CN111592446A - Rectification system and process for preparing ethylene glycol by dimethyl oxalate hydrogenation - Google Patents
Rectification system and process for preparing ethylene glycol by dimethyl oxalate hydrogenation Download PDFInfo
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- C07—ORGANIC CHEMISTRY
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Abstract
The invention discloses a rectification system for preparing ethylene glycol by dimethyl oxalate hydrogenation, which comprises a methanol refining and removing tower system, a dehydration and butanediol removing tower system and an ethylene glycol product refining and recycling tower system, wherein the methanol refining and removing tower system and the dehydration and butanediol removing tower system are connected through a pipeline, and the dehydration and butanediol removing tower system and the ethylene glycol product refining and recycling tower system are connected through a pipeline. According to the physical property characteristics of the oxalate hydrogenation product, a reasonable rectification mode and a reasonable rectification setting are selected, reasonable operation pressure is adopted, and side line extraction is adopted, so that the stability of the product quality is ensured; two feeds are adopted, and energy consumption is reduced by utilizing energy coupling in the system. The ethylene glycol rectification process and the ethylene glycol rectification system ensure the product quality, save the energy consumption, reduce the production cost and bring good economic benefits for enterprises.
Description
Technical Field
The invention belongs to the technical field of ethylene glycol production processes, and particularly relates to a rectification system and a rectification process for preparing ethylene glycol by dimethyl oxalate hydrogenation.
Background
Ethylene glycol is one of basic raw materials for chemical industrial production, and the traditional production method mainly takes ethylene as a raw material, adopts ethylene oxidation to produce ethylene oxide, and produces ethylene glycol by ethylene oxide hydration, which has serious dependence on petroleum resources. Aiming at the current situation of more coal and less oil in China, the method for preparing the ethylene glycol by using the coal as the raw material accords with the national situation of China and has important economic significance and strategic significance. Among the various coal-to-ethylene glycol routes, the route for preparing ethylene glycol by hydrogenating the intermediate product with oxalate is mature and industrialized. Compared with the petroleum route, the hydrogenation product of the oxalate hydrogenation route has higher content of various byproducts, increases the separation difficulty, and causes higher energy consumption and lower yield of ethylene glycol rectification.
In the existing ethylene glycol rectification route, hydrogenation products are combined into one stream and enter a rectification system, so that the consumption of high-grade steam for rectification is increased; the product is extracted from the top of the tower, so that the product is difficult to be qualified; the process steam at the top of the tower is directly cooled by water, thus causing energy waste.
Disclosure of Invention
The invention provides a rectification system for preparing ethylene glycol by dimethyl oxalate hydrogenation, and aims to solve the problems.
The invention is realized in such a way that a rectification system for preparing ethylene glycol by dimethyl oxalate hydrogenation comprises a methanol refining and removing tower system, a dehydration and butanediol removing tower system and an ethylene glycol product refining and recycling tower system, wherein the methanol refining and removing tower system and the dehydration and butanediol removing tower system are connected through a pipeline, and the dehydration and butanediol removing tower system and the ethylene glycol product refining and recycling tower system are connected through a pipeline.
Further, the methanol refining and removing tower system comprises a methanol recovery tower and a methanol removing tower, and the dimethyl oxalate hydrogenation product is roughly divided into two parts and then enters the methanol refining and removing tower system; and feeding the crude methanol after the crude separation into the methanol recovery tower, feeding the crude glycol into the methanol removing tower, and feeding the methanol recovered from the top of the methanol removing tower back to the methanol recovery tower.
Further, the dehydration and butanediol removal tower system comprises a dehydration tower and a dealcoholization tower, wherein the ethylene glycol from which the methanol is removed by the methanol refining and removal tower system enters the dehydration tower from a tower kettle through a pipeline, and the ethylene glycol from which the impurities are removed by the dehydration tower enters the dealcoholization tower from the tower kettle through a pipeline.
