JP7817012B2 - Boiler system and heating method - Google Patents

Description

This disclosure relates to a boiler system and a heating method.

Patent Document 1 discloses a waste heat recovery power generation plant for sintering equipment. Patent Document 2 discloses a waste heat power generation system for a cement calcination plant. Patent Document 3 discloses a clinker cooler for a cement manufacturing device.

Patent No. 6076977 Patent No. 4478674 JP 2010-195663 A

The present disclosure provides a boiler system and heating method that are useful for suppressing a decrease in heat exchange efficiency and tube deterioration.

A boiler system according to one aspect of the present disclosure includes a boiler body that allows exhaust gas from a clinker cooler that cools cement clinker to flow in a predetermined direction; an economizer having tubes arranged within the boiler body that heats water flowing within the tubes by heat exchange with the exhaust gas; a first water supply pipe that introduces water to the economizer; and a circulation unit that introduces a portion of the heated water obtained by heating in the boiler body into the first water supply pipe.

The boiler system may further include a heating unit disposed within the boiler body for further heating the water after it has been heated by the economizer. The circulation unit may introduce a portion of the heated water from a second water supply pipe that conducts water from the economizer to the heating unit to the first water supply pipe.

The circulation unit may include a connecting pipe that connects the first water supply pipe and the second water supply pipe, a pump that is disposed in the connecting pipe and sends heated water to the first water supply pipe, and a check valve that is disposed in the connecting pipe and prevents water from flowing back from the first water supply pipe to the second water supply pipe.

The boiler system may further include a thermometer that measures the temperature of the water introduced into the economizer, and a control unit that adjusts the flow rate of heated water introduced from the circulation unit into the first water supply pipe so that the value measured by the thermometer approaches a target value.

The tubes may be arranged so that the portion located upstream in the water flow in the economizer is located downstream in the exhaust gas flow within the boiler body compared to the portion located downstream.

A heating method according to one aspect of the present disclosure includes the steps of circulating exhaust gas from a clinker cooler that cools cement clinker in a predetermined direction within a boiler body, heating water through heat exchange with the exhaust gas by flowing water through tubes of an economizer disposed within the boiler body, and circulating a portion of the heated water obtained by heating in the boiler body into the water introduced into the economizer.

This disclosure provides a boiler system and heating method that are useful for suppressing a decrease in heat exchange efficiency and tube deterioration.

FIG. 1 is a schematic diagram showing an example of a cement production facility equipped with a boiler system. FIG. 2 is a schematic diagram showing an example of a boiler system. FIG. 3 is a schematic diagram showing an economizer and its surrounding equipment.

One embodiment will be described below with reference to the drawings. In the description, identical elements or elements with identical functions will be assigned the same reference numerals, and duplicate explanations will be omitted.

Figure 1 shows a schematic diagram of a cement production facility equipped with a boiler system according to one embodiment. The cement production facility 1 shown in Figure 1 is a facility for producing cement. The production facility 1 produces cement and generates electricity (waste heat power generation) by utilizing waste heat generated in the cement production process. The production facility 1 includes a clinker production device 10, a boiler system 20, and a power generation system 90. In addition to the production equipment and systems shown in Figure 1, the production facility 1 may also include equipment for performing raw material processes (e.g., a raw material grinder, etc.) and equipment for performing finishing processes (e.g., a cement grinder).

The clinker production apparatus 10 is a device that produces cement clinker (hereinafter simply referred to as "clinker"), an intermediate cement product, by burning cement raw materials. The clinker production apparatus 10 includes a preheater 12, a rotary kiln 14, and a clinker cooler 16.

The preheater 12 preheats the cement raw materials (clinker raw materials) supplied from the equipment performing the raw material process. The preheater 12 is, for example, a new suspension preheater (NSP) having multiple cyclones constituting a multi-stage cyclone system and a calciner. The preheater 12 may have four or five cyclones. Exhaust gas from the rotary kiln 14 is introduced into the preheater 12. The preheater 12 brings the high-temperature exhaust gas into contact with the cement raw materials and separates them in the cyclones. The exhaust gas after being used for heat exchange is discharged from the top cyclone of the preheater 12, and the temperature of this exhaust gas is approximately 400°C. The manufacturing facility 1 may have a boiler system separate from the boiler system 20 to effectively utilize the heat of the exhaust gas from the multi-stage cyclones.

