KR20030054639A - Improvement device for cooling efficiency of burnt lime in rotary kiln - Google Patents

Abstract

PURPOSE: An apparatus for temperature stabilization and improvement of thermal efficiency of a rotary kiln is provided, which is characterized by containing burner frame for supplying heat required in quick lime(CaO) production and improving cooling efficiency of CaO. CONSTITUTION: The apparatus for temperature stabilization and improvement of thermal efficiency of a rotary kiln contains a burner frame installed toward the moving direction of CaO from the center of a circle that is a section of the kiln, for supplying heat to produce CaO efficiently, wherein many heatproof impellers tilted to the direction of the flow of air by 10-40deg.C, being at a distance from the inner wall of the kiln, are attached on the side of the burner frame. Also a plate inducing cold air to the lower part of the kiln is installed under the burner frame, giving a tilt by 30-70degree based on the horizontal plane of a burner room.

Description

Rotary kiln quicklime temperature stabilization and thermal efficiency improving device {Improvement device for cooling efficiency of burnt lime in rotary kiln}

The present invention relates to a rotary kiln quicklime temperature stabilization and thermal efficiency improving apparatus, and more particularly, to improve the cooling efficiency of the quicklime produced in the rotary kiln, and to improve the thermal efficiency required for quicklime calcining, It relates to a thermal efficiency improving device.

Quicklime (CaO) is used as a preparation for refining, such as desulfurization in the steelmaking process, and for the production thereof is usually installed by operating a separate lime firing process, high quality quicklime is required for the production of high clean steel. Quicklime is prepared by calcining limestone (CaCO ₃ ) charged in a rotary kiln or shaft kiln by a flame radiated from a burner and its ambient temperature.

The firing process in the rotary kiln is carried through the charging hopper into the rotating kiln while the charged limestone is inclined, and at this time, it is heated to a flame of 1600 ° C. or more generated at the tip of the burner frame and the ambient temperature to make quicklime Fired. In this process, a quick lime is generated, as shown in Equation 1 below.

CaCO ₃ + heat = CaO + CO ₂

The quicklime calcined as shown in [Equation 1] is temporarily stored in the discharge hopper through a burner room and a cooler, and then used in a steelmaking process after a predetermined time has elapsed. At this time, the temperature of quicklime charged into the cooler is about 1000 ° C.

The quicklime calcined and manufactured by this process is then moved to the next step by a conveyor belt. In normal operation, the temperature of the quicklime is usually 150 ° C or lower based on the operation of the conveyor belt for transport, but in consideration of the occurrence of fire, In the case of, the situation is managed at 100 ° C or less.

1 is a schematic diagram illustrating a calcination and cooling process of limestone charged in a rotary kiln.

When high yields are required, including high summer temperatures, or when the quicklime is undercalcinated, the temperature of the product quicklime is too high, leading to operational disruptions. In order to solve this problem technically, various solutions have been sought. In order to suppress the rise of the quicklime temperature, the flow rate of the cooling air sucked in the lower part of the cooler is increased, or the cutout of the quicklime is stopped from the cooler, and only the coolant is injected. The method has been used. In addition, when not solved by the above method, the flame temperature of the burner is lowered and the production rate is reduced, thereby keeping the temperature of the product below a certain level.

However, the above-described methods have a problem of causing economic losses such as lowering of productivity and waste of power in the process.

2 is a graph showing the correlation between the cooling air flow rate and the COG usage amount according to the cooling air injection ratio according to the productivity shown in a typical rotary kiln operation. As shown in Fig. 2, since the increase in productivity means an increase in the amount of quicklime charged into the cooler after firing, the amount of cooling air should naturally increase. However, this increase in cooling air is directly correlated with the COG air-fuel ratio of the kiln burner. That is, as the combustion air increases, the supply amount of COG as fuel must also increase. In addition, as described above, the increase in the cooling air not only increases the amount of COG used, but also causes an overload of the IDF that sucks the exhaust gas in the kiln.