Further, the ethylene glycol product refining and recycling tower system comprises an ethylene glycol product tower and an ethylene glycol recycling tower, the ethylene glycol from which the low-carbon alcohol is removed by the dehydration and butanediol removal tower system enters the ethylene glycol product tower from a tower kettle through a pipeline, the residual impurities from which the refined ethylene glycol is extracted by the ethylene glycol product tower enter the ethylene glycol recycling tower from the tower kettle through a pipeline, and the ethylene glycol recycled from the top of the ethylene glycol recycling tower enters the ethylene glycol product tower.
Furthermore, the methanol recovery tower ensures the quality of a methanol product through side line extraction, and the ethylene glycol product tower ensures the quality of an ethylene glycol product through side line extraction.
Furthermore, the byproduct low-pressure steam of the ethylene glycol product refining and recycling tower system is used as a heat source of a reboiler of the methanol refining and removing tower system.
The invention also provides a rectification process for preparing ethylene glycol by hydrogenating dimethyl oxalate, which is characterized by comprising the following steps of:
s1: crude methanol generated by hydrogenation of oxalate enters a methanol recovery tower, is rectified at normal pressure, and refined methanol is extracted from the side line of the tower body, and tower kettle materials enter a methanol removal tower;
s2: feeding the methanol recovery tower kettle material and crude glycol generated by oxalate hydrogenation into a methanol removing tower, rectifying at 65-75kPa.A, recovering methanol from the tower top, and returning the methanol to the methanol recovery tower to increase the methanol yield, and feeding the tower kettle material into a dehydration tower;
s3: feeding the tower bottom material of the methanol removing tower into a dehydrating tower, rectifying at 25-35kPa.A, extracting aqueous methanol from the tower top as a fusel oil finished product, and feeding the tower bottom material into the dehydrating tower;
s4: feeding the tower bottom material of the dehydration tower into a dealcoholization tower, rectifying at 15-25kPa.A, collecting low-carbon alcohol containing butanediol as a light fraction finished product from the tower top, and feeding the tower bottom material into an ethylene glycol product tower;
s5: feeding the tower bottom material of the dealcoholization tower into an ethylene glycol product tower, rectifying at 15-25kPa.A, extracting a qualified ethylene glycol product from the tower body side, and feeding the tower bottom material into an ethylene glycol recovery tower;
s6: feeding the material in the bottom of the ethylene glycol product tower into an ethylene glycol recovery tower, rectifying under 5-10kPa.A, returning the ethylene glycol extracted from the tower top to the ethylene glycol product tower to increase the yield, and taking the material in the tower bottom as a heavy fraction finished product.
Compared with the prior art, the invention has the beneficial effects that: according to the physical property characteristics of the oxalate hydrogenation product, a reasonable rectification mode and a reasonable rectification setting are selected, reasonable operation pressure is adopted, and side line extraction is adopted, so that the stability of the product quality is ensured; two feeds are adopted, and energy consumption is reduced by utilizing energy coupling in the system. The ethylene glycol rectification process and the ethylene glycol rectification system ensure the product quality, save the energy consumption, reduce the production cost and bring good economic benefits for enterprises.
Drawings
FIG. 1 is a schematic flow diagram of an ethylene glycol rectification system of the present invention;
FIG. 2 is a schematic flow chart showing a methanol recovery tower and a methanol removal tower in a methanol refining and removal tower system combined into one tower when the apparatus is small in scale;
in the figure: 1. a methanol recovery tower, 2, a methanol removing tower, 3, a dehydrating tower, 4, a dealcoholizing tower, 5, an ethylene glycol product tower, 6 and an ethylene glycol recovery tower.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Further, in the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
Example 1
Referring to fig. 1, the present invention provides a technical solution: a rectifying system for preparing ethylene glycol by dimethyl oxalate hydrogenation comprises a methanol refining and removing tower system, a dehydration and butanediol removing tower system and an ethylene glycol product refining and recovering tower system, wherein the methanol refining and removing tower system and the dehydration and butanediol removing tower system are connected through a pipeline, and the dehydration and butanediol removing tower system and the ethylene glycol product refining and recovering tower system are connected through a pipeline.
