × 2 Size: Φ22 m × 4.5 m Structure: underground reinforced concrete structure, with cover. The feed inlet is in the pretreatment room. The shell of homogenate sand basin adopts the plastic extrusion panel for heat preservation. And there is heating pipe in the basin.
Homogenate basin blender Function: mix the excrement in the basin evenly Model: QJB 11/6 Power: 11kW Number: 4 (2 for every basin)
Spiral sand removal Function: discharge the sand in the bottom of homogenate basin
periodically Model: WLS320-18000 Power: 5.5kW Number: 2 (1 for every homogenate basin)
2.2.2 Anaerobic digestion and after-treatment part 1. Shear pump
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Function: cut chicken feather and foreign material Model: M-OVAS (R)/70-3.0/NC Flow rate: 40-70 m3/h Power: 3kW Number: 2 (1 in service and 1 standby), installed before charge pump
2. Charge pump Function: charge the anaerobic fermentation jar Model: NM090BY01L06V Flow rate: 40 m3/h Head: 40m Power: 11kW Number: 2 (1 in service and 1 standby)
3. Anaerobic digestion jar Function: Anaerobic digestion reactor Volume: 3200 m3 × 6 Size: Φ16 m × 16.5 m Structure: Lipp structure. The part contacting biogas, including cover of anaerobic jar, 1.5m high and above part of the jar wall, and the part above liquid surface, is made of stainless steel. The other part is made of galvanized sheet steel plus corrosion prevention. The angle of inclination in the jar top is 20°. Residence time: 23d Fermentation temperature: middle temperature 38℃ Volumetric gas yield: 1.6 m3/m3·d Anaerobic jar feed and operation manner: The feed rate of this project is 830 m3/d. There are 6 anaerobic jars, all of which have feed openings and discharge openings. And there are pipes connecting 1# jar and 2# jar, 3# jar and 4# jar, 5# jar and 6# jar. Such design makes the operation manner more flexible. It can either conduct parallel operation of 6 jars, or divide them into 3 groups to conduct series operation or parallel operation according to the requirement. Anaerobic jar heating manner: With the residual heat of biogas generating set as heat source, heat the external part of anaerobic jar with heating coil pipe. 5 heating coil pipes form one group, cross-arranged and heating by level to ensure the even heating. Anaerobic jar temperature preservation manner: The anaerobic jar
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temperature preservation adopts the double-layer 16cm-thick warming plate, installed outside of heating coil pipe in a staggered manner. The surface of anaerobic jar is covered with colorful steel plate. Anaerobic jar blender Function: mix the fermentation liquid to promote the contact between fermentation liquid and microorganism to enhance the gas yield. Installation manner: installed in the jar top Power: 11kW Rotating speed: 18rpm Number: 6 (1 for each jar) Anaerobic jar reflux pump: Model: NM063BY01L06V Flow rate: 20 m3/h Head: 20 m Power: 4 kW Number: 6 (1 for each jar)
4. After-fermentation jar (1) 1# biogas liquid after-fermentation jar Function: the biogas liquid after anaerobic fermentation further ferments in the jar, and then enters solid-liquid separation unit Volume: 4000 m3
Size: Φ25 m × 9 m Structure: The jar body adopts the Lipp structure. The top adopts the flexible membrane, which can collect biogas and prevent the emission of stench. Residence time: 5d Stirring machine: power: 7.5kw; number: 3 (2) 2# biogas liquid after-fermentation jar Function: ferment the residual sewage Volume: 4000 m3
Size: Φ25 m × 9 m Structure: The jar body adopts the Lipp structure. The top adopts the flexible membrane, which can collect biogas and prevent the emission of stench. Residence time: 5d Stirring machine: power: 7.5kw; number: 3
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Project Analysis
5. Solid-liquid separation Solid-liquid separator: Model: VAN spiral extruding solid-liquid separator Power: 5.5 kW Number: 6 Working time: 12h Output of solid fertilizer: 60.91 t/d (21.32 tTS/d). The solid fertilizer produced every day is sent to organic fertilizer plant for the production of organic fertilizer.
