Abstract: The three-way ball valve installed on the ammonia water pipeline at the top of the coke oven is an essential device for achieving energy conservation and emission reduction. This paper presents the mechanical control system of the three-way ball valve and its current applications, providing a detailed description of its pneumatic control and operational performance. In coke ovens that employ high-pressure ammonia water for coal charging, the circulating ammonia water supplied from the recovery system to the oven top is separated into high-pressure and low-pressure streams. These two pipelines are connected to the nozzles on the bridge pipe via a three-way ball valve, which is used to switch between the high-pressure and low-pressure ammonia water streams. Under normal operation, the three-way ball valve is connected to the low-pressure ammonia water pipeline, allowing low-pressure ammonia water to be sprayed onto the bridge pipe to cool the raw coal gas. During coal charging, the valve switches to the high-pressure ammonia water pipeline. The high-pressure spray creates suction in the riser pipe and the upper space of the carbonization chamber, facilitating the flow of raw coal gas into the gas collecting main. This effectively reduces smoke generation during coal charging and minimizes the release of dust and fumes from the oven. Therefore, the three-way ball valve is an essential device for achieving energy conservation and emission reduction in coke oven operations.
The three-way ball valve installed on the ammonia water pipeline at the furnace top combines a straight-through floating ball valve with a sleeve-type check valve. The valve model is Y044F-40, with a nominal pressure of 4.0 MPa. For 4.3 m, 6 m, and 7 m coke ovens, the valve has a nominal diameter of 25 mm and a length of 180 mm; for 5.5 m and 6.25 m tamped coke ovens, the nominal diameter is 32 mm with a valve length of 210 mm. Flow is redirected between the high-pressure and low-pressure ammonia water pipelines by rotating the valve stem 90°.
In the early days, the three-way ball valve in coke ovens was operated manually. In some large coke ovens, the switching action was automated using a mechanical control system that worked in coordination with the oven-top vehicles, including coal-charging cars, smoke-eliminating cars, and smoke-guiding cars. The main body of this switching mechanism can be roughly considered a planar four-bar linkage. In coordination with the oven-top vehicle, it sequentially performs the following actions: opening and closing the riser pipe water-seal cover, opening and closing the water-seal valve, and actuating the three-way ball valve. The hydraulic cylinder on the oven-top vehicle drives the crank to rotate the connecting rod, thereby actuating the three-way ball valve. When the hydraulic cylinder is not in use, the valve can also be operated manually using a handle. The three-way ball valve and the switching mechanism are installed in the gap between two adjacent riser pipes, with the switching mechanism mounted on the outer wall of the riser pipe. However, due to construction and installation tolerances of the coke oven and riser pipes, as well as thermal expansion after commissioning, the position of each switching mechanism can shift significantly over time. This makes it difficult to precisely align the hydraulic cylinder on the vehicle with the switching mechanism. Furthermore, once the switching mechanism is deformed by impact, it becomes difficult to repair. As a result, this mechanical control method has been phased out in many coking plants. Consequently, developing a more reliable and easily maintainable alternative control method has become an urgent challenge.
In addition to mechanical control, pneumatic, hydraulic, and electric control methods can also be used. The selection of a control system primarily depends on the operating environment. Three-way ball valves are installed on the top of coke ovens, where the working environment is characterized by high dust levels, open flames, and frequent water splashing. Under such conditions, hydraulic control is unsuitable because hydraulic oil is prone to leakage and combustion, which can create serious safety hazards and cause environmental contamination. Electric control systems also have limitations, as their components offer poor vibration resistance, and accidental contact with conductive materials can result in severe electrical accidents, necessitating strict isolation and protection measures. In contrast, pneumatic control is clean, safe, and reliable. It does not cause environmental pollution, provides inherent fire- and explosion-proof performance, and requires no additional isolation or protection measures. Therefore, pneumatic control is particularly well-suited to the operating conditions of three-way ball valves installed on the tops of coke ovens.
