CN112013371A - Boiler system and control method thereof - Google Patents

Abstract

The present invention provides a boiler system comprising: boiler body, air heater, powder process device, flue and supercritical carbon dioxide circulation heat transfer circuit. The supercritical carbon dioxide circulation heat exchange loop comprises a supercritical carbon dioxide heat absorber, a supercritical carbon dioxide heat radiator, a first loop pipeline, a second loop pipeline and a circulating pump. The supercritical carbon dioxide heat absorber is arranged in the flue. The supercritical carbon dioxide circulation heat exchange loop utilizes supercritical carbon dioxide as a heat exchange medium to exchange heat in the high-temperature flue gas for hot primary air flowing out of the air preheater, and the hot primary air is secondarily heated to raise the temperature of the hot primary air.

Description

Boiler system and control method thereof

Technical Field

The invention relates to the technical field of coal-fired boilers, in particular to a boiler system which takes supercritical carbon dioxide as a heat exchange working medium and improves the temperature of hot primary air and a control method thereof.

Background

The primary air of the large coal-fired boiler is heated by the air preheater and then mixed with part of cold primary air to enter the powder making device, so that the ventilation and drying of the coal mill are realized, and the grinding, separation and conveying of raw coal are realized. When the temperature of the hot primary air of the boiler is insufficient or the coal quality deviates from the design value, in order to make the output of the coal pulverizing device reach the expectation, the hot primary air quantity is generally required to be increased, even the cold primary air is completely closed, and the excessive hot primary air is used for ventilating and drying the coal mill, but the operation can cause the secondary air rate of the boiler to be reduced, the corresponding secondary air quantity and the burning-out air quantity can not reach the design value, so that the problems of the combustion efficiency reduction of the boiler, the difficult control of pollutants, the rise of the exhaust gas temperature of the boiler and the like are caused. Particularly, for a boiler burning high-moisture lignite or low-quality coal, the primary air rate is far higher than a design value due to the fact that the temperature of hot primary air is lower than the design value, but the outlet temperature of a coal mill is still too low, so that the pulverized coal is difficult to burn out in a hearth, and the boiler efficiency is seriously influenced.

Therefore, there is a need to find a technical means for increasing the temperature of the hot primary air, and there are three main technical means for increasing the temperature of the hot primary air in the related art: the first scheme is that a tubular hot primary air heater is arranged at the tail of a boiler, hot primary air at the outlet of a rotary air preheater is sent into the hot primary air heater to be heated again, the hot primary air is sent into a powder making device after the temperature is raised, and the hot primary air heater is generally arranged in a convection heating surface at the tail of the boiler, such as between two stages of coal economizers; the second scheme is that a steam heater is arranged on a hot primary air duct, three-section extraction steam of a steam turbine is used as a heat source to heat hot primary air, and the cooled three-section extraction steam returns to a third high-pressure heater; in the third scheme, a bypass flue is arranged in the convection heating surface area at the tail part of the boiler, for example, flue gas bypass is carried out on two-stage heating surfaces or any one-stage heating surface of a low-temperature superheater and an economizer of the boiler, a tubular hot primary air heater is arranged on the bypass flue, and the temperature of hot primary air at the outlet of an air preheater is raised again by using high-temperature flue gas. However, the above technical solutions have disadvantages: the hot primary air is heated by steam extracted from the boiler side or the steam turbine side, so that the operation mode and the thermal performance of an original thermal system and equipment can be influenced, and the temperature of the hot primary air is also limited by the steam extraction flow; the technical scheme of the tubular flue gas heat exchanger can be limited by the arrangement space of a boiler and the flow trend of a flue gas system, and the heat exchange coefficient of the gas-gas heat exchanger is small, so that the flue gas heat exchanger is overlarge in size, the adjustable characteristic of the heat exchanger is insufficient, the power consumption of a primary fan and a secondary fan can be increased, and the boiler efficiency is reduced.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the embodiment of the invention provides a boiler system for improving the temperature of hot primary air by adopting a supercritical carbon dioxide circulating heat exchange loop and a control method thereof.

A boiler system according to an embodiment of the present invention includes: the boiler comprises a boiler body, a heat exchanger and a heat exchanger, wherein the boiler body is provided with a pulverized coal inlet, a hot secondary air inlet and a flue gas outlet; the air preheater is provided with a primary air inlet, a secondary air inlet, a first hot primary air outlet, a hot secondary air outlet and a flue gas inlet, and the hot secondary air outlet is communicated with the hot secondary air inlet; the coal pulverizing device is provided with a coal powder outlet, a cold primary air inlet and a first hot primary air inlet, and the coal powder outlet is communicated with the coal powder inlet; the flue is connected with the flue gas outlet, and a flue gas outlet of the flue is communicated with the flue gas inlet; the supercritical carbon dioxide heat circulating loop comprises a supercritical carbon dioxide heat absorber, a supercritical carbon dioxide heat radiator, a first loop pipeline, a second loop pipeline and a circulating pump, and the supercritical carbon dioxide heat absorber is arranged in the flue; the supercritical carbon dioxide heat absorber has a first carbon dioxide inlet and a first carbon dioxide outlet, the supercritical carbon dioxide heat radiator is provided with a second carbon dioxide inlet, a second carbon dioxide outlet, a second hot primary air inlet and a second hot primary air outlet, a first end of the first loop pipe is connected with the first carbon dioxide inlet, a second end of the first loop pipe is connected with the second carbon dioxide outlet, the first end of the second loop pipeline is connected with the second carbon dioxide inlet, the second end of the second loop pipeline is connected with the first carbon dioxide outlet, the second primary hot air inlet is communicated with the first primary hot air outlet, the second primary hot air outlet is communicated with the first primary hot air inlet, the circulation pump is provided on one of the first loop pipe and the second loop pipe.

