A four-tower forward-reverse mixed flow four-effect crude methanol refining process method

Abstract

The application provides a four-tower forward-reverse mixed flow four-effect crude methanol refining process method, which comprises the following steps: the bottom effluent of a pre-refining tower, the bottom effluent of a negative pressure refining tower and the bottom effluent of a pressurized refining tower are respectively introduced into the negative pressure refining tower, the pressurized refining tower and the atmospheric pressure refining tower; the overhead effluent of the pressurized refining tower is used for heating at least one reboiler at the bottom of the atmospheric pressure refining tower; and the overhead effluent of the atmospheric pressure refining tower is used for heating at least one reboiler at the bottom of the pre-refining tower and at least one reboiler at the bottom of the negative pressure refining tower. The application can maximize the reasonable distribution and utilization of the heat of the gas phase material at the top of the atmospheric pressure refining tower, and effectively reduce the energy consumption of the methanol refining system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of methanol refining, and particularly relates to a four-tower forward-reverse mixed flow four-effect crude methanol refining process system and a process method thereof. BACKGROUND

[0002] Methanol is an important basic organic chemical raw material and a new type of energy fuel. In industry, almost all of the synthesized methanol adopts the method of pressurized catalytic hydrogenation of carbon monoxide. The process includes gas making, synthesis purification, methanol synthesis, and crude methanol rectification. The main task of methanol rectification is to remove volatile components such as dimethyl ether, and non-volatile ethanol, higher alcohols and water, to produce refined methanol meeting product requirements. With the vigorous development of the coal chemical industry, the scale of methanol rectification devices is also becoming larger and larger. How to reduce the energy consumption of methanol refining devices per ton of refined methanol has become the key to the survival and improvement of competitiveness of enterprises. The majority of scientific researchers and engineering and technical personnel have conducted in-depth research on this object.

[0003] The three-tower methanol rectification (forward flow double-effect rectification) process widely adopted at present is that crude methanol is sequentially rectified and separated through a pre-distillation tower, a pressurized rectification tower, and an atmospheric rectification tower. Methanol products are obtained from the overhead of the pressurized tower and the overhead of the atmospheric tower. The separation sequence is to remove light components in the crude methanol from the pre-distillation tower, and the pre-overhead crude methanol from the tower sump enters the pressurized rectification tower. The condensation latent heat of the methanol steam at the top of the pressurized tower is used as the reboiling heat source of the atmospheric tower to realize forward flow double-effect rectification. The fusel alcohol is taken from the side line of the atmospheric tower, and the waste water is discharged from the bottom of the atmospheric tower. This method is a common crude methanol refining process. The energy consumption of the methanol rectification process is about 2417-3223.7 MJ / ton of refined methanol product. The production energy consumption is relatively high. With the expansion of the scale of methanol refining, the total energy consumption also significantly increases. Under the background of "double carbon", energy-saving process has become the priority target of the industry.

[0004] In order to reduce the energy consumption of methanol rectification, there are currently various solutions for existing devices, such as adding a high-pressure tower, which is coupled with the current pressurized tower to become a five-tower three-effect rectification process, or using heat pump technology. The five-tower rectification modification mode directly leads to other problems such as site limitation, increased tower investment, insufficient safety distance, etc. For heat pump rectification, there are also engineering problems such as increased equipment investment and expansion of the power distribution station.

[0005] The current three-tower three-effect technology and improved three-tower three-effect technology have difficulties in meeting the needs of expansion and energy saving for manufacturers with small tower diameters. In addition, due to the reduced difficulty of separation of methanol and water, and methanol and ethanol under negative pressure, energy consumption can be significantly reduced, thus having engineering advantages. In summary, the overhead heat of the atmospheric tower is fully utilized, and new coupled devices and coupling levels are added, which are expected to become an important tool for energy saving and carbon reduction. SUMMARY

[0006] Therefore, the present application aims to provide a four-tower forward and reverse mixed flow four-effect crude methanol refining process system and method, which can maximize the reasonable distribution and utilization of heat of the overhead gas phase material of the atmospheric distillation tower, and effectively reduce the energy consumption of the methanol distillation system.

[0007] To achieve the above-mentioned purposes, the technical scheme of the present application is as follows:

[0008] A four-tower forward and reverse mixed flow four-effect crude methanol refining process method, which makes the materials taken out from the bottoms of the pre-distillation tower, the negative pressure distillation tower and the pressurized distillation tower enter the negative pressure distillation tower, the pressurized distillation tower and the atmospheric distillation tower, respectively; the material taken out from the top of the pressurized distillation tower provides heat for at least one reboiler at the bottom of the atmospheric distillation tower; and the material taken out from the top of the atmospheric distillation tower provides heat for at least one reboiler at the bottom of the pre-distillation tower and at least one reboiler at the bottom of the negative pressure distillation tower, respectively.

[0009] The material taken out from the top of the pressurized distillation tower provides heat for at least one reboiler at the bottom of the atmospheric distillation tower, and then the non-condensed gas is combined with the material taken out from the top of the atmospheric distillation tower, which provides heat for at least one reboiler at the bottom of the pre-distillation tower and at least one reboiler at the bottom of the negative pressure distillation tower, respectively.

[0010] The heat distribution of the material taken out from the top of the atmospheric distillation tower first meets the heat requirement of the reboiler at the bottom of the negative pressure distillation tower, and then meets the heat requirement of the reboiler at the bottom of the pre-distillation tower.

