Treatment system and treatment method for waste alkali liquor generated by extraction of trioxymethylene

Abstract

The present invention discloses a treatment system and a treatment method for waste alkali liquor generated by extracting trioxymethylene. The system includes a waste alkali liquor pipeline, an air pipeline, a nitrogen pipeline, a heating reaction kettle, an alkali liquor cooler and a solid storage device; the method includes: 1) heating and oxidation; (2) heating and decomposition; (3) cooling. Beneficial effects: The connection relationship of the system of the present invention is simple and easy to implement, realizing zero-emission treatment of waste alkali liquor, protecting the environment, reducing the equipment investment cost, and improving the economic benefits of the enterprise at the same time; effectively treating the organic matter in the high-alkali waste liquor; decomposing and eliminating sodium formate in the waste liquor after heating and oxidation; effectively recovering sodium hydroxide, which can be directly sold or used for preparing an extractant for extracting trioxymethylene, reducing the cost of the enterprise and increasing the economic benefits of the enterprise; realizing the recycling of calcium oxide and reducing the treatment cost of waste alkali liquor.

Description

Technical Field:

[0001] This invention patent belongs to the field of wastewater treatment, and particularly relates to a treatment system and a treatment method for the waste alkali liquor generated by extracting trioxymethylene. Background Art:

[0002] Polyoxymethylene products have excellent properties such as excellent chemical stability, relatively high mechanical strength, and good plasticity, so they are widely used in many fields such as automobile manufacturing, machinery manufacturing, electrical and electronic instruments, building materials, and daily light industry. Among them, the polymerization of trioxymethylene is currently the most important method for producing polyoxymethylene. Therefore, the trioxymethylene synthesis technology is the key technology in the polyoxymethylene synthesis process. In addition to being used in the production of polyoxymethylene resin, trioxymethylene is also an important chemical raw material and can be used in various reactions that require formaldehyde. In particular, when anhydrous formaldehyde is used as a raw material, trioxymethylene has higher application value.

[0003] Currently, in the industrial catalytic synthesis process of trioxymethylene, the generation of formic acid and acetic acid is often accompanied, and there is also unreacted formaldehyde. On the one hand, formic acid, acetic acid, and formaldehyde will affect the product quality of trioxymethylene. On the other hand, the accumulation of formic acid and acetic acid in the reaction system will also affect the normal progress of the trioxymethylene synthesis reaction and is extremely likely to cause corrosion to the equipment. Currently, a sodium hydroxide solution with a concentration of 37% wt is used to extract trioxymethylene to remove formic acid, acetic acid, and formaldehyde therein, that is, the following reactions occur:

[0004] 2HCHO + NaOH = HCOONa + CH 3 OH

[0005] HCOOH + NaOH = HCOONa + H 2 O

[0006] HCOOCH 3 + NaOH = HCOONa + CH 3 OH

[0007] The waste alkali liquor obtained through the above reactions contains 31.5% sodium hydroxide, 54.5% water, 10% organic matter, 4% sodium formate, with a pH as high as 14 and a COD > 20000. Therefore, the viscosity of the above waste alkali liquor is relatively large and it is extremely easy to block pipelines. At the same time, it has strong corrosiveness and weak toxicity and belongs to hazardous waste. If directly discharged, it will cause environmental pollution. If treated as hazardous waste, the treatment cost is as high as 3000 yuan / ton, increasing the cost of the enterprise and reducing the enterprise's benefits.

[0008] Currently, the main methods for treating the waste alkali liquor generated by extracting trioxymethylene are: sulfuric acid acidification technology and CO 2Absorption technology. The sulfuric acid acidification technology is used to convert sodium hydroxide into sodium sulfate, and then sodium sulfate crystals are obtained through evaporation and centrifugation. However, there are the following problems with the above technology: 1. The organic matter in the wastewater is not eliminated, and the treated wastewater still cannot be discharged externally; 2. The viscosity of sodium sulfate is relatively high, and it is extremely easy to block pipelines, causing equipment failures and unable to operate normally; 3. The market value of the prepared sodium sulfate is relatively low, and it cannot bring considerable economic benefits to the enterprise; Using CO 2 Absorption technology is to neutralize and dilute the waste alkali solution through CO 2 to convert sodium hydroxide in the waste alkali solution into sodium salts, and then sodium carbonate / sodium bicarbonate is obtained after filtration; then lignite or red mud is used to adsorb the organic matter in the remaining waste liquid to reduce the COD of the waste liquid; there are the following problems with the above technology: Sodium hydroxide cannot be completely converted into sodium salts by CO 2 and the organic matter cannot be completely adsorbed, its treatment efficiency is relatively low, and at the same time the market value of the obtained sodium carbonate and sodium bicarbonate sodium salts is relatively low, and it cannot bring considerable economic benefits to the enterprise. Summary of the Invention:

[0009] The first object of the present invention is to provide a treatment system for waste alkali liquid generated by extracting trioxymethylene with a simple connection relationship structure and low equipment investment cost.

