CN115738339A - Split-flow methanol multi-effect rectification system - Google Patents
Split-flow methanol multi-effect rectification system Download PDFInfo
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Abstract
The invention discloses a split-flow methanol multi-effect rectification system which comprises a split-flow tower, wherein the top of the split-flow tower is communicated with a light component removal tower through a pipeline, a tower kettle of the split-flow tower is communicated with a medium-pressure tower through a pipeline, the top of the medium-pressure tower is communicated with a medium-pressure tower aftercooler and a medium-pressure tower reflux tank through a pipeline after passing through a heat exchanger communicated with the tower kettle of the split-flow tower and the tower kettle of the light component removal tower respectively, the bottom ends of the medium-pressure tower reflux tank and the light component removal tower are communicated with a fine methanol pipeline, the fine methanol pipeline communicated with the medium-pressure tower reflux tank is communicated to the top of the medium-pressure tower through a branch pipeline, one side of the medium-pressure tower is communicated with a recovery tower through a pipeline, and the top of the recovery tower is communicated to the tower kettle of the light component removal tower through a pipeline. The invention discloses a split-flow methanol multi-effect rectification system, which solves the problem of high energy consumption of the existing methanol rectification device.
Description
Technical Field
The invention belongs to the technical field of methanol rectification, and particularly relates to a multi-effect methanol rectification system by a split-flow method.
Background
The raw material of the methanol rectifying device is crude methanol which contains light components, water and fusel oil, and the feeding temperature is 30 ℃. At present, the four-tower double-effect methanol rectification Lurgi process is commonly adopted in China to produce refined methanol, and the method is mainly characterized in that a methanol rectification tower is divided into two towers, namely a pressurizing tower 02 and an atmospheric tower 03, the operating pressure of the pressurizing tower is improved, so that the gas at the top of the pressurizing tower can supply heat to a kettle of the atmospheric tower, and a pre-rectification tower 01 for removing light components and a recovery tower 04 for recovering methanol in wastewater are added to form a four-tower double-effect forward-pressure rectification process, as shown in figure 1, the process flow is as follows:
1) Crude methanol can be preheated to 116 ℃ through series of heat exchange and is sent to the middle section of the pre-rectifying tower 01 for normal pressure rectification by a feed pump so as to remove light components. The tower is operated under normal pressure, one part of liquid phase in the tower kettle enters a reboiler of a pre-rectifying tower, low-pressure steam is partially gasified and then returns to the tower kettle, the temperature of the tower kettle is 75 ℃, and the material in the tower kettle contains a large amount of methanol, a small amount of water and trace fusel oil and enters the middle lower part of a pressurizing tower 02; the gas phase at the top of the pre-rectifying tower 01 is partially condensed by a tower top condenser and then is totally refluxed, the gas at the top of the tower is washed by water to recover methanol and then returns to the top of the tower, and the temperature at the top of the tower is controlled to be about 45 ℃, so that the gas can be conveniently condensed by circulating water.
2) The operation pressure of the pressurizing tower 02 is increased to 0.8Mpa, so that the gas phase temperature at the top of the tower reaches about 128 ℃, and the material at the tower bottom of the atmospheric tower 03 can be conveniently heated. The temperature of the tower kettle of the tower reaches about 135 ℃, the tower kettle is generally heated by 0.4Mpa steam, the gas phase at the tower top enters a double-effect heat exchanger of the tower kettle of the normal pressure tower to supply heat to the normal pressure tower 03, the gas phase at the tower top enters a reflux tank of the pressurizing tower after being condensed, one part of the gas phase returns to the tower top for reflux, and the other part of the gas phase is taken as a refined methanol product out-of-device; and the residual methanol and water in the tower bottom enter the middle lower part of the atmospheric tower 03 to be continuously rectified.
3) The normal pressure tower 03 operates at normal pressure, the liquid phase part in the tower kettle enters the double-effect heat exchanger in the tower kettle, is gasified by the gas part in the top of the pressurizing tower 02 and returns to the tower kettle, the temperature of the tower kettle is about 116 ℃, fusel oil is extracted from the stripping section and then enters the middle part of the recovery tower 04, and the waste water in the tower kettle is discharged out of the device. The temperature of the top gas is about 72 ℃, the top gas enters a reflux tank after being condensed, one part of the top gas is returned to the top of the tower for reflux, and the other part of the top gas is taken as a refined methanol product out of the device.
4) The recovery tower 04 is operated under normal pressure, tower bottom liquid enters a reboiler of the recovery tower, is partially gasified by low-pressure steam and then returns to the tower bottom, the temperature of the tower bottom is about 105 ℃, and the waste water in the tower bottom is pumped out of the device through a recovery tower bottom pump; the gas at the top of the recovery tower 04 is about 69 ℃, condensed and enters a reflux tank of the recovery tower, one part of the condensed gas is pumped back to the top of the tower to be totally refluxed, and the other part of the condensed gas is taken as a refined methanol product to be discharged out of the device. A fusel oil extraction device is extracted from the side line of the stripping section of the recovery tower.
At present, the steam unit consumption of the similar process of most factories is 1.1-1.3 tons, the process flow adopts the actual feeding of 40 ten thousand tons of refined methanol produced in a certain factory to carry out process simulation calculation, the calculated steam consumption of 0.4MPa per ton of refined methanol product is 1.1 tons, and the energy consumption is still relatively high though full heat exchange is carried out.
