Multi-pipe once-through boiler and method for operating same

Abstract

Obtained is a multi-pipe once-through boiler with which it is possible to suppress ash residue from adhering within a combustion chamber when reclaimed oil (waste oil) is used as a combustion gas for generating consumption steam.　A multi-pipe once-through boiler configured to retrieve consumption steam, wherein the multi-pipe once-through boiler comprises a plurality of nozzles (50, 60, 70) that use reclaimed oil as fuel and that are installed in order to spray steam onto the surfaces of an inner-side water pipe row (3) and an outer-side water pipe row (4), and a spray control device (85) that controls the time for which steam is sprayed from the nozzles, whereby consumption steam is fed back and intermittently sprayed during operation of the multi-pipe once-through boiler (100), and ash residue is suppressed from adhering to the surfaces of the water pipe rows due to combustion of the reclaimed oil resulting from use of the reclaimed oil.

Description

Multi-tube once-through boiler and its operating method

[0001] The present invention relates to a multi-tubular once-through boiler that generates steam by heating a large number of water tubes, and in particular to a structure and operating method for reducing the amount of residual ash that adheres to the combustion chamber in a multi-tubular once-through boiler that can use recycled oil as fuel.

[0002] As shown in Figures 12 and 13 of Patent Document 1, for example, a multi-tube once-through boiler has a plurality of water tubes arranged vertically inside a cylindrical combustion tube with an upper and lower bottom, and two rows of water tubes, an inner water tube row 3 and an outer water tube row 4, connecting an annular upper header 1 and a lower header 2. The spaces between adjacent inner water tube rows 3 and adjacent outer water tube rows 4 are closed (closing fins 8), and some of the spaces between the water tubes in the inner water tube row 3 are opened (inner smoke vents 5), thereby forming combustion gas passages 7 between the inner water tube row 3 and the outer water tube row 4, and boiler water is supplied to each water tube from the lower header 2.

[0003] In the above structure, fuel is supplied to a burner 10 installed in the combustion tube and burned, generating combustion gas in the combustion chamber 9. The combustion gas is then supplied to the outside of the multiple water tubes through the combustion gas passage 7 to heat and evaporate the boiler water in the water tubes, and consumed steam is extracted from the upper header 1. The combustion exhaust gas passes through the combustion gas passage 7 and the outer smoke vent 6 and is discharged from the flue 12 as cooled combustion exhaust gas. The surrounding areas of the upper header 1 and lower header 2 are covered with refractory material 13, and the entire combustion tube is covered with heat insulating material 14.

[0004] However, with the above-mentioned multi-tube once-through boiler, the combustion chamber is sealed, making it difficult to clean the inside of the combustion tube, which limits the fuel for the combustion gas burned by the burner and means that recycled oil made from waste oil, which is prone to leaving ash, cannot be used.

[0005] Therefore, the inventors have proposed the multi-tube once-through boiler of Patent Document 2, which is equipped with a structure that enables recycled oil (waste oil) to be used as fuel for the combustion gas used to generate consumed steam.

[0006] According to this structure, the combustion chamber is cylindrical and extends horizontally, and a door (lid) is formed on one end facing the combustion chamber. This allows the interior to be seen by opening and closing the door (lid), making the combustion chamber easy to clean and enabling recycled oil (waste oil) to be used as fuel for combustion gas (see Patent Document 2).

[0007] Patent No. 2914647 Patent No. 7099864

[0008] However, in the proposed multi-tube once-through boiler, although the inside of the combustion chamber can be cleaned by opening and closing the door (lid), the amount of residual ash generated by using recycled oil (waste oil) was larger than expected, and the cleaning frequency increased accordingly, making the cleaning work complicated. In particular, cleaning by opening and closing the door (lid) was performed after the multi-tube once-through boiler was shut down, which created the problem that it took a long time to completely remove the residual ash that had stubbornly adhered to the inside of the combustion chamber and around the water tubes.

[0009] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a structure for a multi-tube once-through boiler that can suppress the adhesion of residual ash to the surface of water tubes in the combustion chamber when recycled oil (waste oil) is used as combustion gas to generate consumed steam.

[0010] In order to achieve the above object, the present invention is a multi-tubular once-through boiler (100) comprising a combustion chamber (9) to which combustion gas is supplied from a burner (10) installed at one end, a water tube row consisting of a plurality of water tubes installed in the combustion chamber (9), and boiler water supplied into the water tubes by the combustion gas is heated and evaporated to extract consumed steam, the multi-tubular once-through boiler (100) uses recycled oil as fuel, and is equipped with a plurality of nozzles arranged to inject steam onto the surface side of the water tube row, and an injection control device that controls the injection time of steam from the nozzles, thereby intermittently injecting steam during operation of the multi-tubular once-through boiler, thereby suppressing the adhesion of residual ash caused by combustion of the recycled oil to the surface side of the water tube row when the recycled oil is used.