The rotary kiln 14 burns the cement raw materials that have been preheated in the preheater 12. The rotary kiln 14 is a rotary kiln that is configured to rotate around an axis along its longitudinal direction. The rotary kiln 14 has, for example, a drum body and a burner that introduces combustion gas into the drum body. Clinker is produced by burning the cement raw materials in the rotary kiln 14, and the rotary kiln 14 supplies the produced clinker to the clinker cooler 16.

The clinker cooler 16 cools the high-temperature clinker produced in the rotary kiln 14. The clinker cooler 16 cools the clinker using cooling air (gas). The clinker cooler 16 is also called an air quenching cooler. The clinker cooler 16 is configured to transport the clinker using a grate while blowing high-pressure air into the bottom of the grate (see, for example, Patent Document 3, above).

The clinker is cooled (quenched) by heat exchange between the high-pressure air and the clinker. The air, heated to a high temperature by the heat exchange, is returned to the rotary kiln 14 as secondary air, and excess exhaust gas (high-temperature air not returned to the rotary kiln 14) is discharged to the outside via a dust collector. Because a large amount of this excess exhaust gas (exhaust gas) is generated in the clinker cooler 16, the manufacturing facility 1 effectively utilizes the thermal energy of this exhaust gas for power generation. The clinker cooler 16 sends at least a portion of the exhaust gas generated after cooling the clinker to the boiler system 20. The temperature of the exhaust gas sent from the clinker cooler 16 to the boiler system 20 may be 300°C to 420°C, 320°C to 400°C, or 340°C to 380°C.

The boiler system 20 generates steam by heating water using exhaust gas introduced from the clinker cooler 16. The water heated by the boiler system 20 is condensate introduced from the power generation system 90. The boiler system 20 generates steam from the condensate through heat exchange with the exhaust gas introduced from the clinker cooler 16, and discharges the exhaust gas after heat exchange to the outside. The exhaust gas from the boiler system 20 passes through a dust collector (e.g., an electrostatic precipitator) and is released into the atmosphere. The temperature of the exhaust gas discharged from the boiler system 20 after heat exchange may be approximately 80°C to 100°C. The boiler system 20 sends the generated steam to the power generation system 90. Details of the boiler system 20 will be described later.

The power generation system 90 generates electricity using steam delivered from the boiler system 20. In addition to the steam from the boiler system 20, the power generation system 90 may also generate electricity using steam generated in another boiler system by heat exchange with exhaust gas from a multi-stage cyclone. The power generation system 90 includes, for example, a turbine 92, a generator 94, and a condenser 96.

The turbine 92 is a steam turbine that is rotated by steam. The generator 94 converts the kinetic energy generated by the rotation of the rotating shaft of the turbine 92 into electricity. The condenser 96 condenses the steam that has completed its work in the turbine 92 back into water. The condensate generated from the steam in the condenser 96 is pressurized, for example, by a condensate pump and a feedwater pump, and sent to the boiler system 20. The power generation system 90 may send the generated condensate to the boiler system 20 without heating it. The temperature of the water (condensate) sent from the power generation system 90 to the boiler system 20 may be 20°C to 50°C, 25°C to 45°C, or 30°C to 40°C.

Figure 2 shows a schematic diagram of an example boiler system. As shown in Figure 2, the boiler system 20 includes a pre-duster 22, a boiler main body 24, an economizer 40, an evaporator 50, a steam drum 60, and a superheater 70. The pre-duster 22 is configured to remove dust contained in the flue gas sent from the clinker cooler 16 to the boiler system 20. The flue gas sent from the clinker cooler 16 contains clinker dust as dust. The flue gas is introduced into the boiler main body 24 after dust collection in the pre-duster 22.

