A method for producing sodium bicarbonate and ammonium chloride from industrial waste salt

Abstract

The present invention belongs to the technical field of utilization of hazardous wastes in environmental protection treatment, and particularly relates to a method for producing sodium bicarbonate and ammonium chloride from industrial waste salts. The present invention provides a method for resourcefully producing sodium bicarbonate and ammonium chloride from industrial waste salts. The regenerated sodium chloride is prepared by using the ash water obtained from the gasification and detoxification treatment of industrial waste salts. Then, taking the regenerated sodium chloride and ammonium bicarbonate as raw materials, and the ash water generated in the detoxification process as supplementary water, sodium bicarbonate (sodium bicarbonate) and ammonium chloride are generated through a double decomposition reaction. The present invention utilizes the high-temperature gasification and detoxification process, which not only solves the problem of resource utilization of industrial waste salts, but also reduces the limitation of the double decomposition reaction on the raw material sodium chloride, no longer being limited to industrial sodium chloride as the raw material. Moreover, the process flow is optimized, enabling the utilization rate of industrial waste salts to reach 100%, and the yield of sodium bicarbonate to reach 88.35%.

Description

Technical Field

[0001] The present invention belongs to the technical field of utilization of hazardous wastes in environmental protection treatment, and particularly relates to a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt. Background Art

[0002] With the continuous development of the chemical industry and the water treatment industry, the generation amount of industrial slag salt is increasing day by day, and the environmental protection supervision is gradually strengthened. How to safely and effectively dispose of industrial slag salt has become an important factor restricting the development of chemical enterprises. Industrial slag salt mainly comes from industries such as pesticides, pharmaceuticals, and fine chemicals, and contains sodium chloride, sodium sulfate, and their mixed salts, as well as organic substances, insoluble substances, and a small amount of heavy metals, etc., and belongs to hazardous waste.

[0003] Chinese Patent CN1962444A discloses a new process for producing soda ash from industrial salt slag, which includes the following steps: (1) washing the industrial salt slag with saturated brine; (2) preparing it into a saturated solution, adding solid ammonium bicarbonate in an amount of 1:1 to 1:1.05 molar ratio, and carrying out a carbonization reaction in a reaction device to obtain a solid-liquid mixture containing sodium bicarbonate and ammonium chloride; (3) separating sodium bicarbonate from the reaction mother liquor, (4) washing to remove chloride ions (sodium chloride and ammonium chloride), and calcining to obtain the finished soda ash product. Although this method can obtain the intermediate product sodium bicarbonate using industrial salt slag as the preparation raw material, the yield of sodium bicarbonate is low, and the yield of ammonium chloride is unknown. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt. The method provided by the present invention conducts gasification detoxification treatment on industrial waste salt and then uses it. At the same time, a salting-out agent is added to the reaction system of saturated brine and ammonium bicarbonate, which improves the yield of sodium bicarbonate.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt, including the following steps:

[0007] Evaporating and crystallizing the ash water to obtain regenerated sodium chloride, wherein the ash water is obtained by gasification detoxification of industrial waste salt;

[0008] Mixing the regenerated sodium chloride and the ash water to obtain saturated brine;

[0009] After mixing the saturated brine and ammonium bicarbonate, adding a salting-out agent for separation to obtain the sodium bicarbonate and mother liquor I;

[0010] Mixing the mother liquor I and hydrochloric acid, and then successively carrying out concentration and solid-liquid separation to obtain mother liquor II;

[0011] Crystallize and separate the mother liquor II in sequence to obtain the ammonium chloride.

[0012] Preferably, the molar ratio of ammonium bicarbonate to sodium chloride in the saturated brine is 1:1.04 - 1.05.

[0013] Preferably, the molar ratio of the salting - out agent to the regenerated sodium chloride is 1 - 1.1:1.

[0014] Preferably, the salting - out agent is an alcohol solvent.

[0015] Preferably, the concentration is to concentrate the volume of the mixed solution obtained by mixing the mother liquor I and hydrochloric acid to 42 - 44% of the volume of the mother liquor I.

