WO2021035768A1 - 光气合成及盐水蒸发电解一体化处理工艺 - Google Patents

光气合成及盐水蒸发电解一体化处理工艺 Download PDF

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WO2021035768A1
WO2021035768A1 PCT/CN2019/104073 CN2019104073W WO2021035768A1 WO 2021035768 A1 WO2021035768 A1 WO 2021035768A1 CN 2019104073 W CN2019104073 W CN 2019104073W WO 2021035768 A1 WO2021035768 A1 WO 2021035768A1
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brine
phosgene synthesis
phosgene
heat transfer
stage
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English (en)
French (fr)
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文放
赵东科
吴雪峰
马海洋
张宏科
赵楠
董超
陈良进
徐丹
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万华化学集团股份有限公司
万华化学（宁波）有限公司
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Priority to EP19943659.3A priority Critical patent/EP3974382A4/en
Publication of WO2021035768A1 publication Critical patent/WO2021035768A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/80—Phosgene
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/4604—Treatment of water, waste water, or sewage by electrochemical methods for desalination of seawater or brackish water
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/02—Non-contaminated water, e.g. for industrial water supply
    • C02F2103/023—Water in cooling circuits
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds

Definitions

  • the invention relates to an integrated treatment process for phosgene synthesis and brine evaporation and electrolysis.
  • the phosgene synthesis process usually adopts activated carbon to catalyze the synthesis reaction.
  • the large amount of reaction heat generated by the synthesis reaction is more than 300,000 kcal per ton of phosgene synthesized. It is usually removed by water, chlorobenzene, heat transfer oil, etc. ,
  • activated carbon has poor thermal conductivity, and the radial and axial temperature difference is large, resulting in hot spots with a temperature as high as 500-600°C, which can easily cause activated carbon to pulverize.
  • the reaction temperature is usually On the low side, the removed heat is eventually taken away through the circulating water, which brings about the problems of energy waste and large consumption of circulating water.
  • Chinese published patent CN1765740A describes a shell-and-tube reactor, which reduces the hot spot temperature and reduces the pulverization of activated carbon through sufficient heat dissipation;
  • the prior art is aimed at activated carbon powdering.
  • the reaction heat is usually taken away by the circulating water at a temperature of about 30°C.
  • the final energy is consumed in the cooling water tower, and there is a problem of energy waste and large circulating water consumption.
  • the proposed solutions have limitations and cannot achieve energy recycling; or the use of special processed catalysts has problems such as complicated transformation processes, special adhesion catalysts are easy to fall off, and long-term operation cannot be performed.
  • the present invention provides an integrated treatment process for phosgene synthesis and brine evaporation and electrolysis, which realizes rational use of energy, resource utilization of waste brine, and realizes overall circular economy and zero emissions.
  • the present invention provides an integrated treatment process for phosgene synthesis and brine evaporation and electrolysis, which includes the following steps:
  • the first-stage phosgene synthesis tower is provided with a heat transfer agent circulation space, and the transfer The heat transfer agent circulates in the heat agent circulation space for absorbing the reaction heat generated by the synthesis of phosgene;
  • the catalyst is activated carbon or high thermal conductivity composite activated carbon, preferably high thermal conductivity composite activated carbon;
  • step 3 Supply the superheated steam described in step 2) to a brine evaporation concentration device, which uses the superheated steam as a heat source to evaporate and concentrate the brine to obtain concentrated brine; optionally, the concentrated brine Dry salt is obtained by crystallization;
  • step 3) The concentrated brine or dry salt obtained in step 3) is electrolyzed to generate chlorine; in some specific embodiments, the concentrated brine or dry salt is adjusted to saturated brine (the mass concentration of saturated brine is, for example, 23%), and then The saturated brine is electrolyzed to generate chlorine gas.
  • step 1) the mixed gas containing the phosgene obtained from the first-stage phosgene synthesis tower is input into the second-stage phosgene synthesis tower for further reaction, and the remaining chlorine is completely converted into phosgene.
  • the two-stage phosgene synthesis tower uses circulating water to remove the reaction heat, and the use of circulating water to remove the reaction heat is a heat transfer method conventionally used in the art.
  • the catalyst filling area (for example, in a tube) is filled with the mixed catalyst and the inert agent, and the inert agent
  • the material of is selected from one or at least two of silicon carbide, alumina or graphite, preferably silicon carbide.
  • the appearance shape of the inert agent can be a square column, a cylinder, a sphere, a star cone, a spindle, a rectangular saddle, a star or other shapes.
  • the inert agent has one or more (e.g., two More than one, for example, two, three, four, etc.) sharp-angled tips, such as star cone, spindle, star, etc., more preferably the inert agent surface is distributed with multiple sharp-angled tips (such as star );
  • the equivalent diameter of the inert agent is preferably 1-20mm (for example, 1mm, 3mm, 5mm, 8mm, 10mm, 12mm, 13mm, 15mm, 20mm, etc.), preferably 8-15mm.
  • an inert agent with one or more (preferably more than two) sharp-angled tips on the surface for example, star-cone, spindle, star or other inert agents with sharp-angled tips
  • the better effect is to use the filling ratio of the inert agent and the catalyst (the volume of the inert agent accounts for the volume of the inert agent and the catalyst 0.1-0.9 of the total volume, such as 0.1, 0.3, 0.5, 0.7, 0.9, preferably 0.7-0.85).
  • the use of the inert agent of the preferred shape and the packing method of the preferred ratio can improve the heat conduction in the phosgene synthesis tower.
  • the heat conduction in the phosgene synthesis tower can be changed from catalyst-inert agent-catalyst-inert agent-catalyst -Inert agent-tube mode is changed to catalyst-inert agent-tube, which minimizes the unconnected area of the inert agent, thereby improving the heat transfer efficiency, reducing hot spots and lowering the temperature of the hot spots, extending the life of the catalyst, and at the same time.
  • a higher temperature heat transfer agent is obtained at the outlet of the heat transfer agent circulation space to provide a sufficient heat source for subsequent steam generation.
  • the first-stage phosgene synthesis tower of step 1) it is preferable to use high thermal conductivity composite activated carbon as a catalyst, which includes particulate additives and activated carbon, and the mass ratio of the two is (1-10): 100 (E.g. 1:100, 3:100, 5:100, 6:100, 7:100, 8:100, 10:100, etc.), preferably (3-6): 100; the particle additives are selected from alumina, One or at least two of silicon carbide, graphite, and boron carbide, preferably aluminum oxide and/or silicon carbide.
  • the high thermal conductivity composite activated carbon can be prepared by a method including the following steps: mixing activated carbon powder, granular additives and adhesive in water, drying and forming (formed into a desired shape as required), and then steaming at 600- 800°C (such as 600°C, 650°C, 700°C, 750°C, 800°C, etc.) for constant temperature carbonization. Constant temperature carbonization can specifically be treated with water vapor at 600-800°C for 1-10h (such as 1h, 2h, 5h, 8h, 10h).
  • the heat transfer efficiency of the reaction heat can be improved, and the characteristics of fewer hot spots and low hot spot temperature can be maintained under the condition of high temperature operation of the heat transfer agent.
  • existing catalysts such as conventional activated carbon catalysts, if a higher heat transfer temperature is controlled during the heat transfer process, it will cause the hot spot temperature to rise, cause the activated carbon to pulverize, and greatly shorten its life, which affects the operation of the device.
  • the mass ratio of the adhesive to the activated carbon powder is (3-20):100 (for example, 3:100, 5:100, 10:100, 15:100, 20:100, etc.).
  • the mass ratio of activated carbon to water can be (20-50):100, which is convenient for molding.
  • the adhesive used can be, for example, emulsified phenolic resin, activated clay, emulsified coal tar, carboxymethyl cellulose, and the like.
  • the appearance shape of the catalyst used can be cylindrical, spherical, square column, spindle, star cone or other common shapes in the field, preferably cylindrical; preferably the equivalent diameter of the catalyst is 1-10mm (for example, 1mm). , 3mm, 5mm, 7mm, 9mm, 10mm, etc.), preferably 5-10mm.
  • the equivalent diameter such as the equivalent diameter of a catalyst or an inert agent
  • the equivalent diameter of a star-shaped inert agent refers to the diameter of the circumscribed circle of the inert agent
  • the equivalent diameter refers to the diameter of the sphere itself.
  • the volume of the inert agent is calculated according to its equivalent diameter. For example, for a star-shaped inert agent, it is calculated according to the volume of the circumscribed circle of the inert agent; the volume of the catalyst is also calculated in this way.
  • the heat transfer agent is selected from water, chlorobenzene, toluene, decalin, high temperature silicone oil or high temperature mineral oil, preferably high temperature silicone oil or decalin.
  • the high-temperature silicone oil or high-temperature mineral oil mentioned here refers to the high-temperature silicone oil or high-temperature mineral oil with a temperature resistance of 220°C or more.
  • the method for removing the heat of reaction of the heat transfer agent is that the temperature of the liquid heat transfer agent is increased, or the liquid heat transfer agent is vaporized into a gas, preferably the liquid heat transfer agent is vaporized into a gas.
  • the temperature of the heat transfer agent that has absorbed reaction heat output from the heat transfer agent circulation space is 130-265°C, such as 130°C, 150°C, 180°C, 190°C, 200°C. °C, 210 °C, 220 °C, etc., preferably 190-220 °C
  • the pressure is -0.5 Barg to 5 Barg, such as -0.5 Barg, 1 Barg, 3 Barg, 5 Barg, and the like.