6. Biogas liquid storage basin Function: The fermentation liquid after solid-liquid separation can be stored as the liquid fertilizer for the neighboring orchard, grapery, and farmland etc. Volume: 50,000 m3 (original one of the company)
After the treatment of chicken excrement and sewage of the hencoop through the above treatment facility, the COD removing rate for chicken excrement can exceed 95%, and that for sewage can exceed 80%. 2.2.3 Biogas desulfurization and biogas generating set 1. Biogas purification system (1) Biological desulfurization tower
Function: remove H2S in the biogas with biological measure Model: STS-2000 Processing amount of each tower: 220 m3/h Size: Φ2 m × 6 m Number: 6 Power of each tower: 1 kW
(2) Gas-water separator Model: GS-1000 Processing amount: 220 m3/h Number: 6
(3) Water condenser Model: NS-600 Number: 10
(4) Dry-type flame arrester Model: HF-200 Number: 6
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Project Analysis
(5) Biogas flow meter Model: JLQD-100/220 Flow rate: 220 m3/h Number: 6
(6) Biogas component detector Model: BIOGAS-905 Detection item: CH4, H2S, O2, and CO2Number: 3
2. Biogas storing system Double-membrane dry-type gas storing tank Function: store the purified biogas Volume: 2000 m3
Size: Φ16.9 m × 12.7 m Structure: The double-membrane dry-type gas storing tank is composed of external membrane, internal membrane, bottom membrane, and concrete foundation. The cavity formed by internal membrane and bottom is used to store biogas. It is air tight between external membrane and internal membrane. The external membrane is ball-shaped after it is filled with gas. The tank has an explosion prevention blower fan, which can automatically adjust the amount of gas input/output to keep stable the internal gas pressure of the tank. The internal membrane, external membrane, and bottom membrane all adopt the membrane imported from Germany Mehler, which is welded through HF welding procedure. The material surface undergoes special treatment and coated with high-intensity polyester fiber and methacrylate vanish. The gas storing tank is ultraviolet resistant and leakage-proof. The membrane doesn’t react with or is affected by biogas. And its tensile strength is great. The applicable temperature is -30~60 �. Supporting equipment: 1 explosion prevention blower fan, used to provide pressure for the tank; 1 water seal; influent/effluent water pipe and condensed water drainage pipe (pre-buried in the concrete construction period); 1 ultrasonic ranger finder, installed inside of external top membrane and used to measure the height of internal membrane to decide the current gas storing amount; 1 sight glass, installed in the external membrane to observe the inside of the tank; leakage-proof device, used to convey the surplus biogas to the biogas boiler for automatic combustion when the tank is full of biogas, which can effectively prevent the leakage of biogas.
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Project Analysis
3. Biogas power generation system Function: generate power with biogas with fuel to realize the combined heat and power. Generating capacity of biogas: 1.8 kWh/m3
Daily power generating time: 24h Annual working time: 7,200h Installed capacity: 500 kW × 7 (6 in service and 1 standby) Daily energy output: 54,000 kWh Number: 7
4. Hot water storing tank Function: The residual heat of biogas generating sets is stored in the upper part of hot water storing tank in the manner of 90℃ water. After it is used, the 60℃ water returns to the lower part of the tank, and is pumped into the biogas generating sets for heat exchange. Volume: 300 m3
Size: Φ6 m × 12 m Structure: Aboveground Lipp structure. The tank body adopts the polyurethane material for heat preservation.
Circulating pump Function: hot water circulation Model: 80HGR50-12.5 Flow rate: 50 m3/h Heat: 12.5 m Power: 3 kW Number: 2 (1 in service and 1 standby)
2.3 Material balance, water balance, and heat balance
2.3.1 Available broiler chicken excrement resources
The company has 1.3 million breeding broiler chicken (feed every chicken with about
0.7g grit every day) and 3.7 million broiler chicken. The company produces 500t fresh
excrement (with the TS content being about 20%) and 1,000t rinsing water (after the
grille treatment, among them, 330t is used for blending chicken excrement, and the
other 670t goes through the after-fermentation directly) per day.
The mass of dried chicken excrement: 500 t/d x TS20% =100 t/d, and the sand content
in the chicken excrement: 1,300,000 x 0.7 x 10-6 t/d = 0.9 t/d. According to the
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Project Analysis
calculation based on every ton of dried excrement (TS) producing 300m3 biogas, the
daily biogas output is: 100 x 300 = 30,000 m3. After the chicken excrement is
collected, it needs to be prepared into excrement water with TS being 12% in the
homogenate basin, so the demand for water is: 100/12% - 500 = 330 t/d. Such water
mainly comes from the rinsing water of the animal farm. The total mixed excrement
amount is 830t/d.
2.3.2 Material (TS) balance
100t material is fed per day. 0.9t is removed in the pretreatment phase, including mud
and sand and a little excrement dregs, which will be transported and used as compost.
And 66.53t is consumed in the anaerobic phase. Such TS consumption is the main
part for biomass energy conversion and biogas production. In the anaerobic phase, the
TS output is 32.57t. After the solid-liquid separation, 65% (21.32 t/d) of them become
solid organic fertilizer, and the other part goes into the biogas liquid basin. See Table
2.3.1 for the calculation of material (TS) balance.
Table 2.3.1 Calculation of Material (TS) Balance
Phase Processing unit Input amount (t/d) Consumption (t/d)
Pretreatment
phase Homogenate sand basin 100.00 0.90
Anaerobic phase Anaerobic reactor 99.10 59.50
After
fermentation
phase
Biogas after-fermentation
jar 39.60 7.03
Solid-liquid
separation phase Solid-liquid separator 32.57 21.32
Biogas liquid storage unit 11.25 -- Storage phase
Biogas dregs storage unit 21.32 --
According to the calculation result of Table 2.3.1, the daily output of dried biogas
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dregs is 21.32t. See Diagram 2.
