阅读说明：本技术 一种通过碱法钙生产低盐氯化钙的装置及工艺 (Device and process for producing low-salt calcium chloride through alkaline process calcium ) 是由 贺向前 周海峰 李少军 钟辉 刘建军 田智勇 魏志强 于 2020-11-26 设计创作，主要内容包括：本发明涉及一种通过碱法钙生产低盐氯化钙的装置及工艺。该装置包括：经管线依次连接的56wt％钙液蒸发罐、沉降离心机、高温蒸发罐、冷却结片机和片钙干燥包装装置。本发明通过提高钙液蒸发浓缩浓度,将钙液浓度由原来42％提高到56％,然后利用氯化钙与氯化钠溶液的同离子效应,由于氯化钙浓度升高,使得氯化钠溶解度降低、析出,然后选取56％钙液为工艺节点,采用沉降离心机对钙液液相中的固体盐进行离心沉降分离,利用沉降离心机机械力产生的强大离心力场,将钙液液相中的固体盐进行最大化的去除,从而减少后续氯化钙产品中的盐分氯化钠含量,最终得到盐分低于3.5％的氯化钙,满足了市场上客户对低盐的氯化钙产品的需求。(The invention relates to a device and a process for producing low-salt calcium chloride by using alkaline process calcium. The device includes: a 56 wt% calcium liquid evaporating pot, a sedimentation centrifuge, a high-temperature evaporating pot, a cooling flaker and a flaked calcium drying and packaging device which are connected in sequence through pipelines. According to the invention, the concentration of the calcium liquid is increased from 42% to 56% by increasing the concentration of the calcium liquid by evaporation and concentration, then the same ion effect of calcium chloride and a sodium chloride solution is utilized, the solubility of sodium chloride is reduced and sodium chloride is separated out due to the increase of the concentration of calcium chloride, then 56% of the calcium liquid is selected as a process node, a sedimentation centrifuge is adopted to carry out centrifugal sedimentation separation on solid salt in the liquid phase of the calcium liquid, and the solid salt in the liquid phase of the calcium liquid is removed to the maximum extent by utilizing a strong centrifugal force field generated by the mechanical force of the sedimentation centrifuge, so that the content of salt sodium chloride in the subsequent calcium chloride product is reduced, and finally the calcium chloride with the salt content lower than 3.5% is obtained, thereby meeting the requirements of customers on low-salt calcium chloride products in.)

1. An apparatus for producing low-salt calcium chloride by alkaline process calcium, comprising: a 56 wt% calcium liquid evaporating pot (3), a sedimentation centrifuge (4), a high-temperature evaporating pot (5), a cooling flaker (6) and a flaked calcium drying and packaging device (7) which are connected in sequence through pipelines; or

The device includes: 56 wt% calcium liquid evaporating pot (3), sedimentation centrifuge (4), high temperature evaporating pot (5), cooling flaker (6) and dry packing plant of piece calcium (7), wherein the export pipeline of 56 wt% calcium liquid evaporating pot (3) divide into two the tunnel, connect sedimentation centrifuge (4) all the way, another way connects gradually high temperature evaporating pot (5), cooling flaker (6) and dry packing plant of piece calcium (7), the liquid outlet pipeline of sedimentation centrifuge (4) connects the entry of 56 wt% calcium liquid evaporating pot (3).

2. The apparatus of claim 1, further comprising: a 42 wt% calcium liquid evaporating pot (1) and a clarifying barrel (2), wherein the 42 wt% calcium liquid evaporating pot (1) is sequentially connected with the inlet of the clarifying barrel (2) and the inlet of the 56 wt% calcium liquid evaporating pot (3) through pipelines.

3. The device according to claim 1 or 2, wherein the 42 wt% calcium liquid evaporating pot (1) is a low-temperature three-effect evaporation and concentration system, the 56 wt% calcium liquid evaporating pot (3) is a II-effect in a high-temperature two-effect evaporation calcium preparation system, and comprises an alkali-adding neutralization steam washing system, and a heating chamber of the alkali-adding neutralization steam washing system uses secondary steam of the high-temperature evaporating pot (5) as a heat source; preferably, the heating chamber of the 56 wt% calcium liquid evaporating pot (3) is made of Ta10, the inner wall of the alkali-adding neutralization steam-washing system is made of Ta10, parts of the sedimentation centrifuge (4) contacting with the materials are made of Ta10, and a bearing part of the sedimentation centrifuge (4) contacting with the materials is made of TC4 titanium alloy materials.

