阅读说明：本技术 一种钛白粉废硫酸三段式负压蒸发结晶处理工艺及装置 (Titanium white waste sulfuric acid three-stage type negative pressure evaporation crystallization treatment process and device ) 是由 钱钧 于 2020-06-01 设计创作，主要内容包括：本发明公开了一种钛白粉废硫酸三段式负压蒸发结晶处理工艺及装置,首先采用原液结晶系统将钛白粉废硫酸原液中的硫酸亚铁结晶析出并离心分离得到七水硫酸亚铁固体和母液,然后通过二效蒸发系统、单效蒸发系统和浓缩结晶系统的协同配合,杜绝物料在蒸发器中结晶和堵塞的可能性,确保装置的稳定运行；来自原液结晶系统中的离心液在二效蒸发系统中蒸发浓缩提高酸度后进入浓缩结晶系统前段,冷却结晶并压滤出大量的硫酸盐固体,且滤液中硫酸的质量浓度达到50％,滤液继续进入单效蒸发系统中强制循环最大程度的提高废硫酸的浓度,浓缩后的废硫酸液进入浓缩结晶系统后段,冷却结晶并压滤出大量的硫酸盐固体,得到质量浓度≥70％的再生硫酸溶液。(The invention discloses a titanium white waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and a device, wherein a stock solution crystallization system is adopted to crystallize and separate out ferrous sulfate in a titanium white waste sulfuric acid stock solution and carry out centrifugal separation to obtain ferrous sulfate heptahydrate solid and a stock solution, and then a two-effect evaporation system, a single-effect evaporation system and a concentration crystallization system are cooperatively matched to avoid the possibility of crystallization and blockage of materials in an evaporator and ensure the stable operation of the device; the centrifugal liquid from the stock solution crystallization system is evaporated and concentrated in a double-effect evaporation system to improve the acidity, then enters the front section of the concentration crystallization system, is cooled, crystallized and filter-pressed to obtain a large amount of sulfate solids, the mass concentration of sulfuric acid in the filtrate reaches 50%, the filtrate continues to enter a single-effect evaporation system to forcibly circulate to improve the concentration of waste sulfuric acid to the maximum extent, the concentrated waste sulfuric acid liquid enters the rear section of the concentration crystallization system, is cooled, crystallized and filter-pressed to obtain a large amount of sulfate solids, and thus, the regenerated sulfuric acid solution with the mass concentration of more than or equal to 70% is obtained.)

1. A titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process is characterized by comprising the following steps:

s1: performing negative pressure freezing crystallization, namely pumping the titanium dioxide waste sulfuric acid stock solution into a stock solution crystallization kettle in a stock solution crystallization system, performing negative pressure freezing crystallization for a period of time, and performing centrifugal separation on the titanium dioxide waste sulfuric acid crystal slurry in each stock solution crystallization kettle to obtain ferrous sulfate heptahydrate solid and a centrifugal solution;

s2: performing double-effect evaporation and concentration, namely pumping the centrifugate obtained in the step S1 into a first-effect evaporation unit of a double-effect evaporation system, providing saturated steam into the first-effect evaporation unit by using external generated steam, and performing primary negative-pressure countercurrent evaporation on the centrifugate in the first-effect evaporation unit to form primary concentrated solution; the primary concentrated solution is pumped into a secondary evaporation unit, secondary steam generated by the primary evaporation unit enters the secondary evaporation unit, secondary negative-pressure countercurrent evaporation is carried out on the primary concentrated solution in the secondary evaporation unit to form secondary concentrated solution, the secondary concentrated solution is pumped into a concentrated solution crystallization kettle at the front section of a concentration crystallization system, negative-pressure freezing crystallization is carried out for a period of time, the titanium dioxide waste sulfuric acid crystal slurry in the concentrated solution crystallization kettle at the front section of the concentration crystallization system is subjected to pressure filtration to obtain sulfate solid and filtrate, and the sulfate solid is subjected to a post-treatment process;

s3: and (4) single-effect evaporation and concentration, namely pumping the filtrate generated in the front section of the concentration and crystallization system in the step S2 into a single-effect evaporation unit of the single-effect evaporation system, supplying saturated steam into the single-effect evaporation unit by external raw steam, carrying out three-stage negative-pressure countercurrent evaporation on the filtrate in the single-effect evaporation unit to form a three-stage concentrated solution, pumping the three-stage concentrated solution into a concentrated solution crystallization kettle in the rear section of the concentration and crystallization system, carrying out negative-pressure freezing and crystallization for a period of time, and carrying out pressure filtration on the waste sulfuric acid crystal slurry in the concentrated solution crystallization kettle in the rear section of the concentration and crystallization system to obtain titanium dioxide solids and a regenerated sulfuric acid solution, wherein the sulfate solids are subjected to a post-treatment process, and the.

2. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process of claim 1, wherein in the step S1, the mass percentage of sulfuric acid in the titanium dioxide waste sulfuric acid stock solution is 22.5%, and the mass percentage of ferrous sulfate is 4%.

3. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process of claim 2, wherein in the step S2, the temperature of the primary evaporation unit is controlled at 100-104 ℃, and the temperature of the secondary evaporation unit is controlled at 78-82 ℃; in the step S3, the temperature of the single-effect evaporation unit is controlled to be 100-104 ℃.

4. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process according to claim 3, wherein in the step S2, sulfuric acid in the secondary concentrated solution obtained by the two-effect evaporation unit is pumped into a concentrated solution crystallization kettle at the front stage of the concentrated solution crystallization system for freezing crystallization after the mass percentage of sulfuric acid is more than or equal to 50%.

5. The utility model provides a titanium white powder sulfuric acid waste three-period form negative pressure evaporation crystallization processing apparatus which characterized in that, includes stoste crystal system, concentrate crystal system, two effect evaporation system, single effect evaporation system and vacuum system, wherein:

the stock solution crystallization system comprises a stock solution crystallization kettle, a centrifugal machine and a centrifugal liquid tank, wherein the titanium white powder waste sulfuric acid stock solution is pumped into the stock solution crystallization kettle through a feed pump, a discharge port of the stock solution crystallization kettle is connected with the centrifugal machine, a filtrate outlet of the centrifugal machine is connected with the centrifugal liquid tank, the centrifugal liquid tank is connected with the two-effect evaporation system through a centrifugal liquid pump, and a gas outlet of the centrifugal machine is connected into a vacuum system;

the concentrated solution crystallization system comprises a concentrated solution crystallization system front section and a concentrated solution crystallization system rear section, and the concentrated solution crystallization system front section and the concentrated solution crystallization system rear section respectively comprise a concentrated solution crystallization kettle, a filter press and a filtrate tank; the feed inlet of the concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system is connected with the double-effect evaporation system, the discharge outlet of the concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system is connected with a filter press, the filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is connected with the single-effect evaporation system through a filtrate pump; a feed inlet of a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system is connected with the single-effect evaporation system, a discharge outlet of the concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system is connected with a filter press, a filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is connected into the acid liquor collection system through a filtrate pump;

the double-effect evaporation system comprises a first-effect evaporation unit and a second-effect evaporation unit, the first-effect evaporation unit and the second-effect evaporation unit are respectively composed of an evaporator, a separator and a circulating pump, a feed inlet of the separator of the first-effect evaporation unit is connected with a preheater, is used for preheating centrifugate from a stock solution crystallization system by a preheater and then pumping the centrifugate into a separator of a first-effect evaporation unit, a concentrated solution outlet of the separator of the first-effect evaporation unit is connected with a feed inlet of a separator of a second-effect evaporation unit by a feed pump, is used for pumping the concentrated solution reaching the set concentration in the first-effect evaporation unit into the second-effect evaporation unit, the concentrated solution outlet of the separator of the second-effect evaporation unit is connected with the feed inlet of a concentrated solution crystallization kettle in the front section of a concentrated solution crystallization system through a feed pump, the concentrated solution crystallization kettle is used for pumping the concentrated solution reaching the set concentration in the double-effect evaporation unit into the front section of the concentrated solution crystallization system; the shell pass of the evaporator of the first-effect evaporation unit is connected with external saturated raw steam, the secondary steam outlet of the separator of the first-effect evaporation unit is connected with the shell pass of the evaporator of the second-effect evaporation unit, the secondary steam outlet of the separator of the second-effect evaporation unit is connected with a condenser, and the condenser is connected to a vacuum system through a gas-liquid separation tank; a condensate outlet of the condenser is connected with a condensate tank, and the condensate tank is connected to a condensate collecting system through a condensate pump;

the single-effect evaporation system comprises a single-effect evaporation unit, the single-effect evaporation unit consists of an evaporator, a separator and a circulating pump, a feed inlet of the separator of the single-effect evaporation unit is connected with a preheater and used for preheating filtrate from the front section of the concentrated solution crystallization system through the preheater and then pumping the preheated filtrate into the separator of the single-effect evaporation unit, and a concentrated solution outlet of the separator of the single-effect evaporation unit is connected with a feed inlet of a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system through a material passing pump and used for pumping concentrated solution reaching a set concentration in the single-effect evaporation unit into the concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system; the shell pass of the evaporator of the single-effect evaporation unit is connected with external saturated raw steam, the secondary steam outlet of the separator of the single-effect evaporation unit is connected with a condenser, and the condenser is connected to a vacuum system through a gas-liquid separation tank; and a condensate outlet of the condenser is connected with a condensate tank, and the condensate tank is connected into a condensate collecting system through a condensate pump.

6. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation and crystallization treatment device of claim 5, wherein the single-effect evaporation unit, the double-effect evaporation unit and the single-effect evaporation unit are further provided with a feed preheater, a shell side of the feed preheater in the single-effect evaporation unit is connected with a shell side of an evaporator of the single-effect evaporation unit, a shell side of the feed preheater in the double-effect evaporation unit is connected with a shell side of an evaporator of the double-effect evaporation unit, and a feed preheater in the double-effect evaporation unit is connected with a condensate tank in the double-effect evaporation system; the shell pass of the feeding preheater in the single-effect evaporation unit is connected with the shell pass of the evaporator of the single-effect evaporation unit, and the condensed water outlet of the feeding preheater in the single-effect evaporation unit is connected with the boiler for recycling.

7. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation and crystallization treatment device of claim 6, wherein a feed preheater is further provided between the centrifugal liquid tank in the stock solution crystallization system and the primary evaporation unit of the secondary evaporation system, the shell side of the feed preheater is connected with the secondary vapor outlet of the separator of the secondary evaporation unit, and the condensate outlet of the feed preheater is connected with the condensate liquid tank of the secondary evaporation system; and a feed preheater is also arranged between the filtrate tank in the front section of the concentrated solution crystallization system and the single-effect evaporation unit of the single-effect evaporation system, the shell side of the feed preheater is connected with a secondary steam outlet of the separator of the single-effect evaporation unit, and a condensate outlet of the feed preheater is connected with a condensate tank of the single-effect evaporation system.

8. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization processing device of claim 7, wherein the stock solution crystallization system has three groups of stock solution crystallization units, each group of stock solution crystallization unit includes more than two groups of stock solution crystallization kettles, and the stock solution crystallization kettles of each group of stock solution crystallization unit share one centrifuge and one centrifuge tank; the front section of the concentrated solution crystallization system and the rear section of the concentrated solution crystallization system are provided with two groups of concentrated solution crystallization units, each group of concentrated solution crystallization unit comprises more than two groups of concentrated solution crystallization kettles, and the concentrated solution crystallization kettles of each group of concentrated solution crystallization units share one filter press and one filtrate tank.

9. The titanium dioxide waste sulfuric acid three-stage negative pressure evaporative crystallization treatment device of claim 8, wherein the primary evaporation unit and the secondary evaporation unit further comprise a filter tank and a filter press, a discharge port of a separator of the primary evaporation unit is connected with a feed port of the filter tank of the primary evaporation unit, a discharge port of a separator of the secondary evaporation unit is connected with a feed port of the filter tank of the secondary evaporation unit, a liquid outlet of the filter tank of the primary evaporation unit and a liquid outlet of the filter tank of the secondary evaporation unit are both connected with the filter press through a pressure filtration pump, a filtrate outlet of the filter press is connected with the filtrate tank, and the filtrate tank is pumped into a concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system through the filtrate pump; the single-effect evaporation unit is characterized in that a filter tank and a filter press are further arranged in the single-effect evaporation unit, a discharge port of a separator of the single-effect evaporation unit is connected with a feed inlet of the filter tank of the single-effect evaporation unit, a liquid outlet of the filter tank of the single-effect evaporation unit is connected with the filter press through a filter press pump, a filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is pumped into a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system through the filtrate pump.

Technical Field

The invention relates to the technical field of waste sulfuric acid treatment, in particular to a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and a device.

Background

The sulfuric acid is widely applied to the industries of chemical engineering, steel and the like. In many production processes, the utilization rate of sulfuric acid is low, and a large amount of sulfuric acid is discharged along with acid-containing wastewater. If the waste water is discharged into the environment without being treated, the water body or the soil can be acidified, the ecological environment is harmed, and a large amount of resources are wasted.

The waste sulfuric acid discharged by the steel industry or other industries has the characteristics of high metal ion concentration, high sulfuric acid concentration and the like, and is managed by various countries as dangerous waste at present. The United states of America is listed in the resource protection and regeneration Act, and China is also listed in the national records of hazardous wastes. The main hazards caused by illegal discharge of the waste sulfuric acid are as follows: corroding hydraulic structures such as sewer pipes and reinforced concrete; crops are withered, and the growth of aquatic crops is influenced; the waste sulfuric acid permeates into soil, and the soil calcification can be caused after a long time, and the loose state of a soil layer is damaged, so that the growth of crops is influenced; inhibiting microbial proliferation in the biological treatment of wastewater; can kill fish; people and animals can drink the water polluted by the pollution to cause gastrointestinal inflammation and even burn; the pollution to water, the poison to organisms and the final damage to human health are all huge. According to the regulations of the national environmental protection regulations, the waste sulfuric acid is not allowed to be directly discharged. The output of the waste sulfuric acid in China is remarkable, and the phenomenon of stealing is often prohibited.