[0016] Preferably, the gasification detoxification is carried out on the industrial waste salt in the form of a coal - salt mixture, and the coal - salt mixture is obtained by mixing the industrial waste salt and coal.

[0017] Preferably, the viscosity of the coal - salt mixture is 800 - 1200 mPa·s, and the calorific value is 15000 - 18000 J / g.

[0018] Preferably, the temperature of the gasification detoxification is 1200 - 1600 °C, and the time is 2 - 10 s.

[0019] Preferably, the industrial waste salt is a salt composed of sodium ions discarded in industrial production.

[0020] Preferably, the salt composed of sodium ions includes one or more of sodium chloride, sodium sulfate, sodium acetate, sodium sulfide, sodium phosphate, sodium carbonate, sodium bicarbonate, and sodium thiosulfate.

[0021] The present invention provides a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt, comprising the following steps:

[0022] Evaporate and crystallize the ash water to obtain regenerated sodium chloride, and the ash water is obtained by gasification detoxification of industrial waste salt;

[0023] Mix the regenerated sodium chloride and the ash water to obtain saturated brine;

[0024] After mixing the saturated brine with ammonium bicarbonate, add a salting - out agent for separation to obtain the sodium bicarbonate and mother liquor I;

[0025] Mix the mother liquor I with hydrochloric acid and then carry out concentration and solid - liquid separation in sequence to obtain mother liquor II;

[0026] Crystallize and separate the mother liquor II in sequence to obtain the ammonium chloride.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt. The industrial waste salt is subjected to gasification detoxification treatment. During the gasification detoxification process, the organic matter in the industrial waste salt decomposes into syngas - raw coal gas (including CO, CO2, H2, N2 and H2S), heavy metals are fixed in the vitreous coarse slag, fly ash insoluble impurities are separated and collected, and the dissolved inorganic salts enter the ash water. The ash water is evaporated and crystallized to form regenerated sodium chloride, and the ash water is also used as supplementary water for the double decomposition reaction. The gasification detoxification effect of the present invention is more thorough, and there are very few impurities and impurity ions in the ash water. At the same time, a salting - out agent is added to the reaction system of saturated brine and ammonium bicarbonate, which can reduce the solubility of salts in the system, thereby promoting the precipitation of sodium bicarbonate and significantly improving the yield of sodium bicarbonate. The yield of sodium bicarbonate reaches 88.35%.

[0029] Furthermore, the present invention uses coal to couple with industrial waste salt for gasification detoxification (1200 - 1600 °C) treatment and then produces sodium bicarbonate and ammonium chloride. It is a new - type and green technology for harmless treatment and resource utilization of hazardous waste, achieving true "zero emissions" and realizing circular economy. The present invention not only solves the problem of resource utilization of industrial waste salt, but also reduces the limitation of the double decomposition reaction on the raw material sodium chloride, no longer being limited to industrial sodium chloride as the raw material. Moreover, it improves the utilization rate of industrial waste salt. The utilization rate of industrial waste salt raw materials is 100%, and no wastewater is generated during the whole production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 It is the process flow diagram of the resource treatment of industrial waste salt of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention provides a method for producing sodium bicarbonate and ammonium chloride from industrial waste salt, including the following steps:

[0033] The ash water is evaporated and crystallized to obtain regenerated sodium chloride, and the ash water is obtained by gasification detoxification of industrial waste salt;

[0034] The regenerated sodium chloride and the ash water are mixed to obtain saturated brine;

[0035] The saturated brine is mixed with ammonium bicarbonate, and then a salting - out agent is added for separation to obtain the sodium bicarbonate and mother liquor I;

[0036] Mix the mother liquor I with hydrochloric acid, and then conduct concentration and solid-liquid separation in sequence to obtain mother liquor II;

[0037] Conduct crystallization and separation on the mother liquor II in sequence to obtain the ammonium chloride.

[0038] In the present invention, without special instructions, the materials and equipment used are all commercially available products in the art.

