JP2000169196A - Rotary kiln for cement production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and stably supply relatively large combustible waste to a region sufficiently remote from the downstream end of a kiln by using a nozzle with a straight tube part having a specified length from the front end as a throwing nozzle. SOLUTION: A nozzle with a straight tube part having >=5 m, preferably >=7 m length L from the front end is used as a nozzle 4 for throwing combustible waste disposed with a main burner 3. Since the nozzle can impart 20-100 m/sec velocity to combustible waste blown from the front end of the nozzle, the waste can be reliably and stably thrown and dropped into the optimum throwing region located in the range of 20-50 m from the downstream end of a kiln. The combustible waste is not limited if it can be thrown into the kiln by an air flow but the waste having 0.5-30 g mass and 1-50 mm size is preferable. The throwing nozzle 4 is preferably disposed so as to align the front ends of the nozzle 4 and the main burner 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel rotary kiln for cement production (hereinafter simply referred to as a kiln) having a nozzle for charging combustible waste by air flow.
More specifically, the present invention relates to a rotary kiln for cement production having a combustible waste introduction nozzle capable of reliably introducing combustible waste into a kiln firing zone.

[0002]

2. Description of the Related Art A method for producing a cement clinker in which combustible waste is introduced into a kiln by airflow and burned is known, for example, from Japanese Patent Publication No. 57-17867. In this method, crushed combustible waste is put into a kiln firing zone together with air and burned, and the calorie is used for the production of clinker.

However, flammable waste such as waste plastic is generally thrown into a kiln in a relatively large crushed state due to the economics of crushing. The combustion proceeds. By ambient combustible waste is burning a reducing atmosphere, resulting Fe ⁺³ of the baked product in which calcium oxide unreacted relatively large amount remaining in the clinker is reduced unfavorably There is a problem that minerals are generated.

[0004] As a method for solving such a problem, a position where the combustible waste is thrown into the kiln by an air current and dropped is set to a region where the combustible waste is sufficiently exposed to an oxidizing atmosphere after the fall (hereinafter referred to as an optimum charging region). ) Has been proposed. That is, even if a part of the sintering zone in the kiln becomes a reducing atmosphere due to the introduction of flammable wastes by the implementation of the above method, it is obtained by sintering the object to be baked in an oxidizing atmosphere thereafter. The quality of the resulting cement clinker is prevented from deteriorating.

[0005]

However, the above-mentioned optimum charging area varies depending on the size of the kiln,
Generally, the combustible waste is located at a position 20 to 50 m from the downstream end of the cement clinker in the kiln at the take-out side of the cement clinker. However, when the combustible waste is supplied into the kiln as described above, there is a problem in that the drop position of the combustible waste varies, and a large amount of carrier gas is required to put the combustible waste sufficiently far from the downstream end of the kiln. .

Accordingly, an object of the present invention is to provide an injection nozzle capable of accurately and stably supplying the relatively large combustible waste sufficiently far from the downstream end of the kiln in the kiln. A rotary kiln for cement production.

[0007]

Means for Solving the Problems The present inventors have intensively studied to achieve the above object. As a result, the present inventors have found that the object can be achieved by using a nozzle having a straight pipe portion with a specific length from the nozzle tip as a combustible waste input nozzle attached to the main burner,
The present invention has been proposed.

That is, according to the present invention, in addition to the main burner,
A rotary kiln for cement production having a nozzle for charging combustible waste by airflow, wherein a nozzle having a straight pipe portion having a length from the tip of at least 5 m is used as the charging nozzle. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a kiln of the present invention will be described with reference to FIG. 1 showing a typical embodiment thereof, but the present invention is not limited to the drawing.

The cement manufacturing rotary kiln 1 of the present invention has a main burner 3 and a combustible waste injection nozzle 4 provided on a wall constituting a downstream end of a kiln body 2.

In the present invention, as the structures of the kiln body 2 and the main burner 3, known structures are employed without any particular limitation.

For example, the kiln body 2 has a structure in which a refractory layer made of brick is formed in a cylindrical iron pipe. The inner diameter is generally 4 to 6 m, and the length is generally 70 to 100 m. Although not shown, the lower portion of the kiln body 2 is provided with a support portion for supporting and rotating the kiln body 2 at an angle of usually about 4 °.

As the structure of the main burner, a known structure including a multi-pipe or a composite pipe having a pipe for supplying fuel such as heavy oil or pulverized coal, a pipe for supplying air for combustion, and the like is used without any particular limitation. You. In addition, known materials can be used without particular limitation.

