A process for producing methyl methacrylate using acetone cyanohydrin method

Abstract

The invention discloses a process technology for producing methyl methacrylate by using an acetone cyanohydrin method, comprising an acetone cyanohydrin unit and a methyl methacrylate unit: the acetone cyanohydrin unit comprises a reaction process and a refining process; the methyl methacrylate unit comprises an acylation process, an esterification process, an extraction process and a distillation process. The invention relates to the technical field of methyl methacrylate production, has a short process flow and reduces the floor space; acid-base neutralization is changed from liquid phase neutralization to gas phase neutralization, thereby preventing corrosion of pipelines and equipment; less rotating equipment is used, thereby reducing power consumption and maintenance costs; less polymer and solid waste are used, and the operation cycle is long; energy consumption and material consumption are low, and product quality is high.

Description

Technical Field

[0001] The invention relates to the technical field of methyl methacrylate production, in particular to a process technology for producing methyl methacrylate by using an acetone cyanohydrin method. Background Art

[0002] The existing methyl methacrylate production process technology was introduced from Italy in the 1980s. The introduced device has a long process flow, many rotating equipment, a short operation cycle, high energy and material consumption, and easily generated polymers and solid wastes that need to be cleaned up frequently, seriously affecting the long-term operation of the device. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides a process technology for producing methyl methacrylate using the acetone cyanohydrin method, which solves the problems of long process flow, high consumption, and frequent cleaning of polymers and solid wastes easily generated in the production of methyl methacrylate.

[0004] To achieve the above objectives, the present invention is implemented by the following technical scheme: a process technology for producing methyl methacrylate using an acetone cyanohydrin method, comprising an acetone cyanohydrin unit and a methyl methacrylate unit:

[0005] The acetone cyanohydrin unit includes a reaction process and a refining process;

[0006] The methyl methacrylate unit includes an acylation process, an esterification process, an extraction process and a distillation process;

[0007] The reaction process comprises: using an acetone feeding pump to transport acetone from a tank area to an acetone tank, and then transporting the acetone in the acetone tank through the acetone pump, a part of which is sent to the ACH first reactor to participate in the reaction, and the other part is cooled to 0° C. through an acetone cooler and sent to a tail gas absorption tower for treating the exhaust mist flow mainly from the acetone tank, the catalyst tank, the ACH second reactor and the ACH vacuum pump; sending the barreled catalyst into the catalyst tank through a catalyst feeding pump, and the catalyst in the catalyst tank is sent into the reaction system through a catalyst feeding pump, and the acetone and hydrocyanic acid and the recycled condensate from the recycling condensate tank are sent to the ACH first reactor through a recycling condensate pump. The catalyst is fed into the reactor circulation pump outlet side of the reactor by the catalyst feed pump, and enters the ACH first reactor together with acetone and hydrocyanic acid. The reaction mixture of the ACH first reactor overflows from the top into the ACH cooler, and is cooled to 10° C. by the crude ACH from the ACH third reaction tank, and then enters the ACH second reaction tank. The unstable crude ACH entering the ACH third reaction tank will be partially decomposed into acetone and HCN. The crude ACH from the ACH third reaction tank is fed into the ACH cooler by the distillation tower feed pump, and is preheated by the overflow liquid from the ACH first reactor in the ACH cooler, and then goes to the refining process;

[0008] The refining process: the crude ACH from the ACH cooler is further heated by the refined ACH from the ACH distillation tower in the ACH distillation heat exchanger and then enters the ACH distillation tower for distillation, and the light components stripped from the ACH distillation tower are condensed in the top front condenser and the top rear condenser. The condensate flows into the recirculating condensate tank, and the uncondensed steam enters the vacuum system. The refined ACH at the bottom of the ACH distillation tower is pumped into the heat exchanger by the refined ACH product pump, and the crude ACH from the ACH cooler is preheated before entering the ACH product cooler. The refined ACH is further cooled by circulating water in the ACH product cooler and then enters the ACH intermediate storage tank, and the vacuum in the tower is achieved by the vacuum pump;

[0009] The acylation process: the acylation process is divided into two independent lines, ACH is delivered to the ACH storage tank through the ACH delivery pump at the bottom of the ACH distillation tower, and the ACH in the ACH storage tank is delivered to the reactor through the intermediate tank delivery pump. The reaction of ACH and H2SO4 (100%) is carried out in the acylation reactor, the amide salt mixing heater and the amide reactor. ACH is divided into four sections and continuously enters the acylation reactor respectively under the condition of H2SO4:ACH=1.66 (weight ratio) through the intermediate tank delivery pump. ACH and 100% H2 SO4 mixed reaction generates α-formamido isopropyl hydrogen sulfate, which overflows from the top side of the acylation reactor by gravity into the bottom of the amide salt mixing heater, and is heated to a temperature of 91-95° C. to 135-140° C., and then overflows from the top side of the amide salt mixing heater by gravity into the amide reactor, and completes the transposition rearrangement reaction in the amide reactor, and the temperature drops from 135-140° C. to 133-138° C. The reaction mixture coming out of the amide reactor is still carried out by gravity to the first esterification kettle to undergo an esterification reaction with methanol;

[0010] The esterification process: The esterification process is a single-line operation, methanol is transported into the methanol tank by an external network methanol pump, and then transported by a methanol delivery pump in the device area, 80% of the flow of methanol and methacrylamide sulfate (MAAS) flowing from the amide salt reactor, and the extraction water phase coming out from the bottom of the extraction mixer enter the first esterification kettle, and 20% of the flow of methanol enters the second esterification kettle and the third esterification kettle to participate in the esterification reaction;

[0011] The extraction process: crude MMA from the esterification reaction enters the esterification crude MMA tank by gravity, is transported into the extraction mixer by an extraction feed pump for mixed extraction, and the crude MMA after mixed extraction overflows into the bottom of the extraction tower by gravity, is fully contacted with desalted water in the extraction tower, and the methanol-soluble components in the crude MMA are dissolved, so that the organic phase MMA is precipitated and purified again, overflows from the extraction tower by gravity into the extraction crude MMA tank, and the purity of MMA can reach more than 90%, and is then transported by the primary distillation tower feed pump to the rectification process;

[0012] The distillation process: the crude MMA from the crude MMA extraction tank is transported into the primary distillation tower through the primary distillation tower feed pump. The primary distillation tower is a low-boiling-point separation tower. The tower is divided into two sections, the upper and lower sections, which are sieve plate towers. The low-boiling points are evaporated from the top of the upper section of the tower, and are transported back to the tower through the primary distillation tower reflux pump in the primary distillation tower reflux tank. In the middle of the tower, the material is washed with water in the MMA / water separation tank to separate the methanol and water in the material. The organic phase after washing and separation is returned to the lower tower for separation and purification. The MMA and high-boiling points are taken out from the bottom of the tower and go to the distillation tower. The water phase in the MMA / water separation tank is transported by the separation tank water phase pump and divided into three routes to the extraction mixer and MAA separation tank. The tower and acid water vent condenser are recycled, and the crude MMA enters the primary distillation tower. After gas and liquid mass transfer separation, the low-boiling substances coming out of the reflux tank of the primary distillation tower are transported by the primary distillation tower reflux pump and divided into three parts: the first part goes to the crude esterification MMA tank, and then is transported to the extraction mixer for re-extraction and purification through the extraction feed pump, the second part operates normally in the primary distillation tower, and the third part is stored on the side of the low-boiling tank A, and is intermittently sent to the HQ dissolution tank for preparation of inhibitors through the low-boiling pump. The crude MMA enters the MMA / water separation tank by gravity at the bottom of the upper tower of the primary distillation tower. In the MMA / water separation tank, the crude MMA is mixed with desalted water, and the mixed water is washed and divided into two layers The upper organic phase returns to the top of the lower section of the primary distillation tower by gravity for further distillation. The water phase in the lower layer of the MMA / water separation tank contains a small amount of MMA and methanol, which is transported by the separation tank water phase pump to three routes: the first route goes to the extraction mixer feed pipeline to participate in extraction and purification; the second route goes to the MAA separation tower for water phase spraying and enters the esterification vapor phase main pipe and the first esterification kettle to participate in the reaction; the third route goes to the acid water venting condenser for water phase spraying and passes through the acid water stripping condensate tank, stored and transported to the first esterification kettle to participate in the reaction, and the organic phase returned to the lower section undergoes mass transfer and heat transfer in the lower section of the primary distillation tower. While ensuring that the temperature at the bottom of the primary distillation tower is 68°C, it is discharged from the bottom of the tower. A part of the material is transported to the distillation tower to separate the high-boiling substances by the discharge pump at the bottom of the primary distillation tower, and a part of the flow is used as the reflux at the bottom of the primary distillation tower. The main component of the material entering the distillation tower is MMA, with a content of about 99%, and the rest is high-boiling substances. The crude MMA entering the distillation tower is separated from the high-boiling substances by gas and liquid phase mass transfer and heat transfer. MMA is evaporated from the top of the tower, and the purity is above 99.9% and enters the front cooler at the top of the distillation tower. In the front cooler at the top of the distillation tower, it is condensed with circulating cooling water. In the reflux tank of the distillation tower, the pure MMA with a purity of more than 99.9% is transported by the reflux pump of the distillation tower and divided into two parts, one of which enters the pure MMA cooler, or goes to 2.4M6B dissolution tank, prepare 2,4-dimethyl-6-tert-butylphenol (2, 4M6B) inhibitor solution, the other part is sent to the top of the distillation tower for reflux, from the pure MMA cooler, the pure MMA comes out into the MMA intermediate tank, the MMA intermediate tank has an external coil, cooled with refrigerated brine to prevent polymerization due to temperature rise, the pure MMA is sent to storage by the MMA intermediate tank delivery pump, if the MMA does not reach the required purity, it is sent back to the extraction crude MMA tank by the MMA intermediate tank delivery pump, and re-enters the distillation process for refining until it is qualified. .

[0013] Preferably, the exhaust gas flow entering the tail gas absorption tower is washed by acetone from the acetone cooler, the condensed material enters the acetone tank to participate in the reaction again, the uncondensed gas enters the vent condenser through the top of the tail gas absorption tower, the material condensed by the vent condenser enters the acetone tank, the uncondensed gas goes to the tail gas buffer tank, and finally goes to the SAR incinerator for incineration, the flow rate of the frozen brine of the vent condenser is adjusted by the TIC to ensure that the temperature of the uncondensed gas is below -5°C, the uncondensed gas at the outlet of the vent condenser is continuously purged with nitrogen to prevent the accumulation of gaseous components, the flow rate of nitrogen can be adjusted by an on-site rotor flowmeter, the tail gas absorption tower is provided with a monitoring temperature and pressure sensor, the flow rate of the frozen brine of the acetone cooler is adjusted by the TIC to ensure that the temperature of the acetone entering the tail gas absorption tower is 0°C.

