JPH0253094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention makes it possible to efficiently recover and utilize exhaust gas sensible heat in a raw material powder preheating device, for example, a cyclone type multi-stage preheating device, attached to a device for firing cement raw material powder. It is related to the device.

Figure 1 shows an example of equipment used when preheating and firing cement raw materials.This equipment is mainly used as a cyclone as a raw material powder collector.
C ₁ to C ₃ , separation cyclone C ₄ , and a preheating device 1 formed by vertically arranging a calcining furnace 2 with a combustion device that constitutes the lowest heat exchange stage, a calcining furnace 3, and a clinker cooler 4. be done. During these operations, the raw material powder A is sent from the feeder 5 into the duct 7a, heated by the hot gas rising inside the duct 7a, and then separated from the hot gas by the cyclone _C1 . The raw material enters the next gas duct 7b through the raw material chute 8a, and thereafter undergoes the same steps and is sequentially heated. Finally, after being calcined in a calcining furnace 2 equipped with a burner 6a, it enters a separation cyclone _C4 , and is then introduced into the calcining furnace 3 from a raw material chute 8d through a calcining furnace inlet end cover 12.

High-temperature air from the cooler 4 and firing fuel from the burner 6b are introduced into the firing furnace 3, and the clinker that has been fired at high temperature is passed through the clinker cooler 4.
The clinker conveyor 11
It is carried out by. In addition, 9 is a surplus air induction ventilation fan, 10 is a forced air blower, 13 is an air bleed duct, and 14
15 indicates an exhaust gas induced draft fan, and 15 indicates an exhaust gas duct.

The temperature of the exhaust gas discharged from the uppermost cyclone C _i of the preheating device 1 in such a baking device is usually 350°C, although it depends on the heat exchange method and number of stages of the preheating device 1.
The temperature is around 400℃, and there is still a considerable amount of thermal energy left. Therefore, in order to make more effective use of this exhaust gas sensible heat, the exhaust gas duct 1 is installed as shown in Figure 1.
Equipment for utilizing exhaust heat, such as a boiler 16, is installed in the middle of the exhaust gas, and steam is generated through heat exchange with high-temperature exhaust gas, which is used for power generation, etc., thereby improving thermal economy. In addition, in order to cope with the case where the water pipe of the boiler 16 is damaged, a bypass duct 17 is provided to bypass the boiler 16, and a damper 18a is provided in the duct main pipe 15, and a damper 18b is provided in the bypass duct 17. This allows the firing apparatus to continue operating.

However, in such a conventional waste heat utilization device, since the temperature of the exhaust gas in the exhaust gas duct 15 is not so high, the temperature and pressure of the steam generated in the boiler 16 cannot rise sufficiently, resulting in low power generation efficiency in the turbine, and furthermore, the preheating is insufficient. Since the exhaust gas from the device 1 is generally also used as a heat source for drying raw materials, only the surplus can be used for heating in the boiler 16.
As a result, the efficiency of the power generation turbine is not sufficiently high due to the lack of available gas sensible heat.

As a way to compensate for this lack of heat, it is possible to install a combustion chamber at a suitable location in the exhaust gas duct 15 and increase the exhaust gas temperature by supplying fuel and combustion air. This is not desirable in terms of equipment or operation. Moreover, when cheap coal is used as fuel, it becomes difficult to dispose of combustion residual ash generated in the combustion chamber.

The present inventor focused on the above-mentioned circumstances and conducted research to increase the sensible heat of the exhaust gas and improve the heat utilization efficiency of exhaust heat utilization equipment such as boilers for power generation turbines. The present invention was completed as a result of such research, and its configuration consists of vertically arranging multiple stages of raw material powder collectors above the inlet end cover of the firing furnace, as shown in FIG. Cement raw material powder in which exhaust heat utilization equipment is attached to the exhaust gas system of a preheating device which connects the raw material powder collectors and between the lowest raw material powder collector and the inlet end cover by gas ducts, respectively. In the preheating device, in order to increase the temperature of the exhaust gas introduced into the exhaust heat utilization equipment and increase its heat utilization efficiency, one end is opened to the lower stage gas duct or the inlet cover of the firing furnace, and the other end is opened to the exhaust gas system. In addition to installing a short-circuit gas pipe that opens into the exhaust gas duct leading to the waste heat utilization equipment, a dust collector is installed in the middle of the short-circuit gas pipe, and the powder discharge port of the dust collector is connected to the preheating device. The gist is in place or connected to the inlet end of the kiln.

The configuration and effects of the present invention will be explained below based on the drawings showing examples. However, the following are representative examples and do not limit the present invention, and the types, structure, etc. of the raw material powder collector, It is within the technical scope of the present invention to appropriately change the design of not only the number of stages but also the specific configuration of the exhaust heat utilization equipment.

