Seeking advice on the regular drainage of chlorine buffer tanks
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This post was last edited by swl on 2020-3-22 at 15:04. Good morning, Haiyou (friend)! I have a question for my friends. Recently, safety experts came to our company to conduct a safety inspection, and one of the issues they raised was: \"There is a blind plug at the discharge outlet at the bottom of the liquid chlorine vaporization buffer tank.\" Waste is not discharged regularly. ”They are asking us to make corrections to this content. The basis for the rectification is as follows: “In accordance with Article 4 under Section III, ‘Safety technical requirements for the vaporization of liquid chlorine’ in the ‘Guiding Opinions on Safety Facilities and Emergency Technologies for Chlorine’ (China Chlor-Alkali Industry Association, Document No. 070 [2010]): A drain outlet shall be provided at the bottom of the buffer tank; periodic draining is required, and this drain outlet must be connected to an alkali solution absorption pool.” According to the \"Technical Requirements for Safe Use of Liquid Chlorine\" (AQ 3014-2008), 6.2.5.2: Buffers shall be equipped with pressure gauges, drain valves, safety valves, and pressure alarm devices; their installation shall comply with process requirements, and they shall be drained and cleaned regularly. ”2. Current status of the piping in the device: The liquid chlorine vaporization buffer tank takes in chlorine gas from the side, releases it from the top, and has a sewage outlet at the bottom; this outlet is currently sealed with a plug, and no regular sewage discharge is carried out. (At the beginning of the device’s operation, we carried out waste discharge as required, but no foreign substances were found during each discharge, so we stopped performing this operation later on. ) 3. Regarding the above matters, I have two questions I would like to ask my friends: A. Is regular waste discharge carried out for similar equipment in the industry? B. I would like to make an adjustment to the piping of the device: change the outlet for chlorine from the top to the bottom. The purpose of this adjustment is to change the flow pattern of chlorine gas within the buffer tank, preventing dead zones from forming at the bottom of the tank and thus avoiding the accumulation of foreign substances there. Is my idea feasible? If possible, is there any relevant technical support available? Please share your valuable opinions on the above issues as well, fellow sea lovers! Thank you all!
1. Regular discharge is necessary in order to remove NCl3, as NCl3 is prone to explosion; for more details, one can refer to the standards for liquid chlorine as well as the physical and chemical properties of NCl3； 2. Changing the exhaust to the bottom instead of the top is not recommended, as per your description, there may be liquid at the bottom of the carburetor buffer tank; in that case, exhausting from the bottom could lead to issues with gas-liquid two-phase flow
First of all, I’d like to express my sincere gratitude to “Dugu Lingyun” for his enthusiastic responses! I have two points to add here: 1. In my process, the chlorine that enters the chlorine buffer tank is superheated; its actual temperature is higher than the temperature corresponding to the saturated vapor pressure. Additionally, thermal insulation is provided around the chlorine buffer tank, which means that no liquid chlorine will form inside the tank ； 2. Since there is no liquid phase accumulated in the chlorine buffer tank, neither nitrogen trichloride is generated nor concentrated ； Given the above two prerequisites, I believe that after changing the outlet of chlorine from the top to the bottom of the buffer tank, regular drainage from the chlorine buffer tank can be eliminated. I would be grateful if fellow netizens could comment and point out whether my conclusion is sound! Thank you!
The safety experts argue that there is no waste discharge; even if the outlet is moved to the bottom, this does not change the nature of the waste discharge. From the experts’ perspective, this is equivalent to no corrective action having been taken.
Nitrogen trichloride is present in very small amounts in the gas phase; its boiling point is 71 degrees, so there’s practically no nitrogen trichloride at all. Regular discharge during production refers to that of the liquid phase. In actual production, no discharge has ever been observed from any storage equipment for chlorine gas.
I agree with you! The problem now is that in actual production, we do not drain the chlorine buffer tank; although this approach is \"reasonable,\" it still does not comply with the relevant standards (\"Guidelines on Chlorine Safety Facilities and Emergency Response Technologies\" [China Chlor-alkali Industry Association, 2010, Document No. 070]). Is there any reason that can be given to justify not performing this drainage?
There is no clear standard regarding whether gases emit pollutants or not
In my opinion, the discharge from the chlorine liquefied gas drainage tank should be done on a regular basis; as for the buffer tanks that use liquid chlorine directly, they should also be discharged. When gaseous chlorine is used, the temperature in the vaporizer is above 71 degrees, so there is no risk of nitrogen trichloride accumulation. Therefore, it isn’t necessary to have a bottom discharge outlet in those buffer tanks. The existence of such a bottom discharge outlet is mainly intended to facilitate the removal of impurities before inspections of pressure vessels or during regular cleaning procedures