CN211854707U - A kind of coal steam drying rotary furnace to strengthen heat transfer device - Google Patents

Abstract

The utility model belongs to the technical field of coal drying, and specifically discloses an enhanced heat transfer device for a coal steam drying rotary furnace, comprising a coal steam drying rotary furnace, one end of the coal steam drying rotary furnace is a feed port, and the other end of the coal steam drying rotary furnace One end is the discharge port. In the coal steam drying rotary kiln, 2-5 circles of steam tubes are arranged in concentric circles along the length of the furnace. On the inner wall, several low-temperature flue gas tubes are arranged in the coal steam drying rotary furnace along the furnace length. In the coal steam drying rotary furnace, the low temperature flue gas discharged from the coal retorting furnace is used as the heat source, and the drying temperature of the coal can be changed by indirect or direct heat exchange between the flue gas and the coal. Raised to 270 ~ 300 ℃.

Description

A kind of coal steam drying rotary furnace to strengthen heat transfer device

technical field

The utility model belongs to the technical field of coal drying, in particular to an enhanced heat transfer device for a coal steam drying rotary furnace.

Background technique

The drying process of coal is a process in which the moisture in the coal is evaporated and discharged by heating. The drying of wet coal is a process of moving the moisture inside the coal to the surface under the condition of heating, changing from liquid state to vapor state, and then moving the moisture from the surface of the coal into the surrounding gas medium. Coal drying is a comprehensive process of heat transfer and mass transfer: (1) The heat transfer process of coal drying: including the drying medium transferring heat to the coal surface by convection heat transfer, and then transferring heat to the inside of the coal by conduction heat transfer; After the coal surface is heated, the water in the coal vaporizes and evaporates, changing from liquid water to gaseous steam. (2) Out-diffusion process of coal drying: the diffusion of water vapor to the drying medium through the coal surface boundary layer. (3) The internal diffusion process of coal drying: the diffusion of moisture from the interior of the coal to the surface. In the coal drying process, the above three processes are carried out simultaneously.

In the indirect rotary kiln for coal drying, the coal is not in direct contact with the heating medium, and indirect heat transfer is achieved through the solid wall surface, and the wet steam generated during the coal drying process is discharged from the rotary kiln by means of negative pressure suction or a small amount of carrier gas. . According to the different setting forms of the solid wall, drying furnaces are mainly divided into two categories: external heating rotary furnaces and tubular rotary furnaces. Most of the externally heated rotary furnaces use hot flue gas to heat the outer wall of the rotary cylinder, and the coal in the furnace is dried through the cylinder wall; the tubular rotary furnace is a form of externally heated rotary furnaces. The tube dries the coal in the cylinder.

Coal steam drying rotary kiln is a kind of rotary kiln. Its main equipment is a horizontal rotary cylinder. In the cylinder, 2-5 circles of heating pipes running through the entire cylinder are arranged in concentric circles along the length of the furnace. The rib is fixed on the cylinder wall and rotates with the cylinder. The cylinder is installed in a tilted manner with a high feed end and a low discharge end. After the material enters the cylinder, with the rotation of the cylinder, the material is continuously lifted, rolled down, and conducts heat transfer with the heating tube and furnace gas. The steam drying rotary furnace uses steam heat to indirectly heat the coal. The heating steam is passed from the end of the rotary furnace through the steam chamber to the heat exchange tube, and the coal is added to the cylinder from the feed end of the rotary furnace. On the outside of the pipe, the wet coal and the steam pipe wall are in contact for heat exchange. With the rotation of the rotary kiln, the water in the coal absorbs heat and evaporates when the coal moves toward the discharge end. When the coal reaches the discharge end of the rotary kiln, its moisture content reaches the required level, and the dried coal will be discharged from the rotary kiln. The discharge end of the converter is discharged and enters the next process to continue processing. The condensate generated after the steam heat exchange enters the recovery system for recycling. The air entrained in the coal and the water vapor produced by drying are discharged from the upper part of the discharge end of the rotary furnace, and enter the tail gas treatment system to recover the water. In order to improve the mass transfer rate in the drying process of the rotary kiln, a carrier gas is usually introduced into the cylinder so that the moisture removed during the coal drying process can be quickly discharged from the rotary kiln. Fig. 1 is the existing structure diagram of the coal drying rotary kiln.

