JPS5939750A - Lime baking method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lime firing method for firing limestone, dolcomite, etc. using a vertical type solid fuel.

Horizontal rotary furnaces and vertical furnaces are used for firing limestone and dolomites. Among the vertical furnaces, depending on the type of fuel used, there are fluid fuel firing furnaces, fluid/fixed fuel hot firing furnaces, etc. The present invention is directed to a lime kiln which is vertical and uses a solid fuel such as anthracite (for example, anthracite).

This lime kiln has a structure as shown in FIG. 1, for example. In other words, in Figure 1, 1
The lime calcining furnace shown in 2 has a furnace main body 2 which is arranged upright, and an atomic injection device 3 is installed at the upper end thereof.

The raw ore charged into the -C furnace main body by the raw ore input device 3 is conveyed by the skip voices 1 to 4.

At the lower end of the furnace body 2, there are installed 1, 1, 14 and 5 for the fired products, and a blower device 6 for supplying air for cooling 1 and 1 is installed. It is being

The coke used as a fuel under such a structure is mixed in a predetermined amount into the raw material [1],
The raw ore is charged into the furnace using the raw ore charging device 3, or the raw ore and coke are alternately charged using the raw ore charging device 3.

The inside of the furnace body 2 is filled with input raw stone (lime 75 or dolomite, etc.) and coke.
By being continuously extracted by a discharge device 5 provided at the bottom of the furnace, the raw ore and coke gradually descend from the top of the furnace to the bottom. The inside of the furnace is a packed bed that is continuous in the vertical direction, and this packed bed is divided into 1 geometric categories as shown in FIG. 2.

The upper part of the furnace is a preheating zone A, and in this preheating zone A,
Sensible heat from the exhaust gas generated inside the furnace preheats the raw ore to a temperature at which it starts the decarboxylation reaction.

In the preheating zone A, the raw ore is preheated and the fuel coke is preheated to the ignition temperature.

The calcining zone (D', l carbonate zone) B is located below the preheating zone. In this calcining zone B, limestone is decarboxylated by the combustion heat of coke.

Further, a cooling zone C is located below the calcining zone B, that is, at the bottom of the furnace body 2.

In this cooling zone C, air is forcibly blown from the bottom of the furnace, and the quicklime is cooled by this air.

Then, the blown air becomes high temperature by removing the sensible heat from the quicklime, rises to F in the furnace, and becomes combustion air for burning coke in the calcining zone B.

By the way, the position of calcining zone B almost coincides with the coke combustion zone (coke oxidation zone), but it is not fixed and varies depending on the properties of the coke used, especially its particle size (see Figure 3)~ It is known that they move naturally as shown in (C).

In FIGS. 3(A) to 3(C), the symbol E indicates the decarboxylation zone.

FIG. 3 (Δ) shows the case where only coke with a particle size of 40 II 1 wl was used. In this case, most of the coke burns in a wide range and completes combustion at the same time, and the oxidation zone and the carbonate zone 73 (112 and 73) almost coincide, indicating a good combustion condition. It is almost impossible industrially to make the particle sizes of coke the same (generally, the coke is operated under the conditions shown in (B) to (C)).

Among the states shown in FIGS. 3(B) and (C), FIG. 3(C)
The situation shown in Figure 1 has the advantage that the cost of coke is low, but as is clear from this figure, the decarboxylation zone E is shifted upwards relative to the oxidation zone, and as a result, after the decarboxylation reaction is completed, However, the coke combustion continues.

This continued combustion has the following negative effects on quicklime, and is one of the typical drawbacks of solid fuel kilns.

In other words, limestone undergoes a decarboxylation reaction at a temperature of approximately 900°C under atmospheric pressure, but since bowl-shaped limestone is used industrially, the decarboxylation reaction must be performed at higher temperatures. I'm doing it.

Generally, quicklime has the highest chemical reactivity immediately after decarboxylation, and after that, the chemical reactivity decreases in proportion to the temperature and the passage of time, even in an atmosphere with a temperature of 900'C or higher. In addition, AQO contained in limestone
, FeO, coke z 3 23 SiO, which is the main component in the burned ash, and quicklime cause fusion, and the quicklime lumps stick to each other through the fused material, forming large lumps that obstruct normal quicklime production. Become.

As mentioned above, the production of quicklime is carried out at temperatures above 900°0, so this risk is always present, but in the case of solid fuel kilns (especially in the case of solid fuel kilns (see Figure 3 (B),
In case (C), structurally speaking, coke combustion continues even after decarburization, so this tendency is particularly pronounced, leading to the production of quicklime with low chemical reactivity and the generation of lumps of quicklime.

As an example, the preheating zone inside a coke oven, the nlJ carbonate zone (
Figure 4 shows the temperature distribution of the coke oxidation zone.

