1. Energy saving in the steel industry
China's traditional social development model is characterized by "high input, high pollution, and high consumption", which directly leads to the overall deterioration of the ecological environment. However, China is one of the few countries in the world with the least water, ranking 88th in the world in terms of water per capita, only a quarter of the world's per capita water resources. Today, some cities are being forced to restrict water supply, and the situation is very serious.
In the iron and steel industry, industrial water consumption is significant. The wastewater discharged from the steel production process mainly comes from the production of industrial water, equipment and commodity cooling water, soot cleaning, equipment and on-site cleaning water. It can be mainly divided into organic wastewater containing organic pollutants, inorganic wastewater containing inorganic pollutants and cooling water polluted by heat only.
In recent years, Laigang has strengthened the treatment and reuse of industrial wastewater, and the discharge of industrial wastewater from various units has been decreasing day by day, but the abnormal discharge of industrial wastewater still exists, and some sewage has not been effectively treated. In order to implement China's water resources development strategy and water pollution control countermeasures, reduce the shortage of water sources in Laigang, promote sewage recycling, ensure the sustainable development of Laigang's economic construction, and promote the "zero" discharge of industrial wastewater, it is planned to select a suitable site to build comprehensive sewage treatment equipment.
In water treatment plants, energy costs typically account for 30% to 50% of total operating costs. Therefore, scientific electrical installation design plays a vital role in reducing energy consumption, equipment and energy costs. Strict day-to-day energy management can effectively reduce the operating costs of enterprises. This article will introduce the power distribution, motor control design scheme and advanced energy solutions of the sewage treatment plant in combination with the design of the Caigang sewage treatment plant.
Sewage treatment stations can be divided into four sizes according to their size. Micro sewage treatment station: sewage treatment capacity of 1000 5000 m3 per day or covering 1000 10000 people, with a power of 25 125kva. Small sewage treatment plant: sewage treatment capacity of 5000 50000m3 days or covering 10000 100000 people, the power required is 125 1250kva. Medium-sized sewage treatment station: sewage treatment capacity of 50000 200000m3 days or covering 1000000 5000000 people, the power required is 125~5mva。Large-scale sewage treatment station: sewage treatment capacity of 200,000 100,000 m3 per day or coverage of 500,000 100,000,000 people, 5 25,000,000 mva. It should be noted that if reverse osmosis technology is selected for operation in the wastewater treatment process, the power required is much higher than that of traditional sewage treatment, and due consideration should be given to power supply.
Corresponding to different sewage treatment stations, from small to large, they can be connected to the public distribution network: single-circuit power supply of low-voltage or medium-voltage networks; Medium voltage ring network structure: high-voltage double-loop power supply: high-voltage double-loop power supply, double bus wiring, the main configuration methods of medium-voltage circuit are: single loop, single or multiple transformers: open loop, one medium voltage substation or open loop, two high-voltage substations. The basic configuration is a radial single-circuit system and a single transformer. When multiple transformers are used, an open-loop structure is generally used to improve the availability of power supply. When there is a high-power motor, the high-voltage power supply method can be directly adopted to reduce the cable specification. **Reference.
The main configuration methods of the low-pressure circuit section are:
Radial single-loop device, available for reference, is also the simplest. The load receives only a single power supply, providing a minimum level of power availability. Since there is no redundancy in the event of a power outage, it should be used sparingly unless actual conditions are limited. Equipped with 2 transformers. Two transformers that receive the same high-voltage incoming line are selected for power supply. **Reference. When the transformer is fully put into operation, it generally receives the low-voltage main switch plate for parallel operation. 2 transformers, 2 sections of low-voltage main switchgear with normally open section switch. 2 transformers, 2 low-voltage main switchgears: In order to improve the availability of power supply, the normally open sectional switchgear can be used to operate the low-voltage main switchgear in sections in order to improve the availability of power supply. It is equipped with dual terminal power supply and automatic transfer switch. This type of equipment is used to demand the highest availability of power supply, and in principle there are two external power sources, such as two transformers, a transformer and a backup generator, which are supplied by different high-voltage incoming lines; A transformer and a UPSUPS power supply. Select the Automatic Transfer Switch (ATS) to avoid parallel operation of the power supply. This type of equipment allows all higher-level distribution systems to perform preventive or troubleshooting without interrupting the power supply.
