Waste gas heat recovery system in casting industry

Abstract

The invention discloses a casting industry waste gas heat recovery system which is used for recovering waste gas heat of a molding line cooling section and a coating line drying oven and comprises a dust removal main pipe, the bottom of the dust removal main pipe communicates with the top of an inner cavity of a cooling section housing through a plurality of dust removal branch pipes, and a casting conveying system is installed in the housing; a heat exchange pipe is installed in the dust removal main pipe, a sleeve coaxial with the dust removal main pipe is installed outside the dust removal main pipe, a closed clamping cavity is formed between the sleeve and the dust removal main pipe, and a flow guide spiral is installed in the closed clamping cavity. An outer communicating pipe is mounted below the end part of the sleeve; the tail end of the outer communicating pipe is communicated with the bottom of the inner cavity of the heat exchanger; a spiral heat exchange pipe is installed in an inner cavity of the heat exchanger, and the bottom end of the spiral heat exchange pipe is connected with the top of the oven through a waste gas communicating pipe. Heat of high-temperature dust and waste gas generated in the casting conveying process and heat of high-temperature waste gas generated by oven heating before and after casting spraying can be recycled, energy reduction and emission reduction are facilitated, and the service life of a dust removal system can be prolonged.

Description

Technical Field

[0001] The invention relates to a waste gas heat recovery system for the foundry industry, belonging to the technical field of foundry. Background Art

[0002] In the casting production line, castings need to be transported from the pouring area of ​​the molding line to the cooling section, sand-falling area, etc. Castings, especially some large or complex structure castings, have a slow cooling speed, so they still maintain a high temperature during the transportation process, and a sufficiently long cooling section is required to ensure that the temperature drops to an appropriate range before entering the sand-falling area.

[0003] The high-temperature dust and waste gas generated during the conveying and sand dropping process after casting is an important industrial safety and health issue. The causes of high-temperature dust and waste gas are: 1. During the casting process, the temperature of the casting itself is relatively high because the molten metal releases a lot of heat when solidifying. During the transportation process, the surface of the high-temperature casting gradually releases heat, causing the molding sand to scatter due to the heat, forming high-temperature dust.

[0004] 2. The molten iron is poured into the green sand mold. The green sand is heated to produce high-temperature steam containing waste gas.

[0005] 3. The vibration and collision between castings and conveying equipment (such as conveyor belts, rollers, etc.) during transportation cause the molding sand to scatter, dust to fly, and heat to be generated due to vibration and friction.

[0006] 4. Molten castings oxidize and volatilize at high temperatures, easily forming liquid or semi-solid dust particles.

[0007] At present, the high-temperature dust generated during the transportation process after the casting is formed is usually treated by the dust removal system exhaust fan to draw the dust into the bag dust collector. The disadvantage of this treatment method is that the heat of the high-temperature dust cannot be recycled, and the high-temperature dust will reduce the service life of the dust removal system. Especially in winter, a large amount of hot and humid exhaust gas enters the dust bag, forming condensed water, which makes the dust bag stuck with wet dust and loses the dust removal effect.

[0008] Electrostatic spraying is generally used for surface treatment after casting. Usually, the casting is heated in an oven before and after spraying. Heating treatment before spraying can eliminate bubbles inside the casting, increase the surface temperature of the casting, adhere the powder suspended near the surface of the casting during the spraying process, eliminate the problem of weak electrostatic adsorption of powder caused by the influence of electrostatic shielding on the concave corners and inner cavities of the casting, increase the coating thickness, make the coating thickness more uniform, and improve the adhesion of the coating. Heating treatment after spraying can promote the curing of the coating resin, make the coating solidify into a film, and better combine with the surface of the casting to enhance adhesion.

[0009] At present, the high-temperature exhaust gas generated by heating before and after spraying is usually directly drawn into the exhaust gas treatment system by an exhaust fan for catalytic combustion, activated carbon adsorption, plasma or biological treatment, etc. However, the heat of the high-temperature exhaust gas cannot be recovered and utilized, which is not conducive to energy reduction and emission reduction.

