Waste heat recovery device and waste heat recovery method

Abstract

The present invention provides a waste heat recovery device and a waste heat recovery method, which belongs to the technical field of flue gas waste heat recovery. The device includes a high-temperature section air preheater, a medium-temperature section air preheater and a low-temperature section air preheater. The low-temperature section air preheater is connected to the chimney through a low-temperature flue gas outlet pipe, and a temperature sensor is arranged on the low-temperature flue gas outlet pipe; the flue gas inlet of the low-temperature section air preheater is connected to the flue gas outlet of the medium-temperature section air preheater through a medium-temperature flue gas inlet pipe; the low-temperature flue gas outlet pipe and the medium-temperature flue gas inlet pipe are connected through a return pipe; a stop valve is arranged on the low-temperature flue gas outlet pipe, and a return valve is arranged on the return pipe; the temperature sensor is set to 95±5℃, and the detected temperature is lower than the set temperature, the return valve is closed, and the stop valve is opened; the detected temperature is higher than the set temperature, the stop valve is closed, and the return valve is opened; the low-temperature section air preheater includes a low-temperature glass tube. The present invention reduces the final exhaust temperature to improve the thermal efficiency while extending the service life of the low-temperature glass tube.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas waste heat recovery, and in particular relates to a waste heat recovery device and a waste heat recovery method. Background Art

[0002] At present, heating furnaces in the petrochemical industry are generally equipped with flue gas waste heat recovery systems / devices, which use air preheaters to exchange heat between high-temperature flue gas and low-temperature air, reduce the exhaust temperature of flue gas, and increase the temperature of standby air to achieve the purpose of improving thermal efficiency. However, during the combustion process of the fuel used in the heating furnace, the sulfur element in the fuel generates SO 2 , part of SO 2 Further oxidation to SO 3 , and SO 3 It combines with water vapor in the flue gas to form sulfuric acid vapor. When the temperature of the heating surface is lower than the dew point temperature, the sulfuric acid vapor will condense into liquid on the heating surface, thereby corroding the heating surface material and affecting the service life of the heating surface material.

[0003] In order to prevent low-temperature dew point corrosion, in the prior art, the final exhaust temperature is controlled above the dew point temperature, such as controlling the final exhaust temperature above 130° C. However, this will result in a large part of the heat being unable to be recovered, resulting in reduced thermal efficiency. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a waste heat recovery device and a waste heat recovery method, which improves the thermal efficiency by reducing the final exhaust temperature and prolongs the service life of the heating surface material.

[0005] In order to achieve the above-mentioned purpose, in a first aspect, the present invention provides a waste heat recovery device, comprising a high-temperature section air preheater, a medium-temperature section air preheater and a low-temperature section air preheater connected to a tubular heating furnace and arranged in sequence, the flue gas outlet of the low-temperature section air preheater is connected to the chimney through a low-temperature flue gas outlet pipe, and a temperature sensor is arranged on the low-temperature flue gas outlet pipe; the flue gas inlet of the low-temperature section air preheater is connected to the flue gas outlet of the medium-temperature section air preheater through a medium-temperature flue gas inlet pipe; the low-temperature flue gas outlet pipe and the medium-temperature flue gas inlet pipe are connected by a return pipe; a stop valve is arranged on the low-temperature flue gas outlet pipe, the stop valve is located between the temperature sensor and the chimney, and a return valve is arranged on the return pipe; the temperature sensor is set to a temperature of 95±5°C, when the real-time detected temperature is lower than the set temperature, the return valve is closed and the stop valve is opened, when the real-time detected temperature is higher than the set temperature, the stop valve is closed and the return valve is opened;

[0006] The low temperature section air preheater comprises a low temperature glass tube, which comprises the following components by weight: 65-72 parts SiO 2 , 7-10 parts Al 2 O3 , 6-8 parts ZnO, 0.5-0.8 parts CaO, 2-3 parts MgO, 3-5 parts Na 2 O, 0.3-0.5 parts K 2 O, 0.5-1 parts of clarifier, 8-10 parts of composite boron glass powder and 2-3 parts of K 2 ZF 6 The composite boron glass powder is prepared by solution blending of boron glass powder, ceramic powder and polyvinyl chloride.

[0007] Furthermore, an induced draft fan is provided on the medium-temperature flue gas inlet pipe, which is located between the medium-temperature section air preheater and the return pipe.