[0039] In the present invention, the grey water is subjected to evaporation crystallization to obtain regenerated sodium chloride, and the grey water is obtained by subjecting industrial waste salt to gasification detoxification.

[0040] In the present invention, the industrial waste salt is preferably a salt composed of sodium ions discarded in industrial production, and the industrial waste salt preferably includes solid waste salt or salt-containing wastewater.

[0041] In the present invention, the salt composed of sodium ions preferably includes one or more of sodium chloride, sodium sulfate, sodium acetate, sodium sulfide, sodium phosphate, sodium carbonate, sodium bicarbonate, and sodium thiosulfate.

[0042] In the present invention, the gasification detoxification is preferably carried out by gasifying the industrial waste salt in the form of a coal-salt mixture, and the coal-salt mixture is obtained by mixing the industrial waste salt and coal. The present invention has no special requirements for the mass ratio of the industrial waste salt and coal mixture. According to the form of the waste salt, the addition amount of coal is adjusted so that the viscosity of the coal-salt mixture is preferably 800-1200 mPa·s, and the calorific value is preferably 15000-18000 J / g. The coal-salt mixture is a non-Newtonian fluid with fluidity.

[0043] In the present invention, the temperature of the gasification detoxification is preferably 1200-1600 °C, more preferably 1400 °C; the time is preferably 2-10 s, more preferably 5 s. In the specific embodiments of the present invention, the gasification detoxification is carried out in a coal gasification furnace. The coal-salt mixture is continuously sprayed into the gasification furnace by a nozzle to generate a high-temperature mixture, including molten salt, waste salt products of gaseous sodium chloride, and raw coal gas (including CO, CO2, H2, N2, and H2S); the high-temperature mixture is directly quenched with water, and the raw coal gas obtained after quenching is collected for further processing and utilization; the molten ash slag (molten salt) is quickly solidified into a vitreous state of coarse slag during the water quenching process; the waste salt products enter the aqueous phase during the water quenching process to obtain the grey water, and the gasification detoxification of the industrial waste salt is completed.

[0044] The present invention uses coal to couple with industrial waste salt for gasification detoxification treatment, and the detoxification effect is more thorough. There are very few impurities and impurity ions in the grey water, which can make the industrial waste salt be efficiently recycled. At a high temperature of 1200-1600 °C, the organic matter in the industrial waste salt decomposes into raw coal gas, heavy metals are fixed in the vitreous coarse slag, and insoluble impurities such as fly ash are separated and collected, and the dissolved inorganic salts enter the grey water.

[0045] In the present invention, the main components of the grey water are sodium chloride and water, and the chlorine content in the grey water is preferably 100 g / L.

[0046] In the present invention, part of the grey water evaporates and crystallizes to form recycled sodium chloride, and the remaining grey water serves as supplementary water for the metathesis reaction.

[0047] After obtaining the recycled sodium chloride, the present invention mixes the recycled sodium chloride and the grey water to obtain saturated brine.

[0048] The present invention has no special requirements for the mixing method and ratio of the recycled sodium chloride and the grey water, as long as saturated brine can be obtained.

[0049] After obtaining the saturated brine, the present invention mixes the saturated brine with ammonium bicarbonate, adds a salting-out agent for separation, and obtains the baking soda and mother liquor I.

[0050] In the present invention, the molar ratio of ammonium bicarbonate to sodium chloride in the saturated brine is preferably 1:1.04 - 1.05. The present invention preferably adds ammonium bicarbonate to the saturated brine in batches to make the reaction more complete. The number of batches is preferably 3 - 4 times, and the addition amount each time is preferably 25 - 35% of the total mass of ammonium bicarbonate.

[0051] In the present invention, the temperature of the mixing is preferably 30 - 35 °C, more preferably 33 °C, and the time is preferably 0.5 h. During the mixing process, ammonium bicarbonate and sodium chloride undergo a metathesis reaction to obtain a solid-liquid mixture containing sodium bicarbonate and ammonium chloride.

