A tail gas waste heat utilization system and method of a pressure vessel for pressure leaching of nickel oxide

Abstract

The application discloses a tail gas waste heat utilization system and method of a pressurized vessel for nickel-oxygen pressure leaching, and the system comprises the pressurized vessel, a pre-flash evaporation tank, a flash evaporation tank, a first-stage atmospheric leaching tank, a thickener and a second-stage atmospheric leaching tank; the high-temperature tail gas in the pressurized vessel and the flash evaporation tank is introduced into the first-stage atmospheric leaching tank and the second-stage atmospheric leaching tank to heat the ore pulp, so that the fresh steam consumption is reduced, and thus the production cost of the enterprise is greatly reduced; and the problem of environmental pollution caused by disorderly dispersion of a small amount of valuable metal nickel sulfate carried by the tail gas is solved, the valuable metal carried is re-introduced into a production system, the corrosion problem of plant facilities within a certain range around the tail gas is eliminated, and the production environment is obviously improved, so that the application has important significance for the production of non-ferrous metal nickel-oxygen pressure leaching.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous hydrometallurgical technology, and in particular to a system and method for utilizing waste heat from tail gas in a nickel-oxygen pressure leaching reactor. Background Technology

[0002] The traditional oxygen pressure leaching process for nickel and cobalt metals involves two stages of atmospheric leaching followed by pressurized leaching. Both stages require heating the slurry to 70°C to 90°C to reach the reaction temperature for atmospheric leaching. This process consumes a large amount of high-temperature steam. In the pressurized leaching process, the slurry reacts with oxygen to produce nickel sulfate + Q (heat). The waste heat from the pressurized kettle tail gas and the waste heat from the flash evaporation of the pressurized kettle are directly released into the atmosphere. A large amount of valuable waste heat resources are wasted without proper utilization, and the company's costs cannot be effectively reduced. Furthermore, the small amount of valuable nickel sulfate carried in the tail gas is dispersed disorderly, polluting the environment and corroding the plant facilities within a certain range around the tail gas pipe. Summary of the Invention

[0003] The purpose of this invention is to disclose a system and method for utilizing the waste heat of the tail gas from a nickel-oxygen pressure leaching pressurized kettle, so as to realize the utilization of the waste heat of the pressurized leaching tail gas and flash evaporation exhaust gas, and avoid tail gas pollution of the environment and corrosion of infrastructure.

[0004] 1. A waste heat utilization system for tail gas from a nickel-oxygen pressure leaching pressurized kettle, including a pressurized kettle, a pre-flash tank, a flash tank, a first-stage atmospheric pressure leaching tank, a thickener, and a second-stage atmospheric pressure leaching tank.

[0005] The pressure vessel includes a vessel body and multiple agitators. The agitators are mounted on the vessel body and extend into the interior of the vessel body. The top of the vessel body is equipped with a pressure vessel discharge pipe, a tail gas discharge pipe, and a pressure vessel feed pipe. A tail gas regulating valve is also installed on the tail gas discharge pipe, and a check valve is installed on the pressure vessel feed pipe. Inside the vessel body, a partition plate is provided between every two agitators to allow the slurry to overflow from the top. Two adjacent partition plates enclose a compartment. An oxygen branch pipe is provided at the bottom of each compartment. The oxygen branch pipe is connected to the main oxygen pipe located outside the vessel body, and an oxygen regulating valve is installed on each oxygen branch pipe.

[0006] The pre-flash tank and the flash tank form a stepped flash system. A flash control valve is installed at the top of the pre-flash tank and is connected to the discharge pipe of the pressurized vessel through the flash control valve. An overflow pipe of the pre-flash tank is connected to the upper side of the pre-flash tank, and the other end of the pre-flash tank overflow pipe is connected to the flash tank. A flash exhaust gas outlet pipe is installed at the top of the flash tank and is connected to the tail gas discharge pipe. A liquid level monitoring port for the upper part of the flash tank and a liquid level monitoring port for the lower part of the flash tank with an internal liquid level sensor are provided in the middle. A discharge pipe of the flash tank is connected to the bottom of the flash tank, and a discharge regulating valve is installed on the discharge pipe of the flash tank.

