Efficient pressure leaching system and control method thereof

Abstract

The invention discloses an efficient pressure leaching system and a control method thereof, and belongs to the technical field of hydrometallurgy. The system comprises a three-partition four-chamber autoclave, a bottom oxygen introduction module, a temperature control system, a tail gas recycling device and a pre-flash tank. The interior of the autoclave is divided into four compartments through retaining walls, liquid mixing holes are formed in the bottoms of the retaining walls to achieve pulp mixing, and the volume coefficient is not lower than 0.85. The bottom oxygen introduction module adopts a PEEK / 904 composite oxygen pipe and a distribution ring to realize uniform oxygen distribution; the temperature control system is linked with a sensor through a PLC (Programmable Logic Controller) to realize accurate control on temperature and oxygen partial pressure; the tail gas is reused in the normal-pressure leaching tank through the jet mixer; the ore pulp is separated after being subjected to two-stage flash evaporation through the pre-flash evaporation tank and the flash evaporation tank. Through structure optimization and intelligent control, efficient leaching of nickel is achieved, the leaching rate is larger than or equal to 96%, the oxygen utilization rate is larger than or equal to 95%, the steam unit consumption is reduced by 38% or above, and the system is stable and reliable in operation and suitable for wet metallurgy treatment of complex nickel raw materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrometallurgy, in particular to an efficient pressure leaching system and a control method thereof. BACKGROUND

[0002] Currently, the pressure leaching technology in the field of hydrometallurgy, especially the process for treating complex nickel raw materials, still has significant bottlenecks. The high temperature and high pressure acid leaching (HPAL) technology adopted by Sherritt has a huge equipment investment and a high threshold. The conventional pressure leaching system commonly used in China has many problems: low reaction efficiency, low volume coefficient of traditional pressure kettle, uneven oxygen distribution, resulting in nickel leaching rate less than 95%, high nickel content in slag, high energy consumption, low utilization rate of steam and oxygen, a large amount of reaction waste heat is directly discharged without recycling, the steam consumption of the system is generally higher than 2.2t / ton of nickel, low automation level, key parameters such as oxygen partial pressure and temperature rely on manual adjustment, poor control accuracy and response lag, and poor equipment reliability, the discharge valve and flash tank are prone to scaling and wear, and faults occur frequently, and the continuous operation cycle is short. Therefore, it is urgent to develop a new pressure leaching system integrating efficient reaction, intelligent control and resource recycling to comprehensively improve the technical and economic indicators and operation stability. SUMMARY

[0003] The present application provides an efficient pressure leaching system and a control method thereof, aiming to solve the problems of low reaction efficiency, high energy consumption, insufficient automation level and poor equipment reliability of the pressure leaching system in the prior art.

[0004] The technical solution of the present application is realized by the following way: An efficient pressure leaching system mainly comprises a three-separation-four-chamber pressure kettle, a bottom oxygen supply module, a temperature control system, a tail gas recycling device and a pre-flash tank. Double feeding ports and double discharge ports are arranged on the top of the pressure kettle, the inside is divided into four chambers by first, second and third barriers, the height of each barrier is less than the height of the kettle body, and a semicircular liquid hole is arranged at the bottom of the first barrier to realize the communication between the chambers, so that the volume coefficient of the pressure kettle is not less than 0.85. The bottom oxygen supply module comprises a PEEK / 904 composite oxygen pipe and an oxygen distribution ring arranged at the bottom of each chamber, and 5-10mm spray holes are arranged on the distribution ring. The temperature control system comprises a PLC controller and steam branches and cooling liquid branches in each chamber, and the PLC controls the temperature and oxygen partial pressure of each chamber in real time through temperature sensors and pressure sensors. The tail gas recycling device comprises a jet mixer connected to the tail gas pipe between the top of the pressure kettle and the tail of the flash tank. The pre-flash tank is lined with aluminum oxide tiles to reduce the pressure of the ore slurry from 0.8-1.2MPa to 0.15-0.3MPa.

[0005] Preferably, the first and third baffle walls have equal height, and the second baffle wall has a height greater than that of the first baffle wall.

