Flexible methanol rectification method and device capable of producing both MTO-grade and AA-grade methanol

Abstract

The invention discloses a flexible methanol rectification method and device capable of producing both MTO-grade and AA-grade methanol. The raw material crude methanol firstly enters a common stabilizer to remove light components; the crude methanol subjected to light component removal can enter a multi-effect evaporator to be heated and evaporated so as to generate alkali-metal-free methanol vapor, and the alkali-metal-free methanol vapor is condensed to generate the MTO-grade methanol; and the crude methanol subjected to light component removal can also enter a multi-effect rectifier composed of a pressurization tower, an atmospheric tower and a stabilizer to produce the AA-grade methanol by multi-effect rectification. The device is additionally provided with a crude methanol preheater, a first and second tower bottom methanol preheaters, a pressurization tower feed preheater and other units besides the multi-effect evaporator and multi-effect rectifier main body so as to perform repeated preheating, thereby saving the energy consumption. The stabilizer bottom discharging pump can be driven by a variable-frequency motor to satisfy the operation demands for two working conditions for producing the AA-grade methanol and MTO-grade methanol.

Description

technical field [0001] The invention relates to the technical field of methanol preparation, in particular to a flexible methanol rectification method and device that can produce both MTO grade and AA grade methanol by combining multiple effect evaporation and multiple effect rectification. Background technique [0002] In view of the large-scale construction of methanol factories in my country in recent years, it has become a top priority to find downstream markets for methanol products. Under the current conditions, due to the limitation of my country's energy structure with more coal and less oil, the MTO and MTP technologies of producing methanol through coal and then producing olefins through methanol have become a way to break through the inherent constraints of my country's energy structure and open up methanol. Product downstream market. [0003] According to the requirements of the downstream market for methanol products, the specifications of methanol can be divide...

AI Technical Summary

Problems solved by technology

[0006] (1) Although the process of producing MTO-grade methanol by using multi-effect evaporation combined with a stabilization tower is simple and low in energy consumption, it cannot produce AA-grade methanol at all. In this way, there is no way to meet the flexible production demand of adjusting product types according to market demand. Realize the maximization of factory efficiency

[0007] (2) Using refined methanol as the raw material of MTO has a long process flow, and because it is necessary to add lye to remove organic acids in the production of refined methanol, the content of alkali metal in refined methanol will be greatly increased

Ion exchange equipment operates intermittently and requires periodic regeneration, and its ion exchangers have a limited lifetime and are expensive

Therefore, the equipment investment of this process is high, the operation is troublesome, and the energy consumption of producing MTO grade methanol is several times higher than that of the first process

[0008] (3) The disadvantage of setting up two methanol rectification sections in parallel is that the investment is large and the floor area is very large. When producing one specification of methanol, the other set of equipment is completely idle, which artificially leads to a large waste of investment and cannot be used. Generate benefits

Moreover, when switching products, it is necessary to stop one set of devices and start another set of devices. The time required for product switching is long and the operation is complicated.

If the method of hot standby is used to achieve the purpose of rapid switching, the consumption will be huge and the loss outweighs the gain

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