At present, a plurality of treatment methods for waste sulfuric acid exist at home and abroad, and a proper treatment technology needs to be selected according to the specific characteristics of different waste sulfuric acids and the conditions of enterprises. The currently common methods mainly comprise a submerged combustion high-temperature crystallization method, a vacuum concentration freezing crystallization method, a method for producing metal sulfate crystals by adding iron scraps, a natural crystallization-diffusion dialysis method, an acid adding freezing crystallization method and the like. However, the above treatment method has pertinence to each component in the waste sulfuric acid solution, which restricts the universality of the waste sulfuric acid treatment process.

Titanium white waste sulfuric acid is waste sulfuric acid liquid produced in the process of producing titanium white, the treatment of the waste sulfuric acid liquid generally adopts an evaporation concentration process, and the problems of crystallization and scaling of an evaporator and blockage of a material channel are difficult to eliminate. The main component of the crystallized scaling substances is iron ions or calcium ion salts, for example, calcium sulfate is a substance easy to crystallize and scale, the solubility is very low, titanium dioxide waste sulfuric acid is easy to separate out and precipitate in the concentration process to block a material channel of a heat exchanger, and the crystallization phenomenon of ferrous sulfate is also obvious. The concentration of the sulfuric acid and the ferrous sulfate can be synchronously increased through evaporation concentration, because the solubility of the ferrous sulfate is reduced when the sulfuric acid is increased, ferrous sulfate crystallization can be generated in the concentration process, and the ferrous sulfate can be crystallized and separated out by ferrous sulfate monohydrate when the sulfuric acid reaches above a certain concentration.

At present, the technical method for treating titanium dioxide waste sulfuric acid at home and abroad has certain problems mainly because the solubility problem of calcium sulfate and ferrous sulfate in sulfuric acid at a specific temperature is difficult to master, and the special physical properties of the calcium sulfate and the ferrous sulfate lead the titanium dioxide waste sulfuric acid to be treated firstly in the evaporation concentration process, otherwise, the next evaporation concentration process is influenced. Titanium white waste sulfuric acid in the current market basically adopts a two-stage evaporation crystallization process mode, and besides an evaporator is easy to block in the evaporation process, resource loss of a large amount of sulfuric acid and ferrous sulfate is caused. Therefore, the invention aims to provide a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and a device, so as to solve the problem of blockage of an evaporator in the evaporation process of the titanium dioxide waste sulfuric acid and the problem of resource waste of a large amount of sulfuric acid and ferrous sulfate caused by a two-stage evaporation crystallization process mode.

Disclosure of Invention

1. Technical problem to be solved by the invention

The invention aims to overcome the problems that an evaporator is easy to block in the evaporation process of titanium dioxide waste sulfuric acid and a large amount of sulfuric acid and ferrous sulfate resources are wasted in the two-stage evaporation crystallization process in the conventional two-stage evaporation crystallization process for treating waste sulfuric acid, and provides a three-stage negative pressure evaporation crystallization treatment process and a device for titanium dioxide waste sulfuric acid. The possibility of crystallization and blockage of materials in the evaporator is avoided, and the stable operation of the device is ensured; evaporating and concentrating the titanium white waste sulfuric acid centrifugate from the stock solution crystallization system in a two-effect evaporation system to improve the acidity, then feeding the centrifugate into the front section of a concentration crystallization system, cooling, crystallizing and press-filtering to obtain a large amount of sulfate solids, wherein the mass concentration of sulfuric acid in the filtrate reaches 50%, continuously feeding the filtrate into a single-effect evaporation system to continuously and forcibly circulate to improve the concentration of the titanium white waste sulfuric acid to the maximum extent, feeding the concentrated titanium white waste sulfuric acid liquid into the rear section of the concentration crystallization system, cooling, crystallizing and press-filtering to obtain a large amount of sulfate solids, and thus obtaining a regenerated sulfuric acid solution with the mass concentration of more than or equal to 70% and the; the device effectively utilizes the waste heat to reduce the operation cost, simultaneously improves the recovery rate of the sulfuric acid and the ferrous sulfate, fully utilizes the humidity and the latent heat of the whole set of system, saves the consumption of the raw steam and reduces the operation cost.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process comprises the following steps:

s1: performing negative pressure freezing crystallization, namely pumping the titanium dioxide waste sulfuric acid stock solution into a stock solution crystallization kettle in a stock solution crystallization system, performing negative pressure freezing crystallization for a period of time, and performing centrifugal separation on the titanium dioxide waste sulfuric acid crystal slurry in each stock solution crystallization kettle to obtain ferrous sulfate heptahydrate solid and a centrifugal solution;

