According to the 12th Five-Year Plan for National Economic and Social Development, during the 12th Five-Year Plan period, non-fossil energy accounted for 114% of primary energy consumption and 16% of GDP energy consumption and CO2 emissions, respectively. %. Under this general situation, during the 12th Five-Year Plan period, the task of energy conservation and emission reduction of iron and steel enterprises is more arduous, and the laws and regulations are more stringent.

As a typical high-energy-consuming large-scale industrial enterprise, it is both an important task and an important social responsibility for steel companies to vigorously carry out energy conservation and emission reduction work.

Compressed air energy consumption accounts for a considerable proportion of all energy consumption of iron and steel enterprises (about 5%-15% of total electricity consumption of enterprises). Compressed air is an energy medium commonly used by steel companies. It should be noted from production, transportation to use. Strict management and technical improvements to adapt to the situation of energy saving and emission reduction.

This paper focuses on the energy saving potential and countermeasures of the compressed air system of iron and steel enterprises for the exchange of peers.

1 Overview of compressed air systems in steel companies, energy technology, power market theory, data mining, data simulation and forecasting.

The types of air compressor stations in Shanghai Energy Saving 1.1 steel enterprises are generally arranged in the air compressor station of the steel enterprise. There are centrifugal air compressor stations, screw air compressor stations and hybrid air compressor stations (centrifugal air compressors and screw air compressors). Both). Individual steel companies still have piston air compressors that are being phased out.

The centrifuge air compressor station is generally equipped with 2-9 centrifuges, and the exhaust volume is generally from 100m3/min to 300m3/min. According to the needs of production, it is generally set to a plurality of exhaust pressures, for example, and 1.3 MPa, of which 0.38 MPa, 0.5 MPa models are mostly air compressors for steelmaking and continuous casting, and 08 MPa models are power/instrument air compressors. 1.3MPa is the air compressor for blast furnace coal injection.

The screw compressor air compressor station is generally equipped with 2 to 8 screw machines, and the displacement is mostly less than 10m3/min-40m3/min. Most of the screw machines are used as auxiliary air sources for centrifugal air compressors.

According to whether the air compressor station is connected to the Internet, it can be divided into two types: distributed arrangement and centralized networking. Along with the improvement of the operation stability and control management level of air compressor equipment, in the new steel enterprises, the centralized networking is generally used in the old decentralized steel enterprises, and more are being established between the air compressor stations. Reconstruction planning for networking or sub-regional networking.

12 Compressed air main use and gas characteristics The use of compressed air in steel companies is included in all production processes. Its main uses can be divided into: sintering pneumatic conveying, blast furnace injection, continuous casting steam cooling, converter bottom blowing, steel belt surface cleaning, various pneumatic instrument valves, air motors, pulse bag type dust collectors, etc.

According to the production process, the distribution of air compressor stations in the ironmaking unit can be divided into sintering zone, raw material zone, coke oven zone, blast furnace zone. The compressed air in the steelmaking unit is mainly used for continuous casting, converter pneumatic equipment and purging. Continuous casting provides compressed air for aerosol cooling. Compressed air in hot rolling unit is mainly used for gas and purging of pneumatic equipment in rolling mills and heating furnaces. Compressed air in cold rolling units is mainly used for stripping and pickling of rolling mills. Hot-dip galvanizing unit pneumatic equipment and purge.

Generally speaking, in the compressed air system of the steel enterprise, the compressed air produced by the hollow press is treated by the dryer to reduce the water content to the pressure dew point of 3-5C, which is used as power (ordinary) for the user to supply compressed air; or after cooling After the dryer + adsorption dryer is processed, the water content is reduced to the pressure dew point below -20C. The dust is degreased to a dust particle size of less than 5m, the dust content is less than 5mg/m3, and the oil content is not less than 1mg/m3. Air is supplied to the user. In addition, the compressed air used for steam cooling of steelmaking continuous casting does not require the air content of the air to be directly supplied to the continuous casting.

2 Iron and steel enterprises' energy-saving potential and countermeasures for compressed air 21 Unreasonable use of compressed air Typical irrational phenomena a. High-pressure gas is supplied to low-voltage users.

