CN114408949B - Low-salt or ultra-low-salt sodium carbonate production process and device - Google Patents
Low-salt or ultra-low-salt sodium carbonate production process and device Download PDFInfo
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- CN114408949B CN114408949B CN202210096662.8A CN202210096662A CN114408949B CN 114408949 B CN114408949 B CN 114408949B CN 202210096662 A CN202210096662 A CN 202210096662A CN 114408949 B CN114408949 B CN 114408949B
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- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
- C01D7/18—Preparation by the ammonia-soda process
Abstract
The invention provides a low-salt or ultra-low-salt sodium carbonate production process and a device, which are based on the existing sodium carbonate production process, perform secondary ammonia absorption, secondary salt addition and secondary carbonization on primary mother liquor from a sodium carbonate filter, solve the problems of penetration loss and dissolution loss caused by semi-finished heavy alkali solid-liquid separation and product salt control in the sodium carbonate production process, reduce the mother liquor equivalent in the sodium carbonate production ammonia circulation process, improve the utilization rate of raw material salt, reduce material consumption and energy consumption, and simultaneously solve the influence of temperature change on sodium carbonate production. The invention produces low-salt or ultra-low-salt sodium carbonate products, improves the quality of sodium carbonate products, reduces the material consumption and energy consumption in the production process, simultaneously reduces the discharge amount of waste liquid, improves the concentration of calcium chloride in the waste liquid, and reduces the production cost of calcium chloride recovered from the waste liquid.
Description
Technical Field
The invention relates to a production process and a device for producing low-salt or ultra-low-salt sodium carbonate products by controlling sodium chloride content of sodium carbonate product quality indexes without increasing material consumption and energy consumption.
Background
GB210.1-2004 requires that the sodium chloride content (salt for short) of the sodium carbonate class II superior product is less than 0.7%, the salt index requirement of customers on the sodium carbonate product in the production process of an actual sodium carbonate enterprise is controlled to be about 0.4%, partial high-end customers require low-salt sodium carbonate products with the salt content lower than 0.2% or ultra-low-salt sodium carbonate products with the salt content lower than 0.1% in the sodium carbonate, the control of the salt content of the sodium carbonate generally washes semi-finished sodium carbonate by washing water without salt in the production process, the salt content of the sodium carbonate products is controlled by controlling the washing water quantity, and washing water after washing the salt content enters a mother liquor system, so that on one hand, partial product dissolution loss is caused, on the other hand, the salt consumption and steam consumption are increased, and the equivalent of waste liquid is increased. Because of the four seasons, the temperature of the circulating water is high in summer, the cooling of the carbonization process is difficult, the crystallization quality of the product is poor, the carbonization conversion rate is low, the equivalent of the mother solution is large, the utilization rate of the primary salt is low, and the loss of the produced low-salt product is larger. The low-salt or ultra-low-salt sodium carbonate production process has no loss in the process of controlling the salt content of the product, is not influenced by the environmental temperature in four seasons, can stably produce low-salt or ultra-low-salt sodium carbonate products, improves the added value of the sodium carbonate products, improves the product competitiveness of enterprises, meets the quality requirements of high-end customers on the low-salt or ultra-low-salt sodium carbonate products, reduces the discharge amount of waste liquid and waste residues, reduces the material consumption and energy consumption, reduces the carbon emission, and has better economic benefit and social benefit.
The low-salt or ultra-low-salt sodium carbonate product is applied to the glass industry, can improve the quality of glass products, produce high-grade glass products, improve the added value of the glass products, and prolong the service life of a glass kiln. At present, the soda ash production by the synthesis method mainly comprises an ammonia-soda process and a combined soda process, and the low-salt or ultra-low-salt soda ash product produced by the ammonia-soda process has larger influence on yield, material consumption and energy consumption, greatly increases the production cost and increases the waste liquid treatment capacity; the combined soda process can not produce low-salt products and can not produce ultra-low-salt products due to the need of mother liquor balance, solves the problems existing in the production of low-salt or ultra-low-salt sodium carbonate, and simultaneously solves the influence of environmental temperature change on the production of sodium carbonate.
In the existing soda production process, mining underground salt mine containing low sodium chloride or preparing brine by using sodium chloride raw salt with sodium chloride content of more than 95% to obtain nearly saturated crude brine, refining the nearly saturated crude brine with concentration of more than 105 titer (5.25 mol/L) by a lime soda ash method, removing a small amount of calcium and magnesium ions in the crude brine to obtain refined brine, absorbing ammonia recovered from mother liquor by the refined brine to obtain ammonia brine with molar concentration ratio of ammonia to sodium chloride of 1.13-1.19, delivering the ammonia brine to a carbonization process, taking one of a group of four to six carbonization towers as a cleaning tower, adding ammonia brine and cleaning gas (containing about 40% of CO) into the carbonization cleaning tower 2 ) Cleaning alkali scar formed during alkali preparation of the carbonization tower, pre-carbonizing ammonia water to obtain neutralization water, rotating the cleaning tower every 18-24 hr to obtain neutralization water, and delivering the neutralization water to carbonA carbonization alkali-making tower, wherein middle-stage gas (containing about 40% of carbon dioxide) is introduced into the middle lower part of the carbonization alkali-making tower, and lower-stage gas (containing more than 80% of CO) is introduced into the lower part of the carbonization alkali-making tower 2 ) The alkali liquor containing sodium bicarbonate crystal is obtained and sent to a filtering procedure, solid-liquid separation is carried out by an alkali filtering machine, so as to obtain heavy alkali mainly containing sodium bicarbonate, the heavy alkali contains less than 20 percent of water, washing is carried out by water without salt, so as to obtain heavy alkali with sodium chloride content lower than 0.35 percent, and the heavy alkali is sent to a calcining procedure for calcination so as to obtain light sodium carbonate product, and meanwhile, CO-containing product is obtained 2 Furnace gas with concentration of more than 80 percent is washed, cooled and compressed to obtain CO 2 And (3) carrying out carbonization process to prepare alkali at the lower section with the concentration of 80%, and further processing part of the light sodium carbonate product to obtain a heavy sodium carbonate product. And (3) delivering the mother liquor from the alkali filtering machine to a steaming and sucking process, steaming out most of free ammonia and carbon dioxide in a preheating section of a distillation tower, adding lime milk (containing 155-170 titer of calcium hydroxide) into the preheated mother liquor which mainly contains ammonium chloride and does not participate in alkali preparation reaction sodium chloride at about 90 ℃, steaming out most of ammonia by steam after the ammonium chloride reacts with the lime milk, cooling the obtained ammonia gas, absorbing the ammonia gas by refined brine, delivering the obtained ammonia water to a carbonization process for alkali preparation, and simultaneously obtaining calcium chloride waste liquor containing about 10% for calcium chloride production or environmental protection treatment. Sieving outsourced limestone (calcium carbonate content is more than 90%), obtaining qualified raw materials with granularity of 50-120mm and coke (25-50 mm), delivering the qualified raw materials to a lime kiln according to a certain proportion, introducing air into the bottom of the lime kiln, and calcining the limestone by heat generated by burning the coke in the lime kiln to obtain quicklime calcium oxide and CO-containing lime 2 About 40% of kiln gas is digested by adding water into lime milk with calcium hydroxide concentration of 155-170 titer, ammonia is recovered by distillation process, and the produced kiln gas is subjected to dust removal, cooling and compression to obtain the product containing CO 2 The middle gas and the cleaning gas with the concentration of 40 percent are respectively sent to the carbonization process for preparing alkali.