[0011] The apparatus is characterized by including an injection control device (85) for controlling the injection time of steam injected from the nozzle, and by intermittently injecting steam while the multi-tube once-through boiler is in operation.

[0012] The steam injected from the nozzle is characterized by using the consumed steam obtained from the multi-tube once-through boiler (100) by feeding it back.

[0013] The steam is supplied by branching off the consumed steam extracted from a multi-tube once-through boiler.

[0014] The first nozzle row, which is composed of a plurality of nozzles (50), is characterized in that it is arranged at a position facing the water tube row from a partition wall (30) installed in the combustion chamber (9) so that the combustion gas from the burner (10) collides with and flows back.

[0015] The water tube array is composed of an inner water tube array (3) and an outer water tube array (4), and a second nozzle array composed of a plurality of nozzles (60) is disposed at a position facing the gap between the inner water tube array (3) and the outer water tube array (4) from the inner surface side of a closing plate (40a) installed in the combustion chamber (9) on the burner (10) side.

[0016] A third nozzle row consisting of a plurality of nozzles (70) is disposed at a position facing the gap between the inner water tube row (3) and the outer water tube row (4) from the inner surface side of a closing plate (40b) installed at the rear of the partition wall (30) on the opposite side from the burner (10).

[0017] The steam injection angle of each nozzle (50) of the first nozzle row is characterized by being 100 degrees to 115 degrees, and the steam injection angle of each nozzle (60, 70) of the second nozzle row and the third nozzle row is characterized by being 10 degrees to 20 degrees.

[0018] The system is characterized in that a flue (12) communicating with the combustion chamber (9) is arranged, and a cyclone device (90) is connected to the flue (12).

[0019] The flue (12) is characterized in that a bag filter (92) is connected to the outlet of the combustion gas in the cyclone device (90) via a cooling device (91).

[0020] The device is characterized in that one bag filter (92) is connected to the cyclone device (90) and the cooling device (91).

[0021] In addition, in a multi-tube once-through boiler in which both ends of each of a plurality of water tubes are connected to each other and boiler water is supplied to each water tube, while a combustion chamber is formed inside each water tube, and combustion gas from the combustion chamber is supplied to the surface side of the plurality of water tubes to heat and evaporate the boiler water in the water tubes and extract consumed steam, recycled oil is used as fuel, a door (lid body 22) is formed at one end facing the combustion chamber (9), and a burner (10) that supplies combustion gas to the combustion chamber (9) is installed on the outer surface of the door (lid body 22), the combustion chamber (9) is cylindrical and extends horizontally, the water tubes are arc-shaped and arranged on the left and right sides of the combustion chamber (9), and the water tube row arranged on the left side of the combustion chamber (9) is connected by a straight left upper header (1L) arranged at the upper end and a straight left lower header (2L) arranged at the lower end, The water tube rows arranged on the right side of the combustion chamber (9) are connected by a straight right upper header (1R) provided at the upper end and a straight right lower header (1R) provided at the lower end, the water tube rows are composed of an inner water tube row (3) and an outer water tube row (4), each water tube of the outer water tube row (4) is arranged between each water tube of the inner water tube row (3), the water tubes constituting the left and right inner water tube rows (3) are connected by closing fins (8), the water tubes constituting the left and right outer water tube rows (4) are connected by closing fins (8), a partition wall (30) is installed near the end of the inner water tube row (3) where the combustion gas is ejected to partition the combustion chamber (9), so that the supplied combustion gas collides with the partition wall (30) and then all flows back and returns to the door (lid body 22) side, An inner smoke vent (5) is formed between an end water tube of the inner water tube row (3) on the door (lid body 22) side of the combustion chamber (9) and the combustion chamber wall on the door (lid body 22) side, and notches (5A) are formed only in closing fins (8) that number 10 to 20% of the total number of water tubes from the door (lid body 22) side connecting the water tubes of the inner water tube row (3), while a plurality of nozzles (50) for injecting steam are arranged on the combustion chamber (9) side of the partition wall (30) so as to be positioned along and near the inner water tube row (3).

[0022] A flue (12) communicating with the combustion chamber (9) is arranged on the upper surface of the combustion chamber (9) opposite the door side, and upper notches (41) are formed in the plurality of closing fins (8) of the outer water tube row (4) at a position facing the opening of the flue (12).

[0023] A plurality of nozzles (60) for injecting steam into the gap between the inner water tube row (3) and the outer water tube row (4) are arranged on the door side of the combustion chamber (9).

