Switching between black and white operation in continuous reforming

Looking at the method and level of switching, it normally shouldn’t happen.

Now that you know about this problem, you can find ways to prevent it!

I’ll send you the steps from the UOP CycleMax operation manual for switching from black burning to white burning; take a look at how the standard procedures address the issue of the time difference associated with the white-burning air passing through the calcination zone, the oxychlorination zone, and entering the regeneration zone, as you mentioned. Normal startup of UOP regeneration coking: There are two procedures for starting up the regeneration section. The black catalyst startup procedure must be used for the initial startup of the regeneration section. For future startups, if there is a possibility of coked catalyst in the lower part of the regenerator coking zone, the black catalyst startup procedure must also be employed. If not, the white catalyst start-up procedure can be used. A Black Catalyst Startup Procedure 1. Establish the following flow rates and conditions: a. Nitrogen is introduced into the regenerator cooling zone; the required minimum flow rate is to cool the recycled catalyst to 150°C (300°F). b. Nitrogen is introduced into the regeneration dryer section: design nitrogen flow rate for startup. (Note: This flow rate is lower than that of dry air during normal operation.) This flow rate corresponds to the design flow rate of the chlorination area during normal operation. c. Excess air venting: Manually close the excess air manual control valve. d. Flow rate in the chlorination zone: The same as the nitrogen flow rate supplied to the dryer zone and cooling zone of the regenerator. e. Nitrogen “bubble” for the catalyst to be activated: design pressure difference. f. Regenerated catalyst nitrogen “bubbles”: design pressure difference. g. Catalyst to be regenerated isolation system: Open. h. Regenerated catalyst isolation system: Open. i. Nitrogen introduced at the seal of the regeneration fan: design pressure difference. j. Nitrogen supply to the regenerator and reheated gas flow meter: design flow rate. k. Coolant water flows into the regenerative fan water curtain (if applicable). l. The catalyst level in the separation hopper is normal. m. Total lift gas to the catalyst-to-be-fed L-valve assembly: design flow rate. n. Total lift gas to the regenerative catalyst L-valve assembly: design flow rate. o. Regenerator pressure: Design pressure. p. Gas flow rate to the reductant heater booster: design flow rate. q. Purge gas to catalyst collector: design flow rate. r. Start the air dryer according to the manufacturer’s procedures. 2. Start the regeneration fan and the regeneration cooler fan. If the regeneration fan has a two-speed electric drive, activate the low-speed drive. 3. Calibrate and set up the analyzers for normal operation: Hydrogen/hydrocarbons analyzer for the nitrogen main line, oxygen analyzer for gases in the coking zone. Note: Before testing the electric heater, the oxygen concentration in the regenerator should be zero. During calibration, the analyzer must be at the design pressure; otherwise, it will not be able to display accurate readings under normal operating conditions. 4. Place the catalyst flow button in the stop position to interrupt the catalyst circulation. Except for the initial start-up and when catalyst cycling may be required during periods of low catalyst coking, there is no need to initiate catalyst cycling during heating in the regenerator and reduction zones. 5. Ensure that all shutdown bypass switches are in the NOMAL (normal) position. 6. Start the electric heater and heat the regenerator and reduction zone: a. Manually set the temperature controllers at the inlet of each zone – the inlet of the charring zone, the inlet of the drying zone, the inlet of the reduction zone, and the inlet of the reheating zone (if applicable) – and set their values corresponding to the heater’s output to zero. Note: The inlet temperature controller in the charring zone controls the regenerative heater (50–100%) and the regenerative cooler (50–0%). Set its output value at 50%, and the output value of the regenerative heater to zero. b. Press the button of the electric heater to start it. c. Raise the temperature at the inlet of each zone to its design temperature at a rate of 55°C per hour (100°F per hour): 477°C (890°F) at the inlet of the coking zone, 565°C (1050°F) at the inlet of the drying zone, 377°C (710°F) at the inlet of the upper reduction zone, 482°C (900°F) at the inlet of the lower reduction zone (if applicable), and 510°C (950°F) at the inlet of the reheating zone. Note: If the regenerator gas fan is equipped with a two-speed electric drive, it should switch from high speed to low speed once the inlet temperature specified by the fan/motor manufacturer is reached. 7. (If applicable) If necessary, readjust the pressure of the fuel gas tank to maintain the pressure in the regenerator at the design value. The regenerator pressure is maintained above the pressure in the lockhopper, which in turn is maintained above the pressure in the fuel gas tank. 8. Determine the allowable maximum catalyst cycle rate based on the general operation curve (Figure VII-1). Calculations are performed using a coke content determined based on the actual carbon analysis data obtained in the laboratory, along with an oxygen concentration value within the recommended range for the oxygen concentration at the inlet of the charring zone (0.5–1.0 mole percent). See the CCR process variables section. 