LYS series (air preheater) intelligent automatic ash removal device

 Disruptive innovative technology for boiler auxiliary equipment -

           Intelligent automatic ash removal device for tubular air preheater

Replace the sonic soot blower
Replace steam soot blower
Replace pulse soot blower
Anti clogging, anti-corrosion, and anti coking
Thoroughly clean the dust, operate intelligently and automatically, work stably and reliably, have no maintenance costs, and have a long service life

1、 Product Overview

  Air preheater is an important heat exchange device inside the boiler body. At present, there are many types of air preheaters used in the market. Large and medium-sized boilers mainly use rotary air preheaters, while small and medium-sized boilers with hood covers mainly use tubular and heat-conducting air preheaters. These two types of air preheaters have their own advantages and disadvantages, but they all have a common disadvantage - they are prone to ash blockage and corrosion in the low-temperature section. There are many reasons for this, mainly due to the installation of desulfurization and denitrification equipment in the boiler after meeting the mandatory ultra-low emission requirements of the environmental protection department. The produced ammonium bisulfate becomes liquid within the range of 146-270 ℃. The liquid ammonium bisulfate (NH4HSO4) is prone to capture fly ash in the flue gas, forming molten salt like substances that adhere to the outer surface of the air preheater heat exchange tube bundle at the tail of the flue, causing blockage and corrosion of the air preheater. After the corrosion and air leakage of the air preheater tube, the smoke temperature decreases, which further exacerbates low-temperature corrosion and forms a vicious cycle. The intelligent automatic ash removal device developed by our company for non clogging fly ash tubular air preheaters is aimed at addressing the above phenomenon, successfully and effectively solving the problems of wear, ash accumulation, corrosion, and other issues of tubular air preheaters in the current market. At present, the widely used boiler cleaning devices in the market include acoustic soot blowers, steam soot blowers, pulse gas soot blowers, etc. However, all three types of soot blowers have many disadvantages,

1. Disadvantages of sonic soot blowers
(1) A dedicated compressed air station is required, which requires a large one-time investment in equipment;
(2) The energy is relatively small, and for the furnace and convective heating surface, especially for the low-temperature air preheater, slagging, adhesive ash accumulation, severe ash blockage, and hard ash scale cannot be removed;
(3) The effective distance is limited, and the number of acoustic soot blowers installed is higher than that of traditional soot blowers; The installation of acoustic soot blowers with amplification structures is limited in high-temperature areas;
(4) Due to the use of saturated compressed air in the infrasonic soot blower, the filter needs to be drained regularly, and frequent freezing in winter can cause the filter to rupture; The sonic soot blower and oil mist blower need to be refueled regularly;
(5) If the air duct is not equipped with cooling air or the cooling air pressure is low, it will cause severe corrosion of the compressed air duct; If the compressed air pressure used in the sonic soot blower does not meet the requirements and the cleaning area is limited, the soot blowing effect will significantly deteriorate.

2. Disadvantages of steam soot blower
(1) Due to the fact that steam soot blowing relies on steam jet injection, the jet beam has a limited area of action, resulting in a limited medium blowing area;
(2) Due to the fact that the steam soot blower rotates the nozzle deep into the furnace for soot blowing, and the nozzle needs to be removed after soot blowing, there are many moving parts, which results in frequent operation and high probability of failure of the soot blower, as well as a large amount of mechanical and electrical system maintenance and repair;
(3) High steam consumption and high operating costs.

3. Disadvantages of pulse gas soot blower
(1) Blowing ash consumes gas and requires regular replenishment of the gas source; Gas is prone to leakage and poses safety hazards;
(2) Blowing ash mainly has a significant effect on the area near the vertical scouring surface, and there are blind spots in blowing ash;
(3) Long term vibration and erosion of fixed heating surfaces during soot blowing can cause certain damage to the furnace structure.