[0052] In the present invention, the salting-out agent is preferably an alcohol solvent, which is an alcohol solvent with a high boiling point, non-polar, non-toxic and harmless, and does not form an azeotrope with water. The alcohol solvent is preferably diethylene glycol.

[0053] In the present invention, the molar ratio of the salting-out agent to the recycled sodium chloride is preferably 1 - 1.1:1. The addition of the salting-out agent reduces the free water molecules in the solution, decreases the solubility of sodium bicarbonate in the system, and promotes the crystallization and precipitation of sodium bicarbonate. In the specific embodiments of the present invention, after adding the salting-out agent, it is preferably to continue the reaction for 0.5 h to make sodium bicarbonate continue to crystallize and precipitate.

[0054] In the present invention, the separation method is preferably centrifugal separation or filtration.

[0055] In the present invention, after separation, it preferably further includes washing and drying the obtained solid in sequence to obtain the baking soda.

[0056] In the present invention, the washing reagent is preferably pure water or saturated sodium bicarbonate solution, the washing method is preferably rinsing, and the function of washing is to remove chloride ions.

[0057] In the present invention, the drying temperature is preferably 120 - 130 °C, more preferably 125 °C, and the drying method is preferably instant air flow drying.

[0058] After obtaining mother liquor I, in the present invention, the mother liquor I is mixed with hydrochloric acid and then concentrated and solid-liquid separated in sequence to obtain mother liquor II.

[0059] In the present invention, the hydrochloric acid is preferably concentrated hydrochloric acid, the mass fraction of the concentrated hydrochloric acid is preferably 36 - 38%, the pH value of the mixed solution obtained by mixing the mother liquor I and hydrochloric acid is preferably 7 - 7.5, more preferably 7.2, and there is no bubble generation in the mixed solution. The addition of hydrochloric acid is to eliminate bicarbonate in the system.

[0060] In the present invention, the concentration method is preferably evaporation concentration, and the evaporation concentration temperature is preferably 70 - 75 °C, more preferably 72 °C.

[0061] In the present invention, the concentration is preferably to concentrate the volume of the mixed solution obtained by mixing the mother liquor I and hydrochloric acid to 42 - 44% of the volume of the mother liquor I, more preferably 43%; the volume after concentration in the present invention can increase the yield and purity of ammonium chloride; when the concentration degree is high, the purity of the obtained ammonium chloride is high, but the yield is low; when the concentration degree is low, the purity of the obtained ammonium chloride is low.

[0062] In the present invention, the solid-liquid separation method is preferably hot filtration. While obtaining mother liquor II, it is preferably to obtain mixed salts at the same time. The mixed salts are a mixture of sodium chloride and ammonium chloride, and the mixed salts are preferably recycled for preparing saturated brine for recycling.

[0063] After obtaining mother liquor II, in the present invention, the mother liquor II is crystallized and separated in sequence to obtain the ammonium chloride.

[0064] In the present invention, the crystallization is preferably cooling crystallization, and the cooling crystallization temperature is preferably 20 - 25 °C, more preferably 22 °C.

[0065] In the present invention, ammonium chloride slurry is obtained after crystallization. The ammonium chloride slurry is separated in the present invention. While obtaining the ammonium chloride, it is preferably to obtain mother liquor III at the same time. The mother liquor III contains a salting-out agent, and the mother liquor III is preferably recycled for preparing saturated brine to achieve recycling.

[0066] In the present invention, the separation method is preferably centrifugal separation or filtration.

