JPH0353265B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an internal heating type vertical lime calcining apparatus, and more particularly to a vertical lime calcining apparatus that makes it possible to produce quicklime with a low sulfur content (hereinafter referred to as S content). [Prior art] A limestone charging means is provided at the top of an upright shaft, and a fired material discharge mechanism is provided at the bottom of the shaft.
BACKGROUND OF THE INVENTION Vertical lime calcining apparatuses are well known in which limestone blocks are introduced into the shaft and calcined therein. In this device, as shown in Japanese Patent Publication No. 51-21638 and Japanese Patent Application Laid-Open No. 58-26054, a plurality of shafts are provided in parallel, and these are connected by a connecting channel that is a passage for combustion gas and air. Firing may also be performed by alternately switching between combustion and heat storage. In the shaft of such a vertical lime calcining device, quicklime (CaO) and carbon dioxide gas (CO ₂ ) are generated by thermal decomposition of limestone (CaCO ₃ ). on the other hand,
The flammable S content contained in fuel such as heavy oil is 600 to 800.
It becomes SO ₂ gas at ℃ and is mixed in combustion gas. CaO does not absorb SO ₂ at room temperature, but at 300-400
It absorbs at temperatures above 400 degrees Celsius, and reacts quickly at temperatures above 400 degrees Celsius.
Generate _CaSO3 . Furthermore, when the temperature increases from 400℃ to 800℃,
CaSO ₃ partially decomposes into CaS and CaSO ₄ . That is, the following reaction is performed. 4CaSO ₃ →3CaSO ₄ +CaS 4CaO+4SO ₂ →3CaSO ₄ +CaS At temperatures above 800°C, CaCO ₃ and CaS are oxidized to CaSO ₄ , and at even higher temperatures above 1000°C,
CaO loses its ability to absorb and fix SO ₂ . [Problems to be Solved by the Invention] Therefore, in the vertical lime calcining device, by firing at a temperature higher than the thermal decomposition temperature of limestone and as low as possible, the activity of lump quicklime is increased and the heat source is Therefore, except for a part of the firing zone (1200℃), most of the temperature is
The temperature is below 1000℃. Therefore, in the past, there was a risk that the SO ₂ fixed in the lump quicklime would increase and the quality of the product quicklime would deteriorate, and especially when the S content of the fuel was high, the product quality was likely to deteriorate. [Means for Solving the Problems] In order to solve the above problems, the present inventor conducted intensive research and found that the smaller the particle size of quicklime, the less S content is fixed in the quicklime particles during the firing process. It turns out that there is a tendency to increase. The present invention was completed based on such findings, and involves incorporating minute quicklime into the combustion gas during firing to absorb (or adsorb) the S content, thereby removing the S content fixed in the lump quicklime. In a vertical lime sintering device that is configured to significantly reduce the amount of limestone and has a vertically erected shaft and uses the shaft to sinter lump limestone, powdered quicklime is blown into the shaft. A vertical lime firing device is provided with a blowing means and a part where the blown lime powder can come into contact with the combustion gas, and a plurality of said blowing means are installed, and at least one of the blowing means is used for firing the shaft. The gist of the invention is a vertical lime calcining apparatus characterized in that it is installed upstream of a belt or a firing zone in a gas flow direction. [Operation] When powdered quicklime is blown into the shaft from the blowing means, SO ₂ generated by combustion of the fuel reacts with the powdered quicklime, is fixed, and is discharged out of the furnace together with the combustion exhaust gas flow. As mentioned above, the smaller _the particle size of quicklime, the easier it is to absorb (or adsorb) SO _{2 .}
It precedes the absorption (adsorption) of Therefore, the S content fixed in the lump quicklime that becomes the product is significantly reduced. In particular, in the present invention, since powdered quicklime is injected from the firing zone and a region upstream of the gas flow, SO ₂ in the combustion gas is reliably fixed in the powdered quicklime, and the lumps of good quality are always maintained. It is said that it is possible to burn quicklime. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a two-shaft type vertical furnace, in which a limestone charging means 2 and an exhaust gas outlet 3 are provided at the top of each shaft 1. A burner arch 6 with a burner chamber 5 equipped with a main burner 4 for liquid fuel such as heavy oil is installed in the upper part of the shaft 1. Further, a plurality of auxiliary combustion devices 7 are provided at the bottom of the shaft 1, and a table-type discharge device 8 is further provided at the bottom as a discharge mechanism for the fired product. In addition, each shaft 1 has a connecting channel 9 connected to each other at the lower part.
