Flue gas condensation heat recovery device of gas-fired boiler

Abstract

The utility model discloses a gas-fired boiler smoke condensation heat recovery device, which relates to the field of boiler energy conservation and comprises a gas-fired boiler and a boiler smoke exhaust pipeline, a boiler energy saver is arranged at one end of the boiler smoke exhaust pipeline far away from the gas-fired boiler, and a low-temperature smoke exhaust pipeline is arranged at one end of the boiler energy saver far away from the gas-fired boiler. A smoke condensation heat recoverer is arranged at the end, away from the boiler economizer, of the low-temperature smoke exhaust pipeline. A condensation smoke exhaust pipeline and a condensate water recovery pipeline are sequentially arranged outside the smoke condensation heat recoverer, a boiler chimney is arranged at the end, away from the smoke condensation heat recoverer, of the condensation smoke exhaust pipeline, and a weak acid neutralization mechanism is arranged at the end, away from the smoke condensation heat recoverer, of the condensate water recovery pipeline. According to the utility model, the smoke condensation waste heat recovery technology is utilized to realize smoke sensible heat release and vapor vaporization latent heat release, and 10% of high-low heating value difference can be effectively utilized.

Description

Technical Field

[0001] The utility model relates to the field of boiler energy saving, and in particular to a flue gas condensation heat recovery device for a gas boiler. Background Art

[0002] Natural gas and other gas fuels are mainly compounds composed of carbon (C) and hydrogen (H), which can be completely burned. When hydrogen (H) in natural gas is burned inside the boiler, it combines with oxygen to form water. The generated water absorbs the latent heat of vaporization from the heat generated during combustion (high calorific value) and becomes water vapor, which is discharged with the flue gas. After 1Nm³ of natural gas is burned, 1.5-1.71kg / Nm³ of water vapor can be generated, which has a considerable latent heat of vaporization of about 3900kJ / m³, accounting for about 10% of the low calorific value of natural gas. When the exhaust temperature is higher than the water dew point, the water vapor cannot condense and release heat, and is discharged with the flue gas, and the heat is wasted.

[0003] The thermal efficiency of boilers is calculated based on the low calorific value of fuel, without considering the heat loss of latent heat of vaporization in the high calorific value of fuel. Therefore, the thermal efficiency of traditional boilers can generally only reach 88%-92%. Although the thermal efficiency is nominally high, the actual energy utilization rate is not high because the high calorific value and low calorific value of natural gas differ by about 10%.

[0004] Currently, no effective solution has been proposed for the problems in the related technologies. Utility Model Content

[0005] In view of the problems in the related technology, the utility model proposes a gas boiler flue gas condensation heat recovery device to overcome the above technical problems existing in the existing related technology.

[0006] To this end, the specific technical solutions adopted by the utility model are as follows:

[0007] A gas boiler flue gas condensation heat recovery device comprises a gas boiler, a boiler exhaust pipe is arranged at one end of the gas boiler, a boiler economizer is arranged at the end of the boiler exhaust pipe away from the gas boiler, a low-temperature exhaust pipe is arranged at the end of the boiler economizer away from the gas boiler, and a flue gas condensation heat recovery device is arranged at the end of the low-temperature exhaust pipe away from the boiler economizer; a condensation exhaust pipe and a condensate recovery pipe are arranged in sequence on the outside of the flue gas condensation heat recovery device, a boiler chimney is arranged at the end of the condensation exhaust pipe away from the flue gas condensation heat recovery device, and a weak acid neutralization mechanism is arranged at the end of the condensate recovery pipe away from the flue gas condensation heat recovery device.

[0008] Furthermore, in order to be able to replenish water to the gas boiler, deoxygenate and reduce the hardness of water, a boiler softening water supply pipe is also provided on the outside of the flue gas condensation heat recovery device, and a boiler water supply heating pipe is connected between the flue gas condensation heat recovery device and the boiler economizer; a deaerator is provided between the boiler economizer and the gas boiler, and a water supply heating pipe, a steam heating pipe and a boiler water supply pipe are sequentially provided on the outside of the deaerator, and the end of the water supply heating pipe away from the deaerator is connected to the boiler economizer, and the end of the boiler water supply pipe away from the deaerator is connected to the gas boiler.

