CN115924938B - Production process of food-grade potassium carbonate and food-grade potassium bicarbonate - Google Patents
Production process of food-grade potassium carbonate and food-grade potassium bicarbonate Download PDFInfo
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- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 title claims abstract description 228
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 title claims abstract description 153
- 239000011736 potassium bicarbonate Substances 0.000 title claims abstract description 149
- 235000015497 potassium bicarbonate Nutrition 0.000 title claims abstract description 149
- 229910000028 potassium bicarbonate Inorganic materials 0.000 title claims abstract description 149
- 229910000027 potassium carbonate Inorganic materials 0.000 title claims abstract description 111
- 235000011181 potassium carbonates Nutrition 0.000 title claims abstract description 111
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 92
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 67
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 57
- 238000005406 washing Methods 0.000 claims abstract description 54
- 239000007787 solid Substances 0.000 claims abstract description 50
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 47
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 44
- 238000006243 chemical reaction Methods 0.000 claims abstract description 36
- 238000001035 drying Methods 0.000 claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims abstract description 15
- 239000002912 waste gas Substances 0.000 claims abstract description 14
- 239000011259 mixed solution Substances 0.000 claims abstract description 12
- 239000000243 solution Substances 0.000 claims abstract description 12
- 229940072033 potash Drugs 0.000 claims abstract description 6
- 235000015320 potassium carbonate Nutrition 0.000 claims abstract description 6
- 239000010413 mother solution Substances 0.000 claims abstract description 4
- 239000007788 liquid Substances 0.000 claims description 26
- 239000012452 mother liquor Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 13
- 238000000926 separation method Methods 0.000 claims description 9
- 238000002425 crystallisation Methods 0.000 claims description 7
- 230000008025 crystallization Effects 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 6
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 3
- 239000011591 potassium Substances 0.000 claims description 3
- 229910052700 potassium Inorganic materials 0.000 claims description 3
- 239000000126 substance Substances 0.000 abstract description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 abstract 1
- 229910052698 phosphorus Inorganic materials 0.000 abstract 1
- 239000011574 phosphorus Substances 0.000 abstract 1
- 239000003546 flue gas Substances 0.000 description 39
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 38
- 239000007789 gas Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 12
- 238000010521 absorption reaction Methods 0.000 description 10
- 238000001694 spray drying Methods 0.000 description 10
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 8
- 239000000047 product Substances 0.000 description 7
- 239000011552 falling film Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical compound OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 4
- 238000005119 centrifugation Methods 0.000 description 4
- 239000000428 dust Substances 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 3
- 239000010963 304 stainless steel Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 238000012824 chemical production Methods 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 235000016709 nutrition Nutrition 0.000 description 2
- 230000035764 nutrition Effects 0.000 description 2
- SCVFZCLFOSHCOH-UHFFFAOYSA-M potassium acetate Chemical compound [K+].CC([O-])=O SCVFZCLFOSHCOH-UHFFFAOYSA-M 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 208000019025 Hypokalemia Diseases 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 235000015872 dietary supplement Nutrition 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 235000013373 food additive Nutrition 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- 235000010855 food raising agent Nutrition 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000000546 pharmaceutical excipient Substances 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 235000011056 potassium acetate Nutrition 0.000 description 1
- 229940097322 potassium arsenite Drugs 0.000 description 1
- 208000024896 potassium deficiency disease Diseases 0.000 description 1
- HEQWEGCSZXMIJQ-UHFFFAOYSA-M potassium;oxoarsinite Chemical compound [K+].[O-][As]=O HEQWEGCSZXMIJQ-UHFFFAOYSA-M 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Abstract
The invention belongs to the field of phosphorus chemical industry, and provides a production process of food-grade potassium carbonate and food-grade potassium bicarbonate, which comprises the following steps: s1, pretreatment of waste gas: removing impurities and cooling the waste gas containing carbon dioxide; s2, carbonating: carbonating the waste gas after S1 pretreatment with potash solution to obtain mixed solution of potassium carbonate and potassium bicarbonate, and controlling the pH value of the reaction to be not more than 8.5; s3, crystallizing and separating: cooling, crystallizing and centrifugally separating the mixed solution obtained in the step S2 to obtain potassium carbonate mother solution containing potassium bicarbonate and potassium bicarbonate solid containing potassium carbonate; s4, washing and drying: adding pure water dissolved with carbon dioxide into the potassium bicarbonate solid containing potassium carbonate obtained in the step S3 for washing, and drying the washed potassium bicarbonate solid to obtain food-grade potassium bicarbonate; the invention can recycle and convert the waste gas into high-purity food-grade potassium carbonate and food-grade potassium bicarbonate.