[0006] Preferably, the pressurized tail gas pipe of the jet mixer has an extension length of no less than 200 mm, and the flash tail gas suction pressure difference is no more than 0.05 MPa.

[0007] Preferably, the PEEK layer of the PEEK / 904 composite oxygen pipe has a thickness of 2-3 mm, and the temperature resistance is no less than 260 DEG C.

[0008] The application also provides a control method for the system, comprising: slurry of raw materials into 9%-12% concentration of ore slurry; pumping into a pressurized kettle and oxygen reaction under the condition of 0.8-1.2 MPa, 160-180 DEG C; real-time monitoring of oxygen partial pressure and temperature by PLC, oxygen partial pressure calculation and control based on Antoine formula, and automatic injection of cooling liquid when temperature is out of limit; the tail gas of the pressurized kettle and the flash tank is recycled to the atmospheric leaching tank through the jet mixer; the ore slurry is concentrated and separated after two-stage pressure reduction through the pre-flash tank and the flash tank.

[0009] Preferably, the jet mixer directly introduces the high-temperature tail gas below the ore slurry liquid surface of the atmospheric leaching tank.

[0010] Preferably, the ore slurry is sequentially subjected to one-stage pressure reduction through the pre-flash tank and two-stage pressure reduction through the flash tank.

[0011] Preferably, the PLC controller has an oxygen partial pressure monitoring accuracy of ±0.01 MPa and a temperature monitoring accuracy of ±2 DEG C.

[0012] The application has the following beneficial effects: the three-separate four-chamber pressurized kettle structure and the bottom oxygen feeding design improve the reaction efficiency and oxygen utilization rate; the intelligent temperature control system realizes accurate temperature and oxygen partial pressure control; the tail gas recycling device effectively recovers waste heat and reduces energy consumption; the two-stage flash system improves the flash efficiency and reduces equipment wear; the overall system realizes efficient leaching of nickel, and the leaching rate can reach more than 96%, while significantly reducing the operation cost and maintenance frequency. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall structure of the efficient oxygen pressure leaching system.

[0014] Figure 2 It is a cross-sectional view of the internal structure of the three-separate four-chamber pressurized kettle.

[0015] Figure 3 It is a schematic diagram of the structure of the jet mixer. DETAILED DESCRIPTION

[0016] The application will be described in further detail below with reference to the drawings and specific embodiments, but the embodiments of the application are not limited thereto.

[0017] Example 1 This embodiment takes a high-efficiency pressure leaching system for processing nickel sulfide concentrate as an example to illustrate the specific embodiments of the application.

[0018] Referring to Figure 1 As shown in the figure, the high-efficiency pressure leaching system mainly includes a three-separate-four-chamber pressure tank, a pre-flash tank, a flash tank, a jet mixer and an atmospheric leaching tank connected in sequence.

[0019] The top of the three-separate-four-chamber pressure tank is respectively provided with a feed inlet and a discharge outlet. The inside thereof is divided into first to fourth four chambers (I, II, III, IV) by a first baffle, a second baffle and a third baffle. The heights of the first baffle and the third baffle are equal, and the height of the second baffle is slightly higher. The heights of the three baffles are all lower than the tank body, so as to form a semicircular liquid hole at the bottom of the first baffle, so that the ore slurry can flow from the chamber I to the chamber IV in sequence, and the volume coefficient reaches 0.87. A bottom oxygen supply module is arranged at the bottom of each chamber. The module is composed of a vertically arranged PEEK / 904 composite oxygen pipe and an annular oxygen distribution ring. The distribution ring is provided with spray holes with a pore size of 8 mm. The spray holes are used to uniformly distribute oxygen into the ore slurry. The thickness of the PEEK layer is 2.5 mm, and the temperature resistance reaches 280℃.

[0020] Components of a temperature control system are also arranged in each chamber, including steam branch pipes and cooling liquid branch pipes, which are respectively connected with external steam main pipes and cooling liquid main pipes. The steam main pipe is provided with an electromagnetic valve, and the cooling liquid main pipe is provided with a high-pressure cooling liquid pump. A temperature sensor and a pressure sensor are arranged at the top of each chamber. All the sensors and actuators are signal connected with a PLC controller to form a closed-loop control circuit.