[0007] The top of the atmospheric leaching tank is connected to a tail gas waste heat utilization pipe and a steam inlet pipe, and the side is connected to a feed pipe and a discharge pipe; a tail gas utilization regulating valve is installed on the tail gas waste heat utilization pipe and connected to the tail gas discharge pipe through the tail gas utilization regulating valve; a steam regulating valve is installed on the steam inlet pipe and connected to an external steam source through the steam regulating valve.

[0008] The thickener is connected to a discharge pipe at the top, has an overflow pipe for supernatant on the side, and a discharge pipe for underflow at the bottom.

[0009] The top of the two-stage atmospheric leaching tank is connected to two-stage tail gas waste heat utilization pipes, two-stage steam inlet pipes, and two-stage atmospheric pressure liquid distribution pipes, while the sides are connected to two-stage feed pipes and two-stage discharge pipes. Two-stage tail gas utilization regulating valves are installed on the two-stage tail gas utilization pipes and connected to the tail gas discharge pipes via these valves. Two-stage steam regulating valves are installed on the two-stage steam inlet pipes and connected to an external steam source via these valves. Underflow conveying pumps are installed on the two-stage feed pipes and connected to the underflow discharge pipes via these pumps. A pressure pump is installed on the two-stage discharge pipes and connected to the pressure vessel feed pipe via this pressure pump.

[0010] The aforementioned waste heat recovery system also includes a DCS industrial control system, which is connected to the flash control valve, the waste gas regulating valve, the discharge regulating valve, the first-stage waste gas utilization regulating valve, the underflow conveying pump, the pressurizing pump, the second-stage waste gas utilization regulating valve, the oxygen regulating valve, the first-stage steam regulating valve, the second-stage steam regulating valve, and the liquid level sensor signal.

[0011] II. A method for utilizing the waste heat from the tail gas of a nickel-oxygen pressure leaching reactor, comprising the following steps:

[0012] 1) The ambient temperature slurry of nickel ore enters the atmospheric pressure leaching tank through a feed pipe. Steam is introduced through a steam regulating valve opened by the DCS industrial control system to heat the atmospheric pressure leaching slurry to 70℃~90℃ for leaching reaction. The reacted slurry enters the thickener through a discharge pipe.

[0013] 2) After the slurry enters the thickener and settles, the top supernatant is discharged from the supernatant overflow pipe and then filtered to become the finished product. The bottom slurry enters the second-stage atmospheric pressure leaching tank through the bottom discharge pipe, the bottom conveying pump and the second-stage feed pipe for second-stage atmospheric pressure leaching.

[0014] 3) The slurry entering the second-stage atmospheric leaching tank is injected with room temperature acidic solution through the second-stage atmospheric leaching pipe. Then, the second-stage steam regulating valve is opened through the DCS industrial control system to introduce steam to heat the material in the tank to 70℃~90℃ to carry out the leaching reaction. The slurry after the second-stage atmospheric leaching is discharged through the second-stage discharge pipe, the pressurizing pump and the pressurizing kettle feed pipe into the pressurizing kettle.

[0015] 4) The oxygen regulating valve is opened through the DCS industrial control system. The slurry entering the pressurized kettle and the oxygen in the oxygen main pipe are leached under oxygen pressure at a kettle pressure of 0.55~1.4MPa. There is no need to introduce steam for heating in the pressurized kettle. The slurry reacts with oxygen to generate nickel sulfate and heat. The heat automatically heats the gas-liquid-solid three-phase slurry in the kettle to 145℃~200℃.

[0016] 5) The flash control valve is opened via the DCS industrial control system. The high-temperature and high-pressure liquid-solid phase slurry enters the pre-flash tank through the pressurized kettle discharge pipe and flows to the flash tank through the pre-flash tank overflow pipe. When the DCS industrial control system detects a signal from the level sensor in the upper liquid level monitoring port of the flash tank, that is, when the liquid level in the flash tank reaches the upper liquid level, the discharge regulating valve is opened to discharge the pressurized leaching slurry. Conversely, when the DCS industrial control system detects a signal from the level sensor in the lower liquid level monitoring port of the flash tank, that is, when the liquid level in the flash tank reaches the lower liquid level, the discharge regulating valve is closed.

