CN113004120A - Water-saving emission-reducing methanol thermal coupling rectification system and rectification method - Google Patents
Water-saving emission-reducing methanol thermal coupling rectification system and rectification method Download PDFInfo
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- CN113004120A CN113004120A CN202110141540.1A CN202110141540A CN113004120A CN 113004120 A CN113004120 A CN 113004120A CN 202110141540 A CN202110141540 A CN 202110141540A CN 113004120 A CN113004120 A CN 113004120A
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- C07—ORGANIC CHEMISTRY
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- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
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Abstract
The invention belongs to the technical field of rectification, relates to formaldehyde rectification energy-saving equipment and an optimized process, and particularly relates to a methanol thermal coupling rectification system and a rectification method for saving water and reducing emission. Adopt four tower structures in this system, four tower structures still install tower and scrubbing tower in advance before the recovery tower including the pressurized tower, medium-pressure tower, atmospheric tower and the recovery tower of installing in order, install the heat transfer network in the system, this heat transfer network includes multi-stage pre-heater, multi-stage pre-heater install before tower feed side in advance, the high temperature fine methanol product of pressurized tower, medium-pressure tower and atmospheric tower output gets into multi-stage pre-heater's one-level respectively as the heat source, all preheats the crude methyl alcohol raw materials of tower in advance to the input. A corresponding rectification method is extended based on the structure of the system. On one hand, the waste heat of the system is utilized, and on the other hand, the extraction mode of a small amount of fusel in the normal pressure product tower is improved, so that the energy in the system is effectively utilized, and the problem of hazardous waste discharge of the system can be solved.
Description
Technical Field
The invention belongs to the technical field of rectification, relates to formaldehyde rectification energy-saving equipment and an optimized process, and particularly relates to a methanol thermal coupling rectification system and a rectification method for saving water and reducing emission.
Background
Methanol is a very important basic chemical raw material and is a promising clean energy source. Methanol can be used for producing fine chemical products such as dimethyl ether, methane chloride, methylamine, maleates and the like, and can also be used for producing light hydrocarbon products such as ethylene, propylene and the like, and is called as the third basic organic chemical raw material except olefin and aromatic hydrocarbon. The energy condition of China is that more coal is used and less oil is used, and methanol is the 'basic stone' of coal-based chemical products, so the production scale of coal-based methanol is continuously enlarged, and the technology of coal-based methanol is vigorously developed. In recent ten years, the domestic coal chemical industry has been rapidly developed, and the development trend of the methanol production technology in the future is as follows: large-scale, low energy consumption and environment-friendly development, and simultaneously puts higher requirements on the quality of the methanol.
At present, the maximum scale of the methanol device under construction in China reaches 80 ten thousand tons per year, and the ethanol content in the methanol product is required to be less than or equal to 25ppm (even 10ppm), and the acetone content is required to be less than or equal to 10 ppm. The fusel oil which is a byproduct in the production process of the original process is listed as dangerous waste and is not allowed to be sold as a byproduct, so the improvement of the methanol refining process is urgent.
At present, the methanol rectification process is basically a three-tower process and a four-tower process (additionally provided with a methanol recovery tower) developed by Lurgi company, the four-tower process improves the methanol yield compared with the three-tower process, but the energy consumption and the product index of methanol are not improved (the ethanol content in the originally designed methanol product is up to 200ppm), and in view of the factors, new methanol energy-saving and quality-improving technologies are continuously developed at home.
Patent CN107032959A < < a heat pump and multi-effect coupling's methyl alcohol rectification method >, heat pump rectification and differential pressure thermal coupling have been combined, have utilized the latent heat of system, and four tower rectification ordinary has reduced the energy consumption, but the process flow has increased the compressor, greatly increased equipment investment and maintenance degree of difficulty, and the running cost is too high, and actual device can't adopt.
