JPS6036551B2 - Calcining furnace for powder raw materials such as cement raw materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a false dawn furnace for powder raw materials such as cement raw materials.

Generally, when firing cement raw material powder, etc., an appropriate number of stages of cyclone-type heat exchangers or greenhouse-type heat exchangers are arranged to guide the raw material powder sequentially from the top stage to the bottom stage, and at the same time,
A floating child heating device (suspension preheater) is designed to heat gas exchanged with the raw material powder and supply it to the firing furnace by guiding hot gas from the firing furnace such as a cyclone from the bottom stage to the top stage. ) has been used more than ever before.

However, such conventional devices have the following drawbacks.

That is, when considering the combination of this rotary kiln and suspension preheater, all of the heat is provided by the rotary kiln, so there is a considerable loss before it is transferred to the suspension preheater.

Furthermore, it is ideal that the calcining reaction, which absorbs a large amount of heat, be completed in a floating state before being input into a heat exchanger, such as a rotary kiln, which has poor thermal efficiency.
Due to mechanical structural problems in this transition part, characteristics of the raw material being handled (for example, stickiness), and gas temperature must be kept below a certain level, it is still not sufficient. In order to bring this closer to perfection, it is only necessary to provide a heat source for such a reaction, which ultimately consumes a large amount of heat, where it is needed. For example, it has been considered to provide a so-called calciner, in which a burner is attached between the cyclones constituting the suspension preheater, and fuel is supplied there to replenish combustion heat. However, in the intense suspended mixing turbulence layer inside the temporary hearth, the raw material powder absorbs the combustion heat from the flame in a relatively short period of several seconds, resulting in decarboxylation of nearly 100% of all particles. It cannot be expected that the process will be completed instantly, and the hypothetical rate will remain at about 85%. Therefore, if it is decided to supply more fuel than necessary to cause a sufficient pseudo-dawn reaction, the hot gas discharged from the cyclone and introduced into the exhaust fan, which is an induced draft fan, will be at a considerably high temperature. The increase in heat load not only increases the risk of damage to the refractories in the temporary furnace inner cylinder, cyclone inner cylinder, and each duct, but also causes coating troubles such as welding and solidification of raw materials in each gas path.

In this way, in addition to mechanical and thermal troubles, the unit heat consumption also increases, impeding stable continuous operation of the device.
Here, the coaching trouble is when the cement raw material is heated to a higher temperature than necessary and reaches a melting point of 1500 to 160 psi, the cement raw material that is carried along with the gas through the gas passage melts. It sticks to the surface of the firebrick installed on the inner wall of the building.

If a coaching problem occurs, the gas passage becomes narrow or, in some cases, becomes blocked. As a result, the gas and cement raw materials cannot move smoothly, and the entire device cannot function properly. In the present invention, in order to avoid the above-mentioned disadvantages, the heat transfer efficiency of the temporary furnace is improved without increasing the fuel consumption and increasing the gas temperature, thereby reducing the amount of gas discharged from the exhaust fan, which is an induced draft fan. This reduces the temperature of the gas being used to reduce the sensible heat loss of the exhaust gas, which in turn reduces fuel consumption in the calciner, lowers the unit heat consumption, and achieves stable continuous operation of the equipment by reducing damage to refractories and coaching troubles. It is intended that

In the present invention, in order to achieve the above object, the calciner is made into a Yokoreki cylindrical shape, and a burner burns liquid or solid powder fuel from the center of one end in the direction of the wisteria line to generate a flame. The raw material is formed into a long frame that is almost the entire length of the calciner, is separated from the scarlet gas in a cyclone, and is transported from the raw material supply pipe to the rotary kiln exhaust gas supply joint pipe.
The mixture is suspended in the rotary kiln exhaust gas in advance, introduced into the temporary furnace in a tangential direction from the cylindrical side wall near the burner end, and directed to the other end of the temporary furnace while swirling inside the temporary furnace. During the process, a clinker cooler installed on the discharge side of the fired raw material of the rotary kiln is used as secondary air for combustion, so as to promote the swirling force of the airflow in the same swirling direction from multiple appropriate locations in the kiln. The high-temperature air such as cooler air, which is the air that is heated and discharged when cooling the cement raw material, is guided, and while the unburned fuel and materials are completely burnt in the false dawn furnace, it is The water can be discharged from the cylindrical side wall in a tangential direction from the pond edge.