[0011] Specifically, crude methanol enters the pre-distillation tower, light components and a small amount of gaseous methanol are taken out from the top of the pre-distillation tower, and the water-containing methanol material taken out from the bottom of the pre-distillation tower enters the negative pressure distillation tower; the refined methanol material is taken out from the top of the negative pressure distillation tower, and the water-containing methanol material taken out from the bottom of the negative pressure distillation tower enters the pressurized distillation tower; the refined methanol material is taken out from the top of the pressurized distillation tower, provides heat for at least one reboiler at the bottom of the atmospheric distillation tower, and is divided into three streams: one stream returns to the pressurized distillation tower, one stream is the refined methanol material, and one stream is the non-condensed gas combined with the refined methanol material taken out from the top of the atmospheric distillation tower or taken out and treated through other ways; the water-containing methanol material is taken out from the bottom of the pressurized distillation tower and enters the atmospheric distillation tower; the refined methanol material taken out from the top of the atmospheric distillation tower is divided into three streams: one stream provides heat for at least one reboiler at the bottom of the pre-distillation tower, one stream provides heat for at least one reboiler at the bottom of the negative pressure distillation tower, and one stream directly takes out the refined methanol material; and the waste water material is taken out from the bottom of the atmospheric distillation tower.

[0012] Further, the parameters of the pre-distillation tower, the negative pressure distillation tower, the pressurized distillation tower and the atmospheric distillation tower are shown in Table 1.

[0013] Further, the feed composition of the crude methanol is: methanol 80% to 96%, light component content 0.8% to 2.5%, water content 2.0% to 13%. The methanol content in the gas phase material taken out from the top of the pre-distillation column is 60-65w%, the methanol content in the aqueous methanol solution taken out from the bottom is 70-85w%; the methanol content in the gas phase material taken out from the top of the negative pressure distillation column is 99.99-9.995w%, the methanol content in the aqueous methanol solution taken out from the bottom is 70-85w%; the methanol content in the gas phase material taken out from the top of the pressurized distillation column is 99.995-99.999w%, the methanol content in the aqueous methanol solution taken out from the bottom is 60-68w%; the methanol content in the gas phase material taken out from the top of the atmospheric distillation column is 99.994-99.995w%, the methanol content in the aqueous methanol solution taken out from the bottom is 50-100ppm.

[0014] Further, the gas phase material taken out from the top of the pre-distillation column is subjected to gas-liquid separation after at least two condensation coolings, the separated liquid is returned to the pre-distillation column as reflux liquid, and the separated gas is combined with the non-condensable gas after at least two condensations and sent to a subsequent treatment system.

[0015] Further, when the material taken out from the top of the atmospheric distillation column is heated by at least one reboiler at the bottom of the pre-distillation column and at least one reboiler at the bottom of the negative pressure distillation column, the material taken out from the top of the atmospheric distillation column passes through a vertical buffer tank respectively, and is connected to the hot side of the reboilers to be heated respectively in a circulating manner, so as to improve the safety and stability of heat exchange.

[0016] Further, before the material taken out from the top of the atmospheric distillation column is heated by at least one reboiler at the bottom of the pre-distillation column, the material is heated by compression.

[0017] Further, after the material taken out from the top of the atmospheric distillation column is heated by at least one reboiler at the bottom of the pre-distillation column and at least one reboiler at the bottom of the negative pressure distillation column, the refined methanol material is combined with the refined methanol material directly taken out from the top of the atmospheric distillation column after at least sequential condensation coolings, and then the combined material is taken out as refined methanol product after at least one condensation cooling.

[0018] Further, the refined methanol material taken out from the top of the negative pressure distillation column is subjected to at least one condensation cooling, the non-condensable gas is sent to a subsequent treatment system, and a part of the liquid phase is returned to the negative pressure distillation column and a part is taken out as refined methanol product.

[0019] Further, the atmospheric distillation column also takes out fusel alcohol from the middle and lower part of the column body.

[0020] The application also provides a four-tower forward-backward mixed flow four-effect crude methanol refining process system, which comprises a pre-refining tower, a negative pressure refining tower, a pressurized refining tower and an atmospheric pressure refining tower.

[0021] The hot side outlet of the reboiler at the bottom of the atmospheric pressure refining tower connected with the overhead outlet of the pressurized refining tower is connected with the pressurized reflux tank, and the gas phase outlet of the pressurized reflux tank is connected with the overhead outlet of the atmospheric pressure refining tower.

[0022] The pre-refining tower is provided with a crude methanol inlet and an overhead light component outlet, and the bottom material outlet of the pre-refining tower is connected with the tower body inlet of the negative pressure refining tower; the negative pressure refining tower is provided with an overhead refined methanol outlet, and the bottom material outlet of the negative pressure refining tower is connected with the tower body inlet of the pressurized refining tower; the overhead refined methanol outlet of the pressurized refining tower and the pressurized reflux tank are jointly connected with the hot side of at least one reboiler at the bottom of the atmospheric pressure refining tower, the liquid phase outlet of the pressurized reflux tank is also connected with a refined methanol product outlet pipeline, the gas phase outlet of the pressurized reflux tank is connected with the overhead refined methanol outlet of the atmospheric pressure refining tower; the overhead refined methanol outlet of the atmospheric pressure refining tower is divided into three paths, one path and the atmospheric pressure reflux tank are jointly connected with the hot side of at least one reboiler at the bottom of the pre-refining tower directly or indirectly, one path and the atmospheric pressure reflux tank are jointly connected with the hot side of at least one reboiler at the bottom of the negative pressure refining tower directly or indirectly, and one path is connected with the atmospheric pressure reflux tank without passing through or passing through at least one condensing cooler.

[0023] Further, the tower body inlets of the pre-refining tower, the negative pressure refining tower, the pressurized refining tower and the atmospheric pressure refining tower are all located in the middle-lower part of the tower body.

[0024] Further, the overhead light component outlet of the pre-refining tower is sequentially connected with at least two condensing coolers, a pre-tower gas-liquid separator and a pre-tower reflux tank, wherein each condensing cooler before the last one is also provided with a pipeline in communication with the pre-tower reflux tank, the pre-tower reflux tank is also provided with at least one pipeline connected with the pipeline between adjacent condensing coolers, and the last condensing cooler and the pre-tower gas-liquid separator are also respectively provided with a gas phase outlet connected with a flare system.

[0025] Further, the overhead outlets of the atmospheric pressure refining tower are indirectly connected with the hot sides of at least one reboiler at the bottom of the pre-refining tower and at least one reboiler at the bottom of the negative pressure refining tower through a vertical buffer tank.