[0010] In summary, the prior art obviously has inconveniences and defects in practical use, so it is necessary to improve it. Summary of the invention

[0011] In view of the deficiencies in the background technology, the present invention provides a waste gas heat recovery system for the foundry industry, which can recycle the heat of high-temperature dust and waste gas generated during the transportation of castings, as well as the heat of high-temperature waste gas generated by oven heating of castings before and after spraying, which is beneficial to energy reduction and emission reduction, and can extend the service life of the dust removal system.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions: A waste gas heat recovery system for the foundry industry comprises a dust removal main pipe, the bottom of which is connected to the top of the inner cavity of a cooling section housing through a plurality of dust removal branches distributed at equal distances, and a casting conveying system is installed inside the housing; A heat exchange tube is installed inside the dust removal main pipe, and the heat exchange tube is a straight tube or a spiral tube. A sleeve arranged coaxially with the dust removal main pipe is installed outside the dust removal main pipe, and a closed cavity is formed between the inner wall of the sleeve and the outer wall of the dust removal main pipe, and a guide spiral is fixedly installed in the closed cavity; An external connecting pipe is installed below the end of the sleeve, and the tail end of the external connecting pipe is connected to the bottom of the inner cavity of the heat exchanger; a spiral heat exchange tube is installed in the inner cavity of the heat exchanger, and the bottom end of the spiral heat exchange tube is connected to the top of the oven through the exhaust gas connecting pipe, and a plurality of guide plates staggered in the longitudinal direction are installed on the inner wall of the heat exchanger.

[0013] Furthermore, the dust removal main pipe is connected to a gas-liquid separator and a first exhaust fan in sequence near its tail end, and a drain valve is provided at the bottom of the gas-liquid separator; and a plurality of condensate drain pipes are connected to the bottom of the main body of the dust removal main pipe.

[0014] Furthermore, the head end of the heat exchange tube passes through the inner cavity of the dust removal main tube and is connected to the water inlet main tube through a three-way joint. The tail end of the heat exchange tube is installed with an inner connecting tube arranged vertically therewith, and a mixing head is installed on the end of the inner connecting tube away from the heat exchange tube.

[0015] Furthermore, one end of the sealed clamping chamber is connected to the water inlet main pipe through a water inlet branch pipe.

[0016] Furthermore, the inner diameter of the outer communicating tube is larger than the outer diameter of the inner communicating tube, and the inner communicating tube and the mixing head are arranged inside the outer communicating tube.

[0017] Furthermore, the mixing head is threadedly connected to the end of the internal connecting pipe, and a diversion chamber connected to the internal connecting pipe is provided inside the mixing head. A guide cone is provided at the bottom of the diversion chamber, and a plurality of diversion holes distributed in a circular pattern are provided on the periphery of the bottom of the diversion chamber, and the diversion holes are distributed on the periphery of the guide cone.

[0018] Furthermore, a high-pressure pump is installed on the external connecting pipe.

[0019] Furthermore, the heat exchanger is of a vertical structure; a second exhaust fan is installed on the exhaust gas connecting pipe.

[0020] Furthermore, the top end of the spiral heat exchange tube is connected to the exhaust gas outlet pipe, and the end of the exhaust gas outlet pipe is connected to the exhaust gas treatment device.

[0021] Furthermore, a hot water outlet pipe is installed on one side of the top of the heat exchanger.

[0022] After adopting the above technical solution, the present invention has the following advantages compared with the prior art: The cold water in the present invention can be divided into two parts and enter the heat exchange tube and the closed cavity between the sleeve and the dust removal main pipe respectively. The water flowing in the heat exchange tube and the closed cavity in a spiral manner fully absorbs the heat in the dust removal main pipe from both sides inside and outside to achieve temperature increase. After mixing, it is pumped into the heat exchanger and flows from bottom to top in a serpentine shape in the heat exchanger. During the flow, it absorbs the heat of the exhaust gas in the spiral heat exchange tube to achieve temperature increase again. After being heated twice, the water is output from the hot water outlet pipe and can be used as water for employees to take a bath or for daily life, and can also be used for heating in the workshop, etc. The present invention can not only absorb the heat in the high-temperature dust, steam and moisture generated by the casting conveying system, but also absorb the heat of the high-temperature exhaust gas generated by the heating of the casting before and after spraying. It can also cool the high-temperature dust and high-temperature exhaust gas, and can make the high-temperature steam form condensed water for more effective dust removal later, which is beneficial to extend the service life of the dust removal system.