The patent CN107551586A < < a device for producing methanol by using a bulkhead tower to combine multi-effect rectification and rectification >, combines a pre-tower and an atmospheric tower in a conventional four-tower process, designs the pre-tower and the atmospheric tower into a bulkhead tower, and reserves other two towers. The process has the advantages that the equipment investment is reduced, but the design is changed, so that light components at the top of the pre-tower cannot enter a washing tower to recover methanol, a large amount of methanol enters a tail gas system, and the methanol yield is greatly reduced.
The patent CN109761751A < < a methanol thermal coupling multiple-effect rectification method and device > > provides a sequential five-tower four-effect thermal coupling rectification method, the method has the advantages that the energy consumption of methanol products can be further reduced, but the method has the disadvantages that steam with higher pressure and larger equipment investment are needed, and after the multiple-effect rectification exceeds three effects, the energy-saving effect is not obvious, and the economy is lost.
The patent CN101570446A < < a methanol multi-effect rectification process > introduces a five-tower three-effect methanol rectification process, the process realizes the most economical and feasible energy-saving means, and simultaneously considers the utilization of system waste heat and the recycling of waste water. The defects that the waste heat is not utilized in a designed gradient manner, the waste water in the kettle of the recovery tower contains salt and is directly used as washing water in a washing tower, and the quality of a methanol product is influenced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a methanol thermal coupling rectification system and an extended rectification method for saving water and reducing emission, wherein the methanol thermal coupling rectification system utilizes system waste heat, eliminates the corrosion problem of a washing tower, improves the extraction mode of a small amount of fusel in a normal pressure product tower, does not discharge dangerous waste after the system is circulated and reduces the consumption of fresh desalted water.
The technical scheme adopted by the invention is as follows:
the utility model provides a methanol thermal coupling rectification system of water conservation and emission reduction, adopts four tower structures, four tower structures include pressurization tower, medium-pressure tower, atmospheric tower and the recovery tower of installing in order, still install preceding tower and scrubbing tower before the recovery tower, its characterized in that: the system is internally provided with a heat exchange network which comprises a multi-stage preheater, wherein the multi-stage preheater is arranged in front of the feeding side of the pre-tower, high-temperature refined methanol products output by the pressurizing tower, the medium-pressure tower and the normal-pressure tower respectively enter the third stage, the second stage and the first stage of the multi-stage preheater as heat sources, and the crude methanol raw material input into the pre-tower is preheated.
Furthermore, the multi-stage preheater is in three stages, wherein the first-stage preheater is communicated with the normal pressure tower, the second-stage preheater is communicated with the medium pressure tower, and the third-stage preheater is communicated with the pressurizing tower.
Furthermore, the heat exchange network also comprises a plurality of tower body reboilers and pressurized tower heat exchangers, wherein each of the pre-tower, the pressurized tower, the medium-pressure tower, the normal-pressure tower and the recovery tower is provided with a tower body reboiler, and the pressurized tower heat exchangers are arranged between the discharge side of the pre-tower and the feed side of the pressurized tower; and (3) introducing the tower bottom liquid of the pre-tower into the pressurizing tower after heat exchange by the pressurizing tower heat exchanger, wherein steam extracted from the top of the pressurizing tower is used as a heat source of a reboiler configured in the medium-pressure tower, and steam extracted from the top of the medium-pressure tower is used as a heat source of the reboiler configured in the normal-pressure tower.
Furthermore, an alkali liquor adding device is installed in the system, a liquid inlet side of the alkali liquor adding device is communicated with an external liquid source, and a liquid outlet side of the alkali liquor adding device is arranged at four positions, namely a raw material pipeline in front of a feeding side of the pre-tower, a washing water feeding pipeline in the washing tower, and a first-stage condenser and a second-stage condenser in the pre-tower.
Further, the atmospheric tower divide into top, middle part and bottom from top to bottom, wherein the cooling apparatus of top position and outside switches on, the mid-mounting has extraction equipment, this extraction equipment switches on with the recovery tower, the recovery pipeline that switches on with the scrubbing tower is installed to the bottom, installs the cooler in this recovery pipeline.
