RU2735042C1 - Condensation heat recovery unit - Google Patents

Abstract

FIELD: power saving.

SUBSTANCE: invention relates to energy saving and can be used in heat engineering, metallurgy, chemical and other industries with fuel-using power plants for heat recovery and wet cleaning of flue gases (FG) by cooling, with condensation of moisture vapor from them and regeneration of this heat. Power plant 1 is connected to branch pipe 3 of direct supply water, has cooler 2 of heat-stressed elements, burner 4, air intake 5 and exhaust branch pipe 6. Heat recovery unit comprises evaporation type air heater 7 made in the form of U-shaped channel 20, and condensation-type recycling heat exchanger 9 connected to exhaust branch pipe 6 and stack 8. Heat recovery unit comprises pipelines 11 for supply and circulation of condensate with pump 12, condensate processing unit 10, heat exchangers 19, 26 with antifreeze circulation circuit 36 and pump 37, as well as heat exchangers or air heaters 13, 14, 18, 24, 27 and 33, included in reverse supply water supply path 31 with water lines 32 and 34 with bypass 28. There is also flue gas bypass 29 with mixing chamber 30 connected to chimney 8.

EFFECT: utilization of low-grade heat of FG leaving, with its transfer to network water, and increase of CHR operation efficiency.

10 cl, 2 dwg

Description

CONDENSING HEAT RECOVERY

The invention relates to the field of energy saving and can be used in thermal power engineering, metallurgy, chemical and other industries with fuel-using power plants for heat recovery and wet cleaning of flue gases (DG) by deep cooling, with condensation of moisture vapor from them and the recovery of this heat.

Known (RF patent No. 2449224) condensation heat exchanger (CT), installed behind a gas boiler (power plant) in the cylindrical part of the coaxial chimney. KT is made in the form of a counter-flow heat exchanger, a spiral-wound pipe with cold water. KT regenerates the heat of cooling and condensation of moisture vapor from the DG. The heat exchanger is irrigated, with natural irrigation - the heating surface is wetted by the condensate falling from the moisture vapor of the DG, and the condensate drops absorb heat, dust and oxides, which makes it possible to increase both the environmental characteristics and somewhat increase the efficiency of power plants.

The disadvantage of this CT is its low efficiency.

- To perceive the heat of condensation of water vapor, cold water is needed with a temperature not higher than 35-50 ° C, the dew point temperature of the DG. Return mains water is typically 60-70 ° C and therefore CT is ineffective. It is effective only when heating cold water, for example, hot water supply or when using complex heating systems such as "warm floor".

- KT heat exchangers do not use finned tubes and / or heaters, which increase the efficiency of its operation.

- DGs are saturated with small drops of condensate, which are corrosive, therefore corrosion-resistant materials and special equipment, condensate drains, etc. are required in the construction of chimneys and chimneys.

Known closest to the technical nature of the CT (RF patent No. 2659644), which is irrigated with condensate supplied through sprinklers, heat exchangers: an evaporative-type air heater and a condensation-type utilization heat exchanger. These contact heat exchangers (filled with a nozzle) are connected to each other by water supply and circulation lines for condensate with a condensate treatment unit, where condensate is cleaned and removed for further use. At the outlet of these heat exchangers, drop catchers and surface heaters of the outgoing medium, moist air and wet leaving DGs are installed, which eliminates the corrosive activity of these media. Surface heaters are heated with a hot coolant.

The heat released during the cooling of the DG in the utilization condensation heat exchanger is transferred in the KT circuit by circulating condensate, and the condensate is used for air humidification and irrigation, with the creation of an additional contact surface of the media and as a heat carrier. First, the heated condensate transfers heat in a water-to-water heat exchanger to the return network water, which flows after further heating in the boiler to the heat consumer, then with irrigation in the air heater to the air going to the boiler for combustion, and then the cooled condensate cools the DG, utilizing the low-potential exhaust heat. The KT is connected to the boiler burner by air, by DG to the boiler exhaust, and by condensate circulation water pipes and a water-water heat exchanger to the heat consumer.

The disadvantages of the prototype are the low efficiency of CT:

- To perceive the heat of condensation of water vapor, cold water with a temperature below the dew point of the DG is needed. The return network water typically has a temperature of at least 60-70 ° C, and therefore the heat exchanger is ineffective when connected to a typical heating network.

