AU2018256597B2

AU2018256597B2 - Energy-saving system for treating VOC waste gas

Info

Publication number: AU2018256597B2
Application number: AU2018256597A
Authority: AU
Inventors: Wenxing LIU; Xiaozhou LIU; Yu Zhang; Junbo ZHOU
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2017-09-18
Filing date: 2018-03-14
Publication date: 2019-08-29
Anticipated expiration: 2038-03-14
Also published as: WO2019052135A1; AU2018256597A1; CN107676797A

Abstract

The invention discloses an energy-saving system for treating VOC waste gas. The system comprises a paint film drying chamber, an incineration chamber and a first heat exchanger. The paint film drying chamber includes a drying cavity. A plurality of drying gas inlets and VOC waste gas collection outlets are alternately defined on the top wall of the drying cavity. The drying gas inlets are connected to the drying gas main pipe via respective drying gas branch pipe. The VOC waste gas collection outlets are connected to the VOC waste gas collection main pipe via respective VOC waste gas collection branch pipe. The incineration chamber comprises an incineration chamber defined with a first gas inlet, a second gas inlet, a third gas inlet and a flue gas outlet which are connected to the VOC waste gas collection main pipe. The first heat exchanger is provided with a cold air inlet, a middle-temperature flue gas inlet, a hot air outlet and a low-temperature flue gas outlet. The middle-temperature flue gas inlet is connected to the flue gas exhaust outlet of the incineration chamber via a pipeline. The hot air outlet is connected to the drying gas main pipe via the hot air pipeline. The low-temperature flue gas outlet is connected to a chimney.

Description

TECHNICAL FIELD [0001] The present invention relates to a system for treating waste gas, and more particularly to a system for treating Volatile Organic Compound (VOC) waste gas.

BACKGROUD OF THE PRESENT INVENTION [0002] VOCs (Volatile Organic Compounds), which are the general term of volatile organic compounds at normal atmospheric temperature, contain formaldehyde, xylene, toluene, acetone, butanone, halogen compounds, etc. A large amount of VOC waste gas is produced during the production and use process of petrochemical, pharmaceutical, paint, coatings, electronics manufacturing, surface anti-corrosion, shoe making, printing, transportation and other industries. Most of the VOC waste gases has a strong irritation, which not only have a great impact on air quality, but also can do harm to human health by direct contact. Further, a hidden danger of safe will exist because of the flammable properties of the VOC waste gas.

[0003] At present, the study on the disposal of VOC waste gas has become the focus of air treatment in many countries because the VOC waste gas is characterized by high emissions, many species, difficult degradation, strong toxicity and great safety hazard. In the existing technology, the main technologies for treating the VOC waste gas are catalytic combustion, activated carbon adsorption, low temperature plasma and ultraviolet irradiation. Among them, the best way to deal with VOC waste gas is to heat the VOC waste gas to more than 800 degrees centigrade in a combustion furnace, which is realized by the heat release produced by the self-combustion of VOC or by combustion-supporting of fuel gas burners. In such a temperature, the VOC contained in the waste gas is decomposed into CO2 and water, and then discharged into the atmosphere.

[0004] A device and a method of regenerative burning for treating dusty VOC waste gases, whose aim is to realize the high efficient energy saving treatment of high dusty VOC waste gases, are disclosed in Chinese Patent Application No. 201610617956.5. It consists of a set of united action valves, a heat storage and ash cleaning device, a regenerator, an oxidizing incineration chamber, a burner, a heat recovery steam generator as well as a fast cooling and absorption device. The oxidizing incineration chamber, which is placed on the top of the regenerator, is connected to the regenerator. In addition, the heat storage and ash cleaning device is installed at the bottom of the regenerator. The set of united action valves connect the regenerator, an exhaust gas pipe, an opposite blow pipe and a flue gas pipe. Several burners are installed in the oxidizing incineration chamber for combustion-supporting. The regenerator is composed of a plurality of heat storage tanks. The same set of united action valves is installed below each regenerator. However, the patent has the following shortcomings or defects: (1) a large amount of gas fuel need to be burned in the oxidizing incineration chamber for decomposing VOC waste gas; and (2) the energy produced by the combustion of VOC waste gas and the heat given by oxidizing incineration chamber are not fully recovered, and hence it is necessary to install a fast cooling and absorption device for absorbing the heat energy.