FIG. 2 is a schematic explanatory diagram showing an embodiment of the present invention, and the overall configuration can be understood in accordance with the example in FIG. 1. The characteristic part in this example is the preheating device 1
The exhaust gas duct 15 extending from the air to the exhaust heat utilization equipment such as the boiler 16 and the gas duct (7a in the figure) in the preheating device 1 are connected by a short-circuit gas conduit 19, and the uppermost cyclone C _i is connected from the gas duct 7a to The short-circuited and bled hot gas is combined with the exhaust gas discharged from the cyclone C _i and guided to the boiler 16. That is, the hot gas extracted from the gas duct 7a is not used for heat exchange with the cement raw material powder on the downstream side (downstream side as seen in the gas flow direction, the same applies hereinafter) of the extraction section, and maintains a high temperature. Therefore, connect this to the exhaust gas duct 15.
When combined with the exhaust gas inside, the boiler 16 is finally
The temperature of the exhaust gas introduced into the tank increases. Therefore, the heat recovered in the boiler 16 increases significantly, and at the same time,
Since the temperature and pressure of the generated steam are increased, the power generation efficiency of the turbine is significantly improved. The hot gas bleed position is not limited to the example shown in the figure, and the gas ducts 7b, 7
It is also possible to bleed air from c and 7d, or directly from the inlet cover 12 of the calcining furnace 2 or firing furnace 3.
Additionally, air can be extracted from multiple locations if necessary. At this time, the temperature of the hot gas is higher as the air is extracted from the upstream side, so the amount of air extracted to raise the exhaust gas temperature to a constant level is small. On the other hand, the exhaust gas temperature changes depending on the amount of extracted hot gas, and the more the amount is increased, the more the exhaust gas temperature rises. Therefore, as shown in FIG. By adjusting the amount of short-circuited hot gas using the flow rate regulator 20 according to the temperature required to operate the heat utilization equipment efficiently, the temperature of the exhaust gas introduced into the exhaust heat utilization equipment can be raised to an arbitrary temperature. Furthermore, as shown in the figure, a temperature detector 21 is disposed downstream of the joint of the short-circuit gas conduit 19 to the exhaust gas duct 15, and an opening regulator 22 is connected to the flow regulator 20, and the temperature detector 21 is connected to the flow regulator 20. Regulator 2
2 to the control device 23 to control the amount of short-circuit gas so that the exhaust gas temperature detected by the detector 21 becomes a predetermined value, it can be introduced into the exhaust heat utilization equipment even if the operating status of the baking equipment changes. The temperature of the exhaust gas can be maintained as constant as possible. As a result, the amount of heat supplied to the waste heat utilization equipment becomes constant, its operating condition becomes stable, and in the case of a heat generating device, a constant amount of power can always be obtained. Further, the setting of the amount of power generation can be adjusted as necessary, and furthermore, an increase in the amount of fuel used in the firing apparatus due to short-circuiting a part of the high-temperature gas can be minimized. At this time, in order to prevent cement raw material powder from being discharged from the preheating device to the exhaust gas system due to the short-circuit gas, it is necessary to install a dust collector 24 in the middle of the short-circuit gas pipe 19 as shown in the figure. The fine powder discharged together with the gas may be captured by the dust collector 24 and returned through the chute 25 to the inlet end cover 12 of the calciner 3 by the lower heat exchange stage or the calciner 2, for example.

FIG. 3 shows another embodiment of the present invention,
The preheating device 1 does not include a calcining furnace, and the lowermost cyclone C ₄ is directly connected to the calcining furnace inlet cover 12 through a gas duct 7d, and is also connected to the hot gas extraction position and the return of fine powder captured by the dust collector 24. Other than changing the position, the configuration is the same as the example shown in FIG. 2, but since there are many heat exchange stages to be short-circuited, the cross-sectional area of the short-circuit gas pipe 19 and the dust collector can be small, and if necessary, multiple heat exchange stages can be used. A tiered dust collector can be installed.

In this way, in the present invention, a part of the high-temperature gas in the preheating device 1 is short-circuited to the exhaust gas duct without performing heat exchange with the cement raw material powder, and the preheating efficiency of the raw material powder in the preheating device 1 is slightly increased. This increases the temperature of the exhaust gas at a cost, and it becomes necessary to increase the amount of fuel used in the calciner 2 or the calciner 3. However, this increased amount of heat is
The increase in exhaust gas temperature can be fully recovered by effective use of exhaust heat utilization equipment, and the overall energy economy is considerably improved over the conventional example. Moreover, since the fuel originally used in the calciner 2 and the calciner 3 is only increased, there is no fear that the equipment and operational burden will increase compared to the case where fuel is supplied to the exhaust gas system. In addition, even when solid fuel such as pulverized coal is used as fuel, the ash produced by combustion is consumed as part of the cement raw material in the calcination device, so no special ash processing equipment is required.