[0009] Furthermore, in order to generate environmentally friendly products for discharge or utilization and to purify flue gas, the weak acid neutralization mechanism includes a tank body arranged at one end of the condensate recovery pipe away from the flue gas condensation heat recovery device, a plurality of baffles are arranged inside the tank body, and an outlet pipe is arranged at one end of the tank body away from the condensate recovery pipe; a connecting plate is arranged at the bottom end of the baffle, and the connecting plate is connected to the inner bottom of the tank body.

[0010] Furthermore, in order to add alkaline substances to the condensed water, the weak acid neutralization mechanism also includes a tank cover arranged on the top of the tank body, and an alkaline substance adding pipeline is interspersed inside the tank cover.

[0011] The beneficial effects of the utility model are:

[0012] (1) The utility model utilizes flue gas condensation waste heat recovery technology to realize the release of flue gas sensible heat and water vaporization latent heat. The 10% difference in high and low calorific value can be effectively utilized, making full use of energy, reducing the exhaust temperature of natural gas flue gas, recovering the heat in the flue gas, realizing heat energy recovery, and improving the thermal efficiency of the boiler.

[0013] (2) By installing a deaerator, boiler water supply pipe, etc., it is possible to supply water to the gas boiler, deoxygenate it, and reduce the hardness of the water.

[0014] (3) By setting up a weak acid neutralization mechanism, alkaline chemicals can be added to the condensed water for neutralization, generating environmentally friendly products for discharge or utilization, and playing a role in purifying flue gas. At the same time, by setting up a number of baffles, the acidic condensed water and the alkaline substances are fully mixed and neutralized. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1It is a structural schematic diagram of a gas boiler flue gas condensation heat recovery device according to an embodiment of the utility model;

[0017] Figure 2 yes Figure 1 A partial enlarged view of the middle A;

[0018] Figure 3 It is a schematic diagram of the internal structure of a tank in a gas boiler flue gas condensation heat recovery device according to an embodiment of the utility model;

[0019] Figure 4 It is a structural schematic diagram of a tank cover in a gas boiler flue gas condensation heat recovery device according to an embodiment of the utility model.

[0020] In the figure:

[0021] 1. Gas boiler; 2. Boiler exhaust pipe; 3. Boiler economizer; 4. Low-temperature exhaust pipe; 5. Flue gas condensation heat recovery device; 6. Condensation exhaust pipe; 7. Condensate water recovery pipe; 8. Boiler chimney; 9. Weak acid neutralization mechanism; 901. Tank body; 902. Baffle; 903. Water outlet pipe; 904. Connecting plate; 905. Tank cover; 906. Alkaline product adding pipe; 10. Boiler softening water supply pipe; 11. Boiler water supply heating pipe; 12. Deaerator; 13. Water supply heating pipe; 14. Steam heating pipe; 15. Boiler water supply pipe. DETAILED DESCRIPTION

[0022] To further illustrate each embodiment, the present invention provides drawings, which are part of the disclosure of the present invention and are mainly used to illustrate the embodiments. They can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in the field should be able to understand other possible implementation methods and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0023] According to an embodiment of the utility model, a gas boiler flue gas condensation heat recovery device is provided.

[0024] The present invention is now further described in conjunction with the accompanying drawings and specific implementation methods. Figure 1-4As shown, a gas boiler flue gas condensation heat recovery device according to an embodiment of the utility model comprises a gas boiler 1, a boiler exhaust pipe 2 is arranged at one end of the gas boiler 1, a boiler economizer 3 is arranged at the end of the boiler exhaust pipe 2 away from the gas boiler 1, a low-temperature exhaust pipe 4 is arranged at the end of the boiler economizer 3 away from the gas boiler 1, and a flue gas condensation heat recovery device 5 is arranged at the end of the low-temperature exhaust pipe 4 away from the boiler economizer 3; a condensation exhaust pipe 6 and a condensate recovery pipe 7 are arranged on the outside of the flue gas condensation heat recovery device 5 in sequence, a boiler chimney 8 is arranged at the end of the condensation exhaust pipe 6 away from the flue gas condensation heat recovery device 5, and a weak acid neutralization mechanism 9 is arranged at the end of the condensate recovery pipe 7 away from the flue gas condensation heat recovery device 5.