The rectification method of the methanol thermal coupling rectification system applying the water saving and emission reduction is characterized in that:
the method comprises the following steps:
step 1: raw material methanol is respectively subjected to heat exchange with low-temperature methanol, medium-temperature methanol and high-temperature methanol through a three-stage preheater of a heat exchange network and then enters a pre-tower;
step 2: the steam at the top of the pre-tower enters a washing tower, after methanol is recovered by desalted water washing, light components such as carbon monoxide, carbon dioxide, acetone, dimethyl ether and the like in the system are removed to a torch system, and washing liquid flows back to the pre-tower;
and step 3: the alkali liquor adding device adds alkali liquor into the system from four positions, and H2S in the system is completely removed;
and 4, step 4: the tower bottom liquid of the pre-tower enters a pressurizing tower after heat exchange through a pressurizing tower heat exchanger, steam extracted from the tower top is sent to a middle-pressure tower coupling reboiler to serve as a heating source of the middle-pressure tower reboiler, part of condensate is returned to the pressurizing tower to serve as reflux, and part of condensate is sent to a three-stage preheater to serve as a product to be subjected to heat exchange and then is extracted as the product;
and 5: the tower bottom liquid of the pressurized tower enters a medium-pressure tower, steam extracted from the tower top is sent to a coupling reboiler of the normal-pressure tower to be used as a heating source of the reboiler of the normal-pressure tower, a part of condensate is returned to the medium-pressure tower to be used as reflux, and a part of condensate is used as a product to be sent to a secondary heat exchanger for heat exchange and then is extracted as the product;
step 6: the tower bottom liquid of the medium-pressure tower enters an atmospheric tower, steam extracted from the tower top is sent to an atmospheric tower coupling reboiler to serve as a heating source of the atmospheric tower reboiler, a condensate part returns to the atmospheric tower to serve as reflux liquid, a part of the condensate part serves as a product and is sent to a first-stage heat exchanger for heat exchange and then extracted as the product, a small amount of fusel containing methanol is extracted from the middle of the atmospheric tower to a recovery tower, the quality of the methanol product is ensured to meet American AA-level standard, and the tower bottom wastewater of the atmospheric tower is cooled to a;
and 7: and (3) enabling fusel streams extracted from the middle of the atmospheric tower to enter a recovery tower, cooling a fuel alcohol product extracted from the top of the tower to be used as fuel, extracting fusel fractions from the middle of the atmospheric tower to be sent to a gasification device to be used as coal grinding water, cooling waste water in the kettle of the recovery tower by a water cooler in the kettle of the recovery tower, and returning the waste water to a washing tower to recover methanol.
The invention has the advantages and positive effects that:
in the invention, a heat exchange network is optimally designed by utilizing a pinch point technology on the basis of the original four-tower structure, on one hand, high-temperature methanol is used as a heat source to preheat a crude methanol raw material step by step, on the other hand, high-temperature steam extracted by each tower body is used as a heat source of a secondary tower body configuration reboiler to carry out secondary utilization, and the utilization rate of energy is greatly improved.
In the invention, the method for adding the alkali liquor is changed from the original single point location to four point locations for adding respectively, so that residual H2S in the light components at the top of the pre-tower is fully reacted, and the corrosion problem of the washing tower is thoroughly solved.
According to the invention, the extraction mode of a small amount of fusel in the normal pressure product tower is improved, the extraction equipment arranged in the middle adopts a middle gradient extraction mode, and the fusel is collected into the recovery tower, so that the requirement of low ethanol content (less than or equal to 10ppm) of the existing methanol product is ensured, the product purity reaches the American AA standard, the subsequent fusel recovery and utilization are realized, no hazardous waste is discharged from the whole device, and the environment is protected; the method of extracting the fusel stream from the middle gradient side line of the atmospheric tower is adopted, the wastewater at the bottom of the recovery tower hardly contains salt, and the stream water returns to the washing tower through heat exchange, so that the consumption of fresh desalted water can be reduced.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
1-washing tower 2-medium pressure tower 3-normal pressure tower 4-recovery tower kettle water cooler 5-normal pressure tower kettle water cooler 6-recovery tower 7-recovery tower coupling reboiler 8-normal pressure tower coupling reboiler 9-medium pressure tower coupling reboiler 10-pressurized tower coupling reboiler 11-pressurized tower 12-pressurized tower heat exchanger 13-pre-tower 14-pre-tower coupling reboiler 15-methanol product water cooler 16-primary preheater 17-secondary preheater 18-tertiary preheater
Detailed Description
The present invention is further illustrated by the following examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
A methanol thermal coupling rectification system capable of saving water and reducing emission adopts a four-tower structure, wherein the four-tower structure comprises a pressurizing tower 11, a medium-pressure tower 2, a normal-pressure tower 3 and a recovery tower 6 which are sequentially installed, and a pre-tower 13 and a washing tower 1 are also installed in front of the recovery tower.
