KR19980065145A - Combined heat exchanger and method for waste heat recovery. - Google Patents

Abstract

The present invention relates to a waste heat recovery and a complex heat exchange device for recovering condensate generated after combustion and condensate generated after the process. Particularly, the waste heat of an industrial boiler in which hot exhaust gas and high temperature condensed water recovered in a process are generated, and It is invented to be suitable for condensate recovery. It uses the thermosiphon principle of latent heat exchange through the evaporation and condensation of working fluid to recover the waste heat of combustion and consists of a combination of feedwater preheater and air preheater.The high temperature discharged from the trap after steam condensation heat exchange at the steam place. Heat exchanges the condensate with pre-heated combustion air and sends it to the condensate return tank. In addition, a part of the hot air for combustion is returned to the blower suction side (cold air) through the return duct, and is pre-mixed with the cold air before being blown. Therefore, low temperature corrosion by condensation is eliminated, efficient waste heat recovery using the thermosiphon principle, and the air preheater and the cutting machine are integrated, thereby minimizing ventilation resistance, minimizing installation place and reducing manufacturing cost, thereby increasing economic efficiency.

Description

Combined heat exchanger and method for waste heat recovery.

The present invention relates to a waste heat recovery for recovering the waste heat generated during combustion and condensate generated after the process, and to a complex heat exchange device for recovering condensate, in particular, the waste heat of an industrial boiler in which high-temperature exhaust gas and high-temperature condensed water are recovered. It is invented to be suitable for the recovery of condensate. Conventional boiler waste heat recovery device is installed in the water supply preheater (coalizer) for preheating the boiler feed water to the boiler combustion gas outlet side as shown in Figure 1 to recover the waste heat first and then to install the air preheater to preheat the combustion air to recover the waste heat do. The feedwater preheater and the pelletizer are composed of a plurality of bundle tubes in which combustion gas passes in and out of the bundle in a zigzag path and combustion air or cold water for cooling water crosses the exhaust gas. In addition, the steam condensed water condensed in the heat release process is recovered to the condensate recovery tank is used for boiler feed water. The condensate recovery tank is installed open to prevent malfunction due to back pressure of the tube trap.

However, a conventional air preheater or a coal blower has a low heat transfer effect due to convective heat transfer with combustion air or heat exchanged with combustion gas or combustion gas, and an air preheater outlet or combustion gas where low temperature air and high temperature combustion gas are in contact with each other at room temperature. It is inevitable that low temperature corrosion occurs due to sulfuric acid dew point at the outlet of feedwater preheater where cold water is in contact with cold water. In addition, in order to increase the waste heat recovery rate, the combustion gas is refracted and passed through two or three passes to create a ventilation resistance and an excessive installation place is required. Therefore, the air preheater and the water supply preheater are avoided at the same time. And condensate recovery in the process of condensation heat exchange, especially in the production process, has a large amount of heat, so the higher the condensate recovery rate, the more energy loss can be reduced. Is generated and discharged to the atmosphere, which leads to enormous energy loss, increased water treatment cost of boiler feedwater, and scaling of boiler water.

1 is a conventional installation schematic

2 is an assembly diagram of the present invention

3 is a longitudinal cross-sectional view of the present invention.

4 is a partial cross-sectional view of the heat exchanger of the present invention.

5 is a partial cross-sectional view of the heat exchanger of the present invention.

* Explanation of symbols for the main parts of the drawings

DESCRIPTION OF SYMBOLS 1 Working fluid heating tube 2 Fin pipe 3 Feed water heating tube 4 Condensate heat exchanger

5: condensate recovery tank 6: flash steam heat exchanger 7: press-fit blower (F.D.FAN)

8,9: Return duct connecting device 10: Return air volume control tamper 11-a: Lower double cylindrical body 11-b: Upper double cylindrical body 12: Double jacket 13: Steam heating tube 14: Vertical fin tube 15: Half pipe connector 16 : Condensate Recovery Port 17: Cold Water Tank 18: Control Panel