The synthesized product is divided into two feeds after pre-separation. One of the methanol streams has high methanol content and is crude methanol, and the crude methanol enters a methanol recovery tower 1; the other stream is crude glycol with higher glycol content and enters a methanol removing tower 2. The crude separation process of the synthetic product does not need energy consumption, can be realized only by controlling the condensation temperature of the synthetic product, and can greatly reduce the energy consumption of the ethylene glycol rectification working section after the material is separated.
Adopt refined and recovery column system byproduct steam of ethylene glycol product as 1 reboiler heat source of methyl alcohol recovery column, the whole energy consumption of device that can be very big sets up reserve steam reboiler simultaneously, guarantees that under unstable operating modes such as driving, the whole good suitability that has of device.
The operation conditions of the dehydration and butanediol removal tower system can be adjusted within a reasonable range according to the composition of the hydrogenation product, and the dehydration tower 3 and the dealcoholization tower 4 adopt proper reflux ratio and theoretical plate number, so that the product quality and yield are ensured, and the dehydration and butanediol removal tower system has good adaptability to the hydrogenation product.
The methanol recovery tower 1 and the ethylene glycol product tower 5 adopt a side line extraction process, and light component impurities are extracted from the top of the tower and do not enter into methanol and ethylene glycol products, so that the product quality is ensured.
The waste boiler is used for replacing a water cooler at the top of the ethylene glycol product tower 5, and the byproduct steam is supplied to the methanol recovery tower 1, so that the overall energy consumption of the device is reduced.
The lower operation pressure (5-10 kPa. A) and operation temperature are adopted, so that the ethylene glycol recovery tower 6 can recover the ethylene glycol without generating byproducts. And because the ethylene glycol recovery tower 6 has a small tower body and a small reflux amount, the tower can be ensured to have better adaptability by using lower operating pressure.
Example 2
A rectification system for preparing ethylene glycol by dimethyl oxalate hydrogenation is characterized in that a hydrogenation product is subjected to pre-separation and then enters a rectification system in two paths; heating a methanol recovery tower 1 by using byproduct steam of a glycol product refining and recovery tower system to refine a methanol product; removing water, butanediol and other impurities in the ethylene glycol by adopting proper operating conditions; the quality of methanol and glycol products is ensured by adopting a side-draw mode; the ethylene glycol product is refined and the byproduct steam is generated in the recovery tower system, so that the overall energy consumption of the device is reduced; the glycol product is recovered under proper operation conditions, and the yield is improved. The rectification process comprises the following steps:
a) crude methanol generated by hydrogenation of oxalate enters a methanol recovery tower 1, is rectified at normal pressure, and is extracted at the side line of the tower body, and tower kettle materials enter a methanol removing tower 2.
b) The material in the bottom of the methanol recovery tower 1 and the crude glycol generated by the hydrogenation of oxalate enter a methanol removing tower 2, the crude glycol is rectified under 65-75kPa.A, the methanol extracted from the tower top is returned to the methanol recovery tower 1 to increase the yield of the methanol, and the material in the bottom of the tower enters a dehydrating tower 3.
c) And (3) feeding the tower bottom material of the methanol removing tower 2 into a dehydrating tower 3, rectifying at 25-35kPa.A, extracting hydrous methanol from the tower top as a fusel oil finished product, and feeding the tower bottom material into the dehydrating tower 3.
d) And (3) feeding the tower bottom material of the dehydrating tower 3 into a dealcoholization tower 4, rectifying at 15-25kPa.A, collecting low-carbon alcohol containing butanediol at the tower top as a light fraction finished product, and feeding the tower bottom material into an ethylene glycol product tower 5.
e) And (3) feeding the tower bottom material of the dealcoholization tower 4 into an ethylene glycol product tower 5, rectifying at 15-25kPa.A, extracting a qualified ethylene glycol product from the tower body side, and feeding the tower bottom material into an ethylene glycol recovery tower 6.
f) Feeding the material in the bottom of the ethylene glycol product tower 5 into an ethylene glycol recovery tower 6, rectifying under 5-10kPa.A, returning the ethylene glycol extracted from the tower top to the ethylene glycol product tower 5 to increase the yield, and taking the material in the bottom of the tower as a heavy fraction finished product.
