| Dimethylether (DME) is widely used as raw materials with many excellent physical and chemical properties for manufacturing of pharmacy, dye, pesticide etc. It is also a ideal substitute for trichlorofluoromethane as refrigerant or spraying solvent. Recently DME as a new clean fuel, its production capacity has been expanding rapidly with a very promising world market evaluation.This paper makes a fundamental feasibility investigation and engineering study to the suggested project of 100kt/a DME for LuTianhua Group Co., combining with the implemented strategy of downstream products development for the chemical productions based on natural gas processing in the compony. This will be the first DME project with such a large scale in the world. There is no example to follow and most all the "know how" skills keep secret strictly. The author carries out a sound analysis to the problems existing in the 10kt/a DME pilot experimental systems, in which the author accumulated valuable experiences through the design and trial running. The serious disfigurement of energy balance is found in the synthesis loop of the Two-step Methanol Dehydration Process which was imported from TEC Co. of Japan. Through careful analysis and calculation, the following conclusions are obtained:1. The main reason for the energy balance problem existing in TEC technique is the deficiency of heat exchange capability of the heater for methanol pre-heating in the synthesis loop. As a result the temperature of product gas is too high (142 ) at the output end.2. Consequently, the deficiency of process energy lets to a problem. The auxiliary heat exchanger in the synthesis loop designed for system starting operation could not exit under the normal production conditions. This problem would affect the operation very seriously if it is scaled up to the large scale of 100kt/a. Furthermore, the condition of energy deficiency will spread to the distillation loop and cause much more adverse affects to the system,3. The energy balance for the synthetic loop and rational utilization of heat energy in the whole system are very important in affecting the technological and economical performances of DME process process. A optimal analysis must be done to the process layout and equipment design. This would be the key factor for the product to take over the huge market of DME with a competitive advantage of lower price.Based on the the above analyses, the author proposed an optimal design for the 100kt/a DME plant with Two-step Methanol Dehydration Process, using the software ECSS, a detailed material balance is made to the whole system. The process design is completed for the key equipment of heat exchanger for the process streams of inlet and outlet, DME rectifying tower and methanol distillation tower. The characteristic advantages of this design are summarized as follows: full utilization of heat energy within the system, compact and clear flow sheet, moderate process condition and flexibility and facility for operation. And the number of equipment is less than the original technique of TEC Co.. The design makes it possible for all the equipment to be manufactured domestically so the project investment can be greatly reduced.According to the current infrastructure policy and the market price, it is estimated that the total project investment is 138.8 million RMY. The inner yield before income tax is 13.82%, which is higher the basic requirement of yield 12%.The analysis of profit and loss and other benefit index indicate that the risk sustaining ability of this project is very strong.It is proven by this work that the project of 100kt/a DME for LuTianhua Group Co. is in accordance with the country' s current industrial policy and the direction of development of energy market. There is an optimistic prediction of market. The process design is rational and the technique is reliable. The estimation of investment and evaluation of finance indicate the economic profit. All the evidence obtained by this investigation show a positiv... |
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