  • the heat transfer method between the heat transfer agent and the water used for conversion into steam is the temperature drop of the heat transfer agent or the liquefaction of the gas heat transfer agent into a liquid.
  • the pressure of the superheated steam is 2-35 Barg, such as 2 Barg, 5 Barg, 8 Barg, 9 Barg, 10 Barg, 15 Barg, 20 Barg, 25 Barg, 30 Barg, 35 Barg, etc., preferably 8-10 Barg
  • the temperature is 150-260°C, such as 150°C, 180°C, 190°C, 200°C, 230°C, 260°C, etc., preferably 180-200°C.
  • the volume ratio of CO and chlorine in step 1) is 1.01-1.10, preferably 1.015-1.03.
  • the first-stage phosgene synthesis tower and the second-stage phosgene synthesis tower are both tubular phosgene synthesis towers, the diameter of the tubes may be 20mm-80mm, and the distance between the tubes may be 25mm. -100mm, the length of the tube can be 3000mm-4500mm.
  • the catalyst and inert agent are packed in the tubes, and the free space between the tubes and between the tubes and the wall of the first-stage phosgene synthesis tower (that is, the space surrounding the tubes in the phosgene synthesis tower) is used as the transfer
  • the circulation space of the heat agent is provided with tubes and a medium circulation space surrounding the tubes is a conventional structure of a phosgene synthesis tower in this field (see Fig. 5).
  • the difference of the present invention is that the medium circulation space is used as a circulation space for the heat transfer agent.
  • the heat transfer agent circulates between the heat transfer agent circulation space and the steam generator.
  • the filling amount of the catalyst those skilled in the art can determine it according to the needs, for example, it is subject to filling the tube after mixing the catalyst and the inert agent according to the required ratio.
  • the temperature of the first-stage phosgene synthesis tower is 55-270°C, such as 55°C, 100°C, 150°C, 200°C, 210°C, 220°C, 230°C, etc., preferably 200°C. -230°C
  • the pressure is 2.5-5.5 Barg, such as 2.5 Barg, 3.0 Barg, 3.5 Barg, 4.0 Barg, 4.5 Barg, 5.5 Barg, etc., preferably 2.5-3.5 Barg
  • the temperature of the secondary phosgene synthesis tower is 50-60° C
  • the pressure is 2.5-5.5 Barg.
  • the free chlorine concentration at the outlet of the first-stage phosgene synthesis tower described in step 1) is 50 ppm-3%
  • the free chlorine concentration at the outlet of the second-stage phosgene synthesis tower is 20-50 ppm, both of which refer to the mass concentration.
  • the brine is waste brine, for example, the condensed brine produced in the condensation reaction after separating the water layer, or the photochemical formed by neutralizing the lye discharged from the lye absorption tower Brine, specifically, for example, waste brine from MDI production.
  • the mass concentration of sodium chloride in the condensed brine is 10-20%, and the mass concentration of sodium hydroxide is 0.5-3%; the mass concentration of sodium chloride in the actinic brine is 1-15%.
  • the evaporation and concentration adopts evaporation and concentration techniques well known in the art, such as double-effect evaporation, where the first-stage evaporation temperature can be 50-130°C, and the pressure can be 0.1-3.0 Bara; The second-stage evaporation temperature can be 35-100°C, and the pressure can be 0.05-1.0 Bara.
  • the brine to be concentrated supplied to the brine evaporation concentration device is previously neutralized in a neutralization tank, and the acid used for the neutralization is, for example, hydrochloric acid or pure HCl gas.
  • the temperature of the neutralization tank is, for example, 40-80°C, and the pressure is, for example, 0 Barg-0.5 Barg.
  • the mass concentration of sodium chloride is 4%-23%.
  • the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis of the present invention can realize rational use of energy, resource utilization of waste brine, and realize overall circular economy and zero emission.
  • the heat generated by phosgene synthesis can be efficiently removed, avoiding the formation of high temperature hot spots on the catalyst surface, and prolonging the service life of the activated carbon ;
  • the heat of reaction can be removed efficiently, it is beneficial to output a higher temperature heat transfer agent in the heat transfer agent circulation space of the first-stage phosgene synthesis reactor.
  • the use of this higher temperature heat transfer agent can be used in The steam generator exchanges heat with water (such as boiler water) to produce low-pressure steam with a pressure of 0.2-0.6 MPa, or medium-pressure steam with a pressure of 1.4-1.6 MPa, or high-pressure steam with a pressure of 2.8-3.2 MPa.
  • the brine evaporation and concentration device is supplied to provide sufficient heat source; after the waste brine is concentrated and crystallized by evaporation, the obtained dry salt is further electrolyzed in the electrolytic cell to obtain chlorine gas.
  • FIG. 1 is a schematic diagram of the process of Comparative Example 1.
  • FIG. 1 is a schematic diagram of the process of Comparative Example 1.
  • Figure 2 is a schematic diagram of the process of Example 1-2 of the present invention
  • Fig. 3 is a simulation diagram of the catalyst and inert agent in Comparative Example 1 after being filled in the tube;
  • Figure 4 is a simulation diagram of the catalysts and inerts in Examples 1, 3 and Comparative Example 2 after being filled in the tube;
  • Figure 5 is a schematic top view of the inside of the phosgene synthesis tower; it mainly shows the distribution of the tubes and the circulation space of the heat transfer agent.
  • the sodium chloride in the brine is determined by the national standard method GB/T 4348.2-2014.
  • 1% (m/v) potassium iodide is added to the collected synthetic phosgene to react with free chlorine (Cl 2 ) in the phosgene, and the generated iodine is titrated with sodium thiosulfate standard solution.
  • Potassium iodide mixed into 1% (m/v) aqueous solution
  • V 1 The volume of sodium thiosulfate standard solution consumed when titrating the sample, mL;
  • V 2 The volume of the gas sampling bottle, L;
  • the integrated treatment system for phosgene synthesis and brine evaporation and electrolysis mainly includes a mixer 3, a first-stage phosgene synthesis tower 4, a steam generator 6, a second-stage phosgene synthesis tower 5, a circulating water cooler 7, a brine evaporation concentration device 100 and Crystallizer 12.
  • the mixer 3 is connected with the first-stage phosgene synthesis tower 4, and the mixer 3 is also connected with the chlorine gas transmission pipeline 1 and the CO transmission pipeline 2.
  • the mixer 3 is used to mix chlorine and CO, and is supplied to the first stage via the pipeline 13 Phosgene synthesis tower 4.
  • the first-stage phosgene synthesis tower 4 and the second-stage phosgene synthesis tower 5 used in the following embodiments are specifically tubular reaction towers with a diameter of 40 mm, a spacing of 50 mm, and a length of 4000 mm.
  • the tubes of the first-stage phosgene synthesis tower 4 and the second-stage phosgene synthesis tower 5 are filled with mixed catalyst and inert agent, and the heat transfer agent circulation space of the first-stage phosgene synthesis tower 4 (in the first-stage phosgene synthesis tower)
  • the heat transfer agent circulates in the space surrounding the tube; see Figure 5, where 24 is the wall of the phosgene synthesis tower, 25 is the tube set in the phosgene synthesis tower, and 23 is the circulation space for the heat transfer agent.
  • the heat transfer agent outlet 27 of the heat transfer agent circulation space is connected with the heat transfer agent inlet (not shown in the figure) of the steam generator 6 through the pipeline 15, and the heat transfer agent inlet 26 of the heat transfer agent circulation space is connected to the steam generator 6
  • the heat transfer agent outlet (not shown in the figure) is connected through a pipeline 16, and the heat transfer agent circulates between the first-stage phosgene synthesis tower 4 and the steam generator 6.
  • the heat transfer agent absorbs the reaction heat generated in the process of synthesizing phosgene in the first-stage phosgene synthesis tower 4 and then heats up, and flows into the steam generator 6 for heat exchange with boiler water, so that the boiler water is converted into superheated steam.
  • the temperature of the heating agent is lowered and then returned to the first-stage phosgene synthesis tower 4 to continue to participate in the absorption of reaction heat.
  • the superheated steam outlet (not shown in the figure) of the steam generator 6 is connected to the salt water evaporation and concentration device 100, and the superheated steam is supplied to the salt water evaporation and concentration device 100 through the pipeline 17 to provide a heat source for it.
  • the brine evaporative concentration device 100 is used for evaporative concentration of waste brine to obtain concentrated brine.
  • the brine evaporation and concentration device 100 can use a corresponding device well-known in the art.
  • the double-effect evaporation well-known in the art is specifically used.
  • the double-effect evaporation is introduced as follows in conjunction with FIG.
  • the two-stage evaporation unit 101 and the two-stage evaporation unit 102 each include an evaporator (8, 10), a brine tower (9, 11) and a pump 18, respectively.
  • the waste brine first enters the primary evaporator 8 of the primary evaporation unit 101, where it exchanges heat with the superheated steam from the steam generator 6, and then enters the primary brine tower 9, and the primary concentrated brine in the primary brine tower 9 Separate from steam; steam enters the secondary evaporator 10 of the secondary evaporator unit 102 through the pipeline as a heat source, and the primary concentrated brine enters the secondary evaporator 10 and exchanges heat with the steam again, and then enters the secondary brine tower 11; The secondary concentrated brine enters the crystallizer 12 for crystallization to obtain dry salt.
