Method and device for producing baking soda

Abstract

The invention provides a method and device for producing baking soda, and the method for producing baking soda comprises the following steps: adding a solid raw material (sodium bicarbonate and / or light ash) into a slurry tank, and mixing with filtrate from a filtrate barrel to obtain raw material slurry; the raw material slurry enters a heat recovery tower, and solids in the raw material slurry are dissolved under the high-temperature condition in the heat recovery tower. The dissolved solution enters a stripping tower, and the solid raw materials are completely dissolved in the stripping tower. The steam stripping liquid enters a carbonization tower and is subjected to a synthetic reaction with carbon dioxide to generate sodium bicarbonate solid. Carbonization liquid enters a thickener, part of clear liquid on the upper portion of the thickener enters a filtrate barrel, and crystal mush on the lower portion of the thickener is conveyed to a solid-liquid separator. And separating the crystal mush by a solid-liquid separator to obtain solid sodium bicarbonate crystals and filtrate, and feeding the solid sodium bicarbonate crystals to a drying process to obtain baking soda. According to the method, the sodium bicarbonate is directly used as the raw material, investment and operation of a calcination process and a clarification and filtration process are avoided, and the method has the advantages of low energy consumption and low production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and specifically to a method and device for producing sodium bicarbonate. Background Art

[0002] In the industrial production process of applying sodium bicarbonate (sodium hydrogen carbonate), such as in detergents, food additives, feed additives, pharmaceutical raw materials, ore dressing, metal smelting, etc., with the progress of technology, requirements for the production of sodium bicarbonate have been put forward, especially less energy consumption, particularly less steam consumption, long-term stable production, and less maintenance. Meeting the requirements of low cost, long-term stability, and few operating and maintenance personnel has become the development direction of the sodium bicarbonate industry. In the context of the era that increasingly emphasizes energy conservation, consumption reduction, emission reduction, and environmental protection, developing a more energy-saving and environmentally friendly method for producing sodium bicarbonate has great economic and social benefits.

[0003] Heavy soda ash: A solid raw material mainly composed of sodium bicarbonate (a multi-component substance containing sodium carbonate and / or ammonium bicarbonate, etc.) (commonly known as heavy soda ash, and the general composition is shown in the following table).

[0004] General composition of heavy soda ash (other compositions are not listed):

[0005]

[0006] Light soda ash: A solid product mainly composed of sodium carbonate (a multi-component substance containing sodium chloride, etc.) (i.e., industrial sodium carbonate, commonly known as light soda ash, and the general composition is shown in the following table).

[0007] General composition of industrial sodium carbonate (other compositions are not listed):

[0008]

[0009] Sodium bicarbonate: A solid product mainly composed of sodium bicarbonate (a multi-component substance containing sodium chloride, etc.) (industrial sodium bicarbonate, commonly known as sodium bicarbonate, and the general composition is shown in the following table). General composition of industrial sodium bicarbonate (other compositions are not listed):

[0010]

[0011] High-pressure steam: Pressure 2.0 - 5.0 MPa.

[0012] Medium-pressure steam: Pressure 1.0 - 1.5 MPa.

[0013] Low-pressure steam: Pressure 0.3 - 0.5 MPa.

[0014] Inert gas: A gas that does not react with sodium carbonate, such as inexpensive and easily available gases like nitrogen and air.

[0015] Industrial gas: a gas containing carbon dioxide, with the concentration of carbon dioxide generally being 40 - 90% (by volume percentage).

[0016] The conventional method for producing sodium bicarbonate mainly involves high-temperature decomposition of heavy soda ash (commonly known as the calcination process) to produce light ash, and then carbonation reaction with carbon dioxide to produce sodium bicarbonate. This method requires high-temperature decomposition, a large rotary device for calcination, and a complex solid transfer device for transporting solid light ash. It has the disadvantages of high production cost, high consumption of high-pressure steam, high investment, high maintenance cost, complex operation, a large number of maintenance workers, a long process flow, a large number of equipment, and high power consumption. The high-pressure steam consumption in the calcination process of producing light ash from heavy soda ash is 1100 - 1300 kg / t (calculated based on light ash), and 770 - 910 kg / t (calculated based on sodium bicarbonate).