Description
Technical Field
The invention relates to the field of resource utilization, in particular to food-grade potassium carbonate and a production process of the food-grade potassium bicarbonate.
Background
The potassium bicarbonate has application in the fields of chemical production, food processing, medicine and the like. In particular, potassium bicarbonate can be used as a raw material for producing potassium carbonate, potassium acetate and potassium arsenite in chemical production, and can also be used as a fire extinguishing agent for petroleum and chemicals. Can also be used in medicine for supplementing potassium, treating hypokalemia, and as nutritional supplement and excipient. Baking powder, foaming salt and chemical leavening agent are used in the food industry. Potassium bicarbonate is commonly used as an analytical reagent in analytical chemistry. The acid regulator is used in the laboratory. The main consumption field of Chinese potassium bicarbonate is also food field, and the Chinese potassium bicarbonate is used as a food additive to replace sodium bicarbonate in the baking field and the acidity regulator field, and then agricultural fertilizers, animal husbandry, pulp treatment, fire extinguishers and the like. The properties are similar to those of potassium carbonate, but the proportion of carbon nutrition is higher, and the proportion of potassium nutrition is slightly lower.
Carbon dioxide is the greenhouse gas with the largest global yield at present, is an important factor for climate warming, and is reported by the international energy agency, the world carbon dioxide emission in 2010 reaches 331.6 hundred million tons, and the carbon dioxide emission in China is about 83.3 hundred million tons. The flue gas generated by fire coal, fuel gas and the like contains a large amount of carbon dioxide, has the characteristics of stability, concentration, large treatment capacity and the like, and is an important direction for realizing emission reduction. To mitigate pollution, flue gases often require absorption and treatment prior to discharge. Currently, regarding the treatment and utilization of flue gas, carbon dioxide is desorbed and recovered after being absorbed mainly by an alkaline water absorption method, as disclosed in patent (CN 101318651), an apparatus and method for absorbing and recovering carbon dioxide from flue gas using ammonia as an absorbent, the apparatus comprising an absorption tower and a circulation cooler connected to the absorption tower, such that a high temperature absorbent is recovered from the absorption tower, cooled to a preset temperature, and then supplied again into the absorption tower to emit absorption heat generated when absorbing carbon dioxide from flue gas. The method can only recover and store the carbon dioxide in the flue gas, then release and utilize the carbon dioxide, has complex steps and higher recovery cost.
Therefore, how to economically and efficiently absorb and utilize carbon dioxide in flue gas and convert the carbon dioxide into waste is a problem to be solved.
Disclosure of Invention
The invention aims to provide a production process of food-grade potassium carbonate and food-grade potassium bicarbonate, which can economically and efficiently recycle and convert flue gas into high-purity food-grade potassium carbonate and food-grade potassium bicarbonate.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a process for producing food grade potassium bicarbonate, comprising the steps of:
S1, pretreatment of waste gas: washing the waste gas containing carbon dioxide with water, cooling and alkali washing; the flue gas containing carbon dioxide can be flue gas generated by fire coal, fuel gas and the like, and because the flue gas discharged by a natural gas combustion furnace contains a small amount of solid particle impurities and acid gas (SO 2 and NO 2) and has higher temperature (about 120 ℃), the flue gas cannot be directly sent to a carbonation system for reaction, and the flue gas needs to be purified and cooled by a flue gas treatment system, the flue gas treatment system mainly comprises a water scrubber and an alkaline scrubber during pretreatment, the water scrubber mainly aims at removing the solid particle impurities and most of the acid gas (SO 2 and NO 2) in the flue gas and simultaneously cooling the flue gas, and a cooling coil is arranged in the water scrubber or a cooler is arranged at a liquid phase outlet pipeline of the water scrubber, SO that the water scrubber can be reasonably selected according to actual production requirements by a person in the field; the flue gas after water washing and cooling enters an alkaline washing tower, and the alkaline washing liquid is potassium carbonate or potassium bicarbonate or a mixture of the potassium carbonate and the potassium bicarbonate, preferably 5-20% of potassium bicarbonate solution, more preferably 10% of potassium bicarbonate solution, SO that most of acid gases (SO 2 and NO 2) are completely washed and removed.