  • the first-stage evaporation temperature is 130°C (the temperature of the first-stage evaporator 8, the temperature of the first-stage brine tower 9 is similar to it), and the evaporation pressure is 2.7bara (the pressure of the first-stage evaporator 8, the first-stage brine tower The pressure of 9 is similar); the secondary evaporation temperature is 50°C (the temperature of the secondary evaporator 10, and the temperature of the secondary brine tower 11 is similar to it), and the pressure is 0.12bara (the pressure of the secondary evaporator 10) , The pressure of the secondary brine tower 11 is similar to it), and the dry salt is sent to the downstream process for electrolysis to produce chlorine.
  • the phosgene outlet of the first-stage phosgene synthesis tower 4 is connected to the second-stage phosgene synthesis tower 5 through a pipeline 14, and the mixed gas containing phosgene output from the first-stage phosgene synthesis tower 4 enters the second-stage phosgene synthesis tower 5.
  • the stage phosgene synthesis tower 5 completely converts the remaining chlorine gas into phosgene.
  • the tower structure of the second-stage phosgene synthesis tower is the same as that of the first-stage phosgene synthesis tower; the difference is that the second-stage phosgene synthesis tower uses circulating water to remove the reaction heat, that is, the space circulated in the space surrounding the tubes in the second-stage phosgene synthesis tower It is circulating water, and the space surrounding the tube is communicated with the circulating water cooler 7.
  • thermocouple used to monitor the hot spot temperature is installed in the tube of the first-stage phosgene synthesis tower.
  • This embodiment uses the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis.
  • the heat generated by phosgene synthesis is by-product steam; the waste brine generated by condensation and photochemical in the MDI production is evaporated using double-effect evaporation technology to obtain dry salt, and the heat source is light. Gas synthesis by-product steam.
  • the process flow is shown in Figure 2.
  • the phosgene synthesis catalyst used in this example is 4GV-S activated carbon produced by Tsurumi, Japan, with a spherical shape and a size (diameter) of 8mm; the inert agent is domestic (Shanghai Baitu) silicon carbide with a star shape and size The (equivalent diameter) is 20mm, silicon carbide accounts for 75% of the total volume of activated carbon+silicon carbide, and the simulation diagram after the catalyst and inert agent are filled in the tubes of the first-stage phosgene synthesis tower 4 is shown in FIG. 4.
  • the volume ratio of phosgene synthesis feed CO to chlorine is 1.03, the pressure of the first-stage phosgene synthesis tower 4 is 3.0 barg, the temperature of the first-stage phosgene synthesis tower 4 is 220°C, the outlet free chlorine concentration is 1.5%, and the second-stage phosgene
  • the pressure of the synthesis tower 5 is 2.9 barg, the temperature of the second-stage phosgene synthesis tower 5 is 60°C, the outlet free chlorine concentration is 34ppm, the total amount of phosgene produced is 40t/h, and the heat transfer agent in the first-stage phosgene synthesis tower 4 is High-temperature silicone oil (Dow, SL200), the temperature of the high-temperature silicone oil from the heat transfer agent outlet of the first-stage phosgene synthesis tower 4 is 210°C (pressure 2Barg), and the high-temperature silicone oil is sent to the steam generator 6 to produce medium-pressure steam.
  • the pressure is 14 Barg, the temperature of the superheated steam is 195°C, and the by-product steam flow rate is 15t/h; the waste brine is neutralized with HCl, and the sodium chloride mass concentration after neutralization is 20%, and the neutralized brine is sent to the brine
  • the evaporation concentration device 100 performs double-effect evaporation, and the obtained concentrated brine is converted into saturated brine by the dry salt produced by the crystallization of the crystallizer 12, and then electrolyzed to generate chlorine gas.
  • the steam consumption is shown in Table 1
  • the dry salt output is shown in Table 1.
  • This embodiment uses the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis.
  • the heat generated by phosgene synthesis is by-product steam; the waste brine generated by condensation and photochemical in the MDI production is evaporated using double-effect evaporation technology to obtain dry salt, and the heat source is light. Gas synthesis by-product steam.
  • the process flow is shown in Figure 2. The difference from Example 1 is that inert agents of different shapes and combinations are used;
  • the phosgene synthesis catalyst used in this example is 4GV-S activated carbon produced by Tsurumi, Japan, with a spherical shape and a size (diameter) of 8mm; the inert agent is domestic silicon carbide (Shanghai Baitu), and the shape is a star cone.
  • the size (equivalent diameter) is 18mm, and silicon carbide accounts for 80% of the total volume of activated carbon + silicon carbide.
  • the volume ratio of phosgene synthesis feed CO to chlorine is 1.03, the pressure of the first-stage phosgene synthesis tower 4 is 3.0 barg, the temperature of the first-stage phosgene synthesis tower 4 is 220°C, the outlet free chlorine concentration is 1.9%, the second-stage phosgene
  • the pressure of the synthesis tower 5 is 2.9 barg, the temperature of the second-stage phosgene synthesis tower 5 is 60°C, the outlet free chlorine concentration is 36ppm, the total amount of phosgene produced is 40t/h, and the heat transfer agent in the first-stage phosgene synthesis tower 4 is High-temperature silicone oil (Dow, SL200), the temperature of the high-temperature silicone oil from the heat transfer agent outlet of the first-stage phosgene synthesis tower 4 is 210°C (pressure 2Barg), and the high-temperature silicone oil is sent to the steam generator 6 to produce medium-pressure steam.
  • the pressure is 14 Barg, the temperature of the superheated steam is 195°C, and the by-product steam flow rate is 15t/h; the waste brine is neutralized with HCl, and the sodium chloride mass concentration after neutralization is 20%, and the neutralized brine is sent to the brine
  • the evaporative concentration device performs double-effect evaporation, and the obtained concentrated brine is converted into saturated brine by the dry salt produced by the crystallizer crystallization, and then electrolyzed to generate chlorine gas.
  • the steam consumption is shown in Table 1
  • the dry salt output is shown in Table 1.
  • This embodiment uses the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis.
  • the heat generated by phosgene synthesis is by-product steam; the waste brine generated by condensation and photochemical in the MDI production is evaporated using double-effect evaporation technology to obtain dry salt, and the heat source is light.
  • Gas synthesis by-product steam is the difference from Example 1 is that the catalyst is a high thermal conductivity composite activated carbon, and the process flow is shown in FIG. 2.
  • the phosgene synthesis catalyst used in this example is high thermal conductivity composite activated carbon
  • the composite material (particle additive) is alumina
  • the mass ratio of alumina to activated carbon is 5:100
  • the adhesive is emulsified phenolic resin (Shanghai Latex Factory, HX30)
  • the mass ratio of emulsified phenolic resin to activated carbon is 15:100
  • the mass ratio of activated carbon to water is 30:100.
  • the life of activated carbon after use is shown in Table 1;
  • the inert agent is domestic silicon carbide (Shanghai Baitu), the shape is star, the size (equivalent diameter) is 20mm, and silicon carbide accounts for the high thermal conductivity composite 75% of the total volume of activated carbon + silicon carbide, catalysts and inerts are filled in the tubes of the first-stage phosgene synthesis tower 4, as shown in Figure 4, the volume ratio of the phosgene synthesis feed CO to chlorine is 1.03 ,
  • the pressure of the first-stage phosgene synthesis tower 4 is 3.0 barg
  • the temperature of the first-stage phosgene synthesis tower 4 is 220 °C
  • the outlet free chlorine concentration is 1.5%
  • the pressure of the second-stage phosgene synthesis tower 5 is 2.9 barg
  • the second-stage phosgene synthesis tower 5 is 2.9 barg.
  • the temperature of tower 5 is 60°C, the outlet free chlorine concentration is 34ppm, and the total amount of phosgene produced is 40t/h.
  • the heat transfer agent in the first-stage phosgene synthesis tower is high-temperature silicone oil (Dow, SL200).
  • the temperature of the heat transfer agent outlet of the phosgene synthesis tower is 210°C and the pressure is 2barg; the high-temperature silicone oil is sent to the steam generator to produce medium-pressure steam, the pressure of the steam is 14 barg, the temperature of the superheated steam is 195°C, and the flow rate of the by-product steam is 15t/h; neutralize the waste brine with HCl, the mass concentration of sodium chloride after neutralization is 20%, the neutralized brine is sent to the brine evaporation concentration device 100 for double-effect evaporation, and the concentrated brine is passed through the crystallizer 12
  • the dry salt produced by crystallization is adjusted to saturated brine, and then chlorine is produced by electrolysis.
  • the steam consumption is shown in Table 1, and the dry salt output is shown in Table 1.
  • This embodiment uses the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis.
  • the heat generated by phosgene synthesis is by-product steam; the waste brine generated by condensation and photochemical in the MDI production is evaporated using double-effect evaporation technology to obtain dry salt, and the heat source is light. Gas synthesis by-product steam.
  • Example 3 The difference from Example 3 is that the catalyst uses a different high thermal conductivity composite activated carbon, and the process flow is shown in FIG. 2.
  • the phosgene synthesis catalyst used in this example is high thermal conductivity composite activated carbon
  • the composite material (particle additive) is silicon carbide
  • the mass ratio of silicon carbide to activated carbon is 10:100
  • the adhesive is emulsified phenolic resin (Shanghai Latex Factory, HX30)
  • the mass ratio of emulsified phenolic resin to activated carbon is 20:100
  • the mass ratio of activated carbon to water is 30:100.
