CN108793208B - Process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid - Google Patents
Process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid Download PDFInfo
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- CN108793208B CN108793208B CN201810781781.0A CN201810781781A CN108793208B CN 108793208 B CN108793208 B CN 108793208B CN 201810781781 A CN201810781781 A CN 201810781781A CN 108793208 B CN108793208 B CN 108793208B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/40—Magnesium sulfates
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Abstract
The invention discloses a process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid, which comprises the steps of pumping a magnesium hydroxide sodium chloride aqueous solution into a raw material pool through a raw material pump, pumping the solution into a primary centrifuge through a raw material conveying pump for centrifugation, and conveying the centrifuged clear liquid into a clear liquid tank. Hydrogen after centrifugationWashing wet magnesium oxide solid in water tank, adding water to wash tank, and washing solid to obtain Cl‑The mass fraction of the raw material is less than 3 percent, the raw material after being washed is pumped into a secondary centrifuge by a washing pump for centrifugation, and the clear liquid after centrifugation is sent to a clear liquid tank. Has the advantages that: the invention carries out waste recycling treatment on the salt mud and the waste acid, generates magnesium sulfate chemical raw materials, saves energy and reduces environmental pollution.
Description
Technical Field
The invention belongs to the field of chemical industry, and particularly relates to a process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid.
Background
The salt slurry is prepared by removing Ca from salt water and brine in the production process of chlor-alkali and salt manufacturing enterprises2+、Mg2+Solid waste generated during the pretreatment process. The salt slurry contains calcium carbonate, magnesium hydroxide, calcium sulfate, sodium chloride and the like, and because the output is large and the components are complex, the direct discharge brings environmental pollution, and how to comprehensively utilize the salt slurry is a difficult problem which troubles the industry. At present, the research and development of reasonable comprehensive utilization technology of salt mud are the technical problems facing both the chlor-alkali and salt making industries in China, and simultaneously, in the chlorine-hydrogen treatment process of the chlor-alkali industry, a large amount of waste sulfuric acid containing chlorine and having the concentration of about 75 percent is generated in the chlorine-hydrogen drying process. Belongs to dangerous waste, and the treatment is an enterprise problem.
Disclosure of Invention
The invention aims to provide a process for producing magnesium sulfate by comprehensively utilizing salt slurry and waste acid, which has simple process and no secondary pollution.
The invention realizes the purpose through the following technical scheme:
a process for producing magnesium sulfate by comprehensively utilizing salt slurry and waste acid is sequentially carried out according to the following steps:
the method comprises the following steps: pumping the sodium chloride aqueous solution containing magnesium hydroxide into a raw material pool by a raw material pump, pumping the solution into a first-stage centrifuge by a raw material conveying pump, and centrifuging;
step two: the clear liquid obtained after the centrifugation in the step one is sent to a clear liquid tank, the centrifuged magnesium hydroxide wet solid is sent to a water washing tank, a certain amount of water is added into the water washing tank, and the solid is washed to ensure that Cl is contained in the solid material-The mass fraction of (A) is less than 3%;
step three: pumping the raw materials washed in the step two to a secondary centrifuge by a washing pump for centrifugation, feeding the centrifuged clear liquid to a clear liquid tank, and feeding the centrifuged solid to a pulping tank;
step four: adding a certain amount of magnesium sulfate mother liquor into the third pulping tank to prepare pulp with the solid content of about 7-9%, and pulping the pulp into a reaction kettle by a pulping pump;
step five: controlling the flow of sulfuric acid in a sulfuric acid head tank, dropwise adding the sulfuric acid into a reaction kettle, fully reacting the sulfuric acid and magnesium hydroxide slurry in the reaction kettle at a certain temperature, and finishing the reaction when the pH value of the formed magnesium sulfate solution is 5;
step six: discharging the magnesium sulfate solution after the reaction in the step five is finished to a reaction intermediate tank, pumping the magnesium sulfate solution to a filter press through a filter press pump for filter pressing, removing the filter liquor after filter pressing to a filter liquor tank, and pumping the filter liquor in the filter liquor tank to a continuous crystallizer through a continuous crystallization pump for continuous crystallization;
step seven: pumping the solution in the continuous crystallizer in the sixth step into a cooler by a cooling circulating pump for circulating heat exchange to cool the solution, pumping the crystallized magnesium sulfate solution into a thickener by a discharge pump for further crystallization;
step eight: and (3) centrifuging the magnesium sulfate crystals in the thickener by using a centrifuge, centrifuging the mother liquor in a mother liquor tank, pumping the mother liquor to a pulping tank by using a mother liquor pump, drying the centrifuged magnesium sulfate containing free water in an air flow drying manner, and removing dust by using a bag type dust remover to prepare the magnesium sulfate heptahydrate crystals.