When pneumatic control is used, the three-way ball valve is installed outside the control platform railing of the gas-collecting main. The visible on-site control equipment includes the pneumatic actuator and the pneumatic control cabinet. The pneumatic actuator, equipped with a limit switch, is mounted directly onto the three-way ball valve. The pneumatic control cabinet is mounted on a column outside the control platform railing of the gas-collecting main, with one cabinet typically serving every five carbonization chambers. The cabinet features a double-door design, is constructed from stainless steel, and carries an IP65 protection rating. The pneumatic control cabinet houses filters, pressure-reducing valves, solenoid directional valves, speed control valves, relays, and control knobs. In this system, compressed air from a storage tank serves as the air source. The solenoid directional valves and relays act as the control elements, while the pneumatic actuators serve as the actuating elements. The command unit in the central control room integrates the operation of the three-way ball valve into the coal-charging sequence. The working medium can be compressed air or nitrogen, with a supply pressure of 0.4–0.7 MPa.
The central control room issues operation commands according to the coke-pushing sequence. The relays control the solenoid directional valve to shift to the corresponding position, allowing gas from the filter and pressure-reducing valve to flow through. The gas then enters the pneumatic actuator through the speed control valve, causing the actuator to drive the three-way ball valve and complete the operation. Once the operation is completed, the limit switch sends a feedback signal to the central control room to confirm completion. The solenoid directional valve then vents the gas from the pneumatic actuator. After venting, the actuator returns to its neutral state.
The pneumatic actuator is a rack-and-pinion oscillating cylinder. It operates by using the volume change of compressed gas inside the cylinder to drive a piston, which in turn actuates a rack-and-pinion mechanism, converting the piston’s linear motion into rotational motion. The actuator’s inner cavity is coated with a friction-reducing material to minimize wear and prolong its service life. The actuator delivers balanced torque and transmits it through a square drive shaft. The opening and closing time is under one second. The limit switch is a two-wire, single-pole double-throw (SPDT) type. The pneumatic actuator is a double-acting cylinder fitted with a detachable manual lever. When the pneumatic system is shut down, the lever can be used to manually operate the three-way ball valve. The solenoid directional valve is a three-position, five-way, pressure-relief type with a dual-coil design and a manual override. If a coil malfunctions, a special tool can be used to manually operate the solenoid directional valve, thereby actuating the pneumatic actuator. Once the actuator reaches the desired position, the limit switch sends a feedback signal to the system, simultaneously de-energizing both coils of the solenoid directional valve. The valve then returns to its intermediate pressure-relief position, allowing the pneumatic actuator’s air ports to vent and remain depressurized. A local/remote selector switch and an operation knob are installed in the relay control circuit. When the selector switch is set to remote mode, the system is controlled from the central control room. When set to local mode, the system can be operated directly using the on-site knob. The knob has three positions—high pressure, low pressure, and stop—corresponding to the three states of the solenoid directional valve, enabling convenient manual control.
The control system offers four operating modes:
Central control: Under normal conditions, the three-way ball valve is automatically controlled from the central control room.
Local control: When the selector switch on the pneumatic control cabinet is set to local mode, the three-way ball valve is controlled via the cabinet’s operation knob.
Solenoid valve control: If the control circuit malfunctions, the solenoid directional valve can be manually operated to control the three-way ball valve.
Manual lever control: If the pneumatic circuit fails, the lever on the pneumatic actuator can be used to directly operate the three-way ball valve.
The pneumatic control system has been successfully implemented in several major projects, including the Phase IV Technical Renovation Project at Ansteel Chemical Plant, the Integrated Magnesium Project of Qinghai Salt Lake Group, and the 6.25 m Tamping Coke Oven Project of Xiaoyi Jinyan Power Coal Chemical Co., Ltd. The system has been commissioned and is operating reliably at Ansteel, demonstrating stable performance and ease of maintenance.
The three-way ball valve installed on the ammonia water pipeline at the top of the coke oven achieves automatic operation through pneumatic control. This system reduces workers’ labor intensity, increases the automation level of coke oven operations, and lays the foundation for the future implementation of unmanned coke oven vehicles. Pneumatic control provides reliable performance, easy maintenance, long service life, and excellent adaptability to the harsh operating conditions at the top of the coke oven. Therefore, it is a practical and effective control method, suitable for wider industrial application.