The boiler body 24 allows the exhaust gas from the clinker cooler 16 to flow (circulate) in a predetermined direction. The boiler body 24 forms an area (flow passage) through which the exhaust gas flows, and houses the economizer 40, evaporator 50, and superheater 70 within. In FIG. 2, the exhaust gas flowing within the boiler body 24 is indicated by "Ge," and the direction in which the exhaust gas Ge flows is indicated by "D1." The exhaust gas Ge flows from upstream to downstream along direction D1 (predetermined direction). Based on the flow of the exhaust gas Ge, the superheater 70, evaporator 50, and economizer 40 are arranged in this order from upstream to downstream along direction D1. The boiler body 24, economizer 40, evaporator 50, and superheater 70 constitute a boiler apparatus (boiler).

The boiler system 20 may include a vertical boiler device. In this case, direction D1 is the up-down direction, and the superheater 70, evaporator 50, and economizer 40 are arranged in this order from top to bottom. Water introduced into the boiler system 20 (hereinafter referred to as "water W") passes through the economizer 40, evaporator 50, and superheater 70 in this order, and is heated in each device by heat exchange with exhaust gas Ge. Note that the water W has already become steam when it is introduced into the superheater 70.

The boiler system 20 includes a water supply pipe 32 (first water supply pipe). The water supply pipe 32 is a pipe connecting the economizer 40 and the power generation system 90 (condenser 96). The water supply pipe 32 introduces water W delivered from the power generation system 90 into the economizer 40. Exhaust gas Ge, which has been used for heat exchange in the evaporator 50, is introduced into the economizer 40. The economizer 40 heats the water W through heat exchange with the exhaust gas Ge. The temperature of the water W heated by the economizer 40 may be 180°C to 220°C, 185°C to 215°C, or 190°C to 210°C. Hereinafter, the water W heated by the economizer 40 will be referred to as "heated water Wh." The economizer 40 is also referred to as a coal economizer.

The boiler system 20 has a water supply pipe 34 (second water supply pipe). The water supply pipe 34 is a pipe connecting the economizer 40 and the evaporator 50 (heating section). The water supply pipe 34 introduces heated water Wh produced in the economizer 40 into the evaporator 50. The exhaust gas Ge, which has been used for heat exchange in the superheater 70, is introduced into the evaporator 50. The evaporator 50 further heats the water (heated water Wh) heated in the economizer 40 through heat exchange between the exhaust gas Ge and the heated water Wh. The temperature of the water W further heated by the evaporator 50 may be 270°C to 330°C, 280°C to 320°C, or 290°C to 310°C. The water heated by the evaporator 50 is also referred to as heated water Wh. The water supply pipe 34 may conduct the heated water Wh, which has been heated in the economizer 40, from the economizer 40 to the evaporator 50 via the steam drum 60.

The boiler system 20 includes a water supply pipe 36a, a steam pipe 36b, and a steam pipe 38. The water supply pipe 36a connects the evaporator 50 and the steam drum 60. The water supply pipe 36a introduces heated water Wh produced in the evaporator 50 into the steam drum 60. The heated water Wh introduced into the steam drum 60 is separated into water and steam (saturated steam). The steam pipe 36b connects the steam drum 60 and the superheater 70. The steam pipe 36b introduces the saturated steam after separation in the steam drum 60 into the superheater 70.

The superheater 70 receives exhaust gas Ge after dust collection in the pre-duster 22. The superheater 70 superheats saturated steam through heat exchange between the exhaust gas Ge and the saturated steam introduced from the steam drum 60. The temperature of the steam (superheated steam) after being superheated by the superheater 70 may be 350°C to 450°C, 360°C to 440°C, or 370°C to 430°C. The steam pipe 38 is a pipe connecting the superheater 70 to the turbine 92 of the power generation system 90. The steam pipe 38 introduces the superheated steam generated in the superheater 70 into the turbine 92.

