Claims
- 1. A process for treating fly ash found in flue gas to produce effective fly ash electrical resistivity comprising employing an algorithm to determine the optimum amount of sulfur trioxide (SO3) to be added to the flue gas.
- 2. The process of claim 1 wherein the sulfur trioxide results from the burning of coal.
- 3. The process of claim 1 wherein the sulfur trioxide results from the burning of coal plus the extrinsic addition of sulfur trioxide.
- 4. The method of claim 1 wherein the algorithm takes into account 1) flue gas SO3 concentration, 2) initial fly ash resistivity, 3) electrostatic precipitator (ESP) current densities, 4) flue gas temperature and moisture and 5) fly ash composition.
- 5. A process for treating fly ash found in flue gas to produce effective fly ash resistivity comprising the following steps:
Step 1. Obtain the proximate ultimate analyses of coal being burned in boiler and ash mineral analysis for this coal, Step 2. Determine the average temperature of flue gas entering the electrostatic precipitator (ESP), Step 3. Estimate SO3 background level in the flue gas using correlation relating flue gas SO3 to coal type and coal sulfur content, Step 4. Calculate the base ash resistivity using empirical equations relating ash resistivity to ash composition, flue gas moisture and flue gas temperature, Step 5. Use a correlation relating the base fly ash resistivity and flue gas SO3 concentration to determine the flue gas SO3 concentration needed to produce the optimum fly ash resistivity, Step 6. Subtract the background SO3 concentration from the needed SO3 concentration from the needed SO3 that must be added to the flue gas to produce the optimum fly ash resistivity, and Step 7. Send rate of addition signal to the controls that operate the SO3 conditioning system.
- 6. A method for determining a most effective injection rate for SO3 into flue gas comprising the following steps:
Step 1. Obtain the proximate and ultimate analysis of the coal being burned in the boiler and the ash mineral analysis for the coal, Step 2. Determine the average temperature of the flue gas entering the ESP from plant instrumentation, Step 3. Estimate SO3 background level in the flue gas using correlation relating flue gas SO3 to coal type and coal sulfur content, Step 4. The secondary current applied to the electrostatic precipitator is obtained from the controls for each transformer-rectifier set that is powering the precipitators, Step 5. Determine the effective fly ash resistivity level in the ESP using a correlation that relates fly ash resistivity to ESP current density for each electrical field, average the results to produce an effective resistivity for the ESP. Step 6. a. If indicated ash resistivity is equal to or less than optimum resistivity, decrease rate of injection by x percent where x is between 5 and 25, or
b. if indicated ash resistivity is greater than optimum resistivity, increase rate of injection by x percent where x is between 5 and 25, Step 7. Repeat Step 6 until indicated fly ash resistivity passes through optimum resistivity point and then set rate of injection at a point in the range bounded by the levels calculated in the last two interactions, and then Step 8. Every y minutes, where y is number between 5 and 30, restart the process beginning at Step 2.
- 7. A method for determining a most effective injection rate for SO3 into flue gas comprising the following steps:
Step 1. Obtain the proximate and ultimate analysis of the coal being burned in the boiler and the ash mineral analysis for the coal, Step 2. Determine the average temperature of the flue gas entering the ESP from plant instrumentation, Step 3. Estimate SO3 background level in the flue gas using correlation relating flue gas SO3 to coal type and coal sulfur content, Step 4. The secondary current applied to the electrostatic precipitator is obtained from the controls for each transformer-rectifier set that is powering the precipitator, Step 5. Determine the effective fly ash resistivity level in the ESP using a correlation that relates fly ash resistivity to ESP current density for each electrical field, average the results to produce an effective resistivity for the ESP and if this resistivity is not close to, or lower than, the optimum range, proceed with Step 6; otherwise, go to Step 10. Step 6. Use a correlation relating fly ash composition and flue gas temperature and SO3 concentration to fly ash resistivity to determine the flue gas SO3 concentration to needed to produce the optimum fly ash resistivity, Step 7. Subtract the background SO3 from the needed SO3 concentration from Step 6 to determine the amount of SO3 that must be added to the flue gas to produce the optimum fly ash resistivity, Step 8. Send rate of additional signal to the controls that operate the SO3 conditioning system, Step 9. Repeat Steps 4 and 5, Step 10. a. If indicated ash resistivity is equal to or less than optimum resistivity, decrease rate of injection by x percent where x is between 5 and 25, or
b. if indicated ash resistivity is greater than optimum resistivity, increase rate of injection by x percent where x is between 5 and 25, Step 11. Repeat Step 10 until indicated fly ash resistivity passes through optimum resistivity point and then set rate of injection at a point in the range bounded by the levels calculated in the last two interactions, and then Step 12. Every y minutes, where y is number between 5 and 30, restart the process beginning at Step 2.
RELATED APPLICATION
[0001] This application is related to provisional application 60/338,152, filed Dec. 6, 2001, the contents of which are herein incorporated by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60338152 |
Dec 2001 |
US |