4. A process for producing low-salt calcium chloride by using alkaline calcium is characterized by comprising the following steps:

evaporating the calcium liquid in a 56 wt% calcium liquid evaporating tank (3) until the concentration is 54-58 wt%, preferably 56 wt% calcium liquid, then entering a sedimentation centrifuge (4) for sedimentation centrifugal separation to separate solid phase salt remaining in the calcium liquid phase, then entering a clear liquid obtained after sedimentation centrifugal separation into a high-temperature evaporating tank (5) for evaporation, then entering a cooling flaking machine (6) for cooling flaking, and finally drying and packaging through a flaking calcium drying and packaging device (7) to obtain low-salt calcium chloride; or

Evaporating the calcium liquid in a 56 wt% calcium liquid evaporating tank (3) until the concentration is 54-58 wt%, preferably 56 wt% calcium liquid, dividing into two paths, allowing one path of the calcium liquid to enter a sedimentation centrifuge (4) for sedimentation and centrifugal separation to separate solid phase salt remaining in the calcium liquid phase, returning clear liquid obtained after sedimentation and centrifugal separation to the 56 wt% calcium liquid evaporating tank (3), allowing the other path of the calcium liquid to enter a high-temperature evaporating tank (5) for evaporation, then entering a cooling and flaking machine (6) for cooling and flaking, and finally drying and packaging by a calcium flaking drying and packaging device (7) to obtain low-salt calcium chloride; preferably, the volume ratio of the calcium liquid entering the sedimentation centrifuge (4) to the calcium liquid entering the high-temperature evaporation tank (5) is 7: 2-7: 9.

5. the process according to claim 4, wherein the calcium solution with a concentration of 54-58 wt%, preferably 56 wt%, is prepared by the following method:

firstly, evaporating and concentrating calcium mother liquor to obtain 42 +/-2 wt% (preferably 42 +/-1 wt%) calcium liquor through a 42 wt% calcium liquor evaporation tank (1), then clarifying through a clarifying barrel (2) to separate solid salt and other impurities, evaporating clear liquid obtained after clarification and separation to 80 +/-2 ℃ through a 56 wt% calcium liquor evaporation tank (3) under vacuum to obtain 54-58 wt% and preferably 56 wt% calcium liquor; alternatively, the first and second electrodes may be,

evaporating the calcium mother liquor to 80 +/-2 ℃ in vacuum through a 56 wt% calcium liquor evaporation tank (3) to obtain 54-58 wt%, preferably 56 wt% calcium liquor.

6. Process according to claim 4 or 5, characterized in that the rotational speed of the decanter centrifuge (4) is 1000 to 2000r/min, preferably 1400 to 1800 r/min.

7. The process according to any one of claims 4 to 6, wherein the clear liquid after sedimentation and centrifugation enters a high-temperature evaporation tank (5) to be evaporated at 170-180 ℃, preferably 175 ℃.

8. Process according to any of claims 4 to 7, characterized in that the pellets are cooled to below 140 ℃, preferably below 130 ℃ in a cooled pellet mill (6).

9. Process according to any one of claims 4 to 8, characterized in that the low-salt calcium chloride has a salt content of less than 3.5 wt.%, preferably less than 2 wt.%.

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a device and a process for producing low-salt calcium chloride by using alkaline calcium.

Background

At present, the content of salt and sodium chloride in calcium chloride products produced by ammonia evaporation mother liquor of an alkali factory (namely an alkali method calcium production process) in China is higher, and is about 4-5%.

The main components of the mother liquor for producing the calcium chloride product are calcium chloride and sodium chloride, and the salt is the main impurity of the calcium chloride product. The general production process of the alkaline calcium production process is shown in fig. 1.

In production, the calcium mother liquor is evaporated and concentrated at low temperature to reach the calcium chloride content of about 42 percent, and then sodium chloride, calcium carbonate and calcium sulfate impurities in the calcium liquor are removed by centrifugal separation or clarification separation or a series combination of the two methods, and clarification separation is the most common method in China at present.

