HK1018713A

HK1018713A - Device and method for combustion of fuel

Info

Publication number: HK1018713A
Application number: HK99103752.4A
Authority: HK
Inventors: 向井克治; 住谷佳彦; 石鉢俊幸
Original assignee: 住友大阪水泥股份有限公司
Priority date: 1996-12-27
Filing date: 1997-12-25
Publication date: 1999-12-30

Description

Fuel combustion apparatus and method

Technical Field

The present invention relates to an apparatus and a method for combusting at least one fuel selected from the group consisting of pulverized fuel and liquid fuel. More particularly, the present invention relates to an apparatus and a method for burning a pulverized fuel such as a solid pulverized fuel such as fine coal or coke powder and a pulverized fuel containing combustible waste such as plastic powder, garbage powder, wood chips and chaff, or a liquid fuel such as heavy oil or waste oil and a slurry fuel containing combustible powder such as coal powder or coke powder in a rotary kiln, for example, which can be used for producing cement clinker, magnesia clinker or lime.

Background

When a pulverized fuel such as pulverized coal is combusted, a cylinder type combustion apparatus for pulverized coal as disclosed in Japanese examined patent publication No.57-35368 can be used. In the combustion apparatus, a plurality of inner primary air injection holes are arranged in a central portion of the apparatus, a plurality of (4 to 8) fine coal injection holes for injecting a mixture of fine coal powder and air for transporting the fine coal are arranged around the inner primary air injection holes and spaced apart from each other by a partition plate, and an outer circumferential primary air injection slit having a circular cross-sectional profile is provided around the fine coal injection holes. In this device, the coal fines are injected in the form of 4 to 8 jets through the orifices spaced apart from one another, while the inner primary air jets and the annular primary air jet are injected in such a way that the coal fines jets are interposed between the inner primary air jets and the annular primary air jets. Because the flow velocity of the fine coal powder jet flow is lower than that of the inner and outer primary air direct jet flows, the fine coal powder jet flow is accelerated by the inner and outer primary air direct jet flows, and the fine coal powder is blown away far. During the above injection, high-temperature secondary air is introduced into the combustion chamber from a product cooling device disposed downstream of the combustion chamber, passes through the gap of the outer primary air straight jet, enters the interior of the outer primary air straight jet, and is sucked and diffused into the fine coal injection flow, thereby burning the fine coal.

Meanwhile, a burner for burning fine particulate solid fuel, as disclosed in japanese examined patent publication No.2-22,289, is provided with a plurality of inner primary air injection holes annularly arranged in a central portion of the burner and spaced apart from each other by a partition plate, a plurality of fine particulate solid fuel/delivery air injection holes annularly arranged around the inner primary air injection holes, and outer primary air injection holes annularly formed around the above fine particulate solid fuel/delivery air injection holes. In the burner, the flow resistances of the fine particle solid fuels at the injection end surfaces are made different from each other, and the distribution density of the fine particle solid fuels is made uneven, thereby increasing the combustion speed and forming a short flame.

In the case where pulverized fuel and primary air are injected and high-temperature secondary air is mixed into the injected pulverized fuel and primary air flow to burn the pulverized fuel, generally, the combustion of the pulverized fuel is realized by the total amount of the primary air and a certain amount of the secondary air corresponding to the difference between the theoretical combustion air amount and the total amount of the primary air. In this case, the temperature of the primary air is 60 to 80 ℃, and the temperature of the secondary air is 800 to 1000 ℃. Therefore, the superiority and inferiority of combustion depend on the primary air ratio (representing the ratio of the total amount of primary air to the theoretical combustion air amount), and the lower the primary air ratio, the better the combustion.

However, when the primary air ratio is lowered to promote combustion, the flow velocity of the primary air jet is lowered accordingly, and mixing of the secondary air into the combustion mixture becomes insufficient, so that the above-mentioned lowering brings about a disadvantage that the combustion velocity of the pulverized fuel is lowered, the ignition temperature is lowered, and incomplete combustion of the pulverized coal is caused. For this reason, in the method of the conventional apparatus for burning the pulverized fuel, the primary air ratio is generally about 20% to 25%, and it is practically difficult to use a primary air ratio lower than the above level.

Meanwhile, in the conventional apparatus and method for burning a pulverized fuel, the position of the ignition point can be adjusted to some extent by controlling the ratio of the flow rates of the inner primary air injection direct flow stream to the inner primary air injection turning flow stream. However, in practice, the above control of one burner is difficult. The design of the inner primary air direct flow injection holes and the inner primary air turn flow injection holes must be changed according to the performance of the rotary kiln. Meanwhile, in this case, when the inner primary direct air flow is too strong, the generated combustion flame is in the form of a long flame with a narrow angle, and the ignition temperature is insufficient. Meanwhile, when the inner primary air is turned to be too strong, the generated combustion flame is in the form of a short flame with a wide angle. In this case, although the ignition temperature is high, the angle of the flame is too wide, and thus the furnace wall is largely damaged, and in the worst case, the furnace wall is damaged.

Meanwhile, when a liquid fuel is used, in an apparatus and method for combusting a liquid fuel in which a liquid fuel is injected into a combustion furnace, the injected liquid fuel is mixed with primary air and is then mixed with high-temperature secondary air to be combusted. In this case, the combustion of combustible substances in the liquid fuel is carried out on the basis of the total amount of primary air mixed with the liquid fuel and the amount of secondary air corresponding to the difference between the theoretical combustion air amount and the total amount of primary air. Typically, the temperature of the primary air is 60 to 80 ℃ and the temperature of the secondary air is 800 to 1000 ℃. Therefore, the superiority and inferiority of combustion vary with the primary air ratio, which represents the ratio of the total amount of primary air to the theoretical combustion air amount. The smaller the primary air ratio, the higher the air temperature for combustion, and as a result, the combustion temperature increases and the ignition temperature rises, thus resulting in good quality combustion.

However, when the amount of primary air is reduced to make the combustion conditions better, there are generated some disadvantages such as a reduction in the jet flow velocity of the primary air, insufficient mixing of the secondary air, a reduction in the ignition temperature, and incomplete combustion of the liquid fuel. For this reason, when C heavy oil is used as fuel in the conventional apparatus and method for combusting liquid fuel, the primary air ratio is controlled to about 12 to 15%. When the primary air ratio is further decreased below the above level, good combustion of the liquid fuel is difficult to achieve.

In conventional liquid fuel combustion apparatus and methods, it is difficult to adjust the location of the ignition point by controlling the flow velocity ratio of the liquid fuel stream injected into the furnace to the primary air jet formed simultaneously therewith. Therefore, the combustion flame formed in the combustion furnace is in the form of a narrow-angle long flame whose ignition point temperature is not high enough, or in the form of a wide-angle short flame in which the ignition point temperature is high enough and the flame spread is too wide, so that the furnace wall is largely damaged. In the worst case, the furnace wall is damaged.

Next, in the case where pulverized fuel and liquid fuel are used together, an apparatus and a method for burning the pulverized fuel and the liquid fuel are known. In the apparatus and method, a pulverized fuel and a liquid fuel are injected together with primary air and further mixed with high-temperature secondary air. In this case, generally, the combustion of these fuels proceeds according to the total amount of primary air and the amount of secondary air, which corresponds to the difference between the theoretical combustion air amount and the total amount of primary air. In this combustion, the temperature of the primary air is 60 to 80 ℃ and the temperature of the secondary air is 800 to 1000 ℃, so the quality of the combustion varies depending on the primary air ratio (the primary air ratio indicates the ratio of the total amount of the primary air to the theoretical combustion air amount), and the lower the primary air ratio, the higher the temperature of the air used for combustion, and as a result, the combustion speed increases, the ignition temperature becomes high, and good combustion occurs.