Diagram 2 Material (TS) Balance Diagram
A: Remove 0.90t sand per day B: produce 54.78t biogas per day C: produce 7.03t
biogas per day D: homogenate basin E: anaerobic jar F: 1# biogas liquid
after-fermentation tank G: rinsing water H: proliferate 7.76t microorganism per day I:
liquid organic fertilizer J: biogas liquid tank K: solid-liquid separation L: solid
organic fertilizer
The water content of biogas dregs is 65%. The daily output of dried biogas dregs is
21.32t, and the daily output of biogas dregs is 60.91t.
The mass of excrement resource decreases after the pretreatment and anaerobic
digestion. See Table 2.3.2 for the calculation. From the table, we can see that the
decrease rate is 66.5%.
Table 2.3.2 Calculation of Decrease Level
Mass of dried
excrement
(t/d)
Mass of
removed
dried material
(t/d)
Mass of dried
biogas dregs
(t/d)
Mass of dried
biogas
liquid
(t/d)
Decrease (t/d) Decrease rate
(%)
100 0.90 21.32 11.25 66.53 66.50
L
K J11.25 t/d
21.32 t/d
100 t/d
G
99.1 t/d D E
BA C
F 39.60t/d
H 32.57 t/d
11.25 t/dI
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2.3.3 Water balance
1. Water balance calculation
The sewage amount of this project is 1,000t per day, among which 330t is used for
chicken excrement blending, the other 670t is after-fermented directly. See Diagram 3
and Table 2.3.3 for the relationship between water consumption in each processing
unit and total water balance.
Diagram 3 Water Balance Diagram
N
M L
662.95 t/d
39.59
330
H
727.90
E F
A B
G
C
705.40 t/d
670 t/d
K
1332.47
J
D
669.52 t/d
1000 t/d
702.54 t/d
I
A: remove 2.1t sand per day B: produce 22.50t biogas per day C: produce 2.86t biogas per day D:
water collection tank E: homogenate basin F: anaerobic jar G: 1# biogas liquid after-fermentation
jar H: chicken excrement contains 400t water per day. I: produce 0.48t biogas per day J: 2#
fermentation jar K: liquid organic fertilizer L: biogas liquid tank M: solid-liquid separation N:
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Project Analysis
solid organic fertilizer
Table 2.3.3 Water Balance Calculation Table
Processing unit Item Amount (t/d) Solid content
Sewage amount 1,000
Excrement
blending 330 Water collection
tank
After-fermentation
jar treatment 670
--
Dried material 100.00
Water amount 730.00
Removed dried
material 0.90
Water consumed in
removing dried
material
2.10
Water content of
chicken excrement400.00
Supplemented
water amount 330.00
Homogenate
sand basin
Water output 727.90
12.0%
Anaerobic
reaction
Consumed in
anaerobic
consumption
22.50 6.6%
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Project Analysis
Output after
anaerobic
consumption
705.40
Consumption 2.86 1# biogas liquid
after-fermentation jar Output 702.54 5.7%
Consumption 0.48 2# sewage
fermentation jar Output 669.52 --
Water input for
solid-liquid separation 702.54
Solid-liquid
separation Water output after
solid-liquid separation 702.54
--
Water content of
biogas liquid 662.95
Sewage input 669.52
Biogas liquid
storage
Output 1,332.47
1.6%
Biogas dregs
storage
Water content of
biogas dregs 39.59 35.0%
2.3.4 Overall balance
See Table 2.3.4 for the overall balance of water and material (TS) of this project. The
output of biogas liquid is 1343.72 t/d, containing 1332.47t water and 11.25t dried
material, with the solid content being 1%.
Table 2.3.4 Overall Balance of Water and Material (TS)
Item Water (t/d)
Dried
material
(t/d)
Total Processing unit
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Project Analysis
Input 1,400.00 100.00 1,500.00
-- -- -- Water
collection tank
2.10 0.90 3.00 Homogenate
basin
22.50 59.50 82.00 Anaerobic
process
-- -- -- Solid-liquid
separation
2.86 7.03 9.89
1# biogas liquid
after-fermentation
jar
0.48 -- 0.48
2#
fermentation
jar
39.59 21.32 60.91 Biogas dregs
storage
Unit output
1,332.47 11.25 1,343.72 Biogas liquid
storage
Total output 1,400.00 100.00 1,500.00
2.3.4 Calculation of energy conversion of CHP generator
1. Electric power conversion calculation
This system produces 30,000 m3 per day. According to the calculation based on
conversion rate in the actual operation, every m3 of biogas can generate 1.8kWh
electric power, so the daily energy output is: 30,000×1.8 = 54,000 kWh.
2. Calculation of conversion of thermal energy of residual heat system
Recovery of exhaust heat of each generating set: according to the calculation based on
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Project Analysis
every m3 of pure methane generating 3kWh power and air fuel ratio being 15:1, the
total gas (gas and air) consumption of generating set whose normal power is 420kW is:
420÷3×(15+1)=2240m3/h. According to the calculation based on the average
weight being 1.25kg/m3, the total weight of exhaust fume: 2240×1.25=2800kg/h.
The specific heat capacity of exhaust fume, 0.27kcal/(kg·℃), is calculated
according to the flue gas. Assuming that the temperature of exhaust fume is 550℃,
the available exhaust heat is (550-170)×0.27×2800=287,000kcal/h.
