Water tube boiler (1) Single-dose tube water tube boiler Single-dose tube water tube boiler mainly has two structures, one is a single-drum vertical-type water tube boiler, and the other is a single-drum horizontal-type water tube boiler, while the latter structure is often boiler The capacity is relatively large.
1. Single drum vertical water tube boiler
Single-pot vertical water-tube boiler, commonly used models such as DZW (single, vertical, and forward), working pressure is 1.3MPa, evaporation is 4t / h, fast-loading boiler. The combustion equipment is a horizontal reciprocating grate.
The structure of this boiler is shown in Figure 2-9. There is only one drum, which is arranged longitudinally in the center of the top of the boiler. Two sets of convection tube bundles are arranged on the left and right sides of the furnace to form a 'human' shape. The upper ends of the convection tube bundles and the water wall tubes on both sides are connected with the drum, and the lower ends are respectively connected with the lower headers on both sides, thereby eliminating the downcomers of the water wall.
There are two situations in the flue gas process. One is as shown in Figure 2-9(a). The flue gas exits the left side of the combustion chamber on the left side of the furnace, and the left side convection tube bundle area is flown from the back to the front, and the convection tube bundle is flushed laterally. The flue gas passes upwards through the flue of the front end of the drum, flows to the right convection tube bundle area, and then flows from front to back, leaving the boiler body from the rear right side after entering the tail, entering the tail flue, passing the economizer and air. The preheater is discharged to the chimney by the induced draft fan through the precipitator. The other is as shown in Figure 2-9(b). The flue gas leaves the burnout chamber at the back of the furnace, and then divides into two left and right channels, respectively entering the convection tube bundle area on both sides, flowing backward from the front and flushing the convection tube bundle laterally. Then it merges into the upper cigarette case at the front of the boiler, and then flows upwards and downwards through the economizer and air preheater. After the -zui, it is discharged by the chimney through the dust collector and the induced draft fan.
The water circulation loop is relatively simple. The water flows from the t-cylinder into the convection tube bundle on both sides, descends to the lower header, and then rises through the furnace water-cooled wall tube and a part of the heated convection tube bundle, and returns to the drum.
The advantage of this type of boiler is that there is no partition wall in the convection tube bundle, and the flue gas flows once, making the boiler structure compact. The use of a single drum reduces steel consumption and manufacturing effort. The disadvantage is that the water capacity is small, the steam pressure fluctuates greatly during operation, and management is difficult.
2. Single-tube horizontally-disposed water tube boiler The horizontally arranged water tube boiler adopts a ┌â”-shaped arrangement, natural circulation, and the combustion mode is mostly a chain grate, or a circulating fluidized bed. The boiler pressure is generally 1.o~2.5MPa, and the boiler output is generally 19~35t/h. Figure 2-10 shows a circulating fluidized bed boiler.
Ascending along the furnace, the dilute phase zone in the upper part of the furnace exchanges heat with the surrounding water wall, and then enters the separator through the furnace outlet and the convection superheater. A part of the fly ash is separated and burned again through the dense phase zone of the furnace through the ash pipe and the ash return valve. The ash formed by the combustion is discharged outside the furnace through the cold slag pipe and the slag cooler. The role of the slag cooler is 800~900. The hot slag of C is cooled to a lower temperature, and heat is recovered for use.
This type of combustion can not only burn inferior fuel, such as the above boiler is burning stone or stone coal. Moreover, a desulfurizing agent (such as limestone) can be added during the feeding to effectively remove the S02 gas in the flue gas. At the same time, due to the low combustion temperature in the furnace, the formation of nitrogen oxides can be reduced, which is good for environmental protection.
Due to the large amount of fly ash in the furnace, the dense phase of the lower part of the furnace is more seriously worn, and the wear of the convection heating surface is also serious. In the design and operation, attention should be paid to wear prevention. In addition, the dust concentration of the boiler is relatively large, and a dust collector with better performance should be selected.
(2) Double-drum water tube boiler The double-dose tube water tube boiler is also divided into two types: two-pot vertical position and two-pot horizontal arrangement.