[0025] When the wall temperature of the flue gas condensation heat recovery device 5 is lower than the water dew point temperature of the flue gas, the water vapor in the flue gas will be condensed, releasing the latent heat of vaporization, and 10% of the high calorific value can be effectively utilized. However, since the flue gas temperature is lowered below the water dew point, severe acid corrosion will occur. Solving the corrosion of related equipment and pipelines is the key. The utility model adopts 2205 duplex stainless steel as the material of the device. After research, 2205 duplex stainless steel has excellent mechanical properties and corrosion resistance, as well as good weldability. Since the steel has high chromium and molybdenum contents, it has excellent resistance to pitting corrosion and uniform corrosion.

[0026] 2205 duplex stainless steel is a stainless steel in which the proportion of ferrite phase and austenite phase in its solid quenching organization is about half each. The excellent performance of 2205 duplex stainless steel is guaranteed by the appropriate proportion of two-phase organization. 2205 duplex stainless steel has excellent mechanical properties and corrosion resistance, as well as good weldability. It combines the most beneficial properties of ferrite and austenite, and has good resistance to chloride ion stress corrosion cracking. It is a duplex stainless steel composed of 21%-23% chromium, 2.5%-3.5% molybdenum, 2.0% manganese and 4.5%-6.5% nickel-nitrogen alloy. Its yield strength is twice that of austenitic stainless steel. This feature allows designers to reduce weight when designing products. Since the content of chromium and molybdenum in this steel is high, it has excellent resistance to pitting corrosion and uniform corrosion.

[0027] With the help of the above scheme, the utility model utilizes flue gas condensation waste heat recovery technology to realize the release of flue gas sensible heat and water vaporization latent heat. The 10% difference in high and low calorific value can be effectively utilized, making full use of energy, reducing the exhaust temperature of natural gas flue gas, recovering the heat in the flue gas, realizing heat energy recovery, and improving the thermal efficiency of the boiler.

[0028] In one embodiment, for the above-mentioned flue gas condensation heat recovery device 5, a boiler softening water supply pipe 10 is further provided on the outside of the flue gas condensation heat recovery device 5, and a boiler water supply heating pipe 11 is connected between the flue gas condensation heat recovery device 5 and the boiler economizer 3; a deaerator 12 is provided between the boiler economizer 3 and the gas boiler 1, and a water supply heating pipe 13, a steam heating pipe 14 and a boiler water supply pipe 15 are sequentially provided on the outside of the deaerator 12, and the end of the water supply heating pipe 13 away from the deaerator 12 is connected to the boiler economizer 3, and the end of the boiler water supply pipe 15 away from the deaerator 12 is connected to the gas boiler 1, so that water can be supplied to the gas boiler 1, and oxygen can be removed and the hardness of the water can be reduced.

[0029] In one embodiment, for the above-mentioned weak acid neutralization mechanism 9, the weak acid neutralization mechanism 9 includes a tank body 901 arranged at one end of the condensate recovery pipe 7 away from the flue gas condensation heat recovery device 5, a plurality of baffles 902 are arranged inside the tank body 901, a through hole is arranged at the bottom of the baffle 902, and a water outlet pipe 903 is arranged at one end of the tank body 901 away from the condensate recovery pipe 7; a connecting plate 904 is arranged at the bottom of the baffle 902, and the connecting plate 904 is connected to the inner bottom of the tank body 901; the weak acid neutralization mechanism 9 also includes a tank cover 905 arranged at the top of the tank body 901, and an alkaline substance adding pipe 906 is interspersed inside the tank cover 905, so that alkaline chemicals can be added to the condensate water and neutralized, and environmentally friendly products are generated for discharge or utilization, and play a role in purifying flue gas. At the same time, by setting a plurality of baffles 902, the acidic condensate water and the alkaline substances are fully mixed and neutralized.

[0030] The working principle of the weak acid neutralization mechanism 9 is as follows: the mixing time of the condensed water and the alkaline chemicals in the tank 901 can be prolonged through the baffles 902. Alkaline chemicals, such as alkaline solutions or solid alkaline agents, are added to the tank 901 through the alkaline addition pipeline 906. These alkaline chemicals are mixed with the acidic condensed water to perform a neutralization reaction.

[0031] In order to facilitate understanding of the above technical solution of the present invention, the working principle or operation method of the present invention in the actual process is described in detail below.