Therefore, when the quicklime cooling efficiency is improved, the amount of cooling air injected to obtain the same cooling efficiency can be reduced, so that the improvement of productivity, the reduction of fuel usage, and the like can be expected. On the other hand, the applicant has already applied for a patent on a method for improving the quicklime cooling efficiency by installing a heat sink that blocks radiant heat generated from the burner and does not resist the flow of cooling air. (Application No. 2000-072319 )

An object of the present invention for solving the problems of the prior art as described above to improve the cooling efficiency of the quicklime produced in the rotary kiln, and to provide a device for stabilizing and improving the thermal efficiency of the bakery kiln quicklime to improve the thermal efficiency required for calcining the quicklime Is to.

1 is a schematic diagram showing a calcination and cooling process of limestone charged in a rotary kiln,

2 is a graph showing the correlation between the cooling air flow rate and the COG usage rate according to the cooling air injection ratio according to the productivity shown in a typical rotary kiln operation,

3 is a basic design for the heat sink design according to an embodiment of the present invention,

Figure 4 is a detailed design of the heat sink according to an embodiment of the present invention,

5 is a schematic design diagram of a cooling air induction plate according to an embodiment of the present invention,

6 is a detailed design of the cooling air induction plate according to an embodiment of the present invention,

7 is a geometrical setting model diagram for heat transfer and flow analysis,

8 is a diagram showing an X-Z two-dimensional geometric model, respectively, when the heat sink is installed on the basis of the shape of the existing kiln and the case in which both the heat sink and the cooling air induction plate are installed.

9 is a view showing the results of analyzing the mixing ratio of the COG and cooling air for each case according to the heat sink and induction plate installation conditions,

10 is a view showing a change in the flow phenomenon of the cooling air at the tip of the burner frame,

11 is a result of analyzing the flow phenomenon of the cooling air for each case shown in FIG.

12 is a view showing an atmospheric temperature analysis result at the burner frame tip,

13 is a view showing an atmospheric temperature analysis result in a firing region,

14 is a view showing a quicklime temperature analysis results for each position,

FIG. 15 is a view when a real process heat sink and a cooling air induction plate are installed; FIG.

16 is a view showing the results of measuring the temperature of the top of the quicklime and around the heat sink before / after installing the heat sink,

17 is a view showing changes in cooling air flow rate and quicklime product temperature before and after the heat sink is installed,

18 is a view showing the change in the operation data before and after installing the cooling air induction plate,

19 is a view showing a change in the amount of COG usage under the same productivity conditions when the heat sink is installed and the heat sink and induction plate are installed at the same time,

20 is a view comparing the degree of firing before / after the installation of the heat sink and induction plate.

In order to achieve the above object, according to the present invention, in the apparatus for temperature stabilization and thermal efficiency improvement of a rotary kiln, the center of a circle, which is a cross section of a kiln that rotates in order to efficiently supply calories required for calcining of quicklime Burner frame of the rotary kiln is installed to be deflected in the direction of the quicklime movement (Burner Frame), including, a plurality of heat sink blades on one side of the burner frame in the form of an impeller (Impeller) so as to be spaced apart from the inner wall of the kiln at a predetermined interval Provided is a device for stabilizing temperature and improving thermal efficiency of a rotary kiln, which is attached.

Further preferably, the plurality of heat sink blades are attached to one side of the burner frame to be inclined 10 to 45 degrees in the direction of air travel to improve the mixture of combustion air and fuel.

In addition, in the apparatus for stabilizing the temperature and improving the thermal efficiency of the rotary kiln, in consideration of the flow of the cooling air in the burner room, the cooling air flow can be efficiently used for cooling the quicklime. Cooling air induction plate (Plate) is changed to the direction in which the quicklime moves by the lower side of the kiln main body is installed under the burner frame (Burner Frame) characterized in that the temperature stabilization and thermal efficiency improvement apparatus of the rotary kiln to provide.

