Method for reducing content of calcium and magnesium in sodium carbonate product

Abstract

The invention relates to the technical field of sodium carbonate, and provides a method for reducing the content of calcium and magnesium in a sodium carbonate product, which comprises the following steps: adding a monohydrate alkali crystallization protective agent into chemical combination water in a heavy ash process in a sodium carbonate preparation process, and carrying out hydration reaction in a hydration machine. The particle size of sodium carbonate is gt; the content of the product with the particle size of more than 1.18 mm is less than 4%, and the content of the product with the particle size of more than 2 mm is less than 1%. And the magnesium ion index range of the ammonia brine can be reduced to 10-14 mg / L.

Description

Technical Field

[0001] The present invention relates to the technical field of soda ash, and in particular to a method for reducing the calcium and magnesium contents in soda ash products. Background Art

[0002] In plateau areas, due to low air pressure, dense soda ash monohydrate does not crystallize during the production of soda ash. In order to make the dense soda ash meet the quality standards, magnesium chloride must be added to the ammonia salt water in the evaporation and absorption process to improve the adhesion of the monohydrate and play a role in crystallization. The details are as follows:

[0003] Specific operation method of adding magnesium: Use a trolley to pull magnesium chloride from the magnesium chloride yard to the root of the belt, then manually load it to the feeding belt, use the magnesium adding belt to transport magnesium chloride to the silo on the top of the magnesium adding tank, and then enter the magnesium adding tank through the flap under the silo. The refined brine / secondary water / hot waste dilute liquid in the magnesium adding tank and magnesium chloride are completely dissolved by stirring to form a magnesium chloride solution, and then transported to the cold ammonia brine clarification tank by the magnesium adding pump.

[0004] However, the above method has the following disadvantages: the particle size of the final product heavy soda ash is uneven, the calcium and magnesium content is high, and the product turbidity is high, which has a great impact on the use of downstream customers. Summary of the invention

[0005] The purpose of the present application is to provide a method for reducing the calcium and magnesium contents in a soda ash product, in order to solve the above-mentioned problems existing in the products obtained by the existing soda ash production.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] A method for reducing the calcium and magnesium content in a soda ash product comprises adding a monohydrate crystal protective agent to the water in the heavy ash process during the soda ash preparation process, and then feeding the water into a hydration machine for hydration reaction.

[0008] As a possible design, the monohydrate alkaline crystal protective agent is dissolved in water to form a solution, and then mixed with the chemical water.

[0009] As a possible design, the mass ratio of the monohydrate alkali crystal protective agent to water is 0.8 to 1.2:1.

[0010] As a possible design, the mass ratio of the monohydrate alkali crystal protective agent to water is 1:1.

[0011] As a possible design, the amount of the monohydrate alkali crystal protective agent added is determined by the calcium and magnesium content in the heavy ash raw material and the magnesium ion concentration in the evaporation and absorption process.

[0012] As a possible design, after the evaporation and absorption process is completed, the magnesium ion concentration is 10-14 mg / L.

[0013] As a possible design, the soda ash product has a particle size greater than 180 μm accounting for more than 80%, a particle size greater than 1.18 mm accounting for less than 4%, and a particle size greater than 2 mm accounting for less than 1%.

[0014] As a possible design, the calcium content in the soda ash product is less than 0.0033%, and the magnesium content is less than 0.0114%.

[0015] The beneficial effects of the present invention are:

[0016] The present invention adds a monohydrate alkali crystal protective agent into the chemical water of the heavy ash process and enters the hydration machine for careful hydration reaction, continuously or intermittently adds the monohydrate alkali crystal protective agent into the hydration machine, and controls the calcium and magnesium content in the product by reducing the magnesium ion concentration in the evaporation and absorption process, and can simultaneously control the particle size of the product, so that the particle size is more uniform and can meet the requirements, which is convenient for downstream use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a flow chart of adding a monohydrate crystal protective agent in the embodiment of the present application.

