A comprehensive utilization of chlorination method titanium dioxide production system

Abstract

The application provides a comprehensive utilization chlorination method titanium dioxide production system, which comprises a tail gas recovery pipeline, a chlorine gas conveying pipeline, a heat conducting medium conveying pipeline, a first-stage heat exchanger, a second-stage heat exchanger, an oxygen gas heating unit, a TiCl4 heating unit, an oxidation reaction unit and a chlorine gas liquefaction unit; tail gas of the oxygen gas heating unit and the TiCl4 heating unit converges to the tail gas recovery pipeline; high-temperature chlorine gas generated by the oxidation reaction unit converges to the chlorine gas conveying pipeline; the oxidation reaction unit has a flow guide air channel; two gas streams conveyed by the tail gas recovery pipeline and the chlorine gas conveying pipeline respectively enter the first-stage heat exchanger to perform heat exchange, and then the tail gas is supplied to a downstream flash drying unit, and the chlorine gas enters the second-stage heat exchanger to perform heat exchange with heat conducting medium flowing through the second-stage heat exchanger; part of the chlorine gas after heat exchange is liquefied and supplied to the flow guide air channel. The application effectively improves resource utilization efficiency and production economy by coupling multi-stage waste heat recovery and process.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology using the chloride process, and more specifically to a comprehensive titanium dioxide production system using the chloride process. Background Technology

[0002] Currently, oxidation reactors in chloride process titanium dioxide production plants are mostly arranged horizontally. During operation, once the high-temperature molten TiO2 comes into contact with the cooler inner wall of the cooling conduit, it is very prone to scaling and blockage. To prevent this problem, existing technologies generally use salt or sand descaling methods, but these still have the following drawbacks: (1) The descaling operation cannot completely avoid the occurrence of scaling. The system still needs to replace the oxidation reactor and related equipment regularly, which leads to unstable operation of the chlorination system, a significant reduction in effective operating time, and a decrease in production capacity. In addition, the introduction of salt or sand increases the complexity of the system and operating costs.

[0003] (2) The exhaust gas temperature of the oxygen heating unit and the TiCl4 heating unit is only 120℃~150℃. Currently, direct venting is commonly used, resulting in a large amount of heat waste. The 300℃~500℃ hot air required by the downstream flash drying unit relies entirely on direct combustion of natural gas for heating, which results in high energy consumption.

[0004] (3) The heat input to the oxidation reaction unit plus the large amount of reaction heat released by TiO2 generation results in a huge energy scale. The current process generally uses circulating water cooling to dissipate this heat, which not only wastes high-grade waste heat, but also increases the investment in the circulating water station and the overall operating cost of the project. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes a comprehensive titanium dioxide production system using the chloride process.

[0006] This invention proposes a comprehensive titanium dioxide production system using the chloride process, comprising: a tail gas recovery pipeline, a chlorine gas delivery pipeline, a heat transfer medium delivery pipeline, a primary heat exchanger, a secondary heat exchanger, an oxygen heating unit for heating oxygen, a TiCl4 heating unit for heating TiCl4, an oxidation reaction unit for carrying out the oxidation reaction, and a chlorine liquefaction unit for converting chlorine gas into liquid chlorine, wherein: The exhaust gases generated by the oxygen heating unit and the TiCl4 heating unit during operation are combined into the exhaust gas recovery pipeline. The high-temperature chlorine gas generated during the oxidation reaction unit is collected in the chlorine gas delivery pipeline; The oxidation reaction unit has a reaction chamber and a reaction product collection chamber; wherein, the reaction chamber and the reaction product collection chamber are arranged vertically, the reaction product collection chamber is located below the reaction chamber and is connected to the reaction chamber, and an annular guide gas channel connected to the reaction product collection chamber is arranged circumferentially on the outside of the channel connecting the two. The heat transfer medium conveying pipeline is used to transport the heat transfer medium, and the heat transfer medium it transports flows through a secondary heat exchanger; The two gas streams transported by the exhaust gas recovery pipeline and the chlorine gas delivery pipeline respectively enter the first-stage heat exchanger for heat exchange. The exhaust gas after heat exchange is used as heat energy to supply the downstream flash drying unit, while the chlorine gas after heat exchange enters the second-stage heat exchanger. The chlorine gas entering the second-stage heat exchanger exchanges heat with the heat transfer medium flowing through it. The heat transfer medium after heat exchange is used as heat energy to supply the upstream TiCl4 refining unit. The chlorine gas after heat exchange is divided into two paths. One path serves as the chlorine gas source and is supplied to the upstream chlorination furnace through the first pipeline. The other path is liquefied by the chlorine liquefaction unit and used as a cold source, which is then supplied to the guide gas duct through the second pipeline.

