1、 Definition of coal-fired boilers

Coal fired boilers refer to boilers that use coal as fuel. Coal burns and releases heat, which is then converted into steam or hot water. However, not all of the heat can be effectively converted during this process, resulting in some reactive power consumption and efficiency issues. Generally, the efficiency of larger boilers is between 60% and 80%.

2、 Types of coal-fired boilers

（1） Horizontal coal-fired boiler

After the fuel is burned on the grate, the flame passes through the low wall to the combustion chamber, then through the wing shaped flues on both sides to the front smoke box, and then through the smoke pipe bundle to the rear smoke chamber. Finally, it is drawn by the induced draft fan and discharged into the atmosphere through the chimney. Its advantages include preventing the bottom of the pot shell from being exposed to high-temperature radiation from the furnace, reducing the inlet flue gas temperature of the high-temperature tube plate, and assisting with return water injection to eliminate dead water areas at the bottom of the pot drum. It can effectively prevent the tube plate from scaling and furnace bottom bulges due to supercooling and boiling, and the flue gas can be diverted to the smoke chamber to remove dust and reduce the original dust concentration.

（2） Vertical coal-fired boiler

For example, the LSG (vertical) series coal-fired steam boiler adopts a water-cooled tube structure, which is scientifically designed and has the characteristics of fast heating and temperature rise, large steam water space, and good steam quality.

（3） Classified by purpose

1. Coal fired steam boiler

CLSG - vertical atmospheric coal-fired hot water boiler belongs to atmospheric hot water boiler, with compact design structure, small space occupation, convenient installation and transportation, and relatively cheap price, suitable for use as a tea stove and providing hot water, etc; There are also different models of coal-fired steam boilers such as DZL1.4-85/60 chain grate biomass blue charcoal boilers, which can be applied to different industrial scenarios. By burning coal to generate steam, they can meet the steam demand in industrial production processes. For example, in some factories' production and processing links, they are used to drive steam power equipment or provide heat sources for certain production processes.

2. Coal fired hot water boiler

Like the CLSG series vertical atmospheric hot water boiler, it mainly consists of a pot shell head, furnace liner, furnace liner top, lower sealing ring, soaring pipe, and horizontal water pipe. The combustion chamber is arranged inside the furnace liner, and the fuel burns on a fixed grate to produce hot water, which can be used for building heating and other purposes, providing people with the hot water resources needed for daily life, such as heating services for residential areas, office buildings, etc.

3、 Equipment related to coal-fired boilers

（1） Dust collector for small coal-fired boilers

The scope of application is applicable to various coal-fired boilers ranging from 1 to 10 tons.

Working principle and type

Some small coal-fired boiler bag filters mainly include ash removal devices, which work by adopting a spray structure and unique nozzle design. Some small coal-fired boiler dust collectors are new and efficient pulse type bag dust collectors developed based on the characteristics of small coal-fired boiler flue gas. The structure has been greatly improved compared to ordinary pulse dust collectors and is more suitable for high-temperature and corrosive environments of boiler flue gas. Bag dust collectors are mainly used in the production process of coal-fired boilers to process the large amount of small dust containing small sparks, reduce air pollution and harm to human health.

For example, the dust collector of Huaying small coal-fired boilers is a commonly used dust collector equipment for small coal-fired boilers, which can effectively treat boiler flue gas, protect the environment and human health.

4、 Transformation of coal-fired boilers

The reason for the renovation is that when the boiler experiences high exhaust gas temperature, severe wear of the furnace water-cooled wall, severe corrosion of the economizer and air preheater, overheating or low temperature of the superheater, or when the national environmental requirements become increasingly strict, in order to improve the working efficiency of the boiler, extend the service life of the boiler, and meet environmental protection requirements, coal-fired boilers need to be renovated.

Ways of transformation

Flue gas waste heat recovery: The exhaust temperature of industrial boilers is generally high (such as above 180 ℃). By using heat pipe heat exchange technology, flue gas waste heat resources can be recovered and used to preheat boiler combustion air, preheat boiler water supply, or directly produce hot water.

Coal transportation equipment renovation: For layer fired boilers (such as forward chain grate boilers), the original bucket type coal feeding device will be transformed into layer coal feeding. Gravity filters will be used to loosely distribute the raw coal chunks and fines from bottom to top on the grate, which is beneficial for air intake, improving combustion conditions, increasing coal combustion rate, reducing ash carbon content, and achieving a coal saving rate of 5% -20%. The project investment is low, the energy-saving benefits are good, and the recovery is fast.

Oxygen enriched combustion technology: When the boiler flame temperature is insufficient, the carbon content of coal slag is high, the Ringman blackness level of flue gas cannot meet the standard, the boiler combustion efficiency is not high, and the boiler output is insufficient, oxygen enriched combustion technology can be used to increase the oxygen content in the combustion air, make the fuel combustion more complete, while reducing the excess air coefficient, reducing the exhaust emissions after combustion, increasing the flame temperature and reducing the smoke blackness, achieving energy saving of 5% -15%, and increasing boiler output by more than 10%. This technology has good energy-saving and environmental benefits, and the project investment payback period is less than one year

Internal transformation and adjustment: For coal-fired boilers that have not been purchased for a long time and have a relatively long service life, when carrying out gas, biomass, electricity, fuel and other transformations, only individual boiler configurations need to be replaced, and the boiler body and some configurations can be retained. This method is relatively convenient.