In the present invention, the form of the combustible waste is not particularly limited as long as it can be put into the kiln by airflow. 5 to 30 g, preferably 1 to 1
5 g and a size of 1 to 50 mm, preferably 2 to 25 mm are suitable. That is, when the combustible waste having the mass and size less than the above is supplied to the kiln, the combustion is terminated in the space (in a floating state). It is not necessary to apply the present invention for the purpose of dropping on the
Combustible waste larger than the size is difficult to be injected with a carrier gas described below.

[0015] The size of combustible waste refers to the maximum length measured in a straight line distance. For example, a flat piece has a maximum length on a flat surface, a pellet or an irregular shape has a long diameter, a cylindrical one has a cylinder length, and a rectangular parallelepiped has a longest side length. By
Its size is indicated.

The combustible waste is not particularly limited as long as it has combustibility and has the above-mentioned mass and size. For example, the material may be a single or composite material such as plastics, papers, and wood. In addition, as the form of combustible waste, those that exist as granules remain as they are,
In addition, relatively thick waste plastic moldings used for electric equipment casings and the like are used as crushed materials.Furthermore, film materials such as waste plastic films and paper waste are pulverized as necessary, and then a binder is used. Depending on the shape of combustible waste, for example, granules such as wood chips and waste plastic pellets may be used in the form of tablets, with or without use, or as crushed tablets. It can be used in various forms.

The combustible waste is introduced into the kiln from the injection nozzle 4 as a mixed flow with the carrier gas.

A feature of the present invention is that the flammable waste injection nozzle 4 provided with the main burner 3 has a length L from the tip of 5 m or more, preferably 6 m or more, more preferably 7 m or more.
The use of a nozzle having a straight pipe section of m or more.
That is, the present inventors have repeatedly studied the flow velocity of the carrier gas passing through the charging nozzle and the behavior of the combustible waste accompanying the carrier gas. Is determined by the flow velocity of the carrier gas. When the flow velocity of the carrier gas is sufficiently high, it has been found that the velocity is increased in proportion to the length of the straight pipe portion of the nozzle. As a result of further research, by setting the length of the straight pipe to 5 m or more, after being injected into the combustible waste injected from the tip of the nozzle, it flies a certain distance and optimally inserts it. The technology required to provide the necessary speed for dropping the fuel into the area and to control the flow rate of the carrier gas to stably supply the combustible waste to an arbitrary area in the kiln has been completed.

Therefore, if the length L of the straight pipe portion is shorter than 5 m, it is difficult to sufficiently increase the speed of the combustible waste due to the flow rate of the carrier gas, and the combustible waste introduced into the kiln is difficult. Requires a large amount of waste carrier gas to drop the water far enough from the downstream end of the kiln,
This causes a problem that the drop position becomes unstable.

On the other hand, it is difficult to make the length L of the straight pipe portion too long in terms of production. In general, it is preferable to use the straight pipe portion with a length of 15 m or less.

According to the present invention, the combustible waste blown from the nozzle tip can be given a speed of 20 to 100 m / S, preferably 40 to 70 m / S, whereby the optimum The combustible waste can be reliably and stably charged and dropped into any optimal charging region located in the range of 20 to 50 m from the downstream end of the kiln, which is the charging region.

The effect of the present invention can be obtained by forming the length L of the straight pipe portion of the injection nozzle 4 to be longer than the above-mentioned length irrespective of the inner diameter of the injection nozzle 4. In consideration of the size of the waste and the amount of the carrier gas, the inner diameter is preferably 20 to 500 mm, and more preferably 50 to 200 mm.

In the present invention, the charging nozzle supplies the combustible waste in a mixed flow with the carrier gas.
Although a single tube is used, a composite tube or a multi-tube in which a plurality of tubes are arranged in parallel can also be used. Further, the material of the tube constituting the injection nozzle is preferably a material such as iron and stainless steel in consideration of heat resistance, wear resistance and the like. Furthermore, a structure in which the wall constituting the tube is hollow and a coolant such as water flows around the outer periphery thereof, a structure in which a protective layer made of a refractory is formed on the outer periphery of the tube, and the like are also employed as necessary. You.

The mounting of the charging nozzle 4 is not particularly limited as long as it is provided alongside the main burner 3. However, the tip of the main burner 3 and its tip are prevented so that the flame of the main burner 3 does not directly hit the charging nozzle. It is preferable that the tip portions are provided so as to be aligned on the same line. Further, in consideration of the stability at the time of mounting the charging nozzle 4, it is preferable to mount the charging nozzle 4 on the main burner 3 as shown in the figure. In this case, although not shown in the drawing, it is preferable that the straight pipe portion of the charging nozzle projecting from the downstream end of the kiln be supported by a known supporting means.