Next, details of the economizer 40 will be described with reference to Figure 3. The temperature of the exhaust gas Ge introduced into the economizer 40 may be 220°C to 280°C, 230°C to 270°C, or 240°C to 260°C. The temperature of the exhaust gas Ge discharged after heat exchange in the economizer 40 may be 80°C to 120°C, 85°C to 115°C, or 90°C to 110°C. In Figure 3, one direction perpendicular to direction D1 is indicated by "D2," and a direction perpendicular to both direction D1 and direction D2 is indicated by "D3." When a vertical boiler is configured in the boiler system 20, directions D2 and D3 are horizontal.

The economizer 40 has multiple tubes 41, a header 46, and a header 48. The multiple tubes 41 are arranged inside the boiler body 24, and each tube 41 forms a flow path for water W introduced into the economizer 40. The economizer 40 heats the water W flowing through the tubes 41 by heat exchange with the exhaust gas Ge. In Figure 3, one tube 41 is shown, and the other tubes 41 are not shown. The multiple tubes 41 are arranged so as to be aligned in a direction (e.g., direction D3) that intersects with the direction D1 in which the exhaust gas Ge flows. The multiple tubes 41 are arranged in direction D3 to such an extent that the exhaust gas Ge flows between adjacent tubes 41.

The multiple tubes 41 may include a first group of tubes aligned along direction D3 at a first position in direction D1, and a second group of tubes aligned along direction D3 at a second position in direction D1. If the distance between the central axes of adjacent tubes 41 in direction D3 is defined as one pitch, the first group of tubes and the second group of tubes may be offset by half a pitch in direction D3. The distance between the central axes of adjacent tubes 41 in each of the first and second groups of tubes may be approximately 80 mm to 100 mm. The economizer 40 may have, for example, approximately 40 to 100 tubes 41. The multiple tubes 41 are configured similarly to one another.

The header 46 constitutes the inlet for water W in the economizer 40 and is connected to the downstream end of the water supply pipe 32. The upstream ends of each of the multiple tubes 41 are connected to the header 46, and water W introduced from the water supply pipe 32 into the header 46 is introduced into each of the multiple tubes 41. The header 48 constitutes the outlet for water W in the economizer 40 and is connected to the upstream end of the water supply pipe 34. The downstream ends of each of the multiple tubes 41 are connected to the header 48, and water W is introduced from the multiple tubes 41 into the header 48. The water W is then introduced from the header 48 into the water supply pipe 34 as heated water Wh (water W after heating).

The tube 41 has multiple intersections 42 and multiple connection portions 44. The multiple intersections 42 are arranged side by side along direction D1. The positions of the multiple intersections 42 in directions D2 and D3 may be approximately the same. Each of the multiple intersections 42 extends so as to intersect with direction D1 (e.g., along direction D2). Adjacent intersections 42 in direction D1 are arranged with a gap between them. The flow directions of water W are opposite between adjacent intersections 42. The multiple intersections 42 may be arranged at equal intervals in direction D1 (e.g., vertically). The tube 41 may include approximately 8 to 14 intersections 42.

Each of the multiple connection portions 44 connects one end of each of the adjacent intersection portions 42. Here, when the flow of water W is used as the reference, the upstream end of the intersection portion 42 is referred to as "end 42a," and the downstream end of the intersection portion 42 is referred to as "end 42b." When the flow of water W is used as the reference, the connection portion 44 connects the downstream end 42b of the intersection portion 42 located upstream with the upstream end 42a of the intersection portion 42 located downstream. The multiple connection portions 44 are arranged alternately at both ends of the intersection portion 42 in direction D2 so that the tube 41 forms a single flow path between the header 46 and the header 48.

When the flow of water W is used as a reference, the most upstream of the multiple intersections 42 is referred to as "intersection 42A," and the most downstream intersection 42 is referred to as "intersection 42B." In this case, when the flow of exhaust gas Ge in the boiler body 24 is used as a reference, intersection 42A may be located downstream of intersection 42B. As described above, the tubes 41 may be arranged so that the portion located upstream in the water flow in the economizer 40 is located downstream in the flow of exhaust gas Ge within the boiler body 24 compared to the portion located downstream. In other words, the economizer 40 may be a so-called counterflow type. In the economizer 40, the temperature of the water W in the intersection 42 increases from intersection 42A toward intersection 42B due to heat exchange with the exhaust gas Ge.