Further, in the present invention, as shown in FIG.
Although it has been explained that it can be used as a device without the calcination furnace 3, in order to stabilize the operating conditions of the calcination furnace 3, the calcination furnace 2 equipped with a combustion device is connected to the lowest stage gas duct of the preheating device 1, It is preferable to absorb the temperature change caused by hot gas extraction in the preheating device 1 by adjusting the operating conditions of the calciner 2. In addition, the present invention has the following features in order to increase the heat utilization efficiency of the exhaust heat utilization equipment: As mentioned above, since the exhaust gas temperature is increased at the expense of preheating efficiency, when the exhaust heat utilization equipment is not operated, for example, the flow regulator 20 in Figs. 2 and 3 is completely closed to prevent a short circuit of the hot gas. Instead, the preheating device 1 is used in such a way that it exhibits the highest thermal efficiency.

In addition, although the figure shows an example in which one system of preheating equipment is combined with one firing furnace 3, it is also possible to install two or more systems of preheating equipment in conjunction with one firing furnace. It is also possible to apply the technology of the present invention to at least one train, and to combine the exhaust gases from multiple trains and guide them to the exhaust heat utilization equipment. In addition to the boiler for power generation turbines as shown in the figure, exhaust heat utilization equipment includes
Examples include raw material drying equipment such as a rotary dryer, various equipment attached to firing equipment such as raw material drying and simultaneous pulverization equipment using a roller mill, ball mill, etc., and various nearby heat demand equipment.

The present invention is generally configured as described above, but the point is to raise the temperature of the exhaust gas by short-circuiting a portion of the hot gas on the upstream side to the exhaust gas duct by skipping at least one heat exchange stage. As a result, the amount of heat supplied to the waste heat utilization equipment was increased, and its heat utilization efficiency was greatly improved. This increase in the amount of recovered energy more than compensated for the increase in fuel used in the firing furnace, etc., and the energy economy of the entire preheating, firing, and waste heat utilization equipment was significantly improved.
At this time, since a dust collector is disposed in the middle of the short-circuit gas conduit, it is possible to prevent cement raw material powder from escaping from the preheating device to the exhaust gas duct as much as possible.

The device of the present invention has an extremely simple configuration;
It is also easy to apply to existing equipment equipped with exhaust heat utilization equipment. Furthermore, the pressure drop in the preheating device is reduced due to the reduction in the amount of gas passing through the short-circuit heat exchange stage of the preheating device, or the short-circuiting gas reduces the circulation and accumulation of harmful components such as alkaline content in the combustion gas. There are also side effects.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a known raw material powder preheating/calcination and waste heat utilization equipment, Fig. 2 is an explanatory diagram showing an embodiment of the present invention, and Fig. 3 is a main part showing another embodiment of the present invention. It is an explanatory diagram. 1...Preheating device, 2...Calcination furnace, _C1 to _C4 ...
Raw material powder collector, 3...Calcination furnace, 4...Clinker cooler, 7...Gas duct, 15...Exhaust gas duct, 16...Exhaust heat utilization equipment, 19...Short-circuit gas conduit, 20...Flow rate adjustment vessel.

Claims (1)

[Scope of Claims] 1. A plurality of stages of raw material powder collectors are vertically arranged above the inlet end cover of the firing furnace, and between the raw material powder collectors and between the raw material powder collector at the lowest stage and the inlet. In a cement raw material powder preheating device in which exhaust heat utilization equipment is attached to the exhaust gas system of the preheating device, which is connected to the end cover by a gas duct, the temperature of the exhaust gas introduced from the preheating device to the exhaust heat utilization equipment is determined. In order to increase the temperature, a short-circuiting gas conduit is installed to short-circuit a part of the hot gas from the lower stage gas duct or the inlet cover of the firing furnace to the exhaust gas duct up to the waste heat utilization equipment of the exhaust gas system. A cement with exhaust heat utilization equipment, characterized in that a dust collector is disposed in the middle of a short-circuit gas pipe, and the powder discharge port of the dust collector is connected to a suitable position of a preheating device or to an inlet end cover of a kiln. Raw material powder preheating device. 2. A cement raw material powder preheating device according to claim 1, wherein a calciner equipped with a combustion device is connected to a gas duct that connects the lowest raw material powder collector and the inlet end cover of the calciner. 3 In claim 1 or 2, a temperature detector is installed in the exhaust gas duct leading to the exhaust heat utilization equipment, and the short-circuit gas conduit is equipped with a flow rate regulator for passing gas and an opening adjustment for the regulator. Set up a vessel,
The cement raw material powder preheating device further comprises a control device that operates the opening degree adjuster according to a signal from the temperature detector so that the temperature detected by the temperature detector becomes a predetermined value.