In the present invention, as the structure other than the kiln, a known structure is employed without any particular limitation. For example, the carrier gas supplied to the injection nozzle 4 is supplied from a supply pipe using a known blower, for example, a roots blower or the like.
Also, combustible waste is mixed with the carrier gas before or after the blower.

As another facility, as shown in FIG. 1, a suspension preheater is usually provided at the upstream end of the kiln body, and the cement raw material is calcined by this to reach the kiln body. A great cooler 5 for cooling the cement clinker obtained by firing is generally provided at the downstream end of the kiln.

[0027]

As will be understood from the above description, according to the rotary kiln for cement production of the present invention, the combustible waste having a specific mass and size can be controlled by controlling the amount of carrier gas. The fuel can be stably supplied to an arbitrary position in the kiln, and the combustible waste can be burned while ensuring the quality of the obtained cement clinker.

[0028]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following Examples.
Examples are shown, but the present invention is not limited to these examples.

Example 1 As a preliminary experiment, two types of injection nozzles made of iron and having an inner diameter of 74 mm and a straight pipe length of 3 m (comparative example) and 8 m (example) were prepared. The rotary kiln for cement production shown in FIG. 1 was configured. That is, a kiln body 2 having a main burner 2 using pulverized coal as a fuel and having an inner diameter of 5.7 m and a total length of 110 m was provided on the main burner with the charging nozzle 4 mounted thereon, to constitute a rotary kiln for cement production. The feed and fuel were not supplied to the kiln, and air was ventilated at normal temperature from the downstream to the upstream at a speed of 12 m / sec.

For each injection nozzle, air was used as a carrier gas for plastic crushed pieces having an average particle diameter of 20 mm and an average mass of 1.2 g, and 4.5 tons / hour of the plastic crushed pieces were applied to a carrier air amount of 1,000 Nm3.
Per hour, the jet was ejected from the tip of the injection nozzle, and the average speed of the plastic crushed pieces at the outlet of the injection nozzle and the falling distance from the downstream end of the kiln were measured.

As a result, in the injection nozzle having a straight pipe portion having a length of 3 m (Comparative Example 1), the average jet velocity of the plastic crushed pieces from the nozzle was 31 m / sec, and the falling distance from the downstream end of the kiln was 18 to 29 m. On the other hand, in the injection nozzle having a straight pipe portion having a length of 8 m (Example 1), which belongs to the specific range of the present invention, the average nozzle ejection speed of the plastic crushed pieces is 43 m / sec, and the kiln The falling distance from the downstream end was 29 m to 38 m.

Then, using a charging nozzle having a length of 8 m (Example) of the straight pipe portion, a raw material and a fuel were supplied to a cement manufacturing rotary kiln having the same configuration as that of the preliminary experiment. From FIG. 4, the same amount of plastic crushed pieces as in the preliminary experiment was introduced with the same amount of carrier air. As a result, the kiln shell temperature of 31 m to 35 m from the downstream end of the kiln increased by about 30 ° C. as compared with the case where the plastic crushed pieces were not charged.
It was confirmed that the plastic crushed pieces fell into the area of No. 1.

Even after the plastic crushed pieces are charged,
The quality of the obtained cement clinker was normal, and the cement clinker could be produced stably.

On the other hand, the length of the straight pipe portion is 3 m (comparative example).
Tried to perform a similar experiment using the input nozzle of
Immediately after the start of the input of the plastic crushed pieces, the quality of the obtained cement clinker began to deteriorate, so the input was immediately stopped.

As described above, according to the apparatus of the present invention, it can be understood that the kiln body can be reliably and stably charged into the optimum charging area of 20 to 50 m.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a typical embodiment of a rotary kiln for cement production of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary kiln 2 Kiln main body 3 Main burner 4 Input nozzle 5 Great cooler 6 Suspension preheater 7 Burner for calcination

Claims (4)

[Claims] 1. A rotary kiln for cement production having a nozzle for charging flammable waste by airflow, which is provided alongside a main burner, wherein a nozzle having a straight pipe portion having a length of 5 m or more from the tip is used as the charging nozzle. A rotary kiln for cement production. 2. The combustible waste has a mass of 0.5 to 30 g,
The cement-producing rotary kiln according to claim 1, which has a size of 1 to 50 mm. 3. The cement manufacturing rotary kiln according to claim 1, wherein the tip of the main burner and the tip of the charging nozzle are located on the same plane. 4. The cement manufacturing rotary kiln according to claim 1, wherein the charging nozzle is installed in a state of being loaded on the main burner.