[0017] The conventional production method for preparing sodium bicarbonate by carbonation uses light ash as the raw material, mixes it with the filtrate from the solid-liquid separator in the alkali dissolving tank, and passes steam under stirring conditions to promote the dissolution of sodium carbonate (commonly known as the alkali dissolving process). The alkali solution in the alkali dissolving tank is sent to a large-scale clarification and filtration process to obtain a clear alkali solution. The alkali solution enters the carbonation synthesis process to react with carbon dioxide to form sodium bicarbonate crystals, and after filtration, drying, and packaging, the sodium bicarbonate finished product is obtained. This method requires large-scale clarification equipment and complex filtration equipment with high operation difficulty. It has the disadvantages of high production cost, high consumption of medium-pressure steam, high investment, high maintenance cost, complex operation, a large number of maintenance workers, a long process flow, a large number of equipment, and large heat loss. The drawbacks brought by this method are: high steam consumption during the dissolution process of sodium carbonate. The steam consumption for dissolving alkali in general factories is 250 - 500 kg / t of sodium bicarbonate, and in some individual factories, it exceeds 700 kg / t of sodium bicarbonate. The high-pressure steam consumption for producing light ash from heavy soda ash is 770 - 910 kg / t (calculated based on sodium bicarbonate), the medium-pressure steam consumption for the alkali dissolving process when producing sodium bicarbonate from light ash is 250 - 500 kg / t (calculated based on sodium bicarbonate), and the total steam consumption for the calcination process and alkali dissolving process using heavy soda ash as the raw material is 1000 - 1400 kg / t (calculated based on sodium bicarbonate). In the context of increasingly tight energy and environmental protection, this method urgently needs to be changed. Summary of the Invention

[0018] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides a method and device for producing sodium bicarbonate. Using the present invention can avoid the investment and operation of the calcination process, clarification, and filtration processes, and has the advantages of small energy consumption (especially steam), short process flow, and low production cost.

[0019] The technical solution provided by the present invention: A method for producing sodium bicarbonate, comprising the following steps:

[0020] (1) Solid raw materials are added to the slurry tank and mixed with the filtrate from the filtrate barrel to obtain a raw material slurry. The solid raw materials are heavy soda ash, light soda ash, or a mixture of both.

[0021] (2) The raw material slurry enters the heat recovery tower. The high-temperature stripping tower tail gas from the stripping tower enters the heat recovery tower from the lower part and contacts the raw material slurry entering the heat recovery tower from the upper part in a countercurrent manner. The solids (heavy soda ash, or light soda ash, or a mixture of heavy soda ash and light soda ash) in the raw material slurry dissolve under high-temperature conditions in the heat recovery tower.

[0022] (3) The dissolved solution enters the stripping tower, and sodium bicarbonate in the dissolved solution undergoes a decomposition reaction under high-temperature conditions in the stripping tower to form sodium carbonate.

[0023] (4) The stripped liquid enters the carbonation tower and undergoes a synthesis reaction with carbon dioxide in the industrial gas entering the carbonation tower from the lower part of the carbonation tower to form sodium bicarbonate.

[0024] (5) The carbonated liquid enters the thickener. Part of the clear liquid in the upper part of the thickener enters the filtrate barrel, and the crystal slurry in the lower part of the thickener is sent to the solid-liquid separator.

[0025] (6) The crystal slurry is separated by the solid-liquid separator to obtain solid sodium bicarbonate crystals and filtrate. The solid sodium bicarbonate crystals are sent to the drying process, and the dried sodium bicarbonate obtained is the target product, baking soda. The filtrate separated by the solid-liquid separator containing a small amount of escaped crystals is sent to the enrichment barrel.

[0026] (7) The filtrate containing a small amount of escaped crystals enters the enrichment barrel. Part of the clear liquid in the upper part of the enrichment barrel enters the filtrate barrel, and the crystal slurry in the lower part of the enrichment barrel is sent to the thickener.

[0027] (8) The clear liquid from the thickener and the clear liquid from the enrichment barrel enter the filtrate barrel to obtain filtrate. The filtrate in the filtrate barrel is sent to the slurry tank and mixed with the raw material solids to obtain a raw material slurry, completing the liquid cycle. The main components in the filtrate are nearly saturated sodium bicarbonate and unreacted sodium carbonate.

[0028] Furthermore, the temperature range of the raw material slurry is 45 - 90 °C. The raw material slurry mainly contains solid raw materials (heavy soda ash and / or light soda ash), liquid-phase sodium bicarbonate, and liquid-phase sodium carbonate. The mass ratio of the separately used heavy soda ash raw material to the water in the raw material slurry ranges from 1:4 to 9, and the mass ratio of the separately used light soda ash raw material to the water in the raw material slurry ranges from 1:8 to 13.