[0014] Preferably, the feed temperature of the ACH distillation tower is controlled by an ACH distillation heat exchanger. Unreacted acetone and HCN in the crude ACH are removed by distillation. At high temperature, part of the ACH is decomposed into acetone and HCN. In order to minimize the thermal decomposition of the ACH product, the distillation is carried out under vacuum (the pressure at the upper head is about 100 mbar). If the tower top pressure exceeds 180 mbar (absolute pressure), the feed to the ACH distillation tower and the addition of low-pressure steam are stopped by closing the regulating valve FV. The low-pressure steam is obtained by heating the reboiler with low-pressure steam.

[0015] Preferably, the gas discharged from the vacuum pump is cooled by the tail gas cooler and then goes to the washing tower, the liquid condensed by the gas-liquid separation tank and the vacuum pump is sent to the recycling condensate tank, the liquid condensed by the tail gas cooler at the outlet of the vacuum pump is sent to the recycling condensate tank for recovery and treatment, and the condensate entering the recycling condensate tank is pumped into the ACH first reactor by the recycling condensate pump to re-react. In order to avoid HCN polymerization in the recycling condensate tank, the recycling condensate tank is provided with an external companion pipe, and the recycling condensate tank is continuously cooled by refrigerated brine through the external companion pipe, so that the condensate in the recycling condensate tank is maintained at about -1°C. When the temperature of the recycling condensate tank reaches 13°C, the catalyst pump is stopped, the feeding to the reactor is stopped, and the tank is vented to the washing tower to remove gaseous pollution.

[0016] Preferably, 100% H2SO4 is prepared by a waste acid recovery device and transported by a sulfuric acid pump. A portion of it intermittently enters a phenothiazine dissolution tank to prepare an inhibitor sulfuric acid solution, and then enters a phenothiazine inhibitor tank. The other portion continuously enters a mixer and is continuously mixed with the inhibitor sulfuric acid solution transported from the phenothiazine inhibitor tank by a phenothiazine inhibitor pump in the mixer to ensure that the inhibitor (phenothiazine) content in the 100% H2SO4 solution is 200 ppm and enters the acylation reactor from the bottom.

[0017] Preferably, the heat required by the amide salt mixed heater is provided by heating the heat transfer oil through medium-pressure steam. During the acylation reaction, some gases will be generated by side reactions, the main component of which is CO gas. After being washed by the venting washing tower and collected in a closed tail gas emission system, they are sent to the SAR incinerator for incineration. The washing water at the bottom of the venting washing tower is transported to the acid water recovery device through the washing tower circulation pump. The venting washing tower is a baffle tower with six baffles. The tower and the baffles are made of 316L. A nitrogen purge regulating valve is set for the acylation reaction. The nitrogen inlet flow rate is adjusted by the venting system pressure control, so that the entire acylation venting system is in a slightly positive pressure and in a pressure balance state. The pressure is controlled below 0.01MPa to ensure that the toxic gas is discharged smoothly. The acylation system is provided with an MMA accident buffer tank, and a high-temperature alarm and a high-temperature interlock are provided on the accident tank feed pipeline. If abnormal venting occurs, the collected liquid is discharged to the first esterification kettle, and the gas is vented to the torch for incineration.

[0018] Preferably, the heat transfer oil required by the amide salt mixed heater is heated in the heat transfer oil system, and the heat transfer oil system is composed of a closed circulation loop. After the heat transfer oil is added once, it does not need to be supplemented during normal operation. The heat transfer oil is transported to the heat transfer oil feeding tank through a hose through a heat transfer oil replenishing pump, and the heat transfer oil is transported into the heat transfer oil heater and the entire heat transfer oil system through the heat transfer oil feeding pump and the heat transfer oil circulation pump. The heat transfer oil is slowly heated by medium-pressure steam in the heat transfer oil heater, and the heating rate is 2°C per hour. The device is preheated to 100-110°C before feeding and circulated. After the device is fed, when the acylation reactor overflows, the temperature of the heat transfer oil is rapidly raised from 100-110°C to 145-150°C, which is achieved by adjusting the amount of medium-pressure steam added. The heated heat transfer oil enters the amide salt mixed heater to provide the heat required for the reaction, returns to the heat transfer oil expansion tank after heat exchange, and then circulates by the heat transfer oil circulation pump.

[0019] Preferably, the esterification reaction occurs in a group of five kettle reactors connected in series with pipelines whose gas and liquid phases are both zirconium alloys. The liquid phase is transported from the bottom of the first esterification kettle by an acid water pump and enters the second esterification kettle through the bottom of the first esterification kettle. The liquid phase of the second esterification kettle overflows from the upper side by gravity into the third esterification kettle; the liquid phase of the third esterification kettle overflows from the upper side by gravity into the fourth esterification kettle; the liquid phase of the fourth esterification kettle overflows from the upper side by gravity into the fifth esterification kettle, and finally overflows from the upper side of the fifth esterification kettle to the acid water stripping tank, and then is transported by a pump and sent to the acid water recovery device through the acid water stripping tank. When the acid water recovery device cannot receive it, it can also be intermittently sent to the acid water tank. The acid water in the acid water tank is transported by the acid water delivery pump and sent to the acid water recovery device for recovery treatment.

[0020] Preferably, high boiling points are conveyed by a discharge pump at the bottom of a distillation tower into an MMA recovery tower, in which MMA is recovered, the stripped MMA is evaporated from the top of the tower and then enters a pre-cooler at the top of the recovery tower for condensation, the condensate enters a reflux tank of the recovery tower, the uncondensed gas is mixed with the volatilized gas in the reflux tank of the recovery tower and then enters an aftercooler at the top of the recovery tower, where it is condensed by frozen brine, the condensate is mixed with the liquid coming out of the reflux tank of the recovery tower, the non-condensable gas is extracted by a vacuum system, the liquid in the reflux tank of the recovery tower is conveyed by a reflux pump of the recovery tower and divided into two parts, one part is refluxed to the top of the MMA recovery tower as the reflux of the MMA recovery tower, and the other part enters an extraction crude MMA tank and returns to the distillation process again, the purity of MMA recovered by the MMA recovery tower is about 97%, and the high boiling points discharged from the MMA recovery tower contain about 30% MMA, which is continuously conveyed by a discharge pump of the recovery tower for deesterification in the third esterification kettle for recycling again.

[0021] Beneficial Effects

[0022] The present invention provides a process for producing methyl methacrylate using an acetone cyanohydrin method, which has the following beneficial effects:

[0023] 1. Short process flow and reduced floor space;

[0024] 2. Acid-base neutralization is changed from liquid phase neutralization to gas phase neutralization, which eliminates the corrosion of pipelines and equipment;

[0025] 3. Fewer rotating equipment, reducing power consumption and maintenance costs;

[0026] 4. Less polymer and solid waste, longer operation cycle;

[0027] 5. Low energy and material consumption, high product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the acetone tank of the present invention.

[0029] Figure 2Schematic diagram of the reactor of the present invention.

[0030] Figure 3 This is a flow chart of tail gas treatment according to the present invention.

[0031] Figure 4 Schematic diagram of the distillation column of the present invention.

[0032] Figure 5 The figure is a flow chart of the acylation reactor of the present invention.

[0033] Figure 6 It is the flow chart of the esterification kettle of the present invention.

[0034] Figure 7 for Figure 6 Flow chart of the subsequent esterification reactor.

[0035] Figure 8 It is the flow chart of the extraction tower of the present invention.

[0036] Fig. 9 This is a flow chart of the crude distillation tower of the present invention.

[0037] Fig.10 It is a flow chart of the distillation tower of the present invention.

[0038] Fig.11 This is a flow chart of the recovery tower of the present invention.

[0039] Fig.12 It is the flow chart of the dissolving tank of the present invention.

[0040] Fig.13 This is a flow chart of tail gas treatment according to the present invention.

[0041] Fig.14 This is a flow chart of the heat transfer oil feeding tank of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Pregnancy Examination Figure 1-14 The present invention provides a technical solution: a process technology for producing methyl methacrylate using an acetone cyanohydrin method, comprising an acetone cyanohydrin unit and a methyl methacrylate unit:

[0044] The acetone cyanohydrin unit includes a reaction process and a refining process;

[0045] The methyl methacrylate unit includes an acylation process, an esterification process, an extraction process and a distillation process;

[0046] The reaction process is as follows: the acetone is transported from the tank area to the acetone tank 1300-V-1001 using an acetone feed pump, and then the acetone in the acetone tank 1300-V-1001 is transported through the acetone pump 1300-P-1001A / B, a part of which is sent to the ACH first reactor 1300-R-1001 to participate in the reaction, and the other part is cooled to 0°C by the acetone cooler 1300-E-1001, and sent to the tail gas absorption tower 1300-C-1001 for treating the acetone mainly from the acetone tank 1300-V-1001, the catalyst tank 1300-V-1002, and the tail gas absorption tower 1300-C-1001. The exhaust mist flow of CH2 reactor 1300-R-1002 and ACH vacuum pump 1300-P-1009A / B; the barreled catalyst is sent into catalyst tank 1300-V-1002 by catalyst feeding pump 1300-P-1010, the catalyst in catalyst tank 1300-V-1002 is sent into the reaction system through catalyst feeding pump 1300-P-1002A / B, acetone and hydrocyanic acid and recycled condensate from recycling condensate tank 1300-V-1003 are sent into The catalyst is fed into the outlet side of the reactor circulation pump 1300-P-1003A / B of the first ACH reactor 1300-R-1001 by the catalyst feed pump 1300-P-1002A / B, and enters the first ACH reactor 1300-R-1001 together with acetone and hydrocyanic acid. The reaction mixture of the first ACH reactor 1300-R-1001 overflows from the top into the ACH cooler 1300-E-1002 and is taken up by the catalyst from the third ACH reaction tank 1300-R-1002. The crude ACH of 3 is cooled to 10°C and then enters the ACH second reaction tank 1300-R-1002, and then enters the ACH third reaction tank 1300-R-1003. The unstable crude ACH will be partially decomposed into acetone and HCN. The crude ACH of the ACH third reaction tank 1300-R-1003 is sent to the ACH cooler 1300-E-1002 by the distillation tower feed pump 1300-P-1006A / B, and is preheated by the overflow liquid from the ACH first reactor 1300-R-1001 in the ACH cooler 1300-E-1002 and then goes to the refining process;

[0047] Acetone and hydrocyanic acid enter the reactor in equimolar amounts. If the ratio of acetone to hydrocyanic acid (calculated by the flowmeter) deviates greatly from the ratio set point (<-150 kg / h or >150 kg / h), the catalyst pump 1300-P-1002A / B is stopped, and the feed to the ACH first reactor is stopped. The heat generated by the reaction is removed by the circulating cooling water in the ACH first reactor 1300-R-1001 pipe and the frozen brine in the reactant cooler 1300-E-1010. The ACH first reactor 1300-R-1001 material circulation pipeline adjusts the flow of circulating water entering to ensure that the temperature of the reaction mixture entering the ACH first reactor 1300-R-1001 is 37°C. A cooler 1300-E-1010 is also provided on the circulation pipeline to adjust the flow of the reactant entering the ACH first reactor 1300-R-1001. The flow rate of chilled brine in cooler 1300-E-1010 ensures that the temperature of overflow material from ACH first reactor 1300-R-1001 is at 37°C. The circulating material volume of ACH first reactor 1300-R-1001 is 290m3 / h to avoid too rapid temperature rise in the reactor and too high concentration of reactants. If the flow rate is lower than 35m3 / h, stop catalyst pump 1300-P-1002A / B and stop feeding into ACH first reactor 1300-R-1001.

