Blower speed adjustment

As a supplementary point, during normal coal loading and coke pushing, the pressure in the gas collection system fluctuates significantly, and these fluctuations need to be adjusted using automatic flap valves. So, will there be changes in the pressure before the primary cooler? Is it necessary to use a blower for adjustment? Which is better, variable frequency control or hydraulic coupling? Does the speed of the blower need to be adjusted frequently?

1. Either one is fine. 2. As long as there are changes, they can all be used. The maintenance of hydraulic couplings is a bit more complicated; control can also be achieved using the fan guide vanes

Below is some content from a certain factory’s \"technical plan\" for reference: 2.3 The necessity of automatic speed control for blowers. The function of the blowers in coking plants is to transport the gas generated by the coke ovens at the appropriate time. Given that the amount of gas produced by these ovens varies, it is necessary to ensure stable pressure in the gas collection pipes by adjusting the volume of gas delivered by the blowers in line with these changes. This requires the blower to be involved in regulating the pressure in the collector duct; relying solely on the butterfly valve in the collector duct is not sufficient to maintain stable pressure there over the long term. The control methods for blowers mainly include inlet throttling, outlet throttling, (large and small) recirculation, and speed regulation. Among these methods, speed regulation is the most scientific, offering advantages such as system stability, a reduction in the surge zone as the speed decreases, a lower increase in the temperature of the coal gas, and reduced power consumption. 2.4 Feasibility of automatic speed control for blowers: Since the price difference between 380V frequency converters and hydraulic couplings is not significant, 380V motors are generally equipped with frequency converters for speed control ； Motors above 6000V generally still use hydraulic couplings for speed control. Hydraulic couplings are less expensive compared to variable frequency drives, and they enable soft starting and speed control of blowers. (Although their efficiency is lower than that of variable frequency drives, their energy-saving effect is still better than that of other control methods such as large-scale circulation systems; hence, they are widely used in high-pressure, high-power blowers.) However, the vast majority of hydraulic couplings use “manual” speed control – since moving the “speed control spoon” in a hydraulic coupling by 1 mm causes the fan’s rotation speed to change by hundreds of revolutions, the control precision of traditional actuators makes it difficult to move the “speed control spoon” by less than 1 mm each time. Through cooperation with actuator manufacturers, our company has adopted a control scheme that uses \"digital electric actuators\" to regulate the speed of the blowers in hydraulic couplings, and has successfully implemented automatic control of the pressure in the coke oven gas collection systems in dozens of coking plants, with very satisfactory results. The blowers and pressure automatic control devices for air collection pipes produced by our company (with frequency converters used to control the blower speed) have been successfully applied in dozens of coking enterprises over the past few years, which fully demonstrates the maturity of this technology. The fundamental difference between speed control using a hydraulic coupling and speed control using an inverter in terms of automatic control is that the hydraulic coupling has low speed control sensitivity; we have successfully resolved this issue (to date, we have not found any other companies capable of solving it).

The documents provided by Aaron are very detailed, which at least helps us understand the sequence of events. Thank you

You’re welcome, and thanks as well to the moderator for the extra points.

During normal operation, the coke oven undergoes direction changes, which causes fluctuations in suction pressure; this can be adjusted appropriately using couplings. However, once the direction is changed again, the pressure value returns to normal, and adjustments must be made once more!

From the same “technical solution”: A solution to the large pressure fluctuations in the gas collection pipe during switchover of the switch: This is achieved by controlling the source of gas behind the controller, in order to address the issue of significant pressure fluctuations in the gas collection pipe during switchover. We know that furnace gas accounts for 40%–50% of the total gas produced ； The operation process of the switch is to first close the gas valve, then reverse the air-waste gas flow, and finally open the gas valve. During this process, the gas valve remains closed for about ten seconds; during these ten seconds, the gas consumption is reduced by 40%–50%. When this reduction is divided by the number of blowers, the pressure behind the blower increases instantaneously while the suction force in front of it decreases (a characteristic of centrifugal blowers), which results in fluctuations in the pressure in the gas collection pipe. In response to this situation, we can control the vent pipe or the pipe leading to the gas holder; thus, when the exchange is carried out (the gas valve is closed), the electric butterfly valves for the vent pipe or the pipe leading to the gas holder open to the appropriate degree – allowing the gas that is not needed by the coke oven to be discharged from there. This results in stable pressure behind the machine, stable suction force in front of the machine, and stable pressure in the collection pipe.