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Our country is a major coal-producing nation as well as a major consumer of coal. For a considerable period of time, the energy structure based on coal will remain unchanged, but the environmental pollution problems resulting from this are also very severe. Industrial briquettes have become a focus of research at home and abroad due to their high thermal efficiency, energy savings, and reduction of air pollution. However, current briquette production faces issues such as a high ignition point and low thermal efficiency; therefore, improving the combustion properties of coal and enhancing its combustion efficiency hold great practical economic and social significance. The research and application of coal additives aim to improve the combustion properties of coal by adding a small amount of these additives, based on the mechanisms of coal combustion, without altering the coal-fired equipment. This approach helps to lower the ignition point of coal, increase its burn rate and calorific value, thereby achieving energy savings and reduced pollution emissions. This paper selects a coal-fired additive and, by adding amounts of active additives at different gradients, investigates the effect of these addition levels on the combustion performance of briquettes (ignition speed, loss on ignition, calorific value), thereby providing a scientific theoretical basis for future large-scale production. l Experimental materials and testing methods for briquette properties 1.1 Experimental materials: The raw material for the experiment was coal slime obtained from Haitian Coal Washing Plant in Gujiao City, Shanxi Province. Additives: The main components are iron oxide, sodium peroxide, and potassium nitrate. Experimental instruments: SL1002N electronic balance, 101-1-BSⅡ electric heating constant-temperature forced-air drying oven, CT5000A multi-functional calorimeter, SGM5800 artificial intelligence box-type resistance furnace. 1.2 Testing methods for briquette properties: The combustion performance of briquettes is primarily assessed based on factors such as their ignition speed, loss on ignition, and calorific value. The measurement methods are as follows: (1) Ignition speed: The combustion tests of briquettes are carried out in an SGM5800 artificial intelligence box-type resistance furnace. During the experiment, the temperature was set at 800°C to observe the changes in the combustion behavior of the briquettes, and based on these changes, the effect of coal additives with different proportions on the ignition speed of the briquettes was determined. (2) Loss on ignition: Weigh the coal sample used to test the ignition rate before combustion, and record its mass as W1. After the coal sample is burned at 800°C in an SGM5800 resistance furnace for 15 minutes, take it out and weigh it again, recording the mass as W2. The loss on ignition is then calculated as: Loss on ignition = (W1 – W2) / W1 × 100%. (3) Calorific value: The calorific value of briquettes is determined using a CT5000A multi-functional calorimeter. This instrument is capable of automatic ignition and temperature measurement, as well as automatic data processing by computer; it displays in real time the heat released during the combustion of the briquettes, based on the temperature differences between the inner and outer walls of the bomb. 2 Experiment 2.1 Determination of the ignition speed of briquettes: 2 g of coal slurry was taken, to which active additives accounting for 0%, 3%, 6%, 9%, 12%, and 15% of the mass of the coal slurry were added. After thorough mixing, the mixture was shaped in briquette molds. It was air-dried for 3 days, after which the sample was placed in an SGM5800 resistance furnace at 800°C to be burned, with the furnace door left open, so as to observe and record the time it took for the briquette to catch fire. 2.2 Determination of loss on ignition: The briquettes prepared as described above were allowed to air-dry naturally for 3 days; the weight of the sample before combustion was recorded as IV. The samples were then placed in a resistance furnace model SGM5800A set at 800°C, with the furnace door left open. After 15 minutes of burning, the remaining mass after combustion was taken out and weighed as W2. 2.3 Determination of the calorific value of briquettes: The briquettes prepared as described above are allowed to air-dry naturally for 3 days, then crushed and dried in an oven for 2 hours. Samples weighing approximately 0.7 g each are placed into a CT5000A multi-purpose calorimeter for measurement, with the data being observed and recorded. 3 Results and Discussion 3.1 Effect of coal-fired additives on the ignition speed of briquettes The effect of different amounts of additives on the ignition speed of briquettes is shown in Table 1. The gray color that appears in the experiment is due to the coal particles being surrounded by volatiles; oxygen reacts and burns first with the combustible gases. Therefore, the combustion of coal chunks generally lags behind that of the volatiles; the coal chunks can burn only when oxygen in the furnace reaches the surface of the hot coal chunks. The addition of active additives helps to provide the reactive oxygen necessary for combustion in the preheating stage, combustion stage, and burnout stage, thereby promoting the release of combustible volatiles from the coal during combustion. As can be seen from Table 1, overall, the ignition speed increases as the amount of active additive added increases. Among these, there is not much difference in ignition speed when the addition amount is 0%, 3%, or 6%; however, the ignition speed of coal blocks with a 9% addition amount increases significantly. The ignition speed with a 15% addition amount shows a slowdown, but it is still significantly higher than that of samples with 3% or 6% addition amounts. It shows that during the combustion of coal, this additive is capable of lowering the ignition point of briquetted coal, promoting the breakage of C-C bonds in the coal, thereby converting large molecular structures into relatively smaller molecules and releasing volatiles, which accelerates the burning rate of the coal. A addition level of 12% is an abnormality, which may be due to insufficient mixing of the additive with the coal slurry during the briquette preparation process. 3.2 Effect of coal additives on the loss on ignition of briquettes The effect of different amounts of additives on the loss on ignition of briquettes is shown in Table 2. As can be seen from Table 2, the loss on ignition of briquettes increases as the amount of active additive added increases. The loss on ignition of briquettes with an additive content of 3%–9% increases gradually, reaching a peak at 12%, after which it begins to decrease. It shows that during the coal combustion process, due to the catalytic effect of additives, the thermal movement of coal can be accelerated, thereby increasing the rate of oxygen transfer and heat transfer to the coal, allowing it to burn completely. This improves the loss on ignition rate of coal, and there is an optimal amount of such additives to use. When the addition amount of the additive is 12%, the loss on ignition of the coal is relatively high, indicating it to be an optimal dosage. 3.3 Effect of coal additives on the calorific value of briquettes The impact of different amounts of additives on the calorific value of briquettes is shown in Table 3. As can be seen from Table 3, the calorific value of briquettes gradually decreases as the amount of active additive added increases. This is because the additive itself has no calorific value; when a certain proportion of active additive is added to briquetted coal, it does not reduce the calorific value of the coal itself. However, since the amount of briquetted coal is fixed, the proportion of coal in the briquettes decreases as the amount of active additive added increases; as a result, it is the overall calorific value of the briquetted coal that decreases. This indicates that the additive only possesses good catalytic properties, enabling it to accelerate the ignition speed of briquetted coal and increase its loss on ignition rate, but it cannot enhance the calorific value of the coal itself. 4 Conclusions From the above experimental results, it can be concluded that: 4.1 The ignition speed of briquettes increases as the amount of active additive added increases. This indicates that the additive is capable of lowering the ignition point of briquetted coal, promoting the breakage of C-C bonds in the coal, converting large molecular structures into relatively smaller molecules, releasing volatiles, and thus accelerating the combustion rate of the coal. 4.2 The loss on ignition of briquettes increases as the amount of active additive added increases; the burn rate of briquettes is fastest when the additive content is 12%. This shows that during the coal combustion process, due to the catalytic effect of the additives, the thermal movement of the coal is accelerated, thereby increasing the rate of oxygen transfer and heat transfer to the coal, allowing it to burn completely and thus raising its loss on ignition rate. 4.3 The calorific value gradually decreases as the amount of active additive added increases, indicating that this additive cannot raise the calorific value of the coal itself; it only possesses good catalytic properties, which accelerate the ignition speed of briquetted coal and increase its loss on ignition rate.