However, when the primary air ratio is decreased to make the combustion conditions better, there are generated some disadvantages such as a decrease in the jet flow speed, and thus the mixing of the secondary air becomes insufficient, the combustion speed of the pulverized fuel and the liquid fuel becomes slow, the ignition temperature is lowered and the fuel combustion becomes insufficient. For this reason, in the conventional apparatus and method for mixed combustion of fuel, the primary air ratio is generally about 20% to 25%, and it is practically difficult to achieve mixed combustion at an increased combustion speed and an increased ignition point temperature with a reduced primary air ratio. Meanwhile, in the conventional hybrid combustion apparatus and method, the ignition point position can be adjusted to some extent by controlling the flow velocity ratio of the inner primary air straight flow and the inner primary air turning flow formed together with the straight flow. In practice, the above control of one burner is difficult, and therefore the design of the inner primary air direct flow injection holes and the inner primary air turn flow injection holes must be changed according to the properties of the rotary kiln. In this case, when the inner primary air straight jet becomes too strong, the resulting combustion flame takes the form of a narrow-angle long flame in which the ignition point temperature is insufficiently low. When the inner primary air turning flow becomes too strong, the resulting combustion flame is a wide-angle short flame in which the ignition temperature is sufficiently high and the flame becomes too wide, so that the furnace wall suffers great damage. In the worst case, the furnace wall is damaged.

In view of the above-described various conventional combustion apparatuses and methods, there is a strong need for an apparatus and method which can form a narrow-angle short flame form, can sufficiently raise the ignition temperature using a pulverized fuel or a liquid fuel or using a pulverized fuel together with a liquid fuel, and can achieve superior combustion without damaging the furnace wall.

Disclosure of the invention

It is an object of the present invention to provide a fuel combustion apparatus and method capable of forming a combustion flame in the form of a narrow-angle short flame having a sufficiently high ignition temperature with, for example, a pulverized fuel or a liquid fuel or a pulverized fuel together with a liquid fuel, while preventing or reducing damage to the walls of the combustion furnace.

It is another object of the present invention to provide a fuel combustion apparatus and method which can rapidly and efficiently combust a fuel, such as a pulverized fuel or a liquid fuel or a pulverized fuel and a liquid fuel, without overheating the walls of the furnace.

The fuel combustion apparatus and method of the present invention can utilize an inexpensive fuel such as pulverized coal or coke powder, which contains a very small amount of volatile components and is thus considered to be unusable. Meanwhile, the fuel combustion apparatus and method of the present invention can use not only a liquid fuel such as heavy oil but also a slurry of an inexpensive fuel such as pulverized coal or coke powder, thereby reducing fuel costs.

The fuel combustion apparatus of the present invention comprises: a mechanism for injecting at least one fuel selected from the group consisting of pulverized fuel and liquid fuel; an outer primary air injection pipe provided on an outer side of the fuel injection mechanism and having a plurality of outer primary air injection holes through which primary air is injected in parallel with a fuel injection direction of the fuel injection mechanism; and an inner primary air injection pipe provided on an inner side of the fuel injection mechanism and having at least one inner primary air injection hole through which primary air is injected in parallel with a fuel injection direction of the fuel injection mechanism.

The fuel combustion method of the present invention is implemented using the above fuel combustion apparatus of the present invention, and includes: injecting at least one selected component from the group consisting of pulverized fuel and liquid fuel through the fuel injection mechanism; and injects primary air in the same direction as the fuel injection direction through the outer and inner primary air injection holes, thereby forming outer and inner primary air injection jets with the fuel injection jet interposed therebetween.

The above-described fuel injection mechanism, which may be used with the apparatus and method of the present invention, may include a pulverized fuel injection pipe having an annular injection hole through which pulverized fuel is injected together with air for delivering the pulverized fuel; may include a plurality of liquid fuel injection pipes having liquid fuel injection holes provided on one and the same circumference through which the liquid fuel is injected in the radial direction, or may include a pulverized fuel injection pipe having an annular injection hole through which the pulverized fuel is injected together with air for supplying the pulverized fuel, and an additional fuel injection mechanism including a liquid fuel injection pipe disposed on the inner side of the inner primary air injection pipe and having liquid fuel injection holes through which the liquid fuel is injected in the radial direction.

Brief Description of Drawings

FIG. 1 is an explanatory view showing the configuration of the combustion apparatus of the present invention used in a rotary kiln;

FIG. 2 is an explanatory side view of a heating furnace including an embodiment of the combustion apparatus of the present invention, i.e., a pulverized fuel combustion apparatus;

FIG. 3(A) is an explanatory cross-sectional side view showing the constitution of an embodiment of the pulverized fuel combustion apparatus of the present invention;

FIG. 3(B) is an illustrative front view of the apparatus shown in FIG. 3 (A);

FIG. 4 is an explanatory side view of a heating furnace including another embodiment of the combustion apparatus of the present invention, namely, a liquid fuel combustion apparatus;

FIG. 5(A) is an explanatory cross-sectional side view showing the constitution of an embodiment of the liquid fuel combustion apparatus of the invention;

FIG. 5(B) is an illustrative front view of the apparatus shown in FIG. 5 (A);

FIG. 6 is an explanatory side view of a heating furnace including still another embodiment of the combustion apparatus of the present invention, i.e., a pulverized fuel and liquid fuel combustion apparatus;

fig. 7(a) is an explanatory cross-sectional side view showing the constitution of an embodiment of the apparatus for mixed combustion of a pulverized fuel and a liquid fuel of the present invention.

Fig. 7(B) is an illustrative front view of the apparatus in fig. 7 (a).

Best mode for carrying out the invention

The combustion apparatus and the combustion method of the invention are advantageously used in rotary kilns for the production of cement clinker, magnesia clinker or lime. In the present invention, the fuel is at least one of a pulverized fuel and a liquid fuel.

As shown in fig. 1, an outlet portion of the rotary kiln 1 is connected to an inlet portion of the product cooling device 2, and a fuel combustion device 3 is inserted into the outlet portion of the rotary kiln 1 and led to the inlet portion of the rotary kiln. The product produced in the rotary kiln 1 is introduced into the product cooling system 2, cooled by cooling air 4 introduced into the cooling apparatus 2, and high-temperature air 5 generated by heat exchange in the cooling system 2 is returned as second air to enter the rotary kiln 1 through the inlet portion of the cooling apparatus 2 and used for burning fuel.

In the present invention, an illustrative side view of an embodiment of a heating furnace including the pulverized fuel combustion device of the present invention when pulverized fuel is used as fuel is shown in fig. 2. In fig. 2, a cylindrical pulverized fuel combustion device 11 is inserted into a heating furnace such as a rotary kiln through a furnace wall 12. The combustion apparatus 11 includes: a pulverized fuel injection pipe having an annular injection hole through which the pulverized fuel is injected together with air for feeding the pulverized fuel; an inner primary air injection pipe having a plurality of inner primary air injection holes and an outer primary air injection pipe having a plurality of outer primary air injection holes, the inner and outer injection pipes being respectively provided along inner and outer circumferential surfaces of the powder fuel injection pipe.

In fig. 2, in the end portion 13 of the pulverized fuel combustion apparatus 11 disposed outside the heating furnace, a pulverized fuel delivery pipe 14 is provided for delivering a mixed flow of pulverized fuel and fuel delivery air. The delivery pipe 14 is connected to the above-described pulverized fuel injection pipe. Meanwhile, in the end portion 13, a primary air delivery pipe 15 is provided. The duct 15 is branched into an outer primary air duct 16 and an inner primary air duct 17, the outer primary air duct 16 being connected to the outer primary air injecting tube and the inner primary air duct 17 being connected to the inner primary air injecting tube. In the combustion apparatus of fig. 2, two heavy oil or gas burners 18 for ignition are provided in the central portion of the apparatus.

In the combustion device of fig. 2, a stream 19 of pulverized fuel is injected through an annular injection hole, a plurality of inner primary air straight jets 20 are injected into the interior of the annular pulverized fuel stream, and a plurality of outer primary air straight jets are injected outside the annular pulverized fuel stream, the pulverized fuel stream and the inner and outer air streams forming a composite stream, and the high temperature secondary air stream 5 is mixed into the composite stream to combust the pulverized fuel.

The combustion apparatus for pulverized fuel of the present invention is characterized by having a pulverized fuel injection pipe, an outer primary air injection pipe provided along an outer peripheral surface of the pulverized fuel injection pipe, and an inner primary air injection pipe provided along an inner peripheral surface of the pulverized fuel injection pipe; the pulverized fuel injection pipe has an annular injection hole through which the pulverized fuel is injected together with air for feeding the pulverized fuel; the outer primary air injection pipe has a plurality of injection holes through which primary air is injected in the same direction as the direction in which the pulverized fuel is injected through the annular injection holes; the inner primary air injection pipe has a plurality of injection holes through which primary air is injected in the same direction as the direction in which the pulverized fuel is injected through the annular injection holes.

