In the desulfurization and dust removal process of large boilers, after the alkaline solution neutralizes the sulfur-containing flue gas discharged from the coal-fired boiler chimney, the pH of the solution is not neutral but generally acidic. This requires the fully automatic dosing device to inject a strong alkaline solution to adjust the pH of the wastewater. The fully automatic dosing device currently being assembled and manufactured by Henan Lichuang Environmental Protection Equipment Co., Ltd. is for a 45-ton coal-fired boiler system. The sedimentation tank is 20 meters long, 12 meters wide, and 2.5 meters deep. According to calculations and design 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 by personnel. The upper and lower pH limits are set in advance. When the upper limit is reached, the metering pump stops dosing. When the probe detects data at the set lower limit, the automatic dosing device's metering pump automatically starts to inject the alkaline solution.
    The solution of strong alkali sodium hydroxide is highly corrosive. Operators of the fully automatic dosing device 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 working, the PLC automatic control system starts, and the agitator operates first to mix the alkaline solution evenly before the metering begins. This design of the automatic dosing device is more reasonable.
Jiangsu Zhuoya Environmental Protection customizes fully automatic dosing devices 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 devices with automated control, while small enterprises opt for single-pump, single-tank dosing devices.
    The outlet of the metering pump uses a 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 water flow direction and aligned with the centerline of the medium pipe (part of the dosing solution is extruded through the small holes to enhance dosing uniformity). For integrated dosing devices that use sampling monitoring instead of online monitoring, the sampling pipe shape and installation use a 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 pipe at the 2/3 point from the end to allow sampling from different directions, improving 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, non-corrosive gas environment, away from strong magnetic fields, with a temperature below 45°C and humidity below 85%.