Citric acid and its sodium salt co-production system

Abstract

The present invention provides a citric acid and sodium salt co-production system, which includes sequentially connected subsystems of a citric acid pre-concentration system, an anhydrous citric acid evaporation crystallization system, a monohydrate citric acid cooling crystallization system, a sodium citrate reaction system, and a dihydrate sodium citrate evaporation crystallization system, and the subsystems are all connected in parallel with a main control system. The characteristics of the present invention are: first, the traditional production units are integrated into a system using high-efficiency energy-saving devices, which greatly reduces energy consumption; second, the citric acid mother liquor is deeply utilized, which can greatly reduce the mother liquor processing volume while producing anhydrous citric acid products, monohydrate citric acid products, and dihydrate sodium citrate products of different particle sizes and purities, meet the needs of different users, and increase the added value of unit output; third, the output ratio of each product can be flexibly adjusted according to market conditions, and the entire process has a high degree of automation and a fast response speed.

Description

Technical Field

[0001] The invention relates to the technical field of biological fermentation engineering or the chemical industry, and in particular to a citric acid and sodium salt co-production system. Background Art

[0002] The production process of citric acid and the problems faced in the current production process:

[0003] At present, my country's citric acid production capacity accounts for more than 80% of the world's total production capacity, of which almost all citric acid products come from the fermentation method. The energy consumption of citric acid concentration and crystallization in the production process of fermentation citric acid accounts for a considerable proportion of the total energy consumption. As a mass product, the profit of citric acid depends largely on the energy consumption in its production process. On the other hand, due to the needs of storage, transportation and terminal applications, citric acid and its sodium salt products corresponding to specific particle size and high particle size uniformity have a good market and a large profit margin. Therefore, how to effectively reduce energy consumption and improve the crystal quality of citric acid and its sodium salt has become an important factor for major citric acid companies to increase profits and market share.

[0004] In the traditional ion exchange method for extracting citric acid, the citric acid ion exchange liquid is pre-concentrated by a four-effect evaporator. After pre-concentration, one stream of the material enters a single-effect or double-effect evaporation crystallization device for crystallization, and the other stream of the material enters cooling crystallization to generate citric acid monohydrate. The steam energy consumption of this process is relatively high, the double-effect crystallization temperature is high, the control of carbonized substances is not ideal, and the product grade is not high. At the same time, a large amount of anhydrous citric acid mother liquor needs to be refluxed to the front of the ion exchange for reprocessing. During the processing, it should be diluted with water, and after the dilution, it needs to be evaporated and concentrated again, wasting a lot of steam. The production process of sodium citrate is to react citric acid particles with liquid alkali solution, and then evaporate and crystallize to generate sodium citrate dihydrate. This process also causes energy waste, and the overall production capacity is uncontrollable. Summary of the invention

[0005] The purpose of the present invention is to provide a citric acid and sodium salt co-production system to solve the technical problems of high energy consumption, small particle size and uneven particle size distribution in the prior art, and at the same time solve the problems of slow production capacity adjustment, lag, low degree of automation and the like caused by market fluctuations.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The invention provides a citric acid and sodium salt co-production system, comprising sequentially connected subsystems: a citric acid pre-concentration system, an anhydrous citric acid evaporation crystallization system, a monohydrate citric acid cooling crystallization system, a sodium citrate reaction system, and a dihydrate sodium citrate evaporation crystallization system.

[0008] In a preferred embodiment, the citric acid pre-concentration system comprises a main evaporator, a first separator, and a first buffer tank connected in sequence, the first buffer tank is connected to a downstream anhydrous citric acid evaporation and crystallization system; a preheater is connected upstream of the main evaporator;

[0009] The citric acid pre-concentration system further comprises a first MVR compressor, the vapor outlet of the first separator is connected to the gas inlet of the first MVR compressor, and the gas outlet of the first MVR compressor is connected to the heating channel of the main evaporator;

[0010] The preheater comprises a primary preheater and a secondary preheater connected in sequence, the secondary preheater is connected upstream of the main evaporator, the primary preheater is connected upstream of the secondary preheater, the main evaporator heating channel outlet is connected to the heat exchange medium pipeline inlet of the primary preheater; the outlet of the heat exchange medium pipeline of the primary preheater is connected to the first condenser;

[0011] A first-stage mass flowmeter and a first-stage pump are connected in sequence upstream of the first-stage preheater; the liquid outlet of the first separator is divided into two directions, which are respectively connected to the main evaporator and the first buffer tank, a second-stage pump is connected between the main evaporator and the liquid outlet of the first separator, a third-stage pump, a second-stage mass flowmeter, and a first-stage automatic regulating valve are connected in sequence between the liquid outlet of the first separator and the first buffer tank, and a second-stage automatic regulating valve is connected between the first separator and the first-stage automatic regulating valve; the liquid outlet of the main evaporator has a third-stage mass flowmeter and a fourth-stage pump connected in sequence.

[0012] The specific gravity of the citric acid raw material is between 1.05 and 1.2, the specific gravity of the citric acid raw material entering the buffer tank is between 1.3 and 1.4, the mass percentage is between 20% and 50%, and the feed temperature is between 20°C and 60°C.

[0013] In a preferred embodiment, the main evaporator in the citric acid pre-concentration system is a plate evaporator or a pipe evaporator, and the operating temperature range of the main evaporator is between 40°C and 70°C; the first MVR compressor is a centrifugal or Roots type, and the first MVR compressor is single-stage or multi-stage series, wherein multi-stage series means at least two stages in series, and the temperature rise range of the first MVR compressor is between 10°C and 22°C.

