CN107478067A - Heat recovery system - Google Patents

Abstract

The invention provides a heat recovery system for recovering waste heat of flue gas of a boiler, which includes a heat storage module and a first circuit. The heat storage module uses solid heat storage materials for heat storage, and the heat storage module is used to store the waste heat of the flue gas recovered from the boiler; the first circuit includes a heat exchange surface arranged in the final flue of the boiler to transfer the heat passing through the final flue The temperature of the flue gas is lowered to a first predetermined temperature, and the inlet and outlet of the first loop are respectively connected to the heat storage module to input heat into the heat storage module. According to the heat recovery system of the present invention, the temperature of the flue gas is further lowered by exchanging heat with the flue gas through the first circuit arranged in the final flue, which increases the amount of waste heat recovered from the flue gas; Storage does not reduce the energy quality of the recovered flue gas waste heat, improves heat utilization efficiency, and increases the form of heat utilization.

Description

heat recovery system

technical field

The invention relates to a heat recovery system.

Background technique

At present, the "OG system" (oxygen top-blown converter gas recovery system) commonly used in domestic steel mills, the temperature of the flue gas at the outlet of the converter is generally around 1600 °C, and the heat of the flue gas is generally recovered and utilized through the waste heat recovery system, which can be used in the converter. The outlet of the vaporization cooling flue reduces the temperature of the flue gas to 850-900°C, but it is still necessary to reduce the temperature of the flue gas to below 200°C before entering the dust collector. Usually, this process is realized by spraying a large amount of water to cool down. The heat contained in the flue gas is taken away by the water, which cannot be effectively recycled, and the sensible heat of this part of the flue gas is seriously wasted.

In addition, conventional flue gas waste heat recovery systems use steam accumulators to store recovered heat energy. The heat storage time of the steam accumulator is short, the heat loss is large, and it can only output saturated steam lower than the inlet parameters (for example, the inlet steam is 1.6MPa, and the outlet steam is generally about 0.7MPa), and the utilization efficiency of waste heat is low; The steam parameters at the outlet of the heater are limited in the form of waste heat utilization, which can only be used for heating in the factory area or saturated steam power generation, both of which are inefficient forms of energy utilization.

Accordingly, there is a need to provide a heat recovery system that at least partially addresses the above-mentioned problems.

Contents of the invention

A series of concepts in simplified form are introduced in the Summary of the Invention, which will be further detailed in the Detailed Description. The summary of the invention in the present invention does not mean to limit the key features and essential technical features of the claimed technical solution, nor does it mean to try to determine the protection scope of the claimed technical solution.

In order to at least partly solve the above problems, the present invention provides a heat recovery system for recovering waste heat from boiler flue gas, wherein the heat recovery system includes:

A heat storage module, the heat storage module uses solid heat storage materials for heat storage, the heat storage module is used to store the waste heat of the flue gas recovered from the boiler; and a first loop, the first loop includes the The heat exchange surface in the final flue of the boiler is used to lower the temperature of the flue gas passing through the final flue to a first predetermined temperature, and the inlet and outlet of the first circuit are respectively connected to the heat storage module to supply input heat into the heat storage module.

Optionally, the heat storage mode of the heat storage module also includes phase change heat storage.

Optionally, the first loop includes a heat pipe heat exchanger arranged in the last flue.

Optionally, the working fluid used in the first circuit is water or heat transfer oil.

Optionally, the heat recovery system further includes a second loop, and the second loop includes a heat exchange surface arranged in the flue in the middle section of the boiler to reduce the temperature of the flue gas passing through the flue in the middle section to a temperature greater than The first predetermined temperature and the second predetermined temperature, the inlet and the outlet of the second circuit are respectively connected to the heat storage module to input heat into the heat storage module.

Optionally, the range of the second predetermined temperature is 850-900°C.

Optionally, the range of the first predetermined temperature is 350-630°C.

Optionally, the heat recovery system further includes a third loop, an outlet and an inlet of the third loop are respectively connected to the heat storage module to absorb heat from the heat storage module.

Optionally, the third circuit is used to power a steam turbine or a toaster.

Optionally, the heat recovery system is applied to a basic oxygen furnace.