Because the clarification separation method is commonly used in the production of the alkaline calcium, the process generally comprises the step of placing a clarifying tank at a position concentrated to 42% of calcium liquid so as to facilitate the sedimentation separation of the calcium liquid, and the calcium liquid with higher concentration is not suitable for clarification by the clarifying tank due to high viscosity and crystallization during temperature reduction, so that the salt content of the calcium chloride product produced by the alkaline calcium is generally high and is more than 4%. Theoretically 42% calcium liquid, wherein the content of sodium chloride in the liquid phase is 2.1%; according to the calculation, the theoretical value of the salt content sodium chloride of 75 percent of calcium chloride products is 3.75 percent, and the salt content of the calcium chloride products is generally between 4 and 5 percent because the extremely fine solid salt in the calcium liquid phase cannot be separated by hundreds of percent in the solid-liquid separation process.

Since a large part of the customers in the market have higher requirements for the sodium chloride content in the calcium chloride product, for example, the sodium chloride content index in the calcium chloride product is required to be controlled to be between 2% and 3%. Therefore, it is urgently needed to develop a new technology for producing calcium chloride by an alkaline process, so as to control the index of the sodium chloride content in the calcium chloride product to be below 3%, thereby striving for corresponding end users for related enterprises, better meeting the customer requirements, and further effectively maintaining the market share of the calcium chloride product of the related enterprises.

Disclosure of Invention

The invention aims to provide a device and a process for producing low-salt calcium chloride by alkaline calcium aiming at the defects in the existing alkaline calcium production process, so that the index of the sodium chloride content in the calcium chloride product is controlled to be below 3%, and the salt content in the calcium chloride product can meet the requirements of low-salt calcium chloride product customers in the market.

At present, in the alkaline calcium process, solid-liquid separation is carried out when calcium liquid is evaporated and concentrated to 42%, so that the content of sodium chloride in a calcium product is basically over 4%. If the calcium liquid is evaporated and concentrated to 56%, the content of sodium chloride in the liquid phase is only 0.88%, and according to the calculation, 75% of calcium chloride products are produced, the theoretical value of the salt content of the calcium chloride can reach 1.17%, so that the salt content of the calcium chloride products can be basically controlled to be below 3.5% in the production process, and the requirements of low-salt calcium product customers can be met.

However, the practical production of concentrating the calcium solution to 56% and then carrying out solid-liquid separation has the following difficulties:

firstly, the concentration of the calcium solution reaches 56%, at the moment, the content of calcium chloride in the calcium solution reaches more than 900g/L, the concentration is too high, and the calcium solution is solidified due to the crystallization of calcium chloride dihydrate, calcium chloride tetrahydrate and calcium chloride hexahydrate when the temperature of the calcium solution is slightly reduced. In production, the 56% calcium evaporation pot is generally baked by fire and then sent to a laboratory by using a vacuum flask for heat preservation, but even if the laboratory is operated in such a way, the laboratory is not always good in sample, because the calcium is solidified to cause that a straw cannot suck up to cause that the test cannot be carried out. Therefore, the calcium solution with the concentration of 56% is not beneficial to the operations of sedimentation clarification and solid-liquid separation, and the sedimentation clarification separation effect is poor, so that the product quality cannot be ensured. If production trouble or maintenance shut down, though the clearing barrel has heat preservation device, still can be because of the very big calcium liquid that leads to in the clearing barrel of cooling solidifies for gravity subsides and can't go on, and then leads to consequences such as clearing barrel harrow mud ware damage. Even if measures such as concentration reduction by water feeding, heating and the like are taken, the volume of the clarifying tank is generally hundreds of times larger, so that the treatment measures are not only wasteful but also unstable in quality, and finally cause that the actual production cannot be normally carried out.

Secondly, according to Raoult's law, the boiling point of the solution is higher than that of the pure solvent, and this higher part we rise is "boiling point rise". As the calcium chloride concentration is higher, the boiling point thereof is also increased. The boiling point of the 56% calcium liquid is increased to about 40 ℃, and the boiling point of the 42% calcium liquid is increased to about 23 ℃, which causes that the multi-effect evaporation is difficult to carry out or the evaporation effect number is reduced, because the temperature difference of the heat transfer driving force is lacked, and the temperature loss of the boiling point increase of the evaporation system is too large. If the concentration is increased to 56 percent of the concentration of the calcium liquid by continuous evaporation, the first-effect steam inlet pressure needs to be increased, and the total temperature difference of the system is increased by 40 ℃, which is extremely uneconomical.