Disclosure of Invention
The invention discloses a method for preparing ammonia brine by secondary ammonia absorption, salt addition and secondary carbonization of primary mother liquor from an alkali filter, wherein alkali liquor obtained by secondary carbonization is thickened to obtain clear liquid which is secondary mother liquor, the secondary mother liquor with stable concentration of ammonium chloride is sent to an original evaporation and absorption process to replace the primary mother liquor to recycle ammonia for preparing ammonia brine, the thickened alkali liquor and the primary alkali liquor are subjected to solid-liquid separation together to obtain a filter cake with washing water washing control salt content, and the obtained sodium carbonate product salt content can be stably controlled to be less than 0.1% or 0.2%, so that the quality requirement of a high-end customer product is met, the original salt utilization rate is improved, the problem of filtration loss in the sodium carbonate industry is solved, and the problems of heavy alkali dissolution loss, mother liquor expansion and the like of a semi-finished product caused by adding excessive washing water control product salt content are solved.
The invention relates to a low-salt or ultra-low-salt sodium carbonate production process which comprises the following steps:
(1) Refined brine (NaCl content greater than 304g/l, calcium and magnesium content less than 15 mg/l) absorbs ammonia gas to form ammonia water (molar concentration ratio of ammonia salt, for example, 1.13-1.19:1, preferably 1.14-1.18:1), ammonia water and CO 2 Entering a primary carbonization tower for reaction to generate primary alkali liquor, preferably controlling CO 2 The volume flow of the gas and the volume flow of the ammonia brine are controlled to control the internal tower pressure of the carbonization tower to be 290-330KPa, preferably 300-325KPa, and the middle reaction temperature to be 55-75 ℃, preferably 60-70 ℃;
(2) The primary alkali liquor discharged from the primary carbonization tower enters an alkali filtering machine for solid-liquid separation to obtain semi-finished heavy alkali and primary mother liquor;
(3) The primary mother liquor (generally containing 65-72 titer of ammonium chloride) from an alkali filter is firstly sent to a carbonization tail gas ammonia cleaning tower to wash ammonia in carbonization tail gas (one or more of a primary carbonization alkali preparation tower, a primary carbonization cleaning tower, a secondary carbonization alkali preparation tower and a secondary carbonization cleaning tower), then sent to a high vacuum absorption tower (vacuum degree-30 to-60 KPa, preferably-40 kPa to-50 kPa) to absorb ammonia (ammonia is preferably ammonia condensate obtained by cooling ammonia gas distilled from a distillation tower through a cooler and ammonia condensate obtained by cooling calciner gas, the ammonia condensate enters ammonia gas recovered by a weak liquor distillation tower, and the other part of ammonia gas is supplemented by ammonia recovered by secondary mother liquor distillation) to obtain ammonia mother liquor (free ammonia is ammonia mother liquor with 40-55 titer, the temperature is 40-55 ℃), the ammonia mother liquor is sent to a salt dissolving bucket (salt adding bucket), and refined raw salt sodium chloride is added to obtain the molar ratio of free ammonia to sodium chloride is 1.03-1.1:1, further sending the ammonia salt mother liquor of 1.05-1.09 into a secondary carbonization tower, and reacting with carbon dioxide to obtain secondary alkali liquor, wherein the temperature of the middle part of an alkali production tower of the secondary carbonization tower is, for example, 40-60 ℃, preferably 42-58 ℃, preferably 45-55 ℃, preferably 48-52 ℃ and the temperature of the alkali liquor, for example, 33-45 ℃, preferably 34-43 ℃, preferably 35-40 ℃, preferably 36-39 ℃;
(4) And (3) conveying the secondary alkali liquor to a thickener for thickening treatment, returning the thick alkali liquor (containing 30% -50% of sodium bicarbonate crystals) from the bottom of the thickener to an alkali filtering machine in the step (2), carrying out solid-liquid separation together with the primary alkali liquor to obtain a heavy alkali filter cake with reduced salt content after washing with water, and calcining the heavy alkali filter cake to obtain a low-salt or ultra-low-salt sodium carbonate product, wherein the upper part of the thickener is provided with secondary mother liquor.
In the application, the following components are added:
titer: concentration specific units of solution in soda ash production process, titer = molar concentration of a certain solute in solution x valence x 20.
Low salt sodium carbonate: sodium chloride content of less than 0.2wt% sodium carbonate product.
Ultra-low salt sodium carbonate: sodium chloride content of less than 0.1wt% sodium carbonate product.
In the step (4), washing the sodium carbonate with washing water (such as washing water without salt) on an alkali filter to remove most sodium chloride, and controlling the sodium chloride content in the sodium carbonate to be lower than 0.1% or 0.05% by controlling the water washing amount to ensure that the sodium chloride content of a final sodium carbonate product is lower than 0.2% or 0.1%, thereby meeting the quality requirement of a low-salt or ultra-low-salt sodium carbonate product.
Further, the secondary mother liquor obtained in the step (4) is sent to a distillation process for distillation treatment, and the secondary mother liquor is heated to 88-92 ℃ in a preheating section of a distillation tower to remove most of CO in the mother liquor 2 Adding lime milk, adding ammonia gas distilled from steam into a distillation tower, cooling in a cooler, delivering cooled ammonia gas (55-65 ℃) into a low vacuum absorption tower (vacuum degree-10 to-20 kPa), and absorbing with refined brine to generate ammonia brine (a primary carbonization cleaning tower and a primary carbonization alkali preparation tower); the condensate of the cooler and the condensate of the furnace gas are sent to a thin liquid distillation tower (vacuum degree-40 to-60 kpa) for distillation, and the ammonia gas distilled from the thin liquid distillation tower is sent to high vacuum absorptionAnd (3) a tower. The distilled waste liquid of the distillation tower is subjected to primary flash (vacuum degree-10 to-20 kPa), primary flash steam is returned to the distillation tower, primary flash distilled waste liquid is subjected to secondary flash (vacuum degree-40 to-60 kPa), secondary flash steam is sent to the thin liquid distillation tower, and secondary flash waste liquid is subjected to environmental protection treatment. The above steps may be performed as in the prior art method.
Further, the primary carbonization tower comprises a primary carbonization cleaning tower and a primary carbonization alkali preparation tower, and the secondary carbonization tower comprises a secondary carbonization tower and a secondary carbonization alkali preparation tower. In the primary carbonization tower, ammonia brine firstly enters a primary carbonization cleaning tower to contain CO 2 Gas cleaning, and the obtained neutralized ammonia water enters a primary carbonization alkali-making tower and contains CO 2 And (3) carrying out gas reaction to obtain primary alkali liquor. In the secondary carbonization tower, the ammoniacal salt mother liquor firstly enters a secondary carbonization cleaning tower to contain CO 2 Gas cleaning, and the obtained neutralized ammonia salt mother liquor enters a secondary carbonization alkali-making tower and contains CO 2 And (3) carrying out gas reaction to obtain secondary alkali liquor. And in the primary carbonization cleaning tower, the primary carbonization alkali preparation tower, the secondary carbonization tower and the secondary carbonization alkali preparation tower, generated carbonization tail gas is discharged from the top of the carbonization tower.