Example 3
The tower system and the energy coupling mode corresponding to the invention are shown in figure 1, and the specific operation process is as follows:
crude methanol (methanol 94.00%, ethanol 0.94%, water 0.60%, methyl glycolate 0.12%, butanediol 439ppm, ethylene glycol 3.99%, and the balance lower alcohols such as propanol) produced by hydrogenation of oxalate is introduced into the methanol recovery column 1. Rectifying under normal pressure and extracting 45-50 ℃ fraction at the side line of the tower body, which is correspondingly refined methanol; the tower kettle uses the byproduct of 0.2MPag-0.3MPag steam at the top of the ethylene glycol product tower 5 as a part of reboiler heat source, and the tower kettle material enters the methanol removing tower 2.
Crude glycol (methanol 16.42%, ethanol 0.16%, water 0.28%, methyl glycolate 0.33%, butanediol 0.50%, ethylene glycol 80.98%, and the balance lower alcohols such as propanol) generated by hydrogenation of the materials in the bottom of the methanol recovery tower 1 enters the methanol removing tower 2 from different positions, and is rectified at 65-75kPa.A, methanol and the like are extracted from the top of the tower and returned to the methanol recovery tower 1, and the yield of methanol is increased. The tower kettle uses 1MPag-2MPag steam as a heat source of a reboiler, and the materials in the tower kettle enter a dehydration tower 3.
And (3) feeding the material at the bottom of the methanol removing tower 2 into a dehydrating tower 3, rectifying at 25-35kPa.A, and extracting hydrous methanol at the top of the tower to be used as a fusel oil finished product (22.89% of methanol, 31.54% of ethanol, 28.12% of water, and the balance of lower alcohols such as propanol). The tower kettle uses 1MPag-2MPag steam as a heat source of a reboiler, and the materials in the tower kettle enter a dehydration tower 3.
And (3) feeding the material at the bottom of the dehydrating tower 3 into a dealcoholization tower 4, rectifying at 15-25kPa.A, and collecting low-carbon alcohol containing butanediol as a light fraction finished product (10.23% of methyl glycolate, 17.45% of butanediol, 55.94% of ethylene glycol and the balance of low-carbon alcohols such as propanol) at the tower top. The tower bottom uses 1MPag-2MPag steam as a reboiler heat source, and the tower bottom materials enter an ethylene glycol product tower 5.
The material in the tower bottom of the dealcoholization tower 4 enters an ethylene glycol product tower 5, and is rectified at 15-25kPa.A, and qualified ethylene glycol products are extracted from the tower body side (the content of the products, the ultraviolet light transmittance and other indexes reach and exceed the national standard of high-class ethylene glycol products). The waste heat boiler is used at the tower top to replace water cooling, and 0.2MPag-0.3MPag steam is byproduct to be used by the methanol recovery tower 1. The tower bottom uses 1MPag-2MPag steam as a reboiler heat source, and the tower bottom materials enter an ethylene glycol recovery tower 6.
The material at the bottom of the ethylene glycol product tower 5 enters an ethylene glycol recovery tower 6, the rectification is carried out under the pressure of 5-10kPa.A, and the ethylene glycol (99.81 percent of ethylene glycol and 0.19 percent of 1, 3-propylene glycol) extracted from the tower top is returned to the ethylene glycol product tower 5 to increase the yield. The tower still uses 1MPag-2MPag steam as the heat source of the reboiler, and the tower still material is used as the heavy distillate finished product (ethylene glycol 62.93%, triethylene glycol 21.26%, 1, 3-propylene glycol 11.70%).
Example 4
As shown in fig. 2, in the present embodiment, when the scale of the apparatus is small, the methanol recovery column 1 and the methanol removal column 2 in the methanol purification and removal column system may be combined into one column, and the by-product steam of the ethylene glycol product column 5 heats the intermediate reboiler of the column body.
Example 5
(1) Ethylene glycol synthesis
The ethylene glycol synthesis section of the project is provided with two series, and the single series can produce 20 ten thousand tons per year.