  • After mixing the components, it is made into a cylindrical shape with a size (equivalent diameter) of 6mm. After drying for 20h
  • the activated carbon is treated by superheated steam at 800°C for 2h, and the life of activated carbon after use is compared in Table 1.
  • the inert agent is domestic silicon carbide (Shanghai Baitu), the shape is star, the size (equivalent diameter) is 20mm, and silicon carbide accounts for high thermal conductivity.
  • Composite activated carbon + 75% of the total volume of silicon carbide, the simulation diagram of the catalyst and inert agent filled in the tubes of the first-stage phosgene synthesis tower 4 is similar to Figure 4, the volume ratio of the phosgene synthesis feed CO to chlorine is 1.03 ,
  • the pressure of the first-stage phosgene synthesis tower 4 is 3.0 barg, the temperature of the first-stage phosgene synthesis tower 4 is 220 °C, the outlet free chlorine concentration is 1.4%, the pressure of the second-stage phosgene synthesis tower 5 is 2.9 barg, and the second-stage phosgene synthesis tower 5 is 2.9 barg.
  • the temperature of tower 5 is 60°C, the free chlorine concentration at the outlet is 32ppm, and the total amount of phosgene produced is 40t/h.
  • the heat transfer agent in the first-stage phosgene synthesis tower 4 is high-temperature silicone oil (Dow, SL200).
  • the temperature of the heat transfer agent outlet of the stage phosgene synthesis tower 4 is 210°C and the pressure is 2barg; the high-temperature silicone oil is sent to the steam generator 6 to produce medium-pressure steam, the pressure of the steam is 14 barg, the temperature of the superheated steam is 195°C, by-product
  • the steam flow rate is 15t/h; the waste brine is neutralized with HCl, and the mass concentration of sodium chloride after neutralization is 20%.
  • the neutralized brine is sent to the brine evaporation and concentration device 100 for double-effect evaporation, and the obtained concentrated brine is subjected to double-effect evaporation.
  • the dry salt produced by the crystallization of the crystallizer 12 is adjusted to saturated brine and sent to chlor-alkali for salt conversion, after which chlorine is generated by electrolysis.
  • the steam consumption is shown in Table 1, and the dry salt output is shown in Table 1.
  • the chlorine and carbon monoxide are mixed in the mixer 3, they enter the first-stage phosgene synthesizer 4 to synthesize phosgene under the action of the catalyst.
  • the heat generated by the phosgene synthesis is taken away by the circulating water; the condensation and photochemical production in MDI production
  • the waste brine is evaporated using double-effect evaporation technology to obtain dry salt, and the heat source is pipe network steam.
  • the phosgene synthesis catalyst used in this comparative example is 4GV activated carbon produced by Tsurumi, Japan, with a cylindrical shape and a diameter (equivalent diameter) of 8mm.
  • the inert agent is a domestic alumina ceramic ball (Shanghai Baitu), which is spherical in shape.
  • the size (equivalent diameter) is 14mm, the alumina ceramic ball accounts for 60% of the total volume of activated carbon+alumina, and the simulation diagram after the catalyst and inert agent are filled in the tubes of the first-stage phosgene synthesis tower 4 is shown in FIG. 3.
  • the volume ratio of phosgene synthesis feed CO to chlorine is 1.05, the pressure of the first-stage phosgene synthesis tower is 3 barg, the temperature of the first-stage phosgene synthesis tower 4 is 60 °C, the pressure of the second-stage phosgene synthesis tower 4 is 3 barg, and the pressure of the second-stage phosgene synthesis tower 4 is 3 barg.
  • the temperature of the gas synthesis tower 5 is 60°C (pressure is 3barg), and the total amount of phosgene produced is 40t/h.
  • the heat transfer agent in the first-stage phosgene synthesis tower 4 is circulating water. The flow rate is shown in Table 1. The circulating water return water temperature It is 38°C.
  • the content of free chlorine in phosgene is 40ppm; the waste brine is neutralized with HCl, and the mass concentration of sodium chloride after neutralization is 20%.
  • the neutralized brine is sent to the evaporation concentration device 100 for double-effect evaporation (double-effect evaporation and Example 1 is the same, but the difference is that the heat source comes from pipe network steam, not the superheated steam produced by phosgene synthesis).
  • the concentrated brine is converted to saturated brine by the dry salt produced by the crystallization of the crystallizer 12, and then chlorine is generated by electrolysis, and the steam is consumed.
  • the quantity is shown in Table 1, and the dry salt output is shown in Table 1.
  • This comparative example is basically the same as Example 1, except that the waste brine produced by condensation and photochemical in the MDI production does not use the by-product superheated steam for double-effect evaporation to obtain dry salt, but instead discharges the brine into the seawater.
  • the phosgene synthesis catalyst used in this comparative example is 4GV-S activated carbon produced by Tsurumi, Japan, with a spherical shape and a size (diameter) of 8mm.
  • the inert agent is domestic silicon carbide (Shanghai Baitu), with a star shape and size. (Equivalent diameter) is 20mm, silicon carbide accounts for 75% of the total volume of activated carbon + silicon carbide, and the simulation diagram after the catalyst and inert agent are filled in the tubes of the first-stage phosgene synthesis tower is shown in Figure 4.
  • the volume ratio of feed CO to chlorine is 1.04
  • the pressure of the first-stage phosgene synthesis tower is 3.1 barg
  • the temperature of the first-stage phosgene synthesis tower is 205°C
  • the pressure of the second-stage phosgene synthesis tower is 3 barg
  • the temperature of the second-stage phosgene synthesis tower is At 60°C
  • the total amount of phosgene produced is 40t/h
  • the heat transfer agent in the first-stage phosgene synthesis tower is decalin
  • the temperature at the outlet of the decalin from the first-stage phosgene synthesis tower is 198°C. Decahydronaphthalene is sent to the steam generator to produce medium-pressure steam.
  • the pressure of the steam is 14 Barg, the temperature of the superheated steam is 195°C, the flow of by-product steam is 15t/h, and the free chlorine content in phosgene is 40ppm; the waste brine is mixed with HCl After neutralization, the concentration is 20%. After neutralization, the salt water is discharged into the sea.
  • This comparative example uses the integrated treatment process of phosgene synthesis and brine evaporation and electrolysis.
  • the heat generated by phosgene synthesis is a byproduct of steam; the waste brine produced by condensation and photochemical in the MDI production is evaporated using double-effect evaporation technology to obtain dry salt.
  • the heat source is light. Gas synthesis by-product steam. The process flow is shown in Figure 2.
  • the phosgene synthesis catalyst used in this example is 4GV-S activated carbon produced by Tsurumi, Japan, with a spherical shape and a size (diameter) of 8mm; the inert agent is domestic silicon carbide (Shanghai Baitu) with a spherical shape and size (Diameter) is 10mm, and silicon carbide accounts for 75% of the total volume of activated carbon + silicon carbide.
  • the volume ratio of phosgene synthesis feed CO to chlorine is 1.03, the pressure of the first-stage phosgene synthesis tower is 3.0 barg, the temperature of the first-stage phosgene synthesis tower is 220°C, the outlet free chlorine concentration is 1.5%, the second-stage phosgene synthesis tower The pressure is 2.9barg, the temperature of the second-stage phosgene synthesis tower is 60°C, the outlet free chlorine concentration is 34ppm, the total amount of phosgene produced is 40t/h, and the heat transfer agent in the first-stage phosgene synthesis tower is high-temperature silicone oil (Dow , SL200), the temperature of the high-temperature silicone oil from the heat transfer agent outlet of the first-stage phosgene synthesis tower is 210°C, and the high-temperature silicone oil is sent to the steam generator to produce medium-pressure steam.
  • the pressure of the first-stage phosgene synthesis tower is 3.0 barg
  • the pressure of the steam is 14 Barg, and the temperature of the superheated steam is 195°C.
  • the by-product steam flow rate is 15t/h; the waste brine is neutralized with HCl, and the sodium chloride mass concentration after neutralization is 20%.
  • the neutralized brine is sent to the brine evaporation and concentration device for double-effect evaporation, and the obtained concentrated brine
  • the dry salt produced by crystallization in the crystallizer is adjusted to saturated brine, and then chlorine is generated by electrolysis.
  • the steam consumption is shown in Table 1, and the dry salt output is shown in Table 1.
  • the life span is significantly shortened, and the hot spot temperature is higher; while the hot spot temperature of Examples 1-2 using the inert agent with a sharp-pointed shape is significantly lower than that of Comparative Example 3, and the catalyst life is significantly prolonged, and compared with the comparative example that does not by-produce steam 1
  • the results in these two aspects are close. From Examples 1-4, the use of a sharp-shaped inert agent and the use of a composite activated carbon catalyst have a longer catalyst life, and the production can run stably for a long period of time; it can greatly reduce the hot spot temperature and prolong the catalyst life.