1. Double drum horizontally placed water tube boiler This type of boiler with small capacity is SHW (Double·Horizontal) type, SHH (Double·Horizontal) type, working pressure is 1.3MPa, and evaporation is 2t/ h or 4t/h, as shown in Figure 2-11.
The boiler structure is mainly composed of two upper and lower horizontal drums 1 and 4, a convection tube bundle 2 and a water wall tube 11 and the like. The upper drum is slightly smaller than the lower drum. The front and the horizontal lines of the two drums are 80. Intersection angle. The water wall tube is taken out from the front of the upper drum and tilted down to the horizontal line. The angle of intersection, along the front wall, goes down to the upper part of the furnace door, and then passes through the front wall and is welded to the outer horizontal box of the furnace wall. There are three smoke-proof walls in the convection tube bundle. * The roadside smoke wall is built on the right side of the *tube bundle at the back of the furnace, which accounts for about two-thirds of the width of the entire furnace. * The tube bundle is exposed outside the smoke-proof wall, and the absorption radiant heat of the furnace σ is intersected perpendicularly with the *-zone wall. The third smoke-proof wall is generally an iron plate connected to the back wall of the boiler. After entering the convection zone from the left side of the furnace, the flue gas flows in a 'Z' shape along the three flue pipes, and the tube bundle is washed laterally, and then exhausted by the chimney by the chimney.
The water cycle has a two-point system. One is the body water circulation system. After the feed water enters the upper drum, the tube bundle of the third flue is lowered to the lower drum, the dirt in the water is deposited on the lower drum, and the water is raised from the tube bundle of the * and the second flue to the upper pot. The cylinder is continuously circulated and the other is a water-cooled wall water circulation system. The water flows from the descending pipe at both ends of the upper drum to the front cross box, and returns to the upper drum through the water wall tube, and the generated steam enters the steam space and is separated. Water then participates in the cycle.
The advantage of this kind of boiler is that it is compact in structure, easy to manufacture, and each tube bundle is bent into a certain arc, which is rich in elasticity and has sufficient furnace volume, and is suitable for burning various coal types. The disadvantage is that it is difficult to clean the scale and the water quality is strict. Old-fashioned boilers are mostly operated by hand. The labor intensity is high. There is no tail heating surface, the smoke flow is short, and the exhaust gas temperature is high.
Figure 2-12 shows the structure of the SHL20-13 boiler. The boiler body is mainly composed of upper and lower drums, convection tube bundles, water-cooled wall tubes and headers. The tail has cast iron economizer and tubular air preheater. The upper and lower drums are placed on the same vertical plane, and the diameter of the upper pot is slightly larger than that of the lower drum. There are three sets of convection tube bundles between the two drums, and the front group tube bundle has only one row of tubes. There are two smoke-proof walls in the middle of the two sets of tube bundles near the furnace flue gas outlet. The flue gas enters the convection zone from the upper rear of the furnace, first flushing the *group tube bundle vertically downwards, and then turning back 180. The Z-shaped zigzag is flushed to the second and third sets of tube bundles, and then folded from the upper part of the third group of tube bundles into the tail heating surface, and then enters the dust collector through the flue gas outlet, and is exhausted to the atmosphere by the induced draft fan through the chimney.
The furnace is at the front of the boiler and is surrounded by water-cooled wall tubes. The upper ends of the front and rear wall water-cooled wall pipes are directly connected to the upper drum, and the lower ends are connected to the front and rear headers respectively. The water-cooled wall tubes on both sides are divided into three groups: front, middle and rear. The lower ends of the front and middle groups are connected to the anti-focus boxes on both sides, and the upper end is connected to two separate upper headers on both sides, and the steam guide tube and the upper pot are passed. After the tube is connected, the lower end of the group is respectively connected to the side lower header (located in the middle and lower part of the side wall), and the upper end is also connected to the upper header, and is connected to the upper drum through the steam guiding tube. All the lower headers and the anti-focus box are supplied by the down pipe from the R drum.
The design of this type of boiler is anthracite, so a low and long rear arch and a high front arch are used in the furnace, and the front and rear arches form a narrow throat in the furnace, promoting air and coal dust. Mix well to facilitate burning.