The secondary carbonization tower is similar to the primary carbonization tower process, namely, the primary carbonization tower process, 4-6 carbonization towers are arranged in each group, one tower is a cleaning tower, the other towers are alkali-making towers, and the ammonia salt mother liquor (200-500 m 3 And/h) firstly feeding the mixture into a secondary carbonization cleaning tower and feeding the mixture into 2000-5000m 3 CO-containing per hour 2 Purge gas (e.g., 40% + -10%, preferably about 40% CO) 2 Cleaning gas), cleaning alkali scars formed during alkali production of a secondary carbonization tower, pre-carbonizing an ammonia salt mother liquor at the same time, cleaning for 18-24 hours, cleaning alkali scars formed during alkali production in the carbonization tower, changing the alkali production tower into an alkali production tower after recovering the production capacity of the carbonization tower, obtaining a cleaned ammonia salt mother liquor which is called a neutralization ammonia salt mother liquor, controlling the carbon dioxide to be 35-50 titer, sending the neutralization ammonia salt mother liquor to the secondary carbonization alkali production tower, and controlling the ammonia salt mother liquor flow and alkali discharge liquid flow of each secondary carbonization tower to be 50-140m 3 Introducing CO-containing gas into the lower part of the secondary carbonization tower 2 (e.g., 80.+ -. 10%, further about 80% CO) 2 ) The lower gas (same source as the primary carbonization tower) is 1500-3000m 3 /h, in a carbonizerThe lower part is introduced with carbon dioxide (for example, 40% + -10%, preferably about 40% CO) 2 ) 2000-6000m of middle gas (same source as primary carbonization tower) 3 And (3) h, obtaining secondary alkali liquor containing 10-20% of sodium bicarbonate crystals at the temperature of 35-40 ℃, sending the secondary alkali liquor to a thickener, sending the thick alkali liquor containing 30-50% of sodium bicarbonate crystals from the bottom of the thickener, further for example, sending the thick alkali liquor of 35-45% to an alkali filter, carrying out solid-liquid separation together with the primary alkali liquor, washing a filter cake to obtain semi-finished heavy alkali with qualified sodium chloride content, further processing the semi-finished heavy alkali into a low-salt or ultra-low-salt light sodium carbonate product, obtaining clear liquid overflowed from the upper part of the thickener as secondary mother liquor, sending the ammonium chloride content of the secondary mother liquor to about 86 titer, and recycling ammonia in a distillation process.
The secondary mother liquor ammonium chloride is sent to a distillation process, the existing production process can be adopted in the distillation process, the concentration of ammonium chloride in the primary mother liquor can be changed due to the fact that the washing water is added into the primary mother liquor by controlling the salt content of the product, the concentration of ammonium chloride in the secondary mother liquor can be stabilized at about 86 titer, the volume ratio of the secondary mother liquor to the lime milk is controlled to be 1.8-1.95 according to the concentration of calcium hydroxide in the lime milk, and the gray milk amount is only required to be finely adjusted according to the change of the calcium hydroxide concentration in the lime process, so that the calcium hydroxide content index in the waste liquid of the distillation tower is kept stable.
The refined brine can be obtained by the following steps: mining underground salt mine containing low-nitrate sodium chloride and/or preparing brine by using sodium chloride raw salt with sodium chloride content of more than 95% to obtain nearly saturated crude brine, refining by a lime soda ash method (adding proper amount of soda ash liquid and lime milk according to the content of calcium and magnesium in the brine and settling) to remove calcium and magnesium ions in the crude brine, thereby obtaining refined brine (the content of calcium and magnesium is lower than 15mg/L, and the content of NaCl is higher than 304 g/L).
Further, the refined brine absorbs ammonia gas recovered from mother liquor distillation to obtain a molar concentration ratio of ammonia to sodium chloride of 1.13-1.19:1, and delivering the ammonia brine to a carbonization tower in a carbonization process to obtain alkali liquor containing sodium bicarbonate.
A group of four to six carbonization towers of the normal carbonization tower, wherein one carbonization tower is used as a cleaning tower, and ammonia brine are added into the carbonization cleaning towerPurge gas (containing about 40% CO) 2 ) Cleaning alkali scars formed during alkali preparation of the carbonization tower, pre-carbonizing ammonia water to obtain neutralization water, rotating the cleaning tower every 18-24 hours, delivering the neutralization water from the cleaning tower to the carbonization alkali preparation tower, and introducing middle-section gas (containing about 40% CO) into the middle lower part of the carbonization alkali preparation tower 2 ) And lower part is introduced into lower section gas (containing about 80% CO) 2 ) The primary alkali liquor containing sodium bicarbonate crystal is obtained.
The primary alkali liquor from the primary carbonization tower and the thick alkali liquor from the secondary carbonization tower enter an alkali filter for solid-liquid separation to obtain heavy alkali mainly containing sodium bicarbonate, wherein the heavy alkali contains less than 20 percent of water, the heavy alkali is washed by water without salt, the water washing quantity is controlled to obtain heavy alkali with sodium chloride content lower than 0.1 percent or 0.05 percent, and the heavy alkali is sent to a calcination procedure for calcination to obtain a light sodium carbonate product, and meanwhile, the light sodium carbonate product containing CO is obtained 2 Furnace gas with concentration of more than 80 percent is washed, cooled and compressed to obtain CO 2 And (3) carrying out carbonization process to prepare alkali at the lower section with the concentration of about 80%, and further processing part of the light sodium carbonate product to obtain a heavy sodium carbonate product.
In order to improve the crystallization quality of the primary carbonization tower, preferably, the temperature of the alkali liquor discharged from the primary carbonization tower is increased from the existing index of 27-32 ℃ to 35-40 ℃, the utilization rate of crude salt is improved through secondary carbonization, and the primary carbonization is not required to pursue carbonization conversion rate, so that the crystallization quality of the alkali liquor discharged from the carbonization is improved, the crystallization in the alkali liquor is prevented from being thinned due to the fact that the carbonization tower is cooled too rapidly, the salt is convenient to control, meanwhile, the water content of heavy alkali is reduced, and the calcination steam consumption of heavy alkali in a calciner is reduced.