In the coal steam drying rotary furnace, from the point of view of the gas flow in the furnace, in order to improve the heat transfer efficiency, the high temperature furnace gas should be filled with the furnace chamber or flow on the surface of the coal, but for coal steam drying (there is also a small amount of wet nitrogen) from the rotary furnace It is said that the amount of gas generated in the coal drying process is small, and the high-temperature furnace gas cannot fill the furnace space, causing the high-temperature furnace gas to be located near the furnace top, and a lower-temperature gas layer is formed between the high-temperature furnace gas and the coal, and the low-temperature gas layer is formed. The existence of the furnace top tube wall and the heat transfer of the high-temperature furnace gas to the coal "insulate" the effect, reducing the heat transfer in the rotary furnace. Fig. 2 is the furnace gas stratification distribution diagram in the rotary furnace.

In the coal steam drying rotary furnace, the inner and outer surfaces of the heating tubes are smooth surfaces. When the gas medium flows inside and outside the heating tubes, due to the relative velocity between the gas and the wall, a certain thickness will be formed on the wall. gas boundary layer. The thickness of the boundary layer is related to the fluid velocity, and the thicker the boundary layer, the greater the thermal resistance. The existence of the boundary layer where the gas medium flows on the wall surface reduces the heat transfer inside and outside the heating tube. Figure 3 shows the structure of the convective heat transfer boundary layer of the tube wall.

In the coal steam drying rotary furnace, when the heating medium in the steam tube is steam, when the steam contacts the wall surface below the saturation temperature, a film-like solidification will be formed on the wall surface. The wall surface of the film-like solidification is covered by a layer of liquid film, and the latent heat of phase change released by condensation must pass through the liquid film to be transmitted to the cooling wall surface. At this time, the liquid film becomes the main thermal resistance of heat exchange. At the same time, after the liquid film is formed inside the steam tube in the rotary furnace, when the steam flow rate is low, the condensate will accumulate at the bottom of the tube, while the steam is located in the upper part of the tube. As the heat exchange process progresses, the thickness of the liquid film increases continuously, and the heat exchange thermal resistance of the inner wall of the pipeline increases continuously, resulting in the reduction of the heat transfer from the steam tube to the coal. In addition, the low temperature of the steam results in a low drying temperature of the rotary kiln wall, which is also an important factor affecting the heat transfer in the rotary kiln. Figure 4 is a schematic diagram of the internal heat exchange process of the steam tube.

Utility model content

The purpose of the utility model is to solve the problems of low coal drying temperature, low heat exchange efficiency between coal and furnace gas, large thermal resistance inside and outside of the tube, low airflow velocity in the rotary furnace, low coal drying temperature in the existing coal steam drying rotary furnace, In view of the problems of low temperature and the like, a coal steam drying rotary kiln strengthening heat transfer device is provided, which improves the drying temperature of coal in the rotary kiln, improves the heat transfer efficiency and reduces the steam usage.

In order to meet the above-mentioned purpose, the technical scheme adopted by the present utility model is:

An enhanced heat transfer device for a coal steam drying rotary furnace, comprising a coal steam drying rotary furnace, one end of the coal steam drying rotary furnace is a feeding port, the other end of the coal steam drying rotary furnace is a discharging port, and the In the coal steam drying rotary furnace, 2-5 circles of steam tubes are arranged in concentric circles along the length of the furnace and run through the entire cylinder. The steam tubes are fixed on the inner wall of the coal steam drying rotary furnace through ribs. The end of the feed port is provided with a carrier gas inlet, the upper end of the discharge port is provided with a carrier gas outlet, and a number of low-temperature flue gas tubes are arranged in the coal steam drying rotary furnace along the furnace length direction. The tubes are distributed in a star shape along the circumferential direction of the inner wall of the coal steam drying rotary furnace, and the low temperature flue gas tubes are located above the coal material surface in the coal steam drying rotary furnace and are not in contact with the coal.

