What components make up the moisture in coal? What are the hazards of moisture in coal?

The moisture content in coal, as commonly referred to, is the total moisture Mt, which consists of surface moisture Mf and internal moisture Minh. Intrinsic moisture, also known as inherent water content Minh, refers to the moisture present in the plants that formed the coal as well as the moisture that entered during the coal formation process. It cannot be removed by natural air-drying; heating is required to eliminate it. Its content remains stable for a certain type of coal. Surface moisture enters during extraction, storage, and transportation; it is also known as external moisture, and can be removed through natural air drying. The content of surface moisture is greatly influenced by natural conditions, resulting in significant variations in its values. The total moisture content of different coal types varies significantly under different conditions, ranging from just a few percent in some cases to 40–50 percent in others. The presence of moisture not only reduces the combustible components of coal and lowers its calorific value, but also affects the ignition and combustion of the fuel. Burning coal with high moisture content results in a lower combustion temperature, an increased volume of flue gases, which reduces the efficiency of the boiler. It also exacerbates low-temperature corrosion and ash deposition on the heating surfaces at the rear of the boiler. High moisture content in coal makes its transportation and grinding more difficult as well.

The coal used in our plant needs to be mixed with water before it enters the furnace – is that harmful? I’ve really never thought about it seriously before

Reply to 1# dongjiang1001: 1. The forms of moisture present in coal include external moisture, internal moisture, and crystalline water. External moisture refers to the water present on the surface of the coal, while internal moisture refers to the water contained within the pores of the coal. Crystal water is the water that exists in the coal in crystalline form. 2. An increase in moisture will affect the ignition and combustion rate of the fuel, increase the amount of flue gas, raise the heat loss due to exhaust gases, and exacerbate corrosion and ash deposition on the heating surfaces at the rear. It mainly increases heat loss, affecting the response speed.

Could you explain why water needs to be added before it enters the furnace? I always thought that adding water to coal powder would reduce combustion efficiency. Is there any benefit to adding water? Also, is the amount of water added fixed?

For ordinary industrial boilers of the chain grate type, where coal is mixed with water, I have a few personal opinions. First, adding an appropriate amount of water helps to turn the coal into smaller pieces, preventing it from falling through the grate and thus reducing coal loss; therefore, this method is mostly used for coal that contains a high proportion of fragments! Second, once the coal enters the furnace, since it is wet coal, its combustion can be delayed; it burns more slowly at the front arch, thereby preventing the coal bin from catching fire. Third, in terms of energy loss, adding water increases the water content in the flue gas, thereby carrying away more heat!

I’m here to learn *; thank you all for sharing