2250-h long term operation of a water gas shift pilot plant processing tar-rich product gas from an industrial scale dual fluidized bed biomass steam gasification plant

In this paper, the performance of a water gas shift (WGS) pilot plant which processed tar-rich product gas for about 2250 h is investigated. The WGS pilot plant employed a commercial Fe/Cr based catalyst (ShiftMax® 120). The product gas was generated by the industrial scale and commercial dual fluidized bed (DFB) biomass steam gasification plant in Oberwart, Austria. A partial flow of tar-rich product gas was extracted for the WGS pilot plant before the tar scrubber of the gasification plant. The extracted product gas had a temperature of about 150 °C and a GCMS tar content between 2.7 and 8.2 g m−3 (d.b.). In order to investigate the stability of the catalyst and to observe the performance of the WGS pilot plant, extensive chemical analyses were carried out: CO, CO2, CH4, N2, O2, C2H6, C2H4, C2H2, H2S, COS, and C4H4S were measured. In addition, GCMS tar and NH3 analyses were performed. Furthermore, the catalyst's activity was observed by measuring the temperature profiles along the reactors of the three stage WGS pilot plant. During the about 2250 h of operation, no significant catalyst deactivation could be observed. A CO conversion of up to 92% as well as a GCMS tar reduction along the WGS pilot plant was obtained. The results showed that the application of a commercial Fe/Cr based catalyst in a WGS unit seems to be a suitable way for increasing the hydrogen content in a product gas generated by dual fluidized bed biomass steam gasification. Furthermore, with such a technique, it is possible to optimally adjust the required CO/H2 ratio for several synthesis reactions, for example, methanation and Fischer-Tropsch synthesis.