Some thoughts on quenching water~··
Thread Content
For many enterprises, the water used for cooling is generated through a process that involves black water – gray water – deoxygenation pumps – scrubbers – and gasification furnaces. Relatively speaking, the amount of water discharged from the scrubbers is small; most of the sludge is removed in the gasification furnace. So, is it possible to supply deoxygenated water directly to the gasification furnace? A smaller pump can be used for venturi washing in the scrubbers, with the water supply to the scrubber trays being greater than the amount of water discharged from them. In this way, the water temperature in the gasification furnace is lower, resulting in a better quenching effect, and the water in this area is also cleaner·
This setting is unreasonable. (1) It is better if the temperature of the water entering the gasifier is as high as possible, as this is beneficial for both the equipment and energy consumption ； (2) The venturi tube is also a very important washing device; reducing its water flow rate will result in a higher level of carbon black in the process gas, which affects the shift catalyst.
In fact, there are pipes as mentioned by the original poster that supply deoxygenated water directly to the gasification furnace; they are used only when there is a problem with the quench water pump. The temperature of the water entering the gasifier is much lower and it is also cleaner. However, as a multi-stage centrifugal pump, the deoxygenation water pump is expensive to purchase; fluctuations in water volume can cause significant variations in current levels, as well as pressure fluctuations. Such fluctuations are common in systems involving slag injection. Since the cooling water needs to be stable, I believe it is better to use a separate cooling water pump. Personal opinions are not necessarily correct; please feel free to offer plenty of criticism!
If the water temperature entering the vaporizer is too low, it will affect the water vapor
1. The water supply volume for the wash tower trays should not be too low; it is necessary to ensure effective cooling and dust removal of the process gas. Additionally, considering the accumulation of dust on the wash tower, a large amount of water is required for cleaning. 2. When the water volume in the scrubber increases, it needs to be discharged externally; excessive discharge of this wastewater requires higher requirements regarding its flash point ； 3. It is necessary to ensure an adequate amount of quenching water, while also maintaining a high level of water vapor in the process gas. So the current process is the most logical one.
I am not in favor of this change. My reasoning is as follows: 1. The syngas exiting the washing tower requires a certain water vapor ratio, which is beneficial for the operations in subsequent stages; changing this ratio will disrupt that balance. 2. The water film in the downcomer requires a large amount of quenching water, and transporting it from low pressure to high pressure increases both the operational complexity and energy consumption. 3. When cold water enters the quench ring and downcomer, heat exchange with the high-temperature syngas becomes more intense, having a greater impact on the downcomer. 4. Water carryover in syngas is inevitable; if this is changed, severe water carryover will cause fluctuations in the liquid level in the scrubber, thereby increasing the operational difficulties. 5. Also, as mentioned above, if the water supply to the scrubber tower is too low, it will not be possible to ensure an effective cleaning of the syngas. Please feel free to offer your criticism and guidance if there are any mistakes.
I learned a lot of knowledge; I originally thought the same way, hoping that the water entering the quenching loop would be cleaner. It seems that this isn’t possible