Citric acid neutralization and vacuum filtration washing device

Abstract

This utility model discloses a citric acid primary neutralization and vacuum filtration washing device, including a mixed acid tank, a dilute citric acid clear liquid pipe from a citric acid fine filtration unit, and a calcium hydrogen concentrated acid pipe from a vacuum filtration washing unit connected to the inlet of the mixed acid tank. The outlet of the mixed acid tank is connected to the inlet of a mixed acid circulation pump and a mixed acid discharge pump. The outlet of the mixed acid circulation pump is connected to the return port of the mixed acid tank, and the outlet of the mixed acid discharge pump is connected to the inlet of each primary neutralization pot. The top inlet of each primary neutralization pot is also connected to an antifoaming agent pipe and a calcium carbonate stock solution pipe. The bottom outlet of each primary neutralization pot is connected to the slurry distributor of a tricalcium citrate vacuum belt filter through a tricalcium citrate slurry pipe. This device converts dissolved citric acid into stable and easily separable tricalcium citrate solid, improving the recovery rate and purity of citric acid.

Description

Technical Field

[0001] This utility model relates to a citric acid production apparatus, and more particularly to a citric acid primary neutralization and vacuum filtration washing apparatus, belonging to the technical field of citric acid production equipment. Background Technology

[0002] In the production of citric acid, the purification process is a crucial step that determines product quality and production economics. Currently, the industry's conventional citric acid purification process mostly adopts the calcium salt method. The core principle of this process is to utilize the reaction of citric acid with calcium ions to produce calcium citrate and calcium hydrogen citrate. By separating the precipitate and further acidifying it, a high-purity citric acid solution is obtained. The primary neutralization of citric acid is the core step in the calcium salt method for extracting citric acid.

[0003] Conventional calcium salt processes have significant limitations in practical applications. Firstly, the process consumes a high amount of calcium carbonate. The formation of calcium citrate precipitate requires a large quantity of calcium carbonate as a reactant, directly increasing raw material costs. This is particularly problematic when calcium carbonate prices fluctuate significantly, impacting the economic benefits of production enterprises. Secondly, the acidolysis stage of the calcium salt process generates a large amount of calcium sulfate as a byproduct. This calcium sulfate is not only of low purity and has limited application value, but it is also extremely difficult to dispose of. Large accumulations of calcium sulfate occupy substantial land resources, and improper handling could lead to environmental pollution.

[0004] The patent with publication number CN102503812A discloses "a method for improving the yield of citric acid in the calcium salt extraction process". This technical solution improves the yield of citric acid in the calcium salt extraction process without increasing the amount of sulfuric acid used in the acid hydrolysis section. It has made progress in the internal optimization of the calcium salt method, but it has a systemic defect in its combination with chromatographic separation method: it does not take advantage of the high efficiency purification, continuous production and environmental protection of the chromatography method, resulting in the purity, yield, cost and sustainability not reaching the advanced level of the industry.

[0005] In the calcium salt process, the tricalcium citrate slurry produced by the primary neutralization reaction contains a large amount of waste sugar water, the calcium hydrogen citrate slurry produced by the secondary neutralization reaction contains a large amount of concentrated calcium hydrogen acid, and the calcium sulfate slurry produced after the acidolysis reaction still contains a large amount of citric acid. All of these waste sugar water, concentrated calcium hydrogen acid, and citric acid need to be filtered, washed, and dried using a vacuum belt filter to reduce the moisture content and residual acid content of the filter cake.

[0006] Vacuum belt filters are key equipment in the calcium salt process for purifying citric acid. Incomplete unloading can lead to production losses and subsequent cleaning problems. Currently, although a large amount of ordinary pressurized cleaning water is used to rinse the tail unloading area, it is still insufficient to deeply unclog the filter cloth pores, resulting in limited cleaning effectiveness.

