Control of P-274 pressure after shutdown of the Kitakika Seiki or Asahi Kasei zero-gap electrolyzer

I don’t seem to have heard of any problems with this. The sump itself has an overflow pipe, which can also increase the backflow. Parking in a single slot has not a particularly large impact on the system.

When all the cells stop operating, and FCV-232 is turned off or its flow rate is reduced to the minimum, the level in D-273 (the alkali sump) rises rapidly. The level control valve for this tank then closes quickly, which results in an increase in the outlet pressure at P-274! D-273 has an overflow pipe leading to D-270, but overflow can easily cause fluctuations in the gas phase pressure!

Is the upper floor controlled by valve 88#? Has 88# been changed to an automatic valve? If it has been changed to an automatic valve, how is it configured on the DCS?

After the cell stops operating, as required by Asahi Kasei’s operating procedures, the flow rate of the alkali solution entering the cell is reduced. As a result, the level of liquid in D-270 rises sharply, and the flow rate at the outlet of pump P-274 reaches its maximum value; the pressure in the pipeline at the pump’s outlet also increases to its maximum level. Pipelines that have been in use for a long time may experience leaks in their seals. I don’t think there’s any good solution to this problem. In my opinion, it would be advisable to replace the gaskets regularly every two or three years and install splash guards between the pipeline flanges (by wrapping the flanges with a piece of metal). Moreover, this kind of situation doesn’t happen very often; if it does occur, then one can only consider it bad luck.

We encountered a similar situation before: when there was heavy overflow during emergency shutdown at D273, the pressure difference fluctuated. Later, we installed an inverter on motor P274, and the DCS could directly control the inverter to resolve the issue

Variable frequency is also a good option, but after consideration it was abandoned because motors equipped with variable frequency drives tend to stop operating when there are power fluctuations in the grid

I actually have a plan, but I lack the experience and practical evidence to implement it; please help me review it! Add a pneumatic valve at valve 88# so that when all the electrochemical cells stop operating, while all FCVs-232 are commanded to close, the DCS locks it in an open position at a certain degree! Alternatively, another flow meter can be added at valve 88#, and on the DCS a configuration can be set such that the value of the new flow meter plus the FCV of all electrolyzers minus 232 equals a certain value; an additional pneumatic valve can then be used to automatically adjust the flow rate to maintain this value! Please first share how your own device adjusts its operations for such situations Then share your thoughts on the above plan!

This solution is also feasible, but it requires high skill from the operators, and mistakes are likely to occur due to stress in the event of an accident. He went outside and took out what was at the bottom of the box: pumps equipped with frequency converters are a source of concern in summer, as they tend to trip easily. At that time, there was another good solution: when installing another set of systems, we followed Woody Company’s design by changing the manual valve that allowed fluid to flow back from outlet P274 to pipe D270 to an automatic valve, and implemented pressure interlock control between the DCS and the pump outlet, which proved to be very effective. That is, there are two control valves at the P274 outlet: one is used to regulate the level of liquid in D270 outside the system, while the other is used to control the pressure at the pump outlet. No level control valve is needed for D273; the overflow volume in D273 is maintained by controlling the pump outlet pressure, which ensures great stability.

Those of you who use Asahi Kasei and Kitakika please share your opinions! ! ! ! ! !