CN102225889B - Method for preparing dimethyl ether by dehydration of methanol - Google Patents

Abstract

The invention discloses a method for preparing dimethyl ether by dehydration of methanol, belonging to the field of chemicals. The process flow for the method comprises the following steps that: (1) extraneous methanol is sent to a methanol buffer tank to mix with the methanol from the top of a methanol rectifying tower into the raw material methanol; (2) the raw material methanol enters into a methanol vaporization tank for vaporization after preheated in methanol preheaters; (3) vaporized methanol steam enters into a reactor after a thermal reaction, reaction gas after the reaction undergoes heat exchange in a charging discharging heat exchanger, a methanol heat exchanger, a methanol tower gas reboiler, and a dimethyl ether tower charging cooler sequentially and enters into a dimethyl ether tower charging stock tank for condensation into a gas phase and a liquid phase, and the gas phase and the liquid phase respectively enter into a dimethyl ether rectifying tower; (4) steam in the dimethyl ether rectifying tower enters into a dimethyl ether tower condenser from the top of the tower for condensation and flows back to the rectifying tower, dimethyl ether products are produced in side strippers through a dimethyl ether product storage tank, and waste water in the bottom of the rectifying tower is discharged after having changed heat with the raw material methanol in one methanol preheater. The beneficial effects of the invention are as follows: the process flow and the construction of the reactor used in the invention are simple and recovery of the heat of the reaction gas is more effective, enabling upsizing of equipment.

Description

A kind of method of producing dimethyl ether by methanol dehydration

technical field

The invention relates to the technical field of chemical reaction equipment, in particular to a method for preparing dimethyl ether by dehydrating methanol.

Background technique

At present, there are two methods for producing dimethyl ether from methanol dehydration: liquid-phase method and gas-phase method. Distillation process. The production of dimethyl ether from methanol gas phase dehydration is the most mature and widely used production method of dimethyl ether in industry.

Chinese patent document (patent application number 201010287747.1) discloses "a method for producing dimethyl ether from methanol", which is characterized in that: methanol first enters the vaporization and separation tower, removes high boiling point substances and impurities, reacts in a reactor, and dehydrates The product enters the packed rectification column for rectification to obtain dimethyl ether products with different purity.

Chinese patent document (CN 1293029C) discloses "a method for producing dimethyl ether with methanol", which is characterized in that: a vaporization stripping column with a unique process and structure is combined with a dimethyl ether rectification column, and no separation is used. A methanol recovery tower for purifying and recovering the methanol in the mixed liquor of the dimethyl ether rectification tower. However, their disadvantages are that there is room for further improvement in terms of energy saving and environmental protection.

Contents of the invention

The object of the present invention is to provide a more energy-saving and environment-friendly method for preparing dimethyl ether by methanol dehydration on the basis of the prior art.

The gas-phase dehydration of methanol to produce DME must go through the process of raw material heating-reaction-cooling-separation, and the most important technology is how to realize the optimal utilization of heat in the heating and cooling process. On the basis of fully considering the reaction characteristics of methanol dehydration to dimethyl ether, the present invention adopts a three-stage adiabatic inter-stage chilled shock reactor, so that the inlet reaction temperature can be lower, and the temperature of the reaction product is controlled to reach Leave the reactor after reaching the optimum reaction temperature. The reactor with the above structure reduces the temperature of the inlet material and increases the temperature of the outlet material, so that the reaction material can reach the reaction temperature only through heat exchange without steam heating, and also reduces the cooling water consumption of the outlet material, which can greatly save energy. and resources.