Further, more preferably, the cooling air induction plate is installed at an angle of 30 to 70 degrees with respect to the burner room horizontal plane to adjust the flow of cooling air according to the quicklime productivity.

Hereinafter, the rotary kiln quicklime temperature stabilization and thermal efficiency improving apparatus according to an embodiment of the present invention with reference to the accompanying drawings will be described in more detail.

3 is a basic design for the heat sink design according to an embodiment of the present invention. As described above, since the cooling air for quicklime is used for COG combustion inside the kiln, the heat sink is designed to suppress a decrease in combustion efficiency due to a decrease in the mixing ratio of COG and combustion air, and to simultaneously block radiant heat. 3A is a schematic sketch diagram of such a heat sink.

As shown in (b) of FIG. 3, the burner frame of the rotary kiln is not located at the center of the circle, which is a cross section of the rotating kiln, in order to efficiently supply the heat required for the calcining reaction of quicklime. It is installed in the moving direction. That is, as shown in (c) of FIG. 3, the frame is installed by moving about 225 mm from the center of the kiln cross-sectional circle. Therefore, to cover the same part of the whole kiln cross-section circle, the blades of the heat sink were divided into eight equal parts and each wing size and angle were adjusted to be 600 mm away from the inner wall of the kiln, and the eight wings were divided into the divided pipes. Welded at a certain inclination angle (impeller shape) to facilitate installation and removal on the frame.

On the other hand, the blade of the heat sink is preferably inclined relative to the air traveling direction in order to improve the mixing ratio of the combustion air and fuel bar, while changing the inclination angle, the experimental result of the improvement of the mixing ratio, approximately 10 ~ 45 degrees Showed good results.

4 is a detailed design diagram of the heat sink shown in FIG. 3. The cooling air guide plate (Plate) in order to guide the flow of cooling air to the lower part of the kiln body so that the cooling air can be efficiently used for cooling the quicklime in consideration of the flow phenomenon of the cooling air in the burner room. Designed.

5 is a schematic design diagram of the cooling air guide plate. Cooling air passes through the cooler to the burner room by a fan at a pressure of about 500 mmH ₂ O, and the pressure of the burner room is about -10 to -5 mmH ₂ O by the IDF at the end of the kiln. . Therefore, the conventional cooling air will exhibit a flow as shown in FIG. 5A inside the kiln. On the other hand, if the plate that can change the flow of the cooling air in the direction of the quicklime moves as shown in (b) of FIG. 5 (b), also prevents the vortex of the corner portion of the burner room, cooling efficiency of the quicklime It can be predicted that this can be improved.

FIG. 6 is a detailed design of the cooling air guide plate shown in FIG. The guide plate is designed to adjust the angle to about 45 ~ 60 degrees relative to the burner room horizontal plane. In the present embodiment, the angle was designed to be 45 to 60 degrees, but the experimental results showed good efficiency up to a range of about 30 to 70 degrees.

Before installing the heat sink and the induction plate, heat transfer and flow analysis in the kiln were performed to predict changes in the ambient temperature and the quicklime temperature of the inside of the kiln and the burner room.

7 is a geometry setting model diagram for heat transfer and flow analysis. As shown in (a) of FIG. 7, the first half of the kiln cooler, the burner room, and the rotary furnace are modeled in three dimensions to set boundary conditions such as cooling air inflow conditions, initial temperature of quicklime, and COG injection ratio in the real industry. It was.

Heat transfer and flow analysis were calculated through three-dimensional solid modeling (Solid Modeling), and as shown in Fig. 7 (b) shows a result calculated using the isotherm and the velocity vector in a two-dimensional cross section. The above calculation was performed for each case by dividing the case of installing the heat sink and the case of installing both the heat sink and the cooling air induction plate based on the shape of the existing kiln.