[0005] Also, a low pollution device for treating VOC produced by cigarette packaging and printing industry is disclosed in Chinese Patent Application No. 201610138264.2. Its components, such as a waste gas storage device, a purple light purifying device, a fibrous carbon adsorption filter device and a purifying exhaust gas pipe, are set up in turn along the discharge and purification path of the exhaust gas. The first exhaust gas pipe connects the waste gas storage device and workshop. Along the purification route, in turn, the first exhaust gas pipe is provided with a VOC detector and a first exhaust gas pump. The VOC detector is used to work in coordination with the first exhaust gas pipe, and the first exhaust gas pump is used to discharge waste gas in the workshop. The waste gas storage device comprises an elastic airbag of volume expansion. The first exhaust pipe is connected to the elastic airbag, and the elastic airbag is connected to the purple light lamp purifying device. However, the patent has the following shortcomings or defects: (1) the cost of purifying VOC waste gas is high; and (2) the energy possessed by VOC waste gas is not fully utilized.

[0006] Therefore, a system of energy-saving and emission-reduction for treating VOC waste gas is urgently required in the art.

SUMMARY OF PRESENT INVENTION [0007] The objective of the present invention is to provide an energy-saving system for treating VOC waste gas, which is capable of making full use of energy possessed by VOC waste gas. The hot flue gas, which is produced by the combustion and decomposition of VOC waste gas, can not only be used for heating VOC waste gas itself, but also preheat the cold air to form hot air which is used as drying gas in a drying chamber of paint films.

[0008] To achieve the above mentioned purposes, an energy-saving system for treating VOC waste gas is provided in this invention, comprising a paint film drying chamber. The paint film drying chamber comprises a drying cavity. A plurality of drying gas inlets and VOC waste gas collection outlets are alternately defined on the top wall of the drying cavity. A plurality of drying gas inlets are connected to a drying gas main pipe via respective drying branch gas pipe. Also, a plurality of VOC waste gas collection outlets are connected to a VOC waste gas collection main pipe via a respective VOC waste gas branch pipe. The energy-saving system for treating VOC waste gas further comprises an incineration chamber and a first heat exchanger. The incineration chamber includes an incineration cavity for combustion and decomposition of the VOC waste gas. The incineration cavity is provided with a first gas inlet connected to the VOC waste gas collection main pipe, a second gas inlet for supplying fuel gas to the incineration cavity, a third gas inlet for supplying a combustion-supporting gas into the incineration cavity, and a flue gas exhaust outlet. The first heat exchanger has a cold air inlet, a middle-temperature flue gas inlet, a hot air outlet, and a low-temperature flue gas outlet. The middle-temperature flue gas inlet is connected to the flue gas exhaust outlet of the incineration chamber via pipes. Then, the cold air entering the first heat exchanger from the cold air inlet is heated by the flue gas entering the first heat exchanger to become hot air. The hot air outlet is connected to the drying gas main pipe via the drying air pipe to supply the hot air produced by heat exchange to the drying cavity for drying the paint films of products, and the low-temperature flue gas outlet is connected to a chimney.

[0009] In the system described above, the products coated with paint move with the conveyor belt. Under the drying of hot air, the paint on the surface of the products is gradually dried to form a film attached to the products. At the same time, the VOC volatilized from the paint are mixed with the drying gas to form the VOC waste gas which is gradually released. Under the guidance of the VOC waste gas collection branch pipes, VOC waste gas converges to the VOC waste gas collection main pipe for unified treatment.

[0010] Optionally, the first heat exchanger is a heat pipe heat exchanger, which includes an outer shell, a middle baffle for separating an inner space of the outer shell into antiparallel flue gas flow path and air flow path. In addition, a plurality of heat pipes are passing through the middle baffle. Evaporating ends of the heat pipe extend into the flue gas flow path, and the condensation ends of the heat pipe extend into the air flow path. The cold air inlet and the hot air outlet are formed at two ends of the air flow path, respectively. The middle-temperature flue gas inlet and the middle-temperature flue gas outlet are formed at two ends of the flue gas flow path, respectively.

[0011] Preferably, the working medium in the heat pipes of the heat pipe heat exchanger is liquid sodium, potassium or naphthalene which is suitable for working at about 500-800 degrees centigrade.