According to the boiler system provided by the embodiment of the invention, the supercritical carbon dioxide circulating heat exchange loop is arranged, the supercritical carbon dioxide is used as a circulating heat exchange medium, the heat of high-temperature flue gas in the boiler turning chamber area is transferred to the hot primary air, the temperature of the hot primary air is increased, the hot primary air with the increased temperature can meet the drying requirement of the powder making device, and the powder outlet temperature of the powder making device is increased. And because no additional heat source is arranged, the energy consumption can be reduced.

The heat in the flue gas is replaced into the supercritical carbon dioxide by the supercritical carbon dioxide circulating heat exchange loop, and then the heat is transferred to the hot primary air by the supercritical carbon dioxide heat exchange, so that the indirect heating mode avoids the direct heat exchange between the high-temperature flue gas and the hot primary air and is easily limited by the arrangement space of the boiler and the flow direction of a flue gas system, and the indirect heating mode can adapt to the equipment structures of different boilers and has strong applicability. The arrangement of the supercritical carbon dioxide circulating heat exchange loop can not influence the operation of a thermodynamic system in the boiler and the thermodynamic performance of equipment, and can not influence the flow of flue gas.

Because the supercritical carbon dioxide has strong heat exchange capability, the size of the heat exchanger can be reduced, so that the boiler system is more convenient and simpler to install. In addition, due to the excellent heat exchange capacity of the supercritical carbon dioxide and the reasonable design and configuration of the supercritical carbon dioxide circulating heat exchange loop, the lifting space of the temperature of the hot primary air is greatly improved.

The boiler system provided by the embodiment of the invention has the advantages of low energy consumption, no influence on the flow of flue gas and capability of effectively improving the temperature of hot primary air.

In addition, the boiler system according to the present invention has the following additional technical features:

in some embodiments of the invention, the flue comprises a turn-around chamber and a rear flue shaft, the boiler system further comprises a low-temperature superheater and an economizer, the low-temperature superheater and the economizer being provided in the rear flue shaft, the supercritical carbon dioxide heat absorber being provided in the turn-around chamber and the supercritical carbon dioxide heat absorber being located above the low-temperature superheater and the economizer.

In some embodiments of the invention, each of the supercritical carbon dioxide heat absorber, the low temperature superheater and the economizer is a light pipe arranged in-line, and the transverse pitches of each of the supercritical carbon dioxide heat absorber, the low temperature superheater and the economizer are equal to each other.

In some embodiments of the invention, it is characterized by: the supercritical carbon dioxide heat radiator is a finned tube which is arranged in a staggered mode.

In some embodiments of the invention, the supercritical carbon dioxide circulation heat exchange loop further comprises a bypass air duct and a bypass valve, the bypass air duct is connected in parallel with the supercritical carbon dioxide radiator, and the bypass valve is arranged on the bypass air duct.

In some embodiments of the invention, the boiler system further comprises a pressure regulating device, the pressure regulating device comprising: a high pressure carbon dioxide storage device having a carbon dioxide outlet; a carbon dioxide delivery pipe, a first end of the carbon dioxide delivery pipe being connected to the carbon dioxide outlet, a second end of the carbon dioxide delivery pipe being connected to one of the first loop pipe and the second loop pipe; the supply adjusting valve is arranged on the carbon dioxide conveying pipe; a pressure gauge disposed on one of the first loop conduit and the second loop conduit.

In some embodiments of the invention, the pressure regulating device further comprises: an air exhaust pipe, a first end of which is connected with one of the first loop pipeline and the second loop pipeline; and the air exhaust valve is arranged on the air exhaust pipe.

In some embodiments of the invention, the second end of the pair of air exhaust pipes is open to the outside air.

In some embodiments of the invention, the second end of the air exhaust duct is connected to the flue.

In some embodiments of the invention, the supercritical carbon dioxide cycle heat exchange loop comprises a flow meter disposed on one of the first loop conduit and the second loop conduit.

Another embodiment of the present invention further provides a control method of a boiler system, including the steps of: enabling the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop to flow into the supercritical carbon dioxide heat absorber, wherein the supercritical carbon dioxide absorbs the heat of the high-temperature flue gas in the flue in the supercritical carbon dioxide heat absorber so as to obtain high-temperature supercritical carbon dioxide; the high-temperature supercritical carbon dioxide flows into the supercritical carbon dioxide heat releaser, and in the supercritical carbon dioxide heat releaser, the high-temperature supercritical carbon dioxide transfers heat to the hot primary air flowing through the supercritical carbon dioxide heat releaser so as to raise the temperature of the hot primary air, and the high-temperature supercritical carbon dioxide is changed into low-temperature supercritical carbon dioxide; and the low-temperature supercritical carbon dioxide flows into the supercritical carbon dioxide heat absorber and enters the next heat exchange cycle.

