The so-called coal-fired steam boiler startup essentially refers to the start-up of the whole boiler unit, and the so-called coal-fired steam boiler startup essentially refers to the start-up of the whole boiler unit. Even if the steam boiler changes from static state to on load operation, that is, the process from ignition of steam boiler to rated load (unit unit) or integration into steam main pipe (main pipe unit).
In essence, it is a kind of operation under variable working conditions. During the start-up process, the start-up process of coal-fired steam boiler unit. The combustion is gradually strengthened, the furnace temperature is gradually increased, local boiler water is vaporized, water circulation is gradually established, steam is generated, steam pressure is gradually increased, and all parts of the equipment gradually transition to normal operation state. During the start-up process, it is required that all kinds of equipment can be properly maintained, and that the components will not be subject to destructive thermal stress after being heated, and that the startup time can be shortened and the heat loss of working medium can be reduced under allowable conditions.
It is usually divided into cold start-up and hot start-up. Hot start includes three startup modes: warm state (shutdown time > 24h < 48h), hot state (shutdown time > 8h < 24h) and extremely hot state (shutdown time > 2H < 8h). The so-called cold start-up is different according to the state of steam boiler before start-up. It is the start-up of the boiler at room temperature. For example, start-up of steam boiler after maintenance, or start-up of boiler shutdown for a long time and steam pressure has dropped to zero. Hot start-up refers to the boiler which is shut down for a short time for standby. Due to the short shutdown time, the boiler still has a certain steam pressure and a large amount of heat is stored in the boiler. The contents and methods of cold start-up and hot start-up are basically the same, but the hot start-up is based on the cold start-up which has run several processes. Therefore, familiar with the cold start-up process, naturally master the hot start-up.
The starting mode of steam boiler is also different. The connection system between turbine and furnace can be roughly divided into unit system and main pipe system. The connection method of steam pipe between coal-fired steam boiler and steam turbine is different.
The start-up mode of boiler unit can be divided into rated parameter start-up and sliding parameter start-up. It is distinguished according to the steam parameter state of steam turbine during impulse starting.
When the coal-fired steam boiler is started first, when the rated parameters are started. When the steam parameters rise to the rated value, the steam parameters in front of the main steam valve are always maintained at the rated value during the period when the steam parameters change from impulse to rated load. The operation flexibility and economy of this start-up mode are poor. It is only applied to the small-sized units of the main control system, but it is no longer used in the large-scale units operated by the unit system.
Also known as joint start-up. When the boiler is ignited, the unit unit is usually started with sliding parameters. In the process of steam pressure rise and temperature rise, low-temperature and low-pressure steam is used to warm up the steam pipe. When certain parameters are reached, the steam turbine will be run and connected to the grid. With the increase of steam temperature and pressure, the load of steam turbine will be gradually increased. During the whole start-up process, the steam parameters in front of the main steam valve increase with the increase of load.
Steam pipe warming, steam turbine start-up and boiler pressure rise are carried out at the same time. As a result, the start-up time of the whole unit is shortened, and the flexibility of operation scheduling is increased. The heating process of the whole unit starts from the lower temperature and pressure, and the metal expands evenly and the heating surface is well cooled. Since the steam pressure and temperature entering the steam turbine are low, the volume flow of steam is large, and it is easy to overflow the steam turbine The unit with bypass system can recover the heat of working medium and make use of it, reduce the loss of working medium and fuel consumption, and the unit can generate electricity during the start-up process.
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