[0012] Preferably, the system further includes a second heat exchanger which connects the VOC waste gas collection main pipe and the incineration chamber. The second heat exchanger is equipped with a low-temperature VOC waste gas inlet, a high-temperature VOC waste gas outlet, a high-temperature flue gas inlet and a middle-temperature flue gas outlet. The low-temperature VOC waste gas inlet is connected to the VOC waste gas collection main pipe. The high-temperature VOC waste gas outlet is connected to the first gas inlet of the combustion chamber via pipelines. The high-temperature flue gas inlet and the flue gas exhaust outlet of the combustion chamber are connected via pipelines. The middle-temperature flue gas outlet is connected to the middle temperature flue gas inlet of the first heat exchanger via a pipeline.

[0013] In the system described above, the VOC waste gas, whose temperature is 180-190 degrees centigrade, coming from the paint film drying chamber, is heated by the second heat exchanger to become a high-temperature VOC waste gas of 550-650 degrees centigrade. Then, the high-temperature VOC waste gas is mixed with fuel gas to be burned and decomposed in the incineration chamber with the temperature of 750-850 degrees centigrade. The high-temperature flue gas of 750-850 degrees centigrade produced by combustion and decomposed of the VOC waste gas enters the second heat exchanger through the high-temperature flue gas inlet, exchanges heat with VOC waste gas, and becomes a middle temperature flue gas of 290-300 degrees centigrade. Then, the middle-temperature flue gas enters the first heat exchanger through the middle temperature flue gas inlet, exchanges heat with cold air of 20-25 degrees centigrade, and forms a hot air of 180-190 degrees centigrade. Then, the hot air enters the drying gas main pipe and dries the paint films of the products in the drying cavity.

[0014] Preferably, the VOC waste gas collection branch pipes are located at a distal end of the VOC waste gas collection main pipe. The distal end is near the second heat exchanger. The VOC waste gas collection branch pipes are connected to the drying gas main pipe to return 20% to 40% of a total amount of VOC waste gas into the drying cavity for drying.

[0015] Preferably, the VOC waste gas collection branch pipes are equipped with filters to remove impurity particles from the VOC waste gas.

[0016] Preferably, the hot air pipes are provided with a first hot air pipe and a second hot air pipe. The first hot air pipe is connected to the drying gas main pipe to provide 60%~90% of a total amount of the hot air to the drying cavity for drying. The second hot air pipe is connected to the third gas inlet of the incineration chamber to supply 10%~40% of the total amount of the hot air to the incineration chamber as a combustion-supporting gas.

[0017] Optionally, the system also includes a high pressure fan arranged in the VOC waste gas collection main pipe for blowing the VOC waste gas into the second heat exchanger, a first induced draft fan for conveying the pressured cold air to the first heat exchanger, a second induced draft fan arranged in the VOC waste gas collection main pipe for supplying the VOC waste gas into the drying gas main pipe, a third induced draft fan installed in the first hot air pipe for supplying hot air into the drying gas main pipe, and a fourth induced draft fan installed in the second hot air pipe for supplying hot air to the incineration chamber.

[0018] Optionally, the second heat exchanger is a perforated nozzle heat exchanger which includes a heat transfer gas channel arranged between the high-temperature flue gas inlet and the middle-temperature flue gas outlet, and at least one heat exchange cylinder is installed in the heat exchange gas channel. The heat exchange cylinder comprises a front-end with an annular wall as well as a central gas inlet hole, an open back-end, and a perforated nozzle around the gas inlet hole extending from the front-end to the back-end of the at least one heat exchange cylinder. The front-end is connected to the low-temperature VOC waste gas inlet, and back-end is connected to the high-temperature VOC waste gas outlet.

[0019] Optionally, the back-end of the at least one heat exchange cylinder is connected to an exhaust chamber and the high-temperature VOC waste gas outlet is defined on the wall of the exhaust chamber.

[0020] Optionally, the low-temperature VOC waste gas enters the perforated nozzle heat exchanger via the gas inlet hole, and preheated high temperature VOC waste gas flows out of the perforated nozzle heat exchanger through its back-end. Further, the perforated nozzle includes a closed end adjacent to the back-end and a tube extending between the gas inlet hole and the closed end. In addition, a plurality of VOC waste gas jet holes are defined on a circumferential wall of the tube, which ensures that the low-temperature VOC waste gas entering at least one heat exchange cylinder via gas inlet holes is ejected to an inner wall of at least one heat exchange cylinder through the VOC waste gas jet holes. In this way, so that the low-temperature VOC waste gas is capable of quickly exchanging heat with the high-temperature flue gas flowing through an outer wall of at least one heat exchange cylinder.