s2: performing double-effect evaporation and concentration, namely pumping the centrifugate obtained in the step S1 into a first-effect evaporation unit of a double-effect evaporation system, providing saturated steam into the first-effect evaporation unit by using external generated steam, and performing primary negative-pressure countercurrent evaporation on the centrifugate in the first-effect evaporation unit to form primary concentrated solution; the primary concentrated solution is pumped into a secondary evaporation unit, secondary steam generated by the primary evaporation unit enters the secondary evaporation unit, secondary negative-pressure countercurrent evaporation is carried out on the primary concentrated solution in the secondary evaporation unit to form secondary concentrated solution, the secondary concentrated solution is pumped into a concentrated solution crystallization kettle at the front section of a concentration crystallization system, negative-pressure freezing crystallization is carried out for a period of time, the titanium dioxide waste sulfuric acid crystal slurry in the concentrated solution crystallization kettle at the front section of the concentration crystallization system is subjected to pressure filtration to obtain sulfate solid and filtrate, and the sulfate solid is subjected to a post-treatment process;

s3: and (4) single-effect evaporation and concentration, namely pumping the filtrate generated in the front section of the concentration and crystallization system in the step S2 into a single-effect evaporation unit of the single-effect evaporation system, supplying saturated steam into the single-effect evaporation unit by external raw steam, carrying out three-stage negative-pressure countercurrent evaporation on the filtrate in the single-effect evaporation unit to form a three-stage concentrated solution, pumping the three-stage concentrated solution into a concentrated solution crystallization kettle in the rear section of the concentration and crystallization system, carrying out negative-pressure freezing and crystallization for a period of time, and carrying out pressure filtration on the waste sulfuric acid crystal slurry in the concentrated solution crystallization kettle in the rear section of the concentration and crystallization system to obtain titanium dioxide solids and a regenerated sulfuric acid solution, wherein the sulfate solids are subjected to a post-treatment process, and the.

Preferably, in the step S1, the mass percentage of the sulfuric acid in the titanium dioxide waste sulfuric acid stock solution is 22.5%, and the mass percentage of the ferrous sulfate is 4%.

Further preferably, in the step S2, the temperature of the primary evaporation unit is controlled to be 100-104 ℃, and the temperature of the secondary evaporation unit is controlled to be 78-82 ℃; in the step S3, the temperature of the single-effect evaporation unit is controlled to be 100-104 ℃.

Preferably, in the step S2, the second-order concentrated solution obtained by the second-order evaporation unit is fed into a concentrated solution crystallization kettle at the front section of the concentrated solution crystallization system for freezing and crystallizing after the mass percentage of sulfuric acid in the second-order concentrated solution is not less than 50%.

In order to facilitate the smooth application implementation of above-mentioned titanium white powder waste sulfuric acid syllogic negative pressure evaporation crystallization processing technology, a titanium white powder waste sulfuric acid syllogic negative pressure evaporation crystallization processing apparatus is now proposed, including stoste crystal system, concentrate crystal system, two-effect evaporation system, single effect evaporation system and vacuum system, wherein:

the stock solution crystallization system comprises a stock solution crystallization kettle, a centrifugal machine and a centrifugal liquid tank, wherein the titanium white powder waste sulfuric acid stock solution is pumped into the stock solution crystallization kettle through a feed pump, a discharge port of the stock solution crystallization kettle is connected with the centrifugal machine, a filtrate outlet of the centrifugal machine is connected with the centrifugal liquid tank, the centrifugal liquid tank is connected with the two-effect evaporation system through a centrifugal liquid pump, and a gas outlet of the centrifugal machine is connected into a vacuum system;

the concentrated solution crystallization system comprises a concentrated solution crystallization system front section and a concentrated solution crystallization system rear section, and the concentrated solution crystallization system front section and the concentrated solution crystallization system rear section respectively comprise a concentrated solution crystallization kettle, a filter press and a filtrate tank; the feed inlet of the concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system is connected with the double-effect evaporation system, the discharge outlet of the concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system is connected with a filter press, the filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is connected with the single-effect evaporation system through a filtrate pump; a feed inlet of a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system is connected with the single-effect evaporation system, a discharge outlet of the concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system is connected with a filter press, a filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is connected into the acid liquor collection system through a filtrate pump;

