Introduction of Suzhou Electric Heating Boiler Recycling Product Industry Development
In the first half of the 18th century, steam engines used in British coal mines, including the initial steam engine of Watt, used steam pressure equal to atmospheric pressure. The second half of the 18th century switched to steam at atmospheric pressure. In the 19th century, the usual steam pressure increased to about 0.8 MPa. In response to this, the earliest steam boiler was a large-diameter cylindrical vertical boiler shell holding water. Later, it was replaced by a horizontal boiler shell, which was burned in a brick furnace under the boiler shell.
As the boiler gets bigger and bigger, in order to increase the heating area, a fire tube is installed in the pot shell, and the front end of the fire tube is used to burn the fire. It is called a fire tube boiler. At first, only one fire tube was installed, called a single fire tube boiler or a Connex boiler. Later, two fire tubes were added, called a double fire tube boiler or a Lancashire boiler.
Around 1830, after mastering the production and expansion technology of high-quality steel pipes, fire tube boilers appeared. Some fire tubes are installed in the shell of the boiler, forming the main heating surface of the boiler, and the fire (flue gas) flows through the tubes. Install as many fire pipes as possible below the water line of the boiler shell, which is called a horizontal external fire tempering tube boiler. Its metal consumption is low, but it requires large masonry.
In the middle of the 19th century, water tube boilers appeared. The heating surface of the boiler is a water pipe outside the boiler shell, which replaces the boiler shell itself and the fire tube and fire tube inside the boiler shell. The increase in the heating area and steam pressure of the boiler is no longer limited by the diameter of the shell, which is conducive to increasing the boiler evaporation and steam pressure. The cylindrical shell in this boiler was renamed the drum, or drum. In the early days, straight water pipes were used for water tube boilers, and the pressure and capacity of straight water tube boilers were limited.
In the early twentieth century, steam turbines began to develop, which required a boiler with a high capacity and steam parameters. The straight water tube boiler can no longer meet the requirements. With the development of manufacturing process and water treatment technology, bent-tube boilers have appeared. It started with a multi-pot style. With the application of water-cooled walls, superheaters and economizers, and the improvement of steam and water separation elements inside the drum, the number of drums is gradually reduced, which not only saves metal, but also helps to increase the pressure, temperature, capacity and efficiency of the boiler .
In the past, fire tube boilers, fire tube boilers and water tube boilers belonged to natural circulation boilers. Due to the different heating conditions of water vapor in the ascending and descending pipelines, the density difference caused natural flow. While developing natural circulation boilers, once-through boilers have been used since the 1930s, and auxiliary circulation boilers have been used since the 1940s.
Auxiliary circulation boiler is also called forced circulation boiler. It is developed on the basis of natural circulation boiler. A circulation pump is installed in the downcomer system to enhance water circulation on the evaporation heating surface. There is no drum in the once-through boiler, and the feed water is fed into the economizer by the feed water pump, and the water heating wall and superheater are used to evaporate the heating surface to become superheated steam and sent to the steam turbine.
After the Second World War, these two types of boilers developed rapidly, because the generator set required high temperature, high pressure and large capacity. The purpose of the development of these two boilers is to reduce or not use the drum. Small diameter pipes can be used as the heating surface, and the heating surface can be arranged more freely. With the advancement of automatic control and water treatment technology, they have gradually matured. At supercritical pressure, once-through boilers are the only boilers that can be used. The largest single unit in the 1970s was a pressure of 27 MPa and a 1300 MW generator set. Later, a compound cycle boiler composed of an auxiliary cycle boiler and a once-through boiler was developed.