Strengthening industrial energy conservation and emission reduction is an inevitable requirement for practicing Scientific Outlook on Development and taking the road of low-carbon economy and sustainable development. It is also the main way for enterprises to reduce costs and increase efficiency and improve market competitiveness. The electric power industry is also changing its concept in time, increasing investment in energy saving and consumption reduction, and accelerating the development and application of new technologies. Let me share with you the measures to reduce consumption and save energy in thermal power plants. Welcome to read and browse.
I. Overview of equipment
The auxiliary power consumption rate of # 1 and #2 units in Liangcun Thermal Power Plant is about 7.59% and 7.89%, which is different from that of domestic advanced thermal power units. This paper explores the energy-saving potential from the aspects of energy-saving transformation and optimization of operation mode, and minimizes the auxiliary power consumption rate to meet the needs of the development of thermal power plants.
Liangcun thermal power plant in Shijiazhuang is an important power supply and heat source support point in southern Hebei power grid. The boiler produced by Dongfang Boiler is DG11117.4-II12 subcritical primary intermediate reheat natural circulation coal-fired drum boiler. The single machine is equipped with three double-inlet and double-outlet ball mills, two induced draft fans, a blower and a primary fan. The steam turbine is a subcritical, one-time intermediate reheat, three-cylinder double exhaust, single-shaft and two-stage adjustable heating extraction condensing unit produced by Dongfang Steam Turbine. It is equipped with two steam pumps with a BMCR capacity of 50%, an electric pump with a BMCR capacity of 35%, two condensate pumps (one variable frequency regulation) and two circulating pumps. The generator is QFSN-330-2-20 hydrogen-cooled generator produced by Dongfang Electric. The main transformer with a capacity of 370MVA is connected to the 220kV booster station, and the generator outlet is connected to the auxiliary power through the high voltage transformer. The auxiliary power is divided into 6KV and 400V voltage levels. The large-capacity auxiliary machine and low-voltage auxiliary transformer of the unit are connected to the 6KV system, and the low-voltage power supply mode is PC/MCC. Two units are equipped with a high-voltage start-up standby transformer.
Second, the specific measures to reduce the auxiliary power consumption rate
There are many decisive factors for the auxiliary power consumption rate, and the power consumption of auxiliary motors plays a decisive role in the auxiliary power consumption rate. At the same time, reasonable adjustment, operation mode optimization and energy-saving transformation also affect the auxiliary power consumption rate.
After several years of operation, it is found that some equipment has great energy saving potential during operation. Liangcun thermal power plant has achieved remarkable results through energy-saving transformation of equipment, and the auxiliary power consumption rate has been effectively controlled.
1. Modification of high chromium steel ball of coal mill
As the unit is the backbone power plant of Hebei southern power grid, it often participates in the peak shaving of the unit, and it is often in a low load state from 22: 00 at night to 6:00 the next day, and sometimes the load of the unit is only slightly higher than the minimum stable combustion load. At this time, even if the double grinding operation is adopted, the power consumption of the coal mill is still high, resulting in a lot of energy waste. By investigating the use of Cr-Mn-W wear-resistant cast iron balls (high chromium steel balls) to replace the existing medium chromium steel balls, the classification scheme of grinding balls was optimized. First, the transformation test of replacing steel balls was carried out on the 1B mill. After the technical transformation, according to the statistical analysis of operation data, the energy consumption of 1B coal pulverizer decreased obviously under the condition that the output of coal pulverizer and the fineness of pulverized coal remained unchanged. The current is reduced from the previous 140A to15a, and the motor power is reduced from 1200kW/h to1000 kw/h. According to the calculation, about 4800kWh of electricity is saved every day, and the annual cost is about 420,000 yuan. At the same time, by replacing the steel ball, the internal load of 1B mill is reduced, the flow area is increased, the primary air pressure and the electrical consumption of the primary fan are also reduced, the current of two primary fans is reduced for 5 years, and the hourly power is reduced by about 45kW. According to the 0.3 yuan calculation of power supply per kilowatt when the unit runs for 5,500 hours, the annual cost saving is about 74,000 yuan. After successful experience, six mills of two units have been reformed one after another.