[0017] 6) Adjust the opening of the tail gas regulating valve and oxygen regulating valve through the DCS industrial control system to maintain the pressure of the vessel at 0.55~1.4MPa. The high temperature and high pressure gas phase tail gas is discharged through the tail gas discharge pipe.

[0018] 7) Adjust the opening of the tail gas utilization regulating valve of the first stage and the tail gas utilization regulating valve of the second stage by adjusting the opening of the steam regulating valve of the first stage and the steam regulating valve of the second stage to keep the slurry temperature in the first stage atmospheric pressure leaching tank and the second stage atmospheric pressure leaching tank always controlled at 70~90℃.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This system reduces the amount of fresh steam used by heating the ore slurry by introducing the high-temperature tail gas from the pressurized kettle and flash tank into a first-stage and a second-stage atmospheric pressure leaching tank. This significantly reduces energy costs. Furthermore, it solves the environmental pollution problem caused by the disorderly dispersion of small amounts of valuable nickel sulfate entrained in the tail gas, allowing the entrained valuable metal to re-enter the production system. It also eliminates corrosion problems in the plant facilities within a certain range around the tail gas, significantly improving the production environment. This system is of great significance for the oxygen pressure leaching production of non-ferrous metal nickel. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the exhaust gas waste heat utilization system of the present invention.

[0022] Among them, 1-pressurized kettle, 101-kettle body, 102-stirrer, 103-partition plate, 2-pressurized kettle discharge pipe, 3-tail gas discharge pipe, 4-flash evaporation control valve, 5-tail gas regulating valve, 6-pre-flash evaporation tank, 7-pre-flash evaporation tank overflow pipe, 8-flash evaporation tank, 9-flash evaporation exhaust gas outlet pipe, 10-flash evaporation tank upper liquid level monitoring port, 11-flash evaporation tank lower liquid level monitoring port, 12-discharge regulating valve, 13-first stage atmospheric pressure leaching tank, 14-first stage tail gas utilization regulating valve, 15-first stage inlet 16 - Feed pipe, 17 - First stage discharge pipe, 18 - Thickener, 19 - Supernatant overflow pipe, 20 - Underflow discharge pipe, 21 - Second stage atmospheric pressure leaching tank, 22 - Second stage tail gas utilization regulating valve, 23 - Second stage feed pipe, 24 - Second stage discharge pipe, 25 - Pressure pump, 26 - Check valve, 27 - Oxygen main pipe, 28 - Oxygen regulating valve, 29 - First stage steam regulating valve, 30 - Second stage steam regulating valve, 31 - Second stage atmospheric pressure liquid distribution pipe, 32 - Pressure vessel feed pipe. Detailed Implementation

[0023] like Figure 1 As shown, the tail gas waste heat utilization system of the nickel-oxygen pressure leaching pressurized kettle of the present invention includes a pressurized kettle 1, a pre-flash tank 6, a flash tank 8, a first-stage atmospheric pressure leaching tank 13, a thickener 17, and a second-stage atmospheric pressure leaching tank 21.

[0024] The pressure vessel 1 includes a vessel body 101 and multiple agitators 102. The agitators 102 are mounted on the vessel body 101 and extend into the interior of the vessel body 101. The top of the vessel body 101 is provided with a pressure vessel discharge pipe 2, a tail gas discharge pipe 3, and a pressure vessel feed pipe 32. A tail gas regulating valve 5 is also installed on the tail gas discharge pipe 3, and a check valve 26 is installed on the pressure vessel feed pipe 32. Inside the vessel body 101, a partition plate 103 is provided between every two agitators 102 to allow the slurry to overflow from the top. Two adjacent partition plates 103 enclose a compartment. An oxygen branch pipe is provided at the bottom of each compartment. The oxygen branch pipe is connected to an oxygen main pipe 27 located outside the vessel body 101, and an oxygen regulating valve 28 is installed on each oxygen branch pipe. The remaining undescribed parts are the same as the structure of Chinese Invention Patent CN200810185814.1 "Overflow Multi-Compartment Pressure Vessel and its Process".

