Efficient low-temperature waste heat recovery system for boiler tail

Abstract

The utility model discloses an efficient low-temperature waste heat recovery system for the tail of a boiler, which comprises a modular low-temperature coal economizer, a modular low-low-temperature coal economizer, a feed water preheater and a feed water regulating valve group, and the modular low-temperature coal economizer and the modular low-low-temperature coal economizer are sequentially arranged along the motion direction of flue gas. The shell of the modular low-temperature coal economizer is connected with the shell of the modular low-temperature coal economizer through a connecting flue; a water inlet of the water supply preheater is externally connected with a boiler water supply header pipe; an outlet of the modular low-temperature economizer is connected with a water return port of the water supply preheater through a connecting pipeline, a water outlet of the water supply preheater is connected with an inlet of the modular low-temperature economizer through a connecting pipeline, and an outlet of the modular low-temperature economizer is connected with an inlet of the modular low-temperature economizer through a connecting pipeline. The efficient low-temperature waste heat recovery system for the tail of the boiler is installed at the tail of the boiler, flue gas waste heat can be effectively recovered, and the exhaust gas temperature of the waste heat boiler is reduced to 150 DEG C or below.

Description

Technical Field

[0001] The utility model relates to a high-efficiency low-temperature waste heat recovery system for the tail of a boiler, which is mainly suitable for recovering waste heat from flue gas containing SO2 or having certain corrosiveness at the tail of boilers in refining, metallurgy, cement kiln and calcining kiln. Background Art

[0002] At present, the exhaust temperature of waste heat boilers in oil refining catalytic units is generally around 170°C. Compared with the exhaust temperature of coal-fired power plant boilers at 130°C and gas boilers at 110°C, the exhaust temperature of oil refining catalytic units is generally higher, and there is a large space for energy saving. Since the flue gas of waste heat boilers in oil refining catalytic units generally contains a high content of SO2 and the dew point temperature is generally around 135°C, when the flue gas drops to the dew point temperature, the condensed acid in the flue gas will cause strong corrosion to the ordinary heating surface of the tail waste heat boiler. After corrosion to a certain extent, it will cause leakage of the heating surface of the economizer at the tail of the boiler. Utility Model Content

[0003] The purpose of the utility model is to overcome the defects of the prior art and provide a high-efficiency low-temperature waste heat recovery system for the tail of a boiler. The system is installed at the tail of the boiler and can effectively recover the waste heat of flue gas, so that the exhaust temperature of the waste heat boiler is reduced to below 150°C.

[0004] The technical solution to achieve the above purpose is: a high-efficiency low-temperature waste heat recovery system for the tail of a boiler, including a modular low-temperature economizer, a modular low-temperature economizer, a feed water preheater and a feed water regulating valve group, wherein:

[0005] The modular low-temperature economizer and the modular low-low-temperature economizer are arranged in sequence along the direction of flue gas movement, and the shell of the modular low-temperature economizer and the shell of the modular low-low-temperature economizer are connected through a connecting flue, and the shell of the modular low-temperature economizer, the connecting flue and the shell of the modular low-low-temperature economizer constitute a flue gas channel;

[0006] The water inlet of the feed water preheater is externally connected to the boiler feed water main;

[0007] The outlet of the modular low-temperature economizer is connected to the water return port of the feedwater preheater through a connecting pipe, the water outlet of the feedwater preheater is connected to the inlet of the modular low-temperature economizer through a connecting pipe, and the outlet of the modular low-temperature economizer is connected to the inlet of the modular low-temperature economizer through a connecting pipe;

[0008] One end of the feed water regulating valve group is connected to the connecting pipe between the outlet of the modular low-temperature economizer and the return water outlet of the feed water preheater, and the other end is directly connected to the feed water preheater through a connecting pipe;

[0009] Each connecting pipeline is equipped with valves and temperature instruments.