[0007] Preferably, it also includes a refrigeration unit; wherein, the chlorine gas, after heat exchange in the secondary heat exchanger, is cooled by the refrigeration unit and then enters the chlorine liquefaction unit.

[0008] Preferably, the cooling capacity generated by the refrigeration unit after cooling the chlorine gas is supplied to the upstream chlorination furnace tail gas condensation system through a cooling capacity delivery pipeline for condensing TiCl4 in the tail gas.

[0009] Preferably, the refrigeration unit adopts ammonia absorption refrigeration.

[0010] Preferably, the device further includes a rotary cooler, which has a feed inlet, a discharge outlet, an air inlet, and an air outlet; the TiCl4 heating unit heats TiCl4 by combustion; wherein, the rotary cooler is located below the oxidation reaction unit, its feed inlet is connected to the discharge outlet at the bottom of the reaction product collection chamber; its air outlet is connected to the TiCl4 heating unit via an air supply pipe, for supplying combustion air to the TiCl4 heating unit.

[0011] Preferably, both the primary and secondary heat exchangers are plate-fin heat exchangers.

[0012] Preferably, the airflow ejected from the guide airway converges along the axis of the channel connecting the reaction chamber and the reaction product collection chamber.

[0013] Preferably, the outer wall of the air guide channel has a number of tangential air inlets evenly distributed along the circumference, which are tangentially opened along the side wall of the air guide channel; the output end of the second pipeline is divided into multiple branches, and each branch is connected to each tangential air inlet in turn.

[0014] Preferably, the internal space of the reaction product collection chamber is divided into an upper chamber and a lower chamber arranged vertically; the upper chamber adopts a conical bottom structure, and an opening connecting the lower chamber is formed at its lowest point; an exhaust port is opened on the side wall of the upper chamber near its top, and the exhaust port is connected to the chlorine gas delivery pipeline via a bag filter; a discharge port is provided at the bottom of the lower chamber, and a return port is opened on the side wall of the lower chamber below the partition surface; the discharge port of the bag filter is connected to the return port of the lower chamber.

[0015] In this invention, liquid chlorine is used to isolate and cool high-temperature TiO2 and high-temperature chlorine gas, effectively preventing particles from sticking to the walls and avoiding the use of descaling materials. This saves costs and significantly extends equipment maintenance cycles, thereby increasing production capacity within the same equipment scale. Simultaneously, the exhaust gases from the oxygen heating unit and the TiCl4 heating unit are collected and exchanged with the high-temperature chlorine gas produced by the oxidation reaction unit. This brings the exhaust gas temperature to the level required for downstream flash drying, providing a heat source for the flash drying unit and reducing its natural gas consumption. Furthermore, a heat-conducting medium is used to absorb the waste heat from the high-temperature chlorine gas. The heated medium then provides a heat source for the TiCl4 refining process, fully recovering the waste heat from the oxidation reaction. This system, through multi-stage waste heat recovery and process coupling, effectively improves resource utilization efficiency and production economy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the basic structure of a comprehensive titanium dioxide production system using the chloride process proposed in this invention. Detailed Implementation

[0017] Reference Figure 1 The present invention proposes a comprehensive titanium dioxide production system using the chloride process, comprising: a tail gas recovery pipeline 1, a chlorine gas transmission pipeline 2, a heat transfer medium transmission pipeline 3, a primary heat exchanger 4, a secondary heat exchanger 5, an oxygen heating unit 6, a TiCl4 heating unit 7, an oxidation reaction unit 8, and a chlorine liquefaction unit 9 for converting chlorine gas into liquid chlorine.

