JPH0441791A - Dispersion of black liquor and device therefor - Google Patents

Abstract

PURPOSE:To prevent dust from attaching itself to a heat transfer tube and to uniform space dispersion amount of black liquor in a furnace by making a jetting hole of black 1iquor into a crescent-shaped annular passageway. CONSTITUTION:A contraction part 7 of a jetting hole having a hole shrinking in the vicinity of an outlet of a black liquor jetting nozzle 1 to pressurize and feed black liquor and a jetting nozzle 4 of straight pipe part is opened at the tip end of the contraction part. An opening part of the jetting hole 4 is made into a crescent-shaped nonconcentric shape by fixation of a nonconcentric inserting material 6, jetted black liquor is made into an approximately uniform liquid film by a radiated collision plate 3 to disperse and radiate a great number of particles of black liquor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for dispersing black liquor for a recovery boiler, and in particular to a highly concentrated black liquor for a high temperature/high pressure recovery boiler. The present invention relates to a black liquor dispersion method and apparatus capable of preventing excessive scattering of char dust and forming a stable char bed at the bottom of a furnace.

[Prior Art] In a recovery boiler in a paper mill, pulp black liquor is injected under pressure into the boiler furnace using a device called an oscillator and dried. The combustion air blown in from the bottom or wall of the furnace transports the chi particles to the top of the furnace where they are combusted, and the heat is absorbed through the water-cooled walls and heat transfer tubes to create steam (for process or power generation). . Recently, with the goal of improving the efficiency of boilers, there has been a demand for high-quality steam production at higher temperatures and higher pressures. It is becoming essential to improve the functionality of

FIG. 9 schematically depicts the inside of the recovery boiler. A black liquor dispersion device 902 for a recovery boiler in which the valve black liquor is roughly precessed or oscillated in the direction inside the furnace.
(called an oscillator) into the furnace. A pair of black liquor dispersion devices 902 for the recovery boiler are installed facing each other in the lower part of the furnace (although there are exceptions).

In general, black liquor has a heavy specific gravity of about 1.5 and high viscosity (almost a solid at room temperature), so it is heated to over 120°C. The black liquor pressure injection nozzle for spraying and dispersing black liquor is preferably inserted into the furnace, so it is desirable to have a simple structure and excellent durability.

Now, the black liquor droplets that are blown into the furnace from the dispersion device are
The droplet diameter and the amount of dispersion (flux of black liquor droplets per unit area and unit time relative to the furnace bottom position) are the issues. In the case of non-uniform size spray in which a large number of fairly small droplets are mixed in the droplet group, the microparticles become suspended as dust and adhere to the boiler furnace and the downstream heat transfer tube group. If the amount of adhesion exceeds the limit, the boiler combustion gas passage will become clogged, making normal continuous operation impossible. In addition, if the dispersion of black liquor in the furnace space is too large, the charbed 9 at the bottom of the furnace
The formation of 12 becomes extremely unstable.

That is, when char is concentrated and deposited on the furnace wall side, problems arise such that the primary air nozzle 903 becomes clogged and the char bed 912 tends to collapse discontinuously. In such a state, fluctuations in the heat load within the furnace increase, making it impossible to function as a boiler.

As mentioned above, it can be said that the performance of recovery boilers is highly dependent on black liquor dispersion technology.

[Problem to be solved by the invention]

The structure of a conventional black liquor dispersion device is shown in FIGS. 10 and 11. FIG. 10 is a sectional view from all directions, and FIG. 11 is a view of the homeland from above. At the tip of the nozzle 102 for spraying the black liquor 101 under pressure, there is a black liquor jet hole 103 having a circular cross section.
has an opening, and the black liquor 101 injected from there passes through the circular radiation collision plate 10 provided at an angle to the nozzle 102.
5, it splits into droplets and is dispersed into the furnace.

In the above-mentioned conventional black liquor dispersion device for a recovery boiler, as shown in Fig. 13, there is a large variation in the droplet diameter within the fan-shaped spray stream, and while there are many coarse droplets, on the other hand, there are many small droplets. Droplets also occur in large quantities.

The coarse droplets 107 are generated by the splitting of the thick rim 106 at the peripheral edge of the black liquid film. On the other hand, the finer droplet 110 at the center of the liquid film grows from the fine aerodynamic turbulence 108 created on the surface of the black liquid film, which splits into a string-like liquid column 109. Furthermore, it is produced by atomizing the liquid column so that it is elongated with a constriction. This tendency for the splitting phenomenon to be clearly different between the peripheral edge and the center of the liquid film becomes especially noticeable in large-capacity black liquor dispersion devices that spray a large amount of black liquor per bottle. On the other hand, this tendency is more pronounced in recent black liquors that are concentrated to a higher concentration and used in a highly viscous state. The minute black liquor droplets float upward to the upper part of the recovery furnace, become adhesive dust, and adhere to the heat transfer tubes.

