Alkali concentration used in the liquefied gas refining system
Thread Content
What is the concentration of the alkali solution used in the liquefied gas refining system? During operation, when the concentration of the alkali solution drops, it is necessary to remove some of it and then add more to the system. Since the amount of alkali solution that can be removed is limited, the concentration of alkali in the system remains low. We add 30% concentration alkali solution to it, but some companies say that adding 30% concentration alkali solution can easily lead to crystallization. How do you proceed in your operations?
We keep the concentration of the alkaline solution at 25%; it’s generally not advisable to use a too high concentration as this can cause crystallization and blockages.
With heat tracing, will crystallization still occur even at higher temperatures?
Our alkali solution used to be heated by steam, but that method is no longer in use. Do you use hot water for heating?
The fresh alkali solution we use is 30% concentration; we ensure that the alkali concentration remains at least 12%, while the prepared alkali solution has a concentration not exceeding 20%. Alkali should be prepared frequently, as high concentrations can lead to crystallization, and the resulting alkali residue can clog pipes
What is the standard for changing the alkali? Is it based on concentration or time?
It depends on the sulfur content of the raw materials processed in one’s own factory; we keep the concentration of our alkaline solution below 10%, and as a result, our products are generally of satisfactory quality. If the concentration reaches 30%, there is a risk of alkali embrittlement in the equipment and pipelines, and the lower the concentration, the higher the temperature at which alkali embrittlement occurs. That’s why it’s wise for many factories to use hot water for heating purposes.
When replacing the alkali, one factor to consider is the concentration, which should generally be no less than 10%. Another factor is the concentration of sulfides in the alkaline solution; this varies depending on the type of equipment used, the sulfur content of the materials, and the requirements for the final product – there is no uniform standard. Each workshop determines this value based on its own experience. Additionally, the color of the solution matters: if it turns black, starts to smell bad, or appears viscous with particles present, it is necessary to replace it immediately
We used to specify that replacements should be carried out when it reached around 5%, but I personally think that’s a bit low
What is the sulfur content of the raw material? What is the processing capacity? Is the alkali solution replaced frequently?
High concentrations within the system can easily lead to crystallization; adding 30% alkaline solution does not mean that the alkaline concentration in the system is 30%. Alkali solution replacement is determined based on concentration, not time; this is because the sulfur content of the raw materials used in processing varies, and as a result, the sulfur content in the liquefied gas also varies