The boiler system 20 includes a circulation unit 80 and a control unit 28. The circulation unit 80 introduces a portion of the heated water Wh obtained by heating in the boiler body 24 into the water supply pipe 32 (circulates it through the water supply pipe 32). The circulation unit 80, for example, introduces a portion of the heated water Wh flowing through the water supply pipe 34 into the water supply pipe 32. In this case, the circulation unit 80 circulates water W that has been heated in the economizer 40 but not in other heating units from the water supply pipe 34 to the water supply pipe 32. The circulation unit 80 includes, for example, a connecting pipe 81, a pump 82, a check valve 84, an adjustment valve 86, and a thermometer 88.

The connecting pipe 81 is a pipe that connects the water supply pipe 32 and the water supply pipe 34. The pump 82 is disposed on the connecting pipe 81 and delivers heated water Wh to the water supply pipe 32. Due to pressure loss in the economizer 40, the pressure at the connection point between the upstream end of the connecting pipe 81 and the water supply pipe 34 is lower than the pressure at the connection point between the downstream end of the connecting pipe 81 and the water supply pipe 32. Therefore, the circulation unit 80 circulates a portion of the heated water Wh by using the pump 82 to suck in a portion of the heated water Wh from the water supply pipe 34 and deliver it to the water supply pipe 32.

The check valve 84 is disposed in the connecting pipe 81 and prevents water from flowing back from the water supply pipe 32 to the water supply pipe 34. The adjustment valve 86 is disposed in the connecting pipe 81 and is capable of adjusting the flow rate (flow rate per unit time) of water flowing through the connecting pipe 81. The adjustment valve 86 operates based on an operation signal from the control unit 28 and is configured, for example, so that its opening degree can be adjusted. In this case, the flow rate introduced from the circulation unit 80 (water supply pipe 34) to the water supply pipe 32 changes depending on the opening degree of the adjustment valve 86.

The thermometer 88 measures the temperature of the water introduced into the economizer 40 (e.g., header 46). The thermometer 88 measures the temperature of the water resulting from the merging of condensate supplied from the power generation system 90 and water circulated by the circulation unit 80, for example. The thermometer 88 may be configured to measure the temperature of the water W flowing in the section of the water supply pipe 32 between the header 46 and the connection point between the water supply pipe 32 and the downstream end of the connecting pipe 81. The thermometer 88 outputs information indicating the measured temperature to the control unit 28. The connecting pipe 81 may be provided with an on-off valve that opens and closes the flow path within the connecting pipe 81.

The control unit 28 adjusts the flow rate of water introduced from the circulation unit 80 into the water supply pipe 32 so that the value measured by the thermometer 88 approaches the target value (target temperature). For example, based on the deviation between the value measured by the thermometer 88 and the target value, the control unit 28 adjusts the opening of the adjustment valve 86 so that the deviation is reduced. The target value is determined in advance by an operator, for example, and may be set to 50°C to 90°C, 55°C to 85°C, or 60°C to 80°C.

The control unit 28 is a computer device. The control unit 28 includes, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an input/output interface. The control unit 28 may be a part of the function of a computer device that controls the boiler system 20.

The above-described manufacturing equipment 1 can perform a cement manufacturing process for manufacturing cement, a heating process for generating steam from water, and a power generation process for generating electricity using the steam. The cement manufacturing process includes a raw material process, a calcination process, and a finishing process. In the calcination process, clinker is produced using a clinker manufacturing apparatus 10. The calcination process includes a preheating process for preheating the cement raw materials in a preheater 12, a production process for producing clinker by calcining the cement raw materials in a rotary kiln 14, and a cooling process for cooling the clinker. In the cooling process, the clinker is cooled by air in a clinker cooler 16, and at least a portion of the air used for cooling is sent to the boiler system 20 as exhaust gas.

The heating process (heating method) includes a circulation process, a first heating process, a second heating process, a superheating process, and a circulation process. In the circulation process, exhaust gas Ge from the clinker cooler 16 is circulated within the boiler body 24 along direction D1. In the first heating process, water W is heated through heat exchange with the exhaust gas Ge by flowing it through the tubes 41 of the economizer 40 located within the boiler body 24. In the second heating process, heated water Wh produced in the first heating process is further heated by an evaporator 50 located within the boiler body 24.