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is a schematic diagram of the installation of the dust removal pipe in the present invention; Figure 3 It is a schematic diagram of the internal structure of the heat exchanger in the present invention; Figure 4 yes Figure 2 Schematic diagram of the structure at M in the figure.

[0025] In the figure, 1-dust removal main pipe, 2-dust removal branch pipe, 3-cover, 4-casting conveying system, 5-first exhaust fan, 6-heat exchange pipe, 7-tee joint, 8-water inlet main pipe, 9-internal connecting pipe, 10-casing, 11-guiding spiral, 12-water inlet branch pipe, 13-external connecting pipe, 14-high-pressure pump, 15-heat exchanger, 16-spiral heat exchange pipe, 17-exhaust gas connecting pipe, 18-second exhaust fan, 19-exhaust gas outlet pipe, 20-guide plate, 21-hot water outlet pipe, 22-oven, 23-mixing head, 24-guide cone, 25-diverter hole, 26-gas-liquid separator. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0027] like Figure 1-Figure 4 As shown together, the present invention provides a waste gas heat recovery system for the foundry industry, which is used for recovering the waste gas heat from the cooling section of the molding line and the oven of the coating line. It specifically includes a dust removal main pipe 1, the bottom of the dust removal main pipe 1 is connected to the top of the inner cavity of the cooling section cover 3 through a plurality of dust removal branch pipes 2 distributed at equal intervals, and a casting conveying system 4 is installed inside the cover 3.

[0028] The dust removal main pipe 1 is connected to a gas-liquid separator 26 and a first exhaust fan 5 in sequence near its tail end, and a drain valve is provided at the bottom of the gas-liquid separator 26. The first exhaust fan 5 is used to transport the hot exhaust gas in the inner cavity of the housing 3 to the dust removal system, providing power for the exhaust gas flow.

[0029] A plurality of condensate drain pipes are connected to the bottom of the main body of the dust removal main pipe 1. The condensate drain pipes and the gas-liquid separator 26 cooperate with each other to discharge and collect the condensate formed by heat exchange in the dust removal main pipe 1 in time, so as to reduce the humidity of the exhaust gas in the dust removal main pipe 1 and prevent the dust removal bag from being stuck by wet dust, thereby rendering the dust removal effect ineffective.

[0030] A heat exchange tube 6 is installed inside the dust removal main pipe 1. The heat exchange tube 6 is a straight tube or a spiral tube. The head end of the heat exchange tube 6 passes through the inner cavity of the dust removal main pipe 1 and is connected to the water inlet main pipe 8 through a three-way joint 7. The tail end of the heat exchange tube 6 is installed with an internal connecting pipe 9 arranged vertically therewith. A mixing head 23 is installed on the end of the internal connecting pipe 9 away from the heat exchange tube 6.

[0031] A sleeve 10 coaxially arranged therewith is installed outside the dust removal main pipe 1, and a closed cavity is formed between the inner wall of the sleeve 10 and the outer wall of the dust removal main pipe 1, and a guide spiral 11 is fixedly installed in the closed cavity.

[0032] One end of the sealed cavity is connected to the water inlet main pipe 8 through the water inlet branch pipe 12. The cold water in the water network enters the three-way joint 7 from the water inlet main pipe 8 and is divided into two, and then enters the heat exchange tube 6 and the sealed cavity respectively. The water in the heat exchange tube 6 and the sealed cavity flows spirally and fully absorbs the heat in the dust removal main pipe 1 from both sides to achieve temperature rise.