The invention further provides a low-salt or ultra-low-salt sodium carbonate production device, which comprises:
a low vacuum absorption tower, a primary carbonization cleaning tower, a primary carbonization alkali-making tower, an alkali filter, a carbonization tail gas ammonia cleaning tower, a high vacuum absorption tower, a salt adding barrel, a secondary carbonization cleaning tower, a secondary carbonization alkali-making tower, a thickener, a distillation tower, a calciner, a cooler and a light liquid distillation tower,
wherein, the low vacuum absorption tower is provided with a distillation tower ammonia gas feeding pipe and a refined brine feeding pipe, the discharge port of the low vacuum absorption tower is connected with the feed port of the primary carbonization cleaning tower through a middle buffer barrel and a pump, the carbon dioxide feeding pipe is also connected with the feed port of the primary carbonization cleaning tower, the liquid outlet of the primary carbonization cleaning tower is connected with the feed port of the primary carbonization alkali making tower through a pump, preferably, the primary carbonization tower (the primary carbonization alkali making tower and the primary carbonization cleaning tower) is provided with a middle section gas, a lower section gas and a cleaning gas carbon dioxide feed port,
the liquid outlet of the primary carbonization alkali preparation tower is connected with the feed inlet of the alkali filter through an alkali outlet buffer tank, the solid material outlet of the alkali filter is connected with the inlet of the calciner through a heavy alkali belt, the furnace gas outlet of the calciner is connected with the first cooler, and the gas outlet of the first cooler is connected with the gas inlets of the primary carbonization alkali preparation tower and the secondary carbonization alkali preparation tower through a compressor;
The primary mother liquor outlet of the alkali filtering machine is connected with the liquid feeding port of the carbonization tail gas ammonia purifying tower through a pipeline, a mother liquor buffer barrel and a pump, the gas feeding port of the carbonization tail gas ammonia purifying tower is also connected with the tail gas outlet of the primary carbonization tower and the tail gas outlet of the secondary carbonization tower (the secondary carbonization alkali making tower and the secondary carbonization cleaning tower) through a pipeline, the washing liquid outlet of the carbonization tail gas ammonia purifying tower is connected with the inlet of the high vacuum absorption tower through the pump, the inlet of the high vacuum absorption tower is also connected with the ammonia feeding pipe from the ammonia gas feeding pipe of the thin liquid distillation tower and/or the distillation tower (after the ammonia distilled out of the distillation tower is cooled through a cooler), the liquid outlet of the high vacuum absorption tower is connected with the inlet of the salt adding barrel through the pump, the salt adding barrel outlet is connected with the inlet of the secondary carbonization cleaning tower through the ammonia salt buffer barrel and the pump, the washing gas feeding pipe is also connected with the inlet of the secondary carbonization cleaning tower, the liquid outlet of the secondary carbonization cleaning tower is connected with the inlet of the secondary carbonization alkali making tower through the pump, the liquid outlet of the secondary carbonization alkali making tower is connected with the inlet of the thick liquid outlet of the thick liquid, the thick liquid outlet of the thick liquid is connected with the thick liquid inlet of the thick liquid absorption tower through the pump, the bottom outlet of the thick liquid absorption tower is also connected with the inlet of the thin liquid filtering alkali machine, the upper part outlet of the thick liquid is connected with the thin liquid inlet of the thin liquid distillation tower, the upper part of the thin liquid distillation tower is connected with the gas inlet of the thin liquid distillation tower, the thin liquid inlet is also connected with the thin liquid inlet of the thin liquid tower is connected with the thin liquid inlet of the thin liquid tower, and the thin liquid inlet is connected with the thin liquid inlet of the thin liquid tower, and the thin liquid.
THE ADVANTAGES OF THE PRESENT INVENTION
1. The salt content of the sodium carbonate product can be stably controlled to be below 0.1% or 0.2%, so that the quality requirement of high-end customer products is met, and the added value and market competitiveness of the sodium carbonate product can be improved.
2. Reducing the equivalent of mother liquor and waste liquid by 1m 3 Above/t alkali, the steam consumption is reduced, the stone consumption, the coke consumption and the ammonia consumption are reduced, the calcium chloride concentration of the clear waste liquid is improved, the production cost of calcium chloride is reduced, and the environmental protection treatment difficulty of the waste liquid is reduced.
3. The carbonization conversion rate is not required to be excessively pursued, the utilization rate of crude salt is improved by adopting a secondary carbonization process, the carbonization crystallization quality is improved by controlling the carbonization reaction temperature, the water content of heavy alkali is reduced, and the steam consumption of a calciner is reduced.
4. The production process is not affected by the change of the environmental temperature, the salt content of the product is controlled according to the requirements of customers, the production is not affected, and the annual soda ash yield and consumption are relatively stable.
5. And the mother liquor is used for washing the carbonized tail gas and the absorbed tail gas, and then the purified brine is used for washing, so that the ammonia purifying effect of the carbonized tail gas is improved, and the environmental protection level of enterprises is further improved.
6. The system interface is not influenced in the transformation process of the old soda enterprises, and partial carbonization tower, tail gas ammonia purifying tower, absorption tower, salt dissolving barrel, thickener and other matched equipment are added according to the production scale, so that the investment is low, the production capacity of the device is improved by more than 20%, the utilization rate of raw materials is improved, the potential of the whole device is excavated, and the production efficiency of the soda device is improved.
Drawings
FIG. 1 is a process flow diagram of one embodiment of the present application including primary mother liquor ammonia absorption, salt formation, carbonization, thickening.
Fig. 2 is a flow chart of a complete process of the inventive arrangement.
Detailed Description
The application is further illustrated by the following examples in connection with the accompanying drawings. In the present application,% is generally weight percent unless otherwise specified.
As shown in fig. 1 and 2, the low-salt or ultra-low-salt soda ash production device of the present application comprises:
the device comprises a low vacuum absorption tower, a primary carbonization cleaning tower, a primary carbonization alkali preparation tower, an alkali filter, a carbonization tail gas ammonia purification tower, a high vacuum absorption tower, a salt adding barrel, a secondary carbonization cleaning tower, a secondary carbonization alkali preparation tower, a thickener, a distillation tower, a calciner, a cooler and a light liquid distillation tower.
The low vacuum absorption tower is provided with a distillation tower ammonia gas feeding pipe and a refined brine feeding pipe, a discharge port of the low vacuum absorption tower is connected with a feeding port of a primary carbonization cleaning tower through an intermediate buffer barrel and a pump, a liquid outlet of the primary carbonization cleaning tower is connected with a feeding port of a primary carbonization alkali preparation tower through the pump, a liquid outlet of the primary carbonization alkali preparation tower is connected with a feeding port of an alkali filter through an alkali outlet buffer groove, a solid material outlet of the alkali filter is connected with an inlet of a calciner through a heavy alkali belt, a furnace gas outlet of the calciner is connected with a first cooler, and a gas outlet of the first cooler is connected with a gas inlet of the primary alkali preparation tower and a gas inlet of a secondary alkali preparation tower through a compressor;
The primary mother liquor outlet of the alkali filtering machine is connected with the liquid feeding port of the carbonization tail gas ammonia purifying tower through a pipeline, a mother liquor buffer barrel and a pump, the gas feeding port of the carbonization tail gas ammonia purifying tower is also connected with the tail gas outlet of the primary carbonization tower and the tail gas outlet of the secondary carbonization tower through pipelines, the washing liquid outlet of the carbonization tail gas ammonia purifying tower is connected with the inlet of the high vacuum absorption tower through the pump, the inlet of the high vacuum absorption tower is also connected with the ammonia feeding pipe from the thin liquid distillation tower and/or the ammonia feeding pipe of the distillation tower (after the ammonia distilled out from the distillation tower is cooled by a cooler), the liquid outlet of the high vacuum absorption tower is connected with the inlet of the salt adding barrel through the pump, the salt adding barrel outlet is connected with the inlet of the secondary carbonization cleaning tower through the ammonia salt buffer barrel and the pump, the liquid outlet of the secondary carbonization cleaning tower is also connected with the inlet of the secondary carbonization cleaning tower through the pump, the liquid outlet of the secondary carbonization cleaning tower is connected with the inlet of the secondary carbonization alkali preparing tower, the liquid outlet of the secondary carbonization alkali tower is connected with the inlet of the thick liquid outlet of the thick liquid thickener, the bottom outlet of the thick liquid thickener is connected with the inlet of the thick liquid filter, the upper outlet of the thick liquid is connected with the ammonia feeding pipe of the distillation tower (after the distilled out of the ammonia is cooled by the cooling tower), the liquid outlet of the thin liquid is also connected with the gas inlet of the thin liquid distillation tower, the thin liquid is connected with the gas inlet of the thin liquid distillation tower is connected with the gas inlet of the thin liquid.