Figure 2-13 is a double drum horizontally placed room water tube boiler, model SHS20-13. The structure of such a boiler is shown. The upper and lower drums are placed on the same vertical plane. The diameter of the upper drum is slightly larger than that of the lower drum. All the weight is supported by the lower drum through the convection tube bundle, and the lower drum is supported by the steel frame. The front part of the boiler is a furnace, and two pulverized coal burners are symmetrically arranged in the lower part of the side wall. The four walls of the furnace are covered with water-cooled wall pipes, and the water is supplied from the lower pipe connected to the lower drum. The water-cooled wall pipe of the furnace is arranged in a thin exhaust gas outlet at the outlet of the wall of the furnace to form a slag-proof pipe, which is beneficial to prevent A large chunk of coke. The header is arranged outside the furnace wall, which is safe and easy to inspect and clean.
The convection tube bundle is divided into three groups l, * the group has only one row, the tight * anti-capacity tube, and the main road smoke-proof wall is arranged in the middle of the second and third groups. Under the convection tube bundle, there is a falling hopper, which uses the flue gas to turn the separation of the flying plate to reduce the original dust emission of the boiler. An economizer Liqing gas preheater is installed at the tail of the boiler.
The flue gas flow path is as follows: i The high-temperature flue gas rises from the middle of the furnace, passes through the anti-slag discharge pipe and enters the * group convection mine pipe bundle, flows downward, and then turns back 180. In the second and third sets of convection tube bundles, the zigzag turns upwards, and the two sets of tube bundles are longitudinally and laterally flushed, and then flow from the upper part of the third group of tube bundles through the tail heating surface to leave the boiler body and enter the dust collector. , is sent to the chimney by the induced draft fan.
The advantage of this kind of boiler is that it is compact in structure, low in metal consumption, good in elasticity, free to expand after being heated, water circulation can be *, and thermal efficiency is high. The disadvantage is that the top of the furnace is a light furnace wall, which is prone to cracks. When pulverized coal deflagration occurs, the top of the furnace is likely to be destroyed by radiation. The water quality is high, not only the hardness but also the oxygen removal and degreasing. Anti-fouling and corrosion furnaces are easy to slag at the cold ash hopper, and the convection tube bundle is easy to accumulate ash, which requires high technical level of the furnace personnel.
2. Double-drum vertical water tube boiler Double-pot vertical water tube boiler, there are more than one type of furnace. Figure 2-14 is a furnace type that is widely used at present. Its model is SZW (double, vertical, toward), its working pressure is generally 1.3MPa, and the evaporation is 2t/h or 4t/h. The structure of the boiler is mainly composed of pressure elements such as upper drum 1, lower drum 3, water wall tube 7, convection tube bundle 8 and header. The cast iron economizer is installed at the tail 6 . The upper drum is larger in diameter than the lower drum, and the barrel is long, and the two drums are vertically aligned on the same vertical plane. Two sets of convection tube bundles are connected between the drums, and two longitudinal smoke partition walls are arranged in the left front part and the middle rear part of the tube bundle. The furnace is located on the left side of the boiler and parallel to the convection flue to form a D-shape.
The coal depends on its own weight and falls from the coal hopper to the reciprocating grate and enters the furnace to burn. The flue gas enters the convective flue from the right side of the rear of the furnace, first flushing the *group bundle from the back and then turning 180 to the right. Bend into the second set of tube bundles, flowing from front to back, directly from the end of the tube bundle into the tail heating surface, and discharged to the atmosphere through the chimney. There are two water circulation systems: one is the part of the radiant heating surface. There is a drainage cold wall tube on both sides of the furnace, the upper end of which directly communicates with the upper drum, and the lower end is supplied by the lower drum through the lower header to form an independent water circulation system. The other is the convection heating surface section. In the two sets of convection tube bundles, * the tube bundle (rising tube) is heated by the high temperature flue gas, the water or soda mixture has a low density, and the second group of tubes bundles absorbs less heat, the water temperature is low, the density is high, and the flow is downward. A water circulation system is formed between the upper and lower drums.
