Effect of central oxygen flow rate in the Texaco gasifier burner on gasification efficiency
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Generally speaking, a higher oxygen flow rate at the center is beneficial for the atomization of the coal slurry, allowing it to disperse more effectively and thereby improving the gasification efficiency; however, an excessively high flow rate can lead to an increase in the temperature at the upper part, which affects the service life of the arch bricks； If it is too small, it will result in poor atomization of the coal slurry, leading to an increase in the carbon content in the residues; moreover, it causes higher consumption. Additionally, the rise in temperature at the lower part of the furnace affects the use of cone bricks. As a result, many relevant documents do not provide an exact flow ratio, which is why center oxygen flow rate adjustments are often made in a vague manner. It can be said that the most direct approach is to rely on the shape of the ash and slag, as well as carbon residue analysis, furnace temperature, and gas composition; through my years of observation and experimentation, I have found that maintaining the central oxygen flow rate between 16% and 18% is the optimal range. What are your colleagues’ thoughts on this?
Agree with the original poster’s view. Another function of the central oxygen is to regulate the temperature in the slag outlet area, ensuring smooth slag removal.
Currently, the burner structures in different factories vary, as do the sizes of the gasification furnaces; as a result, these values also differ to some extent. The value mentioned by the original poster is quite reasonable. In fact, many factories keep this value between 12% and 15%, and there are recommended values provided in technical specifications based on experience.
The role of central oxygen is mainly to regulate the length-to-diameter ratio of the torch.
Could the original poster explain clearly how a high oxygen level in the center can cause overheating of the vault? Generally, a higher central oxygen level will cause the reaction zone to shift downward; it should not lead to overheating of the dome, but rather serves as a measure to prevent such overheating.
It’s a simple principle: the fire hoses that firefighters use to put out fires – if you remove the nozzles from them, will the water spray far?
A low flow rate of central oxygen results in a low utilization rate of coal slurry, a short residence time in the furnace, and a significantly reduced amount of gas generated. There are also many disadvantages associated with a high flow rate of central oxygen; the author’s analysis is quite accurate. The adjustment of central oxygen varies depending on the type of furnace, and it is necessary to find the appropriate settings based on the operating conditions of each specific furnace
In a single-nozzle gasification furnace, the poster said that a high amount of oxygen at the center would lead to high temperatures at the dome area?? I don’t understand this. The analogy used by the user in post 7 is inappropriate. In our plant, we have been increasing the amount of oxygen at the center during startup and shutdown processes to prevent high temperatures at the dome area.
By increasing the oxygen supply at the center and lengthening the flame, the reaction zone is shifted downward to ensure that the dome does not overheat. Unlike single-nozzle systems, multi-nozzle systems lack areas of impact and deflection; as a result, there is no situation where material deflected toward the vault fails to react completely.
An increase in the oxygen supply at the center lengthens the flame, causing the reaction zone to shift downward; the dome should not experience overheating. However, an excessive amount of oxygen at the center will shorten the lifespan of the cone bottom bricks and reduce the effective gas content.
The central oxygen coal slurry affects the atomization effect and has a certain impact on the atomization angle, though not absolutely; the atomization angle is mainly determined by the burner design. The central oxygen affects the flame diameter, while the outer oxygen determines the flame length; the two influence each other.
The central oxygen flow rate is indeed used to adjust the length of the flame, but its more important role is to improve the atomization of the coal slurry, thereby enhancing the efficiency of the gasification reaction and the carbon conversion rate. Under normal conditions, within a certain range, as the oxygen flow rate at the center increases, the flame length also increases, which leads to an expansion of the jet region; accordingly, the recirculation zone also grows larger, resulting in an increase in the dome temperature (this effect becomes more pronounced when the proportion exceeds 22%). Of course, this cannot be generalized; we should consider different furnace types, burner structures, and their dimensions. Especially for large furnaces these days (those with a relatively large length-to-diameter ratio), it is necessary to conduct regular comparisons of various data during actual operation in order to determine the optimal proportions.
Could you explain the reason in detail?
Generally speaking, the flow rate of the central tube is designed in advance, and there is no need for adjustment. When the type of coal used changes, or when the temperature in a certain area of the furnace wall is high, adjustments can be made. Since there are dark areas inside the furnace and the furnace designs vary, it is not clear whether increasing the flow rate at the center will raise or lower the temperature at the top of the furnace; this needs to be determined through experiments.
Is the issue with central oxygen related to the structure of the burner? Is there a formula that can be used for this value?
For four-nozzle systems, an increase in the central oxygen flow rate leads to overheating at the dome, while for single-nozzle systems, an increase in central oxygen levels causes the flame to move downward. In normal production, the controlled oxygen content at the core is generally 12~15% of the total amount.
How to adjust the slag port temperature, increase or decrease the proportion of central oxygen? Will increasing the proportion of central oxygen make the flame longer or shorter?
What needs to be understood now is the function of this central oxygen; aside from regulating when the furnace wall temperature becomes too high, when else is it necessary to make adjustments? ? I hope everyone can help answer this. . . :(
This post was last edited by jesse2013 on 2014-9-25 at 16:36. For a single nozzle, an increase in the oxygen level at the center causes the flame to elongate. When the slag outlet is clogged with slag, the amount of central oxygen is adjusted to melt the slag. But at the same time, increasing the central oxygen improves the atomization effect, which facilitates flame spread and makes the flame wider as well. However, the proportion of vertical enlargement is greater than that of radial enlargement.