In the application, the secondary mother liquor from the thickener is sent to the original distillation tower, and the modification process does not affect the production of the existing device except the interfaces of ammonia gas, mother liquor, carbon dioxide gas and the original system. The salt washing water dosage is controlled by increasing the alkali filtering machine, the product salt is controlled to produce low-salt or ultra-low-salt sodium carbonate products, primary mother liquor is subjected to secondary ammonia absorption, salt addition and carbonization, the alkali outlet temperature of a primary carbonization alkali preparation tower is increased to 35-40 ℃, the problems that the primary carbonization environment temperature influences the alkali preparation conversion rate of sodium chloride, the added washing water is lost in semi-finished product washing, the secondary mother liquor is a thickener overflow liquid, the product salt washing water is added to the alkali filtering machine, the secondary mother liquor is not fed into the product salt washing water, the problems that the cost is greatly increased, the waste liquid treatment difficulty is high and the like are solved.
Example 1
The method comprises the steps of mining underground salt mine containing low-nitrate sodium chloride to obtain nearly saturated crude brine with the concentration of more than 105 titer (5.25 mol/L), refining by a lime soda ash method (adding a proper amount of soda ash liquid and lime milk according to the content of calcium and magnesium in the brine, and performing sedimentation treatment) to remove a small amount of calcium and magnesium ions in the crude brine to obtain refined brine (the content of calcium and magnesium is lower than 15mg/L and NaCl is higher than 304 g/L).
The refined brine absorbs ammonia gas to obtain ammonia brine (molar concentration ratio of ammonia salt is 1.13-1.19:1), the ammonia brine enters a primary carbonization cleaning tower, and compressed CO containing 40% is introduced 2 The obtained neutralized ammonia water enters a primary carbonization alkali-making tower and contains CO 2 Gas reaction, one-time carbonization alkali preparation tower is introduced with CO from compression 2 Middle gas and CO with concentration of 40% 2 Generating a primary alkali liquor from the lower gas with the concentration of 80%;
the primary alkali liquor from the primary carbonization tower enters an alkali filter for solid-liquid separation, washing the heavy alkali on the alkali filter with washing water without salt to remove most sodium chloride in a filter cake, controlling the sodium chloride content in the heavy alkali to be lower than 0.1%, and enabling the sodium chloride content of a final sodium carbonate product to be lower than 0.1%, thereby meeting the quality requirements of low-salt or ultra-low-salt sodium carbonate products.
The primary mother liquor (containing 65-72 titer of ammonium chloride) from the alkali filtering machine is firstly sent to an ammonia purifying tower of tail gas of carbonization tower to wash ammonia in carbonization tail gas, then sent to a high vacuum absorption tower to absorb ammonia (ammonia in condensate recovered from a thin solution distillation tower is supplemented by ammonia recovered by distillation of secondary mother liquor), ammonia mother liquor (ammonia mother liquor with free ammonia of 40-55 titer and temperature of 40-55 ℃) is obtained, the ammonia mother liquor is sent to a salt dissolving tank, refined raw salt sodium chloride is added, the ammonia salt mother liquor with mole ratio of free ammonia to sodium chloride of 1.03-1.1 is obtained and sent to a secondary carbonization cleaning tower, and CO-containing ammonia salt mother liquor is introduced 2 About 40% purge gas, the resulting neutralized ammoniacal salt mother liquor with 40% CO 2 Middle gas and containing 80% CO 2 And (3) reacting the lower gas to obtain secondary alkali liquor.
The secondary carbonization tower is similar to the primary carbonization tower process, namely, the primary carbonization tower process, wherein each group of carbonization towers has 4 towers, one tower is a cleaning tower, the other towers are alkali-making towers, and ammonia salt mother liquor is firstly sent into the secondary carbonization cleaning tower and is led into the tower with the length of about 3500m 3 Cleaning gas (same source as the primary carbonization tower) per hour, cleaning alkali scar formed during alkali preparation of the secondary carbonization tower, pre-carbonizing ammonia salt mother liquor, cleaning for 18-24 hours, recovering production capacity of the carbonization tower, changing into an alkali preparation tower, obtaining the cleaned ammonia salt mother liquor which is called as neutralization ammonia salt mother liquor, controlling carbon dioxide at 35-50 titer, sending the neutralization ammonia salt mother liquor to the secondary carbonization alkali preparation towers, and controlling ammonia salt mother liquor flow and alkali outlet liquid flow of each secondary carbonization tower to be about 100m 3 Introducing CO-containing gas into the lower part of the secondary carbonization tower 2 About 80% or more of the lower gas (of the same origin as the primary carbonization tower) is about 2000m 3 Introducing CO into the middle and lower part of the carbonization tower 2 About 40% of the middle gas (same source as the primary carbonization tower) is about 3000m 3 And (3) h, obtaining secondary alkali liquor containing 10-20% of sodium bicarbonate crystals at the temperature of 35-40 ℃, conveying the secondary alkali liquor to a thickener, conveying the thick alkali liquor containing 30-50% of sodium bicarbonate crystals out of the bottom of the thickener to an alkali filtering machine, carrying out solid-liquid separation together with the primary alkali liquor, and washing a filter cake to obtain sodium chloride The semi-finished product caustic soda with qualified content is further processed into low-salt or ultra-low-salt sodium carbonate products by calcination, the clear liquid overflowed from the upper part of the thickener is called secondary mother liquor, the ammonium chloride content of the secondary mother liquor reaches about 86 titer, and ammonia is recovered by a distillation process.
The secondary mother liquor is sent to a distillation process, the existing production process can be adopted in the distillation process, the ammonium chloride concentration in the primary mother liquor can be changed due to the fact that the washing water is added into the primary mother liquor by controlling the salt content of the product, the ammonium chloride concentration in the secondary mother liquor can be stabilized at about 86 titer, the volume ratio of the secondary mother liquor to the lime milk is controlled to be 1.8-1.95 according to the calcium hydroxide concentration in the lime milk, and the lime milk amount is only required to be finely adjusted according to the calcium hydroxide concentration change in the lime process, so that the calcium hydroxide content index in the waste liquid of the distillation tower is kept stable. The distillation process comprises heating the secondary mother liquor in a preheating section of a distillation tower to 88-92 ℃ to remove most of CO in the mother liquor 2 Adding lime milk, delivering ammonia gas recovered from the distillation tower into a cooler for cooling, delivering the cooled ammonia gas into a low vacuum absorption tower (vacuum degree-10 to-20 kpa), and absorbing with refined brine to obtain ammonia brine; the ammonia-containing condensate generated by the cooler and the ammonia-containing condensate generated by furnace gas cooling are sent to a thin liquid distillation tower (vacuum degree-40 to-60 kpa, temperature 78-84 ℃) for distillation, and ammonia distilled from the thin liquid distillation tower enters a high vacuum absorption tower. The distilled waste liquid of the distillation tower is subjected to primary flash (vacuum degree-10 to-20 kpa), the primary flash steam is returned to the distillation tower, the primary flash distilled waste liquid is subjected to secondary flash (vacuum degree-40 to-60 kpa), the secondary flash steam is sent to the thin liquid distillation tower, and the secondary flash waste liquid is subjected to environmental protection treatment.