[0014] In a preferred embodiment, the anhydrous citric acid evaporation crystallization system comprises a first fine crystal eliminator, a first thickening flotation device, a first centrifuge, a first fluidized bed dryer, and a first vibrating screening machine connected in sequence to a downstream sodium citrate reaction system;

[0015] The liquid outlet of the first thickening flotation device is connected to the liquid inlet of the first cooling crystallizer, and the crystal outlet of the first crystallizer is connected to the crystal inlet of the first fine crystal eliminator; the liquid outlet of the first centrifuge is connected to the liquid inlet of the first mother liquid tank, and the first mother liquid tank is connected to the liquid inlet of the first cooling crystallizer, and the liquid outlet of the first mother liquid tank is connected to the downstream citric acid monohydrate cooling crystallization system, and the first vibrating screening machine is connected to the first automatic packaging machine;

[0016] A primary pump, a primary automatic regulating valve, and a primary mass flowmeter are sequentially connected between the first thickening flotation device and the first centrifuge; a secondary pump, a secondary automatic regulating valve, and a secondary mass flowmeter are sequentially connected between the first thickening flotation device and the first cooling crystallizer; a tertiary pump, a third-stage mass flowmeter, and a third-stage automatic regulating valve are sequentially connected between the first cooling crystallizer and the first fine crystal eliminator; and a fourth-stage pump, a fourth-stage automatic regulating valve, and a fourth-stage mass flowmeter are sequentially connected between the first mother liquid tank and the first cooling crystallizer;

[0017] The steam outlet of the first cooling crystallizer is connected to the gas inlet of the second MVR compressor, the gas outlet of the second MVR compressor is connected to the heat exchange medium pipeline inlet of the first heat exchanger, and the heat exchange medium pipeline outlet of the first heat exchanger is connected to the first condenser; the liquid outlet of the first cooling crystallizer, the raw material pipeline inlet of the first heat exchanger, the raw material pipeline outlet of the first heat exchanger, and the liquid inlet of the first cooling crystallizer are connected in sequence.

[0018] The particle size of the anhydrous citric acid produced by the anhydrous citric acid evaporation crystallization system is adjustable within the range of 18 meshes to 100 meshes, and the CV value under the corresponding mesh number is below 15%.

[0019] In a preferred embodiment, the citric acid monohydrate cooling crystallization system comprises a raw material pipeline inlet of a primary heat exchanger, a second cooling crystallizer, a second thickening flotation device, a second centrifuge, a second mother liquid tank, and a heat exchange medium pipeline of the primary heat exchanger connected to a downstream sodium citrate reaction system in sequence;

[0020] The liquid outlet of the second cooling crystallizer and the raw material pipeline inlet of the secondary heat exchanger are connected to a primary pump, and the raw material pipeline outlet of the secondary heat exchanger is connected to the liquid inlet of the second cooling crystallizer;

[0021] The solid outlet of the second centrifuge, the second fluidized bed dryer, the second vibrating sieving machine, and the second automatic packaging machine are connected in sequence;

[0022] A first-level mass flowmeter and a first-level automatic regulating valve are connected in sequence between the first-level preheater and the second cooling crystallizer; a second-level pump, a second-level mass flowmeter and a second-level automatic regulating valve are connected in sequence between the second cooling crystallizer and the second thickening flotation device; a third-level automatic regulating valve, a third-level mass flowmeter and a third-level pump are connected in sequence between the second thickening flotation device and the second heat exchanger; a fourth-level pump, a fourth-level automatic regulating valve and a fourth-level mass flowmeter are connected in sequence between the second thickening flotation device and the second centrifuge; a fifth-level pump, a fifth-level automatic regulating valve and a fifth-level mass flowmeter are connected in sequence between the second mother liquid tank and the second cooling crystallizer; a sixth-level pump is connected between the second mother liquid tank and the first-level preheater; and a seventh-level pump and a sixth-level mass flowmeter are connected in sequence at the liquid outlet of the second mother liquid tank.

[0023] In a preferred embodiment, the heat exchanger in the cooling crystallization system of citric acid monohydrate is a tubular forced circulation heat exchanger, and the cooling crystallizer is a DTB type crystallizer or an OSLO type crystallizer. The cooling crystallizer can produce citric acid monohydrate with a particle size of 5 to 60 meshes, and the CV value under the corresponding mesh number is less than 15%. The mother liquor in the buffer tank is set with two discharge directions, one with sodium citrate reaction crystallization feeding, and the other is used to produce anhydrous citric acid after further impurity removal treatment to achieve flexible adjustment of different production requirements.

[0024] In a preferred embodiment, the sodium citrate reaction system comprises a primary reaction crystallizer, a primary fine filtration tube, and a second buffer tank connected in sequence, and also comprises a secondary reaction crystallizer, a secondary fine filtration tube, a primary adsorption tank, a primary decolorization tank buffer tank connected in sequence, and comprises a second buffer tank, a secondary decolorization tank, a secondary adsorption tank, and a tertiary fine filtration tube connected in sequence;

[0025] The upstream of the primary reaction crystallizer is connected to a primary alkali adding system and is sequentially connected to a primary silo and a secondary silo, the upstream of the secondary reaction crystallizer is connected to a secondary alkali adding system, a primary pump is connected between the primary reaction crystallizer and the primary fine filter tube, a secondary pump is connected between the secondary reaction crystallizer and the secondary fine filter tube, and a liquid outlet of the second buffer tank is sequentially connected to a three-stage pump, a primary automatic regulating valve, and a primary mass flowmeter connected to a downstream sodium citrate dihydrate evaporation crystallization system;

[0026] The liquid outlet of the tertiary fine filter tube is connected in sequence with a secondary automatic regulating valve and a secondary mass flow meter connected to a downstream sodium citrate dihydrate evaporation crystallization system.

[0027] In a preferred embodiment, the sodium citrate dihydrate evaporation crystallization system comprises a second fine crystal eliminator, a third thickening flotation device, a third centrifuge, a third fluidized bed dryer, and a third vibrating screening machine connected in sequence;

[0028] The liquid outlet of the third thickening flotation device is connected to the liquid inlet of the third cooling crystallizer, and the crystal outlet of the third cooling crystallizer is connected to the crystal inlet of the second fine crystal eliminator;

[0029] The liquid outlet of the third centrifuge is connected to the liquid inlet of the third mother liquid tank, the third mother liquid tank is connected to the liquid inlet of the third cooling crystallizer, and the second vibration screening machine is connected to the second automatic packaging machine;

[0030] The upstream of the second fine crystal eliminator is connected with a first-stage automatic regulating valve;

