Discussion on Several Issues Concerning Gas Production from Briquetted Coal
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1. Wind pressure and air volume: In addition to enabling a \"strong wind with short duration of blowing\" to reduce CO2 reduction and improve the efficiency of blowing, I believe the important aspect of high wind pressure is its penetration ability. A strong penetration ability means that more carbon participates in the reaction per unit of time, resulting in more intense gasification reactions, and thus greater gas composition and volume； Conversely, the wind pressure is low, resulting in poor penetration; the fire layer concentrates in the lower part, and the gasification reaction is inadequate. Under high wind pressure, the volume of air flow depends on the number of cycles per bucket of coal; maintaining a low number of cycles ensures that the coal added is fully reacted. 2. Steam: Briquettes with a high moisture content require a high steam pressure to facilitate drying; this pressure is generally set between 0.06 and 0.07 MPA. The downward blast should be weak (keep the opening of the downward blast control knob fixed); the duration of the downward blast should be half of the total gas supply time ； The upper blowing is strong and short; the reason for adopting this adjustment mode lies in the good activity and low melting point of the sodium humate coal rods. During the blowing process, the coal pellets are highly active, resulting in high utilization of all the air and a rapid rise in the temperature of the gasification zone; coupled with the low melting point of the ash, this can easily lead to excessively high temperatures in the gasification zone. Therefore, when switching to top-blown gas, a larger steam flow is required to dissipate the heat; the process cannot take too long, otherwise it will disrupt the stability of the vaporization layer inside the furnace ； When switching to the downward blowing gas, due to its low ash melting point, a lower steam flow rate and a longer time are required to stabilize the position of the gasification layer. Control the ratio of steam to air to ensure a high slag formation rate. 3. Temperature: The descending temperature should be between 270°C and 300°C, with as large fluctuations in temperature as possible; under these conditions, both the slag formation rate and air permeability are good, and the gasification reaction proceeds rapidly. 4. Carbon layer height: The pressure loss during blowing is measured, and it is generally kept at around 2.5 meters (the distance from the surface of the carbon layer to the ash tray); this value should be determined based on the specific equipment being used. 5. Gas generation resistance: An appropriate gas generation resistance should be set in order to increase the steam decomposition rate. Please point out any mistakes
The quality of coal, its variety, and the time it took to form also have an impact.
The original poster’s post is quite good; it offers practical advice that can be useful for companies that are starting out with coal rods. Although it may not be 100% accurate, such a sincere attitude is certainly touching. I hope experienced masters will post more similar posts to facilitate communication and achieve mutual improvement.
When burning briquetted coal, problems such as scorching, furnace reversal, and excessive return of ash in the form of balls often occur. Additionally, the gas production per furnace is low and the quality of the gas is poor; the reasons for this are as follows. ①Compared to lump coal, coal balls have a larger carbon surface area, which in turn means a larger vaporization surface area; this leads to faster vaporization and a quicker rise in furnace temperature. If there isn’t an adequate supply of H2O↑ to keep up, it can easily result in localized high temperatures that cause scorching. Additionally, the quality control of coal balls is not sufficient, resulting in poor thermal strength of these coal balls, which causes them to disintegrate rapidly once they enter the furnace. This leads to a rapid increase in furnace temperature on one hand, and an increased amount of waste material being carried away by the gas stream on the other hand. ②Out of concern about scorching occurring due to excessive temperature in the furnace, we operated it at a low load, with the fan outlet closed tightly; as a result, the load on the gas generation furnace was too low. Moreover, we continued to use the same operating approach as when burning lump coal, trying to maintain the temperature by adjusting the speed of the large furnace rods. This had the opposite effect: it led to poor quality of the slag formed from the ash, an abundance of residual ash balls, and even the formation of new balls. Additionally, the gas production per furnace was very low, less than 700 cubic meters per meter per hour, with carbon dioxide levels around 11%.