According to the heat recovery system of the present invention, a first circuit is arranged in the final flue of the boiler, and the heat exchange is performed with the flue gas through the heat pipe heat exchanger, so as to cool down the flue gas in the final flue and increase the recovery amount of waste heat of the flue gas ; In addition, the heat storage technology of solid materials is used to store the recovered flue gas waste heat in the heat storage module through heat exchange, which can generate continuous steam or other thermal fluids with higher parameters, without reducing the energy quality of the recovered flue gas waste heat. The heat utilization efficiency is improved, and the form of heat utilization is increased.

Description of drawings

The following drawings of the embodiments of the present invention are hereby included as part of the present invention for understanding the present invention. Embodiments of the present invention and description thereof are shown in the drawings to explain the principles of the present invention. In the attached picture,

Fig. 1 is a schematic diagram of the vaporization cooling flue of a common oxygen top-blown converter gas recovery system;

2 is a schematic diagram of a heat recovery system according to a first embodiment of the present invention; and

Fig. 3 is a schematic diagram of a heat recovery system according to a second embodiment of the present invention.

detailed description

In the following description, numerous specific details are given in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that embodiments of the invention may be practiced without one or more of these details. In other examples, some technical features known in the art are not described in order to avoid confusion with the embodiments of the present invention.

In order to thoroughly understand the embodiments of the present invention, a detailed structure will be set forth in the following description. It is evident that practice of the embodiments of the invention is not limited to specific details familiar to those skilled in the art.

In the iron and steel industry, more than 80% of the current steel output is refined by the oxygen top-blown converter, and is equipped with an oxygen top-blown converter gas recovery system (OG system) for gas and other gases in the production process (hereinafter collectively referred to as flue gas) to recycle. The flue gas temperature at the outlet of the converter in the OG system is generally around 1600°C, which contains a large amount of heat energy. Recovering this part of the heat energy can greatly improve the energy utilization efficiency.

The heat recovery system according to the present invention will be described in detail below with reference to FIGS. 1 to 3 .

As shown in Figure 1, it is a schematic diagram of the vaporization cooling flue 10 of the OG system, which can be roughly divided into four parts: a movable hood 11, a fixed flue 12 at the furnace mouth, a middle flue 13 and a final flue 14. The movable fume hood 11 is connected with the oxygen top-blown converter and plays the role of collecting and guiding the flue gas. The flue gas flows through the fixed flue 12 at the furnace mouth, the middle flue 13 and the last flue 14 in sequence, and after cooling down, it enters the dust collector for dust removal, and then performs subsequent gas collection or discharge as required. In the heat recovery system shown in the present invention, heat exchange surfaces are arranged in the middle section flue 13 and the end section flue 14 to recover the waste heat of the flue gas.

As shown in Figure 2, it is a schematic diagram of a heat recovery system 100 according to a first embodiment of the present invention, mainly including a heat storage module 110, a first loop 101, a second loop 102, a third loop 103, a steam turbine 120 and a generator 130. Wherein, the heat exchange surface of the second loop 102 is arranged in the middle section flue 13 for cooling the flue gas to a second predetermined temperature through heat exchange, and the heat exchange surface of the first loop 101 is arranged in the end section flue 14 , used to cool the flue gas to a first predetermined temperature through heat exchange. Of course, it can be understood that the second predetermined temperature is greater than the first predetermined temperature. In this embodiment, the range of the second predetermined temperature is 850-900°C, and the range of the first predetermined temperature is 350-630°C. In this way, the flue gas can be reduced to a lower temperature as much as possible before entering the dust collector and the waste heat can be recovered, thereby increasing the recovery of waste heat. Since the temperature of the flue gas in the final flue 14 is relatively low, preferably, the heat exchange surface of the first circuit 101 in the final flue 14 adopts a heat pipe heat exchanger 108 . Compared with ordinary heat exchangers, the heat pipe heat exchanger has better heat exchange performance, which can greatly improve the heat exchange efficiency between the first loop 101 and the lower temperature flue gas in the last flue 14, and optimize the efficiency of heat recovery. Effect.