In this embodiment, the multi-stage preheater is a three-stage preheater, in which the first-stage preheater 16 is conducted to the intermediate-pressure column, the second-stage preheater 17 is conducted to the pressurizing column, and the third-stage preheater 18 is conducted to the pre-column.
In this embodiment, the heat exchange network further comprises a plurality of tower reboilers and pressurized tower heat exchangers 12, wherein each of the pre-tower, the pressurized tower, the intermediate pressure tower, the atmospheric tower and the recovery tower is provided with a tower reboiler, which comprises a pre-tower coupling reboiler 14, a recovery tower coupling reboiler 7 and an atmospheric tower coupling reboiler 8, and the pressurized tower heat exchangers are installed between the pre-tower discharge side and the pressurized tower feed side of the intermediate pressure tower coupling reboiler 9 and the pressurized tower coupling reboiler 10; and (3) introducing the tower bottom liquid of the pre-tower into the pressurizing tower after heat exchange by the pressurizing tower heat exchanger, wherein steam extracted from the top of the pressurizing tower is used as a heat source of a reboiler configured in the medium-pressure tower, and steam extracted from the top of the medium-pressure tower is used as a heat source of the reboiler configured in the normal-pressure tower.
In this embodiment, the system is provided with an alkali liquor adding device, a liquid inlet side of the alkali liquor adding device is communicated with an external liquid source, and a liquid outlet side of the alkali liquor adding device is arranged at four positions, namely, in a raw material pipeline before a feeding side of the pre-tower, in a washing water feeding pipeline inside the washing tower, and in front of feeding sides of a first-stage condenser and a second-stage condenser inside the pre-tower.
In this embodiment, the atmospheric tower divide into top, middle part and bottom from top to bottom, wherein the cooling apparatus of top position and outside switches on, and the mid-mounting has the extraction equipment, and this extraction equipment switches on with the recovery tower, and the bottom is installed and is switched on with the scrubbing tower's recovery pipeline, installs the cooler in this recovery pipeline.
In this embodiment, a methanol product water cooler 15 is installed on the discharge side of the refined formaldehyde product.
In this embodiment, a recovery tower kettle water cooler 4 and an atmospheric tower kettle water cooler 5 are respectively installed in pipelines at tower kettle water discharge positions of the recovery tower and the atmospheric tower.
The using process of the invention is as follows:
the specific embodiment of the rectification system applying the invention is as follows:
TABLE 1 raw material composition
| Serial number | Mass fraction | |
| 1 | H2S | 0.05PPM |
| 2 | CO | 354PPM |
| 3 | CO2 | 0.003 |
| 4 | H2O | 0.02 |
| 5 | METHANOL | 0.97 |
| 6 | ETHANOL | 0.001 |
| 7 | NC3OH | 691PPM |
| 8 | NC4OH | 464PPM |
| 9 | IC4OH | |
| 10 | ACETONE | 294PPM |
| 11 | DME | 522PPM |
| 12 | MF | 193PPM |
| 13 | IC5 | 570PPM |
| 14 | NC5 | 0.001 |
| 15 | NC6 | 980PPM |
The rectification process for the crude methanol raw material is as follows:
step 1: pressurizing a crude methanol raw material (shown in table 1) by a delivery pump, sending the raw material to a heat exchange network for heat exchange, performing heat exchange by a first-stage preheater, a second-stage preheater and a third-stage preheater, raising the temperature to 80-90 ℃, and entering the middle upper part of a pre-tower;
step 2: and removing light components such as carbon monoxide, carbon dioxide, acetone, dimethyl ether, methyl formate and light hydrocarbon in the raw materials at the top of the pre-tower, introducing a small amount of methanol into a washing tower by being carried by the light components, washing the methanol by desalted water, recovering the methanol, and refluxing the methanol to the pre-tower, wherein the use amount of desalted water is 1000-2500 kg/h.
