What is the production process of alumina?

Zhongzhou Aluminum Plant: Sintering Production Line (First Alumina Plant)

The control system of the First Alumina Plant includes AB Company, Rockwell Company and Honeywell Company. Enterprises cooperate with universities to gradually optimize the operation control of alumina process, such as slurry preparation, sedimentation separation and washing system.

Workshop 1: including bauxite crushing, stacking, material taking and conveying: there is no control system at present.

Workshop 2: raw meal grinding and slurry batching: a set of control system is being installed, which adopts the control logic 5000 system of AB company in the United States, including 6 raw meal mills, each throwing pump and batching tank, and each two mills is a set of controllers, each throwing pump and batching tank is a set of controllers, and 4 sets of controllers are connected into a network. At present, it has been installed and not put into use.

Workshop 3: clinker burning, pulverized coal preparation, clinker crushing, electrostatic precipitator and fan screw: each large kiln is equipped with independent controllers, including control logic 5000 series and slc 500 series, including the display of kiln parameters and the start and stop of equipment, excluding the coal grinding system, excluding the control of feed pump and electrostatic precipitator, including the display of some feed parameters. 5, 6# coal trial run a slc 500 system, to control the relevant equipment of coal mill. 1-4 # coal pulverizer is still controlled by conventional instruments.

Workshop 4: Clinker dissolution, red mud separation and red mud washing: 6 dissolution mills are equipped with 3 sets of control logic 5000 control systems, and the separation and washing are still controlled by conventional instruments.

Workshop 5: Crude liquid feed pump, desilication and silicon residue from leaf filter * *:5 groups and 6 groups of desilication are respectively equipped with a set of control logic 5000 control system, 1-4 groups of desilication are controlled by conventional instruments, and leaf filter is equipped with a set of control logic 5000 control system.

Workshop 6: Carbonation decomposition, seed precipitation, aluminum hydroxide filtration and mother liquor evaporation: one set of carbon precipitation slc 500 control system, one set of seed precipitation control logic 5000 control system, one set of five groups and six groups of evaporation TPS system, and 1-4 groups of evaporation are controlled by conventional instruments.

Workshop 7: Plate filtration roasting: Three roasting and three plates are equipped with three TPS systems.

Air compression workshop: lime furnace, carbon dioxide station, high pressure station and low pressure station: five sets of control systems, including control logic 5000 system and slc 500 system, are installed on five lime furnaces.

Zhongzhou Aluminum Plant: 300,000-ton Bayer process production line (second alumina plant)

Bayer process is the first in China and was successfully put into production in early 2004. Five TPS systems were installed in the processes of grinding flotation, high-pressure leaching, red mud separation and washing, and seed evaporation. A set of ABB's control logic 5000 system was installed in the mineral processing workshop, and a set of Honeywell's HC900 control system was installed in the pulp preparation. At present, these systems are being networked.

Ore supply: flotation method, chemicals produced by Zhongzhou Aluminum Plant. 14 sets of video devices to monitor the belt and cone crusher. The control system is controllogic5000 of ABB company.

Raw material preparation: 24 sets of video screen devices to monitor 4 lattice mills, 2 sets of fuzzy control (complex software) developed by Dongda Design Institute, and 2 sets of fuzzy control computer control room. The designed mill load and pulp density participate in the control. Because the imported Finnish pulp particle size analyzer is not easy to use (it is easy to block the sampling tube) and has not achieved complete fuzzy control, the computer control room will be improved and further optimized in the future.

Single tube digestion: 4 pre-desilication tanks, 2 pre-desilication heating tanks, 3 diaphragm pumps, 9 digesters, 10 self-evaporator and 13 heater. Steam enters the bottom of 1 and 2 digesters for heating, and digesters 3 to 9 use waste heat for heating. There is no blender in the digester, and there is basically no stuttering in the digester. 13 level alkali solution heating, the last 3 level stuttering. Less detection and control. The regulating valve is Shanghai Liangguang Factory (located in YTC, North Korea), the steam is pneumatic and the others are electric. Sometimes the electric regulating valve is improperly closed, and the valve pad is easy to leak. Measure the liquid level of self-evaporator with radioactive source level gauge.