Under such conditions, the furnace is likely to become clogged, making stable continuous operation of the recovery furnace impossible over a long period of time.

There is also a problem in that the dispersion flow rate (droplet flux) distribution of black liquor droplets is significantly biased in the circumferential direction of the fan-shaped spray.

In other words, the black liquor droplets concentrate only on both outer peripheral edges of the fan-shaped spray (because coarse droplets concentrate as shown in Figure 13), and this phenomenon causes the formation of stable charbed at the bottom of the furnace. This was causing the problem of not being able to do so. This tendency has also become stronger with the recent use of highly concentrated black liquor.

Prior art attempts to promote the splitting of black liquor include
As shown in the figure, there is a device that premixes a control fluid 126 such as steam into a black liquor 122 that is injected under pressure.
-159609), and in this method, the control fluid 1
As a result of the action of 26, the black liquor 122 is already split at the nozzle portion, and an inefficient phenomenon occurs in which the once split black liquor coalesces on the plate 124. Another problem is that the dispersion state of the black liquor tends to become unstable due to the intermittent breakup of vapor bubbles in the nozzle portion 123.

The above-mentioned problems have delayed technological progress in improving the temperature, pressure, and efficiency of recovery boilers. The purpose of the present invention is to eliminate the above-mentioned problems, promote high efficiency operation of a recovery boiler, suppress dust adhesion to heat transfer tubes, and provide a recovery boiler capable of stable combustion over a long period of time in a stable state. An object of the present invention is to provide a black liquor dispersion device.

[Means to solve the problem]

The problem with the prior art described above is that pressurized black liquor is injected from the jet hole at the tip of the black liquid flow path in the black liquid jet nozzle main body, and the jetted black liquor is formed at a predetermined inclination angle with respect to the jetting direction. In a black liquor dispersion method in which the black liquor is received by a collision plate and dispersed and emitted in granular form, the black liquor jetting hole is formed into a crescent-shaped annular passage, so that the black liquor injected spreads as a nearly uniform radial liquid film on the collision plate. The black liquor dispersion method is characterized in that the black liquor is then dispersed and radiated as a large number of black liquor particles, and the black liquor dispersion method is characterized in that the black liquor is dispersed and radiated as a large number of black liquor particles. A black liquor jetting nozzle body that jets black liquor through a hole, and a collision plate that is provided at a predetermined angle of inclination with respect to an extension of the central axis of the jetting hole and that disperses and radiates the jetted black liquor in the form of particles. The problem is solved by a black liquor dispersing device characterized in that the dispersing device is provided with an insert in the spout hole that is smaller than the diameter of the hole.

[Effect]

The black liquid ejected from the annular nozzle collides with the radiation collision plate in the form of a "chikuwa"-like liquid film (strictly speaking, the annular nozzle is non-concentric, so it becomes a "chikuwa" with uneven thickness). Therefore, a more uniform liquid film is formed in the form of a radiation collision plate, and the droplet dispersion flow rate and droplet size become more uniform in the circumferential direction than in the conventional method. In addition, a thicker jetted liquid stream than before is supplied to the center line of the central part of the radiation collision plate, while a thinner jetted liquid stream is supplied to both left and right ends, so many coarse droplets are concentrated at both left and right ends. In other words, fine droplets that would carry over to the upper part of the furnace are no longer generated on the central axis.

As described above, the technology that equalizes both the dispersion flow rate and the droplet diameter in the circumferential direction will lead to higher concentration, resulting in higher viscosity and uneven splitting. This makes it suitable for liquid use.

〔Example〕

The structure of a black liquor dispersing device embodying the present invention is shown in FIG. 1, FIG. 2-1, and FIG. 2-2. FIG. 1 is a sectional view of the device seen from above, FIG. 2-1 is a sectional view seen from the side, and FIG. 2-2 is a front view.

The black liquor dispersing device according to this embodiment basically comprises a black liquor injection nozzle body 1 to which black liquor 2 is supplied under pressure, and a radiation collision plate 3 with which the injected black liquor collides. The radiation collision plate 3 is joined to the lower part of the black liquor injection nozzle body 1 by welding. The black liquor injection nozzle main body 1 has a flow path 1a through which the black liquor 2 is supplied, and there is a constricted part 7 of the nozzle hole whose diameter contracts near the outlet, and at the tip thereof there is a nozzle hole consisting of a short straight pipe part. 4 is open. Inside this spout 4,
A substantially cylindrical non-concentric insert 6 is attached. Therefore, as shown in Fig. 2-2, the opening of the ejection hole 4 has a crescent-shaped non-concentric annular shape that is symmetrical in the left-right direction, and the opening width is wide at a position far from the radiation collision plate 3, and the insert 6 to the central axis 8 of the black liquid injection nozzle body l. The non-concentric insert 6 is configured to close the opening of the jet hole 4, but in this embodiment, the cross-sectional area of the blocked portion and the opening portion are approximately equal. The area of the opening portion is set to a size commensurate with the required black liquor jetting flow rate. As shown in FIG. 2-1, this non-concentric insert 6 has a rounded tip and tapers toward the upstream side within the constricted portion 7 of the jet hole 4 and toward the downstream side above the radiation collision plate 3. It sticks out like it's hanging out.

