Offline Cleaning Baghouse

The offline cleaning baghouse,also known as an offline pulse baghouse or compartmentalized bag filter,is an advanced dry dust removal equipment optimized based on the conventional online cleaning baghouse.Its core innovation lies in the compartmentalized offline cleaning mechanism,which isolates the target filter compartment from the main gas flow during the cleaning process,effectively solving the problems of secondary dust emission and incomplete cleaning existing in online cleaning.It is widely used in industrial scenarios with high dust concentration,sticky dust,high air volume,and strict requirements for continuous operation and ultra-low emission,such as metallurgy,building materials,chemical industry,and power generation.

Core Working Principle

The operation cycle of the offline cleaning baghouse mainly consists of three stages:filtration,offline cleaning,and ash discharge,which alternate continuously to ensure stable and efficient dust removal.The key difference from the online cleaning type is that the cleaning process is carried out in an isolated state of the filter compartment,without interfering with the normal filtration of other compartments.

1.Filtration Stage:Dust-laden gas enters the hopper of the baghouse through the air inlet,and large-particle dust settles directly into the hopper due to gravity.With the guidance of the flow guide device,the gas is evenly distributed to each independent filter compartment.Fine dust particles are intercepted by the outer surface of the filter bags in the middle box(filter chamber),and a"dust cake"is gradually formed on the surface of the filter bags,which further improves the filtration efficiency.The purified gas passes through the filter bags into the upper box(clean air chamber)and is discharged by the fan through the air outlet.

2.Offline Cleaning Stage:When the dust cake on the surface of the filter bags thickens and the system resistance rises to the preset threshold(usually 1200-1500Pa),the PLC control system automatically triggers the offline cleaning program.First,the intake and exhaust valves(lift valves or flapper valves)of the target filter compartment are closed to completely isolate the compartment from the main gas flow,putting it in an"offline"state without gas passing through.Then,the pulse valve is activated,and high-pressure compressed air(0.4-0.6MPa)is instantly injected into the filter bags through the injection pipe and Venturi tube,generating a reverse shock wave that makes the filter bags expand and vibrate violently,peeling off the attached dust cake.After the cleaning is completed,the valves of the compartment are reopened after a short settling time(a few seconds)to ensure that the peeled dust fully falls into the hopper,and the compartment resumes the"online"filtration state.Each filter compartment is cleaned in turn to ensure the continuous operation of the entire system.

3.Ash Discharge Stage:The dust accumulated in the hopper is regularly discharged through ash discharge devices such as star dischargers,screw conveyors,or air conveying systems.The hopper is designed with a cone shape with an inclination angle of≥60°to prevent dust accumulation,and can be equipped with electric heating devices or vibrators according to working conditions to avoid dust caking and dew formation.The volume of the hopper is usually designed to meet the dust storage capacity of 8-12 hours,and is equipped with a high-level gauge and alarm device to ensure safe and stable operation.

Key Structure Components

The offline cleaning baghouse adopts a modular compartmentalized design,which is composed of core components such as the box body,filter bags,cleaning system,valve system,and electrical control system.Each component cooperates closely to ensure the efficient and stable operation of the equipment.

-Compartmentalized Box Body:It is divided into the upper box(clean air chamber),middle box(filter chamber),and lower box(hopper),all of which adopt a compartmentalized structure.Each filter compartment is independent and equipped with independent air inlet and outlet valves.The box body is made of carbon steel or stainless steel,with anti-corrosion treatment on the surface,which can withstand temperature fluctuations of-20℃to+200℃and positive and negative pressure fluctuations within 0.05MPa.The internal setting of reinforcing ribs enhances the compressive strength,and the flow guide device optimizes the air distribution to avoid local excessive wind speed causing filter bag wear.

-Filter Bags and Bag Cages:The filter bag is the core filtering element,and its material is selected according to the temperature,humidity,and corrosiveness of the dust-laden gas,including polyester(PET),PPS,aramid(Nomex),PTFE,etc.,with a filtering precision of 0.1-10μm.The surface of the filter bag can be treated with water and oil repellency to reduce the adhesion of sticky dust.The bag cage(skeleton)is made of galvanized carbon steel or stainless steel to support the filter bag and prevent it from being crushed.The filter bag and the flower plate are sealed with elastic expansion rings,with a leakage rate of≤0.5%.

-Offline Cleaning System:It is composed of an air bag,pulse valve,injection pipe,and Venturi tube.The air bag volume is designed according to 1.5 times the injection air volume,with a working pressure of 0.5-0.7MPa.The pulse valve adopts a submerged straight-through valve with an opening time of≤0.1s,and the injection pressure can be adjusted in the range of 0.2-0.6MPa.The injection pipe adopts a tapered orifice design to ensure that each filter bag obtains uniform injection force,and the cleaning efficiency is over 90%.

-Valve System:It is the core component to realize offline cleaning,including lift valves or pneumatic flapper valves,which are installed at the air inlet and outlet of each filter compartment to control the opening and closing of the compartment air flow and realize the switching between"online"and"offline"states.The valve has the characteristics of fast response and good sealing performance,ensuring the reliability of the offline isolation effect.

-Electrical Control System:It adopts the PLC+touch screen structure,which can automatically control the start and stop of the equipment,the cleaning cycle,and fault diagnosis.The differential pressure transmitter monitors the system resistance in real time,and the cleaning cycle is adaptively adjusted according to the resistance change(usually 30-60 minutes per cycle).The data recording module can track the emission concentration(stable below 10mg/m³)and equipment energy consumption for a long time,and support remote monitoring.