CN110510583B - Production method of sodium hydrosulfite - Google Patents
Production method of sodium hydrosulfite Download PDFInfo
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- C01—INORGANIC CHEMISTRY
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- C01B17/00—Sulfur; Compounds thereof
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- C01B17/66—Dithionites or hydrosulfites (S2O42-)
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Abstract
The invention provides a production method of sodium hydrosulfite, which comprises the steps of putting extracted sodium formate, mother liquor and pure water into a sodium formate preparation kettle, and stirring into a uniform sodium formate suspension; preparing a sodium metabisulfite suspension: sodium pyrosulfite, refined methanol and SO 2 Mercaptan inputPreparing sodium metabisulfite in a kettle, and stirring to obtain a uniform sodium metabisulfite suspension; adding the prepared sodium formate suspension, sodium metabisulfite suspension, mother liquor, mercaptan solution, liquid sulfur dioxide, methanol and ethylene oxide into a synthesis kettle for synthesis reaction, cooling a large amount of tail gas generated in the reaction process by water, salt and ammonia, separating by a gas-liquid separator, refluxing the liquid to return to the synthesis kettle, and removing the tail gas from the gas to carry out treatment; and carrying out filter pressing, washing, drying and mixing on sodium hydrosulfite suspension generated by the reaction, and separating to obtain sodium hydrosulfite. The purity of the sodium hydrosulfite obtained by the technical scheme of the invention reaches 90.0% or more.
Description
Technical Field
The invention relates to a production method of sodium hydrosulfite, and belongs to the technical field of chemical production.
Background
The synthetic reaction of the sodium hydrosulfite production comprises the operation processes of pH value adjustment, sodium thiosulfate amount adjustment, heat preservation, large dripping, small dripping, heat preservation ripening and the like in the feeding process, and the processes are repeated after each batch is completed, so that the cyclic operation is difficult to form, and the product purity is not high.
The Mitsubishi gas sodium hydrosulfite device is prepared from sodium formate solution, caustic soda solution and methanol-SO 2 After accurate calculation, quantitative addition and synthesis are carried out by a flowmeter, and the reaction pressure and temperature of synthesis are automatically controlled.
A patent for synthesizing continuous large dropping is applied by Zhongjianhui red Sifang limited company in 2013 and 10 months (application number 201310501782.2), and the technical scheme is that after each large dropping is finished, a material with a certain volume is left as a base material for the material which is finished the large dropping operation in a volume limiting and rotating mode when the material is further rotated to a small drop feeding pot. The method needs to carry out the operation of simultaneously dripping AE and ME in the process of synthesizing large dripping, and the operation is staged simultaneously.
Disclosure of Invention
Aiming at the technical problems, the invention provides an industrial continuous production method of sodium hydrosulfite. So as to overcome the defect that the continuous reaction process in large industry is difficult to realize. The specific scheme is as follows:
the production method of the sodium hydrosulfite comprises the following steps:
(1) Putting sodium formate into an extraction kettle, adding refined methanol, stirring, opening a steam valve, heating to 50-55 ℃, and fully dissolving the sodium formate;
(2) Nitrogen is opened to pressurize to 0.45-0.6MPa, solid-liquid separation is carried out through the filter cloth at the bottom of the kettle, the washing methanol after extraction is pressed into a mother liquor tank through the filter cloth to be used as mother liquor, and solid sodium formate is blocked by the filter cloth and is retained in the kettle;
sodium formate and methanol are stirred into uniform suspension, and the suspension is conveyed into a sodium formate preparation kettle for preparation after being opened and steam heated.
The process adopts a methanol extraction method to prepare high-purity sodium formate.