Fresh hydrogen from the H2/CO separation device is mixed with recycle gas at the outlet of a H2 recycle gas compressor, enters a material inlet and outlet heat exchanger, exchanges heat with reaction gas out of an ethylene glycol synthesis tower to recover heat, enters a steam heater (II) to be heated, and enters a DMO evaporation tower.
DMO from a dimethyl oxalate device firstly enters a DMO buffer tank, is pressurized by a DMO feed pump, is heated by a DMO heater and then enters the upper part of a DMO evaporation tower, and is fully gasified and mixed by hydrogen in the DMO evaporation tower. And (3) the mixed recycle gas enters a steam heater (I) for reheating and then enters an ethylene glycol synthesis tower for hydrogenation reaction. Under the action of the high-activity copper catalyst in the ethylene glycol synthetic tower, dimethyl oxalate is subjected to hydrogenation reaction to generate ethylene glycol. The shell-side steam-water mixture enters a steam drum to produce low-pressure steam as a byproduct.
The main reaction for synthesizing the ethylene glycol is as follows:
the first step of the hydrogenation reaction:
(COOCH3)2 + 2H2 = HOCH2COOCH3 + CH3OH （1）
a second step of the hydrogenation reaction:
HOCH2COOCH3 + 2H2 = HOCH2CH2OH + CH3OH （2）
the general reaction formula is as follows:
(COOCH3)2 + 4H2 = HOCH2CH2OH + 2CH3OH
the main side reaction formula of hydrogenation is as follows:
HOCH2CH2OH + H2 = CH3CH2OH + H2O （3）
the reaction is converted into dimethyl oxalate, and the reaction formula is as follows:
(COOCH3)2 + 5H2 = CH3CH2OH + 2CH3OH + H2O
the recarburization reaction of the ethanol and the glycol occurs:
HOCH2CH2OH + CH3CH2OH = HOCH2CHOHCH2CH3 + H2O
the reaction is converted into dimethyl oxalate, and the reaction formula is as follows:
2(COOCH3)2 + 9H2 = HOCH2CHOHCH2CH3 + 4CH3OH + 2H2O
the hydrogenated gas enters a high-pressure separator I for gas-liquid separation after heat exchange with raw material hydrogen through a material inlet and outlet heat exchanger, the gas phase enters a synthetic water cooler for cooling to 40 ℃, then enters a high-pressure separator II for gas-liquid separation again, most of the gas enters an H2 circulating gas compressor to increase the pressure to complete circulation, and a small amount of the gas is sent to a methanol synthesis device as purge gas. The liquid phase of the high-pressure separator I is decompressed by a decompression valve and then enters a low-pressure flash tank I, and then is sent to the lower part of a methanol recovery tower 1 of an ethylene glycol rectification section by the pressure of the liquid phase. And the liquid phase of the high-pressure separator II is decompressed by a pressure reducing valve and then enters a low-pressure flash tank II, and is also sent to the middle part of a methanol recovery tower 1 of an ethylene glycol rectification section by the pressure of the liquid phase. When the crude product needs to be sent to an ethylene glycol intermediate tank area, the liquid phase of the low-pressure flash tank I is firstly cooled to 40 ℃ by a crude ethylene glycol water cooler and then sent to the ethylene glycol intermediate tank area. And feeding the flash steam of the low-pressure flash tank into a fuel gas pipe network or a torch.
(2) H2 circulating gas compression section
There are 2 series of the recycle gas compression sections of the 40 million ton/year ethylene glycol plant H2. A total of 2H 2 recycle gas compressors were provided. The cycle gas compression adopts a centrifugal compressor, and the cycle gas is compressed from 2.8MPa to 3.0MPa at the final stage of the catalyst.
(3) Ethylene glycol rectification section
The ethylene glycol rectification adopts vacuum rectification, and finally obtains polyester grade ethylene glycol products through the technological processes of a methanol recovery tower 1, a dehydration tower 3, a dealcoholization tower 4, an ethylene glycol product tower 5, an ethylene glycol recovery tower 6, a methanol separation tower and an ethanol product tower, and byproducts of ethanol, light dihydric alcohol and heavy dihydric alcohol are obtained.