Wherein, the heavy alkali is sent to the calcination procedure to be calcined to obtain the light sodium carbonate product, and the light sodium carbonate product containing CO is obtained at the same time 2 Furnace gas with the concentration of more than 80 percent is washed, cooled and compressed to obtain the lower gas with the carbon dioxide concentration of 80 percent, and the lower gas is sent to the carbonization process to prepare alkali.
Sieving outsourced limestone (calcium carbonate content is more than 90%), obtaining qualified raw materials with granularity of 50-120mm and coke (25-50 mm), delivering the qualified raw materials to a lime kiln according to a certain proportion, introducing air into the bottom of the lime kiln, and calcining the limestone by heat generated by burning the coke in the lime kiln to obtain quicklime calcium oxide and CO-containing lime 2 About 40 percentLime is added with water to be digested into lime milk with calcium hydroxide concentration of 155-170 titer, and the lime milk is sent to a distillation process to recycle ammonia, and the produced kiln gas is subjected to dust removal, cooling and compression to obtain the CO-containing kiln gas 2 About 40% of the middle gas and the cleaning gas are sent to the carbonization process for alkali preparation.
Example 2
Similar to example 1, except that brine is prepared by using a sodium chloride raw salt with a sodium chloride content of more than 95% to obtain nearly saturated crude brine, the concentration is more than 105 titer (5.25 mol/L), and the nearly saturated crude brine obtained by mining the low-nitrate sodium chloride underground salt mine in example 1 is replaced.
According to the invention, refined sodium chloride brine absorbs ammonia gas to obtain ammonia brine, and CO is introduced into the ammonia brine 2 The primary alkali liquor is obtained after primary carbonization, the primary mother liquor obtained by the solid-liquid separation of the alkali liquor is subjected to secondary ammonia absorption, refined crude salt sodium chloride is added, and secondary carbonization is carried out, the obtained alkali liquor converts sodium chloride into sodium bicarbonate and ammonium chloride, and the ammonium chloride in the alkali liquor can be lifted to about 86 titer from 72-75 titer of the primary alkali liquor. The primary alkali liquor output of the invention does not need to excessively pursue the alkali liquor conversion rate, and the salt which is not converted can be recycled in secondary carbonization, thereby solving the influence on yield, consumption and the like caused by higher cooling water temperature in summer.
The mother liquor entering the distillation system comes from the secondary mother liquor overflowed from the secondary carbonized alkali liquor thickener, the secondary mother liquor does not pass through an alkali filter, the problem of filtration loss in the sodium carbonate industry is solved, meanwhile, the problems of semi-finished heavy alkali dissolution loss, mother liquor expansion and the like caused by adding excessive washing water to control the salt content of a product are solved, and in the process of adding washing water to control the salt content of the product, washing water does not directly enter the distillation process, so that the material consumption and the energy consumption in the sodium carbonate production process are reduced.
The alkali liquor obtained after secondary ammonia absorption, salt addition and secondary carbonization of the mother liquor is thickened by a thickener, the thickened alkali liquor and the primary alkali liquor enter an alkali filtering machine together for solid-liquid separation to obtain semi-finished heavy alkali, and the ammonium chloride of the secondary mother liquor overflowed from the upper part of the thickener can reach about 86tt and is about 14tt higher than the ammonium chloride of the primary mother liquor obtained by filtering the primary alkali liquor, so that the equivalent of the distilled mother liquor is reduced, and the production capacity of the sodium carbonate of a distillation tower is improved by about 20%.
In order to control salt content, the conventional alkali preparation process adds non-salt washing water to wash the semi-finished heavy alkali, and adjusts the consumption of washing water according to different requirements of the salt content of the product, so that the concentration of ammonium chloride in the mother liquor is fluctuated, and the ratio of the gray emulsion to the mother liquor is difficult to control when ammonia is recovered in the distillation process.
The primary carbonization process of the ammonia-soda process needs to pursue carbonization conversion rate and recrystallization quality at the same time, the production process of low-salt or ultra-low-salt sodium carbonate does not need to pursue carbonization conversion rate excessively, carbonization crystallization quality is pursued mainly, the temperature of alkali liquor discharged from a primary carbonization tower can be controlled to be 35-40 ℃, compared with the existing production index, the temperature index of alkali liquor discharged from the primary carbonization tower is improved by 5-10 ℃, adverse effects on carbonization crystallization quality caused by excessive cooling are prevented, the operation difficulty of carbonization process is reduced, the influence on sodium carbonate production caused by higher temperature of production circulating water in summer is solved, and meanwhile, the pressure steam consumption in calcination process is reduced.
The heat alkali solution treatment difficulty is high in the sodium carbonate production process, the problem of heat alkali solution treatment can be solved before the heat alkali solution is mixed into primary mother solution for ammonia absorption according to production requirements, the alkali solution can be recycled, and the heat alkali solution treatment difficulty and the treatment cost are reduced.
The primary mother liquor is used as a primary washing agent for tail gas in carbonization and absorption processes, then refined brine is used for secondary washing, brine and ammonia gas entrained in the tail gas are recovered, primary mother liquor is used for washing the carbonized tail gas, the back brine in the carbonized tail gas is recovered, the temperature of the carbonized tail gas is reduced, the ammonia purifying effect of the tail gas is improved, the ammonia absorption amount required by the mother liquor is reduced, and meanwhile, the concentration of the refined brine is reduced by reducing water vapor in the carbonized tail gas.
The secondary carbonization towers can be arranged into a group independently by referring to the primary carbonization towers, each group comprises four to six carbonization towers, one carbonization tower is used as a secondary cleaning tower, the other carbonization towers are used as secondary alkali-making towers, the secondary cleaning towers are cleaned by ammonia salt mother liquor, and 2000-5000m of ammonia salt mother liquor is introduced into the secondary cleaning towers 3 With about 40% CO per hour 2 The cleaning gas is used for cleaning alkali scars formed during the alkali preparation of the secondary carbonization tower, the cleaning time is 18-24 hours, the production capacity of the secondary carbonization tower is recovered, the obtained neutralized ammonia salt mother liquor after cleaning is sent to the secondary carbonization tower for alkali preparation, the ammonia salt mother liquor flow and the alkali outlet liquid flow are designed according to about twice of the tower for alkali preparation by primary carbonization, the tower type is the same as the tower type of the primary carbonization tower, and the primary carbonization tower and the secondary carbonization tower can be used instead of each other.
The secondary mother liquor ammonia absorption source is that the carbonized tail gas is washed respectively, the concentration of free ammonia in the secondary mother liquor after washing is increased by about 10 tts, the ammonia distilled from the thin liquid distillation tower is absorbed again, the concentration of ammonia in the mother liquor is increased by about 10 tts, the deficiency is supplemented by the ammonia recovered from the mother liquor distillation tower, the operation negative pressure of the secondary mother liquor high vacuum absorption tower is higher than the operation pressure of the low vacuum absorption tower, and the secondary mother liquor ammonia absorption index is convenient to control.