In some embodiments, when the temperature of the hot primary air needs to be increased, the supply adjusting valve is opened so as to supplement the supercritical carbon dioxide to the supercritical carbon dioxide circulation heat exchange loop and/or increase the rotating speed of the circulating pump so as to further increase the temperature of the hot primary air; when the temperature of the hot primary air needs to be reduced, the opposite air exhaust valve is opened so that the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop can be discharged and/or the rotating speed of the circulating pump is reduced.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a schematic diagram of a boiler system according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic view of an air preheater in the boiler system of FIG. 1.

Fig. 3 is a schematic diagram of a supercritical carbon dioxide cycle heat exchange loop according to an embodiment of the present invention.

FIG. 4 is an enlarged schematic view of a supercritical carbon dioxide heat emitter in the boiler system of FIG. 1.

Reference numerals:

a boiler system 100;

a boiler body 1; a hot secondary air inlet 11; a flue gas outlet 12; a combustor 13;

an air preheater 2; a primary air inlet 21; a secondary air inlet 22; a first hot primary air outlet 23; a hot secondary air outlet 24; a flue gas inlet 25;

a pulverizing device 3; a cold primary air inlet 31; a first hot primary air inlet 32;

a flue 4; a turn chamber 41; a rear smoke well 42; a low temperature superheater 421; an economizer 422; an SCR denitration device 43;

a supercritical carbon dioxide circulation heat exchange loop 5; a supercritical carbon dioxide heat absorber 51; a first carbon dioxide inlet 511; a first carbon dioxide outlet 512; a supercritical carbon dioxide heat spreader 52; a second carbon dioxide inlet 521; a second carbon dioxide outlet 522; a secondary hot primary air inlet 523; a second hot primary air outlet 524; a first loop conduit 53; a second circuit pipe 54; a circulation pump 55; a flow meter 56;

a primary air fan 6; a secondary air fan 7; a bypass valve 8;

a high-pressure carbon dioxide storage device 91; a carbon dioxide delivery pipe 92; a supply regulating valve 93; an air exhaust duct 94; an air exhaust valve 95; a pressure gauge 96.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

A boiler system according to an embodiment of the present invention is described below with reference to the accompanying drawings.

As shown in fig. 1 to 4, a boiler system 100 according to an embodiment of the present invention includes a boiler body 1, an air preheater 2, a pulverizing device 3, a flue 4, and a supercritical carbon dioxide heat-recycling loop 5.

As shown in fig. 1, the boiler body 1 has a pulverized coal inlet (not shown), a hot overfire air inlet 11 and a flue gas outlet 12. As shown in fig. 2, the air preheater 2 has a primary air inlet 21, a secondary air inlet 22, a first hot primary air outlet 23, a hot secondary air outlet 24, and a flue gas inlet 25, and the hot secondary air outlet 24 communicates with the hot secondary air inlet 11 of the boiler body 1. The primary air enters the air preheater 2 from the primary air inlet 21, after being heated by the air preheater 2, the hot primary air flows out from the first hot primary air outlet 23, the secondary air enters the air preheater 2 from the secondary air inlet 22, and after being heated by the air preheater 2, the hot secondary air flows out from the hot secondary air outlet 24.

The coal pulverizing device 3 is provided with a coal powder outlet (not shown in the figure), a cold primary air inlet 31 and a first hot primary air inlet 32, the coal powder outlet of the coal pulverizing device 3 is communicated with the coal powder inlet of the boiler body 1, and the coal powder enters the boiler body 1 from the coal pulverizing device 3 through the coal powder outlet and the coal powder inlet. The flue 4 is connected with the flue gas outlet 12 of the boiler body 1, the flue outlet of the flue 4 is communicated with the flue gas inlet 25, and flue gas in the boiler body 1 enters the flue 4 through the flue gas outlet 12, circulates from the flue 4 and then enters the air preheater 2 through the flue gas inlet 25 from the flue outlet of the flue 4.

As shown in fig. 3, the supercritical carbon dioxide circulation heat exchange circuit 5 includes a supercritical carbon dioxide heat absorber 51, a supercritical carbon dioxide heat radiator 52, a first circuit pipe 53, a second circuit pipe 54, and a circulation pump 55.

