Research On CO₂Separation And Purification Of H₂of The Product Of The Coal Gasification In Supercritical Water

Hydrogen production from coal gasification is that coal and gasifying agent aremade in Chemical reactions into the gaseous products which H2and CO are the maincomponents at a certain temperature and pressure conditions, and through the COconversion and separation, purification treatment we obtain a certain purity of hydrogen.Studies have shown that the separation energy of carbon dioxide in conventional coalgasification is as much as12%of the total energy consumption of gasification, whilethe technology of coal gasification in supercritical water is expected to reduce theenergy consumption of CO2separation significantly relying on the unique gasificationcharacteristics of supercritical water.Firstly, based on the high pressure characteristics of coal gasification insupercritical water and combining with the differences of water solubility at highpressure between hydrogen and carbon dioxide, we build the system that using methodof high pressure water absorbing to dissociate CO2. Secondly, this paper select theexisting vapor-liquid equilibrium model, and choose the appropriate model to calculatemole fraction of the gas phase and liquid phase of component in absorption anddesorption processes. Finally, this paper establish energy analysis model and exergyanalysis model for the system of high-pressure water separating carbon dioxide, to studythe process of carbon dioxide separation which is in the hydrogen production of coalgasification in supercritical water,and to explore the changing rule of energy efficiency,exergy efficiency,and carbon dioxide separation energy in carbon dioxide separationprocess when the pressure or temperature changes with coal completely gasifing andpartial gasifing. Research shows that: with the increasing of pressure, the energy efficiency in the process of carbon dioxide separation is gradually increasing, the exergyefficiency begins to decline after a slow increasing, separation energy consumption ofcarbon dioxide is declining, when the pressure is higher than8MPa,the carbon dioxideenergy consumption of coal gasification in supercritical water is lower than that ofconventional coal gasification process. With the increase of temperature, the energyefficiency decreased, exergy efficiency increased and the energy consumption of carbondioxide separation increased rapidly.Through the study of the carbon dioxide separation process, we obtain the optimalpressure and optimal temperature of separation carbon dioxide in coal gasificationproduction of supercritical water and provide the basis for the design of separator in thenew technology of the coal gasification supercritical water hydrogen.