[0007] In summary, while the calcium salt method is mature and stable, its shortcomings in yield, environmental protection, purity, and cost are becoming increasingly apparent. This is prompting the industry to shift towards more efficient and environmentally friendly chromatographic separation processes, using a combination of chromatography and calcium salt methods to compensate for these deficiencies. Therefore, combining chromatography with the traditional calcium salt method can leverage the advantages of the calcium salt method in precipitation separation while utilizing the high separation efficiency of chromatography to reduce calcium carbonate consumption and decrease the generation of the byproduct calcium sulfate. This improves purification efficiency while alleviating the cost and environmental burdens of the conventional calcium salt method, providing a new direction for the optimization and upgrading of citric acid purification processes. Utility Model Content

[0008] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0009] In view of the problems existing in the above and / or prior art, this utility model is proposed.

[0010] The purpose of this invention is to overcome the problems existing in the prior art and provide a citric acid one-time neutralization and vacuum filtration washing device, which converts dissolved citric acid into stable and easily separable tricalcium citrate solid, thereby improving the recovery rate and purity of citric acid.

[0011] To solve the above technical problems, this utility model provides a citric acid primary neutralization and vacuum filtration washing device, including a mixed acid tank 901, a dilute citric acid clear liquid pipe G29 from the citric acid fine filtration unit and a calcium hydrogen concentrated acid pipe G38 from the vacuum filtration washing unit connected to the inlet of the mixed acid tank 901, the outlet of the mixed acid tank 901 connected to the inlet of the mixed acid circulation pump 902 and the mixed acid discharge pump 903, the outlet of the mixed acid circulation pump 902 connected to the return port of the mixed acid tank 901, the outlet of the mixed acid discharge pump 903 connected to the inlet of each primary neutralization pot 904, the top inlet of each primary neutralization pot 904 also connected to a defoamer pipe G26 and a calcium carbonate raw liquid pipe G39; the bottom outlet of each primary neutralization pot 904 is connected to the slurry distributor of the tricalcium citrate slurry pipe G40 and the tricalcium vacuum belt filter 1001.

[0012] Furthermore, the tricalcium vacuum belt filter 1001 is provided with a feeding area, a filtration area, a washing and dehydration area and a cake discharge area in sequence along the filter cloth advancing direction, and the sugar water outlet below is connected to the inlet of the vacuum tank 1002 respectively. The exhaust port at the top of each vacuum tank 1002 is connected to the middle inlet of the gas-water separator 1003. The top of the gas-water separator 1003 is vented to the atmosphere through the vacuum pump 1004. Except for the final stage, the bottom outlet of each vacuum tank 1002 and the bottom outlet of the gas-water separator 1003 are connected to the inlet of the waste sugar water tank 1005. The outlet of the waste sugar water tank 1005 is connected to the waste sugar water pump 1006 and the wastewater treatment station.

[0013] Furthermore, the bottom outlet of the five-stage vacuum tank 1002-5 is connected to the inlet of the sugar water tank 1007, and the sugar water tank 1007 is connected to the primary rinsing water inlet above the washing and dehydration zone via the sugar water pump 1008; the end washing water outlet of the tricalcium vacuum belt filter 1001 is connected to the inlet of the tricalcium washing water tank 1009, and the outlet of the tricalcium washing water tank 1009 is connected to the secondary rinsing water inlet above the washing and dehydration zone via the tricalcium washing water pump 1010; the tertiary rinsing water inlet above the washing and dehydration zone is connected to the condensate supply pipe G15.

[0014] Furthermore, the filter cake discharge port of the tricalcium vacuum belt filter 1001 is connected to the tricalcium slurry preparation tank 1011, the slurry preparation water inlet of the tricalcium slurry preparation tank 1011 is connected to the condensate supply pipe G15, and the outlet of the tricalcium slurry preparation tank 1011 is connected to the secondary neutralization pot 1104 through the tricalcium slurry preparation pump 1012.

[0015] Compared to the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: 1. The diluted citric acid solution produced after filtration of the citric acid mixture is mixed with the concentrated calcium hydrogen acid discharged from the calcium hydrogen citrate filter in a mixing tank. This mixture undergoes a neutralization reaction with excess calcium carbonate to form tricalcium citrate, converting dissolved citric acid into stable and easily separable tricalcium citrate solid. By controlling the excess calcium carbonate, complete reaction of citric acid to tricalcium citrate can be ensured, improving the citric acid recovery rate and purity.

