Recently, the Ministry of Industry and Information Technology, the National Development and Reform Commission and the Ministry of Ecology and Environment jointly issued the "Guiding Opinions on Promoting the High-quality Development of the Iron and Steel Industry", which clearly stated that green and low-carbon development is the top priority of the transformation and upgrading of the steel industry.

The dust generated by the production process of iron and steel enterprises is introduced into the electric dust collector by the dust removal fan, and is discharged into the atmosphere together with the flue gas after adsorption treatment. The traditional dust removal fan runs too high power consumption, and the fan power frequency operation vibration and noise are large, which will shorten the service life of the fan and motor, resulting in high operating costs and maintenance costs, and seriously affecting the economic benefits of steel enterprises. When frequency conversion is used in dust removal fans, the speed of the fan can be effectively regulated, which can not only achieve the effect of dust removal, but also greatly reduce the sintering power consumption and achieve green energy-saving performance, which is a more ideal and economical operation mode.

1.Brief introduction of the project

Fujian Iron and Steel Co., Ltd. is the only steel production enterprise in the province that adopts the long process of coking-sintering-blast furnace-converter-continuous casting-full continuous rolling, and is the largest steel production base in Fujian Province. The company has an independent and complete supply, production, sales system and market-oriented independent operation capabilities, with an annual output of 3.8 million tons of steel scale comprehensive production capacity. The main production equipment fully realizes electronic computer control, and realizes the continuous and automated production process. The continuous rolling bar and high-speed wire rod production lines that have introduced automatic control technology from Italy, Sweden and other countries are at the leading level in China.

The sintering process is to provide ore raw materials for blast furnace operations (from ore, iron oxide contained in ore is liquefied and reduced to iron by high temperature), that is, the mixed ore after the sintering process can be reduced to iron in the blast furnace. Steel production consumes large amounts of fuel and ore during its thermal processing, while emitting large amounts of air pollutants. During the refining process, it is required to meet the ultra-low emission index limit of steel enterprises in the "Opinions on Promoting the Implementation of Ultra-low Emissions in the Iron and Steel Industry", and at the same time meet the requirements of national energy conservation and emission reduction. Our ES9000 high-voltage frequency conversion is applied to the dust removal fan and pipe belt machine of this steel plant.

ES9000 high voltage frequency conversion technology features：

● The drafting unit of the National Standard for High-voltage Inverters for the Metallurgical Industry.

● Support asynchronous motor, excitation synchronous motor and permanent magnet synchronous motor.

● It supports a variety of cooling methods such as air cooling, air water cooling and high-power direct water cooling.

● It adopts the latest generation of magnetic flux optimized space vector PWM control technology, with fast dynamic response and good low-speed performance, which meets the application of fast start and stop, and low-speed large torque in steel/nonferrous metal industry.

● Overcurrent speed drop function and magnetic flux optimization technology - load fluctuation non-stop operation and higher power saving rate power unit hardware bypass, speeding start, power loss crossing a powerful function.

2.High-voltage frequency conversion scheme design

The steel company's sintering machine project equipment has excessive operating power, high throttling loss, and serious waste of electric energy, which urgently requires a new scheme to achieve energy saving and consumption reduction, while meeting the "double carbon" goal.

Through the analysis of the speed regulation method, combined with the actual sintering production of the steel mill, Cumark determined the frequency conversion speed regulation mode and the power frequency operation mode of one drag, and carried out beneficial exploration and solutions for the problems brought by the method. The scheme effectively solves the project problems and hidden dangers, and finally achieves the purpose of improving output, stable quality, energy saving, environmental protection and safe operation with minimal investment.

-ES9000 High Voltage Inverter Operation Screen-

-Motor parameters-

-Supply list-

-System main loop control chart-

The one-to-one manual bypass cabinet contains two isolation knife gates QS1, QS2 and related protective motor equipment. During normal operation, the frequency converter drags the motor to run, and when the frequency conversion fails, the motor frequency conversion control loop can be disconnected, and the power frequency circuit can be closed to keep the production running continuously; QS1 and QS interlock in the bypass cabinet, when QS1 is closed, QS2 cannot be closed to the power frequency side to ensure safe and reliable circuit operation.

3.Cooling system design

The inverter heat dissipation adopts air water cooling to discharge the heat emitted in the operation of the cabinet to the outside, and air water cooling is an efficient, environmentally friendly and energy-saving cooling system.

（1）Air-water cooling exchange system

● Design, manufacture and install all cooling facilities (including mechanical, electrical, instrument automation equipment) to meet the cooling requirements of high-voltage inverter devices. Cooling is provided with air water cooling and power supply to 1 meter where the cooling facility is located.