[0067] To further illustrate the present invention, the method for producing sodium bicarbonate and ammonium chloride from industrial waste salt of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0068] Figure 1 The process flow diagram of the resource treatment of industrial waste salt in the embodiment of the present invention includes the following steps:

[0069] After the industrial waste salt is gasified and detoxified, ash water is obtained. The ash water is evaporated and crystallized to obtain regenerated sodium chloride; the detoxified ash water and regenerated sodium chloride are used to prepare saturated brine; then the saturated brine is mixed with ammonium bicarbonate for a metathesis reaction. After adding a salting-out agent, filtration is carried out to obtain solid sodium bicarbonate (sodium bicarbonate is obtained after washing and drying) and filtrate I; hydrochloric acid is added to filtrate I for neutralization, evaporation and concentration, and hot filtration is carried out to obtain filtrate II and mixed salt (circulated and used in saturated brine); filtrate II is cooled and crystallized, and filtered to obtain ammonium chloride and filtrate III (circulated and used in saturated brine).

[0070] Example 1

[0071] A process for producing sodium bicarbonate and ammonium chloride from industrial waste salt resources, using the ash water (main components are sodium chloride and water) after gasification and detoxification of industrial waste salt, regenerated sodium chloride after crystallization of ash water, and solid ammonium bicarbonate as raw materials, and the production steps are as follows:

[0072] Step 1: Mix industrial waste salt with coal to form a coal-salt mixture, and make the coal-salt mixture enter a coal gasification furnace for high-temperature (reacting at 1400 °C for 5 s) detoxification. The ash water after gasification and detoxification is evaporated and crystallized to obtain regenerated sodium chloride;

[0073] Step 2: Prepare saturated brine (sodium chloride solubility is 26.47%) by mixing regenerated sodium chloride (purity 99%) with ash water, and take 5357 kg of the prepared saturated brine;

[0074] Step 3: Add 1900 kg of ammonium bicarbonate (purity 96%, molar ratio of ammonium bicarbonate to sodium chloride is 1:1.05) to the saturated brine in three equal batches, carry out a metathesis reaction in a reaction kettle, control the reaction temperature at 33 °C, and after 0.5 hours, add 2569 kg of salting-out agent - diethylene glycol (molar ratio of regenerated sodium chloride to salting-out agent is 1:1), and react for another 0.5 hours to obtain a solid-liquid mixture containing sodium bicarbonate and ammonium chloride. After centrifugal separation, 1748 kg of solid sodium bicarbonate and mother liquor I are obtained;

[0075] Step 4: Wash the solid sodium bicarbonate with saturated sodium bicarbonate solution to remove chloride ions, and instantaneously dry it with air flow at 125 °C to obtain 1727 kg of sodium bicarbonate product (sodium bicarbonate) with a purity of 99.2%, and the yield is 88.35%;

[0076] Step 5: Concentrated hydrochloric acid is added to the mother liquor I, and the pH value is adjusted to 7.2 until no more gas is generated. Then it is heated to 72 °C for evaporation and concentration. When the volume is reduced to 43% of the volume of the mother liquor I, stop evaporation and perform hot filtration to obtain 42 kg of a mixed salt of sodium chloride and ammonium chloride and filtrate II;

[0077] Step 6: Cool filtrate II to 22 °C to obtain an ammonium chloride crystal slurry. After centrifugal separation, 988 kg of ammonium chloride product with a purity of 98.5% and a yield of 78.8% and filtrate III (containing salting-out agent) are obtained;

[0078] Step 7: The mixed salt of sodium chloride and ammonium chloride in Step 5 and filtrate III in Step 6 are recycled to Step 2 for preparing saturated brine and used cyclically.

[0079] In the process of resource utilization of industrial waste salt in the present invention, the utilization rate of industrial waste salt is 100%, and no other waste water is generated; the salting-out agent is recycled, and the single loss rate in both Example 1 and Comparative Example 1 is 2.5%.

[0080] Comparative Example 1

[0081] Referring to Example 1, the difference from Example 1 is as follows:

[0082] Step 1: The industrial waste salt is washed and refined according to saturated brine. 1800 kg of industrial waste salt is washed and refined to obtain 1493 kg of washed salt with a purity of 95%;

[0083] Step 2: 1493 kg of washed salt is mixed with water to prepare saturated brine;

[0084] Step 3: 1678 kg of solid sodium bicarbonate is obtained;

[0085] Step 4: 1658 kg of sodium bicarbonate product with a purity of 98.5% and a yield of 84.22% is obtained;

[0086] Step 6: 948 kg of ammonium chloride product with a purity of 98.5% and a yield of 75.61% is obtained.