Disclosure of Invention
The invention aims to provide a multi-effect methanol rectifying system by a split-flow method, which solves the problem of high energy consumption of the existing methanol rectifying device.
The technical scheme adopted by the invention is as follows: a multi-effect rectification system for methanol by a splitting method comprises a splitting tower, wherein the top of the splitting tower is communicated with a light component removal tower through a pipeline, a tower kettle of the splitting tower is communicated with a medium-pressure tower through a pipeline, the top of the medium-pressure tower is communicated with a medium-pressure tower aftercooler and a medium-pressure tower reflux tank through pipelines respectively and sequentially after passing through heat exchangers communicated with the splitting tower kettle and the light component removal tower kettle, the bottoms of the medium-pressure tower reflux tank and the light component removal tower are communicated with a fine methanol pipeline, the fine methanol pipeline communicated with the medium-pressure tower reflux tank is communicated to the top of the medium-pressure tower through a branch pipeline, one side of the medium-pressure tower is communicated with a recovery tower through a pipeline, and the top of the recovery tower is communicated to the light component removal tower kettle through a pipeline.
The present invention is also characterized in that,
the top of the diversion tower is communicated with the diversion tower condenser through a pipeline and then communicated to the top end of the diversion tower reflux tank, the top end of the diversion tower reflux tank is communicated to the middle section of the light component removal tower through a pipeline, and the bottom end of the diversion tower reflux tank is communicated to the top of the diversion tower through a pipeline.
The top of the lightness-removing column is communicated with a lightness-removing column condenser through a pipeline and then communicated to the top end of a lightness-removing column reflux tank, the bottom end of the lightness-removing column reflux tank is communicated to the top end of the lightness-removing column through a pipeline, the top end of the lightness-removing column reflux tank is communicated with a lightness-removing column aftercooler through a pipeline and then communicated to the bottom of a washing column, the bottom end of the washing column is communicated to the top end of a diversion column reflux tank through a pipeline, one side of the washing column is communicated with a water inlet pipeline, and the top end of the washing column is communicated with a noncondensable gas pipeline.
The middle-pressure tower kettle is communicated with a middle-pressure tower reboiler II through a pipeline, the inlet end of the middle-pressure tower reboiler II is communicated to the top of the middle-pressure tower after being communicated with a compressor through a pipeline, and the outlet end of the middle-pressure tower reboiler II is communicated to the middle section of the middle-pressure tower after being communicated with a lightness-removing tower aftercooler, a lightness-removing tower condenser and a splitter tower condenser through pipelines.
The top of the recovery tower is communicated with the condenser of the recovery tower through a pipeline and then communicated to the top of the reflux tank of the recovery tower, the top of the reflux tank of the recovery tower is communicated to the kettle of the light component removal tower through a pipeline, and the bottom of the reflux tank of the recovery tower is communicated to the top of the recovery tower through a pipeline.
The medium-pressure tower kettle is communicated with a medium-pressure tower reboiler I through a pipeline, the inlet end of the medium-pressure tower reboiler I is communicated with a steam pipeline, the outlet end of the medium-pressure tower reboiler I is communicated with a reduced-pressure flash tank through a pipeline, the top end of the reduced-pressure flash tank is communicated to a recovery tower kettle through a secondary steam pipeline, the recovery tower kettle is communicated with a recovery tower reboiler through a pipeline, the inlet end of the recovery tower reboiler is communicated to the bottom end of the reduced-pressure flash tank through a pipeline, and the outlet end of the recovery tower reboiler is communicated with a steam condensate pipeline.
The bottom end of the medium-pressure tower and the bottom end of the recovery tower are communicated with a waste water pipeline, and the middle section of the recovery tower is communicated with a fusel oil pipeline.
The bottom end of the medium-pressure tower double-effect heat exchanger is communicated with a condenser of the pressurizing tower through a pipeline and then communicated to the top end of a reflux tank of the pressurizing tower, the bottom end of the reflux tank of the pressurizing tower is communicated with a fine methanol pipeline and communicated to the top of the pressurizing tower through a branch pipeline, and the middle section of the pressurizing tower is communicated to the middle section of the recovery tower through a pipeline.
The pressurizing tower kettle is communicated with a pressurizing tower reboiler through a pipeline, the inlet end of the pressurizing tower reboiler is further communicated with a steam pipeline, the outlet end of the pressurizing tower reboiler is further communicated with a reduced-pressure flash tank through a pipeline, the top end of the reduced-pressure flash tank is communicated to the recovery tower kettle through a secondary steam pipeline, the recovery tower kettle is communicated with a recovery tower reboiler through a pipeline, the inlet end of the recovery tower reboiler is communicated to the bottom end of the reduced-pressure flash tank through a pipeline, and the outlet end of the recovery tower reboiler is further communicated with a steam condensate pipeline.
The bottom end of the pressurizing tower and the bottom end of the recovery tower are communicated with a waste water pipeline, and the middle section of the recovery tower is communicated with a fusel oil pipeline.
The invention has the beneficial effects that:
1) After the crude methanol is divided by the flow dividing tower, the gas phase at the top of the tower directly enters the light component removal tower, and a heat source is provided for the light component removal tower;
2) In the feeding of the light component removing tower, most of methanol is separated from the tower kettle of the splitter tower and almost all heavy components are taken away, so that the methanol obtained from the tower kettle of the light component removing tower is high-purity refined methanol, the temperature of the tower kettle of the light component removing tower is low, and the methanol steam at the top of the medium-pressure tower can be used for directly supplying heat. In addition, the light component removal tower removes a little of methanol in advance, so that the load of subsequent equipment is reduced, and the size of the subsequent equipment can also be reduced;
3) The liquid phase methanol product is not discharged from the top of the recovery tower, but the gas phase methanol is directly introduced into the light component removal tower for heat supply, so that the heat load of the light component removal tower can be reduced.