Thirdly, because the boiling point of the evaporation system is increased and the temperature loss is too large, the calcium preparation by the alkali method adopts a 'three + two' evaporation mode, namely a low-temperature three-effect evaporation concentration system and a two-effect high-temperature evaporation calcium preparation system, so that the method is economic. The low-temperature triple-effect evaporation concentrates the calcium liquid to 42% concentration, then enters a high-temperature double-effect evaporation calcium preparation system, firstly enters a last-effect calcium liquid evaporation tank with 56% concentration, and then enters a first-effect high-temperature evaporation tank with the material liquid evaporation temperature reaching 175-. And the calcium chloride solution can generate hydrolysis reaction under the high temperature of 170 ℃, HCl gas is generated to be clamped in secondary steam, so that the secondary steam is too strong in corrosivity, and in order to utilize the secondary steam, the heating chamber material of the 56% calcium solution evaporating pot is enough corrosion-resistant, and the secondary steam is treated and added with caustic soda for neutralization and washing. Therefore, an alkali adding neutralization steam washing system is needed to be added, the operation complexity is increased, and faults such as blockage of an alkali adding pipeline and a nozzle, blockage and collapse of a steam washing tower filler, corrosion damage of a steam washing tower body and the like are caused frequently due to the fact that calcium hydroxide is produced by the reaction of caustic soda and calcium chloride liquid drops carried in secondary steam, and are not easy to control, so that the faults are not easy to be compensated, and therefore, a 56% calcium liquid evaporation tank is cancelled by a plurality of manufacturers, and the secondary steam is directly treated and then discharged.

The reason why the process point of solid-liquid separation in the calcium liquid is set at 42% concentration in the existing design is as above.

In order to solve the difficulties, the invention adopts the following technical solutions:

firstly, a 56% calcium liquid evaporating pot is recovered to evaporate or a 56% calcium liquid evaporating pot is arranged, the calcium liquid is firstly evaporated to about 80 ℃ under vacuum and concentrated to a concentration of 54-58%, and the salt content in the liquid phase of the calcium liquid is only about 0.88%. If 56% of evaporating tanks are recovered to carry out high-temperature two-effect evaporation, because the operation of a neutralization steam washing system is not reliable, raw steam can be directly used for evaporation under vacuum to evaporate the raw steam to about 80 ℃, and the raw steam is concentrated to 54-58% of concentration.

Secondly, aiming at the difficulty that calcium liquid with the concentration of about 56 percent at about 80 ℃ is easy to solidify and further solid salt in a liquid phase cannot be settled and separated normally by utilizing gravity, a settling centrifuge is adopted to carry out solid-liquid separation on the calcium liquid. The sedimentation centrifuge has the advantages of high separation factor, small volume, large treatment capacity, full sealing, continuous operation and high automation degree. It is only about 1 minute from feeding to discharging, and the centrifugal settling time is almost negligible. The normal rotating speed of the sedimentation centrifuge is 1400-1800 r/min, the rotating speed is high, the separation force field of the sedimentation centrifuge can reach hundreds and thousands of G, the gravity field of 1G is far from comparable to that of gravity sedimentation separation, and the problem that the calcium liquid with the concentration of 56% is difficult to sedimentate and separate is solved. The characteristics of the sedimentation centrifuge, such as compactness, sealing, short discharging time and continuous production, also solve the problem of cooling and solidification of the calcium liquid, and can be conveniently brushed and stopped. The invention utilizes the characteristics of the sedimentation centrifuge to completely separate out solid-phase salt remained in 56 percent of calcium liquid.

And finally, the clear liquid separated by the sedimentation centrifuge enters a high-temperature evaporation tank controlled at about 175 ℃ for continuous evaporation and discharge, and is cooled to below 140 ℃, such as 140-110 ℃, further such as 120-.

