Energy-saving And Optimization Design Of The Methane Wash Process

Making full use of the CO in coal gasification to develop C1chemical industry can help reduce the carbon emissions into the atmosphere, which is environmentally friendly and meets the new idea of low carbon. C1chemical industry with CO as the source can synthesize a series of important chemical raw materials, which are traditionally acquired from the petroleum. And some carbon-containing compounds can elongate the carbon chain by oxo synthesis reactions which are significant in the synthesis of important chemical products. With the invention of new catalysts and further maturity of the oxonation technology, there lies a promising and broad prospect for the C1chemical industry in the future, which means the preparation of high purity CO is becoming increasingly important.Coal gasification is an important source of CO. And the syngas, which is the product of the coal gasification, mainly contains H2, CO, CO2, CH4, H2S, etc. Before the syngas separation process, the so-called acid gas, such as CO2, H2S, COS must be removed, and the RECTISOL is a widely used method and outstands itself in large petrochemical plants. There are several cryogenic separation methods to separate CO from syngas, such as the partial condensation method, cryogenic distillation method, and methane-wash method. The methane wash process is more efficient if the syngas contains methane. The methane wash is a cryogenic process, so it needs a refrigeration cycle which takes vast energy consumption, as well as a reasonable design based on the parameters of the related devices and the process requirements.Based on the property of the feed gas, this paper selected an appropriate property method and preliminarily calculated the parameter of each separate unit. Upon the completion of the separation task, the separation process is analyzed and improved for the reduction of the separation load and the decrease of the entropy increase caused by the separation process. On the target of saving energy and reducing the operation cost, the usage of the cooling capacity should be minimized upon completion of the separation. Cooling capacity should be recycled from the stream that can be recovered in order to improve the utilization and reduce the loss of cold exergy. The change of the design results in more operating conditions which have interactive influence on each other, and makes the optimal operating conditions hard to reach. Method of exhaustion is used to find the best processing parameter.With the soaring rise in energy prices, the large energy consumption of the refrigeration cycle should be considered. So it needs a reasonable design based on the parameters of the related devices and the process. The factors such as character of refrigeration cycle, the demand for process cooling capacity, the price of different grades of cold, the influence of different temperature difference on the cost of equipment and operation should be well matched to reduce the cost of the refrigeration cycle. In this way, the cost of the refrigeration is minimized, and operating cost of the plant can be lower.