Objective
Development and test operation of a new waste utilization system (radiation boiler) and of further new components for pressurized entrained flow gasification (PRENFLO). The new components besides the radiation boiler were a candle filter (dry dedusting of PRENFLO raw gas), a fly ash recycle system, a catalytic COS hydrolysis and a raw gas desulfurization system (MDEA process).L%
The operability of the radiation boiler concept was demonstrated, the quench gas input dowstream the radiation boiler was reduced to about 20% (equalizing the exit temperature of raw gas). The mechanical cleaning system ensured smooth operation. Different fuels, hard coal, petroleum coke and brown coal were gasified successfully in the modified PRENFLO plant. Material tests confirmed that high quality materials are to be used for the boiler system. The candle filter worked effective. The fly ash was removed from the gas down to < 1 mg/3n. Alkali and metal traces are retained in the filter dust, mercury, arsenic and chlorine largely remain in the raw gas to be removed downstream. Metal traces such as zinc and lead are concentrated in the filter dust, with fly as recycling.
This concentrating behaviour necessitates the discharge of a limited amount of the fly ash separated from the gas. The COS-hydrolysis resulted in high conversion rates at temperatures of 135 deg. C or above (residual COS was < 10 ppmV even at high concentration of COS in the coal gas, when petroleum coke was gasified). The MDEA scrubbing process achieved high H2S absorption rates (residual content 1 ppmV H2S). The height of the absorption column (residence time) and the CO2 - content in the gas determined the necessary solvent/gas ratio. The selectivity of the MDEA scrub for H2S as against CO2 is high and is influenced by the residence time. There were minimal dust residues in the filter of the MDEA system. Sour gas stripping in the desulfurization column was almost complete.
The partial oxidation of solid fuels according to the entrained-flow principle (PRENFLO process) is an exothermic process, approx. 20% of the gross calorific value of the fuel being converted into sensible heat.
Utilization of this large quantity of heat released is indispensible for the energetically optimum of the PRENFLO process in industrial-scale applications. The raw gas leaves the gasifier at a temperature of approx. 1400 deg. C, highy laden - about 160 g/m3 (24 bar) with small molten or doughy ash particles. The heat utilization concept realized to date at Krupp Koppers comprises the cooling of raw gas at the outlet of the gasifier with quench gas to temperatures of less than 1000 deg. C resulting in higher heat losses at temperatures below 250 deg. C.
The hot gas quenching can be avoided by using the new waste heat utilization system for dust-laden PRENFLO raw gas with high optical density. It is based on a radiation boiler with built-in heat exchange elements, the arrangement of which takes account of the temperature and flow profile of the hot raw gas leaving the reactor. Results from the operation of a 48 t/d PRENFLO plant with regard to slag separation in the gasifier, effectiveness of mechanical dedusting devices, decoupling of radiation boiler from gasifier to take account of the vibrational properties (mechanical cleaning device for heat exchangers), and theoretical investigations on heat exchange for optically dense fluids indicated the possibilities of preventing energy losses by quench gas cooling of raw gas. Optimization of the system with regard to the spacing of the heat exchange elements, the cleaning and the geometry of the system result in lower overall height and anticipate efficiency improvements if the system is applied in a CC-power plant. The dry dedusting of PRENFLO gas allows fly ash recycling to the gasifier, thereby a total slagging of the coal ash and a total carbon conversion can be achieved. A high effective filtering system reduces heat losses with the raw gas, when hot dedusted gas from the filter is recycled as quench gas. A candle filter and a pneumatic fly ash recycle system was planned, built and tested. For the desulfurization of the PRENFLO gas a catalytic COS hydrolysis (conversion of COS to H2S) and a H2S absorber (MDEA process) were installed in the test plant to proof the reliability of these process stages for PRENFLO gas in a wide range of operating conditions and to take account of the gas and solid traces in the gas to be treated. Testing and optimization of the waste heat utilization system and the other new components were carried out in the 48 t/d PRENFLO plant in Fuertsenhausen, Saarland.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
45143 Essen
Germany