[0018] Oxygen heating unit 6 is used to heat oxygen by combustion. TiCl4 heating unit 7 is used to heat TiCl4 by combustion. The oxygen heated by oxygen heating unit 6 and the TiCl4 heated by TiCl4 heating unit 7 are respectively transported to oxidation reaction unit 8 through pipelines; the exhaust gas generated by oxygen heating unit 6 and TiCl4 heating unit 7 during operation (the exhaust gas temperature here is about 120℃-150℃) is collected in exhaust gas recovery pipeline 1.

[0019] The high-temperature chlorine gas generated during the reaction in the oxidation reaction unit 8 flows into the chlorine gas delivery pipeline 2. The oxidation reaction unit 8 has a reaction chamber 81 and a reaction product collection chamber 82. The reaction chamber 81 and the reaction product collection chamber 82 are arranged vertically, with the reaction product collection chamber 82 located below and connected to the reaction chamber 81. The internal volume of the reaction product collection chamber 82 is much larger than that of the reaction chamber 81. Furthermore, an annular guide gas channel 821, connected to the reaction product collection chamber 82, is arranged circumferentially outside the channel connecting the reaction chamber 81 and the reaction product collection chamber 82. Specifically, an annular pipe is provided around the outer circumference of the reaction chamber 81 outside the oxidation reaction unit 8. The lower end of this annular pipe is located inside the reaction product collection chamber 82 and is in an open state, thus forming the guide gas channel 821 connected to the reaction product collection chamber 82. This design vertically arranges the reaction chamber 81 and the reaction product collection chamber 82 in the oxidation reaction unit 8, ensuring that the high-temperature reaction products generated by the reaction fall directly into the lower reaction product collection chamber 82 under gravity, thereby reducing turbulent retention and lowering the risk of product scouring the wall. At the same time, the annular jet flow formed outside the connecting channel of the two through the guide air channel 821 not only reduces the temperature of the reaction products, but also constructs an air curtain around the outlet to protect the descending reaction products from directly contacting the inner wall, preventing particles from depositing, sintering, or condensing into scale on the wall due to inertia, diffusion, etc., thus eliminating the need for scale removal materials.

[0020] As a further preferred embodiment, the airflow ejected from the guide air duct 821 in this embodiment converges along the axial direction of the channel connecting the reaction chamber 81 and the reaction product collection chamber 82, thereby forming a gas column or liquid column flow that aggregates along the central axis of the channel. This design effectively constrains and guides the high-temperature TiO2 particles and chlorine gas generated in the reaction to move downward along the axial region, preventing particles from radially diffusing or splashing onto the inner wall of the equipment. On the other hand, the axial convergence of the airflow enhances the cooling and isolation effect of the central region, ensuring that the high-temperature products are fully enveloped and cooled before contacting the wall, thereby fundamentally preventing TiO2 particles from adhering to the wall before hardening, ensuring unobstructed passage, and further eliminating the need for descaling materials.

[0021] Furthermore, the outer wall of the guide air channel 821 is evenly distributed with several tangential air inlets that are tangentially opened along the side wall of the guide air channel 821; the output end of the second pipeline (22) is divided into multiple branches, each branch being connected to each tangential air inlet. By utilizing the characteristic of the tangential air inlets being tangentially opened along the side wall, liquid chlorine enters the guide air channel 821 in a tangential direction, generating a strong swirling or circumferential flow inside the air channel, thereby forming a uniform, stable and continuous ring-sprayed liquid chlorine flow around the outer periphery of the connecting channel between the reaction chamber 81 and the reaction product collection chamber 82. This avoids dead angles and deflection of liquid chlorine spray, improves cooling uniformity and coverage efficiency, and ensures all-round isolation and cooling of high-temperature TiO2 and chlorine by the liquid chlorine flow, preventing TiO2 particles from locally overheating and adhering to the inner wall of the equipment before hardening.