[0010] The second object of the present invention is to provide a treatment method for waste alkali liquid generated by extracting trioxymethylene that realizes effective treatment of the waste alkali liquid and realizes the recovery of sodium hydroxide.

[0011] The technical solution of the present invention discloses a treatment system for waste alkali liquid generated by extracting trioxymethylene, which includes a waste alkali liquid pipeline, an air pipeline, a nitrogen pipeline, a heating reaction kettle, an alkali liquid cooler and a solid storage device; the liquid outlet of the waste alkali liquid pipeline is communicated with the liquid inlet of the heating reaction kettle; the air outlets of the air pipeline and the nitrogen pipeline are both communicated with the air inlet of the heating reaction kettle; the liquid outlet of the heating reaction kettle is communicated with the liquid inlet of the alkali liquid cooler; the discharge port of the alkali liquid cooler is communicated with the feed port of the solid storage device.

[0012] Furthermore, it also includes a water pipeline, a mixing reaction kettle, a reagent storage tank, a filter and an alkali liquid storage device; the discharge port of the solid storage device is communicated with the feed port of the mixing reaction kettle; the water outlet of the water pipeline is communicated with the liquid inlet of the mixing reaction kettle; the discharge port of the reagent storage tank is communicated with the feed port of the mixing reaction kettle; the liquid outlet of the mixing reaction kettle is communicated with the liquid inlet of the filter; the liquid outlet of the filter is communicated with the liquid inlet of the alkali liquid storage device.

[0013] Further, it further includes a calciner, a slag discharge port of the filter is communicated with a feed port of the calciner, and a discharge port of the calciner is communicated with a feed port of a calcium oxide storage tank.

[0014] Further, the medicament in the medicament storage tank is calcium oxide or calcium hydroxide.

[0015] Further, a packing layer is arranged in the heating reactor.

[0016] Further, the packing of the packing layer includes multi-sided hollow balls, ladder rings, Pall rings, etc.

[0017] Further, it further includes a condenser and a combustion furnace; an air outlet of the heating reactor is respectively communicated with an air inlet of the condenser and a fuel gas inlet of the combustion furnace; an air outlet of the condenser is communicated with the fuel gas inlet of the combustion furnace; a water outlet of the condenser is communicated with a water inlet of a water pipeline.

[0018] Another aspect of the present invention also discloses a method for treating waste alkali liquor generated by extracting trioxane, which includes the following steps:

[0019] (1) Heating and oxidation: adding the waste alkali liquor into a heating reactor, introducing air, the amount of air introduced per liter of the waste alkali liquor is 0.1 - 10 L / min, performing heating and oxidation, the oxidation temperature is 90 - 180 °C, and the oxidation time is 30 - 120 min, to obtain dehydrated solid and primary gas;

[0020] (2) Heating and decomposition: continuously heating and raising the temperature of the heating reactor in step 1, when the temperature reaches 250 °C, stop introducing air into the heating reactor, start introducing nitrogen, perform heating and decomposition, the decomposition temperature is 253 - 600 °C, and the decomposition time is 30 - 120 min, to obtain a mixed molten liquid of NaOH and NaCO 3 and secondary gas; the chemical reaction equation occurring is:

[0021] 2HCOONa = Na 2 C 2 O 4 +H 2 ;

[0022] 7Na 2 C 2 O 4 = 7Na 2 CO 3 +CO + 3CO 2 + 3C;

[0023] (3) Cooling: sending the mixed molten liquid in step 2 to an alkali liquor cooler to cool it to room temperature to form a solid mixture.

[0024] Further, the primary gas in Step 1 is a mixture of water vapor, organic vapor, and carbon dioxide; the primary gas is sent to a condenser for condensation, and the non-condensable gas is sent to a combustion furnace as fuel gas for combustion and finally discharged.

