The impact of chlorine quality on the production of chlorinated paraffins
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Our factory produces paraffin chloride-52. In the past, liquid chlorine was transported from chlor-alkali plants using tank trucks or cylinders, and there were no issues with that. Recently, the newly installed liquid chlorine storage tank has been put into use; the liquid chlorine from tank trucks is first unloaded into this tank before it is used. During unloading, the storage tank needs to be depressurized, and the gaseous chlorine in the tank is sent to the workshop for reaction. During pressure relief, the reaction between chlorine gas and liquid wax does not occur effectively; the material mixture takes on a yellow-green color, the reaction temperature drops, and yellow-green gas can be seen in the exhaust gases – this is likely unreacted chlorine gas. And liquid chlorine in the storage tank can be used without problem after being vaporized. I earnestly request the help of all expert teachers to resolve this issue. Thank you :)
It is possible that during unloading (pressure release), the amount of vaporization increases (normal vaporization plus vaporization that occurs during feeding), which leads to an increase in the chlorine flow rate. There isn’t enough time for a reaction to take place, and the liquid appears yellow-green; the increased exhaust gas contains yellow-green-colored fumes that can be seen. The drop in temperature is due to an excess of chlorine in the reactor, with increased evaporation carrying away heat.
Thank you for your reply. In actual production, the vaporization of liquid chlorine is halted during pressure relief; only the chlorine gas used for pressure relief is utilized. An automatic control valve is installed in front of the buffer tank to regulate the chlorine gas pressure, so there is no risk of an excess amount of chlorine gas. Furthermore, the tank has been in use for several months and has had its pressure relieved multiple times, which rules out the possibility of air being present in the newly installed pipes.
It’s likely that the nitrogen and oxygen content in the liquid chlorine is high (the liquid chlorine might pass testing). When the liquid chlorine is unloaded, most of the nitrogen and oxygen ends up in the gas phase, at levels much higher than those in the liquid phase. As a result, the dechlorination process in the gas phase leads to a reduced reaction rate; in particular, the presence of oxygen prevents the formation of free radicals, causing the chain reaction to stop and the temperature to drop. A large amount of chlorine gas does not react and escapes into the gas phase, or it dissolves in the product (giving it a yellow-green color). Now you know how to solve this problem, right?
Thank you for your help. The presence of oxygen in chlorine does indeed inhibit the chlorination of paraffin, but there shouldn’t be much oxygen in liquid chlorine. Other sources state that chlorine dioxide and sulfur dioxide can affect the chlorination reaction; however, due to the lack of appropriate testing facilities in our plant, we are unable to determine the exact cause at this time.
Whether it is chlorine dioxide or sulfur dioxide, it is due to the presence of oxygen; the reason is quite simple
The poster can contact the tank truck filling unit (the upstream chlor-alkali plant) to find out what method is used for filling their tank trucks (submersible pump, vaporization and pressurization of liquid chlorine, air compression, nitrogen compression, etc.), so as to further analyze the cause.
Is there nitrogen in the storage tank? Nitrogen has an inhibitory effect on the reaction.
……This is a post from a few years ago, but the cause has still not been identified… There is no nitrogen in the storage tank; unloading is carried out by vaporizing liquid chlorine to pressurize the tank truck, while loading at the chlor-alkali plant is done using pumps… I visited the chlor-alkali plant as well but was unable to find the cause… There is no problem with using the vaporized liquid chlorine; it’s just that when the gaseous chlorine at the top of the liquid chlorine storage tank is released, it enters the chlorination reactor. If the release time is a bit longer, it becomes evident that the reaction absorption is poor, and the residual chlorine in the exhaust gas appears green-colored. This effect is mainly noticeable in the chlorination reaction of liquid wax… The measure taken now is to reduce the release time, by doing it multiple times over a short period of time :)