According to a first aspect of the present invention, there is provided an apparatus for producing low-salt calcium chloride by alkaline process calcium, the apparatus comprising: a 56 wt% calcium liquid evaporating pot, a sedimentation centrifuge, a high-temperature evaporating pot, a cooling flaker and a flaked calcium drying and packaging device which are connected in sequence through pipelines; or

The device includes: the device comprises a 56 wt% calcium liquid evaporating pot, a sedimentation centrifuge, a high-temperature evaporating pot, a cooling flaker and a calcium tablet drying and packaging device, wherein an outlet pipeline of the 56 wt% calcium liquid evaporating pot is divided into two paths, one path is connected with the sedimentation centrifuge, the other path is sequentially connected with the high-temperature evaporating pot, the cooling flaker and the calcium tablet drying and packaging device, and a liquid outlet pipeline of the sedimentation centrifuge is connected with an inlet of the 56 wt% calcium liquid evaporating pot.

Preferably, the apparatus further comprises: the 42 wt% calcium liquid evaporating pot and the clarifying barrel are connected with the inlet of the clarifying barrel and the inlet of the 56 wt% calcium liquid evaporating pot in turn through pipelines.

Preferably, the 42 wt% calcium solution evaporating pot is a low-temperature three-effect evaporation and concentration system, the 56 wt% calcium solution evaporating pot is a II effect in a high-temperature two-effect evaporation calcium preparation system, the system comprises an alkali-adding neutralization steam-washing system, and a heating chamber of the system utilizes secondary steam of the high-temperature evaporating pot as a heat source, and the secondary steam contains HCl gas; more preferably, the heating chamber of the 56 wt% calcium solution evaporation tank is made of Ta10 (titanium alloy), the inner wall of the alkali-adding neutralization steam-washing system is made of Ta10, the parts of the sedimentation centrifuge contacting the materials are made of Ta10, and the bearing of the sedimentation centrifuge contacting the materials is made of TC4 titanium alloy.

According to a second aspect, there is also provided a process for producing low-salt calcium chloride by alkaline process calcium, comprising the steps of:

evaporating the calcium liquid in a 56 wt% calcium liquid evaporating pot until the concentration is 54-58 wt%, preferably 56 wt% calcium liquid, then entering a sedimentation centrifuge for sedimentation and centrifugal separation to separate solid phase salt remained in the liquid phase of the calcium liquid, then entering a clear liquid after sedimentation and centrifugal separation into a high-temperature evaporating pot for evaporation, then entering a cooling flaking machine for cooling flaking, and finally drying and packaging through a flaking calcium drying and packaging device to obtain low-salt calcium chloride; or

Evaporating the calcium liquid in a 56 wt% calcium liquid evaporating tank until the concentration is 54-58 wt%, preferably 56 wt% calcium liquid, dividing into two paths, allowing one path of the calcium liquid to enter a sedimentation centrifuge for sedimentation and centrifugal separation to separate solid phase salt remaining in the calcium liquid phase, returning clear liquid obtained after sedimentation and centrifugal separation to the 56 wt% calcium liquid evaporating tank, allowing the other path of the clear liquid to enter a high-temperature evaporating tank for evaporation, allowing the clear liquid to enter a cooling and flaking machine for cooling and flaking, and finally drying and packaging the flaked calcium liquid in a flaked calcium drying and packaging device to obtain low-salt calcium chloride; preferably, the volume ratio of the calcium liquid entering the sedimentation centrifuge to the calcium liquid entering the high-temperature evaporation tank is 7: 2-7: 9.

preferably, the calcium solution with the concentration of 54-58 wt%, preferably 56 wt% is prepared by the following method:

evaporating and concentrating the calcium mother liquor to 42 +/-2 wt% (preferably 42 +/-1 wt%) calcium liquor through a 42 wt% calcium liquor evaporation tank, clarifying through a clarifying barrel to separate solid salt and other impurities, and evaporating clear liquid after clarification and separation to 80 +/-2 ℃ through a 56 wt% calcium liquor evaporation tank under vacuum to obtain 54-58 wt% and preferably 56 wt% calcium liquor; alternatively, the first and second electrodes may be,

and (3) evaporating the calcium mother liquor to 80 +/-2 ℃ in vacuum through a 56 wt% calcium liquor evaporation tank to obtain 54-58 wt%, preferably 56 wt% calcium liquor.