2. Transformation of high-low speed switching of circulating water pump motor
Two 300MW units in Liangcun Thermal Power Plant are equipped with four circulating pumps, and each unit is equipped with a two-speed circulating pump. Because of the installation of low-speed power supply, it is impossible to switch between high-speed and low-speed power supply, and the high-speed circulating pump is still running in winter, resulting in high power consumption. At the same time, the end difference of condenser rises to 65438 05℃, which greatly reduces the economy and safety of the unit. Therefore, the power supply of 1B and 2B two-speed circulating pumps was reformed. According to the speed formula of asynchronous motor n=60f/p, the speed can be changed only by changing the frequency f or the number of poles n. For the circulating pump, it is only necessary to adjust the speed infrequently in a small range. Considering the cost and maintenance, it is better to change the speed by changing the number of poles, and switch the high and low speed power supply of the circulating pump by installing a high and low speed power supply switch cabinet. Before the transformation, the running speed of a single circulating pump was 12 pole 496r/min, and the rated power of the motor was 1900KW. After transformation, the running speed of a single circulating pump is 16 pole 373r/min, and the rated power of the motor is 800KW. After the equipment transformation, the operation scheme of matching high and low speed of circulating pump was formulated, and the power consumption rate and auxiliary power consumption rate of circulating pump decreased significantly year-on-year. The data shows that the current of the low-speed circulating pump drops obviously after it is put into operation, from 195A to 120A. Through the data analysis of different ways in winter and summer, the power consumption rate of circulating pump decreased from 0.67% to 0.5%, which was obvious. At the same time, the circulating water runs in parallel, and the start and stop of the circulating pump are arranged reasonably according to the vacuum in winter and summer. After running for a period of time, comparing the data before and after optimization, it is found that the power consumption rate of circulating water pump has decreased from 0.85% in 20 12 years to 0.8% in 20 13 years and 0.79% in 20 14 years, with the decreasing ranges of 0.05% and 0 respectively. After adopting the optimized scheme, the auxiliary power consumption of * * will be saved by about1882,300 kwh in 2004, equivalent to RMB 6211654,380 yuan, with obvious energy-saving effect.
3. Boiler body lighting transformation
There are 546 groups of lamps in the boiler body of Liangcun Thermal Power Plant # 1, all of which are 70W metal halide lamps. As of 20 14, the lamps have been used for more than three years, and the frequency of serious aging damage is extremely high, and the maintenance costs of labor and materials are high. Through transformation, the existing 70W metal halide lamps of # 1 furnace were all replaced by 436 groups of 30W LED energy-saving lamps, which reduced the number of lamps of 1 10 and met the needs of field lighting. The control box is controlled in different areas (long-term partial manual remote control, automatic lighting control/manual switching of night lighting). # 1 There are 546 sets of lamps in the boiler body, and the annual maintenance is about 200 sets. 200 replacement bulbs (82 yuan), ballasts (79 yuan) and triggers (15 yuan) * * * for each set of lamps. The direct material cost is 35,200 yuan, the labor cost10.6 million yuan, and the scaffolding cost is 4,600 yuan. Before the transformation, the electricity consumption of # 1 boiler room was 208,000 kWh; After the transformation, the electricity consumption is 55,700 kWh, saving electricity152,300 kWh. According to our factory's current on-grid electricity price of 0.43 16 yuan, the electricity saving cost is 63,900 yuan/year, and the seven-year electricity bill is 447,300 yuan. Calculated by saving maintenance and electric energy cost, the annual total cost can be saved by 1 19700 yuan; The actual cost of this renovation is 390,000 yuan, and the unit price of lamps is about 902 yuan, with 436 sets. Calculated by annual savings 1 19700 yuan, the investment can be recovered within 3.26 years. In the overhaul of 20 15, the lighting of #2 boiler was also reformed.
4. Reasonably optimize the operation mode of auxiliary machines.
(1) The turbine specialty changed the water supply mode of the condenser to self-priming water supply, stopped the condensate pump, sucked the softened water in the condensate tank into the condenser through the negative pressure of the condenser, and ensured that the liquid level of the condensate tank could not be lower than 4200mm to prevent the condenser from leaking. Under special circumstances, when the self-absorption capacity cannot meet the requirements, the condensate pump is started to replenish water, which greatly shortens the running time of the condensate pump. At the start-up stage of the unit, no electric pump is used to start the steam pump booster pump to supply water to the boiler drum, and the constant speed of the steam pump is set at 3 100 r/min in advance to ensure the water supply requirements of the drum.