[0031] A secondary pump, a primary automatic regulating valve, and a primary mass flowmeter are sequentially connected between the third thickening flotation device and the third centrifuge; a tertiary pump, a secondary automatic regulating valve, and a secondary mass flowmeter are sequentially connected between the third thickening flotation device and the third cooling crystallizer; the third cooling crystallizer is connected to the primary automatic regulating valve; a fourth-stage pump, a third-stage mass flowmeter, and a third-stage automatic regulating valve are sequentially connected between the third cooling crystallizer and the second fine crystal eliminator; a fifth-stage pump, a fourth-stage automatic regulating valve, and a fourth-stage mass flowmeter are sequentially connected between the third mother liquid tank and the third cooling crystallizer; a sixth-stage pump is connected upstream of the third mother liquid tank; the steam outlet of the third cooling crystallizer is connected to the gas inlet of the third MVR compressor, the gas outlet of the third MVR compressor is connected to the heat exchange medium pipeline inlet of the second heat exchanger, and the heat exchange medium pipeline outlet of the second heat exchanger is connected to the condenser; the liquid outlet of the third cooling crystallizer, the raw material pipeline inlet of the second heat exchanger, the raw material pipeline outlet of the second heat exchanger, and the liquid inlet of the third cooling crystallizer are sequentially connected.

[0032] In a preferred embodiment, an inverted cone baffle is provided inside the thickening flotation device, the primary reaction crystallizer is intermittently operated and is provided with an adjustable speed stirring device, the automatic feeding system weighs the citric acid particles in the secondary silo and then adds them to the primary reaction crystallizer at one time, the primary alkali adding system adds liquid alkali according to the return value of the automatic control system, and the secondary alkali adding system can add liquid alkali or alkali flakes.

[0033] In a preferred embodiment, each subsystem is respectively connected to the main control system, and each subsystem uses the connection between its internal pump and mass flow meter to interlock and control the switch of the pump, thereby adjusting the feed flow rate; the mass flow meter feeds back the real-time acquired density, temperature, and flow data to the main control system, thereby realizing the interlocking control of the main control system over the operation of each subsystem; the main control system includes an information receiving and storage module, a self-calculation module, and a feedback control module, wherein the main control system interlocks and controls the operation of each subsystem.

[0034] In a preferred embodiment, a method for co-producing citric acid and its sodium salt comprises the following steps:

[0035] Step 1: pre-concentrating the citric acid solution to obtain a first concentrated solution;

[0036] Step 2: The first concentrated liquid is evaporated and crystallized to obtain anhydrous citric acid crystals and mother liquor;

[0037] Step 3: The mother liquor is cooled and crystallized to obtain citric acid monohydrate crystals and a second concentrated solution;

[0038] Step 4: adding alkali to the second concentrated solution to react to obtain sodium citrate, and then filtering, drying and crystallizing to obtain sodium citrate crystals and a reaction solution;

[0039] Step 5: After thickening, the reaction solution is evaporated and crystallized to obtain sodium citrate dihydrate crystals.

[0040] In a preferred embodiment, the citric acid pre-concentration process includes: the citric acid solution is passed through a main evaporator to obtain a vapor-liquid mixture; the vapor-liquid mixture enters a first separator to generate secondary steam and a first concentrated liquid;

[0041] The secondary steam passes through the first MVR compressor to obtain a solution which enters the main evaporator;

[0042] The first concentrated liquid is compressed and heated in the first buffer tank to provide a heat source for the main evaporator.

[0043] In a preferred embodiment, the anhydrous citric acid evaporation crystallization process comprises: the first concentrated liquid is passed through a first fine crystal eliminator to remove all or part of the crystals, the obtained decrystallized solution enters a first thickening flotation device to obtain a solid-liquid mixture, the solid-liquid mixture is subjected to solid-liquid separation to obtain citric acid crystals and mother liquor, the citric acid crystals are sequentially dried by a first fluidized bed dryer and sieved by a first vibrating sieving machine to obtain anhydrous citric acid crystals.

[0044] In a preferred embodiment, the cooling crystallization process of citric acid monohydrate comprises: the mother liquor enters a second cooling crystallizer to obtain a solution containing crystals, the solution containing crystals enters a second thickening flotation device to obtain a solid-liquid mixture, and the solid-liquid mixture is subjected to solid-liquid separation to obtain crystals and a second concentrated solution;

[0045] The crystals are sequentially dried in a second fluidized bed dryer and sieved in a second vibrating sieving machine to obtain citric acid monohydrate crystals.

[0046] In a preferred embodiment, the sodium citrate reaction crystallization process comprises: anhydrous citric acid crystals and alkali enter a primary reaction crystallizer to react to obtain a first reaction mixture containing crystals, and the reaction mixture enters a second buffer tank through a primary fine filter tube;

[0047] The second concentrated liquid and the alkali enter the secondary reaction crystallizer together to react to obtain a second reaction mixture containing crystals. The second reaction mixture enters the second buffer tank through the secondary fine filtration tube, the primary adsorption tank, the primary decolorization tank and the buffer tank.

[0048] In a preferred embodiment, the reaction mixture in the second buffer tank sequentially passes through a secondary decolorization tank, a secondary adsorption tank, and a tertiary fine filtration tube to enter the sodium citrate dihydrate evaporation crystallization system.

[0049] In a preferred embodiment, the sodium citrate dihydrate evaporation crystallization process comprises: the sodium citrate dihydrate evaporation crystallization process comprises: the reaction liquid is passed through a second fine crystal eliminator to remove all or part of the crystals, the obtained crystal removal solution enters a third thickening flotation device to obtain a solid-liquid mixture, the solid-liquid mixture is subjected to solid-liquid separation to obtain sodium citrate crystals and mother liquor, the sodium citrate crystals are dried through a third fluidized bed dryer and sieved through a third vibrating sieving machine to obtain sodium citrate dihydrate crystals.

