(143c) From Lab to Miniplant: Effective Process Development for Deep Desulfurization of Industrial Coke Oven Gas

As a consequence of the energy revolution and the ambition to reduce emissions, known and in chemical engineering established processes are adapted to convert off-gas of steel plants to basic chemicals. An initial and therefore crucial role in this plan is the development of a process that removes organosulfur compounds from coke oven gas. This is necessary to treat this valuable gas, that consists of approx. 60 vol.% hydrogen, 20 vol.% methane, and 6 vol.% carbon monoxide, with catalysts that are highly sensitive to sulfur (Twigg and Spencer 2001).
In accordance with other desulfurization processes (e.g., natural gas) heterogeneous catalysis in a fixed bed is chosen to fulfil this task since it shows the highest conversion rates compared to other processes. Here, an industrial catalyst is analyzed and investigated for its potential to convert organosulfur compounds like COS or CS2 to H2S which can consequently be removed from the gas by a scrubber or a guard-bed (Rhodes et al. 2000):

COS + H₂ â?? H₂S + CO (1)
CS₂ + 2H₂ â?? 2H₂S + C (2)

However, due to multiple additional components in the gas stream (mainly olefins, benzene, and oxygen) the direct transfer from established processes is not trivial and process modifications are required. Therefore, a full process development is necessary from catalyst screening to the crucial step of tests under real conditions to investigate the influence of side reactions.
In this work, the development of a new catalytic process in a fixed bed reactor will be presented. The two-stage development consists of studies on a lab-scale that are conducted as a first step to effectively screen industrial catalysts. The lab reactor has a diameter of 3 cm and is operated with the main components only. The most promising catalyst candidates are subsequently used for tests with a mobile and modular miniplant on the coke plant ArcelorMittal Bottrop GmbH in Germany. The miniplant is operated with industrial coke oven gas in by-pass to the real plant, therefore, the gas stream contains the full range of components with their fluctuations in concentration. The plant was designed to enable a fast testing of catalysts under industrial conditions for proof of concept and to gain information on (exothermic) side reactions. The miniplant reactor has a diameter of 10 cm and can be filled with a maximum of 5 beds with each 10 cm height. The results of both stages in the process development are used for the development of a model that can be used for simulations with Aspen Plus® to design the complete process.
The results of lab- and miniplant tests will be presented and discussed. It was shown in lab experiments and confirmed in a first measurement campaign with industrial gas, that the catalyst is able to remove up to 98% of the organic sulfur in the gas stream. The influence of side components will be considered and resulting challenges for the transfer from lab to miniplant scale will be elucidated.

References
Rhodes, C., Riddel, S. A., West, J., Williams, B., & Hutchings, G. J. (2000). The low-temperature hydrolysis of carbonyl sulfide and carbon disulfide: a review. Catalysis Today, doi: 10.1016/S0920-5861(00)00309-6.
Twigg, M. V., & Spencer, M. S. (2001). Deactivation of supported copper metal catalysts for hydrogenation reactions. Applied Catalysis A: General, doi: 10.1016/S0926-860X(00)00854-1