S2, carbonating: carbonating the waste gas pretreated in the step S1 with potash-containing substances to obtain a mixed solution of potassium carbonate and potassium bicarbonate, and controlling the pH value of the reaction to be not more than 8.5;
The washed gas enters a carbonation system, the carbonation system mainly comprises a flue gas compressor, a carbonation tower, a tail gas absorption tower and other equipment, the compressor pressurizes the purified flue gas to 0.06MPa (g), the purified flue gas enters the carbonation tower for carbonation reaction to obtain a mixed solution of potassium carbonate and potassium bicarbonate, the reaction temperature is 40-80 ℃, preferably 60 ℃, the unabsorbed carbon dioxide enters the tail gas absorption tower, 30-48% of potash-containing alkaline substances such as potassium hydroxide or potassium carbonate solution or a mixture of the potassium hydroxide and the potassium carbonate solution, preferably 45% of potassium hydroxide, fully absorbs the carbon dioxide to obtain a potassium carbonate dilute solution, and the dilute solution is pumped into the carbonation tower for carbonation reaction; the potassium hydroxide concentration is not lower than 30%, not higher than 48%, and when lower than 30%, the potassium bicarbonate concentration generated during carbonation becomes low, which is not favorable for crystallization; when the concentration is higher than 48%, the concentration of potassium bicarbonate generated during carbonation becomes high, crystals are precipitated during carbonation, and pipelines and equipment are blocked;
The inventors creatively found that: when the carbonation reaction is carried out, when the pH reaches 8.5, the following problems occur if the flue gas is continued to be introduced: firstly, the potassium bicarbonate concentration is slowly increased, and secondly, the potassium bicarbonate has the risk of blocking equipment due to crystal precipitation caused by the increase of the potassium bicarbonate concentration, so that when the pH reaches 8.5, the carbonation reaction is stopped, and the potassium carbonate is obtained: potassium bicarbonate mass ratio of about 3: 1.
S3, crystallizing: cooling the mixed solution obtained in the step S2 to-20 ℃, and crystallizing to separate potassium bicarbonate solid containing a small amount of potassium carbonate;
Pumping the obtained carbonized mixed solution into a crystallization kettle, then introducing cooling water into a jacket of the crystallization kettle, cooling the carbonized mixed solution to-20 ℃, and keeping cold for 10-60 min, preferably 30min, wherein the potassium carbonate in the crystallized solid is due to different solubilities of the potassium carbonate and the potassium bicarbonate: the mass ratio of the potassium bicarbonate is 1: 19-1: 13, potassium carbonate in mother liquor: the mass ratio of potassium bicarbonate is about 5:1 to 8:1.
S4, separating: carrying out centrifugal separation on the mixture obtained in the step S3 to obtain potassium carbonate mother liquor containing a small amount of potassium bicarbonate and potassium bicarbonate solid containing a small amount of potassium carbonate;
S5, washing: adding washing water into the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in the step S4 for washing, and drying the washed potassium bicarbonate solid to obtain food-grade potassium bicarbonate; the washing water is pure water in which carbon dioxide is dissolved.
Specifically, under the condition of 0.1-0.6 MPa (g), preferably 0.2MPa (g), the temperature is 5-30 ℃, preferably 20 ℃, food-grade carbon dioxide is dissolved in pure water, the conductivity of the pure water is 1-50 mu s/cm, CO 2+H2O＝H2CO3,H2CO3 is ionized to form H + and HCO 3 - by CO 2+H2O＝H2CO3,H2CO3, the potassium bicarbonate solid containing a small amount of potassium carbonate is washed by water dissolved with carbon dioxide, under the homoionic effect, HCO 3 - ionized by H 2CO3 can prevent the potassium bicarbonate from dissolving, but can not prevent the potassium carbonate from dissolving, and part of potassium carbonate can be converted into potassium bicarbonate, so that a small amount of potassium carbonate in the potassium bicarbonate is removed by washing and converting, the high-purity potassium bicarbonate solid without potassium carbonate is obtained after washing is finished, and the washed high-purity potassium bicarbonate solid is dried to obtain the food-grade potassium bicarbonate. The washing water is pure water in which carbon dioxide is dissolved, the pressure of the carbon dioxide is 0.1-0.6 MPa (g), the pressure is lower than 0.1MPa (g), the solubility of the carbon dioxide is reduced, potassium bicarbonate is dissolved and carried out during washing, the yield of the potassium bicarbonate is reduced, and the carbonic acid concentration produced by the carbon dioxide and the water is not obviously increased when the pressure is higher than 0.6MPa (g), so that the energy consumption of the device is increased; the temperature of the washing water is lower than 5 ℃, the water is at risk of freezing, and higher than 30 ℃, the solubility of carbon dioxide becomes small, and potassium bicarbonate is dissolved and carried out during washing, so that the yield of potassium bicarbonate is reduced.