Meanwhile, the combustion method of the present invention using the above pulverized fuel combustion apparatus is characterized in that the pulverized fuel is injected through the above annular injection hole together with air for feeding the pulverized fuel, and primary air is injected through a plurality of inner and outer primary air injection holes in the same direction as the pulverized fuel injection flow to form inner and outer primary air straight injection flows between which the pulverized fuel injection flow is interposed.

An illustrative cross-sectional side view and an illustrative front view of one embodiment of the pulverized fuel combustion apparatus of the present invention are shown in fig. 3(a) and 3 (B). Fig. 3(a) is an explanatory sectional view of the apparatus shown in fig. 3(B) along a bending line X-X'.

In fig. 3(a) and 3(B), one outer primary air injection tube 23 is provided inside the outermost peripheral wall 22 of the cylindrical combustion apparatus 11, and a plurality of, for example, 6 to 16, preferably 8 to 14, outer primary air injection holes 24 are formed in one injection end portion of the tube 23. On the inner side of the outer primary air injection pipe 23, a pulverized fuel injection pipe 25 for injecting a mixture of pulverized fuel and air for transporting the pulverized fuel is disposed in concentric relation to the outer primary air injection pipe 23, and in the end portion of the pipe 25, an annular pulverized fuel injection hole 26 is formed. Next, on the inner side of the pulverized fuel injection pipe 25, an inner primary air injection pipe 27 is provided, and a plurality of, for example, 6 to 16, preferably 8 to 14 inner primary air injection holes 28 are formed in an injection end portion of the pipe 27.

The above-described annular powder fuel injection holes 26, the outer primary air injection holes 24, and the inner primary air injection holes 28 are formed such that their injection directions are identical to each other (or parallel to each other). Thus, the pulverized fuel is injected through the annular pulverized fuel injection holes 26 to form a pulverized fuel stream 19 having an annular cross-sectional profile, and the primary air is passed through the outer plurality of primary air injection holes 24 to form a plurality of outer primary air straight jets. These fuel and air streams follow the outer peripheral surface of the stream of powdered fuel 19. At the same time, the primary air is injected through the plurality of inner primary air injection holes 28 to form a plurality of inner primary air straight jet streams, which proceed along the inner peripheral surface of the flow of the powder fuel having an annular cross section. The flow of powder fuel is thus between the inner and outer primary air jets, thereby being accelerated and diffused. The diffused pulverized fuel is mixed with high-temperature secondary air that travels through gaps formed between the outer primary air straight jets, and is combusted. In this procedure, since the outer primary air flow is injected at high velocity into the plurality of separate direct air flows, the high temperature secondary air can easily pass through the plurality of outer primary air direct jets, and can be efficiently mixed with the pulverized fuel flow to form a combustion flame in the form of a narrow angle short flame and produce a high ignition temperature. Moreover, in the combustion process, the plurality of inner primary air direct jets are effective for promoting diffusion of the pulverized fuel while generating an inner circulation flow of high temperature formed in the combustion flame, thereby stabilizing the flame.

In the combustion apparatus for pulverized fuel of the present invention, the form, size and arrangement of the inner primary air injection holes 28 and the outer primary air injection holes 24 are not limited. Preferably, the pitch circle diameters (P, C, D) of the outer primary air injection holes 24 and the inner primary air injection holes 28 are 300 to 800 mm.

As shown in fig. 3(a) and 3(B), preferably, the plurality of outer primary air injection holes 24 of the outer injection pipe 23 and the plurality of inner primary air injection holes 28 of the inner injection pipe 27 are arranged on two concentric circumferences between which the annular powder fuel injection holes 26 of the injection pipe 25 are arranged, and the inner primary air injection holes 28 are located off the straight line extending through the centers of the respective outer primary air injection holes 24 and the centers of the concentric circles. Also, preferably, each inner primary air injection hole is positioned between a pair of straight lines 32 and 33, the pair of straight lines 32 and 33 extending through the center of each pair of adjacent outer primary air injection holes and the center 31 of the concentric circle. The arrangement of the primary air injection holes enables air swirl to be reliably generated on both the inner and outer circumferential surfaces of the annular pulverized fuel injection flow. Meanwhile, since the inner and outer primary air flows are composed of many direct air flows, the air vortex surface area is very large, so that an advantageous effect that the pulverized fuel can be efficiently and intensively combusted can be obtained. In the combustion apparatus of the present invention described above, there is no need for a mechanism for forming a conventional internal primary air-turn flow, which is considered necessary in the conventional combustion apparatus. Of course, the above-described mechanism for forming the inner primary air-turn flow may be optionally added to the combustion apparatus of the present invention.

The combustion method for pulverized fuel of the present invention uses the pulverized fuel combustion apparatus of the present invention. The method is characterized in that the pulverized fuel is injected through annular injection holes together with air for feeding the pulverized fuel, and primary air is injected through inner and outer primary air injection holes in the same direction as the pulverized fuel injection flow to form inner and outer primary air straight injection flows between which the pulverized fuel injection flow is formed.

In the method of the invention, pulverized fuel is injected through an annular injection orifice together with pulverized fuel delivery air, and primary air is injected through a plurality of outer and inner primary air injection orifices in the same direction as the pulverized fuel injection jets to form outer and inner primary air straight jets with the pulverized fuel injection jets therebetween.

In the method of the present invention, there is no limitation on the kind of the pulverized fuel. Generally, solid powder fuels such as pulverized coal and coke powder are used. In addition, various waste materials such as combustible plastic resin powder, refuse powder, wood waste (wood chips), chaff, and the like can also be used.

The method of the invention is very effective for use in rotary kilns for the production of cement clinker, magnesia clinker and lime. In this case, high-temperature secondary air is fed into the rotary kiln through a product cooling device disposed downstream of the rotary kiln. The high temperature secondary air is mixed into a composite stream consisting of an outer primary air straight jet, a pulverized fuel stream having an annular cross section, and an inner primary air straight jet, and the pulverized fuel can be efficiently combusted.

In the method of using the pulverized fuel of the present invention, the injection speed of the pulverized fuel through the annular injection hole is 30 to 50m/sec, preferably 35 to 45m/sec, while the injection speed of the outer and inner primary air flows through the outer and inner injection holes is 200 to 300m/sec, preferably 250 to 300m/sec, whereas the primary air injection speed is about 100m/sec in the conventional method.

When the injection speed is adjusted as described above, the primary air ratio, which represents the ratio of the total amount of air passing through the annular pulverized fuel injection holes and the outer and inner primary air injection holes to the theoretical combustion air amount, is reduced from a conventional value of 20 to 25% to 8 to 15%, preferably 8 to 12%. That is, in the combustion method of the present invention using the combustion apparatus of the present invention, the momentum of the jet flow can be increased by 25 to 35%, and the accompanying momentum and accompanying time of the secondary air can be maintained at a level similar to that of the conventional method. The jet flow amount and the secondary air accompanying momentum can be calculated according to the following equations (1) and (2):

G_o=m_oU_o (1)

G_e=K·(m_o(X/2R)^0.5-1)·V_e (2)

in equations (1) and (2):

G_ois the momentum of the jet

G_eFor secondary air with momentum

m_oFor jet mass flow rate (Kg/sec)

U_oIs the jet velocity (m/sec)

X is the jet axis distance (m)

R is the jet diameter (m)

V_eFor jet suction speed (m/sec)

K is a constant.

In the method of the present invention, when the primary air injection velocity (U) is set_o) From about 100m/sec of the conventional method to 200 to 300m/sec to increase the momentum (G) of the jet stream_o) Such an increase in the injection speed causes the secondary air to follow the momentum (G)_e) Proportional to the momentum (G) of the jet_o) But is increased. However, when the secondary air accompanies momentum (G)_e) And the accompanying time is kept at a level similar to that of the conventional method, the amount of primary air can be reduced because the mixing of the flame jet with air and the combustion in the initial stage are performed to a degree similar to that of the conventional method. In this case, the decrease in the amount of primary air can be compensated for by the high-temperature secondary air, so the combustion speed can be increased and the combustion efficiency can be improved.