[0033] An outer connecting pipe 13 is installed below the end of the sleeve 10 . The inner diameter of the outer connecting pipe 13 is larger than the outer diameter of the inner connecting pipe 9 . The inner connecting pipe 9 and the mixing head 23 are inserted into the outer connecting pipe 13 .

[0034] The mixing head 23 is threadedly connected to the end of the inner connecting pipe 9, and a flow diversion chamber connected to the inner connecting pipe 9 is provided inside the mixing head 23. A flow guide cone 24 is provided at the bottom of the flow diversion chamber, and a plurality of flow diversion holes 25 distributed in a circumference are provided at the periphery of the bottom of the flow diversion chamber. The flow diversion holes 25 are distributed around the periphery of the flow diversion cone 24. The flow diversion holes 25 divert the water in the inner cavity of the flow diversion chamber to the surroundings, mix the heated water in the heat exchange tube 6 with the heated water in the closed clamping chamber, exchange heat, reach the same temperature, and reach a thermal equilibrium state.

[0035] The tail end of the external connecting pipe 13 is connected to the bottom of the inner cavity of the heat exchanger 15. A high-pressure pump 14 is installed on the external connecting pipe 13. The high-pressure pump 14 pumps the water after preliminary heating to the heat exchanger 15 for further heating.

[0036] The heat exchanger 15 is a vertical structure, and a spiral heat exchange tube 16 is installed in the inner cavity of the heat exchanger 15. The bottom end of the spiral heat exchange tube 16 is connected to the top of the oven 22 through an exhaust gas connecting pipe 17, and a second exhaust fan 18 is installed on the exhaust gas connecting pipe 17. The second exhaust fan 18 extracts the high-temperature exhaust gas generated by the oven heating before and after the casting is sprayed into the spiral heat exchange tube 16.

[0037] The top end of the spiral heat exchange tube 16 is connected to the exhaust gas outlet pipe 19, and the end of the exhaust gas outlet pipe 19 is connected to the exhaust gas treatment device.

[0038] A plurality of guide plates 20 are installed on the inner wall of the heat exchanger 15 and are staggered in the longitudinal direction. The guide plates 20 guide the water in a serpentine shape to fully absorb the heat in the spiral heat exchange tube 16 .

[0039] A hot water outlet pipe 21 is installed on one side of the top of the heat exchanger 15 , and the water that has absorbed heat twice is output from the hot water outlet pipe 21 .

[0040] The specific working principle of the present invention is: The cold water in the tap water network enters the three-way joint 7 from the water inlet main pipe 8 and is divided into two, and then enters the heat exchange tube 6 and the closed cavity between the sleeve 10 and the dust removal main pipe 1 respectively. The water spirally flowing in the heat exchange tube 6 and the closed cavity fully absorbs the heat in the dust removal main pipe 1 from both sides inside and outside to achieve temperature increase; the water heated on both sides inside and outside the dust removal main pipe 1 is mixed by the mixing head 23. The advantage of mixing is that it ensures that the temperature fluctuation of the warm water will be relatively small during the subsequent heating process, which is conducive to maintaining the stability of the system; then the high-pressure pump 14 pumps the water after the initial heating to the heat exchanger 15, and flows in the heat exchanger 15 from bottom to top in a serpentine shape. During the flow, it absorbs the heat of the hot exhaust gas in the spiral heat exchange tube 16 to achieve re-heating. The water after the second heating is output from the hot water outlet pipe 21, which can be used as water for employees to take a bath and live, and can also be used for heating in the workshop.

[0041] The present invention can not only absorb the heat of high-temperature dust and high-temperature exhaust gas generated by the casting conveying system, but also absorb the heat of high-temperature exhaust gas generated by heating the casting before and after spraying, and can cool and dehumidify the high-temperature dust to facilitate more effective dust removal later, which is beneficial to extending the service life of the dust removal system.

[0042] The above is an example of the best implementation of the present invention, and the parts not described in detail are common knowledge of ordinary technicians in the field. The protection scope of the present invention shall be based on the content of the claims, and any equivalent transformation based on the technical enlightenment of the present invention is also within the protection scope of the present invention.

