Beam-type Chain Grate Stoker Manual

        Wafangdian City Yongning Grate Manufacturing Co., Ltd.

                  Address: Wafangdian City Yongning Town

                  Tel: 0411-85170774  0411-85170074

                  Mobile: 13364115533     13050579874

           Fax     : 0411-8517128

Post      Code: 116326

                    Website     : www.ynlupai.cn  

                      E—mail:  wfdynlp@126.com

Wafangdian City Yongning Grate Manufacturing Co., Ltd.Founded in 1988, covering an area of 50,000 square meters, it is a specialized manufacturer of boiler auxiliary machines designated by the state, located in southern Liaoning, south of Dalian, west of Bohai Bay, and east of the Shenda Expressway, with convenient transportation and superior location.

In order to adapt to market needs, our factory can design and produce various grates according to user requirements. Strong technology, advanced and complete production equipment, provide a strong foundation for creating excellent products. For many years, we have supplied many domestic boiler manufacturers, with products covering all over the country and exported to neighboring countries such as Japan, Indonesia, and North Korea, receiving high praise.

Our main products: beam-type chain grates, large flake chain grates, small flake chain grates, various slag discharging machines, coal feeding machines, grate reducers, layered coal bunkers, various boiler accessories, and undertake various grate design, transformation, installation, maintenance and other projects.

“Quality is fundamental, sincerity is the way to the world” is the purpose of our factory's development. General Manager Wang Cong is willing to work hand in hand with new and old friends at home and abroad for sincere cooperation and mutual development.

Technical characteristics of beam-type grates:

1. Scope and requirements of use

Beam-type chain grates are a mechanized, compact, and technologically advanced staged combustion device, which can be widely used in large staged combustion boilers (suitable for boilers with an evaporation capacity of 40—100t/h), and can also be used in various heating and drying equipment. It is suitable for burning bituminous coal, lignite, and peat. It uses an automatic coal feeding hopper, and can also be specially designed as a combustion device using materials such as bagasse, wood, and rice husks.

The coal quality used in this grate should meet the following requirements:

a.  The maximum particle size of coal blocks shall not exceed 40mm, and the coal dust below 6mm shall not exceed 50% of the total amount. The coal dust of 0-3mm shall not exceed 25% of the total amount.

b.  The moisture content of the coal should be less than 20%, preferably 8—10%.

c.  The ash content of the coal should not exceed 30%, but should not be less than 10%, and the volatile matter should not be less than 20%.

d.  The melting temperature of the coal ash should be greater than 1250.⁰C.

e.  Caking property should not be strong.

f.  The lower heating value of the coal should be greater than 4226kcal/kg.

g.  If the above coal quality requirements conflict with the coal feeding settings, take the higher value of the two.

The primary air temperature used in this grate must not exceed 200.⁰C.

2.  Structure and technical characteristics of beam-type chain grates:

    Components: 1. Bracket; 2. Upper and lower guide rails; 3. Furnace chain; 4. Front axle assembly and rear axle assembly; 5. Side seal; 6. Ash discharge device; 7. Coal feeding hopper; 8. Front wind door; 9. Air duct.

Specific structure and technical characteristics:

a. The bracket consists of left and right side wall panels and front, rear, and middle beams. The front and rear beams are independent frame components with good rigidity; the space between the beams serves as a combustion air chamber.

b. The upper and lower guide rails are sealed components, connected to the upper and lower surfaces of the front, middle, and rear beams.

c. The chain is formed by linking two links, and the link components are connected together with rollers, through pins, retaining rings, and positioning rivets. The links are equipped with bolt slot holes for connecting and installing the grate pieces on the angle iron beams.

d. The grate is driven by the front axle, which is equipped with a set of sprockets that push the rollers on the chain to move the chain forward; this grate has a rear axle, which rotates with the front axle under the force of the furnace chain, guiding the furnace chain into the lower guide rail. The torque of the front axle is provided by the grate reducer through a coupling.

e. The angle steel is riveted to the T-shaped cast iron small beams to form the beams, and the grate pieces with T-shaped grooves are inserted; the beam components are divided into left, middle, and right types, and are connected to the links of the chain with bolts in the transverse direction of the grate, forming the entire grate surface; one side of the grate piece is cast with a semicircular ventilation groove, and the other side has a flange, with the tail of the grate piece having an arc-shaped kiss, allowing the grate pieces to overlap front and back after installation, and spaced left and right to allow air to enter the ventilation groove.

