Structural composition of the circulating fumigation machine: from core components to system integration

　　1.Host system:the"heart"of equipment operation

　　1.Fan unit:

　　1)Type:axial flow fan(suitable for low pressure and high flow rate),centrifugal fan(suitable for high pressure and low flow rate),selected according to the type of silo(e.g.,centrifugal fans are commonly used in shallow round silos).

　　2)Material:The impeller is made of stainless steel(304 or 316),which is resistant to corrosion from fumigants;the motor is an all-copper explosion-proof motor with a protection level of IP55 or above.

　　3)Performance parameters:Air volume ranging from 500 to 5000 m³/h,and air pressure ranging from 500 to 2000 Pa,ensuring airflow coverage across the entire warehouse.

　　2.Heating/dosing device:

　　1)Heating device:electric heating tube(power 3-15 kW)or gas heater,used to generate high-temperature steam or raise the ambient temperature,with temperature control accuracy of±1℃.

　　2)Dosing device:External quantitative dosing machine(compatible with aluminum phosphide),capable of setting the dosage(5-50kg/time),supporting manual/automatic replenishment;liquid fumigant is equipped with a metering pump and a mixing tank.

　　3.Control system:

　　1)Hardware:PLC controller,touch screen,temperature/humidity/gas concentration sensor(accuracy±2%),solenoid valve,relay.

　　2)Functions:parameter setting(temperature,time,concentration),real-time monitoring,fault alarm(overtemperature,gas leakage,motor overload),data recording(supporting export via USB flash drive).

　　II.Circulation system:The"vascular network"of gas circulation

　　1.Piping system:

　　1)Material:food-grade PVC(for normal temperature)or stainless steel(for high temperature/corrosive gas),with the pipe diameter calculated based on the air volume(e.g.,aΦ150mm pipe is suitable for an air volume of 1000m³/h).

　　2)Layout:

　　Fixed type:The pipeline is installed along the inside and outside of the warehouse wall(external circulation/internal circulation),with branch pipes spaced at 2-3m intervals.A deflector is installed at the air outlet to ensure uniform gas diffusion.

　　Mobile type:It adopts a hose(temperature-resistant-20-120℃)connection,and is used in conjunction with a mobile trolley,suitable for shared use across multiple warehouses.

　　2.Sealing components:

　　1)Interface sealing:Silicone sealing ring(resistant to phosphine),flange connection,with all screw holes coated with sealant.

　　2)Storage body sealing:The grain surface is covered with a 0.14mm thick polyvinyl chloride film,and the doors and windows are sealed with butyl rubber tape to ensure the airtightness of the storage room(pressure half-life≥40 seconds).

　　III.Safety system:ensuring risk-free operation

　　1.Explosion-proof devices:explosion-proof motors,explosion-proof junction boxes,safety valves(with explosion venting pressure of 0.1 MPa),suitable for flammable and explosive environments.

　　2.Gas detection:phosphine sensor(detection range 0-5000ppm),oxygen sensor.In case of exceeding the standard,the machine will automatically shut down and initiate ventilation.

　　3.Emergency system:emergency stop button,backup power supply(maintaining operation for 30 minutes after power failure),toxic gas adsorption device(activated carbon+alkali solution tank).