JPH0222018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calcination furnace for cement raw materials, and particularly to a calcination furnace for cement raw materials suitable for combustion of solid fuel with a slow combustion rate.

In a conventional cement raw material calcining furnace of a rotary kiln with a suspension preheater, fuel combustion and decarboxylation reaction are simultaneously carried out in the calcining furnace, as shown in FIG. That is, raw material a from the suspension preheater enters combustion chamber b, and in this chamber, rotary kiln exhaust gas c
and the gas produced by burning the fuel supplied from the combustion burner e by the cooler bleed air d, and in the combustion chamber b, combustion of the fuel and decarboxylation reaction were performed while forming a spouted bed. . (In the figure, solid line arrows indicate the flow of hot air, and dashed line arrows indicate the flow of raw material powder.) An enlarged space g is formed in the upper part of the combustion chamber b via a throttle part f, and unburned fuel is contained in this space. The combustion of the amount and the calcination of the cement raw material are completed, and the calcined raw material is discharged from the discharge port h.

According to this conventional method, the combustion heat of the fuel is immediately used for the calcination reaction of the raw materials, and the temperature inside the furnace is relatively low, with a partial temperature of 1000℃ and an average temperature inside the furnace of 900℃.
The burning rate of fuel in the furnace was also relatively low.

In this way, conventional methods do not have anything that acts as a spark, so when using pulverized coal with a slow combustion rate, especially coke with a low volatile content, it is necessary to greatly improve combustion efficiency. was decreasing.

The present invention eliminates this drawback and provides a cement raw material calciner that can maintain good combustion efficiency even when using collective fuel with a slow combustion rate. In a cement raw material calciner installed between a rotary kiln, the calciner is composed of a hot air generating furnace and a jet decarboxylation reaction chamber connected above the hot air generating furnace, and the hot air generating furnace introduces kiln exhaust gas into the lower part. A frame holder part (flame holding part) is formed in the center of the side wall and projects outward.
Next, air introduction dust and fuel supply pipes are provided respectively, and a chute is provided on the upper side wall for supplying raw materials from the suspension preheater.
The jet decarboxylation reaction chamber is connected to the top of the hot air generating furnace via a constriction part, and a chute is also provided on the lower side wall of the jet decarboxylation reaction chamber for supplying the raw material from the suspension preheater, and The cement raw material calcining furnace is characterized by having a duct connected to a cyclone on the upper side wall.

The present invention will be described below with reference to illustrated embodiments.

Figure 2 shows an overall view of a rotary kiln with a suspension preheater equipped with a cement raw material calcination furnace. Things are illustrated. 3 is a cooler; 4 is a conduit for guiding the cooler bleed air to the cement raw material calcining furnace 2; ₅ is a suspension preheater;
Equipped with 5 ₄ . 6 is a preheater raw material feeder;
Reference numeral 7 denotes a chute for supplying raw materials from the suspension preheater 5 to the cement raw material calcining furnace 2.

In the figure, the raw material supplied to the preheater by the plater raw material feeder 6 enters the calcination furnace 2 through the chute 7 which has been preheated in the suspension preheater 5.

The calcining furnace 2, for example, as shown in FIG.
₁ and an upper jet chamber ₁₁₂ .

The hot air generating furnace 10 is formed from a frame holder 10 ₁ and a cylindrical portion 10 ₂ . The frame holder portion 10 ₁ has a short cylindrical shape, and is formed at a plurality of locations on the side wall of the cylindrical portion 10 ₂ .

First, the fuel e is combusted by the cooler bleed air d in the frame holder part 10 ₁ to generate combustion heat and form a burner flame. The ignition area i of this burner flame is 1300°C or higher, and furthermore, a local high temperature area j of 1200°C or higher is formed in the center of the hot air generating furnace 10.

Generally, as the combustion temperature increases, the combustion rate increases exponentially. Because of this localized high-temperature region, the combustion rate of the fuel increases significantly, and flame-retardant fuels such as coal and coke with a volatile content of less than 10% cannot be burned sufficiently in conventional calciners. , even low-rank coal can be easily combusted.

On the other hand, a portion a ₁ (0 to 40%) of the raw material a preheated by the suspension preheater 5 is introduced into the inner wall of the hot air generating furnace 10 to protect the furnace wall. The amount of raw material introduced into the hot air generating furnace 10 varies depending on the burning rate of the fuel, and is almost zero for solid fuels with a volatile content of 5% or less.