The supercritical carbon dioxide heat absorber 51 is provided in the flue 4. The supercritical carbon dioxide heat absorber 51 has a first carbon dioxide inlet 511 and a first carbon dioxide outlet 512. The supercritical carbon dioxide heat spreader 52 has a second carbon dioxide inlet 521, a second carbon dioxide outlet 522, a second hot primary air inlet 523, and a second hot primary air outlet 524. A first end of the first loop pipe 53 is connected to the first carbon dioxide inlet 511, and a second end of the first loop pipe 53 is connected to the second carbon dioxide outlet 522, that is, the first loop pipe 53 communicates the supercritical carbon dioxide heat absorber 51 and the supercritical carbon dioxide heat radiator 52. A first end of the second loop pipe 54 is connected to the second carbon dioxide inlet 521, and a second end of the second loop pipe 54 is connected to the first carbon dioxide outlet 512, that is, the second loop pipe 54 communicates the supercritical carbon dioxide heat absorber 51 and the supercritical carbon dioxide heat radiator 52. The second primary hot air inlet 523 is communicated with the first primary hot air outlet 23, and the second primary hot air outlet 524 is communicated with the first primary hot air inlet 32, that is, the primary hot air flows out from the first primary hot air outlet 23 of the air preheater 2, enters the supercritical carbon dioxide heat radiator 52, passes through the supercritical carbon dioxide heat radiator 52, and enters the pulverizing device 3. A circulation pump 55 is provided on one of the first and second circuit pipes 53 and 54.

It should be noted that, in this document, the "carbon dioxide" fields in the first carbon dioxide inlet 511, the first carbon dioxide outlet 512, the second carbon dioxide inlet 521, the second carbon dioxide outlet 522, the high-pressure carbon dioxide storage device 91 and the carbon dioxide delivery pipe 92 all refer to supercritical carbon dioxide. For example, the first carbon dioxide inlet 511 is an opening through which supercritical carbon dioxide flows into the supercritical carbon dioxide heat absorber 51.

As shown in fig. 1 to 4, after the overfire air enters the air preheater 2 from the overfire air inlet 22 and is heated by the air preheater 2, the hot overfire air flows out from the hot overfire air outlet 24 and enters the boiler body 1 from the hot overfire air inlet 11. The dried pulverized coal enters the boiler body 1 from the pulverized coal making device 3 through the pulverized coal outlet and the pulverized coal inlet. A part of the primary air enters the air preheater 2 from the primary air inlet 21, and after being heated by the air preheater 2, the primary heated hot primary air flows out from the first hot primary air outlet 23 and flows into the supercritical carbon dioxide heat radiator 52 from the second hot primary air inlet 523. The other part of the unheated cold primary air enters the pulverizing device 3 from the cold primary air inlet 31.

The supercritical carbon dioxide is used as a heat exchange medium and circulates in the supercritical carbon dioxide circulation heat exchange loop 5. The supercritical carbon dioxide in the supercritical carbon dioxide heat absorber 51 absorbs and stores the heat in the high-temperature flue gas, then flows out of the supercritical carbon dioxide heat absorber 51, flows into the supercritical carbon dioxide heat radiator 52, in the supercritical carbon dioxide heat radiator 52, the stored heat is transferred to the primary hot air for primary heating by the supercritical carbon dioxide, the primary hot air for primary heating is reheated, and the primary hot air after secondary heating enters the powder making device 3 from the primary hot air inlet 32.

According to the boiler system provided by the embodiment of the invention, the supercritical carbon dioxide circulating heat exchange loop is arranged, the supercritical carbon dioxide is used as a circulating heat exchange medium, the heat of high-temperature flue gas in the boiler turning chamber area is transferred to the hot primary air, the temperature of the hot primary air is increased, the hot primary air with the increased temperature can meet the drying requirement of the powder making device, the powder outlet temperature of the powder making device is increased, and the combustion efficiency of the boiler system is improved. And because no additional heat source is arranged, the energy consumption can be reduced.

The heat in the flue gas is replaced into the supercritical carbon dioxide by the supercritical carbon dioxide circulating heat exchange loop, and then the heat is transferred to the hot primary air by the supercritical carbon dioxide, so that the indirect heating mode avoids the direct heat exchange between the high-temperature flue gas and the hot primary air and is easily limited by the arrangement space of the boiler and the flow direction of a flue gas system, and the indirect heating mode can adapt to equipment structures of different boilers and has strong applicability. The arrangement of the supercritical carbon dioxide circulating heat exchange loop can not influence the operation of a thermodynamic system in the boiler and the thermodynamic performance of equipment, and can not influence the flow of flue gas.

Because the supercritical carbon dioxide has strong heat exchange capability, the size of the heat exchanger can be reduced, so that the boiler system is more convenient and simpler to install. In addition, due to the excellent heat exchange capacity of the supercritical carbon dioxide and the reasonable design and configuration of the supercritical carbon dioxide circulating heat exchange loop, the lifting space of the temperature of the hot primary air is greatly improved.

The boiler system provided by the embodiment of the invention has the advantages of low energy consumption, no influence on the flow of flue gas, capability of effectively improving the temperature of hot primary air and high boiler combustion efficiency.

As shown in fig. 1-2, the boiler system may include a boiler body 1, an air preheater 2, a pulverizing device 3, and a flue 4. Further, the boiler system may also comprise a primary fan 6 and a secondary fan 7.

As an example, as shown in fig. 1, the boiler body 1 has a pulverized coal inlet (not shown), a hot overfire air inlet 11 and a flue gas outlet 12, and the boiler body 1 further includes a furnace chamber, in which a burner 13 is disposed, and qualified pulverized coal output from the pulverizing device 3 enters the furnace chamber through the pulverized coal inlet and is combusted by the burner 13, and in some embodiments, the pulverized coal inlet is located on the burner 13.

