CN109232180B - Temperature-controllable methanol synthesis process - Google Patents

Temperature-controllable methanol synthesis process Download PDF

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CN109232180B
CN109232180B CN201811162803.1A CN201811162803A CN109232180B CN 109232180 B CN109232180 B CN 109232180B CN 201811162803 A CN201811162803 A CN 201811162803A CN 109232180 B CN109232180 B CN 109232180B
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heat exchange
water
steam
exchange tube
cooled reactor
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CN109232180A (en
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徐洁
郭文元
许仁春
田贵春
相红霞
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Sinopec Engineering Group Co Ltd
Sinopec Ningbo Engineering Co Ltd
Sinopec Ningbo Technology Research Institute
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Sinopec Engineering Group Co Ltd
Sinopec Ningbo Engineering Co Ltd
Sinopec Ningbo Technology Research Institute
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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
    • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
    • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
    • C07C29/152—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the reactor used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
    • C07C1/0485—Set-up of reactors or accessories; Multi-step processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00106—Controlling the temperature by indirect heat exchange
    • B01J2208/00115—Controlling the temperature by indirect heat exchange with heat exchange elements inside the bed of solid particles
    • B01J2208/00132—Tubes

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  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention relates to a temperature-controllable methanol synthesis process.A water-cooled reactor is internally provided with a first heat exchange tube group and a second heat exchange tube group which are mutually independent; the sum of the cross sectional areas of the inner cavities of the second heat exchange tubes is 15-60% of the sum of the cross sectional areas of the inner cavities of the first heat exchange tubes; heating the mixed gas, then feeding the heated mixed gas into a first water-cooled reactor to perform a primary methanol synthesis reaction to obtain a first reaction gas with the methanol content of 11-14 mol%, and feeding the heated mixed gas into a second water-cooled reactor to perform a secondary methanol synthesis reaction to obtain a second reaction gas; monitoring the methanol content of the reaction gas at the outlets of the two water-cooled reactors on line; when the content of methanol in the outlet reaction gas of the first water-cooled reactor is less than or equal to 10mol%, gradually closing the control valve on the second boiler water pipeline until the control valve is closed, stopping the second heat exchange tube group to work, and when the content of methanol in the outlet reaction gas of the second water-cooled reactor is less than or equal to 13mol%, gradually closing the control valve on the second boiler water pipeline until the control valve is closed, and only the second heat exchange tube group works.

Description

Temperature-controllable methanol synthesis process
Technical Field
The invention relates to a methanol synthesis process, in particular to a temperature-controllable methanol synthesis process.
Background
Methanol synthesis is a reversible exothermic reaction process. For the copper-based methanol synthesis catalyst, the reaction temperature needs to be maintained between 220 ℃ and 280 ℃, the catalyst does not have activity when the temperature is too low, and the service life and the product quality of the catalyst are influenced when the temperature is too high. In order to make the methanol synthesis reaction proceed in a suitable temperature range, heat exchange tubes are usually embedded in the catalyst reaction bed layer, the reaction heat released during the methanol synthesis is removed by the steam generated by the gasification of boiler water in the heat exchange tubes, this type of reactor is called isothermal methanol synthesis reactor, and the methanol synthesis process provided with the isothermal methanol synthesis reactor is called isothermal methanol synthesis process.
Based on the consideration of prolonging the service life of the methanol synthesis catalyst, the reaction temperature of the catalyst is generally controlled between 240 ℃ and 260 ℃ in the initial stage of use, and the reaction temperature of the catalyst is generally controlled between 260 ℃ and 280 ℃ in the later stage of use. When the device is stably operated, the reaction heat removed by the steam generated by the boiler water in the heat exchange tubes is constant, but the reaction temperature slowly rises from 240 ℃ to 280 ℃ along with the aging of the catalyst, the temperature of the boiler water in the corresponding heat exchange tubes slowly rises from 225 ℃ to 270 ℃, and the steam pressure generated by the boiler water gradually rises from 2.7MPaG to 5.4 MPaG. It can be seen that the temperature interval span of the isothermal methanol synthesis process is large, and the pressure fluctuation of the produced steam is also large.