Drawings
FIG. 1 is a schematic diagram of a conventional methanol rectifying apparatus;
FIG. 2 is a schematic diagram of the structure of example 1 of the split-flow methanol multi-effect rectification system of the present invention;
FIG. 3 is a schematic diagram of the configuration of example 2 of the split-flow methanol multi-effect rectification system of the present invention;
FIG. 4 a) is a schematic partial schematic representation of a split-flow methanol multi-effect rectification system of example 3 of the present invention;
FIG. 4 b) is another schematic diagram of a portion of the split methanol multi-effect rectification system of example 3 of the present invention.
In the figure, 01, a prefractionator, 02, a pressurized column, 03, an atmospheric column, 04, a recovery column;
1. a splitter column, 2, a lightness-removing column, 3, a middle-pressure column, 4, a middle-pressure column aftercooler, 5, a middle-pressure column reflux tank, 6, a refined methanol pipeline, 7, a recovery column, 8, a splitter column condenser, 9, a splitter column reflux tank, 10, a lightness-removing column condenser, 11, a lightness-removing column reflux tank, 12, a lightness-removing column aftercooler, 13, a water washing column, 14, a water inlet pipeline, 15, a non-condensable gas pipeline, 16, a middle-pressure column reboiler II, 17, a compressor, 18, a recovery column condenser, 19, a recovery column reflux tank, 20, a middle-pressure column reboiler I, 21, a steam pipeline, 22, a reduced-pressure flash tank, 23, a recovery column and 24, a steam condensate pipeline, 25, a waste water pipeline, 26, a fusel oil pipeline, 27, a pressurizing tower, 28, a medium-pressure tower double-effect heat exchanger, 29, a pressurizing tower condenser, 30, a pressurizing tower reflux tank, 31, a pressurizing tower reboiler, 32, a shunt tower reflux pump, 33, a shunt tower kettle pump, 34, a shunt tower double-effect heat exchanger, 35, a lightness-removing tower double-effect heat exchanger, 36, a medium-pressure tower reflux pump, 37, a lightness-removing tower kettle pump, 38, a lightness-removing tower reflux pump, 39, a recovery tower reflux pump, 40, a medium-pressure tower waste water pump, 41, a recovery tower waste water pump, 42, a medium-pressure tower kettle pump, 43, a pressurizing tower reflux pump, 44, a recovery tower kettle pump and 45, a crude methanol feeding pipeline.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention provides a multi-effect methanol rectification system adopting a flow division method, which comprises a flow division tower 1, wherein the middle section of the flow division tower 1 is communicated with a crude methanol feeding pipeline 45, the top of the flow division tower 1 is communicated with a flow division tower condenser 8 through a pipeline and then communicated to the top of a flow division tower reflux tank 9, the top of the flow division tower reflux tank 9 is communicated to the middle section of a light component removal tower 2 through a pipeline, and the bottom of the flow division tower reflux tank 9 is communicated with a flow division tower reflux pump 32 through a pipeline and then communicated to the top of the flow division tower 1. The tower kettle of the diversion tower 1 is communicated with a diversion tower kettle pump 33 through a pipeline and then communicated with a medium-pressure tower 3, the top of the medium-pressure tower 3 is communicated with a medium-pressure tower aftercooler 4 and a medium-pressure tower reflux tank 5 through pipelines after passing through a diversion tower double-effect heat exchanger 34 and a light component removal tower double-effect heat exchanger 35 respectively, the bottom ends of the medium-pressure tower reflux tank 5 and the light component removal tower 2 are communicated with an accurate methanol pipeline 6, an intermediate-pressure tower reflux pump 36 is arranged on the accurate methanol pipeline 6 communicated with the medium-pressure tower reflux tank 5 and communicated to the top of the medium-pressure tower 3 through a branch pipeline, and a light component removal tower kettle pump 37 is arranged on the accurate methanol pipeline 6 communicated with the light component removal tower 2 to send the accurate methanol out of the system. The top of the lightness-removing column 2 is communicated with a lightness-removing column condenser 10 through a pipeline and then communicated to the top of a lightness-removing column reflux tank 11, the bottom of the lightness-removing column reflux tank 11 is communicated with a lightness-removing column reflux pump 38 through a pipeline and then communicated to the top of the lightness-removing column 2, the top of the lightness-removing column reflux tank 11 is communicated with a lightness-removing column aftercooler 12 through a pipeline and then communicated to the bottom of a water washing column 13, the bottom of the water washing column 13 is communicated to the top of a diversion column reflux tank 9 through a pipeline, one side of the water washing column 13 is communicated with a water inlet pipeline 14, and the top of the water washing column 13 is communicated with a noncondensable gas pipeline 15. One side of the medium-pressure tower 3 is communicated with a recovery tower 7 through a pipeline, the top of the recovery tower 7 is communicated with a recovery tower condenser 18 through a pipeline and then communicated to the top of a recovery tower reflux tank 19, the top of the recovery tower reflux tank 19 is communicated to the tower kettle of the light component removal tower 2 through a pipeline, and the bottom of the recovery tower reflux tank 19 is communicated to the top of the recovery tower 7 through a pipeline and then communicated to a recovery tower reflux pump 39. The bottom end of the medium pressure tower 3 is communicated with a waste water pipeline 25 through a medium pressure tower waste water pump 40 and the bottom end of the recovery tower 7 is communicated with a recovery tower waste water pump 41, and the middle section of the recovery tower 7 is communicated with a fusel oil pipeline 26.