f. In order to meet the needs of combustion at different stages on the grate surface and achieve staged air supply, the grate is divided into several air chambers along its length, and the air chambers are designed to prevent mutual air flow between them, with a complete sealing structure designed for this grate. Special sealing structures are designed between the air chambers, at the front, rear, lower part, and both sides of the grate.

g. Each wind chamber is equipped with a dust removal device. At the bottom of the wind chamber, dust removal base plates with dust removal openings are arranged, and the movable door connected to the dust removal pull rod usually seals the dust removal opening. By pulling the dust removal handle, dust falls from the dust removal opening into the leak below, releasing the fine ash and fine coal collected in the wind chamber.

h. The coal feeding device has now widely adopted a layered coal feeding system, greatly improving the degree of coal combustion.

i. This grate has a compact structure, reasonable layout, and good rigidity, thus it can be wider than the traditional flake structure.

j. The chain of this grate moves within a sealed guide rail and does not bear excessive layer combustion heat transfer, but only bears the pulling force of the grate movement; conversely, the grate plates made of heat-resistant materials are connected in series on the crossbeam, bearing the function of supporting coal combustion but not under pulling force, thus demonstrating the advantages of cast iron.

k. Since the vast majority of chains roll, the torque driving the grate movement is greatly reduced.

l. This grate has a rear axle and no eagle iron, making it less prone to failure at the rear of the grate in the furnace.

m. The chain operates in a tensioned state, does not climb high, does not arch, and has low noise.

n. The sides of the grate and the brackets use a contact-type side sealing structure to prevent coal blocks from leaking into the sides of the grate, while also preventing air leakage from the sides of the grate. Inside the grate, several independent wind chambers that decompose from each other are set up along the longitudinal direction, and the primary air entering the wind chamber slows down due to diffusion and can evenly fill the wind chamber. The air intake of each wind chamber can be adjusted through the air adjustment device.

o. The surface of the grate is flat, the grate plates overlap each other and are arranged closely, making it difficult for coal to leak and preventing plate drop. Moreover, since the grate plates are connected through the crossbeam, replacing the grate plates does not require stopping the furnace and can be quickly replaced shortly before the grate.

p. The ventilation cross-section of this grate is about 6%, and the size and spacing of the grate plates are uniform and accurate. Therefore, the airflow across the entire grate surface is uniform, greatly improving the combustion conditions in the furnace.

q. This grate has a compact structure, operates smoothly and reliably, is easy to install and maintain, and is shipped as separate parts for on-site installation.

Installation of the beam-type chain grate:

1. Installation sequence:

The installation of each part of the grate should be coordinated, and the sequence is generally as follows:

1. Install the brackets; 2. Install the dust removal device; 3. Install the air duct; 4. Install the driving shaft and the driven shaft, and connect the driving shaft to the grate reducer; 5. Install the grate chain; 6. Install the side seal; 7. Install the coal feeding hopper; 8. Install the front wind door.

2. Installation process and precautions:

(1)   Installation of the brackets

Before installation, the foundation dimensions must be checked according to the foundation drawing. Before installing the side plates of the grate, check the straightness of the side plates. If any bending is found, it should be straightened. Use iron plates with dimensions of 200mm×180mm as pads under the side plates to adjust the height of the grate side plates (generally, the number of pads does not exceed 4, and several groups of pads should be placed under each grate side plate as required; the pads should be placed on the embedded iron in the foundation and directly under the web of the grate side plates). After installing the crossbeam, use a level to measure the levelness of the (height) of the two side plates, and also check the parallelism of the two side plates, the levelness of the top of the crossbeam, and the diagonal lines of the two side plates. Adjustments must ensure that the above measurement data is within the specified range. After adjustments are completed, weld the pad group to the foundation iron plate and the lower movable plate of the grate side plate to form a whole. Grout should be filled between the pad groups.

(2)   Installation of the dust removal device

The dust removal device should be installed flat on the Z-shaped steel of the lower guide rail, and the joints between the bottom plates should be well sealed. The limit and pull rod of the valve should be installed after the air duct is installed, and the dust removal opening of the valve and the bottom plate should be well sealed. The pull rod should push and pull the valve flexibly.