[0050] Compared with the existing citric acid extraction production process, the present invention is a device for automatically producing citric acid and its sodium salt. A main control system is used to operate the subsystems of a citric acid pre-concentration system, an anhydrous citric acid evaporation crystallization system, a monohydrate citric acid cooling crystallization system, a sodium citrate reaction system, and a dihydrate sodium citrate evaporation crystallization system to realize a chain control system to produce citric acid and its sodium salt. Each subsystem can be chain-controlled by connecting a pump and a mass flow meter to control the switch of the pump, and the mass flow meter feeds back the density, temperature, and flow data obtained in real time to the main control system, thereby realizing an automatic control system. The present application adopts MVR evaporation and MVR crystallization energy-saving processes, which can save a large amount of fresh steam and alleviate the environmental protection pressure faced by enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The present invention is a simplified flow chart of a system for co-production of citric acid and its sodium salt;

[0052] Figure 2 for Figure 1 The middle dotted box 1 is an enlarged view of the citric acid preconcentration system;

[0053] Figure 3 for Figure 1 The middle dotted box 2 is an enlarged view of the anhydrous citric acid evaporation crystallization system;

[0054] Figure 4 for Figure 1 The middle dotted box 3 is an enlarged view of the cooling crystallization system of citric acid monohydrate;

[0055] Figure 5 for Figure 1 The middle dotted box 4 is an enlarged view of the sodium citrate reaction system;

[0056] Figure 6 for Figure 1 The middle dotted box 5 is an enlarged view of the sodium citrate dihydrate evaporation crystallization system. DETAILED DESCRIPTION

[0057] The following is combined with Figure 1 The present invention is described in further detail.

[0058] Example 1

[0059] like Figure 1 As shown, the present invention provides a citric acid and sodium salt co-production system, comprising: a citric acid pre-concentration system ( Figure 2 ), anhydrous citric acid evaporation crystallization system ( Figure 3 ), citric acid monohydrate cooling crystallization system ( Figure 4 ), sodium citrate reaction system ( Figure 5 ), Sodium citrate dihydrate evaporation crystallization system ( Figure 6 ), and the subsystems are all connected in parallel with the main control system.

[0060] The citric acid preconcentration system ( Figure 2 ), including a main evaporator 1Z01, a separator 1F01, and a buffer tank 1G01 connected in sequence through a material pipeline, wherein: the material outlet of the main evaporator 1Z01 is connected to the separator 1F01, the liquid outlet of the separator 1F01 is connected to the buffer tank 1G01, and a steam outlet is provided at the top of the separator 1F01; a preheater is connected upstream of the main evaporator 1Z01, and the material outlet of the preheater is connected to the material channel inlet of the main evaporator 1Z01; a heating channel is provided in the main evaporator 1Z01 to heat the material channel. A three-stage pump 1P03, a two-stage mass flowmeter 1LL02, and a first-stage automatic regulating valve 1V01 are provided in sequence between the liquid outlet of the separator 1F01 and the buffer tank 1G01. The downstream of the buffer tank 1G01 is connected in sequence with a seven-stage pump 1P07, a four-stage mass flowmeter 1LL04, and a three-stage automatic regulating valve 1V03, and 1O1 downstream of the three-stage automatic regulating valve 1V03 is connected to the fine crystal eliminator 2HH01 of the downstream anhydrous citric acid evaporation crystallization system.

[0061] The anhydrous citric acid evaporation crystallization system ( Figure 3), including a fine crystal eliminator 2HH01, a thickening flotation device 2ZC01, a centrifuge 2LX01, a fluidized bed dryer 2GZ01, a vibrating screen 2SF01, and an automatic packaging machine 2BZ01, which are connected in sequence through material pipelines; wherein the centrifuge 2LX01 is provided with a liquid outlet and a solid outlet, the solid outlet of the centrifuge 2LX01 is connected in sequence to the fluidized bed dryer 2GZ01 and the vibrating screen 2SF01 to obtain qualified crystals, which are then sent to the automatic packaging machine 2BZ01, wherein the unqualified crystals 2O2 (such as crystals with too large particles) screened out by the vibrating screen 2SF01 are connected to the first silo 4LC1 of the downstream sodium citrate reaction system; the liquid outlet of the centrifuge 2LX01 is connected to the mother liquid tank 2G01, and the 2O1 downstream of the mother liquid tank 2G01 is connected to the primary heat exchanger 3H02 of the downstream monohydrate citric acid cooling crystallization system.

[0062] The citric acid monohydrate cooling crystallization system ( Figure 4 ), including a primary heat exchanger 3H02, a cooling crystallizer 3J01, a thickening flotation device 3ZC01, a centrifuge 3LX01, and a mother liquid tank 3G01 which are connected in sequence through a material pipeline, wherein the centrifuge 3LX01 is provided with a liquid outlet and a solid outlet, the liquid outlet of the centrifuge 3LX01 is connected to the mother liquid tank 3G01, the liquid outlet of the mother liquid tank 3G01 is connected to the heat exchange medium pipeline of the heat exchanger 3H02 to the downstream 3O1 connected to the second reaction crystallizer 4J02 of the downstream sodium citrate reaction system.

[0063] The sodium citrate reaction system ( Figure 5 ) includes a first silo 4LC1, a second silo 4LC2, a first reaction crystallizer 4J01, a primary pump 4P01, a third fine filter tube 4GL3, a buffer tank 4G01, a tertiary pump 4P03, an automatic regulating valve 4V02, and a mass flow meter 4LL02, and 4O1 downstream of the mass flow meter 4LL02 is connected to the automatic regulating valve 5V01 of the downstream sodium citrate dihydrate evaporation crystallization system, and a first alkali adding system 4M1 is connected to the first reaction crystallizer 4J01, and a second alkali adding system 4M2 is connected to the second reaction crystallizer 4J02; the downstream of the second reaction crystallizer 4J02 is connected in sequence with a fine filter tube 4GL1, an adsorption tank 4XF1, and a decolorization tank 4TS1, and the decolorization tank 4TS1 is connected to the buffer tank 4G01.

[0064] The sodium citrate dihydrate evaporation crystallization system ( Figure 6) includes an automatic regulating valve 5V01, a fine crystal eliminator 5HH01, a thickening suspender 5ZC01, a centrifuge 5LX01, a fluidized bed dryer 5GZ01, a vibrating screen 5SF01, and a discharge port 5M1, wherein the liquid discharge port of the centrifuge 5LX01 is connected to a mother liquid tank 5G01, and the mother liquid tank 5G01 is connected to a sodium citrate reaction system ( Figure 5 ), through mass flow meter 5LL06, automatic regulating valve 5V06, fine filter tube 4GL2, adsorption tank 4XF2, decolorization tank 4TS2, the decolorization tank 4TS2 is connected to the buffer tank 4G01.