[0025] Further, the solid mixture in Step 3 and the liquid water condensed by the condenser are sent to a mixing reactor to be mixed and configured into a saturated sodium carbonate solution; then a medicament is added, and the mass ratio of the medicament to sodium carbonate in the saturated sodium carbonate solution is 1-1.5:2, and a reaction is carried out for 1-3 h to obtain a mixed solution of calcium carbonate, sodium hydroxide, and calcium hydroxide; the mixed solution is sent to a filter for filtration, and a sodium hydroxide solution is obtained and stored in a lye storage device.

[0026] Further, the medicament is calcium oxide and / or calcium hydroxide.

[0027] Further, the calcium carbonate and calcium hydroxide precipitates filtered out by the filter are sent to a calcination furnace for calcination to obtain calcium oxide.

[0028] Further, the secondary gas in Step 2 is a mixture of hydrogen, carbon monoxide, carbon dioxide, carbon, and nitrogen; the secondary gas is directly sent to a combustion furnace as fuel gas for combustion and finally discharged.

[0029] Advantages of the present invention:

[0030] 1. The system connection relationship of the present invention is simple and easy to implement. Through the heating reactor, the oxidation, decomposition, and elimination of organic matter and sodium formate in the waste lye are effectively realized, and the maximum recovery of sodium hydroxide with high market value is achieved, realizing the zero-emission treatment of the waste lye, protecting the environment, reducing the equipment investment cost, and improving the economic benefits of the enterprise at the same time;

[0031] 2. The method in the present invention oxidizes the organic matter into carbon dioxide and water through heating oxidation, and then the water and part of the organic matter in the waste lye form steam and are discharged at high temperature, and form water and non-condensable gas under the condensation of the condenser. The non-condensable gas is sent to the combustion furnace as fuel gas and forms harmless gas after combustion and is discharged, realizing the effective treatment of the organic matter in the high-alkali waste liquid;

[0032] 3. The method in the present invention decomposes sodium formate through heating decomposition to form carbon monoxide, hydrogen, carbon dioxide, carbon, and sodium carbonate. Among them, carbon monoxide, hydrogen, carbon, and carbon dioxide are sent to the combustion furnace as fuel gas for combustion and form pollution-free gas for discharge, realizing the decomposition and elimination of sodium formate in the waste liquid after heating oxidation;

[0033] 4. In the method of the present invention, by adding calcium oxide and calcium hydroxide, sodium carbonate reacts to generate sodium hydroxide and calcium carbonate. The sodium hydroxide generated by the reaction and the sodium hydroxide in the original waste alkali solution are finally recovered, realizing the effective recovery of sodium hydroxide. It can be directly sold or used to prepare an extractant for extracting trioxymethylene, reducing the cost of the enterprise and increasing the economic benefits of the enterprise.

[0034] 5. The calcium carbonate and excessive calcium hydroxide generated by the method of the present invention are finally calcined in a calciner to form calcium oxide, which is added as a raw material for reacting with sodium carbonate, realizing the recycling of calcium oxide and reducing the treatment cost of the waste alkali solution. BRIEF DESCRIPTION OF THE DRAWINGS:

[0035] Figure 1 It is a schematic diagram of the overall structure of the system according to Embodiment 1 of the present invention.

[0036] Figure 2 It is a gas chromatogram of the pyrolysis of the waste alkali solution under a nitrogen atmosphere.

[0037] Figure 3 It is a gas chromatogram of the pyrolysis of the waste alkali solution under an air atmosphere.

[0038] Waste alkali solution pipeline 1, air pipeline 2, nitrogen pipeline 3, heating reaction kettle 4, packing layer 41, alkali solution cooler 5, solid storage device 6, water pipeline 7, mixing reaction kettle 8, reagent storage tank 9, filter 10, alkali solution storage device 11, calciner 12, condenser 13, combustion furnace 14, calcium oxide storage tank 15. DETAILED DESCRIPTION OF THE EMBODIMENTS:

[0039] The present invention will be further described in detail below with reference to the accompanying drawings through embodiments.

[0040] Embodiment 1: As Figure 1 shown, a treatment system for waste alkali solution generated by extracting trioxymethylene includes a waste alkali solution pipeline 1, an air pipeline 2, a nitrogen pipeline 3, a heating reaction kettle 4, an alkali solution cooler 5, a solid storage device 6, a water pipeline 7, a mixing reaction kettle 8, a reagent storage tank 9, a filter 10, an alkali solution storage device 11, a calciner 12, a condenser 13, and a combustion furnace 14. The liquid outlet of the waste alkali solution pipeline 1 is communicated with the liquid inlet of the heating reaction kettle 4. The gas outlets of the air pipeline 2 and the nitrogen pipeline 3 are both communicated with the gas inlet of the heating reaction kettle 4. The gas outlet of the heating reaction kettle 4 is respectively communicated with the gas inlet of the condenser 13 and the fuel gas inlet of the combustion furnace 14. The gas outlet of the condenser 13 is communicated with the fuel gas inlet of the combustion furnace 14. The water outlet of the condenser 13 is communicated with the water inlet of the water pipeline 7.