Preferably, the rotating speed of the sedimentation centrifuge is 1000-2000 r/min, and is preferably 1400-1800 r/min.

Preferably, the clear liquid after sedimentation and centrifugal separation enters a high-temperature evaporation tank to be evaporated at 170-180 ℃, preferably 175 ℃.

Preferably, the mixture enters a cooling flaker to be cooled to below 140 ℃, preferably below 130 ℃ (for example, 110-.

Preferably, the low-salt calcium chloride has a salt content of less than 3.5 wt.%, preferably less than 2 wt.%.

The technical scheme of the invention has the following advantages:

according to the invention, the concentration of the calcium liquid is increased from 42% to 56% by increasing the concentration of the calcium liquid by evaporation and concentration, then the same ion effect of the calcium chloride and the sodium chloride solution is utilized, the solubility of the sodium chloride is reduced and precipitated due to the increase of the concentration of the calcium chloride, then the 56% calcium liquid is selected as a process node, a sedimentation centrifuge is adopted to carry out centrifugal sedimentation separation on solid salt in the liquid phase of the calcium liquid, and the solid salt in the liquid phase of the calcium liquid is removed to the maximum extent by utilizing a strong centrifugal force field generated by the mechanical force of the sedimentation centrifuge, so that the content of salt sodium chloride in the subsequent calcium chloride product is reduced, and finally the calcium chloride with the salt content lower than 3.5% is obtained, thereby meeting the requirement of customers on low-salt calcium chloride products in the market.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a general process for alkaline calcium production;

FIG. 2 is a schematic view of an apparatus for producing low-salt calcium chloride by alkaline process calcium in comparative example 1 of the present invention;

FIG. 3 is a schematic view of an apparatus for producing low-salt calcium chloride by alkaline process calcium in example 1 of the present invention;

FIG. 4 is a schematic view of an apparatus for producing low-salt calcium chloride by alkaline process calcium in example 2 of the present invention;

wherein: 1-42 wt% calcium liquid evaporating pot, 2-clarifying barrel, 3-56 wt% calcium liquid evaporating pot, 4-sedimentation centrifuge, 5-high temperature evaporating pot, 6-cooling and flaking machine, 7-flake calcium drying and packaging device.

Detailed Description

Comparative example 1

As shown in fig. 2, the apparatus for producing low-salt calcium chloride by alkaline process calcium of this comparative example includes: a 42 wt% calcium liquid evaporating pot 1, a clarifying barrel 2, a 56 wt% calcium liquid evaporating pot 3, a high temperature evaporating pot 5, a cooling and flaking machine 6 and a flake calcium drying and packaging device 7 which are connected in sequence through pipelines. Wherein, the 42 wt% calcium liquid evaporating pot 1 is a low-temperature three-effect evaporation concentration system, the 56 wt% calcium liquid evaporating pot 3 is a II effect in a high-temperature two-effect evaporation calcium preparation system, the system comprises an alkali adding neutralization steam washing system, and a heating chamber of the system utilizes secondary steam of the high-temperature evaporating pot 5 as a heat source.

The process for producing the low-salt calcium chloride by the alkaline method comprises the following steps: the method comprises the steps of firstly evaporating and concentrating calcium mother liquor through a 42 wt% calcium liquor evaporation tank 1 to obtain 42 wt% calcium liquor, then clarifying through a clarifying barrel 2 to separate solid salt and other impurities, evaporating clear liquor after clarification and separation to 80 ℃ through a 56 wt% calcium liquor evaporation tank 3 under vacuum to obtain 56 wt% calcium liquor, feeding 56 wt% calcium liquor in the 56 wt% calcium liquor evaporation tank 3 into a high-temperature evaporation tank 5 to evaporate, then feeding the calcium liquor into a cooling and flaking machine 6 to cool and flake, and finally drying and packaging through a flake calcium drying and packaging device 7 to obtain low-salt calcium chloride. Wherein the rotating speed of the sedimentation centrifuge 4 is 1600r/min, the clear liquid after sedimentation and centrifugal separation enters a high-temperature evaporation tank 5 to be evaporated at 175 ℃, enters a cooling flaker 6 to be cooled to below 130 ℃ to be flaked, and the cooling time is 3.5 s. The theoretical salt content of the 75 percent calcium chloride product produced by the device is 3.75 percent, and the salt content is higher in actual operation, generally between 4 percent and 4.8 percent.