Such as open-air purge injection (aeration, agitation in wastewater treatment process) water atomization dilution phase transportation (dust removal pneumatic conveying).

The air pressure required for the above working conditions is low, and it is conceivable to use the fan air supply to reduce the energy waste caused by the compressed air during the decompression process.

In addition, because individual users need high supply pressure or unreasonable supply pressure requirements, the air compressor station will increase the outlet setting pressure and thus increase the overall energy consumption.

: Use the instrument with compressed air as normal compressed air.

For example, Baosteel's requirements for the instrument gas source in accordance with Baosteel's engineering design are as follows: “The gas dew point is less than 20C (under working conditions). The dust particle size is less than 5 m. The dust content is less than 5mg/m3. The oil content is not less than 1mg/m. The use of compressed air is generally achieved by the use of the instrument gas to supply ordinary gas through the freeze dryer and the adsorption dryer in the air compressor station.

There are no specific data on the unreasonable use of compressed air in different steel companies due to different management levels. According to the American Motor System Challenge Project and the practical experience of China's motor system energy conservation, the reason for the unreasonable use can achieve 5% to 10% energy saving effect. (Note: 1. American Motor System Challenge Project: In 1993, the US Department of Energy (USDOE) launched the Motor System Challenge Project month to improve the energy efficiency and environmental quality of the motor system in Shanghai. The compressed air challenge is an important part of this project. 2. China Motor System Energy Conservation Project In 2001, the Chinese government cooperated with the United Nations Industrial Development Organization (UNIDO), the US Department of Energy (USDOE) and the Energy Foundation (EF) to launch the China Motor System Energy Conservation Project. The project was supported by Lawrence Berkeley of the United States. (LBNL) National Laboratory is responsible for implementation in Shanghai and Jiangsu Province, with the aim of developing a series of training tools and demonstration projects for motor system training.) It is recommended that companies establish professional energy audit teams and systems on a regular basis (recommended annually) for the entire plant. Regional compressed air usage was audited, and rectification suggestions were proposed to reduce the unreasonable use of compressed air by means of rolling optimization.

2.2 Compressed air leakage According to the diameter of the relevant data, the compressed air consumption is 0.98m3/mm at 06MPa, and the power loss is about 6.5kW. The energy waste caused by the leakage is considerable. Leakage problems are common in cylinders, solenoid valves, pneumatic valves, air handling components, etc.

On the other hand, in many steel enterprises, most of the air compressors at the same time, there are gas and water mixing at the same time. It also causes different degrees of waste. The more serious the situation is that the field management personnel have far underestimated the losses caused by the leakage.

The leak point of the compressed air system increases the manager's awareness of the loss of compressed air leakage. i In the case of air-water mixing in the cold-drying shed steam, the advanced non-flushing steam-water separator and liquid level control drainer are used to achieve the effect that the cold-drying machine does not drain the HP gas. Through the above improvements and taking into account the actual operating conditions to take the 50% coefficient, based on experience, the estimated power consumption of compressed air can be reduced by about 3%. The monitoring method of the leakage point is relatively simple. The remediation of the leakage position can be determined by comparative analysis of energy consumption and investment. Whether to rectify. It is recommended to regularly govern by establishing an assessment reward and punishment system.

23 Compressed air system design needs to be optimized. Most of the screw compressor air compressor stations load or unload the air compressor according to the pressure gradient or manually load and unload the air compressor. The lack of intelligent centralized control facilities and energy-saving control means energy. Waste.

Countermeasure and potential analysis The new screw machine concentrator can be equipped with a single pressure belt to maximize energy efficiency while saving energy by optimizing the unloading time of the air compressor.

Phenomenon is increasing due to the continuous increase in the demand for compressed air, and because the compressed air pipe network has not been modified, the ability of the pipe network to deliver compressed air can no longer meet the new demand. The resistance loss during compressed air transport is large. .

Countermeasure and potential analysis Through the analysis of demand, the choice of pipeline design flow rate, reasonable installation of pipelines with less compressed air pipeline loss to save energy; through the Unicom pipeline, adjust the air compressor load in different air compressor stations, less no-load and release energy Consumption.