[0019] Among them, the reference numerals in the figure are:

[0020] 1- Storage tank, 2- Valve, 3- Filter, 4- Auxiliary agent pump, 5- Hydration machine. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0023] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0024] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0025] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0026] The weight of the relevant components mentioned in the examples of this application can not only refer to the specific content of each component, but also indicate the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application can be μg, mg, g, kg, etc.

[0027] The term "PET" is the abbreviation of "Polyethylene terephthalate", which means polyethylene terephthalate; the term "PU" is the abbreviation of "polyurethane", which means polyurethane material and is the abbreviation of polyurethane.

[0028] Example 1

[0029] In this embodiment, the contents of calcium and magnesium ions in the raw materials entering the heavy ash process are as follows: calcium: 5 mg / L, magnesium: 18-23 mg / L.

[0030] The preparation process of soda ash in this embodiment is:

[0031] The cold mother liquor from the carbonization process is transported by a pump to the lower part of the ammonia condenser at the top of the ammonia distillation tower in the distillation and absorption process, and is heat-exchanged with the distilled ammonia gas in the ammonia condenser to form a hot mother liquor. The hot mother liquor comes out from the upper part of the ammonia condenser and enters the upper part of the heating and decomposition section. The condensate produced by the distilled ammonia condenser and the condensate produced by the ammonia mixed gas main flow into the upper part of the distilled ammonia tower by gravity. The mother liquor and the condensate flow down in the tower by gravity, and are heated by the gas coming up from the lower part through the sieve plate, so that most of the free ammonia and almost all the carbon dioxide therein are evaporated. The preheated mother liquor flowing out from the bottom of the heating and decomposition section flows to the upper part of the pre-ash barrel by gravity, and is mixed with the lime milk sent from the ash-making station in the pre-ash barrel (the ammonia mud coming out from the bottom of the ammonia-salt clarification barrel is pumped into the D, E, and F pre-ash barrels by the ammonia mud pump), so that the ammonium chloride in the mother liquor reacts with calcium hydroxide to generate water, ammonia gas, and calcium chloride. Because the reaction is an exothermic reaction, part of the ammonia in the monohydrated ammonia will be decomposed. This part of the ammonia gas is mixed with the ammonia gas from the ash-adding and distillation section and introduced from the upper part of the pre-ash barrel into the bottom of the heating and decomposition section of the sieve plate ammonia distillation tower. The blending liquid in the pre-ash barrel (the blending liquid is the liquid phase mixture generated by the reaction of ammonium chloride and calcium hydroxide) is self-pressed from the lower part of the pre-ash barrel to the upper part of the ash-adding and distillation section by the liquid level height, and at the same time, the sand liquid at the bottom of the pre-ash barrel is transported to the upper part of the ash-adding and distillation section by the sand pump. In the ash-adding distillation section, the liquid contacts the steam from the bottom of the tower in countercurrent from top to bottom, and the ammonia in the liquid is evaporated. The waste liquid of the ammonia distillation tower enters the first-stage flasher from the bottom circle of the tower, and the liquid from the first-stage flasher enters the second-stage flasher. The waste liquid from the second flasher enters the waste liquid concentration tank and is discharged to the slag yard through the waste liquid pump. The first flash steam is connected to the corresponding pre-ash bucket outlet gas, and enters the bottom of the heating and decomposition section of the ammonia distillation tower together with the pre-ash bucket outlet gas; each second flash steam is collected to the second flash steam main pipe and finally sent to the bottom of the light liquid distillation tower as a heat source.

[0032] The exhaust steam sent from the compression process, the flash steam from the light ash condensate device and the low-pressure steam from the power plant enter the bottom of the ammonia evaporation tower as a heat source to distill the blending liquid from the upper part of the ash-adding distillation section; the outlet gas enters the upper part of the pre-ash barrel from the upper part of the ash-adding distillation section, mixes with the outlet gas from the pre-ash barrel and then enters the bottom of the heating decomposition section. This mixed steam distills the hot mother liquor from the upper part, and the ammonia mixed gas comes out from the top of the heating decomposition section and enters the top of the ammonia condenser, and then comes out from the bottom of the ammonia condenser and merges into the ammonia mixed gas main pipe to enter the ammonia cooler at the top of the internal cooling ammonia absorption tower for cooling. After cooling, it is sent to the 12th circle of the internal cooling ammonia absorption tower.

