4 - Methanol-To-Olefin Process

Abstract

The case study deals with the conceptual design and simulation of an energy-efficient and cost-effective methanol-to-olefin (MTO) process. The innovative solution consists in full recovery of the energy generated by reaction. The reactor effluent enthalpy can cover feed preheating, evaporation, and superheating in a sequence of three feed-effluent heat exchanger units. Mechanical vapor compression is employed for upgrading the temperature/enthalpy profile of the condensing water/hydrocarbon mixture. This method recovers a considerable amount of energy, otherwise lost by water quenching. Saved energy may pay back the compressor cost in about 1year. The energy released in reactor is used in a combined heat and power cycle. The power is sufficient for driving the compressors, while the low-pressure steam is valorized by an ammonia absorption refrigeration plant. The olefin separation and purification takes place in a compact scheme of five columns, which is integrated with the reaction and preliminary separation sections from energy saving viewpoint. The ethylene/propylene splitter is designed for high recovery and flexible operation. Heat pump is implemented at propylene purification. Rigorous sizing is performed for the key units. Operation and capital costs are minimized because the process may fully cover the power and heat needs and employ a minimum number of units.