Claims

1. A foundry industry waste gas heat recovery system, characterized by: It comprises a dust removal main pipe (1), the bottom of which is connected to the top of the inner cavity of a cooling section casing (3) through a plurality of dust removal branch pipes (2) distributed at equal intervals, and a casting conveying system (4) is installed inside the casing (3); A heat exchange tube (6) is installed inside the dust removal main pipe (1), and the heat exchange tube (6) is a straight tube or a spiral tube. A sleeve (10) is installed outside the dust removal main pipe (1) and is coaxially arranged therewith. A closed cavity is formed between the inner wall of the sleeve (10) and the outer wall of the dust removal main pipe (1), and a flow guide spiral (11) is fixedly installed in the closed cavity. An external connecting pipe (13) is installed below the end of the sleeve (10), and the tail end of the external connecting pipe (13) is connected to the bottom of the inner cavity of the heat exchanger (15); a spiral heat exchange tube (16) is installed in the inner cavity of the heat exchanger (15), and the bottom end of the spiral heat exchange tube (16) is connected to the top of the oven (22) through the exhaust gas connecting pipe (17); and a plurality of guide plates (20) arranged in a staggered manner along the longitudinal direction are installed on the inner wall of the heat exchanger (15).

2. A foundry industry waste gas heat recovery system as claimed in claim 1, characterized in that: The dust removal main pipe (1) is connected in sequence to a gas-liquid separator (26) and a first exhaust fan (5) at a position close to its rear end, and a drainage valve is provided at the bottom of the gas-liquid separator (26); and a plurality of condensed water drainage pipes are connected to the bottom of the main body of the dust removal main pipe (1).

3. The foundry industry waste gas heat recovery system according to claim 1, characterized in that: The head end of the heat exchange tube (6) passes through the inner cavity of the dust removal main tube (1) and is connected to the water inlet main tube (8) through a three-way joint (7); the tail end of the heat exchange tube (6) is provided with an inner connecting tube (9) arranged vertically therewith; and a mixing head (23) is provided at the end of the inner connecting tube (9) away from the heat exchange tube (6).

4. A foundry industry waste gas heat recovery system as claimed in claim 3, characterized in that: One end of the sealed clamping chamber is connected to the water inlet main pipe (8) via a water inlet branch pipe (12).

5. The foundry industry waste gas heat recovery system as claimed in claim 3, characterized in that: The inner diameter of the outer connecting pipe (13) is greater than the outer diameter of the inner connecting pipe (9), and the inner connecting pipe (9) and the mixing head (23) are arranged inside the outer connecting pipe (13).

6. A foundry industry waste gas heat recovery system as claimed in claim 3, characterized in that: The mixing head (23) is threadedly connected to the end of the internal connecting pipe (9); a flow dividing chamber connected to the internal connecting pipe (9) is provided inside the mixing head (23); a flow guide cone (24) is provided at the bottom of the flow dividing chamber; a plurality of flow dividing holes (25) distributed in a circumferential manner are provided at the periphery of the bottom of the flow dividing chamber; and the flow dividing holes (25) are distributed at the periphery of the flow guide cone (24).

7. The foundry industry waste gas heat recovery system according to claim 1, characterized in that: A high-pressure pump (14) is installed on the external connecting pipe (13).

8. The foundry industry waste gas heat recovery system according to claim 1, characterized in that: The heat exchanger (15) is of a vertical structure; a second exhaust fan (18) is installed on the exhaust gas connecting pipe (17).

9. The foundry industry waste gas heat recovery system according to claim 1, characterized in that: The top end of the spiral heat exchange tube (16) is connected to the exhaust gas outlet pipe (19), and the end of the exhaust gas outlet pipe (19) is connected to the exhaust gas treatment device.

10. The foundry industry waste gas heat recovery system according to claim 1, characterized in that: A hot water outlet pipe (21) is installed on one side of the top of the heat exchanger (15).

Images