[0041] The liquid outlet of the heating reactor 4 is communicated with the liquid inlet of the alkali liquor cooler 5; the discharge outlet of the alkali liquor cooler 5 is communicated with the feed inlet of the solid storage device 6; the discharge outlet of the solid storage device 6 is communicated with the feed inlet of the mixing reactor 8; the water outlet of the water pipeline 7 is communicated with the liquid inlet of the mixing reactor 8; the discharge outlet of the chemical agent storage tank 9 is communicated with the feed inlet of the mixing reactor 8; the liquid outlet of the mixing reactor 8 is communicated with the liquid inlet of the filter 10; the liquid outlet of the filter 10 is communicated with the liquid inlet of the alkali liquor storage device 11; the slag discharge port of the filter 10 is communicated with the feed inlet of the calciner 12, and the discharge outlet of the calciner 12 is communicated with the feed inlet of the calcium oxide storage tank 15.

[0042] The chemical agent in the chemical agent storage tank 9 is calcium oxide and / or calcium hydroxide; a packing layer 41 is arranged in the heating reactor 4 for dispersing air so that the air is evenly dispersed and can fully react with the organic matter; the packing of the packing layer 41 includes Pall rings.

[0043] The system connection relationship of the present invention is simple and easy to implement. Through the heating reactor 4, the oxidation, decomposition and elimination of organic matter and sodium formate in the waste alkali liquor are effectively realized, and the maximum recovery of sodium hydroxide with high market value is achieved. The zero-discharge treatment of the waste alkali liquor is realized, the environment is protected, the equipment investment cost is reduced, and the economic benefit of the enterprise is improved at the same time.

[0044] Example 2: A method for treating waste alkali liquor by using the system of Example 1, which includes the following steps:

[0045] (1) Heating and oxidation: Add the waste alkali liquor into the heating reactor 4, introduce air, the air intake per liter of waste alkali liquor is 0.1 L / min, carry out heating and oxidation, the oxidation temperature is 90 °C, and the oxidation time is 120 min to obtain dehydrated solid and primary gas; the primary gas is a mixture of water vapor, organic vapor and carbon dioxide; send the primary gas to the condenser 13 for condensation, and send the non-condensable gas to the combustion furnace 14 for combustion and finally discharge it; oxidize the organic matter into carbon dioxide and water, then the water and part of the organic matter in the waste alkali liquor form steam and are discharged at high temperature, and form water and non-condensable gas under the condensation of the condenser 13. The non-condensable gas is sent to the combustion furnace 14 as a fuel gas and forms harmless gas after combustion and is discharged, realizing the effective treatment of the organic matter.

[0046] (2) Heating and decomposition: Continuously heat up the heating reactor 4 in step 1. When the temperature reaches 250 °C, stop introducing air into the heating reactor 4 and start introducing nitrogen for heating and decomposition. The decomposition temperature is 253 °C and the decomposition time is 120 min to obtain a mixed molten liquid of NaOH and NaCO 3 with the NaOH concentration content in the mixed molten liquid > 60%; NaCO 3The concentration is 30.73%; the COD is 2750; the reaction equation is as follows:

[0047] 2HCOONa = Na 2 C 2 O 4 +H 2 ;

[0048] 7Na 2 C 2 O 4 = 7Na 2 CO 3 +CO + 3CO 2 + 3C;

[0049] The secondary gas is a mixture of hydrogen, carbon monoxide, carbon dioxide, carbon and nitrogen; the secondary gas is directly sent to the combustion furnace 14 as fuel gas for combustion and finally discharged; formic acid sodium is decomposed to form carbon monoxide, hydrogen, carbon dioxide, carbon and sodium carbonate, among which carbon monoxide, hydrogen, carbon and carbon dioxide are sent to the combustion furnace 14 as fuel gas for combustion to form pollution-free gas for discharge, realizing the decomposition and elimination of formic acid sodium in the waste liquid after heating and oxidation.

[0050] (3) Cooling: Send the mixed molten liquid in step 2 to the alkali liquid cooler 5 to be cooled to room temperature to form a solid mixture, which can be directly sold or used to prepare an extractant for extracting trioxymethylene.

