JPH11264530A - Combustion equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously perform recovery of high-efficient heat generation energy and reduction of an emission gas amount by throttling an air ratio and to achieve reduction of a construction cost, in various kinds of combustion equipment, such as a boiler and a treatment device for waste. SOLUTION: This combustion equipment comprises a partial combustion part 10 to perform combustion by supplying air having an air ratio lower than a theoretical air ratio; a first heat exchanger 15 to recover heat of emission gas emitted from the partial combustion part 10; a complete combustion part 17 to perform complete combustion of emission gas, emitted from the partial combustion part 10, by oxygen having an air ratio higher than the theoretical air ratio; and a second heat-exchanger 20 to recover the heat of emission gas emitted from the complete combustion part 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion facility such as a boiler and a waste treatment facility, and more particularly, to a combustion facility having improved overall thermal efficiency.

[0002]

2. Description of the Related Art Due to recent demands for environmental protection and economy, various types of combustion equipment, such as waste treatment equipment, generally have a high efficiency by recovering heat energy generated by the combustion as efficiently as possible. Planning,
Various energy saving measures are taken. FIG.
This shows an example of a conventional waste treatment facility having this type of heat recovery means. In FIG. 3, reference numeral 1 denotes a vertical shaft furnace utilizing pyrolysis gasification and melting, and an inlet 2 for introducing crushed garbage obtained by crushing waste into an upper side wall thereof is provided. Is provided. In addition, an inlet pipe 3 for supplying oxygen-enriched air for supplying the char obtained by pyrolysis of the refuse to keep the inside at a high temperature is connected to the bottom 1a of the shaft furnace 1. In addition, a forced air blower 4 is provided on a side wall of the shaft furnace 1.
Is connected to a supply pipe 5 for the combustion air sent from the vessel. An exhaust pipe 6 extending from the upper part of the shaft furnace 1 is led to a waste heat boiler 7.

[0003] In the waste treatment facility having the above-mentioned structure, when crushed waste is first introduced through the input hole 2 of the shaft furnace 1, the crushed waste is thermally decomposed therein, so that the pyrolysis gas and carbonaceous material are decomposed. And produce high calorie char. Then, the char reacts with the oxygen-enriched air supplied from the introduction pipe 3 to keep the bottom 1a of the shaft furnace 1 at a high temperature. At the same time, combustion air is supplied from the supply pipe 5. Thereby, in the shaft furnace 1, a drying zone, a pyrolysis zone, a combustion zone to which combustion air is supplied, and a melting zone of the bottom 1 a are sequentially formed from the input port 2 toward the bottom 1 a. You. The incombustibles in the refuse become harmless molten slag (metal or glass melt) in the combustion / melting zone at the bottom, and are continuously discharged from the bottom 1a. On the other hand, the high-temperature gas generated by the reaction at the bottom 1a of the vertical shaft furnace 1 rises inside the furnace and turns the crushed garbage that has been sequentially charged into a pyrolysis gas in the pyrolysis zone. The crushed garbage just introduced from is dried.

Next, the pyrolysis gas is sent from an exhaust pipe 6 to a waste heat boiler 7, and the waste heat is recovered by feed water sent from a boiler feed pipe 8, and the obtained superheated steam is discharged. It is sent from a line 9 to a steam turbine that drives a generator (not shown), and is collected as power by the generator. Further, the exhaust gas from which waste heat is recovered in the waste heat boiler 7 is sent to a dust collector disposed further downstream, and after the fly ash and the like in the exhaust gas are collected, the sulfur dioxide gas and the like contained therein are removed. Removed, rendered harmless and released to the atmosphere from the chimney.

[0005]

However, in a conventional furnace such as a stalker furnace, since it is a solid combustion, 2.
An air ratio of 0 or more (the ratio of the actually supplied air amount to the air amount required for the combustible to theoretically burn) is required. For this reason, the high-temperature combustion gas is cooled by the nitrogen entrained in the air, so that there is a disadvantage that the amount of recovered heat with respect to the amount of generated heat is reduced and the thermal efficiency is reduced. In this regard, in the vertical shaft furnace 1 in the above-mentioned conventional waste treatment facility, since the pyrolysis gas is generated by once partially oxidizing or carbonizing the waste, the combustion becomes gas combustion. Therefore, since complete combustion can be performed at an air ratio of about 1.2, there is an advantage that high efficiency can be easily achieved.