[0008] Furthermore, the preparation method of the composite boron glass powder is as follows:

[0009] A1. Add 5-7 parts of polyvinyl chloride into 30-35 parts of tetrahydrofuran by weight and stir until mixed to obtain a uniform solution;

[0010] A2, add 10-12 parts of boron glass powder and 5-7 parts of ceramic powder into the uniform solution obtained in A1, and disperse by ultrasonic until mixed to obtain slurry;

[0011] A3. Pour the slurry obtained in A2 into a mold, dry it in a vacuum oven, and grind it to obtain composite boron glass powder.

[0012] Furthermore, in A1, the stirring speed is 500-600 r / min, and the stirring time is 30-50 min.

[0013] Furthermore, in A2, ultrasonic dispersion treatment is performed at a power of 100-200 W and the treatment time is 15-30 min.

[0014] Furthermore, in A3, a ball mill is used to grind the material to a particle size of less than 100 nm.

[0015] Furthermore, the clarifier includes sodium nitrate and sodium sulfate, and the mass ratio of the two is 2: (0.7-1).

[0016] Furthermore, the preparation method of the low-temperature glass tube is as follows:

[0017] S1. Mix the components according to the weight ratio, and then heat the mixture to 1560-1580°C at a heating rate of 8-10°C / min in a high-temperature melting furnace, and keep the temperature for 4-5 hours to obtain glass liquid;

[0018] S2. Heat the glass liquid obtained in S1 to 1600-1620°C, clarify for 1-1.2 hours, then cool to 1560-1580°C, homogenize for 20-30 minutes, and then draw into shape at 1070-1110°C to obtain a low-temperature glass tube.

[0019] In a second aspect, the present invention provides a waste heat recovery method, using the above-mentioned waste heat recovery device, the high-temperature flue gas from the tubular heating furnace first flows into the high-temperature section air preheater for heat exchange, and the temperature drops to 300-350°C; then flows into the medium-temperature section air preheater for heat exchange, and the temperature drops to 170-200°C; then flows into the low-temperature section air preheater for heat exchange, and then flows into the low-temperature flue gas outlet pipe for real-time temperature detection by the temperature sensor. When the real-time detected temperature is higher than the set temperature, the stop valve is closed and the reflux valve is opened, and the flue gas above the set temperature flows into the low-temperature section air preheater through the reflux pipe for heat exchange again. When the real-time detected temperature is lower than the set temperature, the reflux valve is closed, the stop valve is opened, and the flue gas below the set temperature enters the chimney for exhaust.

[0020] This application has the following beneficial effects:

[0021] 1. The present invention is provided with a temperature sensor, and through an automated system, the temperature of the flue gas flowing into the chimney for exhaust after heat exchange is automatically controlled to be as low as 95±5°C. Compared with the prior art in which the final exhaust temperature is controlled at a dew point temperature of more than 130°C, the heat recovery rate is significantly improved, and the thermal efficiency is improved; at the same time, the low-temperature section air preheater uses a special low-temperature glass tube, and in its preparation, the co-addition of composite boron glass powder and potassium fluorozirconate can significantly improve the acid resistance (corrosion resistance) of the obtained low-temperature glass tube, thereby extending the service life of the low-temperature glass tube in an environment where the exhaust temperature is as low as 95±5°C.

[0022] 2. In the preparation of the low-temperature glass tube of the present invention, boron glass powder is compounded with ceramic powder and polyvinyl chloride to form a composite material, that is, composite boron glass micropowder is obtained. The protrusions can be introduced into the boron-oxygen triangular sheet network structure that tends to form with potassium fluorozirconate at high temperature in the subsequent process, so that the protrusions can be better embedded in the glass matrix to form a mechanical interlocking, increase the contact area and friction between the two, and thus improve the bonding tightness, effectively reduce the penetration path of the corrosive medium, and improve the corrosion resistance. On this basis, the boron-oxygen triangular sheet network structure can also form uniform local coating points on the glass matrix, and there is a cross-connection relationship in the three-dimensional space between adjacent boron-oxygen triangular sheet network structures, which can further improve the overall bonding tightness and improve the corrosion resistance of the obtained glass tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , a schematic structural diagram of the waste heat recovery device of the present invention;

[0024] Figure 2 , a schematic structural diagram of the low temperature section waste heat recovery mechanism of the present invention;

[0025] Figure 3, a trend chart comparing the acid resistance (corrosion resistance) test data of the low-temperature glass tubes prepared in Examples 1-5 of the present invention and Comparative Examples 1-3.