[0025] The pre-flash tank 6 and the flash tank 8 form a stepped flash system. The top of the pre-flash tank 6 is equipped with a flash control valve 4, which is connected to the discharge pipe 2 of the pressurized vessel. The upper side of the pre-flash tank is connected to the overflow pipe 7, and the other end of the overflow pipe 7 is connected to the flash tank 8. The top of the flash tank 8 is equipped with a flash exhaust gas outlet pipe 9, which is connected to the tail gas discharge pipe 3. The middle part is equipped with an upper liquid level monitoring port 10 and a lower liquid level monitoring port 11 with internal liquid level sensors. The bottom is connected to the flash tank discharge pipe, and a discharge regulating valve 12 is installed on the flash tank discharge pipe.

[0026] A section of atmospheric pressure leaching tank 13 is connected to a section of tail gas waste heat utilization pipe and a section of steam inlet pipe at the top, and a section of feed pipe 15 and a section of discharge pipe 16 are connected to the side; a section of tail gas waste heat utilization pipe is equipped with a section of tail gas utilization regulating valve 14 and is connected to the tail gas discharge pipe 3 through the section of tail gas utilization regulating valve 14; a section of steam inlet pipe is equipped with a section of steam regulating valve 29 and is connected to an external steam source through the section of steam regulating valve 29.

[0027] The thickener 17 is connected to a discharge pipe 16 at the top, has a supernatant overflow pipe 18 on the side, and has a bottom flow discharge pipe 19 at the bottom.

[0028] The top of the two-stage atmospheric leaching tank 21 is connected to a two-stage tail gas waste heat utilization pipe, a two-stage steam inlet pipe, and a two-stage atmospheric pressure liquid distribution pipe 31, and the side is connected to a two-stage feed pipe 23 and a two-stage discharge pipe 24; a two-stage tail gas utilization regulating valve 22 is installed on the two-stage tail gas waste heat utilization pipe and is connected to the tail gas discharge pipe 3 through the two-stage tail gas utilization regulating valve 22; a two-stage steam regulating valve 30 is installed on the two-stage steam inlet pipe and is connected to an external steam source through the two-stage steam regulating valve 30; an underflow conveying pump 20 is installed on the two-stage feed pipe 23 and is connected to the underflow discharge pipe 19 through the underflow conveying pump 20; a pressure pump 25 is installed on the two-stage discharge pipe 24 and is connected to the pressure vessel feed pipe 32 through the pressure pump 25.

[0029] Preferably, the bottom of the first atmospheric pressure leaching tank 13 and the second atmospheric pressure leaching tank 21 are also provided with drain ports to facilitate cleaning of the atmospheric pressure tank.

[0030] It also includes a DCS industrial control system, which is connected to the flash control valve 4, the tail gas regulating valve 5, the discharge regulating valve 12, the first-stage tail gas utilization regulating valve 14, the underflow conveying pump 20, the pressurizing pump 25, the second-stage tail gas utilization regulating valve 22, the oxygen regulating valve 28, the first-stage steam regulating valve 29, the second-stage steam regulating valve 30, and the liquid level sensor signal.

[0031] The working process of the above-mentioned exhaust gas waste heat recovery system is as follows:

[0032] 1) The ambient temperature slurry of nickel ore enters the atmospheric pressure leaching tank 13 through a feed pipe 15. Steam is introduced through a steam regulating valve 29 via the DCS industrial control system to raise the temperature of the atmospheric pressure leaching slurry to 70℃~90℃ for leaching reaction. The reacted slurry enters the thickener 17 through a discharge pipe 16.

[0033] 2) After the slurry entering the thickener 17 settles and separates, the top supernatant is discharged from the supernatant overflow pipe 18 and then filtered to become the finished product liquid. The bottom slurry enters the second-stage atmospheric pressure leaching tank 21 through the bottom discharge pipe 19, the bottom conveying pump 20 and the second-stage feed pipe 23 for second-stage atmospheric pressure leaching.

[0034] 3) The slurry entering the second-stage atmospheric leaching tank 21 is injected with a room-temperature acidic solution through the second-stage atmospheric leaching pipe 31. The second-stage steam regulating valve 30 is opened through the DCS industrial control system to introduce steam to heat the material in the tank to 70℃~90℃ to carry out the leaching reaction. The slurry after the second-stage atmospheric leaching is discharged through the second-stage discharge pipe 24, the pressurizing pump 25 and the pressurizing kettle feed pipe 32 into the pressurizing kettle 1.