The air preheater 2 has a primary air inlet 21, a secondary air inlet 22, a primary hot air outlet 23, a secondary hot air outlet 24, and a flue gas inlet 25. Optionally, the air preheater 2 is a triple bin rotary air preheater. The air preheater 2 stores heat in the flue gas flowing out from the tail of the flue 4 through a heat storage element, and exchanges the stored heat to primary air and secondary air so as to heat the primary air and the secondary air.

As shown in fig. 1, one outlet of the primary air fan 6 is connected to the primary air inlet 21, and the unheated primary air is blown into the air preheater 2, and the temperature of the primary air heated by the air preheater 2 rises, and the primary air is called primary heated hot primary air, which flows out from the primary hot primary air outlet 23.

The secondary air fan 7 is connected with the secondary air inlet 22, unheated secondary air is blown into the air preheater 2 from the secondary air inlet 22, the temperature of the secondary air is increased after the secondary air is heated by the air preheater 2, the secondary air is called hot secondary air, and the hot secondary air flows out from the hot secondary air outlet 24. The hot secondary air outlet 24 is communicated with the hot secondary air inlet 11 on the boiler body 1, the hot secondary air is finally blown into the hearth of the boiler body 1 to provide combustion-supporting air for combustion in the hearth, and further, the final air outlet of the hot secondary air is positioned near the combustor 13 to better play a role in supporting combustion.

The coal pulverizing device 3 is provided with a coal powder outlet (not shown in the figure), a cold primary air inlet 31 and a first hot primary air inlet 32, the coal powder outlet of the coal pulverizing device 3 is communicated with the coal powder inlet of the boiler body 1, and qualified coal powder enters the boiler body 1 from the coal pulverizing device 3 through the coal powder outlet and the coal powder inlet to participate in combustion in the hearth. The primary air fan 6 is also provided with another air outlet, primary air flowing out of the air outlet is not introduced into the air preheater 2 for heating, the primary air flowing out of the air outlet is called cold primary air, the air outlet is connected with a cold primary air inlet 31, and the cold primary air and the hot primary air enter the powder making device 3 together.

The flue 4 is connected with the smoke outlet 12 of the boiler body 1, and the smoke outlet of the flue 4 is communicated with the smoke inlet 25 of the air preheater 2. That is, the high temperature flue gas in the boiler body 1 enters the flue 4 via the flue gas outlet 12, circulates in the flue 4, and then enters the flue gas inlet 25 of the air preheater 2 from the flue outlet of the flue 4, and the heat in the flue gas is stored in the air preheater 2. Further, the flue 4 comprises a turn-around chamber 41 and a rear chimney 42, the turn-around chamber 41 being located above the rear chimney 42, in particular the turn-around chamber 41 being located at the turn between the horizontal flue connected to the flue gas outlet 12 and the vertical rear chimney 42. The rear flue gas shaft 42 may be provided with a low-temperature superheater 421 and an economizer 422, and the low-temperature superheater 421 and the economizer 422 are arranged up and down along the flow direction of flue gas (the up and down directions are indicated by arrows in fig. 1). The low-temperature superheater 421 and the economizer 422 can be used as a low-temperature convection heating surface of the rear smoke well 42. In other embodiments, the low temperature convection heating surface of the aft plume 42 may have other known devices and combinations.

In some embodiments, the boiler system further comprises an SCR denitration device 43, the SCR denitration device 43 being located between the low temperature convection heating surface of the rear flue gas shaft 42 and the air preheater 2.

As shown in fig. 1 to 4, the boiler system further includes a supercritical carbon dioxide circulation heat exchange loop 5, and as shown in fig. 2, the supercritical carbon dioxide circulation heat exchange loop 5 includes a supercritical carbon dioxide heat absorber 51, a supercritical carbon dioxide heat radiator 52, a first loop pipe 53, a second loop pipe 54, and a circulation pump 55.

As shown in fig. 1, the supercritical carbon dioxide heat absorber 51 is provided in the flue 4. As shown in fig. 3, the supercritical carbon dioxide heat absorber 51 has a first carbon dioxide inlet 511 and a first carbon dioxide outlet 512. Preferably, the supercritical carbon dioxide heat absorber 51 is disposed in the diversion chamber 41, and the supercritical carbon dioxide heat absorber 51 is located above the low-temperature convection heating surface (e.g., the low-temperature superheater 421 and the economizer 422) of the rear chimney 42. The supercritical carbon dioxide heat absorber 51 located in the diversion chamber 41 can absorb heat of the high-temperature flue gas. The supercritical carbon dioxide in the supercritical carbon dioxide heat absorber 51 flows from the first carbon dioxide inlet 511 to the first carbon dioxide outlet 512, and in this process, the supercritical carbon dioxide absorbs and stores heat of the high-temperature flue gas, and becomes high-temperature supercritical carbon dioxide. The supercritical carbon dioxide heat absorber 51 is arranged in the steering chamber 41 and is not easily limited by the arrangement of equipment in the boiler and the trend of a flue, so that the boiler system has the characteristics of convenience in installation and strong applicability.