In the superheating process, saturated steam obtained from the heated water Wh produced in the second heating process is superheated by the superheater 70. In the superheating process, the superheated steam obtained by superheating the saturated steam is sent to the power generation system 90. In the circulation process, a portion of the heated water Wh obtained by heating in the boiler body 24 is circulated (merged) with the water introduced into the economizer 40. In the circulation process, for example, a portion of the heated water Wh heated in the first heating process but before being heated in the second heating process is returned to the piping upstream of the economizer 40. In the circulation process, the amount (flow rate) of circulated heated water Wh is adjusted using PID control or the like so that the temperature of the water introduced into the economizer 40 approaches the target value.

In the power generation process, the superheated steam obtained in the superheating process is used to rotate a steam turbine, causing the generator 94 to generate electricity. In the power generation process, the steam that has completed its work in the steam turbine is converted back into water by the condenser 96, and the condensate (water W) is then pressure-fed to the boiler system 20 by a pump or the like.

The boiler system 20 described above is one example and can be modified as appropriate. Unlike the example shown in FIG. 3, the intersection 42A of the economizer 40 (the intersection 42 located most upstream in terms of the water flow) may be located more upstream than the intersection 42B (the intersection 42 located most downstream in terms of the water flow) when the flow of the exhaust gas Ge is used as the reference. Multiple intersections 42 may be arranged side by side along a direction that intersects (e.g., perpendicular to) direction D1, instead of along direction D1.

The circulation unit 80 may introduce a portion of the heated water Wh that has been heated in the economizer 40 and another heating unit into the water supply pipe 32. In one example, the circulation unit 80 may introduce a portion of the heated water Wh into the water supply pipe 32 from the water supply pipe 36a through which the heated water Wh flows after being further heated in the evaporator 50. The circulation unit 80 may also introduce a portion of the heated water Wh that remains after being separated from the saturated steam in the steam drum 60 into the water supply pipe 32.

Instead of automatic control by the control unit 28, the circulation unit 80 may have an operator, such as a worker, check the measurement value from the thermometer 88 and adjust the opening of the control valve 86 to adjust the amount of heated water Wh introduced from the circulation unit 80 to the water supply pipe 32. Alternatively, the circulation unit 80 may continue to introduce heated water Wh into the water supply pipe 32 at a predetermined set flow rate without controlling the temperature of the water introduced into the economizer 40.

[Effects of the embodiment]
It has been discovered that when low-temperature (e.g., about 35°C) condensate is introduced into the economizer in a conventional boiler system, condensation occurs on the outer surface of the tubes in the upstream portion of the water flow (hereinafter referred to as the "upstream portion"). Although some dust is captured in the pre-duster, the flue gas from the clinker cooler 16 still contains fine clinker powder as dust before being introduced into the boiler body. Therefore, when condensation occurs on the outer surface of the economizer tubes, the clinker (fine clinker powder) reacts with the condensed water on the outer surface of the tubes, causing the clinker to adhere and accumulate on the outer surface of the tubes.

When clinker adheres and accumulates on the outer surface of the tubes, the following two problems occur. One is that the accumulation of clinker on the outer surface of the tubes inhibits heat exchange, reducing its efficiency. For example, when the impact of condensation was investigated, it was found that power generation before accumulation was approximately 11,000 to 12,000 kW/h, whereas after accumulation, power generation dropped to approximately 7,000 to 9,000 kW/h. Another problem is that the narrowing of the exhaust gas passage increases the flow rate of the exhaust gas, resulting in ash cut. Ash cut occurs when the clinker contained in the exhaust gas collides with the tubes along with the exhaust gas, causing wear and deterioration of the tubes. Ash cut causes holes to form in the tubes, significantly shortening the lifespan of the economizer, which normally has a service life of several decades, to just a few years.