[0010] The above-mentioned high-efficiency low-temperature waste heat recovery system for the tail of a boiler, wherein the modular low-temperature economizer and the modular low-temperature economizer have the same structure, both consisting of a shell and an upper header, a lower header and a plurality of tube bundles arranged therein;

[0011] The multiple groups of tube bundles are used to absorb the flue gas waste heat in the flue gas channel and transfer heat to the boiler feed water in the tubes;

[0012] The upper header is used as an outlet to collect boiler feed water from the multiple tube bundles and lead them out uniformly;

[0013] The lower header is used as an inlet to distribute water from the boiler feed water main to the multiple groups of tube bundles;

[0014] The shell is used to seal the flue gas and provide a space for heat exchange between the flue gas and boiler feed water.

[0015] The above-mentioned high-efficiency low-temperature waste heat recovery system for the tail of a boiler, wherein the materials of the multiple tube bundles of the modular low-temperature economizer are all made of materials that are resistant to dew point corrosion; the materials of the multiple tube bundles of the modular low-temperature economizer are made of corrosion-resistant materials.

[0016] The above-mentioned high-efficiency low-temperature waste heat recovery system for the tail of a boiler, wherein the material of the multiple tube bundles of the modular low-temperature economizer is 20G or 09CrCuSb steel; the material of the multiple tube bundles of the modular low-temperature economizer is stainless steel 2205 or stainless steel 316L.

[0017] In the above-mentioned high-efficiency low-temperature waste heat recovery system for the tail of a boiler, the tube bundles of the modular low-temperature economizer and the modular low-temperature economizer are made of bare tubes or finned tubes.

[0018] The above-mentioned high-efficiency low-temperature waste heat recovery system for the tail of a boiler, wherein the feed water preheater adopts a U-tube heat exchanger.

[0019] The utility model discloses a high-efficiency low-temperature waste heat recovery system for the tail of a boiler, which is installed at the tail of the boiler and can effectively recover the waste heat of flue gas, so that the exhaust temperature of the waste heat boiler is reduced to below 150°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a high-efficiency low-temperature waste heat recovery system for the tail of a boiler of the utility model;

[0021] Figure 2 This is a schematic diagram of the structure of a modular low-temperature economizer. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the utility model, the specific implementation method thereof is described in detail below in conjunction with the accompanying drawings:

[0023] See also Figure 1 and Figure 2 The best embodiment of the utility model is a high-efficiency low-temperature waste heat recovery system for the tail of a boiler, comprising a modular low-temperature economizer 1, a modular low-temperature economizer 2, a feed water preheater 3 and a feed water regulating valve group 4. The modular low-temperature economizer 1 and the modular low-temperature economizer 2 are arranged in sequence along the direction of flue gas movement, and the shell of the modular low-temperature economizer 1 and the shell of the modular low-temperature economizer 2 are connected through a connecting flue, and the shell of the modular low-temperature economizer 1, the connecting flue and the shell of the modular low-temperature economizer constitute a flue gas channel 8; the water inlet of the feed water preheater 3 is externally connected to the boiler feed water main 9; the outlet of the modular low-temperature economizer 1 is connected to the return water port of the feed water preheater 3 through a connecting pipe 53, the water outlet of the feed water preheater 3 is connected to the inlet of the modular low-temperature economizer 2 through a connecting pipe 51, and the outlet of the modular low-temperature economizer 2 is connected to the inlet of the modular low-temperature economizer 1 through a connecting pipe 52. In this way, the modular low-temperature economizer 1, the modular low-temperature economizer 2 and the feed water preheater 3 are connected in series through the connecting pipes. The connecting pipe 51 and the connecting pipe 52 are connected through the connecting pipe 54, and the connecting pipe 52 and the connecting pipe 53 are connected through the connecting pipe 55.

[0024] One end of the feed water regulating valve group 4 is connected to the connecting pipe 53 between the outlet of the modular low-temperature economizer 1 and the return water port of the feed water preheater 3, and the other end is directly connected to the feed water preheater 3 through the connecting pipe 56;

[0025] Each connecting pipeline is provided with a valve 6 and a temperature meter 7.