19: water supply pump 20: return duct 21: water gauge 22: electronic valve

The present invention is a device for recovering the combustion waste heat in order to fundamentally solve the conventional problems, such as a feedwater preheater (crusher) and air preheater using the thermosiphon principle of latent heat exchange through the evaporation and condensation of the working fluid as a unit After condensation heat exchange at the steam location (process), the hot condensate discharged from the trap is exchanged with the preheated combustion air at the preheating air outlet side of the combined waste heat recovery unit combined with the water preheater and the air preheater. Lower the condensate temperature and send it to the condensate return tank. The low-temperature fresh steam, which is re-evaporated in the condensate recovery tank, is heat-exchanged at the suction low-temperature air side of the combustion inlet blower (F.D.FAN), and is recovered to the condensate tank with condensate water of 100 ° C. or less, where no fresh steam is generated. In addition, a portion of the hot air for combustion that is subjected to latent heat exchange in the exhaust gas and the combined waste heat recovery unit and then heat exchanged with the high temperature condensate is returned to the intake side (cold air) of the blower through the return duct, and is preheated and mixed with the cold air.

The exhaust gas, cold water, and cold air for combustion are indirectly heat-exchanged, and the preheated combustion air is bypassed through the return duct to preheat and mix with the cold air on the suction side of the blower, thereby eliminating low-temperature corrosion due to condensation. Efficient waste heat recovery using the thermosiphon principle, and the air preheater and feed water preheater are integrated to increase the economic efficiency by reducing the installation place and manufacturing cost. In addition, the hot condensate heat discharged from the end trap of the process can be absorbed into the boiler combustion air to prevent energy loss by the flash steam in the condensate tank. Hereinafter will be described in detail with reference to the accompanying drawings. First, the method of the present invention is a heat exchange in the working fluid heating tube (1) in the complex waste heat recovery of the present invention when a high temperature exhaust gas is discharged from the boiler not shown as shown in the second diagram. The working fluid heating tube 1 is vacuumed inside so that low temperature evaporation occurs at a boiling point at atmospheric pressure. The low temperature evaporated working fluid vapor is heat exchanged in the combustion air heating pipe 2 connected to the working fluid heating pipe 1 which is the waste heat absorbing side, and then condensed. In the condensation part of the thermosiphon, there is a fin pipe (2) that exchanges heat with combustion air, and inside the spiral feed water heating tube (3) to preheat the water supplied to the boiler simultaneously with the combustion air. The steam condensate condensed in the heat dissipation process is discharged by the tube trap, and the condensate heat exchanger 4 at the preheating air outlet side of the boiler combustion air inlet exchanges high temperature condensate with preheated combustion air to lower the condensate temperature. Afterwards it is sent to the condensate recovery tank (5). The fresh steam re-regenerated in the condensate recovery tank (5) is heat exchanged with the low-temperature combustion air in the fresh steam heat exchanger (6) located at the inlet side of the FD fan (FD FAN) ⑦. 5) is recovered.

The fresh steam generated by the difference between the steam condensate pressure and the atmospheric pressure is transferred to the combustion air and then lowered below 100 ° C., the boiling point under atmospheric pressure, to be reused in the boiler feed water. The hot air for combustion heat-exchanged with the exhaust gas in the composite waste heat recovery machine is controlled by the combustion air control tamper due to the cause that the air volume of the press-fit blower 7 is excessively designed relative to the combustion amount. A portion of the preheated air, which is excessively hot compared to the amount of combustion, is bypassed in the return duct connector 8 integrated with the condensate heat exchanger 4 and combined with the fresh steam heat exchanger 6 located on the combustion air intake side. Returning to the connecting device 9, the mixture is preheated with cold air and sucked into the blower. The returned preheated air is properly controlled by the air volume control tamper 10. The working fluid enclosed in the combined waste heat exchanger is at the proper level according to the ratio between the steam chamber and the fluid chamber, and the type of working fluid is selected according to the temperature of the incoming exhaust gas (waste heat) and the preheating air temperature to be preheated. . The boiling point at atmospheric pressure of water is 100 ° C, ethyl alcohol is 78 ° C, and Dowsam A, a fruit oil, is around 258 ° C. Therefore, if a high temperature is required, a high boiling point fluid is used. Use fluid The preheated combustion air temperature is determined by the working fluid vapor temperature generated by the boiling point of the working fluid and the internal vacuum level. The internal vacuum can be controlled by the amount of endothermic air and the quantity and discharge temperature of the feed water heater (coalizer) spirally wound in the internal steam chamber.