[0026] In the figure, 1. tubular heating furnace; 21. high temperature section air preheater; 22. medium temperature section air preheater; 3. induced draft fan; 4. low temperature section air preheater; 5. blower; 6. temperature sensor; 7. reflux valve; 8. stop valve; 9. chimney. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to the embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0029] Example 1: Figure 1-Figure 2 As shown, a waste heat recovery device includes a high temperature section air preheater 21, a medium temperature section air preheater 22 and a low temperature section waste heat recovery mechanism connected to a tubular heating furnace 1 and installed and arranged in sequence, and the low temperature section waste heat recovery mechanism includes a low temperature section air preheater 4. Among them, the high temperature section air preheater 21 is a turbulator air preheater, the medium temperature section air preheater 22 is a heat pipe air preheater, and the low temperature section air preheater 4 is a glass tube air preheater, all of which are structural devices of the prior art, and the specific shape and structure of each heat exchanger will not be repeated here.

[0030] In the low-temperature section waste heat recovery mechanism, the flue gas outlet of the low-temperature section air preheater 4 is connected to the chimney 9 through a low-temperature flue gas outlet pipe, and a temperature sensor 6 is installed on the low-temperature flue gas outlet pipe. The flue gas inlet of the low-temperature section air preheater 4 is connected to the flue gas outlet of the medium-temperature section air preheater 22 through a medium-temperature flue gas inlet pipe, and an induced draft fan 3 is installed on the medium-temperature flue gas inlet pipe, which is located between the medium-temperature section air preheater 22 and the return pipe. A blower 5 is installed at the air inlet end of the low-temperature section air preheater 4. The low-temperature flue gas outlet pipe and the medium-temperature flue gas inlet pipe are connected through a return pipe. A stop valve 8 is installed on the low-temperature flue gas outlet pipe, and the stop valve 8 is located between the temperature sensor 6 and the chimney 9. A return valve 7 is installed on the return pipe.

[0031] The temperature sensor 6 is set to 95°C. In the prior art automation system, the temperature sensor 6 cooperates with the controller to realize the control of the opening and closing state of the stop valve 8 and the return valve 7. When the real-time detection temperature of the temperature sensor 6 is lower than its set temperature, the return valve 7 is closed and the stop valve 8 is opened. When the real-time detection temperature of the temperature sensor 6 is not lower than the set temperature, the stop valve 8 is closed and the return valve 7 is opened.

[0032] The following is a further description of the waste heat recovery method using the waste heat recovery device. The high-temperature flue gas from the tubular heating furnace 1 first flows into the high-temperature section air preheater 21 for heat exchange, and the temperature drops to 300-350°C; then flows into the medium-temperature section air preheater 22 for heat exchange, and the temperature drops to 170-200°C; then flows into the low-temperature section air preheater 4 through the induced draft fan 3 and the medium-temperature flue gas inlet pipe for heat exchange, and then flows into the low-temperature flue gas outlet pipe for real-time temperature detection through the temperature sensor 6. When the real-time detected temperature is not lower than the set temperature of 95°C, the stop valve 8 is closed, the return valve 7 is opened, and the flue gas not lower than the set temperature of 95°C flows into the low-temperature section air preheater 4 through the return pipe for heat exchange again. When the real-time detected temperature is lower than the set temperature of 95°C, the return valve 7 is closed, the stop valve 8 is opened, and the flue gas lower than the set temperature of 95°C flows into the chimney 9 through the low-temperature flue gas outlet pipe for exhaust.

[0033] At the same time, the air in the atmosphere is sent to the low-temperature air preheater 4, the medium-temperature air preheater 22 and the high-temperature air preheater 21 by the blower 5 in sequence for heat exchange, and then enters the burner of the tubular heating furnace 1 for combustion. Since the temperature of the flue gas flowing into the chimney 9 for exhaust after heat exchange is as low as below 95°C, that is, the air entering the burner of the tubular heating furnace 1 for combustion exchanges more heat from the flue gas, the temperature of the flue gas is reduced to below 95°C. Compared with the prior art in which the final exhaust temperature is controlled at a dew point temperature of above 130°C, this significantly improves the heat recovery rate and the thermal efficiency.