This is to prevent, as much as possible, sudden changes in the black liquor flow rate or other flow conditions that would adversely affect the splitting state.

FIGS. 3 and 4 schematically depict the black liquor splitting phenomenon in a black liquor dispersion device embodying the present invention. Figure 3 shows the recovery from above, and Figure 4 shows the recovery from the side. In this embodiment, black liquor 22 is blown out from non-concentric annular orifices 5 and non-concentric inserts 6 are installed projecting towards the radiation impingement plate 3. Therefore, the black liquor 2 collides with the tip side portion of the radial collision plate 3, as shown as the black liquor collision surface C (m-shaped hatched area) in FIG.
It does not spread into a thin liquid film on the collision surface, but breaks up into droplets as ligaments a from the edges of the radiation collision plate 3. Incidentally, in the conventional example whose phenomenon is shown in FIG.
A black liquid film forms on top, which splits into thin string-like liquid columns, which in turn form smaller droplets. Such small droplets carry over to the upper part of the furnace and cause clogging of the heat transfer tube group. It breaks up and produces fairly coarse droplets. In other words,
There are small disturbances 108 (
(see Figure 13), it splits into ligament a. Compared to the conventional method shown in Fig. 13,
On the circumference of the radiation collision plate, the size and dispersion flow rate (black liquor droplet flux) of the black liquor droplets generated by the splitting are fairly uniform.

In order to actually confirm whether the black liquor droplets dispersed throughout the furnace were uniform in size, changes in the average diameter of the black liquor droplets in the furnace width direction were investigated. Figure 5 summarizes the changes in the black liquor droplet diameter d3□ in the width direction of the furnace, and shows the embodiment of the present invention (Figures 1 and 2) and the conventional example (the structure is shown in Figure 10). This is a comparison of the characteristics of d on the vertical axis. teeth,
At the central axis, the droplet diameter d obtained with the conventional dispersion device,
□, divided by C and expressed as dimensionless. In the case of the conventional type, a3Z is quite large on the furnace wall side. On the other hand, in the center part (lsz is small and there is a significant deviation in the furnace width direction.On the other hand, in the example of the present invention, dSZ is considerably uniform and it is seen that it is greatly improved.

The experimental results shown in FIG. 6 show the black liquor dispersion flow rate in the furnace width direction, and compare the present invention example with the conventional example. Similar to the results of the average droplet diameter dSZ, it can be seen that black liquor can be sprayed and dispersed more evenly in the furnace by using the example of the present invention.

The effect of improving the black liquor injection dispersion performance as described above results from a reduction in the amount of dust adhering to the heat exchanger tube array in the upper part of the furnace. FIG. 7 shows the relationship between the black liquor temperature and the amount of dust attached, and shows the relationship between the black liquor dispersion device f (FIGS. 1 and 2) according to the present invention and the conventional device M ( Figures 10 and 11
This is a comparison with that in Figure). However, the horizontal axis is divided by the standard temperature, and the vertical axis is divided by the amount of dust attached when using the conventional method at the standard temperature, so that both are dimensionless. Generally, as the black liquor temperature increases, the viscosity decreases rapidly, making it easier to generate fine droplets and increasing the amount of dust attached. In the conventional method, the amount of fine droplets 110 increases (FIG. 13). On the other hand, in this example, as shown in Fig. 3, since the rim a is also created in the center, the amount of droplets carried over to the top of the column is small, and even at high black liquor temperatures, the amount of dust attached is small. was able to suppress the increase in

The experimental results shown in Figure 8 summarize the changes in the amount of dust adhesion with respect to the amount of primary air (the amount of primary air 904 blown along the surface of the charbed 912 from the primary air hole 903 in Figure 9). It is something.

As in the conventional method, if there are many small droplets in the center of the furnace, they are likely to be carried over to the upper part of the furnace, so as the amount of primary air increases, the amount of dust adhering to the heat exchanger tubes and furnace walls increases. go. In contrast, by making the droplet diameter at the center of the furnace uniform,
In this example, the amount of dust attached was reduced by about 25% when compared with the same amount of primary air (experimental results shown in Figure 5).
Can be reduced.

