A LOW COST AND HIGH QUALITY SOLID FUEL FROM BIOMASS AND COAL FINES

Kelly, John T. ; Miller, George ; Namazian, Mehdi

National Energy Technology Laboratory (U.S.)

关键词: Biomass;    Charges;    Sensitivity Analysis;    01 Coal, Lignite, And Peat;    Fuel Pellets;   

DOI  :  10.2172/795777
RP-ID  :  AC26-99FT40157--01
RP-ID  :  AC26-99FT40157
RP-ID  :  795777

美国|英语

来源: UNT Digital Library

【 摘 要 】

Use of biomass wastes as fuels in existing boilers would reduce greenhouse gas emissions, SO2 and NOx emissions, while beneficially utilizing wastes. However, the use of biomass has been limited by its low energy content and density, high moisture content, inconsistent configuration and decay characteristics. If biomass is upgraded by conventional methods, the cost of the fuel becomes prohibitive. Altex has identified a process, called the Altex Fuel Pellet (AFP) process, that utilizes a mixture of biomass wastes, including municipal biosolids, and some coal fines, to produce a strong, high energy content, good burning and weather resistant fuel pellet, that is lower in cost than coal. This cost benefit is primarily derived from fees that are collected for accepting municipal biosolids. Besides low cost, the process is also flexible and can incorporate several biomass materials of interest The work reported on herein showed the technical and economic feasibility of the AFP process. Low-cost sawdust wood waste and light fractions of municipal wastes were selected as key biomass wastes to be combined with biosolids and coal fines to produce AFP pellets. The process combines steps of dewatering, pellet extrusion, drying and weatherizing. Prior to pilot-scale tests, bench-scale test equipment was used to produce limited quantities of pellets for characterization. These tests showed which pellet formulations had a high potential. Pilot-scale tests then showed that extremely robust pellets could be produced that have high energy content, good density and adequate weatherability. It was concluded that these pellets could be handled, stored and transported using equipment similar to that used for coal. Tests showed that AFP pellets have a high combustion rate when burned in a stoker type systems. While NOx emissions under stoker type firing conditions was high, a simple air staging approach reduced emissions to below that for coal. In pulverized-fuel-fired tests it was found that the ground pellets could be used as an effective NOx control agent for pulverized-coal-fired systems. NOx emissions reductions up to 63% were recorded, when using AFP as a NOx control agent. In addition to performance benefits, economic analyses showed the good economic benefits of AFP fuel. Using equipment manufacturer inputs, and reasonable values for biomass, biosolids and coal fines costs, it was determined that an AFP plant would have good profitability. For cases where biosolids contents were in the range of 50%, the after tax Internal Rates of Return were in the range of 40% to 50%. These are very attractive returns. Besides the baseline analysis for the various AFP formulations tested at pilot scale, sensitivity analysis showed the impact of important parameters on return. From results, it was clear that returns are excellent for a range of parameters that could be expected in practice. Importantly, these good returns are achieved even without incentives related to the emissions control benefits of biomass.