JPS62276303A - Method of heating waste-heat boiler in baking device - 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 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a heating method for a waste heat boiler in a cement powder raw material firing apparatus.

(Prior Art) Conventionally, there is a sintering apparatus for powder raw materials for cement, which is constructed as shown in FIG.

In the figure, 1 is a rotary kiln-type firing furnace that produces clinker by firing cement powder raw materials, 2 is a clinker cooler that cools the clinker discharged from the firing furnace 1 with an air flow, and 3 is an exhaust gas from the firing furnace 1. 4 is a raw material supply device that supplies the powder raw material to the preheating device 3.

The clinker outlet side of the firing furnace 1 is connected to the cooler 2 by a firing shade 6 equipped with a fuel supply device 5a. In this firing furnace 1, fuel is combusted using high temperature air from the cooler 2. On the other hand, a forced air blower 7 that supplies clinker cooling air to the cooler 2 is connected to the cooler 2, and an exhaust fan 8 that discharges a portion of high-temperature air from the cooler 2 is connected to an exhaust duct. Connected by 9.

On the other hand, the preheating device 3 has four stages of cyclones 01 to C4, which are stacked vertically and connected to each other, as powder collectors. That is, the gas inlet of each cyclone and the gas outlet of another cyclone located below this cyclone are connected by gas ducts 1la to 11c, respectively. Further, the inlet end layer 12 of the firing furnace 1 and the gas inlet of the cyclone C4 located at the lowest stage are connected to the gas duct 13.
Connected by Further, the gas outlet of the cyclone C1 located at the top stage is connected to the exhaust gas induction fan 14 by an exhaust gas duct 15.

The powder discharge ports of each of the cyclones and the gas inlet side gas ducts of other cyclones located below this cyclone are connected by raw material chutes 17a to 17c, respectively. In addition, the powder outlet of the lowest cyclone C4 is
It is connected to the inlet end layer 12 of the firing furnace l by a raw material chute 18. Furthermore, the raw material supply device 4 is connected to the gas inlet side gas duct lla of the uppermost cyclone C1 through a supply chute 19.

Further, a calciner 21 equipped with a fuel supply device 5b is interposed between the gas inlet side gas duct 13 of the lowermost cyclone C4 and the raw material chute 17c from the cyclone C3 located above the cyclone C4. will be established. This calciner 21 heats the powder raw material with the exhaust gas from the calciner 1 and the combustion gas obtained by burning the fuel, and this calciner 21 and a cooling machine are used to supply air for combustion of the fuel. 2
and are connected by a bleed air duct 22. 23 is a finished product conveyor, which conveys the clinker that has been cooled in cooling Ja and 2 to become a finished product to the next process. In addition, the exhaust gas duct 15 from the preheating device 3 includes an oxygen concentration meter 24 and a thermometer 25 for exhaust gas.
and is provided.

Next, the operating state of the cement powder raw material firing apparatus will be explained. The powder raw material sent to the preheating device 3 by the raw material supply device 4 is fed to the supply chute 1 from the raw material supply device 4.
9 to the gas duct 11a, and the uppermost cyclone c1 accompanies the rising airflow in the gas duct lla.
sent to.

and cyclones C1, C2, C3 and raw material shoe)
17a, 17b, and is sequentially preheated by hot air rising through gas ducts lla, llb, llc. This preheated powder raw material is f: fS3
The stage cyclone c3 is supplied to the calciner 21 through the raw material shoe 17c. On the other hand, from the cooler 2 to the oil duct 2
Fuel supplied from the fuel supply device 5b is combusted in the calciner 21 using high-temperature combustion air induced via the calcination furnace 21. The powder raw material is calcined in the calciner 21 by the heat generated by this fuel combustion and the high temperature exhaust gas drawn into the calciner 21 from the calciner l. The calcined powder raw material passes from the calciner 21 along with the exhaust gas into the cyclone C4 through the gas duct 13, and is then introduced into the calciner l through the raw material chute 18 through the inlet end layer 12 of the calciner l.