the double-effect evaporation system comprises a first-effect evaporation unit and a second-effect evaporation unit, the first-effect evaporation unit and the second-effect evaporation unit are respectively composed of an evaporator, a separator and a circulating pump, a feed inlet of the separator of the first-effect evaporation unit is connected with a preheater, is used for preheating centrifugate from a stock solution crystallization system by a preheater and then pumping the centrifugate into a separator of a first-effect evaporation unit, a concentrated solution outlet of the separator of the first-effect evaporation unit is connected with a feed inlet of a separator of a second-effect evaporation unit by a feed pump, is used for pumping the concentrated solution reaching the set concentration in the first-effect evaporation unit into the second-effect evaporation unit, the concentrated solution outlet of the separator of the second-effect evaporation unit is connected with the feed inlet of a concentrated solution crystallization kettle in the front section of a concentrated solution crystallization system through a feed pump, the concentrated solution crystallization kettle is used for pumping the concentrated solution reaching the set concentration in the double-effect evaporation unit into the front section of the concentrated solution crystallization system; the shell pass of the evaporator of the first-effect evaporation unit is connected with external saturated raw steam, the secondary steam outlet of the separator of the first-effect evaporation unit is connected with the shell pass of the evaporator of the second-effect evaporation unit, the secondary steam outlet of the separator of the second-effect evaporation unit is connected with a condenser, and the condenser is connected to a vacuum system through a gas-liquid separation tank; a condensate outlet of the condenser is connected with a condensate tank, and the condensate tank is connected to a condensate collecting system through a condensate pump;

the single-effect evaporation system comprises a single-effect evaporation unit, the single-effect evaporation unit consists of an evaporator, a separator and a circulating pump, a feed inlet of the separator of the single-effect evaporation unit is connected with a preheater and used for preheating filtrate from the front section of the concentrated solution crystallization system through the preheater and then pumping the preheated filtrate into the separator of the single-effect evaporation unit, and a concentrated solution outlet of the separator of the single-effect evaporation unit is connected with a feed inlet of a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system through a material passing pump and used for pumping concentrated solution reaching a set concentration in the single-effect evaporation unit into the concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system; the shell pass of the evaporator of the single-effect evaporation unit is connected with external saturated raw steam, the secondary steam outlet of the separator of the single-effect evaporation unit is connected with a condenser, and the condenser is connected to a vacuum system through a gas-liquid separation tank; and a condensate outlet of the condenser is connected with a condensate tank, and the condensate tank is connected into a condensate collecting system through a condensate pump.

Furthermore, a feeding preheater is arranged in each of the first-effect evaporation unit, the second-effect evaporation unit and the single-effect evaporation unit, the shell side of the feeding preheater in the first-effect evaporation unit is connected with the shell side of the evaporator of the first-effect evaporation unit, the shell side of the feeding preheater in the second-effect evaporation unit is connected with the shell side of the evaporator of the second-effect evaporation unit, and the feeding preheater in the second-effect evaporation unit is connected with a condensate tank in the second-effect evaporation system; the shell pass of the feeding preheater in the single-effect evaporation unit is connected with the shell pass of the evaporator of the single-effect evaporation unit, and the condensed water outlet of the feeding preheater in the single-effect evaporation unit is connected with the boiler for recycling.

Furthermore, a feeding preheater is arranged between the centrifugal liquid tank in the stock solution crystallization system and the primary-effect evaporation unit of the secondary-effect evaporation system, the shell side of the feeding preheater is connected with a secondary steam outlet of a separator of the secondary-effect evaporation unit, and a condensate outlet of the feeding preheater is connected with a condensate liquid tank of the secondary-effect evaporation system; and a feed preheater is also arranged between the filtrate tank in the front section of the concentrated solution crystallization system and the single-effect evaporation unit of the single-effect evaporation system, the shell side of the feed preheater is connected with a secondary steam outlet of the separator of the single-effect evaporation unit, and a condensate outlet of the feed preheater is connected with a condensate tank of the single-effect evaporation system.

Furthermore, the stock solution crystallization system is provided with three groups of stock solution crystallization units, each group of stock solution crystallization unit comprises more than two groups of stock solution crystallization kettles, and the stock solution crystallization kettles of each group of stock solution crystallization units share one centrifuge and one centrifugal liquid tank; the front section of the concentrated solution crystallization system and the rear section of the concentrated solution crystallization system are provided with two groups of concentrated solution crystallization units, each group of concentrated solution crystallization unit comprises more than two groups of concentrated solution crystallization kettles, and the concentrated solution crystallization kettles of each group of concentrated solution crystallization units share one filter press and one filtrate tank.