[0033] The replenished liquid ammonia enters the 11th circle of the internal cooling ammonia absorption tower. The ammonia mixed gas from the ammonia cooler enters the 12th circle of the internal cooling ammonia absorption tower. After being absorbed by the internal cooling ammonia absorption section and the ammonia washing section, the absorption tail gas is drawn out from the top of the tower 27th circle and enters the low vacuum ammonia purifier. The refined brine from the brine process enters the low vacuum ammonia purifier to wash the ammonia absorption tail gas to produce dilute ammonia brine. The dilute ammonia brine is pumped to the 26th circle of the internal cooling absorption tower to produce ammonia brine. The outlet gas after ammonia purification is then sent to the compression process or emptied on site through a low vacuum pump. The vacuum pump water seal comes from the washing water bucket, and the return water returns to the washing water bucket. The barrel area of ​​the ammonia brine clarification barrel is vacuumed, the dilute liquid storage barrel is vacuumed, and the barrel area of ​​the ammonia brine storage barrel is vacuumed and collected into a main pipe and sent to the 22nd circle of the internal cooling ammonia absorption tower or the 29th circle of the vacuum absorption tower.

[0034] The dilute ammonia brine from the carbonization is cooled by the dilute ammonia brine titanium plate heat exchanger and enters the 26th circle of the internal cooling ammonia absorption tower together with the dilute ammonia brine from the vacuum absorption tower. It passes through the 5 tower ring caps and 8 water tanks of the internal cooling ammonia absorption tower to absorb the ammonia vapor mixed gas and liquid ammonia. Finally, the qualified hot ammonia brine flows from the 11th circle of the tower to the hot ammonia brine clarification tank for clarification. After clarification, the finished ammonia brine is cooled to 38-42℃ by the hot ammonia brine titanium plate heat exchanger and stored in the cold ammonia brine clarification tank, and transported to the carbonization process by the cold ammonia brine pump.

[0035] The steam from the secondary flasher and the supplementary exhaust steam enter the lower part of the dilute liquid distillation section of the dilute liquid distillation tower. The light ash condensate and the condensate from the cooler at the top of the ammonia absorption tower enter the dilute liquid storage tank, are transported to the dilute liquid preheater by the dilute liquid pump, and are sent to the upper part of the dilute liquid distillation section after heat exchange with the waste dilute liquid. In the tower, they are heated from top to bottom by the steam coming up from the lower part of the dilute liquid distillation section, so that the ammonia and carbon dioxide in the condensate evaporate and enter the top condenser of the dilute liquid distillation tower. The cooled ammonia is sent to the top of the vacuum absorption tower. The waste dilute liquid at the bottom of the tower is sent to: a carbonization alkali filter (DN80) or light ash hot alkali liquid tank (DN100 main pipe is divided into two DN50 branches into 1# and 2# hot alkali liquid tanks), b salt water and miscellaneous water tank (DN100), c evaporation and absorption sulfur tank (DN50), d evaporation and absorption waste dilute liquid titanium plate heat exchanger (DN200); the waste dilute liquid is heat exchanged with circulating water in the waste dilute liquid titanium plate heat exchanger and then enters the washing water storage tank or compressed kiln gas washing tower. The water out of the washing water storage tank is sent to the evaporation and absorption vacuum pump (west side, DN100), the tail gas filtration ammonia purifier (east side, DN150), and the light ash furnace gas washing tower (middle position, DN150) through the washing water pump. If the load is low and it is not enough to open the dilute liquid distillation system, the dilute liquid in the dilute liquid tank is pumped to the carbonization cold mother liquor clarification tank by the dilute liquid pump. If the salinity index of the wash water is unqualified and the conditions for external delivery are not met, it needs to be sent to the D, E, and F pre-ash barrels through the ammonia-salt mud pipeline, or the high-salt wash water needs to be replaced to the kiln gas washing tower through the cold wash water pipeline to the washing tower, and the desalted water is added to the wash water barrel for replacement until the wash water index is qualified and the external delivery conditions are met. Stop the replacement and deliver normally; if the ammonia index of the low-load production wash water is too high, the wash water can be sent to the mother liquor barrel through the dilute liquid pipeline to recover ammonia. In addition, under low-load conditions, the dilute liquid system is not turned on. After a long period of circulation of the wash water, the salt and free ammonia will inevitably increase. The wash water at the outlet of the wash water pump can be sent to the dilute liquid preheater through the pipeline of the waste dilute liquid pump outlet, and finally sent to the salt water process or the light ash hot alkali liquid tank, so as to achieve the purpose of external delivery of wash water and water replacement.

