Valorizing Steelworks Gases by Coupling Novel Methane and Methanol Synthesis Reactors with an Economic Hybrid Model Predictive Controller

Abstract

To achieve the greenhouse gas reduction targets formulated in the European Green Deal, energy- and resource-intensive industries such as the steel industry will have to adapt or convert their production. In the long term, new technologies are promising. However, carbon capture storage and utilization solutions could be considered as short-term retrofitting solutions for existing steelworks. In this context, this paper presents a first experimental demonstration of an approach to the utilization of process off-gases generated in a steelworks by producing methane and methanol in hydrogen-intensified syntheses. Specifically, the integration of two methane synthesis reactors and one methanol synthesis reactor into a steel plant is experimentally simulated. An innovative monitoring and control tool, namely, a dispatch controller, simulates the process off-gas production using a digital twin of the steel plant and optimizes its distribution to existing and new consumers. The operating states/modes of the three reactors resulting from the optimization problem to be solved by the dispatch controller are distributed in real time via an online OPC UA connection to the corresponding experimental plants or their operators and applied there in a decentralized manner. The live coupling test showed that operating values for the different systems can be distributed in parallel from the dispatch controller to the test rigs via the established communication structure without loss. The calculation of a suitable control strategy is performed with a time resolution of one minute, taking into account the three reactors and the relevant steelworks components. Two of each of the methane/methanol synthesis reactors were operated error-free at one time for 10 and 7 h, respectively, with datasets provided by the dispatch controller. All three reactor systems were able to react quickly and stably to dynamic changes in the load or feed gas composition. Consistently high conversions and yields were achieved with low by-product formation.

Hydrogen intensified synthesis processes to valorise process off-gases in integrated steelworks

“…Online tests proved that the DC is suitable to obtain sufficiently smooth control strategies in real time with a temporal resolution of 1 minute and a forecasting horizon of 2 hours. Safe and flexible operations and high conversion rates were obtained during the dispatchcontrolled operations of all the three i 3 upgrade reactors [38]. In particular, for REAC1, full methane yield was obtained after a two-stage methanation with intermediate water separation; for REAC2, high CO x conversion rates of over 99% on average were reached; for REAC3, CO and CO 2 conversions were over 99% and between 70-78% respectively.…”

Pathways towards full use of hydrogen as reductant and fuel

“…Use of BFG in such downstream processes could replace externally supplied natural gas. Moreover, there are interesting options for chemical valorisation of BFG, for example by synthesising into byproducts like methane and methanol [7][8][9][10]. The steel mill could be seen in a larger context, guided by symbiosis structures involving additional value-streams and providing an overall positive result on decarbonisation.…”

Application-based catalytic methanation of steelworks gases under dynamic operating conditions

“…Gas composition of synthetic steelworks gases per gas type. For the design of the experiments listed in section #C the theoretical studies of Dettori et al (2021), Matino et al (2019) and Hauser et al (2022) were used as input, who modelled a steel plant using deep learning and neuronal network-based approaches, with the target to forecast the off-gas production and consumption in a basic oxygen furnace. The authors provide a simulated dataset for volume flow of BOFG as well as hydrogen in surplus (σ H2 = 1.04).…”