The above are two examples limited to the evaluation of the amount of dust adhesion, but the effects of the present invention have been demonstrated. The effectiveness of the present invention is particularly enhanced when a highly viscous and highly concentrated black liquor is used.

The injection device according to the present invention, like the black liquor dispersion device targeted specifically, requires a droplet generation technology that allows the dispersed droplets to be relatively uniform and neither too small nor too coarse. It is possible to apply it to what is being done. For example, it can be applied to a method of generating droplets from molten pig iron slag. Molten slag has high viscosity and high specific gravity, etc.
It has many similar physical properties (however, its specific gravity is much higher than that of black liquor). In the case of slag granulation, the means for black liquor which is the object of the present invention alone are insufficient, and it is necessary to assist the splitting and cooling effects with water or air currents. The slag formed into granules is
It is also easier to handle and is expected to be used effectively as a building material and raw material for concrete.

〔Effect of the invention〕

By carrying out the present invention, the amount of spatial distribution of black liquor in the recovery boiler furnace becomes uniform, the layer height and temperature of the bottom charbed are stabilized, and the droplets of black liquor dispersed in the furnace become uniform. The size of the particles is made uniform, and the amount of dust adhering is reduced because the number of scattered fine droplets is reduced. Therefore, the number of times the soot blowing device is used for the heat transfer tubes can be reduced, and the amount of steam used can be reduced.

[Brief explanation of drawings]

FIGS. 1, 2-1, and 2-2 are explanatory diagrams of an embodiment of the black liquor dispersion device according to the present invention, and FIGS. 3 and 4 are explanatory diagrams of the black liquor injection situation in the above embodiment. , FIG. 5 is a distribution diagram of the diameter of black liquor droplets in the furnace in the present invention and the prior art;
FIG. 6 is a diagram showing the amount of black liquor dispersed into the furnace in the present invention and the prior art, FIGS. 7 and 8 are comparison diagrams of the amount of dust adhesion in the present invention and the prior art, and FIG. FIG. 10, FIG. 11, and FIG. 12 are explanatory diagrams of a conventional black liquor dispersion device, and FIG. 13 is an explanatory diagram of a black liquor splitting phenomenon in the prior art. 1... Black liquor injection nozzle body, 2... Black liquor, 3...
Radiation collision plate, 4... Ejection hole, 5... Eccentric annular ejection hole, 6... Eccentric insert, 7... Contraction part of injection hole, 901
...Recovery boiler body, 902...Black liquor dispersion device for recovery boiler, 903...Primary air hole, 904...Primary air, 905...Secondary air hole, 906...2 Air, 907...Floating dust, 908...Superheater, 91
2...Charbetsudo. Applicant Babcock Hitachi Co., Ltd. Agent Patent Attorney Takeshi Kawakita The vertical axis in the width direction of the long furnace is made dimensionless by the dispersed flow rate qdc at the position of the conventional dispersion device. C: Collision surface of black liquor 6: Non-concentric insert 9: Central axis of non-concentric insert Fig. View from B-B' direction Fig. Non-dimensional dust adhesion Fig. Fig. Non-dimensional in furnace width direction Amount of dust attached Primary air hole Primary air Secondary air hole Secondary air Floating dust Superheater Subot Upper drum 9] 3: Black liquor droplet group 9] 4: Furnace bottom 101: Black liquor 102: Black liquor pressurization Spray nozzle 103: Black liquid jet hole 104: Nozzle center IL]05: Radiation collision plate 10゛Figure B-B' direction view No. 11 A-A' direction view"B

Claims (4)

[Claims] (1) Pressurized black liquor is injected from the outlet at the tip of the black liquor flow path in the black liquor injection nozzle body, and this injected black liquor is received by a collision plate having a predetermined inclination angle with respect to the injection direction to form particles. In the black liquor dispersion method, the black liquor jetting hole is formed into a crescent-shaped annular passage, so that the jetted black liquor expands as a nearly uniform radial liquid film on the collision plate, and then forms a large number of black liquors. A black liquor dispersion method characterized in that the black liquor is dispersed and radiated as liquid particles. (2) a black liquor injection nozzle body that has a black liquor flow path inside and sprays pressurized black liquor through a jet hole at the tip of the black liquor flow path;
In a black liquor dispersion device equipped with a collision plate which is provided at a predetermined angle of inclination with respect to the extension of the central axis of the nozzle hole and which disperses and radiates the injected black liquor in the form of particles, the black liquor dispersion device is provided with a collision plate having a size smaller than the diameter of the hole in the nozzle hole. A black liquor dispersion device characterized by being provided with an insert. (3) The black liquor dispersing device according to claim (2), wherein the insert body is provided inscribed in the ejection hole. (4) The black liquor dispersing device according to claim 2 or 3, wherein the insert extends to the collision surface of the collision plate.