Furthermore, a filter tank and a filter press are arranged in the first-effect evaporation unit and the second-effect evaporation unit, a discharge port of a separator of the first-effect evaporation unit is connected with a feed port of the filter tank of the first-effect evaporation unit, a discharge port of a separator of the second-effect evaporation unit is connected with a feed port of the filter tank of the second-effect evaporation unit, a liquid outlet of the filter tank of the first-effect evaporation unit and a liquid outlet of the filter tank of the second-effect evaporation unit are both connected with the filter press through a filter press pump, a filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is pumped into a concentrated solution crystallization kettle in the front section of the concentrated solution crystallization system through the filtrate pump; the single-effect evaporation unit is characterized in that a filter tank and a filter press are further arranged in the single-effect evaporation unit, a discharge port of a separator of the single-effect evaporation unit is connected with a feed inlet of the filter tank of the single-effect evaporation unit, a liquid outlet of the filter tank of the single-effect evaporation unit is connected with the filter press through a filter press pump, a filtrate outlet of the filter press is connected with a filtrate tank, and the filtrate tank is pumped into a concentrated solution crystallization kettle in the rear section of the concentrated solution crystallization system through the filtrate pump.

3. The invention has the advantages and beneficial effects that:

(1) the invention relates to a titanium dioxide waste sulfuric acid three-stage type negative pressure evaporation crystallization treatment process and a device, wherein by adopting the technical scheme of the invention, a stock solution crystallization system is firstly adopted to crystallize and separate ferrous sulfate in titanium dioxide waste sulfuric acid stock solution to the maximum extent and centrifugally separate the ferrous sulfate to obtain ferrous sulfate heptahydrate solid and titanium dioxide waste sulfuric acid centrifugate, and then the titanium dioxide waste sulfuric acid centrifugate is further treated by the cooperative cooperation of a double-effect evaporation system, a single-effect evaporation system and a concentration crystallization system; the device needs low evaporation temperature, can ensure continuous and stable production, simultaneously reduces engineering investment, adopts forced circulation for the two-effect evaporation system and the single-effect evaporation system, avoids the possibility of crystallization and blockage of materials in the evaporator, and ensures the stable operation of the device; evaporating and concentrating the titanium white waste sulfuric acid centrifugate from the stock solution crystallization system in a two-effect evaporation system to improve the acidity, then feeding the centrifugate into the front section of a concentration crystallization system, cooling, crystallizing and press-filtering to obtain a large amount of sulfate solids, feeding the filtrate into a single-effect evaporation system to continuously and forcibly circulate to improve the concentration of the titanium white waste sulfuric acid to the maximum extent, feeding the concentrated titanium white waste sulfuric acid into the rear section of the concentration crystallization system, cooling, crystallizing and press-filtering to obtain a large amount of sulfate solids, thus obtaining a regenerated sulfuric acid solution with the mass concentration of more than or equal to 70% and the metal ion content of less than or equal to 40g/L, and simultaneously ensuring the high recovery rate of ferrous;

(2) the invention relates to a titanium dioxide waste sulfuric acid three-section type negative pressure evaporation crystallization treatment device, wherein a two-effect evaporation system and a single-effect evaporation system both adopt an external heating type evaporator combined forced circulation mode, the staggered arrangement of the evaporator and a separator with high and low heights is adopted in the process arrangement, under the dual action of gravity difference and heat difference and the vacuum condition of the system, the materials in the evaporator are heated to flow upwards, and the relatively cold materials in the separator are reduced to strongly circulate, so that the forced circulation mode is realized, the circulation speed of the materials is ensured to be more than 2m/s, the crystallization and scaling phenomena of the evaporator are reduced, and the elutriation period of the evaporator is prolonged to 60 days;

(3) according to the titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and device, a heating system has the characteristics of high heat transfer efficiency, short heating time and the like due to high average distribution coefficient and high repeated utilization rate of steam heating, so that the device has the advantages of energy conservation, consumption reduction, low steam consumption, low cooling water circulation amount and the like;

(4) the invention relates to a titanium white waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and a device thereof, which have the advantages of negative pressure evaporation, low evaporation temperature, reduces the corrosion to the material of the equipment pipeline, does not need to add other auxiliary agents in the treatment process, has corrosion resistance and durability to the equipment and the pipeline material, has low treatment cost and obvious environmental protection benefit, wherein the total steam consumption of the double-effect negative pressure evaporation system is 1/2 of common evaporation equipment, the total operation power is 1/2 of the traditional evaporation equipment, the single-effect negative pressure evaporation is that enough space is reserved in the separator for gas-liquid separation, the steam directly enters the condenser from the top of the separator, the gas-liquid separation is completed in the separator, the heat loss of the led-out steam is reduced, and the consumption of the generated steam is saved, therefore, the whole system fully utilizes the wet and latent heat, saves the consumption of the raw steam and reduces the operation cost;

(5) according to the titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process, the negative pressure process is adopted in the whole evaporation process, so that the safety of material production is ensured, the workshop sanitation requirement and the environmental protection requirement are ensured, the evaporation temperature is greatly reduced, and the energy saving, consumption reduction and environmental protection requirements are met;

(6) according to the titanium dioxide waste sulfuric acid three-section type negative pressure evaporation crystallization treatment device, heating steam condensate water of the evaporator is introduced into the preheater through the drain valve, and the condensate water is discharged from the preheater, so that steam loss is avoided, and noise and pollution of the steam trap are also avoided;

(7) according to the titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment process and device, the purity of the recycled regenerated sulfuric acid is high, and the recycled regenerated sulfuric acid is not used in a workshop and does not have any adverse effect on the production process.