In contrast, the boiler system 20 described above comprises a boiler body 24 through which exhaust gas Ge from the clinker cooler 16 that cools the clinker flows in direction D1, an economizer 40 having tubes 41 arranged within the boiler body 24 and heating the water flowing within the tubes 41 through heat exchange with the exhaust gas Ge, a water supply pipe 32 that introduces water to the economizer 40, and a circulation section 80 that introduces a portion of the heated water Wh obtained by heating in the boiler body 24 into the water supply pipe 32.

In the boiler system 20, a portion of the heated water Wh is returned to the water in the water supply pipe 32, thereby increasing the temperature of the water introduced into the economizer 40 compared to when a portion of the heated water Wh is not returned to the water introduced into the economizer 40. When the temperature of the water introduced into the economizer 40 is high, the temperature difference between the water flowing in the flow path in the upstream portion of the tubes 41 and the exhaust gas Ge flowing outside that upstream portion is reduced. This reduces the likelihood of condensation forming on the outer surface of the upstream portion of the tubes 41. As a result, the likelihood of clinker adhering or accumulating on the outer surface of the tubes 41 is reduced. Therefore, the boiler system 20 is useful for preventing a decrease in heat exchange efficiency and preventing deterioration of the tubes 41.

The boiler system 20 described above may further include a heating unit (evaporator 50) disposed within the boiler body 24 that further heats the water after it has been heated by the economizer 40. The circulation unit 80 may introduce a portion of the heated water Wh into the water supply pipe 32 from the water supply pipe 34, which conducts water from the economizer 40 to the heating unit. In this case, the temperature difference between the returned heated water Wh and the water in the water supply pipe 32 is smaller than when a portion of the heated water Wh obtained by heating in both the economizer 40 and the heating unit is returned to the water supply pipe 32. This reduces the impact of returning the heated water Wh at the junction of the water supply pipe 32 and the flow path of the circulation unit 80. As a result, the water supply pipe 32 can be simplified, which is useful for simplifying the boiler system 20.

The circulation unit 80 may include a connecting pipe 81 connecting the water supply pipe 32 and the water supply pipe 34, a pump 82 disposed on the connecting pipe 81 and sending heated water Wh to the water supply pipe 32, and a check valve 84 disposed on the connecting pipe 81 to prevent backflow of water from the water supply pipe 32 to the water supply pipe 34. Due to pressure loss occurring in the tube 41 of the economizer 40, the pressure in the downstream water supply pipe 34 is lower than the pressure in the upstream water supply pipe 32. In this case, even if the water supply pipe 32 and the water supply pipe 34 are connected by a pipe, water can flow from the water supply pipe 32 to the water supply pipe 34. In the above configuration, the provision of the pump 82 and the check valve 84 prevents backflow from the water supply pipe 32 to the water supply pipe 34, allowing a portion of the heated water Wh to circulate more reliably.

The boiler system 20 described above may further include a thermometer 88 that measures the temperature of the water introduced into the economizer 40, and a control unit 28 that adjusts the flow rate of heated water Wh introduced from the circulation unit 80 into the water supply pipe 32 so that the value measured by the thermometer 88 approaches a target value. In this case, the temperature of the water introduced into the economizer 40 after merging with the heated water Wh is stabilized. This makes it possible to stably suppress the occurrence of condensation on the outer surfaces of the upstream portions of the tubes 41. This is therefore even more useful for suppressing a decrease in heat exchange efficiency and suppressing deterioration of the tubes 41.

The tubes 41 may be arranged so that a portion located upstream in the water flow in the economizer 40 (e.g., intersection 42A) is located downstream in the flow of exhaust gas Ge within the boiler body 24 compared to a portion located downstream (e.g., intersection 42B). In this case, the temperature of the exhaust gas Ge flowing around the upstream portion of the tubes 41 is lower than when the upstream portion of the tubes 41 is located upstream in the flow of exhaust gas Ge. Therefore, in the upstream portion of the tubes 41, water droplets generated by the temperature difference between the water in the tubes 41 and the exhaust gas Ge are less likely to evaporate, making condensation more likely to occur. However, circulating a portion of the heated water Wh suppresses the occurrence of condensation. Therefore, in the above configuration, circulating a portion of the heated water Wh to raise the temperature of the water introduced into the economizer 40 is even more useful.