In this embodiment, the sulfuric acid in the sulfuric acid head tank in the fifth step is sulfuric acid with a concentration of 70-80% after treatment generated in the chlor-alkali drying process, and is transported to the sulfuric acid head tank from the outside.
In this embodiment, the certain temperature in the fifth step is 80-85 ℃.
In this embodiment, the cooling temperature in the seventh step is 25-35 ℃.
In this embodiment, the eight-step pneumatic drying method is a method of dispersing and suspending the granular solid material in the high-speed hot air flow and drying the granular solid material under pneumatic transmission. The drying temperature is 50-55 ℃, and the pressure is lower than 0.01 MPa.
Has the advantages that: the invention carries out waste recycling treatment on the salt mud and the waste acid, generates magnesium sulfate chemical raw materials, saves energy and reduces environmental pollution.
Detailed Description
The specific steps of the present invention are further illustrated by the following examples:
the embodiment of the process for producing the magnesium sulfate by comprehensively utilizing the salt mud and the waste acid sequentially comprises the following steps:
the method comprises the following steps: pumping 33.45t/h (magnesium hydroxide 1%, sodium chloride 21%, water 77.98%, and other 0.02%) of magnesium hydroxide waste liquid formed in the brine refining process into a raw material pool by a raw material pump, pumping the solution into a primary centrifuge by a raw material conveying pump, and centrifuging;
step two: 32.61t/h (21% of sodium chloride and 79% of water) of the centrifuged clear liquid in the step one is sent to a clear liquid tank, 0.84t/h (40% of magnesium hydroxide, 12% of sodium chloride, 47.2% of water and 0.8% of other water) of the centrifuged magnesium hydroxide-containing wet solid is sent to a water washing tank, 10t/h of water is added into the water washing tank, and the solid is washed, so that the sodium chloride contained in the solid is removed;
step three: pumping the raw materials washed by water in the step two to a secondary centrifuge by a water washing pump for centrifugation, wherein 10t/h (1% of sodium chloride and 99% of water) of the centrifuged clear liquid is delivered to a clear liquid tank, and 0.84t/h (40% of magnesium hydroxide, 0.59% of sodium chloride, 58.61% of water and 0.8% of the rest) of the centrifuged solid magnesium mud is delivered to a pulping tank;
step four: and (3) adding 2.48t/h of magnesium sulfate mother liquor (the content of magnesium sulfate is 31 percent, the content of sodium chloride is 2 percent and the content of water is 63 percent) and 0.02t/h of water into the pulping tank in the third step, and pulping the pulped pulp into a reaction kettle by a pulping pump.
Step five: conveying 75% sulfuric acid into a sulfuric acid head tank from the outside, wherein the sulfuric acid is treated sulfuric acid generated in the chlor-alkali drying process, the flow of the sulfuric acid is controlled to be 0.74t/h (75% of sulfuric acid and 25% of water), the sulfuric acid is dripped into a reaction kettle in the fourth step, the reaction temperature is controlled to be 80-85 ℃, and the reaction is finished when the pH value of the formed magnesium sulfate solution is 5;
step six: discharging 4.08t/h (35.5% of magnesium sulfate, 0.2% of other magnesium sulfate, 1.2% of sodium chloride and 63.1% of water) of the magnesium sulfate solution after the reaction in the fifth step to a reaction intermediate tank, pumping the magnesium sulfate solution to a filter press through a filter press pump, performing filter pressing on filter residues for 0.02t/h (40% of other magnesium sulfate, 0.1% of sodium chloride and 59.9% of water), removing the filter pressed filtrate to a filter liquor tank, and pumping 4.07t/h (35.5% of magnesium sulfate, 1.3% of sodium chloride and 63.2% of water) of the filtrate to a continuous crystallizer through a continuous crystallization pump for continuous crystallization;
step seven: pumping the solution in the continuous crystallizer in the step six into a cooler by a cooling circulating pump for circulating heat exchange so as to cool the solution to 25-35 ℃. Pumping the crystallized magnesium sulfate solution into a thickener by a discharge pump, further crystallizing, and conveying the magnesium sulfate crystals in the thickener to a centrifuge for centrifugation;
step eight: and (3) conveying 2.48t/h (magnesium sulfate content is 31%, sodium chloride content is 2%, and water content is 63%) of the mother liquor obtained after the centrifugation in the seventh step into a mother liquor tank, pumping the mother liquor into a pulping tank through a mother liquor pump, conveying 1.58t/h (magnesium sulfate heptahydrate content is 88%, sodium chloride content is 0.3%, and water content is 11.7%) of the centrifuged magnesium sulfate containing free water into a dryer, and drying and packaging the magnesium sulfate containing free water at the drying temperature of 50-55 ℃ and under the pressure of lower than 0.01 MPa.
