JPS5932176B2 - Calcination equipment for powder and granular raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a calcination device for granular material interposed between a kiln and a suspension preheater.

Recently developed suspension preheater kilns with calcining furnaces focus on the fact that a large amount of heat is consumed in the thermal decomposition (calcination) process of raw materials during the cement firing process, and the A separate calciner for carbonic acid (carbonic acid) is provided, and the
A method is adopted in which 0% to 60% is directly supplied to the calcining furnace.

The present invention aims to provide an apparatus capable of efficiently carrying out the combustion reaction of fuel in such a calcining furnace, thereby sufficiently calcining powdered raw materials. This is a calcining device for powder and granular materials installed between the rising tact and the suspension preheater at the bottom of the kiln. Connected to the rising duct,
A cylindrical part is provided directly above the inverted cone-shaped part, a cone-shaped constriction part is provided at the top of the cylindrical part, and the conical part has a lower part shaped like an inverted cone and an upper part formed into a cylindrical shape. The upper part of the expanded space is connected to the cyclone of the suspension preheater via an exhaust pipe, and a fuel supply device and a raw material supply device are installed on the side wall of the furnace body between the opening and the throttle section. The present invention provides a calcination device for granular raw materials, which further includes a combustion air supply port provided in a side wall of the furnace body close to a fuel supply device.

The illustrated example is an inverted cone-shaped portion 4' at the bottom of the lower furnace body 4 in a calcination device for powder raw material provided between a rotary kiln and a suspension preheater. an opening 3 is provided at the bottom thereof, which is connected to the riser duct 2 of the rotary kiln 1, and a cylindrical upper furnace body 9 is connected to the upper part of the lower furnace body 4 via a constriction part 8, The upper part of the cylindrical upper furnace body 9 is connected to the cyclone 12 of the suspension preheater, and a fuel burner 6, a combustion air supply lower, and a raw material supply device 5 are provided between the opening 3 and the throttle part 8. This is a calcining device for powder raw materials.

In the figure, 6' is a fuel burner provided on the side wall of the inverted conical portion 4', 10 is a collision wall, and 11 is an exhaust pipe.

The combustion exhaust gas discharged from kiln 1 is transferred to riser duct 2.
It passes through the opening 3 and is introduced into the lower furnace body 4 as an upward jet.

On the other hand, fuel is supplied from the fuel burner 6 or fuel burner 6.61, combustion air is introduced from the secondary air introduction lower, and the open lower 3 mentioned above is supplied with granular material from the chute 5. Since this is connected to the inverted cone-shaped part 4', a spouted layer of the raw material is formed by the above-mentioned upward jet flow, so that the residence time of the raw material in the furnace is long.

As described above, since the residence time of the raw material in the furnace is long, the input raw material is efficiently calcined by the combustion heat of the fuel.

Furthermore, since a constriction part 8 is provided at the upper part of the lower furnace body 4, the combustion exhaust gas containing unburned components from the lower furnace body 4 passes through the constriction part 8 and the enlarged space of the upper furnace body 9. , the combustion exhaust gas flow is given speed changes of acceleration and deceleration, and due to the mixing effect due to the speed change, the unburned contents and the remaining oxygen come into sufficient contact with each other, so that the unburned contents are combusted in the upper furnace body 9.

Therefore, combustion efficiency is good.

Furthermore, there is no problem of coating adhesion during the preheating process due to unburned content.

At this time, if it is desired to perform denitration along with calcination, fuel is supplied from the fuel burner 6, 6', but the amount of fuel in the fuel burner 6' is changed depending on the degree of denitration required.

A case in which the calcination device of the present invention is applied to cement calcination equipment to perform denitrification along with calcination will be described in detail below.

In FIG. 1, combustion exhaust gas generated in a kiln 1 undergoes heat exchange inside the kiln, and then is introduced into a calcining furnace as an upward jet from an opening 3 at a temperature of 1000 to 1300°C.

The raw material preheated to 550 to 650°C by the chute 5 is supplied to the calcining furnace, and the raw material is fluidized by the above-mentioned upward jet flow, a part of which is calcined, and the upper part of the opening 3 has a
A spouted bed of cement raw material and its calcined product CaO is formed.

This spouted bed is maintained at a temperature of 820 to 950°C, which is lower than the temperature of the combustion exhaust gas, due to the endothermic decomposition of the raw material.

