How to reduce the carbon content in gas generation furnace slag

Since both of these gas generation furnaces were modified from the original model with a diameter of φ1980 by reducing the thickness of the water jackets to increase the furnace diameter, the ash tray was not enlarged accordingly. As a result, the angle of repose of the ash and slag becomes too large, which can lead to unstable furnace operation, as well as issues such as red carbon accumulating at the bottom of the ash bin and uneven flow of the slag. The conical shape of the water jackets makes it even more likely for such problems to occur. This can be addressed by adding fake ash disks and modifying the shape of the slag strips, in order to stabilize the furnace conditions and reduce the carbon content in the slag.

In my opinion, the level of gas production in a fixed-bed system can be determined by looking at the ash produced on site； Based on what you said, my analysis is that it is mainly due to a low temperature in the gasification layer and a low gasification intensity; for a carbon content of 30%, the slag formation rate in the ash is very low ； To achieve a high gasification intensity, it is generally required to operate at 50 degrees below the ash fusion point (T2) ； For a given raw material, a proper air flow rate, an appropriate carbon layer thickness, suitable amounts of steam supplied from above and below (it should be noted that the steam must be superheated), and an appropriate rotation speed for the grating system – all these factors are important. To achieve better results, it is necessary to conduct further experimentation while keeping the raw material unchanged ； Here is a couplet I wrote for our workshop: “Observe diligently and think deeply; stable load ensures good gas supply.” I share it with you as a reference and to encourage one another.

⑴A long upper blowing time in the gas generator or high steam consumption cause the gasification layer to rise, preventing the fuel from burning completely and ending up in the ash zone； ⑵The particle size of the raw material is uneven; the variation in particle sizes is too large, or there is an excessive amount of coal gangue along with high powder content, resulting in a low temperature in the fuel layer and incomplete combustion of the fuel ； ⑶Scarring inside the furnace or the presence of air pockets, resulting in carbon leakage ； ⑷Uneven carbon addition results in a large variation in the height of the carbon layer across the furnace cross-section, leading to different resistances in those carbon layers ； ⑸The ventilation area of the grate is small or the ventilation is uneven, resulting in poor slag breaking capacity ； ⑹The ash disk rotates too fast, and the fuel fails to burn completely, ending up in the ash layer.

The main reasons for the high carbon content in the gas generator slag are as follows: 1. The temperature in the gasification zone is low, resulting in insufficient combustion and gasification of carbon; 2. The rate at which ash is discharged is too fast, preventing the formation of an effective ash layer; 3. There are localized defects inside the furnace, causing uneven gas flow and preventing some of the carbon from being fully gasified; 4. The gasification zone moves upward, and the excessive upward airflow leads to a low temperature at the bottom of the furnace, again preventing proper gasification of the carbon. When the low temperature in the gasification zone prevents sufficient combustion and gasification of carbon, it is possible to increase the temperature by adjusting relevant parameters, such as extending the blowing time, increasing the volume of air blown, or reducing the amount of steam used, thereby enabling the carbon to participate fully in the gasification process. Since an overly fast ash discharge rate results in a too-thin ash layer and thus a high carbon content in the slag, it is possible to increase the height of the ash layer appropriately, while simultaneously reducing the output of the slag strips; this helps to lower the speed of the slag strip machine and thus the ash discharge rate, avoiding the phenomenon of excessive consumption and drawing, and enabling the formation of a reasonable and effective ash layer. When uneven flow occurs due to local scarring inside the furnace, the temperature coefficient can be appropriately reduced to control the temperature of the gasification zone and prevent further local scarring. In addition, parameters such as the temperature of the empty space, the temperature at the furnace bottom, and the flow coefficient should be analyzed comprehensively, and the ratio of upper to lower air injection should be adjusted accordingly to ensure thorough combustion of the ash and slag. When the gasification layer rises and the amount of upward steam flow is too high, resulting in an excessively low temperature at the furnace bottom, it is necessary to lower the position of the gasification layer as well as the height of the ash and slag. At the same time, the amount of downward steam flow should be increased and the amount of upward steam flow reduced, in order to raise the temperature at the furnace bottom appropriately.