(3) Preparing a sodium formate suspension: putting the extracted sodium formate, the mother liquor obtained in the step (2) and pure water into a sodium formate preparation kettle, and stirring the mixture into a uniform sodium formate suspension;
(4) Preparing a sodium metabisulfite suspension: sodium pyrosulfite, refined methanol and SO 2 Adding mercaptan into a sodium metabisulfite preparation kettle, and stirring to obtain a uniform sodium metabisulfite suspension;
(5) Adding the prepared sodium formate suspension, sodium metabisulfite suspension, mother liquor, mercaptan solution, liquid sulfur dioxide, methanol and ethylene oxide into a synthesis kettle for synthesis reaction, separating by a gas-liquid separator after water cooling, salt cooling and ammonia cooling of a large amount of tail gas generated in the reaction process, refluxing the liquid to return to the synthesis kettle, and removing the tail gas from the gas to be treated; and carrying out filter pressing, washing, drying and mixing on the sodium hydrosulfite suspension generated by the reaction, and separating to obtain the sodium hydrosulfite.
The synthesis reaction process must be buffered and synchronized. In the case of large drops, na 2 S 2 O 5 +SO 2 (ME) quick addition, low pH, large amount of NaHSO 3 Possibly precipitating SO 2 A gas. Esterification reaction to produce HCOOCH 3 And (3) decomposition reaction under acidic condition: 2Na 2 S 2 O 4 +H 2 O＝Na 2 S 2 O 3 +2NaHSO 3
2Na 2 S 2 O 4 +H 2 SO 3 ＝S↓+2SO 2 ↑+2Na 2 SO 3 +H 2 O
The main reaction formula is as follows: 2HCOONa 2 S 2 O 5 +2SO 2 ＝2Na 2 S 2 O 4 +2CO 2 ↑+H 2 O
Step-by-step reaction: na (Na) 2 S 2 O 5 +H 2 O＝2NaHSO 3
HCOONa+SO 2 +H 2 O＝NaHSO 3 +HCOOH
2NaHSO 3 +HCOOH＝Na 2 S 2 O 4 +CO 2 ↑+2H 2 O
pH value: if the pH value is less than 4.2 during the large dropping process, the sulfur is precipitated. When HCOONa is excessive in quantity, the pH layer stock solution turns white, particles are fine, and ME cannot be added at the same time with AE. The pH is too low during the small addition, which causes decomposition of the acid.
Alcohol-water ratio: at the general reaction end point, the ratio of methanol to water is (78-80): (22-20), namely the mass ratio. The feed alcohol-water ratio is higher than the end point alcohol-water ratio. Because water is generated in the reaction process, the methanol with HCOOCH is volatilized 3 And other side reactions, generally about 2% higher than the end point alcohol-water ratio. The alcohol-water ratio is low, the water is more, the sodium hydrosulfite is largely decomposed by reacting with the water at high temperature; high alcohol-water ratio, naHSO 3 And part of the impuritiesThe precipitation of the sodium hydrosulfite also influences the crystallization of the sodium hydrosulfite.
Material balance: the materials in the reaction process are balanced and condensed under certain pressure (namely 0 to-10 ℃) for reflux, SO that SO is reduced 2 ，CH 3 OH，HCOOCH 3 And the material balance is ensured by volatilization.
The specific gravity of the mother liquor is 0.920-0.960, na 2 S 2 O 3 ≤5.06g/L、NaHSO 3 ≤75g/L。
Mixing under the condition of micro negative pressure in the step (3), heating to 45-65 ℃ after mixing, and pulping; the mass ratio of the sodium formate to the mother liquor to the pure water is 0.2-0.4:0.9-1.1:1.
mixing under the condition of micro negative pressure in the step (4); sodium metabisulfite, refined methanol and SO 2 The volume ratio of the mercaptan is 0.2-0.4:1.8-2.2:0.9-1.6:1.9-1.2.
In the step (5), the adding speed of the sodium formate suspension is 0.5-0.55t/h, the adding speed of the sodium metabisulfite suspension is 0.5-0.55t/h, the adding speed of the mercaptan solution is 0.022-0.026t/h, the adding speed of the liquid sulfur dioxide is 600-1000L/h, the adding speed of the methanol is 0.02-0.05t/h, and the adding speed of the ethylene oxide is 10-20L/h.