[0024] A plurality of nozzles (70) for injecting steam into the gap between the inner water tube row (3) and the outer water tube row (4) are arranged on the inner surface of a closing plate (40b) installed on the opposite side of the door side of the combustion chamber (9).

[0025] A method for operating a multi-tubular once-through boiler includes connecting both ends of each of a plurality of water tubes and supplying boiler water to each water tube, while forming a combustion chamber inside each water tube, and supplying combustion gas from a burner installed on one end of the combustion chamber to the surface side of a water tube row consisting of a plurality of water tubes to heat and evaporate the boiler water in the water tubes and extract consumed steam.The method is characterized in that recycled oil is used as fuel, and steam is intermittently injected from a plurality of nozzles arranged on the surface side of the water tube row while the multi-tubular once-through boiler is in operation, thereby suppressing the adhesion of residual ash caused by combustion of the recycled oil to the surface side of the water tube row when recycled oil is used.

[0026] The method for operating a multi-tube once-through boiler is characterized in that the intermittent injection of steam is performed for 5 to 15 seconds every 1 to 2 hours.

[0027] According to the present invention, in a multi-tube once-through boiler that uses recycled oil as combustion fuel, steam is intermittently injected from a plurality of nozzles (50, 60, 70) while the multi-tube once-through boiler is in operation, thereby making it possible to suppress the adhesion of residual ash caused by the combustion of recycled oil to the surface side of the water tube rows (3, 4).

[0028] By intermittently injecting steam during operation of the multi-tubular once-through boiler, it is possible to suppress a decrease in the temperature of the water tube rows (3, 4).

[0029] By using the consumed steam obtained from the multi-tubular once-through boiler (100) as feedback, steam can be injected from the nozzles (50, 60, 70) without adding a steam generator.

[0030] By branching (84) the consumed steam obtained from the multi-tube once-through boiler (100), the consumed steam can be fed back and used.

[0031] By arranging the first nozzle row (nozzle 50) at a position facing the water tube row from the partition wall (30), it is possible to suppress the generation of residual ash that adheres to the water tube row (inner water tube row 3) when combustion gas from the burner (10) collides and flows back.

[0032] During operation of a multi-tube once-through boiler that uses recycled oil as combustion fuel, steam is sprayed from a plurality of nozzles (60) installed on the door side of the combustion chamber (9), which suppresses the generation of residual ash adhering to the gap between the inner water tube row (3) and the outer water tube row (4), and prevents combustion gas from accumulating on the door side, thereby making the flow smoother.

[0033] During operation of a multi-tube once-through boiler (100) that uses recycled oil as combustion fuel, steam is sprayed from a plurality of nozzles (70) installed on the door side and the opposite side of the combustion chamber (9), thereby suppressing the generation of residual ash adhering to the gap between the inner water tube row (3) and the outer water tube row (4).

[0034] By setting the steam injection angle of the nozzle (50) to a wide range of 100 to 115 degrees, the injected steam is more likely to hit the periphery of the water tube rows (3, 4), effectively suppressing the generation of residual ash adhering to this area.By setting the steam injection angle of the nozzle (60, 70) to a narrow range of 10 to 20 degrees, the injected steam is injected in a straight line, making it more likely to enter the gap between the inner water tube row (3) and the outer water tube row (4), effectively suppressing the generation of residual ash adhering to this area.

[0035] A cyclone device (90) can be connected to the flue (12) to remove solids (powder) from the combustion gas.

[0036] By connecting a bag filter (92) to the combustion gas outlet via a cooling device (91), the powder in the combustion gas can be reliably removed by the bag filter (92).

[0037] By connecting one bag filter (92) to a plurality of cyclone devices (90) and cooling devices (91), the use efficiency of the bag filter (92) can be improved and the configuration can be simplified.

[0038] During operation of a multi-tubular once-through boiler (100) that uses recycled oil as combustion fuel, steam is injected from a plurality of nozzles (50), thereby suppressing the generation of residual ash adhering to the inner water tube row (3).

[0039] By forming upper notches (41) in the plurality of closing fins (8) of the outer water tube row (4), the combustion gas in the combustion chamber (9) can flow out of the outer water tube row (4) from the upper notches (41) and be guided to the flue (12).