[0048] The alkaline catalyst is continuously added to the ACH first reactor 1300-R-1001, so that the pH value of the material in the ACH first reactor 1300-R-1001 is maintained between 6.8 and 7.0, the amount of catalyst added is adjusted by the catalyst feed pump 1300-P-1002A / B, and the amount of catalyst added is detected by the conductivity measuring device (existing mature technology). When the circulating reaction mixture of the ACH first reactor 1300-R-1001 is lower than 25°C or higher than 45°C, the catalyst pump 1300-P-1002A / B is stopped, and the feeding to the ACH first reactor 1300-R-1001 is stopped;

[0049] The ACH second reaction tank 1300-R-1002 is a horizontal container which is separated into two chambers by an overflow weir. The first chamber provides most of the residence time and receives the feed from the ACH first reactor 1300-R-1001. The material in the first chamber of the ACH second reaction tank 1300-R-1002 is sent by the crude ACH circulation pump 1300-P-1005A / B to the crude ACH cooler 1300-E-1003A / B and cooled to -5°C. Then, the material enters the ACH second reaction tank 1300-R-1002 to cool the reaction mixture from the ACH first reactor 1300-R-1001 and eliminate the reaction heat of generating ACH.

[0050] The liquid level in the first chamber of the ACH second reactor 1300-R-1002 is maintained at about 60% by the overflow weir, so that in the event of a runaway reaction or when the material in the ACH first reactor 1300-R-1001 is completely discharged into the ACH second reactor 1300-R-1002, there is enough volume to hold the material, and the ACH in the first chamber overflows through the overflow weir into the second chamber, and then flows into the ACH third reactor 1300-R-1003 by gravity;

[0051] Sulfuric acid is added to the ACH third reactor 1300-R-1003 tank through the sulfuric acid pump 1300-P-1013A / B to control the pH value to about 2.0 in order to minimize the decomposition. The state of the stable reaction is observed by the conductivity meter CI and pH meter set on the circulation pipeline of the ACH third reactor 1300-R-1003. In order to ensure that the materials in the ACH third reactor 1300-R-1003 tank are mixed evenly, the ACH third reactor 1300-R-1003 is provided with an external circulation loop and a liquid jet mixer is used to mix the materials in the ACH third reactor 1300-R-1003 tank. The exhaust of the ACH third reactor is removed by the tail gas absorption tower 1300-C-1001 to remove gaseous pollutants;

[0052] The refining process: the crude ACH from the ACH cooler 1300-E-1002 is further heated in the ACH distillation heat exchanger 1300-E-1004 by the refined ACH from the ACH distillation tower 1300-C-1002 and then enters the ACH distillation tower 1300-C-1002 for distillation, and the light components stripped out from the ACH distillation tower 1300-C-1002 are condensed in the top pre-condenser 1300-E-1007 and the top post-condenser 1300-E-1008. The condensate flows into the recycling condensate tank 1300-V-1003, and the uncondensed steam enters the vacuum system. The refined ACH at the bottom of the ACH distillation tower 1300-C-1002 is sent to the heat exchanger 1300-E-1004 by the refined ACH product pump 1300-P-1007A / B, and the crude ACH from the ACH cooler 1300-E-1002 is preheated and then enters the ACH product cooler 1300-E-1006. The refined ACH is cooled in the ACH product cooler. After being further cooled by circulating water in the device 1300-E-1006, it enters the ACH intermediate storage tank 1300-T-4101A / B / C, and the vacuum in the tower is achieved through the vacuum pump 1300-P-1009A / B; the vacuum pump and external equipment and instrumentation equipment are purchased from the manufacturer as a complete set of units, and are existing mature equipment. The control system is controlled by the integrated control system provided by the manufacturer, and the control system communicates with the DCS through a serial interface. In order to prevent the vacuum pump inlet temperature and pressure from being too high, TI and PI are provided on the inlet pipeline of the vacuum pump 1300-P-1009A / B. When the vacuum pump stops running, interlock I is activated to close the pneumatic shut-off valve at the vacuum pump inlet. When the vacuum pump starts, interlock I is activated to open the pneumatic shut-off valve at the vacuum pump inlet. When the oxygen content at the vacuum pump suction port exceeds the standard, the shut-off valve is closed through the interlock UZ action, the vacuum pump is stopped, and the low-pressure steam regulating valve FV and the shut-off valve at the distillation tower inlet are closed;

[0053] The acylation process: The acylation process is divided into two independent lines A / B, ACH is transported to the ACH storage tank 1300-T-4101-A / B / C through the ACH delivery pump 1300-P-1007A / B at the bottom of the ACH distillation tower 1300-C-1002, and the ACH in the ACH storage tank 1300-T-4101-A / B / C is transported into the reactor 1300- R-2001A / B, ACH and H2SO4 (100%) react in the acylation reactor 1300-R-2001A / B, the amide salt mixing heater 1300-E-2007A / B and the amide reactor 1300-R-2002A / B, ACH is continuously delivered in four stages through the intermediate tank delivery pump 1300-P-4101A / B at a ratio of H2SO4:ACH = 1.66 (weight ratio). ACH is introduced into the acylation reactor 1300-R-2001A / B, and ACH and 100% H2SO4 are mixed and reacted to form α-formamido isopropyl hydrogen sulfate, which overflows from the top side of the acylation reactor 1300-R-2001A / B by gravity into the bottom of the amide salt mixing heater 1300-E-2007A / B, and the temperature is raised from 91-95°C to 135-140°C by heating, and then from the amide salt mixing heater 1300 -The top side of E-2007A / B still overflows into the amide reactor 1300-R-2002A / B by gravity, and the transposition rearrangement reaction is completed in the amide reactor 1300-R-2002A / B, and the temperature drops from 135-140°C to 133-138°C. The reaction mixture coming out of the amide reactor 1300-R-2002A / B still flows by gravity to the first esterification kettle 1300-R-2003 to react with methanol for esterification;

[0054] The three feed lines entering the ACH tank 1300-T-4101A / B / C are equipped with pneumatic valve groups. The control room personnel can automatically switch and select the feed tank according to the tank liquid level and ACH purity, so that ACH can be continuously fed into the ACH tank 1300-T-4101-A / B / C. The three tanks are equipped with nitrogen sealing and venting systems, which are controlled by three sets of pressure regulators PICA to complete the nitrogen sealing of the ACH tank 1300-T-4101A / B / C venting system, ensuring that the tank pressure is around 20-50mbar;

[0055] The thermal oil expansion tank 1300-V-2001 is also equipped with an on-site liquid level gauge LG. When the device is operating normally, the low liquid level overflow valve is closed and the high liquid level overflow valve is opened. When the liquid level is higher than 80%, the thermal oil will overflow from the high liquid level overflow pipeline to the thermal oil feeding tank 1300-V-2002 to prevent the thermal oil from entering the venting pipeline; when the liquid level is lower than 20%, the on-site operator must open the low liquid level overflow valve to observe whether there is any outflow of thermal oil. If there is no outflow, thermal oil needs to be added. If there is outflow, the low liquid level overflow valve is closed again. No thermal oil needs to be added, and the accuracy of the liquid level gauge should be checked at the same time. The thermal oil expansion tank 1300-V-2001 and the thermal oil feeding tank 1300-V-2002 of the thermal oil system are vented and connected, and the gas is vented to the atmosphere after passing through the thermal oil sealing tank 1300-V-2056;

[0056] The esterification process: the esterification process is a single-line operation, methanol is transported into the methanol tank 1300-T-4103 by the external network methanol pump, and then transported by the methanol delivery pump 1300-P-4103A / B in the device area, 80% of the flow of methanol and methacrylamide sulfate (MAAS) flowing from the amide salt reactor 1300-R-2002A / B, and the extraction water phase coming out from the bottom of the extraction mixer 1300-V-2013 enter the first esterification kettle 1300-R-2003, 20% of the flow of methanol enters the second esterification kettle 1300-R-2004 and the third esterification kettle 1300-R-2005 to participate in the esterification reaction;

[0057] The esterification vapor phase is evaporated from the top of the first esterification kettle 1300-R-2003, the second esterification kettle 1300-R-2004, the third esterification kettle 1300-R-2005, the fourth esterification kettle 1300-R-2006, and the fifth esterification kettle 1300-R-2007 respectively. The vapor phases from the tops of the five esterification kettles are combined in the total vapor phase pipeline and then enter the first esterification kettle 1300-R-2003 through three steam distributors to provide heat for the esterification reaction. The vapor phase evaporated from -R-2003 is evaporated from the top of the first esterification kettle 1300-R-2003 and enters the MAA separation tower 1300-C-2005. After vapor-liquid exchange, the vapor phase evaporated from the top of the MAA separation tower 1300-C-2005 enters the crude MMA primary cooler 1300-E-2001. The condensate enters the esterification gas-liquid separation tank 1300-V-2039 through the crude MMA primary cooler 1300-E-2001 and goes to the MAA separation tower. Gas-liquid exchange separation is carried out in 1300-C-2005, so that most of the methacrylic acid components with high boiling points in the evaporated gas phase are condensed back to the first esterification kettle 1300-R-2003 to participate in the esterification reaction again (the condensate in the esterification gas-liquid separation tank 1300-V-2039 can also be directly returned to the first esterification kettle 1300-R-2003 to participate in the esterification reaction again). The uncondensed methacrylic acid components are separated in the MAA separation tower 1300-C-2005 and the methacrylic acid components entering The gaseous ammonia is neutralized, and the flow rate is adjusted by the pH value displayed by the pH meter on the discharge pipeline of the crude MMA cooler 1300-E-2004, so that the gaseous ammonia entering the MAA separation tower 1300-C-2005 can be fully mixed with the methacrylic acid component, and the methacrylic acid entrained in the gas phase is completely neutralized while controlling the pH value to 7-8. The MAA separation tower 1300-C-2005 is equipped with two-point temperature monitoring, the bottom temperature is TI, and the top temperature is TIC.