- Heat in this KT is transferred to the heating system in an inefficient indirect way, circulating condensate through a water-to-water heat exchanger, moreover, the KT does not use heaters and / or finned pipes that increase its efficiency.

The purpose of the invention is to utilize the low-grade heat of the leaving DG, with the transfer of it to the network water, and to increase the efficiency of the CT.

Considering the problem of heat recovery from the exhaust of wet DGs, the share of which is especially significant in gas boilers, about 10-20% of the total heat release, it should be noted that this heat with a low potential in such a volume can be perceived only in the heating network. The return network water typically has a temperature above the dew point and the technical effect required to solve the technical problem is its preliminary cooling.

DG cooling is possible due to heating the air entering the boiler for combustion, moreover humidified, with a large supply of heat, which goes to evaporate moisture into the air, as well as due to heating of other, colder streams available in the CT. Cooling of DGs during heat recovery with low potential with cooled network water is accompanied by natural irrigation of the heating surface (RF patent No. 2449224) and can be enhanced by additional irrigation both by supplying cold condensate and by developing a contact surface. In this case, the direct transfer of heat to the return network water through the wall of the heat exchange surface is more efficient, which can additionally be developed to increase efficiency, made of heaters and / or equipped with ribbing.

This goal is achieved by the fact that in KT, which includes condensate irrigated, supplied through sprinklers and having droplet separators at the outlet and surface heaters of the outlet medium, a condensing-type utilization heat exchanger connected to the boiler exhaust, and an evaporative-type air heater installed in front of the boiler burner in the duct blast supply connected by water supply and circulation lines of condensate with a condensate processing unit, according to the invention, it is proposed to install a water-to-water condensate heater in front of the air heater sprinkler, and to make the air heater and utilization heat exchanger with countercurrently connected, irrigated heat exchange surfaces and form from these elements a line for supplying network water to a boiler, including a return water inlet pipe, a water-to-water condensate heater, heat exchange surfaces of the air heater and utilization heat exchanger and a boiler.

In this case, the return network water coming from the heating network may have a temperature higher than the dew point temperature of the DG. First, it is cooled in a water-to-water condensate heater and in an evaporative-type air heater, heating irrigating air, condensate and humidified air in them, respectively, with a large heat removal for evaporation of condensate into the air stream. Further, cold water with a temperature below the dew point temperature of the DG is heated, utilizing the low-potential heat of condensation of moisture vapor and cooling of the DG in a condensation-type heat exchanger with condensate release from the DG, with direct heating of network water from the DG through the wall of the heating surface of the utilization heat exchanger. Thus, the proposed technical solution ensures efficient utilization of low-grade heat from the outgoing DG with its transfer to the heating water.

After CT, the network water is heated to the required temperature in the boiler (in the general case in the power plant) and supplied to the consumer. The heat exchanger can have natural irrigation, its heating surface is wetted by condensate falling out of the DG moisture vapor, or it can have additional irrigation with additional heat transfer by condensate through the sprinklers.

In an additional item 2, it is proposed to additionally include a DG surface heater and a surface air heater in the mains water supply path to the boiler between the return water supply pipe and the water-to-water condensate heater. This will provide not only an additional increase in the efficiency of the CT due to the cooling of the network water with colder wet streams of leaving DG and air in the surface heaters of DG and air, but also the evaporation of condensate drops from them, which eliminates the corrosive activity of these media along their supply path. For example, this is important when reconstructing a boiler with a KT installation, since the drops evaporate during heating, and there is no need to replace chimneys, a smoke exhauster, a chimney and other elements of the installation with corrosion-resistant ones.

In additional item 3, it is proposed to install a bypass parallel to the mains water supply path to the boiler between the return water supply pipe and the boiler. This will reduce the flow rate of heating water passing through the heat exchangers in the heating water supply path, increasing the depth of its cooling. As a result, this makes it possible to establish, for example, by adjusting the valve, the most effective, optimal mode of operation of the CT.