[0022] Furthermore, the internal space of the reaction product collection chamber 82 is divided into an upper chamber and a lower chamber arranged vertically. The upper chamber adopts a conical bottom structure, with an opening at its lowest point connecting to the lower chamber. This facilitates the collection of TiO2 particles under gravity to the lowest opening and fall into the lower chamber, achieving preliminary gas-solid separation. An exhaust port is provided on the side wall near the top of the upper chamber, and this exhaust port is connected to the chlorine gas delivery pipeline 2 via the bag filter 10. A discharge port is provided at the bottom of the lower chamber, and a return port is provided on the side wall below the partition. The discharge port of the bag filter 10 is connected to the return port of the lower chamber. During operation, the exhaust port at the top of the upper chamber draws out chlorine gas containing TiO2, which is then recovered by the bag filter 10 and sent to the chlorine gas delivery pipeline 2. The fine TiO2 powder particles collected by the bag filter 10 are returned to the lower chamber for unified collection through the return port.

[0023] The heat transfer medium conveying pipeline 3 is used to transport the heat transfer medium, which flows through the secondary heat exchanger 5. Specifically, the heat transfer medium transported is heat transfer oil. The two gas streams transported by the tail gas recovery pipeline 1 and the chlorine gas conveying pipeline 2 respectively enter the primary heat exchanger 4 for heat exchange. The primary heat exchanger 4 is a plate-fin heat exchanger. The tail gas, whose temperature has increased after heat exchange (at this point, the tail gas temperature is approximately 300℃-400℃), is transported to the downstream flash drying unit to provide heat energy, thereby reducing the natural gas consumption of the downstream flash drying unit.

[0024] After heat exchange, the chlorine gas, whose temperature has decreased, enters the secondary heat exchanger 5. The secondary heat exchanger 5 is a plate-fin heat exchanger. The chlorine gas entering the secondary heat exchanger 5 exchanges heat with the heat-conducting medium flowing through it. The heat-conducting medium, whose temperature has increased after heat exchange (at this point, the temperature of the heat-conducting medium is approximately 150℃-250℃), is supplied as heat energy to the upstream TiCl4 refining unit. The chlorine gas, whose temperature has decreased further after heat exchange (at this point, the temperature of the chlorine gas is approximately 180℃), is divided into two paths. One path serves as the chlorine gas source and is supplied to the upstream chlorination furnace through the first pipeline 21. The other path is liquefied by the chlorine gas liquefaction unit 9 and serves as a cold source, which is supplied to the guide gas channel 821 through the second pipeline 22. With the guiding effect of the guide gas channel 821, a ring-shaped liquid chlorine flow is formed around the outer periphery of the connecting channel between the reaction chamber 81 and the reaction product collection chamber 82. The system utilizes its own liquefied chlorine gas as a cooling source, which is supplied to the guide gas channel 821 via the second pipeline 22. This liquid chlorine flow serves two purposes: firstly, it acts as an air curtain to prevent high-temperature TiO2 particles from directly contacting the wall surface; secondly, the heat absorbed by the vaporization of liquid chlorine effectively cools the reaction products and surrounding area, causing the TiO2 particles to rapidly cool and harden before contacting the wall. Thus, without the need for additional descaling materials or external cooling sources, particle adhesion and scaling can be prevented at the source.