[0029] Further, ammonium bicarbonate in the raw slurry of dense soda decomposes under the high-temperature condition in the heat recovery tower. The decomposed ammonia and carbon dioxide enter the tail gas recovery process along with the tail gas, and no such reaction occurs with light soda ash raw materials. The raw materials are dissolved at the bottom of the heat recovery tower to obtain a dissolved solution. The dissolved solution mainly contains incompletely dissolved solid raw materials (dense soda ash and / or light soda ash), liquid-phase sodium bicarbonate, liquid-phase sodium carbonate, and incompletely decomposed ammonium bicarbonate (when dense soda ash is used as the raw material). The residence time of the dissolved solution in the heat recovery tower ranges from 30 to 300 min, and the internal temperature of the heat recovery tower ranges from 45 to 120 °C.

[0030] Further, sodium bicarbonate in the dissolved solution (sodium bicarbonate brought in by the dense soda ash raw materials and the filtrate) decomposes to form sodium carbonate under the high-temperature condition in the stripping tower. This reaction is controlled by the carbon dioxide partial pressure, so it is necessary to reduce the carbon dioxide partial pressure to promote the progress of this decomposition reaction. The heat medium (low-pressure steam or a mixture of low-pressure steam and inert gas) enters the stripping tower from the lower part of the stripping tower, reducing the carbon dioxide partial pressure in the solution while providing heat. The solid raw materials (dense soda ash and / or light soda ash) are completely dissolved in the stripping tower. After stripping, a stripped solution is obtained at the bottom of the stripping tower. The stripped solution mainly contains liquid-phase sodium carbonate and liquid-phase sodium bicarbonate. The residence time of the stripped solution in the stripping tower ranges from 30 to 300 min, and the internal temperature of the stripping tower ranges from 70 to 150 °C.

[0031] Further, the stripped solution enters the carbonation tower and undergoes a synthesis reaction with carbon dioxide in the industrial gas entering the carbonation tower from the lower part of the carbonation tower to form solid sodium bicarbonate. This reaction is controlled by the carbon dioxide partial pressure, so it is necessary to increase the carbon dioxide partial pressure to promote the progress of this synthesis reaction. The unreacted industrial gas is discharged from the top of the carbonation tower and sent to the tail gas treatment process. After synthesis, a carbonated solution is obtained at the bottom of the carbonation tower. The carbonated solution mainly contains solid sodium bicarbonate crystals, liquid-phase sodium bicarbonate, and liquid-phase sodium carbonate. The residence time of the carbonated solution in the carbonation tower ranges from 30 to 300 min; the internal temperature of the carbonation tower ranges from 40 to 110 °C.

[0032] Further, when using dense soda ash raw materials, the low-pressure steam consumption of the stripping tower (equivalent to the calcination process and the alkali dissolution process of dense soda ash) is 400 - 550 kg / t (calculated based on sodium bicarbonate).

[0033] As a conventional method for comparison: the total steam consumption of the calcination process and the alkali dissolution process using dense soda ash as the raw material is 1000 - 1400 kg / t (calculated based on sodium bicarbonate), and the steam is high-pressure and medium-pressure respectively.

[0034] Further, when using light soda ash raw materials, the low-pressure steam consumption of the stripping tower (equivalent to the alkali dissolution process of light soda ash) is 100 - 200 kg / t (calculated based on sodium bicarbonate).

[0035] Conventional method for comparison: When producing sodium bicarbonate using light ash as raw material, the medium-pressure steam consumption in the causticizing process is 250 - 500 kg / t (calculated based on sodium bicarbonate), and the steam is medium-pressure.