It communicates with Therefore, in this embodiment, inside the burner chamber 5,
An appropriate number of powder quicklime injection ports 12a, 12b, and 12c are provided in the combustion air pipe 10 above the shaft and in the cooling air pipe 11 below the shaft, respectively. Powdered quicklime is distributed and supplied from the blowing ports 12a to 12c. As a result, SO ₂ in the combustion gas is fixed in contact with the powdered quicklime, and is discharged out of the furnace together with the combustion air in the form of CaSO ₄ and CaS. The discharged powder is collected using a cyclone, electrostatic precipitator (EP), etc. The firing action in the apparatus of this embodiment will be explained below. By the damper part of the limestone charging means 2, the limestone lumps charged into one shaft 1a from the top thereof descend through both sides of the burner arch 6.
On the other hand, heavy oil is burned in the main burner 4. Since the volume of the burner chamber 5 is small, some of the heavy oil is gasified and burned, but the majority is not gasified.
While covering the surface of the limestone blocks, it gasifies and burns as it descends from the preheating zone to the firing zone. At this time, the combustion air is forced into the shaft from the top of the shaft. The combustion gas generated by the combustion of heavy oil descends through the firing zone, then enters the other shaft 1b through the connecting channel 9 in the center and turns upward, transferring the sensible heat it possesses to the material to be fired in the shaft 1b. and is discharged from the top of the shaft 1b as exhaust gas. In the next cycle, the direction in which the limestone charging means 2 supplies the lump limestone is switched, firing is performed in the other shaft 1b, and heat is stored in the one shaft 1a by the combustion gas introduced from the shaft 1b. In this way, switching between combustion and heat storage is performed alternately between both shafts 1a and 1b, and operation continues. Next, the flow of internal air, combustion gas, and materials to be fired in the shafts 1a and 1b will be described in detail. Note that the first
In the figure, the flows of air and combustion gas are shown by solid lines and broken lines, respectively. Further, hereinafter, the shaft on the combustion side may be referred to as a combustion shaft, and the shaft on the heat storage side may be referred to as a heat storage shaft. If one of the shafts 1a is a combustion shaft, as shown in the figure, the cooling air _L1 introduced from the bottom of the shaft 1a rises while cooling the descending baked product, and is combusted in the connecting channel 9. The other shaft 1b which merges with the gas and serves as a heat storage shaft
to go into. In this case, in the shaft 1a, the combustion air is forced in from the top, so the combustion gas is diffused in a conical shape, while the shaft 1a, which is a heat storage shaft,
In b, the diffusion of combustion gases, together with the upward flow of cooling air _L2 introduced from the bottom of shaft 1b,
It is biased toward the connection channel 9 side. That is, when measuring the porosity distribution of the material to be fired charged into the shaft, the porosity of the wall surface portion is larger than the porosity of the inside of the shaft. Therefore, the cooling air _L2 introduced from the bottom of the shaft 1b tends to rise along the wall surface of the shaft 1b, but on the inner wall side (i.e., the side closer to the shaft 1a), the combustion gas flow from the combustion shaft 1a is Since it flows in like an air curtain, it mainly flows into the outer wall side (i.e. the shaft 1a).
As a result, as mentioned above, the diffusion of the combustion gases in the shaft 1b is biased towards the continuous channel 9 side. As described above, the combustion gas does not necessarily flow uniformly inside the shaft of the vertical lime burning apparatus, but may be partially biased. In this embodiment, powdered quicklime is blown into the shafts 1a and 1b.