The phenomenon is calculated according to the specific power of the air compressor of the cold rolling unit of a steel enterprise. The specific power of the air compressor is 65kW/(m3/min), and the drying device is 8.7kW/(m3/min). After the pressure drop, it becomes 9.6 kW / (m3 / min). According to the actual situation, it is considered that there is gas-water mixing in the drainage of the freeze dryer and regeneration gas consumption (about 7%) of the micro-heat regeneration adsorption dryer is the main reason for the large increase in specific power.

Countermeasure and potential analysis Using a compression heat dryer (regeneration gas consumption of about 2%) instead of a micro-heat regenerative dryer can save about 5% of gas consumption, but often because the compressed air dryer outlet air dew point (water content) can not be stabilized Auxiliary electric heating. Considering that the use of a compression heat dryer instead of a micro-heat regenerative dryer has a large potential for energy saving should be promoted as soon as possible.

24 screw machine frequency conversion needs to be promoted screw machine frequency conversion technology for the more mature technology through the transformation of frequency conversion energy-saving, change the motor speed of gas production according to the system pressure value for smooth adjustment energy-saving effect is obvious. According to the experience of Baosteel's second phase coke oven air compressor station, the energy consumption is reduced by about 20%. 25 Air compressor oil is converted into synthetic oil by Baosteel 2 color-coated air compressor station and 1420 air compressor station. Has achieved good results in Shanghai energy-saving fruit, the current screw machine energy consumption reduced by about 5%, centrifuge energy consumption reduction 3 Baosteel compressed air energy-saving practice Baosteel compressed air system a large number of applications roughly estimate annual electricity consumption of at least 500 million kWh. Baosteel's compressed air system is relatively independent in each plant. The main installed capacity of screw compressors and centrifugal compressors is 130,000 kW. Although Baosteel's compressed air system is in good overall condition, it can meet the production gas. need. However, there is still a large potential for energy savings. According to the author's investigation, the main problems existing at present are as follows: the gas used in the terminal gas equipment is unreasonable; the gas supply pressure and the gas pressure are reasonably matched; 0 the compressed air system energy measurement and assessment; the existence of the above problems will produce energy consumption of the compressed air system. Great impact, but by taking certain technical measures and management means, energy saving and consumption reduction can be achieved.

The energy saving of Baosteel's compressed air system is mainly considered from four levels: “saving gas” on the terminal gas equipment, in addition to enhancing the energy-saving responsibility of the gas-using personnel in management, avoiding unreasonable gas consumption, gas waste, etc. The improvement of the terminal gas equipment (such as the nozzle) improves the use efficiency of the gas; the improvement of the performance of the unit includes the optimization design of the compressor body, the variable speed adjustment technology of the compressor system, the improvement of the auxiliary equipment technology, and the improvement of the smell oil system; The design of the pipe network of the compressed air system, the matching of operating parameters and the usual management and maintenance; 4) the use of advanced energy-saving technologies such as pressure flow control technology, centralized control technology of air compressors and waste heat recovery technology of air compressors.

At present, Baosteel has specially set up a compressed air system energy-saving team to sort out the energy-saving potential of the whole plant's compressed air system through a large number of research and technical exchanges. More than ten energy-saving renovation projects are forming an annual electricity saving of more than 20 million kWh. This work is in progress.

4 Conclusions Compressed air systems are a major energy consumer in steel companies. Compressed air is an "expensive" source of energy. The huge potential for energy savings in compressed air systems should be given enough attention by the state and enterprises.

Energy-saving retrofit of high-energy-consumption compressed air system to improve its operating efficiency is a system engineering mainly including high-efficiency motor and compressor optimization matching air compressor design and manufacturing technology and air compressor adjustment technology update optimization compressed air operation Technical applications such as parameters and waste of compressed air.

Doing a good job of reducing the consumption of the air compressor system has a certain effect and significance for reducing the production and operation costs of iron and steel enterprises and alleviating the shortage of power supply in China.

This paper mainly analyzes the generation, use and use characteristics of compressed air in steel enterprises, and analyzes the energy saving potential of compressed air systems prevalent in iron and steel enterprises, and proposes corresponding countermeasures. The analysis shows that the energy saving potential of compressed air systems in steel enterprises is very huge. It is necessary to promote the energy consumption level of low-enterprise enterprises with compressed air system energy-saving technologies in steel enterprises.

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