Highly flexible and energy-efficient process for converting coke-oven gas and pulverized coke into methanol and ammonia using chemical looping technology

Abstract

The efficient conversion of coke-oven gas (COG), an abundant by-product in steel production, into added-value chemicals such as methanol is a highly desired technological process. The state-of-the-art processes for the synthesis of methanol from COG possess several limitations such as poor utilization of hydrogen, low yields, and high energy consumption, leading to high production cost. The main technical issues are poor carbon supply and the need for energy intensification of the process. In this paper, we propose a new, more efficient method for the conversion of COG and pulverized coke (PC) into methanol and ammonia using chemical looping of hydrogen generation (CLHG), (PCCLHG-CGTMA). The PCCLHG-derived H2 and N2 are utilized for ammonia production. The new process has high adjustability in the production of methanol and ammonia. In order to obtain the best performance of carbon and hydrogen elements utilization efficiency, exergy and energy efficiency, several operational parameters and conditions have been optimized. Compared with different technologies for the conversion of COG to methanol or ammonia, the new system acclaims an excellent hydrogen element utilization efficiency of 88.8% and a high exergy efficiency of 78.7%. And the relative CO2 reduction ratio of this new system is 0.67. Considering the current market value and demands, 0.576 Mt/y COG and 0.175 Mt/y PC could be utilized in this process for the production of 0.44–0.86 Mt/y methanol and 0–0.36 Mt/y of ammonia. The present method offers exergy efficiency of 60.7–78.7% and energy efficiency of 54.4–70.1%. This study is a pioneering work in the utilization of all carbon resources during the coking process, which improves energy efficiency and reduces carbon emission and might represent a significant upgrade of coking industry.