And step 3: meanwhile, alkali liquor is divided into four paths, and the four paths of alkali liquor are respectively added from a raw material pipeline, a desalination water pipeline and inlets of a first-stage condenser and a second-stage condenser at the top of the pre-tower to eliminate residual H2S in the raw materials, wherein the operating pressure of the pre-tower is 120-160 KPa, and the operating temperature of a tower kettle is 65-80 ℃.
TABLE 2 Process flow specific operating conditions for each column
| Pre-tower | Pressurized tower | Medium pressure column | Atmospheric tower | Recovery tower | |
| Operating pressure Kpa | 130 | 1400 | 750 | 120 | 120 |
| Temperature of the bottom of the column/. degree.C | 73 | 153 | 130 | 109 | 109 |
| Reflux ratio/amount of washing water (kg) | 1500 | 2.08 | 2.5 | 2.2 | 4 |
(the concrete operating conditions of each column are shown in Table 2)
And 4, step 4: the method comprises the following steps that (1) tower bottom liquid of a pre-tower enters the middle-lower part of a pressurizing tower after being subjected to heat exchange to 105-112 ℃ by a pressurizing tower heat exchanger, steam extracted from the top of the pressurizing tower is sent to a middle-pressure tower coupling reboiler to serve as a heating source of the middle-pressure tower reboiler, condensate liquid is partially returned to the pressurizing tower to serve as reflux liquid, and partially serves as a product and is sent to a three-stage preheater to be subjected to heat exchange to 85-; cooling the mixture to 45 ℃ in a methanol product water cooler, and removing the cooled mixture to a product tank. Wherein the operation pressure of the pressurizing tower is 1300-1500 KPa, the operation temperature of the tower kettle is 145-160 ℃, and the reflux ratio is 1.8-2.5.
And 5: and (3) allowing tower bottom liquid of the pressurizing tower to enter the middle-lower part of the medium-pressure tower, extracting steam from the tower top, sending the steam to a coupling reboiler of the constant-pressure tower to serve as a heating source of the reboiler of the constant-pressure tower, returning a part of condensate to the medium-pressure tower to serve as reflux liquid, sending a part of condensate to a secondary heat exchanger as a product to exchange heat to 64-75 ℃, and then sending the condensate to a water cooler of a methanol product to be cooled to. Wherein the operating pressure of the medium-pressure tower is between 650 and 850KPa, the operating temperature of the tower kettle is between 125 and 135 ℃, and the reflux ratio is between 2.05 and 3.
Step 6: and (3) allowing tower bottom liquid of the medium-pressure tower to enter the middle part of an atmospheric tower, extracting a methanol product from the top of the atmospheric tower, conveying the methanol product by a reflux pump, returning part of the methanol product as reflux liquid into the tower, allowing part of the methanol product as a product to enter a first-stage preheater for heat exchange to 47-55 ℃, and then allowing the product to enter a methanol product water cooler for cooling to 45 ℃ and then to enter a product tank. And a small amount of fusel distillate is extracted from the middle of the atmospheric tower and sent to a recovery tower, and the extraction amount is 800-1600 kg/h, so that the quality of the methanol product is ensured to reach American AA level. Wherein the operating pressure of the atmospheric tower is 120-150 KPa, the operating temperature of the tower kettle is 104-115 ℃, and the reflux ratio is 1.8-2.8.