Crude methanol and crude glycol from an ethylene glycol synthesis section enter different positions of a methanol recovery tower 1, vapor at the top of the tower is dimethyl ether, methyl formate, methanol, trace ethanol and other vapor, after the vapor is subjected to cryogenic condensation by a methanol recovery tower 1 primary cooler, a methanol recovery tower 1 secondary cooler and the methanol recovery tower 1, part of condensate liquid reflows, part of condensate liquid is extracted from a methanol removal separation tower to separate ethanol, and noncondensable gas is extracted by a methanol recovery tower 1 vacuum system to maintain the required vacuum degree. The refined methanol product is extracted from the side line at the upper part of the tower and is pumped to a methanol recovery tank. The tower bottom liquid enters the dehydrating tower 3 after being pressurized by a feeding pump of the dehydrating tower 3.
In the dehydration tower 3, the gas phase at the top of the tower is steam containing light components such as C2-C5 alcohols, methyl glycolate, dimethyl oxalate and the like, after the steam is condensed by a condenser of the dehydration tower 3 and a deep cooler of the dehydration tower 3, the liquid phase partially refluxes, part of the extracted steam and the extracted steam at the top of the methanol recovery tower 1 are carried out in a methanol separation tower, and noncondensable steam is extracted by a vacuum system of the dehydration tower 3 to maintain the vacuum degree of the dehydration tower 3. The material discharged from the kettle of the dehydrating tower 3 is sent to the dealcoholization tower 4 after the pressure is raised by a feeding pump of the dealcoholization tower 4.
In the dealcoholization tower 4, the gas phase at the top of the tower is mainly the vapor of glycols (such as 2, 3-butanediol, 1, 2-propanediol and 1, 2-butanediol) which are lighter than ethylene glycol, after the vapor is condensed by a condenser of the dealcoholization tower 4 and a deep cooler of the dealcoholization tower 4, part of the liquid phase flows back, and part of the liquid phase is extracted and sent to a light dihydric alcohol storage tank of a tank area after being cooled. The discharging material from the kettle 4 of the dealcoholization tower is pumped into an ethylene glycol product tower 5 by a feeding pump of the ethylene glycol product tower 5.
In the ethylene glycol product tower 5, after tower top steam is condensed by a waste boiler of the ethylene glycol product tower 5, a secondary cooler of the ethylene glycol product tower 5 and a deep cooler of the ethylene glycol product tower 5, a liquid phase part reflows, a part of the liquid phase part is taken as a 98% ethylene glycol extraction liquid phase hydrogenation unit, and noncondensable gas is extracted through a vacuum system of the ethylene glycol product tower 5 so as to maintain the vacuum degree of the ethylene glycol product tower 5. Polyester-grade ethylene glycol products are extracted from the upper side of the ethylene glycol product tower 5 and sent to a tank field. The discharging material from the kettle 5 of the ethylene glycol product tower is pumped into an ethylene glycol recovery tower 6 by a feeding pump of the ethylene glycol recovery tower 6.
In the ethylene glycol recovery tower 6, after the steam at the top of the tower is condensed by a condenser of the ethylene glycol recovery tower 6 and a deep cooler of the ethylene glycol recovery tower 6, part of liquid phase reflows, part of the liquid phase is extracted and sent to a liquid phase hydrogenation unit together with 98 percent of ethylene glycol at the top of the product tower, and non-condensable gas is extracted through a vacuum system of the ethylene glycol product tower 5 so as to maintain the vacuum degree of the ethylene glycol recovery tower 6. And (4) pumping the kettle liquid to a heavy dihydric alcohol storage tank in the tank field through a heavy component output pump.
In the methanol separation tower, the vapor at the top of the tower is condensed by a condenser of the methanol separation tower, the liquid phase enters a reflux tank of the methanol separation tower for partial reflux, and the rest is taken as a product at the top of the tower, is cooled and then is sent to a methanol recovery tank. The bottoms are pumped through an ethanol product column feed pump to an ethanol product column.