[0051] Send the solid mixture and the liquid water condensed by the condenser 13 to the mixing reaction kettle 8 to be mixed and configured into a saturated sodium carbonate solution; then add medicaments, the medicaments are calcium oxide and / or calcium hydroxide, and the mass ratio of the medicaments to sodium carbonate in the saturated sodium carbonate solution is 1:2, react for 1 h to obtain a mixed solution of calcium carbonate, sodium hydroxide and calcium hydroxide; send the mixed solution to the filter 10 for filtration to obtain a sodium hydroxide solution and store it in the alkali liquid storage device 11, and the recovery rate of sodium hydroxide > 85%. By adding calcium oxide and calcium hydroxide, sodium carbonate reacts to generate sodium hydroxide and calcium carbonate, and the sodium hydroxide generated by the reaction and the sodium hydroxide in the original waste alkali liquid are finally recovered, realizing the effective recovery of sodium hydroxide, which can be directly sold or used to prepare an extractant for extracting trioxymethylene, reducing the cost of the enterprise and increasing the economic benefits of the enterprise; the calcium carbonate and calcium hydroxide precipitates filtered out by the filter 10 are sent to the calcination furnace 12 for calcination to obtain calcium oxide, and the calcium oxide is added as a raw material for reacting with sodium carbonate, realizing the recycling of calcium oxide and reducing the treatment cost of waste alkali liquid.

[0052] Example 3: A method for treating waste alkali liquid using the system of Example 1, which includes the following steps:

[0053] (1) Heating oxidation: Add the waste alkali liquor into the heating reactor 4, introduce air, with an air flow rate of 10 L / min per liter of waste alkali liquor, conduct heating oxidation at an oxidation temperature of 180 °C for 30 min to obtain dehydrated solids and primary gas; the primary gas is a mixture of water vapor, organic vapor, and carbon dioxide; send the primary gas to the condenser 13 for condensation, and send the non-condensable gas as fuel gas to the combustion furnace 14 for combustion, and finally discharge it; oxidize the organic matter into carbon dioxide and water, then at high temperature, the water in the waste alkali liquor and part of the organic matter form steam and are discharged, and form water and non-condensable gas under the condensation of the condenser 13, and the non-condensable gas is sent to the combustion furnace 14 as fuel gas, and after combustion, harmless gas is discharged, realizing the effective treatment of the organic matter.

[0054] (2) Heating decomposition: Continuously heat up the heating reactor 4 in step 1. When the temperature reaches 250 °C, stop introducing air into the heating reactor 4 and start introducing nitrogen for heating decomposition at a decomposition temperature of 600 °C for 120 min to obtain a mixed molten liquid of NaOH and NaCO 3 with the NaOH concentration in the mixed molten liquid being > 60%; the NaCO 3 concentration is 36%; the COD is 175; the reaction equation that occurs is:

[0055] 2HCOONa = Na 2 C 2 O 4 +H 2 ;

[0056] 7Na 2 C 2 O 4 = 7Na 2 CO 3 +CO + 3CO 2 + 3C;

[0057] The secondary gas is a mixture of hydrogen, carbon monoxide, carbon dioxide, carbon, and nitrogen; directly send the secondary gas as fuel gas to the combustion furnace 14 for combustion, and finally discharge it; decompose sodium formate to form carbon monoxide, hydrogen, carbon dioxide, carbon, and sodium carbonate, among which carbon monoxide, hydrogen, carbon, and carbon dioxide are sent to the combustion furnace 14 as fuel gas for combustion, and form pollution-free gas for discharge, realizing the decomposition and elimination of sodium formate in the waste liquid after heating oxidation.

[0058] (3) Cooling: Send the mixed molten liquid in step 2 to the alkali liquor cooler 5 to cool it to room temperature to form a solid mixture.

[0059] The solid mixture and the liquid water condensed by the condenser 13 are sent to the mixing reactor 8 to be mixed and configured into a saturated sodium carbonate solution; then a medicament is added, and the medicament is calcium oxide and / or calcium hydroxide. The mass ratio of the medicament to sodium carbonate in the saturated sodium carbonate solution is 1.5:2. After reacting for 3 hours, a mixed solution of calcium carbonate, sodium hydroxide and calcium hydroxide is obtained; the mixed solution is sent to the filter 10 for filtration, and the sodium hydroxide solution is stored in the alkali solution storage device 11, and the NaOH recovery rate is 98%; by adding calcium oxide and calcium hydroxide, sodium carbonate reacts to generate sodium hydroxide and calcium carbonate, and the sodium hydroxide generated by the reaction and the sodium hydroxide in the original waste alkali solution are finally recovered, realizing the effective recovery of sodium hydroxide, which can be directly sold or used to prepare an extractant for extracting trioxymethylene, reducing the cost of the enterprise and increasing the economic benefits of the enterprise; the calcium carbonate and calcium hydroxide precipitates filtered out by the filter 10 are sent to the calciner 12 for calcination to obtain calcium oxide, and the calcium oxide is added as a raw material for reacting with sodium carbonate, realizing the recycling of calcium oxide and reducing the treatment cost of waste alkali solution.

