What is the relationship between fixed carbon content and lower heating value?

Your question, OP – it’s hard to answer, and yet it’s easy to answer as well. Those who have been in a laboratory can mention it casually. However, in addition to fixed carbon, indicators such as ash and moisture are also required. To answer your question: I’ve worked in a laboratory before. For coals with a calorific value of around 40% (a low value), that corresponds to a calorific value of about 4000. By making a simple estimation, I think bituminous coal with a calorific value of 5800–6000 kcal per kilogram contains approximately 50% fixed carbon, 20% volatiles, about 20% ash, and around 5% moisture.

The lower calorific value of coal is related to both its volatile matter and fixed carbon. As for the relationship with fixed carbon, could a knowledgeable member explain it?

The test results for the coal used by our company are as follows: fixed carbon 68%, volatile matter 3.8%, ash content 26%, moisture 12%, and low calorific value of 4900 kcal. Can such test results be false?

Is it incorrect if the sum of fixed carbon + moisture + volatile matter + ash in the test results is greater than 100%? Also, one of the indicators in the test results is called “rise in water level”; what is the relationship between this indicator and “moisture”?

Reply to 4# Retro Cow: Volatilization fraction of 3.8%? The activity of this coal is really poor, isn’t it? Was it a mistake? Additionally, the sum of the industrial analysis values for coal is definitely 100%, and fixed carbon is calculated by addition and subtraction.

Fujian Class II anthracite is just like that – there’s no mistake possible. I really haven’t heard of bituminous coal having 20% volatiles, as mentioned on the 2nd floor!

The problem is that the moisture content of your bituminous coal is 10% – it needs to be watered.

The industrial analysis of coal includes four parameters: moisture, ash, volatile matter, and fixed carbon content. The fixed carbon content is calculated as 100 minus moisture minus ash minus volatile matter. The difference between lower heating value and higher heating value lies in the fact that the latent heat of vaporization of the water contained in coal is deducted, including the water produced by the hydrogen in the organic compounds of the coal during combustion, as well as the free water and bound water present in the coal. Therefore, a high moisture content in raw coal affects the lower calorific value. Bituminous coal has a volatility content of less than 10% on a dry basis; its internal moisture content is generally low as well. For coal with a calorific value of 5,000–6,000 kcal, the fixed carbon content should be between 60% and 70%.

Fixed carbon is unlikely to be this high. You can find some information online for reference. The Cilinshan Coal Mine, which is located in the area where Linshan Coal Mine is situated, was established in 1953 and put into operation in 1955. It has a history of mining that spans 47 years to date. The mine has undergone several technical upgrades, evolving from a small coal mine with an annual production capacity of 50,000 tons to a modern mine with a production capacity of over 500,000 tons per year. The mine utilizes mechanized processes for mining, excavation, and transportation, as well as a monitoring and control system for ensuring safe production; its degree of mechanization reaches 90.4%. Since 1986, the mine has been repeatedly recognized by the former **Ministry of Energy and the Ministry of Coal Industry as a mine with standardized quality. The coal seam currently being mined is Coal No. 3 in the Gaoping mining area of the Qinsui coalfield; it is a low-quality coal. The main products are coal of grade 13 and mixed coal of grade 12. The coal quality parameters are as follows: analytical moisture content is 2.09% ； Dry basis ash content is 13.13% ； Volatile matter is 12.50% ； Fixed carbon is 74.36% ； The cinder characteristics are 3 ； Sulfur content is 0.37% ； The calorific value is 31.25 million joules per kilogram. The Xiadian Coal Mine is located to the north of Fanjialing Village, Xiadian Town, 10 KM west of Xiangyuan County town. The designed production capacity of the mine is 210,000 tons per year, with total assets amounting to 26.21 million yuan. At present, the area of the mining field has been expanded from 8.09 square kilometers to 13.05 square kilometers, and the recoverable reserves of coal seam #3 have increased to 36.94 million tons. The coal being mined from the Carboniferous-Permian period belongs to the category of low-gray, low-phosphorus, low-sulfur, high-calorific-value lean coal; its quality parameters are as follows: ash content of 15.16% ； Moisture content: 0.97% ； Volatile matter 13.16% ； Fixed carbon is 70.71% ； Sulfur content is 0.32% ； The calorific value is 30.643 million joules/kg. On November 1, 2001, the technical renovation project for the mine with a production capacity of 600,000 tons per year was officially launched. The total investment in this renovation amounted to 82.7592 million yuan; after the renovation, the mine’s production capacity would reach 900,000 tons per year. The completion of this renovation was scheduled for June 2004. The Qingyuan Briquette Plant is a subsidiary facility; it is located to the east of the railway line in the Cilinshan mining area. Construction on this plant began in July 2000, with an estimated investment of 15 million yuan, and its designed production capacity is 200,000 tons per year. Two production lines with a capacity of 50,000 tons each have been built, bringing the total production capacity to 100,000 tons per year; production has already begun. The quality of the briquettes is good, and the sales market is favorable, so the prospects are very optimistic. The main products are industrial gas-producing briquettes, boiler and household briquettes. The technical specifications for industrial gas-producing briquettes are as follows: particle size of 50 g per piece, diameter of φ50 mm, cold strength of 80 kg per piece, hot strength of 30 kg per piece, water absorption strength of 20 kg per piece, fall strength of 95%, moisture content of 0.85%, ash content of 17%, sulfur content of 0.7%, volatile matter content of 11%, fixed carbon content of 70%, and calorific value of 6950 kcal/kg ； The technical specifications for boilers and domestic briquettes are as follows: particle size of 50 g per piece, diameter of φ50 mm, cold strength of 60–70 kg per piece, heat strength that remains unchanged, water absorption strength such that it does not disintegrate after 24 hours of immersion in water, drop strength of 90%, moisture content of 0.85%, ash content of 16.5%, sulfur content of 0.2%, volatile matter content of 11.8%, fixed carbon content of 70%, and calorific value of 6500–6900 kcal/kg.

Fixed carbon refers to the active component of coal, which is the combustible material remaining after removing ash, volatiles, sulfur, and moisture. It has a high fixed carbon content and thus a high calorific value; however, when its calorific value is low, the furnace temperature needs to be kept at a lower level, with the furnace temperature controlled between 1000–1100°C. The calorific value of coal refers to the heat (MJ) generated by 1 kg of coal when it burns. The calorific value is generally divided into high calorific value and low calorific value. The total calorific value of coal is known as the high heating value; it includes the latent heat of condensation of the water vapor produced during the combustion of the fuel ； The calorific value of coal, excluding the latent heat of water vapor condensation, is called the lower calorific value. Calorific value is an important indicator for measuring the quality of coal, with units of MJ/kg or kcal/kg. **Coal with a lower heating value of 29.270 MJ/kg is referred to as standard coal. .