[0036] Another technical solution provided by the present invention: A device for producing sodium bicarbonate, comprising a slurry tank, a heat recovery tower, a stripping tower, a carbonation tower, a thickener, a solid-liquid separator, an enrichment tank, and a filtrate tank connected in sequence;

[0037] The bottom discharge port of the slurry tank is connected to the upper feed port of the heat recovery tower through a pipeline, the lower discharge port of the heat recovery tower is connected to the upper feed port of the stripping tower through a pipeline, the lower discharge port of the stripping tower is connected to the upper feed port of the carbonation tower through a pipeline, the tail gas outlet at the top of the stripping tower is connected to the lower inlet of the heat recovery tower through a pipeline, the discharge port of the carbonation tower is connected to the feed port of the thickener through a pipeline, the upper discharge port of the thickener is connected to the upper feed port of the filtrate tank through a pipeline, the bottom discharge port of the thickener is connected to the feed port of the solid-liquid separator through a pipeline, the solid discharge port of the solid-liquid separator is connected to the sodium bicarbonate drying process through a chute, the liquid discharge port of the solid-liquid separator is connected to the feed port of the enrichment tank through a pipeline, the upper discharge port of the enrichment tank is connected to the upper feed port of the filtrate tank through a pipeline, the bottom discharge port of the enrichment tank is connected to the feed port of the thickener through a pipeline, and the discharge port of the filtrate tank is connected to the feed port of the slurry tank through a pipeline.

[0038] Further, the tail gas outlet at the top of the heat recovery tower is connected to the tail gas recovery process through a pipeline, and the tail gas outlet at the top of the carbonation tower is connected to the tail gas treatment process through a pipeline.

[0039] Further, two inlets are provided on each side at the lower part of the stripping tower, one of which is an inert gas inlet and the other is a steam inlet. When low-pressure steam is directly provided from outside the system, the discharge port of the steam main pipe is connected to the steam inlet of the stripping tower through a pipeline, the inert gas is provided from outside the system, and the discharge port of the inert gas main pipe is connected to the inert gas inlet of the stripping tower through a pipeline.

[0040] Further, the slurry tank is a thickener, a clarification tank, a mixer, a stirring device or a combination thereof, and the solid-liquid separator is a belt vacuum filter, a rotary drum vacuum filter, a disc filter, a plate and frame filter press, a centrifuge or a sedimentation tank.

[0041] The present invention can adjust the amounts (temperature, mass flow rate, concentration, solubility) of sodium carbonate and sodium bicarbonate in the stripping liquid and the amount (temperature, flow rate, concentration) of the heat medium entering the stripping tower according to the amount (temperature, mass flow rate, concentration, solubility) of the reaction liquid discharged from the carbonation tower. The amounts (temperature, mass flow rate, concentration) of sodium carbonate and sodium bicarbonate in the stripping liquid can be adjusted according to different temperatures, solubilities, and amounts (temperature, mass flow rate, concentration) of the liquid in the stripping tower.

[0042] The present invention has the following beneficial effects compared with the prior art:

[0043] A method and device for producing sodium bicarbonate according to the present invention directly uses heavy soda as a raw material, avoiding the investment and operation of the calcination process, and circumventing the disadvantages of high production cost, high consumption of high-pressure steam, high investment, high maintenance and repair cost, complex operation, many maintenance workers, long process flow, many equipment, and high power consumption in the calcination process.

[0044] A method and device for producing sodium bicarbonate according to the present invention avoid the investment and operation of the clarification and filtration processes, and circumvent the disadvantages of high production cost, high consumption of medium-pressure steam, high investment, high maintenance and repair cost, complex operation, many maintenance workers, long process flow, many equipment, and large heat loss in the clarification process and the filtration process.

[0045] A method and device for producing sodium bicarbonate according to the present invention, through reasonable process settings, make full use of the physical and chemical properties of the raw materials, and use low-cost low-pressure steam to realize the use of heavy soda raw materials.

[0046] A method and device for producing sodium bicarbonate according to the present invention, through reasonable process settings, make full use of the heat of the tail gas to heat the low-temperature raw materials, realizing the cascade utilization of energy. First, the stripping tower uses the heat of low-pressure steam to complete the decomposition reaction and dissolution. Second, the heat recovery tower uses the heat of the stripping tower tail gas to complete heating and dissolution.

[0047] A method and device for producing sodium bicarbonate according to the present invention change the traditional conveying method of solid materials, use liquid to convey solid materials, reducing investment, reducing failure points, and reducing floor space.

