In the desulfurization and dust removal process of large boilers, after the alkaline solution is neutralized by sulfur-containing flue gas discharged from coal-fired boiler chimneys, the pH of the solution is not neutral but generally acidic. This requires the use of an automatic dosing system to inject a strong alkaline solution to adjust the pH of the wastewater. Henan Lichuang Environmental Protection Equipment Co., Ltd. is currently assembling an automatic dosing system for a 45-ton coal-fired boiler system. The sedimentation tank measures 20 meters in length, 12 meters in width, and 2.5 meters in depth. According to calculations and designs by metering engineers, the system is equipped with two 120-liter-per-hour stainless steel diaphragm plunger pumps, a 2-ton PE top-opening solution tank, a Siemens PLC automatic control system, a PHG-20 pH online monitor with a composite electrode, high and low level alarms, and a sturdy steel ladder platform for easy maintenance and dosing. Pre-set upper and lower pH limits are established. When the upper limit is reached, the metering pump stops dosing. When the probe detects the lower limit, the automatic dosing system's metering pump automatically starts to inject the alkaline solution.
    The solution of strong alkali sodium hydroxide is highly corrosive. Operators of automatic dosing systems must pay attention to safety. It is best to first dilute the alkaline solution in a dedicated container, during which the solution temperature will rise significantly. Once the alkaline solution cools to room temperature, it can be pumped into the solution tank using a corrosion-resistant lift pump or manually poured into the tank to prevent splashing onto the body. When the alkali dosing system is operating, the PLC automatic control system starts, and the agitator works first to mix the alkaline solution uniformly before the metering begins. This design of the automatic dosing system is more reasonable.
Jiangsu Zhuoya Environmental Protection customizes automatic dosing systems according to customer requirements. Basic information such as dosing volume, whether automatic control is needed, the type of chemical to be dosed, and the application site must be provided. Our technical designers will then develop a reasonable manufacturing plan. Generally, industrial boilers and high-end hotels use integrated dosing systems with automated control, while small enterprises opt for single-pump, single-tank dosing systems.
    The outlet of the metering pump uses a Φ10-15mm 304 stainless steel pipe. Approximately ten Φ2mm small holes are evenly drilled around the end of the pipe. During installation, the pipe is angled opposite to the flow direction and aligned with the centerline of the medium pipe (this allows part of the dosing solution to be extruded through the small holes, enhancing dosing uniformity). For integrated dosing systems that use sampling monitoring instead of online monitoring, the sampling tube is made of Φ20×3mm stainless steel pipe. The pipe is slightly angled and inserted into the medium pipe to a depth of 3/4D. Several Φ3mm small holes are drilled inside the sampling tube at 2/3 of its length, allowing sampling from different directions to increase the representativeness of the sample water. The distance between the dosing device and the sampling point should be 5-10 meters, depending on the specific conditions of each plant. The distance from the sampling point to the pH online monitor should be ≤20 meters to facilitate shorter transmission. The control cabinet should be placed in a clean, bright, corrosion-free environment, away from strong magnetic fields, with temperatures below 45°C and humidity below 85%.