9. Start the combustion air at the upper part and begin the in-reactor coking of the coking catalyst in the coking zone. (See Figure VII-2). a. Confirm that the tie-line valve (XV-14, see Figure VII-2) is in the closed position. b. Confirm that the upper combustion air control valve is in the closed position, and open the manual valve at the combustion air inlet on that pipeline. c. Record the temperature distribution in the burned area. d. Press the AIR ON button to open the air valve (XV-13). As required, the combustion air from above is introduced into the charring zone circuit through the start-up pipeline, to achieve the oxygen concentration value specified in step 7 above. e. Keep the oxygen concentration and the upper combustion air flow rate stable, then connect the upper combustion air flow rate controller and the oxygen analyzer controller in series. f. Maintain the required oxygen concentration level during the in-reactor charring process. The amount of coke in the burned area will gradually decrease. Ultimately, some of the oxygen that enters the catalyst bed will begin to circulate through the bed to the regeneration fan and return to the inlet of the coking zone. This will significantly reduce the amount of upper combustion air required to maintain the desired inlet oxygen concentration. 10. When the upper combustion air flow rate drops to about half of its original value (step 9e), start the catalyst cycle: a. Set the catalyst flow rate at or below the allowable maximum catalyst circulation rate (general operation curve in Figure VII-1). b. Press the Catalyst Flow On button to start the catalyst circulation program. 11. Maintain charring under the following conditions: Inlet temperature of the charring zone – 477°C (890°F); outlet temperature of the charring zone – not more than 565°C (1050°F); ΔT in the charring zone – not more than 88°C (160°F); bed temperature in the charring zone – not more than 593°C (1100°F). Oxygen concentration at the inlet of the charring zone: according to the general operating curve, it should be not less than 0.5% by mole ； Not more than 1.0% molar) (if applicable) Reheating zone inlet: 510°C (950°F) Drying zone inlet: 565°C (1050°F) Drying zone inlet pressure: 2.5 kg/cm2 (35 psi gauge pressure) Nitrogen supplied to the drying zone; design value for operation. Nitrogen supplied to the cooling zone. The temperature of the nitrogen-sealed tank is maintained at 150°C (300°F). Upper reduction zone inlet: 377°C (710°F) Lower reduction zone inlet: 482°C (900°F) Catalyst circulation rate: According to the general operating curve (not more than the design value). Exit temperature of the reduction gas heat exchanger shell side: 65°C (150°F) Pressure of the gas from the compressor going to the lockhopper: 150°C (300°F) 12. Sampling of the regenerated catalyst: After one cycle in the regenerator, samples of the regenerated catalyst are taken every two hours beneath the nitrogen-sealed tank for carbon analysis. Continuous sampling shall show that the catalyst meets all of the following criteria: (1) The coke content shall be 0.1% (by weight) or less. (2) The catalyst pellets should have no focal center (able to split into multiple pellets). (3) There are almost no whole black balls. When sampling the regenerated catalyst twice in a row shows that it meets the above three criteria, a dual-air circulation system is established. 13. Begin injecting air into the drying zone and the cooling zone, and establish dual-path air injection following these steps: a. During this step of establishing dual-path air circulation, it is necessary to monitor the inlet temperature of the regeneration fan, as well as the temperatures of the beds in the burning zone, the reheating zone, and the chlorination zone, along with the outlet temperature of the cooling zone. If there is any significant increase in temperature, immediately activate nitrogen and stop feeding air into the air heater. b. Ensure that the nitrogen flow rate into the drying zone is at the design value for startup. Ensure that the excess air vent control valve is in the manually closed position. c. Ensure that when the air supply to the lower section of the drying zone is activated, the current flow rate of the combustion air in the upper section is sufficient to enable continuous cascade control of the air there, and that this current flow rate is also adequate to maintain the apparent flow rate of chlorine gas at its current value. Note: After activating the air flow control at the lower part of the drying zone, the air flow rate into the upper part of the charring zone must also be reduced to counteract the effect of the lower air flow on the oxygen balance in the regenerator. The upper air flow rate must be reduced, by an amount approximately equal to the lower air flow rate. Therefore, the reduced remaining upper air flow rate must still be large enough to allow control of the oxygen content in the charring zone through the upper air control valve. Example VII-1: If the current operating conditions of the regeneration section are as follows: an air flow rate of 400 Nm3/hour (150,000 standard cubic feet per hour) at the upper level, and a nitrogen flow rate of 267 Nm3/hour (10,000 standard cubic feet per hour) at the lower level, then after starting the air supply at the lower level, the operating conditions will be approximately: an air flow rate of 133 Nm3/hour (5,000 standard cubic feet per hour) at the upper level, and a nitrogen flow rate of 267 Nm3/hour (10,000 standard cubic feet per hour) at the lower level. Therefore, before enabling the air flow at the lower level, it is necessary to ensure that a flow rate of 133 Nm3/hour (5,000 standard cubic feet per hour) is sufficient for the upper-level air control valve to regulate the oxygen content in the charring zone. Generally, it is sufficient for control if the upper air flow rate is 20% greater than the lower air flow rate. d. Place the upper combustion air in local automatic control mode. e. Press the Tie Line button to open the tie line valve (XV-14). f. Once the communication line valve is opened, press the (nitrogen button) to close the nitrogen valve (XV-15). g. After the nitrogen valve has been opened for 20 to 30 seconds, reduce the upper air flow rate to counteract the effect of the lower air on the oxygen content in the regenerator. In the example above, the upper air flow rate decreases from 400 Nm3/h to 133 Nm3/h; at this point, it is necessary to closely monitor the oxygen content analyzer. h. Maintain stable oxygen concentration and upper combustion air flow rate. Then, the upper combustion air flow controller is cascaded back to the oxygen analyzer controller. 