Method for producing dimethyl ether with methanol gas-phase dehydration

Abstract

The invention provides a method for preparing dimethyl ether by methanol vaporphase dehydration, which solves the problem of long technical flow path, high investment and large energy consumption of the prior similar method. Carbinol is gasified to enter in the dehydration reactor (5) to do dehydrating reaction and the dehydrated reaction crude product enters in the dimethyl ether rectifying tower (7). The dimethyl ether product is obtained from the upper or top of the rectifying tower (7). The liquid-phase carbinol is returned to the system from the rectifying tower as raw material to be used and the liquid-phase carbinol in the carbinol storage tank (1) after gasifying in the evaporator (3) exchanges heat with high temperature of the dehydration reactor (5) in the heat exchanger (4) and then enters into the dehydration reactor (5) to having dehydration. The carbinol in the high-temperature crude product after exchanging heat in the heat exchanger (4) enters in the middle part of dimethyl ether rectifying tower (7), and dimethyl ether vapor enters in the tower top condenser (9) from the top or upper of the dimethyl ether rectifying tower. The liquid-phase or gas-phase carbinol is produced from the area above the reaction crude product feed inlet of the dimethyl ether rectifying tower or the tower board of the below area, which is returned in the carbinol storage tank (1) through cooling or condensing as raw material. The waste water is generated from bottom discharge reaction of the dimethyl ether rectifying tower and a slight quantity of non-condensible tail gas is discharged from the top of the condenser (9).

Description

Technical field: [0001] The invention relates to a method for producing dimethyl ether by using methanol as a raw material. Background technique: [0002] Among the process methods for the production of dimethyl ether by methanol gas-phase dehydration, there are many methods in the published documents and patents at home and abroad. The basic processes are similar to each other. A representative example is the Chinese patent application number 95113028.5 dimethyl ether. Production method: After the raw material methanol is vaporized, it enters a multi-stage cold shock reactor equipped with a composite solid acid catalyst for dehydration reaction. The crude product of dehydration reaction contains water, dimethyl ether, unreacted methanol and a small amount of by-produced light components. After the product is cooled and condensed to remove a small amount of non-condensable gas produced by the reaction, the condensate mainly composed of dimethyl ether, methanol, and water enters t...

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Problems solved by technology

[0003] In this method, the high-temperature reaction crude product is cooled and condensed, and the condensed liquid phase enters the dimethyl ether rectification tower after removing the non-condensable gas in the reaction vapor, which not only wastes the heat generated by the reaction; It is used for the large amount of refrigeration required for the cooling and condensation of the crude product, and increases the heat required for the vaporization of the crude product in the dimethyl ether rectification process; secondly, in the recovery of methanol in the rectification column still liquid containing methanol and water and other components In the process, there is a special methanol recovery tower, and methanol is obtained at the top of the methanol recovery tower. Under a certain reflux ratio, the vaporization, cooling, and condensation of methanol need to consume a lot of heat and cooling capacity, and the process is relatively long.

[0004] Since then, some process improvement methods for reducing energy consumption have also been proposed in domestic and foreign published documents and patents, such as the Chinese Patent Publication No. CN 1562927A (2005) proposed in the method for producing dimethyl ether with methanol to be composed of methanol and water The bottom liquid of the rectification tower is returned to the methanol vaporization tower for treatment. Although the methanol recovery tower can be omitted like this, a very simple vaporization tower is changed into a two-meter-high complex vaporization and stripping tower. A large amount of heat has not been fully utilized, so the effect of reducing investment and saving energy is not very obvious

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