[0026] Further, one of the overhead outlet of the atmospheric rectification tower is firstly connected with a compressor, and then connected with the hot side of at least one reboiler at the bottom of the pre-rectification tower.

[0027] Further, the liquid phase outlet of the pressurized reflux tank is connected with a product pipeline of refined methanol through at least one condensing cooler.

[0028] Further, the overhead refined methanol outlet of the negative pressure rectification tower is sequentially connected with at least one condensing cooler and a negative pressure reflux tank, the negative pressure reflux tank is further provided with a liquid phase outlet connected with a product pipeline of refined methanol through at least one condensing cooler, and the negative pressure reflux tank is further provided with a gas phase outlet connected with a post-processing system through at least one condensing cooler.

[0029] Further, the overhead outlet of the atmospheric rectification tower is sequentially connected with at least one condensing cooler and an atmospheric reflux tank, and the atmospheric reflux tank is further provided with a liquid phase outlet connected with a product pipeline of refined methanol through at least one condensing cooler.

[0030] Further, the bottom of the atmospheric rectification tower is provided with a waste water outlet, and the lower part of the tower body is provided with a fusel outlet.

[0031] Compared with the prior art, the system and method of the present application have the advantages and positive effects that:

[0032] (1) In the present application, the heat at the top of the atmospheric tower is utilized twice in two ways, forming a quasi-four-effect heat energy utilization effect, which can maximize the rational distribution and utilization of the heat of the gas phase material at the top of the atmospheric rectification tower, and effectively reduce the energy consumption of the methanol rectification system.

[0033] (2) In the present application, all heat sources of the pre-rectification tower, the negative pressure rectification tower and the atmospheric rectification tower come from the methanol steam at the top of the pressurized rectification tower, and the heat flow at the bottom of the pressurized rectification tower is utilized in multiple stages, so that the comprehensive energy consumption per ton of refined methanol can be reduced to 0.61 tons of steam, which is reduced by 0.24-0.29 tons of steam compared with 0.85-0.90 tons of steam consumed by the three-tower three-effect rectification.

[0034] (3) Since the capacity of the pressurized tower is different in different factories, the diameter of some equipment, the heat exchange area of the reboiler and the gas-liquid flux of the tower internals are limited, and the implementation difficulty of the three-tower three-effect modification scheme is relatively large; compared with the traditional three-tower parallel flow double-effect process and the three-tower three-effect rectification tower process, the four-tower parallel and reverse flow four-effect crude methanol refining process method of the present application can greatly reduce the implementation difficulty of the project modification by simply modifying one negative pressure rectification tower and two negative pressure tower reboilers and one pre-tower reboiler, and effectively improve the energy saving level of the existing factory. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the overall schematic diagram of a specific structure of the present application.

[0036] Figure 2 is the partial enlarged view of the pre-distillation column and the pressurized distillation column part of Figure 1

[0037] Figure 3 is the partial enlarged view of the atmospheric distillation column part of Figure 1

[0038] Figure 4 is the partial enlarged view of the negative pressure distillation column part of Figure 1 DETAILED DESCRIPTION

[0039] The technical solutions of the present application are further described below in combination with the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application. In addition, to help fully understand, a large number of details are disclosed in the embodiments of the present application, but should not be regarded as the only embodiment of the present application deviating from the main inventive concept, and become undue limitations.

[0040] As shown in Figure 1 the present application is a four-tower forward-backward mixed flow four-effect crude methanol refining process system, which comprises a pre-distillation column T101, a negative pressure distillation column T103, a pressurized distillation column T102 and an atmospheric distillation column T104. The bottom discharge port of each column of the pre-distillation column T101, the negative pressure distillation column T103 and the pressurized distillation column T102 is respectively connected with the column body feed port of the negative pressure distillation column T103, the pressurized distillation column T102 and the atmospheric distillation column T104. The top sampling outlet of the pressurized distillation column T102 is cyclically connected with the hot side of at least one reboiler at the bottom of the atmospheric distillation column T104. The top sampling outlet of the atmospheric distillation column T104 is respectively cyclically connected with the hot side of at least one reboiler at the bottom of the pre-distillation column T101 and the hot side of at least one reboiler at the bottom of the negative pressure distillation column T103.

[0041] ​​​Through the connection of the above process system, when the system is running smoothly, the heat at the bottom of the pressurized rectification tower T102 can be utilized in multiple stages. Firstly, the heat of the vapor-liquid heat transfer in the pressurized rectification tower T102 itself is utilized in the first stage by the refined methyl alcohol collected at the top of the tower. Then, the heat of the refined methyl alcohol collected at the top of the pressurized rectification tower T102 is all supplied to the reboiler at the bottom of the atmospheric rectification tower T104, and the heat is utilized in the second stage in the atmospheric rectification tower T104. Then, the heat of the refined methyl alcohol collected at the top of the atmospheric rectification tower T104 (which can be further utilized together with the residual heat of the non-condensable gas after the utilization of the reboiler at the bottom of the atmospheric rectification tower T104) is utilized in the third stage by the reboiler at the bottom of the pre-rectification tower T101 and the negative pressure rectification tower T103, respectively, forming a further optimized heat utilization scheme, which is beneficial to simplify the system modification scheme, improve the yield, and further reduce the energy consumption of the crude methyl alcohol refining. Through the heat energy utilization and distribution of the present application, the comprehensive energy consumption of each ton of refined methyl alcohol can be reduced to less than 0.65 tons of steam, and as low as 0.61 tons of steam. However, in the existing process method, the comprehensive energy consumption of each ton of refined methyl alcohol is basically not less than 0.7 tons of steam.

[0042] As a further optimization of the above process system, the hot side outlet of the reboiler at the bottom of the atmospheric rectification tower T104 connected with the top outlet of the pressurized rectification tower T102 is connected with the pressurized reflux tank V104, and the gas phase outlet of the pressurized reflux tank V104 is connected with the top outlet of the atmospheric rectification tower T104. Thus, after the heat at the top of the pressurized rectification tower T102 is utilized by the reboiler at the bottom of the atmospheric rectification tower T104, the heat of the non-condensable gas and the heat of the refined methyl alcohol collected at the top of the atmospheric rectification tower T104 are reused again.