Example 1

As shown in fig. 3, the apparatus for producing low-salt calcium chloride by alkaline process calcium in this embodiment includes: 42 wt% calcium liquid evaporating pot 1, settling cask 2, 56 wt% calcium liquid evaporating pot 3, sedimentation centrifuge 4, high temperature evaporating pot 5, cooling flaker 6 and piece calcium dry packing device 7, wherein, 42 wt% calcium liquid evaporating pot 1 connects the inlet of settling cask 2 and 56 wt% calcium liquid evaporating pot 3 in proper order through the pipeline, the outlet pipeline of 56 wt% calcium liquid evaporating pot 3 is divided into two routes, connect sedimentation centrifuge 4 on the one way, another way connects high temperature evaporating pot 5, cooling flaker 6 and piece calcium dry packing device 7 in proper order, the outlet pipeline of sedimentation centrifuge 4 connects the inlet of 56 wt% calcium liquid evaporating pot 3. Wherein, the 42 wt% calcium liquid evaporating pot 1 is a low-temperature three-effect evaporation concentration system, the 56 wt% calcium liquid evaporating pot 3 is a II effect in a high-temperature two-effect evaporation calcium preparation system, the system comprises an alkali adding neutralization steam washing system, and a heating chamber of the system utilizes secondary steam of the high-temperature evaporating pot 5 as a heat source.

The process for producing the low-salt calcium chloride by the alkaline method comprises the following steps: firstly, evaporating and concentrating calcium mother liquor to 42 wt% calcium liquor through a 42 wt% calcium liquor evaporation tank 1, then clarifying through a clarifying barrel 2 to separate solid salt and other impurities, and evaporating clear liquid after clarification and separation to 80 ℃ through a 56 wt% calcium liquor evaporation tank 3 under vacuum to obtain 56 wt% calcium liquor; the 56 wt% calcium liquid in the 56 wt% calcium liquid evaporating pot 3 is divided into two paths, one path enters a sedimentation centrifuge 4 for sedimentation and centrifugal separation to separate solid phase salt remained in the liquid phase of the calcium liquid, then clear liquid after sedimentation and centrifugal separation returns to the 56 wt% calcium liquid evaporating pot 3, the other path enters a high temperature evaporating pot 5 for evaporation, then enters a cooling and flaking machine 6 for cooling and flaking, and finally, the low-salt calcium chloride is obtained after drying and packaging by a flaking calcium drying and packaging device 7. Wherein, the volume ratio of the calcium liquid entering the sedimentation centrifuge 4 to the calcium liquid entering the high-temperature evaporation tank 5 is about 7: 5, the rotating speed of the sedimentation centrifuge 4 is 1600r/min, the clear liquid after sedimentation and centrifugal separation enters a high-temperature evaporation tank 5 to be evaporated at 175 ℃, the clear liquid enters a cooling flaker 6 to be cooled to below 130 ℃ to be flaked, the cooling time is 3.5s, and the salt content in the low-salt calcium chloride is lower than 3.5 wt%.

The salt calcium co-production device of the salt calcium workshop of the first branch company of Su salt well Shen Bing Ltd slightly modifies the original alkali method calcium preparation process at the end of 3 months in 2020, and produces the first batch of low-salt calcium chloride products in 22 days in 4 months, wherein the yield is 92 tons. A second batch of high-end low-salt calcium chloride is produced in 29 days after 4 months, and the yield reaches 487 tons. The production of the third batch of low-salt calcium is started in 5 days after 8 months, 1319 tons of low-salt calcium are produced, the average content of the sodium chloride in the tablet calcium is 3.1-3.5%, and the minimum content is reduced to 1.7%.

The heating chamber of the 56% evaporation tank is made of all Ta10 material, the inner wall of the neutralization steam washing tank is also made of Ta10 material, the cleaning is carried out regularly, the operation is standardized, and the current running condition is stable.