Along with the large-scale and multi-series methanol synthesis device, the amount of rich steam is more and more, but the existing isothermal methanol synthesis process can not solve the problems of steam pressure fluctuation, increase of investment of related equipment and pipeline engineering and the like all the time, and the method is mainly embodied as follows:
(1) considering from the design pressure, because the pressure of the steam generated in the heat exchange tube fluctuates between 2.7MPaG and 5.4MPaG, the equipment and the pipeline related to the heat exchange tube need to consider higher design pressure, otherwise, the steam pressure requirement of 5.4MPaG at the later stage of the catalyst cannot be met, and the increase of the wall thickness of the equipment and the pipeline increases the engineering investment;
(2) in view of rich steam, although the high-quality steam of 5.4MPaG can be rich in the later stage of the catalyst, the balance of the steam pipe network of the whole plant is determined by the steam of 2.7MPaG at the initial stage of the catalyst, and only the high-quality steam of 5.4MPaG can be decompressed and degraded for use in engineering design, so that pipeline valves and automatic control instrument elements related to decompression are required to be added, and certain impact is also caused on the steam pipe network of the whole plant.
In short, the pipelines and equipment of a boiler water system in a methanol synthesis reactor need to be designed according to the harsh temperature and pressure, and meanwhile, the medium-pressure steam produced in the later stage of the catalyst is degraded for use, so that the investment and the balance of a whole plant steam pipe network are not economical and reasonable.
Chinese patent publication No. CN 107162872A discloses a low pressure methanol synthesis process in which heat exchange tubes are embedded in a reaction bed of a methanol synthesis reactor, methanol synthesis is carried out in a catalyst bed, and the released reaction heat is removed by boiler water in the heat exchange tubes. However, the steam pressure of the rich product in the later period of the catalyst is increased, and the related equipment and pipelines have to be designed according to the steam pressure and the temperature in the later period, so that the engineering investment is increased; meanwhile, when the balance design of the steam pipe network of the whole plant is carried out by the process system, the process system can only be designed according to the lower steam pressure and steam quality at the initial stage of the catalyst, but certain impact is caused on the steam pipe network of the whole plant at the later stage of the catalyst.
Disclosure of Invention
The invention aims to solve the technical problem of providing a methanol synthesis process which has the advantages of quick and adjustable heat removal capacity, controllable bed layer temperature and capability of maintaining constant yield in the whole active period of a catalyst without increasing the wall thickness of equipment aiming at the current situation of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: the temperature-controllable methanol synthesis process comprises a water-cooled reactor, wherein a plurality of heat exchange tubes are arranged in the water-cooled reactor, the inlet of each heat exchange tube is connected with the boiler water outlet of a steam drum through a boiler water pipeline, and the outlet of each heat exchange tube is connected with the steam inlet of the steam drum through a steam recovery pipeline; the method is characterized in that:
the heat exchange tubes in the water-cooled reactor comprise a first heat exchange tube group consisting of a plurality of first heat exchange tubes and a second heat exchange tube group consisting of a plurality of second heat exchange tubes; the sum of the cross sectional areas of the inner cavities of the second heat exchange tubes is 15-60% of the sum of the cross sectional areas of the inner cavities of the first heat exchange tubes;
correspondingly, two boiler water pipelines are arranged;
the inlet of each second heat exchange tube is connected with a second boiler water pipeline, and the inlet of each first heat exchange tube is connected with a first boiler water pipeline; a valve is arranged on the second boiler water pipeline;
the water-cooled reactor comprises a first water-cooled reactor and a second water-cooled reactor; a boiler water pipeline and a steam recovery pipeline of the first water-cooled reactor are connected with a first steam drum; a boiler water pipeline and a steam recovery pipeline of the second water-cooled reactor are connected with a second steam drum;
the temperature from upstream is 60-80 ℃, and the pressure is 5-10 MPaG, H2The mixed gas with the mol ratio of 5-6/CO enters a first heat exchanger, is preheated to 195-215 ℃, enters a second heat exchanger, is heated to 230-240 ℃, and enters a first water-cooled reactor for methanol synthesis reaction; the medium-pressure boiler water with the temperature of 230-250 ℃ and the pressure of 3.7-4.0 MPaG in the first steam drum enters a first water-cooled reactor from a first heat exchange tube group and a second heat exchange tube group, the reaction heat of a reaction bed layer is taken away, and medium-pressure saturated steam of 3.7-4.0 MPaG is a byproduct;
supplementing medium-pressure boiler water with the temperature of 220-240 ℃ and the pressure of 3.9-4.2 MPaG into the first steam drum;
the outlet of the first water-cooled reactor obtains a first reaction gas with the temperature of 250-260 ℃ and the methanol content of 11-14 mol%, the first reaction gas enters the second heat exchanger to preheat the mixed gas, and the temperature is reduced to 210-230 ℃ and then the first reaction gas enters the second water-cooled reactor to carry out methanol synthesis reaction;
the medium and low pressure boiler water with the temperature of 170-210 ℃ and the pressure of 1.3-2.0 MPaG in the second steam drum enters a second water-cooled reactor from the first heat exchange tube group and the second heat exchange tube group, the reaction heat of the reaction bed layer is taken away, and medium and low pressure saturated steam of 1.3-2.0 MPaG is a byproduct; and supplementing medium and low pressure boiler water with the temperature of 165-200 ℃ and the pressure of 1.5-2.2 MPaG into the second steam drum.