For realizing above-mentioned object, the technical scheme that the present invention takes is:

A method for producing dimethyl ether by methanol dehydration, characterized in that its technological process comprises:

(1) The raw material methanol from the outside world (methanol tank farm) is sent to the methanol buffer tank and mixed with methanol from the top of the methanol rectification tower to form methanol raw material;

(2) Methanol raw materials are preheated by No. 1 methanol preheater, No. 2 methanol preheater and No. 3 methanol preheater, and then enter the methanol vaporization tank for vaporization;

(3) The vaporized methanol vapor passes through the feed and discharge heat exchanger for superheating reaction to a temperature of 240-250°C, and enters the reactor from the top of the reactor; Excited heat exchange; the temperature of the reaction gas coming out of the reactor is about 365-370°C, which is exchanged through the feed and discharge heat exchanger, No. 3 methanol heat exchanger, methanol tower gas reboiler, and dimethyl ether tower feed cooler. After heating, the temperature is 120-125°C and enters the feed tank of the dimethyl ether tower; the reaction gas is condensed in the feed tank of the dimethyl ether tower into two phases of vapor and liquid, which are respectively passed into the dimethyl ether rectification tower;

(4) The steam at the top of the dimethyl ether distillation tower enters the condenser of No. 1 dimethyl ether tower to condense and then flows back to the rectification tower. After passing the test, the dimethyl ether product is extracted from the side line through the dimethyl ether product storage tank; The waste water in the tower kettle is output after heat exchange with methanol raw material by No. 1 methanol preheater.

The reactor described in step (3) adopts a three-stage adiabatic inter-stage chilled reactor, and its inlet reaction temperature is relatively low, but through the heat exchange between the two stages, the temperature of the reaction product can be controlled to reach the optimum reaction temperature before leaving the reaction device.

Part of the light components extracted from the top of the condenser of the dimethyl ether tower enters the alcohol washing tower above the methanol buffer tank after being cooled by the condenser, and the dimethyl ether therein is recovered from part of the fresh methanol, and the gas is discharged at the top of the tower.

The still liquid in the tower tank of the dimethyl ether rectification tower enters the methanol rectification tower, and the methanol vapor at the top of the tower is condensed by the condenser of the No. 2 dimethyl ether tower and then refluxed to the rectification tower. Methanol returns to the methanol buffer tank to mix with the methanol raw material from the outside.

The process flow of the present invention includes the following systems: ① three-stage adiabatic intermittent chilling reactor for methanol dehydration to dimethyl ether, ② methanol preheating and vaporization system, ③ dimethyl ether rectification system, ④ methanol recovery system .

The difference between the present invention and its closest comparative technology "a method for producing dimethyl ether from methanol" (Chinese patent, application number 201010287747.1 ) is:

(1) The comparative technology does not specify what type of reactor is used

The present invention adopts a three-stage adiabatic interrupted shock reactor, so that the inlet reaction temperature can be lower, and through the heat exchange between the two stages, the temperature of the reaction product is controlled to reach the optimum reaction temperature and then leaves the reactor. The reactor reduces the temperature of the inlet material and increases the temperature of the outlet material, so that the reaction material can reach the reaction temperature only through heat exchange without steam heating, and also reduces the cooling water consumption of the outlet material, which greatly saves energy and resources.

(2) The process of the comparative technology is: raw material preheating-flash tank-methanol vaporization tower-methanol dehydration reactor-dimethyl ether rectification tower-scrubbing tower; Methanol vaporization tower treatment, the methanol vaporization tower has two functions of separating the liquid methanol in the rectification tower and preheating the raw material of methanol);

The flow process of the present invention is: raw material preheating—flash tank—methanol dehydration reactor—methanol rectification tower, which is obviously more refined in the flow process; (methanol vaporization tower and dimethyl ether rectification tower are not set in the process flow The still liquid is processed by the methanol rectification tower, and the liquid phase methanol is obtained from the top of the tower and mixed with fresh methanol raw materials for recycling);

From a process point of view, the comparative technology not only has a long process and more equipment (one more scrubber and three heat exchangers) but also increases the energy consumption of the equipment (the flash tank needs steam heating), especially the methanol vaporization tower, due to the change The single methanol separation function greatly increases the energy consumption.