However, in the vertical shaft furnace 1, when the air ratio approaches 1.0, that is, the theoretical air ratio as shown in FIG. 4, the temperature of the exhaust gas entering the waste heat boiler 7 becomes extremely high. I will. For example, when the air ratio is 1.2, low-quality waste (1000 kca
l / kg), even if the temperature exceeds 900 ° C and the quality of waste (about 3000 kcal / kg)
It exceeds 1600 ° C. As a result, in the waste heat boiler 7, the water supply (heat receiving body) is mainly composed of radiant heat transfer and requires a large space, and when the exhaust gas temperature at the inlet of the waste heat boiler 7 becomes high, the nitrogen oxides ( Inconveniences such as promoting accelerated generation of Nox) and inducing slag of ash are caused. In addition, there is a problem that expensive heat-resistant materials must be used as various members along the flow path of the exhaust gas.

In order to maintain the exhaust gas temperature at the inlet of the waste heat boiler 7 at 900 ° C. by lowering the exhaust gas temperature, a method of separately diluting with air has been adopted. However, this is, for example, 2600 kcal / kg
In order to apply the method to general waste having a calorific value, it is necessary to dilute the air to an air ratio of about 2.5, which is higher than the air ratio required by a conventional furnace such as the stalker furnace described above. As a result, there is a problem that the cooling effect of the entrained nitrogen causes a decrease in thermal efficiency, increases the capacity of the entire exhaust gas, and significantly increases the load on the exhaust gas processing system on the downstream side. In addition, when the heat recovery rate in the waste heat boiler 7 is to be improved with respect to the exhaust gas, the temperature of the exhaust gas at the outlet of the waste heat boiler 7 becomes too low, and as a result, the sulfide contained in the general waste and There is a problem in that low-temperature corrosion is induced in downstream equipment by sulfurous acid gas or chlorine gas generated due to chloride.

The present inventors have conducted intensive studies to effectively solve the various restrictions and problems in increasing the efficiency of such conventional combustion equipment. If the condition of complete combustion above the stoichiometric air ratio is reversed and partial combustion below the stoichiometric air ratio is daringly performed, the above-mentioned restrictions and problems can be avoided to achieve high efficiency. Of knowledge. That is, FIG.
As shown in the figure, the temperature of the exhaust gas at the inlet of the heat recovery device, when the combustion is performed by supplying air at a theoretical air ratio or less,
It will decrease almost in proportion to the decrease in the air ratio.
Incidentally, the exhaust gas temperature at the inlet of the heat recovery device is, assuming that only the combustible material corresponding to the air ratio burns and the rest does not change in composition, the case where complete combustion is performed at the air ratio of about 2.5 and the case of about 0 It is almost equal to the case where the partial combustion is performed at an air ratio of 0.4.

Therefore, after partially burning at a stoichiometric air ratio or less and recovering the heat of the exhaust gas by a heat exchanger,
Furthermore, if the remaining combustibles are completely burned at the same air ratio as before, and the heat is recovered by a heat recovery unit, the temperature of the exhaust gas will become slag, or the accelerated generation of Nox in the exhaust gas will be promoted. It is possible to perform combustion at a low air ratio while maintaining the temperature in a low temperature range where no combustion occurs, and therefore, it is possible to increase the efficiency of the entire combustion equipment.

The present invention has been made on the basis of the above findings, and in various combustion facilities such as a boiler and a waste treatment apparatus, by reducing the air ratio, it is possible to efficiently recover exothermic energy and reduce the amount of exhaust gas. It is an object of the present invention to provide a combustion facility capable of simultaneously achieving the reduction of the construction cost and achieving the reduction of the construction cost.

