Problems with water removal using hydrochloric acid

First, it is necessary to understand the difference between 50PPm and 300PPm. Without considering mist removal, the process of condensing water involves a gas-liquid phase equilibrium; in this process, the amount of water in the gas phase is calculated based on this equilibrium state. The operating pressure is considered to be the sum of the HCl partial pressure and the water vapor partial pressure. Generally, the acid concentration at this stage is around 40%, and using this value along with the operating temperature and pressure, it is possible to determine the maximum water content. For example, if the operating pressure is 40 KPa and the operating temperature is -15 degrees Celsius, then the water vapor partial pressure is 16.0119 Pa, resulting in a water content of 400PPm. After passing through the mist remover, this value is reduced to 50PPm. Currently, it is only possible to reduce the water content to 300PPm; it’s not likely that there is a leak in the condenser, as that would increase resistance. The problem most likely lies with the mist remover – it’s advisable to check whether its insulation is damaged, and it may be necessary to replace the filter element

I am a manufacturer of HCL gas analysis instruments, and I have encountered this problem as well. Currently, to measure the moisture content in HCL gas, weight measurement is commonly used, but this results in large measurement errors. Alternatively, laboratory analysis instruments can be used, but their readings are not accurate either. What we produce are online analysis instruments with a measurement precision of 0.1 ppm, 50 ppm, and 300 ppm. The analysis method plays a significant role in determining the accuracy, as does the analysis instrument itself. You might want to check whether such factors are responsible for the inaccuracies in your measurement data

You cannot use the vapor pressure equilibrium to calculate the water content in hydrogen chloride

So, are there any good solutions upstairs? :handshake

Just saying that on the 4th floor isn’t enough; I wonder how you think it should be calculated?

I just replaced the filter element of the demister recently, and its effectiveness has not yet been tested

Due to the strong binding ability between hydrogen chloride and water, if a proper demister is not used, the moisture content in the hydrogen chloride gas produced is generally higher than the actual value. The weight-based method is highly affected by environmental factors; it is best to use electrolytic or infrared online analysis instead

It is closely related to the efficiency of the condenser

Regarding the moderator’s separate view, I think that a demister is used to remove small water droplets from hydrogen chloride gas, not water vapor. In your example: with an operating pressure of 40 KPa and an operating temperature of -15 degrees, the partial pressure of water is 16.0119 Pa; at this point, the concentration of water is 400 PPm. After passing through the demister, this concentration is reduced to 50 PPm. ” It doesn’t seem quite accurate. This post was last edited by yunzhongwu6753 on 2008-10-14 21:32.]

My calculation is a conservative one; strictly speaking, it is based on the gas-liquid equilibrium of hydrochloric acid and hydrogen chloride. However, the actual production value is higher than the calculated value, as hydrochloric acid forms an \"aerosol\". So generally, it is calculated based on water, using the higher value. In this way, the composition of the gas entering the demister is determined, and then the filtration area of the demister is calculated sequentially.