A second reaction gas with the temperature of 210-230 ℃ and the methanol content of 14-18 mol% obtained at the outlet of the second water-cooled reactor enters a first heat exchanger to preheat the mixed gas, and the temperature is reduced to 110-135 ℃ and then enters a downstream system;
in the running process of the first water-cooled reactor and the second water-cooled reactor, monitoring the methanol content of the reaction gas at the outlets of the two water-cooled reactors on line;
when the content of methanol in the outlet reaction gas of the first water-cooled reactor is less than or equal to 10mol%, gradually closing a control valve on a second boiler water pipeline at a speed of gradually decreasing the volume flow of boiler water in the second boiler water pipeline connected with the first steam drum at 10%/h, and closing the control valve on the second boiler water pipeline when the temperature of a catalyst bed layer reaches 270-290 ℃, wherein only the first heat exchange tube group works; at the moment, the mixed gas exchanges heat to 250-275 ℃, the temperature of the reaction gas at the outlet of the first water-cooled reactor is 270-290 ℃, and medium-pressure saturated steam of 3.7-4.0 MPaG is still produced; the content of methanol in the outlet reaction gas is 11 to 14mol percent;
when the content of methanol in the outlet reaction gas of the second water-cooled reactor is less than or equal to 13mol%, gradually closing a control valve on a second boiler water pipeline according to the decreasing speed of 10%/h by the volume flow of boiler water in the second boiler water pipeline connected with a second steam drum, and closing the control valve on the second boiler water pipeline when the temperature of a catalyst bed layer reaches 240-260 ℃, so that only the first heat exchange tube group works; at the moment, the heat exchange of the first reaction gas is carried out to 235-255 ℃, the temperature of the reaction gas at the outlet of the second water-cooled reactor is 240-260 ℃, and the content of methanol is more than 14 mol%; still produce 1.3-2.0 MPaG medium and low pressure saturated steam.
In the scheme, the first heat exchange tubes in the water-cooled reactor can be uniformly arranged on the cross section of the catalyst bed layer, and the second heat exchange tubes are uniformly arranged on the cross section of the catalyst bed layer; so that the first heat exchange tube bank can still uniformly take heat from the catalyst bed layer after the second heat exchange tube bank is closed.
Preferably, in order to facilitate processing and manufacturing, in the same water-cooled reactor, the second heat exchange tubes are uniformly arranged on the cross section of the catalyst bed layer; each first heat exchange tube is arranged around the corresponding second heat exchange tube, and at least three first heat exchange tubes, preferably six first heat exchange tubes, are arranged around each second heat exchange tube; each first heat exchange tube is uniformly arranged on a circumferential line which takes the corresponding second heat exchange tube as a circle center; according to the structure, after the second heat exchange tube group is closed, because the number of the second heat exchange tubes is small, the area vacated by the closed second heat exchange tubes can be uniformly shared by the surrounding first heat exchange tubes, and the first heat exchange tube group can also uniformly or nearly uniformly extract heat from the catalyst bed layer.
Each second heat exchange tube and each first heat exchange tube arranged around the second heat exchange tube form a heat exchange tube pair.
Further, a part of the first heat exchange tube is shared between adjacent heat exchange tube pairs.
The steam recovery pipeline comprises a steam connecting pipe and a steam collecting pipe which are connected with the steam drum, and the outlet of the steam collecting pipe is connected with the steam connecting pipe; and the outlet of each first heat exchange tube and the outlet of each second heat exchange tube are communicated with the inlets of the steam collecting tubes.
