Biomass boiler dust collector system solution

1. Overview

(1) The amount of combustion dust is very large. The ash-to-slag ratio after biomass combustion is (10:0~8:2), which means that the slag content is very small and almost becomes ash, so the dust concentration in the flue gas will be very large. Due to the small particle size of combustion dust and the large specific resistance, biomass-fired boiler dust removal is only suitable for bag dust collectors and is not suitable for any other dust removal methods.

(2) Secondary combustion, because the biomass cannot be completely burned in the furnace, and cannot be burned again in the flue due to insufficient oxygen content. The larger dust will maintain the combustion temperature due to the short heat exchange time of the flue gas, so once it is in the oxygen If the conditions are met, for example, it will burn again if placed in the air.

(3) The bulk density of combustion materials is very small. The bulk density of biomass after combustion is generally 0.18-0.5T/m³, which will not increase the capacity of the volumetric ash conveying equipment.

(4) Combustion coking. The ash after combustion contains tar and other substances. Once the temperature of the equipment drops, coking may occur and cause blockage. Due to the consideration of boiler coking and corrosion problems, the exhaust gas temperature may be between 160-190°C.

(5) The supporting equipment requires stability and high reliability. The boiler cannot stop running at will, and the supporting equipment must be stable and reliable.

2. Selection of bamboo chip boiler dust removal process

In view of the above characteristics of the boiler, the following dust removal process is proposed as shown in the figure:

(1) As the biomass combustion tail gas dust contains viscous components such as carbon black, which can easily cause sticky bags, a powder spraying system is installed and placed on the flue between the cyclone separator and the bag dust collector.

(2) The dust is fine, and it is easy to entrain small lumps and carbides that are not fully burned, and it is easy to cause secondary combustion. A cyclone dust collector is installed in front of the bag dust collector to serve as a combustion settling chamber.

(3) The powder spraying system of the bag dust collector can wrap the small particles of dust that have not been removed by the cyclone dust collector, which is convenient for dust cleaning and avoids the occurrence of diffusion phenomenon.

(4) According to the composition analysis of biomass and the analysis of ash produced by combustion, the ash content in the flue gas composition analysis is about 8%, the contents of S and CI are 0.22% and 0.6% respectively, and the MgO, CaO, Na2O, The proportion of alkaline substances such as K2O in the ash is as high as 30%. That is, the alkaline substances in the plant ash can be used to remove SO2, HCI, HF and other substances in the flue gas under the conditions of humidification, activation and full mixing. To reduce the dew point temperature of flue gas, the bag dust collector filter bag uses polyphenylene sulfide (PPS) filter material, which has been treated with waterproof, oil-proof, and flame retardant.

3. Structure of pulse bag dust collector

(1) Divide the dust collector into several units, taking into account thorough dust cleaning and troubleshooting. This can ensure that fine dust will not be adsorbed again, and can also be maintained without shutting down to achieve stable operation.

(2) Bypass setting to protect the dust collector when abnormal conditions occur in the boiler, such as the temperature exceeds 190°C, or the four pipes burst, ash transport failure cannot be eliminated in time, ignition and oiling are added, etc.

(3) Fully automated control can achieve full automation requirements, reduce operational manpower input, and improve operational reliability.

(4) Powerful blockage and arch breaking device. Since dust may agglomerate and arch in the dust collector, it will cause the dust collector to be unloaded smoothly. A powerful air cannon is used to break the blockage.

(5) Fixed tube injection pulse cleaning technology. Fixed tube injection pulse cleaning technology is a dust cleaning technology commonly used in the dust removal industry today. It avoids the easy damage of rotating injection bearings and the difficulty in lubrication, resulting in high failure rates. Undesirable phenomena occur, and the problem of high equipment resistance caused by insufficient backwash air cleaning is avoided. It uses the processed compressed air to induce the purified air in the upper box to instantly spray into the inner tube of the filter bag, forming pulse jitter. Under this sudden strong jitter, the dust adhered to the outer surface of the filter bag breaks away from the filter bag and falls into the ash hopper. middle.

4. Bag dust collector cleaning

When the dust on the surface of the filter bag reaches a certain amount, the dust cleaning control device opens the electromagnetic pulse valve according to the set program and blows the compressed gas through each pulse valve in a very short time and through the nozzle on the blow pipe to induce several times the blowing force. A large amount of air enters the filter bag, forming an air wave, which causes the filter bag to expand rapidly and impact vibration from the bag mouth to the bottom, resulting in a strong dust cleaning effect and shaking off the dust on the filter bag.

The bypass protection system is activated when the boiler tube bursts or the smoke temperature is abnormal.

After the dust falling into the ash hopper is discharged through the ash unloading system, it is sent out centrally using pneumatic ash conveying facilities.

The dust collector has online and offline two-state dust cleaning functions and offline maintenance functions.

All maintenance work is performed in the clean air chamber of the dust collector without entering the filter chamber of the dust collector.

5. Main equipment of the system

(1) Cyclone dust collector.

(2) Main body of bag dust collector

Equipment main body: equipment support structure, upper box, middle box and ash hopper, etc.

Filter bag, keel and flower board: The filter bag and keel form the dust filtration system of the dust collector. The flower board is used to support the filter bag assembly and separate the filter chamber and the clean air chamber. It is also used as a maintenance platform for the dust collector filter bag assembly. The filter bag Components are loaded from the ceiling.

Powder spraying system: including calcium oxide powder bin, dust discharge valve, high-pressure fan, etc.

Air intake system: including air inlet duct and air inlet manual regulating valve.

Exhaust system: A dust collector purified gas emission system consisting of exhaust pipes, etc.

Ash unloading system: The clog-clearing air cannon and manual gate valve installed on the dust hopper of the dust collector form the dust unloading system of the dust collector.

Maintenance platform for platforms, railings, ladders and manual (pneumatic) valves.

(3) Control system: PLC control