The first loop 101 and the second loop 102 are respectively connected to the heat storage module 110, and the heat storage module 110 exchanges heat with the first loop 101 and the second loop 102 to transfer the working fluid in the first loop 101 and the second loop 102 The contained residual heat recovered from the flue gas is absorbed and stored. The third circuit 103 is connected to the heat storage module 110, and the working fluid in the third circuit 103 absorbs the heat stored in the heat storage module 110, and then delivers it to other application modules that require heat energy supply. In this embodiment, the third circuit 103 is a steam-water power generation system, in which the working medium is water, and the water in the third circuit 103 is converted into steam under the action of the heat storage module 110 and sent to the steam turbine 120 for driving the steam turbine 120 Rotate to drive the generator 130 to generate electricity, so as to realize the recovery and utilization of waste heat.

The heat storage module 110 adopts TES (Thermal Energy Storage) heat storage technology. TES heat storage technology is a heat storage technology based on solid heat storage materials. It mainly uses the characteristics of solid materials with good sensible heat storage capacity, and embeds heat transfer fluid pipes in solid materials to form heat storage modules. When the high-temperature working fluid flows through the heat storage module, it releases heat to the solid material to store heat in the heat storage module. When the low-temperature working fluid flows through the heat storage module, it absorbs heat from the solid material to output the heat stored in the heat storage module. Taking solid concrete heat storage as an example, a heat transfer fluid pipe is embedded in the concrete material. When heat is stored, the high-temperature working fluid flows in the pipe, and the heat is transferred to the concrete material in time and stored. When the heat is released, the low-temperature working medium flows in the opposite direction. , Exchange the heat stored in the concrete and supply it to heat users. Preferably, the heat storage material in the heat storage module may also include a heat storage material capable of phase change, and the heat storage capacity of the heat storage module is further increased by the latent heat of the phase change of the heat storage material.

Compared with conventional steam accumulators, the heat storage module 110 does not have the link of changing saturated steam into saturated water for storage, and then changing into saturated steam through flash evaporation for thermal energy output. Therefore, the quality of the output energy is not reduced. That is, when the input energy form and parameters are the same, the parameters of the steam in the third loop 103 are higher than those of the steam output from the steam accumulator (such as higher pressure and temperature), and the higher parameters of the steam The work efficiency is higher, and the application occasions are wider, thereby improving the utilization efficiency of waste heat.

Since the heat storage module 110 is used for heat storage, the working medium in the first circuit 101 and the second circuit 102 can be in various forms, such as water or heat transfer oil. Those skilled in the art can make a specific selection according to actual conditions and application occasions.

In this embodiment, the second circuit 102 uses water as a working medium. The second circuit 102 may include a steam drum 104 , a first passage 105 , a second passage 106 and a third passage 107 . Among them, the steam drum 104 plays the role of steam-water separation, and buffers the fluctuation of the flow. The inlet and outlet of the first channel 105 are respectively connected to the heat storage module 110 and the water side of the steam drum 104 for transporting water from the heat storage module 110 to the steam drum 104 . The inlet and the outlet of the second passage 106 are respectively connected to the water side and the gas side of the steam drum 104, and the second passage 106 has a heat exchange surface arranged in the middle section flue 13 for connecting the water in the steam drum 104 with the middle section The flue gas in the flue 13 performs heat exchange for waste heat recovery. The inlet and outlet of the third passage 107 are respectively connected to the gas side of the steam drum 104 and the heat storage module 110, and are used to transport the steam containing the waste heat recovered from the flue gas to the heat storage module 110, so as to store the recovered waste heat in the Inside the heat storage module 110. Therefore, through such an arrangement, the second loop 102 can provide saturated steam with better quality (stable parameters, and no water), which is beneficial for heat exchange in the heat storage module 110 to store waste heat.

As shown in FIG. 3 , it is a schematic diagram of a heat recovery system 200 according to a second embodiment of the present invention. It has the same structure as the heat recovery system 100 according to the first embodiment in the heat exchange with the flue gas for waste heat recovery, and for the sake of brevity, it will not be repeated here, and only the differences will be introduced in detail.