Preferably, the first steam drum is installed at a position higher than the first water-cooled reactor; the installation position of the second steam drum is higher than that of the second water-cooled reactor. The scheme enables boiler water in the steam drum to naturally circulate in the corresponding water-cooled reactors under the action of density difference, avoids using forced circulation equipment of a pump, and has good energy-saving and consumption-reducing effects.
In order to absorb thermal stress during thermal expansion, an expansion joint may be provided at the steam connection pipe.
In order to facilitate the uniform distribution of the cooling water, the boiler water pipes preferably comprise a first boiler water pipe and a second boiler water pipe, wherein the outlet of the first boiler water pipe is connected with a first pipe box, and the first pipe box is connected with the inlets of the first heat exchange pipes; the second boiler water pipeline is connected with a second pipe box, and the second pipe box is connected with the inlets of the second heat exchange pipes.
The device has high catalyst activity at the initial operation stage, controls the two groups of heat exchange tubes to work simultaneously, removes more reaction heat, and keeps the catalyst bed layer at the catalyst activity temperature for methanol synthesis reaction, so that the yield is constant at a set value. In the later stage of the operation of the device, the activity temperature of the catalyst is increased due to the reduction of the activity of the catalyst; in order to maintain the parameters of the steam drum, boiler water, steam pressure and the like in the steam drum, the opening of the upper valve of the second boiler water pipeline is adjusted until the second boiler water pipeline is closed, the second heat exchange pipe group stops working, the heat removal amount of the catalyst bed layer is reduced, the temperature of the catalyst bed layer rises to the activity temperature of the catalyst in the later period, the methanol synthesis reaction is normally carried out, the yield is still maintained at the design value, the steam pressure of the steam outlet drum is unchanged, the parameters of a matched pipeline and equipment do not need to be changed, and the impact on the steam pipe network is small.
Drawings
FIG. 1 is a schematic process flow diagram of an embodiment of the present invention;
FIG. 2 is a longitudinal cross-sectional view of an embodiment of the present invention;
FIG. 3 is a transverse cross-sectional view of an embodiment of the present invention;
fig. 4 is a partially enlarged view of a portion a in fig. 3.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
As shown in fig. 1 to 4, the water-cooled reactor in this embodiment includes a first water-cooled reactor a4 and a second water-cooled reactor a6, which are arranged in series, and the two water-cooled reactors have the same structure and each include:
the furnace body 1 is of a conventional structure and comprises an upper seal head 11, a lower seal head 12 and a cylinder body 13 connected between the upper seal head 11 and the lower seal head 12.
The catalyst frame 2 is disposed in the cylinder 13. The catalyst frame 2 can be any one of the prior art according to the requirement, the embodiment is a radial reactor, and the mixed gas enters the catalyst frame from the mixed gas distribution pipe 3; a plurality of synthesis gas outlet holes are formed in the side wall of the catalyst frame; after the mixed gas is subjected to methanol synthesis catalytic reaction in the catalyst bed layer, the mixed gas is discharged from each synthesis gas outlet hole on the catalyst frame, enters a channel between the catalyst frame and the furnace body, enters a synthesis gas outlet through the channel, and finally is sent out of the furnace body 1 through a synthesis gas pipeline 33 connected with the synthesis gas outlet.
The mixed gas distribution pipe 3 is used for distributing mixed gas, is arranged in the middle position in the cavity of the catalyst frame 2, and is formed by sequentially and detachably connecting a plurality of sections of cylinder bodies 31, and in the embodiment, the cylinder bodies 31 are connected through flanges 34; a plurality of footsteps 32 are sequentially arranged on the inner side wall of the cylinder 31 at intervals along the axial direction. The end cover is detachably connected to the lower port of the mixed gas distribution pipe 3, the upper port of the mixed gas distribution pipe 3 is connected with a mixed gas inlet at the top of the furnace body, and the mixed gas inlet is connected with a mixed gas pipeline 35; the lower port of the mixed gas distribution pipe 3 is closed; a plurality of air outlets are arranged on the side wall of the mixed gas distribution pipe 3 at intervals, and the mixed gas entering the mixed gas distribution pipe 3 enters the catalyst bed layer through each air outlet.
The space between the mixed gas distribution pipe 3 and the catalyst frame is filled with a catalyst to form a catalyst bed.
The heat exchange tubes are arranged in the catalyst bed layer in a penetrating manner and comprise a first heat exchange tube group consisting of a plurality of first heat exchange tubes 41 and a second heat exchange tube group consisting of a plurality of second heat exchange tubes 42.