[0048] The process flow of the present invention is short, the number of equipment is small, the energy consumption is small, the production cost is low, the liquid is used to convey materials, the floor space is small, the failure points are few, the production is long-term, the production is stable, the operation is simple, and the management is convenient. Brief Description of the Drawings

[0049] Figure 1 is a schematic diagram of Embodiment 1 of the present invention;

[0050] Figure 2 is a schematic diagram of Embodiment 2 of the present invention;

[0051] Figure 3 is a schematic diagram of Embodiment 3 of the present invention;

[0052] In the figure: 1—slurry tank, 2—heat recovery tower, 3—stripping tower, 3-1—steam inlet, 3-2—inert gas inlet, 4—carbonation tower, 5—thickener, 6—solid-liquid separator, 7—enrichment bucket, 8—filtrate bucket. Detailed Embodiments

[0053] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0054] Embodiment 1

[0055] A method for producing sodium bicarbonate, the specific steps are as follows: Solid raw materials (heavy soda raw materials) are added to a slurry tank and mixed with the filtrate from a filtrate barrel to obtain a raw material slurry; the raw material slurry contains solid raw materials; the solid raw materials in the slurry tank are mainly mixed, secondly, a small amount of dissolution occurs, and thirdly, a trace amount of decomposition occurs. The raw material slurry enters a heat recovery tower, and the solid raw materials in the raw material slurry mainly recover the heat of the stripping tower tail gas in the heat recovery tower, secondly, the dissolution of the solid raw materials is promoted by this heat, and thirdly, the decomposition of ammonium bicarbonate and / or sodium bicarbonate is promoted by this heat; the carbon dioxide and / or ammonia generated by the decomposition enter the recovery process with the tail gas. The dissolved liquid mainly contains incompletely dissolved solid raw materials, liquid-phase sodium bicarbonate, liquid-phase sodium carbonate, and incompletely decomposed ammonium bicarbonate (using heavy soda as the raw material). The dissolved liquid enters a stripping tower, and in the stripping tower, the dissolved liquid mainly decomposes sodium bicarbonate and / or ammonium bicarbonate, and secondly, makes a small amount of solid raw materials in the dissolved liquid completely dissolve; the carbon dioxide and / or ammonia generated by the decomposition enter the heat recovery tower with the tail gas. The stripped liquid mainly contains liquid-phase sodium carbonate and liquid-phase sodium bicarbonate. The stripped liquid enters a carbonation tower and undergoes a synthesis reaction with the carbon dioxide in the industrial gas entering the carbonation tower from the lower part of the carbonation tower to generate solid sodium bicarbonate. Secondly, the supersaturation is controlled to continuously grow the crystal size of sodium bicarbonate; the unreacted carbon dioxide enters the treatment process with the tail gas. The carbonated liquid mainly contains solid sodium bicarbonate crystals, liquid-phase sodium bicarbonate, and liquid-phase sodium carbonate. The carbonated liquid enters a thickener, and a part of the clear liquid in the upper part of the thickener enters the filtrate barrel, and the crystal slurry in the lower part of the thickener is sent to a solid-liquid separator. The crystal slurry is separated by the solid-liquid separator to obtain solid sodium bicarbonate crystals and filtrate. The solid sodium bicarbonate crystals are sent to the drying process, and the obtained dried sodium bicarbonate is the target product sodium bicarbonate. The filtrate containing a small amount of escaped crystals separated by the solid-liquid separator is sent to an enrichment barrel. The filtrate containing a small amount of escaped crystals enters the enrichment barrel, and a part of the clear liquid in the upper part of the enrichment barrel enters the filtrate barrel, and the crystal slurry in the lower part of the enrichment barrel is sent to the thickener. The clear liquid from the thickener and the clear liquid from the enrichment barrel enter the filtrate barrel to obtain filtrate, and the filtrate from the filtrate barrel is sent to the slurry tank and mixed with the raw material solids to obtain a raw material slurry, completing the liquid cycle.