By using the combustion apparatus and method for pulverized fuel of the present invention, a combustion flame in the form of a narrow-angle short flame can be formed using pulverized fuel, so that the swirl number (which is a dimensionless quantity representing the rotation intensity, as expressed by equation (3) shown below) can be made zero and a natural jet flow can be formed. Also, in the conventional apparatus and method, the content of volatile materials in the coal that can be utilized for the conventional apparatus and method must be 18% or more. However, with the apparatus and method of the present invention, the lower limit of the volatile matter content of the coal that can be utilized can be reduced to about 10%.

SW=G_φ/G_XR (3)

In equation (3):

SW is the number of the vortexes,

G_φfor the flux of angular momentum in the axial direction,

G_Xin order to provide a thrust force in the axial direction,

and R is the jet diameter of the burner.

In the present invention, a liquid fuel may be used as the fuel. Fig. 4 shows an explanatory side view of an embodiment of a heating furnace including the liquid fuel combustion apparatus of the present invention.

In fig. 4, a cylindrical liquid fuel combustion device 11a is inserted into a heating furnace (e.g., rotary kiln 1) through a furnace wall 12 of the heating furnace. In this combustion apparatus 11a, a plurality of liquid fuel injection pipes 25a having liquid fuel injection holes 26a for injecting liquid fuel in the radial direction are arranged on one and the same circumference, and an inner primary air injection pipe 27 having one or more inner primary air injection holes 28 for injecting primary air and an outer primary air injection pipe 23 having a plurality of outer primary air injection holes 24 for injecting primary air are arranged along the inner side and the outer side of the circumference on which the liquid fuel injection pipes 25 are arranged, respectively.

Referring to fig. 4, in the end portion 13 of the liquid fuel combustion device 11a disposed outside the heating furnace, a liquid fuel delivery pipe 14a is provided and connected to the above-described liquid fuel injection pipe. Meanwhile, a primary air delivery pipe 15 is provided in the end portion 13. The primary air delivery pipe 15 is branched into an outer primary air delivery pipe 16 and an inner primary air delivery pipe 17. The outer primary air delivery tube 16 is connected to the outer primary air injection tube and the inner primary air delivery tube 17 is connected to the inner primary air injection tube. In the combustion device 11a of fig. 4, one or more heavy oil or gas burners (not shown in fig. 4) for ignition may be provided.

In the combustion device 11a of fig. 4, the liquid fuel stream 19a is injected radially through the injection hole, the inner primary air straight jet 20 is injected inside the liquid fuel stream 19a, and the outer primary air straight jet 21 is injected outside the liquid fuel stream 19a, whereby a composite stream is formed from these streams, and the high-temperature secondary air 5 is mixed into the composite stream, thereby combusting the liquid fuel.

The liquid fuel combustion apparatus of the present invention is characterized by comprising: a plurality of liquid fuel injection pipes arranged on one and the same circumference and having liquid fuel injection holes through which liquid fuel is injected in a radial direction; an outer primary air injection pipe having a plurality of outer primary air injection holes provided outside the liquid fuel injection holes, through which primary air is injected in a direction parallel to a central axial direction of the liquid fuel injection holes; and an inner primary air injection pipe having at least one inner primary air injection hole provided inside the liquid fuel injection hole, through which primary air is injected in a direction parallel to a central axial direction of the liquid fuel injection hole.

Meanwhile, the liquid fuel combustion method of the present invention uses the liquid fuel combustion apparatus of the present invention, which is characterized in that the liquid fuel is injected in a radial direction through the liquid fuel injection hole, and the primary air is injected through the outer primary air injection hole and the inner primary air injection hole which are parallel to the central axial direction of the liquid fuel injection hole, thereby mixing the injected liquid fuel flow with the direct outer and inner primary air flows to combust the injected liquid fuel.

Fig. 5(a) and 5(B) show an explanatory cross-sectional side view and an explanatory front view, respectively, of an embodiment of a liquid fuel combustion apparatus. Fig. 5(a) shows an illustrative cross-sectional side view of the apparatus of fig. 5(B) along bend line Y-Y'.

In fig. 5(a) and 5(B), one outer primary air injection tube 23 is provided inside the outermost peripheral wall 22 of the cylindrical liquid-fuel combustion apparatus 3, and a plurality of, for example, 5 to 20, preferably 8 to 18 outer primary air injection holes 24 are formed in the injection end portion of the injection tube 23. On the inner side of the outer primary air injection pipe 23, one or more, for example, 1 to 6, preferably 1 to 4 liquid fuel injection pipes 25a are provided for injecting liquid fuel. At one end of each injection pipe, a liquid fuel injection hole 26a is formed to inject liquid fuel in the radial direction. One or more liquid fuel injection holes 26a are provided on one and the same circumference around the center 31, and the center axes of the liquid fuel injection holes 26a are parallel to each other. Next, an inner primary air injection pipe 27 is provided on the inner side of the liquid fuel injection pipe 25a, and at one end of the injection pipe, one or more, for example, 1 to 12, preferably 1 to 8 inner primary air injection holes 28 are formed.

The outer primary air injection holes 24 and the inner primary air injection holes 28 are formed in such a manner that the injection directions of these holes are the same (parallel) to the central axis direction of the liquid fuel injection hole 26 a. Liquid fuel is injected through each liquid fuel injection hole 26a to form a radial flow, and primary air is injected through the outer primary air injection hole 24 disposed outside the injection hole to form an outer primary air straight jet that proceeds outside the flow of liquid fuel and mixes with the injected liquid fuel. At the same time, the primary air is injected through one or more inner primary air injection holes 28 to form inner primary air straight jets 20 that travel inside the flow of liquid fuel and mix with the injected liquid fuel. The liquid fuel stream is thus mixed with, and accelerated and diffused by, outer and inner primary air straight jets flowing outside and inside, respectively, the liquid fuel stream, and is further mixed and combusted with the high temperature secondary air traveling through the outer primary air straight jets. In this method, the outer primary air stream is projected at high velocity to form a direct stream of air, preferably a plurality of separate direct streams of air. The high temperature secondary air can thus easily pass between the plurality of primary air straight jets and can be efficiently mixed with the liquid fuel stream to form a combustion flame in the form of a narrow angle short flame with a high ignition temperature. Moreover, when a plurality of inner primary air injection holes 24 are formed, the inner primary air straight jets generated advantageously serve to promote the diffusion of the liquid fuel stream and simultaneously create a high temperature internal circulation flow in the combustion flame, thus stabilizing the flame.

In the liquid fuel combustion apparatus of the present invention, there is no limitation in the form and size of the inner primary air injection holes 28 and the outer primary air injection holes 24. In general, the pitch circle diameter (P.C.D.) of the outer primary air injection holes 24 and the inner primary air injection holes 28 is preferably 300 to 800 mm.

Meanwhile, each of the liquid fuel injection pipes 25a having the liquid fuel injection hole forms one conical injection nozzle expanding outward. For example, when a C heavy oil is used as the liquid fuel, it is preferable to heat the C heavy oil to a temperature of 85 to 100 ℃ to reduce its viscous resistance to 20 to 30cst and place it at 30 to 40kg/cm²G, pressure.

As shown in fig. 5(a) and 5(B), in the case where the inner primary air injection pipe 27 has a plurality of inner primary air injection holes 28, it is preferable that the plurality of inner primary air injection holes 28 and the plurality of outer primary air injection holes 24 are arranged on concentric circumferences around a center point 31 of a circumference on which the plurality of liquid fuel injection holes 26a are disposed. Meanwhile, in the case where the inner primary air injection tube 27 has only one inner primary air injection hole 28, it is preferable that the center point of the one inner primary air injection hole is the same as the center point 31 of the circumference on which the plurality of liquid fuel injection holes 26a are disposed, and the circumference on which the plurality of outer primary air injection holes 24 are disposed and the circumference on which the plurality of liquid fuel injection holes 26a are disposed are concentric circles around the center point 31. The above-described arrangement of the primary air injection holes 24 and 28 enables a swirl to be reliably generated on both the outer and inner sides of the flow of liquid fuel, while the primary air is uniformly mixed with the liquid fuel. Preferably, the inner and outer primary air streams each form a plurality of direct air streams. In this case, the vortex surface area can become large, and therefore the liquid fuel can be vigorously burned with high efficiency. In the liquid fuel combustion apparatus of the present invention, there is no need for a conventional mechanism for forming the inner primary air-turn airflow, which is necessary for the conventional apparatus. However, the conventional mechanism for forming the secondary air-turning airflow may be optionally added to the combustion apparatus of the present invention.