[0011]

According to a first aspect of the present invention, there is provided a combustion facility for supplying air having a stoichiometric air ratio or less to perform combustion, and for exhaust gas generated from the partial combustion portion. A first heat exchanger for recovering heat, a complete combustion unit for completely burning exhaust gas discharged from the partial combustion unit with oxygen having a theoretical air ratio or more, and recovering heat of exhaust gas discharged from the complete combustion unit And a second heat exchanger.

Here, the invention according to claim 2 is characterized in that the partial combustion section is provided with a waste inlet, and combustion air having an air ratio in the range of 0.1 to 0.8 is provided therein. A partial combustion zone to be supplied is formed, and a pyrolysis gasification furnace provided with an exhaust unit that discharges pyrolysis gas generated from the waste, and the first heat exchanger includes: The complete combustion section is a gas combustion furnace that is provided downstream of the partial combustion zone of the pyrolysis gasification furnace and completely burns at least the pyrolysis gas discharged from the pyrolysis gasification furnace. It is characterized by the following.

[0013] In the combustion equipment according to the first or second aspect, first, in the partial combustion section, air having a stoichiometric air ratio or less is supplied to partially burn fuel or waste.
Further, the heat of the exhaust gas is recovered by the first heat exchanger. Thus, low-temperature exhaust gas containing unburned combustibles is discharged. Next, the combustibles remaining in the exhaust gas are completely burned by air having a stoichiometric air ratio or more in the complete combustion section. At this time, since the heat generated is only due to the combustion of the combustibles remaining in the exhaust gas, the temperature of the exhaust gas can be reduced to about the same level as when the conventional exhaust gas is diluted with a large amount of air. Will be possible. Therefore, next, this exhaust gas is sent to the second heat exchanger to recover the heat of the exhaust gas.

As described above, according to the above-mentioned combustion equipment, it is possible to control the temperature in the partial combustion section and the complete combustion section so as not to exceed a predetermined temperature, and to further reduce the consumption in the partial combustion section and the complete combustion section. Since the total air ratio corresponding to the total amount of air to be reduced becomes small, it is possible to suppress a decrease in thermal efficiency due to nitrogen in the air. Further, since it is not necessary to separately dilute the exhaust gas with air or the like in order to suppress an increase in the temperature of the exhaust gas, the capacity of the exhaust gas does not increase. In addition, as a result that the inlet temperature of the second heat exchanger can be suppressed to a predetermined temperature or less, the generation of Nox in the exhaust gas can be suppressed at an accelerated rate, and the slag of ash can be suppressed, and the exhaust gas can be suppressed. It is not necessary to use expensive heat-resistant materials as various members along the flow path, and it is possible to reduce the construction cost.

[0015]

FIG. 1 shows an embodiment in which the combustion equipment of the present invention is applied to a waste treatment equipment provided with a direct melting furnace for treating waste by pyrolysis gasification and melting. is there. In FIG. 1, reference numeral 10 denotes a direct melting furnace (partial combustion section, pyrolysis gasification furnace). This direct melting furnace 10
Is provided with an inlet 11 for introducing crushed refuse obtained by crushing waste on the side wall, and a bottom 10
A is connected to an inlet pipe 12 for supplying oxygen-enriched air separated from air by a PSA separator or the like. And, on the side wall of the direct melting furnace 10,
A supply pipe 14 for combustion air having a stoichiometric air ratio or less sent from the push-in blower 13 is connected, and an evaporator (first heat exchanger) 15 is provided above the supply pipe 14.
Is provided.

An exhaust pipe (exhaust section) 16 is connected to the upper part of the direct melting furnace 10, and the other end of the exhaust pipe 16 is introduced into a gas combustion furnace (complete combustion section) 17.
The gas combustion furnace 17 is for completely combusting exhaust gas with air having a stoichiometric ratio or more sent from the push-in blower 13 through the supply pipe 18. From 19, it is introduced into a waste heat boiler (second heat exchanger) 20.

