A system and method for recovering carbon dioxide in a neutralization process of sulfuric acid method titanium dioxide wastewater

Abstract

A kind of sulphuric acid method titanium dioxide wastewater neutralization process carbon dioxide recovery processing system, comprising: adjusting pool, adjusting pool is equipped with stirring device;Calcium slurry pool, calcium slurry pool is equipped with stirring device;The outlet of adjusting pool and calcium slurry pool is connected to the inlet of neutralization pool by pump body, and neutralization pool is equipped with stirring device, and overflow port is arranged on the neutralization pool, and overflow port is connected to secondary neutralization pool by pipeline;Gas outlet is arranged on the neutralization pool, and gas outlet is connected to buffer tank by pipeline, and the top of buffer tank is equipped with buffer tank gas outlet, and buffer tank gas outlet is connected to Roots blower by pipeline, and the gas outlet of Roots blower is connected to composite washing tower;The gas outlet of composite washing tower is connected to ammonia pre-cooler by pipeline, and the outlet of ammonia pre-cooler is connected to gas-water separator.

Description

TECHNICAL FIELD

[0001] The application relates to a waste recycling and disposal technology in the production process of titanium dioxide by the sulfuric acid method, in particular to a carbon dioxide recycling and processing system and method in the neutralization process of sulfuric acid method titanium dioxide wastewater. BACKGROUND

[0002] Titanium dioxide is a white pigment, the main component of which is titanium dioxide, and is widely used in the fields of coating, plastic, papermaking, rubber and ink, and food. The production process of titanium dioxide has two processes, namely the sulfuric acid method and the chlorination method. In 2020, the total production of titanium dioxide in China was more than 3.51 million tons, mainly using the sulfuric acid method, of which the production of titanium dioxide by the sulfuric acid method was 3.2 million tons, accounting for 90% of the total production capacity.

[0003] In 2020, the total production of titanium dioxide in China was more than 3.51 million tons, mainly using the sulfuric acid method, of which the production of titanium dioxide by the sulfuric acid method was 3.2 million tons, accounting for 90% of the total production capacity. In the industrial production process of titanium dioxide by the sulfuric acid method, titanium ore is reacted with concentrated sulfuric acid to obtain titanyl sulfate solution, and after purification and purification, metatitanic acid is prepared by hydrolysis. In the iron removal process of metatitanic acid, a large amount of acidic wastewater is produced, about 20 m³ of 3-5% sulfuric acid is produced per ton of titanium white product, and the total amount of sulfuric acid is about 1 ton. Due to the lack of waste acid concentration system and iron precipitation device in some enterprises, the reuse of dilute acid is less, resulting in more total sulfuric acid emissions. The common process currently adopted for these discharged dilute sulfuric acid is lime neutralization, and calcium carbide slag is neutralized. In recent years, due to the rise in energy prices, the production capacity of lime calcination plants is limited, and in order to save costs, the neutralization method of titanium dioxide enterprises has gradually changed from the existing lime neutralization to calcium carbonate + lime neutralization. First, the pH value of calcium carbonate is neutralized to 5, and then the pH value of lime is neutralized to 6-9. In the neutralization process of calcium carbonate, a large amount of CO2 gas is released into the atmosphere. Preliminary calculation shows that for the production of 1 ton of titanium dioxide product, the theoretical CO2 emission is 460 kg when calcium carbonate is used for neutralization in the wastewater treatment process. Even if lime is used for neutralization, the total CO2 emission is more than 500 kg, including the CO2 emission from fuel combustion during lime calcination and the CO2 emission from calcium carbonate decarburization. If all the acidic wastewater produced in the production of titanium dioxide by the sulfuric acid method is treated by calcium carbonate neutralization, the annual CO2 emission is 161.5 million tons, which is equivalent to the consumption of 5,000 hectares of broad-leaved forest for one year. With the implementation of the national carbon peak and carbon neutral high-quality development plan, how to realize carbon capture of the emitted CO2 and realize carbon resource recycling is an urgent demand of every enterprise.

