High Temperature Winkler Gasification of Rhenish Lignite in an Optimized 500 kW _th Pilot Plant

Abstract

The volatile renewable energy generation leads to large fluctuations in the electric grid. Polygeneration is one possibility to stabilize the grid. Furthermore, compared to existing power plants the utilization of parts of the plant is increased and the profitability improves. At Technical University of Darmstadt, a polygeneration concept from the fuel to the product was investigated. The process consists of a 0.5 MW_th fluidized bed gasifier, a gas cleaning unit and a catalyst test rig. This paper presents experimental results from the stand-alone operation of the gasifier in order to investigate the behavior of the gasification of two feedstocks, a dried lignite steam coal and a commercially available low sulfur, low ash lignite. Furthermore, the results of the gasification of the gasifier start-up material hearth furnace coke are given. The reactor with a height of 11 m and an inner diameter of 400 mm was operated at up to 870 °C. Carbon dioxide, steam and oxygen can be introduced into the reactor through different nozzle levels.
Four test campaigns were conducted and seven balance points with different feedstock and loads were investigated. The results show carbon conversions of almost 96% and cold gas efficiencies up to 65% with WTA coal showing the highest cold gas efficiencies and carbon conversions. Several trace gases were measured by FTIR and a positive correlation between benzene and methane concentration is detected.
The experience gained serves as a basis for the gasification step in the polygeneration process and for gasification of other feedstock, especially biogenic and anthropogenic residues.

Keywords: Gasification, HTW, pilot plant, experimental data, polygeneration