[0043] As a further optimization of the above process system, the heat of the refined methyl alcohol collected at the top of the atmospheric rectification tower T104 (or the non-condensable gas after the heat at the top of the pressurized rectification tower T102 is utilized by the reboiler at the bottom of the atmospheric rectification tower T104) is distributed to first meet the heat requirement of the reboiler at the bottom of the negative pressure rectification tower T103, and then to meet the heat requirement of the reboiler at the bottom of the pre-rectification tower T101. However, in general, the heat of both can be fully met.

[0044] The further detailed working process is as follows:

[0045] The crude methanol (material M00) is preheated by the pre-column preheater E104 and enters the pre-distillation column T101. Through the gas-liquid full contact of the 52 high-efficiency DVST trays in the column or several sections of packing, the light components and a small part of the methanol in the crude methanol are taken out from the top of the column in a gaseous form (material M10), which is sequentially connected to the gas phase inlet of the pre-column first condensing cooler E105 and the pre-column second condensing cooler E106 and the pre-column gas-liquid separator V103. The non-condensable gas outlets (CO, CO2, H2, N2, CH4, multi-carbon alkanes, ethyl acetate, dimethyl ether, etc.) of the pre-column second condensing cooler E106 and the pre-column gas-liquid separator V103 enter the subsequent post-processing and flare system at 40°C, 0.12 MPa (A), and 3.0-50.0 m3 / h. The condensate outlets of the pre-column first condensing cooler E105 and the pre-column gas-liquid separator V103 are connected to enter the pre-column reflux tank V102. After being pressurized by the pre-column reflux pump P103, it enters the top 52 trays of the pre-distillation column T101 for reflux. The top of the pre-distillation column T101 is provided with interlocking control devices L for the flare system and the pre-column reflux tank V102, thereby controlling the amount of methanol taken out. The connecting pipeline between the pre-column first condensing cooler E105 and the pre-column second condensing cooler E106 is also connected with the pre-column reflux tank V102 to release excess gas from the pre-column reflux tank V102. 3

[0046] Three reboilers are arranged at the bottom of the pre-distillation column T101, namely the pre-column first reboiler E101, the pre-column second reboiler E102, and the pre-column third reboiler E103. The pre-column second reboiler E102 and the pre-column third reboiler E103 can be heated by conventional external steam, which can provide sufficient heat energy supply during equipment startup or unstable operation and other special situations. The pre-column first reboiler E101 is heated by one of the vapors taken from the top of the atmospheric distillation column T104 (material M501) after being pressurized by the compressor C101 to 70 KPa (material M20). A pre-column vertical buffer tank V101 is connected in circulation on the hot side of the pre-column first reboiler E101. One of the vapors taken from the top of the atmospheric distillation column T104 is pressurized by the compressor C101 and enters the pre-column vertical buffer tank V101, and then flows out after being circulated by the pre-column heat exchange pump P101 and connected by the pipeline to enter the atmospheric column reflux tank V106 of the atmospheric distillation column T104. The indirect heat exchange between the pre-column vertical buffer tank V101 and the pre-column first reboiler E101 improves the safety and stability of the heat exchange of the pressurized vapor. The pre-column vertical buffer tank V101 and the pipeline after heat exchange are provided with interlocking control devices L to control the flow of the material.

[0047] ​After the removal of light components in the pre-distillation column T101, the water-containing methanol solution is collected by the pre-column bottom pump P102 and enters the negative pressure rectification column T103. In the negative pressure rectillation column T103, the gas-liquid exchanges heat and mass through high-efficiency trays or fillers, and the water, ethanol, fusel alcohol and the like in the methanol are fully removed. The gas phase (material M30) at the top of the column enters the negative pressure column first condenser E120 for condensation and cooling, and then enters the negative pressure column reflux tank V107. The non-condensable gas enters the negative pressure column second condenser E121 for further condensation. Most of the methanol is condensed and then refluxed into the negative pressure column reflux tank V107. A small amount of non-condensable gas enters the post-processing system for subsequent processing. The liquid in the negative pressure column reflux tank V107 is pressurized by the negative pressure column reflux pump P109 and then returned to the top of the negative pressure rectification column T103 as reflux liquid. Another pipeline controlled by the interlocking control device L controls the flow rate of the liquid from the negative pressure column reflux tank V107 into the negative pressure column refined methanol condenser E119, which is cooled by circulating water and then combined with the refined methanol collected from the top of the atmospheric distillation column T104 and cooled, and then transported to the refined methanol tank area. An interlocking control device L is also provided between the top of the negative pressure rectification column T103 and the reflux pipeline to control the reflux flow rate.

[0048] The negative pressure rectification column T103 is provided with two reboilers, namely the negative pressure column first reboiler E117 and the negative pressure column second reboiler E118. The negative pressure column second reboiler E118 can be heated by conventional external steam, which can provide sufficient heat energy supply during equipment start-up or unstable operation and the like. The negative pressure column first reboiler E117 is heated by one of the steam (material M502) collected from the top of the atmospheric distillation column T104. A negative pressure column vertical buffer tank V108 is connected in series with the heat side of the negative pressure column first reboiler E117. One of the steam collected from the top of the atmospheric distillation column T104 enters the negative pressure column vertical buffer tank V108 and then flows out through the negative pressure column heat exchange circulating pump P110 and enters the atmospheric column reflux tank V106 of the atmospheric distillation column T104 through the pipeline connection. The indirect heat exchange between the negative pressure column vertical buffer tank V108 and the negative pressure column first reboiler E117 improves the safety of steam heat exchange and the stability of heat exchange heat. An interlocking control device L is provided between the negative pressure column vertical buffer tank V108 and the pipeline connected after heat exchange to control the flow rate of the material flowing through the heat exchange.