Further preferably, the supercritical carbon dioxide heat absorber 51 is a light pipe arranged in an in-line manner, the supercritical carbon dioxide can flow in the light pipe, and the transverse pitch of the supercritical carbon dioxide heat absorber 51 is equal to that of the low-temperature superheater 421 and the economizer 422. This design allows the flue gas to flow through the flue 4 without being excessively resistant by the supercritical carbon dioxide heat sink 51. That is to say, the boiler system of the invention can utilize the supercritical carbon dioxide circulation heat exchange loop 5 to increase the temperature of the hot primary air on the premise of not excessively influencing the circulation of the flue gas in the flue 4.

As shown in fig. 4, the supercritical carbon dioxide heat spreader 52 has a second carbon dioxide inlet 521, a second carbon dioxide outlet 522, a second hot primary air inlet 523, and a second hot primary air outlet 524. In the process in which the supercritical carbon dioxide in the supercritical carbon dioxide radiator 52 flows from the second carbon dioxide inlet 521 to the second carbon dioxide outlet 522, the high-temperature supercritical carbon dioxide releases heat by exchanging the heat to the hot primary air, and becomes low-temperature supercritical carbon dioxide.

The first end of the first loop pipeline 53 is connected to the first carbon dioxide inlet 511, and the second end of the first loop pipeline 53 is connected to the second carbon dioxide outlet 522, that is, the first loop pipeline 53 communicates the supercritical carbon dioxide heat absorber 51 with the supercritical carbon dioxide heat radiator 52, so that the supercritical carbon dioxide with heat exchanged and low temperature can flow from the supercritical carbon dioxide heat radiator 52 to the supercritical carbon dioxide heat absorber 51 through the first loop pipeline 53. The first end of the second loop pipeline 54 is connected to the second carbon dioxide inlet 521, and the second end of the second loop pipeline 54 is connected to the first carbon dioxide outlet 512, that is, the second loop pipeline 54 communicates the supercritical carbon dioxide heat absorber 51 and the supercritical carbon dioxide heat radiator 52, so that the high-temperature supercritical carbon dioxide which has absorbed the heat of the flue gas can flow from the supercritical carbon dioxide heat absorber 51 to the supercritical carbon dioxide heat radiator 52 through the second loop pipeline 54. A circulation pump 55 is provided on one of the first and second loop pipes 53, 54 to power the circulation of the supercritical carbon dioxide in the circulation loop. Optionally, the circulation pump 55 is a variable frequency regulated pump. The heat absorption and heat release circulation of the high-temperature and low-temperature supercritical carbon dioxide in the loop can continuously convert the heat of the high-temperature flue gas from the flue 4.

As shown in fig. 1-4, the second primary hot air inlet 523 of the supercritical carbon dioxide heat radiator 52 is communicated with the first primary hot air outlet 23, and the second primary hot air outlet 524 is communicated with the first primary hot air inlet 32, that is, the primary hot air flows out from the first primary hot air outlet 23 of the air preheater 2 and enters the supercritical carbon dioxide heat radiator 52, and is secondarily heated by the supercritical carbon dioxide heat radiator 52, so that the temperature of the secondarily heated primary hot air is further raised, which is called secondary heated primary hot air, and the primary hot air enters the pulverizing device 3.

Preferably, the supercritical carbon dioxide heat spreaders 52 are finned tubes arranged in a staggered arrangement. The design can increase the area of the heat exchange surface and improve the heat exchange efficiency.

In some embodiments, as shown in fig. 1, the supercritical carbon dioxide heat recycling loop 5 further includes a bypass air duct and a bypass valve 8, the bypass air duct is connected in parallel with the supercritical carbon dioxide radiator 52, and the bypass valve 8 is disposed on the bypass air duct. When the supercritical carbon dioxide heat radiator 52 is in split operation or fails, the bypass valve 8 is opened, so that the hot primary air can be switched into the bypass air duct, the operation resistance of the hot primary air is reduced, and the maintenance of the supercritical carbon dioxide heat radiator 52 is facilitated.

Further, in some embodiments, as shown in fig. 3, the boiler system further comprises a pressure regulating device for regulating the pressure in the supercritical carbon dioxide cyclic heat exchange loop 5. In some embodiments, the pressure regulating device includes a high pressure carbon dioxide storage device 91, a carbon dioxide delivery pipe 92, a make-up regulating valve 93, an air exhaust pipe 94, an air exhaust valve 95, and a pressure gauge 96.

The high pressure carbon dioxide storage device 91 has a carbon dioxide outlet. A first end of carbon dioxide delivery pipe 92 is connected to the carbon dioxide outlet, and a second end of carbon dioxide delivery pipe 92 is connected to one of first loop pipe 53 and second loop pipe 54. The supply adjustment valve 93 is provided on the carbon dioxide transport pipe 92.

When the operating pressure in the supercritical carbon dioxide circulation heat exchange loop 5 is lower than the set value, the supply regulating valve 93 is opened, and the supercritical carbon dioxide flows out of the high-pressure carbon dioxide storage device 91 and enters the supercritical carbon dioxide circulation heat exchange loop 5 through the carbon dioxide conveying pipe 92, so that the operating pressure of the circulation loop can be increased to the set value.