8 is a diagram illustrating an X-Z two-dimensional geometric model, respectively, when the heat sink is installed on the basis of the shape of the existing kiln and the case where both the heat sink and the cooling air induction plate are installed.

When adjusting the flow of cooling air in the kiln to improve the cooling efficiency of quicklime, the most important point is to evaluate the effect on the combustion of COG. This is because, if the flow of cooling air is changed only to improve the quicklime cooling efficiency, the mixing ratio of COG and combustion air is lowered, which may cause combustion problems.

9 is a view showing a result of analyzing the mixing ratio of the COG and cooling air for each case according to the heat sink and induction plate installation conditions. As shown in FIG. 9, the phenomenon in which the mixing region of the combustion air and the COG is enlarged as the heat sink is installed, and the combustion focus moves to the burner frame tip portion. That is, as the cooling air introduced from the lower portion passes through the heat sink and forms a vortex, it is possible to predict the enlargement of the combustion region by increasing the mixing ratio of the combustion air and COG. The expansion of the combustion zone increases the calorific value of the calcined circuit moving to the bottom of the rotating kiln body, which means that the calcining degree of limestone can be improved.

10 is a view showing a change in the flow phenomenon of the cooling air at the tip of the burner frame. According to the installation of the heat sink, unlike the case 1, a pressure drop occurs in the front side of the heat sink A, and thus, a phenomenon in which the cooling air introduced to the upper side presses the flame downward. In the lower portion of the quicklime, the cooling air flow rate of the portion directly below the heat sink increases as the heat sink is installed, but after the position B of FIG. 10, a reverse flow is formed. However, as in Case 3, the flow rate of the cooling air also increased in the quicklime moving part B 'under the heat sink according to the installation of the induction plate.

FIG. 11 is a result of analyzing the flow phenomenon of cooling air for each case shown in FIG. 10 (Y-Z cross section, X = 7.000mm), and is a result of comparing the flow phenomenon in the Y-Z cross section.

As shown in FIG. 11, it can be seen that the installation of the heat sink and the induction plate has a larger vortex generation at the tip of the nozzle than in the past, and the width of the flame can be predicted from these results. In other words, by increasing the mixing ratio of combustion air and COG according to the installation of the heat sink and the cooling air flow rate of the quicklime moving part by installing the induction plate, the supply of heat required for calcining the limestone is increased, and the cooling efficiency of the quicklime is improved after firing. It can be predicted that can be obtained simultaneously. From the analysis results, it can be seen that there is no decrease in combustion efficiency due to the flow change of the cooling air.

FIG. 12 is a view showing an atmospheric temperature analysis result at the burner frame tip (Y-Z cross section, X = 3m), which shows the ambient temperature at each heat sink installation position, that is, at the position where the quicklime cooling starts. When the heat sink and the induction plate are installed as compared to the existing temperature distribution, it can be seen that the temperature range of 500 ° C. or more shown in FIG. 12 is narrowed. According to the heat sink and the induction plate installation, the upper part of the kiln and the high temperature region in the quicklime direction narrowed at the same time, and this result means that the atmospheric temperature at the point where the quicklime is cooled after firing can be predicted to improve the cooling efficiency.

Fig. 13 is a diagram showing the results of the atmospheric temperature analysis in the firing region (Y-Z cross section, X = 7m), in which the atmosphere temperature caused by the flame at the position where the firing reaction occurs is represented by isothermal lines in the Y-Z cross section. According to FIG. 13, it can be seen that the isothermal region is widely spread around the flame according to the installation of the heat sink and the induction plate.

14 is a view showing the results of the quicklime temperature analysis by location, according to FIG. 14, it can be seen that the quicklime temperature in the cooling zone decreases linearly with the installation of the heat sink and the induction plate, and increases in the firing zone. Able to know. From these results, when the same firing conditions are maintained, it can be expected that the reduction of the amount of COG to be used can also be expected.

It is a figure in the case of installing a real process heat sink and a cooling air induction plate.