In the ethanol product tower, the vapor at the top of the tower is condensed by an ethanol product tower condenser and an ethanol product tower deep cooler (E-53045), the liquid phase enters an ethanol product tower reflux tank, part of the liquid phase reflows, and the rest of the liquid phase is extracted as a tower top product, cooled and then sent to the ethanol product tank. And (3) cooling the higher alcohols product extracted from the side line of the ethanol product tower, and then sending the cooled higher alcohols product to a fusel oil storage tank in the methanol tank area.
The tail gas of each vacuum pump contains methanol and the like, and can not be directly discharged into air, so that the corresponding tail gas is required to be sent to a vacuum pump tail gas washing tower for treatment, fresh water is adopted to wash methanol, methyl formate and the like in the tail gas washing tower, the treated gas can be directly discharged into the atmosphere, and the methanol-containing wastewater in the tower kettle is sent to a wastewater treatment section by a vacuum pump tail gas washing wastewater conveying pump for treatment.
(4) Glycol dealdehyding section
The glycol aldehyde removing device mainly improves the ultraviolet light transmittance of glycol products and removes aldehydes in the glycol products through a resin tower, so that the ultraviolet light transmittance of the glycol aldehyde removing device reaches the glycol polyester grade index.
When the device leaks or other abnormal conditions occur, a small amount of air can leak into the rectifying tower due to the negative pressure operation of the rectifying tower, so that partial alcohol in the tower is oxidized to generate aldehyde, the content of the aldehyde in the ethylene glycol product exceeds the standard, the unqualified ethylene glycol needs to be pumped into a No. 2 resin tower at the moment, and the ethylene glycol is adsorbed by HC-2 resin, sampled and analyzed to be qualified and then sent into a tank product tank.
When the content of glycol aldehyde and the ultraviolet light transmittance output from the side line of the device are not up to the standard, unqualified glycol is pumped into a No. 1 resin tower, is adsorbed by HC-1 resin and then is sent into a No. 2 resin tower, is adsorbed by HC-2 resin, and is sent into a tank product tank after being sampled and analyzed to be qualified.
(5) Liquid phase hydrogenation section
The liquid phase hydrogenation unit is used for deeply hydrogenating impurities in the industrial grade ethylene glycol extracted by ethylene glycol rectification and returning the impurities to the rectification system for separation so as to obtain the polyester grade ethylene glycol with high yield.
The industrial grade glycol extracted from the top of the product rectifying tower and the top of the recovery tower of the glycol rectifying system is heated by a feed preheater and then mixed with hydrogen from outside the battery limits to enter a hydrogenation reactor, trace impurities in the glycol and the hydrogen are subjected to hydrogenation reaction under the action of a catalyst, trace substances influencing the purity and the ultraviolet light transmittance of the glycol in the product are converted, and the product returns to the glycol rectifying dealcoholization tower 4 to separate the trace substances after hydrogenation, so that the quality of the product at the side line is improved. And (3) decompressing the excessive hydrogen, sending the excessive hydrogen to a torch, flashing the hydrogenated glycol by a gas-liquid separator to obtain hydrogen and light components dissolved in the liquid phase, sending the liquid phase glycol back to the glycol rectification process by a product pump, feeding part of the liquid phase glycol into a dealcoholization tower 4, and feeding part of the liquid phase glycol into a product tower.
(6) Glycol refrigeration station workshop section
The ethylene glycol freezing station provides ethylene glycol/water cooling freezing liquid for the dimethyl oxalate device (2400) and the ethylene glycol device (2500) through the screw compressor.