As shown in fig. 3, a first end of the air exhaust pipe 94 is connected to one of the first and second loop pipes 53 and 54. An air exhaust valve 95 is provided in the air exhaust pipe 94. Alternatively, the second end of the air exhaust pipe 94 is open to the outside air, or the second end of the air exhaust pipe 94 is connected to the stack 4. When the operating pressure in the supercritical carbon dioxide circulation heat exchange loop 5 is higher than a set value, the air exhaust valve 95 is opened, and the supercritical carbon dioxide is released from the supercritical carbon dioxide circulation heat exchange loop 5, so that the amount of the supercritical carbon dioxide in the circulation loop is reduced, and the purpose of reducing the operating pressure of the circulation loop is achieved. The supercritical carbon dioxide can be discharged into the outdoor atmosphere through the air exhaust pipe 94, so that the carbon dioxide is prevented from being deposited in a boiler room and causing a suffocation accident, and can also be discharged into a tail flue of the boiler by utilizing negative pressure formed by suction of a draught fan.

A pressure gauge 96 is provided on one of the first loop pipe 53 and the second loop pipe 54 for monitoring the pressure in the supercritical carbon dioxide cycle heat exchange loop 5, so as to adjust and control the pressure in the loop.

The supercritical carbon dioxide cycle heat exchange circuit 5 includes a flow meter 56, and the flow meter 56 is provided on one of the first circuit pipe 53 and the second circuit pipe 54. The flow meter 56 is used for monitoring the flow rate of carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop 5, and the flow rate of carbon dioxide can be adjusted by adjusting the rotation speed of the circulation pump 55.

Through supercritical carbon dioxide's pressure and flow in the regulation return circuit, and then can adjust supercritical carbon dioxide circulation heat transfer loop 5's heat transfer volume, realize satisfying the requirement of reality to the control and the regulation of the hot primary air temperature through the secondary heating to reduce the cold primary air volume of sneaking into in the powder process device 3, realize the promotion of boiler efficiency.

Another embodiment of the present invention further provides a control method of a boiler system, where the boiler system provided in the above embodiment is a boiler system, and the following takes the boiler systems shown in fig. 1 to 4 as examples to describe steps of the control method in the embodiment of the present invention:

as shown in fig. 1 to 4, the supercritical carbon dioxide is used as a heat exchange medium and circulated through the supercritical carbon dioxide circulation heat exchange circuit 5. The supercritical carbon dioxide heat absorber 51 is positioned in the diversion chamber 41, the supercritical carbon dioxide flowing into the supercritical carbon dioxide heat absorber 51 from the first carbon dioxide inlet 511 absorbs the heat of the high-temperature flue gas in the flue 4, the temperature of the supercritical carbon dioxide rises to become high-temperature supercritical carbon dioxide, the high-temperature supercritical carbon dioxide flows out from the first carbon dioxide outlet 512, flows into the supercritical carbon dioxide heat radiator 52 from the second carbon dioxide inlet 521 via the second loop pipeline 54, in the supercritical carbon dioxide heat radiator 52, the high-temperature supercritical carbon dioxide transfers the heat to the hot primary air flowing through the supercritical carbon dioxide heat radiator 52, the hot primary air is heated for the second time, the temperature rises, the high-temperature supercritical carbon dioxide becomes low-temperature supercritical carbon dioxide, and the low-temperature supercritical carbon dioxide flows out from the second carbon dioxide outlet 522, returns to the supercritical carbon dioxide heat absorber 51 via the first loop pipe 53, and enters the next heat exchange cycle. Through the circulation, the temperature of the hot primary air is improved.

In some embodiments, when it is desired to increase the temperature of the hot primary air, makeup regulator valve 93 is opened to replenish supercritical carbon dioxide into supercritical carbon dioxide cyclical heat exchange loop 5 and/or to increase the rotational speed of circulation pump 55 to further increase the temperature of the hot primary air. The flow velocity of the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop 5 can be increased by increasing the rotation speed of the circulation pump 55, so that the heat exchange amount of the supercritical carbon dioxide and the hot primary air can be increased. Supplementing supercritical carbon dioxide into the supercritical carbon dioxide circulation heat exchange loop 5 can increase the pressure in the supercritical carbon dioxide circulation heat exchange loop 5, and further can increase the heat exchange amount of supercritical carbon dioxide and hot primary air, thereby increasing the temperature increase amount of the hot primary air.

When the temperature of the hot primary air needs to be reduced, the air exhaust valve 95 is opened so as to exhaust the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop 5 and/or the rotating speed of the circulating pump 55 is reduced. Reducing the rotation speed of the circulation pump 55 can reduce the flow rate of the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop 5, thereby reducing the heat exchange amount of the supercritical carbon dioxide and the hot primary air. The supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop 5 is discharged, so that the pressure in the supercritical carbon dioxide circulation heat exchange loop 5 can be reduced, the heat exchange amount of the supercritical carbon dioxide and the hot primary air can be further reduced, and the temperature increase amount of the hot primary air is reduced.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (12)

