Abstract: Based on a typical gas composition from a methanol-to-propylene (MTP) reactor, and guided by a requirement to recover both propylene and ethylene, three separation strategies are studied and simulated by using PROⅡ package. These strategies are sequential separation, front-end dethanization, and front-end depropanization. The process does not involve an ethylene refrigeration system, using the separated stream as absorbent, and absorbing further the medium-pressure demethanization, and a proprietary technology by combining intercooling oil absorption and throttle expansion. Influences of different process streams as absorbent are studied on energy consumptions, propylene and ethylene recovery percentages, and other key-performance indicators of the separation strategies. Based on a commercial MTP plant with a methanol capacity of 1700 kt·a^-1, the simulated results show that the front-end dethanization using the C₄ mixture as absorbent is the optimal separation strategy, in which the standard fuel oil consumption (a key-performance indicator of energy consumption) is 18.97 kt·h^-1, the total power consumption of two compressors is 22.4 MW, the propylene recovery percentage is 99.70%, and the ethylene recovery percentage is 99.70%. For a further improvement, the pre-dethanization and thermal coupling methods are applied. By using front-end pre-dethanization (partial cutting) with debutanizeroverhead, i.e. the C4 mixture, as absorbent, the power consumption of the compressors decreases to 19.9 MW, an 11% reduction compared with the clear-cutting method. The energy consumption for the dual compressors for crude gaseous product mixture and main product propylene refrigeration is 16.69 MW, 16.55% lower than that of the present MTP industrial plant with the same scale, and a total energy consumption of 20 MW for the triple compressors including product gas mixture compression, and ethylene and propylene refrigeration.

Key words: Heat integration distillation, Methanol to propylene, Ethylene, Propylene

摘要： Based on a typical gas composition from a methanol-to-propylene (MTP) reactor, and guided by a requirement to recover both propylene and ethylene, three separation strategies are studied and simulated by using PROⅡ package. These strategies are sequential separation, front-end dethanization, and front-end depropanization. The process does not involve an ethylene refrigeration system, using the separated stream as absorbent, and absorbing further the medium-pressure demethanization, and a proprietary technology by combining intercooling oil absorption and throttle expansion. Influences of different process streams as absorbent are studied on energy consumptions, propylene and ethylene recovery percentages, and other key-performance indicators of the separation strategies. Based on a commercial MTP plant with a methanol capacity of 1700 kt·a^-1, the simulated results show that the front-end dethanization using the C₄ mixture as absorbent is the optimal separation strategy, in which the standard fuel oil consumption (a key-performance indicator of energy consumption) is 18.97 kt·h^-1, the total power consumption of two compressors is 22.4 MW, the propylene recovery percentage is 99.70%, and the ethylene recovery percentage is 99.70%. For a further improvement, the pre-dethanization and thermal coupling methods are applied. By using front-end pre-dethanization (partial cutting) with debutanizeroverhead, i.e. the C4 mixture, as absorbent, the power consumption of the compressors decreases to 19.9 MW, an 11% reduction compared with the clear-cutting method. The energy consumption for the dual compressors for crude gaseous product mixture and main product propylene refrigeration is 16.69 MW, 16.55% lower than that of the present MTP industrial plant with the same scale, and a total energy consumption of 20 MW for the triple compressors including product gas mixture compression, and ethylene and propylene refrigeration.

关键词: Heat integration distillation, Methanol to propylene, Ethylene, Propylene