On the other hand, the boiler feedwater is sent from the inlet pipe 21 to the waste heat boiler 20 and is preheated, and then sent to the steam drum 22. The steam drum 22 sends the wastewater to the evaporator 15 via the circulation line 23. After being sent to the heat boiler 20 and partially evaporated by the pyrolysis gas, the steam is returned to the steam drum 22, and the saturated steam in the steam drum 22 is superheated by the waste heat boiler 20, and the obtained superheated steam is not shown. It is sent to a steam turbine. Further, the exhaust gas from which heat is recovered by the waste heat boiler 20 is sent to a separate exhaust gas treatment device, rendered harmless, and then released to the atmosphere.

In the waste treatment facility having the above-described structure, the operation of the crushed refuse supplied from the charging hole 2 in the direct melting furnace 10 to be converted into molten slag and discharged from the bottom 10a is shown in FIG. It is the same as shown. At this time, in the waste treatment facility, first, in the direct melting furnace 10, by supplying air having a theoretical air ratio or less, preferably an air ratio of 0.1 to 0.8 from the supply pipe 18, The partial combustion of the pyrolysis gas is performed using the combustion zone as a partial combustion zone. Thereby, for example, when combustion is performed at an air ratio of 0.4, 40% of the pyrolysis gas is burned.
Is directly burned in the melting furnace 10, and the remaining 60% is burned in the gas fuel furnace 17 in the subsequent stage. The pyrolysis gas partially burned in this way is supplied to the evaporator 15.
By partially evaporating the saturated water sent from the circulation line 23, the heat is recovered. As a result, low-temperature exhaust gas containing combustibles is discharged from the exhaust pipe 16.

Next, as described above, the pyrolysis gas is completely burned in the gas combustion furnace 17 by air having a stoichiometric air ratio or higher sent from the supply pipe 18. At this time, since the generated heat is only due to the combustion of the combustibles remaining in the exhaust gas, by appropriately setting the air ratio, the exhaust gas temperature was conventionally diluted with a large amount of air. This can be reduced to the same extent as in the case. Then, next, this exhaust gas is sent from the flow path 19 to the waste heat boiler 20, and the heat is recovered by superheating the boiler feedwater. Then, the superheated steam obtained in the waste heat boiler 20 drives a turbine (not shown), so that the thermal energy of the exhaust gas is recovered as electric power via a generator. On the other hand, the exhaust gas from which the waste heat is recovered is sent to a dust collector such as a bag filter disposed further downstream, and after fly ash and the like in the exhaust gas are collected,
The contained sulfurous acid gas and the like are removed and rendered harmless, and are discharged from the chimney to the atmosphere.

As described above, according to the waste treatment equipment described above, the temperature of the exhaust gas directly generated in the melting furnace 10 is low, so that even when the gas is completely burned in the gas combustion furnace 17, the air ratio is appropriately set. Thus, the temperature can be controlled so as not to exceed a predetermined temperature, and the total air ratio in the direct melting furnace 10 and the gas combustion furnace 17 decreases, so that a decrease in thermal efficiency due to nitrogen in the air can be suppressed. .

Further, in order to suppress the temperature rise of the exhaust gas,
Since there is no need to separately dilute with air or the like, an increase in the capacity of the exhaust gas does not occur, so that it is possible to reduce the size of the exhaust gas processing device in the subsequent stage. In addition, as a result that the inlet temperature of the waste heat boiler 20 can be suppressed to a predetermined temperature or less, the generation of Nox in the exhaust gas can be suppressed at an accelerated rate, the slag of ash can be suppressed, and the flow path of the exhaust gas can be suppressed. There is no need to use expensive heat-resistant materials as various members along the line 19, and construction costs can be reduced.

[0022]

FIG. 2 shows the results of calculations performed to verify the effects of the waste treatment equipment shown in FIG. In the calculation, 2600 kcal / kg
The air ratio in the gas combustion furnace 17 is set to 9 when the inlet temperature of the waste heat boiler 20 is 9
The precondition was that the temperature of the waste heat boiler 20 was adjusted to 00 ° C. and that the heat was recovered to 250 ° C. In addition, the total thermal efficiency is determined by the direct melting furnace (partial combustion section,
Pyrolysis gasification furnace) 10 and gas combustion furnace (complete combustion section) 17
Is the total value of the thermal efficiencies, and the total air ratio is
The air recovery ratio is an air ratio corresponding to the amount of air supplied for combustion in the gas combustion furnace 17 and the heat recovery device is the waste heat boiler 20 in FIG.

