Coking problem in the waste-pan type Texaco gasifier!

After coking, the slag in the gasifier flows in a molten state downward through the throat, blocking the dead zone; as a result, the temperature in that dead zone rises while the temperature at the inflection point drops sharply.

3# ykzl: We use Texaco’s wet-pressure gasification process. A radiant heat exchanger is connected below the gasification furnace. Coking mainly occurs on the water-cooled walls of this radiant heat exchanger; once coking takes place, the heat exchange efficiency drops significantly, which in turn leads to further increase in coking, creating a vicious cycle. Eventually, this can result in the blockage of the second channel at the bottom, forcing a shutdown of the system in order to remove the coke.

This post was last edited by shanxg on 2009-9-12 at 13:07. Coking in the furnace occurs for 1. high furnace temperature, and 2. uneven air distribution inside the furnace, resulting in high local temperatures. 4# jinhua68

It’s water-coal slurry; you guys might not be aware of it. It’s for observation only

By coking, you mean the slag accumulation on the surface of the waste boiler, right? And by dead zone, do you mean the space at the top of the waste boiler’s interior passage, on the outside of its throat section? Or does it refer to the top space of the outer passage? Does slag hanging occur first on the lower connecting box?

Coking mainly occurs when slag accumulates on the water-cooled walls of the waste heat boiler; over time, this accumulation leads to the formation of coke-like substances. If the system is not operating stably, coking can occur in a very short period of time, within just one or two days. However, if the system operates steadily, the likelihood of coking is relatively low； The dead zone refers to the outer part of the laryngeal tube. Those who have different opinions are welcome to share their views.

In my opinion: 1. With the Texaco fluidized bed and liquid slag discharge, the occurrence of coking and slag accumulation is not due to a high furnace temperature, but rather to a low operating temperature, which results in poor flow of the slag and thus slag accumulation； 2. Changes in vaporization pressure lead to an increase in the pressure difference in the vaporization furnace. 3. Treatment method: First, determine whether there has been a change in the coal quality, which may have resulted in an increase in its FT value. Next, check whether the amount of solubilizer added is appropriate. Third, verify whether the furnace temperature reading is too high. For specific situations, analyze them in more detail.

I asked our supervisor today; the so-called dead zone should be the space between the outside of the second channel and the waste boiler shell, rather than just the area outside a single throat.

The reason for slag accumulation on the water-cooled wall may be: 1) The channels in the inner cylinder of the radial waste boiler are too small; slag particles disperse as the jet enters the radial waste boiler, but ash and slag accumulation occurs when the slag temperature is above 800°. 2) When the furnace temperature is controlled too high, far beyond the FT level, the slag in the radiant waste heat exchanger has not reached a low enough temperature to come into contact with or collide with the water-cooled walls, resulting in slag formation. This problem is most likely to occur in the area near the turning point, that is, in the region where the inner tube transitions to the outer tube annulus. What was said on the 9th floor is correct: when the type of coal changes, the operating conditions should also be adjusted accordingly. It is sufficient to control the furnace temperature to ensure liquid slag discharge; if it is too high, slag will form inside the waste heat boiler, resulting in a loss of thermal energy and a decrease in thermal efficiency! Therefore, it is very important to analyze the ash and slag of the feed water-coal slurry; the correct viscosity-temperature relationship must be determined before any decisions can be made!