(49c) Catalyst Bed Reactor for Online Removal of Coke from Catalyst in Reforming of Coke Oven Gas

Authors: 
Ito, N. - Presenter, Nippon Steel & Sumitomo Metal Corporation

A catalytic reactor that removes byproduct coke powder from the catalyst bed in steam reforming or cracking was developed. This 'reciprocating bed' reactor has a simple composition, with permeable plates for the catalyst retainers, an elevating device which can withstand temperatures up to 800 C, and a device actuator located outside of the heated reactor. The catalyst beds are raised and lowered intermittently by the elevating device. As a result of friction between the side edge of the catalyst beds and the inner wall of the reactor, this up and down movement causes velocity distribution and shear stress in the catalyst bed, and the relative positions among catalysts are renewed in each up and down cycle. Thus, byproduct coke powder, which can fill up the space between catalysts and thereby increase the flow resistance on the working gas through the catalyst bed, is removed during the reciprocating cycle. Because this coke removal mechanism is based on shear stress between catalysts, the required bed elevation speed was less than 10 mm/s. Whereas, conventional coke removal methods require higher speed for catalyst movement with steps such as hammering the reactor wall or shaking the reactor, which can subsequently damage reactor equipment in the high reaction temperature. In the reciprocating cycles in the currently developed method, the filling factor in the catalyst bed varied, with the filling factor increasing during the raising stroke and decreasing during descending stroke. However, the average filling factor remained constant after the first several cycles. This reactor was introduced into a 30 Nm3/h bench scale plant for steam reforming / cracking of coke oven gas (including tar gas) extracted from an ironworks coke oven in order to enrich the reformed gas with hydrogen. The processing was performed successfully for 24 h with a total of 50 online coke removal operations performed by the reciprocating bed reactor.

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