Biomass Drying – Commercial Dryers

Mediums:

-Air

- Flue gas

- SuperheatSteam

Rotary dryer Belt dryer Flash dryer Fluidized bed

Small particle

High corrosion

Fire risk after drying

Leakage in steam dryer

Variable particle sizes

Robust

Low temperature drying

Steam – heat recycle

Reasonable dimension

Steam – heat recycle

Uniform & low temperature

High M/H transfer

Variable particle sizes

Reasonable dimension

Robust

Larger dimension of dryer

Fire risk inside dryer

- high hazard risk

Corrosion and erosion

Blocked by long bark

Fire risk after drying

Small & uniform particle

Abrasion among particles

Leakage in steam dryer

Advantages

Disadvantages

Biomass Drying– Case Study: Evaluation of the Biomass Drying Process

40% flue gas250 oC – 450 oC;647 - 336 t/h

60% hot water90 oC; 737 t/h

Heating Sources

100 MW

Biomass

Heating Sources

40 MW

Drying

Biomass Drying – Case Study

Mflue , HCf,in, Tf,in, Hf,in Mflue , HCf,out, Tf,out, Hf,out

Mwood, MCw,in, Tw,in, Hw,in Mwood, MCw,out, Tw,out, Hw,out

Mflue , Tf,,out

Dryer

Mass and Heat Balances:

Flue Gas Drying

MS, Ps,in, Ts,in, Hs,inMwat, Twat, HwatMS, Ps,out, Ts,out, Hs,out

Mwood, MCw,in,

Tw,in, Hw,in

Mwood, MCw,out,

Tw,out, Hw,out

Pre-heater

Dryer

R

Mflue , Tf,in

Mflue , Tf,,out

Steam Drying

Biomass Drying – Case Study

Mflue , HCf,out, Tf,out

Mwood, MCw,in, Tw,in Mwood, MCw,out, Tw,out

Mflue , HCf,in, Tf,in

A Continuous Cross-Flow Belt Dryer

Biomass Drying – Estimation of Profitability

Flue gas drying

Initial MC=1.5 kg-w/kg-wood

Cumulative cash flow 10 year NPV

Final MC=0.1, 0.3 kg-w/kg-wood Final MC=0.1 kg-w/kg-woodFuel price = 14 €/MWH Fuel price = 14 €/MWH

Biomass Drying – Estimation of Profitability

Steam drying

Cumulative cash flow 10 year NPV

Final MC=0.1, 0.3 kg-w/kg-wood Final MC=0.1 kg-w/kg-woodFuel price = 14 €/MWH Fuel price = 14 €/MWH

Biomass Drying – Estimation of Profitability

Effect of fuel prices

Initial MC=1.5 kg-w/kg-wood

Final MC=0.1 kg-w/kg-wood

10 year NPV

Bacho industryKirkenaerMEC companyMitchell Dryers Ltd

Rotary

Belt

Flash

GEA; DryCo; Einco

Flue gas150-700 C

* 10000-26000 kg/h** 3.7 MJ/kg-H2O

Steam150 C

* 6000-30000 kg/h** 0.4-1.0 MJ/kg-H2O

Fluidized Bed

Niro A/S

Steam190 C

* 3600 kg/hFlue gas160-280 C

* 800-7000 kg/h

**5.8 MJ/kg-H2O

Cost (not including

Biomass Drying – commercial dryers

* Evaporation rate of water ** Heat consumption

Belt

Swiss Combi, Bruks Klöckner, Mabarex, Andritz Fiber

** 0.4-1.0 MJ/kg-H2O

Air30-110 C

* 500-40000 kg/h

Cost (not includingInstallation):$22-106 /kg/h Including installation-$300-796 /kg/h ,$1.6-5.3 millionfor 15-130 MW bioler;-$761 /kg/h$ 5.4 millionfor 55 tonnes/h boiler

Cost (excluding installation)

$ 18-160 /kg/h

Including installation

-$335/kg/h, 180tonnes/h

burning bark

-$550-1600 /kg/h

$ 3.5-10.6 million

for 15-130 MW boiler

Biomass Drying – other options

Advantages:- high power density-reducing drying time- high energy efficiency, avoid warm up and cool down- improved quality, compared with conventional drying.- avoids combustible gas by- products, environmental friendly

Disadvantages:- not uniform dried (hot spot or cold spot)- penetration achievable, depended on biomass properties.- insufficient knowledge of the interaction between wood

Microwave dryer

- insufficient knowledge of the interaction between wood and process parameters as well as the higher investment expenses.

Supercritical CO2Advantages: - using CO2(green house gas)- low temperature (saving energy)- low fire risk- high quality (avoiding high temperature heating biomass)

Disadvantages:- high pressure equipmentand processes

Task3 Task3 -- Sheffield ; high efficiencySheffield ; high efficiency

l Novel technology

l Industrial condensing boilers

l Low temperature, < dew point

l Boiler design

l External system

Condensing boilersCondensing boilersl Benefits:

– High efficiency: recovery of sensible and latent heat

– Emission reduction: absorption by the condensate

Dew point

Dew point

Re-vaporisation of the condensate

Condensing boilersCondensing boilersl Application/Case Studies

– Oriketo heating station in Finland (Condenser: 12MWth)

– Vimmerby Energy AB in Sweden (Condenser: 2MWth)

– CHP power plant in Harnosand, Sweden (11 MWe, 26MWth, Condenser: 7MWth)

– Nitrate Stress Corrosion Cracking in Waste Heat Recovery Boilers in the Netherlands in 1990’s (Leferink et al. 2003)

» Ammonia Nitrate» Ammonia Nitrate

» Carbon steel and low alloy steel are sensitive to attack

Oriketo heating station

Condensing boilers with Radiator & floor heatingCondensing boilers with Radiator & floor heating

l Return water from a heating system should be 30-50°C, well below the dew point of flue gas

l A floor heating system or large surface area radiator is required.

Condensing boilers with a heat pumpCondensing boilers with a heat pump

l A heat pump can be used between the condenser and the hot return water– Conventional electrically driven compression heat pump

– An absorption heat pump

Thermoacoustic EngineThermoacoustic Enginel Thermoacoustic engines of which nearly all are thermoacoustic

stirling engines;

l It is a technology that uses high-amplitude sound waves in a pressurized gas to pump heat from one place to another;

l or uses a heat temperature difference to induce sound, which can be converted to electricity with high efficiency, with a (piezoelectric) loudspeaker;(piezoelectric) loudspeaker;

l The most efficient thermoacoustic devices built to date have an efficiency approaching 40% of the Carnot limit, or about 20% to 30% overall (depending on the heat engine temperatures).

Thermoacoustics Engine Thermoacoustics Engine (Standing (Standing --wave)wave)

Stack Total power

Acoustic power

Standing-wave engine example, Scale drawing, and power distribution of Tektronix researchers (G. W. Swift, 2002)

Branch to refrigerator

InsulationAmbient heat exchanger

Stack

Hot heat exchanger138 cm

Branch

Thermoacoustics Engine Thermoacoustics Engine (Traveling(Traveling--wave)wave)

Tapered pulse tube

Regenerator

Traveling-wave refrigerator example, Schematic and power distribution: Cryenco 2-kW orifice pulse-tube refrigerator (G.

W. Swift, 2002)

Acoustic power

Total power

Thermoacoustic Engine (Malone Thermoacoustic Engine (Malone Refrigeration)Refrigeration)

Thermoacoustic refrigeratorThe Sonic Compressor