CN204543614U - Purifying ethylene glycol piece-rate system - Google Patents

Abstract

The utility model discloses an ethylene glycol refining and separating system, which solves the problems of complex process, difficult separation, high equipment investment and high energy consumption in the prior art. Including ethylene glycol synthesis system, methanol recovery tower, degreasing tower, light removal tower and refining tower connected in sequence, wherein, ethylene glycol synthesis system is first connected with the second gas-liquid separator through the reboiler of the degreasing tower, and the The gas phase outlet of the second gas-liquid separator is connected with the first gas-liquid separator through the reboiler of the methanol recovery tower, the gas phase outlet of the first gas-liquid separator is connected with the ethylene glycol synthesis system, and the liquid phase outlet is connected with the methanol The feed port of the recovery tower is connected, and the bottom liquid outlet of the methanol recovery tower is connected with the liquid phase outlet of the second separator and the feed port of the degreasing tower. The utility model has the advantages of simple process, convenient operation, low equipment investment and operation cost, good impurity separation effect and high yield.

Description

Ethylene glycol refining separation system

technical field

The utility model relates to an ethylene glycol separation system, in particular to an ethylene glycol refining separation system.

Background technique

The ethylene oxide hydration method is the most widely used in the preparation of ethylene glycol. Due to the impact of the oil crisis in recent years, research on the preparation of ethylene glycol by non-petroleum routes is increasing at home and abroad. The CO gas-phase oxidative coupling method instead of the petroleum route to prepare ethylene glycol has the advantages of abundant raw material sources, low cost, no pollution, mild reaction conditions, high product purity, continuous production, etc. It is an advanced clean production and environment-friendly green chemistry process. Its successful development and development has an important role and significance in changing the existing traditional process routes of oxalate esters, ethylene glycol, and certain pharmaceutical and dye intermediates.

CO gas-phase oxidative coupling method to prepare ethylene glycol not only saves petroleum resources, but also introduces impurities that are not found in petroleum synthesis processes, among which low-level carboxylic acids and other alcohol esters are significantly increased, especially 1,2-butanediol The introduction of alcohol, because the boiling points of 1,2-butanediol and ethylene glycol are relatively close, it is easy to form an azeotrope, and the difficulty of separation and energy consumption are increased. How to separate the impurities in the ethylene glycol product, especially 1,2-butanediol, to finally obtain a qualified ethylene glycol product, and at the same time ensure that the separation process is simple and effective and the energy consumption is reasonable, which becomes the refining process of ethylene glycol. focus of the separation study.

On the other hand, in the past, when the reaction synthesis gas from the ethylene glycol synthesis system was used for the first step of methanol recovery, gas-liquid separation was required, so that the liquid phase containing methanol entered the methanol recovery tower to separate methanol, and the liquid volume of this part was large. It often requires a bulky methanol recovery tower for processing, which has the problems of large equipment volume, high investment and operating costs, and high energy consumption.

Contents of the invention

The purpose of this utility model is to solve the above-mentioned technical problems, and provide an ethylene glycol refining and separating system with simple process, easy operation, low equipment investment and operation cost, good impurity separation effect and high yield.

The system of the utility model comprises an ethylene glycol synthesis system, a methanol recovery tower, a degreasing tower, a light removal tower and a refining tower connected in sequence, wherein the ethylene glycol synthesis system is first separated from the second gas-liquid by the reboiler of the degreasing tower The gas-phase outlet of the second gas-liquid separator is connected with the first gas-liquid separator through the reboiler of the methanol recovery tower, and the gas-phase outlet of the first gas-liquid separator is connected with the ethylene glycol synthesis system, The liquid phase outlet is connected to the feed port of the methanol recovery tower, and the bottom liquid outlet of the methanol recovery tower is connected to the liquid phase outlet of the second separator and the feed port of the degreasing tower.

The methanol recovery tower is provided with 45-60 trays, and the distance between the feed inlet and the bottom of the tower is 5-8 trays; the degreasing tower is provided with 15-40 trays, and the distance between the feed inlet and the bottom of the tower is 4-8 trays; the number of trays is 90-120 in the light removal tower, and the feed port is 10-15 blocks away from the bottom of the tower; the number of trays in the refining tower is 50-70, and the feed port and the tower The distance between the bottom is 5-8 trays, and the distance between the outlet of the side line and the top of the tower is 4-8 trays.