[0034] In this embodiment, the low temperature section air preheater includes a low temperature glass tube. In order to increase the service life of the low temperature glass tube in an environment where the flue gas temperature is as low as 95°C or below, the low temperature glass tube includes the following components by weight: 70 parts SiO 2 , 8 parts Al 2 O 3 , 7 parts ZnO, 0.7 parts CaO, 2.5 parts MgO, 4 parts Na 2 O, 0.4 parts K 2 O, 0.6 parts of clarifier, 9 parts of composite boron glass powder and 2.2 parts of K 2 ZF 6 (Potassium fluorozirconate). Among them, potassium fluorozirconate was purchased from Shandong Kaiyue Chemical Co., Ltd.

[0035] The specific preparation method of the low-temperature glass tube is as follows:

[0036] S1. Mix the components according to the weight ratio, then heat the mixture to 1570°C at a heating rate of 9°C / min in a high-temperature melting furnace, and keep the temperature for 4.5 hours to obtain molten glass.

[0037] Specifically, all components are uniformly mixed using an automatic batching system, loaded into a material tank, transported to the charging bin in front of the high-temperature melting furnace, and added to the high-temperature melting furnace through a screw feeder. The temperature is heated to 1570°C at a heating rate of 9°C / min, and kept warm for 4.5 hours to obtain glass liquid.

[0038] S2. The glass liquid obtained in S1 is heated to 1610°C, clarified for 1 hour, then cooled to 1570°C, homogenized for 25 minutes, and then drawn into shape at 1080°C to obtain a low-temperature glass tube.

[0039] Specifically, the glass liquid obtained in S1 is heated to 1610°C, clarified for 1 hour, then passed into a material channel, cooled to 1570°C, stirred at 4 r / min, homogenized for 25 minutes, and then passed into a material trough. The flow rate of the glass liquid is controlled by a trough gate system to obtain a ribbon glass, and then the mold is rotated at a speed of 20 r / min to form a tube. At 1080°C, a traction machine is used at a traction speed of 250 m / min to draw a glass tube with an inner diameter of 19 mm and a wall thickness of 2.2 mm, that is, a low-temperature glass tube.

[0040] The clarifier includes sodium nitrate and sodium sulfate, and the mass ratio of the two is 2:1.

[0041] The composite boron glass powder is prepared by solution blending of boron glass powder, ceramic powder and polyvinyl chloride. The specific preparation method is as follows:

[0042] A1. Add 6 parts of polyvinyl chloride into 34 parts of tetrahydrofuran by weight, stirring at a speed of 520 r / min for 40 min until mixed to obtain a uniform solution.

[0043] A2. According to the same standard weight proportions, add 11 parts of boron glass powder and 6 parts of ceramic powder into the uniform solution obtained in A1, and perform ultrasonic dispersion treatment at a power of 180 W for 25 min until uniformly mixed to obtain a slurry.

[0044] A3. Pour the slurry obtained in A2 into a mold, dry it in a vacuum oven (temperature 65°C, time 24h), and then grind it using a ball mill to a particle size of less than 100nm to obtain composite boron glass powder.

[0045] Among them, boron glass powder (item number 005) was purchased from Lingshou County Yingbo Mineral Products Processing Plant. Ceramic powder (325 mesh) was purchased from Lingshou County Shifeng Mining Processing Plant. Tetrahydrofuran (effective content 99%) was purchased from Jinan Lianshun Chemical Co., Ltd.

[0046] Example 2: The difference between this example and example 1 is that the low temperature glass tube includes the following components by weight: 65 parts SiO 2 , 7 parts Al 2 O 3, 6 parts ZnO, 0.5 parts CaO, 2 parts MgO, 3 parts Na 2 O, 0.3 parts K 2 O, 0.5 parts of clarifier, 8 parts of composite boron glass powder and 2 parts of K 2 ZF 6 .

[0047] The specific preparation method of the low-temperature glass tube is as follows:

[0048] S1. Mix the components according to the weight ratio, then heat the mixture to 1560°C at a heating rate of 8°C / min in a high-temperature melting furnace, and keep the temperature for 4 hours to obtain molten glass.