[0016] 2. Install defoaming electrodes, online pH sensors, and automatic feeding systems on the neutralization tank. By detecting foam and adjusting the pH value online, the neutralization process can be precisely controlled. Combined with a stable automatic control program, the system can be kept running stably, reducing labor costs.

[0017] 3. Install a variable frequency stirring device on the primary neutralization tank to prevent local over-alkaliness, and add a mixed acid reflux pump to ensure uniform acidity before the neutralization reaction.

[0018] 4. Countercurrent washing is used during vacuum filtration and washing to reduce the amount of washing water by utilizing the concentration gradient; a dual cleaning system of high-pressure water cleaning and back-blowing air is used at the tail end to deeply regenerate and unblock the pores of the filter cloth after vacuum filtration and washing, thereby extending the service life of the filter cloth, reducing production costs, and improving the recovery rate of citric acid products. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit this utility model. Wherein: Figure 1 This is a flowchart of the primary neutralization unit in this utility model; Figure 2 This is a flowchart of the tricalcium citrate vacuum filtration and washing unit in this utility model; Reference numerals: 424 for pre-concentrated condensate pump; 606 for two-stage plate and frame filter press; Mixed acid tank 901; Mixed acid circulation pump 902; Mixed acid discharge pump 903; Primary neutralization pot 904; Tricalcium vacuum belt filter 1001; Vacuum tank 1002; Gas-water separator 1003; Vacuum pump 1004; Waste sugar water tank 1005; Waste sugar water pump 1006; Diluted sugar water tank 1007; Diluted sugar water pump 1008; Tricalcium cloth washing water tank 1009; Tricalcium cloth washing water pump 1010; Tricalcium slurry preparation tank 1011; Tricalcium slurry preparation pump 1012; Secondary neutralization vessel 1104; calcium hydrogen acid pump 1206; Condensate supply pipe G15; Defoamer pipe G26; Dilute citric acid clear liquid pipe G29; Calcium hydrogen hydrate concentrated acid pipe G38; Calcium carbonate stock solution pipe G39; Tricalcium citrate slurry pipe G40. Detailed Implementation

[0020] In the following description of this utility model, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device must have a specific orientation.

[0021] To make the technical means, creative features, achieved objectives and effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] like Figure 1As shown, in the citric acid primary neutralization and vacuum filtration washing device of this invention, the dilute acid produced after the citric acid mixture is filtered by the two-stage plate and frame filter press 606 is introduced into the mixed acid tank 901 through the dilute citric acid clear liquid pipe G29. The concentrated calcium hydrogen acid from the downstream concentrated calcium hydrogen acid pump 1206 is also introduced into the mixed acid tank 901 through the concentrated calcium hydrogen acid pipe G38. The outlet of the mixed acid tank 901 is connected to the inlet of the mixed acid circulation pump 902 and the mixed acid discharge pump 903. The outlet of the mixed acid circulation pump 902 is connected to the return port of the mixed acid tank 901. The outlet of the mixed acid discharge pump 903 is connected to the inlet of each primary neutralization pot 904. The top inlet of each primary neutralization pot 904 is also connected to the defoamer pipe G26 and the calcium carbonate raw liquid pipe G39. The bottom outlet of each primary neutralization pot 904 is connected to the slurry distributor of the tricalcium citrate vacuum belt filter 1001 through the tricalcium citrate slurry pipe G40.

[0024] After the mycelium is removed from the citric acid fermentation broth by a two-stage plate and frame filter press 606, soluble inorganic salts and some residual sugars remain. These soluble impurities must be removed to obtain pure calcium citrate. The purpose of the first neutralization step is to react the calcium carbonate slurry with the dilute acid produced after filtration by the two-stage plate and frame filter press 606 and the concentrated calcium hydrogen acid sent from the calcium hydrogen acid tube G38 to generate insoluble calcium citrate. This removes the soluble inorganic salts and residual sugars, resulting in pure, impurity-free solid calcium citrate.