In additional item 4, it is proposed to install a heated air outlet to the ventilation system at the outlet of the air heater. At the same time, not only the combustion air is humidified and heated, but also the ventilation air, which increases the air consumption, heat, the depth of both the cooling of the heating water in the air heater, and the heat recovery from the DG, and the efficiency of the CT with the provision of ventilation of the premises.

In additional item 5, it is proposed to install a DG bypass along the DG flow in parallel with the utilization heat exchanger. This reduces the consumption of DG and the depth of their cooling in the DG. Then, behind the CT, hot and cooled diesel generators are mixed with the flow temperature maintaining above the dew point temperature. As a result, this provides simple protection against the corrosive activity of the DG with the efficient operation of the CT.

In the additional item 6, it is proposed to install cold surface-type heat exchangers included in the antifreeze circulation loop at the inlet to the air heater and at the outlet from the utilization heat exchanger. This protects the CT from defrosting and increases the efficiency of the CT by increasing the temperature head by using low and negative temperatures in the antifreeze circuit.

In additional clause 7, it is proposed to make the air heater with two heating stages and place it in the U-shaped air channel, and install its second, by air, stage on the ascending side, and make it in the form of a foam apparatus with a bundle of pipes cooling the mains water located above air distribution grille. This increases the efficiency of the CT operation by increasing the intensity of heat transfer in the foam layer.

In the additional paragraph 8, it is proposed that the utilization heat exchanger be made in the form of a lowering channel of a DG with connected in a counter-current scheme and sequentially located irrigated surface heaters of return network water, hot water supply and antifreeze. Surface heaters along the descending flows of DG and reflux condensate are arranged in order of decreasing temperature in them, and they effectively absorb heat from the DG at the maximum temperature difference.

In an additional claim 9, it is proposed at least in part of the surface-type heat exchangers to use heaters and / or finned tubes as heat exchangers. At the same time, the heat exchange surface increased due to ribbing increases the efficiency of the CT.

In additional clause 10, it is proposed that the heating surfaces, drip catchers and other elements in contact with a corrosive medium, including the DG bypass, used in the utilization heat exchanger and air heater, be made of corrosion-resistant materials. At the same time, the efficiency of CT increases by increasing its reliability.

FIG. 1 and FIG. 2 shows two examples of the technological scheme of a CT operating as part of a hot-water gas boiler or power plant, then a boiler.

KT is used as part of boiler 1 and has a main heating water heater 2 in the form of firewalls and boiler bundles, or it is, for example, a cooler 2 of heat-stressed elements of a power plant, connected by an outlet to the pipe 3 of direct heating water. The boiler 1 also has a burner 4, an air intake 5 and an exhaust pipe 6. The KT itself contains an evaporative-type air heater 7 located between the air intake 5 and the burner 4, as well as a condensation-type waste heat exchanger 9 connected to the exhaust pipe 6 and chimney 8, which are interconnected and with a condensate treatment unit 10 with water pipelines 11 for supplying and circulating condensate with a pump 12.

The air heater 7 has surface heat exchangers turned on countercurrently to the air flow: an upstream heat exchanger 13 and a heat exchanger 14 of an evaporative-irrigated type with a sprinkler 15. Through a droplet separator 16 with a condensate collector 17 and a heater 18 for heating humid air with its outlet, the air heater 7 is connected to the burner 4. On the other side, behind cold heat exchanger 19 can be installed with air intake 5.

Cold 19 and upstream 13 heat exchangers are auxiliary, they are effective in cold climates, in general they may not be installed. Structurally, the air heater 7 can be located in a vertical channel, Fig. 1, or in a U-shaped channel 20, Fig. 2. In the second case, the surface heat exchanger 14 of the evaporative-irrigation type is installed in the foam apparatus 21, which has an air distribution grid 22 and a drain channel 23, which sets the filling level of the foam apparatus 21.

The waste heat exchanger 9 contains a group of surface heat exchangers. These are condensers 24, 25 and 26, arranged in decreasing order of the temperature of the medium, respectively: network water, hot water and antifreeze, Fig. 1. The waste heat exchanger 9 is connected through a droplet separator 16 with a condensate collector 17 and a wet exhaust heating coil 27 to the chimney 8. It can also be performed as an irrigated surface heater located in the lowering channel of the DG, Fig. 2, or in the form of a foam apparatus of type 21 in the lifting channel DG.