[0065] The working process of the citric acid and sodium salt co-production system provided in this embodiment is as follows:

[0066] Dilute citric acid solution 1MI01 enters the citric acid pre-concentration system ( Figure 2 ), after being heated by the preheater, the gas-liquid mixture is obtained by the main evaporator 1Z01, and the gas-liquid mixture is separated by the separator 1F01 to obtain the pre-concentrated citric acid material, which is sent to the buffer tank 1G01 to obtain 1O1 and enter the anhydrous citric acid evaporation crystallization system ( Figure 3 ) of the fine crystal eliminator 2HH01, remove the crystals in the material A to obtain the material B, the material B enters the thickening flotation device 2ZC01 to obtain the material C, the material C enters the centrifuge 2LX01 for solid-liquid separation to obtain the crystals and the material D, the crystals are successively passed through the boiling bed dryer 2GZ01, the vibration sieving machine 2SF01, and the automatic packaging machine 2BZ01 for drying, sieving, and packaging to obtain the anhydrous citric acid crystals, wherein the solution 2O2 containing the anhydrous citric acid crystals is also obtained in the vibration sieving machine 2SF01 and enters the sodium citrate reaction system ( Figure 6 )'s first silo 4LC1; Material D enters the mother liquid tank 2G01 to obtain 2O1 which enters the citric acid monohydrate cooling crystallization system ( Figure 4 ) of the first heat exchanger 3H02; 2O1 passes through the first heat exchanger 3H02 for heat exchange, enters the cooling crystallizer 3J01 for crystallization treatment to obtain material E, material E enters the thickening flotation device 3ZC01 to obtain material F, material F enters the centrifuge 3LX01 for solid-liquid separation to obtain monohydrate citric acid crystals and material G, material G passes through the heat exchange medium pipeline of the heat exchanger 3H02 to obtain 3O1 and enters the sodium citrate reaction system ( Figure 6 ) of the second reaction crystallizer 4J02, 2O2 and alkali 4M1 enter the crystallizer 4J01 through a two-stage hopper and enter the buffer tank 4G01, 3O1 and alkali 4M2 enter the crystallizer 4J02 and enter the fine filter tube 4GL1, adsorption tank 4XF1, decolorization tank 4TS1 buffer tank 4G01 to obtain 4O1 and enter the sodium citrate dihydrate evaporation crystallization system ( Figure 6) passes through the automatic regulating valve 5V01, passes through the fine crystal eliminator 5HH01 to obtain material H, passes through the thickening flotation device 5ZC01 to obtain material I, and then passes through the centrifuge 5LX01 to obtain sodium citrate crystals and material J. Material J passes through the mother liquid tank 2G01 to obtain material K. The sodium citrate crystals pass through the boiling bed dryer 5GZ01 and the vibration screening machine 5SF01 to obtain dried sodium citrate crystals. The sodium citrate crystals are passed through the automatic packaging machine 5BZ01 to obtain the finished sodium citrate crystals, of which the 4O2 passing through the mother liquid tank 5G01 and the pump 5P06 flows back to the sodium citrate reaction system ( Figure 5 ), flows back to the buffer tank 4G01 through the mass flow meter 5LL06, automatic regulating valve 5V06, fine filter tube 4GL2, adsorption tank 4XF2, and decolorization tank 4TS2.

[0067] In the citric acid and sodium salt co-production system described in this embodiment, the overall yield of citric acid (including citric acid and sodium citrate) can reach 98%.

[0068] Example 2

[0069] Reference Figure 2 Based on Example 1, the citric acid pre-concentration system provided in this example also includes an MVR compressor 1Y01, the steam outlet of the separator 1F01 is connected to the gas inlet of the MVR compressor 1Y01, and the gas outlet of the MVR compressor 1Y01 is connected to the heating channel inlet of the main evaporator 1Z01.

[0070] The preheater includes a primary preheater 1H02 and a secondary preheater 1H03 which are connected in sequence. The secondary preheater 1H03 is connected upstream of the main evaporator 1Z01, and the primary preheater 1H02 is connected upstream of the secondary preheater 1H03. The outlet of the heating channel of the main evaporator 1Z01 is connected to the inlet of the heat exchange medium pipeline of the primary preheater 1H02.

[0071] The outlet of the heat exchange medium pipeline of the primary preheater 1H02 is connected to the condenser 1H01. One outlet of the condenser 1H01 is divided into two branches, each of which is provided with a five-stage pump 1P05 and a six-stage pump 1P06.

[0072] The upstream of the primary preheater 1H02 is provided with a primary mass flow meter 1LL01 and a primary pump 1P01 connected in sequence.

[0073] The outlet of the heating channel of the main evaporator 1Z01 is provided with a waste discharge branch, on which a three-stage mass flow meter 1LL03 and a four-stage pump 1P04 are arranged in sequence.

[0074] The working method of this embodiment is as follows:

[0075] The gas separated by the separator 1F01 is sent to the MVR compressor 1Y01 for compression and temperature increase, and then sent to the heating channel of the main evaporator 1Z01 to exchange heat with the material in the main evaporator 1Z01 to heat the material in the main evaporator 1Z01. The fluid after heat exchange is sent to the heat exchange medium pipeline inlet of the primary preheater 1H02 to exchange heat with the material in the primary preheater 1H02 to preheat the material in the primary preheater 1H02, thereby realizing the reuse of exhaust gas and waste heat utilization.

[0076] The fluid after heat exchange passes through the primary preheater 1H02, is sent to the condenser 1H01 for cooling, and then is discharged through the pump 1P05 or 1P06.

[0077] The other heating fluid 1S01 passes through the secondary preheater 1H03, exchanges heat with the material entering the secondary preheater 1H03, and further heats the material preheated by the primary preheater 1H02.

[0078] Example 3

[0079] Reference Figure 3 Based on Example 1, the anhydrous citric acid evaporation crystallization system provided in this embodiment also includes a crystallizer 2J01, and the crystallizer 2J01 is provided with a first outlet, a second outlet, and a third outlet.