The fabrication and installation of the heat sink and the induction plate were performed by installing the heat sink and the induction plate one by one using the clean water period in the actual process, and analyzing the operation data for each installed period, thereby analyzing the effect. The shape of the heat sink was made so that all the wings were separated by the same distance from the inner wall of the cylindrical kiln. During the installation work, all the sensors on the rear were moved to one place, and only one side of the heat sink was removed.

Cooling air induction plate was installed to incline the flow of cooling air by installing an inclined plate at an angle of about 45 degrees from directly underneath the burner frame, and was manufactured to control the angle to 60 degrees by connecting a wire to the upper part of the plate. .

16 is a view showing the results of measuring the temperature of the top of the quicklime and the heat sink surrounding before and after installing the heat sink. Points A and B shown in FIG. 16 are the burner frame portions behind the heat sink, and point C is around the flame about 1 m forward from the heat sink installation position.

The temperature of point A and B dropped about 200 degreeC by the installation of a heat sink, and the temperature of point C around a flame increased 40 degreeC rather. In addition, the ambient temperature immediately above the quicklime falling into the cooler was reduced by about 200 to 300 ° C. These results are also in agreement with the above-described heat transfer analysis results, and it is expected to improve the cooling efficiency and increase the degree of plasticity according to the heat sink installation.

FIG. 17 is a view showing changes in cooling air flow rate and quicklime product temperature before and after heat sink installation, and quicklime productivity is layered based on 450 t / d.

Before installing the heat sink, the flow rate of cooling air was about 14,000 Nm ³ / hr to manage the temperature of the quicklime product at about 50 ℃, but after installing the heat sink, the flow rate of cooling air required for cooling the quicklime decreased to 10,000 Nm ³ / hr. there was. That is, it can be confirmed that the cooling efficiency of the quicklime is improved by installing the heat sink. Table 1 below shows the statistical analysis results of the operation index of the above period.

TABLE 1

As shown in Table 1 above, the average product temperature of quicklime is almost similar at 51 ° C and 55 ° C, although the cooling air flow rate has decreased about 25% from 13,810 Nm ³ / hr to 10,350 Nm ³ / hr. Value, and the variation in product temperature was greatly reduced. From this, it can be seen that stabilization of the quicklime cooling pattern can be achieved by installing a heat sink. In addition, the amount of COG used also decreased by about 3.3% after the heat sink was installed. Therefore, it is also possible to confirm the increase in the calorific value according to the combustion efficiency improvement in the heat transfer analysis result described above.

FIG. 18 is a view showing changes in operation data before and after installation of a cooling air induction plate, and only data with a productivity of 490 t / day was used.

As shown in FIG. 18, when the heat sink and the induction plate were installed at the same time, the cooling air flow rate decreased by about 12% from 11,950 Nm ³ / hr to 10,490 Nm ³ / hr. Quicklime temperatures are similar at 67.2 ° C and 68.7 ° C. That is, it can be seen that the flow rate of the cooling air for cooling the calcined quicklime to the same temperature is reduced.

The decrease in the cooling air flow rate due to the improvement of the cooling efficiency has a direct correlation with the above-mentioned reduction in the amount of COG used, but in addition, it is possible to obtain additional effects such as securing the IDF margin, reducing the number of raw power units, and reducing the total amount of dust generated.

19 is a view showing a change in the amount of COG usage under the same productivity conditions when the heat sink is installed and when the heat sink and induction plate are installed at the same time. As illustrated in FIG. 19, when the productivity index Stroke is based on the same data, the amount of COG used decreased by about 80 Nm ³ / hr according to the installation of the cooling air induction plate. These results are in good agreement with the results of quicklime temperature analysis by accelerating heat transfer from the quicklime circuit from the flame in the firing zone. In other words, it was confirmed that there is also an effective use of cooling air according to the installation of the heat sink and the induction plate, and the effect of reducing the amount of COG used due to the increase in the combustion efficiency.