Preferably, the ratio of the amount of wash water to the mass of potassium bicarbonate solids (wet basis) is 1:1 to 1: between 10, preferably 1: and 5, drying the washed high-purity potassium bicarbonate solid to obtain the food-grade potassium bicarbonate.
The inventor creatively proposes the idea of converting flue gas into a mixture of potassium carbonate and potassium bicarbonate, and then separating the mixture to obtain high-purity products respectively; the invention adopts a mode of washing water dissolved with carbon dioxide to respectively prepare high-purity potassium bicarbonate and potassium carbonate, other impurities are not introduced, the reaction time is short, and the energy consumption is greatly reduced.
Preferably, the potassium bicarbonate solid, when dried: the high-purity potassium bicarbonate solid is transferred to a potassium bicarbonate drying system, and the potassium bicarbonate drying system mainly comprises an air heater, a vibrating fluidized bed, a cyclone separator, a bag-type dust remover, a blower and an induced draft fan; those skilled in the art can make reasonable selections according to actual production requirements. The air heater heats air to 140-160 ℃ and then enters a vibrating fluidized bed, the flow rate of the hot air in the fluidized bed is 0.01-0.5 m/s, the temperature of the bed is 100-120 ℃, the temperature of an air outlet is 70-90 ℃, the potassium bicarbonate stays in the vibrating fluidized bed for about 5min, and the water in the potassium carbonate is evaporated to obtain the potassium bicarbonate meeting the GB 1886.247-2016 standard; the tail gas is discharged into the atmosphere after dust removal by a cyclone separator and a bag-type dust remover, wherein the aperture of a bag in the bag-type dust remover is 130-160 meshes. The finished dried potassium bicarbonate is cooled to 40 ℃ and packaged.
The preparation process of the food-grade potassium carbonate comprises the following steps: concentrating mother liquor obtained by centrifugal separation, wherein the obtained mother liquor contains 20-35% of potassium carbonate and 2-8% of potassium bicarbonate; concentrating at 120-180 deg.c and vacuum degree-0.02-0.088 MPa (g) to 40-50 wt% of potassium carbonate, spray drying, and other drying modes may be selected by one skilled in the art based on practical production requirement, and the drying temperature is 220-260 deg.c.
Preferably, when drying the potassium carbonate: the invention relates to a potassium carbonate drying system, which mainly comprises a heat exchanger, a falling film concentrator, a natural gas burner, a centrifugal spray drying tower, a cyclone separator, a tail gas washing tower, a blower and an induced draft fan. The mother liquor after solid-liquid separation firstly enters a tail gas washing tower, the tail gas from a centrifugal spray drying tower at about 120 ℃ is washed, the tail gas emission reaches the standard, the heat in the tail gas is utilized to enable the temperature of the mother liquor to be increased to about 40 ℃, then the mother liquor is pumped into a heat exchanger, the mother liquor is heated again by utilizing steam condensate of a falling film concentrator, the temperature of the mother liquor is increased to about 60 ℃, then the mother liquor enters the falling film concentrator, the steam pressure is about 0.2MPa (g), the temperature is about 125 ℃, the vacuum degree of the falling film concentrator is about-0.035 MPa, the material outlet temperature is about 120 ℃, the potassium carbonate is concentrated to about 45% by mass, then the potassium carbonate is pumped into the centrifugal spray drying tower, the mother liquor is contacted and dried with high-temperature gas at 220-260 ℃ from a natural gas burner, a small amount of potassium bicarbonate in a potassium carbonate solution is decomposed into potassium carbonate at high temperature, the potassium carbonate is collected by a cyclone separator, and the dried potassium carbonate solid is packaged after the temperature is cooled to 40 ℃ to obtain the food grade potassium carbonate meeting the GB 25588-2010 standard.
In addition, in order to adjust the yield of the potassium bicarbonate according to market conditions, part or all of the mother solution concentrated by the falling film concentrator can be pumped into a carbonization tower for cyclic carbonation, and the potassium carbonate in the mother solution is converted into the potassium bicarbonate, so that the yield of the potassium bicarbonate is increased.