[0004] Currently, industrial liquid CO2 is mainly used for the synthesis of urea, ammonium bicarbonate, carbonates, methanol, formic acid, salicylic acid and its derivatives, gas shielded welding, mining, supercritical fluid extraction, and fertilizer production, with its usage and application scope expanding year by year. If carbon dioxide can be recovered from the sulfuric acid process in titanium dioxide production, it can increase the economic benefits for enterprises. This application has conducted research in this direction. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a carbon dioxide recovery and treatment system and method for the neutralization process of sulfuric acid titanium dioxide wastewater. This system can recover and treat CO2 emitted from the neutralization process of acidic wastewater in the sulfuric acid titanium dioxide production process. After multi-stage treatment to remove water and liquefy it, industrial liquid CO2 is produced, meeting the current high-quality development requirements of carbon peaking and carbon neutrality.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution.

[0007] A carbon dioxide recovery and treatment system for the neutralization process of sulfuric acid titanium dioxide wastewater includes: an equalization tank equipped with a stirring device; a calcium slurry tank equipped with a stirring device; the outlets of the equalization tank and the calcium slurry tank are connected to the inlet of a neutralization tank via a pump body; the neutralization tank is equipped with a stirring device and has an overflow port connected to a secondary neutralization tank via a pipeline; the neutralization tank has a gas outlet connected to a buffer tank via a pipeline; the top of the buffer tank has a buffer tank outlet connected to a Roots blower via a pipeline; the outlet of the Roots blower is connected to a composite scrubbing tower; the outlet of the composite scrubbing tower is connected to an ammonia precooler via a pipeline; and the outlet of the ammonia precooler is connected to a gas-liquid separator.

[0008] In a preferred embodiment, the outlet of the gas-water separator is connected to a primary compressor, and the outlet of the primary compressor is connected to a primary cooler for cooling and removing moisture from the gas.

[0009] In a preferred embodiment, the outlet of the primary cooler is connected to the secondary compressor, and the outlet of the secondary compressor is connected to the secondary cooler for cooling and removing moisture from the gas.

[0010] The carbon dioxide recovery treatment method of the carbon dioxide recovery treatment system in the sulphuric acid method titanium dioxide wastewater neutralization process in the application comprises the following steps: S10: placing the acidic wastewater in the sulphuric acid method titanium dioxide production process in the adjusting tank, and placing the calcium carbonate slurry in the calcium slurry tank; S20: sending the acidic wastewater in the adjusting tank and the calcium carbonate slurry in the calcium slurry tank to the neutralization tank for neutralization reaction, tail gas generated in the reaction is used as a gas source, and the gas source is sent to the buffer tank through a pipeline; S30: the gas in the buffer tank enters the cooling system through the buffer tank gas outlet at the upper end thereof, a large amount of water in the gas source is removed, and the gas is subjected to multiple cooling operations so as to improve the carbon dioxide recovery rate.

[0011] In a preferred embodiment, step S30 further comprises the following steps: S31: the gas in the buffer tank enters the ammonia pre-cooler through the buffer tank gas outlet at the upper end thereof, and is cooled, the outlet of the ammonia pre-cooler is connected to the gas-water separator, and a large amount of water in the gas source is removed; S32: the gas in the gas-water separator enters the primary cooler through the primary compressor, is further cooled, and a part of the carbon dioxide is recovered; S33: the gas in the primary cooler enters the secondary cooler through the secondary compressor, is further cooled, a large amount of water in the gas source is removed, and the carbon dioxide recovery rate is improved.

[0012] In a preferred embodiment, the recovered carbon dioxide is uniformly stored in liquid state in a liquid carbon dioxide low-temperature storage tank device.

[0013] In a preferred embodiment, the devices in the system are controlled by a DCS control system.

[0014] Compared with the prior art, the application has the following beneficial effects: the application provides a sulphuric acid method titanium dioxide wastewater neutralization process carbon dioxide recovery treatment system and method, which can realize recovery treatment of tail gas CO2 discharged in the neutralization process of acidic wastewater in the sulphuric acid method titanium dioxide production process, remove water through multiple stages of treatment, liquefy, produce industrial liquid CO2, and meet the high-quality development demand of current carbon peak and carbon neutralization. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 FIG. 1 is a schematic diagram of the carbon dioxide recovery treatment system in the application. DETAILED DESCRIPTION

[0016] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0017] In the following embodiments, the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout, and the following embodiments described by referring to the drawings are exemplary and are only used to explain the application, and cannot be understood as a limitation on the application.