[0040] 12 is an explanatory side view of a multi-tubular once-through boiler according to one embodiment of the present invention. FIG. 13 is an explanatory front view of a multi-tubular once-through boiler according to one embodiment of the present invention. FIG. 14 is an explanatory front view of an inner water tube row and an outer water tube row. FIG. 15 is an explanatory partial cross-sectional view showing the connection structure between an upper header and inner and outer water tubes. FIG. 16 is an explanatory side view showing an inner water tube row and an outer water tube. FIG. 17 is a perspective explanatory plan view for explaining the structure inside the main body of a multi-tubular once-through boiler. FIG. 18 is a perspective explanatory side view for explaining the structure inside the main body of a multi-tubular once-through boiler. FIG. 19 is a cross-sectional explanatory view taken along VIII-VIII in FIG. 6 for explaining the location of a nozzle installation. FIG. 19 is a perspective explanatory view of the main body viewed from the lid side for explaining the location of a nozzle installation. FIG. 19 is a perspective explanatory view of the main body viewed from the combustion chamber side for explaining the location of a nozzle installation. FIG. 19 is a system configuration diagram for explaining the flow of combustion exhaust gas when multiple multi-tubular once-through boilers are used. FIG. 19 is a configuration explanatory view showing the schematic structure of a conventional multi-tubular once-through boiler. FIG. 19 is an explanatory cross-sectional view taken along A-A in FIG.

[0041] An embodiment of a multi-tubular once-through boiler of the present invention will be described with reference to the drawings.

[0042] 1 and 2 show the appearance of a multi-tube once-through boiler 100. A lid 22, which serves as a door for opening and closing the front side of the main body 20, is rotatably attached to a hinge portion 21 attached to a cylindrical main body 20 with a bottom and both ends closed by closure plates 40a and 40b, and is disposed horizontally. A burner 10 is installed on the outer surface of the lid 22, and fuel is supplied to the burner 10 and burned (at approximately 1500°C), generating combustion gases in a combustion chamber 9 sandwiched between the closure plates 40a and 40b on the lid 22 side inside the main body 20. The area surrounding the burner 10 on the combustion chamber 9 side is covered with a refractory material 13.

[0043] The combustion gas generated in the combustion chamber 9 of the main body 20 heats the surface of multiple water pipes installed inside the main body 20 and is discharged as combustion exhaust gas from the flue 12 installed above the main body 20. Water is supplied to the multiple water pipes, and the area around each water pipe is heated by the combustion gas generated in the combustion chamber 9, generating steam. The steam is discharged to the outside as consumed steam through a piping line 81 via a steam separator 80 that removes large water droplets from the steam. The steam separator 80 is equipped with a pressure gauge 82 for measuring the steam pressure and a safety valve 83 for releasing steam when the pressure rises.

[0044] The multi-tubular once-through boiler 100 of the present invention uses only recycled oil as fuel for the combustion gas used to generate consumed steam. As a result of extensive research, it was discovered that injecting steam into the combustion chamber during operation is effective in preventing the adhesion of residual ash inside the combustion chamber, and a structure for this purpose is proposed.

[0045] Recycled oils include various types of used mineral waste oils such as engine oil, waste cooking oils such as used tempura oil, waste animal and vegetable oils obtained mainly from animal fats and oils, and grease trap oil obtained by separating and storing oil from wastewater containing grease and fats discharged from kitchens of restaurants and other establishments using grease traps (oil interceptors).

[0046] The internal structure of the main body 20 of the multi-tubular once-through boiler 100 will be described below with reference to FIGS.

[0047] A cylindrical combustion chamber 9 with a bottom extending horizontally is formed in the center of the main body 20, and a plurality of arc-shaped water tubes are arranged to surround the periphery of the combustion chamber 9. Of the plurality of arc-shaped water tubes, the group of water tubes arranged on the left inside of the combustion chamber 9 is designated as the inner water tube row 3L, with their upper ends connected by a linear left upper header 1L and their lower ends connected by a linear left lower header 2L. Similarly, the group of water tubes arranged on the right inside of the combustion chamber 9 is designated as the inner water tube row 3R, with their upper ends connected by a linear right upper header 1R and their lower ends connected by a linear right lower header 2R. In addition, the water tubes constituting the left and right inner water tube rows 3L, 3R are connected by closing fins 8.

[0048] Outside the inner water tube rows 3, water tubes are arranged between the water tubes in the inner water tube rows 3, and these water tube groups constitute outer water tube rows 4. The outer water tube rows 4 are arranged outside the left and right inner water tube rows 3, and like the left and right inner water tube rows 3, the upper ends of the left water tube group are connected to the left upper header 1L and the lower ends are connected to the left lower header 2L, and the upper ends of the right water tube group are connected to the right upper header 1R and the lower ends are connected to the right lower header 2R. Also, like the inner water tube rows 3, the water tubes constituting the left and right outer water tube rows 4 are connected by closing fins 8.