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Abstract

本发明提供光气合成及盐水蒸发电解一体化处理工艺，包括如下步骤： 1)将预先混合的CO和氯气通入一级光气合成塔内，合成光气；所述一级光气合成塔设有移热剂流通空间，所述移热剂流通空间内流通移热剂；2)将所述移热剂流通空间内吸收了反应热的移热剂通入蒸汽发生器中，与水换热以产生过热蒸汽，将换热后的移热剂返回至移热剂流通空间，用于继续吸收合成光气产生的反应热；3)将过热蒸汽供应至盐水蒸发浓缩装置，所述盐水蒸发浓缩装置以所述过热蒸汽为热源对盐水进行蒸发浓缩；4)将步骤3)得到的浓盐水或干盐通过电解产生氯气。本发明提供的光气合成及盐水蒸发电解一体化处理工艺，可实现能源合理利用，废盐水资源化利用。

Description

光气合成及盐水蒸发电解一体化处理工艺 技术领域
本发明涉及一种光气合成及盐水蒸发电解一体化处理工艺。
背景技术
光气合成工艺通常采用活性炭催化合成反应得到，合成反应伴随产生的大量反应热，每合成一吨光气所能产生的热量超过30万大卡，通常采用水、氯苯、导热油等移除，热量移除过程中，活性炭导热性能较差，径向和轴向温差较大，导致存在有温度高达500-600℃的热点，易引起活性炭粉化，为避免热点温度过高，通常反应温度偏低，移除的热量最终通过循环水带走，带来能量浪费、循环水消耗量大的问题。
根据公开专利报道，解决活性炭粉化问题通常有以下几种方法：
中国公开专利CN104415770A描述可使用碱金属盐对活性炭涂层/泡沫碳化硅结构催化剂表面进行改性，以降低催化剂床层的径向和轴向温度差；
中国公开专利CN1765740A描述一种管壳式反应器，通过充分的热量消散，降低热点温度，减少活性炭粉化；
综上，现有技术针对活性炭粉化，为了避免热点温度偏高，反应热通常由温度30℃左右的循环水带走，最终能量消耗在凉水塔中，存在能量浪费、循环水消耗大的问题，提出的解决措施有局限性，无法实现能量回用；或采用特殊加工制作的催化剂，存在改造工艺较复杂、特殊粘附上的催化剂易于脱落、无法长周期运行等问题。此外，化工园区通常限制外排盐水总量，缩合盐水占用大量外排配额，制约园区各装置总体运转，且外排前需进行TOC脱除，需要消耗成本；而外排盐水中盐浓度较高，盐资源浪费较为严重。需要一种循环绿色工艺，代替现有工艺，解决光气合成热量浪费、缩合盐水外排的问题。
发明内容
有鉴于此，本发明提供一种光气合成及盐水蒸发电解一体化处理工艺，实 现能源合理利用，废盐水资源化利用，实现整体循环经济、零排放。
本发明为达到其目的，提供如下技术方案：
本发明提供一种光气合成及盐水蒸发电解一体化处理工艺，包括如下步骤：
1)将预先混合的CO和氯气通入一级光气合成塔内，在催化剂作用下CO和氯气反应合成光气；所述一级光气合成塔设有移热剂流通空间，所述移热剂流通空间内流通移热剂，用于吸收合成光气所产生的反应热；所述催化剂为活性炭或高导热复合活性炭，优选高导热复合活性炭；
2)将所述移热剂流通空间内吸收了反应热的移热剂通入蒸汽发生器中，与用于转化为蒸汽的水换热以产生过热蒸汽，将和所述用于转化为蒸汽的水换热后的移热剂返回至所述一级光气合成塔的移热剂流通空间，用于继续吸收合成光气产生的反应热；
3)将步骤2)中所述的过热蒸汽供应至盐水蒸发浓缩装置，所述盐水蒸发浓缩装置以所述过热蒸汽为热源对盐水进行蒸发浓缩，得到浓盐水；任选的，所述浓盐水经结晶得到干盐；
4)将步骤3)得到的浓盐水或干盐通过电解产生氯气；一些具体实施方式中，将所述浓盐水或干盐调为饱和盐水(饱和盐水的质量浓度例如为23％)，之后将该饱和盐水电解产生氯气。
一些实施方案中，步骤1)中，将所述一级光气合成塔得到的含有所述光气的混合气输入二级光气合成塔进一步反应，将剩余的氯气完全转化为光气。一些实施方案中，二级光气合成塔采用循环水移除反应热，利用循环水移除反应热为本领域常规采用的移热方式。
一些实施方案中，在所述一级光气合成塔、二级光气合成塔内的催化剂装填区域(例如列管中)中，装填有混匀的所述催化剂和惰性剂，所述惰性剂的材质选自碳化硅、氧化铝或石墨中的一种或至少两种，优选为碳化硅。
所述惰性剂的外观形状可以为方柱状、圆柱形、圆球形、星锥形、纺锤形、矩鞍形、星形或其他形状，优选所述惰性剂表面带有一个或多个(例如两个以上，例如两个、三个、四个等)呈锐角的尖端，例如星锥形、纺锤形、星形等，更优选所述惰性剂表面分布有多个呈锐角的尖端(例如星形)；惰性剂的当量直径优选为1-20mm(例如1mm、3mm、5mm、8mm、10mm、12mm、13mm、15mm、 20mm等)，优选8-15mm。
本发明人发现，使用表面带有一个或多个(优选两个以上)呈锐角的尖端的惰性剂(例如星锥形、纺锤形、星形或其他带有呈锐角的尖端的形状的惰性剂)，能减少催化剂与催化剂之间的接触概率，提高移热效率，降低热点温度，从而延长催化剂寿命；效果更佳的采用优选惰性剂和催化剂的装填比例(惰性剂的体积占惰性剂和催化剂的总体积的0.1-0.9，例如0.1、0.3、0.5、0.7、0.9，优选0.7-0.85)。采用优选形状的惰性剂和优选比例的装填方式，能使光气合成塔内的热传导情况得到良好的改善，例如使光气合成塔内的热传导情况由催化剂-惰性剂-催化剂-惰性剂-催化剂-惰性剂-列管的方式，改变为催化剂-惰性剂-列管，最大程度的减少惰性剂的不连接区域，从而能提高移热效率，减少热点并降低热点温度，延长催化剂寿命，同时还利于在移热剂流通空间出口获得温度较高的移热剂，为后续蒸汽产生提供充足的热源。
本发明的优选实施方案中，在步骤1)的一级光气合成塔内，优选使用高导热复合活性炭作为催化剂，其包括颗粒添加剂和活性炭，二者的质量比为(1-10):100(例如1:100、3:100、5:100、6:100、7:100、8:100、10:100等)，优选(3-6)：100；所述颗粒添加剂选自氧化铝、碳化硅、石墨、碳化硼中的一种或至少两种，优选氧化铝和/或碳化硅。所述高导热复合活性炭具体可采用包括如下步骤的方法制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀，干燥成型(根据需要而成型为所需形状)，之后用水蒸气在600-800℃(例如600℃、650℃、700℃、750℃、800℃等)进行恒温碳化，恒温碳化具体可以用水蒸气在600-800℃下处理1-10h(例如1h、2h、5h、8h、10h)。通过采用这种特定组成和工艺得到的高导热复合活性炭为催化剂，可以改善反应热的移热效率，在移热剂高温操作的情况下仍能维持热点少、热点温度低的特点。然而，现有的催化剂，例如常规的活性炭催化剂，若在移热过程中控制较高的移热温度，将会引起热点温度升高，造成活性炭粉化，使其寿命大幅缩短，影响装置的运行。进一步优选的，所述胶黏剂与所述活性炭粉的质量比为(3-20):100(例如3:100、5:100、10:100、15:100、20:100等)。活性炭与水的质量比可为(20-50):100，便于成型。所用的胶黏剂例如可以是：乳化酚醛树脂、活性黏土、乳化煤焦油、羧甲基纤维素等。
所用的所述催化剂外观形状可以为圆柱形、圆球形、方柱形、纺锤形、星锥形或其他本领域常见的形状，优选为圆柱形；优选催化剂的当量直径为1-10mm(例如1mm、3mm、5mm、7mm、9mm、10mm等)，优选5-10mm。
本发明中，所述的当量直径，例如催化剂或惰性剂的当量直径，均指其外接圆直径，例如星形惰性剂的当量直径指该惰性剂的外接圆的直径；对于圆球形的惰性剂和催化剂，该当量直径即指该圆球形本身的直径。惰性剂的体积按照其当量直径来计算，例如对于星形惰性剂，按照该惰性剂的外接圆的体积来计算；催化剂的体积也按照该方式来计算。
在光气合成塔内优选使用高导热复合活性炭，结合上述特定形状和比例装填的惰性剂和催化剂，更有利于改善光气合成催化剂粉化、运行周期短的问题，进一步延长催化剂寿命和降低热点温度；由于能实现更长的运行周期，因而可避免反复开停车，能利用光气合成的反应热稳定副产过热蒸汽，且由于能高效移热，能在移热剂流通空间出口获得温度较高的移热剂，保证热源的提供；将光气合成和蒸汽产生及盐水浓缩等相耦合，利用过热蒸汽对废盐水进行蒸发浓缩，减少废盐水外排，而蒸发得到的浓盐水或任选地将所述浓盐水经结晶得到的干盐进一步用于电解生成氯气，实现MDI(二苯基甲烷二异氰酸酯)生产中的光气合成、盐水处理、氯碱工业三大高能耗工艺的紧密结合，能量合理利用，废盐水资源化利用，实现整体循环经济、零排放。
一些实施方案中，步骤1)中，所述移热剂选自水、氯苯、甲苯、十氢化萘、高温硅油或高温矿物油，优选高温硅油或十氢化萘。此处所述的高温硅油或高温矿物油是指耐温220℃以上的高温硅油或高温矿物油。
本发明中，移热剂移除反应热的移除方式为液态移热剂温度升高，或液态移热剂气化为气体，优选为液态移热剂气化为气体。一些实施方案中，步骤2)中，由所述移热剂流通空间输出的吸收了反应热的移热剂的温度为130-265℃，例如130℃、150℃、180℃、190℃、200℃、210℃、220℃等，优选190-220℃，压力为-0.5Barg至5Barg，例如-0.5Barg、1Barg、3Barg、5Barg等。