According to the calculation, the heat of one 500GF1-1RZ gas generating set
available through needle tube heat exchanger is 287,000kcal/h (amounting to 333kW),
so the available exhaust heat of six 500GF1-1RZ gas generating sets per hour is
287,000kcal/h×6=1,722,000kcal/h (amounting to 1,998kW).
3. Calculation of balance of supply and demand of heat energy
The heating of material is an important condition for the middle-temperature
anaerobic digestion. In order to ensure the digestion tank operates normally in the
38� condition, the material needs to be heated. There is 500t chicken excrement to be
prepared into 830t reacting material whose solid content is 12% every day, and 330t
rinsing water is needed per day. According to the local air temperature, assume that
both the chicken excrement temperature and the sewage temperature are 5�in the
coolest month. Assuming that the specific heat capacity of fecal sewage is equivalent
to that of fresh water, considering the heat loss and increasing the temperature of the
above material by 40�, the needed heat quantity is: 830×1000× (40-5) = 2.905×107
kcal, which can be supplied with the residual heat of generator. In winter, the heat
needed to heat the feed of anaerobic jar is 2.905×107kcal÷24=1,211,000 kcal/h. And
the remaining heat is 1,722,000-1,211,000=511,000 kcal/h (amounting to 594kW).
Therefore, the area of hencoop heated with remaining heat: 594×1000÷50=
11880m2 (assuming that heating of every square meter needs 50W).
In summer, the residual heat of generating sets can all be used to cool the hencoop
(late-phase project). Assuming that the thermal coefficient of lithium bromide
refrigerating unit is 1.39, the refrigerating capacity is: 1,722,000kcal/h×1.39=
2,393,600kcal/h (amounting to 2,783kW), so the hencoop refrigeration area is: 2,783
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Project Analysis
×1,000÷30=92,767m2 (assuming that the refrigeration of every square meter needs
30W).
III. Analysis of Pollution-Preventing Measures
3.1 Prevention of exhaust gas pollution
The waste gas of this project mainly comes from the fume of the biogas generating set
and the foul gas produced during hydrolysis acidification of the chicken excrement.
3.1.1 Exhaust fume of generating set
The generating set burns the biogas. After purification, the CH4 content in the biogas
reaches 60%, and the H2S content is less than 200mg/l, which meets the requirement
for gas by gas generating set: CH4>40%, and H2S content<200ppm.
According to the information provided by the factory, the amount of pollutant in the
exhaust gas discharge of the 500GF1-1RZ biogas generating set is: nitric oxides
0.30g/kWh; SO2=consumption of fuel gas (m3/d)×H2S content in gas (mg/m3)×
2.857/daily energy output (kWh/d)= 0.32 g/kWh. The daily energy output is
54,000kWh, so the exhaust gas of the generating set can be calculated as Table 3.1.2:
Table 3.1.2 Exhaust Emission Table
Exhaust gas amount (10,000 m3/a)
SO2 NOX
(t/a) mg/m3 (t/a) mg/m311,773
6.3 53.5 5.9 50.1
The exhaust emission is in line with the Class Two standard of Table 2 of Integrated
Emission Standard of Air Pollutants (GB16297-1996) (Because the exhaust emission
standard for biogas generating set hasn’t been issued in China, the above standard is
implemented.)
The generating set has one exhaust mast, which is set 10.5m above the roof of power
house (4.5m high), with the overall height being 15m and inside diameter of outlet
being 0.45m. According to the relevant regulations of Integrated Emission Standard of
Air Pollutants concerning the height of newly established exhaust mast, the exhaust
mast shall be no less than 15m high, and the exhaust mast of newly established project
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Project Analysis
shall be at least 5m higher than the highest construction within 200m away from the
exhaust mast, or the emission standard 50% stricter than the emission rate
corresponding its height shall be implemented. The highest construction within 200m
away from the generator room is 5m in height, so the height of exhaust mast reaches
the standard requirement.
3.1.2 Foul gas
The exhaust gas produced in this project is mainly the foul gas produced during the
operation of each excrement treatment unit, which is mainly composed of hydrogen
sulfide and ammonia etc. Apart from the pretreatment, other working procedures, such
as anaerobic digestion, are carried out in the sealed jar, so the foul gas will not have
influence on the environment. In the pretreatment procedure, there are grille water
collection tank and homogenate sand basin, which are closed with cover. In addition,
the pretreatment room has the biological deodorization device to remove the stench.
However, the biogas liquid storage basin is open mouthed, so the gas emission is
unavoidable. In order to prevent the stench pollution, the protective green belt is set
for isolation, the basin emitting high-value odor is screened with production building,
the plant is fully greened, and the protective isolated area is set in different sections.
All these measures can effectively reduce the influence of odor on the ambient
environment. Through the above measures, it can meet the limit as regulated in Class
Two standard of Emission Standard for Odor Pollutants (GB14544-2001).