In the step (5), the synthesis reaction is carried out at the temperature of 80-85 ℃, the pressure of 0.1-0.35MPa and the pH of 4.2-4.3, large dripping is carried out after the materials are layered, small dripping is carried out after the large dripping is finished, and the sodium hydrosulfite is obtained after heat preservation.
In the large dropping process, the temperature is 81-85 ℃, the pressure is 0.15-0.25MPa, the pH value is 4.2-4.5, the Na2S2O3 is controlled to be less than or equal to 10g/L, and the flow rate of the ethylene oxide is 15-25L/h; AE. The ME suspension liquid is completely added to form a large dripping end point, nitrogen is used for purging the pipeline when the large dripping is finished, the residual materials in the pipeline are purged completely to prevent the pipeline from being blocked, and the pressure in the kettle is prevented from being overhigh in the process of purging the pipeline; if the sodium formate suspension is added firstly, the coke sub-suspension is not much left, and the sodium formate suspension can be continuously added under the condition that the pH value is not lower than 4.3; if the coke is left in the suspension liquid, stopping and preserving heat, and adding the residual coke when the pH is more than or equal to 4.4; if the coke sub-suspension is added first, the pH value is measured to be more than 4.4 and more sodium formate suspension can be properly supplemented with SO 2 Ensure the pH value is normalContinuously adding the rest sodium formate suspension in the range;
the whole large dripping time is controlled to be 60-80 minutes, and the temperature is kept for at least 10 minutes after the large dripping is finished. In the small dripping process, the temperature is 80-85 ℃, the pressure is 0.15-0.22 MPa, the pH value is 4.2-4.6 2 S 2 O 3 Less than or equal to 10g/L; the droplet addition time is controlled to be 120-210 minutes.
In the process of heat preservation, when Na is added 2 S 2 O 4 ≥85％，NaHSO 3 Not more than 75g/L, the temperature is controlled between 80 and 85 ℃ during heat preservation, the pressure is 0.1 to 0.15MPa 2 S 2 O 3 The content is less than or equal to 10g/L, the EO flow is adjusted, good backflow is ensured, when the pH is more than or equal to 4.9 2 S 2 O 3 ≤10g/L，NaHSO 3 ≤75g/L，Na 2 S 2 O 4 The temperature preservation end point is more than or equal to 86 percent, E0 is not required to be added in the heat preservation process, sulfur dioxide and water are not added, and the heat preservation time is 30-60 minutes.
That is, during the course of the synthesis reaction,
content of mother liquor sodium thiosulfate: less than or equal to 10g/L; the consequence of deviating from the normal working condition is that the sodium hydrosulfite is decomposed in a partial acid way.
The performance of the sodium hydrosulfite obtained by adopting the technical scheme of the invention is as follows:
Detailed Description
Example 1
Purification of by-product sodium formate
Before batching, the preparation tank and the connected pipelines are checked to test pressure without leakage points. Checking whether the on-site temperature and pressure display of the preparation tank is normal. Checking whether the stirring of the preparation tank, the power supply of the motor is supplied and the wiring is normal or not, turning the vehicle, and inching the motor to test the running direction. The requirements are stable operation and low noise.
And (5) putting 1.5 tons of solid sodium formate to the preparation tank by connecting a forklift, and recovering the feeding manhole. The tail gas valve of the preparation tank is opened, stirring is started, and the methanol adding valve is opened to add 3m3 of methanol into the tank. And opening a steam valve to heat the preparation tank to 48-53 ℃, ensuring the pulping time to be 1 hour, and stopping stirring the preparation tank.
Closing the tail gas valve of the preparation tank, opening an N2 valve to pressurize to be less than or equal to 0.1Mpa, opening a mother liquid valve to transfer the mother liquid to a newly-added qualified mother liquid tank, observing that a large amount of bubbles overflow through a sight glass to dry the mother liquid, and closing a nitrogen valve and a mother liquid main valve.