[0058] The uncondensed gas of the crude MMA primary cooler 1300-E-2001 evaporates from the top of the esterification gas-liquid separation tank 1300-V-2039, is fully condensed through the crude MMA aftercooler 1300-E-2002A / B and enters the crude MMA cooler 1300-E-2004. After deep cooling through the crude MMA cooler 1300-E-2004, it enters the esterification crude MMA storage tank 1300-V-2010 by gravity, and is transported to the extraction mixer for purification through the extraction feed pump 1300-P-2013A / B. The uncondensed gas in the crude MMA aftercooler 1300-E-2002A / B enters the vent condenser 1300-E-2003 using chilled brine as a refrigerant. After being fully condensed, the liquid returns to the crude MMA cooler. In 1300-E-2004, the remaining non-condensable gas enters the exhaust emission system and is collected in a closed manner and then sent to the SAR device incinerator for incineration; the crude MMA primary cooler 1300-E-2001 is cooled by circulating cooling water, and the condensate temperature TIC of the esterification gas-liquid separation tank 1300-V-2039 is used to control and adjust the return flow rate of circulating cooling water, so that the temperature is controlled at 78-82°C; the crude MMA aftercooler 1300-E-2002A / B is also cooled by circulating cooling water, so that the condensate temperature is controlled at 40-45°C; the crude MMA cooler 1300-E-2004 is cooled by chilled brine, and the temperature TIC on the discharge pipeline of the crude MMA cooler 1300-E-2004 is used to control and adjust the return flow rate of chilled brine, so that the temperature is controlled at 3-5°C.

[0059] The heat required for the esterification reaction is provided by direct low-pressure steam and jacket medium-pressure steam. Direct low-pressure steam is added from the bottom distributors of the second esterification kettle 1300-R-2004, the third esterification kettle 1300-R-2005, the fourth esterification kettle 1300-R-2006, and the fifth esterification kettle 1300-R-2007. Medium-pressure steam is added from the second esterification kettle 1300-R-2004, the third esterification kettle 1300-R-2005, the fourth esterification kettle 1300-R-2006, the fifth esterification kettle 1300-R-2007 are added to the upper part of each kettle jacket, and the bottom of each kettle jacket is discharged into the steam condensate main pipe through the steam trap. The addition of straight low-pressure steam and jacket medium-pressure steam ensures the heat required for esterification reaction and stripping in the esterification system, so that the temperature of each esterification kettle is controlled at the optimal temperature state. The gas and liquid phase temperatures of the first esterification kettle 1300-R-2003 are 95-98℃ / 98-105℃;

[0060] The gas and liquid phase temperatures of the second esterification reactor 1300-R-2004 are 105-110°C / 120-125°C;

[0061] The gas and liquid phase temperatures of the third esterification reactor 1300-R-2005 are 115-125°C / 125-130°C;

[0062] The gas and liquid phase temperatures of the fourth esterification reactor 1300-R-2006 are 120-130°C / 130-135°C;

[0063] The gas and liquid phase temperatures of the fifth esterification reactor 1300-R-2007 are 125-135°C / 135-140°C;

[0064] The extraction process: the crude MMA from the esterification reaction enters the esterification crude MMA tank 1300-V-2010 by gravity, and is transported into the extraction mixer 1300-V-2013 through the extraction feed pump 1300-P-2013A / B for mixed extraction. The crude MMA after mixed extraction overflows into the bottom of the extraction tower 1300-C-2004 by gravity, and is fully contacted with desalted water in the extraction tower to dissolve the methanol-soluble components in the crude MMA, so that the organic phase MMA is precipitated and purified again, and overflows from the extraction tower 1300-C-2004 by gravity into the extraction crude MMA tank 1300-V-2017. The purity of MMA can reach more than 90%, and then enters the primary distillation tower. The material pump 1300-P-2017A / B transports the gas to the distillation process; the vapor phase of the acid water stripping tank 1300-V-2040A / B and the acid water tank 1300-V-2055A / B enters the acid water venting condenser 1300-E-2006A / B through the venting pipeline of the acid water stripping tank 1300-V-2040A / B for full condensation, and the condensed liquid enters the acid water stripping condensate tank 1300-V-2038, and the acid water stripping condensate tank 1300-V-2038 returns to the first esterification kettle 1300-R-2003 by controlling the frequency conversion of the acid water stripping condensate pump 1300-P-2032A / B motor, and the uncondensed gas is collected and treated in a closed manner in the tail gas emission system. When the esterification system experiences emergency pressure relief and abnormal venting occurs, the vapor phase enters the vent main of the acid water stripping tank 1300-V-2040A / B through the pressure relief pipeline, and then enters the acid water vent condenser 1300-E-2006A / B for full condensation, and the non-condensable gas is collected and treated in a closed manner in the tail gas emission system. During normal production, one acid water vent condenser 1300-E-2006A / B is open and the other is on standby. The acid water vent condenser 1300-E-2006A / B uses circulating cooling water or 0℃ cold brine as the refrigerant, and the temperature is controlled at 40-50℃; the desalted water used for extraction is introduced from the boundary area main and cooled by the desalted water cooler 1300-E-2005;

[0065] The distillation process: the crude MMA from the extraction crude MMA tank 1300-V-2017 is transported into the primary distillation tower 1300-C-2001 through the primary distillation tower feed pump 1300-P-2017A / B. The primary distillation tower 1300-C-2001 is a low-boiling-point separation tower. The tower is divided into two sections, which are sieve plate towers. The low-boiling points are evaporated from the top of the upper section of the tower under reduced pressure operation. In the primary distillation tower reflux tank 1300-V-2027, the primary distillation tower reflux pump 1300-P-2019A / B is transported back to the tower. In the middle of the tower, the material is washed with water in the MMA / water separation tank 1300-V-2026 to separate the methanol and water in the material. The organic matter after washing and separation is The phase returns to the lower tower for separation and purification, MMA and high boiling points are taken out from the bottom of the tower and go to the distillation tower 1300-C-2002, the water phase of the MMA / water separation tank 1300-V-2026 is transported through the separation tank water phase pump 1300-P-2046A / B to the extraction mixer 1300-V-2013, MAA separation tower 1300-C-2005, and acid water venting condenser 1300-E-2006A / B for recycling, the crude MMA enters the primary distillation tower 1300-C-2001, and is separated by gas and liquid mass transfer. The low boiling points coming out of the primary distillation tower reflux tank 1300-V-2027 are transported through the primary distillation tower reflux pump 1300-P-2019A / B transportation is divided into three parts: the first part goes to the crude esterification MMA tank 1300-V-2010, and then is transported to the extraction mixer 1300-V-2013 through the extraction feed pump 1300-P-2013A / B for re-extraction and purification; the second part operates normally in the primary distillation tower 1300-C-2001; the third part is stored on the side of the low-boiling tank 1300-V-2025A, and is intermittently sent to the HQ dissolution tank 1300-V-2028 for preparation of inhibitors through the low-boiling pump 1300-P-2045A / B. The crude MMA enters the MMA / water separation tank 1300-V-2026 by gravity at the bottom of the upper tower of the primary distillation tower 1300-C-2001, and in the MMA The crude MMA in the A / water separation tank 1300-V-2026 is mixed with desalted water, and the mixture is washed with water and separated into two layers. The upper organic phase returns to the top of the lower section of the primary distillation tower 1300-C-2001 by gravity for further distillation. The water phase in the lower layer of the MMA / water separation tank 1300-V-2026 contains a small amount of MMA and methanol, which is transported by the separation tank water phase pump 1300-P-2046A / B and divided into three routes: the first route goes to the extraction mixer 1300-V-2013 feed pipeline to participate in extraction and purification; the second route goes to the MAA separation tower 1300-C-2005 for water phase spraying and enters the esterification vapor phase main pipe and the first esterification kettle 1300-R-2003 to participate in the reaction;The third route of deacidification of water is vented from the condenser 1300-E-2006A / B for water phase spraying and is stored in the acid water stripping condensate tank 1300-V-2038 and transported to the first esterification kettle 1300-R-2003 to participate in the reaction. The organic phase returned to the lower section passes through the mass transfer and heat transfer of the lower section of the primary distillation tower 1300-C-2001. Under the condition of ensuring that the bottom temperature of the primary distillation tower 1300-C-2001 is 68°C, it is transported from the bottom of the tower by the primary distillation tower bottom discharge pump 1300-P-2018A / B, and a part of it is transported to the distillation tower 1300-C-200 2. A part of the flow is used as the bottom reflux of the primary distillation tower 1300-C-2001. The main component of the material entering the distillation tower 1300-C-2002 is MMA, with a content of about 99%. The rest is high-boiling substances. The crude MMA entering the distillation tower 1300-C-2002 is separated from the high-boiling substances by gas and liquid phase mass transfer and heat transfer. MMA is evaporated from the top of the tower with a purity of more than 99.9% and enters the top pre-cooler 1300-E-2012 of the distillation tower. It is condensed with circulating cooling water in the top pre-cooler 1300-E-2012 of the distillation tower. The pure MMA with a purity of more than 99.9% in the tower reflux tank 1300-V-2029 is transported by the distillation tower reflux pump 1300-P-2023A / B and divided into two parts. One part enters the pure MMA cooler 1300-E-2018 or goes to the 2.4M6B dissolution tank 1300-V-2030 to prepare 2,4-dimethyl-6-tert-butylphenol (2, 4M6B) inhibitor solution, and the other part is transported to the top reflux of the distillation tower 1300-C-2002. The pure MMA coming out of the pure MMA cooler 1300-E-2018 enters MMA intermediate tank 1300-T-4102A / B / C, MMA intermediate tank 1300-T-4102A / B / C has an external coil, cooled with refrigerated brine to prevent polymerization due to temperature increase, pure MMA is transported to storage through MMA intermediate tank delivery pump 1300-P-4102A / B, if MMA cannot reach the required purity, it is transported back to the extraction crude MMA tank 1300-V-2017 by MMA intermediate tank delivery pump 1300-P-4102A / B, and re-enters the distillation process for refining until it is qualified;

[0066] The crude MMA from the primary distillation tower goes to the distillation tower 1300-C-2002, whose vacuum system consists of three vacuum pumps 1300-P-2025A / B / C and two vapor-liquid separation tanks 1300-V-2036 and 1300-V-2037. The liquid at the inlet of the vacuum system is discharged to the low-boiling-point storage tank 1300-V-2025A for recycling. The gas extracted from the vacuum system is separated by vapor and liquid in the vapor-liquid separation tank 1300-V-2037 and then goes to the tail gas system for incineration. The liquid is discharged to the low-boiling-point storage tank 1300-V-2025B and transported to the outside of the boundary area for incineration through the low-boiling-point pump 1300-P-2045A / B.