[0021] The discharge outlet of the pressure tank is connected to the pre-flash tank through a pipeline. The pre-flash tank is lined with aluminum oxide ceramic bricks, and the design pressure drop is 1.0 MPa to 0.2 MPa. The outlet of the pre-flash tank is connected to the flash tank for secondary pressure reduction. The DN50 pressure exhaust pipe at the top of the pressure tank and the DN250 flash exhaust pipe at the tail of the flash tank are jointly connected to the jet mixer. The mixed exhaust gas is introduced below the liquid level of the atmospheric leaching tank.

[0022] The control method is implemented according to the following steps: Ore slurry preparation: send nickel sulfide concentrate (composition: Ni 50.63%, Cu 2.1%, Fe 28.5%, S 16.8%), process water and concentrated sulfuric acid into an intensive slurry tank in proportion to prepare ore slurry with a concentration of 10.5%.

[0023] Pressure leaching: the ore slurry is fed into the three-separate-four-chamber pressure tank at a flow rate of 16.9 m 3The flow rate of 4 m3 / h of the pump is pumped into the three-compartment four-chamber pressurized kettle. The total pressure in the kettle is controlled at 1.0 MPa, and the temperature is maintained at 170 DEG C. At the same time, pure oxygen is introduced into each compartment through the bottom oxygen module, and the total flow rate is controlled at 65 Nm3 / h. 3 / h.

[0024] Intelligent control: The PLC controller collects the temperature (precision ± 1.5 DEG C) and oxygen partial pressure (precision ± 0.01 MPa) data of each compartment in real time. Based on the Antoine formula, the oxygen valve opening is dynamically calculated and adjusted to stabilize the oxygen partial pressure at 0.25 MPa. When the temperature of the second compartment (II) rises to 175 DEG C due to the exothermic reaction, the PLC immediately starts the cooling liquid pump to inject cooling liquid (nickel sulfate solution) into the cooling liquid branch of the compartment at a flow rate of 4 m3 / h, and the temperature is adjusted to the set value within 30 seconds. 3 / h.

[0025] Tail gas reuse: The high-temperature tail gas (mainly composed of O2, CO2 and water vapor) discharged from the pressurized kettle and the secondary flash tail gas discharged from the flash tank are mixed in a jet mixer and then sent into the ore pulp in the atmospheric leaching tank to directly utilize the sensible heat and latent heat thereof.

[0026] Flash and separation: The high-temperature ore pulp (about 170 DEG C) after reaction is first introduced into a pre-flash tank, and the pressure is reduced to 0.2 MPa; then the ore pulp is introduced into a flash tank, and the pressure is reduced to atmospheric pressure. The ore pulp after flash is sent into a thickener for solid-liquid separation to obtain a nickel-rich solution and a leaching residue.

[0027] Implementation effect: After detection, the direct recovery rate of nickel reaches 96.3%, and the nickel content in the leaching residue is reduced to 0.42%. Due to the high-efficiency reuse of tail gas waste heat by the jet mixer, the temperature of the ore pulp at the inlet of the atmospheric leaching tank is stably increased from 70 DEG C to 85 DEG C, the overall steam consumption of the system is reduced to 1.82 t / ton of nickel, and the energy saving is about 38% compared with the traditional single-stage flash system. The bottom oxygen design makes the oxygen utilization rate as high as 95.8%. The system has been continuously and stably operated for more than 30 days, and the key equipment (such as the discharge valve and the flash tank) has not been fouled, blocked or seriously worn out, and the failure rate has been reduced by more than 60%.

[0028] It should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-efficiency pressurized leaching system, characterized in that, include: The three-compartment, four-chamber pressurized vessel has two feed inlets and two discharge outlets on its top two sides. The interior of the pressurized vessel has a first baffle wall, a second baffle wall, and a third baffle wall arranged vertically. The height of the three baffle walls is less than the height of the vessel body, and they divide the space inside the vessel into a first compartment, a second compartment, a third compartment, and a fourth compartment. A semi-circular liquid passage is opened at the bottom of the first baffle wall to connect the first compartment and the second compartment. The volume coefficient of the pressurized vessel is not less than 0.