Our factory has a total of 5 gas generation buildings, and I am in Building No. 4. Carbon often forms in Building 4. We often associate lower carbon formation with low furnace temperature, but in fact the situation is exactly the opposite. The furnace temperature is too high, causing scarring inside the furnace; when ash is removed, these scabs carry out carbon as well. Similar situations rarely occur in other gas generation buildings. The reasons we have analyzed are as follows: Subjectively, fewer furnace bars were pulled ； The two vaporizing agents, air and water vapor, are unevenly distributed. Objectively: High-sulfur coal has a high ash content, resulting in insufficient steam pressure. Regarding the issue of insufficient steam pressure, we have already explored all possible solutions. Normally, as soon as the steam pressure is low, the shortcut next to the automatic control is activated, along with the upper and lower blowing handwheels; this results in low steam pressure before pressure reduction occurs, and the steam pressure becomes uncontrolled. As a consequence, the temperature at the bottom of multiple furnaces drops, which prompts an increase in the speed of the furnace rod motor, ultimately leading to carbon formation at the bottom of the furnaces and increased consumption. For discussions on this topic, feel free to add me on QQ: 546504124

1. The speed of the grate drive in the gas generation furnace is high, resulting in incomplete combustion of coal. 2. The ash layer is not thick enough, leading to uneven gas distribution, which may cause a decrease in the decomposition rate. 3. Increasing the thickness of the ash layer appropriately can improve the gas distribution. 4. The slag-breaking bars and ash spades are not effective at breaking up the slag

In response to the moderator: To reduce the residual carbon in a fixed-bed batch gas production furnace, I believe it is necessary to conduct an analysis from the following aspects: 1. Process analysis: For different types of coal, it is essential to select an appropriate air volume, a reasonable percentage, a suitable steam pressure, the optimal ratio of upward and downward movement, as well as stable and appropriate furnace grates. 2. Improvements are needed on the equipment in the following areas: improvement of the automatic fuel distribution device, installation of anti-flow devices, addition of secondary air distribution, and selection of the most suitable grate. 3. In terms of careful operation, it is necessary to carry out thorough maintenance, make frequent fine adjustments, be bold yet cautious, respond promptly, and take decisive action.

The height-to-diameter ratio of the gas generator is unreasonable; at the initial stage of adopting new processes, equipment modifications sometimes occur. There are still some issues at present: during equipment modifications, the height-to-diameter ratio of 2.2/1 is strictly followed (including for insulation and ash storage bins). The gas generation furnaces are not designed properly, and equipment modifications sometimes occur in the early stages of adopting new processes. There are still some issues present. When modifying equipment, technical experts and operators should work together. The adjustment of process valves and the circulation percentages is inadequate; the proportions of the upper and lower blowout valves are not balanced, and the percentage allocation is unreasonable, which affects changes in furnace temperature. It is necessary to determine appropriate upper and lower temperature levels, and use these as a basis for adjusting the upper and lower blowout valves as well as the circulation percentages. Frequent start-up and shutdown of the furnace, due to fluctuations in load, leads to an increase in CO2 levels. Strict control of furnace temperature during start-up and shutdown is required, along with extending the heating time

Strengthen the analysis of the fixed carbon content in raw coal; poor mechanical strength requires an increase in the content of sodium humate as a binder; the resistance in the blowing systems is high – it is necessary to monitor the resistance of each blowing system at least once a week and keep proper records. Testing should also be conducted on the ash discharge from each dust collector. Strict inspection procedures must be followed in terms of operational practices, and assessments should be intensified. Given the high amount of steam used, adjustments should be made promptly based on changes in the quality of the steam and the conditions of ash discharge. Static equipment and pipeline systems accumulate ash, which leads to high resistance; therefore, the resistance of each blowing system should be monitored at least once a week, with proper recording kept. Testing should also be carried out on the ash discharge from each dust collector. In the case of internal leakage in the process valves, maintenance plans for those valves should be developed, and maintenance should be carried out promptly in accordance with those plans

Corresponding input factor, testing method, testing date: Coal balls – low fixed carbon content; random sampling, July 15, 2006. Coal balls – poor mechanical strength; random sampling, July 20, 2006. High resistance in the blowing system; system testing, July 8, 2006. Inadequate operation by personnel; comparative analysis, July 14, 2006. High steam consumption; theoretical data, July 12, 2006. Ash accumulation in the system, resulting in high resistance; random sampling, July 8, 2006. Internal leakage in process valves; random sampling, July 10, 2006. Poor air distribution in the gas generator’s grates; check design drawings, July 10, 2006. Unappropriate slag removal strips in the gas generator; check record files, July 10, 2006. Incorrect selection of the gas generator model; check design drawings, July 10, 2006. Non-representative sampling for measurements; random sampling, July 12, 2006