[0032] In actual application, the utility model is based on the flue gas condensation waste heat recovery technology, and uses a relatively low temperature working medium (water or air) to cool the flue gas, so that the wall temperature of the flue gas condensation heat recovery device 5 is reduced to below the water dew point. In the area close to the wall of the flue gas condensation heat recovery device 5, the water vapor in the flue gas condenses, and the sensible heat release of the flue gas and the latent heat of vaporization of water vapor are released at the same time, and the 10% difference in high and low calorific value can be effectively utilized. The water or air in the flue gas condensation heat recovery device 5 absorbs heat and is heated, realizing heat energy recovery and improving the thermal efficiency of the boiler. The relationship between the sensible heat and the latent heat of vaporization in the flue gas of a natural gas boiler is shown in Table 1:

[0033] Table 1

[0034] High calorific value of natural gas Latent heat of vaporization Low heat generation 9450kcal / Nm³ 950kcal / Nm³ 8500kcal / Nm³

[0035] High calorific value of natural gas - latent heat of vaporization = low calorific value

[0036] 9450kcal / Nm³-950kcal / Nm³=8500kcal / Nm³

[0037] Generally speaking, natural gas combustion exhaust contains CO2 and NOx, which are harmful gases that can promote the generation of acid rain or greenhouse effect, induce the destruction of the atmospheric ozone layer or affect the generation of ozone. When using flue gas condensation waste heat recovery technology, this environmental pollution phenomenon can be greatly alleviated.

[0038] CO2 and NO x In the tail flue of the condensing waste heat recovery boiler, it combines with the condensed H2O to generate the corresponding acid, which is discharged from the exhaust pipe along with the condensed water. x The content is greatly reduced, CO2 is reduced by about 40%, NO x About 25%-30% reduction. The condensed water from the flue gas is acidic because it contains H2CO3, HNO2, and HNO3, and is generally not suitable for direct discharge. In actual use, the pH value of the condensed water discharge is 6-7, which is weakly acidic. It can be neutralized by adding conventional alkaline chemicals such as MgO, lime water, and gypsum to generate environmentally friendly products for discharge or utilization. From this point of view, the flue gas condensation waste heat recovery technology also plays a role in purifying the flue gas.

[0039] The utility model can reduce the exhaust gas temperature to about 20-30°C, and fully recover the sensible heat and vaporization latent heat in the flue gas.

[0040] The utility model is a heat exchange device which condenses most of the water vapor in the flue gas of a gas boiler and recovers and utilizes the sensible heat and latent heat of the flue gas. It has various heat exchange forms such as finned tube heat exchanger, heat pipe heat exchanger, plate heat exchanger, spray heat exchanger, etc.

[0041] The finned tube heat exchanger is characterized by good heat exchange effect, small size, low cost and high cost performance.

[0042] 1. Fin tube heat exchanger performance

[0043] Finned tubes mainly expand the heat transfer area to enhance the convective heat transfer of gases with low surface heat transfer coefficients. Its main performance is reflected in the following aspects:

[0044] Strong heat transfer capacity. Compared with plain tubes, finned tubes can increase the heat transfer area by 2 to 30 times. At the same time, due to the disturbance of the airflow by the fins, the surface heat transfer coefficient can also be increased by 1 to 2 times. Therefore, its heat transfer capacity is much stronger than that of plain tubes.

[0045] Compact structure. Due to the small fin spacing, the heat transfer area arranged in a unit volume is greatly increased, and at the same time, the surface heat transfer coefficient is also increased, so that the volume of the heat exchanger is greatly reduced when transferring the same amount of heat, and the structure is more compact.

[0046] Prevent dust or scale from accumulating on the heat transfer surface. Due to the enhanced heat transfer capacity on the fin surface, the heat transfer temperature difference will be reduced compared with the bare tube, and the thickness of dust or scale on the heat transfer surface will be reduced. In addition, a uniform overall dust layer or scale layer will not be formed on the fin surface, but a parallel dust layer or scale layer will be formed along the edge of the fin, or a discontinuous dust layer or scale layer will be formed between the fin roots on the outer surface of the tube. This dust layer or scale layer will automatically fall off under the expansion and contraction of the fin tube.