[0056] As Figure 1A device for producing sodium bicarbonate is shown, with the raw material being heavy soda ash. Low-pressure steam enters the stripping tower 3, and industrial gas with a concentration of 40% enters the carbonation tower 4. A device for producing sodium bicarbonate includes a slurry tank 1, a heat recovery tower 2, a stripping tower 3, a carbonation tower 4, a thickener 5, a solid-liquid separator 6, an enrichment bucket 7, and a filtrate bucket 8, which are connected in sequence. The bottom discharge port of the slurry tank 1 is connected to the feed port at the upper part of the heat recovery tower 2 through a pipeline. The discharge port at the lower part of the heat recovery tower 2 is connected to the feed port at the upper part of the stripping tower 3 through a pipeline. The tail gas outlet at the top of the heat recovery tower 3 is connected to the tail gas recovery process through a pipeline. The discharge port at the lower part of the stripping tower 3 is connected to the feed port at the upper part of the carbonation tower 4 through a pipeline. The tail gas outlet at the top of the stripping tower 3 is connected to the lower feed port of the heat recovery tower 2 through a pipeline. The discharge port of the carbonation tower 4 is connected to the feed port of the thickener 5 through a pipeline. The tail gas outlet at the top of the carbonation tower 4 is connected to the tail gas treatment process through a pipeline. The discharge port at the upper part of the thickener 5 is connected to the feed port at the upper part of the filtrate bucket 8 through a pipeline. The discharge port at the bottom of the thickener 5 is connected to the feed port of the solid-liquid separator 6 through a pipeline. The solid discharge port of the solid-liquid separator 6 is connected to the sodium bicarbonate drying process through a chute. The liquid discharge port of the solid-liquid separator 6 is connected to the feed port of the enrichment bucket 7 through a pipeline. The discharge port at the upper part of the enrichment bucket 7 is connected to the feed port at the upper part of the filtrate bucket 8 through a pipeline. The discharge port at the bottom of the enrichment bucket 7 is connected to the feed port of the thickener 5 through a pipeline. The discharge port of the filtrate bucket 8 is connected to the feed port of the slurry tank 1 through a pipeline.

[0057] The device for producing sodium bicarbonate further includes a steam process. When low-pressure steam is provided from outside the system, those skilled in the art should pay attention to the water balance of the system and control water expansion. When low-pressure steam is generated by heating the dissolution liquid, stripping liquid or filtrate inside the system, those skilled in the art should pay attention to the water balance of the system and control water contraction. There are two inlets on each side at the lower part of the stripping tower. One is the inert gas inlet 3-2, and the other is the steam inlet 3-1. When low-pressure steam is directly provided from outside the system, the outlet of the steam main pipe is connected to the steam inlet 3-1 of the stripping tower through a pipeline. When low-pressure steam is generated by indirectly heating the dissolution liquid, stripping liquid or filtrate sent to the steam process through a heat transfer wall in the steam process outside the system; when steam is generated from the dissolution liquid, the outlet at the lower part of the heat recovery tower 2 is connected to the inlet of the steam process through a pipeline, the outlet of the steam process is connected to the inlet at the upper part of the stripping tower 3 through a pipeline, and the steam outlet of the steam process is connected to the steam inlet 3-1 at the lower part of the stripping tower 3 through a pipeline. When steam is generated from the stripping liquid, the outlet at the lower part of the stripping tower 3 is connected to the inlet of the steam process through a pipeline, the outlet of the steam process is connected to the inlet at the upper part of the carbonation tower 4 through a pipeline, and the steam outlet of the steam process is connected to the steam inlet 3-1 at the lower part of the stripping tower 3 through a pipeline. When steam is generated from the filtrate, the outlet at the lower part of the filtrate tank 8 is connected to the inlet of the steam process through a pipeline, the outlet of the steam process is connected to the inlet at the upper part of the slurry tank 1 through a pipeline, and the steam outlet of the steam process is connected to the steam inlet 3-1 at the lower part of the stripping tower 3 through a pipeline. Preferably, steam is generated from the stripping liquid. The main body of the steam generating device can be a boiler, hot water furnace, heater, water heater, molten salt furnace, organic heat carrier furnace, waste incinerator or three-waste co-combustion furnace, etc.; the low-temperature heat medium entering and leaving the steam process is low-pressure steam, high-temperature hot water, molten salt or heat-conducting oil, hot air and other heat media.

[0058] The device for producing sodium bicarbonate further includes an inert gas system. Inert gas is generally provided from outside the system. The outlet of the inert gas main pipe is connected to the inert gas inlet 3-2 of the stripping tower through a pipeline.

[0059] The device for producing sodium bicarbonate further includes an industrial gas process. Industrial gas is generally provided from outside the system. The outlet of the industrial gas main pipe is connected to the industrial gas inlet at the lower part of the carbonation tower 4 through a pipeline.

[0060] The temperature range of the raw material slurry is 65°C, the mass ratio range of the separately used heavy soda raw material to the water in the raw material slurry is 1:6, the residence time range of the dissolution liquid in the heat recovery tower is 200 min, and the temperature range inside the heat recovery tower is 105°C.

[0061] The residence time of the stripping liquid in the stripping tower ranges from 220 min, and the temperature inside the stripping tower ranges from 125 °C. The residence time of the carbonated liquid in the carbonation tower ranges from 150 min; the temperature inside the carbonation tower ranges from 90 °C.