Through the way, the methanol multi-effect rectification system adopting the split-flow method has the advantages that the split flow is realized through the split-flow tower 1, the gas phase at the top of the tower directly enters the light component removal tower 2, and a heat source (equivalent to an intermediate reboiler) is provided for the light component removal tower 2; in the feeding of the light component removal tower 2, most of methanol is separated from the tower bottom of the splitter tower 1 and almost all heavy components are taken away, so that the methanol at the tower bottom of the light component removal tower 2 is high-purity refined methanol; and the temperature is lower by 72 ℃, and methanol steam at 92.8 ℃ at the top of the medium-pressure tower 3 can be used for directly supplying heat. In addition, the light component removal tower 2 removes a little of 30% of methanol in advance, so that the load of subsequent equipment is reduced, the size of the subsequent equipment can be reduced, and the investment of the device is saved; the liquid phase methanol product is not discharged from the top of the recovery tower 7, but the gas phase methanol is directly fed into the light component removing tower 2 for heat supply, so that the heat load of the light component removing tower can be reduced by 7.5 percent.
As a further improvement of the invention, the tower kettle of the medium-pressure tower 3 is communicated with a medium-pressure tower reboiler I20 through a pipeline, the inlet end of the medium-pressure tower reboiler I20 is also communicated with a steam pipeline 21, the outlet end of the medium-pressure tower reboiler I20 is also communicated with a reduced-pressure flash tank 22 through a pipeline, the top end of the reduced-pressure flash tank 22 is communicated to the tower kettle of the recovery tower 7 through a secondary steam pipeline, the tower kettle of the recovery tower 7 is communicated with a recovery tower reboiler 23 through a pipeline, the inlet end of the recovery tower reboiler 23 is also communicated to the bottom end of the reduced-pressure flash tank 22 through a pipeline, and the outlet end of the recovery tower reboiler 23 is also communicated with a steam condensate pipeline 24. Through the flash distillation of stepping down again after the multistage heat transfer of the heating steam condensate to medium pressure column reboiler I20, produce the direct entering of secondary steam and retrieve 7 tower cauldron heats, the condensate then gets into recovery column reboiler 23 and as the heat source, can satisfy recovery column 7 heat supply completely.
As shown in figure 3, the split-flow methanol multi-effect rectification system has the remarkable characteristics that the system pressure is reduced through split-flow, and favorable conditions are provided for the application of a heat pump flow: the tower kettle of the medium pressure tower 3 is communicated with a medium pressure tower reboiler II 16 through a pipeline, the inlet end of the medium pressure tower reboiler II 16 is communicated to the top of the medium pressure tower 3 after being communicated with a compressor 17 through a pipeline, and the outlet end of the medium pressure tower reboiler II 16 is communicated to the middle section of the medium pressure tower 3 after being communicated with a lightness-removing tower aftercooler 12, a lightness-removing tower condenser 10 and a diversion tower condenser 8 through pipelines. A part of methanol steam on the top of the medium pressure tower 3 is separated out and enters a compressor 17 to be compressed to about 145 ℃, the methanol steam enters a medium pressure tower reboiler II 16 to heat wastewater at about 133 ℃ in the bottom of the medium pressure tower 3, and then enters a light component removal tower aftercooler 12, a light component removal tower condenser 10 and a diversion tower condenser 8 respectively to be decompressed and gasified, evaporation latent heat is used for providing cold energy, and the gasified methanol cold steam returns to a rectifying section of the medium pressure tower 3 to complete a heat pump cycle, so that steam can be further saved, and the consumption of circulating cold water on the top of the tower can be saved.
As shown in fig. 4 a) and 4 b), the split-flow methanol multi-effect rectification system of the invention can be used for not only the four-tower double-effect rectification but also the five-tower triple-effect, six-tower four-effect, seven-tower five-effect and other multi-effect methanol rectification, taking the five-tower triple-effect methanol rectification as an example: the connection mode of the diversion tower 1 and the light component removal tower 2 is the same as that of the four-tower double-effect rectification, and the difference is that a pressurizing tower 27 is communicated between the medium-pressure tower 3 and the recovery tower 7, the bottom end of the medium-pressure tower 3 is communicated with a medium-pressure tower kettle pump 42 through a pipeline and then communicated to the middle section of the pressurizing tower 27, the tower kettle of the medium-pressure tower 3 is communicated with a medium-pressure tower double-effect heat exchanger 28 through a pipeline, the inlet end of the medium-pressure tower double-effect heat exchanger 28 is communicated to the top of the pressurizing tower 27 through a pipeline, the outlet end of the medium-pressure tower double-effect heat exchanger 28 is communicated with a pressurizing tower condenser 29 through a pipeline and then communicated to the top end of a pressurizing tower reflux tank 30, the bottom end of the pressurizing tower reflux tank 30 is communicated with a fine methanol pipeline 6, a pressurizing tower middle section reflux pump 43 is arranged on the fine methanol pipeline 6 and communicated to the top of the pressurizing tower 27 through a branch pipeline, the middle section of the pressurizing tower 27 is communicated to the middle section of the recovery tower 7 through a pipeline, the bottom end of the recovery tower 27 and the bottom end of the recovery tower 7 are communicated with a waste water pipeline 25, a recovery tower kettle pump 44 is arranged on the waste water pipeline 25, and the recovery tower 7 is communicated with a fusel pipeline 26. By adding the pressurizing tower 27, the tower bottom liquid of the medium-pressure tower 3 can be further rectified, and the tower top methanol steam of the pressurizing tower 27 can also heat the tower bottom of the medium-pressure tower 3 through the medium-pressure tower double-effect heat exchanger 28, so that the materials in the tower are kept in a gaseous state as far as possible, the energy-saving effect of the thermal coupling is greatly exerted, the unit consumption of steam for producing each ton of refined methanol can be directly reduced from 0.94 ton to 0.65 ton, and the reduction amplitude reaches about 45%.