[0025] The citric acid mixture is filtered by a two-stage plate and frame filter press 606, and the resulting dilute acid is sent to the mixed acid tank 901 via the dilute citric acid clear liquid pipe G29. The calcium hydrogen acid concentrated acid pump 1206 is also sent to the mixed acid tank 901 via the calcium hydrogen acid concentrated acid pipe G38. After mixing in the mixed acid tank 901, in order to ensure the uniformity of acidity in the mixed acid tank 901 and the neutralization effect of each batch, the mixed acid circulation pump 902 is used for circulation mixing.

[0026] The diluted citric acid, after being mixed evenly, is pumped into the primary neutralization pot 904 through the mixed acid discharge pump 903, where it undergoes a primary neutralization reaction with 45%wt excess calcium carbonate from the calcium carbonate raw liquid pipe G39 to produce tricalcium citrate.

[0027] To prevent localized over-alkaliness during neutralization, a variable frequency stirrer is added to the primary neutralization tank. A large amount of foam is generated during the neutralization reaction, which can lead to unstable neutralization. To ensure the stability of the neutralized liquid, a foam sensor XP-904 is installed on the wall of the primary neutralization tank (tank 904), interlocked with the defoamer feed valve on the defoamer pipe G26. When foam reaches a certain height, the defoamer feed valve opens; when the foam drops to a certain height, the defoamer feed valve closes.

[0028] To detect the neutralization endpoint and reduce the labor costs associated with manual pH titration, an electromagnetic flow meter and regulating valve were installed on the calcium carbonate feed line. These were interlocked with the pH sensor PH-904 installed on the wall of the primary neutralization reactor 904 to monitor the pH value. When the pH reached 4-5 and the residual acid was 0.2-0.4%, the calcium carbonate feed valve was closed, and stirring continued for approximately 20 minutes. The pH and residual acid were then re-measured, indicating that the primary neutralization endpoint had been reached. Discharge then began, and the tricalcium citrate slurry was transported via the G40 pipe to the tricalcium citrate vacuum filtration and washing unit for filtration and washing.

[0029] like Figure 2 As shown, in the tricalcium citrate vacuum filtration and washing unit, the tricalcium citrate slurry pipe G40 is connected to the slurry distributor of the tricalcium vacuum belt filter 1001 through a flow meter and a regulating valve.

[0030] The tricalcium vacuum belt filter 1001 is provided with a feeding area, a filtration area, a washing and dehydration area and a cake discharge area in sequence along the filter cloth forward direction. The sugar water outlet below is connected to the inlet of the vacuum tank 1002. The exhaust port at the top of each vacuum tank 1002 is connected to the middle inlet of the gas-water separator 1003. The top of the gas-water separator 1003 is vented to the atmosphere through the vacuum pump 1004. Except for the final stage, the bottom outlet of each vacuum tank 1002 and the bottom outlet of the gas-water separator 1003 are connected to the inlet of the waste sugar water tank 1005. The outlet of the waste sugar water tank 1005 is connected to the waste sugar water pump 1006 and the wastewater treatment station.

[0031] The bottom outlet of the five-stage vacuum tank 1002-5 is connected to the inlet of the sugar water tank 1007. The sugar water tank 1007 is connected to the primary rinsing water inlet above the washing and dehydration zone via the sugar water pump 1008. The end washing water outlet of the tricalcium vacuum belt filter 1001 is connected to the inlet of the tricalcium washing water tank 1009. The outlet of the tricalcium washing water tank 1009 is connected to the secondary rinsing water inlet above the washing and dehydration zone via the tricalcium washing water pump 1010. The tertiary rinsing water inlet above the washing and dehydration zone is connected to the condensate supply pipe G15.

[0032] The filter cake discharge port of the tricalcium vacuum belt filter 1001 is connected to the tricalcium slurry preparation tank 1011. The slurry preparation water inlet of the tricalcium slurry preparation tank 1011 is connected to the condensate supply pipe G15. The outlet of the tricalcium slurry preparation tank 1011 is connected to the secondary neutralization pot 1104 through the tricalcium slurry preparation pump 1012.

[0033] The tricalcium citrate slurry also contains soluble inorganic salts and residual sugars. It is fed into the tricalcium vacuum belt filter 1001 through the tricalcium citrate slurry pipe G40 for solid-liquid separation to remove the soluble inorganic salts and residual sugars from the tricalcium citrate slurry and obtain pure tricalcium citrate salt.