(3) The reaction gas from the reactor of the comparative technology passes through the gas heat exchanger, vaporization tower reboiler 1, rectification tower reboiler 1, methanol preheater 2, methyl ether cooler, and then enters the second Methyl ether distillation column;

In the present invention, the reaction gas coming out of the reactor passes through the feed and discharge heat exchanger, the No. 3 methanol heat exchanger, the methanol tower gas reboiler, the dimethyl ether tower feed cooler, and then enters the dimethyl ether tower after heat exchange. Feed tank, the reaction gas is condensed into vapor-liquid two phases in the feed tank of the dimethyl ether tower and passed into the dimethyl ether rectification tower respectively;

There is an obvious difference between the two: the present invention adopts a three-stage adiabatic intermittent chilling reactor, so that the inlet reaction temperature is 10-20°C lower than that of the comparison technology, and the temperature of the reaction product is controlled to reach the optimum through heat exchange between the two stages After leaving the reactor after the reaction temperature, the temperature of the outlet material is increased by 10-15 °C compared with the comparison technology;

In the present invention, the raw materials do not need to be heated by steam before entering the reactor, while the raw materials in the comparative technology need to be heated by the steam of the flash tank to reach the reaction temperature.

(4) The dimethyl ether product of the comparative technology is discharged from the top of the rectification tower; the dimethyl ether product of the present invention is discharged from the side line of the rectification tower; the difference between the two in terms of equipment is that the side line discharge is in the second block of the tower board, less non-condensable gas components in dimethyl ether products.

(5) The bottom liquid of the dimethyl ether tower and the liquid phase of the flash tank of the comparative technology are sent to the methanol vaporization tower for treatment, and the methanol vapor obtained from the top of the methanol vaporization tower is mixed with the vapor phase separated from the flash tank and then passed through the gas heat exchanger and reacted The gas is heat-exchanged to the reaction temperature and enters the methanol dehydration reactor for reaction. The present invention separates the dimethyl ether rectification tower still liquid from the methanol rectification tower, and the liquid phase methanol obtained at the top of the tower returns to the methanol buffer tank and mixes with the raw material methanol;

In the comparative technology, the dimethyl ether tower liquid and the flash tank liquid entering the methanol vaporization tower do not undergo vapor-liquid separation, which increases the burden on the methanol vaporization tower.

(6) In the comparative technology, E5 enters the dimethyl ether rectification tower without the separation of vapor and liquid. The present invention separates vapor and liquid through the vapor-liquid separator 103 and enters different trays for separation, thereby greatly saving energy consumption .

(7) The scrubbing tower is installed in the comparative technology, indicating that the discharge from the top of the dimethyl ether distillation tower contains non-condensable components. Since only heat exchangers are used to condense, the gas phase contains dimethyl ether products, which need to be increased A washing tower recycles the dimethyl ether product, which not only increases equipment investment, but also increases the burden on the flash tank. The side line discharge of the dimethyl ether product of the present invention does not have the above-mentioned problems.

Description of drawings

Accompanying drawing is a process flow diagram of a method for producing dimethyl ether by methanol dehydration in the present invention.

Detailed ways

A specific embodiment of a method for producing dimethyl ether by methanol dehydration is given below in conjunction with the accompanying drawings, but it should be pointed out that the implementation of the present invention is not limited to the following embodiments.

A method for producing dimethyl ether by dehydration of methanol, its technological process is:

(1) Send the raw material methanol from the outside (methanol tank farm) into the methanol buffer tank (101) and mix it with the methanol from the top of the methanol rectification tower (302) to form methanol raw material;

(2) Methanol raw material is preheated by No. 1 methanol preheater (209), No. 2 methanol preheater (210) and No. 3 methanol preheater (201), and then enters the methanol vaporization tank (102) for vaporization;

(3) The vaporized methanol vapor passes through the feed and discharge heat exchanger for superheating reaction to a temperature of 250-260°C, and enters the reactor (401) from the top of the reactor; the methanol vaporization tank ( 102) for a stream of raw material gas for cooling and shock heat exchange; the reaction gas with a temperature of 320-360 °C coming out of the reactor (401) passes through the feed and discharge heat exchanger, No. 3 methanol heat exchanger (201), methanol The tower gas reboiler (207), the DME tower feed cooler (203) enter the DME tower feed tank (103) after heat exchange; the reaction gas is condensed in the DME tower feed tank (103) The two phases of vapor and liquid are respectively passed into the dimethyl ether rectification tower (301);