移热剂与用于转化为蒸汽的水的换热方式为移热剂温度下降或气体移热剂液化为液体。一些实施方案中，步骤2)中，所述过热蒸汽的压力为2-35Barg， 例如2Barg、5Barg、8Barg、9Barg、10Barg、15Barg、20Barg、25Barg、30Barg、35Barg等，优选8-10Barg，温度为150-260℃，例如150℃、180℃、190℃、200℃、230℃、260℃等，优选180-200℃。
一些实施方案中，步骤1)中所述的CO和氯气的体积比例为1.01-1.10，优选1.015-1.03。
一些实施方案中，步骤1)中，所述一级光气合成塔和二级光气合成塔均为列管式光气合成塔，列管直径可为20mm-80mm，列管间距可为25mm-100mm，列管长度可为3000mm-4500mm。催化剂和惰性剂装填在列管中，而列管之间及列管和一级光气合成塔的塔壁之间的自由空间(即光气合成塔内围绕列管的空间)作为所述移热剂流通空间，设有列管和围绕列管的介质流通空间是本领域光气合成塔的常规结构(可参见图5)，本发明所不同在于该介质流通空间作为移热剂流通空间。移热剂在移热剂流通空间和蒸汽发生器之间循环流动。关于催化剂的装填量，本领域技术人员可以根据需要来确定，例如以将催化剂和惰性剂按照所需比例混合后装满列管为准。
一些实施方案中，步骤1)中，所述一级光气合成塔温度为55-270℃，例如55℃、100℃、150℃、200℃、210℃、220℃、230℃等，优选200-230℃，压力为2.5-5.5Barg，例如2.5Barg、3.0Barg、3.5Barg、4.0Barg、4.5Barg、5.5Barg等，优选2.5-3.5Barg；二级光气合成塔温度为50-60℃，压力为2.5-5.5Barg。
一些实施方案中，步骤1)所述的一级光气合成塔出口游离氯浓度为50ppm-3％，二级光气合成塔出口游离氯浓度为20-50ppm，二者均指质量浓度。
一些实施方案中，步骤3)中，所述盐水为废盐水，例如来自缩合反应中产生的分离出水层后的缩合盐水，或碱液吸收塔中外排的碱液经中和后形成的光化盐水，具体例如来自MDI生产中的废盐水。
一些实施方案中，所述缩合盐水中氯化钠质量浓度为10-20％、氢氧化钠质量浓度为0.5-3％；所述光化盐水中氯化钠质量浓度为1-15％。
一些实施方案中，步骤3)中，所述蒸发浓缩采用本领域所熟知的蒸发浓缩技术，例如双效蒸发，其中第一级蒸发温度可为50-130℃，压力可为 0.1-3.0Bara；第二级蒸发温度可为35-100℃，压力可为0.05-1.0Bara。
一些实施方案中，步骤3)中，供应至盐水蒸发浓缩装置的待浓缩的盐水，预先在中和罐中中和，中和所用的酸类例如为盐酸或纯HCl气。中和罐的温度例如为40-80℃，压力例如为0Barg-0.5Barg。经过中和罐中和的盐水，氯化钠质量浓度为4％-23％。
关于催化剂寿命的评价，为本领域技术人员所熟知的。例如在本发明的实施例和对比例中，当二级光气合成塔循环水用量变大超过5％、循环水温度出现大于0.5℃的温升时，表明二级光气合成塔内存在大量的光气转化、一级光气合成塔光气转化效率下降、催化剂已粉化到不可接受的程度，必须更换催化剂，由此来判断催化剂寿命。
本发明提供的技术方案具有如下有益效果：
本发明的光气合成及盐水蒸发电解一体化处理工艺，能实现能源合理利用，废盐水资源化利用，实现整体循环经济、零排放。
在本发明的优选方案中，通过使用高导热复合活性炭为催化剂，与惰性剂按特定比例和形状混合装填，光气合成产生的热量可以高效移除，避免催化剂表面形成高温热点，延长活性炭使用寿命；同时，由于能高效的移除反应热，利于在一级光气合成反应器的移热剂流通空间中输出温度较高的移热剂，利用这种温度较高的移热剂，可在蒸汽发生器中和水(例如锅炉水)换热，产生压力为0.2-0.6MPa的低压蒸汽、或者压力为1.4-1.6MPa的中压蒸汽、或者压力为2.8-3.2MPa的高压蒸汽，进而能将供给盐水蒸发浓缩装置，为其提供充足的热源；废盐水经蒸发浓缩、结晶后，得到的干盐进一步在电解池中电解得到氯气。因而，借助本发明的方案，可实现MDI生产中的光气合成、盐水处理、氯碱工业三大高能耗工艺的紧密结合，能量合理利用，废盐水资源化利用，实现整体循环经济零排放。
附图说明
图1是对比例1的工艺示意图。
图2是本发明实施例1-2的工艺示意图
图3是对比例1中催化剂和惰性剂在列管内装填后的模拟图；
图4是实施例1、3和对比例2中催化剂和惰性剂在列管内装填后的模拟图；
图5是光气合成塔内的俯视示意图；主要示意出其中的列管分布和移热剂流通空间。
部分附图标记说明：
1：氯气输送管线；2：CO输送管线；3：混合器；4：一级光气合成塔；5：二级光气合成塔；6：蒸汽发生器；7：循环水冷却器；8：一级蒸发器；9：一级盐水塔；10：二级蒸发器；11：二级盐水塔；12：结晶器；13-17：管线；18：泵；19：圆柱状催化剂；20：球形惰性剂；21：星形惰性剂；22：球形催化剂；23：移热剂流通空间；24：光气合成塔塔壁；25：列管。
具体实施方式
为了更好的理解本发明的技术方案，下面结合实施例进一步阐述本发明的内容，但本发明的内容并不仅仅局限于以下实施例。以下实施例中未特别说明的试验方法，均采用本领域常规方法进行，未特别说明的设备，均为本领域常规设备。
盐水中的氯化钠均采用国标方法GB/T 4348.2-2014测定。
光气中的游离氯含量的检测方法如下：
(1)原理
将采集的合成光气中加入1％(m/v)的碘化钾与光气中的游离氯(Cl 2)反应，生成的碘用硫代硫酸钠标准溶液滴定。
(2)试剂和溶液
碘化钾：配成1％(m/v)的水溶液；
淀粉：配成0.5％(m/v)的水溶液；
硫代硫酸钠标准溶液：C(Na 2S 2O 3)＝0.01mol/L；
(3)测定
将收集了光气的集气瓶(1000ml容量)进行冷冻约20分钟；把集气瓶和漏斗用乳胶管连接，然后将50ml碘化钾溶液加入漏斗中，打开集气瓶活塞，使碘化钾溶液进入冷却后成为负压状态的集气瓶中，关闭活塞，将集气瓶震荡约 5分钟，将集气瓶中的溶液移入具塞三角瓶中，用30ml水充分洗涤集气瓶，溶液收入三角瓶中；用硫代硫酸钠标准溶液滴定至淡黄色，加入1ml淀粉溶液，继续用硫代硫酸钠标准溶液滴定至蓝色恰好消失为终点。
(4)结果计算
Figure PCTCN2019104073-appb-000001
式中：Cl—游离氯含量，mg/L；(可按照1mg/L＝226.66ppm将其表示为基于质量的游离氯浓度(ppm))
V 1—滴定试样时消耗的硫代硫酸钠标准溶液的体积，mL；
V 2—气体取样瓶的体积，L；
C—硫代硫酸钠标准溶液的实际浓度，mol/L。
下面结合图2对以下实施例中所用到的光气合成及盐水蒸发电解一体化处理系统进行说明：
光气合成及盐水蒸发电解一体化处理系统主要包括混合器3、一级光气合成塔4、蒸汽发生器6、二级光气合成塔5、循环水冷却器7、盐水蒸发浓缩装置100和结晶器12。其中混合器3和一级光气合成塔4连通，混合器3还与氯气输送管线1以及CO输送管线2连接，混合器3用于对氯气和CO进行混合，并经管线13供应至一级光气合成塔4。以下实施例中所用的一级光气合成塔4和二级光气合成塔5具体为列管式反应塔，列管直径为40mm，列管间距为50mm，列管长度4000mm。在一级光气合成塔4和二级光气合成塔5的列管内装填混匀的催化剂和惰性剂，在一级光气合成塔4的移热剂流通空间(一级光气合成塔内围绕列管的空间)内流通移热剂；可参见图5，其中24为光气合成塔的塔壁，25为设于光气合成塔内的列管，23为移热剂流通空间。移热剂流通空间的移热剂出口27与蒸汽发生器6的移热剂入口(图中未示出)通过管线15连通，移热剂流通空间的移热剂入口26与蒸汽发生器6的移热剂出口(图中未示出)通过管线16连通，移热剂在一级光气合成塔4和蒸汽发生器6之间循环流动。移热剂在一级光气合成塔4吸收合成光气过程中所产生的反应热后 升温，并流动至蒸汽发生器6内与锅炉水进行热交换，使锅炉水转化为过热蒸汽，而移热剂温度降低再返回至一级光气合成塔4继续参与反应热的吸收。
蒸汽发生器6的过热蒸汽出口(图中未示出)与盐水蒸发浓缩装置100相连接，将过热蒸汽通过管线17供应至盐水蒸发浓缩装置100，为其提供热源。盐水蒸发浓缩装置100用于废盐水的蒸发浓缩，从而得到浓盐水。盐水蒸发浓缩装置100可采用本领域所熟知的相应装置，例如在以下实施例中具体采用的是本领域所熟知的双效蒸发，为便于理解，结合图2对双效蒸发介绍如下：包括一级蒸发单元101和二级蒸发单元102，二者分别均包括蒸发器(8、10)、盐水塔(9、11)和泵18。废盐水首先进入一级蒸发单元101的一级蒸发器8，在其中与来自蒸汽发生器6的过热蒸汽进行热交换，之后进入一级盐水塔9，一级盐水塔9中的一级浓盐水与蒸汽分离；蒸汽经管线进入二级蒸发单元102的二级蒸发器10中作为热源，而一级浓盐水则进入二级蒸发器10与蒸汽再次热交换，之后进入二级盐水塔11；得到的二级浓盐水进入结晶器12结晶，得到干盐。其中第一级蒸发温度为130℃(为一级蒸发器8的温度，一级盐水塔9的温度与之相近)，蒸发压力为2.7bara(为一级蒸发器8的压力，一级盐水塔9的压力与之相近)；二级蒸发温度为50℃(为二级蒸发器10的温度，二级盐水塔11的温度与之相近)，压力为0.12bara(为二级蒸发器10的压力，二级盐水塔11的压力与之相近)，干盐送入下游工序进行电解生产氯气。