A bypass 28 of return water is installed in the CT along the flow of return heating water in parallel to the air heater and the utilization heat exchanger, and parallel to the utilization heat exchanger downstream of the DG bypass 29 DG with a mixing chamber 30 DG.

The supply pipe 31 of the return network water with the help of a water pipe 32 is connected in series to a wet exhaust heating heater 27, to a wet air heater 18, to a water-to-water heater 33 for irrigation condensate, to a surface heat exchanger 14 of an evaporative-irrigated type and to a surface upstream heat exchanger 13 of an air heater 9. Further, the air heater 9 is connected by a water supply line 34 of cooled network water with a condenser 24 with network water and through the main heater 2 with a pipe 3 of direct network water. The listed elements 27, 18, 33, 14, 13 and 24 ensure the utilization of low potential heat and, together with the water pipelines 32 and 34, form a path for supplying heating water from the inlet pipe 31 to the boiler 1.

At a high temperature of the incoming DGs in the exhaust pipe 6, an additional heating water heater 35 can be installed, FIG. 2. Installed at the inlet to the air heater 7 and at the outlet from the utilization heat exchanger 9, heat exchangers 19 and 26 are included in the circulation circuit 36 of antifreeze with a pump 37. At the outlet of the air heater, a branch pipe 38 for supplying excess heated air to the supply ventilation can be installed, and in the bypass 28 of return network water and bypass 29 DG can be installed respectively regulating the flow rates of the device: valve 39 and gate 40.

The proposed variety of execution of the air heater 7, the utilization heat exchanger 9 and their constituent elements expands the range of applicability of the CT and provides the specification of its design with the choice of the most optimal option, which further increases its efficiency.

When the boiler 1 is operating, hot network water from the main heater 2 of the network water flows through the pipe 3 of the direct network water and the heating main to the consumer. In this case, the recovered heat is released in the boiler 1 due to the combustion of fuel, for example, gas supplied to the burner 4 together with the air that comes from the air intake 5, and spent DGs go through the exhaust pipe 6 to the CT.

Air in winter with temperatures down to -40 ° C and below enters the air heater 7. Here it is heated and humidified in surface heat exchangers included in countercurrent air flow, first in heat exchanger 19 with antifreeze, and without its freezing and icing. Further, the air is heated by return water in the upstream heat exchanger 13 and then in the evaporative-irrigated heat exchanger 14 of the second stage with the sprinkler 15, and with its concomitant humidification when it is irrigated with condensate heated in a water-water heater 33. Then, passing through the drip tray 16 with a condensate collector 17 and air heater 18, humid air is heated, becomes dry and safe in terms of corrosion, goes to burner 4 through standard air ducts without the risk of corrosion and condensate accumulation in them. Part of the heated and humidified air through the branch pipe 38 is supplied to the supply ventilation of the premises with additional heat removal, and this enhances the cooling and efficiency of the CT.

When using an evaporative-irrigated heat exchanger 14, located in the U-shaped channel 20, in the foam apparatus 21, Fig. 2, the work proceeds in a similar way, but more efficient contact of air with the heated surface and condensate, which is supplied through the sprinkler 15. The foam layer is maintained an air distribution grid 22 with a height that is set by the level of the liquid drain hole into the drain channel 23. The foam layer itself is created due to the passage of air through the condensate in the form of floating bubbles.

Heating and humidification of the air is carried out by the heat of the return network water with the transfer of energy to it, and this heat energy is added to the heat of combustion of the fuel. The return network water, at least part of its flow, enters through the inlet pipe 31 of the return network water, sequentially passes through the water supply line 32 and is cooled, heating and drying in the heater 27 in front of the chimney 8 the wet exhaust of the DG, in the heater 18 humid air, as well as heating condensate in a water-to-water heater 33. The final cooling of the return network water occurs in the surface heat exchangers of the second stage 14 and the upstream heat exchanger 13, and then through the water supply 34 of the cooled network water it enters the utilization heat exchanger 9.

Some of the return heating water flows directly into the main heater 2 through bypass 28 parallel to the air heater and the utilization heat exchanger, and this allows the operation of the CT to be optimized using the valve 39 due to the optimal cooling depth of the return heating water in the air heater depending on weather conditions.