85. The bottom oxygenation module includes a PEEK / 904 composite oxygen pipe vertically installed at the bottom of each compartment and an oxygen distribution ring connected thereto. The oxygen distribution ring is provided with nozzles with a diameter of 5-10mm. The temperature control system includes a PLC controller and steam branch pipes and coolant branch pipes installed in each compartment. The ends of the steam branch pipes and coolant branch pipes are respectively connected to a steam main pipe and a coolant main pipe. A solenoid valve is installed on the steam main pipe, and a coolant delivery pump is installed on the coolant main pipe. The PLC controller is connected to the solenoid valves and the coolant delivery pumps respectively. The temperature and oxygen partial pressure of each compartment are monitored and fed back in real time by temperature sensors and pressure sensors installed on the top of each compartment. The exhaust gas recycling device includes a jet mixer, wherein the first inlet of the jet mixer is connected to the top of the pressurized vessel through a DN50 pressurized exhaust gas pipe, and the second inlet is connected to the tail of the flash tank through a DN250 flash exhaust gas pipe. The pre-flash tank has its inlet connected to the discharge port of the pressurized vessel and its outlet connected to the flash tank. The tank is lined with alumina ceramic tiles and is used to reduce the pressure of the slurry from the pressurized vessel from 0.8-1.2 MPa to 0.15-0.3 MPa.

2. The high-efficiency pressure leaching system according to claim 1, characterized in that, The first and third retaining walls are of equal height, while the second retaining wall is of greater height than the first retaining wall.

3. The high-efficiency pressure leaching system according to claim 1, characterized in that, The extension length of the pressurized tail gas inlet of the jet mixer is not less than 200 mm, and the pressure difference of the flash tail gas intake at the second inlet of the jet mixer when it is working is not greater than 0.05 MPa.

4. The high-efficiency pressure leaching system according to claim 1, characterized in that, The PEEK layer of the PEEK / 904 composite oxygen tube has a thickness of 2-3 mm and a temperature resistance of not less than 260℃.

5. A control method for using the high-efficiency pressurized leaching system as described in any one of claims 1-4, characterized in that, Includes the following steps: Slurry preparation steps: The raw materials are processed by a pulping system to form a slurry with a concentration of 9%-12%; Pressure leaching step: The slurry is pumped into the three-compartment, four-chamber pressure vessel, and the pressure inside the vessel is controlled at 0.8-1.2 MPa and the temperature at 160-180℃. Simultaneously, oxygen is introduced through the bottom oxygenation module at a rate of 50-80 Nm³ / h. 3 Oxygen is introduced at a flow rate of / h; Control steps: The PLC controller monitors the oxygen partial pressure and temperature inside the reactor in real time, calculates and controls the oxygen partial pressure based on the Antoine formula; when the temperature of any compartment exceeds the limit, the coolant branch pipe is automatically opened at a flow rate of 3-5m. 3 Inject coolant at a flow rate of / h; Tail gas reuse step: The high-temperature and high-pressure tail gas discharged from the pressurized kettle and the flash tail gas discharged from the flash tank are introduced into the jet mixer for mixing, and the mixed tail gas is reused in the atmospheric pressure leaching tank. Flash separation step: The slurry discharged from the pressurized kettle is sequentially fed into the pre-flash tank and the flash tank for two-stage depressurized flash evaporation. After flash evaporation, the slurry is concentrated to obtain a nickel solution.

6. The control method according to claim 5, characterized in that, In the tail gas reuse step, the jet mixer directly introduces the high-temperature tail gas below the slurry surface of the atmospheric pressure leaching tank.

7. The control method according to claim 5, characterized in that, In the flash separation step, the slurry is subjected to a first decompression in a pre-flash tank and a second decompression in a flash tank.

8. The control method according to claim 5, characterized in that, In the control steps, the PLC controller monitors the oxygen partial pressure with an accuracy of ±0.01MPa and the temperature with an accuracy of ±2℃.

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