COG reduction has the advantage of lowering the manufacturing cost and reducing the harmful substances in the flue gas in kiln operation, but this advantage must satisfy the condition that the calcining rate of quicklime is kept constant. In order to investigate the change of the quicklime calcining degree according to the improvement of cooling efficiency and COG reduction according to the installation of the heat sink and the induction plate, the quicklime sampling was carried out before and after installation and the calcined degree was measured. The degree of calcination was calculated by calcining a certain amount of quicklime at a reaction temperature of 1000 ° C. for 1 hour and then subtracting the weight from the reduced weight by 100, that is, using the weight ratio of carbon dioxide remaining in the kiln in the kiln.

20 is a diagram comparing the degree of plasticity before and after installing the heat sink and induction plate, and shows the results of 10 experiments each.

As shown in FIG. 20, when comparing the present invention with the existing plasticity, there was almost no difference, but rather the result was slightly improved. That is, it was confirmed that there is no deterioration of quicklime quality due to COG reduction due to the installation of the heat sink and the induction plate.

When the effects of the installation conditions are summarized and indexed, they can be expressed as shown in Table 2 below.

TABLE 2

Quicklime temperature tends to rise slightly before / after installation, but below about 5 ° C., no disruption to operation. Therefore, the cooling air flow rate reduction and COG usage reduction effect excluding the quicklime temperature problem are as shown in the above [Table 2].

Although the cooling air reduction and COG reduction are not theoretically consistent, the installation of heat sinks and induction plates reduced the use of COG by about 5.5% compared to before.

According to the results of the present invention, a heat sink and an induction plate can be designed to control the flow of cooling air used for cooling of quicklime and COG combustion in a rotary kiln operation. Numerical analysis was performed for. In addition, based on the numerical analysis results, the heat sink and the cooling air induction plate were installed directly in the actual process to grasp the effect during normal operation. As a result, the reduction of the cooling air flow rate and COG reduction required for the cooling of quicklime was confirmed, and the reduction of the quicklime manufacturing cost could be expected.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, according to the present invention, when operating the rotary kiln, the same cooling by applying a device that prevents heat transferred from the burner flame to the quicklime, widens the flame, and induces the flow of cooling air in the quicklime direction By improving the cooling efficiency of quicklime at an air flow rate, there is an effect of reducing the fuel use cost of the rotary kiln to maintain a constant firing degree.

Claims (4)

In the temperature stabilization and thermal efficiency improvement apparatus of the rotary kiln (Rotary Kiln), A burner frame of a rotary kiln, which is deflected in a direction of moving quicklime at a center of a circle, which is a cross section of a rotating kiln, in order to efficiently supply calories required for calcining quicklime. And a plurality of heat sink blades are attached to one side of the burner frame in an impeller form so as to be spaced apart from the inner wall of the kiln by a predetermined interval. The method of claim 1, The plurality of heat sink blades are attached to one side of the burner frame inclined 10 to 45 degrees in the air direction to improve the mixture of combustion air and fuel temperature stabilization and thermal efficiency improvement apparatus of the kiln. In the temperature stabilization and thermal efficiency improvement apparatus of the rotary kiln (Rotary Kiln), Cooling that directs the flow of cooling air to the lower part of the kiln body to change the direction of quicklime movement so that the cooling air can be efficiently used for cooling the quicklime in consideration of the flow phenomenon of the cooling air in the burner room. Temperature stabilization and thermal efficiency improvement device of the rotary kiln, characterized in that the air induction plate (Plate) is installed under the burner frame (Burner Frame). The method of claim 3, wherein The cooling air induction plate is a temperature stabilization and thermal efficiency improvement device of the rotary kiln, characterized in that installed at an angle of 30 to 70 degrees relative to the horizontal plane of the burner room (Burner Room) to adjust the flow of cooling air according to the quicklime productivity .