And (3) opening the tail gas valve to exhaust the pressure of the tank body, closing the tail gas valve, disassembling a feeding manhole cover, sampling in the tank by using a sampling rake, and performing sodium formate content analysis after the tank is fried to be dry by using a synthetic stir-frying table (a mark post is more than or equal to 99%).
Starting the preparation tank for stirring, opening a tail gas valve to release pressure less than or equal to 0.05Mpa, then opening a mother liquor adding valve to add 4m < 3 > of mother liquor into the tank, and measuring the specific gravity of the mother liquor when half of the mother liquor is added.
Opening a steam valve to heat the preparation tank to 50-65 ℃ for pulping for 15 minutes, then opening a nitrogen valve to pressurize to less than or equal to 0.1Mpa, and opening a discharge valve to discharge all the materials to the sodium formate preparation A kettle.
And after the materials are discharged, closing a nitrogen valve and a discharge valve of the preparation tank in time, stopping stirring the preparation tank in time, and opening an exhaust valve to exhaust the pressure.
According to the calculation of 88% of yield after sodium formate washing, 1200kg of sodium formate is replenished in the preparation kettle again, water is added according to the specific gravity of the mother liquor, finally methanol is replenished to the normal liquid level of the preparation kettle, the temperature is increased to 50-65 ℃, and the metering kettle is pressed for standby.
AE suspension formulation
Check the liquid level of qualified mother liquor tank before batching, guarantee that there is enough amount of mother liquor to prepare AE to this mother liquor of sample analysis: specific gravity of 0.920-0.960, na 2 S 2 O 3 ≤5.06g/L、NaHSO 3 ≤75g/L。
The residual pressure of a sodium formate preparation kettle is exhausted through a tail gas valve, when the pressure of the preparation kettle is zero, a tail gas valve is closed, a vacuumizing valve is opened to enable the interior of the kettle to be in a micro negative pressure state, a large cover of a material pouring port is opened, 2-3 tons of sodium formate is added into the sodium formate preparation kettle, during the feeding process, large blocks of solid sodium formate, woven bags and other sundries are strictly forbidden to be added into the kettle (if the materials are accidentally brought in, the materials are timely fished out), after the materials are poured, the cover of the hole is closed, and the vacuumizing valve is closed to guarantee the sealing performance of the kettle.
And starting the qualified mother liquor pump, opening a mother liquor adding valve on the sodium formate preparation kettle, adding 8000L of the qualified mother liquor (added through reading records of a flowmeter) into the sodium formate preparation kettle, and closing the mother liquor adding valve.
And opening the process water valve, and closing the process water adding valve after adding corresponding process water according to the specific gravity of the mother liquor (adding through the reading record of the flowmeter).
Closing an exhaust valve of the preparation kettle, starting stirring and pulping, opening a jacket, raising the temperature to 45-65 ℃ by steam, and keeping the pulping time not less than 20 minutes.
During the batching process, valves are slowly opened and closed to prevent leakage of materials due to rapid rise and drop of pipeline pressure, and related material pipeline valves are carefully checked to prevent material channeling before batching.
ME suspension formulation
Before coke is prepared, the liquid level conditions of a fine methanol tank and a sulfur dioxide storage tank are checked to ensure that enough amount is supplied for the preparation.
Opening a tail gas emptying valve on the coke oven preparation kettle, keeping the pressure relief zero, closing a tail gas valve, opening a vacuumizing valve to enable the interior of the kettle to be in a micro negative pressure state, opening a methanol flowmeter valve, accurately adding 2500L of methanol, opening the ME kettle for stirring, and opening a large cover of a material pouring port; and pouring the ready-for-use sodium pyrosulfite into a pyroya preparation kettle. And (4) after pouring, putting a manhole cover, and closing the vacuumizing valve to ensure the sealing property of the vacuumizing valve.
Opening SO 2 Flow meter valve for accurate addition of SO 2 Measuring 700-800L and then closing SO 2 Valves before and after the flowmeter.
Stirring and pulping in an ME kettle for later use.