[0036] The ammonia gas mixture from the dilute liquid distillation tower enters from the top 29th circle of the vacuum absorption tower, and the dilute ammonia brine enters the 28th circle of the tower. From top to bottom in the tower, the gas and liquid are absorbed in parallel. The tail gas after absorption is drawn out from the 14th circle of the vacuum absorption tower and enters the high vacuum ammonia purifier. After the ammonia is purified by the refined brine from the brine process in the high vacuum ammonia purifier, the outlet gas is sent to the compression process or emptied on the spot by the high vacuum pump. The dilute ammonia brine flowing down from the vacuum absorption tower is transported to the 26th circle of the internal cooling ammonia absorption tower together with the dilute ammonia brine from the high and low vacuum ammonia purifiers through the dilute ammonia brine pump.

[0037] The magnesium chloride is transported from the magnesium chloride yard to the root of the belt by a trolley, and then manually loaded onto the loading belt. The magnesium chloride is transported to the silo on the top of the magnesium adding tank by the magnesium adding belt, and then enters the magnesium adding tank through the flap below the silo. The refined brine / secondary water / hot waste dilute liquid and magnesium chloride in the magnesium adding tank are completely dissolved by stirring to form a magnesium chloride solution, which is then transported to the cold ammonia brine clarification tank by the magnesium adding pump.

[0038] The heavy alkali from the filtering station is distributed to the feeding screw conveyor of each furnace through the heavy alkali belt conveyor through the plow-shaped feeder, and then sent to the steam calcining furnace to mix with the return alkali at the head of the calcining furnace, and then calcined and decomposed in the calcining furnace. The heavy alkali is indirectly heated by medium-pressure steam in the furnace and decomposed to produce light ash and furnace gas. The light ash passes through the alkali outlet star feeder and enters the collective buried scraper conveyor to remove the heavy ash process.

[0039] The furnace gas generated by decomposition in the calcining furnace is separated and dusted by the furnace gas separator and then enters the hot alkali liquid tower. It is washed and heat-exchanged by the circulating hot alkali liquid from top to bottom, washing away most of the alkali dust in the furnace gas. When the concentration of the hot alkali liquid reaches a certain level, a small part of the hot alkali liquid is sent to the alkali tank of the heavy ash process through the hot alkali liquid pump, and most of it is circulated to wash the furnace gas pipeline. The furnace gas enters the furnace gas condensation tower again, where the furnace gas indirectly exchanges heat with the circulating water. Most of the water vapor in the furnace gas is condensed into water in the tower, and the condensate enters the condensate storage tank at the bottom of the tower, and then is sent to the evaporation and absorption process through the condensate pump (P0501AB) to evaporate the ammonia in the condensate. The condensed furnace gas enters the furnace gas washing tower, and after being washed with clean ammonia washing water, it is drawn out from the top of the furnace gas washing tower and sent to the compression process, while the furnace gas washing liquid is sent to the filtration process as washing water through the cold washing liquid pump (P0502AB).