Using the method of the above system, including cooling the reaction mixture gas from the ethylene glycol synthesis system to 40-60°C and then separating the gas and liquid through the first gas-liquid separator, and sending the gas phase back into the ethylene glycol synthesis system as hydrogen-containing circulating gas, The liquid phase is sent to the methanol recovery tower, and methanol is produced at the top of the tower. The reaction mixture gas is first cooled to 120-140°C and then sent to the second gas-liquid separator for gas-liquid separation. The gas phase is further cooled to 40-60°C and sent to the The first gas-liquid separator, the liquid phase is mixed with the bottom liquid from the methanol recovery tower and then sent to the skimming tower. Quality alcohol, the liquid in the bottom of the tower is sent to the refining tower, the top of the refining tower produces qualified ethylene glycol, the side line produces high-quality ethylene glycol, and the liquid in the bottom of the tower is heavy alcohol.

The reaction mixture first enters the reboiler of the degreasing tower as a heat source and cools down to 120-140°C, then sends it to the second gas-liquid separator for gas-liquid separation, and then sends the gas phase to the reboiler of the methanol recovery tower as a heat source to cool down to 40°C After -60°C, it is sent to the first gas-liquid separator.

The top temperature of the methanol recovery tower is controlled at 50-65°C, and the bottom temperature is controlled at 85-95°C; the top temperature of the degreasing tower is controlled at 40-55°C, and the bottom temperature is controlled at 140-160°C; The top temperature of the stripping tower is controlled at 130-150°C, and the bottom temperature is controlled at 143-145°C; the top temperature of the refining tower is controlled at 130-149°C, and the bottom temperature is controlled at 145-165°C.

The methanol recovery tower is provided with 45-60 trays, and the distance between the feed inlet and the bottom of the tower is 5-8 trays; the degreasing tower is provided with 15-40 trays, and the distance between the feed inlet and the bottom of the tower is 4-8 trays; the number of trays is 90-120 in the light removal tower, and the feed port is 10-15 blocks away from the bottom of the tower; the number of trays in the refining tower is 50-70, and the feed port and the tower The distance between the bottom is 5-8 trays, and the distance between the outlet of the side line and the top of the tower is 4-8 trays.

Beneficial effect:

(1) Carry out gas-liquid separation twice at different temperatures for the reaction mixture. First, the temperature of the reaction mixture is lowered to 120-140°C and then sent to the second gas-liquid separator for gas-liquid separation. This temperature is at the boiling point of methanol Above, so most of methanol will exist in the gas phase in gaseous form, at this time, the gas-liquid separation is carried out, and the separated liquid phase is not sent to the methanol recovery tower, but is sent to the degreasing tower together with the bottom liquid of the methanol recovery tower. Through pre-separation, reduce the amount of gas entering the first gas-liquid separator, and then further reduce the temperature to make the gas phase temperature of the second gas-liquid separator drop to 40-60°C and then send it to the first gas-liquid separator. Below the boiling point of methanol, most of methanol will exist in liquid form, and the liquid phase containing methanol enters the methanol recovery tower. Due to the gas-liquid separation at two different temperatures, while ensuring the recovery rate of methanol, the final methanol The liquid volume of the recovery tower is greatly reduced, thereby reducing the volume and height of the methanol recovery tower, reducing manufacturing costs and control difficulties, and has the advantage of low energy consumption of the reboiler.

(2) Aiming at the obvious increase of low-level carboxylic acids and other alcohol esters in the reaction mixture, a methanol recovery tower, a degreasing tower, a light removal tower and a refining tower were set up to recover methanol, mixed alcohol esters, light alcohols, and ethyl alcohol respectively. Diols and heavy alcohols adopt a four-tower rectification system, which is simpler than the traditional ethylene glycol rectification method and reduces equipment costs. Strict control improves the recovery efficiency of high-quality ethylene glycol, and the recovery rate of high-quality ethylene glycol can reach 95%.

(3) The high-temperature reaction mixed gas in the synthesis reactor provides heat for the degreasing tower and the reboiler of the methanol recovery tower in turn, and the waste heat is rationally used to achieve the purpose of energy saving.

(4) The process of the utility model has the advantages of simple and reliable flow, good separation effect, high yield of high-quality products, reduced equipment volume, thereby reducing equipment investment and operating costs, low energy consumption, and environmental friendliness.

Description of drawings

Fig. 1 is process flow chart and system diagram of the utility model.

Among them, 1-ethylene glycol synthesis system, 2-second gas-liquid separator, 3-first gas-liquid separator, 4-methanol recovery tower, 4.1-reboiler, 5-skimming tower, 5.1-reboiler , 6- Light removal tower, 6.1- Reboiler, 7- Refining tower, 7.1- Reboiler, 7.2- Side outlet, 8- Condenser, 9- Separator, 10- Vacuum equipment.