Synthetic bottoming and value-adjusting operations
And (3) decompressing the synthesis kettle to below 0.05MPa, opening a mother liquor adding valve, adding 1000L of qualified mother liquor into the synthesis kettle, and starting stirring.
Opening a nitrogen valve of the sodium formate metering kettle to pressurize the sodium formate metering kettle to 0.45MPa, opening a discharge valve of the synthesis kettle, opening a sodium formate feed valve on the synthesis kettle, pressing 1000L of sodium formate suspension from the sodium formate metering kettle to the synthesis kettle to serve as a bottom material, and after bottoming, decompressing and back blowing the sodium formate metering kettle to prevent pipe blockage.
Checking whether the liquid level of the EO metering tank meets the production requirement, if not, adding EO to the normal liquid level in time in relation to the shift, opening nitrogen to pressurize to 0.35MPa, and opening the EO metering tank to a root valve of the synthesis kettle.
And (3) starting steam to heat the synthesis kettle to 70-75 ℃, then regulating the steam to be small or closing the steam according to the steam pressure, opening a reflux valve of the synthesis kettle, opening an EO adding valve, and controlling the flow rate to be 10-20L/h.
Opening SO 2 Metering valve control SO 2 The flow rate is 600-1000L/h, the temperature is controlled to be 78-85 ℃, the PH value is 4.2-4.3, the pressure is 0.10-0.15MPa, na is added into the solution 2 S 2 O 3 Less than or equal to 10g/L, and the whole process requires SO 2 Stable flow, timely PH value measurement and Na analysis 2 S 2 O 3 The content of the active ingredients in the feed liquid, and the color condition of the feed liquid are checked so as to be adjusted in time.
In the process of adjusting the value, sampling and analyzing in time and observing the layering condition of the material, if the layering is not rapid, the supernatant is turbid, the value is continuously adjusted, if the layering is rapid, the supernatant is clear, and SO is closed 2 And finishing the adjustment.
Controlling the temperature to be 80-85 ℃ after the value adjustment is finished, and preserving the heat for 10-15 minutes to ensure that the reaction is fully carried out, wherein the time of the whole value adjustment process is controlled to be 15-20 minutes, and the heat preservation is carried out according to Na 2 S 2 O 3 The EO flow is adjusted in time.
Large drop operation
Conditions to be met at the beginning of the large dropwise addition: the materials are layered quickly, the supernatant is clear and transparent, the pH value is 4.2-4.5 2 S 2 O 3 ≤10g/L。
And (4) starting steam according to the kettle temperature to heat the synthesis kettle, and beginning to dropwise add when the temperature is raised to 82 ℃.
In the process of large dripping, the temperature should be controlled to be 81-85 ℃, the pressure should be controlled to be 0.15-0.25MPa, the pH value should be controlled to be 4.2-4.5, and Na should be controlled 2 S 2 O 3 The flow rate of AE/ME suspension is observed in time and is less than or equal to 10g/L for 10 minutesThe pH value is measured once from left to right, the flow of AE, ME and EO is adjusted in time according to the pH value, and the backflow is adjusted well.
The large dropping feeding follows the principle of 'slow first and fast last'. When feeding materials, the materials are slowly added into the synthesis kettle according to the proportion of the total amount of the materials, and the EO flow is adjusted to be 15-25L/h.
The temperature is kept for at least 2 to 3 times during the large dripping period so as to ensure that the materials are fully reacted. Sampling and analyzing Na during each heat preservation 2 S 2 O 3 And (4) content, namely adjusting the EO flow in time according to an analysis result, and observing the material color and the reaction condition in the kettle during sampling.
AE. And the ME suspension is added to be a large dripping end point, nitrogen is used for purging the pipeline when the large dripping is finished, the residual materials in the pipeline are purged completely to prevent the pipeline from being blocked, and the pressure in the kettle is prevented from being overhigh in the process of purging the pipeline.