[0062] Example 2

[0063] As Figure 2 shown, a device for producing sodium bicarbonate, with light ash as the raw material, low-pressure steam enters the stripping tower 3, and at the same time nitrogen enters the stripping tower 3, and industrial gas with a concentration of 90% enters the carbonation tower; other contents of the device are the same as those in Example 1.

[0064] Specific control conditions for the method of producing sodium bicarbonate: the temperature range of the raw material slurry is 85 °C, the mass ratio of the separately used light ash raw material to the water in the raw material slurry ranges from 1:8, the residence time of the dissolving liquid in the heat recovery tower ranges from 120 min, and the temperature inside the heat recovery tower ranges from 95 °C.

[0065] The residence time of the stripping liquid in the stripping tower ranges from 120 min, and the temperature inside the stripping tower ranges from 115 °C. The residence time of the carbonated liquid in the carbonation tower ranges from 120 min; the temperature inside the carbonation tower ranges from 100 °C.

[0066] Example 3

[0067] As Figure 3 shown, a device for producing sodium bicarbonate, with heavy soda ash and light ash as the raw materials, the mass ratio of heavy soda ash to light ash is 9:1, low-pressure steam enters the stripping tower 3, and industrial gas with a concentration of 60% enters the carbonation tower; other contents of the device are the same as those in Example 1.

[0068] Specific control conditions for the method of producing sodium bicarbonate: the temperature range of the raw material slurry is 80 °C, the mass ratio of heavy soda ash and light ash to the water in the raw material slurry ranges from 1:7, the residence time of the dissolving liquid in the heat recovery tower ranges from 150 min, and the temperature inside the heat recovery tower ranges from 100 °C.

[0069] The residence time of the stripping liquid in the stripping tower ranges from 150 min, and the temperature inside the stripping tower ranges from 120 °C. The residence time of the carbonated liquid in the carbonation tower ranges from 135 min; the temperature inside the carbonation tower ranges from 95 °C.

[0070] The present invention avoids the production method in which heavy soda ash is decomposed into light ash at high temperature by a large rotary device and conveyed by a cumbersome solid transfer device, then the light ash is dissolved with high-price high-pressure steam (causticization process), and clear caustic liquor is produced through a large clarification device (clarification process) and a large filtration device (filtration process), and then the caustic liquor reacts with carbon dioxide to form sodium bicarbonate. The production method of the present invention has low production cost, small energy consumption (especially steam), short process flow, and few equipment.

[0071] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes made without departing from the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for producing sodium bicarbonate, characterized in that, It includes the following steps: (1) Add the solid raw material into the slurry tank and mix it with the filtrate from the filtrate bucket to obtain the raw material slurry. The solid raw material is heavy soda ash or light soda ash or a mixture of both. (2) The raw material slurry enters the heat recovery tower. The high-temperature stripping tower tail gas from the stripping tower enters the heat recovery tower from the lower part and contacts the raw material slurry entering the heat recovery tower from the upper part in countercurrent. The solid in the raw material slurry dissolves under the high-temperature condition in the heat recovery tower. (3) The dissolved solution enters the stripping tower, and sodium bicarbonate in the dissolved solution undergoes a decomposition reaction under the high-temperature condition in the stripping tower to generate sodium carbonate. (4) The stripping solution enters the carbonation tower and undergoes a synthesis reaction with carbon dioxide in the industrial gas entering the carbonation tower from the lower part of the carbonation tower to generate sodium bicarbonate. (5) The carbonated liquid enters the thickener. Part of the clear liquid in the upper part of the thickener enters the filtrate bucket, and the crystal slurry in the lower part of the thickener is sent to the solid-liquid separator. (6) The crystal slurry is separated by the solid-liquid separator to obtain solid sodium bicarbonate crystals and filtrate. The solid sodium bicarbonate crystals are sent to the drying process, and the obtained dried sodium bicarbonate is the target product baking soda. The filtrate separated by the solid-liquid separator containing a small amount of escaped crystals is sent to the enrichment bucket. (7) The filtrate containing a small amount of escaped crystals enters the enrichment bucket. Part of the clear liquid in the upper part of the enrichment bucket enters the filtrate bucket, and the crystal slurry in the lower part of the enrichment bucket is sent to the thickener. (8) The clear liquid from the thickener and the clear liquid from the enrichment bucket enter the filtrate bucket to obtain filtrate. The filtrate in the filtrate bucket is sent to the slurry tank and mixed with the raw material solid to obtain the raw material slurry, completing the liquid circulation.