2、 Working principle of intelligent automatic ash removal device for tubular air preheater

The intelligent automatic ash removal device of the tubular air preheater relies on the tubular air preheater component in the boiler body as the support. The whole machine is mainly composed of a driving device, a servo reducer integrated machine, a telescopic rod, a guide component, a scraper component, and an electrical control system composed of a PLC controller and sensors. During the operation of the tubular air preheater, fly ash continuously accumulates on the outer surface of the heat exchange tube bundle from the vertical direction of the flue, partially adhering to the heat exchange tubes. With the increase of attachments, the flue gradually becomes blocked, and the exhaust gas temperature rises, endangering the safe operation of the boiler. At this time, the ash removal device passes through the pre-set time difference in the system. After receiving the action command, the system starts the program, and the driving device pushes the telescopic rod to push the comb shaped scraper assembly. It performs back and forth scraping in the gap between the heat exchange tube layers of the air preheater, so that the attachments adhered to the surface of the tube layer can be cleaned in a timely manner. Otherwise, the hydrogen sulfate ammonia formed continuously ferments on the tube wall, and when it increases to a certain extent, it is difficult to remove, causing blockage of the air preheater. This completely solves the problems of dust blockage and corrosion in the air preheater. The comb shaped scraper is made of special soft materials, which will not cause wear to the heat exchange tubes, and also solves the problems of heat exchange tube wear and heat transfer. This technology can be implemented on the tube type air preheater components of the original boiler, or it can be installed in conjunction with the air preheater that comes with the new boiler. It can be used for retrofitting the original tubular air preheater, or as a supporting feature for adding additional functions to new boiler projects, with great flexibility and practicality in selection. The following figure is a 3D schematic diagram of the automatic ash removal device of the air preheater. The figure only shows a single set of ash removal devices. According to the structural dimensions of the boiler air preheater components, multiple sets of ash removal devices can be set up in parallel, installed in parallel, and operated independently or simultaneously.

Outline drawing of intelligent automatic ash removal device for air preheater

3、 Product advantages
1. The ash removal scraper is made of high-quality aluminum alloy material, which is relatively soft compared to carbon steel heat exchange tubes. In addition, it has been verified through practice to have a suitable operating clearance, which will not cause wear to the air preheater heat exchange tubes;
2. Each scraper body is equipped with an overload automatic breaking structure. Once there is a hard object between the pipes causing jamming, the scraper will automatically break without affecting the operation of the entire device;
3. The scraper component is assembled with bolt fasteners and is a detachable connection, making maintenance and replacement convenient and fast;
4. Due to the use of PLC program automatic control mode in the device, remote control can be integrated into the boiler DCS control system to achieve remote and local intelligent control, with flexible operation and adjustable ash removal frequency;
5. The service life can reach 20 years;
6. The relative reduction of fan resistance in the crew is 1/3;
7. This technology product has a particularly significant effect on preventing low-temperature corrosion.

4、 Main technical parameters of the product (single group)
1. Power supply: 1N+PE,~ 220VAC±10%,50/60Hz；
2. Power consumption: ≤ 3kW;
3. Servo reducer integrated machine: 130T-M15015, 2.2kW, 1450rpm;
4. Ash removal working mode: intermittent;
5. Ash removal frequency: (fast, medium, slow) adjustable in three gears;
6. Remote power on/off control switch conduction current: ≤ 5mA, switch withstand voltage: ≥ 36V;
7. Temperature switch conversion temperature: 100 ℃.

5、 Product Usage
This product is mainly used for the efficiency improvement and selection matching of horizontally arranged tubular heat exchanger components, especially for the low-temperature section renovation of tubular air preheaters. It is particularly effective for the low-temperature section upgrade and renovation of boilers used in biomass waste power plants and other applications. It is particularly effective in preventing corrosion of the air preheater tube bundle caused by weak acids and bases. Modifications can also be made to the economizer inside the furnace and other tubular heat exchangers in the flue.

6、 Ordering Notice
1. Provide drawings of the air preheater tube box, air preheater components, and their associated internal and external structural dimensions of the boiler flue;
2. Specific blockage situation description;
3. Whether to upgrade or renovate;
4. Material requirements;
5. Construction period.

7、 Equipment selection table