And (3) in the later stage of large dropwise adding: if the sodium formate suspension is added, the sodium formate suspension is continuously added under the condition that the PH value is not lower than 4.3, if the sodium formate suspension is remained more, the heat preservation is stopped, and the residual sodium formate suspension is slowly added until the PH value is more than or equal to 4.4; if the coke sub-suspension is added first, the pH value is measured to be more than 4.4 and the residual sodium formate suspension can be supplemented with SO properly 2 The remaining sodium formate suspension was continued to be added over the normal pH range.
The whole large dripping time is controlled to be 60-80 minutes, and the temperature is kept for at least 10 minutes after the large dripping is finished.
After the large dripping is finished, transferring the mixture to a small dripping kettle to continuously perform small dripping, and under special conditions, performing small dripping in the kettle, wherein various technological indexes are strictly controlled in the material transferring process.
Small drop operation
Conditions to be met for the start of the small dropwise addition: the temperature is 80-85 ℃, the pressure is 0.15-0.22 MPa, the PH value is 4.2-4.6 2 S 2 O 3 ≤10g/L。
Small drop addition of SO 2 The principle of 'fast early stage, stable middle stage and slow later stage' is followed. Normally, the cumulative addition of SO should be carried out 1.5 hours earlier 2 600-700L, 200-250L should be added in the middle 1 hour, and 1 hour should be added in the later period100-150L, the stir-fried content reaches 82% -85% after the droplets are added for two hours, and a proper amount of 100-200L/h of flow is started according to the reaction condition.
The process index control in the small dripping process is that the PH value in the middle early stage is 4.2 to 4.5, the PH value in the later stage is more than or equal to 4.4, the reaction temperature is 80 to 85 ℃, the reaction pressure is 0.15 to 0.25MPa, and Na is added 2 S 2 O 3 The concentration is less than or equal to 10g/L, the reflux is well controlled, and the reaction condition in the kettle is often observed.
In the course of small dropwise addition, at pH and Na 2 S 2 O 3 In case of normal content, not stopping SO as much as possible 2 According to Na 2 S 2 O 3 The EO flow is adjusted in time. However, there are a number of factors that lead to pH < 4.2 or Na 2 S 2 O 3 > 10g/L, at which point the addition of SO must be stopped 2 Continuing to add SO after various technological indexes are recovered to normal 2 。
Late phase NaHSO of droplet addition 3 The content is lower than 80g/L, the content of sodium hydrosulfite is analyzed by stir-frying, and if the content reaches more than 82 percent, SO is slowly added 2 Closely focusing on the pH variation trend, na was analyzed every 10-20 minutes 2 S 2 O 3 At this time, if the temperature and pressure are abnormally increased and the pH value is low, the acid addition is stopped, and a sample is immediately taken for Na analysis 2 S 2 O 3 The EO content is increased simultaneously if the content is NaHSO 3 The water addition can be continued or terminated according to actual conditions in the water tank below 75 g/L.
Judging the end point by adding small drops, sampling, analyzing and frying the sample when Na is contained 2 S 2 O 4 ≥85％，NaHSO 3 Less than or equal to 75g/L, when the color of the feed liquid is normal, the reaction is terminated, the reaction can be carried out in a heat preservation stage, and Na is analyzed in a heat preservation manner 2 S 2 O 4 The content should reach 86%.
The small dropping time is generally controlled to be 120 to 210 minutes.
SO should be checked and turned off after the addition of the droplets 2 All valves on the pipeline.
Operation of keeping warm
When Na is present 2 S 2 O 4 ≥85％，NaHSO 3 ≤75g/L，The heat-preserving operation can be entered. The temperature is controlled to be 80-85 ℃ and the pressure is controlled to be 0.1-0.15MPa when the temperature is kept 2 S 2 O 3 The content is less than or equal to 10g/L, the EO flow is adjusted, good backflow is ensured, when the PH is more than or equal to 4.9 2 S 2 O 3 ≤10g/L，NaHSO 3 ≤75g/L，Na 2 S 2 O 4 The temperature preservation end point is more than or equal to 86 percent.