[0049] S2. The glass liquid obtained in S1 is heated to 1600°C, clarified for 1 hour, then cooled to 1560°C, homogenized for 20 minutes, and then drawn into shape at 1070°C to obtain a low-temperature glass tube.

[0050] Example 3: The difference between this example and example 1 is that the low temperature glass tube includes the following components by weight: 72 parts SiO 2 、10 parts Al 2 O 3 , 8 parts ZnO, 0.8 parts CaO, 3 parts MgO, 5 parts Na 2 O, 0.5 parts K 2 O, 1 part clarifier, 10 parts composite boron glass powder and 3 parts K 2 ZF 6 .

[0051] The specific preparation method of the low-temperature glass tube is as follows:

[0052] S1. Mix the components according to the weight ratio, then heat the mixture to 1580°C at a heating rate of 10°C / min in a high-temperature melting furnace, and keep the temperature for 5 hours to obtain molten glass.

[0053] S2. The glass liquid obtained in S1 is heated to 1620°C, clarified for 1.2 hours, then cooled to 1580°C, homogenized for 30 minutes, and drawn into shape at 1110°C to obtain a low-temperature glass tube.

[0054] Example 4: The difference between this example and Example 1 is that the specific preparation method of the composite boron glass powder is as follows:

[0055] A1. Add 5 parts of polyvinyl chloride into 30 parts of tetrahydrofuran by weight, stirring at a speed of 500 r / min for 30 min until mixed to obtain a uniform solution.

[0056] A2. According to the same standard weight proportions, 12 parts of boron glass powder and 7 parts of ceramic powder were added to the uniform solution obtained in A1, and ultrasonic dispersion treatment was performed at a power of 180 W for 25 minutes until uniformly mixed to obtain a slurry.

[0057] A3. Pour the slurry obtained in A2 into a mold, dry it in a vacuum oven, and grind it using a ball mill until the particle size is less than 100 nm to obtain composite boron glass powder.

[0058] Example 5: The difference between this example and Example 1 is that the specific preparation method of the composite boron glass powder is as follows:

[0059] A1. By weight, add 7 parts of polyvinyl chloride into 35 parts of tetrahydrofuran, stirring at a speed of 600 r / min for 50 min until mixed to obtain a uniform solution.

[0060] A2. According to the same standard weight proportions, 12 parts of boron glass powder and 7 parts of ceramic powder were added to the uniform solution obtained in A1, and ultrasonic dispersion treatment was performed at a power of 180 W for 25 minutes until uniformly mixed to obtain a slurry.

[0061] A3. Pour the slurry obtained in A2 into a mold, dry it in a vacuum oven, and grind it using a ball mill until the particle size is less than 100 nm to obtain composite boron glass powder.

[0062] Comparative Example 1: The difference between this comparative example and Example 1 is that the composite boron glass powder and potassium fluorozirconate are deleted from the components of the low-temperature glass tube.

[0063] Specifically, the low temperature glass tube includes the following components by weight: 70 parts SiO 2 , 8 parts Al 2 O 3 , 7 parts ZnO, 0.7 parts CaO, 2.5 parts MgO, 4 parts Na 2 O, 0.4 parts K 2 O and 0.6 parts of clarifier.

[0064] The specific preparation method of the low-temperature glass tube is as follows:

[0065] S1. Mix the components according to the weight ratio, then heat the mixture to 1570°C at a heating rate of 9°C / min in a high-temperature melting furnace, and keep the temperature for 4.5 hours to obtain molten glass.

[0066] S2. The glass liquid obtained in S1 is heated to 1610°C, clarified for 1 hour, then cooled to 1570°C, homogenized for 25 minutes, and then drawn into shape at 1080°C to obtain a low-temperature glass tube.

[0067] Comparative Example 2: The difference between this comparative example and Example 1 is that in the components of the low-temperature glass tube, the composite boron glass powder is replaced by boron glass powder, and potassium fluorozirconate is deleted.

[0068] Specifically, the low temperature glass tube includes the following components by weight: 70 parts SiO 2 , 8 parts Al 2 O 3 , 7 parts ZnO, 0.7 parts CaO, 2.5 parts MgO, 4 parts Na 2 O, 0.4 parts K 2 O, 0.6 parts of clarifier and 9 parts of boron glass powder.