[0021] Optionally, the second heat exchanger includes a first heat exchange cylinder, a second heat exchange cylinder and a third heat exchange cylinder, which are installed, in turn, in the heat transfer gas channel along a direction of the high temperature flue gas flow. Also, the second the heat exchanger includes a first connection channel and a second connection channel which are arranged outside the heat transfer gas channel. The first connection channel connects the first heat exchange cylinder with the third heat exchange cylinder end to end along a flow direction of the VOC waste gas. The second connection channel connects the third heat exchange cylinder with the second heat exchange cylinder end to end along the flow direction of the VOC waste gas. The low-temperature VOC waste gas enters the first heat exchange cylinder via the gas inlet hole of the first heat exchange cylinder. Then, the low-temperature VOC waste gas in turn flows through the first connection channel, the third heat exchange cylinder, the second connection channel and the second heat exchange cylinder. Then, the preheated high-temperature VOC waste gas flows out of the second heat exchange cylinder via its back-end.

[0022] Optionally, a burner is installed in each of the drying gas branch pipes, and each burner is connected to a fuel gas source via a pipeline.

[0023] Optionally, the fuel gas used for the incineration of VOC waste gas is biomass gas, methane, coal gas, liquefied petroleum gas or natural gas.

[0024] Optionally, the energy-saving system for treating VOC waste gas can be used to treat the VOC waste gas produced by paint films or coating materials drying, such as the application in an automobile factory, a spare parts factory, a furniture factory and so on.

[0025] The beneficial technical effects of the invention are presented as follows: [0026] (1) The VOC waste gas is preheated and then enters into the incineration chamber for high temperature combustion, which can greatly recover the waste heat of the flue gas and improve the combustion and decomposition efficiency of the VOC waste gas and ensures that the emission of the flue gas conforms to the environmental emission standard.

[0027] (2) The first heat exchanger installed can be further used to effectively recover the heat possessed by the flue gas produced by the combustion and decomposition of VOC waste gas, which can heat the cold air to become hot air. The hot air can not only be used as a drying gas, but also be provided to the incineration chamber as a combustion-supporting gas, which can make full use of the heat energy possessed and carried by the VOC waste gas, thus improving the energy utilization ratio.

[0028] (3) The perforated nozzle heat exchanger, which is adopted as the second heat exchanger, can improve the efficiency of heat exchange, and is more energy-efficient and environmentally friendly.

[0029] (4) 20%~40% of the total amount of VOC waste gas is returned to the drying gas main pipe, for drying the paint film of the product in the drying chamber again, which realizes the energy recycling and reduces the nitrogen and oxygen compounds in the flue gas.

DESCRIPTION OF THE DRAWINGS [0030] Figure 1 is a structural illustration of an energy-saving system for treating VOC waste gas according to the present invention; and [0031] Figure 2 is a structural illustration of a second heat exchanger according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0032] Embodiments of the invention will be described in detail below with reference to the accompanying drawings. Referring to the drawings, like numbers, if any, indicate like components or components with like functions throughout the views.

The following embodiments with reference to the drawings are exemplary, which is intended to interpret the present invention rather than to be regarded as a limitation to the invention.

[0033] Now referring to Figure 1, according to one unlimited embodiment of the present invention, an energy-saving system for treating VOC waste gas comprises a paint film drying chamber 100, an incineration chamber 200, a first heat exchanger 300, a second heat exchanger 400 and a chimney 500.

[0034] In the energy-saving system, the paint film drying chamber 100 includes a drying cavity 110. Four drying gas inlets 120 and three VOC waste gas collection outlets 130 are alternately defined on the top wall of the drying cavity 110. The drying gas inlets 120 are connected to a drying gas main pipe 160 via drying gas branch pipes 140. The VOC waste gas collection outlets 130 are connected to a VOC waste gas collection main pipe 170 via VOC waste gas collection branch pipes 150.

[0035] In this unlimited embodiment, the incineration chamber 200 includes an incineration cavity 210 for combustion and decomposition of the VOC waste gas. The incineration cavity 210 is provided with a first gas inlet to input the VOC waste gas, a second gas inlet 230 for supplying fuel gas to the incineration cavity 210, a third gas inlet 240 for supplying combustion-supporting gas into the incineration cavity 210, and a flue gas exhaust outlet 250 via which the high-temperature flue gas is discharged out of the incineration cavity 210.