Preferably, the coal steam drying rotary furnace is provided with several lifting plates along the furnace length direction, and one side of the lifting plates is welded on the inner cylindrical wall of the coal steam drying rotary furnace.

Preferably, the outer surfaces of the steam tubes and the low-temperature flue gas tubes of the coal steam drying rotary furnace are provided with fins that are self-integrated with the wall surface, and the expanded surface area of the fins is 2-7 times that of the smooth surface.

Preferably, a twist-shaped metal insert is added inside the steam tube and the low-temperature flue gas tube of the coal steam drying rotary furnace.

Preferably, the carrier gas of the coal steam drying rotary furnace adopts the low-temperature flue gas at 300-350° C. discharged from the retort furnace, and the low-temperature flue gas and the coal adopt the form of co-current heat exchange.

Preferably, the low-temperature flue gas at 300-350° C. discharged from the retort is used in the steam tube and low-temperature flue gas tube of the coal steam drying rotary furnace, and the low-temperature flue gas and the coal adopt a countercurrent heat exchange method.

Preferably, a jacket cylinder is provided on the inner side of the cylinder wall of the coal steam drying rotary kiln, a jacket is formed between the jacket cylinder and the inner wall of the coal steam drying rotary kiln, and the annular jacket passes through The low-temperature flue gas at 300-350°C discharged from the retort furnace transfers heat to the rotary furnace through the residual heat of the low-temperature flue gas in the jacket.

Preferably, a furnace gas circulating fan is arranged outside the coal steam drying rotary furnace, and the furnace gas circulating fan pressurizes a part of the furnace gas discharged from the carrier gas outlet of the coal steam drying rotary furnace through the circulating fan, and then removes it from the coal. The feed end of the steam drying rotary kiln is blown in.

The beneficial effects of the present utility model are:

(1) In the coal steam drying rotary furnace, the low-temperature flue gas discharged from the coal retort furnace is used as the heat source, and the drying temperature of the coal can be increased to 270-300 ℃ by indirect or direct heat exchange between the flue gas and the coal;

(2) In the coal steam drying rotary furnace, by arranging a lifting plate on the inner side of the furnace body, inserting pieces on the inner side of the tube, fins on the outer side of the tube, and a jacket on the inner side of the cylinder wall of the furnace body, it can be Strengthen the heat transfer efficiency of coal and improve the drying quality of coal;

(3) In the coal steam drying rotary furnace, the low-temperature flue gas discharged from the coal retort furnace is used as the carrier gas, and the low-temperature flue gas of 300-350 ℃ discharged from the dry distillation furnace is also used in each tube, and the furnace gas circulation is set. The device strengthens the heat transfer in the coal steam drying rotary furnace, achieves the purpose of increasing the coal drying capacity, and at the same time improves the reuse of energy, and achieves the effect of environmental protection and energy saving.

Description of drawings

Fig. 1 is the existing structure diagram of coal drying rotary kiln;

Fig. 2 is the furnace gas layered distribution diagram in the rotary furnace in the prior art;

Fig. 3 is the convective heat transfer boundary layer structure of the tube wall in the prior art;

Fig. 4 is the internal schematic diagram of the steam tube in the prior art;

5 is a schematic structural diagram of the utility model;

Fig. 6 is the structural schematic diagram of adding a jacket cylinder and a lifting plate in the rotary kiln;

Fig. 7 is the structural schematic diagram that the outer wall of each tube is provided with fins and the inner wall is provided with inserts;

Fig. 8 is the axonometric view of fins arranged on the outer wall of each tube;

Figure 9 is a cross-sectional view of inserts provided inside each tube;

In the picture: 1. Coal steam drying rotary furnace, 2. Feed inlet, 3. Outlet, 4. Steam tube, 5. Low temperature flue gas tube, 6. Lifting plate, 7. Jacketed cylinder, 8. Jacket, 9. Fins, 10. Metal insert, 11. Carrier gas inlet, 12. Carrier gas outlet.