High-temperature air from the cooling a2 and firing fuel from the fuel supply device 5a are introduced into the firing furnace 1, and the clinker formed by firing at high temperature enters the cooler 2 and is cooled. In this case, air for clinker cooling is supplied to the cooler 2 by the forced air blower 7, and is heated by heat exchange with the clinker. A part of this heated high-temperature air is recovered as combustion air in the calcination furnace 21 and the calcination furnace 1, and the excess air that is not recovered is exhausted by the exhaust fan 8 (in the figure, the gas flow is indicated by the solid line arrow). (the flow of the powder raw material is indicated by the dashed arrow).

When firing powder raw materials in the above-mentioned firing apparatus, conventional efforts have been made to minimize the fuel consumption required for clinker firing in the firing apparatus. That is, when burning the fuel supplied from the fuel supply devices 5a and 5b in the firing furnace 1 and the calcining furnace 21, the minimum amount of excess air is supplied to these fuel combustion parts within a range that does not cause incomplete combustion. The amount of combustion air is controlled accordingly. In this case, the exhaust gas from the firing apparatus is controlled to have an oxygen intensity as low as possible, specifically to 3% or less as measured by the oxygen concentration meter 24.

However, even if the firing device is operated to minimize fuel consumption as described above, the temperature of the exhaust gas from the preheating device 3 will vary depending on the properties of the raw materials and the presence or absence of the calciner 21. In device 3, the temperature was 350°C as measured by thermometer 25.
The temperature is about ~400°C, and a considerable amount of heat energy still remains. Therefore, attempts have been made to utilize this exhaust gas sensible heat more effectively.

That is, an exhaust heat boiler 27 is interposed in the middle of the exhaust gas duct 15 as equipment for utilizing exhaust heat of exhaust gas.

Then, steam is generated by heat exchange with high-temperature exhaust gas,
Thermal economy is improved by using this steam for power generation. On the other hand, the surplus air discharged from the cooler 2 by the exhaust fan 8 usually has a temperature of 200°C to 250°C. An exchanger 28 is interposed. This heat exchanger 28 is used, for example, as a feed water heater for the waste heat boiler 27.

(Problems to be Solved by the Invention) By the way, in the above firing method, the fuel consumption required for firing the clinker is suppressed to a minimum. Therefore, the temperature of the exhaust gas from the preheater @3 is not high enough to be effectively used by the waste heat boiler 27, so the temperature and pressure of the steam generated in the waste heat boiler 27 do not rise sufficiently, and the power generation efficiency of the turbine decreases. Moreover, since the exhaust gas from the preheating device 3 is generally used as a ripening material for drying raw materials, only the surplus can be used for heating in the waste heat boiler 27, and in the end, the usable sensible heat of the gas is reduced. Due to this shortage, the efficiency of power generation turbines is not high enough.

On the other hand, the surplus air line of the cooler 2, that is, the exhaust duct 9
In the heat exchanger 28, the temperature of the available surplus air is lower than the exhaust gas from the preheating device 3, and the temperature of the surplus air fluctuates significantly due to the operating characteristics of the cooler 2. There are disadvantages in that the operation lacks stability and the effectiveness of its use is also poor.

Moreover, when burning fuel in the firing equipment, excess air is reduced to the necessary minimum, so if a disturbance occurs, such as a change in the raw material composition or fuel properties, or a change in the state of coating adhesion inside the firing equipment, , there is a possibility that the operating status of the firing apparatus cannot be adjusted to sufficiently follow these disturbances.

In this case, incomplete combustion occurs during fuel combustion, resulting in not only a thermoeconomic loss but also the inconvenience of generating unburned gas.

Furthermore, the firing apparatus may be forced to operate at a low raw material firing capacity due to reasons such as adjusting clinker inventory. In such a case, in the conventional firing method, the amount of exhaust gas introduced from the preheating device 3 to the waste heat boiler 27 decreases in almost proportion to the amount of clinker produced, so the amount of power generated by the waste heat power generation equipment also decreases due to the amount of electricity generated by the waste heat power generation equipment. It will decrease depending on the raw material firing capacity of the equipment. For this reason, when the firing apparatus is operated at low capacity, there is also the disadvantage that the capacity of the waste heat power generation equipment cannot be fully utilized.