[0035] 4) The oxygen regulating valve 28 is opened through the DCS industrial control system. The slurry entering the pressure vessel 1 and the oxygen in the oxygen main pipe 27 are leached under oxygen pressure at a pressure of 0.55~1.4MPa. There is no need to introduce steam for heating in the pressure vessel. The slurry reacts with oxygen to generate nickel sulfate and heat. The heat automatically heats the gas-liquid-solid three-phase slurry in the vessel to 145℃~200℃.

[0036] 5) The flash control valve 4 is opened through the DCS industrial control system. The high-temperature and high-pressure liquid-solid phase slurry enters the pre-flash tank 6 through the pressurized kettle discharge pipe 2, and then flows to the flash tank 8 through the pre-flash tank overflow pipe 7. When the DCS industrial control system detects that the liquid level sensor in the upper liquid level monitoring port 10 of the flash tank sends a signal, that is, when the liquid level in the flash tank reaches the upper liquid level, the discharge regulating valve 12 is opened to discharge the pressurized leaching slurry to the pressurized leaching thickener (not shown in the figure). Conversely, when the DCS industrial control system detects that the liquid level sensor in the lower liquid level monitoring port 11 of the flash tank sends a signal, that is, when the liquid level in the flash tank reaches the lower liquid level, the discharge regulating valve 12 is closed to prevent the high-temperature exhaust gas generated in the flash tank from being discharged from the flash tank discharge regulating valve 12.

[0037] The pressure leaching thickener and the thickener 17 in the atmospheric leaching section have the same function: to produce finished liquid. The underflow slurry produced by the pressure leaching thickener is re-mixed through a feed pipe 15 and then enters an atmospheric leaching tank 13 to enrich metal elements and avoid metal loss.

[0038] 6) Adjust the opening of the tail gas regulating valve 5 and the oxygen regulating valve 28 through the DCS industrial control system to maintain the pressure in the pressurized vessel 1 at a stable pressure of 0.55~1.4MPa. The high temperature and high pressure gas phase tail gas is discharged through the tail gas discharge pipe 3.

[0039] Preferably, the pressure in the vessel is controlled at 0.8~1.4 MPa.

[0040] 7) Adjust the opening of the tail gas utilization regulating valve 14, the tail gas utilization regulating valve 22, the steam regulating valve 29, and the steam regulating valve 30 in the first stage tail gas utilization regulating valve 14, the second stage tail gas utilization regulating valve 22, the first stage steam regulating valve 29, and the second stage steam regulating valve 30 through the DCS industrial control system to keep the slurry temperature in the first stage atmospheric pressure leaching tank 13 and the second stage atmospheric pressure leaching tank 21 always controlled at 70~90℃.

[0041] Furthermore, this invention also discloses a cascade flash evaporation treatment method, based on the above-mentioned exhaust gas waste heat utilization system, comprising the following steps:

[0042] 1) When the liquid level in the pressure vessel 1 reaches the limit, the flash control valve 4 automatically opens, and the pressurized leaching slurry enters the pre-flash tank 6 through the flash control valve 4. The slurry undergoes initial flash evaporation in the flash control valve 4, and the pressure is reduced to 0.7~1.0MPa and the temperature drops to 145~170℃.

[0043] 2) The pressurized leaching slurry enters the pre-flash tank 6 for secondary flash evaporation, where the pressure is reduced to 0.4~0.5MPa and the temperature drops to 130~140℃. The leaching slurry gradually rises from the bottom of the pre-flash tank 6 and overflows through the pre-flash tank overflow pipe 7, spraying onto the liquid surface inside the flash tank 8.

[0044] Preferably, the liquid level in flash tank 8 is controlled at 1.5m. Controlling the liquid level appropriately can prevent flash vapor from entering the outlet pipe and causing cavitation.

[0045] 3) The leaching slurry undergoes a third flash in the flash tank 8, the pressure is reduced to 0.15~0.25MPa, and the temperature drops to 100~120℃; the flash steam enters the tail gas waste heat utilization system from the flash exhaust gas outlet pipe 9, and the slurry is discharged from the discharge regulating valve 12 and enters the pressurized leaching thickener for liquid-solid separation.

