H2 and CO purification by CO2 removal from syngas coupling membrane module and water-absorption unit: An economic analysis

Hydrogen represents today a necessary alternative to fossil fuels to limit the greenhouse gas effect due to the CO2 emissions. In this work, a plant configuration able to get pure H2 and concentrated CO (about 94%) from a syngas mixture is proposed and simulated by coupling a selective membrane unit and a water absorption column. In addition, an economic assessment on the simulated plant is carried out to estimate the feasibility of this process in terms of economic potential, studying its dependence on several parameters, such as raw material price, membrane cost, membrane feed pressure, column temperature and feed flow rate. Separation performance is improved by the higher feed membrane pressure (greater H2 recovery and CO purity), whereas the increment of the column temperature especially affects the CO recovery. Hence, the economic potential presents a maximum with pressure and temperature (e.g., about 246ꞏ103 $/y at 40 bar of feed membrane pressure and about 282ꞏ103 $/y at 50 °C of column temperature), due to the balance between the higher compression/solvent cost and the increment of H2 or CO recovery. In addition, the simulated plant shows a positive economic potential in a wide range of syngas price (e.g., from 0.126 to 0.25 $/Nm3), being also not affected significantly by the cost of the palladium-based membrane module. A bigger plant size (i.e., feed flow rate from 10 to 100 kmol/h) can lead to a twelve times greater economic potential (from about 242ꞏ103 to about 2954ꞏ103 $/y at 30 bar), reducing the H2 purification cost and making the net present value positive.