[0067] A 2,4M6B inhibitor solution prepared from pure MMA was added to the top of the condenser 1300-E-2012 of the high-boiling-matter de-distillation tower 1300-C-2002 and the top reflux line of the high-boiling-matter de-distillation tower 1300-C-2002 to prevent MMA from polymerizing in the high-boiling-matter de-distillation tower 1300-C-2002;

[0068] The crude MMA from the primary distillation tower is purified in the distillation tower 1300-C-2002, and the high-boiling substances extracted from the bottom of the tower contain about 93% MMA, which is transported by the distillation tower bottom discharge pump 1300-P-2022A / B, part of which is transported to the 1300-C-2003 tower to recover MMA, and the other part is refluxed to the bottom of the distillation tower;

[0069] The hydroquinone solution inhibitor required by this device is prepared from low-boiling substances (methanol). The hydroquinone solution prepared with low-boiling substances (methanol) is carried out in HQ dissolving tank 1300-V-2028, intermittent operation, and prepared about once a day. First add low-boiling substances (methanol) to HQ dissolving tank 1300-V-2028, and then pour solid hydroquinone. HQ dissolving tank 1300-V-2028 is equipped with a stirrer to make hydroquinone fully dissolved in low-boiling substances (methanol), and then put it into the inhibitor storage tank 1300-V-2052. HQ dissolving tank 1300-V-2028 is equipped with a liquid level display high liquid level alarm LICA and a high liquid level interlock I. When the liquid level of HQ dissolving tank 1300-V-2028 is 80%, interlock I actuates the low-boiling substance (methanol) feed pneumatic solenoid valve XV to close. The inhibitor storage tank 1300-V-2052 is provided with a liquid level display and a high and low liquid level alarm LIA. The inhibitor solution prepared with low boiling point (methanol) is transported by a metering pump 1300-P-2047A / B.

[0070] The 2,4-dimethyl-6-tert-butylphenol (2,4M6B) solution prepared with pure MMA is prepared in the 2.4M6B dissolving tank 1300-V-2030, and after preparation, it is placed in the inhibitor storage tank 1300-V-2053. The MMA liquid extracted from the top of the high-boiling distillation tower 1300-C-2002 is first added to the 2.4M6B dissolving tank 1300-V-2030, and then the inhibitor 2,4M6B is added. The 2.4M6B dissolving tank 1300-V-2030 is equipped with a stirrer to fully dissolve the inhibitor in the MMA. The inhibitor 2 and 4M6B solutions prepared with pure MMA are transported by pump 1300-P-2048A / B, and after being measured by rotor flowmeter, they are respectively supplied to the reflux pipeline of the distillation tower top precooler 1300-E-2012 and the high-boiling-substance removal distillation tower 1300-C-2002;

[0071] Furthermore, the exhaust gas flow entering the tail gas absorption tower 1300-C-1001 is washed by acetone from the acetone cooler 1300-E-1001, and the condensed material enters the acetone tank 1300-V-1001 to participate in the reaction again, and the uncondensed gas enters the vent condenser 1300-E-1009 through the top of the tail gas absorption tower 1300-C-1001, and the material condensed by the vent condenser 1300-E-1009 enters the acetone tank 1300-V-1001, and the uncondensed gas goes to the tail gas buffer tank 1300-V-1009, and finally goes to the SAR incinerator. Incineration, the flow rate of frozen brine in the vent condenser 1300-E-1009 is regulated by TIC to ensure that the temperature of the uncondensed gas is below -5°C. The uncondensed gas at the outlet of the vent condenser 1300-E-1009 is continuously purged with nitrogen to prevent the accumulation of gaseous components. The flow rate of nitrogen can be adjusted by an on-site rotor flowmeter. The tail gas absorption tower 1300-C-1001 is equipped with a temperature and pressure monitoring sensor. The flow rate of frozen brine in the acetone cooler 1300-E-1001 is regulated by TIC to ensure that the temperature of the acetone entering the tail gas absorption tower 1300-C-1001 is 0°C.

[0072] Furthermore, the feed temperature of the ACH distillation tower 1300-C-1002 is controlled by the ACH distillation heat exchanger 1300-E-1004. Unreacted acetone and HCN in the crude ACH are removed by distillation. At high temperature, part of the ACH is decomposed into acetone and HCN. In order to minimize the thermal decomposition of the ACH product, distillation is carried out under vacuum (the pressure at the upper head is about 100 mbar). If the top pressure exceeds 180 mbar (absolute pressure), the feeding and addition of low-pressure steam to the ACH distillation tower 1300-C-1002 are stopped by closing the regulating valve FV. The low-pressure steam is obtained by heating the reboiler 1300-E-1005 using low-pressure steam.

[0073] Furthermore, the gas discharged from the vacuum pump 1300-P-1009A / B is cooled by the tail gas cooler 1300-E-1011 and then goes to the washing tower 1300-C-1001, the gas-liquid separation tank 1300-V-1007 and the liquid condensed by the vacuum pump go to the recycling condensate tank 1300-V-1003, the liquid condensed from the tail gas cooler 1300-E-1011 at the outlet of the vacuum pump 1300-P-1009A / B goes to the recycling condensate tank 1300-V-1003 for recycling and treatment, and the condensate entering the recycling condensate tank 1300-V-1003 is then sent to the ACH first reactor 1300-R by the recycling condensate pump 1300-P-1008A / B. -1001 re-participates in the reaction. In order to avoid HCN polymerization in the recycling condensate tank 1300-V-1003, the recycling condensate tank 1300-V-1003 is provided with an external companion pipe. The recycling condensate tank 1300-V-1003 is continuously cooled by frozen brine through the external companion pipe to keep the condensate in the recycling condensate tank 1300-V-1003 at about -1°C. When the temperature of the recycling condensate tank 1300-V-1003 reaches 13°C, the catalyst pump 1300-P-1002A / B is stopped, and the feeding to the reactor 1300-R-1001 is stopped. The 1300-V-1003 tank is vented to the washing tower 1300-C-1001 to remove gaseous pollution.

[0074] Furthermore, 100% H2SO4 is prepared by the waste acid recovery device and transported by a sulfuric acid pump. A part of it intermittently enters the phenothiazine dissolution tank 1300-V-2006 to prepare the inhibitor sulfuric acid solution, and then enters the phenothiazine inhibitor tank 1300-V-2007, and the other part continuously enters the mixer 1300-M-2002, and is continuously mixed with the inhibitor sulfuric acid solution sent from the phenothiazine inhibitor tank 1300-V-2007 through the phenothiazine inhibitor pump 1300-P-2001A / B in the mixer 1300-M-2002, ensuring that the inhibitor (phenothiazine) content in the 100% H2SO4 solution is 200ppm and enters the acylation reactor 1300-R-2001A / B from the bottom.

[0075] Furthermore, the heat required by the amide salt mixing heater 1300-E-2007A / B is provided by medium-pressure steam heating of the heat transfer oil. During the acylation reaction, some gases will be produced by side reactions, the main component of which is CO gas. After being washed by the venting washing tower 1300-C-2006 and collected in a closed exhaust emission system, the gas is sent to the SAR incinerator for incineration. The washing water at the bottom of the venting washing tower 1300-C-2006 is transported to the acid water recovery device through the washing tower circulation pump 1300-P-2016A / B. The venting washing tower 1300-C-2006 is a baffle tower. Six baffles are installed. The tower and baffles are made of 316L. A nitrogen purge regulating valve is installed for the acylation reaction. The nitrogen inflow flow is regulated by the venting system pressure control to make the entire acylation venting system in a slightly positive pressure and pressure balance state. The pressure is controlled below 0.01MPa to ensure the smooth discharge of toxic gases. The acylation system is equipped with an MMA emergency buffer tank 1300-V-2012. The emergency tank feed pipeline is equipped with a high-temperature alarm and a high-temperature interlock. If abnormal venting occurs, the collected liquid is discharged to the first esterification kettle 1300-R-2003, and the gas is vented to the flare for incineration.

[0076] Furthermore, the heat transfer oil required by the amide salt mixed heater 1300-E-2007A / B is heated in the heat transfer oil system. The heat transfer oil system is composed of a closed circulation loop. After the heat transfer oil is added once, it does not need to be replenished during normal operation. The heat transfer oil is transported to the heat transfer oil feeding tank 1300-V-2002 through the heat transfer oil replenishing pump 1300-P-2008 with a hose, and the heat transfer oil is transported into the heat transfer oil heater 1300-E-2008 and the entire heat transfer oil system through the heat transfer oil feeding pump 1300-P-2006 and the heat transfer oil circulation pump 1300-P-2007A / B. -2008, medium-pressure steam is used to slowly heat the heat transfer oil at a heating rate of 2°C per hour. The device is preheated to 100-110°C and circulated before feeding. After the device is fed, when the acylation reactor 1300-R-2001A / B overflows, the temperature of the heat transfer oil is rapidly raised from 100-110°C to 145-150°C, which is achieved by adjusting the amount of medium-pressure steam added. The heated heat transfer oil enters the amide salt mixing heater 1300-E-2007A / B to provide the heat required for the reaction, and returns to the heat transfer oil expansion tank 1300-V-2001 after heat exchange, and then circulates by the heat transfer oil circulation pump 1300-P-2007A / B.