[0025] As a further preferred embodiment, this embodiment also includes a refrigeration unit 14, specifically employing ammonia absorption refrigeration. Chlorine gas, after heat exchange in the secondary heat exchanger 5, enters the refrigeration unit 14 and is further cooled before entering the chlorine liquefaction unit 9 to liquefy into liquid chlorine. The cooling capacity generated by the refrigeration unit 14 after cooling the chlorine gas is supplied to the upstream chlorination furnace tail gas condensation system via a cooling capacity pipeline. This design, by recovering the cooling capacity generated by the refrigeration unit 14 after cooling the chlorine gas and supplying it to the upstream chlorination furnace tail gas condensation system for condensing TiCl4 in the tail gas, achieves cascade utilization of cooling capacity, avoids the need for a separate refrigeration unit for tail gas condensation, reduces equipment investment, and lowers operating costs due to additional refrigeration energy consumption.

[0026] As a further preferred embodiment, this embodiment also includes a rotary cooler 11, which has a feed inlet, a discharge outlet, an air inlet, and an air outlet. The TiCl4 heating unit 7 heats TiCl4 by combustion. The rotary cooler 11 is located below the oxidation reaction unit 8, with its feed inlet connected to the discharge outlet of the lower chamber. Its air outlet is connected to the upstream TiCl4 heating unit 7 via an air supply pipe 12, thereby recovering the waste heat during the material cooling process and supplying it as combustion air to the upstream TiCl4 heating unit 7. This design effectively reduces the fuel consumption of the TiCl4 heating unit 7, reduces operating costs, and achieves cascaded utilization of thermal energy within the system.

[0027] As a further preferred embodiment, this embodiment also includes an AlCl3 generator 13; the TiCl4 heating unit 7 is connected to the oxidation reaction unit 8 via the AlCl3 generator 13. By adding the AlCl3 generator 13, the high-temperature TiCl4 output from the TiCl4 heating unit 7 flows through the AlCl3 generator 13, directly carrying the generated AlCl3 into the oxidation reaction unit 8. This eliminates the need for additional conveying equipment, improves reaction efficiency, and further saves energy.

[0028] As shown above, this invention utilizes liquid chlorine to isolate and cool high-temperature TiO2 and high-temperature chlorine gas, effectively preventing particles from sticking to the wall and avoiding the use of descaling materials. This saves costs while significantly extending equipment maintenance cycles, thereby increasing production capacity within the same equipment scale. Simultaneously, the exhaust gases from the oxygen heating unit 6 and the TiCl4 heating unit 7 are collected and exchanged with the high-temperature chlorine gas produced by the oxidation reaction unit 8, raising the exhaust gas temperature to the level required for downstream flash drying. This provides a heat source for the flash drying unit, reducing its consumption of natural gas. Furthermore, a heat-conducting medium absorbs the waste heat from the high-temperature chlorine gas, and the heated medium provides a heat source for the TiCl4 refining process, fully recovering the waste heat from the oxidation reaction. This system, through multi-stage waste heat recovery and process coupling, effectively improves resource utilization efficiency and production economy.