[0049] The bottom material of the negative pressure rectification tower T103 is sent to the pressurized tower preheater E107 through the tower kettle pump P108 of the negative pressure tower, and after preheating, it is introduced into the middle and lower tower plate of the pressurized rectification tower T102. A interlock control device L is arranged between the bottom material of the negative pressure rectification tower T103 and the outflow pipeline, which is used to control the flow of the bottom material. The hot side of the pressurized tower preheater E107 (the side through which external steam is introduced to heat the material) and the feed pipeline of the pressurized rectification tower T102 are also provided with an interlock control device L, which is used to control the flow of heating steam, so that the material is preheated to a sufficient temperature.

[0050] The gas-liquid in the pressurized rectification tower T102 is subjected to gas-liquid mass transfer and heat transfer through high-efficiency DVST tower plates or fillings. The refined methanol at the top is introduced into the hot side of the first reboiler E112 of the atmospheric tower through the pipeline (material M40) to exchange heat. After heat exchange, the condensed liquid of the refined methanol returns to the pressurized reflux tank V104. One of the materials in the pressurized reflux tank V104 is pressurized by the pressurized reflux pump P104 and returned to the top of the pressurized rectification tower T102 as reflux liquid. The other is sequentially cooled by the first condensing cooler E110 and the second condensing cooler E111 of the pressurized tower, and then combined with the refined methanol cooled and collected from the top of the atmospheric rectification tower T104, and transported to the refined methanol tank area. Further, the gas phase outlet of the pressurized reflux tank V104 can be connected with the top collection outlet of the atmospheric rectification tower T104. Thus, the heat is reused. In some schemes, the gas phase outlet of the pressurized reflux tank V104 can also not be connected with the top collection outlet of the atmospheric rectification tower T104, but the part of the gas phase is further processed through other ways, such as combustion, solution absorption, etc. An interlock control device L is arranged between the top of the pressurized rectification tower T102 and the reflux pipeline to control the reflux flow. An interlock control device L is also arranged between the pressurized reflux tank V104 and the output pipeline of the second condensing cooler E111 of the pressurized tower to control the output flow.

[0051] Two reboilers are arranged at the bottom of the pressurized rectification tower T102, which are the first reboiler E108 and the second reboiler E109 of the pressurized tower, both of which are heated by external steam. An interlock control device L is arranged between the hot side of the first reboiler E108 and / or the second reboiler E109 of the pressurized tower and the steam conveying pipeline to control the flow of heating steam. The water-containing methanol solution collected from the bottom of the pressurized rectification tower T102 is introduced into the atmospheric rectification tower T104 through the interlock control device between the bottom of the pressurized rectification tower T102 and the collection pipeline to control the collection flow.

[0052] In the atmospheric distillation column T104, the gas-liquid passes through high-efficiency trays or fillings for gas-liquid heat and mass transfer, and the water, ethanol, fusel alcohol and the like in the methanol are fully removed. The gaseous phase (material M50) taken out from the top of the column can be separately subjected to subsequent treatment, or can be combined with the gaseous phase (total amount is very small, and has little effect on the total amount of the material M50) output from the pressurized reflux tank V104 for subsequent treatment. The gaseous phase taken out from the top of the atmospheric distillation column T104 (or the combination of the gaseous phase from the pressurized reflux tank V104) is divided into three streams: one stream (material M502) is preferentially transported to the negative pressure column vertical buffer tank V108, and is connected to the heat side of the first reboiler E117 of the negative pressure column for heat supply, so as to reduce or replace the steam heat supply of the other reboilers at the bottom of the negative pressure distillation column T103. Then, the negative pressure column heat exchange circulating pump P110 flows out, and is connected into the atmospheric distillation column T104 through the pipeline connection. One stream (material M501) is secondly preferentially transported to the compressor C101 for pressurization, and then enters the pre-column vertical buffer tank V101, and is connected to the heat side of the first reboiler E101 of the pre-column for heat supply, so as to reduce or replace the steam heat supply of the other reboilers at the bottom of the pre-distillation column T101. Then, the pre-column heat exchange circulating pump P101 flows out, and is connected into the atmospheric distillation column T104 through the pipeline connection. The other stream (material M503) enters the atmospheric column condenser E115 for condensation and cooling, and then enters the atmospheric reflux tank V106. The liquid in the atmospheric reflux tank V106 is pressurized by the atmospheric reflux pump P106, one stream (material M60) returns to the top of the atmospheric distillation column T104 as reflux liquid, and the other stream enters the atmospheric column fine methanol condenser E116, is cooled by circulating water, and is combined with the fine methanol cooled by the pressurized column second condenser E111 and the fine methanol cooled by the negative pressure column fine methanol condenser E119, and is transported to the fine methanol tank area. The atmospheric distillation column T104 and the reflux pipeline are provided with interlocking control devices L to control the reflux flow. The atmospheric reflux tank V106 and the pipeline connected to the atmospheric column fine methanol condenser E116 are provided with interlocking control devices L to control the fine methanol output flow.

[0053] The lower part of the atmospheric distillation column T104 is provided with a fusel alcohol outlet. The enriched ethanol and other fusel alcohols pass through the fusel alcohol condenser E114 and the fusel alcohol buffer tank V105 (material M70), and are transported to the fusel alcohol tank area by the fusel alcohol outlet pump P107. The fusel alcohol buffer tank V105 and the fusel alcohol outlet pipeline are provided with interlocking control devices L to control the fusel alcohol outlet flow.

[0054] The waste water at the bottom of the atmospheric rectification tower T104 is pressurized by the atmospheric waste water pump P105, and then cooled by the circulating water of the waste water condensing cooler E113, so that the methanol content is reduced to less than 0.1%, and the COD is reduced to less than 200. After being tested and qualified, the waste water is transported to a sewage treatment plant for biochemical treatment. A linkage control device L is arranged on the waste water outlet pipeline of the atmospheric rectification tower T104 to control the waste water outlet flow.

[0055] The linkage control device in the present application can be selected according to the control needs, and has suitable functions, including but not limited to a liquid level linkage control device, a temperature linkage control device, a pressure linkage control device, etc.