Sedimentation washing: Flocculants produced by Zhongzhou Aluminum Factory are automatically added into the sedimentation tank, and the thickness of mud layer in the sedimentation tank is measured by Australian interface instrument (measured by radioactive source, sometimes inaccurate), and the density of underflow liquid is measured by densimeter (basically accurate), and some valves are leaking. The control room will improve and further optimize the control in the future.

Decomposition system; 1 1 video device for monitoring field equipment, FLENDER vertical filter motor, ABB frequency converter, FISHER regulating valve, KROHNE electromagnetic flowmeter and E+H densimeter.

Evaporation system: the regulator is a product of Fisher Company, the regulator is used for the stock solution inlet, the outlet flow of 1 effect, 2-effect and 3-effect flash mother solution, the 2-5-effect variable frequency pump controls the liquid level, the conductivity meter is a product of Rosemount Company, and the liquid level meter is EJA differential pressure transmitter.

Roasting furnace: using gas as fuel, advanced control. The combustion station is made by JASPER in Germany. Sometimes, the leak detection valve is improperly closed, the valve is corroded, the pressure measuring instrument is blocked (requiring maintenance and cleaning), and the burner sometimes stutters (requiring maintenance and cleaning), which affects the ignition. Pressure sensor for material level detection in AH warehouse, and AH belt adopts products of Schenk Company. Measuring gas flow with A Niu flowmeter needs maintenance and cleaning.

Zhongzhou Aluminum Plant: Special Alumina Production Line (No.3 Alumina Plant)

Zhongzhou Aluminum Factory has developed and produced more than ten kinds of special alumina products in three series according to market demand, which has promoted the diversified development of enterprises. The control system adopts three sets of JX-300 distributed control systems controlled by Zhejiang University, and the factory implements automatic control. The three systems are networked through the backbone network, and some parameters are shared online. The dispatching center network can monitor the production situation at any time.

Pingguo Aluminum Factory: Pure Bayer Production Line

The design scale is an annual output of 650,000 tons of concentrate, 300,000 tons of alumina and 654.38+10,000 tons of electrolytic aluminum. In 2003, the annual output of alumina was 850,000 tons. Advanced technology and equipment from several industrialized countries have been introduced, and the latest scientific research results of China aluminum industry have been obtained. Except for ore and raw material storage yard and partial transportation, I/A distributed control system of FOXBORO Company in the United States is adopted in high-pressure dissolution, decomposition, sedimentation, filtration, leaf filtration, evaporation and roasting, which realizes automatic control of the process, and the process parameters of the whole alumina process can be seen at every operator station. Limited by the operation authority, the operator can only operate in this position and observe other positions, and realize networking in the whole alumina production process, and all control systems are networked with the OA system of the branch company.

Raw material workshop: the stacking and transportation of ore and fuel, and the ore is turned into manual operation. Vertical lime furnace: limestone and coke (or coal) belt weighing and batching (PLC control, Yuyao 1, Toledo 1), furnace body control (1 furnace top temperature, 1 furnace top pressure, 4 preheating zone temperatures, 4 calcining zone temperatures and 4 cooling zone temperatures, 6544. 1 phase is industrial computer control (AB company PLC), and phase II is computer system control (I/A system). 3) The ash remover adopts frequency conversion control to adjust the flow. 4) Preparation of slurry: There are four groups of mills (each group 1 rod mill and 1 ball mill). Shandong Weifang belt weigher 10, two mother liquor flowmeters (produced by FOXBORO Company), two radar level meters for sewage tanks (produced by VEGA Company), six temperature detectors (main motor, bearing and transmission system of rod ball mill), lubricating oil pressure gauges 16, temperature measuring points 16 and 65438+. The temperature of calcination zone and cooling zone of lime furnace is mainly controlled by the air volume of belt scale (limestone and coke or coal) and fan. 1 The phase furnace control scheme was changed to computer system control (I/A system), and the electric ash discharge valve was changed to pneumatic valve. Due to the high price of coke, coal is the main fuel, and the furnace temperature of some tests is 2℃ higher than the specified value, with little fluctuation. The automatic control of slurry preparation is basically realized, but the mill load and slurry composition analysis control are not realized.