The high temperature combustion gas generated in the hot air generating furnace 10 passes through the throttle section 12 and enters the two-stage jet decarboxylation reaction chamber 1.
1. The two-stage jet decarboxylation reaction chamber consists of two upper and lower jet chambers, and forms upper and lower spouted layers with the constricted portion 13 as a boundary.

100 to 60% of the raw material preheated by preheater 5 is
It is introduced into the lower jet chamber 11 ₁ of the two-stage jet decarboxylation reaction chamber, and the decarboxylation reaction is carried out within the chamber 11 . In addition, the unburned portion from the hot air generating furnace 10 is mixed due to the reduction and expansion of the throttle portions 12 and 13.
It is sufficiently re-burned in the reaction chamber 11.

Thus, in the embodiment shown in FIG. 3, the hot air generation area (), the lower jet decarboxylation reaction area (), and the above-mentioned reburning area () are formed, and the cement raw material is calcined using a solid fuel with a slow combustion rate. can be done efficiently.

Note that the cross section of the cylindrical portion 10 ₂ of the hot air generating furnace 10 may be the same as the cross section of the two-stage jet decarboxylation reaction chamber 11, or may be larger.

In addition, in order to provide the calcination furnace of the present invention with a function of reducing nitrogen oxides, the air for reheating and calcination is supplied to the two-stage jet decarboxylation reaction chambers 11 ₁ , 11 ₂ or the inlet duct 8 of the separation cyclone 5 ₄ or the separation cyclone 5 . It is also possible to introduce a partial branch to ₄ .

The above explanation has been about the embodiment of the present invention based on the conventional device shown in FIG. 1, but it goes without saying that the present invention can be modified in various ways within the scope of its gist.

For example, as shown in FIG.
1, the constriction section 13 can be removed. The symbols of each part in FIG. 4 correspond to those in FIG. 3.

Since the calcination furnace of the present invention is provided with a flame holder part in the hot air generating furnace, the radiant heat generated by the red-hot part and the formation of a localized high temperature area can be effectively used for igniting the flame, and flame-retardant fuel can be can also be burned sufficiently.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of a conventional cement raw material calcining furnace.
Figure 2 is an overall conceptual diagram of a rotary kiln with a suspension preheater incorporating the cement raw material calciner of the present invention, Figure 3 is a conceptual diagram of the cement raw material calciner of the present invention, and Figure 4 is a cement raw material calciner of the present invention. FIG. 3 is a conceptual diagram of another embodiment of the raw material calcining furnace. DESCRIPTION OF SYMBOLS 10...Hot air generation furnace, ₁₀₁ ...Frame holder part, ₁₀₂ ...Cylindrical part, 11...Two-stage jet decarboxylation reaction chamber, ₁₁₁ ...Lower jet chamber, ₁₁₂ ...Upper jet chamber, 12, 13... Aperture section.

Claims (1)

[Scope of Claims] 1. A cement raw material calcining furnace disposed between a suspension preheater and a rotary kiln, which comprises a hot air generating furnace and a jet decarboxylation reaction chamber connected above the hot air generating furnace. The above hot air generating furnace is equipped with a kiln exhaust gas inlet at the bottom, and a frame holder part (flame holding part) that protrudes outward in the center of the side wall.
A secondary air introduction duct and a fuel supply pipe are provided in the frame holder part, and a chute for supplying raw materials from the suspension preheater is provided on the upper side wall of the frame holder, and the top part of the hot air generating furnace is The jet decarboxylation reaction chamber is connected to the jet decarboxylation reaction chamber through a constriction part, and the lower side wall of the jet decarboxylation reaction chamber is also provided with a chute for supplying the raw material from the suspension preheater, and the upper side wall is connected to a cyclone. A cement raw material calcining furnace characterized by being equipped with a duct for heating. 2 The jet decarboxylation reaction chamber is composed of two or more stages of jet decarboxylation reaction chambers, the lowest jet chamber is provided with a chute for supplying the raw material from the suspension preheater, and the upper side wall of the uppermost jet chamber is The cement raw material calcining furnace according to claim 1, further comprising a duct connected to a cyclone.