5.5M Tackling the Challenge of Regulating the Pressure in Coke Oven Collectors

The pressure in the coke oven gas collection pipe is an important process parameter in coke oven production. In production, the automatic pressure control of the coke oven raw gas collection duct is susceptible to various pulsating interference signals. Some interference signals exceed the set adjustment value. Achieving automatic control to regulate the set value within ±10 Pa is somewhat difficult. In some coking plants, despite multiple technical upgrades, the control systems still cannot operate stably. We adopted fast dampers in the control system to solve this problem, achieving good economic and social benefits. The rapid damper is a patented technology developed by our company. The damper does not require a power source or air supply during operation; it relies on its damping mechanism to reduce interference and smooth out pulsating pressure signals within 0.1 seconds, thereby enabling automatic pressure adjustment within the range of ±10 Pa. After the control system is put into operation, the liquid level in the glass U-tube on the gas collection pipe can be observed directly. The human eye has difficulty detecting changes in pressure. Each coking plant operates under different conditions; based on these varying conditions, we work together with the owners to develop technical improvement plans that are practical and feasible. For example: We worked with Shanxi Xingyuan Coking Plant, which previously used manual methods to adjust pressure. Without shutting down production, we implemented measures such as adding a large reflux system and electrostatic tar collectors, thereby achieving single-stage control of the pneumatic butterfly valves in the coke oven gas collection pipes. Without shutting down production, the two coke ovens were connected using DN400 seamless steel pipes; a DN600 large return pipe was added to the system, and an electric tar catcher was installed. After the technical upgrades, with the stable operation of automatic gas collection system pressure regulation, the impurities in the return gas were significantly reduced, and blockages caused by heating gas were markedly diminished. The temperature of the coke oven has increased by several dozen degrees Celsius compared to before. As the furnace temperature increased, a positive feedback loop was established in production, and the control system achieved automatic regulation at 80±10 Pa. In the pressure regulation of the coke oven gas collection system, we employ a two-stage regulation approach. The first stage is for rough adjustment, and for this purpose various methods can be used, such as large-scale reflux, hydraulic couplings, or frequency conversion regulation. Stable coarse adjustment can accommodate the random variations in the raw gas production load of coke ovens. The coarse adjustment pressure is stabilized within the range of -4 KPa to -6 KPa. The second stage is fine tuning, which involves stabilizing the pressure in the gas collection pipe within a range of ±10 Pa. Pressure regulation of the coke oven gas collector: the pressure setpoint is generally between 80 and 140±10 Pa. That is, the slight positive pressure control applied in the coke oven, with the aim of preventing air from entering the oven from outside. Set value for the pressure control system of the vertical furnace gas collection duct at the former Nanjing Coal-to-Gas Plant: ±10 Pa; oxygen content in the gas <1%, (normally 0.2–0.5%). From an environmental protection perspective, the author believes that a set value of 0±10 Pa for the pressure in the coke oven gas collection system is worth considering; for every 12 meters increase in altitude, the atmospheric pressure decreases by 151 Pa. The magnitude of the negative pressure generated can be calculated based on the height of the carbonization chamber in the coke oven. This negative pressure value is equivalent to the suction force of a chimney (also known as the buoyant force due to heat rise); we believe that the furnace walls of a coke oven are capable of withstanding this negative pressure of several dozen Pa. For the sake of environmental protection and ease of operation, it is worth considering and implementing automatic pressure regulation of ±10 Pa for the coke oven gas collection pipes. For the pressure regulation of the coke oven gas collection system, anti-interference technical measures are employed; three methods—large reflux regulation, hydraulic coupling regulation, and frequency conversion regulation—can all ensure long-term stable operation.