The heating method implemented in the boiler system 20 described above includes the steps of circulating exhaust gas Ge from the clinker cooler 16, which cools clinker, in the boiler body 24 along direction D1; heating water through heat exchange with the exhaust gas Ge by flowing water through the tubes 41 of the economizer 40 disposed within the boiler body 24; and circulating a portion of the heated water Wh obtained by heating in the boiler body 24 into the water introduced into the economizer 40. In this heating method, circulating a portion of the heated water Wh increases the temperature of the water introduced into the economizer 40, thereby reducing the temperature difference between the water flowing in the flow path within the upstream portion of the tubes 41 and the exhaust gas Ge flowing outside that upstream portion. This reduces the likelihood of condensation forming on the outer surfaces of the upstream portion of the tubes 41. As a result, the likelihood of clinker adhering or accumulating on the outer surfaces of the tubes 41 is reduced. Therefore, the heating method described above is useful for preventing a decrease in heat exchange efficiency and preventing deterioration of the tubes 41.

1...Cement manufacturing equipment, 10...Clinker manufacturing device, 20...Boiler system, 24...Boiler body, Ge...Exhaust gas, 28...Control unit, 32, 34...Water supply pipe, W...Water, Wh...Heated water, 40...Economizer, 41...Tube, 50...Evaporator, 80...Circulation unit, 81...Connecting pipe, 82...Pump, 84...Check valve, 86...Control valve, 88...Thermometer, 90...Power generation system.

Claims (6)

a boiler body that allows exhaust gas from a clinker cooler that cools cement clinker to flow in a predetermined direction;
an economizer having tubes arranged in the boiler body and heating water flowing through the tubes by heat exchange with the exhaust gas;
a first water supply pipe for introducing water into the economizer;
a circulation section that introduces a portion of the heated water obtained by heating in the economizer into the first water supply pipe;
a heating section disposed in the boiler body and configured to further heat the water heated by the economizer;
a second water supply pipe that guides water from the economizer to the heating section ,
the heating unit is an evaporator adjacent to the economizer in the predetermined direction,
A boiler system in which the circulation section includes a connecting pipe connecting the first water supply pipe and the second water supply pipe, and introduces a portion of the heated water from the second water supply pipe to the first water supply pipe via the connecting pipe . The boiler system according to claim 1 , wherein condensate from a power generation system is sent to the first water supply pipe without being heated. The circulation section includes :
a pump disposed in the connecting pipe and configured to send the heated water to the first water supply pipe;
3. The boiler system according to claim 1, further comprising: a check valve disposed on the connecting pipe to prevent backflow of water from the first water supply pipe to the second water supply pipe. a thermometer for measuring the temperature of the water introduced into the economizer;
A boiler system as described in any one of claims 1 to 3, further comprising a control unit that adjusts the flow rate of the heated water introduced from the circulation unit to the first water supply pipe so that the measurement value by the thermometer approaches a target value. A boiler system as described in any one of claims 1 to 4, wherein the tubes are arranged so that the portion located upstream in the water flow in the economizer is located downstream in the exhaust gas flow within the boiler body compared to the portion located downstream. a step of circulating exhaust gas from a clinker cooler that cools cement clinker in a predetermined direction within the boiler body;
a step of heating the water by heat exchange with the exhaust gas by flowing the water through tubes of an economizer disposed in the boiler body;
introducing water to the economizer through a first water supply pipe;
a step of circulating a portion of the heated water obtained by heating in the economizer into the water introduced into the economizer;
Further heating the water heated by the economizer in a heating section disposed in the boiler body;
and directing water from the economizer to the heating section through a second water supply pipe ;
the heating unit is an evaporator adjacent to the economizer in the predetermined direction,
A heating method in which, in the process of circulating a portion of the heated water into the water introduced into the economizer, a portion of the heated water is introduced from the second water supply pipe to the first water supply pipe via a connecting pipe connecting the first water supply pipe and the second water supply pipe .