As shown in FIG. 2, according to the present embodiment, even if the exhaust gas temperature at the evaporator 15 and the waste heat boiler 20 inlet above the direct melting furnace 10 is 900 ° C., the total air ratio is 1. 7 can be reduced. On the contrary,
Similarly, when the inlet exhaust gas temperature is set to 900 ° C. based on the conventional theory of complete combustion, the air ratio becomes 2.5. Therefore, in the present embodiment, the total air ratio is set to 2.
Since it can be reduced from 5 to 1.7, the thermal efficiency is improved by 6%, and as a result of reducing the air ratio, the amount of exhaust gas can be reduced by about 30%.

In the above embodiment, only the case where the combustion equipment of the present invention is applied to waste treatment equipment has been described. However, the present invention is not limited to this. The present invention can be similarly applied to other incinerators such as a cracked gasification type waste incinerator and a boiler.

[0025]

As described above, claim 1 or claim 2
According to the combustion equipment described in the above, the temperature of the exhaust gas generated in the partial combustion section can be controlled so as not to be higher than a predetermined temperature even in the complete combustion section, and the exhaust gas can be consumed in the partial combustion section and the complete combustion section. Since the total air ratio corresponding to the total amount of air to be reduced becomes small, it is possible to suppress a decrease in thermal efficiency due to nitrogen in the air and to separately dilute with air or the like in order to suppress a high temperature of exhaust gas. Since there is no need, there is no increase in the capacity of exhaust gas. In addition, as a result that the inlet temperature of the second heat exchanger can be suppressed to a predetermined temperature or less, the generation of Nox in the exhaust gas can be suppressed at an accelerated rate, and the slag of ash can be suppressed, and the exhaust gas can be suppressed. It is not necessary to use expensive heat-resistant materials as various members along the flow path, and it is possible to reduce the construction cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a combustion facility of the present invention.

FIG. 2 is a characteristic diagram showing a result of an example of the present invention.

FIG. 3 is a schematic configuration diagram showing a waste treatment facility, which is a type of conventional combustion facility.

FIG. 4 is a graph showing the relationship between the calorific value of combustibles, the air ratio, and the exhaust gas temperature at the inlet of the heat recovery device.

FIG. 5 is a graph showing the relationship between the air ratio and the exhaust gas temperature at the inlet of the heat recovery device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Direct melting furnace (partial combustion part, pyrolysis gasification furnace) 13 Push blower 14, 18 Air supply pipe 15 Evaporator (first heat exchanger) 17 Gas combustion furnace (complete combustion part) 20 Waste heat boiler ( Second heat exchanger) 21 Inlet pipe for water supply 22 Steam drum 23 Circulation line

Claims (2)

[Claims] 1. A partial combustion section for supplying air having a stoichiometric air ratio or less to perform combustion, a first heat exchanger for recovering heat of exhaust gas generated from the partial combustion section, and discharging from the partial combustion section. Combustion comprising: a complete combustion section for completely burning the exhaust gas with oxygen having a theoretical air ratio or higher; and a second heat exchanger for recovering heat of the exhaust gas discharged from the complete combustion section. Facility. 2. The partial combustion section is provided with a waste inlet, and forms a partial combustion zone in which combustion air having an air ratio in a range of 0.1 to 0.8 is supplied. A pyrolysis gasification furnace provided with an exhaust unit for discharging pyrolysis gas generated from the waste;
The heat exchanger is provided on the downstream side of the partial combustion zone of the pyrolysis gasification furnace, and the complete combustion section completely removes at least the pyrolysis gas discharged from the pyrolysis gasification furnace. The combustion equipment according to claim 1, wherein the combustion equipment is a gas combustion furnace for burning.