〈Special Topic〉Discussion on Pulverized Coal Gasification Technology I: Is forced circulation or non-forced circulation better for the design of the gasifier water wall?

Personally, I think it depends on the structure of the water wall; if it is a coiled tube design, similar to that used in GSPs and space furnaces, forced circulation is preferable, as the pressure drop in such a coiled tube design is relatively high, and forced circulation helps ensure the safety of the coiled tubes. If it is a vertical tube array structure similar to that of Shell, it can be either mandatory or not; the key lies in the choice of process design.

The original poster’s question should be changed to: Is forced circulation of the coil better, or is unforced circulation of the vertical pipes better? As far as I know, German technologies such as GSP and Choren use coil-driven forced circulation; the coils in space furnaces, influenced by Shell, do not employ forced circulation instead, steam is generated directly within the coils. Personally, I think forced cycling is better.

I agree with what was said on the 3rd floor. In fact, the heat generated by the system can be reused in subsequent processes. It’s just that the process becomes longer, and the equipment costs might be higher, but forced circulation provides better protection; this is indeed the original purpose of designing water wall systems……

The advantage of forced circulation is that the circulation ratio can be controlled; in other words, the steam dryness at the outlet of the water wall in the gasifier can be regulated manually. This helps to protect the water wall, preventing individual tubes from overheating when there are significant thermal imbalances. But the downside is that forced circulation requires an expensive circulation pump, which increases energy consumption during operation; moreover, if the overall height of the gasifier is not large, special attention must be paid to the cavitation problem associated with the circulation pump. In order to ensure proper resistance matching among the various tubes of the water wall, hydraulic calculations are necessary, and throttle rings of different sizes must be installed at the inlets of each water wall tube. Natural circulation is simple; it does not require any additional energy to enable the endothermic phase change of water. It also possesses self-balancing capabilities: in tubes where more heat is absorbed, steam production is higher, the dryness degree is greater, the density difference between steam and water is larger, which results in a higher effective head and thus a greater water flow rate. Ultimately, in the entire water wall, the tubes that are subjected to greater heating have a higher flow rate, while those that absorb less heat have a lower flow rate. That’s its advantage. However, the problem with natural circulation is that the effective head that can be generated is limited. When there is high pipe resistance and the structure is complex, if the head generated by the density difference alone is not sufficient to overcome the circulation resistance, water circulation problems will arise. What remains has already been mentioned by everyone above, so I won’t repeat it here.

The ultimate goal is to protect the water wall; the advantage of forced circulation is that the circulation ratio can be controlled, which means that the steam dryness at the outlet of the water wall in the gasifier can be adjusted manually. The HT-L space coal pressurized gasification furnace uses forced circulation.

Forced circulation is good. Due to the high steam pressure generated within the water wall, it is sometimes not possible to supply water solely relying on the gravity of the water; this occurs in situations such as low liquid levels, unstable pressure of the deionized water, or substandard quality of the deionized water.

May I ask what forced circulation means? Is it something to do with applying pressure?

Is Fanfan’s nonsense useful or interesting? Technology exists to serve needs; first, consider the people you are dealing with. 1. Complex furnace and water wall (is the gasifier entirely made up of straight-tube panels?) ! ) 2.10 times the heat intensity of conventional boilers. 3. The furnace, which is under pressure and at high temperatures, has the water wall acting as a safety barrier. Based on these points, which circulation method should you choose? If you don’t understand the requirements, just knowing that there are differences between men and women and then asking whether men or women are better, or why women exist in the world – is that meaningful?

Add a water pump to apply pressure inward.