(3)   Installation of the air duct

After connecting the air duct to the side plates of the grate, connect the dust removal pull rod to the drag device in the air duct, and adjust the position to make the dust removal valve slide conveniently and flexibly; the air adjustment plate of the air duct should rotate flexibly without any jamming; the pull rod, air adjustment plate, and air duct interface should be well sealed to reduce air leakage.

(4)   Installation of the upper and lower guide rails

The upper guide rail should be straight, and the spacing between the guide rails should strictly follow the requirements of the drawings. The bottom surface of the lower guide rail should be flat, and the welds at the joints of the two lower guide rails should be smooth without protrusions.

(5)   Installation of the driving shaft and rear axle

The driving shaft is assembled and delivered to the site. During installation, the bearing should be disassembled for inspection, oil stains and impurities should be removed, and lubricants should be applied. After installing the front and rear axles on the brackets, check the parallelism of the front and rear axles. Finally, connect the driving shaft to the grate reducer through the coupling.

(6)   Installation of the grate chain

Connect the chain links with pins, and under the same pulling force, measure the length of the chain. The lengths of several chains on the same grate should be equal. Then start the grate gearbox, rotate the driving shaft to bring the chain into the upper and lower guide rails, and connect them into a complete loop. The installation of the crossbeam must ensure that the same row of crossbeams is straight, and the distance between the front and rear rows of crossbeams is equal. Then install the grate plates on the beams, ensuring that the grate plates are neatly arranged on the crossbeams and leave room for thermal expansion. After installing the grate plates, they should align both horizontally and vertically.

(7)   Installation of the side seal

The side seals should be arranged neatly, and the gaps between the side seals and between the side seals and the grate chain should meet the requirements of the drawings. There should be thermal expansion gaps between the side seals and the left and right collecting boxes of the boiler.

(8)   Installation of the coal feeding hopper

The coal hopper is installed at the construction site. It is fixed on the side wall of the grate. During installation, attention should be paid to the sealing at the junction with the side wall, and the flexibility of the coal gate's lifting should be checked after installation.

(9)   Installation of the front wind door

This device should be installed after the cold state debugging of the grate, and the sealing at all gaps must be ensured during installation.

Three, quality requirements for installation:

(1) During the thermal operation of the grate, the longitudinal expansion towards the rear and the lateral expansion from the centerline of the grate to both sides must not be obstructed;

(2) The gap between the side seal and the edge grate plates must strictly comply with the drawing requirements;

(3) The diagonal deviation of the two side wall panels should not exceed 4mm;

(4) The parallel span deviation of the two side wall panels^+3₀mm;

(5) The longitudinal height difference between the left and right side wall panels must not exceed 3mm;

(6) The top of the support beam must be guaranteed to be on the same horizontal plane, with a deviation of no more than 2mm between the highest and lowest points;

(7) The upper guide rail should be straight, and the spacing between the guide rails must strictly comply with the drawing requirements.

(8) The lower guide rail should be aligned with the corresponding upper guide rail, and the distance between two adjacent lower guide rails should comply with the drawing requirements;

(9) The axis of the driving shaft and the transverse axis of the rear shaft should be parallel and comply with the drawing requirements;

(10) The height difference between the axis of the driving shaft and the output shaft of the grate reducer should not exceed 0.5mm;

(11) After the chain is straightened at the same tension level, the relative length difference of all chains on the same grate should not exceed 8mm;

(12) An expansion gap of 6mm should be reserved between adjacent cross beams on the same cross-section installed on the chain, and insufficient gaps should be ground;

(13) After the furnace chain is installed, the grate plates should be neat, and there should be no jamming or falling off during no-load operation;

(14) The assembly of the front wind door should not have warping or unevenness;

(15) The sealing between the coal hopper and the side wall panels must be tight;

(16) The lifting of the coal gate in the coal hopper should be flexible;

(17) The grate air duct, air chamber, and ash discharge door should be sealed, and the ash discharge pull rod should be flexible;

(18) It is not allowed to have iron or other debris lost or trapped anywhere on the grate.

Four, no-load test after installation:

(1)   It should run continuously for 24 hours, at low speed for 6 hours, medium speed for 6 hours, and high speed for 12 hours.