一级光气合成塔4的光气出口与二级光气合成塔5通过管线14相连接，一级光气合成塔4输出的含有光气的混合气进入二级光气合成塔5，二级光气合成塔5将剩余的氯气完全转化为光气。二级光气合成塔的塔结构与一级光气合成塔相同；不同在于二级光气合成塔采用循环水移除反应热，即二级光气合成塔内围绕列管的空间内流通的是循环水，该围绕列管的空间与循环水冷却器7连通。
在一级光气合成塔的列管内设用于监测热点温度的热电偶。
实施例1
本实施例使用光气合成及盐水蒸发电解一体化处理工艺，光气合成产生的热量副产蒸汽；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为光气合成副产蒸汽。其工艺流程参见图2所示。
本实施例使用的光气合成催化剂为日本鹤见产的4GV-S活性炭，形状为圆球形，尺寸(直径)为8mm；惰性剂为国产(上海百图)碳化硅，形状为星形，尺寸(当量直径)为20mm，碳化硅占活性炭+碳化硅总体积的75％，催化剂和惰性剂在一级光气合成塔4的列管内装填后的模拟图如附图4所示。光气合成进料CO与氯气的体积比为1.03，一级光气合成塔4压力为3.0barg，一级光气合成塔4温度为220℃，出口游离氯浓度为1.5％，二级光气合成塔5压力为2.9barg，二级光气合成塔5温度为60℃，出口游离氯浓度为34ppm，产生光气总量为40t/h，一级光气合成塔4内的移热剂为高温硅油(陶氏，SL200)，高温硅油从一级光气合成塔4的移热剂出口的温度为210℃(压力为2Barg)，高温硅油送往蒸汽发生器6产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往盐水蒸发浓缩装置100进行双效蒸发，得到的浓盐水经结晶器12结晶产生的干盐调为饱和盐水，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1。
实施例2
本实施例使用光气合成及盐水蒸发电解一体化处理工艺，光气合成产生的热量副产蒸汽；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为光气合成副产蒸汽。其工艺流程参见图2所示。与实施例1的区别在于使用了不同形状的惰性剂及组合；
本实施例使用的光气合成催化剂为日本鹤见产的4GV-S活性炭，形状为圆球形，尺寸(直径)为8mm；惰性剂为国产碳化硅(上海百图)，形状为星锥形，尺寸(当量直径)为18mm，碳化硅占活性炭+碳化硅总体积的80％。光气合成进料CO与氯气的体积比为1.03，一级光气合成塔4压力为3.0barg，一级光气合成塔4温度为220℃，出口游离氯浓度为1.9％，二级光气合成塔5压力为2.9barg，二级光气合成塔5温度为60℃，出口游离氯浓度为36ppm， 产生光气总量为40t/h，一级光气合成塔4内的移热剂为高温硅油(陶氏，SL200)，高温硅油从一级光气合成塔4的移热剂出口的温度为210℃(压力为2Barg)，高温硅油送往蒸汽发生器6产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往盐水蒸发浓缩装置进行双效蒸发，得到的浓盐水经结晶器结晶产生的干盐调为饱和盐水，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1。
实施例3
本实施例使用光气合成及盐水蒸发电解一体化处理工艺，光气合成产生的热量副产蒸汽；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为光气合成副产蒸汽。与实施例1的区别在于催化剂为高导热复合活性炭，其工艺流程参见图2所示。
本实施例使用的光气合成催化剂为高导热复合活性炭，复合材料(颗粒添加剂)为氧化铝，氧化铝与活性炭质量比为5:100，胶黏剂为乳化酚醛树脂(上海乳胶厂，HX30)，乳化酚醛树脂与活性炭的质量比为15:100，活性炭与水的质量比为30:100，将各组分混匀后，制成圆球形，尺寸(直径)为8mm，干燥处理20h后，通入800℃过热蒸汽处理2h，使用后的活性炭寿命对比见表1；惰性剂为国产碳化硅(上海百图)，形状为星形，尺寸(当量直径)为20mm，碳化硅占高导热复合活性炭+碳化硅总体积的75％，催化剂和惰性剂在一级光气合成塔4的列管内装填后的模拟图如附图4所示，光气合成进料CO与氯气的体积比为1.03，一级光气合成塔4压力为3.0barg，一级光气合成塔4温度为220℃，出口游离氯浓度为1.5％，二级光气合成塔5压力为2.9barg，二级光气合成塔5温度为60℃，出口游离氯浓度为34ppm，产生光气总量为40t/h，一级光气合成塔内的移热剂为高温硅油(陶氏，SL200)，高温硅油从一级光气合成塔的移热剂出口的温度为210℃，压力为2barg；高温硅油送往蒸汽发生器产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往盐水蒸发浓缩装置100进行双效蒸发，得到的浓盐水经结晶器 12结晶产生的干盐调为饱和盐水，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1；
实施例4
本实施例使用光气合成及盐水蒸发电解一体化处理工艺，光气合成产生的热量副产蒸汽；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为光气合成副产蒸汽。与实施例3的区别在于催化剂使用了不同的高导热复合活性炭，其工艺流程参见图2所示。
本实施例使用的光气合成催化剂为高导热复合活性炭，复合材料(颗粒添加剂)为碳化硅，碳化硅与活性炭质量比为10:100，胶黏剂为乳化酚醛树脂(上海乳胶厂，HX30)，乳化酚醛树脂与活性炭的质量比为20:100，活性炭与水的质量比为30:100，将各组分混匀后，制成圆柱形，尺寸(当量直径)为6mm，干燥处理20h后，通入800℃过热蒸汽处理2h，使用后的活性炭寿命对比见表1；惰性剂为国产碳化硅(上海百图)，形状为星形，尺寸(当量直径)为20mm，碳化硅占高导热复合活性炭+碳化硅总体积的75％，催化剂和惰性剂在一级光气合成塔4的列管内装填后的模拟图与附图4类似，光气合成进料CO与氯气的体积比为1.03，一级光气合成塔4压力为3.0barg，一级光气合成塔4温度为220℃，出口游离氯浓度为1.4％，二级光气合成塔5压力为2.9barg，二级光气合成塔5温度为60℃，出口游离氯浓度为32ppm，产生光气总量为40t/h，一级光气合成塔4内的移热剂为高温硅油(陶氏，SL200)，高温硅油从一级光气合成塔4的移热剂出口的温度为210℃，压力为2barg；高温硅油送往蒸汽发生器6产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往盐水蒸发浓缩装置100进行双效蒸发，得到的浓盐水经结晶器12结晶产生的干盐调为饱和盐水，送往氯碱进行化盐，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1；
对比例1
本对比例的工艺流程图如图1所示。其和图2所示的工艺流程相同之处不做赘述，二者的主要区别在于：图1的工艺流程中，一级光气合成塔4和二级光气合成塔5均采用循环水来移除反应热；且未副产蒸汽，光气生产未与盐水蒸发浓缩装置100相结合。
氯气和一氧化碳在混合器3中混合后，进入一级光气合成器4中，在催化剂作用下合成光气，光气合成产生的热量由循环水带走；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为管网蒸汽。
本对比例使用的光气合成催化剂为日本鹤见产的4GV活性炭，形状为圆柱形，直径(当量直径)为8mm，惰性剂为国产氧化铝瓷球(上海百图)，形状为圆球形，尺寸(当量直径)为14mm，氧化铝瓷球占活性炭+氧化铝总体积的60％，催化剂和惰性剂在一级光气合成塔4的列管内装填后的模拟图如附图3所示。光气合成进料CO与氯气的体积比为1.05，一级光气合成塔压力为3barg，一级光气合成塔4温度为60℃，二级光气合成塔4压力为3barg，二级光气合成塔5温度为60℃(压力为3barg)，产生光气总量为40t/h，一级光气合成塔4内的移热剂为循环水，流量见表1，循环水回水温度为38℃。光气中游离氯含量为40ppm；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往蒸发浓缩装置100进行双效蒸发(双效蒸发与实施例1相同，不同在于，热源来自管网蒸汽，而不是光气合成副产的过热蒸汽)得到的浓盐水经结晶器12结晶产生的干盐调为饱和盐水，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1。
对比例2
本对比例与实施例1基本相同，不同在于MDI生产中缩合、光化产生的废盐水未利用副产的过热蒸汽进行双效蒸发来得到干盐，而是将盐水排放至海水中。