[0069] The specific preparation method of the low-temperature glass tube is as follows:

[0070] S1. Mix the components according to the weight ratio, then heat the mixture to 1570°C at a heating rate of 9°C / min in a high-temperature melting furnace, and keep the temperature for 4.5 hours to obtain molten glass.

[0071] S2. The glass liquid obtained in S1 is heated to 1610°C, clarified for 1 hour, then cooled to 1570°C, homogenized for 25 minutes, and then drawn into shape at 1080°C to obtain a low-temperature glass tube.

[0072] Comparative Example 3: The difference between this comparative example and Example 1 is that in the components of the low-temperature glass tube, the composite boron glass powder is replaced by boron glass powder.

[0073] Specifically, the low temperature glass tube includes the following components by weight: 70 parts SiO 2 , 8 parts Al 2 O 3 , 7 parts ZnO, 0.7 parts CaO, 2.5 parts MgO, 4 parts Na 2 O, 0.4 parts K 2 O, 0.6 parts of clarifier, 9 parts of boron glass powder and 2.2 parts of K 2 ZF 6 (Potassium fluorozirconate).

[0074] The specific preparation method of the low-temperature glass tube is as follows:

[0075] S1. Mix the components according to the weight ratio, then heat the mixture to 1570°C at a heating rate of 9°C / min in a high-temperature melting furnace, and keep the temperature for 4.5 hours to obtain molten glass.

[0076] S2. The glass liquid obtained in S1 is heated to 1610°C, clarified for 1 hour, then cooled to 1570°C, homogenized for 25 minutes, and then drawn into shape at 1080°C to obtain a low-temperature glass tube.

[0077] Test example: Test object: Low-temperature glass tubes were prepared according to Examples 1-5 and Comparative Examples 1-3.

[0078] Test item: Acid resistance (corrosion resistance).

[0079] Test basis: According to GB / T 15782-1995 Gravimetric test method and classification of glass resistance to boiling hydrochloric acid erosion, the test is carried out and the number of milligrams of glass loss per square decimeter (mg / dm 2 ) value. The smaller the value, the stronger the acid resistance (corrosion resistance).

[0080] Test results: See Table 1.

[0081] Table 1. Test example data

[0082] <![CDATA[Loss amount (mg / dm 2 )]]> Example 1 1.04 Example 2 0.97 Example 3 1.03 Example 4 1.07 Example 5 0.96 Comparative Example 1 2.05 Comparative Example 2 1.71 Comparative Example 3 2.46

[0083] Result analysis: Analyze examples 1-5 and combine the data in Table 1 and Figure 3 It can be seen that the test loss of the low-temperature glass tube prepared by the present invention is as low as 1.07 mg / dm 2 Below, acid resistance H 1 Grade, excellent acid resistance (corrosion resistance).

[0084] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figure 3 From the comparison between Comparative Example 1 and Comparative Example 2, it can be seen that the addition of the component boron glass powder alone can improve the acid resistance (corrosion resistance) of the obtained low-temperature glass tube.

[0085] From the comparison between Comparative Example 1 and Comparative Example 3, it can be seen that the addition of the components boron glass powder and potassium fluorozirconate together will cause the acid resistance (corrosion resistance) of the low-temperature glass tube to decrease instead of increase.

[0086] This is because when potassium fluorozirconate and boron glass powder coexist, as the temperature rises, the boron oxide in the boron glass powder will gradually melt and form a liquid. In this process, the fluoride ions (F - ) and zirconium ions (Zr 4 + ) will enter the molten boron oxide, interact with it, and promote the formation of non-bridging oxygen, thereby destroying the original continuous network structure, increasing the openness of the structure, and increasing the permeability of the structure, causing the structure of the boron oxide to change from the original three-dimensional network structure to a two-dimensional lamellar network structure, making it easier for corrosive media to penetrate into the interior of the glass, thereby reducing the corrosion resistance of the glass.

[0087] From the comparison between Example 1 and Comparative Examples 1-3, it can be seen that the acid resistance (corrosion resistance) of the low-temperature glass tube can be significantly improved by making the boron glass powder into the composite boron glass powder of the present invention and then adding it together with potassium fluorozirconate, and the improvement effect is significantly better than when the component boron glass powder is added alone.