3.2 Prevention of sewage pollution
3.2.1 Factory sewage disposal The biogas engineering of this project processes 365,000t sewage every year, which is
mainly the rinsing water of the animal farm of the company, and produces 490,000t
liquid organic fertilizer, biogas liquid. Each generating set of the generation
engineering makes cycling use of 40t water per hour, with 12t fresh water
supplemented per day. The water for residual heat utilization system is enclosed and
circulated.
The drain water produced in the production is biogas liquid, the raw material of
organic fertilizer. Its output is 1,343.72 t/d, among which the water content is
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Project Analysis
1,332.47 t/d, and the dried material content is 11.25t/d, with the solid content being
1.6%. The annual output is 490,000t, which is used as organic fertilizer for farmland:
● In the farming and fertilization season, the biogas liquid is conveyed to biogas
liquid storage tank, orchard, nursery, and farmland etc. (through pipeline and
sealed tank car) as liquid organic fertilizer.
● Out of the farming and fertilization season, the biogas liquid is conveyed and
stored in the biogas liquid storage tank for future use.
Sulfurous acid, product from biological desulfurization, can be returned to the biogas
liquid to keep the nutritive equilibrium of biogas liquid as organic fertilizer.
3.2.2 Domestic sewage disposal
The domestic sewage of this project is collected through the sewage pipeline network
of the plant, and enters the water collection tank for treatment.
3.3 Prevention of noise pollution
The noise source of this project mainly includes pump, blower, cooling tower and
heat exchanger of biogas generating set. The noise reduction measures to be adopted
include:
Blower: install noise eliminator and blast deflector in the air absorption inlet to
reduce the noise and remove the vibration resulting from airflow. Besides, the
acoustic enclosure is set to reduce noise. Number: 2, laid indoors; source intensity:
85~90dB(A).
Heat exchanger: install muffler; lay it indoors; source intensity: 85 dB(A).
Water pump and cooling tower: adopt the low-noise equipment, adopt anti-vibration
measures for the pump foundation, and lay it indoors; source intensity: 75~80 dB(A).
Apply plastic cement washer at the bottom of cooling tower, and arrange fine-meshed
nylon net on water surface to reduce the water spraying noise, and lay it on the roof;
source intensity: 75 dB(A).
It is estimated that with the door and window closed, the influence of noise on the
plant can meet the requirement of ClassⅡstandard.
3.4 Prevention of solid waste pollution
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3.4.1 Production solid waste
This biogas engineering project processes 182,500t fresh excrement every year. The
water content of produced biogas dregs is 65%, the output of biogas dregs is 60.91 t/d
(TS 35%), and the output of dried biogas dregs is 21.32t/d. After the dehydration in
Phase Two project, it will produce 10,376t biogas dregs (TS 75%) whose water
content is lower than 25%. After reaching the requirement of Standard for Biological
Organic Fertilizer (NY884-2004), it will be sold as organic fertilizer for farmland. 0.9t
sand and excrement dregs are produced per day in the homogenate sand basin, which
will be transported to be buried in Penglai innocent garbage disposal plant. The sulfur,
product from biological desulfurization, can be recovered and sold.
3.4.2 Domestic garbage
There is about 2.8t domestic garbage/a, which is cleared and transported and treated
by the local environmental sanitation department.
3.5 Influence of electromagnetic radiation
The output line of this project coincides with the input line of the former project,
mainly passing through mountainous areas and farmland, keeping away from villages.
And it adopts 10KV voltage for transmission, which will not affect the local residents.
3.6 Conclusion
To sum up, in order to have the emission meet the standards and prevent pollution, the
construction unit is suggested to adopt further measures, which are to put biological
deodorant at the passage of the carrier vehicles, to set water jet pump and spray gun,
to rinse the residue at the bottom of vehicle and in the tank with activation solution, to
clean the vehicle, and to spray the vehicle upon its arrival.
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Project Analysis
Chapter Two Alternative Proposal
Evaluation
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 29
Project Analysis
I. Comparison between Implementing and not Implementing the Project
This program analysis focuses on the comparison about the influence on the
environment between implementing and not implementing the project from the angle
of environment improvement.
Program One: biogas engineering project for excrement treatment and resource
utilization
Program Two: no activity and no project
See Table 1 for the merits and demerits of the above two programs.
Table 1 Comparison between Implementing and not Implementing the Project Program One Program Two S/N
Through anaerobic fermentation, the chicken excrement produces a large amount of quality biogas, which is used for power generation. The electric power is integrated into the power grid and sold, which can bring considerable economic benefits. Through the anaerobic fermentation, the chicken excrement can produce 30,000 m3 per day, which can be used to generate 54,000kWh electricity per day. Assuming the electricity rate is 0.594Yuan/kWh, it can bring the revenue of 11.70774 million Yuan every year.
None
1
2
Reduce the emission of greenhouse gasses and recover the waste. Through the anaerobic fermentation, the chicken excrement can produce 10,376t biogas dregs (TS 75%) and 490,000t biogas liquid, which can be used as high-analysis organic fertilizer. It not only reduces the production costs of directly producing organic fertilizer with chicken excrement, but also such high-analysis fertilizer has the disease and insect-proof function. Such fertilizer cannot only increase the yield, but also can be used to produce environment-friendly and nuisance-free farm products to increase the
Maintain the present situation: much far from the state environmental protection requirement.