[0056] In the above process, one preferred control parameter range of the pre-rectification tower T101, the negative pressure rectification tower T103, the pressurized rectification tower T102 and the atmospheric rectification tower T104 can be as shown in Table 1:

[0057] Table 1

[0058] Apparatus Theoretical plate number Overhead temperature °C Overhead pressure MPa A Reflux ratio Bottom temperature °C Bottom pressure MPa A Pre-fractionator column T101 37-45 63.5-72.5 0.102-0.132 3.8-5.9 73.5-82.1 0.122-0.152 Vacuum fractionator column T103 50-65 54.9-62.5 0.052-0.083 1.2-1.6 60.5-64.8 0.067-0.098 Pressurized fractionator column T102 54-58 120.2-128.5 0.513-0.857 2.3-3.2 125.6-135.8 0.553-0.897 Atmospheric fractionator column T104 56-65 70.6-82.9 0.102-0.195 1.8-2.3 111.5-123.6 0.152-0.245

[0059] The composition of the crude methanol M00 in the present application can be within the range of compositions suitable for conventional systems, and exemplary general compositions include: methanol: 80% to 96%, light component content: 0.8% to 2.5%, and water content: 2.0% to 13.0%. The methanol content in the gas phase material collected at the top of the pre-rectification tower T101 is 60-65 w%, and the methanol content in the aqueous methanol solution collected at the bottom is 70-85 w%; the methanol content in the gas phase material collected at the top of the negative pressure rectification tower T103 is 99.99-9.995 w%, and the methanol content in the aqueous methanol solution collected at the bottom is 70-85 w%; the methanol content in the gas phase material collected at the top of the pressurized rectification tower T102 is 99.995-99.999 w%, and the methanol content in the aqueous methanol solution collected at the bottom is 60-68 w%; and the methanol content in the gas phase material collected at the top of the atmospheric rectification tower T104 is 99.994-99.995 w%, and the methanol content in the aqueous methanol solution collected at the bottom is 50-100 ppm.

[0060] As two specific embodiments of the above process, the compositions of M00-M70 can be as shown in Table 2 and Table 3, respectively:

[0061] Table 2 Embodiment 1

[0062] Stream number M00 M10 M20 M30 M40 M50 M501 M502 M503 M60 M70 Phase state Liquid Vapor Vapor Vapor Vapor Vapor Vapor Vapor Vapor Liquid Liquid Temperature °C 40 70.55861 79.71371 54.94491 123.1892 70.99115 70.99115 70.99115 70.99115 70.99081 40 Pressure KG / CM2 5.0986 1.1237 1.8256 0.7 7.138 1.3256 1.3256 1.3256 1.3256 1.3256 1.498165 Mass flow rate KG / HR 96720 46002.34 52000 45588.3 105838.7 101122.3 52000 46000 3122.272 32620.09 2000.07 Volume flow rate M3 / HR 119.1821 56.85412 65.35918 57.30009 133.029 127.1013 65.35918 57.81773 3.924407 41.00042 2.150521 Hydrogen 0.0011 0.002453 1.31E-18 6.38E-11 4.49E-11 1.31E-18 1.31E-18 1.31E-18 1.31E-18 1.31E-18 0 Carbon monoxide 0.0028 0.005988 0 6.11E-13 4.30E-13 0 0 0 0 0 0 Carbon dioxide 2.170098 5.42744 2.25E-14 1.84E-06 1.29E-06 2.25E-14 2.25E-14 2.25E-14 2.25E-14 2.25E-14 0 Methane 0.0139 0.030321 0 4.80E-11 3.38E-11 0 0 0 0 0 0 Ethane 0.005 0.013691 3.99E-15 2.71E-08 1.91E-08 3.99E-15 3.99E-15 3.99E-15 3.99E-15 3.99E-15 0 Nitrogen 0.0105 0.022436 0 1.87E-12 1.32E-12 0 0 0 0 0 0 Methanol 87.94961 86.30091 99.99462 99.99043 99.98715 99.99462 99.99462 99.99462 99.99462 99.99462 16.58963 Ethanol 0.15 4.95E-07 0.005 0.002137 0.007318 0.005 0.005 0.005 0.005 0.005 7.033674 Dimethyl ether 0.04 0.091664 1.58E-17 1.41E-08 9.91E-09 1.58E-17 1.58E-17 1.58E-17 1.58E-17 1.58E-17 0 Pentane 0.006667 0.01557 6.28E-17 1.86E-08 1.31E-08 6.28E-17 6.28E-17 6.28E-17 6.28E-17 6.28E-17 0 Isopentane 0.006667 0.015498 6.73E-17 1.72E-08 1.21E-08 6.73E-17 6.73E-17 6.73E-17 6.73E-17 6.73E-17 0 Octane 0.006667 0.016635 5.08E-15 1.32E-07 9.29E-08 5.08E-15 5.08E-15 5.08E-15 5.08E-15 5.08E-15 0 Isobutanol 0.029249 1.83E-19 2.74E-17 3.31E-17 5.05E-19 2.74E-17 2.74E-17 2.74E-17 2.74E-17 2.74E-17 1.41445 Propanol 0.029249 1.21E-16 1.15E-13 3.69E-17 1.00E-14 1.15E-13 1.15E-13 1.15E-13 1.15E-13 1.15E-13 1.41445 n-Butanol 0.029249 1.25E-22 9.64E-22 8.33E-18 4.82E-24 9.64E-22 9.64E-22 9.64E-22 9.64E-22 9.64E-22 1.41445 Pentanol 0.029249 0 0 2.00E-18 0 0 0 0 0 0 1.41445 Ethyl acetate 0.028 0.727541 5.75E-06 0.001642 0.001152 5.75E-06 5.75E-06 5.75E-06 5.75E-06 5.75E-06 9.38E-16 Acetone 0.007 0.176167 0.000364 0.005785 0.003817 0.000364 0.000364 0.000364 0.000364 0.000364 2.76E-11 Water 9.484994 7.15369 5.93E-06 2.63E-08 0.000558 5.93E-06 5.93E-06 5.93E-06 5.93E-06 5.93E-06 70.7189

