Problems with the chlorate decomposition tank
Thread Content
Our factory’s chlorate decomposition tank has been having problems. Initially, the pump couldn’t draw in liquid properly; there was constant difficulty in pumping it out, and the pressure at the pump outlet fluctuated greatly. Later, it became necessary to add water at the pump inlet to cool the liquid before it could be pumped out. There was also an issue with low decomposition efficiency. Eventually, two titanium partitions were added to the chlorate decomposition tank (previously, there was nothing inside the tank). One partition enclosed the inlet where saltwater and acid were mixed, ensuring that the liquid could only enter the tank from below. Another partition was placed at the outlet, so that the reaction liquid had to rise above this partition before it could flow out. This solved the problem; the pump could now pump the liquid out due to proper pressure. However, when the flow rate of saltwater and hydrochloric acid entering the tank increased, pumping became difficult again. A return pipe with a DN25 diameter was then added at the pump outlet, connecting it directly back to the tank, which stabilized the pressure and allowed the liquid to be pumped out. Now we are seeking advice from colleagues as well as Huawei: 1. What is the structure of the chlorate decomposition tanks in your factory? Are there partitions, or is it a more complex design? Or is there nothing inside the tank, just a single vessel? 2. How can decomposition efficiency be improved? In our factory, we increase the amount of hydrochloric acid added to the tank, but this results in wasted alkali used for dechlorination. 3. Is there any reflux at the pump outlet of your chlorate decomposition tanks? We’ve found that reflux plays a significant role here; once the reflux valve leaked, the pump stopped pumping effectively, and the pressure at the pump outlet fluctuated greatly. 4. The gas phase from our decomposition tank is connected to the main chlorine pipeline, with a pressure of -1 KPA before the scrubber. When the reflux to the tank was turned off, the pumping performance deteriorated. When the reflux was turned back on, positive pressure appeared before the scrubber. Could it be that turning on the reflux improved the reaction efficiency, resulting in more chlorine being produced? 5. If what I mentioned above is true, could we increase the diameter of the return pipe at the pump outlet? This way, even without changing the amount of saltwater and hydrochloric acid added to the tank, more liquid could return to the tank for a second reaction. 6. The chlorate content at the outlet of the electrolysis tank is 6.8 G/L. The flow rate of saltwater in the decomposition tank is 7 cubic meters per hour, and the flow rate of hydrochloric acid is 750 L/h. The chlorate content at the outlet of the decomposition tank is around 0.7 G/L. How can this value be further reduced?
1. Personally, it seems that the use of baffle plates yields better results. 2. The factors that affect the decomposition of chlorates are mainly temperature, the amount of acid added, and the residence time in the tank; appropriate high temperatures, higher amounts of acid, and longer residence times contribute to better decomposition. The optimal parameters can be determined by adjusting these three factors. 3. It appears that the unstable pumping pressure is caused by air entrapment
This post was last edited by nanren2 on 2020-12-12 at 10:08. 1. Pay attention to the reaction ratio of hydrochloric acid and chlorate levels; the reaction will only be effective when there is more than 6 times as much hydrochloric acid present! 2. Currently, all chlorate decomposition tanks that use pumps for transportation suffer from this problem: severe gas emission! It can be solved by diverting the flow to D-280 or the chlorine tank!
Is titanium used as a material for chlorate decomposition tanks, and what is the corrosion situation after its use?
I’ve learned that when the pH is below 2, corrosion of titanium materials due to chlorates is quite severe. What’s the situation regarding corrosion after adding titanium plates?
The normal ways to decompose chlorates are raising the temperature within acceptable limits, extending the reaction time, and increasing acidity. The function of the baffle is, relatively speaking, to extend the reaction time and prevent the liquid from taking a short circuit; failure to pump in material is caused by gas entrapment. As the experts here have said, if one wants more decomposition without increasing the consumption of dechlorination agents, then the amount of acid should remain unchanged, while the flow rate of the brine and its temperature should be adjusted to find the most suitable parameters for the existing decomposition tank. The maximum amount of chlorate that can be decomposed can be calculated based on the analysis results. The height of the baffle also plays a role – increasing it can further enhance the decomposition effect. As for reflux, I think its main purpose is to remove gases
These are just my humble opinions; I hope they can help you. 1. What is the structure inside the chlorate decomposition tank in your factory? Is there a partition, or is it a more complex design? Or is there nothing inside the tank – just a container? Most manufacturers’ chlorate decomposition tanks do not have partitions; they only have distributors for feeding the material in. 2. How to improve the decomposition efficiency? At our plant, we currently increase the amount of hydrochloric acid added to the decomposition tank. However, this results in a waste of a large amount of alkali used for dechlorination. Yes, while an excess amount of acid improves decomposition efficiency, it also increases the amount of caustic soda needed for dechlorination. 3. Is there any reflux at the pump outlet of your chlorate decomposition tank? We’ve found that reflux plays a significant role here. Once the reflux valve leaked, the pump stopped pumping effectively, and there were large fluctuations in the pressure at the pump outlet. A reflux pipe at the outlet is necessary; the pressure fluctuations are caused by chlorine present in the brine, which causes air entrapment in the pump. 4. The gas phase from our decomposition tank is connected to the main chlorine pipeline. The pressure before the scrubber tower is -1 KPA. When the reflux in the decomposition tank was turned off, the performance of the pump deteriorated. When the reflux was turned back on, positive pressure appeared suddenly before the scrubber tower. Could it be that the reaction improved once the reflux was activated, resulting in more chlorine being produced? Turning on the reflux means less brine is sent out; this returning brine affects the liquid level and enhances mixing, thereby increasing the amount of chlorine produced in the decomposition tank. 5. If what was said above is true, could we increase the diameter of the reflux pipe at the pump outlet? By keeping the amount of brine fed into the tank and the amount of hydrochloric acid unchanged, more liquid from the outlet could return to the decomposition tank for a second reaction. However, this isn’t necessary. The valve opening for reflux also needs to be adjusted according to the liquid level in the decomposition tank; sometimes it’s necessary to close the valve completely to meet the pumping requirements. 6. The chlorate content at the outlet of the electrolyzer is 6.8 G/L, the flow rate of brine in the decomposition tank is 7 cubic meters, and the hydrochloric acid flow rate is 750 L/h. The chlorate content at the outlet of the decomposition tank is around 0.7. How can we further improve this? Apart from using an excessive amount of acid, you can improve mixing efficiency or reduce the pressure at the chlorine outlet