The liquid fuel combustion method of the present invention uses the above-described liquid fuel combustion apparatus of the present invention. In this method, liquid fuel is injected in a radial direction through a liquid fuel injection hole, and primary air is injected through outer and inner primary air injection holes parallel to the central axis direction of the liquid fuel injection pipe, whereby the injected liquid fuel flow is mixed with the outer and inner primary air flows to burn the liquid fuel.

In the method of the present invention, there is no limitation on the kind of the liquid fuel. Generally, the liquid fuel may be selected from liquid fuels such as heavy oil, waste oil and reclaimed oil, and slurry fuels containing combustible powders such as pulverized coal, coke powder and combustible plastic powder, or waste powders such as garbage, waste wood pieces (wood chips) and chaff. The medium of the slurry may be a liquid fuel (e.g., heavy oil, waste oil, or reclaimed oil) or water.

The method of the invention can be very advantageously used in rotary kilns for the production of cement clinker, magnesia clinker and lime. In this application, high temperature secondary air is fed into the rotary kiln through a product cooling device located downstream of the rotary kiln. The high temperature secondary air is mixed into a composite stream formed by the outer primary air jet, the fluid fuel jet and the inner primary air jet to efficiently combust the liquid fuel.

In the process of the present invention, the liquid fuel injection program through the liquid fuel injection holes 26a is controlled to such an extent that the particle diameter of the injected liquid fuel droplets is preferably 10 to 300 μm, more preferably 10 to 150 μm. The droplet diameter is determined according to the kind and viscosity of the liquid fuel and the form and size of the injection hole. The desired droplet size can be obtained by controlling the pressure applied to the liquid fuel and the form and size of the ejection holes.

The ejection speed of the outer and inner primary air at each ejection hole is preferably 200 to 300m/sec, more preferably 250 to 300m/sec, while the conventional ejection speed is about 100 m/sec. Under the above conditions, the primary air ratio (representing the ratio of the total amount of air injected through the liquid fuel injection holes and the outer and inner primary air injection holes to the theoretical amount of combustion air) can be reduced from 12 to 15% of the conventional value to 5 to 10%, preferably 6 to 9%. That is, in the combustion method using the combustion apparatus of the present invention, the jet momentum of the liquid fuel can be increased by 25 to 35% of the conventional momentum, while the secondary air accompanying momentum and accompanying time are maintained at a level similar to that of the conventional method.

The jet flow momentum of the liquid fuel and the accompanying momentum of the secondary air can be calculated in accordance with the above equations (1) and (2) in the same manner as the pulverized fuel.

In the method of the present invention, when the primary air injection velocity (U) is set_o) From about 100m/sec of the conventional method to 200 to 300m/sec to increase the momentum (G) of the jet stream_o) This increase, in turn, results in secondary air accompanying momentum (G)_e) Proportional to the momentum (G) of the jet_o) But is increased. In this case, when the secondary air accompanies momentum (G)_e) And accompanying time kept at a level similar to that of the conventional method, the mixing of the flame flow with air and the combustion in the initial stage are performed to a degree similar to that of the conventional method, and therefore the amount of primary air can be reduced. In this case, since the reduction in the amount of primary air can be compensated for by the high-temperature secondary air, the combustion speed can be increased and the combustion efficiency can be improved.

By using the liquid fuel combustion apparatus and method of the present invention, a combustion flame in the form of a narrow-angle short flame can be produced in a manner similar to that using pulverized fuel. Therefore, the swirl number (the swirl number is a dimensionless quantity expressing the strength of rotation defined by the above equation (3)) can be made zero and a natural jet flow can be formed. Also, in the conventional apparatus and method, there is a limit to the kind of liquid fuel that can be used. However, with the apparatus and method of the present invention, the range of liquid fuels that can be used can be expanded.

In the present invention, a pulverized fuel may be used together with a liquid fuel. FIG. 6 shows an illustrative side view of an embodiment of a furnace incorporating the hybrid combustion device of the present invention described above.

Referring to fig. 6, a cylindrical hybrid combustion apparatus 11b for supplying a pulverized fuel and a liquid fuel is inserted into a heating furnace such as a rotary kiln through a wall 12 of the heating furnace. This hybrid combustion apparatus, which will be described below with reference to fig. 7, includes: a pulverized fuel injection pipe 25 having an annular injection hole 26 for injecting pulverized fuel together with air for feeding the pulverized fuel; an inner primary air injection pipe 27 having a plurality of inner primary air injection holes 28 for injecting primary air and provided along an inner circumferential surface of the pulverized fuel injection pipe 25; an outer primary air injection pipe 23 having a plurality of outer primary air injection holes 24 for injecting primary air, provided along an outer circumferential surface of the pulverized fuel injection pipe 25; and a liquid fuel injection pipe 39 having liquid fuel injection holes 38 for injecting liquid fuel in the radial direction, provided inside the inner primary air injection pipe 24.

In fig. 6, in the end portion 13 of the hybrid combustion device 11b disposed outside the heating furnace, a pulverized fuel delivery pipe 14 for delivering a mixed flow of pulverized fuel together with pulverized fuel delivery air is provided, and the pulverized fuel delivery pipe 14 is connected to the above-mentioned pulverized fuel injection pipe. Meanwhile, a primary air delivery pipe 15 is provided in the end portion 13, and the delivery pipe is branched into an outer primary air delivery pipe 16 and an inner primary air delivery pipe 17, the outer primary air delivery pipe 16 being connected to the outer primary air ejection pipe, and the inner primary air delivery pipe 17 being connected to the inner primary air ejection pipe.

In the hybrid combustion device 11b of fig. 6, one or more liquid fuel delivery pipes 18a are disposed in the central portion of the device. Meanwhile, in the central portion, one or more heavy oil burners or gas burners for ignition may be provided.

In the hybrid combustion device of fig. 6, the pulverized fuel stream 19 is injected through an annular injection hole, the inner primary air straight jet 20 is injected inside the annular pulverized fuel stream, the outer primary air straight jet 21 is injected outside the annular pulverized fuel stream, and the radial liquid fuel injection jet 37 is injected inside the inner primary air straight jet, thereby forming a composite stream from the above streams, and the high-temperature secondary air 5 is mixed into the composite stream to combust the pulverized fuel and the liquid fuel.

The mixed combustion apparatus for pulverized fuel and liquid fuel of the present invention comprises: a pulverized fuel injection pipe having an annular injection hole for injecting pulverized fuel together with the pulverized fuel feed air; an outer primary air injection pipe having a plurality of outer primary air injection holes provided along an outer circumferential surface of the pulverized fuel injection pipe and capable of injecting primary air in the same direction as the pulverized fuel injection direction through the annular hole; an inner primary air injection pipe having a plurality of inner primary air injection holes provided along an inner peripheral surface of the pulverized fuel injection pipe, capable of injecting primary air in the same direction as the pulverized fuel injection direction through the annular injection holes; and a liquid fuel injection pipe having a liquid fuel injection hole provided inside the inner primary air injection pipe and capable of injecting the liquid fuel in a radial direction.

Meanwhile, the mixed combustion method for pulverized fuel and liquid fuel of the present invention uses the above-described mixed combustion apparatus for pulverized fuel and liquid fuel of the present invention, and includes: injecting pulverized fuel through an annular injection hole together with pulverized fuel delivery air; injecting primary air in the same direction as the pulverized fuel injection flow through a plurality of outer and inner primary air injection holes to form outer and inner primary air direct injection flows, and the pulverized fuel injection flow is interposed between the outer and inner primary air direct injection flows; and injecting liquid fuel in a radial direction through the liquid fuel injection hole, thereby mixing the pulverized fuel and the liquid fuel with the primary air flow to combust the pulverized fuel and the liquid fuel.

Fig. 7(a) and 7(B) show an explanatory cross-sectional side view and an explanatory front view, respectively, of an embodiment of a hybrid combustion apparatus for pulverized fuel and liquid fuel of the present invention. Fig. 7(a) is an illustrative cross-sectional side view of the apparatus shown in fig. 7(B) along bend line Z-Z'.