[0049] Furthermore, a combustion chamber 9 is defined by installing a partition wall 30 made of refractory material 13 near the end of the inner water tube row 3 where the combustion gas is injected inside the main body 20, and the combustion gas injected from the burner 10 is configured to flow back entirely after impinging on the partition wall 30. On the combustion chamber 9 side of the partition wall 30, a refractory material 13 is arranged that has a sufficient thickness to prevent deformation even when high-temperature combustion gas impinges. A heat insulating material 14 is also arranged on the inner part of the closing plate 40b to prevent deformation.

[0050] On the combustion gas supply side (lid 22 side), an inner smoke vent 5 is formed between the inner wall of the lid 22 and the end water tube, and a notch (inner smoke vent 5A) is formed in the closing fin 8 connecting the water tubes of the inner water tube row 3. That is, as shown in FIG. 6, a notch (hatched area in FIG. 5) is formed in each of the three closing fins 8 from the lid 22 side. The notch is formed as a three-stage opening with the largest notch area on the lid 22 side. This is because the notch is larger near the combustion gas outlet of the burner 10 (see FIG. 5), making it easier for combustion gas that collides with the partition wall 30 and flows back to return to the vicinity of the lid 22 side.

[0051] In this example, notches (shaded areas) are formed in only three closing fins 8 for a total of 19 water tubes, but the number of closing fins 8 for which notches are formed should preferably be about 10 to 20% of the total number of water tubes, i.e., two to three notches for a total of 19 water tubes in this example, so as not to create resistance to the flow of combustion gas and to ensure that the combustion gas flows back.

[0052] Next, the configuration of the nozzle row installed in the combustion chamber 9, which is a characteristic feature of the present invention, will be described with reference to FIGS.

[0053] A plurality of nozzles 50 for injecting steam are arranged in an annular pattern (first nozzle group) on the inner surface of the partition wall 30 installed on the opposite side of the door side of the combustion chamber 9, along the inside of the inner water tube array 3. Specifically, as shown in Figures 6 and 8, a plurality of nozzles 50 whose injection ports face the combustion chamber 9 are provided in a circular pipe 51 arranged along the inside of the inner water tube array 3 in the combustion chamber 9.

[0054] Furthermore, at a position facing the gap between the inner water tube row 3 and the outer water tube row 4 on the cover body 22 side of the combustion chamber 9, a plurality of nozzles 60 for injecting steam into this gap are arranged annularly along the gap between the water tube rows (second nozzle group). Specifically, as shown in Figures 6, 9 and 10, a pair of semicircular pipes 61 are installed in the combustion chamber 9, and steam is supplied to each semicircular pipe 61 from the outside via pipes 62, so that steam is supplied along the semicircular pipes 61 and is injected from the plurality of nozzles 60 provided on the semicircular pipes 61.

[0055] Furthermore, on the partition wall 30 side of the combustion chamber 9, at a position facing the gap between the inner water tube row 3 and the outer water tube row 4, a plurality of nozzles 70 for injecting steam into this gap are arranged in an annular pattern along the gap between the water tube rows (third nozzle group). Specifically, as shown in Figures 6 and 8, the plurality of nozzles 70 are provided in a circular pipe 71 that is arranged between the inner water tube row 3 and the outer water tube row 4 inside the combustion chamber 9.

[0056] 2 and 6, the consumed steam discharged from the multi-tubular once-through boiler 100 is branched 84 to these multiple nozzles 50, 60, 70, and is supplied via an injection control device 85 from pipes 52, 62, 72 through circular pipe 51, semicircular pipe 61, and circular pipe 71, respectively. By branching 84, a portion of the consumed steam discharged from the multi-tubular once-through boiler 100 is fed back and can be used as injection steam from each of the nozzles 50, 60, 70.

[0057] Furthermore, injection control device 85 controls the injection time and injection pressure of the steam, so that steam is intermittently injected from the tips of nozzles 50, 60, and 70 at a pressure of 0.4 to 0.8 MPa for 5 to 15 seconds at intervals of 1 to 2 hours. During operation of multi-tube once-through boiler 100, which produces consumed steam at a pressure of 0.49 to 0.98 MPa, the temperature inside combustion chamber 9 reaches 900 to 1000°C, so injecting steam at approximately 150 to 175°C from each nozzle would lower the temperature of the water tubes, but intermittent injection of steam can prevent this from happening.

[0058] In the above example, the steam supplied to each nozzle is the consumed steam discharged from the multi-tubular once-through boiler 100, which is branched off 84 and adjusted by the injection control device 85, but steam supplied from a separate line may be used instead of the consumed steam from the multi-tubular once-through boiler 100. The supply time and pressure of the steam supplied from the separate line may be controlled by, for example, a flow rate regulator or a pressure regulator, and the steam may be intermittently injected into the combustion chamber 9.