As a result, due to the various problems mentioned above, the energy economy of the entire system of the firing apparatus including the exhaust heat utilization equipment is low.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to improve the energy economy of the entire system of a firing apparatus including exhaust heat utilization equipment.

(Structure of the Invention) A feature of the present invention for achieving the above-mentioned object is that the high-temperature exhaust air from the cooler is sufficiently recovered to the fuel combustion section of the sintering device, so that the exhaust heat boiler can be transferred from the preheating device to the exhaust heat boiler. The oxygen concentration in the exhaust gas introduced into the exhaust gas is set to 4% or more, and the temperature of this exhaust gas is set to 400°C to 500°C.

(Example) The present invention will be described in detail below. The configuration of the cement powder raw material firing apparatus including the exhaust heat utilization equipment is the same as that of the conventional example. Therefore, the method for heating the waste heat boiler in the firing apparatus of the present invention will be explained using FIG. 1 showing a conventional example.

The high-temperature exhaust air from the cooler 2 is sufficiently recovered to supply excess high-temperature air to the firing furnace l and the calcining furnace 21, which are fuel combustion parts in the firing apparatus. Then, the excess air is used to burn fuel in the firing furnace 1 and the calcining furnace 21. In this case, in a firing apparatus equipped with a preheating device 3 having four stages of cyclones, such as the example shown in FIG. Although it depends on the scale and operating conditions of the equipment, the exhaust gas temperature increases by about 15°C and the exhaust gas amount also increases by about 6%.

In this case, the fuel consumption of clinker and dust is approximately 7Kca.
1, from the cooler 2 to the calcining furnace 1 and the calcining furnace 2.
Approximately 9% more combustion air needs to be recovered.

On the other hand, the temperature of the exhaust gas introduced from the preheating device 3 to the waste heat boiler 27 is 400°C to
Temperatures between 500°C and 420°C to 460°C are suitable.

Therefore, if the amount of excess air during fuel combustion in the firing furnace 1 and cooler 2 is increased to make the oxygen concentration in the exhaust gas from the preheater 3 4% or more, the temperature of the exhaust gas introduced into the waste heat boiler 27 will be The temperature will be 400°C to 500°C.

However, the above waste heat boiler heating method involves an increase in the amount of exhaust gas passing through the preheating device 3 and a rise in temperature. It is necessary to select the device 3 to be large in size. In addition, when using existing firing equipment, it can be implemented by reducing the amount of clinker produced.

In carrying out the above waste heat boiler heating method, a calciner 21 equipped with a fuel supply device is connected to the gas duct 13 on the gas inlet side of the cyclone C4 at the lowest stage of the preheating device 3, as shown in the example shown in the figure. However, it is preferable to absorb the temperature change of the entire preheating device 3 by adjusting the operating conditions of the calcination furnace 21 mentioned above and stabilize the operating conditions of the calcination furnace 1. It can also be applied to

In addition, when implementing the above waste heat boiler heating method,
It can also be used in combination with other methods of increasing the temperature of the exhaust gas from the preheating device 3, such as short-circuiting part of the powder raw material or exhaust gas within the preheating device 3.

Furthermore, the type and structure of the powder collector, gas duct, etc. constituting the preheating device 3, as well as the specific structure of the waste heat boiler, etc. may be changed as necessary.

(Effects of the Invention) Conventionally, when firing powder raw materials for cement using a sintering device, by burning the fuel while keeping the excess air supplied to the fuel combustion section to a minimum, the amount of clinker required in this sintering device was reduced. The amount of fuel consumed per unit weight is minimized, and the sensible heat of the exhaust gas discharged from the preheating device is simply used effectively.

However, according to this invention, by sufficiently recovering high-temperature exhaust air from the cooler to the fuel combustion section of the sintering device, the oxygen concentration in the exhaust gas introduced from the preheating device to the waste heat boiler can be reduced to 4%. Assuming the above, this exhaust gas temperature is 400℃
~500°C. That is, by burning the fuel using a moderately large amount of excess air, the temperature of the exhaust gas from the preheating device can be raised to a temperature suitable for waste heat power generation.