According to the characteristics of Laigang comprehensive wastewater water body, the sewage treatment station adopts the method of combining biological contact oxidation, ultrafiltration and reverse osmosis. **Reference. It not only fully removes pollutants from the water, but also rinses the residue of ironmaking and steelmaking with raw water, and the water that has undergone advanced ultrafiltration and reverse osmosis treatment can be reused in the industrial circulating water system, truly achieving zero discharge. Therefore, the power consumption of the plant is relatively large, and the calculated load is 13457kw，1118.4. Reactive load KVAR, in order to improve the stability of power supply and avoid power supply interruption as much as possible, combined with the power supply conditions of Laigang, two transformers are used for power supply, and two low-voltage main switchgears are set up: transformer power supply of different sections of bus of the same high-voltage station, and in drinking water and sewage treatment stations, motors are used to drive various equipment: water pumps; mobile terminal (scraper, sludge scraper); agitators (water and silt); sludge treatment equipment (worms, centrifuges, pressures, conveyor belts); Blowers (for aeration in biological treatment), etc. According to the characteristics of different equipment, different control methods should be adopted.
Centrifugal pumps are a commonly used type of pump in water treatment. A centripetal force is created by the rotational motion of the side impellers that separates the water from the pump. Centrifugal pumps are used in a wide range of applications and can meet a wide range of volume pressure requirements. The displacement of the centrifugal pump can be conveniently controlled by adjusting the gate valve or rotation speed of the pump. Centrifugal pumps and multistage pumps are designed for high-pressure membrane water flow in reverse osmosis processes. Centrifugal pumps have a wide power range (1 kW to more than 1 MW), and the rotation distance is a quadratic function of the rotational speed. It is highly recommended to choose a controlled, gradual deceleration process to prevent water hammer from impacting the pipe.
The dosing pump is a high starting torque, low power (10 kW) motor, which is generally used to inject liquid agents in seasoned tank systems where effective mixing is difficult. A screw pump is a stable, low-speed motor driven by a reduction gear that is used to add large quantities of water or sludge at a limited height. Mixers are typically medium-power (1 to 50 kW) motors with steady speeds, and the pulp is driven by reduction gears to homogenize the liquid.
In addition, there are grids and valves for motion control, as well as conveyor belts, grinders, wash arms, filter presses, centrifugal separators and scrapers for sludge handling.
In general, the cost of electricity accounts for a large proportion of the total operating costs of water treatment facilities, and special attention should be paid to energy conservation and emission reduction. The following optimization measures can be taken: through the installation of a power monitoring system, it can help users to use equipment rationally, improve property, use new transformers in Laigang sewage treatment station, reduce no-load losses, widely use metal halide lamps, and play a role in energy efficiency. In addition, by setting reactive power compensation, the power factor is adjusted to 09 or more, but also avoid the power company to charge reactive electricity fees, reduce power consumption.