For the sake of distinction, each second heat exchange tube 42 is indicated by a solid circle and each first heat exchange tube 41 is indicated by a hollow circle in fig. 3.
Wherein the second heat exchange tubes 42 are uniformly arranged in the cavity between the catalyst frame and the mixed gas distribution tube; the first heat exchange tubes 41 are uniformly arranged around the second heat exchange tubes 42; at least three first heat exchange tubes 41 are uniformly distributed around each second heat exchange tube 42; in this embodiment, six first heat exchange tubes 41 are arranged around each second heat exchange tube 42, and the six first heat exchange tubes 41 are uniformly arranged on the same circumferential line L with the corresponding first heat exchange tube as the center of circle.
Each second heat exchange tube 42 forms a heat exchange tube pair with each first heat exchange tube 41 disposed therearound; a part of the first heat exchange tubes 41 are shared between adjacent heat exchange tube pairs, that is, the circumferential lines L of the first heat exchange tubes in the adjacent heat exchange tube pairs are arranged crosswise.
The number of the first heat exchange tubes in each pair of heat exchange tubes may be designed to be other numbers, for example, three, four, five or more, depending on the scale of the apparatus and the specification of the reactor.
The sum of the cross sectional areas of the second heat exchange tubes 42 is 15-60%, in this embodiment 50%, of the sum of the cross sectional areas of the first heat exchange tubes 41.
And the boiler water pipelines are connected with the corresponding steam drums and the corresponding heat exchange pipes, and each boiler water pipeline connected to each steam drum comprises a first boiler water pipeline 51 and a second boiler water pipeline 52. The outlet of the first boiler water pipeline 51 is connected with a first pipe box 55, and the first pipe box 55 is connected with the inlet of each first heat exchange pipe 41; the second boiler water pipe 52 is connected to a second pipe box 54, and the second pipe box 54 is connected to the inlet of each second heat exchange pipe 42. A valve 56 is arranged on the second boiler water pipeline 52.
The first and second header tanks 55 and 54 may have a ring pipe structure, as shown in fig. 2 of the present embodiment; the two tube boxes can also be box structures which are arranged in an up-and-down overlapping mode, and the two tube boxes can also be hollow tube plate structures.
The steam pipeline comprises a steam connecting pipe 59 and a steam collecting pipe 58, wherein the steam connecting pipe 59 is connected with the steam drum, and the outlet of the steam collecting pipe 58 is connected with the steam connecting pipe 59; the outlet of each first heat exchange tube and the outlet of each second heat exchange tube are communicated with the inlet of each steam collecting tube 58. The steam collection pipe 58 may be of a loop configuration, a box configuration, or other configuration.
And an expansion joint 59a provided on the steam connection pipe 59 for absorbing thermal stress.
In the early stage of the operation of the device, the temperature of the upstream feed is 70 +/-5 ℃, and the temperature of the upstream feed is 5-10 MPaG and H2The mixed gas with/CO approximately equal to 5.5 (molar ratio) enters a first heat exchanger A2 to be preheated to 205 ℃ +/-5 ℃, then enters a second heat exchanger A3 to be heated to 235 ℃ +/-5 ℃, and then enters a first water-cooled reactor A4 to carry out methanol synthesis reaction, wherein the activity temperature of the catalyst is 250-255 ℃.
Boiler water with the temperature of 240 ℃ and the pressure of 3.7-4.0 MPaG in the first steam pocket A5 simultaneously enters a first heat exchange tube group and a second heat exchange tube group of the first water-cooled reactor A4, reaction heat of a catalyst bed layer is taken away to generate medium-pressure saturated steam of 3.7-4.0 MPaG, the medium-pressure saturated steam returns to the first steam pocket A5 from a steam connecting pipe 59, and after gas-liquid separation, the medium-pressure saturated steam is discharged out of the first steam pocket A5 and sent to a steam pipe network; during the operation of the device, medium-pressure boiler water with the temperature of 225 ℃ and the pressure of 3.9 MPaG-4.2 MPaG is supplemented into the first steam drum A5.
The temperature of the reaction gas at the outlet of the first water-cooled reactor A4 is 250-260 ℃, the reaction gas enters a second heat exchanger A3 to heat the mixed gas, the temperature is reduced to 220 +/-5 ℃, the mixed gas is sent to a second water-cooled reactor A6 to carry out methanol synthesis reaction, and the activity temperature of the catalyst of the second water-cooled reactor A6 is 215-220 ℃; the content of methanol in the reaction gas at the outlet of the first water-cooled reactor A4 is 12-13 mol%.