In the heat preservation process, E0 cannot be stopped to be added, sulfur dioxide is strictly forbidden to be added, cold water is strictly forbidden to be cooled, a large tail gas valve is opened to release pressure, the reflux is well regulated, the color of the feed liquid and the reaction condition in the kettle are observed, and Na is analyzed once every 30 minutes 2 S 2 O 3 And (4) content.
The heat preservation time is 30-60 minutes and is not less than 30 minutes.
And after the heat preservation is finished, all valves of the EO pipeline and the steam valve are checked and closed.
Cooling operation
After the heat preservation is finished, the PH value is more than or equal to 4.9, circulating water can be started to cool, and the temperature is reduced to 70 +/-5 ℃ (the water is cooled for 3-5 minutes under the general condition).
If the dry kettle is not empty and can not discharge materials in time, circulating water is not needed to be boiled for cooling, and a large tail gas valve can be properly opened for cooling.
1.8 discharging operation points
If Na 2 S 2 O 3 ≤5.06g/L，NaHSO 3 Less than or equal to 75g/L, the PH value is more than or equal to 4.9, the temperature is 70 +/-5 ℃, and a drying station can be informed to discharge.
And during discharging, closing the sampling tube root valve, the reflux and tail gas valve and the circulating water cooling valve, opening nitrogen gas, pressurizing to 0.35MPa, opening the discharge valve, and discharging to a drying kettle.
And after the discharging is finished, opening a reflux valve to flush out the accumulated materials at the bottom of the kettle, and closing a nitrogen valve and a synthesis discharging valve.
If EO consumption for the batch is normal, na 2 S 2 O 3 Not more than 5.06g/L, and if the color of the mother liquor is normal, informing a drying station to recover the mother liquor to a qualified mother liquor tank, and if Na is contained, adding sodium chloride 2 S 2 O 3 >6.33g/L or E0 is consumed seriously excessively, and the color of the mother liquor turns yellow and dark, a drying station is informed to recycle the batch of the mother liquor toUnqualified mother liquor tank and increased methanol washing amount and soaking time of the batch.
The discharging temperature is controlled to be 65-75 ℃, if the temperature is lower than 65 ℃, the temperature is increased to 65-75 ℃, and sodium hydrosulfite is prevented from entering a drying kettle in a dihydrate salt form.
In the above process, the following should be noted:
the product obtained by adopting the technical scheme of the invention has the following physical and chemical properties:
Claims (7)
1. the production method of the sodium hydrosulfite is characterized by comprising the following steps:
(1) Putting sodium formate into an extraction kettle, adding refined methanol, stirring, opening a steam valve, heating to 50-55 ℃, and fully dissolving the sodium formate;
(2) Nitrogen is introduced and pressurized to 0.45-0.6MPa, solid-liquid separation is carried out through the filter cloth at the bottom of the kettle, the extracted washing methanol is pressed into a mother liquor tank through the filter cloth to be used as mother liquor, and solid sodium formate is blocked by the filter cloth and is retained in the kettle;
(3) Preparing a sodium formate suspension: putting the extracted sodium formate, the mother liquor obtained in the step (2) and pure water into a sodium formate preparation kettle, and stirring to obtain a uniform sodium formate suspension;
(4) Preparing a sodium metabisulfite suspension: sodium pyrosulfite, refined methanol and SO 2 Adding mercaptan into a sodium metabisulfite preparation kettle, and stirring to obtain a uniform sodium metabisulfite suspension;
(5) Adding the prepared sodium formate suspension, sodium metabisulfite suspension, mother liquor, mercaptan solution, liquid sulfur dioxide, methanol and ethylene oxide into a synthesis kettle for synthesis reaction, separating by a gas-liquid separator after water cooling, salt cooling and ammonia cooling of a large amount of tail gas generated in the reaction process, refluxing the liquid to return to the synthesis kettle, and removing the tail gas from the gas to be treated; carrying out filter pressing, washing, drying and mixing on sodium hydrosulfite suspension generated by the reaction, and separating to obtain sodium hydrosulfite;
the adding speed of the sodium formate suspension is 0.5-0.55t/h, the adding speed of the sodium metabisulfite suspension is 0.5-0.55t/h, the adding speed of the mercaptan solution is 0.022-0.026t/h, the adding speed of the liquid sulfur dioxide is 600-1000L/h, the adding speed of the methanol is 0.02-0.05t/h, and the adding speed of the ethylene oxide is 10-20L/h; carrying out synthesis reaction at the temperature of 80-85 ℃, the pressure of 0.1-0.35MPa and the pH value of 4.2-4.3, carrying out large dropping after materials are layered, carrying out small dropping after the large dropping is finished, carrying out heat preservation to obtain sodium hydrosulfite, controlling the temperature of 81-85 ℃, the pressure of 0.15-0.25MPa and the pH value of 4.2-4.5 in the large dropping process, and controlling Na 2 S 2 O 3 Less than or equal to 10g/L, and the flow rate of the ethylene oxide is 15-25L/h; AE. The ME suspension is added completely to be the end point of large dripping.