In this embodiment, the third loop 203 is connected to the heat storage module 210 and the heat exchanger 220 respectively. The working fluid in the third circuit 203 may be water or heat transfer oil or other suitable working fluid. In addition, the heat recovery system 200 also includes a fourth loop 204 . The fourth loop 204 is connected to the heat exchanger 220, and the working fluid therein is air. In the heat exchanger 220 , the working fluid in the third circuit 203 exchanges heat with the air in the fourth circuit 204 to heat the air into hot air. The hot air in the fourth loop 204 can be used for the heating process of the baker 230 in the steelmaking process. As the temperature of the air entering the burner is increased, the consumption of coal gas can be significantly reduced, and the waste heat of flue gas can be recovered and utilized.

The heat recovery system according to the present invention has been exemplified above. However, it can be understood that the heat recovery system according to the present invention can also be applied to other boiler systems except the basic oxygen furnace. The flue gas recovered and stored Waste heat can also be used in other occasions, such as heating, etc., and is not limited to the above-mentioned utilization forms. In addition, the heat transfer fluid used in each circuit of the heat recovery system according to the present invention may be water or heat transfer oil, or other heat transfer fluids. Those skilled in the art can make a specific selection according to the actual situation.

According to the heat recovery system of the present invention, by redesigning the tail of the vaporization cooling flue (ie, the final flue), adding a heat pipe heat exchanger, the temperature of the flue gas is further reduced, and the recovery of sensible heat of the flue gas is increased; and The heat storage technology of special solid heat storage materials is used to replace the steam heat accumulator, and the sensible heat of the flue gas is stored in the heat storage module through heat exchange, and can generate continuous steam or other thermal fluids with higher parameters for production use. The quality of the waste heat recovered from the flue gas will not be reduced, the utilization form of the waste heat will be increased, and the energy utilization efficiency will be improved.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terminology used herein is only for the purpose of describing a specific implementation, and is not intended to limit the present invention. Terms such as "disposed" appearing herein may mean that one component is directly attached to another component or that one component is attached to another component through an intermediary. Features described herein in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in that other embodiment or stated otherwise.

The present invention has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of illustration and description, and are not intended to limit the present invention within the scope of the described embodiments. Those skilled in the art can understand that more variations and modifications can be made according to the teaching of the present invention, and these variations and modifications all fall within the scope of protection claimed by the present invention.

Claims (10)

1. A kind of 1. heat recovery system, for being reclaimed to the fume afterheat of boiler, it is characterised in that the heat recovery system bag Include：

   Heat accumulation module, the heat accumulation module carry out heat accumulation using solid heat accumulating, and the heat accumulation module is used to store from described The fume afterheat of boiler recovery；

   First loop, first loop include the heat-transfer surface that is arranged in the latter end flue of the boiler will pass through the end Flue gas cool-down to the first predetermined temperature, the entrance and exit in first loop of section flue is respectively connecting to the heat accumulation module To input heat into the heat accumulation module.
2. 2. heat recovery system according to claim 1, it is characterised in that the heat accumulation pattern of the heat accumulation module also includes phase Become heat accumulation.
3. 3. heat recovery system according to claim 1, it is characterised in that first loop includes being arranged in the latter end Heat exchange of heat pipe in flue.
4. 4. heat recovery system according to claim 1, it is characterised in that the working medium that first loop uses is water or led Deep fat.
5. 5. heat recovery system according to claim 1, it is characterised in that the heat recovery system also includes second servo loop, The heat-transfer surface that the second servo loop includes being arranged in the interlude flue of the boiler is with by by the interlude flue Flue gas cool-down to the second predetermined temperature for being more than first predetermined temperature, the entrance and exit of the second servo loop connects respectively To the heat accumulation module to input heat into the heat accumulation module.
6. 6. heat recovery system according to claim 5, it is characterised in that the scope of second predetermined temperature be 850~ 900℃。
7. 7. heat recovery system according to claim 6, it is characterised in that the scope of first predetermined temperature be 350~ 630℃。
8. 8. heat recovery system according to claim 1, it is characterised in that the heat recovery system also includes tertiary circuit, The outlet of the tertiary circuit and entrance are respectively connecting to the heat accumulation module to absorb heat from the heat accumulation module.
9. 9. heat recovery system according to claim 8, it is characterised in that the tertiary circuit is used for for steam turbine or roasting bag Device energizes.
10. 10. heat recovery system according to claim 1, it is characterised in that the heat recovery system is applied to oxygen top blown Converter.