[0088] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0089] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A waste heat recovery device, characterized in that: It includes a high-temperature section air preheater, a medium-temperature section air preheater and a low-temperature section air preheater which are connected to the tubular heating furnace and arranged in sequence. The flue gas outlet of the low-temperature section air preheater is connected to the chimney through a low-temperature flue gas outlet pipe, and a temperature sensor is arranged on the low-temperature flue gas outlet pipe; the flue gas inlet of the low-temperature section air preheater is connected to the flue gas outlet of the medium-temperature section air preheater through a medium-temperature flue gas inlet pipe; the low-temperature flue gas outlet pipe and the medium-temperature flue gas inlet pipe are connected through a return pipe; a stop valve is arranged on the low-temperature flue gas outlet pipe, the stop valve is located between the temperature sensor and the chimney, and a return valve is arranged on the return pipe; the temperature sensor is set to 95±5℃, when the real-time detection temperature is lower than the set temperature, the return valve is closed and the stop valve is opened, when the real-time detection temperature is higher than the set temperature, the stop valve is closed and the return valve is opened; The low-temperature section air preheater comprises a low-temperature glass tube, which comprises the following components by weight: 65-72 parts of SiO2, 7-10 parts of Al2O3, 6-8 parts of ZnO, 0.5-0.8 parts of CaO, 2-3 parts of MgO, 3-5 parts of Na2O, 0.3-0.5 parts of K2O, 0.5-1 parts of a clarifier, 8-10 parts of composite boron glass powder and 2-3 parts of K2ZrF6; the composite boron glass powder is prepared by solution blending of boron glass powder, ceramic powder and polyvinyl chloride; The preparation method of the composite boron glass powder is as follows: A1. Add 5-7 parts of polyvinyl chloride into 30-35 parts of tetrahydrofuran by weight and stir until mixed to obtain a uniform solution; A2, add 10-12 parts of boron glass powder and 5-7 parts of ceramic powder into the uniform solution obtained in A1, and disperse by ultrasonic until mixed to obtain slurry; A3. Pour the slurry obtained in A2 into a mold, dry it in a vacuum oven, and grind it to obtain composite boron glass powder.

2. The waste heat recovery device according to claim 1, characterized in that: The medium-temperature flue gas inlet pipe is provided with an induced draft fan, which is located between the medium-temperature section air preheater and the return pipe.

3. The waste heat recovery device according to claim 1, characterized in that: In A1, the stirring speed is 500-600 r / min and the stirring time is 30-50 min.

4. The waste heat recovery device according to claim 1, characterized in that: In A2, ultrasonic dispersion treatment is performed at a power of 100-200 W and the treatment time is 15-30 min.

5. The waste heat recovery device according to claim 1, characterized in that: In A3, a ball mill was used to grind the particles to a particle size of less than 100 nm.

6. The waste heat recovery device according to claim 1, characterized in that: The clarifier includes sodium nitrate and sodium sulfate, and the mass ratio of the two is 2: (0.7-1).

7. The waste heat recovery device according to claim 1, characterized in that: The preparation method of the low temperature glass tube is as follows: S1. Mix the components according to the weight ratio, and then heat the mixture to 1560-1580°C at a heating rate of 8-10°C / min in a high-temperature melting furnace, and keep the temperature for 4-5 hours to obtain glass liquid; S2. Heat the glass liquid obtained in S1 to 1600-1620°C, clarify for 1-1.2 hours, then cool to 1560-1580°C, homogenize for 20-30 minutes, and then draw into shape at 1070-1110°C to obtain a low-temperature glass tube.

8. A waste heat recovery method, using the waste heat recovery device according to any one of claims 1 to 7, characterized in that: The high-temperature flue gas from the tubular heating furnace first flows into the high-temperature section air preheater for heat exchange, and the temperature drops to 300-350℃; then it flows into the medium-temperature section air preheater for heat exchange, and the temperature drops to 170-200℃; then it flows into the low-temperature section air preheater for heat exchange, and then flows into the low-temperature flue gas outlet pipe for real-time temperature detection by the temperature sensor. When the real-time detected temperature is higher than the set temperature, the stop valve is closed and the reflux valve is opened, and the flue gas above the set temperature flows into the low-temperature section air preheater through the reflux pipe for heat exchange again; when the real-time detected temperature is lower than the set temperature, the reflux valve is closed, the stop valve is opened, and the flue gas below the set temperature enters the chimney for exhaust.

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