If more fuel is supplied from the burner 6' into the spouted bed than is necessary to consume the excess air contained in the kiln exhaust gas, part of the fuel will be burned, and the remaining part will be absorbed by the intense mixing action within the bed and the above-mentioned temperature. By 820-950℃, CO,
It is decomposed into reducing substances such as H2, CH, etc., and the inside of the layer becomes a highly active reducing atmosphere.

The NOx molecules introduced together with the exhaust gas from the kiln exhaust gas introduction opening 3 repeatedly collide and disperse violently with the calcined material CaO, which acts as a raw material and catalyst in the spouted bed, in the reducing atmosphere at 820 to 950°C. According to
will be promptly refunded.

The rate at which NOx contained in kiln exhaust gas is reduced is
It can be controlled by the amount of fuel supplied into the spouted bed from the burner 6'.

Normally, the amount of fuel required to reduce the total amount of NOx is about 20% of the fuel required for firing cement raw materials,
On the other hand, since the fuel required for calcination is 60%, theoretically, with that amount of fuel, the amount of NOx generated from the entire calcination equipment can be reduced to a negligible trace amount.

A floating layer is formed above the spouted bed by the raw materials and calcined material supplied from the chute 5.

Secondary air is supplied from the introduction lower, and fuel is supplied from the burner 6 provided adjacent to it.

The fuel gasified in the spouted bed receives new supply of oxygen in the floating layer and combusts rapidly, calcining the cement raw material.

However, due to the endothermic effect of decomposition of the suspended raw materials, the combustion within the floating layer does not rise to a high temperature of 950° C. or higher (therefore, there is no risk of newly generating NOx due to combustion).

In the illustrated embodiment, a mixed layer having an aperture 8, an upper furnace body 9, a collision wall 10, and an exhaust pipe 11 is installed above the floating layer.

In this mixed layer, the combustion gas containing unburned components that has risen from the floating layer is first accelerated by the contraction section 8, enters the enlarged space section of the upper furnace body 9, and is decelerated, and then passes through the collision wall 10.
By colliding with and reversing, the unburned content and the remaining oxygen come into sufficient contact with each other due to the mixing effect due to the speed change and direction change, and the unburned content is combusted during that time.

The waste combustion gas is then sent from the upper furnace body 9 to the cyclone 12 through the exhaust pipe 11.

The calcination device of the present invention is a calcination device for granular raw materials that is installed between a rising duct at the bottom of a kiln and a suspension preheater, and has a lower part shaped like an inverted cone and an opening at the bottom. A cylindrical part is provided directly above the inverted cone-shaped part, a cone-shaped constriction part is provided in the upper part of the cylindrical part, and a cone-shaped constriction part is provided in the upper part of the cone-shaped part, and this is connected to the rising duct of the kiln bottom. An enlarged space portion having an inverted conical shape at the bottom and a cylindrical upper portion is connected, and the upper portion of the enlarged space is connected to the cyclone of the suspension preheater via an exhaust pipe, and the opening and the constriction portion are connected to each other. Since the fuel supply device and the raw material supply device are provided on the side wall of the furnace body between the two, the residence time of the raw material in the furnace is long, and the raw material can be calcined efficiently.

Additionally, since the fuel is almost completely combusted in the calciner, problems with coating adhesion caused by unburned components during the preheating process can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a calcination device for granular raw materials according to the present invention. 1...Kiln, 2...Rising duct,
3...Opening for introducing exhaust gas, 4...Lower furnace body, 4'...Inverted conical part, 5...
Raw material supply device (chute), 6゜6'...Fuel supply device (burner), 7...Secondary air inlet,
8... Reduced part, 9... Upper furnace body, 10
...Collision wall, 11...Exhaust pipe, 12.
·····Cyclone.

Claims (1)

[Claims] 1. A calcining device for granular raw materials installed between a rising duct at the bottom of a kiln and a suspension preheater, the lower part of which is formed into an inverted conical shape and an opening provided at the bottom. Connected to the rising duct of the butt, a cylindrical part is provided just above the inverted cone-shaped part, a cone-shaped constricted part is provided in the upper part of the cylindrical part, and a lower part of the conical part is connected to the inverted cone-shaped part. The upper part of the enlarged space is connected to the cyclone of the suspension preheater via an exhaust pipe, and the upper part of the enlarged space is connected to the cyclone of the suspension preheater, and the upper part of the enlarged space is connected to the cyclone of the suspension preheater. A calcination device for granular raw materials, which is provided with a fuel supply device and a raw material supply device, and further includes a combustion air supply port on a side wall of a furnace body close to the fuel supply device.