[0077] Furthermore, the esterification reaction takes place in a group of five kettle reactors in which pipelines of gas phase and liquid phase are connected in series, and the liquid phase is transported from the bottom of the first esterification kettle 1300-R-2003 by the acid water pump 1300-P-2009A / B, and enters the second esterification kettle 1300-R-2004 through the bottom of the first esterification kettle 1300-R-2003. The liquid phase of the second esterification kettle 1300-R-2004 overflows from the upper side by gravity into the third esterification kettle 1300-R-2005; the liquid phase of the third esterification kettle 1300-R-2005 overflows from the upper side by gravity into the fourth esterification kettle 1300-R-2006; the fourth esterification kettle 1300-R-2007 is a kind of esterification reaction vessel. The liquid phase of 300-R-2006 overflows from the upper side by gravity into the fifth esterification kettle 1300-R-2007, and finally overflows from the upper side of the fifth esterification kettle 1300-R-2007 to 1300-V-2040A / B, and is then transported by pump 1300-P-2030A / B and sent to the acid water recovery device through the acid water gas lift tank 1300-V-2040A / B. When the acid water recovery device cannot receive it, it can also be intermittently sent to the acid water tank 1300-V-2055A / B. The acid water in the acid water tank 1300-V-2055A / B is transported by the acid water delivery pump 1300-P-2031A / B to the acid water recovery device for recovery and treatment.

[0078] Furthermore, high boiling substances are transported by the distillation tower bottom discharge pump 1300-P-2022A / B into the MMA recovery tower 1300-C-2003, in which MMA is recovered, and the stripped MMA is evaporated from the top of the tower and enters the recovery tower top pre-cooler 1300-E-2016 for condensation, and the condensate enters the recovery tower reflux tank 1300-V-2050, and the uncondensed gas is mixed with the volatilized gas in the recovery tower reflux tank 1300-V-2050 and enters the recovery tower top after-cooler 1300-E-2019, in which it is condensed by frozen brine, the condensate is mixed with the liquid coming out of the recovery tower reflux tank 1300-V-2050, and the non-condensable gas is extracted by the vacuum system. The liquid in the reflux tank 1300-V-2050 is transported by the recovery tower reflux pump 1300-P-2049A / B and divided into two parts. One part refluxes to the top of the MMA recovery tower 1300-C-2003 as the reflux of the MMA recovery tower 1300-C-2003, and the other part enters the extraction crude MMA tank 1300-V-2017 and returns to the distillation process. The MMA purity obtained by the MMA recovery tower from the 1300-C-2003 tower is about 97%. The high boiling materials discharged from the MMA recovery tower 1300-C-2003 contain about 30% MMA, which is continuously transported by the recovery tower discharge pump 1300-P-2044A / B to the third esterification kettle 1300-R-2005 for esterification and recycling again.

[0079] By those skilled in the art, the components in this case are connected in sequence. The specific connection and operation sequence should refer to the following working principle. The detailed connection means are well-known technologies in the field. The following mainly introduces the working principle and process.

[0080] Embodiment: The process technology includes two production units: an acetone cyanohydrin unit and a methyl methacrylate unit, wherein: the acetone cyanohydrin unit includes a reaction process and a refining process; the methyl methacrylate unit includes an acylation process, an esterification process, an extraction process and a distillation process;

[0081] Reaction process: Use an acetone feeding pump to transport acetone from the tank area to the acetone tank, then transport the acetone in the acetone tank through the acetone pump, a part of it is sent to the ACH first reactor to participate in the reaction, and the other part is cooled to 0°C by an acetone cooler and sent to the tail gas absorption tower to treat the exhaust mist flow mainly from the acetone tank, catalyst tank, ACH second reactor and ACH vacuum pump; the barreled catalyst is sent to the catalyst tank by the catalyst feeding pump, the catalyst in the catalyst tank is sent into the reaction system through the catalyst feeding pump, and the acetone and hydrocyanic acid and the recycled condensate from the recycling condensate tank are sent to the ACH first reactor through the recycling condensate pump. The catalyst is fed into the ACH cooler from the top of the reactor circulation pump inlet side, and the catalyst is fed into the ACH cooler from the outlet side of the reactor circulation pump by the catalyst feed pump, and enters the ACH first reactor together with acetone and hydrocyanic acid. The reaction mixture of the ACH first reactor overflows from the top into the ACH cooler, and is cooled to 10°C by the crude ACH from the ACH third reactor tank, and then enters the ACH second reactor tank. The unstable crude ACH entering the ACH third reactor tank will be partially decomposed into acetone and HCN. The crude ACH from the ACH third reactor tank is fed into the ACH cooler by the distillation tower feed pump, and is preheated by the overflow liquid from the ACH first reactor in the ACH cooler, and then goes to the refining process.

[0082] Refining process: The crude ACH from the ACH cooler is further heated by the refined ACH from the ACH distillation tower in the ACH distillation heat exchanger and then enters the ACH distillation tower for distillation. The light components stripped from the ACH distillation tower are condensed in the top front condenser and the top rear condenser. The condensate flows into the recirculating condensate tank, and the uncondensed steam enters the vacuum system. The refined ACH at the bottom of the ACH distillation tower is pumped into the heat exchanger by the refined ACH product pump, and the crude ACH from the ACH cooler is preheated before entering the ACH product cooler. The refined ACH is further cooled by circulating water in the ACH product cooler and enters the ACH intermediate storage tank, and the vacuum in the tower is achieved by the vacuum pump;

[0083] Acylation process: The acylation process is divided into two independent lines. ACH is delivered to the ACH storage tank through the ACH delivery pump at the bottom of the ACH distillation tower. The ACH in the ACH storage tank is delivered to the reactor through the intermediate tank delivery pump. The reaction of ACH and H2SO4 (100%) is carried out in the acylation reactor, the amide salt mixing heater and the amide reactor. ACH is divided into four sections and continuously enters the acylation reactor respectively through the intermediate tank delivery pump according to the ratio of H2SO4:ACH=1.66 (weight ratio). ACH and 100% H2S O4 mixed reaction generates α-formamido isopropyl hydrogen sulfate, which overflows from the top side of the acylation reactor by gravity into the bottom of the amide salt mixing heater, and is heated to a temperature of 91-95° C. to 135-140° C., and then overflows from the top side of the amide salt mixing heater by gravity into the amide reactor, and completes the transposition rearrangement reaction in the amide reactor, and the temperature drops from 135-140° C. to 133-138° C. The reaction mixture coming out of the amide reactor is still carried out by gravity to the first esterification kettle to undergo an esterification reaction with methanol;

[0084] Esterification process: The esterification process is a single-line operation. Methanol is transported into the methanol tank by the external network methanol pump, and then transported by the methanol delivery pump in the device area. 80% of the flow of methanol, methacrylamide sulfate (MAAS) flowing from the amide salt reactor, and the extraction water phase coming out from the bottom of the extraction mixer enter the first esterification kettle together. 20% of the flow of methanol enters the second and third esterification kettles to participate in the esterification reaction.

[0085] Extraction process: The crude MMA from the esterification reaction enters the esterification crude MMA tank by gravity, and is transported into the extraction mixer by the extraction feed pump for mixed extraction. The crude MMA after mixed extraction overflows into the bottom of the extraction tower by gravity, and is fully contacted with desalted water in the extraction tower to dissolve the methanol-soluble components in the crude MMA, so that the organic phase MMA is precipitated and purified again, and overflows from the extraction tower into the extraction crude MMA tank by gravity. The purity of MMA can reach more than 90%, and then it is transported to the distillation process by the primary distillation tower feed pump;

[0086] Distillation process: The crude MMA from the crude MMA extraction tank is transported into the primary distillation tower through the primary distillation tower feed pump. The primary distillation tower is a low-boiling-point separation tower. The tower is divided into two sections, the upper and lower sections, which are sieve plate towers. The low-boiling-point separation tower is operated under reduced pressure. The low-boiling-point is evaporated from the top of the upper section of the tower and transported back to the tower through the primary distillation tower reflux pump in the primary distillation tower reflux tank. In the middle of the tower, the material is washed with water in the MMA / water separation tank to separate the methanol and water in the material. The organic phase after washing and separation is returned to the lower tower for separation and purification. The MMA and high-boiling-point are taken out from the bottom of the tower to the distillation tower. The water phase of the MMA / water separation tank is transported by the separation tank water phase pump to the extraction mixer and MAA separation tank in three ways. The tower and acid water vent condenser are recycled, and the crude MMA enters the primary distillation tower. After gas and liquid mass transfer separation, the low-boiling substances coming out of the reflux tank of the primary distillation tower are transported by the primary distillation tower reflux pump and divided into three parts: the first part is de-esterified to the crude MMA tank, and then transported to the extraction mixer for re-extraction and purification through the extraction feed pump, the second part operates normally in the primary distillation tower, and the third part is stored on the side of the low-boiling tank A, and is intermittently sent to the HQ dissolution tank for preparation of inhibitors through the low-boiling pump. The crude MMA enters the MMA / water separation tank by gravity at the bottom of the upper tower of the primary distillation tower. In the MMA / water separation tank, the crude MMA is mixed with desalted water, and the mixed water is washed and divided into two layers The upper organic phase returns to the top of the lower section of the primary distillation tower by gravity for further distillation. The water phase in the lower layer of the MMA / water separation tank contains a small amount of MMA and methanol, which is transported by the separation tank water phase pump to three routes: the first route goes to the extraction mixer feed pipeline to participate in extraction and purification; the second route goes to the MAA separation tower for water phase spraying and enters the esterification vapor phase main pipe and the first esterification kettle to participate in the reaction; the third route goes to the acid water venting condenser for water phase spraying and passes through the acid water stripping condensate tank, stored and transported to the first esterification kettle to participate in the reaction, and the organic phase returned to the lower section undergoes mass transfer and heat transfer in the lower section of the primary distillation tower. While ensuring that the temperature at the bottom of the primary distillation tower is 68°C, it is discharged from the bottom of the tower. A part of the material is transported to the distillation tower for separation of high-boiling substances by the discharge pump at the bottom of the primary distillation tower, and a part of the flow is used as the reflux at the bottom of the primary distillation tower. The main component of the material entering the distillation tower is MMA, with a content of about 99%, and the rest is high-boiling substances. The crude MMA entering the distillation tower is separated from the high-boiling substances by gas and liquid phase mass transfer and heat transfer. MMA is evaporated from the top of the tower, and the purity is above 99.9% and enters the front cooler at the top of the distillation tower. It is condensed with circulating cooling water in the front cooler at the top of the distillation tower. The pure MMA with a purity of more than 99.9% in the reflux tank of the distillation tower is transported by the reflux pump of the distillation tower and divided into two parts, one of which enters the pure MMA cooler or goes to 2.4M6B dissolution tank, prepare 2,4-dimethyl-6-tert-butylphenol (2, 4M6B) inhibitor solution, the other part is sent to the top of the distillation tower for reflux, the pure MMA from the pure MMA cooler enters the MMA intermediate tank, the MMA intermediate tank has an external coil, cooled with refrigerated brine to prevent polymerization due to temperature increase, the pure MMA is sent to storage by the MMA intermediate tank delivery pump, if the MMA does not reach the required purity, it is sent back to the extraction crude MMA tank by the MMA intermediate tank delivery pump and re-enters the distillation process for refining. .