[0040] The medium-pressure steam (3.6Mpa) from the heating center is cooled and reduced in pressure to 3.2Mpa, and enters the steam chamber from the central sleeve of the calcining furnace steam shaft, and is distributed to four rows of heating pipes from the steam chamber. The steam condensate enters the condensate storage tank from the outer sleeve of the steam shaft and then goes to the flasher. After flashing, the steam with a pressure of about 0.4MPa is sent to the low-pressure pipeline network, and the condensate returns to the heating center.

[0041] Simultaneous production process of light ash and heavy ash

[0042] The soda ash monohydrate from the hydration machine (R0601A-E) enters the calcining furnace (R0602A-E) through the feeding screw conveyor of the heavy ash calcining furnace. Under the indirect heating of 2.5MPa steam, the bound water is removed to obtain heavy soda ash. Part of it returns to the furnace head as alkali return, and the rest is taken out from the furnace head and enters the heavy ash buried scraper conveyor (L0604AB) through the heavy ash star feeder (M0601A-D) and is sent to the heavy ash cooling station.

[0043] Part of the light ash is screened by the light ash distribution scraper conveyor (L0602AB) and the light alkali screen (M0607), and the qualified ones enter the light ash cooling alkali furnace; the unqualified light ash with large particles is crushed by the crusher (M0605), and the crushed light ash enters the light ash cooling alkali furnace.

[0044] All production processes of light ash

[0045] Sometimes, according to market requirements, all light ash needs to be produced. In this case, a light ash cooling furnace obviously cannot meet the cooling requirements. Therefore, according to the actual situation, all light ash is produced. The process of producing all light ash is described as follows:

[0046] The light soda ash from the light ash process is sent to the light ash distribution buried scraper conveyor (L0602AB), part of which is removed from the alkali tank to prepare the soda ash solution, and part of which is sent to the packaging workshop through the light ash alkali screen and the light ash cooling furnace. The remaining light ash from the light ash section is sent to the heavy ash bucket elevator (L0605AB) through the heavy ash buried scraper conveyor (L0604AB), and the heavy ash distribution buried scraper conveyor (L0606AB). After being screened by the heavy alkali screen (M0602A-D), the soda ash enters the heavy powder flow cooler (F0601A-D). The cooled light soda ash is discharged from the discharge port of the heavy powder flow cooler (F0601A-D). The qualified light alkali is sent to the packaging workshop by the finished product heavy ash buried scraper conveyor (L0607AB), while the oversized particles are crushed by the crusher (M0603A-D) and sent to the heavy ash buried scraper conveyor (L0604AB) through the particle alkali buried scraper conveyor (L0608) for secondary screening.

[0047] In addition, the powder flow cooler system can be opened less or not at all according to the production load and the temperature of the light ash after cooling. The light ash is sent to the packaging process through the light ash distribution buried scraper conveyor (L0602AB), the heavy ash buried scraper conveyor (L0604AB), the heavy ash bucket elevator (L0605AB), the heavy ash distribution buried scraper conveyor (L0606AB) and the chute (SAH0637-PS3).

[0048] The desalted water from the external pipe network enters the heat exchange tube of the heavy alkali powder flow cooler (F0601A-D), exchanges heat with the high-temperature heavy alkali indirectly, and then returns to the soft water barrel.

[0049] The process flow of crystallization protective agent input: the solution in the crystallization protective agent solution storage tank in the heavy ash pump room passes through the crystallization protective agent filter, filters out impurities and then enters the crystallization protective agent pump, and is transported to the chemical water main on the second floor of the heavy ash through the crystallization protective agent pump, connected to the grid and integrated into the chemical water main, and then enters the hydration machine for hydration reaction.

[0050] The calcined furnace gas enters the furnace gas condensation tower after being washed by alkali liquid circulation, and is extracted by the furnace gas induced draft fan, and then emptied after the alkali liquid is removed by the demisting tank. The alkali liquid in the demisting tank enters the circulating washing tank. The condensed water after the furnace gas condenses enters the storage barrel at the bottom of the condensation tower and is sent to the hydration station by the condensed water pump.