Similarly, heating steam can be added in the five-tower triple-effect methanol rectification, a tower kettle of the pressurizing tower 27 is communicated with a pressurizing tower reboiler 31 through a pipeline, an inlet end of the pressurizing tower reboiler 31 is also communicated with a steam pipeline 21, an outlet end of the pressurizing tower reboiler 31 is also communicated with a reduced-pressure flash tank 22 through a pipeline, the top end of the reduced-pressure flash tank 22 is communicated to a tower kettle of the recovery tower 7 through a secondary steam pipeline, the tower kettle of the recovery tower 7 is communicated with a recovery tower reboiler 23 through a pipeline, an inlet end of the recovery tower reboiler 23 is also communicated to the bottom end of the reduced-pressure flash tank 22 through a pipeline, and an outlet end of the recovery tower reboiler 23 is also communicated with a steam condensate pipeline 24. Through using the steam of higher pressure grade to pressurization tower 27 tower cauldron pressurization tower reboiler 31, rethread decompression flash distillation, the secondary steam lets in recovery tower 7 tower cauldron direct heat supply, and the steam condensate of high temperature position then gets into recovery tower 7 tower cauldron recovery tower reboiler 23 heat supply, make full use of the heat of steam.
Example 1
The split-flow four-tower double-effect methanol rectification process adopts the same feeding and the same product quality requirement as the background technology, and the process flow and the simulation calculation operating conditions are briefly described as follows:
1) Crude methanol is subjected to a series of heat exchange to about 70 ℃, and is sent to the middle section of a splitter tower 1 by a feed pump, the tower is operated at normal pressure, a liquid phase at a tower bottom enters a double-effect heat exchanger 34 of the splitter tower, is gasified by a gas phase heating part at the top of a medium-pressure tower 3 and then returns to the tower bottom, the temperature of the tower bottom is 79.5 ℃, and materials at the tower bottom mainly comprise methanol, a small amount of water and a trace amount of fusel oil, and are sent to the middle section of the medium-pressure tower 3 by a tower bottom pump 33 of the splitter tower; the gas phase at the top of the tower mainly comprises methanol and light components, enters a reflux tank 9 of the diversion tower after being partially condensed by a condenser 8 of the diversion tower, and is pumped back to the top of the diversion tower 1 by a reflux pump 32 of the diversion tower to perform total reflux; the gas-phase light components in the reflux tank 9 of the flow splitting tower enter the middle section of the lightness-removing tower 2 under the self-pressure. The overhead temperature was 71.6 ℃.
2) The light component removal tower 2 is operated at normal pressure, liquid phase in a tower kettle enters a double-effect heat exchanger 35 of the light component removal tower, is gasified by gas phase part at the top of the medium-pressure tower 3 and then returns to the tower kettle, the temperature of the tower kettle is 72 ℃, the material in the tower kettle is high-purity refined methanol, and can be sent out of the system through a light component removal tower kettle pump 37 after crude methanol can be preheated; the gas phase at the top of the tower is 68 ℃, enters a light component removal tower condenser 10 for partial condensation, then enters a light component removal tower reflux tank 11, and the liquid phase is pumped back to the top of the light component removal tower 2 through a light component removal tower reflux pump 38 for total reflux; the temperature of a reflux tank 11 of the light component removal tower is 45 ℃, the non-condensable gas contains more methanol, the non-condensable gas is further condensed and cooled by a cooler 12 after the light component removal tower enters a water washing tower 13 to be removed with the methanol by water, the non-condensable gas is discharged out of the system through a non-condensable gas pipeline 15, and washing water enters a reflux tank 9 of the diversion tower.
3) The operation pressure of the medium pressure tower 3 is 0.3Mpa, the temperature of the tower bottom is 133 ℃, the liquid phase part of the tower bottom enters a reboiler I20 of the medium pressure tower, the liquid phase part is gasified by steam and then returns to the tower bottom, and the waste water of the tower bottom is sent out of the system through a waste water pump 40 of the medium pressure tower or can be sent out of the system after crude methanol is preheated. The medium-pressure tower reboiler I20 is heated by adopting 0.4MPa steam, steam condensate is decompressed to 0.2MPa and enters a decompression flash tank 22, secondary steam directly enters a tower kettle 7 of the recovery tower for heat supply, and the condensate is 143 ℃ for heat supply for a reboiler 23 of the recovery tower. In addition, a stream of low-pressure steam can be arranged in the reduced-pressure flash tank 22 for standby; the gas phase at the top of the medium pressure tower 3 is 92.8 ℃, one part of the gas phase enters the double-effect heat exchanger 34 of the diversion tower, is condensed by the liquid phase at the tower bottom of the diversion tower 1, the other part of the gas phase enters the double-effect heat exchanger 35 of the light component removal tower, is condensed by the tower bottom liquid of the light component removal tower 2, the two condensate liquids are mixed and then enter the medium pressure tower aftercooler 4 for full condensation, and then enter the medium pressure tower reflux tank 5, the liquid phase of the medium pressure tower reflux tank 5 is sent back to the top of the medium pressure tower 3 for reflux through the medium pressure tower reflux pump 36, and the other part of the liquid phase is discharged out of the system through the refined methanol pipeline 6. Fusel oil is extracted from the side line of the medium-pressure tower 3 and enters a recovery tower 7.