No matter which one is used as the combustion shaft,
Powdered quicklime is always injected from the firing zone and a region upstream of the firing zone in the gas flow direction. Therefore, SO ₂ in the combustion gas is reliably fixed in the powdered quicklime, making it possible to always burn out lumpy quicklime of good quality. In addition, by supplying powdered quicklime at various locations within the shaft 1 in this way, the combustion gas and powdered quicklime will come into contact evenly, so there will be no waste of powdered quicklime due to excessive supply. ,
SO ₂ can be fixed efficiently. In addition, in this embodiment, the injection ports 12a to 12c for powdered quicklime provided in the burner chamber 5, the cooling air pipe 11, and the combustion air pipe 10 have an appropriate number of openings arranged in a circumferential manner. It supplies quicklime. In particular, the inlet 12a in the burner chamber 5 is made of a cylinder made of a highly heat-resistant alloy or ceramic, and uses mechanical force or compressed air to disperse and supply powdered quicklime over as wide an angle as possible, thereby
This powder quicklime is made to penetrate more uniformly and more deeply between the lumpy limestone descending on both sides of the burner arch 6. This makes it possible to bring the powdered quicklime into contact with the combustion gas more uniformly. In addition, if the particle size of the powdered quicklime to be blown becomes large, it becomes difficult to pass between lumpy limestone or quicklime, so it is preferable that the average particle size is about 100 μm or less. In addition, the amount of powdered quicklime used is 1 S content in the fuel.
It is preferably about 1 to 5 parts by weight. If the amount used is less than 1 part by weight, the effect will be small, and if it exceeds 5 parts by weight, the cost will increase and the blown lime powder will collect in the center of the shaft, so that the overall desulfurization effect cannot be expected to increase much. In the above embodiments, a calcination device that uses heavy oil as fuel has been described, but the present invention may use pulverized coal or COM as fuel, or mix solid fuel such as coke with powdered quicksilver or powdered quicklime. It is also possible to adopt a firing method in which the materials are alternately charged into the shaft. In addition, in the above embodiment, a so-called M kiln is illustrated, but the present invention can be applied to a double inclined kiln, a double cylindrical vertical kiln, a B kiln,
It can also be applied to various other types of firing equipment such as S kiln, N kiln, Kunii type lime heavy oil kiln, or cross beam type lime kiln. A suitable experimental example is shown below. In this experimental example, the auxiliary combustion device 7 is omitted.
A shaft firing device was used. 3 parts by weight of powdered quicklime per 1 part by weight of S content in the fuel was dispersed and supplied from the powdered quicklime supply port at a rate of 80m ³ /Hr using 0.4Kg/cm ² compressed air, and was injected from the burner. It was put into the combustion gas along with heavy oil. Samples for comparing the amount of S in product quicklime were collected on the product discharge belt at approximately 300g every 20 minutes for one day.
Automatic samples were taken 36 times. Table 1 shows the analysis results.

[Table] * Product quicklime particle size From Table 1, it is clear that according to the present invention, the S content in product quicklime can be reduced by about 30 to 50%. [Effects] As detailed above, the present invention provides a vertical lime firing apparatus in which powdered quicklime is blown into the shaft and brought into contact with combustion gas, and SO ₂ in the combustion gas is fixed in the powdered quicklime and released into the shaft. Since the product can be discharged from the shaft, the S content contained in the product quicklime taken out from the shaft can be reduced and the product quality can be improved. Particularly, in the present invention, powdered quicklime is blown from the firing zone and a region upstream of the gas flow. Therefore, SO ₂ in the combustion gas is reliably fixed in the powdered quicklime, making it possible to always burn out lumpy quicklime of good quality. Furthermore, since powdered quicklime is supplied into the shaft at multiple locations, the combustion gas and powdered quicklime come into contact evenly, so there is no wastage of powdered quicklime due to excessive supply, and SO ₂ can be fixed efficiently. Additionally, existing firing equipment can be improved to the structure of the present invention with simple construction.
It is also highly practical.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. 1 (1a, 1b)...shaft, 2...limestone charging means, 3...exhaust gas outlet, 4...main burner,
5... Burner chamber, 6... Burner arch, 7... Auxiliary combustion device, 8... Discharge device, 12a, 12b,
12c...Injection port for powdered quicklime.

Claims (1)

[Claims] 1. In a vertical lime burning device that has a vertically erected shaft and uses the shaft to burn lump limestone, a blowing means for blowing powdered quicklime into the shaft is used to cause the blown powdered quicklime to combust. A vertical lime sintering device installed in a part that can come into contact with gas, wherein a plurality of the blowing means are installed, and at least one of them is installed in a sintering zone of the shaft or on the upstream side of the gas flow from the sintering zone. A vertical lime sintering device characterized by being installed in.