[0034] The Tricalcium Vacuum Belt Filter 1001 is a continuous solid-liquid separation device. Its working principle is based on the combination of vacuum adsorption force and continuous movement of filter cloth. Through the synergistic effect of multiple processes, it realizes material feeding, filtration, washing, dewatering and cake discharge.

[0035] Feeding Zone: The tricalcium citrate slurry generated from the primary neutralization reaction flows into the slurry distributor of the tricalcium citrate vacuum belt filter 1001 at a stable flow rate through a flow meter and regulating valve, and is evenly distributed on the rotating filter cloth. The vacuum pump 1004 generates vacuum suction to form a vacuum chamber below the filter cloth, initially creating negative pressure. The tricalcium citrate slurry begins to permeate through the filter cloth into the vacuum chamber, and solid particles initially accumulate on the surface of the filter cloth to form an initial filter cake, which then enters the filtration zone.

[0036] Filtration Zone: The filter cloth, carrying the tricalcium citrate slurry, enters the main filtration zone with a high vacuum. Under continuous negative pressure, a large amount of liquid is drawn into the vacuum chamber, gradually increasing the thickness of the filter cake and compacting it. The vacuum chamber is connected to a vacuum pump via pipes. The extracted filtrate waste sugar water is separated by vacuum tank 1002 and gas-liquid separator 1003, and then enters waste sugar water tank 1005. It is then pumped away by waste sugar water pump 1006 for sludge removal, while the gas is discharged by the vacuum pump. Since the filter cake still contains a small amount of residual sugar, it needs to enter the washing and dehydration zone for further washing and dehydration.

[0037] Washing and dehydration zone: To ensure maximum washing efficiency and product recovery rate, a countercurrent washing method is adopted, utilizing the concentration gradient to reduce the amount of washing water used. In order to completely separate the residual sugar in the tricalcium citrate filter cake, a three-stage countercurrent washing is used: the third stage uses clean water, the second stage uses the collected filter cloth washing water, and the first stage uses the third-stage filtrate. The concentration of the filtrate obtained after washing also increases sequentially. The condensate from the pre-concentrated condensate pump 424 and condensate supply pipe G15 is used as the third-stage clean water to wash the filter cake. The flow rate of the clean water is controlled by controlling the flow meter and the opening of the regulating valve. The residual sugar is completely washed away. Under vacuum, the filtrate and residual sugar are pumped together into the fifth-stage vacuum tank 1002. Since the residual sugar concentration in the filtrate is low, it can enter the dilute sugar water tank 1007 as the first-stage washing water. The dilute sugar water pump 1008 pumps it to the first-stage washing area to wash the filter cake. The washed filtrate is pumped into the second-stage vacuum tank 1002. Its residual sugar concentration is higher, so it enters the waste sugar water tank 1005 for discharge. The completely cleaned and dried filter cake (tricalcium citrate) then enters the unloading area for unloading. After unloading, the water used to clean the filter cloth under high pressure flows into the tricalcium citrate washing water tank 1009. In order to recover the small amount of tricalcium citrate solid particles contained in the filter cloth water, it is used as secondary cleaning water and pumped by the tricalcium citrate washing water pump 1010 to clean the tricalcium citrate filter cake. The small amount of tricalcium citrate solid particles are trapped by the filter cloth to form a filter cake. The filtrate contains a certain amount of residual sugar, which is discharged into the waste sugar water tank 1005 through the third-stage vacuum tank.

[0038] After the filter cake from the tricalcium vacuum belt filter 1001 is unloaded, it enters the tricalcium slurry preparation tank 1011. After adding condensate from the pre-concentration condensate pump 424 and the condensate supply pipe G15 for slurry preparation, the tricalcium citrate slurry is sent to the secondary neutralization pot 1104 by the tricalcium slurry preparation pump 1012.