Detailed ways

Below in conjunction with accompanying drawing, the utility model system is further explained:

Ethylene glycol synthesis system 1, methanol recovery tower 4, degreasing tower 5, light removal tower 6 and refining tower 7 are connected sequentially, wherein, ethylene glycol synthesis system 1 first passes through reboiler 5.1 of degreasing tower 5 and the second gas-liquid The separator 2 is connected, and the gas phase outlet of the second gas-liquid separator 2 is connected with the first gas-liquid separator 3 through the reboiler 4.1 of the methanol recovery tower 4, and the gas phase outlet of the first gas-liquid separator 3 is connected with the first gas-liquid separator 3. The ethylene glycol synthesis system 1 is connected, and the liquid phase outlet is connected with the feed port of the methanol recovery tower 4, and the tower bottom liquid outlet of the methanol recovery tower 4 is connected with the liquid phase outlet of the second separator 2 and the feed of the degreasing tower 5 port connection. The methanol recovery tower 4 is provided with 45-60 trays, and the distance between the feed inlet and the bottom of the tower is 5-8 trays; the degreasing tower 5 is provided with 15-40 trays, and the distance between the feed inlet and the bottom of the tower is The distance is 4-8 trays; the delightening tower 6 is provided with 90-120 trays, and the feed port is 10-15 trays away from the bottom of the tower; the refining tower 7 is provided with 50-70 trays. The distance between the feed port and the bottom of the tower is 5-8 trays, and the distance between the side line outlet and the top of the tower is 4-8 trays.

A condenser 8 is arranged on the top of each tower, and the condenser 8 is connected to a separator 9, the gas outlet of the separator is connected to the atmosphere or vacuum equipment 10, and the liquid outlet is connected to the corresponding towers through a pump. That is, the gas phase at the top of the tower is sent to the separator 9 for gas-liquid separation after being condensed by the condenser 8 to obtain non-condensable gas and condensate. The condensed gas is connected to the vacuum equipment 10 to generate the vacuum condition required by the tower, and the condensed liquid in the separator 9 is partially refluxed after being pressurized by the pump, and the rest is taken out as a product.

The process flow chart is shown in Figure 1. The raw material is the reaction mixture gas from ethylene glycol synthesis reactor 1, mainly composed of hydrogen, dimethyl oxalate, ethylene glycol, methanol, 1,2-butanediol, methyl glycolate It is composed of ester, nitrogen, ethanol, methane and carbon monoxide, among which the mass fraction of hydrogen is 30-40%, the mass fraction of ethylene glycol is 15-20%, the mass fraction of 1,2-butanediol is 0.05-0.08%, and the mass fraction of methanol The fraction is 24-30%, the mass fraction of methyl glycolate is 0.1-0.3%, the mass fraction of ethanol is 0.2-0.5%, the content of nitrogen, methane and carbon monoxide is 15-25%, and the others are heavy alcohols with complex components.

Taking an annual output of 127,000 tons of high-quality ethylene glycol as an example, assuming that the annual working time of the device is 8,000 hours, the volume of the methanol recovery tower is 180m ³ , and the volume of the methanol recovery tower can be reduced by 18%.