To this end, in the present invention, a burner is provided in the center of one end of the cylindrical calciner, and is arranged in the axial direction of the calciner, leading from the exhaust gas discharge part of the rotary kiln, and The end of the rotary kiln exhaust gas supply pipe, which is connected to the raw material supply joint pipe in the middle, is connected tangentially near the end of the cylindrical side wall of the falsification furnace, and is installed on the discharge side of the fired raw material of the rotary kiln. The ends of the combustion air introduction pipe led from the cement cooler are connected to multiple points on the cylindrical side wall in the middle of the temporary furnace, and the ends are connected to the cylindrical side wall at the pond end opposite to the burner installation side of the temporary furnace. , the pipes for discharging the exhaust gas from the coke furnace and the precooked raw material toward the separation cyclone are connected tangentially, and the conduits are installed on the inner wall of the coke furnace so that they gradually increase in height toward the inner surface along the swirling direction of the air flow. A plurality of sets of protuberances are provided over the entire length of the furnace or an appropriate length, and the tangential connection direction of the kiln exhaust gas supply pipe to the falsification furnace and the tangential connection direction of the combustion air introduction pipe are provided. The structure is such that the rising direction of the bulge on the inner wall of the pseudomorphic furnace, and the tangential extraction direction of the conduit for discharging exhaust gas and pseudocoagulant raw material are in the same direction.

Next, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 1 explains one embodiment of the present invention, and in the figure, reference numeral 1 indicates a scale blower, which is connected to a raw material heater 2. In FIG.

Reference numeral 3 indicates a calciner, which is an important part of the present invention, and CI indicates a separation cyclone. The raw material preheater 2 is a combination of multiple cyclones, and is a subheater that has been widely used in the past.Including the separation cyclone CI, the raw material preheater 2 is a combination of multiple cyclones. Become.

The quasi-dawn furnace 3 has a structure as shown in FIGS. 2 to 4. That is, the calcining furnace 3 is formed as a horizontally arranged cylinder, and the inside is lined with refractory bricks. A burner 5 is provided at one end of the false dawn furnace 3, at the center of the left end in FIG. This flame is the fourth
It is indicated by the symbol F in the figure.

At the end of the calcining furnace 3 on the side where the burner 5 is provided, an exhaust gas supply pipe 7 led from the front end side of the rotary kiln 6 is connected tangentially to the cylindrical side wall of the calcining furnace 3. Furnace 3
The other end is connected to a conduit 8 which is connected to a separation cyclone CI.

The raw material outlet of the cyclone C2 of the raw material subheater 2 and the rotary kiln exhaust gas supply pipe 7 are connected by a raw material supply pipe 9.

By the way, as is clear from the cross-sectional view of FIG. 3, inside the pseudo-dark furnace 3, there is a bulge that gradually becomes thicker along the swirling direction of the swirling flow generated by the exhaust gas flow led from the exhaust gas supply pipe 7. 10 are formed symmetrically.

These bulges are formed by assembling refractory bricks, and are formed continuously or intermittently from one end of the calciner 3 to the pond end, with the cross-sectional structure shown in FIG. Therefore, the raw materials introduced into the furnace together with the kiln exhaust gas move in the tangential direction on the swirling flow inside the temporary furnace, and at the same time,
Due to the presence of the bulge 10 that gradually increases along the turning direction, the rice bran receives a force toward the center of the bran bran 3, is thrown toward the center of the bran bran oven, and generates mutual movement in the radial direction with the airflow. In addition, as shown in FIG. 3, several secondary air introduction pipes 11 are attached to the temporary furnace 3 along the connection direction.
In these secondary air introduction pipes 11, combustion air introduction pipe 1 from a clinker cooler 12 provided at one end of the kiln 6 is used.
Connected to 3.

Moreover, what is indicated by the reference numeral 14 is a burner for the kiln 6. Next, the operation of this embodiment configured as above will be explained.

The powdered cement raw material is introduced into a conduit 2a that connects the uppermost cyclone C4 of the raw material heater 2 and the second cyclone C3 from above, and is then transferred to C4, C3, C2, and then the lower cyclone. It is preheated via

The flow of this raw material is similar to that of a conventional cyclone type raw material heater. The raw material discharged from the cyclone C2 of the raw material heater 2 flows into the simulated furnace 3 as a swirling flow into the furnace along with the airflow supplied from the exhaust gas supply pipe 7 via the raw material supply pipe 9. The calciner 3 is conveyed while rotating along the inner wall of the calciner 3, and at this time, it receives heat from the flame F from the burner 5, and at the same time receives convective heat transfer from the air current, and is efficiently calcined. Ru. During temporary coagulation riding on this swirling airflow, the raw material receives a force toward the center of the furnace due to the bulge 101, and is thrown toward the center, while at the same time creating mutual movement in the radial direction with the airflow.