[0039] Currently, the production process uses a large amount of ordinary pressure cleaning water to flush the tail discharge area, but this still cannot deeply unclog the filter cloth pores. To solve the above problems, this device introduces high-pressure water and compressed air into the filter cake cleaning area, forming two complementary cleaning systems: high-pressure water cleaning and back-flushing air. The tail discharge area of ​​the citric acid belt vacuum filter is equipped with an inside-out back-flushing air system. The main purpose is to use 0.2~0.3MPa compressed air to penetrate from the inside of the filter cloth to the outside in reverse, completely peeling off the residual filter cake adhering to the filter cloth, thereby solving the problem of incomplete discharge caused by material adhesion. After the back-flushing air peels off large pieces of filter cake, high-pressure water at 8~12MPa is used for deep cleaning, achieving deep regeneration of the filter cloth and unclogging of pores, ensuring continuous and stable filtration efficiency.

[0040] The above description is merely a preferred embodiment of the present utility model, showing and describing the basic principles, main features, and advantages of the present utility model. It is not intended to limit the scope of patent protection of the present utility model. Those skilled in the art should understand that the present utility model is not limited to the above embodiments. In addition to the above embodiments, the present utility model may have other implementations without departing from the spirit and scope of the present utility model. Various changes and improvements to the present utility model are also possible. All technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present utility model. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents. Technical features not described in the present utility model can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A device for one-time neutralization and vacuum filtration washing of citric acid, comprising a mixed acid tank (901), characterized in that: The dilute citric acid clear liquid pipe (G29) from the citric acid fine filtration unit and the calcium hydrogen concentrated acid pipe (G38) from the vacuum filtration and washing unit are connected to the inlet of the mixed acid tank (901). The outlet of the mixed acid tank (901) is connected to the inlet of the mixed acid circulation pump (902) and the mixed acid discharge pump (903). The outlet of the mixed acid circulation pump (902) is connected to the return port of the mixed acid tank (901). The outlet of the mixed acid discharge pump (903) is connected to the inlet of each primary neutralization pot (904). The top inlet of each primary neutralization pot (904) is also connected to the defoamer pipe (G26) and the calcium carbonate stock liquid pipe (G39). The bottom outlet of each primary neutralization pot (904) is connected to the slurry distributor of the tricalcium citrate vacuum belt filter (1001) through the tricalcium citrate slurry pipe (G40).

2. The citric acid once neutralized and vacuum filtration washing device according to claim 1, characterized in that: The tricalcium vacuum belt filter (1001) is provided with a feeding area, a filtration area, a washing and dehydration area and a cake discharge area in sequence along the filter cloth forward direction, and the sugar water outlet below is connected to the inlet of the vacuum tank (1002). The exhaust port at the top of each vacuum tank (1002) is connected to the middle inlet of the gas-water separator (1003). The top of the gas-water separator (1003) is vented to the atmosphere through a vacuum pump (1004). Except for the final stage, the bottom outlet of each vacuum tank (1002) and the bottom outlet of the gas-water separator (1003) are connected to the inlet of the waste sugar water tank (1005). The outlet of the waste sugar water tank (1005) is connected to the waste sugar water pump (1006) and the wastewater treatment station.

3. The citric acid primary neutralization and vacuum filtration washing apparatus according to claim 2, characterized in that: The bottom outlet of the five-stage vacuum tank (1002-5) is connected to the inlet of the sugar water tank (1007), and the sugar water tank (1007) is connected to the primary rinsing water inlet above the washing and dehydration zone via the sugar water pump (1008); the end washing water outlet of the tricalcium vacuum belt filter (1001) is connected to the inlet of the tricalcium washing water tank (1009), and the outlet of the tricalcium washing water tank (1009) is connected to the secondary rinsing water inlet above the washing and dehydration zone via the tricalcium washing water pump (1010); the tertiary rinsing water inlet above the washing and dehydration zone is connected to the condensate supply pipe (G15).

4. The citric acid primary neutralization and vacuum filtration washing apparatus according to claim 3, characterized in that: The filter cake discharge port of the tricalcium vacuum belt filter (1001) is connected to the tricalcium slurry preparation tank (1011), the slurry preparation water inlet of the tricalcium slurry preparation tank (1011) is connected to the condensate supply pipe (G15), and the outlet of the tricalcium slurry preparation tank (1011) is connected to the secondary neutralization pot (1104) through the tricalcium slurry preparation pump (1012).

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