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 requiresfully automatic dosing systemsto inject strong alkaline solutions to adjust the pH of the wastewater. Henan Lichuang Environmental Protection Equipment Co., Ltd. is currently assembling a fully automatic dosing system for a 45-ton coal-fired boiler system, with a sedimentation tank measuring 20 meters long, 12 meters wide, and 2.5 meters deep. According to calculations and designs by measurement engineers, it 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 water 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 data at the set lower limit, theautomatic dosing system's metering pump automatically starts to inject alkaline solution.
    The solution of strong alkali sodium hydroxide is highly corrosive. Operators of fully automatic dosing systems need to 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 solution tank to prevent splashing onto the body. When the alkali dosing device is operating, the PLC automatic control system starts, and the mixer works first to stir the alkaline solution evenly before the metering begins. This design of the automatic dosing system is more reasonable.
Jiangsu Zhuoya Environmental Protection customizesfully automatic dosing systemsaccording to actual 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. Then, our technical designers will develop a reasonable production 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 is typically made of Φ10-15mm 304 stainless steel pipe. Around the end of the pipe, approximately 10 Φ2mm small holes are evenly drilled. 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 rely on sampling monitoring rather than online monitoring, the sampling pipe shape and installation use 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 internally at the 2/3 point of the sampling pipe end, allowing sampling from different directions to improve 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 area free of corrosive gases, away from strong magnetic fields, with temperatures below 45°C and humidity below 85%.