[0026] The feed water preheater 3 is a standard U-tube heat exchanger, and its main function is to use the outlet hot water of the modular low-temperature economizer 1 to heat the inlet cold water of the modular low-temperature economizer 2, so that the inlet water temperature of the modular low-temperature economizer 2 is controlled above the corrosion tolerance temperature of the tube bundle material of the modular low-temperature economizer.

[0027] The feed water regulating valve group 4 is a set of precisely controlled pneumatic regulating valve groups, which are used to control the hot water flow of the feed water preheater 3, thereby precisely adjusting the inlet water temperature of the modular low-temperature economizer 2.

[0028] The connecting pipeline is used to connect in series the modular low-temperature economizer 1, the modular low-temperature economizer 2, the feed water preheater 3 and the feed water regulating valve group 4, and complete the process of preheating the boiler feed water through the economizer.

[0029] The main function of the valve 6 on each connecting pipe is: when one of the modular low-temperature economizer 1 or the modular low-temperature economizer 2 fails, the valve can be closed to completely cut off the modular low-temperature economizer 1 or the modular low-temperature economizer 1 without affecting the operation of the entire boiler.

[0030] The temperature instrument 7 is mainly used to indicate the inlet and outlet flue gas temperature and the inlet and outlet feed water temperature of the modular low-temperature economizer 1 and the modular low-temperature economizer 2.

[0031] The connecting flue is used to connect the equipment before and after the waste heat boiler, the modular low-temperature economizer 1 and the modular low-temperature economizer 2 to ensure the flue gas sealing.

[0032] The modular low-temperature economizer 1 and the modular low-temperature economizer 2 have the same structure, both consisting of a shell 24 and an upper header 22, a lower header 23 and multiple tube bundles 21 arranged therein; the multiple tube bundles 21 are used to absorb the flue gas waste heat in the flue gas channel 8 and transfer it to the boiler feed water in the tube, converting the flue gas waste heat into effectively usable hot water; the upper header 22 serves as an outlet to collect the boiler feed water of the multiple tube bundles 21 and lead them out uniformly; the lower header 23 serves as an inlet to distribute the water from the boiler feed water main to the multiple tube bundles 21; the shell 24 is used to seal the flue gas and provide space for heat exchange between the flue gas and the boiler feed water.

[0033] The multiple tube bundles of the modular low-temperature economizer 1 are made of materials that are resistant to dew point corrosion, preferably 20G or 09CrCuSb steel; the tube bundles are generally designed as plain tubes or finned tubes. The modular low-temperature economizer 1 is assembled and inspected by the factory into an integral module before leaving the factory.

[0034] The material of the multiple tube bundles of the modular low-temperature economizer 2 is corrosion-resistant material, preferably stainless steel 2205 (022Cr23Ni5Mo3N) or stainless steel 316L (022Cr17Ni12Mo2). The tube bundle design is generally a plain tube or a finned tube.

[0035] The modular low-temperature economizer 1 and the modular low-temperature economizer 2 are manufactured using modular design, and the upper header 22, the lower header 23 and the multiple tube bundles 21 are integrated in the shell 24 and shipped together as a whole.

[0036] The feed water regulating valve group 4 is used to control the amount of cold water flowing through the two economizers to fully absorb the waste heat in the flue gas, thereby achieving the purpose of efficient recovery. The feed water regulating valve group 4 is used to control the inlet water temperature entering the modular low-temperature economizer 1 within the tolerance range of the corrosion-resistant stainless steel 2205 (022Cr23Ni5Mo3N) or stainless steel 316L (022Cr17Ni12Mo2), thereby ensuring the long-term operation of the equipment.