[0018] Referring to Figure 1 The application relates to a carbon dioxide recovery treatment system for a sulfuric acid method titanium dioxide wastewater neutralization process, which comprises an adjusting tank 1, wherein a stirring device is arranged; a calcium slurry tank 2, wherein a stirring device is arranged; the outlets of the adjusting tank 1 and the calcium slurry tank 2 are connected to the inlet of a neutralization tank 3 through a pump body, a stirring device is arranged in the neutralization tank 3, an overflow port is arranged on the neutralization tank 3, the overflow port is connected to a secondary neutralization tank 6 through a pipeline, a gas outlet is arranged on the neutralization tank 3, the gas outlet is connected to a buffer tank 4 through a pipeline, a buffer tank gas outlet 41 is arranged on the top of the buffer tank 4, the buffer tank gas outlet 41 is connected to a Roots blower 7 through a pipeline, the gas outlet of the Roots blower 7 is connected to a composite washing tower 8, the gas outlet of the composite washing tower 8 is connected to an ammonia pre-cooler 81 through a pipeline, and the outlet of the ammonia pre-cooler 81 is connected to a gas-water separator 82.

[0019] Specifically, in the application, the gas outlet of the gas-water separator 82 is connected to a primary compressor 821, the outlet of the primary compressor 821 is connected to a primary cooler 83, which is used for cooling and removing water in the gas, the gas outlet of the primary cooler 83 is connected to a secondary compressor 831, and the outlet of the secondary compressor 831 is connected to a secondary cooler 84, which is used for cooling and removing water in the gas.

[0020] In addition, the carbon dioxide recovery treatment method of the carbon dioxide recovery treatment system for the sulfuric acid method titanium dioxide wastewater neutralization process in the application comprises the following steps: S10: acidic wastewater in a sulfuric acid method titanium dioxide production process is placed in an adjusting tank 1, and calcium carbonate slurry is placed in a calcium slurry tank 2; S20: the acidic wastewater in the adjusting tank 1 and the calcium carbonate slurry in the calcium slurry tank 2 are sent to a neutralization tank 3 to perform a neutralization reaction, tail gas generated in the reaction is used as a gas source, the gas source is sent to a buffer tank 4 through a pipeline, S30: the gas in the buffer tank 4 enters a cooling system through a buffer tank gas outlet 41 at the upper end of the buffer tank 4, a large amount of water in the gas source is removed, and the gas is subjected to multiple cooling operations so as to improve the carbon dioxide recovery rate.

[0021] Specifically, in the application, the gas outlet of the gas-water separator 82 is connected to a primary compressor 821, the outlet of the primary compressor 821 is connected to a primary cooler 83, which is used for cooling and removing water in the gas, the gas outlet of the primary cooler 83 is connected to a secondary compressor 831, and the outlet of the secondary compressor 831 is connected to a secondary cooler 84, which is used for cooling and removing water in the gas.

[0022] Finally, the purified carbon dioxide gas from the secondary cooler 84 is cooled and recovered carbon dioxide is stored in a liquid state in a liquid carbon dioxide cryogenic storage tank device 90.

[0023] In the present application, the devices in the system are controlled by the DCS control system.

[0024] In one embodiment of the present application, the steps are as follows.

[0025] The acid wastewater in the production process of sulfuric acid method titanium dioxide is placed in the adjusting tank 1, and the calcium carbonate slurry is placed in the calcium slurry tank 2, and then the acid wastewater in the adjusting tank 1 and the calcium carbonate slurry in the calcium slurry tank 2 are sent to the neutralization tank 3 for neutralization reaction.

[0026] In this process, the acid wastewater and the calcium carbonate slurry are transported through independent pipelines to the neutralization tank 3, and controllable pump bodies are provided on the pipelines to provide power, which can be controlled according to the program setting to open, close and control the flow.