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 30
Project Analysis
quality of farm product. It realizes the clean production and zero discharge of waste of domestic animal and poultry. It can reduce the discharge of 104,682t equivalent weight of CO2 and bring remarkable environmental benefit. Comply with the requirement of the overall plan of Minhe, promote the excrement treatment level, and enhance the sustainable development ability
Maintain the present situation: influence the future development of the company.
3
Improve the excrement treatment problem, promote the living quality of local residents, and facilitate the development of social relations.
Maintain the present situation: If it continues this way, it may influence the relationship between the Party and the local residents, which is not good for the stable development of society.
4
A little dust, drain water, noise, and solid waste are produced in the construction period, which destroys the vegetation and causes soil erosion; Temporarily increase the traffic pressure and destroy the landscape of construction site.
None
5
The new construction occupies some land permanently, and thus changes the utilization manner of such land.
None 6
From Table 1-1, we can see that after the implementation of Program One, though it
has certain influence on the environment during the project construction and operation,
such influence is limited in time or space, which can be eliminated or reduced to the
minimum through all kinds of measures and will not exert large unfavorable influence
on the regional environment. In addition, with the implementation of Program One,
the reduction and innocent treatment of the chicken farm waste, as well as turning it
into resource, are very promising and have active social benefit, ecological benefit
and economic benefit. After the establishment of this project, its sewage discharge
will reach the standard, and it will improve the regional ecological environment,
enhance the quality of people’s living environment, and promote the local sustainable
development, which meets the willing of the public. Therefore, according to the
assessment, it’s reasonable to implement this project.
II. Factory Site Selection
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 31
Project Analysis
2.1 Principle for Site selection
Apart from considering the overall plan of the company and the excrement
distribution, the following principles shall be observed:
The factory site selection should make the wastewater system layout
economical and reasonable;
Conform to the overall plan of the city;
Try to select the place not threatened by the flood;
Give priority to place of good geologic setting, low ground water level, and
large bearing capacity of foundation to reduce the costs as far as possible and
facilitate construction;
Around the factory site, there should be good sanitary environment to
facilitate the setting of protective belt;
Consider the transportation condition and water and electricity supply etc.
The planned land has sufficient construction and development space, does not
occupy or occupies less fertile land, and has land for future expansion;
Keep sufficient distance from village and residential area to avoid or reduce
the influence on society as much as possible.
2.2 Comparison on and selection of factory site
The breeding farms of Shandong Minhe Animal Husbandry Co., Ltd (Minhe hereafter)
are distributed in three areas of Penglai City. So after several discussions with
construction unit and onsite investigation for many times, there are three sites
available for comparison and choice (See Attached Diagram 3 Factory site
Comparison and Selection). The transportation and natural terrain condition of the
three sites are all suitable for the biogas engineering project, but there are limitations
and unfavorable factors in the economic condition. The comprehensive analysis and
comparison are conducted as follows:
Program A: Qujiagou Village, Beigou Town, the most centralized area with the largest
raising amount of the company.
Program B: Western suburb of Penglai City, near the headquarters of the company.
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 32
Project Analysis
Program C: Northeast of Penglai City, between Xujia Village and Dazao Village.
Table 2 Comprehensive Analysis and Comparison of Factory Sites
Item Program A Program B Program C
600,000 sets of parent breeding broiler chicken and 3,700,000 commercial broiler chicken
Breeding 300,000 sets of parent breeding broiler chicken.
Breeding 400,000 sets of parent breeding broiler chicken.
Raising scale
Transport capacity Little Less Large
Qujiagou Village, Beigou Tow, about 7.5km away
from the urban area
West suburb of Penglai City, about 2.5km away
from the urban area
Northeast of Penglai City, between Xujia Village and Dazao Village
Geographic location
Lie in the lowest place, 2km away from the northernmost of this raising area, with the drop height being 16m, and 0.6km away from the southernmost of the area, with the drop height being 2m. It is favorable for the natural flow of sewage of the whole raising area so as to centralize sewage.
The cultivation farm is decentralized, and the
sewage can’t be centralized through
natural flow.
The cultivation farm is decentralized, and the
sewage can’t be centralized through
natural flow.
Terrain
Around it is wood land and farmland.
Around it is woodland and farmland.
Around it is wood land and farmland. And it is about 2km away from the Yellow Sea in the
north.
Ambient environment
Relocation of residents None None None
Water and electricity supply condition
Good Good Good
Distance from the nearest residential area
800m 600m 700m
Lie in the leeward of the predominant wind direction of city, so the stench will not
influence the urban area.
Lie in the leeward of the predominant wind
direction of city, so the stench will not influence
the urban area.
Not lie in the predominant wind
direction of city, so the stench will not
influence the urban area.
Wind direction
Plan
Conform to the plan of the company and Penglai City and have the reserved place
of the company.
Neighboring the urban area, it will be moved to new place in the future.
Neighboring the economic and technological
development area, it will be moved to new
place in the future.