Dissolution workshop: there is no pre-desilication process, and the main detection and control are: 5 radar level meters in dilution tank and back tank, before dissolution tank and hot water tank; 5 mass flow meters for fresh steam and secondary steam (Rosemount); 1 differential pressure transmitter is used for cooling water, and 20 differential pressure transmitters (E+H company) are used to measure the liquid level of separator, flash tank, condensate tank and sewage tank; 34 Pressure transmitter (FOXBORO Company) is used to measure the pressure of autoclave, pulse buffer, flash tank and steam pipeline; 60 pressure gauges (econosto Company and Shangyi No.4 Factory) are used to measure the pressure of diaphragm pump, autoclave, flash tank, condensation tank and dilution tank; Two export condensate conductivity meters (Rosemount Company); Cs 137 source is used for three pulp density meters in the pulse buffer and post-dissolving tank, and Co60 source is used for six liquid level switches of the pulse buffer; The CS 1 to1class flash tank is Cs 137 source, the 12 class flash tank is Co60 source, and the radiation instrument is a product of BERTHOLD Company in Germany. Forty-six platinum resistors (Shangyi No.17 Factory) are used to measure the top of autoclave and condensate water, single-tube condensate water and secondary steam. The control valve includes: 10 pneumatic disc valve control valve, which is used for the flow control of new steam and secondary steam, and the pressure and flow control of steam and condensate; 12 pneumatic eccentric rotary regulating valve is used for dissolving liquid flow, pre-dissolving tank level, flash tank level, condensing tank level, red mud washing liquid flow, single pipe condensate flow, qualified and unqualified tank level, and four electromagnetic switching valves are used for compressed air flow in and out of the pulse buffer. The liquid level in the dilution tank is controlled by a variable frequency pump, and the above control valve is manufactured by SIIC No.7 Factory. I/A control system. The RP analysis system is in the experimental stage.

Sedimentation workshop: there are 5 1 sedimentation tanks, 4 1 standby, 4 horizontal filters and 4 vertical filters. The main detection and control measures are: 10 thermal resistor (No.17 factory in Sichuan) is used to measure the temperature of sedimentation tank, coarse liquid tank, * * tank and hot water tank. 10 radar level gauge (Tianjin Tianwei Company) is used to measure the material level of sedimentation tank, coarse liquid tank, * * tank, lime milk tank, causticization tank and hot water tank; 14 electromagnetic flowmeter (FOXBORO Company) is used to measure the flow of red mud slurry, coarse liquid, alkali liquor and hot water; and eight pressure gauges (Shangyi No.4 Factory) are used to measure red mud slurry and hot water.

Decomposition workshop: The 16 thermal resistor in each decomposition process is used to measure the outlet temperature of decomposition liquid in decomposition tank, circulating water of heat exchanger and slurry pipe, and the 10 electromagnetic flowmeter (FOXBORO Company) is used to measure the flow of * *, mother liquor, circulating water, shaft seal water of air compressor and vacuum pump, and 8 electric regulating valves (Shangyi No.7 Factory) control the flow of circulating water and steam. 10 radar level gauge is used to measure the slurry density at the outlet of cyclone, and the liquid level and flow rate are controlled by variable frequency pump. The control of decomposition system is generally single loop control, and there is no interlocking control between grading tank control.

Evaporation workshop: 16 differential pressure transmitter is used to measure the liquid levels of 1 to 6-effect and forced-effect evaporators, condensate tanks and flashers, 4 radar liquid level gauges are used to measure the liquid levels of stock solution tanks, qualified tanks and sewage tanks, and 4 pneumatic control valves are used to control fresh steam, 1 effect slurry, 2-6-effect and forced-effect evaporators and stock solution tanks. 16 branch thermal resistor is used to measure the temperature of 1 6 effect evaporator, forced effect evaporator, condensate tank, flash evaporator and steam, 8 electromagnetic flowmeters are used to measure the flow of steam and evaporator stock solution, mother liquor and condensate, 2 conductivity meters are used to measure the conductivity of condensate, and 3 density meters (Cs 137 source) are used to measure stock solution,/. The control of evaporation system is relatively high, and the measurement of forced evaporator discharge density is not easy to use. I am going to dismantle this densimeter.