Referring to fig. 7(a) and 7(B), one outer primary air injection tube 23 is disposed inside the outermost peripheral wall 22 of the cylindrical mixed combustion apparatus, and in one injection end portion of the injection tube 23, a plurality of, for example, 5 to 20, preferably 8 to 18 outer primary air injection holes 24 are disposed. Inside the outer primary air injection tube 23, a pulverized fuel injection tube 25 for injecting pulverized fuel together with pulverized fuel carrying air is provided in a concentric circular relationship with the outer primary air injection tube 23, and in the end portion of the pulverized fuel injection tube, an annular injection hole is formed. Next, an inner primary air injection pipe 27 is provided inside the pulverized fuel injection pipe 25, and a plurality of, for example, 6 to 16, preferably 8 to 14 inner primary air injection holes 28 are formed in one end portion of the inner primary air injection pipe 27.

Inside the inner primary air injection tube 27, one or more (2 in fig. 7(a) and 7 (B)) liquid fuel injection tubes 39 are provided, and a liquid fuel injection hole 38 for injecting liquid fuel in the radial direction is formed in one end portion of each injection tube 39. As shown in fig. 7(a), in the liquid fuel injection hole 38, an outwardly expanding conical nozzle space is formed, and the liquid fuel is injected radially through the liquid fuel injection hole 38 and mixed with the primary air.

The above-described ring-shaped injection holes 26, outer primary air injection holes 24, and inner primary air injection holes 28 are formed in such a manner that the injection directions through these holes are identical (parallel) to each other. Thus, the pulverized fuel is injected through the annular injection hole 26 to form the pulverized fuel flow 19 having an annular cross section, and the liquid fuel delivered through the liquid fuel injection pipe 39 is injected in the radial direction through the liquid fuel injection hole. Secondly, the primary air is injected through the outer primary air injection holes 24 to form outer primary air straight jets which follow the outer side of the flow of powder fuel 19. At the same time, the primary air is injected through the plurality of inner primary air injection holes 28 to form a plurality of inner primary air straight jets that proceed along the inside of the flow of powder fuel 19 having an annular cross-sectional shape. The flow of pulverized fuel 19 is therefore interposed between the inner and outer primary air jets and is thus accelerated and diffused and burnt by mixing with the high-temperature secondary air passing through the outer primary air jets. In this case, since the outer primary air stream is injected at high velocity in the form of a direct stream, preferably a plurality of separate direct streams, high temperature secondary air can easily pass between the centers of the plurality of direct primary air streams to be efficiently mixed with the pulverized fuel stream 19 and the liquid fuel jet stream, thereby forming a combustion flame in the form of a narrow angle short flame and producing a high ignition temperature. At the same time, in this case, the direct inner primary air flow helps to promote the diffusion of the streams of powdered fuel 19 and liquid fuel 37, while at the same time creating a high temperature internal circulation flow in the combustion flame to stabilize the flame.

In the hybrid combustion apparatus of the present invention, there is no limitation in the form and size of the inner primary air injection holes 28 and the outer primary air injection holes 24. In general, the pitch circle diameter (P.C.D.) of the outer and inner primary air injection holes 28 and 24 is preferably 300 to 800 mm. Meanwhile, the liquid fuel injection holes 38 of the liquid fuel injection pipe 39 form an outwardly expanding conical injection nozzle. For example, if a C heavy oil is used as the liquid fuel, it is preferable to heat the C heavy oil to a temperature of 80 to 100 ℃ so as to reduce the viscous resistance of the fuel to 20 to 30cst and place it at 30 to 40kg/cm²G, under pressure.

As shown in fig. 7(a) and 7(B), it is preferable that the plurality of outer primary air injection holes 24 of the outer primary air injection pipe 23 and the plurality of inner primary air injection holes 28 of the inner primary air injection pipe 27 are respectively provided on two concentric circumferences of the outer and inner faces between which the annular hole 26 of the pulverized fuel injection pipe 25 is disposed. Meanwhile, it is preferable that the inner primary air injection holes 28 are located to be spaced apart from a straight line extending through the center point of the outer primary air injection holes 24 and the center point of the concentric circumference. Second, it is more preferable that each inner primary air injection hole 28 is disposed between a pair of straight lines 32 and 33, and the pair of straight lines 32 and 33 extend through the center point of each pair of adjacent outer primary air injection holes 24 and the center point 31 of the concentric circumference.

The above-described arrangement of the primary air injection holes contributes to reliably generating a swirl on the outer and inner sides of the annular flow of powder fuel. Preferably, the inner and outer primary air streams are comprised of a plurality of direct air streams. In this case, the surface area of the vortex becomes very large, and as a favorable result, the pulverized fuel and the liquid fuel can be vigorously burned with high efficiency. In the above-described hybrid combustion apparatus of the present invention, the conventional mechanism for forming the inner primary air turning airflow, which is necessary in the conventional apparatus, is not required. However, a mechanism for forming the inner primary air-turning airflow may be optionally added to the hybrid combustion apparatus of the present invention. Meanwhile, if necessary, one or more ignition burners (heavy oil burners or gas burners) may be provided in the central portion of the hybrid combustion apparatus of the present invention.

The mixed combustion method for pulverized fuel and liquid fuel of the present invention uses the pulverized fuel and liquid fuel mixed combustion apparatus of the present invention. In the method, pulverized fuel is injected together with air for feeding the pulverized fuel through an annular injection hole, primary air is injected through a plurality of outer and inner primary air injection holes in the same direction as the pulverized fuel injection holes to form outer and inner primary air direct airflows with the pulverized fuel injection holes therebetween, and liquid fuel is injected through liquid fuel injection holes in the radial direction and mixed with the primary air, thereby mixing and combusting the pulverized fuel and the liquid fuel.

In the mixed combustion method of the present invention, the mixed fuel is not limited. Typically, the pulverized fuel comprises a solid pulverized fuel, such as pulverized coal or coke powder. In addition, as the pulverized fuel, waste materials such as combustible plastic powder, waste garbage, waste wood chips (wood chips) and chaff can be utilized.

The kind of the liquid fuel used in the mixed combustion method of the present invention is not limited. It is preferable to use general liquid fuels such as heavy oil, waste oil and reclaimed oil and slurry fuels containing combustible powders such as slurry containing pulverized coal, coke powder, combustible plastic powder and combustible rubber powder. Meanwhile, as a medium of the slurry, water and liquid fuels (heavy oil, waste oil, and reclaimed oil) can be used.

The hybrid combustion method of the present invention can be very advantageously used in rotary kilns for producing cement Clinker (Clinker), magnesia Clinker and lime. In this case, high-temperature secondary air is fed into the rotary kiln from a product cooling apparatus disposed downstream of the rotary kiln. The high temperature secondary air is introduced into and mixed with a composite stream consisting of an outer primary air straight jet, a pulverized fuel stream having an annular cross-section, an inner primary air straight jet, and a radially expanding liquid fuel jet, while the pulverized fuel and the liquid fuel can be efficiently combusted.

In the mixed combustion method of the present invention, the pulverized fuel is preferably injected through the annular injection hole 26 at an injection speed of 30 to 50m/sec, more preferably 35 to 45m/sec, while the outer primary air and the inner primary air are respectively injected through the inner and outer injection holes preferably at an injection speed of 200 to 300m/sec, more preferably 250 to 300m/sec, whereas the conventional primary air injection speed is about 100 m/sec. Meanwhile, in the mixed combustion method of the present method, the droplet diameter of the liquid fuel injected through the injection hole is preferably controlled to 10 to 300 μm, more preferably to 10 to 150 μm. By performing the pulverized fuel injection, the primary air injection and the liquid fuel injection in the above-described manner, the primary air ratio, which represents the ratio of the total amount of primary air injected through the annular pulverized fuel injection holes and the outer and inner primary air injection holes to the theoretical combustion air amount, can be reduced from 20 to 25% of the conventional value to 8 to 15%, preferably 8 to 12%, while the reduction in the primary air amount is compensated for by the increase in the high-temperature secondary air amount, so that the combustion can be performed to such an extent that the combustion speed is increased, the combustion flame is formed in the form of a narrow-angle short flame, and the ignition point temperature can be satisfactorily increased without damage to the furnace wall. That is, in the combustion method using the hybrid combustion apparatus of the invention, the amount of the jet flow can be increased by 25 to 35% as compared with the conventional method, while the accompanying momentum and accompanying time of the secondary air are maintained at a level similar to that of the conventional method.

