I have a question for everyone: what is the scientific formula for calculating the dosage of dispersant in the ash and water treatment system for Texaco’s coal-to-gas process?
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I would like to ask: what is the scientific formula for calculating the dosage of dispersant to be used in the ash water treatment system for Texaco’s coal-to-gas process? Our plant operates in a two-unit operation with one unit on standby; the amount of ash water generated is around 420 T/H, and the amount of water added to compensate for this loss is also about 50 T/H. If I want to set the dispersant dosage at 80 ppm, then how much ash water dispersant do I need to add per day? (The solid content of the dispersant is 28.5%) Also, it seems to us that the structure of the graywater pipelines in our plant is problematic. In 2015, the average calcium ion level in the graywater was 920, the turbidity was 44, the suspended solids level was 29, the conductivity was 3950, and the hardness was 1010. I don’t think these values are particularly bad for a Texaco graywater system; then why is scaling so severe? Could it be due to insufficient amounts of fresh water being supplied? I would like to ask everyone whether there is a healthy range of values for calcium ions, conductivity, and hardness in similar devices. Thank you all!
If the dosage concentration of the dispersant is 80 ppm, the daily dosage is approximately 800 Kg. The dosage in the graywater system is calculated based on the circulation volume. Based on the graywater quality results you provided, the turbidity and suspended solids are not high, but the calcium hardness is somewhat high. Scaling is much more difficult to control. What is the total alkalinity of the graywater? The formation of scale may be due to issues with the chemicals used, or it could be a problem related to the quality of the graywater. It is recommended that you send over the water quality report for your facility’s graywater.
Thank you for your response. The total alkalinity of the graywater ranges between 480 and 510. I have compared the levels of calcium ions, magnesium ions, and hardness in this graywater system over the past three years, and these values have been increasing steadily each year. Could this be due to some issue with the process, such as excessively high process temperatures? Or, if there is a change in the type of coal, in such cases it is possible that the calcium ion concentration exceeds the limit of the scale-inhibiting capacity of the dispersant; in this case, the dosage of the chemical can be increased, or more directly, the volume of water discharged and added to the ash-water system can be increased (but this option cannot be used due to the processing capacity of the SBR treatment tank). Another thing I would like to ask is: for the graywater systems using Texaco technology, what level of calcium ions is considered healthy? Thank you again!
Total hardness is constantly changing, mainly depending on the type of coal used, the amount of water added, and the gasification conditions. If the total alkalinity is around 500 ppm, the sum of calcium hardness and total alkalinity can reach as high as 1400 ppm, which is indeed difficult to control. But dispersants are generally added in large quantities, so there should be no problem. If scaling is severe, there is likely an issue with the dispersant; you can contact the chemical supplier directly.
What is your typical alkalinity level?