JP2008224173A - Two-tower type exhaust heat recovery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-tower type exhaust heat recovery system capable of controlling the temperature of flowing air ejected from a heat exchanger without installing a heat exchanger and a cooling air blower and furthermore reducing the damage of the heat exchanger. <P>SOLUTION: The two-tower type exhaust heat recovery system comprises a radiation type heat exchanger for introducing high temperature gas such as exhaust gas from a heat source device of a fluidized incinerator or the like, to recover heat, and a shell and tube type heat exchanger for introducing the high temperature gas lowered in temperature from the radiation type heat exchanger to further recover heat and exhausting the high temperature gas to the outside. A preheated fluid is introduced into the shell and tube type heat exchanger to raise the temperature with the recovered heat, and a preheated fluid which has become high in temperature is introduced into the radiation type heat exchanger to further raise the temperature with the recovery heat. The preheated fluid which has become high in temperature is fed into the heat source device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a two-column exhaust heat recovery system using a combination of a radiation heat exchanger and a shell and tube heat exchanger.

Shell and tube heat exchangers are commonly used in many processes. FIG. 5 shows an example of a fluid incineration facility for sewage sludge. In a fluid incineration facility for sewage sludge, a heat exchanger 3 for the purpose of recovering exhaust heat from the fluid incinerator 1 and preheating fluidized air is usually installed. In order to prevent the combustion temperature in the furnace from becoming abnormally high, the heat exchanger 4 and the cooling air blower B2 for cooling the fluidized air that has been once heated are required. When the combustion temperature in the furnace is normal, the heat exchanger 4 does not require cooling of the flowing air. Therefore, normally, the cooling air is not ventilated, and only 650 ° C. to 700 ° C. flowing air passes. It becomes. Therefore, an expensive heat-resistant steel must be used as the metal material used for the heat exchanger 4.
On the other hand, since the heat exchanger 3 that preheats the fluid air needs to preheat the fluid air introduced from the fluid air blower B1 to 650 ° C. to 700 ° C. using exhaust gas at 850 ° C. to 900 ° C. Due to the high recovery of exhaust heat, the operation method, etc., cracks due to thermal fatigue of the tube sheet are likely to occur, which may hinder the operation of the fluidized incinerator 1.
Japanese Patent No. 3296258 Japanese Patent Laid-Open No. 10-325688

  The present invention makes it possible to control the temperature of the flowing air P3 discharged from the heat exchanger 3 without installing the heat exchanger 4 and the cooling air blower B2, and further reduce damage to the heat exchanger 3. It is an object of the present invention to provide a two-column exhaust heat recovery system.

  The two-column exhaust heat recovery system of the present invention includes a radiant heat exchanger that recovers heat by introducing a high-temperature gas such as exhaust gas from a heat source device such as a fluidized incinerator, and a temperature drop from the radiant heat exchanger. A shell and tube heat exchanger that introduces the high temperature gas to further recover heat and discharges the high temperature gas to the outside, and introduces a preheating fluid into the shell and tube heat exchanger to The temperature of the preheating fluid is increased by the above, and the high temperature preheating fluid is introduced into the radiant heat exchanger to be further increased by the recovered heat, and the high temperature preheating fluid is sent to the heat source device. It is characterized by. Further, the present invention is characterized in that the preheating fluid introduced into the shell-and-tube heat exchanger is distributed to the upstream side and the downstream side of the high-temperature gas. Further, the flow rate of the preheated fluid to be distributed is controlled by a preheated fluid flow rate adjusting valve.

By adopting the two-column exhaust heat recovery system of the present invention, the heat exchanger 4 for cooling the temperature of the preheating fluid P3 and the blower B2 for cooling air, which are conventionally installed to change the temperature of the preheating fluid P3. Installation is unnecessary and the economy is improved.
Further, the temperature of the exhaust gas introduced into the shell-and-tube heat exchanger 3 can be lowered, and the heat load on the tube plates located at the exhaust gas introduction part and the preheating fluid discharge part can be reduced. Since the preheating fluid temperature in the tube heat exchanger can also be lowered, it is possible to reduce tube sheet cracking due to thermal fatigue of the conventional shell and tube heat exchanger.

Hereinafter, the present invention will be described in more detail based on illustrated embodiments.
In FIG. 1, 1 is a fluidized incinerator, 2 is a radiant heat exchanger, and 3 is a shell and tube heat exchanger.

The exhaust gas F1 discharged from the fluidized incinerator 1 is introduced from the upper part of the radiant heat exchanger 2, exchanges heat with the preheating fluid P2, and is then discharged from the lower part. Subsequently, the exhaust gas discharged from the radiant heat exchanger 2 is introduced into the lower part of the shell-and-tube heat exchanger 3, and after exchanging heat with the preheating fluid P1, it is discharged from the upper part as exhaust gas F2 having a lowered temperature. Is done.

On the other hand, the preheating fluid P <b> 1 is sent out from the preheating fluid blower B <b> 1, distributed by the preheating fluid flow rate adjusting valves V <b> 1 and V <b> 2, and introduced into the inlets installed above and below the shell and tube heat exchanger 3. The introduced preheating fluid P1 rises in temperature by heat exchange with the exhaust gas in the shell-and-tube heat exchanger 3 and becomes a preheating fluid P2 and is discharged from the lower discharge port. The heated preheating fluid P2 is sent to the upper inlet installed in the radiant heat exchanger 2, and after the temperature is further increased by heat exchange with the exhaust gas F1, the radiant heat exchanger is used as the preheating fluid P3. 2 is discharged from the lower discharge port 2 and fed into the fluidized incinerator 1.