In the above examples, the loss during drying was 0.189577t/h (magnesium sulfate heptahydrate 6.3%, water 93.7%) of 1.388889t/h (magnesium sulfate heptahydrate 99.13, sodium chloride 0.3%, water 0.5%) of the final product after drying.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (4)
1. A process for producing magnesium sulfate by comprehensively utilizing salt slurry and waste acid is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: pumping the water solution containing magnesium hydroxide and sodium chloride into a raw material pool through a raw material pump, and pumping the solution into a first-stage centrifuge through a raw material conveying pump for centrifugation;
step two: the clear liquid obtained after the centrifugation in the step one is sent to a clear liquid tank, the centrifuged magnesium hydroxide wet solid is sent to a water washing tank, a certain amount of water is added into the water washing tank, and the solid is washed to ensure that Cl is contained in the solid material-The mass fraction of (A) is less than 3%;
step three: pumping the raw materials washed in the step two to a secondary centrifuge by a washing pump for centrifugation, feeding the centrifuged clear liquid to a clear liquid tank, and feeding the centrifuged solid to a pulping tank;
step four: adding a certain amount of magnesium sulfate mother liquor into the third pulping tank to prepare pulp with the solid content of 7-9%, and pulping the pulp into a reaction kettle by a pulping pump;
step five: controlling the flow of sulfuric acid in a sulfuric acid head tank, dropwise adding the sulfuric acid into a reaction kettle, fully reacting the sulfuric acid and magnesium hydroxide slurry in the reaction kettle at the temperature of 80-85 ℃, and finishing the reaction when the pH value of the formed magnesium sulfate solution is 5;
step six: discharging the magnesium sulfate solution after the reaction in the step five is finished to a reaction intermediate tank, pumping the magnesium sulfate solution to a filter press through a filter press pump for filter pressing, removing the filter liquor after filter pressing to a filter liquor tank, and pumping the filter liquor in the filter liquor tank to a continuous crystallizer through a continuous crystallization pump for continuous crystallization;
step seven: pumping the solution in the continuous crystallizer in the sixth step into a cooler by a cooling circulating pump for circulating heat exchange to cool the solution, pumping the crystallized magnesium sulfate solution into a thickener by a discharge pump for further crystallization;
step eight: and (3) centrifuging the magnesium sulfate crystals in the thickener by using a centrifuge, centrifuging the mother liquor, pumping the mother liquor to a pulping tank by using a mother liquor pump, drying the centrifuged magnesium sulfate containing free water in an air flow drying manner, and removing dust by using a bag type dust remover to obtain magnesium sulfate heptahydrate crystals.
2. The process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid according to claim 1, which is characterized in that: and in the fifth step, the sulfuric acid in the sulfuric acid head tank is treated sulfuric acid with the concentration of 70-80% generated in the chlor-alkali drying process, and is conveyed into the sulfuric acid head tank from the outside.
3. The process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid according to claim 1, which is characterized in that: and the cold treatment temperature in the seventh step is 25-35 ℃.
4. The process for producing magnesium sulfate by comprehensively utilizing salt mud and waste acid according to claim 1, which is characterized in that: the eighth step of airflow drying is a method for dispersing and suspending the granular solid materials in high-speed hot airflow and drying the granular solid materials under pneumatic transmission, wherein the drying temperature is 50-55 ℃, and the pressure is lower than 0.01 MPa.
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| CN112429896B (en) * | 2020-10-29 | 2022-10-25 | 河南佰利联新材料有限公司 | Treatment method of salt mud produced in chlor-alkali production |
| CN114409144B (en) * | 2022-03-29 | 2022-06-03 | 山东海化集团有限公司 | Method and device for treating acidic wastewater after bromine extraction by using waste salty mud |
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| CN1137488A (en) * | 1995-06-08 | 1996-12-11 | 福建省福州第二化工厂职工技术协会 | Process for preparing magnesium sulfate by using chlorine alkali offscum salt slurry |
| KR20010097371A (en) * | 2000-04-21 | 2001-11-08 | 우명우 | Manufacturing magnesium sulfate by waste sulfuric acid. |
| CN102476818A (en) * | 2010-11-26 | 2012-05-30 | 江油市雄晖化工厂 | Method for comprehensively utilizing waste acid and waste alkali for producing high-purity magnesium sulfate |
| CN105523573B (en) * | 2016-01-21 | 2017-06-30 | 青海盐湖工业股份有限公司 | A kind of epsom salt and preparation method thereof |
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