The Design of the Residual Heat Utilization System For the Forging Furnaces’ Flue Gas
Gu Pingdao , Zhang Huasong
School of Environmental Science and Engineering, Dong Hua
University, Shanghai, China
Sustainable Thermal Energy Management in the Process
Industries International Conference SusTEM2011
October 25th – 26th, United Kingdom
OUTLINE
1. Aims and Objectives
2. Energy Consumptions in the Forging Plant
3. Waste Heat Available in the Production
Process
4. Waste Heat Utilization System
5. Results and Analyses
6. Conclusions
Aims and Objectives
Analyses and measurement of the waste
heat from the forging furnaces’ flue gas
Using the waste heat to generate cooling for
the production process and for air-
conditioning in the workshop
Using the waste heat to generate steam and
hot water
Energy Consumption in the Plant
Vast ice consumption during heat treatment (hardening) process - The capacity of centrifugal compression refrigeration units is 4800 kW and they consume 1.50x107
kWh of electrical energy each year
Air-conditioning Station generates cooling for workshops and it consumes electrical energy 8.41×108 kWh each year and generate 2.4x1012 kWh of cooling
Air conditioning in offices and living area consumes 3.0x106 kWh electricity each year
Steam consumption is 6160 ton per year
Hot water supply for washing and bath
Energy consumption data in 2009 & 2010
Year
Heavy oil (t)
Natural gas(m3)
Syngas
from coal (m3)
Electricity (kWh)
Coal (t)
2009
173,79 37,562,468 211,905,183 75,844,429 117,607
2010
5,781
42,082,500
169,527700
51,883,400
96,678
Energy consumptions of the furnaces
Type Number Consumption Energy
Heavy oil-fired heating furnace
7(7) 5781 t 2.32 x 1011KJ
Natural heating furnace
14(4)
42,082,535m3
1.497x1012KJ Natural heat
treatment furnace
14(9)
Gas heat treatment furnace
19 162,819,734m3
1.70x1012KJ
Cold water-sinks
No
Name
Size
volume
Cooling quantity
1 8m Ф8000*8000 402m3 20260800KJ
2 1# Ф5000*28000 550m3 27720000KJ
3 2# Ф4800*18200 350m3 17640000KJ
4 3# Ф5000*14000 196m3 9878400KJ
5 4# Ф5000*10000 402m3 20260800KJ
6 5# Ф11000*8800 836m3 42134400KJ
7 6# 3000*3000*3000 27m3 1360800KJ
8 New workshop Ф11000*8000 760m3 38304000KJ
9 Middle sink Ф8000*8000 2800m3
Station air-conditioning
workshop The number of station cooling capacities
First forging workshop 62 The total: 8.41×108 kw.h/year
First forging workshop 72
Heat treatment workshop 104
New workshop 44
Machining Workshop 38
Flue gas data statistics
1 Average flue gas volume
(Nm3/h) 205×103
2 Maximum flue gas volume (Nm3/h) 341×103
3 Minimum flue gas volume (Nm3/h) 100×103
4 Average flue gas temperature (℃) 650
5 Maximum flue gas temperature
(℃) 738
6 Minimum flue gas temperature (℃) 430
The generation of cooling
Flue gas volume(m3)
Inlet temperature of flue gas(℃)
Outlet temperature of flue gas(℃)
COP
the total cooling capacity QL (KW)
205000
650
170
1.4
53934
The generation of saturated steam
Flue gas volume(m3)
Inlet temperature of flue gas(℃)
Outlet temperature of flue gas(℃)
Inlet temperature of water (℃)
Outlet temperature of saturated steam(℃)
the total saturated steam (T)
205000
170
110
20
100
605,000
The generation of hot water
Flue gas volume(m3)
Inlet temperature of flue gas(℃)
Outlet Temperature of flue gas(℃)
Supply water temperature (℃)
Return water temperature (℃)
the total hot water (kg/h)
the total heat
Qr (kw)
205000
110
75
65
30
792637.6
32336
Summary of Economic Benefits Analysis
Numb
er Name
Initial
investment
(104 yuan)
Economic
efficiency
(104
yuan/year)
Payback
period
(year)
Coal-
saving
(104
t/year)
CO2
emission
reduction
(104
t/year)
One
residual flue gas heat
refrigeration
system for replacing
the ice consumption
1498 468.3 3.2 0.097 0.24
Two
residual flue gas heat
refrigeration
system for replacing
centrifugal
compression
refrigeration
2939.8 1175.5 2.5 0.586 1.46
Three
residual flue gas heat
refrigeration
system for station air-
conditioning and
production air-
conditioning
2697 869.9 3.1 0.434 1.08
Four
residual flue gas heat
refrigeration
system for office and
living area air
conditioning and hot
water supply
11841.4 5148.4 2.3 0.306 7.6
Analysis of Economic Benefits
Making use of the hot waste flue gas not only conserves energy, but also reduces overall CO2 emissions. Furthermore, the payback period is short; therefore the system is both reliable and highly efficient.
Analysis of Environmental Benefits
Through the application of the system, high temperature flue gas is reduced to the low temperature. It can successfully reduce waste heat and thermal pollution. At the same time, we can see that CO2 emission reduction is 10.38× 104t/year.
Analysis of Social Benefits
Energy conservation and emission reduction is a project that aims to benefit the ecological environment and protect the health of individuals.
Once the energy conservation and emission reduction projects completed, energy will be conserved whilst also reducing the volume of pollutants that affect the surrounding water and atmospheric environment.
The waste heat utilization system for the forging
furnaces’ flue gas is feasible
High temperature waste heat in flue gas may be used
to produce refrigeration/cooling, steam and hot
water
The waste heat utilisation system creates substantial
economic, environmental and social benefits.
Conclusions