Scrubber Crystals

[79teepak]

I hope someone could give me a lead here! I have read a lot of topics in this forum about the formation of carbonates through the absorbtion of Carbon Dioxide by Sodium Hydroxide.

At our plant we have 11 scrubbers. Two of those scrubber have the tendency to form crystals when the temperature outside drop below 40 F. The crystals form on the face of the packing material causing the air flow through the scrubber to decrease. Ultimately I begn to see H2S concentrations in the process area being to climb.

The air in the ventilation system is comprised of H2S, Ammonia, and CO2. Our scrubber solution used to scrub the H2S is 2-3% NaOH, 8-9% Carbonates, 7-8% Sulfides. I know that the crystals we are seeing are either Ammonium Carbonate or Sodium Carbonate.

Would this problem reduce if I started to remove the carbonates by chilling the scrubber solution? I have tried it in a lab and found that I was able to remove about 70% of the carbonates from the solution by separating the crystals from the mother liquer. Would the reduction by 70% be enough to curve this problem or would the kinitics be against me?

 

[bimr]

If you start removing carbonates from solution, you will cause the pH to drop and worsen the operating efficiency.

There are two possible solutions to your problem.

1. You can install a small heater to maintain the temperatur of the scrubber water. This will help to maintain efficiency of the process.

2. You can decrease the scrubber solution strength slighly to keep the carbonate in solution.

By the way, are you with Teepak? I thought they went out of business. I did a little work in the Teepak plant in SC.