[0036] The first heat exchanger 300 has a cold air inlet 310, a middle-temperature flue gas inlet 320, a hot air outlet 330, and a low-temperature flue gas outlet 340. Cold air is inputted through the cold air inlet 310 to the first heat exchanger 300 by a first fan Fl, and exchanges heat with the middle-temperature flue gas of about 300 degrees centigrade from the middle-temperature flue gas inlet 320 to become a hot air of about 200 degrees centigrade. The hot air outlet 330 is connected to the drying gas main pipe 160 via a hot air pipe 350. Thus, the hot air produced by heat exchange is provided to the drying cavity 110 to dry the products, and the low-temperature flue gas of about 120 degrees centigrade produced by heat exchange is discharged via the low-temperature flue gas outlet 340 to the chimney 500.

[0037] As one of the alternative embodiments, before the VOC waste gas enters the incineration chamber 200, the VOC waste gas is discharged, via the high pressure fan

HF, into the second heat exchanger 400 connected between the VOC exhaust collection main pipe 170 and the incineration chamber 200. The second heat exchanger 400 is equipped with a low-temperature VOC waste gas inlet 410, a high-temperature VOC waste gas outlet 420, a high-temperature flue gas inlet 430 and a middle-temperature flue gas outlet 440. The low-temperature VOC waste gas inlet 410 is connected to the VOC waste gas collection main pipe 170, thus, the low-temperature VOC waste gas can exchange heat with the VOC waste gas discharged from the paint film drying chamber 110. The high-temperature VOC waste gas outlet 420 is connected to the first gas inlet 220 of the incineration chamber 200 via pipelines. The high-temperature flue gas inlet 340 and the flue gas exhaust outlet 250 of the incineration chamber 200 are connected via pipelines. The middle-temperature flue gas outlet 440 is connected to the middle-temperature flue gas inlet 320 of the first heat exchanger 300 via a pipeline.

[0038] In this unlimited embodiment of the present invention, the VOC waste gas collection branch pipe 180 is located at the distal end of the VOC waste gas collection main pipe 170. The distal end is near the second heat exchanger 400. The VOC waste gas collection branch pipe 180 is connected to the drying gas main pipe 160. The temperature of VOC waste gas discharged from the drying chamber 110 is higher than 180 degrees centigrade and oxygen content of the VOC waste gas is relatively high. Therefore, by using a second induced draft fan F2 installed in the VOC waste gas collection branch pipe 180, about 30% of the total amount of the VOC waste gas can be returned to the drying gas main pipe 160 and mixed with the hot air from the first heat exchanger 300. In the drying chamber 110, the mixture of flue gas and air dries the products 800 on the conveyor belt 900.

[0039] Due to the existence of some impurity particles in the VOC waste gas, a filter 600 is set on the VOC waste gas collection branch pipe 180 adjacent to the second induced draft fan F2 to remove part of the impurity particles in the VOC waste gas. [0040] Besides, a burner 190 connected to a fuel gas source via a pipeline is respectively installed in each of the drying gas branch pipes 140, which can increase the temperature within the drying cavity 110 by the combustion of fuel gas as well as air and provide more heat for the drying cavity 110. Moreover, the solid particles in the VOC waste gas which returns to the drying cavity 110 from the VOC waste gas collection branch pipe 180 can be burned out to ensure that the gas entering the drying chamber 110 is cleaner.

[0041] As another alternative embodiment, the hot air pipeline 350 is provided with a first hot air pipe 3501 and a second hot air pipe 3502. The first hot air pipe 3501 is equipped with a third induced draft fan F3 and the second hot air pipe 3502 is provided with a fourth induced draft fan F4. In addition, the first hot air pipe 3501 is connected to the drying gas main pipe 160, so that 80% of the total volume of the hot air produced by heating can be supplied to the drying cavity 110 for drying by using the third induced draft fan F3. The second hot air pipe 3502 is connected to the third gas inlet 240 of the incineration chamber 200, so that 20% of the total volume of the hot air produced by heating can be supplied to the incineration chamber 200 as combustion-supporting gas by using the fourth induced draft fan F4. The high-temperature air entering the incineration chamber 200 can greatly increase the temperature of the incineration chamber 200, which can effectively reduce the consumption of fuel gas and save energy.