[0029] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A comprehensive titanium dioxide production system using the chloride process, characterized in that, include: The system includes: a tail gas recovery pipeline (1), a chlorine gas delivery pipeline (2), a heat transfer medium delivery pipeline (3), a primary heat exchanger (4), a secondary heat exchanger (5), an oxygen heating unit (6) for heating oxygen, a TiCl4 heating unit (7) for heating TiCl4, an oxidation reaction unit (8) for carrying out oxidation reactions, and a chlorine liquefaction unit (9) for converting chlorine gas into liquid chlorine. The exhaust gases generated by the oxygen heating unit (6) and the TiCl4 heating unit (7) during operation are combined into the exhaust gas recovery pipeline (1). The high-temperature chlorine gas generated in the oxidation reaction unit (8) during the reaction process flows into the chlorine gas delivery pipeline (2); The oxidation reaction unit (8) has a reaction chamber (81) and a reaction product collection chamber (82); wherein the reaction chamber (81) and the reaction product collection chamber (82) are arranged vertically, the reaction product collection chamber (82) is located below the reaction chamber (81) and is connected to the reaction chamber (81), and an annular guide gas channel (821) connected to the reaction product collection chamber (82) is arranged circumferentially on the outside of the channel connecting the two. The heat transfer medium conveying pipeline (3) is used to convey the heat transfer medium, and the heat transfer medium conveyed therethrough flows through the secondary heat exchanger (5). The two streams of gas transported by the tail gas recovery pipeline (1) and the chlorine gas transport pipeline (2) enter the first-stage heat exchanger (4) for heat exchange. The tail gas after heat exchange is used as heat energy to supply the downstream flash drying unit, and the chlorine gas after heat exchange enters the second-stage heat exchanger (5). The chlorine gas entering the second-stage heat exchanger (5) exchanges heat with the heat-conducting medium flowing through the second-stage heat exchanger (5). The heat-conducting medium after heat exchange is used as heat energy to supply the upstream TiCl4 refining unit. The chlorine gas after heat exchange is divided into two paths. One path is used as a chlorine gas source and is supplied to the upstream chlorination furnace through the first pipeline (21). The other path is liquefied by the chlorine gas liquefaction unit (9) and used as a cold source and is supplied to the guide gas channel (821) through the second pipeline (22).

2. The comprehensive utilization titanium dioxide production system using the chloride process according to claim 1, characterized in that, It also includes a refrigeration unit (14); wherein, the chlorine gas after heat exchange by the secondary heat exchanger (5) is cooled by the refrigeration unit (14) and then enters the chlorine liquefaction unit (9).

3. The comprehensive utilization titanium dioxide production system using the chloride process according to claim 2, characterized in that, The cooling unit (14) generates cooling energy after cooling chlorine gas, which is then supplied to the upstream chlorination furnace tail gas condensation system through the cooling energy transmission pipeline.

4. The comprehensive utilization titanium dioxide production system using the chloride process according to claim 2, characterized in that, The refrigeration unit (14) adopts ammonia absorption refrigeration.

5. The comprehensive utilization titanium dioxide production system using the chloride process according to claim 1, characterized in that, It also includes a rotary cooler (11), which has a feed inlet, a discharge outlet, an air inlet and an air outlet; wherein, the rotary cooler (11) is located below the oxidation reaction unit (8), and its feed inlet is connected to the discharge outlet located at the bottom of the reaction product collection chamber (82); its air outlet is connected to the TiCl4 heating unit (7) via an air supply pipe (12).

6. The comprehensive utilization titanium dioxide production system using the chloride process according to claim 1, characterized in that, Both the primary heat exchanger (4) and the secondary heat exchanger (5) are plate-fin heat exchangers.

7. The comprehensive utilization titanium dioxide production system using the chloride process according to any one of claims 1-6, characterized in that, The airflow ejected from the guide airway (821) converges along the axis of the channel connecting the reaction chamber (81) and the reaction product collection chamber (82).

8. The comprehensive utilization titanium dioxide production system using the chloride process according to any one of claims 1-6, characterized in that, The outer wall of the air guide (821) is evenly distributed with several tangential air inlets that are tangentially opened along the side wall of the air guide (821); the output end of the second pipeline (22) is divided into multiple branches, and each branch is connected to each tangential air inlet.

9. The comprehensive utilization titanium dioxide production system using the chloride process according to any one of claims 1-6, characterized in that, The internal space of the reaction product collection chamber (82) is divided into an upper chamber and a lower chamber arranged vertically. The upper chamber adopts a conical bottom structure and forms an opening at its lowest end that connects to the lower chamber. An exhaust port is provided on the side wall of the upper chamber near its top, and the exhaust port is connected to the chlorine gas delivery pipeline (2) via a bag filter (10). The bottom of the lower chamber has a discharge port, and a return port is provided on the side wall of the lower chamber located below the partition. The discharge port of the bag filter (10) is connected to the return port of the lower chamber.

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