Boiler water with the temperature of 185 ℃ and the pressure of 1.3-2.0 MPaG in the second steam pocket A7 simultaneously enters a first heat exchange tube group and a second heat exchange tube group of a second water-cooled reactor A6, reaction heat of a catalyst bed layer is taken away to generate medium-low pressure saturated steam of 1.3-2.0 MPaG, the medium-low pressure saturated steam returns to the second steam pocket A7 from a steam connecting pipe 59, and after gas-liquid separation, the medium-low pressure saturated steam is discharged out of the second steam pocket A7 and sent to a steam pipe network; during the operation of the device, medium and low pressure boiler water with the temperature of 175 ℃ and the pressure of 1.5 MPaG-2.2 MPaG is supplemented into the first steam drum A5.
The temperature of the reaction gas at the outlet of the second water-cooled reactor A6 is 215 ℃ plus or minus 5 ℃, the reaction gas enters a first heat exchanger A2 to heat the mixed gas, and the temperature is reduced to 125 ℃ plus or minus 5 ℃ and then the mixed gas is sent to a downstream system; the methanol content in the reaction gas at the outlet of the second water-cooled reactor A46 was about 16% (mole fraction).
And in the running process of the device, the methanol content of the reaction gas at the outlets of the two water-cooled reactors is monitored on line. When the methanol content of the reaction gas at the outlet of the first water-cooled reactor A4 decreased to 10% (mole fraction). At this time, the catalyst activity is reduced, and the catalyst activity temperature needs to be increased to maintain the conversion rate of CO and increase the methanol content of the outlet reaction gas. The boiler water volume flow in the second boiler water pipeline connected with the first steam pocket is gradually reduced by closing the control valve 56 on the second boiler water pipeline at the speed of 10%/hour decrement, and the activity temperature of the catalyst is gradually increased from 255 ℃ to 280 ℃. When the activity temperature of the catalyst is increased to 280 ℃, the second heat exchange tube group of the first water-cooled reactor A4 is closed, and only the first heat exchange tube group works. At the moment, the mixed gas at the inlet of the first water-cooled reactor A4 exchanges heat to 265 ℃, the temperature of the reaction gas at the outlet is 280 ℃, and the medium-pressure saturated steam of 3.7-4.0 MPaG is still produced; the methanol content of the outlet reaction gas is kept around 12% (mole fraction). After the second heat exchange tube group is closed, compared with the two heat exchange tube groups which work simultaneously, the heat exchange area is reduced by 33 percent, and the temperature of the catalyst bed layer is maintained in an active temperature range by reducing the heat exchange area; boiler water in the first steam drum A5 only enters the first group of heat exchange tubes of the first water-cooled reactor A4, the boiler water in the first group of heat exchange tubes exchanges heat with reaction heat of the catalyst bed layer, and generated medium-pressure saturated steam with the pressure of 3.7-4.0 MPaG and the temperature of 247-252 ℃ returns to the first steam drum A5.
When the methanol content of the reaction gas at the outlet of the second water-cooled reactor A6 decreased to 13% (mole fraction). At this time, the catalyst activity is reduced, and the catalyst activity temperature needs to be increased to maintain the conversion rate of CO and increase the methanol content of the outlet reaction gas. The boiler water volume flow in the second boiler water pipeline connected with the second steam pocket is gradually reduced by the control valve 56 on the second boiler water pipeline according to the decreasing speed of 10%/h, and the activity temperature of the catalyst is gradually increased from 220 ℃ to 250 ℃. When the active temperature of the catalyst is increased to 250 ℃, the second heat exchange tube group of the second water-cooled reactor A6 is closed, and only the first heat exchange tube group works. At the moment, the mixed gas at the inlet of the second water-cooled reactor A6 exchanges heat to 245 ℃, the temperature of the reaction gas at the outlet is 250 ℃, and medium-low pressure saturated steam of 1.3MPaG to 2.0MPaG is still produced; the methanol content of the outlet reaction gas is kept around 15% (mole fraction). After the second heat exchange tube group is closed, compared with the two heat exchange tube groups which work simultaneously, the heat exchange area is reduced by 33 percent, and the temperature of the catalyst bed layer is maintained in an active temperature range by reducing the heat exchange area; boiler water in the second steam drum A7 only enters the first group of heat exchange tubes of the second water-cooled reactor A6, the boiler water in the first group of heat exchange tubes exchanges heat with reaction heat of a catalyst bed layer, and medium-low pressure saturated steam with the generated pressure of 1.3 MPaG-2.0 MPaG and the temperature of 195-215 ℃ returns to the second steam drum A7.