In the present invention, the injection pressure applied to the liquid fuel and the form and size of the injection hole, the injection speed, and the injection are appropriately controlled according to the kind and viscosity of the liquid fuelThe injection temperature can be adjusted to 10 to 300 μm in droplet size of the injected liquid fuel. The droplet diameter of the injected liquid fuel can be calculated according to the following equation:

d is the average droplet diameter [ m ]

V_eAs fuel injection velocity [ m/s ]]

δ_gIs the density of the ambient gas [ kg/m³]

δ_eAs fuel density [ kg/m ]³]

σ_eAs surface tension of fuel [ N/m ]]

D is the diameter of the injection hole [ m ]

d_maxIs the maximum droplet size [ m ]]

μ_eAs viscosity of fuel [ Pa.S ]]

The momentum of the jet flow and the accompanying momentum of the secondary air can be calculated according to the above equations (1) and (2).

In the hybrid combustion method of the present invention, the injection velocity (U0) of the primary air is increased from a conventional value of about 100m/sec to a level of 200 to 300m/sec, thereby increasing the momentum of the injection flow, the accompanying momentum (G) of the secondary air_e) With the momentum (G) of the jet_o) Increasing in proportion. However, when the secondary air accompanies the momentum (G)_e) And with the time kept at a level similar to that in the conventional method, the mixing of the flame jet with air and the combustion in the initial stage are achieved under conditions similar to those in the conventional method, and therefore, the amount of primary air can be reduced. In this case, the reduction in the amount of primary air is compensated for by the high-temperature secondary air, so the combustion speed increases and the combustion efficiency improves.

With the hybrid combustion apparatus and method of the present invention, it is possible to produce a combustion flame of a narrow-angle short flame type, so that the swirl number (which is a dimensionless quantity expressing the rotation intensity defined by the above equation (3)) can be made zero and the flame flow can be formed as a natural jet flow.

Examples of the present invention

Example 1 and comparative example 1

In example 1, a powder fuel combustion apparatus of the present invention as shown in fig. 2, 3(a) and 3(B) was used for a rotary kiln for calcining cement produced by the rotary kiln under the conditions shown in table 1. The results are shown in Table 1.

In comparative example 1, cement was produced using a conventional pulverized coal combustion plant under the conditions shown in table 1. The results are shown in Table 1.

TABLE 1

	Example 1	Comparative example 1
	Example 1	Comparative example 1	Production conditions calorific value of coal (kcal/kg) fineness of fine coal powder (% residue on mesh of 90 μm)	680010 to 20	680010 to 20
Primary air ratio of primary air turning velocity (m/sec) within primary air direct flow velocity (m/sec) within outer primary air direct flow velocity (m/sec) and pulverized coal flow velocity (m/sec)	250 to 300250 to 30030 to 50 has no more than 11	100 to 12080 to 030 to 500 to 8020		680010 to 20	680010 to 20
	250 to 300250 to 30030 to 50 has no more than 11	100 to 12080 to 030 to 500 to 8020	As a result of the ratio of the momentum of the jet(s) ((^)₁The ratio of secondary air to accompanying momentum (^)₁Ratio of secondary air accompanying time (^*)₁Swirl number (SW) productivity (T/day) combustion ratio (kcal/kg) CO amount at the furnace end temperature (. degree. C.) (%)	125-135100-11090-100028007191040 were not detected	1001001000.03-0.10279574410901-2

[ Table 1 Note ]

(^*)₁… Each of the values of example 1 is a relative value to the value of 100 of comparative example 1

As is clear from table 1, in example 1, even when the secondary air accompanying momentum and accompanying time are maintained at similar levels as those of comparative example 1, the momentum of the jet flow can be increased by 25 to 35%, the number of vortices can be reduced, the productivity can be improved, the combustion ratio can be lowered, and the furnace end temperature can be lowered.

Example 2 and comparative example 2

In example 2, a liquid fuel combustion apparatus of the present invention as shown in fig. 4, 5(a) and 5(B) was used for a rotary kiln for calcining cement produced by the rotary kiln under the conditions shown in table 2. The results are shown in Table 2.

In comparative example 2, cement was produced using a conventional heavy oil combustion apparatus under the conditions shown in Table 2. The results are shown in Table 2.

TABLE 2

	Example 1	Comparative example 1
	Example 1	Comparative example 1	Production conditions Heat value of liquid Fuel (C heavy oil) (kcal/kg)	10,200	10,200
Primary air turning flow velocity (m/sec) primary air ratio within droplet size (μm) of liquid fuel within primary air direct flow velocity (m/sec) within external primary air direct flow velocity (m/sec)	250 to 300250 to 300150 has no 7	100 to 12080 to 01500 to 8015		10,200	10,200
	250 to 300250 to 300150 has no 7	100 to 12080 to 01500 to 8015	As a result of the ratio of the momentum of the jet(s) ((^)₁The ratio of secondary air to accompanying momentum (^)₁Ratio of secondary air accompanying time (^*)₁Amount of CO at calorific value (kcal/kg) furnace end (%)	125-135100-11090-10002880719 were not detected	1001001000.03-0.1027957441-2

(^*)1: based on the value of 100 in comparative example 2

As is clear from table 2, in example 2, even when the secondary air accompanying momentum and accompanying time were maintained at similar levels as in comparative example 2, the momentum of the jet flow could be increased by 25 to 35%, the number of vortices could be reduced, the productivity could be improved, the combustion ratio could be lowered, and the furnace end temperature could be lowered.

Example 3 and comparative example 3

In example 3, a hybrid combustion apparatus of the present invention as shown in FIGS. 6, 7(A) and 7(B) was used for a rotary kiln for calcining cement produced by the rotary kiln under the conditions shown in Table 3. The results are shown in Table 3.

In comparative example 3, cement was produced using a conventional pulverized coal and liquid fuel mixed combustion apparatus under the conditions shown in Table 3. The results are shown in Table 3.

TABLE 3

	Example 1	Comparative example 1
	Example 1	Comparative example 1	Production conditions calorific value of coal (kcal/kg) fineness of fine coal powder (% residue on mesh of 90 μm)	680010 to 20	680010 to 20
Primary air jet velocity (m/sec) in outer primary air jet velocity (m/sec) in pulverized coal velocity (m/sec) in primary air turning velocity (m/sec)	250 to 300250 to 30030 to 50	100 to 12080 to 030 to 500 to 80		680010 to 20	680010 to 20
	250 to 300250 to 30030 to 50	100 to 12080 to 030 to 500 to 80	Liquid fuel calorific value (kcal/kg) droplet diameter (mum)	C heavy oil 10,200150	C heavy oil 10,200150
Primary air ratio	11	20		C heavy oil 10,200150	C heavy oil 10,200150
Primary air ratio	11	20	As a result of the ratio of the momentum of the jet(s) ((^)₁The ratio of secondary air to accompanying momentum (^)₁Ratio of secondary air accompanying time (^*)₁Calorific value (kcal/kg) generated by vortex number (SW) productivity (T/day) CO amount at furnace end temperature (. degree. C.) (%)	125-135100-11090-100028807191040 were not detected	1001001000.03-0.10279574410901-2

As is clear from table 3, in example 3, even when the secondary air accompanying momentum and accompanying time were maintained at similar levels as in comparative example 3, the momentum of the jet flow could be increased by 25 to 35%, the number of vortices could be reduced, the productivity could be improved, the combustion ratio could be lowered, and the furnace end temperature could be lowered.

INDUSTRIAL APPLICABILITY

With the combustion apparatus and method of the present invention, a pulverized fuel or a liquid fuel or a pulverized fuel and a liquid fuel can be combusted to form a flame of a short flame type with a narrow angle, and the ignition temperature can be sufficiently increased without damaging the furnace wall. Therefore, the practical effects of the apparatus and method of the present invention are very good.