In Figure 4, the temperature of the core (center of limestone) is 90
The temperature up to 0° C. is the actual carbonation zone, and the period thereafter up to the point at which coke combustion is completed is the portion that causes the above-mentioned drawbacks.

At the bottom of FIG. 4, an example of the oxygen concentration in a conventional furnace is added.

In other words, the oxygen concentration at the time when the combustion (oxidation) of the coke is completed is 21% due to the blown lime cooling air.
%, but at the coke ignition point, oxygen is consumed due to coke combustion and decreases to 1.0%.

The gas temperature distribution in the furnace at this time is as shown in FIG. 5, and the shaded area is the area where coke is being burned.

By the way, when coke is combusted, the amount of oxygen used for its combustion, whether the coke is partially combusted or whether it is burned by goldstone, is proportional to the absolute amount of oxygen supplied.
The combustion rate (time) is inversely proportional to the oxygen density (oxygen concentration),
It is known that the combustion temperature is inversely proportional to the amount of oxygen-containing gas (eg, air) injected.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a lime firing method that eliminates the above-mentioned problems that could not be avoided in conventional furnaces.

In order to achieve the above object, the present invention uses exhaust gas discharged from the furnace to control the position and length of the coke oxidation zone (coke combustion zone) inside the furnace and the oxygen concentration to control the combustion temperature. A quicklime firing method with adjusted configuration was adopted.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In this figure, the same or equivalent parts as those in FIG.

In the present invention, in J3, 7 is a waste circulation vibrator.

An FA adjustment damper 8 is provided at the upper end of the exhaust gas circulation vibrator 7, and a popular injection material 9 is connected to the middle.

A popular skewer adjusting tamper 10 is installed in the middle of the air blowing pipe 9.

11 and 12 are flow rate measuring devices.

In this way, a mixed gas with a relatively low oxygen concentration, which is a mixture of popular and 111 gases, is used in the air stream for product cooling.

The mixing ratio is determined by varying the flow rate and the flow rate measuring device 11.
．． 12, and according to the results, the tamper ε3.10 can be arbitrarily adjusted by manually or automatically using a ratio setting device or the like. In this way υ
] The following advantages can be obtained by circulating gas.

(1) Since the atmosphere guarantees the absolute amount of oxygen and dilutes it with the extremely small amount of exhaust gas in oxygen-containing row 1, the oxygen concentration in the furnace becomes low, and as a result, the coke burning rate in the furnace decreases. li, and the combustion zone becomes longer in the longitudinal direction.

(2> Since the amount of gas inside the furnace increases, the gas distribution in the radial direction inside the furnace becomes better, the humidity inside the furnace decreases, and local heating inside the furnace can be prevented.

(3) Since the combustion zone in the furnace is wide and the temperature is low, the particle size range of the coke that can be used can be widened.

(4) As a result of the above advantages, the decarboxylation zone of lime and the coke oxidation zone almost coincide, heating after decarboxylation is prevented, and a decrease in the chemical reactivity of the quicklime product is prevented;
Fusion with impurities is prevented.

As is clear from the above description, according to the present invention, a structure is adopted in which exhaust gas with a low oxygen concentration is blown in from the bottom, so that the decarboxylation zone of lime and the oxidation zone of fuel almost coincide. Therefore, heating after decarboxylation is prevented, and excellent lime calcination can be performed in which the chemical reactivity of the quicklime product can be prevented from decreasing and fusion with impurities can be prevented.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional calcining furnace, Figure 2 is an explanatory diagram of general functional valves in the calciner (I) is not shown, and Figure 3 shows the particle size of the coke used and the decarbonation zone, Figure 4 is a diagram that does not show the positional relationship with the coke oxidation zone, Figure 4 is a diagram that does not show the temperature distribution in the furnace, Figure 5 is a diagram that shows the temperature distribution of the gas in the furnace, and Figure 6 is a diagram that does not show the temperature distribution in the furnace. 1 is a schematic configuration diagram of an embodiment for implementing the invention; FIG. 1 is a lime calcining furnace, 2 is a furnace body, 3 is a rough stone input equipment, 4 is a skip small ist, 5 is a discharge device, 6 is a feeding JII device,
7 is an exhaust gas circulation vibrator, 8.10 is a damper, 9 is an air blowing pipe, and 11.12 is a diversion measuring device. Patent applicant Ube Industries Co., Ltd. Figure 1 5 Figure 5 Figure 3 Figure 6

Claims (1)

[Claims] In the lime firing method, which is arranged in a vertical manner and performs firing by charging fixed fuel and baking powder from the top of the furnace, the exhaust gas of the furnace is mixed with heat and circulated as cooling air to maintain the temperature inside the furnace. 1. A lime firing method characterized in that the weak carbonic acid zone and the oxidized zone of the fuel are substantially aligned to prevent heating after decarboxylation.