The beneficial effects of the invention are as follows:
1. The inventor creatively proposes the idea of converting flue gas into a mixture of potassium carbonate and potassium bicarbonate, and then separating the mixture to obtain high-purity products respectively; the invention adopts a mode of washing water dissolved with carbon dioxide to respectively prepare high-purity potassium bicarbonate and potassium carbonate, other impurities are not introduced, the reaction time is short, and the energy consumption is greatly reduced.
2. In the invention, in order to ensure the separation of potassium carbonate and potassium bicarbonate, the temperature, pH and potassium hydroxide concentration of the carbonation reaction are controlled, so that the concentration of the produced potassium bicarbonate is higher, and the speed of the carbonation reaction and the normal operation of the subsequent crystallization reaction are improved; thereby enabling a higher purity of the final product to be obtained.
Drawings
FIG. 1 is a flow chart of the production process of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the present invention will be further described with reference to specific embodiments. The examples were conducted under conventional conditions or conditions recommended by the manufacturer without specifying the specific conditions. The reagents used, or together with the manufacturer's instructions, are conventional products available commercially. All of the features disclosed in this specification, except for mutually exclusive features or/and steps, may be combined in any manner.
The following examples will provide those skilled in the art with a more complete understanding of the present invention and are not intended to limit the invention in any way.
It should be noted in the following examples that: 1. potassium hydroxide is produced by an ion membrane method; 2. the carbonization tower and the tail gas absorption tower are made of 316L stainless steel, and the rest equipment is made of 304 stainless steel; 3. the pipelines in all the liquid pipelines are made of 304 stainless steel, and the gaskets are made of polytetrafluoroethylene; 4. the water is pure water.
In the following examples, the subject was flue gas, and the flue gas composition in this example is shown in Table 1:
TABLE 1 analysis of flue gas composition after Natural gas Combustion
| Substance (B) | CO2 | SO2 | Water vapor | N2 | O2 | NO2 | Particles | Totalizing |
| Mass fraction (%) | 12.465 | 0.005 | 9.773 | 72.243 | 5.511 | 0.002 | 0.001 | 100 |
Example 1
The embodiment provides a production process of food-grade potassium carbonate and food-grade potassium bicarbonate, which comprises the following steps:
S1, pretreatment of waste gas: washing the flue gas with water to remove impurities, cooling, and then washing with 15% potassium bicarbonate solution with alkali to remove impurities;
S2, carbonating: carbonating the flue gas pretreated in the step S1 with 45% potassium hydroxide collecting liquid, wherein the reaction temperature is 60 ℃, the reaction pressure is 0.06MPa (g), and the mixed liquid of potassium carbonate and potassium bicarbonate is obtained, and the reaction pH is controlled to be not more than 8.5; the unabsorbed carbon dioxide is circularly absorbed by 45 percent potassium hydroxide solution to obtain potassium hydroxide trapping liquid containing a small amount of potassium carbonate, and the potassium hydroxide trapping liquid can be continuously used in carbonation reaction;
S3, crystallizing and separating: cooling the mixed solution obtained in the step S2 to 10 ℃, crystallizing to separate potassium bicarbonate solids containing a small amount of potassium carbonate, and carrying out solid-liquid separation on the slurry by adopting a centrifugal method to obtain potassium carbonate mother liquor containing a small amount of potassium bicarbonate and potassium bicarbonate solids containing a small amount of potassium carbonate;
(1) Preparation of food grade potassium bicarbonate: washing and drying the solid obtained in the step S3: under the condition of 0.2MPa (g), the temperature is 20 ℃, the food-grade carbon dioxide is dissolved in pure water, the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in S3 is washed by water dissolved with the carbon dioxide, the high-purity potassium bicarbonate is obtained, and the ratio of the consumption of washing water to the mass of the potassium bicarbonate solid (wet basis) is 1:1, drying the washed high-purity potassium bicarbonate solid to obtain the food-grade potassium bicarbonate.
(2) Preparing food-grade potassium carbonate: and (3) concentrating the potassium carbonate mother liquor containing a small amount of potassium bicarbonate, which is obtained in the step (S3), wherein the concentration temperature is 150 ℃, the vacuum degree is-0.05 MPa (g), concentrating until the mass fraction of the potassium carbonate is 45%, and then performing spray drying, wherein the spray drying temperature is 240 ℃, so that the food-grade potassium carbonate is finally obtained.