14. Establish an excessive flow rate of dry air and stop the supply of combustion air at the upper section: a. Once the oxygen concentration reaches a stable level, the flow rate of air injected at the lower section will be increased to the designed air flow rate for the regenerator (on-site – automatic control). At the same time, open the manual control valve (local – manual) to increase the air flow rate by venting excess air. The apparent chlorine gas flow rate remains at the current value. b. Ensure that when the supply of combustion air at the upper level is stopped, the current excess air vent flow is sufficient to control the oxygen concentration in the charring zone. Note: When stopping the supply of upper air to the burned zone, the excess air coming from the drying zone must be reduced to offset the effect of the upper air on the oxygen content in the regenerator. The excess air vent flow rate must be reduced, with the reduction amount being roughly equal to the upper air flow rate value. Therefore, the excess air vent flow rate must remain sufficient, even after being reduced, to control the oxygen content in the charring zone via the excess air control valve. Example VII-2: If the current operating conditions of the regeneration section are as follows: upper air flow rate of 133 Nm3/hour (150,000 standard cubic feet per hour), excess air vent flow rate of 267 Nm3/hour (10,000 standard cubic feet per hour), and lower air flow rate of 534 Nm3/hour (20,000 standard cubic feet per hour), then after stopping the supply of air from the upper part, the operating conditions will be approximately: upper air flow rate of 0 Nm3/hour (0 standard cubic feet per hour), excess air vent flow rate of 133 Nm3/hour (5,000 standard cubic feet per hour), and lower air flow rate of 534 Nm3/hour (20,000 standard cubic feet per hour). Therefore, it is necessary to ensure that a flow rate of 133 Nm3/hour (5,000 standard cubic feet per hour) is sufficient before stopping the upper air supply, so that the excess air control valve can maintain the appropriate oxygen level in the burning zone. c. Place the upper combustion air under local-automatic control. d. Reduce the excess air vent flow; the reduction amount is equal to the upper combustion air flow rate. e. 10 to 20 seconds after the excess air exhaust flow decreases, close the upper combustion air control valve to an appropriate position to counteract the effect of the lower air on the oxygen balance in the regenerator. f. Maintain stable oxygen concentration and excess air vent flow rate. Then, turn on the oxygen analyzer – the controller operates the excess air vent control valve. g. Isolate the upper combustion air supply pipeline in the burned area. 15. Set the chloride button to the “ON” position and adjust the stroke of the injection pump to establish an optimal injection flow rate of organic chlorides in the chlorination zone. 16. Sampling of the regenerated catalyst: a. When the catalyst is in a ready state after completing one cycle in the chlorination zone, drying zone, and cooling zone of the regenerator, sampling is taken from below the nitrogen-sealed tank to analyze the chloride content of the regenerated catalyst. b. Adjust the chloride injection rate to reach the chloride level required by the regenerated catalyst. 17. Continue to monitor the burning process. The operating conditions are as follows: Inlet temperature of the coking zone – 477°C (890°F); outlet temperature of the coking zone – not more than 565°C (1050°F); ΔT in the coking zone – not more than 88°C (160°F); bed temperature in the coking zone – not more than 593°C (1100°F). Oxygen concentration at the inlet of the coking zone: according to the standard operating curve, it should be not less than 0.5% by mole ； Not more than 1.0% molar) (if applicable) Reheating zone inlet: 510°C (950°F) Drying zone inlet: 565°C (1050°F) Drying zone inlet pressure: 2.5 kg/cm2 (35 psi gauge pressure) Air supplied to the drying zone. Design value for regeneration. Air supplied to the cooling zone. The temperature of the nitrogen-sealed tank is maintained at 150°C (300°F). Upper reduction zone inlet: 377°C (710°F) Lower reduction zone inlet: 482°C (900°F) Catalyst circulation rate: Based on the general operating curve (maximum CCR design value). Outlet of the reduction gas heat exchanger shell side: 65°C (150°F) Pressure of gas from the compressor to the lockhopper: 150°C (300°F). 18. The regeneration section shall remain in normal operation. 19. Stop feeding water into the CCR reformer (if feeding is in progress) after the catalyst in the regenerator has completed one cycle and subsequent steps 8 have been completed for the lockhopper and reduction zone. 20. After the catalyst in the regenerator has completed one cycle and the lockhopper and reduction zone have completed subsequent step 14, stop injecting chlorides into the feed to the CCR reformer (if injection is in progress). This requires operating at the designed full-load catalyst circulation rate for about 14 hours.

For Building 4#, you’re referring to UOP’s version; our unit uses AXENS. The principle of operation is the same, but there are some differences in actual operation.

Is there a general manual for axsen that I could exchange?