● The air water-cooled air duct iron plate is 1.2mm thick hot-dip galvanized sheet, the flange plate is 2mm hot-dip galvanized sheet, the air duct and the inverter hood are connected with flanges, all connections are fixed with M8mm galvanized bolts, and sealing (flange and flange; flange and air duct interface) measures are taken.

● Control system: The start-stop and related logic of the air-water cooling system are completed by the frequency converter.

● Air-water cooling units are all installed outdoors.

● All the air ducts and filters of the water-cooled devices involved in the air-cooled inverter device need to be supplied, and civil information such as specific quantities and installation locations are provided.

● The above design, manufacturing, guidance installation and acceptance standards are strictly implemented in accordance with the relevant national safety and fire protection, environmental protection, technology and occupational health standards.

-Schematic diagram of installation of air-water cooling unit-

（2） Technical requirements for air-water cooling device

● According to the operating conditions of the inverter room, the design provides the air water cooling equipment used this time, and ensures that the air outlet temperature of the air water cooling equipment is not higher than the inlet water temperature of 5 °C under the full load operation of the inverter, that is, the inlet water temperature is ≤ 30 °C and the temperature of the air cooling outlet in time and space is ≤ 35 °C.

● Each set of high-pressure inverter exhaust port is equipped with an air-water cooling system and an emergency exhaust valve.

● The air-water cooling system is installed outdoors and belongs to the outdoor installation type equipment, with sufficient mechanical strength and waterproof function.

● The power supply is independent power supply, 380VAC, three-phase five-wire system; The air-water cooling system is protected by a total circuit breaker, each fan is protected by overcurrent and overload, and each heat exchanger is equipped with a water leakage alarm function.

● The booster fan is independently equipped in the cooling device, and the booster fan adopts a brand of high-quality and high-volume fan that meets the on-site working conditions. The booster fan is installed reliably, the fan wind pressure and air volume are redundant design, each fan power supply is controlled separately, and it can be switched at any time, and the electrical control part is connected conveniently and reliably.

● The air-water cooling system is designed with cooler operation and fault detection functions, and the cooler reserves remote start and stop operation interfaces, provides water leakage alarm, fan fault alarm signal (passive contact, indicating fault when closed), and provides signal connection terminal with the inverter.

● The air water cooling system heat exchanger adopts copper tube string aluminum foil fin structure, the cooling water working water pressure is 0.2-0.4Mpa, the circulating water quality requirements should be clean, in line with the industrial cooling circulating water quality standards, and there is no corrosion to the copper metal of the heat exchanger of the air water cooling equipment.

● The air-water cooling system should be designed with access doors and lifting devices to facilitate installation, overhaul and maintenance.

4.How well the system runs

Fujian Quanzhou steel sintering reconstruction project adopts Cumark ES9000 high-voltage frequency converter, and the drive equipment in the plant has been running continuously and trouble-free. The excellent performance and high reliability design of ES9000 can fully meet the process needs of the sintering machine on site, and the effect is remarkable in reducing the equipment failure rate, improving the level of system automation and reducing the amount of on-site equipment maintenance, while saving a lot of electric energy, effectively responding to the call of the national energy conservation and consumption reduction, and the economic and social benefits are very considerable.

ES9000 high voltage inverter transformation effect：

● Energy saving and consumption reduction

The ES9000 high-voltage inverter is adopted according to the needs of on-site production by changing the operating speed of the fan and motor, and the average power saving rate is more than 30%, and the power saving effect is remarkable.

● Soft start and soft stop reduce the impact on the equipment

Reasonable setting of acceleration and deceleration time, so that the impact of the equipment in the process of starting and stopping is significantly improved, the average running speed is reduced, the pressure and wear are greatly reduced, the service life of the equipment is prolonged, and the maintenance cost is reduced.

● Air water cooling, efficient and environmentally friendly heat dissipation scheme

Compared with the traditional cooling scheme, the air-water cooling scheme has the advantages of low dust degree, small maintenance, and improved equipment safety and stability. It is of positive significance to reduce the operating costs of the auxiliary cooling system and maximize the benefits of high-voltage frequency conversion energy-saving projects.

Relying on years of application experience in the automation industry, Cumark has always shouldered the historical mission of "the driver of green steel and the leader of low-carbon life" in the new period, not only has unique solution capabilities in the process of the steel industry, but also has professional and mature automation solution strength in coal, nonferrous metals, petroleum, chemical industry, equipment manufacturing and other fields; While continuously achieving significant economic benefits for enterprises, it is also firmly practicing China's development goal of energy conservation and consumption reduction.