Claims

1. A fuel combustion apparatus comprising: a mechanism for injecting at least one fuel selected from the group consisting of pulverized fuel and liquid fuel; an outer primary air injection pipe (23) provided on the outer side of the fuel injection mechanism and having a plurality of outer primary air injection holes (24) through which primary air is injected in parallel with the fuel injection direction of the fuel injection mechanism; and an inner primary air injection pipe (27) provided on the inside of the fuel injection mechanism and having at least one inner primary air injection hole (28) through which primary air is injected in parallel with the fuel injection direction of the fuel injection mechanism.

2. The fuel combustion apparatus as claimed in claim 1, wherein the fuel injection mechanism includes a pulverized fuel injection pipe (25) having an annular injection hole (26) through which pulverized fuel is injected together with air for feeding pulverized fuel.

3. The fuel combustion apparatus as set forth in claim 2, wherein the plurality of air injection holes (24) of the outer primary air injection tube (23) and the plurality of injection holes (28) of the inner primary air injection tube (27) are arranged on the concentric circumference in such a manner that the annular injection hole of the pulverized fuel injection tube is positioned between the outer air injection hole and the inner air injection hole, and the inner primary air injection hole is positioned apart from a straight line extending through the outer primary air injection hole center point and the concentric circumference center point.

4. The fuel combustion apparatus as claimed in claim 1, wherein the fuel injection mechanism includes a plurality of liquid fuel injection pipes (25a) having liquid fuel injection holes (26a) for injecting the liquid fuel in the radial direction, which are arranged on one and the same circumference.

5. The fuel combustion apparatus as claimed in claim 4, wherein the inner primary air injection pipe (27) has a plurality of inner primary air injection holes (28), and the plurality of inner primary air injection holes 28 and the plurality of outer primary air injection holes (24) are respectively arranged on concentric circumferences whose center points are identical to a center hole (31) of a circumference on which the plurality of liquid fuel injection holes (26a) are arranged.

6. A fuel combustion apparatus as claimed in claim 4, wherein the inner primary air injection tube (27) has an inner primary air injection hole (28); the center point of the inner primary air injection hole (28) is the same as the center hole (31) of the circumference on which the plurality of liquid fuel injection holes (26a) are arranged; and the plurality of outer primary air injection holes (24) are arranged on a concentric circle having the same center point as the center point (31) of the circle on which the plurality of liquid fuel injection holes (26a) are arranged.

7. The fuel combustion apparatus as set forth in claim 5, wherein the inner primary air injection holes (28) are located apart from a straight line extending through a center point (31) of a circumference on which the liquid fuel injection holes (26a) are arranged and a center point of the outer primary air injection holes (24).

8. A fuel combustion device as claimed in claim 5 or 6, wherein the liquid fuel injection holes (26a) are located spaced from a line extending through the centre point of the outer and inner primary air injection holes (24,28) located closest to one of the liquid fuel injection holes.

9. A fuel combustion device as claimed in claim 1, wherein the fuel injection means comprises a pulverized fuel injection pipe (25) having an annular injection hole (26) for injecting the pulverized fuel together with air for feeding the pulverized fuel, and an additional fuel injection device provided on the inner side of the outer primary air injection pipe (27) and comprising at least one liquid fuel injection pipe (39) having a liquid fuel injection hole (38) through which the liquid fuel is injected in the radial direction.

10. The fuel combustion apparatus as claimed in claim 9, wherein the plurality of outer primary air injection holes (24) of the outer primary air injection pipe (23) and the plurality of inner primary air injection holes (28) of the inner primary air injection pipe (27) are arranged on outer and inner concentric circumferences, respectively, with the annular injection hole (26) of the powder fuel injection pipe (25) interposed therebetween, and the inner primary air injection holes (28) are located apart from a straight line extending through a center point of the outer primary air injection holes (24) and a center hole of the concentric circumferences.

11. A method of combusting fuel using the fuel combustion apparatus of claim 1, comprising: injecting at least one selected component from the group consisting of pulverized fuel and liquid fuel through the fuel injection mechanism; and injects primary air in the same direction as the fuel injection direction through the outer and inner primary air injection holes, thereby forming outer and inner primary air injection jets with the fuel injection jet interposed therebetween.

12. A method of combusting pulverized fuel using the fuel combustion apparatus as claimed in claim 2 or 3, comprising: injecting a pulverized fuel through the annular fuel injection hole together with air for delivering the pulverized fuel; and injecting primary air through the outer and inner primary air injection holes in the same direction as the pulverized fuel injection flow to form inner and outer primary air straight injection flows with the pulverized fuel injection flow interposed therebetween.

13. A fuel combustion method as defined in claim 12, wherein, when the pulverized fuel is combusted in the rotary kiln, a high-temperature secondary air flow is introduced into the rotary kiln from a product cooling system disposed downstream of the rotary kiln; and the introduced high-temperature secondary air is mixed into the combustion flame of the pulverized fuel.

14. The fuel combustion method as set forth in claim 12, wherein the pulverized fuel is injected through the annular fuel injection hole at an injection speed of 30 to 50m/sec, and the direct flows of the outer and inner primary air are injected through the air injection hole at an injection speed of 200 to 300 m/sec.

15. The fuel combustion method as set forth in claim 12, wherein the total amount of air injected through the annular powder fuel injection holes and the outer and inner primary air injection holes is controlled to be within 8 to 15% of the theoretical combustion air amount.

16. A fuel combustion method using the fuel combustion apparatus according to any one of claims 4 to 8, comprising injecting liquid fuel in a radial direction through the liquid fuel injection hole; primary air is injected through the outer primary air injection hole and the inner primary air injection hole in a direction parallel to the central axis of the liquid fuel injection hole, whereby the injected liquid fuel stream is mixed with the direct outer and inner primary air streams and combusted in the mixed stream.

17. A method of combusting fuel as claimed in claim 16, wherein the liquid fuel is selected from the group consisting of liquid fuel and slurry fuel containing combustible powder.

18. The fuel combustion method as set forth in claim 16, wherein when the liquid fuel is combusted in the rotary kiln, high-temperature secondary air is introduced into the rotary kiln from a product cooling system disposed downstream of the rotary kiln, and the introduced high-temperature secondary air is mixed into the combustion flame of the liquid fuel.

19. The fuel combustion method as set forth in claim 16, wherein the direct flows of the outer and inner primary air are injected through the inner and outer injection holes at injection speeds of 200 to 300m/sec, and the liquid fuel droplet diameter injected through the liquid fuel injection hole is controlled to be in the range of 10 to 300 μm.

20. The fuel combustion method as set forth in claim 16, wherein the total amount of air injected through the liquid fuel injection holes and the outer and inner primary air injection holes is controlled to 5 to 10% of the theoretical combustion air amount.

21. A fuel combustion method using the fuel combustion apparatus as claimed in claim 9 or 10, wherein the pulverized fuel is injected together with the pulverized fuel delivery air through an annular fuel injection hole; the primary air is injected along the same direction with the jet flow of the powdered fuel through a plurality of outer and inner primary air injection holes, so that inner and outer primary air direct jet flows are formed, and the jet flow of the powdered fuel is arranged between the two air flows; a liquid fuel is injected radially through the liquid fuel injection hole to be mixed into the primary air flow; the pulverized fuel and the liquid fuel are co-combusted.

22. A method of combusting fuel as defined in claim 21, wherein the liquid fuel is selected from the group consisting of liquid fuel and slurry fuel containing combustible powder.

23. A fuel combustion method as set forth in claim 21, wherein when the pulverized fuel and the liquid fuel are combusted together in the rotary kiln, high-temperature secondary air is introduced into the rotary kiln from a product cooling system disposed downstream of the rotary kiln, and the introduced high-temperature secondary air is mixed into the combustion flames of the pulverized fuel and the liquid fuel.

24. The fuel combustion method as claimed in claim 21, wherein the pulverized fuel is injected through the annular fuel injection hole at an injection speed of 30 to 50 m/sec; the outer and inner primary air direct streams are ejected through the inner and outer ejection holes at an ejection speed of 200 to 300 m/sec; and the liquid fuel droplet particle diameter injected through the liquid fuel injection hole is controlled to 10 to 300 μm.

25. The fuel combustion method as set forth in claim 21, wherein the total amount of air injected through the annular pulverized fuel injection holes and the outer and inner primary air injection holes is controlled to 8 to 15% of the theoretical combustion air amount.