Application of Process Control Instrument-- Iron and Steel Industry:
1. Waste water and waste gas treatment
2. Process industry - turning raw materials into semi-finished products
Process of iron and steel smelting: from ore to steel
What is iron and steel smelting?
Iron and steel smelting is the general name of the iron and steel metallurgy process.
Characteristics of Iron and Steel Smelting
(1) Resource intensive and energy intensive. In the iron and steel complex, 0.7~0.8t (standard coal), 1.5~1.65 t iron ore, and 3~8t fresh water will be consumed per ton of steel.
(2) The production scale is large and the logistics throughput is large. The basic levels of modern steel plants are roughly divided into 1 million to 2 million tons, 3 million to 4 million tons, and 6 million to 8 million tons. The logistics involved in each ton of steel will be 5 to 6 tons.
(3) There are many manufacturing processes and complex structures. The manufacturing process is accompanied by a large number of substances and energy emissions, forming a complex environmental interface.
Technological process of iron and steel smelting
The task of iron and steel smelting is to smelt iron ore into qualified steel materials. According to the degree of deoxidation and decarburization process of different iron and steel products from iron ore, the process flow of iron and steel smelting can be roughly divided into the following categories:
(1) Indirect steelmaking consists of blast furnace ironmaking and converter ironmaking. First, the ore is melted and reduced to pig iron (with high carbon content), then the pig iron is put into the steelmaking furnace for oxidation and refined into steel, also known as indirect steelmaking. Due to its mature process, high productivity, and low cost, it is the main method for large-scale production of modern iron and steel smelting.
(2) Direct steelmaking. The method of one-step smelting iron ore into steel is also called direct steelmaking. This method does not use a blast furnace and expensive coke. Instead, iron ore is put into the direct reduction furnace, and semi-molten sponge iron with low carbon (<1%) and impurities is reduced by gas or solid reductant. This kind of iron can be used to replace scrap steel as raw material for electric furnace steelmaking, thus forming a new steel production process of direct reduction - electric furnace series production of steel. This process has few procedures, but the iron recovery rate is low, requiring the use of high-grade concentrate and high-quality primary energy, and high power consumption.
(3) Melt reduction method. The non-blast furnace ironmaking process, in which iron ore is reduced to metallic iron by carbon in a high-temperature molten state, produces liquid pig iron, which can be refined into steel in a traditional converter.
What instruments are required for the steel complex?
- Material level measurement: Ultrasonic level gauge, guided wave radar level gauge, radar level gauge, static pressure level gauge
- Flow measurement: Coriolis mass flowmeter, electromagnetic flowmeter, vortex flowmeter, ultrasonic flowmeter, turbine flowmeter
- Pressure measurement: Pressure transmitter, differential pressure transmitter
- Temperature measurement: Temperature transmitter, integrated temperature transmitter
- Liquid analysis and measurement: pH/ORP, conductivity, dissolved oxygen, turbidity/TSS, sludge concentration, sludge interface, COD, ammonia nitrogen, total phosphorus, total oxygen, phosphate, etc.
Batching section - process control instrument recommendation
- The instruments of the batching system are mainly level meters, and ultrasonic level meters or radar level meters are recommended.
- It is recommended to continuously measure material level with a solid radar level meter with a good dust resistance effect.
- It is recommended to use a capacitive level switch for limit detection, alarm, and interlock control.
Sintering section - instrument recommendation
1. Distribution section:
- Material level measurement of bedding silo
- Thickness measurement of bedding material
- Material level thickness measurement (multiple points)
2. Ignition section:
- Airflow, temperature, and pressure measurement
- Measurement of calorific value, flow, temperature, and pressure of the gas
- Temperature and pressure measurement in an ignition furnace
3. Sintering section:
- Temperature and pressure in the sintering machine (negative pressure)
- Material layer surface temperature
- The temperature at each point along the height of the material layer
- Induced draft fan pressure
- Temperature and pressure in each bellows
Sintering section - crushing, cooling, granulating, and finished product system
The temperature of sintered ore after sintering by a sintering machine is about 600-1000 ° C, which is generally cooled to below 150 ° C.
Main purpose:
- 1. Protect the sinter transport equipment.
- 2. Protect the top equipment and ore trough of the blast furnace.
- 3. Improve the working conditions and environmental sanitation of blast furnaces and sintering plants.
- 4. It has created conditions for sintering ore granulation and separation of bedding materials.
- 5. Create conditions for realizing the modernization of blast furnace production technology.
Instrument application points of the sinter cooling system mainly include:
- Temperature and pressure measurement in the annular cooler
- Air flow measurement of the blower
- Material level measurement of finished sinter silo
- The recommended instruments in this process are a radar level gauge, vortex flowmeter, temperature instrument, and pressure transmitter.
Flue gas dedusting, desulfurization and denitration, waste heat recovery and utilization
- In order to improve working conditions, reduce energy consumption and improve economic efficiency, enterprises reuse the products that were abandoned in the past.
- Generally, the waste gas generated by the sintering machine and annular cooler is comprehensively utilized in the sintering plant.
- Waste heat: used to heat the boiler to generate steam, or even generate electricity.
- Exhaust gas: recycled after dedusting, desulfurization, and denitration.
Recommended instruments for flue gas dedusting, desulfurization and denitration, waste heat recovery and utilization
- Radar level meter -- silo, storage tank, reaction tank
- Ultrasonic level meter -- silo and storage tank
- Electromagnetic flowmeter -- process water treatment, tap water treatment, cooling water measurement
- Vortex flowmeter -- air, gas
- Thermometer -- air, water, reactor, etc
- Pressure transmitter -- pipe, storage tank, reactor
The cooling water circulation system of the blast furnace body in the first blast furnace section
- Model selection: electromagnetic flowmeter.
- Tested medium: cooling water.
- Application: measure the loss and leakage of blast furnace cooling water. Compare with an electromagnet at the inlet and outlet respectively.
- Solution: The solution with temperature compensation can improve the measurement accuracy of cooling water leakage.