2. Energy conservation in agricultural irrigation
The high-efficiency water-saving irrigation in the implementation plan mainly refers to sprinkler irrigation, micro irrigation, pipeline irrigation (pipeline water irrigation) and other irrigation methods. The "Implementation Plan" pointed out that during the "Twelfth Five-Year Plan" period, China's high-efficiency water-saving irrigation has the characteristics of socialization, technological integration, large-scale construction, application of farmland, and specialization of services. The local departments concerned have implemented the construction of water conservancy facilities for small farmland, the water-saving and grain increase in the four northeastern provinces (autonomous regions), the water-saving transformation of large-scale irrigation areas, and the demonstration of large-scale water-saving irrigation efficiency, thus promoting the rapid development of high-efficiency water-saving irrigation. By the end of 2015, China's irrigated area was 108.1 billion mu, of which 2 are high-efficiency water-saving irrigation6.9 billion mu, the annual water-saving capacity of high-efficiency water-saving irrigation is about 27 billion cubic meters, and the effective utilization rate of irrigation water in the country has reached 053。
However, by the end of the "Twelfth Five-Year Plan", China's high-efficiency water-saving irrigation area accounted for only about 25% of the irrigated area. Restricted by factors such as water pollution, uneven distribution of time and space, and widespread agricultural water use patterns, the potential of efficient water-saving irrigation to support the development of modern agriculture in China has not been fully developed, and there is still a lot of room for development. By the end of 2015, Beijing, Hebei, Xinjiang, Tianjin, Inner Mongolia and other provinces (autonomous prefectures, municipal districts) accounted for % of the irrigated area; Hunan, Guangdong, Anhui, Jiangxi, Sichuan and other provinces (regions) have a low proportion of high-efficiency water-saving irrigation area in irrigated area, which is %.
Construction objectives and main tasks.
1.Construction goals.
The implementation plan clearly pointed out that during the "13th Five-Year Plan" period, China added 100 million mu of high-efficiency water-saving irrigation area. By 2020, the area of efficient water-saving irrigation will reach 36.9 billion mu, accounting for more than 32% of the country's irrigated area. The efficient utilization rate of agricultural irrigation water will reach 055 or more, the new grain production capacity will reach 11.4 billion kilograms, and the new annual water-saving capacity will reach 8.5 billion cubic meters. At the same time, we should promote the reform and innovation of the system and mechanism, and give full play to the benefits of the project.
2.The main task.
The implementation plan puts forward two tasks: engineering construction and institutional reform and innovation.
1) Engineering construction tasks. During the "13th Five-Year Plan" period, China added 100 million mu of high-efficiency water-saving irrigation area, including 40.15 million mu of pipeline irrigation area, 20.74 million mu of sprinkler irrigation area, and 39.11 million mu of micro irrigation area. The area of efficient water-saving irrigation of cultivated land is 86.72 million mu, including 32 million mu of large and medium-sized irrigation, 18.68 million mu of small irrigation area, and 36.04 million mu of pure well irrigation area; The area of non-cultivated land with efficient water-saving irrigation is 13.28 million mu, of which 6 million mu is pastoral area.
Judging from the construction tasks announced by the provinces (autonomous regions), Xinjiang, Hebei, Inner Mongolia, Shandong, Henan and other five provinces (regions) have a large amount of tasks, respectively 12 million mu, 10 million mu, 10 million mu, 9.5 million mu and 6.5 million mu, with a total of 48 million mu, accounting for the new high-efficiency water-saving irrigation area in the country during the "Twelfth Five-Year Plan" period.
Nearly half. 2) The task of reform and innovation of system and mechanism. The "Implementation Plan" clearly regards the comprehensive reform of agricultural water prices as the "bull's nose" of farmland water conservancy reform, and comprehensively promotes the reform of the reserve system and mechanism. The first is to innovate the construction management model. Actively explore construction methods such as private support, incentives and subsidies, and construction subsidies, and encourage and guide rural households, farmers' water cooperative organizations, and new agricultural business entities to become the main body of construction and management of high-efficiency water-saving irrigation projects. The second is to establish and improve the operation and maintenance protection mechanism. Clarify the repayment of property rights for high-efficiency water-saving irrigation projects, implement the management and protection subjects, responsibilities, systems and funds, and establish a management and protection mechanism with clear responsibilities, clear rights and responsibilities, standardized management and efficient operation. The third is to establish and improve the mechanism for the formation of agricultural water prices. Through the formulation of agricultural water prices at different levels, we should explore classified water prices, gradually implement graded water prices, and establish and improve the formation mechanism of agricultural water prices that reasonably reflect the cost of water supply and are conducive to the innovation of water-saving farmland water conservancy system, which is in line with the investment and financing system. Fourth, establish a precise subsidy and water-saving incentive mechanism.
Regional layout and technical model.