In addition, in the waste heat recovery that does not cause corrosion, such as gas combustion, the operating fluid in contact with the hot exhaust gas uses a high boiling oil type and the low temperature exhaust gas portion uses alcohol having a low boiling point. By rapidly lowering the temperature, the amount of waste heat recovery can be maximized.

According to the configuration for realizing the above method, a plurality of fin pipes are arranged vertically to the upper double horizontal cylindrical body 11-b through which the preheating air for combustion passes through the upper and lower two double cylindrical devices 11 combined in a combination set. 2) there is condensation heat exchange with combustion air, and inside the double cylindrical body (11-b), the spiral cold water heating tube (3) simultaneously performs condensation heat exchange with working fluid steam, and the lower double horizontal type through which combustion gas (waste heat) passes. In the cylindrical body 11-a, a working fluid is enclosed in a plurality of vertically arranged heating tubes 1 and a double jacket 12 to perform endothermic exchange with the combustion gas waste heat. The combustion gas passes outside the heating tube 1 and the double jacket 12 to increase the heat transfer area. Inside the lower double cylindrical cylinder (11-a) there is a steam heating tube (13) for arbitrary heating of the working fluid so that the working fluid in the steam heating tube (13) when non-condensable gas or other gas is present to disturb the heat transfer. Heating is used to remove non-condensable gases or to achieve the required vacuum level using volumetric expansion and heat of condensation.

The return duct connector 9 coupled with the fresh steam heat exchanger 6 having a plurality of vertical fin tubes in the cylindrical side at the suction side of the press-fit blower 7 is controlled by the return air volume control tamper 10 and preheated. On the air outlet side, the excess air amount is bypassed in the return duct connector 8 coupled with the high temperature condensate heat exchanger 4. Inside the flash steam heat exchanger 6 and the high temperature condensate heat exchanger 4 a number of vertical fin tubes 14 are mounted and the hot condensate or fresh steam is condensed in a plurality of half pipe connectors 15 above the double cylindrical jacket. Recovered to the recovery port 16. The return duct coupling devices 8 and 9 combined with the condensate and steam heat exchangers 4 and 6 become double cylindrical to suck or discharge the return air at the orifice-shaped cutout of the inner cylinder.

Air preheater and feed water preheater (coalizer) are combined to reduce installation place and manufacturing cost to a minimum, exhaust gas passes through one pass to minimize ventilation resistance, and latent heat exchange based on thermosiphon principle maximizes waste heat recovery and high temperature. Minimizes energy loss by using condensate fresh steam as boiler combustion air preheating, and reduces the replenishment water by eliminating the air discharge of fresh steam, reducing the cost of water treatment, preventing the scale of boiler water, and bypassing the preheated combustion air. It is effective in preventing corrosion and corrosion of waste heat recovery device at low temperature corrosion and low load.

Claims (2)

In the waste heat heat exchanger, the air preheater and the feed water preheater are integrally coupled to the upper and lower double cylinder bodies to achieve latent heat exchange based on the thermosiphon principle, and bypass the part of the preheated combustion air to prevent corrosion of the waste heat recovery device at low load. And heat-exchanging steam condensate and fresh steam by boiler combustion air preheating. The upper double horizontal cylindrical body (11-b) through which the preheating air for combustion passes through the upper and lower two double cylindrical bodies (11), there are a plurality of fin pipes (2) in a vertical arrangement and the double cylindrical body (11). (b) A spiral cold water heating tube (3) is mounted inside, and a working fluid is enclosed in a plurality of heating tubes (1) and a double jacket (12) arranged vertically in a lower double horizontal cylindrical body (11-a). The return duct connector 9 coupled with the fresh steam heat exchanger 6 having a plurality of vertical fin tubes inside the cylindrical fuselage on the suction side of the inlet blower 7 is controlled by the return air volume control tamper 10 and preheated. On the air outlet side, the excess air volume is bypassed in the return duct connector 8 combined with the hot condensate heat exchanger 4, and the hot condensate or fresh steam is condensed in a plurality of half pipe connectors 15 on the double cylindrical fuselage jacket. Recovery port (16) The return duct coupling device (8,9), which is recovered and is combined with the condensate and steam heat exchanger (4,6), has a double cylindrical shape and waste heat, characterized by suction or discharge of return air from the orifice-shaped cutout of the inner cylinder. Recovery device.