[0080] The first outlet of the crystallizer 2J01 is connected to the fine crystal eliminator 2HH01 through the first-stage pump 2P01, the fourth-stage mass flowmeter 2LL04, and the fourth-stage automatic regulating valve 2V04 in sequence, and the fine crystal eliminator 2HH01 is connected to the thickening flotation device 2ZC01 through the second-stage mass flowmeter 2LL02, the second-stage automatic regulating valve 2V02, and the third-stage pump 2P03 in sequence.

[0081] The material pipeline between the thickening flotation device 2ZC01 and the centrifuge 2LX01 is provided with a four-stage pump 2P01, a first-stage automatic regulating valve 2V01, and a first-stage mass flow meter 2LL01 in sequence.

[0082] The second outlet of the crystallizer 2J01 is connected to the material pipeline inlet of the heat exchanger 2H01 through the secondary pump 2P02, and the material pipeline outlet of the heat exchanger 2H01 is connected to the crystallizer 2J01.

[0083] The heat exchange medium pipeline outlet of the heat exchanger 2H01 is connected to the condenser 2H02.

[0084] The condenser 2H02 is provided with two outlets, the first outlet is provided with a seven-stage pump 2P07 and a five-stage mass flowmeter 2LL05 in sequence; the second outlet is provided with an eight-stage pump 2P08.

[0085] The inlet of the heat exchanger 2H01 is connected to the outlet of the MVR compressor 2Y01, and the inlet of the MVR compressor 2Y01 is connected to the crystallizer 2J01.

[0086] The third outlet of the crystallizer 2J01 is connected to the mother liquid tank 2G01 through a three-stage mass flow meter 2LL03, a three-stage automatic regulating valve 2V03, and a five-stage pump 2P05 in sequence.

[0087] The working method of this embodiment is as follows:

[0088] The gas discharged from the crystallizer 2J01 is sent to the MVR compressor 2Y01 for compression and temperature increase, and then sent to the heat exchanger 2H01. The hot gas discharged from the heat exchanger 2H01 is cooled and discharged through the condenser 2H02; the solution 1 of the thickening flotation device 3ZC01 flows to the fine crystal eliminator 2HH01 through the crystallizer 2J01; the solution 2 in the crystallizer 2J01 flows back to the crystallizer 2J01 through the heat exchanger 2H01; the mother liquor in the mother liquor tank 2G01 flows back to the crystallizer 2J01.

[0089] Example 4

[0090] Reference Figure 4 Based on Example 1, the cooling crystallization system of citric acid monohydrate provided in this embodiment includes a primary heat exchanger 3H02, a cooling crystallizer 3J01, a thickener flotation device 3ZC01, a centrifuge 3LX01, and a mother liquid tank 3G01 which are connected in sequence through a material pipeline, wherein the centrifuge 3LX01 is provided with a liquid outlet and a solid outlet, and the liquid outlet of the centrifuge 3LX01 is connected to the mother liquid tank 3G01.

[0091] The material pipeline between the primary heat exchanger 3H02 and the cooling crystallizer 3J01 is provided with a primary mass flow meter 3LL01 and a primary automatic regulating valve 3V01 in sequence.

[0092] The cooling crystallizer 3J01 is provided with two outlets, the first outlet is connected to the thickening flotation device 3ZC01 through the tertiary pump 3P03, the secondary mass flow meter 3LL02 and the secondary automatic regulating valve 3V02 in sequence; the second outlet is connected to the raw material pipeline inlet of the secondary heat exchanger 3H01 through the primary pump 3P01, and the raw material pipeline outlet of the secondary heat exchanger 3H01 is connected to the cooling crystallizer 3J01.

[0093] The material pipeline between the raw material pipeline inlet of the secondary heat exchanger 3H01 and the thickener flotation device 3ZC01 is provided with a secondary pump 3P02, a tertiary mass flow meter 3LL03, and a tertiary automatic regulating valve 3V03 in sequence.

[0094] The material pipeline between the thickening flotation device 3ZC01 and the centrifuge 3LX01 is provided with a four-stage pump 3P04, a four-stage automatic regulating valve 3V04, and a four-stage mass flow meter 3LL04 in sequence.

[0095] The mother liquid tank 3G01 is provided with three outlets, the first outlet is connected to the first outlet of the cooling crystallizer 3J01 through a five-stage pump 3P05, a five-stage automatic regulating valve 3V05, and a five-stage mass flowmeter 3LL05; the second outlet is connected to the heat exchange medium pipeline of the first-stage heat exchanger 3H02 through a seven-stage pump 3P07; the third outlet is connected to a six-stage pump 3P06 and a six-stage mass flowmeter 3LL06 in sequence.

[0096] The solid outlet of the centrifuge 3LX01 is connected in sequence to the dryer 3GZ01, the screening machine 3SF01 and the automatic packaging machine 3BZ01.

[0097] The working method of this embodiment is as follows:

[0098] The solution 3 in the cooling crystallizer 3J01 flows back to the cooling crystallizer 3J01 through the heat exchanger 3H01; the solution 4 in the heat exchanger 3H01 flows to the thickening flotation device 3ZC01; the solution 5 in the mother liquid tank 3G01 flows back to the cooling crystallizer 3J01 through the five-stage pump 3P05, the five-stage automatic regulating valve 3V05, and the five-stage mass flowmeter 3LL05.

[0099] Example 5

[0100] Reference Figure 6 Based on Example 1, the sodium citrate dihydrate evaporation crystallization system provided in this embodiment also includes a crystallizer 5J01, and the crystallizer 5J01 is provided with a first outlet, a second outlet, and a third outlet.

[0101] The first outlet of the crystallizer 5J01 is connected to the fine crystal eliminator 5HH01 through the first-stage pump 5P01, the fourth-stage mass flowmeter 5LL04, and the fourth-stage automatic regulating valve 5V04 in sequence, and the fine crystal eliminator 5HH01 is connected to the thickening flotation device 5ZC01 through the second-stage mass flowmeter 5LL02, the second-stage automatic regulating valve 5V02, and the third-stage pump 5P03 in sequence.