Baking workshop: 16 pressure transmitter is used to measure P0 1, P02, P03, C0 1, C02, C03, C04, K0 1, K02, t1,t. For fresh steam pressure, six differential pressure transmitters are used to measure the flow rates of A02 and P04, two A Niu flowmeters are used to measure the flow rate of gas, eight vortex flowmeters are used to measure the flow rates of K0 1, K02, filtered compressed air and fresh steam, and eight electromagnetic flowmeters are used to measure the outlet flow rates of K0 1, K02 cooling water, filtered fresh water from hot water tank and aluminum hydroxide slurry pump. 1 aluminum hydroxide belt weigher (Schenk, Germany), 1 oxygen analyzer (Rosemount), 1 carbon monoxide analyzer (SATEKNIKAS), 1 1 temperature thermocouple, 20 temperature-measuring thermal resistors, 4 pneumatic control valves for filtering fresh water and steam, 5.

Shanxi Aluminum Factory: 6,543,8+400,000 tons production line with mixed connection method.

Plant 1 (raw material preparation by sintering method and Bayer method): crushing and stacking plant, dumper, raw fuel conveying (workshop 1), alkalization, raw material grinding, feeder (workshop 2), winch and lime furnace (lime furnace workshop), desilication and compressor;

The second plant (sintering production line): coal grinding, feeding, sintering, cooling, dust removal (three workshops), medium crushing and separation, trigger (four workshops), desilication, series pump and leaf filter (five workshops); Washing tank, compressor (washing workshop); Backwater, relay pump and discharge pump (red mud workshop);

The third branch plant (Bayer production line): old evaporation group 1 and group 2 (seventh workshop); Evaporation, stock solution tank, blending and evaporation (evaporation workshop); Instrument air compressor station, Dutch pump, desilication, I series II series (eight workshops), sedimentation, flocculant, filtration and leaf filtration;

The fourth plant (sintering method and Bayer method): seed separation, vertical disc filtration, bag filtration (seed separation workshop), 1# roaster, instrument air compressor station, flat disc filtration (roaster workshop 1), 2#3# roaster, flat disc filtration, dense phase transportation (roaster workshop 2) and seed separation filtration.

The application of DCS is basically concentrated in Bayer process production. At present, the overall level from process detection to automatic control in sintering production is still very low, and the detection technology has matured in a few processes, while the detection means and automation level are very low due to problems such as scarring in washing and old evaporation. Although Bayer process is higher than sintering process in general, there is still an automation gap between the fourth evaporation and alkali liquor preparation. Generally speaking, the automatic control of workshop and process level has been basically realized at present, and the processes that can operate normally are: air compressor station, evaporation, decomposition, carbon separation, seed separation and aluminum hydroxide roasting; 3# clinker kiln, high pressure digestion, two groups of five evaporation and raw meal grinding adopt Foxboro company's I/A system; * * Preparation (φ42m precipitation, filtration, leaf filtration) adopts Emerson's DeltaV system; The TPS and PKS systems of Honeywell Company are used for seed separation, carbon separation, bag filter and roaster. The systems under construction include: 6# lime furnace system, plant-wide dispatching network system, etc.

Shanxi Aluminum Plant: Expansion of Bayer Process Production Line in 800,000 Tons Alumina Plant

Workshop 1: Raw fuel unloading and storage yard, lime firing, lime milk preparation and the first analysis station;

Workshop 2: grinding, pre-desilication, dissolution and pickling system of raw ore pulp;

Workshop 3: red mud settling, separation and washing, red mud conveying, red mud, ash yard and blade filtration;

Workshop 4: seed decomposition, seed filtration and cooling, seed mother fine filtration, mother liquor evaporation and the second analysis station;

Workshop 5: aluminum hydroxide filtration, aluminum hydroxide roasting, aluminum oxide storage and transportation.

It was completed in 2005. I/A system of Foxboro Company is adopted in five major processes: raw material crushing, evaporation, high-pressure dissolution, seed crystal decomposition and roasting. Raw material transportation, lime kiln and alumina storage and transportation adopt AB PLC small system. The combustion station of lime kiln and roaster adopts Siemens S7-300 PLC system, which is directly connected with DCS through PROFIBUS-DP and MODBUS communication interfaces respectively.

Zhengzhou aluminum plant: combined method

Alumina production in Zhengzhou Aluminum Plant adopts Bayer process and sintering process, and there are many kinds of control equipment, with more than 12000 detection control points. The control system adopts the products of Honeywell Company of the United States: TDC-3000, PKS and PLANTSCAPE SCADA system, and the PLC adopts the products of Mitsubishi, ABB, Honeywell and Siemens. It has a three-level network of branches, factories and workshop control rooms, which are connected with each other through PLC, DCS, PC, key positions and dispatching at all levels.