And 7: fusel streams are extracted from the middle of the atmospheric tower and enter a recovery tower, fuel alcohol products extracted from the top of the atmospheric tower are cooled and then used as fuel, fusel fractions are extracted from the middle of the atmospheric tower and sent to a gasification device to be used as coal grinding water, waste water in a kettle of the recovery tower is cooled by a water cooler in the kettle of the recovery tower and then returned to a washing tower to recover methanol, and the whole methanol device does not generate hazardous waste. Wherein the water content of the fuel alcohol product at the top of the tower is 2-7%, the content of methanol in water at the bottom of the tower is less than 50PPM, the operating pressure of the recovery tower is 120-150 KPa, the operating temperature of the bottom of the tower is 104-114 ℃, and the reflux ratio is 3-5.
TABLE 3 product index
| Methanol | Acetone (II) | Ethanol | Moisture content | Yield of refined methanol | Steam consumption |
| 99.9％ | 9ppm | 8ppm | 25ppm | 99.3％ | 0.76 |
As shown in Table 3, in the invention, the extraction mode of a small amount of fusel in the normal pressure product tower is improved, the extraction equipment arranged in the middle adopts an intermediate gradient extraction mode, and the fusel is collected into the recovery tower, so that the requirement of low ethanol content (less than or equal to 10ppm) of the existing methanol product is ensured, the product purity reaches the American AA standard, the subsequent fusel recovery and utilization are realized, no hazardous waste is discharged from the whole device, and the environment is protected; the method of extracting the fusel stream from the middle gradient side line of the atmospheric tower is adopted, the wastewater at the bottom of the recovery tower hardly contains salt, and the stream water returns to the washing tower through heat exchange, so that the consumption of fresh desalted water can be reduced.
In the invention, a heat exchange network is optimally designed by utilizing a pinch point technology on the basis of the original four-tower structure, on one hand, high-temperature methanol is used as a heat source to preheat a crude methanol raw material step by step, on the other hand, high-temperature steam extracted by each tower body is used as a heat source of a secondary tower body configuration reboiler to be secondarily beneficial, and the utilization rate of energy is greatly improved.
In the invention, the method for adding the alkali liquor is changed from the original single point location to four point locations for adding respectively, so that residual H2S in the light components at the top of the pre-tower is fully reacted, and the corrosion problem of the washing tower is thoroughly solved.
Claims (6)
1. The utility model provides a methanol thermal coupling rectification system of water conservation and emission reduction, adopts four tower structures, four tower structures include pressurization tower, medium-pressure tower, atmospheric tower and the recovery tower of installing in order, still install preceding tower and scrubbing tower before the recovery tower, its characterized in that: the system is internally provided with a heat exchange network which comprises a multi-stage preheater, wherein the multi-stage preheater is arranged in front of the feeding side of the pre-tower, high-temperature refined methanol products output by the pressurizing tower, the medium-pressure tower and the normal-pressure tower respectively enter one stage of the multi-stage preheater as heat sources, and the high-temperature refined methanol products all preheat crude methanol raw materials input into the pre-tower.
2. The methanol thermal coupling rectification system capable of saving water and reducing emission according to claim 1, characterized in that: the multi-stage preheater is three-stage, wherein the first-stage preheater is communicated with the medium-pressure tower, the second-stage preheater is communicated with the pressurizing tower, and the third-stage preheater is communicated with the pre-tower.
3. The methanol thermal coupling rectification system capable of saving water and reducing emission as claimed in claim 1 or 2, wherein: the heat exchange network also comprises a plurality of tower body reboilers and pressurized tower heat exchangers, wherein the pre-tower, the pressurized tower, the medium-pressure tower, the normal-pressure tower and the recovery tower are respectively provided with one tower body reboiler, and the pressurized tower heat exchanger is arranged between the discharge side of the pre-tower and the feed side of the pressurized tower; and (3) introducing the tower bottom liquid of the pre-tower into the pressurizing tower after heat exchange by the pressurizing tower heat exchanger, wherein steam extracted from the top of the pressurizing tower is used as a heat source of a reboiler configured in the medium-pressure tower, and steam extracted from the top of the medium-pressure tower is used as a heat source of the reboiler configured in the normal-pressure tower.