Detailed ways

Below in conjunction with accompanying drawing and working principle, the utility model is further described:

In the coal steam drying rotary furnace, when the heating tube is within the coal seam in the rotary furnace, the heat transfer process between the tube wall and the coal includes: (1) Heat is first transferred from the steam in the tube by condensation or convection heat transfer. to the inner wall of the heating tube; ② the inner wall of the heating tube transfers the received heat to the outer wall of the heating tube by heat conduction; ③ the outer wall of the heating tube transfers the heat from the outer wall of the heating tube to the fabric layer close to the wall in the form of conduction heat transfer and radiation heat transfer. (4) The particles in the material layer close to the wall transfer heat to the particles in the material layer far from the wall surface by means of radiation heat transfer and conduction heat transfer; (5) The particles transfer heat from the surface to the particles by conduction heat transfer. internal.

In the coal steam drying rotary furnace, when the heating tube is above the coal seam, the heat transfer process includes: (1) the steam in the tube transfers its own heat to the inner wall of the heating tube by condensation or convection heat transfer; (2) the inner wall of the heating tube will The received heat is transferred to the outer wall of the heating tube by heat conduction; ③The outer wall of the heating tube transfers the heat to the furnace gas, the furnace wall that is not in contact with the coal, and the coal on the surface of the material layer in the form of conduction heat transfer and radiation heat transfer; ④ Furnace gas , The furnace wall that is not in contact with the coal transfers the received heat to the coal on the surface of the material layer in the form of convection and radiation;

An enhanced heat transfer device for a coal steam drying rotary furnace, comprising a coal steam drying rotary furnace 1, one end of the coal steam drying rotary furnace 1 is a feed port 2, the other end of the coal steam drying rotary furnace 1 is a discharge port 3, In the steam drying rotary furnace 1, 2-5 circles of steam tubes 4 are arranged in concentric circles along the furnace length direction and run through the entire cylinder. The steam tubes 4 are fixed on the furnace inner wall of the coal steam drying rotary furnace 1 through ribs. A carrier gas inlet 11 is arranged at the 2 end of the feeding port, a carrier gas outlet 12 is arranged at the upper end of the material outlet 3, and a number of low-temperature flue gas tubes 5 are arranged in the coal steam drying rotary furnace 1 along the furnace length direction. The pipes 5 are distributed in a star shape along the circumferential direction of the inner wall of the coal steam drying rotary furnace 1. The low temperature flue gas tubes 5 are located above the coal material surface in the coal steam drying rotary furnace 1 and are not in contact with the coal. On the basis of the original steam tube 4, a plurality of low-temperature flue gas tubes 5 are added along the furnace length direction, and the plurality of low-temperature flue gas tubes 5 are distributed in a star shape along the circumferential direction of the rotary furnace. The heat of the flue gas is used as a supplementary heat source for the coal steam drying rotary furnace 1. The additional low-temperature flue gas column 5 is located above the coal material surface and does not contact the coal. The heat transfer by convection and radiation transfers the heat to the inner wall of the tube, and then transfers the heat to the outer wall of the tube through the conduction of the tube wall. Furnace gas, coal not in contact with the furnace wall and the surface of the material layer, through the implementation of this heat transfer method, the output of a single furnace of the rotary furnace can be increased, and the temperature of the coal discharged from the rotary furnace can be increased to 220-250 ℃. Figure 5 is a diagram of adding a low-temperature flue gas tube in the rotary furnace.

The coal steam drying rotary furnace 1 is provided with several lifting plates 6 along the furnace length direction, and one side of the lifting plates 6 is welded on the inner wall of the cylinder of the coal steam drying rotary furnace 1. The original structure of the coal steam drying rotary furnace 1 On the basis of the furnace length, a plurality of lifting plates 6 are added along the length of the furnace, and one side of the lifting plates 6 is welded to the inner wall of the cylinder. The top of the cylinder is thrown down, and the thrown coal will move relative to the high-temperature gas in the rotary furnace during the falling process, which can increase the convection and radiation heat transfer between the coal and the furnace gas; 2) The lifting plate is welded on the furnace wall. The inner side of the rotary furnace increases the contact area between the coal and the lifting plate, and improves the heat transfer from the inner wall of the cylinder to the coal; 3) During the rotation of the rotary kiln, the lifting plate lifts part of the coal, which reduces the crescent shape at the bottom of the cylinder. The thickness of the material layer of the coal makes it easy for the moisture in the coal inside the material layer to be discharged from the inside of the coal. Figure 6 shows the structure of a lifting plate in the rotary furnace.

