The Science Behind Coal Combustion in Industrial Steam Boilers

Introduction

Industrial boiler is a indispensable power plant, widely used in chemical industry, papermaking, textile, and food industries. As a main fuel, coal’s combustion efficiency and environmental performance can directly affect boiler operation. This article will introduce scientific principles, the stage of coal combustion in industrial steam boiler.

What is coal combustion？

Coal combustion is a process of chemical reaction in which carbon, hydrogen, and other combustible elements in coal undergo oxidation reactions with oxygen, releasing large amounts of thermal energy. Thermal energy can be absorbed by water in the boiler, producing steam or hot water, applying in industrial production or heating.

Types of coal used in industrial steam boilers

The types of coal used in industrial steam boilers are diverse, mainly including anthracite, bituminous coal, lignite, etc. Different types of coal have different calorific values, volatile matter contents and ash contents, and these characteristics directly affect the combustion efficiency and pollutant emissions. For instance, anthracite has a high calorific value and stable combustion, but it has a low volatile matter content and is difficult to ignite; bituminous coal has a high volatile matter content, which makes ignition easy, but during combustion, it is prone to produce black smoke.

Coal combustion process in steam boiler

Coal combustion process in steam boiler can be generally divided into the following processes or stages.

• Drying stage: After the coal enters the furnace, the surrounding flue gas heat the coal and the moisture in the coal will be evaporated.
• Volatile components release stage: When the temperature rise to a certain value, the combustible component in the coal will be out and the gas can be combust.
• Coke combustion stage: After the combustion of volatile components, the remaining coke will be releasedand the coke will be burned with the oxygen, a lot of heat will be out.
• Exhaust stage: After the combustion of coke, the remaining ash and residualcarbon are discharged.

Combustion technology in industrial coal-fired boiler

Industrial coal-fired boilers use different combustion technology to improve the combustion efficiency and reduce the pollution.

• Coal powder combustion technology: Coal grind into powder and then feed into the furnace, the combustion efficiency of this technology is very high and it is widely used in large boiler.
• Circulating fluidized bed combustion technology: the coal and the air in the furnace arein a boiling state, the fuel and the oxygen can be in a good contact and then combustion, the combustion efficiency of this technology is very high and the pollution is low.
• Gasification combustion technology: Involves burning coal in a gasification chamber, where the produced gas is then combusted in a separate combustion chamber. This process ensures smokeless combustion.

Combustion efficiency is affected by many factors

Coal quality: Coal with high calorific value and low ash content has higher efficiency

• Combustion technology: Advanced combustion technologyimproves combustion efficiency and reduces pollutant emissions.
• Air supply：It is required that sufficient air, but excessair will cause thermal loss.
• Furnace temperature: Higher furnace temperature is advantageous for complete combustion of coal.

Emissions from coal combustion

During the process of coal combustion, various pollutants are produced, including:

• Sulfur dioxide: Mainly derived from the sulfur content in coal, which can be reduced through desulfurization devices.
• Nitrogen oxides: Formed under high-temperature conditions, which can be reduced through staged combustion technology.
• Particulate matter: Comprising dust and soot, which can be reduced through dust removal devices.

How to improve the coal combustion efficiency in industrial boiler

Optimize the combustion technology: Use efficient coal powder combustion technology or circulating fluidized bed combustion technology.

Improve the coal quality: Use the coal with less ash and high calorific value.

Equipment maintenance: Regularly check and maintenance the combustion equipment.

Install environmental protection equipment: Install efficient desulfurization, denitrification and dust removal equipment.

Conclusion

Coal combustion is an important energy for industrial steam boiler. But the combustion efficiency of coal and the environmental performance of coal should be improved continuously. If we use advanced combustion technology, improve the coal quality and install environmental protection equipment, we can improve the combustion efficiency, reduce pollution, promote the sustainable development of industrial production. If you have any needs, please feel free to contact us at any time.