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Advanced Slurry-Phase Transport System for Pressurized, Fluidized Bed Combustion Ash-Letdown--ENSPEC Engineering, Inc., 276 West Bagley Road, Suite 106, Berea, OH  44017; 440-239-8422

Mr. John D. Neeson, Principal Investigator

Ms. Vivien L. Gow, Business Official

DOE Grant No. DE-FG02-00ER83001

Amount:  $97,600

 

Pressurized fluidized-bed combustion ash-letdown systems are plagued with several reliability and operational problems.  These system deficiencies include mechanical lockups resulting from expansive thermally-induced forces, high wear rates due to the abrasive nature of fast-moving ash particles and significant difficulty in maintaining system pressure resulting from excessive gas leakage across existing lock-hopper systems.  A very simple system concept has been conceived as an alternative to the unreliable high-pressure lock-hoppers systems, rotary valves or solid let-down pumps presently utilized in today’s commercial pressurized fluidized-bed combustors.  The approach involves a single ash quench pressure vessel operated at system pressure.  The quench vessel receives ash flowing by gravity from the attached high-pressure coal combustor.  This hot-ash is directly water quenched as gravity-fed solids particles are fed from the main combustor vessel.  The density of the ash-water slurry is controlled by recycled make-up water fed to the quench drum.  The slurry mixture flows across a single control valve to lower the pressure of the stream.  A quench drum level controller maintains a constant liquid head to prevent any high-pressure gas from escaping, thus providing a leak-tight seal on the coal combustor.  The byproduct liquid water-ash slurry is processed in conventional sludge handling and separation equipment.  The proposed Phase I SBIR research effort is to develop a prototype design of an Advanced Slurry-Phase High-Pressure Let-Down and Transport System for Coal Ash.  A detailed thermal, mass transport and fluid flow analysis of the system is planned, a representative design basis will be selected to establish representative capacity requirements, two-phase density and pressure vessel level control algorithms shall be developed, equipment-component specifications including materials and sizes will be generated.  Additionally, specific recommendations for the Phase II SBIR program shall be formulated.  The detailed analytical results of an ash-water-steam fluid flow and transport model of the high-pressure let-down system shall be reported upon.

 

Commercial Applications and Other Benefits as described by the awardee:  Typical applications for the slurry-phase ash transport system include commercial use and installation in both new and existing pressurized fluidized-bed combustors and high-pressure coal gasification complexes.  The benefits of this system concept are its design simplicity, low cost, few moving parts, ash metering capability and zero gas leakage from the adjacent high-pressure combustor vessel.  The market for this type of system would principally be the United States, but would also have commercial potential in world-wide energy sectors.