(2) According to the output of the coal mill, the boiler specialty regularly arranges to clean the separator and add steel balls to ensure the best output of the pulverizing system and reduce the power consumption rate of the pulverizing system. According to the operating output of the unit, stop the operation of 1C and 2C coal mills in time, and minimize the operation of c coal mills under the principle of ensuring that the load is not blocked. At the same time, the soot blowing of the heating surface and the air preheater should be strengthened to ensure that the pressure difference of the air preheater does not increase and the heating surface does not accumulate dust, thus reducing the power consumption of the wind turbine.
(3) The electrical specialty will control the automatic operation of the transformer cooling fan, and try to avoid manual operation. On-site lighting is based on the principle of ensuring the necessary brightness of the production site and saving auxiliary electricity as much as possible. According to the field situation, only one way is controlled separately, and the multi-way control is half open. The principle of on-site air conditioning control is to ensure the temperature of indoor equipment. Because the on-load voltage regulator of lighting transformer is adjusted to 380V due to the high lighting voltage of 402V, the working voltage is reduced to save electricity, the service life of lamps is prolonged, and the non-production electricity consumption of offices is controlled to save energy.
(4) The ultrafiltration effluent lifting pump of chemical engineering specialty is operated by frequency conversion pump, and the frequency pump is stopped as far as possible. Keep the demineralized water tank running at a high level, and flow to the condensate to replenish the water tank by the liquid level difference, so as to reduce the running time of the demineralized water pump. When unloading liquid ammonia, the liquid level is balanced by the pressure difference between the liquid ammonia storage tank and the liquid ammonia tanker, so as to reduce the start-up time of the liquid ammonia compressor and reduce the power consumption. Sewage and wastewater discharge pumps operate automatically according to liquid level control to avoid idling.
(5) Coal conveying specialty shortens coal loading time to avoid belt overload operation and long-term low-flow operation. In case of coal blockage, equipment failure and other upstream equipment tripping, the downstream equipment will stop running after the coal is emptied, so as to avoid the downstream equipment idling for a long time in the process of defect treatment, and strive to reduce the idling time of coal conveying equipment and reduce the power consumption rate of coal conveying.
(6) Under the premise of meeting the requirements of environmental protection, the ash removal specialty adjusts the high-voltage parameters of the dust collector and limits the secondary current limit of each electric field. Start and stop the air compressor in time according to the load of the unit and the air compressor, and adjust the set value of the ash conveying end pressure in time according to the ash conveying pressure curve of the boiler to reduce the consumption of compressed air and the output of the air compressor.
After nearly three years of technical transformation practice, Liangcun Thermal Power Plant has achieved remarkable results. By June of 20 15, the auxiliary power consumption rates of # 1 and #2 generator sets are about 6.85% and 7. 19% respectively. In the second half of 20 15, due to the comprehensive transformation of electrostatic precipitation and desulfurization and denitrification, a large number of energy-consuming equipment were added, and the auxiliary power consumption rate increased. With the deepening of the national energy conservation and emission reduction policy, as a power generation enterprise, it should actively respond to the national policy and take reducing the auxiliary power consumption rate as a long-term issue.
Third, the potential of energy-saving transformation
1, adopting new technology, frequency conversion and energy-saving transformation of auxiliary machines.
The output of auxiliary machinery in thermal power plant changes with the load of generator, the load of power grid changes at any time, the output power of generator changes, and the output of main auxiliary machinery such as fans and pumps should be adjusted accordingly. For fans and pumps regulated by regulating valves or baffles, the characteristics in operation are: when the rotating speed changes within 20%, its operating efficiency changes little, its flow rate is proportional to the first power of rotating speed, pressure is proportional to the square of rotating speed, and shaft power is proportional to the third power of rotating speed. When the speed decreases, the shaft power decreases with the cubic power of the speed, and the electric power required by the motor driving the fan and the water pump can also be reduced accordingly, so speed regulation is an important way to save energy for the fan and the water pump. In the flow regulation of fans and pumps, throttling regulation is the simplest and most widely used regulation method at present, and its main disadvantage is high energy consumption. Because frequency conversion speed regulation is incomparable to AC speed regulation in frequency range, dynamic response, slip compensation, power factor and working efficiency, it is imperative to save energy and reduce consumption by frequency conversion speed regulation.