4) The recovery tower 7 is operated at normal pressure, and the temperature of the tower bottom is 105 ℃. Part of the tower bottom liquid enters a reboiler 23 of the recovery tower, the condensate with the temperature of 143 ℃ in the reduced-pressure flash tank 22 is used for supplying heat to the reboiler 23 of the recovery tower, so that part of the tower bottom liquid in the recovery tower 7 is gasified and then returns to the tower kettle, and the secondary steam with the temperature of 143 ℃ in the reduced-pressure flash tank 22 directly enters the tower kettle of the recovery tower 7 for supplying heat; the gas at the top of the recovery tower 7 enters a recovery tower condenser 18 to be partially condensed and then enters a recovery tower reflux tank 19, wherein the condensed liquid is pumped back to the top of the tower to be totally refluxed through a recovery tower reflux pump 39, the gas phase enters a light component removal tower 2 to provide a partial heat source, and the energy consumption of the tower can be saved by about 7.5%. The fusel oil extraction device is extracted from the middle section side line of the recovery tower 7, a small amount of waste water at the tower bottom is cooled to 40 ℃, and then the waste water is sent out of the system through a waste water pump 41 of the recovery tower.
In this embodiment, the actual feeding of 40 ten thousand tons of refined methanol produced in a certain plant is also adopted to perform process simulation calculation, and the calculated steam consumption of 0.4MPa per ton of refined methanol product is 0.94 tons, which saves 15% of steam compared with the current lurgi process with good operation.
Example 2
Split-flow four-tower double-effect methanol rectification process (flow process with heat pump)
The process flow of the embodiment 2 is substantially the same as that of the embodiment 1, and the difference is that in the embodiment 2, a part of methanol steam at the top of the medium pressure tower 3 is divided into a part, the part is compressed to about 145 ℃ by a compressor 17, the part is fed into a medium pressure tower reboiler II 16 to heat wastewater at about 133 ℃ in the tower kettle of the medium pressure tower 3, and then the part is respectively fed into a light component removal tower aftercooler 12, a light component removal tower condenser 10 and a splitter tower condenser 8 to be decompressed and gasified, latent heat of evaporation is utilized to provide cold energy, and the gasified methanol cold steam is fed back to a rectifying section of the medium pressure tower 3 to complete a heat pump cycle, so that steam can be further saved, and the consumption of circulating cold water at the top of the tower can be saved.
Example 3
The five-tower three-effect methanol rectification process adopts the same feeding and the same product quality requirement as the prior art, and the process flow and the simulation calculation operating conditions are briefly described as follows:
1) The splitter column 1 was operated at atmospheric pressure with temperatures at the top and bottom of the column of 71.6 ℃ and 79.2 ℃ respectively. Crude methanol is sent to the middle section of the diversion tower 1 by a feed pump after a series of heat exchange, the liquid phase at the tower bottom enters a double-effect heat exchanger 34 of the diversion tower, the liquid phase is gasified by the gas phase heating part at the top of the medium-pressure tower 3 and then returns to the tower bottom, the materials at the tower bottom are the residual methanol, a small amount of water and a trace amount of fusel oil, and the residual methanol, the small amount of water and the trace amount of fusel oil are sent to the middle section of the medium-pressure tower 3 by a diversion tower bottom pump 33; the overhead gas is methanol and light components, enters a diversion tower reflux tank 9 after being partially condensed by a diversion tower condenser 8, and is pumped back to the top of the diversion tower 1 by a diversion tower reflux pump 32 for total reflux; the gas phase of the reflux tank 9 of the diversion tower enters the middle section of the lightness-removing tower 2 under self-pressure.
2) The light component removing tower 2 is operated under normal pressure, and the temperatures of the tower top and the tower bottom are 68 ℃ and 72 ℃ respectively. The liquid phase in the tower kettle enters a double-effect heat exchanger 35 of the light component removal tower, is partially gasified by the top gas of the medium-pressure tower 3 and then returns to the tower kettle; and a gas phase of a reflux tank 11 of the light component removing tower is 45 ℃, the methanol is further condensed and cooled to 40 ℃ by a cooler 12 of the light component removing tower, the methanol is removed in a water washing tower 13, the non-condensable gas is discharged out of the system, the washing water enters a reflux tank 9 of a diversion tower, the high-purity refined methanol is obtained in a tower kettle 2 of the light component removing tower, and the high-purity refined methanol is discharged out of the system by a tower kettle pump 37 of the light component removing tower. The gas phase at the top of the tower enters a light component removal tower condenser 10 to be partially condensed and then enters a light component removal tower reflux tank 11, and the liquid phase is pumped back to the top of the tower to be totally refluxed through a light component removal tower reflux pump 38.