In the utilization heat exchanger 9, the thermal energy of the exhaust gas from the boiler 1 is recovered, with its transfer in surface heat exchangers, condensers 24, 25 and 26, respectively, to the heating water, hot water supply and antifreeze, and at a high temperature of the diesel generator and in the additional heating water heater 35 ... In this case, antifreeze with a negative temperature can be supplied to the heat exchanger 26, which is included in the circulation circuit 36 of the antifreeze with the pump 37. The operation of the utilization heat exchanger 9 with surface heat exchangers 24, 25, 26 and 35 in Fig. 1 or Fig. 2 is not very different, but in the case of condensate supply through the sprinklers 15, the heat of its heating is used and more efficient contact with the DG is provided.

The supply from the air heater 7 of the return network water cooled below the dew point temperature, cold DHW water and cold, possibly negative temperature antifreeze in the utilization heat exchanger 9 ensures deep heat recovery with condensation of moisture vapor. In this case, the heat is first perceived by the return network water in the heat exchanger 24.

Further, the DGs pass a droplet separator 16 with a condensate collector 17 and a heater 27, heat up, become dry and safe in terms of corrosion. Dehumidification and heating of wet DG after the droplet separator 16 can be ensured without air heater 27, regulated by gate 40 by supplying 10-20% DG through the bypass 29 DG. DG streams are mixed in the mixing chamber 30 and dry DGs are discharged through typical chimneys and a typical chimney 8 without the danger of corrosion and condensate accumulation in them. The condensate is cleaned and collected in the condensate treatment unit 10 and in the required amount is supplied to the CT by the pump 12 through the water pipes 11.

Claims (10)

1. Condensing heat exchanger, including condensate sprayed through sprinklers, having drop catchers at the outlet and surface heaters of the outlet medium, a condensing-type utilization heat exchanger connected to the boiler exhaust, and an evaporative-type air heater installed in front of the boiler burner in the blast feed path, connected to each other Condensate supply and circulation water pipes with a condensate treatment unit, characterized in that a water-to-water condensate heater is installed in front of the air heater sprinkler, and the air heater and utilization heat exchanger are made with countercurrent, irrigated heat exchange surfaces, and these elements form a network water supply path to the boiler: water, water-to-water condensate heater, heat exchange surfaces of the air heater and utilization heat exchanger, boiler. 2. Condensation heat exchanger according to claim 1, characterized in that a surface heater of flue gases and a surface air heater are included in the path of supplying network water to the boiler between the branch pipe for supplying the return water and the water-to-water condensate heater. 3. Condensing heat exchanger according to claim 1 or 2, characterized in that a bypass is installed parallel to the mains water supply path to the boiler between the return water supply pipe and the boiler. 4. Condensing heat exchanger according to claim 1 or 2, characterized in that at the outlet of the air heater there is a branch pipe for withdrawing heated air into the ventilation system. 5. Condensing heat exchanger according to claim 1, characterized in that a flue gas bypass is installed parallel to the utilization heat exchanger along the flue gas flow. 6. Condensing heat exchanger according to claim 1 or 2, characterized in that cold surface-type heat exchangers are installed at the inlet to the air heater and at the outlet from the utilization heat exchanger included in the antifreeze circulation loop. 7. Condensing heat exchanger according to claim 1 or 2, characterized in that the air heater is made with two heating stages and is located in the U-shaped air channel, and its second air stage is installed on the ascending side and is made in the form of a foam apparatus with a bundle of cooling network water pipes located above the air distribution grille. 8. Condensing heat exchanger according to claim 1 or 2, characterized in that the utilization heat exchanger is made in the form of a downward channel of flue gases with connected in a counterflow scheme and sequentially located irrigated surface heaters of return network water, hot water supply and antifreeze. 9. Condensing heat exchanger according to any one of claims 1 to 7, characterized in that at least part of the surface-type heat exchangers are heat exchangers and / or finned tubes. 10. Condensing heat exchanger according to any one of claims 1 to 8, characterized in that the heating surfaces, droplet separators and other elements in contact with a corrosive medium, including the flue gas bypass, used in the utilization heat exchanger and air heater, are made of corrosion-resistant materials.

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