In the whole process of the device operation, the steam pressure does not need to be changed, the equipment requirement on the steam pipe network is reduced, and the stable operation of the steam pipe network and the device is ensured; meanwhile, the constant yield of the reaction gas is ensured, and the device runs stably.
Comparative example
Taking a methanol synthesis device of 50 ten thousand tons/year as an example, effective gas (H)2+ CO) is about 133000N/m3/h，H2[ CO ] 2.3 (molar ratio)). All the operating conditions are consistent with those of the embodiment, and the difference is that the water-cooled reactor adopts a common water-cooled reactor, only one group of heat exchange tubes is arranged, all the heat exchange tubes work simultaneously in the whole process of the device operation, and table 1 lists the main investment parameters of the steam drum system and the pipeline in the embodiment and the comparative example.
TABLE 1
Figure BDA0001820389710000071
As can be seen from table 1, for the conventional methanol synthesis apparatus, the pressure fluctuation of the medium-pressure steam and the medium-pressure steam as by-products of the water-cooled reactor is significantly reduced, the design pressure of the steam drum, the design pressure of the boiler water pipe network and the steam pipe network, and the design pressure of the water-cooled reactor are both greatly reduced, so that the design thickness of the equipment is reduced, the equipment investment is significantly reduced, the direct investment of the equipment and the pipeline can be reduced by about 230 ten thousand yuan, and simultaneously, compared with the steam pipe network pressure of the comparative example which fluctuates in a large range, the pressure of the steam pipe network produced by the present invention is more stable, which is beneficial to the operation of the apparatus and the long-term stable operation of the steam pipe network and the apparatus.

Claims (7)

1. A temperature-controllable methanol synthesis process comprises a water-cooled reactor, wherein a plurality of heat exchange tubes are arranged in the water-cooled reactor, the inlet of each heat exchange tube is connected with the boiler water outlet of a steam drum through a boiler water pipeline, and the outlet of each heat exchange tube is connected with the steam inlet of the steam drum through a steam recovery pipeline; the method is characterized in that:
the heat exchange tubes in the water-cooled reactor comprise a first heat exchange tube group consisting of a plurality of first heat exchange tubes and a second heat exchange tube group consisting of a plurality of second heat exchange tubes; the sum of the cross sectional areas of the inner cavities of the second heat exchange tubes is 15-60% of the sum of the cross sectional areas of the inner cavities of the first heat exchange tubes;
correspondingly, two boiler water pipelines are arranged;
the inlet of each second heat exchange tube is connected with a second boiler water pipeline, and the inlet of each first heat exchange tube is connected with a first boiler water pipeline; a valve is arranged on the second boiler water pipeline;
the water-cooled reactor comprises a first water-cooled reactor and a second water-cooled reactor; a boiler water pipeline and a steam recovery pipeline of the first water-cooled reactor are connected with a first steam drum; a boiler water pipeline and a steam recovery pipeline of the second water-cooled reactor are connected with a second steam drum;
the temperature from upstream is 60-80 ℃, and the pressure is 5-10 MPaG, H2The mixed gas with the mol ratio of/CO of 5-6 enters a first heat exchanger, is preheated to 195-215 ℃, enters a second heat exchanger, is heated to 230-240 ℃, and enters a first water-cooled reactor for methanol synthesis reaction; the medium-pressure boiler water with the temperature of 230-250 ℃ and the pressure of 3.7-4.0 MPaG in the first steam drum enters a first water-cooled reactor from the first heat exchange tube group and the second heat exchange tube group, the reaction heat of a reaction bed layer is taken away, and medium-pressure saturated steam of 3.7-4.0 MPaG is a byproduct;
a first reaction gas with the temperature of 250-260 ℃ and the methanol content of 11-14 mol% is obtained at the outlet of the first water-cooled reactor, enters the second heat exchanger to preheat the mixed gas, and enters the second water-cooled reactor to perform a methanol synthesis reaction after the temperature is reduced to 210-230 ℃;
the medium and low pressure boiler water with the temperature of 170-210 ℃ and the pressure of 1.3-2.0 MPaG in the second steam drum enters a second water-cooled reactor from the first heat exchange tube group and the second heat exchange tube group, the reaction heat of the reaction bed layer is taken away, and medium and low pressure saturated steam of 1.3-2.0 MPaG is a byproduct;