The outer surfaces of the steam tube 4 and the low-temperature flue gas tube 5 of the coal steam drying rotary furnace 1 are provided with fins 9 that are integrated with the wall surface. In the steam drying rotary furnace 1, the gas medium outside the tube is mainly diatomic gas such as N2, H2, CO, etc., that is, there is no radiation force and no radiation absorption, so there is only convection heat transfer, but when the coal is dried, moisture enters the gas medium After that, because water vapor belongs to triatomic gas, it can produce certain radiation heat transfer. Therefore, the heat transfer enhancement on the outside of the tubes in the rotary furnace is mainly to reduce the thermal resistance of the boundary layer of the gas flow. Usually, the method of increasing the gas flow rate in the furnace can reduce the thickness of the boundary layer near the tube wall, thereby reducing the thickness of the boundary layer. The heat transfer resistance is improved, and the convective heat transfer is improved; based on the above principles, the utility model adds a rib 9 that is self-integrated with the wall surface on the outer surface of the tube. Extended surface for significantly improved tube heat dissipation. The tube with fins 9 can increase the heat transfer area and increase the airflow disturbance, thereby improving the heat transfer on the outer surface of the tube. FIG. 7 is a diagram showing the arrangement of fins on the outer walls of the tubes, and FIG. 8 is a structural diagram showing the arrangement of heat conducting fins on the outer walls of the tubes.

A twist-shaped metal insert 10 is added inside the steam tube 4 and the low-temperature flue gas tube 5 of the coal steam drying rotary furnace 1. In the coal steam drying rotary furnace 1, the heat exchange efficiency inside the tube is directly related to the coal steam Drying the overall heat exchange performance of the rotary furnace 1, and at the same time, the tubes will be scaled after long-term operation, and the fouling will deposit on the surface of the heat exchange tubes, which will increase the flow resistance of the fluid, resulting in a decrease in the heat transfer efficiency of the tubes. A twist-shaped metal insert 10 is inserted into the tube, and its functions are as follows: ①Increase the flow rate and stroke of the air flow, and generate a continuous rotating vortex in the tube, thereby thinning or destroying the boundary layer on the inner wall of the tube; ②Increasing the change in the tube Heat area, strengthen the heat transfer in the tube, and remove the dirt in the tube; based on the above principle, adding a twist-shaped metal insert 10 inside the tube of the coal steam drying rotary furnace 1 can improve the heat transfer of steam to the inner wall of the tube. FIG. 7 is a diagram of inserting pieces arranged on the inner wall of the column tube, and FIG. 9 is a structural diagram of the insert piece arranged inside the column tube.

The carrier gas of the coal steam drying rotary furnace 1 adopts the low-temperature flue gas of 300-350 ℃ discharged from the retort furnace, and the low-temperature flue gas and the coal adopt the form of co-current heat exchange. While the heat transfer efficiency is improved, the temperature of the material discharged from the rotary kiln is greatly increased.

The steam tube 4 and low temperature flue gas tube 5 of the coal steam drying rotary furnace 1 use the low temperature flue gas of 300-350°C discharged from the dry distillation furnace. The waste heat of flue gas can greatly increase the drying temperature of coal in the rotary furnace without using steam, which is a kind of reuse of resources, environmental protection and energy saving.

The inner wall of the coal steam drying rotary furnace 1 is provided with a jacket cylinder 7, a jacket 8 is formed between the jacket cylinder 7 and the inner wall of the coal steam drying rotary furnace 1, and the annular jacket 8 is passed into the dry distillation furnace and discharged. The low temperature flue gas at 300-350°C is transferred to the rotary furnace through the residual heat of the low temperature flue gas in the jacket 8, and the temperature of the inner wall of the coal steam drying rotary furnace 1 is heated by the low temperature flue gas in the jacket 8, which can increase The drying temperature of coal in the coal steam drying rotary kiln 1.