After the ethylene glycol aqueous solution is prepared in the ethylene glycol solution storage tank, the ethylene glycol aqueous solution is conveyed to the evaporator of the screw water chilling unit by the ethylene glycol solution conveying pump. The temperature is reduced to-20 ℃ by an evaporator of the screw water chilling unit, and the temperature is sent to a cold spot for a process device by an outer pipe network, so that the aim of refrigeration is achieved by circulation. The glycol solution delivery pump is provided with a minimum flow pipeline, so that the flow of the secondary refrigerant can be adjusted, and the adjustment of the cold load is realized.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The utility model provides a rectification system of dimethyl oxalate hydrogenation system ethylene glycol, includes that methyl alcohol is refined and desorption tower system, dehydration and take off butanediol tower system, ethylene glycol product are refined and recovery tower system, its characterized in that: the methanol refining and removing tower system and the dehydration and butanediol removing tower system are connected through a pipeline, and the dehydration and butanediol removing tower system and the ethylene glycol product refining and recycling tower system are connected through a pipeline.
2. The rectification system of claim 1, wherein: the methanol refining and removing tower system comprises a methanol recovery tower and a methanol removing tower, and the dimethyl oxalate hydrogenation product is roughly divided into two parts and then enters the methanol refining and removing tower system; and feeding the crude methanol after the crude separation into the methanol recovery tower, feeding the crude glycol into the methanol removing tower, and feeding the methanol recovered from the top of the methanol removing tower back to the methanol recovery tower.
3. The rectification system of claim 2, wherein: the dehydration and butanediol removal tower system comprises a dehydration tower and a dealcoholization tower, the glycol which is subjected to methanol removal through the methanol refining and removal tower system enters the dehydration tower from a tower kettle through a pipeline, and the glycol which is subjected to impurity removal through the dehydration tower enters the dealcoholization tower from the tower kettle through a pipeline.
4. The rectification system of claim 3, wherein: the ethylene glycol product refining and recycling tower system comprises an ethylene glycol product tower and an ethylene glycol recycling tower, ethylene glycol from which low-carbon alcohol is removed by the dehydrating and butanediol removing tower system enters the ethylene glycol product tower from a tower kettle through a pipeline, residual impurities from which refined ethylene glycol is extracted by the ethylene glycol product tower enter the ethylene glycol recycling tower from the tower kettle through a pipeline, and ethylene glycol recycled from the top of the ethylene glycol recycling tower enters the ethylene glycol product tower.
5. The rectification system of claim 4, wherein: the methanol recovery tower ensures the quality of a methanol product through side line extraction, and the ethylene glycol product tower ensures the quality of an ethylene glycol product through side line extraction.
6. The rectification system of any one of claims 1 to 5, wherein: and the byproduct low-pressure steam of the ethylene glycol product refining and recycling tower system is used as a heat source of a reboiler of the methanol refining and removing tower system.
7. A rectification process for preparing ethylene glycol by dimethyl oxalate hydrogenation is characterized by comprising the following steps:
s1: crude methanol generated by hydrogenation of oxalate enters a methanol recovery tower, is rectified at normal pressure, and refined methanol is extracted from the side line of the tower body, and tower kettle materials enter a methanol removal tower;
s2: feeding the methanol recovery tower kettle material and crude glycol generated by oxalate hydrogenation into a methanol removing tower, rectifying at 65-75kPa.A, recovering methanol from the tower top, and returning the methanol to the methanol recovery tower to increase the methanol yield, and feeding the tower kettle material into a dehydration tower;
s3: feeding the tower bottom material of the methanol removing tower into a dehydrating tower, rectifying at 25-35kPa.A, extracting aqueous methanol from the tower top as a fusel oil finished product, and feeding the tower bottom material into the dehydrating tower;
s4: feeding the tower bottom material of the dehydration tower into a dealcoholization tower, rectifying at 15-25kPa.A, collecting low-carbon alcohol containing butanediol as a light fraction finished product from the tower top, and feeding the tower bottom material into an ethylene glycol product tower;
s5: feeding the tower bottom material of the dealcoholization tower into an ethylene glycol product tower, rectifying at 15-25kPa.A, extracting a qualified ethylene glycol product from the tower body side, and feeding the tower bottom material into an ethylene glycol recovery tower;
s6: feeding the material in the bottom of the ethylene glycol product tower into an ethylene glycol recovery tower, rectifying under 5-10kPa.A, returning the ethylene glycol extracted from the tower top to the ethylene glycol product tower to increase the yield, and taking the material in the tower bottom as a heavy fraction finished product.
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