Measures to prevent blockage of the black liquid discharge pipeline at the bottom of the carbon scrubber tower
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Our plant has two black liquid discharge pipes at the bottom of the carbon scrubbing tower; one is located at the bottom of the conical section at the base of the tower, and the other is at three-quarters of the height of that conical section. After exiting these two pipes, the liquids merge into a main pipe that leads to the high-flash tank. During normal operation, both outlets of these pipes are open, but the pipe at the base of the cone is almost always blocked. This problem occurs mainly during the startup phase, and it remains blocked even after normal operation resumes, and it cannot be resolved. I would like to ask fellow sailors: What is the structure of the outlet at the bottom of the carbon scrubber in your factory? Has there been any blockage, and how was it dealt with?
Both the cone bottom and the bypass lines are equipped with manual valves. First, ensure that during shutdown for maintenance, both the main and bypass lines are fully unobstructed. Second, during normal operation, the bypass line should be closed to ensure that the black water flows through the cone bottom; otherwise, if the bypass line is used primarily, the cone bottom will inevitably get clogged, and when shutting down next time, the entire cone bottom will be filled with slag. Third, at the beginning of feeding, the pipelines leading to the vacuum system must be unobstructed, so that any scale that forms due to temperature changes in the pipes won’t accumulate at the cone bottom
However, at the beginning of operation the carbon scrubber has no pressure, and the black water pipeline at the bottom of the cone remains stagnant; this makes it impossible to prevent ash from accumulating at the bottom, which inevitably leads to blockage there
If they’re all opened, if not you then who will block it?
During maintenance, ensure that both pipelines are unobstructed; open only the manual valve on the cone-bottom side. After feeding the material, increase the external drainage volume, and ensure that there is a continuous flow of wastewater during normal operation.
The design is basically the same in all cases. Our plant also suffers from frequent blockages. Each time, we increase the drainage volume after feeding materials in order to reduce the shedding of scale particles due to thermal vibrations, which could otherwise cause blockages in the drainage pipes. Additionally, before feeding materials, we drain water from the carbon scrubber tower into sewers or slag ponds. It is risky to switch to operational mode once pressure is increased after starting the feeding process.
The design of the equipment is basically the same, especially GE’s technology follows such a design approach. However, it depends on specific circumstances to determine which setup is better. For coal types with particularly high ash fusion points that require the use of fluxes, both the total hardness and total alkalinity of the black water and ash water are high; even with scale inhibitors in place, scaling still occurs over time. If the black water discharge pipeline at the bottom of the cone of the scrubber tower is used, there are no issues during the initial operation phase. But after a short shutdown and subsequent restart, scaling occurs due to differences in thermal expansion coefficients, and the scale easily breaks off. Large pieces of scale can easily block the black water discharge pipeline at the bottom of the cone. In such cases, it is necessary to use the black water discharge pipeline located at 3/4 of the way down. The design of the cone at the bottom of the scrubber tower itself also helps to trap scale deposits. Therefore, I believe that as long as the upper black water discharge pipeline remains unobstructed, it should be sufficient.
I’ve learned it, thank you all! ! !
It should be okay to use a pipe connected to compressed air or steam for backwashing; it can be tried as long as it doesn’t affect the main processing process
It generally follows this structure; the conical bottom of the water wash tower tends to get clogged during startup and shutdown, mainly due to scale fragments falling and blocking the bottom of the cone. When the system pressure is only a few kilograms while the machine is stopped, it is possible to open the bottom of the cone-shaped section in order to drain waste fluid. During complete shutdown for maintenance, it is necessary to enter the water washing tower to remove scale deposits, cleaning both the bottom and the walls of the tower of such deposits. During normal operation, it is best not to open the outlet at the upper part; instead, let the water from the scrubber tower drain preferentially through the bottom of the cone. This is because the resistance at the upper outlet is lower and flow is smoother compared to that at the bottom of the cone, so the water drains mainly through the upper outlet. The flow velocity at the bottom of the cone is slower, and when the flow velocity there is low, blockages are more likely to occur. Finally, during the operation phase, the self-regulating valve of the drainage pipeline of the water scrubber is opened periodically to carry away the slag at the bottom of the cone
This shouldn’t work in normal production, right?