A furnace gas circulating fan is arranged outside the coal steam drying rotary furnace 1, and the furnace gas circulating fan pressurizes a part of the furnace gas discharged from the carrier gas outlet 12 of the coal steam drying rotary furnace 1, and then dries it from the coal steam after being pressurized by the circulating fan. The feeding end 2 of the rotary furnace 1 is inflated, and the circulation of the circulating gas in the coal steam drying rotary furnace 1 can increase the airflow velocity in the furnace, thereby improving the convective heat transfer of the coal, and the furnace gas circulation can evenly distribute the airflow in the furnace. , to prevent the existence of low temperature gas layer in the furnace.

Claims (8)

1. an enhanced heat transfer device for a coal steam drying rotary furnace, comprising a coal steam drying rotary furnace, one end of the coal steam drying rotary furnace is a feed port, and the other end of the coal steam drying rotary furnace is a discharge port, In the coal steam drying rotary kiln, 2-5 circles of steam tubes are arranged in concentric circles along the length of the furnace and run through the entire cylinder. The steam tubes are fixed on the inner wall of the coal steam drying rotary kiln through ribs. , the end of the feed port is provided with a carrier gas inlet, and the upper end of the discharge port is provided with a carrier gas outlet, characterized in that: the coal steam drying rotary furnace (1) is provided with a number of low-temperature smoke along the furnace length direction Gas tube (5), the low-temperature flue gas tube (5) is distributed in a star shape along the circumferential direction of the inner wall of the coal steam drying rotary furnace (1), and the low-temperature flue gas tube (5) is located in the coal steam drying return Above the coal feed level in the converter (1) and not in contact with the coal. 2 . The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1 , wherein the coal steam drying rotary furnace ( 1 ) is provided with several lifting plates ( 6 ) along the furnace length direction, 2 . One side of the lifting plate (6) is welded on the inner cylinder wall of the coal steam drying rotary furnace (1). 3. The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1, characterized in that: the steam tube (4) and the low temperature flue gas tube (5) of the coal steam drying rotary furnace (1) ) is provided with a rib (9) which is self-integrated with the wall surface, and the expanded surface area of the rib (9) is 2-7 times that of the light surface. 4. The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1, characterized in that: the steam tube (4) and the low temperature flue gas tube (5) of the coal steam drying rotary furnace (1) ) inside is additionally provided with a twist-shaped metal insert (10). 5 . The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1 , wherein the carrier gas of the coal steam drying rotary furnace ( 1 ) adopts the low temperature smoke of 300-350° C. discharged from the retort furnace. 6 . The low-temperature flue gas and coal adopt the form of co-current heat exchange. 6 . The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1 or 4, characterized in that: the steam tube (4) and the low temperature flue gas tube of the coal steam drying rotary furnace (1) (5) The low-temperature flue gas at 300-350°C discharged from the retort furnace is used, and the low-temperature flue gas and the coal adopt a countercurrent heat exchange method. 7 . The enhanced heat transfer device for a coal steam drying rotary kiln according to claim 1 , characterized in that: a jacket cylinder ( 7 ) is arranged on the inner side of the cylindrical wall of the coal steam drying rotary kiln ( 1 ). A jacket (8) is formed between the jacketed cylinder (7) and the inner wall of the coal steam drying rotary furnace (1). The flue gas transfers heat to the rotary furnace through the residual heat of the low-temperature flue gas in the jacket (8). 8 . The enhanced heat transfer device for a coal steam drying rotary furnace according to claim 1 , wherein a furnace gas circulating fan is provided outside the coal steam drying rotary furnace (1), and the furnace gas circulating fan Part of the furnace gas discharged from the carrier gas outlet (12) of the coal steam drying rotary furnace (1) is pressurized by a circulating fan, and then blown in from the feed end (2) of the coal steam drying rotary furnace (1).

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