(3) The vaporized methanol vapor passes through the feed and discharge heat exchanger for superheating reaction to a temperature of 240-250°C, and enters the reactor (401) from the top of the reactor; it is passed into the methanol vaporization tank between the sections of the reactor (401) (102) a stream of raw material gas is subjected to cooling and shock heat exchange; the reaction gas with a temperature of 365-370 ° C from the reactor (401) passes through the feed and discharge heat exchanger, No. 3 methanol heat exchanger (201), The methanol column gas reboiler (207) and the DME column feed cooler (203) enter the DME column feed tank (103) at a temperature of 120-125°C after heat exchange; the reaction gas enters the DME column feed tank (103); Condensation in the material tank (103) into a vapor-liquid two-phase is respectively passed into the dimethyl ether rectification tower (301);

(4) The steam at the top of the dimethyl ether distillation tower (301) enters the No. 1 dimethyl ether tower condenser (104) to condense and then flows back to the rectification tower (203). After passing the test, the dimethyl ether product passes through the side line The storage tank (106) extracts the dimethyl ether product; the waste water in the tower kettle is output after heat exchange with methanol raw material by No. 1 methanol preheater.

In addition, part of the light components extracted from the top of the dimethyl ether tower condenser (104) is cooled by the condenser and then enters the alcohol washing tower above the methanol buffer tank (101), and the dimethyl ether in it is recovered from part of the fresh methanol, and the gas discharge at the top of the tower.

The still liquid from the bottom of the dimethyl ether rectification tower (301) enters the methanol rectification tower (302), and the methanol vapor at the top of the tower is condensed by the No. 2 dimethyl ether tower condenser (105) and then refluxed to the rectification tower ( 203 ), the partially produced methanol is returned to the methanol buffer tank (101) and mixed with the methanol raw material from the outside after passing the test.

Claims (1)

1. a method for producing dimethyl ether by methanol dehydration, is characterized in that, its technological process comprises: (1) The raw material methanol from the outside is sent to the methanol buffer tank and mixed with methanol from the top of the methanol rectification tower to form methanol raw material; (2) Methanol raw materials are preheated by No. 1 methanol preheater, No. 2 methanol preheater and No. 3 methanol preheater, and then enter the methanol vaporization tank for vaporization; (3) The vaporized methanol vapor passes through the feed and discharge heat exchanger for superheating reaction to a temperature of 240-250°C, and enters the reactor from the top of the reactor; Excited heat exchange; the temperature of the reaction gas coming out of the reactor is about 365-370°C, which is exchanged through the feed and discharge heat exchanger, No. 3 methanol heat exchanger, methanol tower gas reboiler, and dimethyl ether tower feed cooler. After heating, the temperature is 120-125°C and enters the feed tank of the dimethyl ether tower; the reaction gas is condensed in the feed tank of the dimethyl ether tower into two phases of vapor and liquid, which are respectively passed into the dimethyl ether rectification tower; The reactor adopts a three-stage adiabatic inter-stage chilled shock reactor, and its inlet reaction temperature is relatively low, but through heat exchange between two stages, the temperature of the reaction product can be controlled to reach the optimum reaction temperature before leaving the reactor; (4) The steam at the top of the dimethyl ether distillation tower enters the condenser of No. 1 dimethyl ether tower to condense and then flows back to the rectification tower. After passing the test, the dimethyl ether product is extracted from the side line through the dimethyl ether product storage tank; Part of the light components extracted from the top of the condenser of the dimethyl ether tower enters the alcohol washing tower above the methanol buffer tank after being cooled by the condenser, and the dimethyl ether therein is recovered from part of the fresh methanol, and the gas is discharged at the top of the tower; The still liquid in the tower tank of the dimethyl ether rectification tower enters the methanol rectification tower, and the methanol vapor at the top of the tower is condensed by the condenser of the No. 2 dimethyl ether tower and then refluxed to the rectification tower. Methanol returns to the methanol buffer tank and mixes with the methanol raw material from the outside; The waste water in the tower kettle is output after heat exchange with methanol raw material by No. 1 methanol preheater.