[0102] The material pipeline between the thickening flotation device 5ZC01 and the centrifuge 5LX01 is provided with a four-stage pump 5P01, a first-stage automatic regulating valve 5V01, and a first-stage mass flow meter 5LL01 in sequence.

[0103] The second outlet of the crystallizer 5J01 is connected to the material pipeline inlet of the heat exchanger 2H01 through the secondary pump 5P02, and the material pipeline outlet of the heat exchanger 5H01 is connected to the crystallizer 5J01.

[0104] The heat exchange medium pipeline outlet of the heat exchanger 5H01 is connected to the condenser 5H02.

[0105] The condenser 5H02 is provided with two outlets, the first outlet is provided with a seven-stage pump 5P07 and a five-stage mass flowmeter 5LL05 in sequence; the second outlet is provided with an eight-stage pump 5P08.

[0106] The inlet of the heat exchanger 5H01 is connected to the outlet of the MVR compressor 5Y01, and the inlet of the MVR compressor 5Y01 is connected to the crystallizer 5J01.

[0107] The third outlet of the crystallizer 5J01 is connected to the mother liquid tank 5G01 through a three-stage mass flow meter 5LL03, a three-stage automatic regulating valve 5V03, and a five-stage pump 5P05 in sequence.

[0108] The working method of this embodiment is as follows:

[0109] The gas discharged from the crystallizer 5J01 is sent to the MVR compressor 5Y01 for compression and temperature increase, and then sent to the heat exchanger 5H01. The hot gas discharged from the heat exchanger 5H01 is cooled and discharged through the condenser 5H02; the solution 6 of the thickening flotation device 5ZC01 flows to the fine crystal eliminator 5HH01 through the crystallizer 5J01; the solution 7 in the crystallizer 5J01 flows back to the crystallizer 5J01 through the heat exchanger 5H01; the mother liquor in the mother liquor tank 5G01 flows back to the crystallizer 5J01.