The advantage of this kind of boiler is that the distance between the upper and lower drums can be changed, and the number of rows of convection tubes, the distance between the pipes, and the like can be changed to keep the flow rate of the flue gas within the required range, and the flue partition wall follows the pot. The center line of the tube is arranged to facilitate the removal of the dust in the lower part of the tube bundle. In order to match the depth of the furnace, the grate is longer, which is beneficial to full combustion and reduce the carbon content of the -k ash. The disadvantage is that there is usually no water front and rear wall in the furnace, and it is not convenient to arrange the furnace arch.
Another form of double vertical tube boiler has an evaporation capacity of 6.5t/h or 16t/h, and has two configurations: long upper drum (Figure 2-15) and short upper drum (Figure 2-16).
The main body of the boiler is mainly composed of two upper and lower vertical drums, a convection tube bundle, a water wall tube and a header, and the like, and an economizer and an air preheater at the tail. The lower drum shown in Figure 2-15 is about half shorter than the upper drum and is located in the lower part of the second half of the boiler. The first half of the upper drum extends to the top of the furnace. The two drums are connected by a curved water pipe, which is divided into three flue gas passages by two horizontal smoke-proof walls. Water-cooled walls are arranged on the front, back, left and right sides of the furnace. The upper end of the water wall tube is expanded with the upper pot, the lower end is welded to the lower header, and the rear end of the lower tank extends to the bottom of the drum, and the water supply down pipe is connected to the lower drum. The upper drum shown in Figure 2-16 is shorter and only longer than the lower drum. It is a modified furnace type in Figure 2-15. It eliminates the water wall of the front wall, adds two side upper headers, and welds to the upper end of the water wall tube on both sides of the furnace. Each side of the header has a steam pipe connected to the upper drum to increase the burnout chamber. The position of the drum under the side wall cold wall tube is 3m higher than the operating floor, which raises the elevation of the entire furnace body and the furnace.
Most of the combustion equipment uses a wind-driven mechanical slinger and a hand-cranked grate, as well as a chain grate or a vibrating grate. When burning, the flue gas flows from the upper right side of the furnace to the convection tube bundle zone, and the horizontal 'Z'-shaped route along the two smoke blocking walls is bent back from the front to the back, laterally flushing the bundle, and then entering the tail from the lower left side of the furnace wall. After the heating surface, zui passes through the dust collector and is sent to the chimney by the induced draft fan to discharge to the atmosphere. There are five or six water circulation systems that can be summarized into two parts. First, the convection heating surface part: After the water supply enters the upper drum, the convection tube bundle at the rear is lowered to the lower drum, and after the dirt is deposited in the lower drum, the convection tube bundle from the front rises to the upper drum to form a water circulation system. The second part is the radiation heating surface part: the front, rear, left and right water wall tubes of the upper boiler tube, each of which constitutes an independent water circulation system. There are four short upper boiler tubes, although the water wall tube before the Yuan, but increased The water-cooled wall tubes on the left and right sides of the burnout chamber constitute a total of five independent water circulation systems.
The advantage of this type of boiler is that it has a compact structure and a small outer shape. The flue gas laterally flushes the tube bundle, and the heat transfer effect is good. The disadvantage is that, due to the use of coal shovel to feed coal, it belongs to semi-suspended combustion, and the smoke is large. The high carbon content of fly ash requires high water quality. The feed water must be softened, especially in the boiler tube, such as water shortage or poor water quality. It is easy to deform the drum and bulge.
(III) Angle tube boilers In recent years, China's industrial boiler industry has introduced angle tube boiler products manufactured by Warren, Denmark, which has aroused the interest and great concern of domestic water circulation experts for such boilers.
The angle tube type boiler is a name of a water tube boiler in which four sides are arranged with an unheated down pipe and has a self-supporting effect, and the drum is generally arranged in a single drum type.
1. The basic principle of the angle tube boiler The basic principle of the angle tube boiler is to use a piping system as the frame (or skeleton) of the boiler. This frame acts as both a downcomer, a lower distribution header, and an upper header, and completes a certain degree of soda separation. In general, the frame is the support frame for the entire boiler, and all boiler loads are absorbed by it.
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