Discussion on the pressurization scheme for the slag lockhopper

Just use water pressure; I think it’s better than air pressure – firstly because the cost is lower, and secondly because heat can be recovered. Criticism and suggestions are welcome!

Grey water pressure is sufficient; I’d like to add what was mentioned on the second floor. The issue of using N2 for pressure application has not been studied yet. I’m thinking that if there is a leak in the inlet valve of the lock hopper, N2 will enter the vaporization furnace, which could affect subsequent processes. Additionally, N2 used for pressure application is likely to be high-pressure N2 – probably N2 that has been pressurized twice – and that would represent a waste of energy. These are just my personal opinions

If water is used for pressurization, the process is relatively fast. With N2 for pressurization, water is first filled to a certain volume, and then N2 is used to apply pressure; not much N2 is required, and even in the event of a leak, the amount leaked is small. In my humble opinion, the amount of leakage and energy consumption are within acceptable limits. I welcome any criticism or suggestions

It’s better to use water jetting; it seems that GE uses water jetting for this purpose as well. The effect is pretty good.

If water is used for pressing, the water that has been used can be recycled. But if nitrogen is used for pressing, has the person asking considered the issues related to recycling and costs?

If nitrogen is used for pressurization and the pressure is not fully reduced to atmospheric levels before discharging the slag, it is possible for the slag pool cover to be flipped over. It is strictly prohibited to discharge slag into the slag pool when there is pressurized gas present. Nanhua has experienced incidents where the slag pool cover was flipped over

In a Shell furnace, water is first filled to a certain volume, and then N2 is used to pressurize it; a small amount of N2 is required, and during the pressurization and depressurization processes, control is achieved through two pressure self-regulating valves.

The comment upstairs mentioned no reason – I’m not sure which option it refers to: is it no reason for pressurization with water, or no reason for pressurization with N2?

Locking punch stamping mostly uses hydraulic pressure; due to the low compressibility of water, the pressure is released into a flushing tank, which is equipped with a vent pipe. If N2 is pressurized, the key issue is that currently the pressure of N2 often does not match the pressure in the vaporization furnace. If the N2 pressure is too high, it needs to be monitored, but this monitoring can be delayed, resulting in excessive pressure on the lock hopper. Therefore, most current devices use water hammering; once the pump model is selected and the head is determined, the hammering force remains essentially constant. If the control level is high, and moreover the N2 pressure of the utility systems matches the gasification pressure fairly well, it is convenient to first fill the lockhopper with water and then use an N2 pipeline for purging.

At present, it is unrealistic to ensure no internal leakage in valves used for controlling powder media, whether they are ball valves, hemispherical valves, or track valves. Therefore, the approach of switching from water to gas requires careful consideration from various aspects. The feasibility of both options is beyond dispute; a decision must be made after taking into account safety, cost, and other factors. This is for reference only.

Using gas pressure when the lockhopper inlet valve is open can cause fluctuations in the level of liquid in the vaporizer, as well as backflow of the settled slag. Moreover, gas compression requires a high amount of energy.

Regarding the use of nitrogen to purge the lockhopper in the gasification furnace, I would like to point out two things: First, it causes changes in the composition of the gas, resulting in a higher proportion of inert gases. Second, when the lockhopper is emptied, it leads to fluctuations in the liquid level in the quenching chamber. Water has two advantages: 1) It can be reused, which not only allows for its effective utilization but also speeds up the emptying process and helps prevent blockages at the outlet. 2) The pressure of water is easy to control. If you want to discuss this further, please join group 62933919

The water supplied from the high-pressure graywater system can be used for flushing; it is used for flushing during the startup of the cooling water system, and it can also serve as a backup for high-pressure sealing water (for the lock-hopper circulation pump) for flushing purposes

Our company uses water pressure for inflation, which is quite suitable! ! ! High-pressure gray water and water from the cooling water pump are used! ! !

Lock-hammer punching mostly uses water for punching. Due to the low compressibility of water, there is little change in volume during either punching or pressure release, which has a minimal impact on the entire system. This makes it easier to operate and control the process. Moreover, systems typically use high-pressure ash water pumps for punching, and the pressure of these pumps is not very different from that of the gasification furnace, allowing for stable punching. Regarding the use of nitrogen for flushing, I don’t think it’s very appropriate. First of all, it’s not possible to ensure that the lock chamber is completely filled with water; using gas for flushing is a slow process. Additionally, there is the issue of leakage at the junctions between the gas and liquid pipelines. During pressure relief, if too much air is present in the lock hopper (this inevitably occurs during production since the hopper is not completely filled with water; it’s just a matter of how much air there is, as it’s impossible for the hopper to be completely filled with water), the released gas exerts energy that can have an impact, whether it is on the water used for flushing the lock hopper or on the slag tank. Therefore, gas ramming is not recommended. We have high-pressure nitrogen between the safety valve and the lockhopper outlet valve, with the aim of preventing bridging in the gasification furnace; usually, a blind plate is used to separate them!

The discussion was lively; as a follow-up, using nitrogen instead of water for pressurization can achieve higher quality control of the connections. The slag discharge pipe of the lock-hopper tank needs to be modified so that nitrogen is stored only in its upper part

Switching to nitrogen for pressurization of the lock cylinder: 1. Pressurizing with high-pressure nitrogen involves certain risks. During the operation of the lock hopper, there is a certain amount of gas space in the flow; as a result, the volume of compressed gas increases, which leads to greater impact force on the slag pool during slag discharge. 2. Pressurization with nitrogen is theoretically feasible, but gasification furnaces operating at different pressure levels require appropriate high-pressure nitrogen; sourcing such nitrogen presents difficulties, and the associated investment costs increase. 3. Nitrogen inflation increases consumption and thus raises costs. These are just my personal opinions; please feel free to offer criticism and suggestions.

Only the first point will be explained: slag discharge is carried out after pressure release, and there is no such thing as pressurized gas being discharged into the slag tank during slag discharge. That is, there is no need to use nitrogen for pressurization; as the slag and water in the lock hopper are discharged, gas will also be present inside the hopper!

You can give it a try. We are waiting for news of your victory.

Everyone, I’m new to this field, and I’m not sure about what the original poster meant by using nitrogen for pressurization. In my understanding, the purpose of pressurization is to make the pressure inside the slag holding tank equal to that in the quenching chamber; once these pressures are equal, the slag holding valve will open. So if nitrogen is used for pressurization, it will enter the quenching chamber, thereby causing fluctuations in its pressure. I’m not sure if I understand correctly; please advise!