And (3) index control of a secondary carbonization tower: the temperature of the alkali liquor is 35-40 ℃, the temperature of the ammoniacal salt mother liquor is 40-55 ℃, the middle reaction temperature is 45-60 ℃, and the gas quantity of the lower section is 1500-3000m 3 /h, middle section gas 2000-6000m 3 /h。
And (3) carrying out high vacuum distillation on ammonia-containing condensate from the calcination process and the evaporation process, absorbing the obtained ammonia gas by using a secondary mother liquor, supplementing the insufficient part by using a mother liquor distillation tower, and improving the total ammonia of the ammonia mother liquor from 95 to 110 to 120tt and the free ammonia from 25 to 30tt to 40 to 55tt.
Adding salt into the ammonia mother solution in a salt adding barrel to obtain ammonia salt mother solution with equivalent weight of 5.0-7.0m 3 And the ratio alpha of free ammonia to sodium chloride is controlled to be 1.03-1.1, the total chlorine is controlled to be 110-120tt, and ammonium chloride crystallization is prevented in the secondary carbonization process.
The process can adopt full salt to prepare alkali, or can adopt part of brine and part of refined salt to prepare alkali, and adopts brine and refined salt to prepare alkali, wherein the refined salt is added for the second time to account for about 20% -40% of the total salt, and the utilization rate of the refined salt added for the second time reaches more than 90%.
Carbonizing ammonia salt mother liquor to obtain secondary alkali liquor with temperature controlled at 35-40deg.C, and equivalent weight of alkali liquor after secondary thickening of 0.8-2m 3 Alkali/t, the equivalent weight of overflowed secondary mother liquor is 4.2-5.0m 3 And/t base.
Because the quality of the re-alkali crystallization is good, the change rate of alkali liquid solid-liquid separation is not excessively pursued, a centrifugal machine can be used for the alkali filtering machine, the alkali liquid solid-liquid separation process flow is simplified, equipment such as a vacuum machine, a filtered tail gas ammonia cleaning tower and the like is not needed, the power consumption of the vacuum machine is reduced, a large amount of vacuum tail gas is not generated any more, the discharge of vacuum waste gas required by the alkali liquid solid-liquid separation is reduced, the influence of the discharge of waste gas on the environment is reduced, meanwhile, the water content of the re-alkali is reduced, and the medium-pressure steam consumption of a calciner is reduced.
The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and not of limitation. Many modifications and equivalents may be made to the invention without departing from the spirit and scope of the invention, and these modifications and equivalents are intended to be included within the scope of the invention.
Claims (17)
1. A low-salt or ultra-low salt sodium carbonate production process, which comprises the following steps:
(1) The refined brine absorbs ammonia gas to form ammonia brine, and the molar concentration ratio of ammonia in the ammonia brine to sodium chloride is 1.13-1.19:1, ammonia brine and CO 2 The refined brine enters a primary carbonization tower for reaction to generate primary alkali liquor, the temperature of the alkali liquor discharged from the primary carbonization tower is 35-40 ℃, wherein the NaCl content in the refined brine is more than 304g/L, and the calcium and magnesium content is less than 15mg/L;
(2) The primary alkali liquor discharged from the primary carbonization tower enters an alkali filtering machine for solid-liquid separation to obtain semi-finished heavy alkali and primary mother liquor;
(3) The primary mother liquor from the alkali filtering machine contains 65-72 titer of ammonium chloride, ammonia in carbonized tail gas is washed by a carbonized tail gas ammonia purifying tower, then ammonia is absorbed by a high vacuum absorption tower with the vacuum degree of-30 to-60 kPa to obtain ammonia mother liquor, free ammonia in the ammonia mother liquor is 40-55 titer, the ammonia mother liquor is sent to a salt dissolving tank, refined raw salt sodium chloride is added, and the molar ratio of the free ammonia to the sodium chloride is 1.03-1.1:1, sending the ammonia salt mother liquor to a secondary carbonization tower, and reacting with carbon dioxide to obtain secondary alkali liquor;
(4) The secondary alkali liquor is sent to a thickener, the thick alkali liquor containing 30 to 50 percent of sodium bicarbonate crystals which is sent out from the bottom of the thickener is returned to an alkali filter in the step (2) and is subjected to solid-liquid separation together with the primary alkali liquor to obtain a heavy alkali filter cake, the heavy alkali filter cake is calcined to obtain a low-salt or ultra-low-salt sodium carbonate product, the clear liquid which is sent out from the upper part of the thickener is secondary mother liquor, the secondary mother liquor obtained in the step (4) is sent to a distillation procedure for distillation treatment,
In the step (4), washing heavy alkali by using washing water on an alkali filter, removing most sodium chloride in the heavy alkali by controlling washing water amount, controlling the sodium chloride content in the heavy alkali to be lower than 0.1 percent,
wherein the content of sodium chloride in the low-salt sodium carbonate product is lower than 0.2 weight percent, and the content of sodium chloride in the ultra-low-salt sodium carbonate product is lower than 0.1 weight percent.
2. The process of claim 1, wherein the carbonization tail gas is from one or more of a primary carbonization caustic tower, a primary carbonization purge tower, a secondary carbonization caustic tower, and a secondary carbonization purge tower exhaust.
3. The process of claim 1 wherein the high vacuum absorber has a vacuum level of from-40 kPa to-50 kPa.
4. The process according to claim 1, wherein the ammonia absorbed by the high vacuum absorption tower is ammonia condensate obtained by cooling ammonia distilled from the distillation tower by a cooler and ammonia condensate obtained by cooling calciner gas, the ammonia condensate enters ammonia recovered by the weak liquor distillation tower, and the rest of the ammonia is supplemented by ammonia recovered by the secondary mother liquor distillation.
5. The process of claim 1, wherein the wash water used in step (4) is a salt-free wash water.
6. The process according to claim 1, wherein in step (4), the heavy alkali is washed with washing water on an alkali filter, most of sodium chloride in the heavy alkali is removed by controlling the washing water amount, and the sodium chloride content in the heavy alkali is controlled to be lower than 0.05%.
7. The process according to any one of claims 1 to 6, wherein the secondary mother liquor is heated to 88 to 92 ℃ in a preheating section of the distillation column to remove a substantial portion of the CO in the mother liquor 2 Adding lime milk, steaming out ammonia with steam, cooling ammonia gas from the distillation tower in a cooler, vacuum-10-20 kPa low-vacuum absorption tower, and absorbing ammonia gas with refined brine to obtain ammonia salt water; and (3) delivering the ammonia-containing condensate generated by the ammonia distillation cooler and the ammonia-containing condensate generated by the condensation of the calciner gas into a light liquid distillation tower for distillation, and delivering the ammonia distilled from the light liquid distillation tower into a high vacuum absorption tower.
8. The process of claim 7 wherein the cooled ammonia gas has a temperature of 55-65 ℃.
9. The process of claim 7, wherein the refined brine is refined brine after washing carbonized tail gas ammonia.
10. The process according to claim 7, wherein the distillation waste liquid from the distillation column is flashed, the flash vapor from the flash is returned to the distillation column, the distillation waste liquid from the flash is sent to the flash distillation column, and the flash vapor from the flash distillation column is sent to the thin film distillation column for use as a heat source.
