15 High H2S
Digester gas samples are collected and evaluated each morning.
- If the sample concentration is less than 100 PPM, ferrous chloride injections are not required at the Gravity Thickener and no further action is required.
- If the sample concentration is equal to or less than 238 PPM, further monitoring is required at 8 hour intervals.
- If the sample concentration is greater than 238 PPM, the Air Control District must be notified and further monitoring is required at 4 hour intervals.
Monitor the air quality that is associated with digester gas production.
- Operator I
- Knowledge of digester gas sample collection
- Knowledge of the effects of ferrous chloride on digester gas
- Draeger Pump
- Draeger Tube
- Record activity and sample concentrations to log book.
- Notify Air Control District of concentration violations.
Note: The H2S Limit is 238 ppm, as required by the Air Control District. 1. Obtain digester gas sample. This step is performed each morning. a. Use the Draeger pump and H2S Draeger Tube to obtain a digester gas sample. 2. Evaluate digester gas sample. a. If the sample H2S concentration is equal to or less than 100 PPM, discontinue the ferrous chloride injection at the Gravity Thickener (if in service). No further steps are required. b. If the sample H2S concentration is greater than 100 PPM, go to step 3. 3. Inject ferrous chloride at the Gravity Thickener. a. Locate the in service Ferrous Chloride Injection Pump {tag nos. 1610PMP/MTR/VSD6100, 1610PMP/MTR/VSD6200, 1610PMP/MTR/VSD6300} and adjust the feed rate. A typical feed rate adjustment is a 30% increase. If H2S levels are extremely high, the feed rate may be increased by as much as 100%. 4. Fill out the Compliance Log. Click here for a copy of the Compliance Log. 5. If the sample H2S concentration is greater than 238 PPM, go to step 5.a. If the sample H2S concentration is equal to or less than 238 PPM, go to step 5.b. b. Continue to monitor the sample H2S concentration every 8 hours. Notify the supervisor of the results. Go to Step 6. 6. Determine the cause of the high H2S concentration and take corrective action. 7. Continue resampling at 4 hour or 8 hour intervals, depending on H2S concentration level. 8. Return to Step 2 and repeat the process until H2S concentration levels fall below 100 ppm. |
- H2S Concentration less than 100 PPM indicates that ferrous chloride injection to the Gravity Thickener is not required.
- H2S Concentrations greater than 238 PPM violate the air permit.
Inject ferrous chloride to the Gravity Thickener until concentrations are acceptable. Adjust the ferrous chloride injection rate as required to achieve acceptable concentrations.
|