The issue of ammonia-to-carbon ratio in the CO2 stripping method
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Our plant has a CO2 stripping unit with an annual production capacity of 300,000 tons, and we have the following questions for everyone’s assistance: 1. The CO2 flow meter is inaccurate; when the load is increased, the pressure at the output of both compressors is 170 KPa (the designed capacity of the compressors is 10,480 standard cubic meters, and the flow rate of urine going into the tower remains around 38 tons). How can we use these data to calculate and determine the accurate load? 2. Under a load condition where the outlet pressure of the two compressors is 170 KPa, the frequency conversion drive for the liquid ammonia pump is typically set at 62%, while that for the ammonium methylate pump is around 56%. The flow rate of liquid ammonia indicated by the pump is 20.8 T. Based on the ratio of 1000 cubic meters per unit volume to 2.4 cubic meters of ammonia, it seems to me that we might be adding too little ammonia; however, judging from the analysis results and the system’s temperature and pressure, it appears that there is enough ammonia present
Judging from the system temperature and analysis data, it’s even easier as long as you get it right.
I’d like to add that when two compressors are in operation, the output pressure is 170 KPa; each compressor alone also has an output pressure of 170 KPa
It should also be added that if the CO2 flow meter is inaccurate, what good methods do you have for determining the load?
Your situation is similar to ours; it’s fine as long as the temperature of the entire system remains within the specified range. Our feed N/C ratio is around 2.8, and after discharge, it drops to about 1.85. If we use a feed N/C ratio of 2.05, it would be excessive. If your flow meter is inaccurate, you can calculate the amount of CO2 by reversing the calculation based on the NH3 added theoretically; for N/C, a value of 2.05 can be used. When the flow meter is inaccurate, it is necessary to rely on various indicators and analysis data from the high-pressure system to make judgments. However, the composition should not be severely out of balance, as this makes it very difficult to make adjustments. In such cases, it may be necessary to shut down the high-pressure system for discharge and then restart it, provided that the amount of water added remains unchanged. In this way, it is possible to determine with high accuracy whether N/C is too high or too low
The production load of the CO2 stripping process unit is primarily calculated based on the amount of ammonia fed in. It is difficult to obtain accurate values for the N/C ratio of the fed material due to various interference factors during production; however, analysis data from the high-pressure system can provide a more accurate value for the synthetic N/C ratio.