China has a vast territory, different natural conditions in the north and south, different water resource endowments, and complex and changeable planting structures. According to the climatic characteristics, water resources conditions, agricultural planting structure and other factors in the northeast, northwest, north and south, the focus and technical methods of regional development during the 13th Five-Year Plan period were determined. In the "Implementation Plan", the northeast region refers to the eastern part of Liaoning, Jilin, Heilongjiang and Inner Mongolia Autonomous Prefectures; Northwest China refers to the central and western regions of Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang and Inner Mongolia Autonomous Prefectures; North China refers to the six provinces (municipalities) of Beijing, Tianjin, Hebei, Shanxi, Shandong and Henan; The southern region refers to the provinces (autonomous regions and municipalities) along and south of the Yangtze River.
1.Regional layout.
During the 13th Five-Year Plan period, the layout of the four major regions of high-efficiency water-saving irrigation area is as follows:
1) The area of high-efficiency water-saving irrigation in Northeast China is 18.4 million mu, including 2.6 million mu of pipe irrigation, 8.55 million mu of sprinkler irrigation and 7.25 million mu of micro irrigation.
2) The area of efficient water-saving irrigation in Northwest China is 28.3 million mu, including 5.17 million mu of pipe irrigation, 1.88 million mu of sprinkler irrigation and 21.25 million mu of micro irrigation.
3) The area of high-efficiency water-saving irrigation in North China is 29.8 million mu, including 20.74 million mu of pipe irrigation, 4.3 million mu of sprinkler irrigation and 4.76 million mu of micro irrigation.
4) The area of high-efficiency water-saving irrigation in the south is 23.5 million mu, including 11.64 million mu of pipe irrigation, 6.01 million mu of sprinkler irrigation and 5.85 million mu of micro irrigation.
2.Technical approach.
1) According to the carrying capacity of water resources, the Northeast region should rationally develop drip irrigation and sprinkler irrigation technology, and actively select drought-tolerant water-sitting species; In areas with large-scale farming requirements, large and medium-sized mechanized walking sprinkler irrigation is intensively developed.
2) Priority should be given to the development of high-efficiency water-saving irrigation in inland river areas and traditional well irrigation areas in Northwest China. In irrigation areas where surface water is over-exploited or water supply contradictions are prominent, drip irrigation, sprinkler irrigation and pipe irrigation technologies should be promoted according to local conditions on the basis of accelerating the water-saving transformation of backbone pressure testing channels. In development areas with too many water sources, the watering surface should be appropriately reduced to maintain ecological security: in grassland pastoral areas, high-efficiency water-saving irrigation grasslands should be developed according to water source conditions, and surface water should be strictly controlled in ecologically sensitive areas to irrigate artificial grasslands.
3) It is forbidden to improve the irrigation area in the over-exploited groundwater area in North China, dig deep groundwater in agricultural irrigation, scientifically carry out the construction of high-efficiency water-saving irrigation projects in the groundwater source replacement area, and rationally use rainwater resources, brackish water, reclaimed water, etc.; In the pure well irrigation area and the combined irrigation area of well and canal, with pipeline irrigation as the core, the integrated development of sprinkler irrigation and micro-irrigation in combination with water and fertilizer, the promotion of water metering and intelligent control technology, to achieve the dual control of watering and groundwater; In surface water irrigation areas, vigorously promote high-efficiency and convenient management of high-standard pipeline irrigation and areas with mature conditions, and carry out the construction of sprinkler irrigation and micro-irrigation projects according to the time and conditions.
4) In the southern region, the pipeline irrigation of the previous surface water irrigation areas should be actively developed: in the "five small water conservancy" projects built in hilly and mountainous areas, high-efficiency water-saving irrigation technology should be promoted to improve the ability to resist drought and reduce disasters; In orchards, tea trees, facility agriculture areas and other high economic value-added crop areas, vigorously promote sprinkler irrigation and micro-irrigation technology: vigorously promote sprinkler irrigation and micro-irrigation technology in sugar cane planting areas.