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 33
Project Analysis
Favorable for centralized management
Unfavorable for centralized management
Unfavorable for centralized
management Management
Program A is more economical and reasonable than Program B and Program C. Conclusion
From Table 2-1, we can see that Program A is more economical and reasonable than
Program B and Program C in every aspect. It conforms to the company’s overall plan
and the policies for local atmospheric pollutant prevention and the protections of
water resource, environment, natural landscapes, famous scenic sites, and cultural
relics. And this location will occupy no farmland or woodland, nor will there be any
need to relocate residents, so Program A is adopted for the factory site selection.
III. Comparison on Technological Process
3.1 Comparison and selection of anaerobic technique
3.1.1 Description of technical performance of all kinds of anaerobic reactors
1) Continuous stirred tank reactor (CSTR)
CSTR is suitable for the anaerobic digestion of sludge and high-solid-content organic
wastewater of urban sewage disposal plant. It can adopt single-stage digestion or
two-stage digestion. The single-stage digestion should adopt the middle temperature
or normal temperature. For the two-stage digestion, provided that the temperature of
material liquid is enough, the first stage should adopt the high-temperature digestion,
and the second stage should adopt the middle-temperature digestion. The effective
volume of CSTR should be determined according to the hydraulic residence time or
volume load. See Table 3 for the design parameters of some kinds of common
fermentation material for CSTR.
Table 3 Relevant Parameters of CSTR
Normal temperature (15~25℃) Middle temperature (35~38℃) Raw
material Hydraulic residence
time Volume load
Hydraulic
residence time Volume load
Pig
excrement 20~40 d 1.0~2.0 kgTS/(m3·d) 15 d
3.0~4.0
kgTS/(m3·d)
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 34
Project Analysis
liquid
20~60 d 1.0~2.0 kgTS/(m3·d) 15 d
3.0~4.0
kgTS/(m3·d)
Chicken
excrement
liquid
20~60 d 1.3~2.0 kgTS/(m3·d) 15 d
3.0~4.0
kgTS/(m3·d)
Cattle
excrement
liquid
Alcohol
waste water 6~15 d
3.0~5.0
kgCOD/(m3·d)
The cycle of circulating working procedures, such as charge, discharge, blending, and
idling of CSTR, as well as the running time of each working procedure, should be
determined according to the property of fermentation material, digestion temperature,
and effluent water quality requirement. The intermittent agitation equipment should
be able to agitate the material liquid in the reactor at least once within 5-10h. It adopts
the agitation and heating technology in the biogas fermentation jar, which is a major
breakthrough for the biogas fermentation technique. The agitation and heating greatly
increase the biogas fermentation rate, so CSTR is also called high-velocity biogas
fermentation jar, which is characterized by high solid concentration, with TS being
6-12%, enabling the biogas fermentation treatment for all domestic animal excrement.
Its merits include large processing capacity, large biogas output, convenient
management, easy startup, and low transportation fees. It is generally suitable for the
area that mainly produces biogas and where the liquid organic fertilizer (water manure)
is used widely. Because this technique is suitable for treating the high suspended
matter content animal excrement and organic waste and has merits incomparable by
other high-efficiency biogas fermentation technique, it is widely used in such areas as
Europe, where the biogas engineering is very developed.
2) Anaerobic contact reactor
The anaerobic contact technique is suitable for treating the organic wastewater of high
suspended matter concentration and high organic matter concentration. The volume of
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 35
Project Analysis
anaerobic contact reactor should be calculated according to the organic volume load
or hydraulic residence time. In the condition of middle temperature or near middle
temperature, the volume load should better be 2.0~5.0 kgCOD/m3·d, or should be
determined according to the type and property of fermentation material, and the
required treatment degree, or the test and the actual operation data of anaerobic
digestion engineering of similar raw material. The return sludge amount is determined
according to the sludge amount in the reactor, feed pH and temperature, which should
better be 50%~200%.
The anaerobic contact reactor is the completely mixing-type reactor. The mixed liquid
discharged from the reactor first goes through the solid-liquid separation in the
sedimentation basin. The sewage is discharged from the upper part of the
sedimentation basin, while the sludge in the lower part of the sedimentation basin is
returned to the anaerobic digestion basin. Such technological process not only ensures
that the sludge is not drained, but also promotes the sludge concentration in the
anaerobic digestion basin, and thus promotes the organic load rate. In comparison
with the common anaerobic digestion basin, it reduces the hydraulic residence time.
Currently, the completely mixing-type anaerobic contact reactor has been used in the
treatment of high-analysis organic wastewater of high SS concentration.
3) Up-flow anaerobic sludge bed (UASB)
UASB is suitable for treating the organic wastewater with the suspended matter
concentration ≤2 g/L. The wastewater to be treated is introduced to the bottom of
UASB, up-flows and passes the flocculent or granular anaerobic sludge bed. With the
contact between sewage and sludge, the anaerobic reaction takes place, and the biogas
thus produced causes the agitation of sludge bed. Part of the biogas produced in the
sludge bed adheres to the sludge grain. The free bubble and the bubble adhering to the
sludge grain flow up to the upper part of the reactor. And the gas-liquid-solid
separation is realized through the three-phase separator in the upper part of the reactor.