[0047] 2. System structure

[0048] In the exhaust channel, a finned tube waste heat recovery heat exchanger (flue gas condensation heat recovery device 5) is set. The flue gas passes through the finned tube heat transfer surface in the channel, and the temperature drops below the water dew point temperature. The sensible heat in the flue gas and the latent heat of vaporization of water vapor heat the water in the finned tube. The water vapor in the flue gas condenses in the finned tube heat exchanger and is discharged through the set drain pipe, while absorbing part of the CO2 and NO in the flue gas. x , cleans the flue gas and plays an environmental protection role.

[0049] Using a heat exchanger to heat boiler feed water or return water for winter heating systems can save boiler energy and achieve the goal of energy saving for gas boilers.

[0050] In summary, the utility model utilizes flue gas condensation waste heat recovery technology to realize the release of flue gas sensible heat and the release of water vapor vaporization latent heat. The 10% difference in high and low calorific value can be effectively utilized, making full use of energy, reducing the exhaust temperature of natural gas flue gas, recovering the heat in the flue gas, realizing heat energy recovery, and improving the thermal efficiency of the boiler. By setting a deaerator, a boiler water supply pipeline, etc., it is possible to replenish water to the gas boiler 1, deoxygenate, and reduce the hardness of the water. By setting a weak acid neutralization mechanism 9, it is possible to add alkaline chemicals to the condensed water and neutralize it, generating environmentally friendly water for discharge or utilization, and playing a role in purifying the flue gas. At the same time, by setting a number of baffles 902, the acidic condensed water and the alkaline substances are fully mixed and neutralized.

[0051] In the present utility model, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the utility model according to the specific circumstances.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A gas boiler flue gas condensation heat recovery device, comprising a gas boiler (1), characterized in that: A boiler smoke exhaust pipe (2) is provided at one end of the gas boiler (1); a boiler economizer (3) is provided at one end of the boiler smoke exhaust pipe (2) away from the gas boiler (1); a low-temperature smoke exhaust pipe (4) is provided at one end of the boiler economizer (3) away from the gas boiler (1); and a flue gas condensation heat recovery device (5) is provided at one end of the low-temperature smoke exhaust pipe (4) away from the boiler economizer (3); The outside of the flue gas condensation heat recovery device (5) is provided with a condensation smoke exhaust pipe (6) and a condensation water recovery pipe (7) in sequence; a boiler chimney (8) is provided at one end of the condensation smoke exhaust pipe (6) away from the flue gas condensation heat recovery device (5); and a weak acid neutralization mechanism (9) is provided at one end of the condensation water recovery pipe (7) away from the flue gas condensation heat recovery device (5).

2. A gas boiler flue gas condensation heat recovery device according to claim 1, characterized in that: A boiler softening water supply pipe (10) is also provided outside the flue gas condensation heat recovery device (5), and a boiler water supply heating pipe (11) is connected between the flue gas condensation heat recovery device (5) and the boiler economizer (3).

3. A gas boiler flue gas condensation heat recovery device according to claim 1 or 2, characterized in that: A deaerator (12) is provided between the boiler economizer (3) and the gas boiler (1), and a water supply heating pipe (13), a steam heating pipe (14) and a boiler water supply pipe (15) are provided outside the deaerator (12) in sequence, and an end of the water supply heating pipe (13) away from the deaerator (12) is connected to the boiler economizer (3), and an end of the boiler water supply pipe (15) away from the deaerator (12) is connected to the gas boiler (1).

4. A gas boiler flue gas condensation heat recovery device according to claim 3, characterized in that: The weak acid neutralization mechanism (9) comprises a tank body (901) arranged at one end of the condensate recovery pipe (7) away from the flue gas condensation heat recovery device (5), a plurality of baffles (902) are arranged inside the tank body (901), and a water outlet pipe (903) is arranged at one end of the tank body (901) away from the condensate recovery pipe (7).

5. A gas boiler flue gas condensation heat recovery device according to claim 4, characterized in that: A connecting plate (904) is provided at the bottom end of the baffle (902), and the connecting plate (904) is connected to the inner bottom of the tank body (901).

6. A gas boiler flue gas condensation heat recovery device according to claim 5, characterized in that: The weak acid neutralization mechanism (9) further comprises a tank cover (905) arranged at the top of the tank body (901), and an alkaline substance adding pipeline (906) is interspersed inside the tank cover (905).

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