[0087] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions. The sentence "includes an element defined by ... does not exclude the existence of other identical elements in the process, method, article or device including the element".

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for producing methyl methacrylate using an acetone cyanohydrin method, characterized in that: Comprising acetone cyanohydrin units and methyl methacrylate units: The acetone cyanohydrin unit includes a reaction process and a refining process; The methyl methacrylate unit includes an acylation process, an esterification process, an extraction process and a distillation process; The reaction process is as follows: the acetone is transported from the tank area to the acetone tank 1300-V-1001 using an acetone feed pump, and then the acetone in the acetone tank 1300-V-1001 is transported through the acetone pump 1300-P-1001A / B, a part of which is sent to the ACH first reactor 1300-R-1001 to participate in the reaction, and the other part is cooled to 0°C by the acetone cooler 1300-E-1001, and sent to the tail gas absorption tower 1300-C-1001 for treating the acetone mainly from the acetone tank 1300-V-1001, the catalyst tank 1300-V-1002, The exhaust mist flow of ACH reactor 1300-R-1002 and ACH vacuum pump 1300-P-1009A / B; the barreled catalyst is fed into catalyst tank 1300-V-1002 by catalyst feeding pump 1300-P-1010, the catalyst in catalyst tank 1300-V-1002 is fed into the reaction system by catalyst feeding pump 1300-P-1002A / B, acetone and hydrocyanic acid as well as the recycled condensate from the recycling condensate tank 1300-V-1003 are fed into the reaction system by recycling condensate pump 1300-P-1008A / B. The catalyst is fed into the outlet side of the reactor circulation pump 1300-P-1003A / B of the first ACH reactor 1300-R-1001 by the catalyst feed pump 1300-P-1002A / B, and enters the first ACH reactor 1300-R-1001 together with acetone and hydrocyanic acid. The reaction mixture of the first ACH reactor 1300-R-1001 overflows from the top into the ACH cooler 1300-E-1002 and is taken up by the catalyst from the third ACH reaction tank 1300-R-1002. The crude ACH of 3 is cooled to 10°C and then enters the ACH second reaction tank 1300-R-1002, and then enters the ACH third reaction tank 1300-R-1003. The unstable crude ACH will be partially decomposed into acetone and HCN. The crude ACH of the ACH third reaction tank 1300-R-1003 is sent to the ACH cooler 1300-E-1002 by the distillation tower feed pump 1300-P-1006A / B, and is preheated by the overflow liquid from the ACH first reactor 1300-R-1001 in the ACH cooler 1300-E-1002 and then goes to the refining process; The refining process: the crude ACH from the ACH cooler 1300-E-1002 is further heated in the ACH distillation heat exchanger 1300-E-1004 by the refined ACH from the ACH distillation tower 1300-C-1002 and then enters the ACH distillation tower 1300-C-1002 for distillation, and the light components stripped out from the ACH distillation tower 1300-C-1002 are condensed in the top pre-condenser 1300-E-1007 and the top post-condenser 1300-E-1008. The condensate flows into the recycling condensate tank 1300-V-1003, and the uncondensed steam enters the vacuum system. The refined ACH at the bottom of the ACH distillation tower 1300-C-1002 is sent to the heat exchanger 1300-E-1004 by the refined ACH product pump 1300-P-1007A / B, and enters the ACH product cooler 1300-E-1006 after preheating the crude ACH from the ACH cooler 1300-E-1002. The refined ACH is further cooled by the circulating water in the ACH product cooler 1300-E-1006 and enters the ACH intermediate storage tank 1300-T-4101A / B / C, and the vacuum in the tower is realized by the vacuum pump 1300-P-1009A / B. The acylation process: The acylation process is divided into two independent lines A / B, ACH is transported to the ACH storage tank 1300-T-4101-A / B / C through the ACH delivery pump 1300-P-1007A / B at the bottom of the ACH distillation tower 1300-C-1002, and the ACH in the ACH storage tank 1300-T-4101-A / B / C is transported into the reactor 1300- R-2001A / B, ACH and H2SO4 (100%) react in the acylation reactor 1300-R-2001A / B, the amide salt mixing heater 1300-E-2007A / B and the amide reactor 1300-R-2002A / B, ACH is continuously delivered in four stages through the intermediate tank delivery pump 1300-P-4101A / B at a ratio of H2SO4:ACH = 1.66 (weight ratio). ACH is introduced into the acylation reactor 1300-R-2001A / B, and ACH and 100% H2SO4 are mixed and reacted to form α-formamido isopropyl hydrogen sulfate, which overflows from the top side of the acylation reactor 1300-R-2001A / B by gravity into the bottom of the amide salt mixing heater 1300-E-2007A / B, and the temperature is raised from 91-95°C to 135-140°C by heating, and then from the amide salt mixing heater 1300 -The top side of E-2007A / B still overflows into the amide reactor 1300-R-2002A / B by gravity, and the transposition rearrangement reaction is completed in the amide reactor 1300-R-2002A / B, and the temperature drops from 135-140°C to 133-138°C. The reaction mixture coming out of the amide reactor 1300-R-2002A / B still flows by gravity to the first esterification kettle 1300-R-2003 to react with methanol for esterification; The esterification process: the esterification process is a single-line operation, methanol is transported into the methanol tank 1300-T-4103 by the external network methanol pump, and then transported by the methanol delivery pump 1300-P-4103A / B in the device area, 80% of the flow of methanol and methacrylamide sulfate (MAAS) flowing from the amide salt reactor 1300-R-2002A / B, and the extraction water phase coming out from the bottom of the extraction mixer 1300-V-2013 enter the first esterification kettle 1300-R-2003, 20% of the flow of methanol enters the second esterification kettle 1300-R-2004 and the third esterification kettle 1300-R-2005 to participate in the esterification reaction; The extraction process: the crude MMA from the esterification reaction enters the esterification crude MMA tank 1300-V-2010 by gravity, and is transported into the extraction mixer 1300-V-2013 by the extraction feed pump 1300-P-2013A / B for mixed extraction. The crude MMA after mixed extraction overflows into the bottom of the extraction tower 1300-C-2004 by gravity, and is fully contacted with desalted water in the extraction tower to dissolve the methanol-soluble components in the crude MMA, so that the organic phase MMA is precipitated and purified again, and overflows from the extraction tower 1300-C-2004 by gravity into the extraction crude MMA tank 1300-V-2017, and the purity of MMA can reach more than 90%, and is then transported to the distillation process by the primary distillation tower feed pump 1300-P-2017A / B; The distillation process: the crude MMA from the extraction crude MMA tank 1300-V-2017 is transported into the primary distillation tower 1300-C-2001 through the primary distillation tower feed pump 1300-P-2017A / B. The primary distillation tower 1300-C-2001 is a low-boiling-point separation tower. The tower is divided into two sections, which are sieve plate towers. The low-boiling points are evaporated from the top of the upper section of the tower under reduced pressure operation. In the primary distillation tower reflux tank 1300-V-2027, the primary distillation tower reflux pump 1300-P-2019A / B is transported back to the tower. In the middle of the tower, the material is washed with water in the MMA / water separation tank 1300-V-2026 to separate the methanol and water in the material. The organic matter after washing and separation is The phase returns to the lower tower for separation and purification, MMA and high boiling points are taken out from the bottom of the tower and go to the distillation tower 1300-C-2002, the water phase of the MMA / water separation tank 1300-V-2026 is transported through the separation tank water phase pump 1300-P-2046A / B to the extraction mixer 1300-V-2013, MAA separation tower 1300-C-2005, and acid water venting condenser 1300-E-2006A / B for recycling, the crude MMA enters the primary distillation tower 1300-C-2001, and is separated by gas and liquid mass transfer. The low boiling points coming out of the primary distillation tower reflux tank 1300-V-2027 are transported through the primary distillation tower reflux pump 1300-P-2019A / B transportation is divided into three parts: the first part is deesterified in crude MMA tank 1300-V-2010, and then transported to extraction mixer 1300-V-2013 through extraction feed pump 1300-P-2013A / B for re-extraction and purification, the second part operates normally in primary distillation tower 1300-C-2001, the third part is stored on the side of low-boiling tank 1300-V-2025A, and intermittently sent to HQ dissolution tank 1300-V-2028 for preparation of inhibitor through low-boiling pump 1300-P-2045A / B, the crude MMA enters MMA / water separation tank 1300-V-2026 by gravity at the bottom of the upper tower of primary distillation tower 1300-C-2001, and in MMA The crude MMA in the A / water separation tank 1300-V-2026 is mixed with desalted water, and the mixture is washed with water and separated into two layers. The upper organic phase returns to the top of the lower section of the primary distillation tower 1300-C-2001 by gravity for further distillation. The water phase in the lower layer of the MMA / water separation tank 1300-V-2026 contains a small amount of MMA and methanol, which is transported by the separation tank water phase pump 1300-P-2046A / B and divided into three routes: the first route goes to the extraction mixer 1300-V-2013 feed pipeline to participate in extraction and purification; the second route goes to the MAA separation tower 1300-C-2005 for water phase spraying and enters the esterification vapor phase main pipe and the first esterification kettle 1300-R-2003 to participate in the reaction;The third deacidification water venting condenser 1300-E-2006A / B is sprayed with water phase and stored through the acid water stripping condensate tank 1300-V-2038 and transported to the first esterification kettle 1300-R-2003 to participate in the reaction. The organic phase returned to the lower section undergoes mass transfer and heat transfer in the lower section of the primary distillation tower 1300-C-2001. While ensuring the bottom temperature of the primary distillation tower 1300-C-2001 at 68°C, it is transported from the bottom of the tower to the distillation tower 1300-C-2002 by the primary distillation tower bottom discharge pump 1300-P-2018A / B. A part of the bottom of the primary distillation tower 1300-C-2001 is transported to the de-distillation tower 1300-C-2002, and a part of the flow is used as the bottom reflux of the primary distillation tower 1300-C-2001. The main component of the material entering the distillation tower 1300-C-2002 is MMA, with a content of about 99%, and the rest is high-boiling substances. The crude MMA entering the distillation tower 1300-C-2002 undergoes gas-liquid mass transfer and heat transfer to separate MMA from the high-boiling substances. MMA is evaporated from the top of the tower with a purity of more than 99.9% and enters the distillation tower top pre-cooler 1300-E-2012. It is condensed with circulating cooling water in the distillation tower top pre-cooler 1300-E-2012. In the distillation tower reflux tank 1300-V-2029, pure MMA with a purity of more than 99.9% is transported by the distillation tower reflux pump 1300-P-2023A / B and divided into two parts. One part enters the pure MMA cooler 1300-E-2018 or goes to the 2.4M6B dissolution tank 1300-V-2030 to prepare 2 ,4-dimethyl-6-tert-butylphenol (2, 4M6B) inhibitor solution, the other part is transported to the top of the distillation tower 1300-C-2002 for reflux, the pure MMA from the pure MMA cooler 1300-E-2018 enters the MMA intermediate tank 1300-T-4102A / B / C, the MMA intermediate tank 1300-T-4102A / B / C has an external coil, cooled with frozen brine to prevent polymerization due to temperature increase, the pure MMA is transported to storage by the MMA intermediate tank delivery pump 1300-P-4102A / B, if the MMA does not reach the required purity, it is transported back to the extraction crude MMA tank 1300-V-2017 by the MMA intermediate tank delivery pump 1300-P-4102A / B, and re-enters the distillation process for refining until it is qualified. ; 2. A process for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The exhaust gas flow entering the tail gas absorption tower 1300-C-1001 is washed by acetone from the acetone cooler 1300-E-1001, and the condensed material enters the acetone tank 1300-V-1001 to participate in the reaction again, and the uncondensed gas enters the vent condenser 1300-E-1009 through the top of the tail gas absorption tower 1300-C-1001. The material condensed by the vent condenser 1300-E-1009 enters the acetone tank 1300-V-1001, and the uncondensed gas goes to the tail gas buffer tank 1300-V-1009 and finally goes to the SAR incinerator for incineration. The flow rate of frozen brine of the vent condenser 1300-E-1009 is regulated by TIC to ensure that the temperature of the uncondensed gas is below -5°C. The uncondensed gas at the outlet of the vent condenser 1300-E-1009 is continuously purged with nitrogen to prevent the accumulation of gaseous components. The flow rate of nitrogen can be adjusted by an on-site rotor flowmeter. The tail gas absorption tower 1300-C-1001 is equipped with a temperature and pressure monitoring sensor. The flow rate of frozen brine of the acetone cooler 1300-E-1001 is regulated by TIC to ensure that the temperature of the acetone entering the tail gas absorption tower 1300-C-1001 is 0°C.

3. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The feed temperature of ACH distillation tower 1300-C-1002 is controlled by ACH distillation heat exchanger 1300-E-1004. Unreacted acetone and HCN in crude ACH are removed by distillation. At high temperature, part of ACH is decomposed into acetone and HCN. In order to minimize the thermal decomposition of ACH product, distillation is carried out under vacuum (the pressure at the upper head is about 100 mbar). If the top pressure exceeds 180 mbar (absolute pressure), the feeding and addition of low-pressure steam to ACH distillation tower 1300-C-1002 are stopped by closing regulating valve FV. The low-pressure steam is obtained by heating the reboiler 1300-E-1005 using low-pressure steam.

4. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The gas discharged from the vacuum pump 1300-P-1009A / B is cooled by the tail gas cooler 1300-E-1011 and then goes to the washing tower 1300-C-1001. The gas-liquid separation tank 1300-V-1007 and the liquid condensed by the vacuum pump go to the recycling condensate tank 1300-V-1003. The liquid condensed by the tail gas cooler 1300-E-1011 at the outlet of the vacuum pump 1300-P-1009A / B goes to the recycling condensate tank 1300-V-1003 for recycling and treatment. The condensate enters the recycling condensate tank 1300-V-1003 and is then sent to the ACH first reactor 1300-R-1008 by the recycling condensate pump 1300-P-1008A / B. 01 re-participates in the reaction. In order to avoid HCN polymerization in the recycling condensate tank 1300-V-1003, the recycling condensate tank 1300-V-1003 is provided with an external companion pipe. The recycling condensate tank 1300-V-1003 is continuously cooled by frozen brine through the external companion pipe to keep the condensate in the recycling condensate tank 1300-V-1003 at about -1°C. When the temperature of the recycling condensate tank 1300-V-1003 reaches 13°C, the catalyst pump 1300-P-1002A / B is stopped, and the feeding to the reactor 1300-R-1001 is stopped. The 1300-V-1003 tank is vented to the washing tower 1300-C-1001 to remove gaseous pollution.

5. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: 100% H2SO4 is prepared by the waste acid recovery device and transported by a sulfuric acid pump. A part of it intermittently enters the phenothiazine dissolution tank 1300-V-2006 to prepare the inhibitor sulfuric acid solution, and then enters the phenothiazine inhibitor tank 1300-V-2007, and the other part continuously enters the mixer 1300-M-2002, and is continuously mixed with the inhibitor sulfuric acid solution sent from the phenothiazine inhibitor tank 1300-V-2007 through the phenothiazine inhibitor pump 1300-P-2001A / B in the mixer 1300-M-2002, ensuring that the inhibitor (phenothiazine) content in the 100% H2SO4 solution is 200ppm and enters the acylation reactor 1300-R-2001A / B from the bottom.

6. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The heat required by the amide salt mixing heater 1300-E-2007A / B is provided by heat transfer oil through medium-pressure steam heating. During the acylation reaction, some side reactions will produce some gases, the main component of which is CO gas. After being washed by the venting washing tower 1300-C-2006 and collected in a closed exhaust emission system, it is sent to the SAR incinerator for incineration. The washing water at the bottom of the venting washing tower 1300-C-2006 is transported to the acid water recovery device through the washing tower circulation pump 1300-P-2016A / B. The venting washing tower 1300-C-2006 is a baffle tower with six The tower and baffles are made of 316L. A nitrogen purge regulating valve is installed in the acylation reaction. The nitrogen inflow rate is adjusted by the venting system pressure control to make the entire acylation venting system in a slightly positive pressure and pressure balance state. The pressure is controlled below 0.01MPa to ensure the smooth discharge of toxic gases. The acylation system is equipped with an MMA emergency buffer tank 1300-V-2012. The emergency tank feed pipeline is equipped with a high-temperature alarm and a high-temperature interlock. If abnormal venting occurs, the collected liquid is discharged to the first esterification kettle 1300-R-2003, and the gas is vented to the flare for incineration.

7. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The heat transfer oil required by the amide salt mixed heater 1300-E-2007A / B is heated in the heat transfer oil system. The heat transfer oil system consists of a closed circulation loop. After the heat transfer oil is added once, it does not need to be replenished during normal operation. The heat transfer oil is transported to the heat transfer oil feeding tank 1300-V-2002 through the heat transfer oil replenishing pump 1300-P-2008 with a hose, and then transported to the heat transfer oil heater 1300-E-2008 and the entire heat transfer oil system through the heat transfer oil feeding pump 1300-P-2006 and the heat transfer oil circulation pump 1300-P-2007A / B. In 08, medium-pressure steam is used to slowly heat the heat transfer oil at a heating rate of 2°C per hour. The device is preheated to 100-110°C and circulated before feeding. After the device is fed, when the acylation reactor 1300-R-2001A / B overflows, the temperature of the heat transfer oil is rapidly raised from 100-110°C to 145-150°C, which is achieved by adjusting the amount of medium-pressure steam added. The heated heat transfer oil enters the amide salt mixing heater 1300-E-2007A / B to provide the heat required for the reaction, and returns to the heat transfer oil expansion tank 1300-V-2001 after heat exchange, and then circulates by the heat transfer oil circulation pump 1300-P-2007A / B.

8. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The esterification reaction takes place in a group of five reactors in which gas and liquid phases are connected in series by pipelines of zirconium alloy. The liquid phase is transported from the bottom of the first esterification reactor 1300-R-2003 by the acid water pump 1300-P-2009A / B, and enters the second esterification reactor 1300-R-2004 through the bottom of the first esterification reactor 1300-R-2003. The liquid phase of the second esterification reactor 1300-R-2004 overflows from the upper side by gravity into the third esterification reactor 1300-R-2005; the liquid phase of the third esterification reactor 1300-R-2005 overflows from the upper side by gravity into the fourth esterification reactor 1300-R-2006; the fourth esterification reactor 1300 -R-2006 liquid phase overflows from the upper side by gravity into the fifth esterification kettle 1300-R-2007, and finally overflows from the upper side of the fifth esterification kettle 1300-R-2007 to 1300-V-2040A / B, and is then transported by pump 1300-P-2030A / B, and sent to the acid water recovery device through the acid water gas lift tank 1300-V-2040A / B. When the acid water recovery device cannot receive it, it can also be intermittently sent to the acid water tank 1300-V-2055A / B. The acid water in the acid water tank 1300-V-2055A / B is transported by the acid water delivery pump 1300-P-2031A / B to the acid water recovery device for recovery and treatment.

9. The process technology for producing methyl methacrylate using the acetone cyanohydrin method according to claim 1, characterized in that: The high boiling point is transported by the distillation tower bottom discharge pump 1300-P-2022A / B into the MMA recovery tower 1300-C-2003, in which MMA is recovered, and the stripped MMA is evaporated from the top of the tower and condensed in the recovery tower top pre-cooler 1300-E-2016, and the condensate enters the recovery tower reflux tank 1300-V-2050, and the uncondensed gas is mixed with the volatilized gas in the recovery tower reflux tank 1300-V-2050 and enters the recovery tower top after-cooler 1300-E-2019, in which it is condensed by frozen brine, and the condensate is mixed with the liquid coming out of the recovery tower reflux tank 1300-V-2050, and the non-condensable gas is extracted by the vacuum system. The liquid in tank 1300-V-2050 is transported by recovery tower reflux pump 1300-P-2049A / B and divided into two parts, one part refluxes to the top of MMA recovery tower 1300-C-2003 as the reflux of MMA recovery tower 1300-C-2003, and the other part enters the extraction crude MMA tank 1300-V-2017 and returns to the distillation process. The purity of MMA obtained by MMA recovery tower from 1300-C-2003 tower is about 97%, and the high boiling point discharged from MMA recovery tower 1300-C-2003 contains about 30% MMA, which is continuously transported by recovery tower discharge pump 1300-P-2044A / B to the third esterification kettle 1300-R-2005 for esterification and recycling again.

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