3) The operating pressure of the medium pressure tower 3 is 0.33Mpa, and the temperatures of the tower top and the tower bottom are respectively 96 ℃ and 103 ℃. The liquid phase in the tower bottom enters the double-effect heat exchanger 28 of the medium-pressure tower, is returned to the tower bottom after being partially gasified by the gas phase at the top of the pressurizing tower 27, and the material in the tower bottom is sent to the middle section of the pressurizing tower 27 by a medium-pressure tower bottom pump 42; one part of the tower top gas with the temperature of 96 ℃ enters the diversion tower double-effect heat exchanger 34, is condensed by tower bottom liquid of the diversion tower 1, the other part enters the light component removal tower double-effect heat exchanger 35, is condensed by tower bottom liquid of the light component removal tower 2, the two condensed liquids are mixed and then enter the medium pressure tower aftercooler 4 for full condensation, and then enter the medium pressure tower reflux tank 5, liquid phase of the medium pressure tower reflux tank 5 is partially sent back to the top of the medium pressure tower 3 through the medium pressure tower reflux pump 36 to be used as reflux, and the other part can be discharged out of the system after crude methanol is preheated.
4) The pressure of the pressurizing tower 27 is 0.72MPa, and the temperatures of the top and bottom of the tower are 123 ℃ and 166 ℃ respectively. The tower bottom liquid part enters a pressurizing tower reboiler 31, is partially gasified by 1.0MPa steam and then returns to the tower bottom, the steam condensate enters a reduced pressure flash tank 22 after heat exchange and is decompressed and flashed to 184 ℃, the tower bottom material of the pressurizing tower 27 can be preheated for crude methanol and then is merged into a tower bottom pump 44 of a recovery tower to be sent out of the system, and fusel oil extracted from the middle section side of the pressurizing tower 27 enters the middle section of a recovery tower 7. The gas at the top of the pressurizing tower 27 is 123 ℃, enters the medium-pressure tower double-effect heat exchanger 28, is condensed by the bottom liquid of the medium-pressure tower 3, enters the pressurizing tower condenser 29, is condensed to 103 ℃, can preheat the crude methanol, is cooled to 80 ℃, enters the pressurizing tower reflux tank 30, the liquid phase of the pressurizing tower reflux tank 30 is partially sent back to the top of the pressurizing tower 27 through the pressurizing tower reflux pump 43 to be used as reflux, and the other part of the liquid phase is taken as a refined methanol outlet system through the refined methanol outlet pipeline 6.
5) The recovery column 7 was operated at atmospheric pressure with column top and column bottom temperatures of 69 ℃ and 105 ℃ respectively. The tower bottom liquid is waste water, part of the waste water enters a reboiler 23 of the recovery tower, 184 ℃ liquid phase in the reduced pressure flash tank 22 firstly preheats the feed of the pressurizing tower 27, and the liquid phase is cooled to 148 ℃ to supply heat to the reboiler 23 of the recovery tower, so that the tower bottom liquid of the recovery tower 7 is partially gasified and then returns to the tower bottom; the tower bottom wastewater is sent out of the system through a recovery tower bottom pump 44; the secondary steam in the reduced-pressure flash tank 22 directly enters the tower bottom of the recovery tower 7 for heat supply; the gas at the top of the recovery tower 7 enters a recovery tower condenser 18 for partial condensation and then enters a recovery tower reflux tank 19, the gas is pumped back to the top of the recovery tower 7 through a recovery tower reflux pump 39 for total reflux, and the gas-phase methanol at the temperature of 69 ℃ enters a tower kettle of a lightness-removing tower 2 for heat supply. Fusel oil is extracted from the side line of the middle section of the recovery tower 7 and is discharged out of the system through a fusel oil pipeline 26.
In this embodiment, the actual feeding of 40 ten thousand tons of refined methanol produced in a certain plant is also adopted to perform process simulation calculation, and the calculated steam consumption of 0.4MPa per ton of refined methanol product is 0.65 ton, which saves steam by 41% compared with the current lurgi process with good operation.
Claims (10)
1. A multi-effect rectification system for methanol by a splitting method is characterized by comprising a splitting tower (1), wherein the top of the splitting tower (1) is communicated with a light component removal tower (2) through a pipeline, the bottom of the splitting tower (1) is communicated with a medium-pressure tower reflux tank (5) through a pipeline, the top of the medium-pressure tower (3) is communicated with a medium-pressure tower aftercooler (4) and a medium-pressure tower reflux tank (5) through a heat exchanger communicated with the bottom of the splitting tower (1) and the bottom of the light component removal tower (2) in sequence, the medium-pressure tower reflux tank (5) and the bottom of the light component removal tower (2) are communicated with a fine methanol pipeline (6), the fine methanol pipeline (6) communicated with the medium-pressure tower reflux tank (5) is communicated to the top of the medium-pressure tower (3) through a branch pipeline, one side of the medium-pressure tower (3) is communicated with a recovery tower (7) through a pipeline, and the top of the recovery tower (7) is communicated with the light component removal tower (2) through a pipeline.
2. The multi-effect rectification system for methanol by splitting flow as claimed in claim 1, wherein the top of the splitting column (1) is communicated with the splitting column condenser (8) through a pipeline and then communicated to the top of the splitting column reflux tank (9), the top of the splitting column reflux tank (9) is communicated to the middle section of the light component removal column (2) through a pipeline, and the bottom of the splitting column reflux tank (9) is communicated to the top of the splitting column (1) through a pipeline.