[0037] The high-efficiency low-temperature waste heat recovery system for the tail of the boiler of the utility model has the following specific working process:

[0038] Flue gas flow: high-temperature flue gas flows from top to bottom, absorbs heat through modular low-temperature economizer 1 and modular low-temperature economizer 2, and then is discharged to the subsequent desulfurization unit;

[0039] Feedwater process: 104℃ deoxygenated water (boiler feed water) first enters the tube side of feedwater preheater 3 to be preheated to 130℃, then absorbs heat and heats up to 170℃ through modular low-temperature economizer 2 and modular low-temperature economizer 1. The heated high-temperature water enters the shell side of feedwater preheater 3 to be cooled to ~146℃ to remove the waste heat boiler upper heating surface;

[0040] Adjustment process: When the water temperature entering the modular low-temperature economizer 2 is higher than 130°C, open the regulating valve of the feed water regulating valve group 4 to reduce the hot water flow entering the shell side of the feed water preheater 3, thereby maintaining the water temperature entering the inlet of the modular low-temperature economizer 3 at around 130°C.

[0041] In summary, the high-efficiency low-temperature waste heat recovery system for the tail of the boiler of the utility model is installed at the tail of the boiler, which can effectively recover the waste heat of the flue gas, so that the exhaust temperature of the waste heat boiler is reduced to below 150°C.

[0042] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A high-efficiency low-temperature waste heat recovery system for the tail of a boiler, arranged at the tail of the boiler, characterized in that: It includes modular low-temperature economizer, modular low-temperature economizer, feed water preheater and feed water regulating valve group, among which: The modular low-temperature economizer and the modular low-low-temperature economizer are arranged in sequence along the direction of flue gas movement, and the shell of the modular low-temperature economizer and the shell of the modular low-low-temperature economizer are connected through a connecting flue, and the shell of the modular low-temperature economizer, the connecting flue and the shell of the modular low-low-temperature economizer constitute a flue gas channel; The water inlet of the feed water preheater is externally connected to the boiler feed water main; The outlet of the modular low-temperature economizer is connected to the water return port of the feedwater preheater through a connecting pipe, the water outlet of the feedwater preheater is connected to the inlet of the modular low-temperature economizer through a connecting pipe, and the outlet of the modular low-temperature economizer is connected to the inlet of the modular low-temperature economizer through a connecting pipe; One end of the feed water regulating valve group is connected to the connecting pipe between the outlet of the modular low-temperature economizer and the return water outlet of the feed water preheater, and the other end is directly connected to the feed water preheater through a connecting pipe; Each connecting pipeline is equipped with valves and temperature instruments.

2. The high-efficiency low-temperature waste heat recovery system for the tail of a boiler according to claim 1, characterized in that: The modular low-temperature economizer and the modular low-temperature economizer have the same structure, both consisting of a shell and an upper header, a lower header and a plurality of tube bundles arranged therein; The multiple groups of tube bundles are used to absorb the flue gas waste heat in the flue gas channel and transfer heat to the boiler feed water in the tubes; The upper header is used as an outlet to collect boiler feed water from the multiple tube bundles and lead them out uniformly; The lower header is used as an inlet to distribute water from the boiler feed water main to the multiple groups of tube bundles; The shell is used to seal the flue gas and provide a space for heat exchange between the flue gas and boiler feed water.

3. The high-efficiency low-temperature waste heat recovery system for the tail of a boiler according to claim 2, characterized in that: The materials of the multiple tube bundles of the modular low-temperature economizer are all anti-dew point corrosion materials; the materials of the multiple tube bundles of the modular low-temperature economizer are anti-corrosion materials.

4. The high-efficiency low-temperature waste heat recovery system for the tail of a boiler according to claim 3, characterized in that: The material of the multiple tube bundles of the modular low-temperature economizer is 20G or 09CrCuSb steel; the material of the multiple tube bundles of the modular low-temperature economizer is stainless steel 2205 or stainless steel 316L.

5. The high-efficiency low-temperature waste heat recovery system for the tail of a boiler according to claim 2, characterized in that: The tube bundles of the modular low-temperature economizer and the modular low-temperature economizer adopt plain tubes or finned tubes.

6. The high-efficiency low-temperature waste heat recovery system for the tail of a boiler according to claim 1, characterized in that: The feed water preheater adopts a U-tube heat exchanger.

Images