Regarding the vaporization temperature of liquid chlorine
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Regarding the specifications for the vaporization temperature of liquid chlorine, I am aware of the following three: 1. According to clause 5.3.2 of GB11984—2008 \"Safety Regulations for Chlorine Gas\", when using the liquid chlorine vaporization method to feed liquid chlorine into storage tanks, it is necessary to strictly control the pressure and temperature of the vaporizer. The liquid chlorine vaporizer should be heated with hot water, not with steam; the temperature of the water entering the vaporizer should not exceed 40°C, and the vaporization pressure should not exceed 1.0 MPa. 2. According to 5.1.6 of AQ3014—2008 \"Technical Requirements for Safe Use of Liquid Chlorine\", open flames or steam should not be used to directly heat the gas cylinders; warm water at a temperature below 40°C can be used for heating. 3. China Chlor-Alkali Industry Association (2010), Notice No. Xie Zi 070 regarding the issuance of the \"Guidelines on Safety Facilities and Emergency Response Techniques for Chlorine\": It is recommended to use a coil-type or sleeve-type vaporizer for the complete vaporization of liquid chlorine; the vaporization temperature of liquid chlorine should not be lower than 71°C, with a recommended control temperature for hot water of 75–85°C. A special vaporizer (steam-heated) is used, with the temperature not exceeding 121°C. The vaporization pressure is under interlocked control with the feed control valve, while the vaporization temperature is under interlocked control with the steam control valve. ” After synthesis, the following questions arise: 1. When unloading liquid chlorine using a vaporizer, the temperature of the hot water should not exceed 40°C, whereas in processes that use chlorine vaporizers, the temperature of the hot water should be no less than 71°C. I’m not sure if my understanding is correct 2. As for the validity of the regulations set by the Chlor-Alkali Industry Association, our company’s internal experts believe that national standards are higher than those of the association; therefore, the temperature of the hot water in the vaporizer should be in accordance with national standards, not exceeding 40°C, and not based on the standards set by the Chlor-Alkali Association. And during the review of the safety section, the experts asked which temperature should be used – that of the Chlor-Alkali Association or another? 3. Why is the temperature in the chlor-alkali association so high? Is it related to the vaporization of nitrogen trichloride? Some say it is to vaporize nitrogen trichloride and prevent its accumulation. However, 71°C is its boiling point at standard pressure; in our normal processes, chlorine is used under pressure, and its boiling point is higher than 71°C, so nitric trichloride does not vaporize. Why has the Chlor-Alkali Association set this temperature so high? I also searched the forum for similar posts from 2018, but no conclusions were reached in those discussions; I’m quite confused. I earnestly ask the experts to help clarify this: handshake
The vaporization temperature is determined based on the properties of nitrogen trichloride; this is done to ensure safety by guaranteeing that all of the nitrogen trichloride vaporizes and does not accumulate. It should be 75-85, regardless of what you use it for.
When heating the liquid chlorine cylinder, use water with a temperature below 40°C； For devices equipped with a vaporizer, the temperature of the hot water circulating within the vaporizer is controlled at 75–85 degrees℃
Could you please explain why it should be 75–85°C?
It is recommended to keep the temperature of hot water at 75–85°C. If the water temperature is even higher, it begins to vaporize gradually, generating gas, which has a certain impact on the equipment as well as on the heat exchange efficiency – that’s my personal opinion
Nitrogen trichloride has a boiling point of 71°C at normal pressure; however, the vaporization pressure in most processes is not at normal pressure. For example, in my case the vaporization occurs at 0.2 MPa, and at this pressure the boiling point of nitrogen trichloride is around 110°C. In other words, the vaporization temperature lies between 75–85°C, and under such conditions nitrogen trichloride will not vaporize
It’s not very meaningful to worry about this; what’s mentioned above is just a suggestion. When the operating conditions change, the parameters also change. As for nitric trichloride not vaporizing under these conditions, you can use methods such as waste discharge or other alternatives.
To ensure that nitrogen trichloride can be completely vaporized, the temperature must be at least 71℃
If it were pure NCl3, it certainly couldn’t be vaporized at 0.2 MPa and 75°C; but this is a mixture. As you can see, the dew point corresponding to 0.2 MPa is definitely below 75°C, so it can be completely vaporized