[0059] The reason for injecting steam from each nozzle is to spray steam with mass to blow away residual ash and prevent it from adhering to the surroundings of the water tubes that make up the water tube rows 3 and 4, and also to use high-temperature steam to prevent damage to the water tubes in the combustion chamber 9, which is filled with combustion gas and has a high temperature (900 to 1000°C), even if the steam comes into contact with the water tubes.

[0060] The nozzle holes of each nozzle 50 in the first nozzle row are selected so that the spray angle is 100 to 115 degrees. By setting the angle to a wide angle of about 110 degrees, the spray range is widened to ensure that the spray is directed onto the inner wall surface of the inner water pipe 3, thereby preventing the adhesion of residual ash.

[0061] The nozzle holes of the nozzles 60, 70 of the second nozzle row and the third nozzle row are selected so that the spray angle is 10 to 20 degrees. By narrowing the spray angle, the steam is sprayed in a straight line, which makes it easier for the steam to enter the gap between the inner water tube row 3 and the outer water tube row 4.

[0062] The pressure of the injected steam is preferably about 0.4 to 0.8 MPa to prevent the adhesion of residual ash around the water tube.

[0063] According to the above-described structure, by injecting steam from the multiple nozzles 50, 60, 70 while the multi-tube once-through boiler 100 is in operation, the first nozzle group can suppress the generation of residual ash adhering to the surface of the inner water tube row 3 in the combustion chamber, and the second and third nozzle groups can suppress the generation of residual ash adhering to the gap between the inner water tube row 3 and the outer water tube row 4.

[0064] In addition, by providing a plurality of nozzles 60 (second nozzle group) on the door side, when the flow of combustion gas that has reversed within the combustion chamber 9 flows from the door (lid body 21) side to the closing plate 40b side in the gap between the inner water tube row 3 and the outer water tube row 4, the flow of combustion gas can be made smooth by injecting steam at the part where the flow stagnates in the cutout portion 5A.

[0065] A flue 12 for carrying out combustion exhaust gas, which communicates with the combustion chamber 9, is arranged on the upper surface of the combustion chamber 9 opposite the door side. Upper cutouts 41 corresponding to the upper semicircles are formed in the plurality of closing fins 8 (three water tubes in the illustrated example) of the outer water tube row 4 at a position facing the opening 12a of the flue 12. The presence of the plurality of upper cutouts 41 allows the combustion exhaust gas to flow out of the outer water tube row 4 through the gap between the inner water tube row 3 and the outer water tube row 4 on the closing plate 40b side, via the upper cutouts 41.

[0066] The three upper cutouts 41 are formed so that the opening area increases as they approach the partition wall 30. This is to allow the flow of combustion gas to reach as far back as possible, increasing the contact area with the water tube array and improving the efficiency of heat exchange with the combustion gas.

[0067] A cyclone device 90 for separating powder (residual ash) from the combustion exhaust gas is connected above the flue 12. The cyclone device 90 is a powder separator that uses centrifugal force to separate powdery residual ash mixed with the gas, and a cyclone device having a general structure for separating gas and powder is used.

[0068] A water supply port 23 is provided on the underside of each of the left lower header 2L and right lower header 2R, and a steam exhaust port 24 is provided on the upper surface of each of the left upper header 1L and right upper header 1R.

[0069] With the above-described structure, when water is supplied from each water inlet 23 of the left lower header 2L and the right lower header 2R, boiler water is supplied to each of the multiple water tubes arranged in an arc shape, and when combustion gas is supplied from the burner 10 to the combustion chamber 9, the combustion gas from the combustion chamber 9 comes into contact with the inner surface (the surface facing the combustion chamber 9) of each water tube of the inner water tube row 3, heating the boiler water in the water tubes.

[0070] The combustion gas bounces off the partition wall 30 installed at the end of the combustion chamber 9 and is returned to the lid body 22 side, but as shown in Figure 6, it is led from the inner smoke vent 5 and the cutout portion (inner smoke vent 5A) to the combustion gas passage 7 between the inner water tube row 3 and the outer water tube row 4, and comes into contact with the inner surfaces of the inner water tube row 3 and the outer water tube row 4, heating the boiler water in the water tubes.

[0071] The boiler water in the water tubes of the inner water tube row 3 and the outer water tube row 4 is heated to become steam, which is taken out from the steam outlets 24 provided in the left upper header 1L and the right upper header 1R via the steam separator 80, the piping line 81, and the branch 84, and is consumed at the desired supply location. The combustion gas lowers in temperature by heating the boiler water in the water tubes, and is separated into combustion exhaust gas and powder via the flue 12 and the cyclone device 90 and discharged to the outside.

