A comparison was made of two simulated carbon capture technologies—calcium looping and membrane separation—used in the steelmaking process in Thailand with and without a coke production unit, including a techno-economic assessment. The study was based on a steel plant producing about 1.2 t of liquid steel per hour at >99% purity by weight. The proposed model used common raw materials and operations widely applied in Thailand. The results showed that the steel plant with a coke production unit was more profitable if the coke price exceeded THB 7.93/kg. Additional membrane separation technology with a coke production unit had a higher level of carbon capture purity (92.04% by weight) with the highest profitability (12.83%ROI, a payback period of 7.37 years, and 11.33%DCFRR).