Environmental Benefits of Low-vacuum Heating in Coal-fired Gangue Thermal Power Plant

Discussion on Environmental Protection of Coal Mines in Low-vacuum Heating Environment in Yanshiyanshi Power Plant Yang Weihua (Department of Urban Construction, Hebei University of Architecture and Technology, Handan 056038, Hebei, China) Heating in a small-scale power plant with a low-vacuum heating operation has high temperature; The economic and environmental benefits.

As the current power supply is relatively modest, the national energy policy has been adjusted to adopt a policy of closing deadlines for small condensing steam turbine generator sets with high energy consumption and large pollution. In order to obtain a living space, many small power plants in the vicinity of small cities have taken the road of cogeneration. The small coal pit power plant with a single coal capacity of 6MW has taken advantage of the convenience conditions near the mining area. The condensing unit will be changed to a heating unit and will provide heat for the mining area during the heating period. These small pit power plants are more energy-intensive and polluting than large and medium-sized power plants, but they have greater advantages in terms of energy conservation and environmental protection than decentralized small-scale heating and heating boiler houses. The more commonly used method is to change the condensing generator unit to a low-vacuum heating unit. The so-called low-vacuum heating is to reduce the steam exhaust vacuum operation of the turbine, and accordingly increase the exhaust temperature of the steam turbine, so that the circulating cooling water temperature of the generator set will increase, will increase the temperature of the circulating cooling water input heating system, instead of heating The system's thermal network circulating water will disperse the heat that should have been dispersed into the atmosphere in the cooling tower into the room to achieve indoor heating.

1 The environmental benefits of low-vacuum heating The content of elemental bonds in the turbulent zone has reached the national standard for mineral water.

Controlled by stratigraphic geological formations and groundwater turbulence pathways, mineral waters have obvious banding and stability.

With the reduction of raw coal production in the mining area, consideration should be given to increasing the comprehensive utilization of mine water, broadening the use of mine water, and actively investing in the development of water resources. The national south-to-north water diversion project will pass through the eastern part of the mining area. According to estimates by experts, the cost of a ton of water per ton of water from the South-to-North Water Diversion Project will be between Beijing and Tianjin, and the cost will be between 3 and 5 yuan. If the mine water is treated as a sediment, 0.1Gt will be transferred. The north pipe network, calculated in terms of one ton of water per ton, will establish a new economic growth point for Jiaozuo and the mining area economy.

Utilizing the leverage of the market economy, the development strategy of mining wells and the road of joint development with scientific research, development, and sales will be used to open up new economic pillars for the old mines.

1.1 Reducing waste slag row placement A certain thermal power plant in northern Hebei province is taken as an example. The heat recoverable for low-vacuum heating in each heating season is approximately 22x104G, which is equivalent to 28,293 tons of raw coal consumed. It is calculated based on the local crude oil content of 42%, which can be calculated annually. Less waste discharged more than 10,000 tons. The actual situation in the local area was: before the implementation of centralized heating, the heating area was less than 0.12 Mm2, there were six small boiler rooms, and the total evaporation was 54 t/h. The six boiler rooms formed six large garbage sites in winter. Because the boiler room is in the living and working area, the furnace can often not be transported outside in time, affecting the environment and blocking traffic. If windy weather is encountered, the environment will become even worse. After achieving low-vacuum heating, these "heaps" naturally disappear. The slag of the power plant can be used as a raw material for manufacturing slag bricks and cement, turning waste into treasure, which completely solves the problem of slag contamination in the area.

1.2 Reducing emissions of exhaust gas and dust After the realization of low-vacuum heating, power plant heating replaced scattered small-scale heating boiler houses. Taking a mining bureau as an example, when a small boiler room is heated, the boiler capacity is below 4t/h, and the stack height Most of them are below 20m. In the days without wind, the black smoke emitted from the chimney cannot drift away in time, causing the entire mining area to be immersed in black smoke. After the realization of low-vacuum heat supply, the operation of the small boiler room was stopped, and smoke pollution caused by the small boiler room was naturally avoided. In each heating season, less 4Mm3 of boiler flue gas can be emitted, 1700 tons of sulfur dioxide emissions can be reduced, and dust emissions can be reduced by 2500 tons. Since the power plant has more perfect dust removal equipment and the chimney is high, the smoky scene has rarely been seen since this mine.

1.3 Reducing Wastewater Emissions In the case of distributed heating in small boiler rooms, each boiler room has a set of water treatment equipment that uses salt to regenerate. Due to the small size of the equipment, the technical level of the workers is uneven, and in the process of water treatment, the utilization of raw water is low, and the consumption of salt is large, causing relatively large pollution to the environment. With the suspension of the operation of these small boiler rooms, the pollution of this part of the wastewater has been solved.

2 Parameters to be recorded during low-vacuum heating operation The low-vacuum heating operation is actually an 'abnormal' operating state regulated by the steam generator set operating rules. In order to ensure absolute safe operation of the steam turbine, all parameters except for normal power generation are to be recorded. In addition to strict monitoring, the following parameters should also be closely monitored. If the original parameters of these parameters are only in-situ instruments, when the low-vacuum heating technology is reformed, the vast majority of instruments will be added to monitor and adjust at any time. These parameters are: Main steam pressure Main steam temperature Main steam flow Power generation load Steam turbine shaft Direction of Displacement Turbine Vibration in Each Direction Thrust Pad Temperature (or Oil Temperature) Exhaust Vacuum Degree S Temperature After Cylinder Temperature Circulation Water Into Condenser Pressure Circulation Water Into Condenser Temperature Condenser Outlet Circulation Water Temperature Peak Heater Outlet Water temperature Hot water circulating water Heat meter circulating pump Current heating system Feed pump current Turbine condensing steam Turbine condensing water temperature Coal consumption and calorific value It is necessary to point out that the handle is low vacuum heating operation, due to the unit performance Not the same, therefore, the above parameters can only vary from factory to factory. The operating parameters of each plant can only be gradually explored through debugging. When debugging, take a certain parameter as the main factor, take into account other parameters, and get the best value of the parameter. Then comprehensive analysis, according to the barrel principle, find out the most unfavorable parameters to control the low vacuum operation, and use this as a reference standard to determine the corresponding values ​​of other parameters. For the emergency shutdown system of the steam turbine, its operating parameters are recommended to be more than 0.01 MPa above the minimum vacuum that the turbine can withstand.

3 Conclusion Low-vacuum heating is a new technology developed in recent years. It combines heat supply and power generation closely, and recovers the loss of cold source during power generation without affecting power generation. The new energy-saving technology also has high environmental benefits. However, its operation process takes into account both the power generation and heating, and in particular, the steam turbine is in an “abnormal” operating state, which increases the difficulty of operation. In addition, the unit conditions of the units are not the same, so all units must be based on The actual operation, combined with the low-vacuum heating debugging situation, to develop operating procedures for their own units, must not be blindly copied, affecting the safe operation of the unit.

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