[0087] Comparative Example 2

[0088] Referring to Example 1, the difference from Example 1 is as follows:

[0089] Step 3: No salting-out agent is added, and 1385 kg of solid sodium bicarbonate is obtained;

[0090] Step 4: 1368 kg of sodium bicarbonate product with a purity of 98.5% and a yield of 69.49% is obtained;

[0091] Step 6: 525 kg of ammonium chloride product with a purity of 98.5% and a yield of 41.87% is obtained.

[0092] Comparative Example 3

[0093] Referring to Example 1, the difference from Example 1 is as follows:

[0094] Step 3: Add 2055 kg of salting-out agent - diethylene glycol (the molar ratio of regenerated sodium chloride to salting-out agent is 1:0.8) to obtain 1661 kg of solid sodium bicarbonate;

[0095] Step 4: Obtain 1642 kg of sodium bicarbonate product with a purity of 99.2%, and the yield is 84.01%;

[0096] Step 6: Obtain 928 kg of ammonium chloride product with a purity of 98.5%, and the yield is 74.01%.

[0097] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments according to the embodiments of the present invention without creative work, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for producing sodium bicarbonate and ammonium chloride from industrial waste salt, characterized in that, The steps are as follows: Evaporate and crystallize the grey water to obtain regenerated sodium chloride. The grey water is obtained by gasification detoxification of industrial waste salt. The gasification detoxification is carried out by gasifying the industrial waste salt in the form of a coal-salt mixture. The coal-salt mixture is obtained by mixing industrial waste salt and coal. The viscosity of the coal-salt mixture is 800 - 1200 mPa·s, and the calorific value is 15000 - 18000 J / g. The process of the gasification detoxification is as follows: The gasification detoxification is carried out in a coal gasifier. The coal-salt mixture is continuously sprayed into the gasifier by a nozzle to generate a high-temperature mixture, including molten salt, waste salt products of gaseous sodium chloride, and raw coal gas. The high-temperature mixture is directly quenched with water, and the raw coal gas obtained after quenching is collected. The molten salt is quickly solidified into a vitreous state of coarse slag during the water quenching process. The waste salt products enter the aqueous phase during the water quenching process to obtain the grey water after gasification detoxification. The temperature of the gasification detoxification is 1200 - 1600 °C, and the time is 2 - 10 s. Mix the regenerated sodium chloride and the grey water to obtain saturated brine. After mixing the saturated brine with ammonium bicarbonate, add a salting-out agent for separation to obtain the baking soda and mother liquor I. The salting-out agent is diethylene glycol. During the mixing process, a double decomposition reaction occurs between ammonium bicarbonate and sodium chloride to obtain a solid-liquid mixture containing sodium bicarbonate and ammonium chloride. The molar ratio of the salting-out agent to the regenerated sodium chloride is 1 - 1.1:

1. After mixing the mother liquor I with hydrochloric acid, carry out concentration and solid-liquid separation in sequence to obtain mother liquor II. Carry out crystallization and separation on the mother liquor II in sequence to obtain the ammonium chloride.

2. The method according to claim 1, characterized in that, The molar ratio of ammonium bicarbonate to sodium chloride in the saturated brine is 1:1.04 - 1.

05.

3. The method according to claim 1, characterized in that, The concentration is to concentrate the volume of the mixed solution obtained by mixing the mother liquor I with hydrochloric acid to 42 - 44% of the volume of the mother liquor I.

4. The method according to claim 1, characterized in that, The industrial waste salt is a salt composed of sodium ions discarded in industrial production.

5. The method according to claim 4, characterized in that, The salt composed of sodium ions includes one or more of sodium chloride, sodium sulfate, sodium acetate, sodium sulfide, sodium phosphate, sodium carbonate, sodium bicarbonate, and sodium thiosulfate.

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