[0060] Example 4: A method for treating waste alkali solution using the system of Example 1, which includes the following steps:

[0061] (1) Heating oxidation: Add the waste alkali solution to the heating reactor 4, introduce air, and the amount of air introduced per liter of waste alkali solution is 5 L / min. Carry out heating oxidation, the oxidation temperature is 105 °C, and the oxidation time is 75 min to obtain dehydrated solid and primary gas; the primary gas is a mixed gas of water vapor, organic vapor and carbon dioxide; send the primary gas to the condenser 13 for condensation, and the non-condensable gas is sent to the combustion furnace 14 as fuel gas for combustion and finally discharged; oxidize the organic matter into carbon dioxide and water, and then the water and part of the organic matter in the waste alkali solution form steam and are discharged at high temperature, and form water and non-condensable gas under the condensation of the condenser 13. The non-condensable gas is sent to the combustion furnace 14 as fuel, and harmless gas is formed after combustion and discharged, realizing the effective treatment of organic matter.

[0062] (2) Heating decomposition: Continuously heat up the heating reactor 4 in step 1. When the temperature reaches 250 °C, stop introducing air into the heating reactor 4 and start introducing nitrogen for heating decomposition. The decomposition temperature is 427 °C and the decomposition time is 75 min to obtain a mixed molten liquid of NaOH and NaCO 3 and secondary gas, where the NaOH concentration in the mixed molten liquid is > 60%; the NaCO 3 concentration is 31%; the COD is 1568; the reaction equation that occurs is:

[0063] 2HCOONa = Na 2 C 2 O 4 +H 2 ;

[0064] 7Na 2 C 2 O 4 = 7Na 2 CO 3 + CO + 3CO 2 + 3C;

[0065] The secondary gas is a mixture of hydrogen, carbon monoxide, carbon dioxide, carbon and nitrogen; the secondary gas is directly sent to the combustion furnace 14 as fuel gas for combustion and finally discharged; formic acid sodium is decomposed to form carbon monoxide, hydrogen, carbon dioxide, carbon and sodium carbonate, wherein carbon monoxide, hydrogen, carbon and carbon dioxide are sent to the combustion furnace 14 as fuel gas for combustion to form pollution-free gas for discharge, realizing the decomposition and elimination of formic acid sodium in the waste liquid after heating and oxidation.

[0066] (3) Cooling: Send the mixed molten liquid in step 2 to the alkali liquid cooler 5 and cool it to room temperature to form a solid mixture.

[0067] Send the solid mixture and the liquid water condensed by the condenser 13 to the mixing reactor 8 to be mixed and configured into a saturated sodium carbonate solution; then add medicaments, the medicaments are calcium oxide and / or calcium hydroxide, and the mass ratio of the medicaments to sodium carbonate in the saturated sodium carbonate solution is 1.3:2, react for 2 h to obtain a mixed solution of calcium carbonate, sodium hydroxide and calcium hydroxide; send the mixed solution to the filter 10 for filtration to obtain a sodium hydroxide solution and store it in the alkali liquid storage device 11, and the NaOH recovery rate is 88%; by adding calcium oxide and calcium hydroxide, sodium carbonate reacts to generate sodium hydroxide and calcium carbonate, and the sodium hydroxide generated by the reaction and the sodium hydroxide in the original waste alkali liquid are finally recovered, realizing the effective recovery of sodium hydroxide, which can be directly sold or used to prepare an extractant for extracting trioxymethylene, reducing the cost of the enterprise and increasing the economic benefits of the enterprise; the calcium carbonate and calcium hydroxide precipitates filtered out by the filter 10 are sent to the calcination furnace 12 for calcination to obtain calcium oxide, and the calcium oxide is added as a raw material for reacting with sodium carbonate, realizing the recycling of calcium oxide and reducing the treatment cost of the waste alkali liquid.