[0051] 2.5MPa steam from the external pipe enters the calcining furnace, and after indirect heat exchange with monohydrate caustic soda, it becomes condensed water and enters the condensate tank and flasher. After flashing, 0.5MPa steam enters the 0.5MPa steam network, and the condensed water after flashing is sent to the condensate return network.

[0052] The monohydrated alkali protective agent involved in this embodiment is mixed with water before being mixed with the combined water, and the mass ratio of the monohydrated alkali protective agent to water is 1:1 to form a solution.

[0053] like Figure 1 As shown, the solution is filtered before the pump and then pumped into the combined water pipeline by the auxiliary pump, and then mixed with the combined water and enters the hydration machine.

[0054] Specifically, it includes: a storage tank 1 for storing a solution; the liquid outlet of the storage tank 1 is connected to an auxiliary agent pump 4, a filter 3 is also arranged between the auxiliary agent pump 4 and the storage tank 1, valves 2 are respectively arranged at both ends of the inlet and outlet of the filter 3, the liquid outlet end of the auxiliary agent pump 4 is connected to the liquid inlet end of a chemical combiner 5, the solution is mixed with chemical water in the chemical combiner 5, and then sent to the hydration machine.

[0055] The addition rate of the solution is 0.15-0.2 kg / ton of alkali, which is selected according to the amount of alkali fed into the hydration machine.

[0056] During the operation of the process, under the premise of ensuring the quality of heavy alkali products, the ammonia brine in the evaporation and absorption process begins to gradually remove magnesium, as follows:

[0057] Step 1: Reduce the original index from 18-22 mg / L to 14-18 mg / L and run for 30 hours.

[0058] Step 3: Distill and absorb the magnesium ion concentration of ammonia brine to 10-14 mg / L and run for 30 hours.

[0059] The soda ash products obtained by the evaporation process have a particle size of >180μm accounting for 85.87%, a particle size of greater than 1.18mm accounting for 3.24%, and a particle size of more than 2mm accounting for 0.82%. The calcium content in the soda ash product is 0.0033%, and the magnesium content is 0.0114%.

[0060] Before improvement: the magnesium ion index range of ammonia brine was 18-24 mg / L, the calcium content in the end product was 0.0033%, and the magnesium content was 0.0114%.

[0061] After improvement: the magnesium ion index range of ammonia brine is 12-15 mg / L, the calcium content in the final product is 0.00289%, and the magnesium content is 0.0045%.

[0062] Conclusion: The magnesium ion content of ammonia brine was relatively reduced by 6-9 mg / L, the calcium content in the end product was reduced by 0.00041%, and the magnesium content was reduced by 0.0069%.

[0063] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for reducing the calcium and magnesium contents in a soda ash product, characterized in that: In the process of preparing soda ash, a monohydrate crystal protective agent is added to the water in the heavy ash process and the water enters the hydration machine for hydration reaction.

2. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 1, characterized in that: The monohydrate alkaline crystal protective agent is dissolved in water to form a solution, and then mixed with the combined water.

3. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 2, characterized in that: The mass ratio of the monohydrate alkali crystal protective agent to water is 0.8-1.2:

1.

4. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 2, characterized in that: The mass ratio of the monohydrate alkali crystal protective agent to water is 1:

1.

5. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 1, characterized in that: The amount of the monohydrate alkali crystal protective agent added is determined by the calcium and magnesium content in the heavy ash raw material and the magnesium ion concentration in the ammonia brine in the evaporation and absorption process.

6. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 5, characterized in that: After the evaporation and absorption process is completed, the magnesium ion concentration is 10-14 mg / L.

7. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 5, characterized in that: In the soda ash product, the proportion of particles with a particle size greater than 180 μm is greater than 80%, the proportion of particles with a particle size greater than 1.18 mm is less than 4%, and the proportion of particles with a particle size greater than 2 mm is less than 1%.

8. The method for reducing the calcium and magnesium contents in a soda ash product according to claim 5, characterized in that: The calcium content of the soda ash product is less than 0.0033%, and the magnesium content is less than 0.0114%.

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