Purity of hydrogen in the hydrochloric acid production process

The purity of hydrogen has decreased, with other gases being introduced, probably nitrogen and the like. But safety is the most important thing. These data need to be accumulated in large quantities during production

During the synthesis of hydrochloric acid, since combustion is used as the method, the purity of hydrogen is restricted by its explosive limit; moreover, the purity of chlorine at the time of ignition must not be lower than the upper limit of this explosive limit, which is 97.5%. This 97.5% refers to the amount of hydrogen contained in the air, with the impurity gas being air itself. Below this purity level, an explosion will occur during ignition. Therefore, what the original poster mentioned is not the main factor affecting the three-in-one furnace; the key issue is the explosion limit.

Reply to 3# huawei: Our factory uses hydrogen chloride furnaces to produce hydrogen chloride gas, which is then sent to the monomer production process. However, recently, while the hydrogen chloride furnaces were operating normally, the analysts reported that the purity of the hydrogen gas was low; the lowest purity level reached was 90.6%. How did you arrive at the conclusion that the purity of hydrogen must be no less than 97.5%?

The poster mentioned that the purity of hydrogen should be above 98%; does that mean the purity of chlorine in your case is also above 98%? In hydrogen chloride production, it is common to use an excess of hydrogen (at a ratio of 1:1.05–1.1), as using too much excess hydrogen is not economical. If the purity of hydrogen is too low, then, with the same ratio, it is easy to end up with an excess of chlorine. Moreover, three-in-one furnaces generally operate under negative pressure, which makes control difficult; if there are fluctuations in the pressure of chlorine and hydrogen, it is easy to have an excess of chlorine. Sometimes, too much chlorine can lead to explosions. Therefore, I believe that the purity of hydrogen should be kept high, at least on par with that of chlorine, in order to improve safety during production. Furthermore, a high purity of hydrogen is also beneficial for the efficiency of your upstream processes as well as for production costs. I’m not sure if what I said is correct

Reply to 5# wangxb198377: How did you arrive at the conclusion that the purity of hydrogen must be no less than 97.5%? Could you send me the calculation process? Thank you!

The original poster can try calculating using HCL’s reaction formula.

The requirement must be no less than 98%; otherwise, there is a risk of too much air, which can lead to an excessive amount of oxygen in hydrogen, posing a **risk. Moreover, the chlorine-to-hydrogen ratio is unstable, leading to easy over-chlorination

Agree with what was said above. The hydrogen purity is low. Sure, hydrogen with a high oxygen content is preferable; in our case, the oxygen content in hydrogen is generally less than 0.3. Therefore, the purity of hydrogen should be higher. It’s also beneficial for using units of gas later on.

This post was last edited by DaLangFeiSha on 2010-8-22 at 21:19. In the production of vinyl chloride, it is essential to prevent the level of free chlorine in hydrogen chloride from exceeding acceptable limits; otherwise, chloroacetylene may be produced, leading to explosions. During the synthesis of hydrogen chloride, the molar ratio of chlorine to hydrogen is 1:1. In normal production, the purity of hydrogen is 99% (containing some other gases such as N2, CO2, O2, etc.), but it must not be lower than 98%. An excess of hydrogen can reduce the purity of hydrogen chloride, and it is also not economical. On the other hand, too little hydrogen can result in low purity of hydrogen chloride as well as an elevated level of free chlorine, posing safety risks. In actual production, there is a surplus of about 0.05 in hydrogen.