[0042] Thus, when the energy-saving system for treating VOC waste gas operates, the VOC waste gas, with the temperature of 180 degrees centigrade, coming from the film drying chamber flows through the second heat exchanger 400 and become high-temperature VOC waste gas of about 600 degrees centigrade by heat exchange. Then, the high-temperature VOC waste gas is decomposed within the incineration chamber 200 at the temperature as high as 800 degrees centigrade, and high-temperature flue gas of about 800 degrees centigrade produced by burning enters the second heat exchanger 400 via the high-temperature inlet 430. After exchanging heat with the VOC waste gas, the high-temperature flue gas becomes middle-temperature flue gas of 300 degrees centigrade. Then, the middle-temperature flue gas enters the first heat exchanger 300 through the middle temperature flue gas inlet 320 and exchanges heat with the cold air with the temperature of about 20 degrees centigrade to become the hot air with the temperature of about 190 degrees centigrade.

[0043] As shown in Figure 2, in an alternative embodiment of the present invention, the second heat exchanger 400 is a perforated nozzle heat exchanger which includes a heat transfer gas channel 450 arranged between the high-temperature flue gas inlet 430 and the middle-temperature flue gas outlet 440. A first heat exchange cylinder 460, a second heat exchange cylinder 470 and a third heat exchange cylinder 480, which are installed, in turn, in the heat transfer gas channel 450 along a flow direction of the high-temperature flue gas. Also, the second heat exchanger 400 includes a first connection channel 481 and a second connection channel 482 which are arranged outside the heat transfer gas channel 450. The first connection channel 481 connects the first heat exchange cylinder 460 with the third heat exchange cylinder 480 end to end along the flow direction of the VOC waste gas. The second connection channel 482 connects the third heat exchange cylinder 480 with the second heat exchange cylinder 470 end to end along the flow direction of the VOC waste gas. In this embodiment of the present invention, the back-end of the second heat exchange cylinder 470 is connected to an exhaust chamber 471, and the high-temperature VOC waste gas outlet 420 is set on the wall of the exhaust chamber 471.

[0044] As shown in Figure 2, the structures of the first heat exchange cylinder 460, the second heat exchange cylinder 470 and the third heat exchange cylinder 480 are similar. All of them are straight tube-shaped and are extended into the inner walls of the heat exchange gas channel 450, while the first connection channel 481 and second connection channel 482 are both set at the outside of the inner walls of the heat exchange gas channel 450. The first heat exchange cylinder 460 is connected to the third heat exchange cylinder 480 via the curved first connection channel 481, and the third heat exchange cylinder 480 is connected to the second heat exchange cylinder 470 via the second connection channel 482. The first heat exchange cylinder 460, the second heat exchange cylinder 470 and the third heat exchange cylinder 480 all contain a perforated nozzle 461.

[0045] The first heat exchange cylinder 460 is taken as an example to illustrate the structure of each heat exchange cylinder. The first heat exchange cylinder 460 comprises a front-end with an annular wall as well as a central gas inlet hole 462, and a back-end near the first connection channel 481. The back-end is open and is directly connected to the first connection channel 481. In the first heat exchange cylinder 460, the perforated nozzle 461 extends from the front-end to the back-end around the hole 462. The perforated nozzle 461 comprises a closed end 4611 adjacent to the first connecting channel 481 and a tube 4612 extending between the gas inlet hole 462 and the closed end 4611.

[0046] A large number of VOC gas injection holes 4613 are arranged on the circumferential wall of the tube 4612. Thus, after entering the tube 4612 from the gas inlet hole 462, the VOC waste gas is ejected rapidly via a lot of VOC gas injection holes 4613 to the inner wall of the first heat exchange cylinder 460. Thereby, the high-temperature flue gas flowing through the outer wall of the first heat exchange cylinder 460 rapidly exchanges heat with the VOC waste gas. As a result, the VOC waste gas is rapidly preheated and the first heat exchange cylinder 460 is cooled in time. The VOC waste gas enters the perforated nozzle heat exchanger after being pressurized by the high pressure fan HF. When the high pressure VOC waste gas enters the perforated nozzle, the high pressure VOC waste gas will be ejected quickly from ejection holes of the VOC waste gas with small diameters and impinges on the inner wall of the heat exchanger cylinder at high speed and high pressure, which can ensure the rapid and effective heat exchange between the low-temperature gas inside the heat exchange cylinder and the high-temperature flue gas outside the heat exchange cylinder and makes the VOC gas temperature rise rapidly.