Example 2
The embodiment provides a production process of food-grade potassium carbonate and food-grade potassium bicarbonate, which comprises the following steps:
S1, pretreatment of waste gas: washing the flue gas with water to remove impurities, cooling, and then washing with 5% potassium bicarbonate solution with alkali to remove impurities;
S2, carbonating: carbonating the flue gas pretreated in the step S1 with 40% potassium hydroxide collecting liquid, wherein the reaction temperature is 50 ℃, the reaction pressure is 0.05MPa (g), so as to obtain a mixed liquid of potassium carbonate and potassium bicarbonate, and controlling the reaction pH to be not more than 8.5; the unabsorbed carbon dioxide is circularly absorbed by 45 percent potassium hydroxide solution to obtain potassium hydroxide trapping liquid containing a small amount of potassium carbonate, and the potassium hydroxide trapping liquid can be continuously used in carbonation reaction;
S3, crystallizing and separating: cooling the mixed solution obtained in the step S2 to 0 ℃, crystallizing to separate potassium bicarbonate solids containing a small amount of potassium carbonate, and carrying out solid-liquid separation on the slurry by adopting centrifugation to obtain potassium carbonate mother liquor containing a small amount of potassium bicarbonate and potassium bicarbonate solids containing a small amount of potassium carbonate;
(1) Preparation of food grade potassium bicarbonate: washing and drying the solid obtained in the step S3: under the condition of 0.3MPa (g), the temperature is 10 ℃, the food-grade carbon dioxide is dissolved in pure water, the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in the step S3 is washed by the water dissolved with the carbon dioxide, so that the high-purity potassium bicarbonate is obtained, and the ratio of the consumption of washing water to the mass of the potassium bicarbonate solid (wet basis) is 1: and 5, drying the washed high-purity potassium bicarbonate solid to obtain the food-grade potassium bicarbonate.
(2) Preparing food-grade potassium carbonate: and (3) concentrating the potassium carbonate mother liquor containing a small amount of potassium bicarbonate, which is obtained in the step (S3), wherein the concentration temperature is 140 ℃, the vacuum degree is-0.04 MPa (g), concentrating until the mass fraction of the potassium carbonate is 43%, and then performing spray drying, wherein the spray drying temperature is 230 ℃, so that the food-grade potassium carbonate is finally obtained.
Example 3
The embodiment provides a production process of food-grade potassium carbonate and food-grade potassium bicarbonate, which comprises the following steps:
s1, pretreatment of waste gas: washing the flue gas with water to remove impurities, cooling, and then washing with 20% potassium bicarbonate solution with alkali to remove impurities;
S2, carbonating: carbonating the flue gas pretreated in the step S1 with 35% potassium hydroxide collecting liquid, wherein the reaction temperature is 70 ℃, the reaction pressure is 0.07MPa (g), and the mixed liquid of potassium carbonate and potassium bicarbonate is obtained, and the reaction pH is controlled to be not more than 8.5; the unabsorbed carbon dioxide is circularly absorbed by 45 percent potassium hydroxide solution to obtain potassium hydroxide trapping liquid containing a small amount of potassium carbonate, and the potassium hydroxide trapping liquid can be continuously used in carbonation reaction;
S3, crystallizing and separating: cooling the mixed solution obtained in the step S2 to-5 ℃, crystallizing to separate potassium bicarbonate solids containing a small amount of potassium carbonate, and carrying out solid-liquid separation on the slurry by adopting centrifugation to obtain potassium carbonate mother liquor containing a small amount of potassium bicarbonate and potassium bicarbonate solids containing a small amount of potassium carbonate;
(1) Preparation of food grade potassium bicarbonate: washing and drying the solid obtained in the step S3: under the condition of 0.5MPa (g), the temperature is 25 ℃, so that the food-grade carbon dioxide is dissolved in the pure water; washing the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in the step S3 with water dissolved with carbon dioxide to obtain high-purity potassium bicarbonate, wherein the ratio of the amount of washing water to the mass of the potassium bicarbonate solid (wet basis) is 1: and 8, drying the washed high-purity potassium bicarbonate solid to obtain the food-grade potassium bicarbonate.
(2) Preparing food-grade potassium carbonate: and (3) concentrating the potassium carbonate mother liquor containing a small amount of potassium bicarbonate, which is obtained in the step (S3), wherein the concentration temperature is 160 ℃, the vacuum degree is-0.07 MPa (g), concentrating until the mass fraction of the potassium carbonate is 48%, and then performing spray drying, wherein the spray drying temperature is 250 ℃, so that the food-grade potassium carbonate is finally obtained.
