How to discharge NCl3 from the liquid chlorine intermediate tank
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This post was last edited by sunjl1981 on 2013-1-6 at 20:12. Our company uses two 3-ton liquid chlorine intermediate tanks, and for filling purposes, we employ two liquid chlorine submersible pumps manufactured by Dalian Roland. The two intermediate channels are located in cement channels 1.5 meters below the ground level. (In other words, the two intermediate tanks are half above ground and half below ground.) The waste pipe is located at the bottom of the intermediate tanks and is designed for drainage; that is, the liquid chlorine discharged from these tanks is not specified to go anywhere in particular. When starting work, discussions were held with the design institute, and the designers said that there is no need for waste discharge at all during production! (We are an ion-exchange membrane caustic plant.) But what should we do when waste discharge is required? Where should this liquid chlorine be sent? The design institute won’t say. Some people say that when discharge is necessary, a caustic soda tank should be placed behind the pipe to discharge liquid chlorine into it. Some people also suggest digging a small alkali tank behind the sewage pipe and directing the waste there. I have four questions for the experts here: First, is it necessary to discharge waste water when using ion-exchange membrane caustic in production? Second, where should the scheduling be done? (Due to the extremely limited space at the bottom of the intermediate tank, not even a bowl can be placed there, let alone a bucket.) Can the waste pipe be connected to the waste drain? Can it get in? (The sewage trough is 1.5 meters above the ground level.) Even if the liquid can be discharged into the sewage tank, since liquid chlorine flows from lower to higher levels, could nitric trichloride accumulate partially in the sewage pipes, leading to problems over time? Regarding the design institutes, other than being angry at them, I have nothing else to say. Please help me think of a solution. Thank you all! # ， ， &
Based on the four issues you mentioned, here are my personal opinions: 1. There is no need to use a fixed waste discharge device. 2. If discharge is necessary, a temporary PTFE hose can be used, connected to the outlet valve at the bottom of the intermediate tank; a temporary container for alkaline solution can also be set up on the ground to absorb any remaining chlorine gas and nitrogen trichloride resulting from decomposition. 3. It’s not necessary to do this, unless the intermediate tank does not have a bottom valve. 4. Temporary pipelines will not present the aforementioned problems. As for why I think this way: The gas-liquid separator used for liquefying chlorine removes the vast majority of nitrogen trichloride, so by the time it reaches the intermediate tank, very little nitrogen trichloride remains. Therefore, there is no need for regular discharge of nitrogen trichloride. Since the pumps in the intermediate tank operate in a one-active-one-redundant configuration, it is necessary to discharge any remaining liquid chlorine and nitrogen trichloride from the bottom during pump maintenance and repairs. The generation of nitrogen trichloride needs to be controlled at the source; strict control is required over the water and raw materials added in various processes to ensure proper levels of total amines. There is no need for regular discharge from the intermediate tank. Moreover, since the intermediate tank is under pressure, if one insists on carrying out this process, it can be done anywhere on the ground – simply by drawing the liquid up through the bottom valve of the intermediate tank.
The design of a submersible pump is intended to remove nitrogen trichloride from the intermediate tank, as such pumps can stir the bottom of the tank (at a depth of about 300 mm). Nitrogen trichloride does not accumulate there, so there is indeed no need to worry about discharge issues.
There is no need to consider the discharge of waste from the intermediate tank NCL3. It is sufficient to drain the gas-liquid separator and the liquefier regularly once a week.
Normally, there is no need to discharge waste water, but the poster’s concerns are not unfounded. Our company’s approach is to use a small, movable alkali tank; when it’s time to drain the waste regularly, a hose is connected to the drainage outlet, with the other end placed inside the alkali tank. The time doesn’t need to be long; usually 5-10 minutes is sufficient.
The intermediate tank does not require regular sludge discharge, but this does not mean that there is no nitrogen trichloride at the bottom. Therefore, bottom discharge must be carried out during pump maintenance or major system overhauls in order to decompose the nitrogen trichloride, as well as chlorine and other substances, remaining on the bottom walls. The level of nitrogen trichloride in our chlorine is not high, but an explosion occurred in the intermediate tank during one pump maintenance session; at that time, water had been added to the tank and discharged (without using alkaline water as required), and the explosion was caused by electric sparks generated during welding work in the liquid chlorine storage tank.
There is no need to drain water from the intermediate tank; the submersible pump can remove nitrogen trichloride while it is in operation. It is unlikely for nitrogen trichloride to accumulate, so there is no need to worry. If you’re really worried, you can take care of it while servicing the submersible pump – just rinse it with water!
Submersible pumps are always in operation, which prevents the accumulation of nitrogen trichloride. In our workshop, the submersible pumps are cleaned during each major maintenance session.
Intermediate tanks generally do not require drainage; if drainage is necessary, it is best to connect them to the emergency tower. The sealing gas for the submersible pump also needs to be directed to the emergency tower. Chlorine liquors typically require regular drainage, as nitrogen trichloride tends to accumulate at the bottom of the evaporator.