[0110] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A system for co-producing citric acid and its sodium salt, characterized in that: It includes subsystems connected in sequence: citric acid pre-concentration system, anhydrous citric acid evaporation crystallization system, monohydrate citric acid cooling crystallization system, sodium citrate reaction system, and dihydrate sodium citrate evaporation crystallization system; Each of the subsystems is connected to the main control system, and each subsystem uses the connection between the pump and the mass flow meter inside to interlock and control the switch of the pump, thereby adjusting the feed flow rate; The mass flow meter feeds back the density, temperature and flow data acquired in real time to the main control system, thereby realizing the interlocking control of the main control system over the operation of each subsystem; The main control system includes an information receiving and storage module, a self-operation module, and a feedback control module, wherein the main control system interlocks and controls the operation of each subsystem; The citric acid pre-concentration system comprises a main evaporator, a first separator, and a first buffer tank which are connected in sequence, and the first buffer tank is connected to a downstream anhydrous citric acid evaporation and crystallization system; a preheater is connected upstream of the main evaporator; The citric acid pre-concentration system further comprises a first MVR compressor, the vapor outlet of the first separator is connected to the gas inlet of the first MVR compressor, and the gas outlet of the first MVR compressor is connected to the heating channel of the main evaporator; The preheater comprises a primary preheater and a secondary preheater connected in sequence, the secondary preheater is connected upstream of the main evaporator, the primary preheater is connected upstream of the secondary preheater, the main evaporator heating channel outlet is connected to the heat exchange medium pipeline inlet of the primary preheater; the outlet of the heat exchange medium pipeline of the primary preheater is connected to the first condenser; The liquid outlet of the separator is divided into two directions, connected to the main evaporator and the buffer tank respectively; The anhydrous citric acid evaporation crystallization system comprises a first fine crystal eliminator, a first thickening flotation device, a first centrifuge, a first fluidized bed dryer, and a first vibrating screening machine which are connected in sequence and connected to a downstream sodium citrate reaction system; The liquid outlet of the first thickening flotation device is connected to the liquid inlet of the first cooling crystallizer, and the crystal outlet of the first cooling crystallizer is connected to the crystal inlet of the first fine crystal eliminator; the liquid outlet of the first centrifuge is connected to the liquid inlet of the first mother liquid tank, and the outlet of the first mother liquid tank is connected to the liquid inlet of the first cooling crystallizer, and the liquid outlet of the first mother liquid tank is connected to the downstream citric acid monohydrate cooling crystallization system, and the first vibrating screening machine is connected to the first automatic packaging machine; The steam outlet of the first cooling crystallizer is connected to the gas inlet of the second MVR compressor, the gas outlet of the second MVR compressor is connected to the heat exchange medium pipeline inlet of the second heat exchanger, and the heat exchange medium pipeline outlet of the second heat exchanger is connected to the first condenser; the liquid outlet of the first cooling crystallizer, the raw material pipeline inlet of the second heat exchanger, the raw material pipeline outlet of the second heat exchanger, and the liquid inlet of the first cooling crystallizer are connected in sequence; The citric acid monohydrate cooling crystallization system comprises a primary heat exchanger, a second cooling crystallizer, a second thickening flotation device, a second centrifuge, a second mother liquid tank, and a heat exchange medium pipeline of the primary heat exchanger connected to a downstream sodium citrate reaction system. The raw material pipeline outlet of the secondary heat exchanger is connected to the liquid inlet of the second cooling crystallizer; the solid outlet of the second centrifuge, the second fluidized bed dryer, the second vibrating sieving machine, and the second automatic packaging machine are connected in sequence; The sodium citrate reaction system comprises: First-stage reaction crystallizer, first-stage fine filter tube, second buffer tank, second-stage reaction crystallizer, second-stage fine filter tube, first-stage adsorption tank, first-stage decolorization tank, second-stage decolorization tank, second-stage adsorption tank, third-stage fine filter tube, The outlet of the primary reaction crystallizer is connected to the inlet of the primary fine filter tube, and the outlet of the primary fine filter tube is connected to the inlet of the second buffer tank. The outlet of the secondary reaction crystallizer is connected to the inlet of the secondary fine filter tube, the outlet of the secondary fine filter tube is connected to the inlet of the primary adsorption tank, the outlet of the primary adsorption tank is connected to the inlet of the primary decolorization tank, and the outlet of the primary decolorization tank is connected to the inlet of the second buffer tank. The outlet of the second buffer tank is connected to the inlet of the secondary decolorization tank, the outlet of the secondary decolorization tank is connected to the inlet of the secondary adsorption tank, and the outlet of the secondary adsorption tank is connected to the inlet of the tertiary fine filter tube; The upstream of the primary reaction crystallizer is connected to a primary alkali adding system and is connected to a primary silo and a secondary silo in sequence, and the upstream of the secondary reaction crystallizer is connected to a secondary alkali adding system. The liquid outlet of the second buffer tank is connected to the downstream sodium citrate dihydrate evaporation crystallization system, and the liquid outlet of the tertiary fine filter tube is connected to the downstream sodium citrate dihydrate evaporation crystallization system; The sodium citrate dihydrate evaporation crystallization system comprises a second fine crystal eliminator, a third thickening flotation device, a third centrifuge, a third fluidized bed dryer, and a third vibrating screening machine connected in sequence; The liquid outlet of the third thickening flotation device is connected to the liquid inlet of the third cooling crystallizer, and the crystal outlet of the third cooling crystallizer is connected to the crystal inlet of the second fine crystal eliminator; The liquid outlet of the third centrifuge is connected to the liquid inlet of the third mother liquid tank, the outlet of the third mother liquid tank is connected to the liquid inlet of the third cooling crystallizer, and the second vibration screening machine is connected to the second automatic packaging machine; The upstream of the second fine crystal eliminator is connected with a first-stage automatic regulating valve; The steam outlet of the third cooling crystallizer is connected to the gas inlet of the third MVR compressor, the gas outlet of the third MVR compressor is connected to the heat exchange medium pipeline inlet of the second heat exchanger, and the heat exchange medium pipeline outlet of the second heat exchanger is connected to the second condenser; The liquid outlet of the third cooling crystallizer, the raw material pipeline inlet of the second heat exchanger, the raw material pipeline outlet of the second heat exchanger, and the liquid inlet of the third cooling crystallizer are connected in sequence; The dilute citric acid solution 1MI01 enters the citric acid pre-concentration system, is heated by the preheater, and then passes through the main evaporator to obtain a gas-liquid mixture. The gas-liquid mixture passes through a separator for gas-liquid separation to obtain a pre-concentrated citric acid material. The pre-concentrated citric acid material is sent to a buffer tank to obtain 1O1, which enters the fine crystal eliminator of the anhydrous citric acid evaporation and crystallization system to remove the crystals in material A to obtain material B; Material B enters the thickening flotation device to obtain material C; Material C enters the centrifuge for solid-liquid separation to obtain crystals and material D. The crystals are sequentially dried, screened, and packaged in a fluidized bed dryer, a vibrating sieving machine, and an automatic packaging machine to obtain anhydrous citric acid crystals. The vibrating sieving machine also obtains a solution 2O2 containing anhydrous citric acid crystals and enters the first silo of the sodium citrate reaction system. Material D enters the mother liquid tank to obtain 2O1 which enters the primary heat exchanger of the cooling crystallization system of citric acid monohydrate; 2O1 is heat exchanged through the primary heat exchanger and enters the cooling crystallizer for crystallization to obtain material E; Material E enters the thickening flotation device to obtain material F, and material F enters the centrifuge for solid-liquid separation to obtain citric acid monohydrate crystals and material G; Material G passes through the heat exchange medium pipeline of the heat exchanger to obtain 3O1 which enters the second reaction crystallizer of the sodium citrate reaction system. 2O2 and alkali 4M1 enter the crystallizer through a two-stage hopper and enter the buffer tank. 3O1 and alkali 4M2 enter the crystallizer and enter the fine filter tube, adsorption tank, decolorization tank, and buffer tank to obtain 4O1 which enters the sodium citrate dihydrate evaporation crystallization system and passes through an automatic regulating valve and a fine crystal eliminator to obtain material H. The material I obtained by the thickening flotation device is then passed through a centrifuge to obtain sodium citrate crystals and material J; Material J is passed through the mother liquid tank to obtain material K, and the sodium citrate crystals are passed through a fluidized bed dryer and a vibrating sieving machine to obtain dried sodium citrate crystals, which are then passed through an automatic packaging machine to obtain finished sodium citrate crystals. The 4O2 from the mother liquid tank and the pump flows back to the sodium citrate reaction system, and then flows back to the buffer tank through a mass flow meter, an automatic regulating valve, a fine filter tube, an adsorption tank, and a decolorization tank.

2. A citric acid and sodium salt co-production system according to claim 1, characterized in that: The main evaporator is of plate type or tubular type, and the operating temperature range of the main evaporator is between 40℃ and 70℃; the first MVR compressor is of centrifugal type or Roots type, and the first MVR compressor is single-stage or multi-stage in series, and the temperature rise range of the first MVR compressor is between 10℃ and 22℃.

3. The system for co-producing citric acid and its sodium salt according to claim 1, characterized in that: The thickening flotation device is internally provided with an inverted cone baffle, the primary reaction crystallizer is intermittently operated and is internally provided with an adjustable speed stirring device, the automatic feeding system weighs the citric acid particles in the secondary silo and then adds them into the primary reaction crystallizer at one time, the primary alkali adding system adds liquid alkali according to the return value of the automatic control system, and the secondary alkali adding system can add liquid alkali or alkali flakes.

4. A method for co-producing citric acid and its sodium salt, based on the system of claims 1-3, characterized in that: include: - Step 1: The citric acid solution is pre-concentrated by a citric acid pre-concentration system to obtain a first concentrated solution; Step 2: The first concentrated solution is evaporated and crystallized through an anhydrous citric acid evaporation and crystallization system to obtain anhydrous citric acid crystals and mother liquor; Step 3: The mother liquor is cooled and crystallized through a citric acid monohydrate cooling crystallization system to obtain citric acid monohydrate crystals and a second concentrated solution; Step 4: adding alkali to the second concentrated solution to react to obtain sodium citrate, and then filtering and drying the crystals through a sodium citrate dihydrate evaporation crystallization system to obtain sodium citrate crystals and a reaction solution; Step 5: After thickening, the reaction solution is evaporated and crystallized to obtain sodium citrate dihydrate crystals.

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