Example 4
The embodiment provides a production process of food-grade potassium bicarbonate, which comprises the following steps:
S1, pretreatment of waste gas: washing the flue gas with water to remove impurities, cooling, and then washing with 15% potassium bicarbonate solution with alkali to remove impurities;
S2, carbonating: carbonating the flue gas pretreated in the step S1 with 40% potassium hydroxide collecting liquid, wherein the reaction temperature is 65 ℃, the reaction pressure is 0.055MPa (g), and the mixed liquid of potassium carbonate and potassium bicarbonate is obtained, and the reaction pH is controlled to be not more than 8.5; the unabsorbed carbon dioxide is circularly absorbed by 45 percent potassium hydroxide solution to obtain potassium hydroxide trapping liquid containing a small amount of potassium carbonate, and the potassium hydroxide trapping liquid can be continuously used in carbonation reaction;
S3, crystallizing and separating: cooling the mixed solution obtained in the step S2 to 5 ℃, crystallizing to separate potassium bicarbonate solids containing a small amount of potassium carbonate, and carrying out solid-liquid separation on the slurry by adopting centrifugation to obtain potassium carbonate mother liquor containing a small amount of potassium bicarbonate and potassium bicarbonate solids containing a small amount of potassium carbonate;
(1) Washing and drying the solid obtained in the step S3: under the condition of 0.25MPa (g), the temperature is 15 ℃, the food-grade carbon dioxide is dissolved in pure water, the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in the step S3 is washed by the water dissolved with the carbon dioxide, so that the high-purity potassium bicarbonate is obtained, and the ratio of the consumption of washing water to the mass of the potassium bicarbonate solid (wet basis) is 1: and 6, drying the washed high-purity potassium bicarbonate solid to obtain the food-grade potassium bicarbonate.
(2) Concentrating the potassium carbonate mother liquor containing a small amount of potassium bicarbonate obtained in the step S3: and (3) sending all the concentrated mother liquor to S2 for recycling treatment, and finally obtaining the food-grade potassium bicarbonate.
Comparative example 1
The difference between this comparative example and example 1 is that: the solid obtained in S3 was not washed.
Comparative example 2
The difference between this comparative example and example 1 is that: the solid obtained in S3 was washed with pure water.
Comparative example 3
The difference between this comparative example and example 1 is that: the carbonation temperature in S2 was 20 ℃.
Comparative example 4
The difference between this comparative example and example 1 is that: the carbonation temperature in S2 was 90 ℃.
Experimental example
1. The composition analysis of the flue gas after washing with water in example 1 is shown in table 2, and the composition analysis of the flue gas after alkaline washing is shown in table 3:
TABLE 2 analysis of the components after washing of flue gas
| Substance (B) | CO2 | SO2 | H2O | N2 | O2 | NO2 | Particles | Totalizing |
| Mass fraction (%) | 13.435 | 0.035 | 2.615 | 77.995 | 5.95 | 0.0015 | 0 | 100 |
TABLE 3 analysis of the Components of flue gas after alkaline washing
| Substance (B) | CO2 | SO2 | H2O | N2 | O2 | NO2 | Particles | Totalizing |
| Mass fraction (%) | 13.4377 | 0.0002 | 2.634 | 77.998 | 5.93 | 0.0001 | 0 | 100 |
2. Analysis of the components of the products prepared in example 1 and comparative examples 1-2 are shown in the comparative table 4 (i.e., the solids obtained after crystallization and centrifugation are washed in different manners for comparison):
TABLE 4 analysis of influence of washing modes on products
3. The analytical pair of product components obtained by the preparation of example 1 and comparative examples 3 to 4 are shown in Table 5:
TABLE 5 analysis of the impact of carbonation temperature on product
3. The quality of the food-grade potassium bicarbonate and the quality of the food-grade potassium carbonate obtained in the examples and comparative examples of the present invention are shown in tables 6 and 7:
TABLE 6 quality of food grade potassium bicarbonate
TABLE 7 quality of food grade Potassium carbonate
In summary, the carbonation reaction process can separate potassium carbonate from potassium bicarbonate more thoroughly, so that the concentration of the potassium bicarbonate obtained in subsequent production is higher, and the carbonation reaction speed and the normal operation of subsequent crystallization reaction are improved; in the embodiment, the potassium bicarbonate solid containing a small amount of potassium carbonate is washed by adopting the water dissolved with carbon dioxide, so that the high-purity potassium bicarbonate and potassium carbonate can be respectively prepared, other impurities can not be introduced, the reaction time is short, and the energy consumption is greatly reduced.