2. Optimal selection of electrical equipment.
For electrical equipment that needs to be rebuilt or added in the future, technical and economic comparison should be made from the perspective of energy saving, and the bid evaluation and selection of electrical equipment should be done well.
(1) High-efficiency motor is preferred.
High-efficiency motor refers to the motor whose total loss is reduced by more than 20% compared with the standard series motor. Because the stator core and rotor core of high-efficiency motor adopt high-quality electrical silicon steel sheets with high permeability and low loss, the manufacturing process is advanced, the motor loss is low, the power factor is high, the thermal stability is good, and the operation life is long. Under the same conditions, the efficiency of high-efficiency motor is 3% higher than that of standard motor, but the manufacturing cost is 30% higher than that of standard motor. It is an effective method to replace traction motor with high-efficiency motor for auxiliary machines that do not need state adjustment in thermal power plants.
(2) Adopt energy-saving transformer.
Due to the continuous development of material technology and the continuous improvement of transformer factory structure, energy-saving transformers have developed rapidly, and now they have developed to S 10 or even S 1 1. Compared with S 1 1 transformer with better energy-saving effect, S9 transformer with energy-saving technical characteristics has become "energy-consuming". S 1 1 transformers are widely used, and their performance level is higher than that of S9 transformers, with an average reduction of 30% in no-load loss and 70% in no-load current. Therefore, energy-saving transformer S 1 1 or newer energy-saving transformer should be preferred. When selecting distribution transformers (with a capacity of 2500KVA or less), priority should be given to S 1 1 dry-type transformers to replace oil-immersed transformers or other dry-type transformers with the same capacity, which can obviously reduce reactive power loss.
3. Reduce the auxiliary power consumption rate by adjusting the economic voltage of auxiliary power.
Under the condition of high voltage, it not only endangers the insulation of the motor, but also greatly increases the loss of the motor. Excessive working voltage will increase unnecessary waste of electric energy. Therefore, it is necessary to optimize a reasonable operating voltage range for auxiliary equipment, further tap the energy-saving potential of equipment and reduce the auxiliary power consumption rate. The electric power industry standard and enterprise standard "Regulations" stipulate that the operating voltage range of the motor is 95% ~ 1 10% of the rated voltage, and the total loss of the motor is different within this range. The purpose of analyzing the applied voltage is to find the most economical working voltage. It is very complicated to find out the functional expression of the minimum motor loss of all auxiliary machines in the whole plant. Therefore, we can find out the extreme value of the function by testing the self-loss (voltage regulation) of several auxiliary motors in the whole plant, so as to find out the corresponding 6kV bus voltage Uj, that is, the economic voltage. Judging from the current operating voltage of 400V auxiliary section, it should be feasible to appropriately reduce the auxiliary bus voltage by adjusting the tap, and the expected power saving is considerable. Referring to the effect of voltage reduction and power saving of peers, the auxiliary power consumption rate can be reduced by about 0. 1%.
4. Reduce the ferromagnetic loss in the transmission process of the closed bus of the generator set.
Large generator sets use closed bus to transmit power from generator to main transformer to reduce ferromagnetic loss during transmission. Due to the lax magnetic shielding at the local connection position of closed bus and the closed loop formed by steel structure installation, steel will produce eddy current loss and hysteresis loss under the action of alternating magnetic field, which is called ferromagnetic loss. If the ferromagnetic loss is too large, it will cause local overheating of steel, threatening personal safety, equipment safety or structural safety, and will also cause a lot of power loss. To reduce ferromagnetic loss, we should reduce the use of steel materials in alternating magnetic field, increase shielding, avoid forming a closed loop, and improve the spatial relationship between steel materials and current-carrying conductors.
5. Effectively control the overheating of electrical equipment.
Electrical equipment, such as switches, buses, etc., due to improper design, installation, inadequate maintenance, bad environmental conditions and other reasons, often lead to overheating of switch isolation contacts and bus joints in operation, which not only threatens the safe operation of equipment, but also consumes some electric energy. In the case of insufficient design and installation capacity, it is necessary to upgrade the equipment in a targeted manner. In the case that the maintenance is not in place and the environment is affected, the maintenance process standards are strictly implemented, the overheated parts are treated, and conductive paste is used. After cleaning the switch contacts and bus joints carrying load current, the contact resistance is reduced by 25% ~ 95% and the temperature rise is reduced by 25% ~ 70% compared with that without coating, which can save active power.
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