2. A method for producing sodium bicarbonate according to claim 1, characterized in that, The temperature range of the raw material slurry is 45 - 90 °C. The mass ratio range of the separately used heavy soda ash raw material to the water in the raw material slurry is 1:4 - 9, and the mass ratio range of the separately used light soda ash raw material to the water in the raw material slurry is 1:8 - 13.

3. A method for producing sodium bicarbonate according to claim 1, characterized in that: The residence time range of the dissolved solution in the heat recovery tower is 30 - 300 min, and the temperature range inside the heat recovery tower is 45 - 120 °C.

4. A method for producing sodium bicarbonate according to claim 1, characterized in that: The residence time range of the stripping solution in the stripping tower is 30 - 300 min, and the temperature range inside the stripping tower is 70 - 150 °C.

5. A method for producing sodium bicarbonate according to claim 1, characterized in that: The residence time range of the carbonated liquid in the carbonation tower is 30 - 300 min; the temperature range inside the carbonation tower is 40 - 110 °C.

6. A method for producing sodium bicarbonate according to claim 1, characterized in that: When using the heavy soda ash raw material, based on baking soda, the low-pressure steam consumption of the stripping tower is 400 - 550 kg / t.

7. A method for producing sodium bicarbonate according to claim 1, characterized in that: When using the light soda ash raw material, based on baking soda, the low-pressure steam consumption of the stripping tower is 100 - 200 kg / t.

8. An apparatus for producing sodium bicarbonate, which is implemented by the method according to any one of claims 1-7, characterized in that, It includes a slurry tank (1), a heat recovery tower (2), a stripping tower (3), a carbonation tower (4), a thickener (5), a solid-liquid separator (6), an enrichment bucket (7), and a filtrate bucket (8) connected in sequence. The bottom discharge port of the slurry tank (1) is connected to the feed port at the upper part of the heat recovery tower (2) through a pipeline. The discharge port at the lower part of the heat recovery tower (2) is connected to the feed port at the upper part of the stripping tower (3) through a pipeline. The tail gas outlet at the top of the heat recovery tower (2) is connected to the tail gas recovery process through a pipeline. The discharge port at the lower part of the stripping tower (3) is connected to the feed port at the upper part of the carbonation tower (4) through a pipeline. The tail gas outlet at the top of the stripping tower (3) is connected to the lower inlet of the heat recovery tower (2) through a pipeline. The discharge port of the carbonation tower (4) is connected to the feed port of the thickener (5) through a pipeline. The tail gas outlet at the top of the carbonation tower (4) is connected to the tail gas treatment process through a pipeline. The discharge port at the upper part of the thickener (5) is connected to the feed port at the upper part of the filtrate tank (8) through a pipeline. The discharge port at the bottom of the thickener (5) is connected to the feed port of the solid-liquid separator (6) through a pipeline. The solid discharge port of the solid-liquid separator (6) is connected to the sodium bicarbonate drying process through a chute. The liquid discharge port of the solid-liquid separator (6) is connected to the feed port of the enrichment tank (7) through a pipeline. The discharge port at the upper part of the enrichment tank (7) is connected to the feed port at the upper part of the filtrate tank (8) through a pipeline. The discharge port at the bottom of the enrichment tank (7) is connected to the feed port of the thickener (5) through a pipeline. The discharge port of the filtrate tank (8) is connected to the feed port of the slurry tank (1) through a pipeline.

9. The device for producing sodium bicarbonate according to claim 8, characterized in that, Two inlets are respectively arranged on both sides at the lower part of the stripping tower (3), one of which is an inert gas inlet (3-2), and the other is a steam inlet (3-1). When low-pressure steam is directly provided from outside the system, the discharge port of the steam main pipe is connected to the steam inlet (3-1) of the stripping tower through a pipeline. The inert gas is provided from outside the system, and the discharge port of the inert gas main pipe is connected to the inert gas inlet (3-2) of the stripping tower through a pipeline.

10. The device for producing sodium bicarbonate according to claim 8, characterized in that, The slurry tank (1) is a thickener, a clarifying tank, a mixer, a stirring device or a combination thereof. The solid-liquid separator (6) is a belt vacuum filter, a rotary drum vacuum filter, a disc filter, a plate and frame filter press, a centrifuge or a sedimentation tank.

Images