The present invention is not limited to the above embodiments, and any person should know the structural changes made under the teaching of the present invention, and all the technical solutions that are the same or similar to the present invention fall within the protection scope of the present invention.
Claims (9)
1. A process for the production of food grade potassium carbonate and food grade potassium bicarbonate, comprising the steps of:
s1, pretreatment of waste gas: removing impurities and cooling the waste gas containing carbon dioxide;
S2, carbonating: carrying out carbonation reaction on the waste gas pretreated in the step S1 and potash-containing liquid to obtain mixed liquid of potassium carbonate and potassium bicarbonate, and controlling the pH value of the reaction to be not lower than 8.5;
s3, crystallization separation: cooling, crystallizing and centrifugally separating the mixed solution obtained in the step S2 to obtain potassium carbonate mother solution containing a small amount of potassium bicarbonate and potassium bicarbonate solid containing a small amount of potassium carbonate;
S4, washing and drying: adding washing water into the potassium bicarbonate solid containing a small amount of potassium carbonate obtained in the step S3 for washing, and drying the washed potassium bicarbonate solid to obtain food-grade potassium bicarbonate; the washing water is pure water dissolved with carbon dioxide, the pressure of the carbon dioxide in the washing water is 0.1-0.6 MPa, and the temperature is 5-30 ℃.
2. The process for producing food grade potassium carbonate and food grade potassium bicarbonate according to claim 1, wherein in S1, the pretreatment comprises water washing, temperature reduction and alkali washing; the alkaline washing liquid added during alkaline washing is potassium carbonate or potassium bicarbonate or a mixture of the two.
3. The process for producing food-grade potassium carbonate and food-grade potassium bicarbonate according to claim 1, wherein the reaction temperature is 40 to 80 ℃ and the reaction pressure is 0.04 to 0.08mpa when the carbonation reaction is performed in S2.
4. The process for the production of food grade potassium carbonate and food grade potassium bicarbonate according to claim 1, wherein the unreacted carbon dioxide from the carbonation reaction in S2 is recycled to the potash containing solution to give a potash containing lye containing a small amount of potassium carbonate and is further used in the carbonation reaction.
5. The process for the production of food grade potassium carbonate and food grade potassium bicarbonate according to claim 1, wherein the potassium-containing lye is potassium hydroxide or a potassium carbonate solution or a mixture of both; the concentration of the water is 30% -48%.
6. The process for producing food grade potassium carbonate and potassium bicarbonate according to claim 1, wherein the mass ratio of the washing water to the potassium bicarbonate solids at the time of washing in S4 is 1: 1-1: 10.
7. The process for the production of food grade potassium carbonate and potassium bicarbonate according to claim 1, further comprising s5 concentrating the mother liquor: and (3) concentrating the potassium carbonate mother liquor containing a small amount of potassium bicarbonate obtained in the step (S3).
8. The process for producing food grade potassium carbonate and food grade potassium bicarbonate according to claim 7, wherein in S5, the concentrated mother liquor is dried to obtain food grade potassium carbonate;
Or returning part or all of the concentrated mother liquor to the step S2 again for S2-S4 to obtain the potassium bicarbonate.
9. The process for producing food-grade potassium carbonate and food-grade potassium bicarbonate according to claim 8, wherein the concentration temperature is 120-180 ℃ and the vacuum degree is-0.02 to-0.088 MPa; the drying temperature during drying is 220-260 ℃.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5618504A (en) * | 1995-05-10 | 1997-04-08 | Solvay Minerals, Inc. | Method for recovery of alkali values from trona using sequential crystallization |
| CN103663505A (en) * | 2013-11-23 | 2014-03-26 | 福建师范大学 | Method for treating potassium feldspar according to sub-molten salt method to prepare potassium carbonate |
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5618504A (en) * | 1995-05-10 | 1997-04-08 | Solvay Minerals, Inc. | Method for recovery of alkali values from trona using sequential crystallization |
| CN103663505A (en) * | 2013-11-23 | 2014-03-26 | 福建师范大学 | Method for treating potassium feldspar according to sub-molten salt method to prepare potassium carbonate |
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