Biomass Drying Commercial Dryers

Transcription

1 Biomass Drying Commercial Dryers Mediums: - Air - Flue gas - Superheat Steam Rotary dryer Belt dryer Flash dryer Fluidized bed Advantages Variable particle sizes Reasonable dimension Robust Variable particle sizes Robust Low temperature drying Steam heat recycle Reasonable dimension Steam heat recycle Uniform & low temperature High M/H transfer Disadvantages Corrosion and erosion Blocked by long bark Fire risk after drying Larger dimension of dryer Fire risk inside dryer - high hazard risk Small particle High corrosion Fire risk after drying Leakage in steam dryer Small & uniform particle Abrasion among particles Leakage in steam dryer

2 Biomass Drying Case Study: Evaluation of the Biomass Drying Process 40% flue gas 250 o C 450 o C; t/h 60% hot water 90 o C; 737 t/h Heating Sources 40 MW 100 MW Biomass Drying

3 Biomass Drying Case Study Mass and Heat Balances: M flue, HC f,in, T f,in, H f,in Dryer M flue, HC f,out, T f,out, H f,out M wood, MC w,in, T w,in, H w,in Mflue, Tf,,out Flue Gas Drying M wood, MC w,out, T w,out, H w,out R M wat, T wat, H wat Pre-heater M flue, T f,in M S, P s,in, T s,in, H s,in Dryer M S, P s,out, T s,out, H s,out M wood, MC w,in, M wood, MC w,out, T w,in, H w,in T w,out, H w,out Steam Drying

4 Biomass Drying Case Study M flue, HC f,out, T f,out M wood, MC w,in, T w,in M wood, MC w,out, T w,out M flue, HC f,in, T f,in A Continuous Cross-Flow Belt Dryer

5 Biomass Drying Estimation of Profitability Flue gas drying Initial MC=1.5 kg-w/kg-wood Cumulative cash flow Final MC=0.1, 0.3 kg-w/kg-wood Fuel price = 14 /MWH 10 year NPV Final MC=0.1 kg-w/kg-wood Fuel price = 14 /MWH

6 Biomass Drying Estimation of Profitability Steam drying Cumulative cash flow Final MC=0.1, 0.3 kg-w/kg-wood Fuel price = 14 /MWH 10 year NPV Final MC=0.1 kg-w/kg-wood Fuel price = 14 /MWH

7 Biomass Drying Estimation of Profitability Effect of fuel prices 10 year NPV Initial MC=1.5 kg-w/kg-wood Final MC=0.1 kg-w/kg-wood

8 Biomass Drying commercial dryers Rotary Bacho industry Kirkenaer MEC company Mitchell Dryers Ltd Flue gas C * kg/h **5.8 MJ/kg-H2O Cost (not including Installation): $ /kg/h Including installation -$ /kg/h, $ million for MW bioler; -$761 /kg/h $ 5.4 million for 55 tonnes/h boiler Flash GEA; DryCo; Einco Flue gas C * kg/h ** 3.7 MJ/kg-H2O Steam 150 C * kg/h ** MJ/kg-H2O Cost (excluding installation) $ /kg/h Including installation -$335/kg/h, 180tonnes/h burning bark -$ /kg/h $ million for MW boiler Fluidized Bed Niro A/S Steam 190 C * 3600 kg/h Belt Swiss Combi, Bruks Klöckner, Mabarex, Andritz Fiber Air C * kg/h * Evaporation rate of water ** Heat consumption

9 Biomass Drying other options Microwave dryer 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 and process parameters as well as the higher investment expenses. Supercritical CO 2 Advantages: Disadvantages: - using CO 2 (green house gas) - high pressure equipment - low temperature (saving energy) and processes - low fire risk - high quality (avoiding high temperature heating biomass)

10 Task3 - Sheffield ; high efficiency l Novel technology l Industrial condensing boilers l Low temperature, < dew point l Boiler design l External system

11 Condensing boilers l Benefits: High efficiency: recovery of sensible and latent heat Emission reduction: absorption by the condensate Dew point Dew point Re-vaporisation of the condensate

12 Condensing boilers l Application/Case Studies Oriketo heating station in Finland (Condenser: 12MW th ) Oriketo heating station Vimmerby Energy AB in Sweden (Condenser: 2MW th ) CHP power plant in Harnosand, Sweden (11 MW e, 26MW th, Condenser: 7MW th ) Nitrate Stress Corrosion Cracking in Waste Heat Recovery Boilers in the Netherlands in 1990 s (Leferink et al. 2003)» Ammonia Nitrate» Carbon steel and low alloy steel are sensitive to attack

13 Condensing boilers with Radiator & floor heating l Return water from a heating system should be C, well below the dew point of flue gas l A floor heating system or large surface area radiator is required.

14 Condensing 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

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16 Thermoacoustic Engine l 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; 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).

17 Thermoacoustics Engine (Standing -wave) Stack Total power Acoustic power Branch Stack Branch to refrigerator Ambient heat exchanger Hot heat exchanger 138 cm Insulation Standing-wave engine example, Scale drawing, and power distribution of Tektronix researchers (G. W. Swift, 2002)

18 Thermoacoustics Engine (Traveling-wave) Regenerator Tapered pulse tube Acoustic power Total power Traveling-wave refrigerator example, Schematic and power distribution: Cryenco 2-kW orifice pulse-tube refrigerator (G. W. Swift, 2002)

19 Thermoacoustic Engine (Malone Refrigeration) Thermoacoustic refrigerator The Sonic Compressor