The decanter centrifuge was a model LWM800 × 3200 decanter centrifuge available from supreme machinery manufacturing ltd, suzhou, with a separation factor of up to 2100G, with all parts in contact with the material being TA10, and the load bearing member being a TC4 titanium alloy material. The discharge of a 56% calcium liquid evaporating tank is connected with a branch, a part of feed liquid enters the sedimentation centrifuge to completely separate solid salt in the feed liquid, the separated clear liquid returns to the feed of the 56% calcium liquid evaporating tank, the circulation is carried out, and the rest calcium production is still carried out as before, because the mode only carries out the complete desalination on a part of the feed liquid, although the salt content in the terminal calcium chloride product can not reach the minimum value, the salt content of the final calcium chloride product can reach 1.7% from the actual production condition. The production mode of separating one part of feed liquid has the following advantages: the salt content of the calcium product can be controlled according to actual requirements, and can be randomly adjusted to be high or low, so that the production benefit is maximized. The method for adjusting the salt content is to adjust the ratio of the amount entering the settling machine to the amount directly entering the high-temperature evaporation tank. Generally, the quantity ratio control range is 7: 2-7: 9. the feeding amount of the sedimentation centrifuge is basically unchanged at 35 tons/hour, the feeding amount entering the high-temperature evaporation tank is adjusted, and the control amount adjustment range is 10 tons-45 tons/hour. According to theoretical calculation, when the feeding amount of the high-temperature evaporation tank is controlled to be 10 tons/hour, the theoretical minimum salt content of 75 percent calcium tablet products is 1.61 percent, and when the feeding amount is increased to be 45 tons/hour, the theoretical minimum salt content of 75 percent calcium tablet products is 2.5 percent, which is basically consistent with the data of actual production. If the salt content is not very low, the production can be unnecessary and the yield loss caused by removing more salt can be reduced, thereby realizing the maximization of the benefit.

Example 2

As shown in fig. 4, the apparatus for producing low-salt calcium chloride by alkaline process calcium in this embodiment includes: a 42 wt% calcium liquid evaporating pot 1, a clarifying barrel 2, a 56 wt% calcium liquid evaporating pot 3, a sedimentation centrifuge 4, a high-temperature evaporating pot 5, a cooling flaker 6 and a flaked calcium drying and packaging device 7 which are connected in sequence through pipelines; wherein, the 42 wt% calcium liquid evaporating pot 1 is a low-temperature three-effect evaporation and concentration system, the 56 wt% calcium liquid evaporating pot 3 comprises II effects in a high-temperature two-effect evaporation calcium preparation system, the system comprises an alkali-adding neutralization steam-washing system, and a heating chamber of the system utilizes secondary steam of the high-temperature evaporating pot 5 as a heat source. A decanter centrifuge as described above is used.

The process for producing the low-salt calcium chloride by the alkaline method comprises the following steps: firstly, evaporating and concentrating calcium mother liquor to 42 wt% calcium liquor through a 42 wt% calcium liquor evaporation tank 1, then clarifying through a clarifying barrel 2 to separate solid salt and other impurities, and evaporating clear liquid after clarification and separation to 80 ℃ through a 56 wt% calcium liquor evaporation tank 3 under vacuum to obtain 56 wt% calcium liquor; and (3) allowing 56 wt% calcium liquid with the concentration of 56 wt% in the 56 wt% calcium liquid evaporating pot 3 to enter a sedimentation centrifuge 4 for sedimentation and centrifugal separation so as to separate solid phase salt remaining in the liquid phase of the calcium liquid, allowing clear liquid obtained after sedimentation and centrifugal separation to enter a high-temperature evaporating pot 5 for evaporation, allowing the clear liquid to enter a cooling flaking machine 6 for cooling flaking, and finally drying and packaging the flaked calcium liquid by a flaked calcium drying and packaging device 7 to obtain the low-salt calcium chloride. Wherein the rotating speed of the sedimentation centrifuge 4 is 1600r/min, and clear liquid after sedimentation and centrifugal separation enters a high-temperature evaporation tank 5 to be evaporated at 175 ℃. Cooling in a cooling flaker 6 to below 130 deg.C for 3.5s, wherein the salt content in low-salt calcium chloride is less than 2 wt%. The theoretical salt content of the 75% calcium chloride product produced by the device is 1.18%, and the salt content is slightly higher in actual production but not more than 2%.