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FREQUENTLY ASKED QUESTIONS
1. Where do I buy the absorbent chemicals and what do they cost?
CANSOLV absorbents are supplied by CTI. The initial fill of CANSOLV SO2 amine for a power plant will cost roughly $3 per installed kW.The initial fill of CANSOLV NOx-Mercury solvent will cost between $1.25 and $2 per kW, depending on operating parameters. Approximately 10% to 15% of the solvent volume will need to be made up each year.
2. What are the principal operating costs of the Cansolv Multipollutant Process?
In the SO2 portion of the process, the biggest cost component is low pressure steam. In a typical application, the CANSOLV unit will condense between 5 and 8 percent of the steam in the power cycle at low pressure. The net impact on the power cycle will be between 1.4% and 2% of power production (less if the cycle is condenser capacity limited). Steam consumption for NOx-Mercury regeneration is about 10% of the SO2 process.
Total pressure drop across a CANSOLV Multipollutant unit will be in the order of 18 inches of water (10 inches for prescrubber / SO2 and 8 inches for NOx-Mercury) so adequate fan capacity is required.
3. Are particulates a problem for the CANSOLV process?
Particulates need to be designed for in a Cansolv unit.CANSOLV units make use of structured packing to maximize mass transfer performance and adequately stage the SO2 and NOx - Mercury absorption process. If the feed gas contains more than 30 mg/Nm3 particulates, the prescrubber will be designed to provide additional particulate removal to meet the requirements.
4. Does a Cansolv unit require special abrasion or corrosion resistant materials?
The Cansolv Multipollutant process operates exclusively in liquid and gas phase so abrasion does not occur. For corrosion resistance, 316L stainless steel is the most suitable alloy for the SO2 and NOx-Mercury tower sections (pH>5). FRP may also be used for these sections given the relatively low temperatures and lack of abrasion. For the prescrubber section, a concrete shell and corrosion liner design is recommended as the pH drop to 1 depending on the concentration of strong acids in the gas (Cl, F, SO3).
5. What happens to chloride, fluoride and other strong acids in a Cansolv Unit?
Strong acids will for the most part be removed in the prescrubber. The rate of removal will depend on the prescrubber design criteria. These acids will leave the unit in the prescrubber blowdown and can be neutralized with caustic in a water treatment step. The strong acids that slip into the CANSOLV SO2 section will be removed in the amine purification unit and will not affect the solvent’s efficiency in SO2 capture. The amine purification unit will be designed for this.
6. What byproduct purity can be expected from the CANSOLV multipollutant process?
Particulates, ionic metals and strong acids from the flue gas that are captured by the CANSOLV SO2 solvent are not released from the solution when it is regenerated. The byproduct SO2 from the CANSOLV process is therefore 99.99% pure on a dry basis withtraces of oxygen, nitrogen and carbon dioxide making up the difference. Sulfuric acid made from the byproduct SO2 will be correspondingly pure.
7. How should a utility manage the market risk created by selling a chemical byproduct?
To manage the risk of interruption in the byproduct offtake, CTI recommends installing an alkali metal (calcium or sodium) backup neutralization system. This will allow temporary uncoupling of boiler operations from the byproduct production.
8. Can CANSOLV processes be used for IGCC (gasification) emissions control?
CTI is an ideal solution for emissions control from IGCC sulfur plants.When properly integrated, Cansolv SO2 tail gas scrubbing can be used to reduce inert load through the sulfur plant and avoid unwanted CO2 recycle. A CANSOLV SO2 tail gas unit can also value engineering flexibility for gasifier AGR design.