Therefore, although the amount of fuel required to produce a unit weight of clinker in the firing apparatus is somewhat higher, the energy economy of the entire system of the firing apparatus including the waste heat power generation equipment can be improved.

In other words, the temperature of the exhaust gas introduced from the preheating device to the waste heat boiler increases, and the amount of exhaust gas also increases, so the heat recovered in the waste heat boiler increases significantly, and the temperature and pressure of the generated steam increases, causing the turbine The power generation efficiency and turbine efficiency will be significantly improved. At this time, since the exhaust gas temperature is changed by the amount of excess air during fuel combustion, the waste heat power generation equipment can always be operated stably by adjusting the amount of excess air.

Incidentally, as the amount of excess air increases, it becomes necessary to increase the amount of fuel used in the calciner or firing furnace. However, this increased amount of heat is used to increase the amount of heat recovered in the waste heat boiler due to the rise in exhaust gas temperature and increase in the amount of exhaust gas, and to improve the heat utilization efficiency, so it is not beneficial for the energy economy of the overall system. be.

Moreover, since sufficient excess air is present during combustion in the firing device, complete combustion of the fuel can be easily achieved. Therefore, even if a disturbance occurs in the firing device, incomplete combustion will not occur, and solid fuel or low-grade fuel can be easily used.

In addition, even when the firing equipment needs to be operated at a low raw material firing capacity, by further increasing excess air and keeping the absolute amount of combustion gas passing through the firing equipment almost constant, the production Tt and amount can be reduced. It is possible to prevent a decrease in the capacity of the waste heat power generation equipment and to always operate the waste heat power generation equipment to its full capacity.

Furthermore, the incremental amount of excess air introduced into the firing device is recovered from the hot side of the cooler. For this reason, the utility value of the surplus air discharged from the cooler decreases both in terms of temperature and quantity. It is possible to secure more power generation than the conventional example using only the waste heat boiler. Therefore, it is not necessary to provide a heat exchanger on the excess air discharge side of the cooler as in the conventional example, thereby reducing the equipment cost for the heat exchanger and simplifying and stabilizing the operation of the firing apparatus.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a cement powder raw material firing apparatus. l.. Calciner (fuel combustion section), 2.. Cooler, 3.. Preheating device, 5a, 5b.. Fuel supply device, 21.. Calciner (fuel combustion section), 27-. Exhaust heat boiler , CI , c2
．． cal ca...Cyclone (powder collector)
.

Claims (1)

[Scope of Claims] 1. A firing furnace for producing clinker by firing cement powder raw materials, a cooler for cooling the clinker discharged from the firing furnace with an air flow, and an exhaust gas introduced from the firing furnace. A preheating device for preheating the powder raw material with this exhaust gas is provided, and the preheating device is composed of four stages of powder collectors stacked vertically and connected to each other, and at least electricity is generated on the exhaust gas outlet side of the preheating device. A method for heating a waste heat boiler in a firing device equipped with a waste heat boiler, the heating method comprising: recovering a sufficient amount of high-temperature exhaust air from a cooler to a fuel combustion section of the firing device; The oxygen concentration in the exhaust gas introduced into the exhaust gas is set to 4% or more, and the exhaust gas temperature is
A method for heating a waste heat boiler in a firing apparatus, characterized in that the temperature is 0°C to 500°C. 2. A method for heating a waste heat boiler in a firing apparatus according to claim 1, characterized in that the temperature of the exhaust gas introduced from the preheating device to the waste heat boiler is 420°C to 460°C. 3. A method for heating a waste heat boiler in a firing device according to claim 1 or 2, characterized in that the waste heat boiler is provided only on the exhaust gas outlet side of the preheating device. 4. Claims 1 to 3, characterized in that a preheating device includes a calciner equipped with a fuel supply device on the gas inlet side of the powder collector located at the lowest stage. A method for heating a waste heat boiler in the firing apparatus according to any one of the above.