[0046] 4) The slurry entering the pressure leaching thickener undergoes a fourth flash evaporation, with the pressure reduced to 0 MPa and the temperature dropping to 70~90℃, at which point the step flash evaporation ends.

[0047] In summary, this invention enables the recovery and utilization of waste heat from the pressure vessel tail gas and flash evaporation, ensuring the production of high-quality nickel liquid while reducing the amount of fresh steam used, thereby significantly reducing enterprise production costs. Furthermore, it solves the environmental pollution problem caused by the disorderly dispersion of small amounts of valuable nickel sulfate entrained in the tail gas, allowing the entrained valuable metal to re-enter the production system, eliminating corrosion problems in plant facilities within a certain range around the tail gas, and significantly improving the production environment. This invention is of great significance for the production of non-ferrous metal nickel oxygen pressure leaching.

[0048] In this invention, in addition to using a DCS control system, a PLC control system can also be used for process control; all other aspects not described herein use equivalents in the prior art that achieve the same function / effect, and will not be elaborated here.

Claims

1. A waste heat recovery system for tail gas from a nickel-oxygen pressure leaching reactor, characterized in that, It includes a pressure vessel (1), a pre-flash tank (6), a flash tank (8), a first-stage atmospheric leaching tank (13), a thickener (17), and a second-stage atmospheric leaching tank (21); The pressurizing vessel (1) includes a vessel body (101) and multiple agitators (102). The agitators (102) are arranged on the vessel body (101) and extend into the interior of the vessel body (101). The top of the vessel body (101) is provided with a pressurizing vessel discharge pipe (2), a tail gas discharge pipe (3) and a pressurizing vessel feed pipe (32). A tail gas regulating valve (5) is also installed on the tail gas discharge pipe (3), and a check valve (26) is installed on the pressurizing vessel feed pipe (32). Inside the vessel body (101), there is a partition plate (103) between every two agitators (102) that allows the slurry to overflow from the top. Two adjacent partition plates (103) enclose a compartment. An oxygen branch pipe is provided at the bottom of each compartment. The oxygen branch pipe is connected to the oxygen main pipe (27) located outside the vessel body (101), and an oxygen regulating valve (28) is installed on each oxygen branch pipe. The pre-flash tank (6) and flash tank (8) form a stepped flash system; a flash control valve (4) is installed on the top of the pre-flash tank (6) and is connected to the discharge pipe (2) of the pressurized vessel through the flash control valve (4); an overflow pipe (7) of the pre-flash tank is connected to the upper side; the other end of the overflow pipe (7) of the pre-flash tank is connected to the flash tank (8); a flash exhaust gas outlet pipe (9) is installed on the top of the flash tank (8); the flash exhaust gas outlet pipe (9) is connected to the tail gas discharge pipe (3); a flash tank upper liquid level monitoring port (10) and a flash tank lower liquid level monitoring port (11) with an internal liquid level sensor are provided in the middle; a flash tank discharge pipe is connected to the bottom; and a discharge regulating valve (12) is installed on the flash tank discharge pipe. The top of the atmospheric leaching tank (13) is connected to a tail gas waste heat utilization pipe and a steam inlet pipe, and the side is connected to a feed pipe (15) and a discharge pipe (16); a tail gas utilization regulating valve (14) is installed on the tail gas waste heat utilization pipe and is connected to the tail gas discharge pipe (3) through the tail gas utilization regulating valve (14); a steam regulating valve (29) is installed on the steam inlet pipe and is connected to an external steam source through the steam regulating valve (29); The thickener (17) is connected to a discharge pipe (16) at the top, and has an overflow pipe (18) for supernatant on the side and a discharge pipe (19) for underflow at the bottom. The top of the two-stage atmospheric leaching tank (21) is connected to a two-stage tail gas waste heat utilization pipe, a two-stage steam inlet pipe and a two-stage atmospheric liquid distribution pipe (31), and the side is connected to a two-stage feed pipe (23) and a two-stage discharge pipe (24); a two-stage tail gas utilization regulating valve (22) is installed on the two-stage tail gas waste heat utilization pipe and is connected to the tail gas discharge pipe (3) through the two-stage tail gas utilization regulating valve (22); a two-stage steam regulating valve (30) is installed on the two-stage steam inlet pipe and is connected to an external steam source through the two-stage steam regulating valve (30); an underflow conveying pump (20) is installed on the two-stage feed pipe (23) and is connected to the underflow discharge pipe (19) through the underflow conveying pump (20); a pressure pump (25) is installed on the two-stage discharge pipe (24) and is connected to the pressure vessel feed pipe (32) through the pressure pump (25); The bottom of the first atmospheric pressure leaching tank (13) and the second atmospheric pressure leaching tank (21) are provided with drainage ports.