Measuring instrument: belt scale: Nanjing Huapu, Shenke, Toledo Company, with good effect; Automobile and train weighing instruments: Toledo; Roaster natural gas: Shanghai Henghe vortex flowmeter; Water and mud: Shanghai Henghe E+H electromagnetic flowmeter; Wind and steam: Shanghai Henghe vortex flowmeter and orifice flowmeter.

The detection and control of raw fuel storage yard and slurry preparation are general, and there are many failures of pressure and temperature instruments.

Pipeline dissolution: It is best to measure pulp and mud with densimeter. The detection and control of settling washing and decomposition are general, but there are many faults in material level and flowmeter.

Evaporation system: the regulating valve is made by Shanghai Liangguang Factory (the positioner is YTC of Korea), the regulating valve is used for the stock solution inlet, 1 effect, 2-effect and 3-effect flash mother liquor outlet flow, the 2-5-effect variable frequency pump is used for controlling the liquid level, the conductivity meter is made by Rosemount Company, and the liquid level meter is made by EJA differential pressure transmitter.

Roaster: natural gas as fuel, advanced control. The combustion station is made by oilon Company, and the leak detection valve sometimes fails to close properly, which affects the ignition. Pressure sensor for material level detection in AH warehouse, and AH belt adopts products of Schenk Company. The sampling part of carbon monoxide and oxygen analyzer is easily blocked and needs to be cleaned frequently.

Luneng Jinbei Aluminum Industry: Bayer Process in Phase I

It is planned to build Bayer process production line first, then add flotation process, and finally build sintering process to form serial production. There are six DCS systems in the whole plant, including raw ore pulp grinding (rod and ball grinding), autoclave digestion, Bayer red mud (preparation with flocculant and red mud discharge), seed decomposition (cooling with * * and seed filtration), mother liquor evaporation, aluminum hydroxide filtration and roasting. PCS7 system of Siemens Company is adopted, with raw material stacking yard, air compression station, lime digestion, lime crushing and roasting. All motor control units, frequency converters and some electromagnetic valves in the whole plant are directly connected with DCS through PROFIBUS-DP communication interface. It is planned to set up a central operation control room and several regional operation control rooms in the whole plant. The central operation control room is networked with the regional operation control room, which drives more than 60 subsystems, transmits instructions to the regional operation control room, and guides and controls the whole production process.

Sanmenxia Cayman Aluminum Industry: Bayer Process

The five DCS systems of grinding raw ore pulp, boiling and dissolving, seed separation, mother liquor evaporation, aluminum hydroxide filtration and roasting in the whole plant adopt the ControlLogix system of Rockwell Company, which is simple and convenient for networking, but there are many problems in the process instruments, especially some transmitters and actuators.

The application of process control in domestic alumina production enterprises started late, and it was not until 1980s that automatic detection and automatic control equipment were gradually adopted in alumina production in China. In particular, many sintering processes are characterized by high temperature, high pressure, easy jamming, easy wear and blockage, and some processes are multivariable, strongly coupled, strongly nonlinear and difficult to detect, so the level of measurement and control instruments needs to be improved urgently. Advanced detection and analysis equipment and control management system should be gradually adopted, and process optimization setting technology, intelligent modeling technology, fault diagnosis and preparation technology, and production process information integration technology should be adopted. Optimize production control management. In recent years, Shandong Aluminum Factory and Zhengzhou Aluminum Factory have cooperated with relevant units to analyze the composition of raw meal slurry online by neutron activation analysis technology in the process of raw meal grinding and batching, and achieved good application results. Hungary FL series sodium aluminate solution on-line analyzer was successfully introduced into evaporation mother liquor of Shanxi Aluminum Plant. Some non-contact primary detection instruments, such as infrared thermometer and radioactive density meter, have also been widely used in major alumina plants in China. Guixi Aluminum, Zhengzhou Aluminum, Jiaozuo Future and other enterprises use the mud layer detector developed by a company in Zhengzhou based on the principle of blowing detection to measure the key parameters of automatic control of settlement and washing-underflow density and density and height of each layer on line, and the effect is good. In recent years, with the rapid development of computer network technology, some domestic alumina plants have also accelerated the pace of network facilities construction, improved the automation level and management efficiency of production process, and achieved good economic benefits.