[0027] Through the work of the pump body, V volume of acid wastewater is first transported to the neutralization tank 3, and the stirring rod in the neutralization tank 3 is in stirring state, then 1 / 4V volume of calcium carbonate slurry is transported to the neutralization tank 3, and stirring reaction is carried out, at this time, the temperature of the reaction liquid in the neutralization tank 3 is monitored by the temperature sensor in the neutralization tank 3, when the temperature is 75℃, 1 / 4V volume of calcium carbonate slurry is transported to the neutralization tank 3, stirring reaction is carried out and the reaction temperature is monitored, when the temperature is lower than 70℃, 1 / 2V volume of calcium carbonate slurry is transported to the neutralization tank 3, stirring reaction is carried out and the reaction temperature is monitored.

[0028] When the temperature is lower than 50℃, repeat the operation of step (2) to continuously carry out stable and controllable neutralization reaction and generate gas source.

[0029] The buffer tank 4 is provided with a gas pressure sensor, and the upper limit P of the gas pressure is set, when the gas pressure reaches P, the stirring speed in the neutralization tank 3 is reduced to 1 / 5 of the original, and the feeding of acid wastewater and calcium carbonate slurry is temporarily stopped, until the gas pressure is reduced to 0.85P, and then the feeding and stirring reaction are restarted.

[0030] In one embodiment of the present application, multiple overflow openings of different heights are provided on the side wall of the neutralization tank 3, which are connected to the overflow pipe and ultimately to the secondary neutralization tank 6 through pipelines. For example, three overflow openings of high, medium and low positions are provided, which are located at the positions of 70%, 55% and 45% of the height of the neutralization tank 3, respectively. Among them, the overflow openings of medium and low positions are provided with controllable valves. When the temperature in the neutralization tank 3 is higher than 80℃, the overflow openings of medium and / or low positions can be opened (one or both can be opened according to the height of the reaction liquid), and the opening time is 5-10 seconds, so that part of the reaction liquid is transferred to the secondary neutralization tank 6 to reduce the reaction intensity in the neutralization tank 3. After 5-10 seconds, the valves are closed, and the reaction temperature in the neutralization tank 3 is monitored. If the reaction temperature is always above 80℃ within 20 seconds, the overflow openings of medium and / or low positions are continuously opened for 5-10 seconds, and the temperature is monitored again until the reaction temperature is below 80℃.

[0031] Since the pH value of the acidic wastewater is a variable value, generally pH 1-3, and the concentration of the calcium carbonate slurry also varies within a certain range, the neutralization reaction intensity corresponding to different batches of acidic wastewater and calcium carbonate slurry will be different. Therefore, in the present application, the reaction intensity in the neutralization tank 3 is continuously monitored and controlled to ensure the continuous and stable progress of the neutralization reaction and improve the service life of the equipment.

[0032] As can be seen from the above description, in the present application, the tail gas released by the neutralization of acidic wastewater and calcium carbonate is used as the gas source. Since the tail gas from acidolysis neutralization is a chemical reaction by-product, it has a simple composition, which consists of water vapor, non-condensable gas (air brought in by the material conveying belt), CO2, and no sulfide. The subsequent treatment is simple, and only the dehydration effect needs to be ensured, which is lower in operation cost than the process of using other tail gas as the gas source to produce industrial liquid CO2 at present in China.

[0033] In the present application, a composite washing tower is used for cooling and washing the gas source. The acidic components in the gas source (mainly generated by the material entraining acid mist) are washed, and the washing liquid is circulated and cooled. The circulation process is indirect heat exchange circulation in the heat exchanger, and the excess condensate in the circulation cooling process is returned to the production system for use. The circulation cooling temperature is controlled at 35-40℃.