[0072] A bag filter 92 is connected to the cyclone device 90 via a cooling device 91 for cooling the combustion exhaust gas. If the combustion exhaust gas is too hot, dust (powder) will adhere to the surface of the filter cloth of the bag filter 92, damaging the filter cloth and preventing the dust from adhering. This configuration makes it possible for the combustion exhaust gas discharged from the bag filter 92 to be discharged with most of the solid content removed.

[0073] When using multiple multi-tubular once-through boilers with the above-described structure, a cyclone device 90 and a cooling device 91 can be connected to each multi-tubular once-through boiler 100, and the discharge paths from each cooling device 91 can be combined into one and introduced into a bag filter 92, as shown in Figure 11.

[0074] According to the multi-tubular once-through boiler 100 having the above-described structure, when recycled oil (waste oil) is used as the combustion fuel for the burner 10, steam is intermittently injected from the multiple nozzles 50, 60, 70 arranged in the first nozzle row, second nozzle row, and third nozzle row while the multi-tubular once-through boiler 100 is in operation, generating an airflow around the water tube rows and suppressing the generation of residual ash adhering around the inner water tube row 3 and outer water tube row 4 within the combustion chamber 9.

[0075] In particular, since steam is injected around the water tube row while the multi-tubular once-through boiler 100 is in operation, the adhesion of residual ash is suppressed, and the situation in which the adhered residual ash remains firmly attached even after the multi-tubular once-through boiler is shut down can be prevented.

[0076] In addition, by injecting steam intermittently, it is possible to suppress a decrease in the temperature of the surface of the water tube rows (3, 4) caused by steam at a temperature (approximately 150 to 175°C) lower than the temperature inside the combustion chamber (approximately 900 to 1000°C), thereby preventing any interference with the heating of the water tube rows.

[0077] DESCRIPTION OF SYMBOLS 1...Upper header 2...Lower header 3, 3L, 3R...Inner water tube row 4, 4L, 4R...Outer water tube row 5...Inner smoke vent 5A...Notch 6...Outer smoke vent 7...Combustion gas passage 8...Closing fin 9...Combustion chamber 10...Burner 12...Fluid 13...Refractory material 14...Insulating material 20...Main body 21...Hinge 22...Cover body (door) 23...Water supply port 24...Steam outlet 30...Partition wall 40a, 40b...Closing plate 41...Upper notch 50...Nozzle (first nozzle group) 51...Circular piping 60...Nozzle (second nozzle group) 61...Semicircular piping 70...Nozzle (third nozzle group) 71...Circular piping 80...Steam separator 82...Pressure gauge 83...Safety valve 84...Branch 85... Injection control device 90... Cyclone device 91... Cooling device 92... Bag filter 100... Multi-tube once-through boiler

Claims

1. A multi-tube once-through boiler is provided with a combustion chamber to which combustion gas is supplied from a burner installed at one end, a water tube row consisting of a plurality of water tubes is installed in the combustion chamber, and boiler water supplied to the water tubes is heated and evaporated by the combustion gas to extract consumed steam. The water tube row is configured by connecting a plurality of arc-shaped water tubes with closing fins, The recycled oil is used as fuel, and a plurality of nozzles are provided for injecting steam onto the surface of each water tube row in a direction perpendicular to the water tube row, A multi-tube once-through boiler characterized in that steam is injected during operation of the multi-tube once-through boiler to suppress the adhesion of residual ash caused by combustion of recycled oil on the surface side of the water tube row when recycled oil is used.

2. 2. The multi-tubular once-through boiler according to claim 1, further comprising an injection control device for controlling the injection time of steam injected from the nozzles, so that steam is injected intermittently during operation of the multi-tubular once-through boiler.

3. 2. The multi-tubular once-through boiler according to claim 1, wherein the steam injected from the nozzles is fed back using the consumed steam obtained from the multi-tubular once-through boiler.

4. 4. A multi-tubular once-through boiler according to claim 3, wherein the steam is supplied by branching off consumed steam extracted from the multi-tubular once-through boiler.

5. 2. A multi-tube once-through boiler according to claim 1, wherein the first nozzle row, consisting of a plurality of nozzles, is arranged at a position facing the water tube row from a partition wall installed in the combustion chamber so that the combustion gas from the burner collides and flows back.

6. the water tube row is composed of an inner water tube row and an outer water tube row, 2. A multi-tube once-through boiler according to claim 1, wherein a second nozzle row consisting of a plurality of nozzles is arranged at a position facing the gap between the inner water tube row and the outer water tube row from the inner surface side of a closing plate installed in the combustion chamber on the burner side.

7. 7. A multi-tube once-through boiler according to claim 6, wherein a third nozzle row consisting of a plurality of nozzles is disposed on the inner surface of a closing plate installed at the rear of the partition wall on the opposite side from the burner, at a position facing the gap between the inner water tube row and the outer water tube row.