[0063] Table 3 Embodiment 2

[0064] Stream number M00 M10 M20 M30 M40 M50 M501 M502 M503 M60 M70 Phase state Liquid Vapor Vapor Vapor Vapor Vapor Vapor Vapor Vapor Liquid Liquid Temperature °C 40 70.55853518 87.88356316 54.94490818 123.188539 81.21541282 81.21541282 81.21541282 81.21541282 81.21508786 40 Pressure KG / CM2 5.0986 1.1237 2.4256 0.7 7.138 1.9256 1.9256 1.9256 1.9256 1.9256 2.09816462 Mass flow rate KG / HR 96720 45999.99814 52000 45588.3 112248.5001 102497.8881 52000 46000 4497.888067 32030.58999 2000.01276 Volume flow rate M3 / HR 119.1821489 56.85095942 65.35917273 57.30008747 141.0855759 128.8303302 65.35917273 57.81772973 5.653427752 40.25947815 2.3013521 Hydrogen 0.001100082 0.002453185 1.58E-18 6.38E-11 4.50E-11 1.58E-18 1.58E-18 1.58E-18 1.58E-18 1.58E-18 0 Carbon monoxide 0.002799833 0.005988662 0 6.11E-13 4.30E-13 0 0 0 0 0 0 Carbon dioxide 2.170098313 5.427689143 2.36E-14 1.84E-06 1.29E-06 2.36E-14 2.36E-14 2.36E-14 2.36E-14 2.36E-14 0 Methane 0.013899911 0.030322412 0 4.80E-11 3.38E-11 0 0 0 0 0 0 Ethane 0.004999998 0.013691676 4.22E-15 2.72E-08 1.91E-08 4.22E-15 4.22E-15 4.22E-15 4.22E-15 4.22E-15 0 Nitrogen 0.010500409 0.022436851 0 1.87E-12 1.32E-12 0 0 0 0 0 0 Methanol 87.94961028 86.29819745 99.99459339 99.99043329 99.99163977 99.99459339 99.99459339 99.99459339 99.99459339 99.99459339 46.0519825 Ethanol 0.149999935 4.95E-07 0.004999928 0.002137041 0.003142144 0.004999928 0.004999928 0.004999928 0.004999928 0.004999928 7.10229173 Dimethyl ether 0.039999983 0.09166911 1.72E-17 1.41E-08 9.92E-09 1.72E-17 1.72E-17 1.72E-17 1.72E-17 1.72E-17 0 Pentane 0.006666664 0.015571301 7.26E-17 1.86E-08 1.31E-08 7.26E-17 7.26E-17 7.26E-17 7.26E-17 7.26E-17 0 Isopentane 0.006666664 0.015498589 7.68E-17 1.72E-08 1.21E-08 7.68E-17 7.68E-17 7.68E-17 7.68E-17 7.68E-17 0 Octane 0.006666664 0.016635769 5.89E-15 1.32E-07 9.29E-08 5.89E-15 5.89E-15 5.89E-15 5.89E-15 5.89E-15 0 Isobutanol 0.029249367 1.83E-19 2.72E-16 2.89E-21 1.67E-19 2.72E-16 2.72E-16 2.72E-16 2.72E-16 2.72E-16 1.4144894 Propanol 0.029249367 1.21E-16 6.73E-13 2.27E-19 3.32E-15 6.73E-13 6.73E-13 6.73E-13 6.73E-13 6.73E-13 1.41448939 n-Butanol 0.029249367 1.25E-22 1.77E-20 5.82E-25 1.66E-24 1.77E-20 1.77E-20 1.77E-20 1.77E-20 1.77E-20 1.41449033 Pentanol 0.029249367 0 5.77E-29 9.48E-22 0 5.77E-29 5.77E-29 5.77E-29 5.77E-29 0 1.41449036 Ethyl acetate 0.028000401 0.729810735 5.64E-06 0.001642316 0.001151909 5.64E-06 5.64E-06 5.64E-06 5.64E-06 5.64E-06 2.94E-15 Acetone 0.006999583 0.17618984 0.000373286 0.00578528 0.003815517 0.000373286 0.000373286 0.000373286 0.000373286 0.000373286 4.27E-10 Water 9.484993813 7.153844779 2.78E-05 2.63E-08 0.000249219 2.78E-05 2.78E-05 2.78E-05 2.78E-05 2.78E-05 41.1877663

[0065] The scheme of the embodiments one and two can be used to transform the traditional three-tower countercurrent double-effect process and three-tower three-effect rectification tower process. 3 In a certain methanol plant, the traditional three-tower countercurrent double-effect process is used, the feed quantity is 105 m

[0066] The protection scope of the present application is not limited to this, any person skilled in the art can easily make changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A four-tower forward-backward mixed flow four-effect crude methanol refining process method, the bottom effluent of each tower of a pre-refining tower (T101), a negative pressure rectifying tower (T103) and a pressurized rectifying tower (T102) is respectively introduced into the negative pressure rectifying tower (T103), the pressurized rectifying tower (T102) and an atmospheric pressure rectifying tower (T104); the overhead product of the pressurized rectifying tower (T102) provides heat for at least one reboiler at the bottom of the atmospheric pressure rectifying tower (T104); the overhead product of the atmospheric pressure rectifying tower (T104) respectively provides heat for at least one reboiler at the bottom of the pre-refining tower (T101) and at least one reboiler at the bottom of the negative pressure rectifying tower (T103); The heat distribution of the overhead product of the atmospheric pressure rectifying tower (T104) prioritizes meeting the heat needs of the reboiler at the bottom of the negative pressure rectifying tower (T103), and then meeting the heat needs of the reboiler at the bottom of the pre-refining tower (T101); The pre-refining tower (T101) has a theoretical plate number of 37-45, a top temperature of 63.5-72.5℃, a top pressure of 0.102-0.132 MPa A, a reflux ratio of 3.8-5.9, a bottom temperature of 73.5-82.1℃ and a bottom pressure of 0.122-0.152 MPa A; The negative pressure rectifying tower (T103) has a theoretical plate number of 50-65, a top temperature of 54.9-62.5℃, a top pressure of 0.052-0.083 MPa A, a reflux ratio of 1.2-1.6, a bottom temperature of 60.5-64.8℃ and a bottom pressure of 0.067-0.098 MPa A; The pressurized rectifying tower (T102) has a theoretical plate number of 54-58, a top temperature of 120.2-128.5℃, a top pressure of 0.513-0.857 MPa A, a reflux ratio of 2.3-3.2, a bottom temperature of 125.6-135.8℃ and a bottom pressure of 0.553-0.897 MPa A; The atmospheric pressure rectifying tower (T104) has a theoretical plate number of 56-65, a top temperature of 70.6-82.9℃, a top pressure of 0.102-0.195 MPa A, a reflux ratio of 1.8-2.3, a bottom temperature of 111.5-123.6℃ and a bottom pressure of 0.152-0.245 MPa A.

2. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 1, wherein, The overhead product of the pressurized rectifying tower (T102) is combined with the overhead product of the atmospheric pressure rectifying tower (T104) after being heated by at least one reboiler at the bottom of the atmospheric pressure rectifying tower (T104), and then is respectively heated for at least one reboiler at the bottom of the pre-refining tower (T101) and at least one reboiler at the bottom of the negative pressure rectifying tower (T103).

3. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 1, wherein, The crude methanol enters a pre-distillation column (T101), light components and a small amount of gaseous methanol are taken from the top of the pre-distillation column (T101), and the water-containing methanol material taken from the bottom of the pre-distillation column (T101) enters a negative pressure distillation column (T103); the refined methanol material is taken from the top of the negative pressure distillation column (T103), and the water-containing methanol material taken from the bottom of the negative pressure distillation column (T103) enters a pressurized distillation column (T102); the refined methanol material is taken from the top of the pressurized distillation column (T102), and after being heated by at least one reboiler at the bottom of an atmospheric pressure distillation column (T104), the refined methanol material is divided into three streams: one stream returns to the pressurized distillation column (T102) as reflux, one stream is taken as refined methanol material, and one stream is combined with the refined methanol material taken from the top of the atmospheric pressure distillation column (T104) or taken out of the system through other ways for treatment; the water-containing methanol material taken from the bottom of the pressurized distillation column (T102) enters the atmospheric pressure distillation column (T104); the refined methanol material taken from the top of the atmospheric pressure distillation column (T104) is combined with the non-condensable gas taken from the top of the pressurized distillation column (T102) after being heated by at least one reboiler at the bottom of the atmospheric pressure distillation column (T104), and then divided into three streams: one stream is taken as refined methanol material after being heated by at least one reboiler at the bottom of the pre-distillation column (T101), one stream is taken as refined methanol material after being heated by at least one reboiler at the bottom of the negative pressure distillation column (T103), and one stream is directly taken as refined methanol material; the wastewater material is taken from the bottom of the atmospheric pressure distillation column (T104).

4. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 3, wherein, The feed composition of the crude methanol is: 80% to 96% of methanol, 0.8% to 2.5% of light components, and 2.0% to 13% of water; the methanol content in the gaseous phase material taken from the top of the pre-distillation column (T101) is 60-65 w%, and the methanol content in the water-containing methanol solution taken from the bottom of the pre-distillation column (T101) is 70-85 w%; the methanol content in the gaseous phase material taken from the top of the negative pressure distillation column (T103) is 99.99-9.995 w%, and the methanol content in the water-containing methanol solution taken from the bottom of the negative pressure distillation column (T103) is 70-85 w%; the methanol content in the gaseous phase material taken from the top of the pressurized distillation column (T102) is 99.995-99.999 w%, and the methanol content in the water-containing methanol solution taken from the bottom of the pressurized distillation column (T102) is 60-68 w%; the methanol content in the gaseous phase material taken from the top of the atmospheric pressure distillation column (T104) is 99.994-99.995 w%, and the methanol content in the water-containing methanol solution taken from the bottom of the atmospheric pressure distillation column (T104) is 50-100 ppm.

5. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 3, wherein, The gaseous phase material taken from the top of the pre-distillation column (T101) is subjected to gas-liquid separation after being condensed and cooled at least twice, the separated liquid is returned to the pre-distillation column (T101) as reflux, and the separated gas is combined with the non-condensable gas after being condensed at least twice and sent to a subsequent treatment system.

6. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 3, wherein, The overhead material of the atmospheric distillation column (T104) is heated by at least one reboiler at the bottom of the pre-distillation column (T101) and at least one reboiler at the bottom of the negative pressure distillation column (T103), respectively, and the overhead material of the atmospheric distillation column (T104) is respectively passed through a vertical buffer tank and then through the heat side of the reboiler to be heated.

7. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 3, wherein, Before the overhead material of the atmospheric distillation column (T104) is heated by at least one reboiler at the bottom of the pre-distillation column (T101), the material is heated by compression.

8. The four-column, cross-flow, four-effect, crude methanol refining process method of claim 3, wherein, After the overhead material of the atmospheric distillation column (T104) is heated by at least one reboiler at the bottom of the pre-distillation column (T101) and at least one reboiler at the bottom of the negative pressure distillation column (T103), the refined methanol material is combined with the refined methanol material directly taken from the top of the atmospheric distillation column (T104) after at least sequential condensation and cooling, and then the combined material is condensed and cooled at least once to be taken as refined methanol product; The refined methanol material taken from the top of the negative pressure distillation column (T103) is condensed and cooled at least once, and then the non-condensable gas enters the post-treatment system, and the liquid phase part flows back into the negative pressure distillation column (T103), and part of the liquid phase is taken as refined methanol product; The atmospheric distillation column (T104) also takes out fusel alcohol from the middle and lower part of the column body.

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