13. Holzenergie-Symposium!

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www.holzenergie-symposium.ch! 13. Holzenergie-Symposium! Leitung:!Prof. Dr. Thomas Nussbaumer!

1 13. Holzenergie-Symposium! Leitung:!Prof. Dr. Thomas Nussbaumer!!Verenum Zürich und Hochschule Luzern! Patronat:!Bundesamt für Energie! Ort:!ETH Zürich! Datum:!Zürich, 12. September 2014! Verenum

2 Vergleich von Rost- und Wirbelschichtfeuerung Technik, Kosten, Anwendungen Philipp Kolbitsch philipp.kolbitsch@bertsch.at

3 Business segments of BERTSCHenergy Solid Fuel Boiler Plants Electricity and Heat from Biomass Process Heat Recovery Systems and Pressure Equipment Steam, Heat and Equipment for Process Plants Combined-Cycle / Cogeneration HRSG Electricity and Heat from Gas and Oil Service Optimal Maintenance and Service Waste Heat Recovery Boilers Steam from Waste Heat in Industrial Processes

4 Business segments of BERTSCHenergy Solid Fuel Boiler Plants Electricity and Heat from Biomass design (from conception to detail) Steam parameters: t/h, bar, C EPC solutions (lot wise or turnkey) in house design Air cooled grate Bubbling fluidized bed Water tube boiler After sales services 24 references in 6 countries

5 Fuel Spectrum Wood chips Wood from Landscape preservation Short-rotation plantation Waste wood RDF Municipal waste

6 Criteria for choice of technology Given fuel quality is the main criteria for the choice of combustion system 1. Water content of fuel Lower Heating Value Ash content, impurities, Particle size Grate firing Bubbling fluidized bed firing

Grate Firing Air cooled reciprocating grate with optimized grate bar geometry for highest availability and life time Fuel input with pusher and chute onto fuel feeder grate Active control of fire

7 Grate Firing Air cooled reciprocating grate with optimized grate bar geometry for highest availability and life time Fuel input with pusher and chute onto fuel feeder grate Active control of fire position on grate for highest efficiency Each grate zone with variable controlled primary air supply Staged combustion with primary and secondary air Temperature control in combustion chamber with recirculated flue gas (beneath and above grate)

Bubbling Fluidized Bed Firing Bubbling fluidized bed

of bed with a mixture of air and recirculation gas

Staged combustion with primary and secondary air

8 Bubbling Fluidized Bed Firing Bubbling fluidized bed integrated in boiler open nozzle floor Fluidization of bed with a mixture of air and recirculation gas (temperature control) Start up burners in freeboard Staged combustion with primary and secondary air Deashing with reliable conveyors Sand classifier and sand recycling

9 Fuel quality Grate BFB Reason Economic Effect LHV max 15 MJ/kg >20MJ/kg wear on grate maintenance cost LHV min MJ/kg 3-4 MJ/kg intensified heat transfer in BFB choice of technology Co-combustion of wet fuel (LHV < 0) low quantity possible high quantity possible intensified heat transfer in BFB choice of technology Fuel grain size (screen size) < 350 mm (max. pieces > 1m) < 100 mm (sum of edge length < 300mm) fuel feeding / dosing higher costs for fuel treatment with BFB Metal content high content acceptable (depending on species), removal recommended must be removed as far as possible (spec. Al, bulk particles) agglomeration in BFB; blocking of deashing system higher cost for fuel preparation with BFB

10 Emissions - General Grate BFB Reason Economic Effect CO mg/nm³ (6%O 2, dry) 0 50 mg/nm³ (6%O 2, dry) homogeneous combustion with BFB none (efficiency difference is negligible) NO x fuel dependant; BFB approx. 50% of grate firing lower combustion temperature with fewer temperature peaks for BFB Investment and operating costs for SNCR Mean TOC (ash) 3% 0-3% Residence time, Fluidized bed normally low, can be interesting for high ash content in fuel N 2 O slightly higher for BFB combustion lower combustion temperature for BFB none

11 Emissions Reference plants Plant Fuel NO x emissions [mg/nm³, 6%O 2 dry] BFB, No 1 demolition wood, W BFB, No 2 natural biomass with 30% demolition wood, W BFB, No 3 natural biomass, W BFB, No 4 natural biomass with 30% demolition wood, W Grate firing, No 1 natural biomass, W Grate firing, No 2 natural biomass, W Grate firing, No 3 natural biomass (mostly bark), W60 375

12 Other figures Grate BFB Reason Economic Effect Boiler efficiency slightly increased for BFB - air / fuel ratio - unburnt in ash slightly lower fuel costs for BFB Load change rate low moderate fuel residence time on grate / in BFB interesting for e.g. paper industry and peak load plants Electric power consumption moderate ( % of fuel thermal input) high ( % of fuel thermal input) - BFB requires high pressure primary air - BFB often has higher rec. flue gas ratio net electricity production Investment cost The boiler including firing has more or less equal investment cost. The overall cost strongly depend on the fuel type and fuel quality.

13 Resource consumption Grate BFB Reason Economic Effect Cleaning intervals of soot blowers 1 3 cycles / day 0 1 cycle / day - combustion temperature - self-cleaning effect - reduced wear from soot blowers - HP steam consumption Quartz sand demand none approx. 2-3kg/MWh - efficiency of sand separation system - sand attrition costs for sand acquisition Start-up burners not required, sometimes executed required BFB requires bed material preheating to the solid fuel ignition temperature fuel costs, investment costs Pressurized air variable - bag filter or ESP - SNCR - deashing system - etc. costs for pressurized air production

14 Disposal and maintenance costs Grate BFB Reason Economic Effect Slag (from grate), bed ash Boiler / filter ash low high high low - BFB: bed ash consists of coarse particles only - BFB: all other ash is boiler / filter ash - Grate: ash is only partially discharged with the flue gas; major fraction is slag from grate benefit of grate firing since slag / bed ash is usually easier / cheaper disposable compared to filter ash Wear high (depending on fuel) low - BFB: no moving parts - Grate layer is a wear part which needs to be changed regularly (5 10 years) wear parts and maintenance costs

Summary Main advantage of grate firing is low demand on fuel preparation Fuel particle size Inorganic impurities (ceramics, glass, Fe and non Fe) Main advantages of bubbling fluidized bed are:

15 Summary Main advantage of grate firing is low demand on fuel preparation Fuel particle size Inorganic impurities (ceramics, glass, Fe and non Fe) Main advantages of bubbling fluidized bed are: Emissions (usually no need for SNCR) Efficiency Wide LHV and water content range, high fine content in fuel possible Operational costs are similar Maintenance costs are lower for BFB Investment costs depend very much on the overall situation Boilers including firing have very similar investment costs In case extensive fuel preparation is required, grate technology is usually less expensive

Thermal Exploitation of Wastes in Lignite Combustion Facilities

43 rd INTERNATIONAL ENERGY AGENCY - FLUIDIZED BED CONVERSION MEETING 22-23 NOVEMBER 2001, LISBON, PORTUGAL Thermal Exploitation of Wastes in Lignite Combustion Facilities P. Grammelis, G. Skodras, Em.