[0034] In the present application, the sealed neutralization tank 3 is adopted, the liquid seal design is adopted for the outlet liquid of the neutralization tank 3, the material overflow is to the secondary neutralization tank 6, and the liquid seal is to the bottom of the secondary neutralization tank, so as to prevent other gases from being brought into the neutralization tank 3, to ensure the CO2 concentration in the tail gas, to facilitate the subsequent compression and purification, and to reduce the gas amount of the compressor purification. In addition, in the present application, the low-temperature and low-pressure liquefaction technology is adopted to carry out the gas-water separation, dehydration and purification process by step-by-step compression and step-by-step dehydration, so as to not only ensure the dehydration efficiency, but also reduce the dehydration energy consumption and save the production cost. The ammonia cooler is adopted for precooling, that is, the ammonia pre-cooler 81 is adopted to cool and dehydrate the waste gas source, the temperature is controlled to 5-8 DEG C, a large amount of water in the gas source is removed, and the carbon dioxide gas is purified by step-by-step cooling and dehydration, and finally the carbon dioxide gas is liquefied and stored.

[0035] The above, the present application provides a kind of sulfuric acid method titanium dioxide waste water neutralization process carbon dioxide recovery processing system and method, can realize sulfuric acid method titanium dioxide production process acidic waste water neutralization process discharge tail gas CO2 recovery processing, by multi-stage processing, remove water, liquefy, produce industrial liquid CO2, meet current carbon peak, carbon neutralization High-quality development needs.

[0036] The protection scope of the present application includes but is not limited to the above embodiments, and the protection scope of the present application is subject to the claims, any replacement, deformation, improvement of the present technology easily thought by the person skilled in the art falls within the protection scope of the present application.

Claims

1. A system for recovering carbon dioxide in a neutralization process of sulfuric acid method titanium dioxide wastewater, characterized by, It comprises: a conditioning tank (1) provided with stirring device; a calcium slurry tank (2) provided with stirring device; the outlet of the conditioning tank (1) and the calcium slurry tank (2) is connected to the inlet of a neutralization tank (3) through a pump body, the neutralization tank (3) is provided with stirring device, and an overflow port is arranged on the neutralization tank (3), which is connected to a secondary neutralization tank (6) through a pipeline; an air outlet is arranged on the neutralization tank (3), which is connected to a buffer tank (4) through a pipeline, a buffer tank air outlet (41) is arranged on the top of the buffer tank (4), the buffer tank air outlet (41) is connected to a Roots blower (7) through a pipeline, and the air outlet of the Roots blower (7) is connected to a composite washing tower (8); the air outlet of the composite washing tower (8) is connected to an ammonia pre-cooler (81) through a pipeline, the outlet of the ammonia pre-cooler (81) is connected to a gas-water separator (82); the air outlet of the gas-water separator (82) is connected to a primary compressor (821), the outlet of the primary compressor (821) is connected to a primary cooler (83); the air outlet of the primary cooler (83) is connected to a secondary compressor (831), the outlet of the secondary compressor (831) is connected to a secondary cooler (84), and the air outlet of the secondary cooler (84) is connected to a liquid carbon dioxide low-temperature storage tank device (90).

2. The carbon dioxide recovery treatment method of the carbon dioxide recovery treatment system for the sulfuric acid process titanium dioxide sludge neutralization process according to claim 1, characterized by, It comprises the following steps: S10: placing the acid wastewater in the production process of sulfuric acid titanium dioxide into the conditioning tank (1), and placing the calcium carbonate slurry into the calcium slurry tank (2); S20: sending the acid wastewater in the conditioning tank (1) and the calcium carbonate slurry in the calcium slurry tank (2) to the neutralization tank (3) for neutralization reaction, and the tail gas generated in the reaction is used as a gas source, which is sent to the buffer tank (4) through a pipeline; S31: the gas in the buffer tank (4) enters the composite washing tower (8) through the buffer tank air outlet (41) at the upper end thereof, and after being washed in the composite washing tower (8), the gas enters the ammonia pre-cooler (81) for cooling, and the outlet of the ammonia pre-cooler (81) is connected to the gas-water separator (82) to remove the water in the gas source; S32: the gas in the gas-water separator (82) enters the primary cooler (83) through the primary compressor (821), further cools and removes the water in the gas source, and improves the carbon dioxide recovery rate; S33: the gas in the primary cooler (83) enters the secondary cooler (84) through the secondary compressor (831), further cools and removes the water in the gas source, and improves the carbon dioxide recovery rate; The recovered carbon dioxide is stored in liquid state in the liquid carbon dioxide low-temperature storage tank device (90); The equipment in the system is controlled by a DCS control system.

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