8. 6. The multi-tube once-through boiler according to claim 5, wherein the steam injection angle from each nozzle in the first nozzle row is 100 degrees to 115 degrees.

9. 8. The multi-tube once-through boiler according to claim 7, wherein the nozzles of the second nozzle row and the third nozzle row each have a steam injection angle of 10 degrees to 20 degrees.

10. 2. A multi-tube once-through boiler according to claim 1, further comprising a flue communicating with said combustion chamber, said flue being connected to a cyclone device.

11. 11. The multi-tube once-through boiler according to claim 10, wherein a bag filter is connected to the flue at an outlet of the combustion gas in the cyclone device via a cooling device.

12. 12. The multi-tube once-through boiler according to claim 11, wherein one bag filter is connected to a plurality of cyclone devices and cooling devices.

13. In a multi-tube once-through boiler, both ends of a plurality of water tubes are connected to each other, boiler water is supplied to each water tube, a combustion chamber is formed inside each water tube, combustion gas from the combustion chamber is supplied to the surface side of the plurality of water tubes to heat and evaporate the boiler water in the water tubes, and consumed steam is taken out. Using recycled oil as fuel, a door is formed on one end side facing the combustion chamber, and a burner for supplying combustion gas to the combustion chamber is installed on an outer surface of the door; The combustion chamber has a cylindrical shape extending horizontally, The water tubes are arc-shaped and arranged on the left and right sides of the combustion chamber, a left-side upper header provided at an upper end and a left-side lower header provided at a lower end, the left-side upper header being linear and connected to the water tube row disposed on the left side of the combustion chamber; a water tube row disposed on the right side of the combustion chamber is connected to a straight right upper header provided at an upper end thereof and a straight right lower header provided at a lower end thereof, the water tube rows are composed of an inner water tube row and an outer water tube row, each water tube of the outer water tube row is disposed between each water tube of the inner water tube row, the water tubes constituting the left and right inner water tube rows are connected by closing fins, and the water tubes constituting the left and right outer water tube rows are connected by closing fins, A partition wall is provided near the end of the inner water tube row where the combustion gas is injected to partition the combustion chamber, so that the supplied combustion gas collides with the partition wall and then flows back to the door side. An inner smoke vent is formed between an end water tube of the inner water tube row on the door side of the combustion chamber and the combustion chamber wall on the door side, and notches are formed only in closing fins that are 10 to 20% of the total number of water tubes from the door side connecting the water tubes of the inner water tube row, A multi-tube once-through boiler is characterized in that a plurality of nozzles for injecting steam from a direction perpendicular to each water tube row are arranged on the combustion chamber side of the partition wall so as to be positioned along the vicinity of the inner water tube row.

14. 14. A multi-tube once-through boiler as described in claim 13, wherein a flue communicating with the combustion chamber is arranged on the upper surface of the combustion chamber opposite the door side, and upper cutouts are formed in a plurality of closing fins of the outer water tube row at a position facing the opening of the flue.

15. 15. A multi-tube once-through boiler according to claim 13, characterized in that a plurality of nozzles for injecting steam into a gap between the inner water tube row and the outer water tube row are arranged on the door side of the combustion chamber at a position facing the gap.

16. 15. A multi-tube once-through boiler according to claim 13, wherein a plurality of nozzles for injecting steam into the gaps between the inner water tube row and the outer water tube row are arranged on the inner surface of a closing plate installed on the opposite side of the combustion chamber from the door side, at positions facing the gaps.

17. 14. The multi-tubular once-through boiler according to claim 13, further comprising an injection control device that intermittently controls the steam injected from the nozzles while the multi-tubular once-through boiler is in operation.

18. A method for operating a multi-tube once-through boiler in which both ends of each of a plurality of water tubes are connected to each other and boiler water is supplied to each water tube, while a combustion chamber is formed inside each water tube, and combustion gas from a burner installed at one end of the combustion chamber is supplied to the surface side of a water tube row consisting of a plurality of water tubes to heat and evaporate the boiler water in the water tubes and extract consumed steam, The water tube row is configured by connecting a plurality of arc-shaped water tubes with closing fins, A method for operating a multi-tubular once-through boiler, characterized by using recycled oil as fuel and intermittently injecting steam from a plurality of nozzles arranged on the surface side of each water tube row from a direction perpendicular to the water tube row during operation of the multi-tubular once-through boiler, thereby suppressing the adhesion of residual ash caused by the combustion of recycled oil to the surface side of the water tube row when using recycled oil.

19. 19. The method for operating a multi-tubular once-through boiler according to claim 18, wherein the intermittent injection of steam is performed for 5 to 15 seconds every 1 to 2 hours.