[0047] The structure and working process of the perforated nozzle 461 are illustrated using the first heat exchange cylinder 460 as an example. In this unrestricted embodiment, both the second heat exchange cylinder 470 and the third heat exchange cylinder 480 have the same structure as the first heat exchange cylinder 460, and their structure as well as working principle is not repeated here.

[0048] As such, the low-temperature VOC waste gas enters the first heat exchange cylinder 460 via the gas inlet hole 462 of the first heat exchange cylinder 460 and flows sequentially through the first connection channel 481, the third heat exchange cylinder 480, the second connection channel 482, and the second heat exchange cylinder 470. The preheated high-temperature VOC gas flows out of the second heat exchanger 400 via the back-end of the second heat exchange cylinder 470.

[0049] In the description of the present specification, the description of reference terms one embodiment, a plurality of embodiments, examples, specific examples, or a plurality of examples, etc. means that the specific features, structures or characteristics combined with the described embodiment or example are included in at least one embodiment or example of the invention. In the present specification, it is not necessary for a schematic representation of the above-mentioned terms to aim at the same embodiment or example. Furthermore, without contradicting each other, one skilled in the art may combine or unite the different embodiments, examples or the corresponding characteristics described in the present specification.

[0050] Although the embodiments of the present invention have been illustrated and described in detail herein, it is understood that above-mentioned embodiments are illustrative and cannot be regarded as a limitation to the present invention. One of ordinary skill in the art will be able to implement other variations, modifications, alternatives and amendments without departing from the nature and scope of the present invention. For example, the first or the second heat exchanger can be a heat pipe heat exchanger or a tube-type heat exchanger.

Claims

What is claimed is:

1. An energy-saving system for treating Volatile Organic Compound (VOC) waste gas, comprising:

a paint film drying chamber comprising a drying cavity, wherein a plurality of drying gas inlets and a plurality of VOC waste gas collection outlets are alternately defined on the top wall of the drying cavity, the drying gas inlets are connected to a drying gas main pipe via respective drying gas branch pipes, and the VOC waste gas collection outlets are connected to a VOC waste gas collection main pipe by respective VOC waste gas collection branch pipes;