a second reaction gas with the temperature of 210-230 ℃ and the methanol content of 14-18 mol% obtained at the outlet of the second water-cooled reactor enters a first heat exchanger to preheat a mixed gas, and the temperature is reduced to 110-135 ℃ and then enters a downstream system;
in the running process of the first water-cooled reactor and the second water-cooled reactor, monitoring the methanol content of the reaction gas at the outlets of the two water-cooled reactors on line;
when the content of methanol in the outlet reaction gas of the first water-cooled reactor is less than or equal to 10mol%, gradually closing a control valve on a second boiler water pipeline at a speed of gradually decreasing the volume flow of boiler water in the second boiler water pipeline connected with the first steam pocket according to 10%/hour, and closing the control valve on the second boiler water pipeline when the temperature of a catalyst bed layer reaches 270-290 ℃, so that only the first heat exchange tube group works; at the moment, the mixed gas exchanges heat to 250-275 ℃, the temperature of the reaction gas at the outlet of the first water-cooled reactor is 270-290 ℃, and medium-pressure saturated steam of 3.7-4.0 MPaG is still produced; the methanol content in the outlet reaction gas is 11-14 mol%;
when the content of methanol in the outlet reaction gas of the second water-cooled reactor is less than or equal to 13mol%, gradually closing a control valve on a second boiler water pipeline according to the decreasing speed of 10%/h by the volume flow of boiler water in the second boiler water pipeline connected with a second steam drum, and closing the control valve on the second boiler water pipeline when the temperature of a catalyst bed reaches 240-260 ℃, so that only the second heat exchange tube group works; at the moment, the heat exchange of the first reaction gas is carried out to 235-255 ℃, the temperature of the reaction gas at the outlet of the second water-cooled reactor is 240-260 ℃, and the content of methanol is more than 14 mol%; still producing medium and low pressure saturated steam of 1.3-2.0 MPaG;
in the same water-cooled reactor, the second heat exchange tubes are uniformly arranged on the cross section of the catalyst bed layer; each first heat exchange tube is arranged around the corresponding second heat exchange tube, at least three first heat exchange tubes are arranged around each second heat exchange tube, and each first heat exchange tube is uniformly arranged on a circumferential line which takes the corresponding second heat exchange tube as the center of a circle;
each second heat exchange tube and each first heat exchange tube arranged around the second heat exchange tube form a heat exchange tube pair.
2. The process according to claim 1, wherein six first heat exchange tubes are arranged around each second heat exchange tube.
3. A process for the synthesis of temperature-controllable methanol as claimed in claim 2, wherein a portion of the first heat exchange tubes are shared between adjacent pairs of heat exchange tubes.
4. The temperature-controllable methanol synthesis process according to any one of claims 1 to 3, wherein the steam recovery pipeline comprises a steam connecting pipe connected with the steam drum and a steam collecting pipe, and an outlet of the steam collecting pipe is connected with the steam connecting pipe; and the outlet of each first heat exchange tube and the outlet of each second heat exchange tube are respectively communicated with the inlets of the steam collecting tubes.
5. The temperature-controlled methanol synthesis process of claim 4, wherein the first steam drum is installed at a position higher than the first water-cooled reactor; the installation position of the second steam drum is higher than that of the second water-cooled reactor.
6. The process according to claim 4, wherein the steam connecting pipe is provided with an expansion joint.
7. The temperature-controllable methanol synthesis process according to claim 5, wherein the second boiler water pipeline is connected with each second heat exchange pipe through a second pipe box; the first boiler water pipeline is connected with the first heat exchange pipes through first pipe boxes.
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107382665A (en) * 2017-07-13 2017-11-24 南京国昌化工科技有限公司 The technique and device of a kind of methanol-fueled CLC

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Publication number Priority date Publication date Assignee Title
CN107382665A (en) * 2017-07-13 2017-11-24 南京国昌化工科技有限公司 The technique and device of a kind of methanol-fueled CLC

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"双塔并联式甲醇合成工艺运行总结";孙西英等;《化工设计通讯》;20130630;第39卷(第3期);第71页图1 *

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