(2)   During the no-load test, the following items should be checked:

A. The temperature rise of the reducer lubricating oil should not exceed 35℃.

B. The current and voltage of the motor should not exceed the rated values, and the temperature should not exceed 60℃.

C. The temperature rise of the bearing should not exceed 40℃.

D. The operation of the grate should be stable and neat, with no jamming, and the noise should be below 70 decibels.

E. Measure the grate speed to meet the specified requirements.

Five, usage of the beam-type chain grate:

1. Ignition of the grate

For igniting combustible coal (lignite and volatile matter not less than 20% bituminous coal), first open the front wind door and the ash discharge door for natural ventilation, lay a thin layer of coal on top of the first air chamber of the grate, and cover it with 200-300mm thick dry firewood, using oil cotton to ignite. When the firewood catches fire, close the front wind door and the ash discharge door, and mechanically blow air into the first air chamber. After the firewood burns vigorously, add a small amount of coal on top of the burning firewood. Once the coal in the first air chamber ignites, the semi-burnt coal moves to the second air chamber area, while continuously adding coal on top of the first air chamber and mechanically blowing air into it. Following the same procedure, the coal will sequentially move through the grate to the rear, igniting the entire grate.

For igniting difficult-to-burn coal, lay a layer of coal with higher volatile matter on top of the first air chamber, and cover it with firewood, following the same ignition procedure as above.

2. Operation management of the grate

(1)   The wind pressure in the air chamber (the amount of incoming air) is adjusted by the air door switch of the air inlet pipe. During operation, adjust the wind pressure according to the actual situation, and be careful not to sharply reduce or stop the air supply to the combustion area;

(2)   The thickness of the coal layer should be maintained at a certain level, not too thin or too thick. Only when changing the type of coal or when there is a significant change in boiler load should the thickness of the coal layer be adjusted;

(3)   The amount of coal burned is adjusted by changing the linear speed of the grate and the thickness of the coal layer. The fuel should be completely burned out 300-600mm before reaching the rear slider. According to this principle, reduce the thickness of the coal layer and increase the speed of the grate, or increase the thickness of the coal layer and reduce the speed to ensure the output of the boiler and the complete combustion of the fuel;

(4)   Ensure that the coal burns evenly across the grate. If there are fire spots, black flames, or uneven coal layers, use a fire poker to level it out;

(5)   It is strictly forbidden to have positive pressure combustion. If positive pressure occurs, check whether the blower and induced draft fan are working properly, and whether the flue gas ducts inside and outside the boiler are blocked, and eliminate any issues in a timely manner;

(6)   Avoid coal combustion extending to the coal gate under the coal feeding device. If found, immediately stop the air supply to the first air chamber or take other measures to slow down the ignition of the coal (such as increasing the moisture content of the coal);

(7)   If coking occurs (with coke blocks larger than 200mm), measures should be taken to remove it in a timely manner, and it should not be allowed to continue growing;

(8)   During the operation of the grate, the ash and coal leaks in each air chamber should be cleared regularly to avoid affecting the air supply and causing combustion. To ensure the normal operation of the grate, the boiler operator should remove ash 3 times per shift;

(9)   The emergency shutdown of the grate is generally carried out in the following order:

A. Stop adding coal to the grate.

B. Reduce the grate to the lowest speed until the ash is completely discharged.

C. Mechanical ventilation should be maintained before the furnace cools down.

3. Maintenance and Repair of the Grate

(1)   During operation, the bearings on the front and rear axles and the coal feeding device, as well as all locations set for lubrication, should be regularly filled with the specified grade of lubricant as required. Special attention should be paid to the timely lubrication of the drive axle and front support bearings;

(2)   Burnt grate bars and elongated or deformed grate chains should be replaced in a timely manner;

(3)   If the grate shows signs of deviation, it should be adjusted in a timely manner;

(4)   When the grate is out of operation for a long time, the coal in the coal hopper should be removed to prevent corrosion, and anti-corrosion agents should be applied to all transmission parts;

(5)   During normal operation, the tension of the grate chain should be ensured. After a new furnace has been in continuous operation for one month, it should be shut down for adjustment to tighten the grate chain. When the grate is running continuously, attention should also be paid to the tension of the chain, and adjustments should be made in a timely manner.