Kleinekorte Johanna, Leitl Matthias, Zibunas Christian, Bardow André
Institute for Technical Thermodynamics, RWTH Aachen University, Schinkelstraße 8, 52062Aachen, Germany.
Energy and Process Systems Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Tannenstrasse 3, 8092Zurich, Switzerland.
Environ Sci Technol. 2022 Sep 20;56(18):13294-13304. doi: 10.1021/acs.est.2c02888. Epub 2022 Aug 29.
Both the global steel and chemical industries contribute largely to industrial greenhouse gas (GHG) emissions. For both industries, GHG emissions are strongly related to the consumption of fossil resources. While the chemical industry often releases GHGs as direct process emissions, steel mills globally produce 1.78 Gt of off-gases each year, which are currently combusted for subsequent heat and electricity generation. However, these steel mill off-gases consist of high value compounds, which also can be utilized as feedstock for chemical production and thereby reduce fossil resource consumption and thus GHG emissions. In the present work, we determine climate-optimal utilization pathways for steel mill off-gases. We combine a nonlinear, disjunctive model of the steel mill off-gas separation system with a large-scale linear model of the chemical industry to perform environmental optimization. The results show that the climate-optimal utilization of steel mill off-gases depends on electricity's carbon footprint: For the current electricity grid mix, methane, hydrogen, and synthesis gas are recovered as feedstocks for conventional chemical production and enable a methanol-based chemical industry. For low electricity footprints in the future, the separation of steel mill off-gases supports CO-based production processes in the chemical industry, supplying up to 30% of the required CO. By coupling the global steel and chemical industry, industrial GHG emissions can be reduced by up to 79 Mt CO-equivalents per year. These reductions provide up to 4.5% additional GHG savings compared to a stand-alone optimization of the two industries, showing a limited potential for this industrial symbiosis.
全球钢铁行业和化工行业都在很大程度上导致了工业温室气体（GHG）排放。对于这两个行业来说，温室气体排放都与化石资源的消耗密切相关。化工行业通常将温室气体作为直接的工艺排放物释放出来，而全球的钢铁厂每年会产生1.78亿吨废气，目前这些废气被燃烧以用于后续的供热和发电。然而，这些钢铁厂废气中含有高价值化合物，这些化合物也可以用作化工生产的原料，从而减少化石资源的消耗，进而减少温室气体排放。在本研究中，我们确定了钢铁厂废气的气候最优利用途径。我们将钢铁厂废气分离系统的非线性析取模型与化工行业的大规模线性模型相结合，以进行环境优化。结果表明，钢铁厂废气的气候最优利用取决于电力的碳足迹：对于当前的电网组合，甲烷、氢气和合成气被回收用作传统化工生产的原料，从而形成一个以甲醇为基础的化工行业。对于未来低电力碳足迹的情况，钢铁厂废气的分离支持化工行业基于一氧化碳的生产过程，可提供高达30%所需的一氧化碳。通过将全球钢铁行业和化工行业结合起来，每年可减少高达7900万吨二氧化碳当量的工业温室气体排放。与这两个行业单独优化相比，这些减排量可额外节省高达4.5%的温室气体，这表明这种产业共生的潜力有限。