3. Energy saving of heating units
The heat network circulating pump is one of the most important equipment in the heating unit, and its reasonable selection and equipment design are directly related to the normal operation of the heating system. As far as the heat network circulating pumps on the market are concerned, some pumps are designed with high head, which leads to serious throttling loss of outlet valves, which not only reduces the economic benefits of operation, but also increases the potential safety hazards of machine operation [11]. In this regard, this paper optimizes the design of the circulating pump drive for energy saving and discusses the improvement process in conjunction with case studies, with the aim of proposing the best remedial measures.
Energy savings and consumption reductions enhance the meaning of the design.
As far as the global energy distribution is concerned, China's energy distribution is less and resources are scarce. After the reform and opening up, the country's borders have been opened, the domestic economy has developed rapidly, the major industries have developed rapidly, and the overall industrial level is relatively high. However, with the acceleration of industrialization, a series of energy problems and environmental problems have emerged. According to the relevant research results, [21], the actual utilization rate of energy in China is relatively low, so the concept of energy conservation and consumption reduction is gradually deeply rooted in people's hearts, and more and more people have begun to pay attention to the application of energy conservation and consumption reduction measures. The state has put forward a "resource-saving" social development strategy, established key industries for energy conservation and emission reduction, including electricity, and established China's top ten energy-saving projects, including power energy-saving projects. It can be seen that the application of energy-saving and consumption-reducing measures is imminent. As far as the current development of the domestic power industry is concerned, the energy consumption is relatively large, and the consumption trend is increasing year by year. As a large power company, Datang Zhangjiakou Plant has always had a large demand for electricity and energy consumption. Some trends indicate that its energy consumption is increasing. In the final analysis, it is mainly related to the development of the industry, and it is also closely related to the problems of small installed power generation capacity and backward system. However, with the continuous development of the industry, the contradiction between energy and energy is becoming increasingly prominent, and our company has gradually realized the importance of energy conservation and consumption reduction, and actively regarded it as one of the key contents of industry development. The company continues to adopt and deepen economic construction countermeasures, comprehensively adjust industry equipment, and hope to improve machine operation efficiency and reduce energy consumption through equipment adjustment, and ultimately promote the sustainable development of the industry and society.
Heating unit heat network circulating pump drive energy-saving optimization measures.
The heating time in northern China is long, and the equipment needs to run for a long time. As one of the important ways for heating units to transport heating medium, the heat network circulating pump has relatively high energy consumption. In order to effectively improve the energy-saving efficiency of the heat network circulation pump, the following energy-saving measures were expounded: the back pressure machine drove the heat network circulation pump. This scheme reduces the application of the variable frequency speed control device in the electric pump scheme, and its speed can be adjusted [3]. The driving steam source adopts the industrial pumping method, and the parameter level is high. It can discharge the waste heat through the back pressure machine, directly feed the exhaust air into the heat network heater, and finally use it as heat network water. Due to the high level of relevant parameters of industrial pumping, it has strong working capacity. Since the efficiency of the small steam turbine is lower than that of the main steam turbine, from the perspective of energy saving and economy, there is still a lot of room for improvement in the way the industrial pumping method drives the small steam turbine and finally pushes the heat network circulation pump. See, there's still some room for improvement. The specific program includes the following points:
1.Measurement of thermal processes.
Firstly, the shaft power of the circulating pump was established, and the shaft power of the circulating pump of the heat network was calculated according to the flow, efficiency, head and density parameters of the circulating pump. The specific calculation formula is: heat network circulating pump shaft power =.
2.Determine the parameter values of the small steam turbine.
Set the relevant parameters of the small steam turbine, and set its power, speed, exhaust temperature, inlet temperature, inlet pressure, and back pressure to 1400kw and 1500rmp, respectively5mpa、0.2mpa。Since small machines need to work, the amount of heating steam entering the heat exchanger should be increased to further meet the original heat exchange load [4]. Therefore, it is necessary to calculate the amount of steam to be heated according to the principle of thermal equilibrium and the relevant calculation methods. The specific process should first use heated steam to drive the small steam turbine to work, and then use the small steam turbine exhaust to heat the hot network water, making full use of the energy gradient of low-grade steam.