11. The process of any one of claims 1-6, wherein the primary carbonization tower comprises a primary carbonization cleaning tower and a primary carbonization caustic tower, and the secondary carbonization tower comprises a secondary carbonization cleaning tower and a secondary carbonization caustic tower; in the primary carbonization tower, ammonia brine firstly enters a primary carbonization cleaning tower and is introduced with CO-containing water 2 The obtained neutralized ammonia water enters a primary carbonization alkali-making tower and contains CO 2 Gas reaction to obtain primary alkali liquor; in the secondary carbonization tower, the ammoniacal salt mother liquor firstly enters a secondary carbonization cleaning tower and is introduced with CO-containing liquid 2 The obtained neutralized ammonia salt mother liquor enters a secondary carbonization alkali-making tower and contains CO 2 Gas reaction to obtain secondary alkali liquor; and in the primary carbonization cleaning tower, the primary carbonization alkali preparation tower, the secondary carbonization tower and the secondary carbonization alkali preparation tower, generated carbonization tail gas is discharged from the top of the carbonization tower.
12. The process according to any one of claims 1 to 6, wherein in the secondary carbonization tower and the primary carbonization tower, 4 to 6 carbonization towers are arranged in each group, one tower is a cleaning tower, the other towers are alkali-making towers, and the ammonia salt mother liquor is 200 to 500m 3 The flow rate of/h is firstly sent into a secondary carbonization cleaning tower and 2000-7000m is introduced 3 /h contains CO 2 The cleaning gas of (2) is used for cleaning alkali scars formed during the alkali preparation of the secondary carbonization tower, simultaneously pre-carbonizing the ammonia salt mother liquor, changing the ammonia salt mother liquor into an alkali preparation tower after cleaning the alkali scars to restore the production capacity of the carbonization tower, and obtaining the cleaned ammonia salt mother liquor which is called as a neutralization ammonia salt mother liquor, and CO 2 The mother liquor of the neutralized ammonia salt is controlled at 35-50 titer and is sent to a secondary carbonization alkali preparation tower for treatment, so as to obtain secondary alkali liquor containing 10-20% of sodium bicarbonate crystals at the temperature of 35-40 ℃, the secondary alkali liquor is sent to a thickener, the thick alkali liquor containing 30-50% of sodium bicarbonate crystals which is sent out from the bottom of the thickener is sent to an alkali filter, the alkali filter and the primary alkali liquor are together subjected to solid-liquid separation, a filter cake is washed to obtain semi-finished heavy alkali with qualified sodium chloride content, the semi-finished heavy alkali is further processed into low-salt or ultra-low-salt light sodium carbonate products, clear liquid overflowed from the upper part of the thickener is called secondary mother liquor, and ammonia is recovered in a distillation procedure.
13. The process according to claim 12, wherein the flow rate of ammonia salt mother liquor and the flow rate of alkali outlet liquor of each secondary carbonization alkali preparation tower are controlled to be 50-140m 3 Introducing CO into the lower part of the secondary carbonization alkali-making tower 2 1500-3000m lower gas 3 Introducing CO into the middle lower part of the secondary carbonization alkali-making tower 2 Middle gas 2 of (2)000-6000m 3 /h。
14. The process according to any one of claims 1 to 6, wherein the refined brine is obtained by: mining underground salt mine containing low-nitrate sodium chloride or preparing brine by using sodium chloride raw salt with sodium chloride content more than 95% to obtain nearly saturated crude brine, wherein the concentration is more than 105 titer, and refining by a lime soda ash method to remove a small amount of calcium and magnesium ions in the crude brine to obtain refined brine with calcium and magnesium content less than 15 mg/l.
15. The process of claim 14, wherein the refined brine absorbs ammonia gas from the distillation recovery of the secondary mother liquor to give a molar ratio of ammonia to sodium chloride of 1.13 to 1.19:1, the ammonia brine is sent to a primary carbonization tower, and a primary alkali liquor containing sodium bicarbonate is obtained.
16. A low-salt or ultra-low salt soda ash production device, comprising: a low vacuum absorption tower, a primary carbonization cleaning tower, a primary carbonization alkali-making tower, an alkali filter, a carbonization tail gas ammonia cleaning tower, a high vacuum absorption tower, a salt adding barrel, a secondary carbonization cleaning tower, a secondary carbonization alkali-making tower, a thickener, a distillation tower, a calciner, a cooler and a light liquid distillation tower,
the low vacuum absorption tower is provided with a distillation tower ammonia gas feeding pipe and a refined brine feeding pipe, a discharge port of the low vacuum absorption tower is connected with a feed port of a primary carbonization cleaning tower through an intermediate buffer barrel and a pump, a carbon dioxide feeding pipe is also connected with the feed port of the primary carbonization cleaning tower, a liquid outlet of the primary carbonization cleaning tower is connected with a feed port of a primary carbonization alkali preparation tower through the pump, a liquid outlet of the primary carbonization alkali preparation tower is connected with a feed port of an alkali filtering machine through an alkali discharging buffer tank, a solid material outlet of the alkali filtering machine is connected with an inlet of a calciner through a heavy alkali belt, a furnace gas outlet of the calciner is connected with a first cooler, and a gas outlet of the first cooler is connected with a gas inlet of the primary carbonization alkali preparation tower and a gas inlet of a secondary carbonization alkali preparation tower through a compressor;
The primary mother liquor outlet of the alkali filtering machine is connected with the liquid feed inlet of the carbonized tail gas ammonia purifying tower through a pipeline, a mother liquor buffer barrel and a pump, the gas feed inlet of the carbonized tail gas ammonia purifying tower is also connected with the tail gas outlet of the primary carbonized tower and the tail gas outlet of the secondary carbonized tower through a pipeline, the washing liquid outlet of the carbonized tail gas ammonia purifying tower is connected with the inlet of a high vacuum absorption tower through a pump, the inlet of the high vacuum absorption tower is also connected with an ammonia feed pipe from a thin liquid distillation tower and/or an ammonia feed pipe cooled by a distillation tower, the liquid outlet of the high vacuum absorption tower is connected with a salt adding barrel inlet through a pump, the salt adding barrel outlet is connected with the inlet of a secondary carbonized cleaning tower through an ammonia salt buffer barrel and a pump, the cleaning gas feed pipe is also connected with the inlet of the secondary carbonized cleaning tower, the liquid outlet of the secondary carbonized cleaning tower is connected with the inlet of the secondary carbonized alkali preparing tower through a pump, the liquid outlet of the secondary carbonized alkali preparing tower is connected with the inlet of a thick liquid filter, the upper outlet of the thick liquid is connected with the feed inlet of the distillation tower through a mother liquor buffer barrel and a pump, the lime milk and the vapor is also connected with the gas inlet of the distillation tower, the gas inlet of the second distillation tower is also connected with the gas inlet of the thin liquid distillation tower is connected with the inlet of the thin liquid distillation tower, the gas inlet of the thin liquid cooling tower is also connected with the inlet of the thin liquid distillation tower is connected with the inlet of the thin liquid distillation tower,
Wherein the content of sodium chloride in the low-salt sodium carbonate product is lower than 0.2 weight percent, and the content of sodium chloride in the ultra-low-salt sodium carbonate product is lower than 0.1 weight percent.
17. The low-salt or ultra-low-salt soda ash production device according to claim 16, wherein the primary carbonization tower is provided with a middle gas, a lower gas and a purge gas carbon dioxide feed port.
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