Process embodiment: the reaction mixture gas (crude ethylene glycol reaction gas, mass flow rate is 82340Kg/h) that comes from ethylene glycol synthesis reactor 1 enters the reboiler 5.1 of degreasing tower 5 as its heat source, and its temperature The temperature is 190-210°C, the pressure is 1.8-2.1MPa, the temperature of the reaction mixture is reduced to 120-140°C after heat exchange, and then sent to the second gas-liquid separator 2 for gas-liquid separation, wherein the gas phase (mass flow rate is 70669.5Kg/h) is sent to the reboiler 4.1 of methanol recovery tower 4 to provide heat for it, and the gas phase is reduced to 40-60°C through reboiler 4.1 and enters the first gas-liquid separator 3 for gas-liquid separation again. The liquid phase (mass flow rate is 25004Kg/h) enters the methanol recovery tower 4 from the feed port, and the gas phase is sent back to the ethylene glycol synthesis reactor 1 for recycling as hydrogen-containing circulating gas. The methanol recovery tower 4 is provided with 45-60 plates, The distance between the feed inlet and the bottom of the tower is 5-8 trays, the pressure at the top of the tower is 90-110KPa, the pressure at the bottom of the tower is 100-120KPa, and the temperature at the top of the tower is controlled at 40-65°C. Into the separator 9 for gas-liquid separation, the non-condensable gas is vented, the condensate is partially refluxed after being pressurized by the pump, and the reflux ratio is set to 35-40, and the rest of the condensate is extracted as a methanol product, and the temperature at the bottom of the tower is controlled at 85-95°C. The liquid in the bottom of the tower is pressurized by the pump and sent to the deesterification tower 5; the number of theoretical plates in the deesterification tower 5 is 15-40, the distance between the feed port and the bottom of the tower is 4-8 tower blocks, and the pressure at the top of the tower is 70-90KPa. The pressure at the bottom of the tower is 80-100KPa, and the temperature at the top of the tower is controlled at 40-55°C. After being condensed by the top condenser 8, it is sent to the separator 9 for gas-liquid separation. The non-condensable gas is connected to the vacuum device 10 to generate a vacuum. Partial reflux after the pump is pressurized, the reflux ratio is set to 2-5, the rest of the condensate is extracted as a mixed alcohol ester product, the temperature at the bottom of the tower is controlled at 140-160°C, and the liquid in the tower is sent into the light removal tower after being pressurized by the pump . Light removal tower 6 has 90-120 theoretical plates, the feeding position is 10-15 blocks away from the bottom of the tower, the pressure at the top of the tower is 10-20KPa, the pressure at the bottom of the tower is 15-25KPa, and the temperature at the top of the tower is controlled at 130-150°C. After being condensed by the top condenser 8, it is sent to the separator 9. The non-condensable gas is connected to the vacuum equipment 10 to generate a vacuum. The condensate is partially refluxed after being pressurized by the pump. The reflux ratio is set to 80-120, and the rest of the condensate is used as a light The alcohol product is extracted, the temperature at the bottom of the tower is controlled at 143-155°C, and the liquid in the bottom of the tower is pumped and then sent into the refining tower. The refining tower 7 adopts the form of side line extraction, the number of theoretical plates is 50-70, the distance between the feed port and the bottom of the tower is 5-8 blocks, the distance between the side line outlet 7.2 and the top of the tower is 4-8 blocks, and the distance between the top and bottom of the tower is 4-8 blocks. The pressure is 10-15KPa, the pressure at the bottom of the tower is 15-20KPa, the temperature at the top of the tower is controlled at 130-149°C, after being condensed by the top condenser 8, it is sent to the separator 9 for gas-liquid separation, and the non-condensable gas is connected to the vacuum equipment 10 A vacuum is generated, the condensate is partially refluxed after being pressurized by the pump, the reflux ratio is set to 30-50, and the rest of the condensate is extracted as a qualified product of ethylene glycol. The temperature is controlled at 145-165°C, and the tower bottom liquid is heavy alcohol.

In this embodiment, the mass flow rate of methanol is 17259Kg/h, and the methanol content is >99%; , methyl glycolate 0.208, ethanol 0.244; the light alcohol adopts a mass flow rate of 1242.5Kg/h, and the mass composition is ethylene glycol 0.885, 1,2-butanediol 0.006, dimethyl oxalate 0.005, and others are boiling points Light alcohols lower than ethylene glycol (such as 2,3-butanediol); the production mass flow rate of qualified ethylene glycol is 600Kg/h, the mass fraction of ethylene glycol is >0.994, and the mass fraction of ethylene glycol qualified products is The mass flow rate is 15864.7Kg/h, and the mass flow rate for heavy alcohols is 100.3Kg/h; the mass flow rate for high-grade ethylene glycol is 15864.7Kg/h, and the annual output is 127,000 tons.

Claims (2)

1. a purifying ethylene glycol piece-rate system, it is characterized in that, comprise the ethylene glycol synthesis system connected successively, methanol distillation column, degreasing tower, lightness-removing column and treating column, wherein, ethylene glycol synthesis system is first connected with the second gas-liquid separator through the reboiler of degreasing tower, the gaseous phase outlet of described second gas-liquid separator is connected with the first gas-liquid separator through the reboiler of methanol distillation column, the gaseous phase outlet of described first gas-liquid separator is connected with ethylene glycol synthesis system, liquid-phase outlet is connected with the charging aperture of methanol distillation column, the tower bottoms outlet of described methanol distillation column is connected with the charging aperture of degreasing tower with the liquid-phase outlet of the second separator.

2. purifying ethylene glycol piece-rate system as claimed in claim 1, it is characterized in that, described methanol distillation column arranges number of plates 45-60 block, charging aperture with at the bottom of tower apart from being 5-8 block column plate; Described degreasing tower arranges number of plates 15-40 block, and at the bottom of charging aperture and tower, distance is 4-8 block column plate; Described lightness-removing column arranges number of plates 90-120 block, 10-15 block column plate at the bottom of charging aperture distance tower; Described treating column arranges number of plates 50-70 block, and at the bottom of charging aperture and tower, distance be 5-8 block column plate, and side line discharge and tower top are apart from being 4-8 block column plate.