本对比例使用的光气合成催化剂为日本鹤见产的4GV-S活性炭，形状为圆球形，尺寸(直径)为8mm，惰性剂为国产碳化硅(上海百图)，形状为星形，尺寸(当量直径)为20mm，碳化硅占活性炭+碳化硅总体积的75％，催化剂和惰性剂在一级光气合成塔的列管内装填后的模拟图如附图4所示，光气合成进 料CO与氯气的体积比为1.04，一级光气合成塔压力为3.1barg，一级光气合成塔温度为205℃，二级光气合成塔压力为3barg，二级光气合成塔温度为60℃，产生光气总量为40t/h，一级光气合成塔内的移热剂为十氢化萘，十氢化萘从一级光气合成塔的移热剂出口的温度为198℃，十氢化萘送往蒸汽发生器产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h，光气中游离氯含量为40ppm；将废盐水与HCl进行中和，中和后浓度为20％，中和后盐水排放大海。
对比例3
本对比例的工艺流程图如图2所示。
本对比例与实施例1的区别在于未使用形状改良的惰性剂。本对比例使用光气合成及盐水蒸发电解一体化处理工艺，光气合成产生的热量副产蒸汽；MDI生产中缩合、光化产生的废盐水使用双效蒸发技术蒸发得到干盐，热源为光气合成副产蒸汽。其工艺流程参见图2所示。
本实施例使用的光气合成催化剂为日本鹤见产的4GV-S活性炭，形状为圆球形，尺寸(直径)为8mm；惰性剂为国产碳化硅(上海百图)，形状为圆球形，尺寸(直径)为10mm，碳化硅占活性炭+碳化硅总体积的75％。光气合成进料CO与氯气的体积比为1.03，一级光气合成塔压力为3.0barg，一级光气合成塔温度为220℃，出口游离氯浓度为1.5％，二级光气合成塔压力为2.9barg，二级光气合成塔温度为60℃，出口游离氯浓度为34ppm，产生光气总量为40t/h，一级光气合成塔内的移热剂为高温硅油(陶氏，SL200)，高温硅油从一级光气合成塔的移热剂出口的温度为210℃，高温硅油送往蒸汽发生器产生中压蒸汽，蒸汽的压力为14Barg，过热蒸汽的温度为195℃，副产蒸汽流量为15t/h；将废盐水与HCl进行中和，中和后氯化钠质量浓度为20％，中和后的盐水送往盐水蒸发浓缩装置进行双效蒸发，得到的浓盐水经结晶器结晶产生的干盐调为饱和盐水，之后电解产生氯气，蒸汽消耗量见表1，干盐产量见表1。
表1实验效果对比
Figure PCTCN2019104073-appb-000002
注：表1涉及的各实验均在光气合成量40t/h，废盐水总量30m 3/h下进行。
从上表可以看出，光气合成及盐水蒸发电解一体化处理工艺对于降低蒸汽消耗、循环水消耗，减少盐水外排量，增加干盐产量有显著效果。从对比例3和实施例1-2来看，对于未改性的活性炭催化剂，采用不带尖端形状的惰性剂时，将其用于光气合成及盐水蒸发电解一体化处理工艺中，催化剂的寿命显著 缩短，且热点温度较高；而采用带尖端形状的惰性剂的实施例1-2，其热点温度明显低于对比例3，且催化剂寿命显著延长，并与不副产蒸汽的对比例1在这两方面的结果接近。从实施例1-4来看，采用带尖端形状的惰性剂，并采用复合活性炭催化剂，具有更长的催化剂寿命，生产能长周期稳定运行；能大幅降低热点温度，延长催化剂寿命。
本领域技术人员可以理解，在本说明书的教导之下，可对本发明做出一些修改或调整。这些修改或调整也应当在本发明权利要求所限定的范围之内。

Claims (13)

  1. 光气合成及盐水蒸发电解一体化处理工艺，其特征在于，包括如下步骤：
    1)将预先混合的CO和氯气通入一级光气合成塔内，在催化剂作用下CO和氯气反应合成光气；所述一级光气合成塔设有移热剂流通空间，所述移热剂流通空间内流通移热剂，用于吸收合成光气所产生的反应热；所述催化剂为活性炭或高导热复合活性炭，优选高导热复合活性炭；
    2)将所述移热剂流通空间内吸收了反应热的移热剂通入蒸汽发生器中，与用于转化为蒸汽的水换热以产生过热蒸汽，将和所述用于转化为蒸汽的水换热后的移热剂返回至所述一级光气合成塔的移热剂流通空间，用于继续吸收合成光气产生的反应热；
    3)将步骤2)中所述的过热蒸汽供应至盐水蒸发浓缩装置，所述盐水蒸发浓缩装置以所述过热蒸汽为热源对盐水进行蒸发浓缩，得到浓盐水；任选的，所述浓盐水经结晶得到干盐；
    4)将步骤3)得到的浓盐水或干盐通过电解产生氯气。
  2. 根据权利要求1所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤1)中，将所述一级光气合成塔得到的含有所述光气的混合气输入二级光气合成塔。
  3. 根据权利要求2所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，在所述一级光气合成塔、二级光气合成塔内的催化剂装填区域中，均装填有混匀的所述催化剂和惰性剂，所述惰性剂的材质选自碳化硅、氧化铝或石墨中的一种或至少两种，优选为碳化硅；
    所述惰性剂的外观形状为方柱状、圆柱形、圆球形、星锥形、纺锤形、矩鞍形、星形或其他形状，优选所述惰性剂表面带有一个或多个呈锐角的尖端，更优选所述惰性剂表面分布有多个呈锐角的尖端；惰性剂的当量直径优选为1-20mm；
    优选的，所述催化剂装填区域中，所装填的所述惰性剂的体积占惰性剂和 催化剂的总体积的0.1-0.9，进一步优选0.7-0.85。
  4. 根据权利要求1-3任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，所述高导热复合活性炭包括颗粒添加剂和活性炭，二者的质量比为(1-10):100；所述颗粒添加剂选自氧化铝、碳化硅、石墨、碳化硼中的一种或至少两种；
    优选的，所述高导热复合活性炭采用包括如下步骤的方法制备：将活性炭粉、颗粒添加剂和胶黏剂在水中混匀，干燥成型，之后用水蒸气在600-800℃进行恒温碳化；进一步优选的，所述胶黏剂与活性炭粉的质量比为(3-20):100,所述活性炭粉与水的质量比为(20-50):100。
  5. 根据权利要求1-4任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，所述催化剂外观形状为圆柱形、圆球形、方柱形、纺锤形、星锥形或其他形状；优选催化剂的当量直径为1-10mm。
  6. 根据权利要求1-5任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤1)中，所述移热剂选自水、氯苯、甲苯、十氢化萘、高温硅油或高温矿物油，优选高温硅油或十氢化萘。
  7. 根据权利要求1-6任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤2)中，由所述移热剂流通空间输出的所述吸收了反应热的移热剂的温度为130-265℃，优选190-220℃，压力为-0.5Barg至5Barg。
  8. 根据权利要求1-7任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤2)中，所述过热蒸汽的压力为2-35Barg，优选8-10Barg，温度为150-260℃，优选180-200℃。
  9. 根据权利要求2-8任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤1)中所述的CO和氯气的体积比例为1.01-1.10，优选1.015-1.03；
    和/或，步骤1)中，所述一级光气合成塔和二级光气合成塔均为列管式光气合成塔，列管直径为20mm-80mm，列管间距为25mm-100mm，列管长度为3000mm-4500mm。
  10. 根据权利要求2-9任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤1)中，所述一级光气合成塔温度为55-270℃，优选 200-230℃，压力为2.5-5.5Barg，优选2.5-3.5Barg；二级光气合成塔温度为50-60℃，压力为2.5-5.5Barg。
  11. 根据权利要求2-10任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤1)所述的一级光气合成塔出口游离氯浓度为50ppm-3％，二级光气合成塔出口游离氯浓度为20-50ppm。
  12. 根据权利要求1-11任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤3)中，在所述盐水蒸发浓缩装置中进行蒸发浓缩的所述盐水为废盐水，例如来自缩合反应中产生的分离出水层后的缩合盐水，或碱液吸收塔中外排的碱液经中和后形成的光化盐水。
  13. 根据权利要求1-12任一项所述的光气合成及盐水蒸发电解一体化处理工艺，其特征在于，步骤3)中，所述蒸发浓缩采用双效蒸发，其中第一级蒸发温度为50-130℃，压力为0.1-3.0Bara；第二级蒸发温度为35-100℃，压力为0.05-1.0Bara。
PCT/CN2019/104073 2019-08-30 2019-09-02 光气合成及盐水蒸发电解一体化处理工艺 WO2021035768A1 (zh)

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