2. The method for producing sodium hydrosulfite according to claim 1, wherein the specific gravity of the mother liquor is 0.920-0.960, na 2 S 2 O 3 ≤5.06g/L、NaHSO 3 ≤75g/L。
3. The production method of sodium hydrosulfite according to claim 1, wherein in the step (3), mixing is carried out under the condition of micro negative pressure, and after mixing, the temperature is raised to 45-65 ℃ for pulping; the mass ratio of the sodium formate to the mother liquor to the pure water is 0.2-0.4:0.9-1.1:1.
4. the method for producing sodium hydrosulfite according to claim 1, wherein in the step (4), the mixing is carried out under the condition of slight negative pressure; sodium metabisulfite, refined methanol and SO 2 The volume ratio of the mercaptan is 0.2-0.4:1.8-2.2:0.9-1.6:1.9-1.2.
5. The production method of sodium hydrosulfite according to claim 1, wherein nitrogen is used for purging the pipeline when the large dropwise addition is finished, the residual materials in the pipeline are purged to prevent the pipeline from being blocked, and the pressure in the kettle is prevented from being overhigh in the process of purging the pipeline; if the sodium formate suspension is added to the coke sub-suspension, the sodium formate suspension is continuously added under the condition that the pH value is not lower than 4.3; if the coke is left in the suspension liquid, stopping and preserving heat, and adding the residual coke when the pH is more than or equal to 4.4; if the coke sub-suspension is added first, the pH value is measured to be more than 4.4 and more sodium formate suspension is left, SO is added properly 2 The residual sodium formate suspension is continuously added within the normal range of the pH value;
the whole large dripping time is controlled to be 60-80 minutes, and the temperature is kept for at least 10 minutes after the large dripping is finished.
6. The method for producing sodium hydrosulfite according to claim 1, wherein the temperature in the droplet adding process is 80-85 ℃, the pressure is 0.15-0.22 MPa, the pH value is 4.2-4.6, na 2 S 2 O 3 Less than or equal to 10g/L; the droplet addition time was controlled to 120 to 210 minutes.
7. The method for producing sodium hydrosulfite according to claim 1, wherein in the heat preservation process, na is added 2 S 2 O 4 ≥85%，NaHSO 3 Not more than 75g/L, the temperature is controlled between 80 and 85 ℃ during heat preservation, the pressure is 0.1 to 0.15MPa 2 S 2 O 3 The content is less than or equal to 10g/L, the EO flow is adjusted, good backflow is ensured, when the pH is more than or equal to 4.9 2 S 2 O 3 ≤10g/L，NaHSO 3 ≤75g/L，Na 2 S 2 O 4 More than or equal to 86 percent is the end point of heat preservation, EO is not required to be stopped adding in the heat preservation process, sulfur dioxide and water are not added, and the heat preservation time is 30 to 60 minutes.
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