(The black dots in the furnace shown in FIG. 3 indicate typical flow trajectories of the raw material powder.) As a result, the raw material is subjected to the fly's action and is thermally efficiently cooled. Furthermore, since the raw material is densely distributed along the inner wall of the furnace, it also has the effect of protecting the furnace wall, and furthermore, since the raw material powder is relatively sparsely dispersed in the central part of the furnace,
The flame F can be easily formed and stable combustion can be maintained. The raw material that has been almost completely prephosphorized in the calciner 3 in this way is sent to the separation cyclone CI via the conduit 8 together with the waste heat gas.

The temporary phosphorized raw material separated from the scarlet gas by the separation cyclone CI is supplied to the rotary kiln 6 via the raw material delivery pipe 15, and the final clinker firing is performed by burning the fuel with the burner 14. The clinker fired in the rotary kiln 6 is taken out, cooled by a clinker cooler 12, and sent to the next process. Further, in the separation cyclone CI, the noble E hot gas from which the raw material has been separated is supplied to the cyclone C2 of the raw material preheater 2 via the conduit 16.

After that, the 8E hot gas gradually moves to the upper cyclone while exchanging heat with the raw material, and finally reaches the uppermost cyclone C.
4, it is discharged to the outside of the system by the exhaust fan 1. Note that the flow of exhaust gas in the raw material preheater 2 is exactly the same as in the known conventional device. FIG. 5 is for explaining another embodiment of the present invention. In this embodiment, the installation side of the burner 5 is provided on the conduit 8 side that discharges the raw material together with the exhaust gas. This is different from the embodiments described above.

Since the present invention has the above-described configuration, the following excellent effects can be achieved.

'1- High thermal efficiency and low unit heat consumption. ■ The raw material not only undergoes convection heat transfer with the airflow, but also moves in a spiral pattern from the time it enters the furnace to the time it is discharged, rotating around the direction in which the flame is formed by the burner. It can receive radiant heat.

■ Due to the effect of the ridges on the inner wall of the furnace, there is mutual movement in the radial direction with the airflow even during swirling, resulting in a high heat transfer effect.

■ Since the swirling force is aided by secondary air, a strong swirling airflow is always maintained from the time it flows in until it is discharged.
It provides good results for heat transfer and allows longer residence time in the furnace.

■ Because the raw materials entering the furnace are densely distributed near the furnace wall due to the swirling flow, local heating of the furnace wall is prevented and the refractory bricks are protected, and there is less coaching trouble due to fusion of raw materials and continuous stable operation is possible. can.

3) When the fuel is solid combustion such as pulverized coal, the raw material powder is thin in the center of the furnace axis where the flame is to be formed, so a stable combustion space can be maintained, resulting in excellent combustibility. .

(4) Because of the machine-shaped arrangement, the structure of the pseudo-dark reactor, which was conventionally a high-rise structure, can be made as low as possible, reducing construction costs.

{5) Unlike a vertical calciner, the airflow requires less power to raise the raw material, so the pressure loss is relatively small, and the equipment cost and power cost for the exhaust fan can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic horizontal view of the entire temporary holding device to which the temporary storage furnace according to the present invention is applied, and FIG. FIG. 5 is a longitudinal side view illustrating another embodiment of the present invention. 1 is an exhaust fan, 2 is a raw material fermenter, 3 is a temporary bran furnace, CI is a separation cyclone, 6 is a rotary kiln, 7 is an exhaust gas supply pipe,
8 is a conduit, 9 is a raw material supply pipe, 10 is a bump, 11 is a secondary air supply pipe, and 12 is a clinker cooler. Kiyoshi/Zuushi 2 zu moat 3 heinous 4 zu kiyoshi yo

Claims (1)

[Claims] 1. A burner is installed in the center of one end of a horizontal cylindrical calciner and is arranged in the axial direction of the calciner, leading from the exhaust gas discharge part of the rotary kiln, and a raw material supply pipe is connected in the middle. The end of the rotary kiln exhaust gas supply pipe is tangentially connected near the end of the cylindrical side wall of the calciner, and the combustion gas is guided from the cement cooler installed on the discharge side of the fired raw material of the rotary kiln. The ends of the air introduction pipe are connected to multiple points on the middle cylindrical side wall of the calciner, and the other end of the cylindrical side wall opposite to the burner installation side of the calciner is connected to Conduits for discharging the calcined raw material towards the separation cyclone are connected tangentially, and the inner wall of the calciner is provided with a protuberance that gradually increases in height toward the inner surface along the swirling direction of the air flow, and is installed along the entire length of the furnace. Alternatively, a plurality of sets may be formed over an appropriate length, and the tangential connection direction of the kiln exhaust gas supply pipe to the calciner, the tangential connection direction of the combustion air introduction pipe, and the protrusion of the inner wall of the calciner. A calcining furnace for powder raw materials such as cement raw materials, characterized in that the rising direction and the tangential take-out direction of a conduit for discharging exhaust gas and calcined raw materials are in the same direction.