Gas Catalytic Upgrading in a Two-Zone Fluidized Bed Reactor Coupled to a Cogasification Plant

An integrated system has been designed and started up for sewage sludge and coal cogasification + desulfurization + gas reforming in a two-zone fluidized bed reactor (TZFBR). The system is capable of reforming tar compounds to nondetectable levels and improving gasification gas quality in terms of higher H-2 and CO concentrations. The use of a TZFBR enables both the catalytic upgrading of the gasification gas and the regeneration of the catalyst deactivated by coke deposition in a single vessel. Both an increase of 37% of gas LHV and a reduction of tar compounds to nondetectable levels are achieved in the best conditions used, with a 2 vol % of oxygen in the regeneration flow. Dolomite was used in the desulfurization unit at 800 degrees C, allowing the reduction of the H2S content in the produced gas from 1100 ppm to less than 300 ppm, and a tar reduction from 15 g/m(3)(STP) to 0.2 g/m(3)(STP). With this novel integrated system, the catalytic cracking and reforming of a real gasification gas stream produced in the cogasification of sewage sludge and coal has been achieved, operating in a stable mode.