The characteristic of UASB is that it can maintain high sludge concentration and high
influent water volume load rate, and thus greatly promotes the processing capacity of
unit volume of anaerobic reactor. But it is not suitable for the fecal sewage of high SS
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 36
Project Analysis
content, and the investment cost is high.
The volume design of UASB should be determined according to the volume load. See
Table 4 for the volume load of UASB under the different temperature conditions.
Table 4 Designed Volume Load of UASB under Different Temperature Conditions
Designed volume load (kgCOD/m3·d) Temperature (℃)
High temperature (50~55) 10~20
Middle temperature (35~38) 5~10
Normal temperature (15~25) 2~5
Low temperature (10~15) 1~2
The influent system of UASB may adopt various types, but the following principles
should be observed to ensure the function of water proportioning and hydraulic
agitation: a) ensure the water inflow of each unit area is basically same, i.e. one point
of inflow is set every 2~4 m2; b) spare no effort to meet the requirement of hydraulic
agitation; c) easy to find the influent pipe blocking; d) easy to clear the blocking.
The effluent system is set at the top of USAB. The multi-slot effluent weir should be
adopted. And the scum board should be set between the effluent weirs.
4) Up-flow solid reactor (USR)
USR is a kind of new reactor specially used to treat those of high solid content, whose
characteristic is that no three-phase separator or other components are set in the
reactor.
The up-flow solid biogas fermentation technique is suitable for treating the waste
organic liquid with the solid content (TS) being 3-8%. When the wastewater
containing high-analysis organic solid (TS 3-8%) enters from the water distribution
system at the bottom and flows up and passes the solid bed containing high-analysis
anaerobic microorganism at certain speed depending on the dynamic force from
feeding and gas production, the organic substance is decomposed and fermented and
produces biogas. The biogas thus produced goes up with the water flow has the
function of agitation and blending, which makes the remaining undigested solid
further contact with the microorganism and oxidize, and realizes high removing rate
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 37
Project Analysis
SHANDONG ACADEMY OF ENVIRONMENTAL SCIENCE 38
and biogas yield finally. When TS is more than 6%, the partial intensified agitation
measures need to be adopted. The volume of USR should be determined according to
the volume load. And the volume load should be determined according to the type and
property of material and the required treatment degree, as well as the digestion
temperature etc. In the middle-temperature or near middle-temperature digestion
condition, it is suitable for the volume load of treating animal excrement to be 3-6
kgCOD/m3·d.
3.1.2 Selection of and decision on anaerobic technique
Mid
dle
tem
pera
ture
or h
igh
tem
pera
ture
Suita
ble
for a
naer
obic
dig
estio
n
of
high
-sol
id
orga
nic
was
te
wat
er. T
he so
lid c
onte
nt (T
S) o
f
feed
is
8~
12%
. In
term
itten
t
feed
is g
ener
ally
ado
pted
.
Mid
dle
tem
p.:
20~3
0 d
Hig
h te
mp.
:
15 d
200~
3000
m3
Hig
h fe
ed
conc
entra
tion,
an
d
high
vo
lum
e ga
s
yiel
d,
com
mon
ly
betw
een
1.5
and
3.0
C
onve
nien
t
man
agem
ent
and
easy
oper
atio
n an
d
mai
nten
ance
Low
lum
p-su
m i
nves
tmen
t co
sts.
The
mai
n op
erat
ion
cost
s co
me
from
feed
ing
pum
p an
d ag
itato
r.
The
inte
grat
ed
use
of
ferm
enta
tion
liqui
d is
requ
ired.
Mid
dle
tem
pera
ture
or h
igh
tem
pera
ture
Suita
ble
for t
reat
ing
the
orga
nic
was
tew
ater
of
high
sus
pend
ed
mat
ter
conc
entra
tion
and
high
orga
nic
mat
ter c
once
ntra
tion
Bas
ical
ly
sam
e as
that
of C
STR
200~
3000
m3
Feed
co
ncen
tratio
n
and
gas
yiel
d ar
e
sim
ilar w
ith th
ose
of
CST
R
Con
veni
ent
man
agem
ent
and
easy
oper
atio
n an
d
mai
nten
ance
Nee
d to
es
tabl
ish
new
sl
udge
sedi
men
tatio
n ba
sin
& r
eflu
x un
it,
whi
ch
incr
ease
s th
e in
vest
men
t.
The
mai
n op
erat
ion
cost
s co
me
from
fee
ding
pum
p, a
gita
tor,
and
slud
ge re
flux
pum
p et
c.
The
inte
grat
ed
use
of
ferm
enta
tion
liqui
d is
requ
ired.
peci
al C
hapt
er fo
r Pro
ject
ana
lysi
s
Shan
dong
Aca
dem
y of
Env
ironm
enta
l Sc
ienc
e
Tabl
e 5
Com
paris
on o
n M
ain
Para
met
ers a
mon
g th
e Fo
ur A
naer
obic
Te