[0068] Experiment 1:

[0069] Gas phase analysis was carried out on the waste alkali liquor after heating decomposition treatment by gas chromatography. 20 ml of waste alkali liquor was placed in two corundum tubes respectively, and then the two corundum tubes were placed in a heating reaction kettle for heating. The heating rate of the heating reaction kettle was set at 2 °C / min for programmed heating, and heat preservation was carried out for 30 min at 254 °C, 320 °C and 450 °C respectively; When heating the first corundum tube, nitrogen with an air flow rate of 0.1 L / min was introduced, and when heating the second corundum tube, air with an air flow rate of 0.1 L / min was introduced; Gas chromatography analysis was carried out on the gas phase after heating treatment under different atmosphere conditions, and the detailed results are as Figure 2 and Figure 3 .

[0070] As Figure 2 shown, under nitrogen atmosphere, with the increase of pyrolysis temperature, H 2 and CO were slowly generated at 100-250 °C; Near 250 °C, the gas generation rate increased significantly; Around 270 °C, the generation amount of H 2 tended to be stable, while the generation amount of CO continued to increase until the end of the reaction.

[0071] Under nitrogen atmosphere, the waste alkali liquor mainly undergoes decomposition reaction, and its main reaction equations are as follows:

[0072] 2HCOONa = Na 2 C 2 O 4 + H 2 ;

[0073] 7Na 2 C 2 O 4 = 7Na 2 CO 3 + CO + 3CO 2 + 3C;

[0074] HCOONa starts to melt at 253 °C, and as the temperature further rises to about 330 °C, decomposition reaction begins to occur, generating sodium carbonate, hydrogen, carbon monoxide and a small amount of oxalic acid; When the temperature further rises to 400 °C, HCOONa undergoes a violent reaction, releasing a large amount of heat and H 2 , generating Na 2 C 2 O 4 ; When the temperature is higher than 440 °C, sodium oxalate undergoes deep decomposition to generate sodium carbonate; Therefore, combined with Figure 2 gas chromatography analysis, at 253 °C, the decomposition reaction of formate begins, and H 2and CO; during the stage of 253 - 280 °C, the decomposition reaction of sodium formate mainly occurs, and after 280 °C, the decomposition reaction of sodium formate tends to be stable as the reaction temperature increases; between 254 and 500 °C, sodium oxalate continuously undergoes decomposition reactions to release CO.

[0075] As Figure 3 shown, in an air atmosphere, during the period of 200 - 320 °C, a small amount of H 2 is generated, and then a large amount of H 2 is produced. After 350 °C, the production amount tends to be stable; in Figure 3 , the production amount of CO shows a step - by - step increase at 250 °C, 320 °C, 420 °C, and 450 °C, and then tends to be stable. By comparison Figure 2 it can be seen that the production amounts of H 2 and CO have both increased significantly. Due to the introduction of air, some organic substances in the waste alkali liquor undergo oxidation reactions. The main reaction equations are as follows:

[0076] 2CH 3 R + 3O 2 = 2HCOOR + 2H 2 O;

[0077] HCOOR + NaOH = HCOONa + ROH;

[0078] 2HCOONa = Na 2 C 2 O 4 + H 2 ;

[0079] 7Na 2 C 2 O 4 = 7Na 2 CO 3 + CO + 3CO 2 + 3C;

[0080] Combining the above formulas with gas chromatography analysis, due to the oxidation of oxygen, the organic substance CH Figure 3 R in the waste alkali liquor is oxidized to HCOOR, and HCOOR reacts with NaOH to form sodium formate. Sodium formate decomposes into sodium oxalate and hydrogen at high temperatures, and sodium oxalate decomposes into sodium carbonate, carbon monoxide, carbon dioxide, and carbon at high temperatures. Therefore, the production amounts of H 3 and CO have both increased. However, the reaction of HCOOR and NaOH reduces the content of sodium hydroxide in the molten solution, resulting in an increase in the dosage of the agent for producing sodium hydroxide by reacting with sodium carbonate in the later stage, increasing the recovery production cost of sodium hydroxide; at the same time, there is a threat of oxidation explosion reactions between oxygen in the air and H 2 and CO at high temperatures. 2