4. The methanol thermal coupling rectification system capable of saving water and reducing emission as claimed in claim 1 or 2, wherein: the system is internally provided with an alkali liquor adding device, the liquid inlet side of the alkali liquor adding device is communicated with an external liquid source, and the liquid outlet side of the alkali liquor adding device is arranged at four positions, namely a raw material pipeline in front of the feeding side of the pre-tower, a washing water feeding pipeline in the washing tower and positions in front of the feeding sides of a first-stage condenser and a second-stage condenser in the pre-tower.
5. The methanol thermal coupling rectification system capable of saving water and reducing emission as claimed in claim 1 or 2, wherein: the atmospheric tower divide into top, middle part and bottom from top to bottom, wherein top position and outside cooling arrangement switch on, the mid-mounting has extraction equipment, this extraction equipment switches on with the recovery tower, the recovery pipeline that switches on with the scrubbing tower is installed to the bottom, installs the cooler in this recovery pipeline.
6. The rectification method of the methanol thermal coupling rectification system for saving water and reducing emission according to any one of claims 1 to 5 is characterized in that: the method comprises the following steps:
step 1: raw material methanol is respectively subjected to heat exchange with low-temperature methanol, medium-temperature methanol and high-temperature methanol through a three-stage preheater of a heat exchange network and then enters a pre-tower;
step 2: the steam at the top of the pre-tower enters a washing tower, after methanol is recovered by desalted water washing, light components such as carbon monoxide, carbon dioxide, acetone, dimethyl ether and the like in the system are removed to a torch system, and washing liquid flows back to the pre-tower;
and step 3: the alkali liquor adding device adds alkali liquor into the system from four positions, and H2S in the system is completely removed;
and 4, step 4: the tower bottom liquid of the pre-tower enters a pressurizing tower after heat exchange through a pressurizing tower heat exchanger, steam extracted from the tower top is sent to a middle-pressure tower coupling reboiler to serve as a heating source of the middle-pressure tower reboiler, part of condensate is returned to the pressurizing tower to serve as reflux, and part of condensate is sent to a three-stage preheater to serve as a product to be subjected to heat exchange and then is extracted as the product;
and 5: the tower bottom liquid of the pressurized tower enters a medium-pressure tower, steam extracted from the tower top is sent to a coupling reboiler of the normal-pressure tower to be used as a heating source of the reboiler of the normal-pressure tower, a part of condensate is returned to the medium-pressure tower to be used as reflux, and a part of condensate is used as a product to be sent to a secondary heat exchanger for heat exchange and then is extracted as the product;
step 6: the tower bottom liquid of the medium-pressure tower enters an atmospheric tower, steam extracted from the tower top is sent to an atmospheric tower coupling reboiler to serve as a heating source of the atmospheric tower reboiler, a condensate part returns to the atmospheric tower to serve as reflux liquid, a part of the condensate part serves as a product and is sent to a first-stage heat exchanger for heat exchange and then extracted as the product, a small amount of fusel containing methanol is extracted from the middle of the atmospheric tower to a recovery tower, the quality of the methanol product is ensured to meet American AA-level standard, and the tower bottom wastewater of the atmospheric tower is cooled to a;
and 7: and (3) enabling fusel streams extracted from the middle of the atmospheric tower to enter a recovery tower, cooling a fuel alcohol product extracted from the top of the tower to be used as fuel, extracting fusel fractions from the middle of the atmospheric tower to be sent to a gasification device to be used as coal grinding water, cooling waste water in the kettle of the recovery tower by a water cooler in the kettle of the recovery tower, and returning the waste water to a washing tower to recover methanol.
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| CN202110141540.1A CN113004120A (en) | 2021-02-02 | 2021-02-02 | Water-saving emission-reducing methanol thermal coupling rectification system and rectification method |
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| CN101570466A (en) * | 2009-05-18 | 2009-11-04 | 张君涛 | Multi-effect rectifying process of methanol |
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