3.Analyze its economics.
After applying the above scheme, the power consumption of the motor drive mode can be effectively saved, but compared with the motor drive mode, this scheme will increase the steam extraction, and the increased steam extraction will eventually lead to the loss of the output of the main engine because it is not working in the main steam turbine. If the increment of the former is greater than the output loss of the latter, it can be seen that the scheme has a high advantage compared with the motor drive scheme, which can be regarded as the scheme obtains a larger driving capacity with a small loss, and also reflects the better economy of the scheme to a certain extent. Conversely, if the output loss is greater, the motor drive mode is better. This study shows that the automotive machine strategy has a strong economic value. There are two important reasons for the output loss of the host in this scheme: one is that the automobile machine extrudes some heating pumping when exhausting and heating the heating network water, and this part of the heating pumping will work on the main engine. Second, the car machine consumes steam, but there is no loss caused by working on the main engine.
4.Compare the energy savings of different extraction strategies.
In order to clarify the energy-saving effect of different drive strategies, this paper takes the 330MW double condensing steam turbine unit as an example, and adopts different drive schemes for a single heat network circulating pump. Its economic value ultimately shows the turbine consumption, drive-induced industrial extraction increment, inlet enthalpy, exhaust enthalpy, exhaust pressure, and output loss of the industrial extraction drive strategy. Compared with the motor strategy, the energy-saving energy is 27370kg h, 27370kg h, and 3208kj kg·h-1., respectively3050k/kg·h.4mpa、1370w/kw、60kw。Compared with the motor strategy, the energy-saving energy of the steam consumption, heating increment caused by the drive, intake enthalpy, exhaust enthalpy, exhaust pressure and output loss of the small steam turbine is 30155kg h, 71kg h, and 3023k kg·hk kg·h., respectively16mpa、10w/kw、1419kw。The comparison of the two sets of data shows that compared with the motor drive scheme, the industrial steam extraction drive scheme can save 60 kW, and compared with the motor drive mode, the heating exhaust drive mode can save 1419 kW, but the latter is 2785 kg more than the former total steam consumption. In the final analysis, the main consideration is that the former has high industrial extraction parameters and large energy consumption losses. Since the main engine output loss caused by working in the main steam turbine is similar to the motor power, the actual energy savings are relatively small. The parameters of the latter heating and pumping method are low, the function of the host is small, the working pressure of the primary heating network heater is lower than that of the secondary heating network heater, and the enterprise flow rate is the exhaust heat of the primary heater and the heat released by the unit flow heating and pumping in the secondary heater are roughly the same, so part of the heating and pumping is used in the automobile machine before heating the heating network water, and the total amount of heating and pumping is very small.
Finally, the above studies show that the first of the three heat network circulating pump driving modes has a low steam taste, which can realize energy gradient utilization and has the highest economy after comprehensive operation. Compared with the third driving mode, the second driving mode is similar to the overall operating economy, but the former can effectively reduce the power consumption rate of the factory, and the energy saving effect is not much different. To sum up, the choice of automobile pump scheme can improve the economic benefits and comprehensive thermal benefits of enterprises to a certain extent. However, it is necessary to adjust the speed correctly according to the water flow and pressure changes of the heating network, improve the operation efficiency of the equipment, eliminate the valve flushing, reduce the loss of part of the throttling, and finally improve the system safety and effectively improve the operating environment of the power system.
In order to effectively save resources, the heat pump is used to drive the small steam turbine drive pump, and the economy of the three schemes of industrial pump drive, motor drive and heat pump drive is calculated, and finally it is found that the heat pump drive scheme is more energy-saving. However, as far as this study is concerned, the research direction is still not comprehensive, and the authors will conduct in-depth research and analysis in the future, and strive to propose more energy-saving designs and improvement schemes, improve the energy-saving effect of equipment, and ensure the sustainable development of the industry.
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