1. A boiler system, characterized in that the boiler system comprises:

the boiler comprises a boiler body, a heat exchanger and a heat exchanger, wherein the boiler body is provided with a pulverized coal inlet, a hot secondary air inlet and a flue gas outlet;

the air preheater is provided with a primary air inlet, a secondary air inlet, a first hot primary air outlet, a hot secondary air outlet and a flue gas inlet, and the hot secondary air outlet is communicated with the hot secondary air inlet;

the coal pulverizing device is provided with a coal powder outlet, a cold primary air inlet and a first hot primary air inlet, and the coal powder outlet is communicated with the coal powder inlet;

the flue is connected with the flue gas outlet, and a flue gas outlet of the flue is communicated with the flue gas inlet; and

the supercritical carbon dioxide heat circulating loop comprises a supercritical carbon dioxide heat absorber, a supercritical carbon dioxide heat radiator, a first loop pipeline, a second loop pipeline and a circulating pump, and the supercritical carbon dioxide heat absorber is arranged in the flue;

the supercritical carbon dioxide heat absorber has a first carbon dioxide inlet and a first carbon dioxide outlet, the supercritical carbon dioxide heat radiator is provided with a second carbon dioxide inlet, a second carbon dioxide outlet, a second hot primary air inlet and a second hot primary air outlet, a first end of the first loop pipe is connected with the first carbon dioxide inlet, a second end of the first loop pipe is connected with the second carbon dioxide outlet, the first end of the second loop pipeline is connected with the second carbon dioxide inlet, the second end of the second loop pipeline is connected with the first carbon dioxide outlet, the second primary hot air inlet is communicated with the first primary hot air outlet, the second primary hot air outlet is communicated with the first primary hot air inlet, the circulation pump is provided on one of the first loop pipe and the second loop pipe.

2. The boiler system according to claim 1,

the flue is including turning to room and back cigarette well, boiler system further includes low temperature over heater and economizer, the low temperature over heater with the economizer is established in the back cigarette well, the supercritical carbon dioxide heat absorber is established turn to in the room just the supercritical carbon dioxide heat absorber is located the low temperature over heater with the top of economizer.

3. The boiler system according to claim 2, wherein each of the supercritical carbon dioxide heat absorber, the low temperature superheater and the economizer is a light pipe arranged in-line, and a lateral pitch of each of the supercritical carbon dioxide heat absorber, the low temperature superheater and the economizer is equal to each other.

4. The boiler system of claim 1, wherein the supercritical carbon dioxide heat spreaders are finned tubes arranged in a staggered arrangement.

5. The boiler system of claim 1, wherein the supercritical carbon dioxide cycle heat exchange loop further comprises a bypass air duct and a bypass valve, the bypass air duct being connected in parallel with the supercritical carbon dioxide heat emitter, the bypass valve being provided on the bypass air duct.

6. The boiler system of claim 1, further comprising a pressure regulating device, the pressure regulating device comprising:

a high pressure carbon dioxide storage device having a carbon dioxide outlet;

a carbon dioxide delivery pipe, a first end of the carbon dioxide delivery pipe being connected to the carbon dioxide outlet, a second end of the carbon dioxide delivery pipe being connected to one of the first loop pipe and the second loop pipe;

the supply adjusting valve is arranged on the carbon dioxide conveying pipe; and

a pressure gauge disposed on one of the first loop conduit and the second loop conduit.

7. The boiler system according to claim 6, wherein the pressure regulating device further comprises:

an air exhaust pipe, a first end of which is connected with one of the first loop pipeline and the second loop pipeline; and

and the air exhaust valve is arranged on the air exhaust pipe.

8. The boiler system according to claim 7, wherein the second ends of the air exhaust pipes are open to the outside air.

9. The boiler system according to claim 7, wherein the second ends of the pair of air exhaust pipes are connected to the flue.

10. The boiler system of claim 1, wherein the supercritical carbon dioxide cycle heat exchange loop comprises a flow meter disposed on one of the first loop conduit and the second loop conduit.

11. A control method of a boiler system, characterized in that the boiler system is a boiler system according to claims 1-10, the control method comprising the steps of:

enabling the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop to flow into the supercritical carbon dioxide heat absorber, wherein the supercritical carbon dioxide absorbs the heat of the high-temperature flue gas in the flue in the supercritical carbon dioxide heat absorber so as to obtain high-temperature supercritical carbon dioxide;

the high-temperature supercritical carbon dioxide flows into the supercritical carbon dioxide heat releaser, and in the supercritical carbon dioxide heat releaser, the high-temperature supercritical carbon dioxide transfers heat to the hot primary air flowing through the supercritical carbon dioxide heat releaser so as to raise the temperature of the hot primary air, and the high-temperature supercritical carbon dioxide is changed into low-temperature supercritical carbon dioxide; and

and the low-temperature supercritical carbon dioxide flows into the supercritical carbon dioxide heat absorber and enters the next heat exchange cycle.

12. The control method of a boiler system according to claim 11,

when the temperature of the hot primary air needs to be increased, opening the supply adjusting valve so as to supplement supercritical carbon dioxide to the supercritical carbon dioxide circulating heat exchange loop and/or increase the rotating speed of the circulating pump, so as to further increase the temperature of the hot primary air;

when the temperature of the hot primary air needs to be reduced, the opposite air exhaust valve is opened so that the supercritical carbon dioxide in the supercritical carbon dioxide circulation heat exchange loop can be discharged and/or the rotating speed of the circulating pump is reduced.

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