In the heat exchange process, the temperature of the preheating fluid P3 can be changed by changing the distribution amount of the preheating fluid P1 by the preheating fluid regulating valves V1 and V2.
That is, by increasing the flow rate on the fluid flow rate adjustment valve V1 side and decreasing the flow rate on the fluid flow rate adjustment valve V2 side, the temperature of the preheating fluid P3 can be increased, and conversely, the fluid flow rate adjustment By increasing the fluid flow rate on the valve V2 side, the temperature of the preheating fluid P3 can be lowered.

FIG. 2 shows a longitudinal section of the radiant heat exchanger 2 and the shell-and-tube heat exchanger 3, and FIGS. 3 and 4 show crossings of the radiant heat exchanger 2 and the shell-and-tube heat exchanger 3, respectively. Show the surface.
In the present embodiment, the exhaust gas F1 is introduced into the heat exchanger from the exhaust gas inlet 23 of the radiant heat exchanger 2, and falls while heating the heat transfer tube 5 by the gas radiation (gas radiation) heat of the exhaust gas. It is discharged from the discharge chamber 11.

On the other hand, the preheating fluid P2 is introduced from the preheating fluid introduction port 6, guided to the preheating fluid introduction side annular header 7, and descends inside the heat transfer tube 5 arranged on the circumference as shown in FIG. Then, the heat of the heated heat transfer tube 5 is absorbed and the temperature is raised to a predetermined temperature, and is discharged as a preheated fluid P3 from the preheated fluid discharge port 9 through the preheated fluid discharge side annular header 8.

Further, the exhaust gas discharged from the radiant heat exchanger 2 is introduced from the exhaust gas introduction chamber 20 of the shell and tube heat exchanger 3 in FIG. 2, and is arranged in the outer cylinder 19 as shown in FIG. After exchanging heat while moving up in the heat transfer pipe 12, it is discharged as exhaust gas F <b> 2 from the exhaust port 22 via the exhaust gas discharge chamber 21.

On the other hand, the preheating fluid P1 is distributed by the preheating fluid flow rate adjusting valves V1 and V2 and introduced from the preheating fluid introduction ports 13 and 16, respectively. The preheated fluid introduced from the preheated fluid introduction port 13 is guided into the outer cylinder 19 in the preheated fluid introduction side header 14 so as to be orthogonal to the multiple heat transfer tubes 12 from the direction in which the heat exchange rate is highest. The preheating fluid P1 guided into the outer cylinder 19 is rectified into a flow perpendicular to and parallel to the heat transfer pipe 12 by baffle plates (baffle plates) 15 installed in the outer cylinder 19, while Heat exchange between. The preheating fluid P1 whose temperature has been raised by heat exchange joins with the preheating fluid P1 distributed from the preheating fluid flow rate adjusting valve V2 in the preheating fluid discharge header 17, and is discharged as the preheating fluid P2 from the preheating fluid discharge port 18. .

In the system of the present embodiment, the radiant heat exchanger 2 and the shell and tube heat exchanger 3 are respectively designed so as to be adjustable to the required temperature depending on the temperature range of the preheating fluid P3 sent to the fluidized incinerator 1. .

It is a schematic front view using an incinerator and each heat exchanger using the system of the present invention. It is a longitudinal cross-sectional view of each heat exchanger of the Example of FIG. It is a cross section of AA of the radiation type heat exchanger of FIG. It is a cross-sectional view of BB of the shell and tube heat exchanger of FIG. It is a schematic front view in which a conventional incinerator and a heat exchanger are provided together.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluidized incinerator 2 Radiation type heat exchanger 3 Shell-and-tube heat exchanger 4 Air cooling heat exchanger 5 Heat transfer tube 6 Preheating fluid introduction port 7 Introduction side annular header 8 Preheating fluid discharge side annular header 9 Preheating fluid discharge port 10 Outer cylinder 11 Exhaust gas discharge chamber 12 Heat transfer tube 13 Preheating fluid introduction port 14 Preheating fluid introduction side header 15 Baffle plate (baffle plate)
16 Preheating fluid introduction port 17 Preheating fluid discharge side header 18 Preheating fluid discharge port 19 Outer cylinder 20 Exhaust gas introduction chamber 21 Exhaust gas discharge chamber 22 Exhaust gas discharge port 23 Exhaust gas introduction port B1 Fluid air blower B2 Cooling air blower P1 Preheating fluid P2 Preheating fluid P3 Preheating fluid V1 Preheating fluid flow rate adjustment valve V2 Preheating fluid flow rate adjustment valve

Claims (3)

A radiant heat exchanger that recovers heat by introducing high-temperature gas such as exhaust gas from a heat source device such as a fluidized incinerator, and further recovers heat by introducing the above-mentioned high-temperature gas whose temperature has decreased from the radiant heat exchanger. And a shell-and-tube heat exchanger that discharges the high-temperature gas to the outside. The preheated fluid is introduced into the shell-and-tube heat exchanger to increase the temperature by the recovered heat, and the preheated to a high temperature. A two-column exhaust heat recovery system configured to introduce a fluid into the radiant heat exchanger so as to further increase the temperature by the recovered heat and to feed the preheated fluid that has reached a high temperature to the heat source device. 2. The two-column exhaust heat recovery system according to claim 1, wherein the preheating fluid introduced into the shell and tube heat exchanger is distributed to the upstream side and the downstream side of the high-temperature gas, respectively. The two-column exhaust heat recovery system according to claim 2, wherein the flow rate of the preheated fluid to be distributed is controlled by a preheat fluid flow rate adjusting valve.