2. The waste heat recovery system for tail gas from a nickel-oxygen pressure leaching reactor as described in claim 1, characterized in that: It also includes a DCS industrial control system, which is connected to the flash control valve (4), tail gas regulating valve (5), discharge regulating valve (12), first-stage tail gas utilization regulating valve (14), underflow conveying pump (20), pressurizing pump (25), second-stage tail gas utilization regulating valve (22), oxygen regulating valve (28), first-stage steam regulating valve (29), second-stage steam regulating valve (30) and liquid level sensor signal.

3. A method for utilizing exhaust gas waste heat using the exhaust gas waste heat utilization system described in claim 2, characterized in that, Includes the following steps: 1) The ambient temperature slurry of nickel ore enters the atmospheric pressure leaching tank (13) through a feed pipe (15). Steam is introduced by opening a steam regulating valve (29) through the DCS industrial control system, so that the atmospheric pressure leaching slurry is heated to 70℃~90℃ for leaching reaction. The slurry after reaction enters the thickener (17) through a discharge pipe (16). 2) After the slurry enters the thickener (17) and settles and separates, the top supernatant is discharged from the supernatant overflow pipe (18) and then filtered to make the finished liquid. The bottom slurry enters the second-stage atmospheric pressure leaching tank (21) through the bottom discharge pipe (19), the bottom conveying pump (20) and the second-stage feed pipe (23) for second-stage atmospheric pressure leaching. 3) The slurry entering the second-stage atmospheric leaching tank (21) is injected with room temperature acidic solution through the second-stage atmospheric leaching pipe (31) and then the second-stage steam regulating valve (30) is opened through the DCS industrial control system to introduce steam to heat the material in the tank to 70℃~90℃ to carry out the leaching reaction. The slurry after the second-stage atmospheric leaching is discharged through the second-stage discharge pipe (24), the pressurizing pump (25) and the pressurizing kettle feed pipe (32) into the pressurizing kettle (1). 4) Open the oxygen regulating valve (28) through the DCS industrial control system. The slurry entering the pressurized kettle (1) and the oxygen in the oxygen main pipe (27) are leached under oxygen pressure at a kettle pressure of 0.55~1.4MPa. There is no need to introduce steam for heating in the pressurized kettle. The slurry reacts with oxygen to generate nickel sulfate and heat. The heat automatically heats the gas-liquid-solid three-phase slurry in the kettle to 145℃~200℃. 5) Open the flash control valve (4) through the DCS industrial control system. The high temperature and high pressure liquid-solid phase slurry enters the pre-flash tank (6) through the pressurized kettle discharge pipe (2) and flows to the flash tank (8) through the pre-flash tank overflow pipe (7). When the DCS industrial control system detects that the liquid level sensor in the upper liquid level monitoring port (10) of the flash tank sends a signal, that is, when the liquid level in the flash tank reaches the upper liquid level, open the discharge regulating valve (12) to discharge the pressurized leaching slurry. Conversely, when the DCS industrial control system detects that the liquid level sensor in the lower liquid level monitoring port (11) of the flash tank sends a signal, that is, when the liquid level in the flash tank reaches the lower liquid level, close the discharge regulating valve (12). 6) Adjust the opening of the tail gas regulating valve (5) and oxygen regulating valve (28) through the DCS industrial control system to maintain the pressure in the pressurized kettle (1) at 0.55~1.4MPa. The high temperature and high pressure gas phase tail gas is discharged through the tail gas discharge pipe (3). 7) Adjust the opening of the tail gas utilization regulating valve (14), tail gas utilization regulating valve (22), steam regulating valve (29) and steam regulating valve (30) through the DCS industrial control system to keep the slurry temperature in the first atmospheric pressure leaching tank (13) and the second atmospheric pressure leaching tank (21) always controlled at 70~90℃.

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