an incineration chamber comprising an incineration cavity for combustion and decomposition of the VOC waste gas, wherein the incineration cavity is provided with a first gas inlet connected to the VOC waste gas collection main pipe, a second gas inlet for supplying a fuel gas to the incineration cavity, a third gas inlet for supplying a combustion-supporting gas to the incineration cavity, and a flue gas exhaust outlet; and a first heat exchanger provided with a cold air inlet, a middle-temperature flue gas inlet, a hot air outlet, and a low-temperature flue gas outlet, wherein, the middle-temperature flue gas inlet is connected to the flue gas exhaust outlet of the incineration chamber, so that the heat produced by the flue gas entering the first heat exchanger changes the cold air which enters he first heat exchanger through the cold air inlet into hot air, the hot air outlet is connected to the drying gas main pipe by a hot air pipeline to provide the hot air produced by heat exchange to dry paint films of products in the drying chamber, and the low-temperature flue gas exhaust outlet is connected to a chimney.
2. The energy-saving system for treating VOC waste gas according to claim 1, further comprising a second heat exchanger connected between the VOC waste gas collection main pipe and the incineration chamber, wherein, the second heat exchanger is provided with a low-temperature VOC waste gas inlet, a high-temperature VOC waste gas outlet, a high-temperature flue gas inlet and a middle-temperature flue gas outlet; the low-temperature VOC exhaust gas inlet is connected to the VOC waste gas collection main pipe; the high-temperature VOC waste gas outlet is connected to the first gas inlet of the incineration chamber via a pipeline; the high-temperature flue gas inlet is connected to the flue gas exhaust outlet of the incineration chamber via a pipeline; and the middle-temperature flue gas outlet is connected with the middle-temperature flue gas inlet of the first heat exchanger via a pipeline.
3. The energy-saving system for treating VOC waste gas according to claim 1, characterized in that the first heat exchanger is a heat pipe heat exchanger; the heat pipe heat exchanger includes an outer shell, a middle baffle for separating an inner space of the outer shell into antiparallel flue gas flow path and air flow path, and a plurality of heat pipes passing through the middle baffle; and evaporating ends of the heat pipes extend into the flue gas flow path, and condensation ends of the heat pipes extend into the air flow path.
4. The energy-saving system for treating VOC waste gas according to claim 2, characterized in that a VOC waste gas collection branch pipe is located at a distal end of the VOC waste gas collection main pipe which is close to the second heat exchanger, the VOC waste gas collection branch pipe is connected to the drying gas main pipe to return 20% to 40% of a total amount of the VOC waste gas into the drying cavity for drying.
5. The energy-saving system for treating VOC waste gas according to claim 4, characterized in that the hot air pipeline is provided with a first hot air pipe and a second hot air pipe, the first hot air pipe is connected to the drying gas main pipe to provide 60%~90% of a total amount of the hot air to the drying cavity for drying, the second hot air pipe is connected to the third gas inlet of the incineration chamber to supply 10%~40% of the total amount of the hot air to the incineration chamber as a combustion-supporting gas.
6. The energy-saving system for treating VOC waste gas according to claim 5, further comprising a high pressure fan arranged in the VOC waste gas collection main pipe for blowing the VOC waste gas into the second heat exchanger, a first induced draft fan for conveying pressured cold air into the first heat exchanger, a second induced draft fan arranged in the VOC waste gas collection main pipe for supplying the VOC waste gas into the drying gas main pipe, a third induced draft fan installed in the first hot air pipe for supplying hot air into the drying gas main pipe, and a fourth induced draft fan installed in the second hot air pipe for supplying hot air into the incineration chamber.
7. The energy-saving system for treating VOC waste gas according to claim 2, characterized in that the second heat exchanger is a perforated nozzle heat exchanger which includes a heat transfer gas channel arranged between the high-temperature flue gas inlet and the middle-temperature flue gas outlet, and at least one heat exchange cylinder installed in the heat exchange gas channel; the at least one heat exchange cylinder comprises a front-end with an annular wall and a central gas inlet hole, an open back-end, and a perforated nozzle around the gas inlet hole extending from the front-end to the back-end of the at least one heat exchange cylinder; the front-end is connected to the low-temperature VOC waste gas inlet, and the back-end is connected to the high-temperature VOC waste gas outlet.
8. The energy-saving system for treating VOC waste gas according to claim 7, characterized in that the low-temperature VOC waste gas enters the perforated nozzle heat exchanger via the gas inlet hole, and the preheated high-temperature VOC waste gas flows out of the perforated nozzle heat exchanger via the back-end; the perforated nozzle includes a closed end adjacent to the back-end, and a tube extending between the gas inlet hole and the closed end; and a plurality of VOC waste gas jet holes defined on a circumferential wall of the tube ensure that the low-temperature VOC waste gas entering the at least one heat exchange cylinder via the gas inlet hole is ejected to an inner wall of the at least one heat exchange cylinder via the VOC waste gas jet holes, so that the low-temperature VOC waste gas is capable of quickly exchanging heat with the high-temperature flue gas flowing through an outer wall of the at least one heat exchange cylinder.
9. The energy-saving system for treating VOC waste gas according to claim 8, characterized in that the second heat exchanger includes a first heat exchange cylinder, a second heat exchange cylinder and a third heat exchange cylinder, which are installed, in turn, in the heat transfer gas channel along a direction of the high temperature flue gas flow; the second the heat exchanger further includes a first connection passage and a second connection passage which are arranged outside the heat transfer gas channel; the first connection passage connects the first heat exchange cylinder with the third heat exchange cylinder end to end along a flow direction of the VOC waste gas; the second connection passage connects the third heat exchange cylinder with the second heat exchange cylinder end to end along the flow direction of the VOC waste gas; the low-temperature VOC waste gas enters the first heat exchange cylinder via the gas inlet hole of the first heat exchange cylinder, and then, the low-temperature VOC waste gas, in turn, flows through the first connection passage, the third heat exchange cylinder, the second connection passage and the second heat exchange cylinder; and the preheated high-temperature VOC waste gas flows out of the second heat exchange cylinder via a back-end of the second heat exchange cylinder.
10. The energy-saving system for treating VOC waste gas according to any one of claims 1-9, characterized in that a burner is installed in each of the drying gas branch pipes, and each burner is connected to a fuel gas source via a pipeline.