3. The multi-effect rectification system of methanol by split stream as claimed in claim 2, wherein the top of the light component removal tower (2) is communicated with the light component removal tower condenser (10) through a pipeline and then communicated with the top of the light component removal tower reflux tank (11), the bottom of the light component removal tower reflux tank (11) is communicated with the top of the light component removal tower (2) through a pipeline, the top of the light component removal tower reflux tank (11) is communicated with the light component removal tower aftercooler (12) through a pipeline and then communicated with the kettle of the water washing tower (13), the bottom of the water washing tower (13) is communicated with the top of the split stream tower reflux tank (9) through a pipeline, one side of the water washing tower (13) is communicated with a water inlet pipeline (14), and the top of the water washing tower (13) is communicated with a noncondensable gas pipeline (15).
4. The multi-effect methanol rectification system by means of flow division according to claim 3, characterized in that the kettle of the medium pressure column (3) is communicated with a medium pressure column reboiler II (16) through a pipeline, the inlet end of the medium pressure column reboiler II (16) is communicated with the compressor (17) through a pipeline and then communicated to the top of the medium pressure column (3), and the outlet end of the medium pressure column reboiler II (16) is communicated with the light component removal column aftercooler (12), the light component removal column condenser (10) and the splitter column condenser (8) through pipelines and then communicated to the middle section of the medium pressure column (3).
5. The multi-effect rectification system of the methanol by splitting method according to claim 1, characterized in that the top of the recovery tower (7) is communicated with the recovery tower condenser (18) through a pipeline and then communicated to the top of the recovery tower reflux tank (19), the top of the recovery tower reflux tank (19) is communicated to the bottom of the light component removal tower (2) through a pipeline, and the bottom of the recovery tower reflux tank (19) is communicated to the top of the recovery tower (7) through a pipeline.
6. The multi-effect rectification system of methanol by a flow splitting method according to claim 1, wherein the tower bottom of the medium-pressure tower (3) is communicated with a medium-pressure tower reboiler I (20) through a pipeline, the inlet end of the medium-pressure tower reboiler I (20) is further communicated with a steam pipeline (21), the outlet end of the medium-pressure tower reboiler I (20) is further communicated with a reduced-pressure flash tank (22) through a pipeline, the top end of the reduced-pressure flash tank (22) is communicated to the tower bottom of the recovery tower (7) through a secondary steam pipeline, the tower bottom of the recovery tower (7) is communicated with a recovery tower reboiler (23) through a pipeline, the inlet end of the recovery tower reboiler (23) is further communicated to the bottom end of the reduced-pressure flash tank reboiler (22) through a pipeline, and the outlet end of the recovery tower (23) is further communicated with a steam condensate pipeline (24).
7. The multi-effect rectification system for methanol by split stream as recited in claim 1, characterized in that the bottom end of the medium-pressure tower (3) and the bottom end of the recovery tower (7) are communicated with a waste water pipeline (25) together, and the middle section of the recovery tower (7) is communicated with a fusel oil pipeline (26).
8. The split-flow methanol multi-effect rectification system as claimed in any one of claims 1 to 5, characterized in that a pressurizing tower (27) is communicated between the medium pressure tower (3) and the recovery tower (7), the bottom end of the medium pressure tower (3) is communicated to the middle section of the pressurizing tower (27) through a pipeline, the kettle of the medium pressure tower (3) is communicated with a medium pressure tower double-effect heat exchanger (28) through a pipeline, the inlet end of the medium pressure tower double-effect heat exchanger (28) is communicated to the top of the pressurizing tower (27) through a pipeline, the outlet end of the medium pressure tower double-effect heat exchanger (28) is communicated to a pressurizing tower condenser (29) through a pipeline and then to the top end of a pressurizing tower reflux tank (30), the bottom end of the pressurizing tower reflux tank (30) is communicated with a refined methanol pipeline (6) and is communicated to the top of the pressurizing tower (27) through a branch pipeline, and the middle section of the pressurizing tower (27) is communicated to the middle section of the recovery tower (7) through a pipeline.
9. The split-flow methanol multi-effect rectification system as claimed in claim 8, wherein the tower kettle of the pressurizing tower (27) is communicated with a pressurizing tower reboiler (31) through a pipeline, the inlet end of the pressurizing tower reboiler (31) is further communicated with a steam pipeline (21), the outlet end of the pressurizing tower reboiler (31) is further communicated with a reduced-pressure flash tank (22) through a pipeline, the top end of the reduced-pressure flash tank (22) is communicated with the tower kettle of the recovery tower (7) through a secondary steam pipeline, the tower kettle of the recovery tower (7) is communicated with a recovery tower reboiler (23) through a pipeline, the inlet end of the recovery tower reboiler (23) is further communicated with the bottom end of the reduced-pressure flash tank (22) through a pipeline, and the outlet end of the recovery tower reboiler (23) is further communicated with a steam condensate pipeline (24).
10. The multi-effect rectification system for methanol by split stream as recited in claim 8, characterized in that the bottom end of the pressurizing tower (27) and the bottom end of the recovery tower (7) are communicated with a waste water pipeline (25), and the middle section of the recovery tower (7) is communicated with a fusel oil pipeline (26).
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| CN202211523120.0A CN115738339A (en) | 2022-11-30 | 2022-11-30 | Split-flow methanol multi-effect rectification system |
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| CN202211523120.0A CN115738339A (en) | 2022-11-30 | 2022-11-30 | Split-flow methanol multi-effect rectification system |
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