Drawings

FIG. 1 is a flow chart of a titanium dioxide waste sulfuric acid three-stage type negative pressure evaporation crystallization treatment process;

FIG. 2 is a process flow diagram of a stock solution crystallization system in a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment device; in the figure, R201 and a first stock solution crystallization kettle; r202, a second stock solution crystallization kettle; r203, a third stock solution crystallization kettle; r204, a fourth stock solution crystallization kettle; r205 and a fifth stock solution crystallization kettle; r206, a sixth stock solution crystallization kettle; r207 and a seventh stock solution crystallization kettle; r208, an eighth stock solution crystallization kettle; r209 and a ninth stock solution crystallization kettle; e201, a stock solution recovery condenser; v101, a stock solution tank; v201, a balance tank; v202, a first centrifuge tank; v203, a second centrifuge tank; v204, a third centrifuge tank; v205, a first recovery liquid tank; p201, a feed pump; p202, a first centrifugal liquid pump; p203, a second centrifugal liquid pump; p204, a third centrifugal liquid pump; p205, a stock solution crystallization system vacuum unit; p206, a first recovery liquid pump; LD201, stock solution refrigerating unit; m201, a first centrifuge; m202, a second centrifuge; m203, a third centrifuge;

FIG. 3 is a process flow diagram of a two-effect evaporation system in a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment device; in the figure, S201, a first effect separator; s202, a two-effect separator; e202, a one-effect evaporator; e203, a double-effect evaporator; e204, a two-effect condenser; e205, a primary preheater; e206, a secondary preheater; e207, a three-stage preheater; v206, a one-effect filter tank; v207, a first filtrate tank; v208, a two-effect filtering tank; v209, a double-effect condensing tank; v210, a two-effect gas-liquid separation tank; p207, a one-effect circulating pump; p208, a one-effect filter press pump; p209, a material passing pump; p210, a first filtrate pump; p211, a two-effect circulating pump; p212, a two-effect pressure filtration pump; p213, a two-effect discharge pump; p214, a two-effect condensate pump; p215, a two-effect vacuum pump; t201, a cooling tower; y201, a first filter press;

FIG. 4 is a process flow diagram of a concentrated solution crystallization system in a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment device; in the figure, E208, recovery condenser; r210, a first concentrated solution crystallization kettle; r211 and a second concentrated solution crystallization kettle; r212, a third concentrated solution crystallization kettle; r213 and a fourth concentrated solution crystallization kettle; r214, a fifth concentrated solution crystallization kettle; r215 and a sixth concentrated solution crystallization kettle; r216 and a seventh concentrated solution crystallization kettle; r217 and an eighth concentrated solution crystallization kettle; p216, a cooling water pump; p217, a first crystal slurry pump; p218, second filtrate pump; p219, a second wafer pump; p220, a third filtrate pump; p221, a third slurry pump; p222, a fourth filtrate pump; p223, a fourth crystal slurry pump; p224, fifth filtrate pump; p225, a concentrated solution crystallization system vacuum unit; p226, second recovery liquid pump; v211, a second filtrate tank; v212, a third filtrate tank; v213, fourth filtrate tank; v214, fifth filtrate tank; v215, a second recovery tank; y202, a second filter press; y203, a third filter press; y204, a fourth filter press; y205, fifth filter press; LD202, concentrated solution refrigerating unit;

FIG. 5 is a process flow diagram of a single-effect evaporation system in a titanium dioxide waste sulfuric acid three-stage negative pressure evaporation crystallization treatment device; in the figure, S203, a single-effect separator; e209, a single-effect evaporator; e210, a single-effect condenser; e211, a four-stage preheater; e212, a five-stage preheater; p227, single-effect circulating pump; p228, single-effect filter press pump; p229, a single-effect filtrate pump; p230, a single-effect discharge pump; p231, a single-effect condensate pump; p232, a single-effect vacuum pump; v216, a single-effect filter tank; v217, a single-effect filtrate tank; v218, a single-effect condensate tank; v219, a single-effect gas-liquid separation tank; y206, single-effect filter press.

Detailed Description

The following description of the embodiments of the present invention will be made with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.