[0081] The above are the preferred embodiments of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A treatment system for waste alkali liquor generated by extracting trioxane, characterized in that, it includes a waste alkali liquor pipeline, an air pipeline, a nitrogen pipeline, a heating reactor, an alkali liquor cooler, a solid storage device, a condenser, a combustion furnace, a water pipeline, a mixing reactor, a chemical agent storage tank, a filter and an alkali liquor storage device; The liquid outlet of the waste alkali liquor pipeline is communicated with the liquid inlet of the heating reactor; the gas outlets of the air pipeline and the nitrogen pipeline are both communicated with the gas inlet of the heating reactor; The liquid outlet of the heating reactor is communicated with the liquid inlet of the alkali liquor cooler; the discharge port of the alkali liquor cooler is communicated with the feed port of the solid storage device; The gas outlet of the heating reactor is respectively communicated with the gas inlet of the condenser and the fuel gas inlet of the combustion furnace; the gas outlet of the condenser is communicated with the fuel gas inlet of the combustion furnace; the water outlet of the condenser is communicated with the water inlet of the water pipeline; The discharge port of the solid storage device is communicated with the feed port of the mixing reactor; the water outlet of the water pipeline is communicated with the liquid inlet of the mixing reactor; the discharge port of the chemical agent storage tank is communicated with the feed port of the mixing reactor; The liquid outlet of the mixing reactor is communicated with the liquid inlet of the filter; the liquid outlet of the filter is communicated with the liquid inlet of the alkali liquor storage device; The chemical agent in the chemical agent storage tank is calcium oxide or calcium hydroxide; The oxidation, decomposition and elimination of organic substances and sodium formate in the waste alkali liquor are realized through the heating reactor, so that sodium formate decomposes to form carbon monoxide, hydrogen, carbon dioxide, carbon and sodium carbonate, and carbon monoxide, hydrogen, carbon and carbon dioxide are sent to the combustion furnace as fuel gas for combustion; A packing layer is arranged in the heating reactor for dispersing air so that the air is evenly dispersed and can fully react with the organic substances.

2. The treatment system for waste alkali liquor generated by extracting trioxane according to claim 1, characterized in that, it further includes a calcining furnace, the slag discharge port of the filter is communicated with the feed port of the calcining furnace, and the discharge port of the calcining furnace is communicated with the feed port of the calcium oxide storage tank.

3. The treatment system for waste alkali liquor generated by extracting trioxane according to claim 1, characterized in that, The packing of the packing layer includes multi-faceted hollow balls, cascade rings and Pall rings.

4. A treatment method for waste alkali liquor generated by extracting trioxane, characterized in that, it includes the following steps: (1) Heating oxidation: adding the waste alkali liquor into the heating reactor, introducing air, the amount of air introduced per liter of the waste alkali liquor is 0.1 - 10 L / min, carrying out heating oxidation, the oxidation temperature is 90 - 180 °C, and the oxidation time is 30 - 120 min to obtain dehydrated solids and primary gas; the primary gas is a mixture of water vapor, organic vapor and carbon dioxide; sending the primary gas to the condenser for condensation, and sending the non-condensable gas as fuel gas to the combustion furnace for combustion and finally discharging it; (2) Thermal decomposition: Continuously heat up the heating reactor in step (1). When the temperature reaches 250 °C, stop introducing air into the heating reactor and start introducing nitrogen for thermal decomposition. The decomposition temperature is 253 - 600 °C, and the decomposition time is 30 - 120 min to obtain a mixed molten liquid of NaOH and NaCO 3 and secondary gas; the secondary gas is a mixture of hydrogen, carbon monoxide, carbon dioxide, carbon, and nitrogen; directly send the secondary gas as fuel gas to the combustion furnace for combustion and finally discharge it; (3) Cooling: sending the mixed molten liquid in step (2) to the alkali liquor cooler to cool it to room temperature to form a solid mixture.

5. A treatment method for the waste alkali liquor generated by extracting trioxymethylene according to claim 4, characterized in that, the solid mixture in step (3) and the liquid water condensed by the condenser are sent to a mixing reaction kettle to be mixed and configured into a saturated sodium carbonate solution; then a medicament is added, and the mass ratio of the medicament to sodium carbonate in the saturated sodium carbonate solution is 1-1.5:2, and the reaction is carried out for 1-3 h to obtain a mixed solution of calcium carbonate, sodium hydroxide and calcium hydroxide; the mixed solution is sent to a filter for filtration, and the obtained sodium hydroxide solution is stored in an alkali liquor storage device.

6. A treatment method for the waste alkali liquor generated by extracting trioxymethylene according to claim 5, characterized in that, the medicament is calcium oxide and / or calcium hydroxide.

7. A treatment method for the waste alkali liquor generated by extracting trioxymethylene according to claim 5, characterized in that, the calcium carbonate and calcium hydroxide precipitates filtered out by the filter are sent to a calcination furnace for calcination to obtain calcium oxide.

Images