JP5984289B2 - Small-scale power generation system in a stoker-type incinerator - Google Patents

Description

  The present invention relates to an improvement of a waste heat recovery power generation system applied to a stoker-type incinerator. A heat exchanger is disposed in a primary combustion chamber of a stoker-type incinerator and a low boiling point heat medium is generated by radiant energy in the combustion chamber. By rotating the steam turbine generator with the generated heat medium steam, the facility and running costs can be greatly reduced, and waste generation with the desired output can be performed easily and economically. The present invention relates to a small-scale power generation system in such a stoker-type incinerator.

  Conventionally, in municipal waste incineration facilities, the main purpose has been to reduce the volume of incineration without causing environmental pollution and to make effective use of the generated waste combustion heat. Various technologies have been developed to achieve this.

  For this reason, in large city waste incineration facilities in large cities, steam is generated using the heat of the waste incinerator, and the steam turbine generator is driven using this steam to generate waste or to generate residual heat. It has been used to hot water and melt snow (Patent Document 1, Patent Document 2, etc.).

  However, even in this type of large-scale waste incineration facilities, there are many facilities that do not generate waste power, especially in small-scale industrial waste incineration facilities, etc., waste heat boilers and steam turbine generators Many of them do not generate power by recovering waste heat, and many problems remain due to the recent energy situation. .

  On the other hand, in recent years, waste generation has attracted attention from the viewpoint of energy saving, and there is an increasing demand for not only large-scale waste generation facilities but also a small-scale waste generation system that uses simple and economical waste heat recovery. In response to these demands, so-called binary power generation systems using a low boiling point heat medium have been developed and put into practical use.

  That is, a power generation system using the low boiling point heat medium (hereinafter referred to as a binary power generation system) is known as a geothermal power generation system or a low-temperature waste heat recovery power generation system (Patent Document 3, Patent Document 4). As shown in FIG. 3, the hot water or steam B from the waste heat boiler (heat source) A is sent to the first heat exchanger C, where the low boiling point heat medium D is heated to generate the low boiling point heat medium steam E. At the same time, the steam turbine generator F is rotationally driven by the heat medium steam E to generate power.

Further, the low boiling point heat medium steam E from the steam turbine generator F is cooled by the cooling water Wc in the second heat exchanger G and returned to the liquid low boiling point heat medium D as shown in FIG. cooling water W _H heated by the second heat exchanger G is cooled by air I in cooler H.
In FIG. 3, P ₁ is a circulating pump for hot water or steam B, P ₄ is a chemical injection pump, P ₂ is a circulating pump for a low boiling point heat medium D, P ₃ is a circulating pump for cooling water W _C , F Reference numeral ₁ denotes a cooling fan.

  The binary power generation system shown in FIG. 3 is capable of efficiently recovering low-temperature waste heat (for example, 80 to 250 ° C.) by selecting the low boiling point heat medium D to be used, and increasing the waste heat recovery rate. It has excellent utility.

However, the binary power generation system shown in FIG. 3 requires many stages of heat exchange despite a relatively small power generation output. That is, since a low-boiling-point heat medium circulation pump P ₂ and a cooling water circulation pump P ₃ require a hot water (steam) circulation pump P ₁ and a chemical liquid injection pump P ₄ , much power is consumed. As a result, there is a drawback that the available power is reduced.

  Also, for example, in FIG. 3 above, exhaust gas from an incinerator or a waste heat boiler (heat source) is sent to the first heat exchanger C instead of hot water or steam, and the low boiling point heat medium steam E is generated here. In this case, there is a problem that the utilization efficiency of the waste heat cannot be increased because the heat transfer rate by the contact heat transfer between the exhaust gas and the low boiling point heat medium is low.

Therefore, in order to reduce pump power, the inventor of the present application eliminates the use of the hot water (steam) circulation pump P ₁ with only the low-boiling point heat medium as the heat medium, and does not use water as the heat medium. Eliminating the use of the chemical injection pump P ₄ for the purpose of suppressing scale adhesion to the inner surface, and using the radiant heat energy in the combustion chamber of the waste incinerator, an efficient low-boiling point heating medium With the idea of generating steam, we created a waste heat recovery power generation system as shown in FIG. 1 and conducted various tests to put it into practical use.

And Thus, the In such waste heat recovery power generation system of FIG. 1, for recovering waste heat by the hot water (steam) to eliminate the use of the circulation pump P ₁ low-boiling heat transfer medium, the heat exchange using Cold corrosion of the vessel becomes a problem.
That is, moisture inside the combustion exhaust gases of the waste incinerator, such as incinerators, corrosive gas such as HCl and SO _X are inevitably contained, and sulfuric anhydride of the combustion exhaust gas (SO ₃₎ Will cause cold corrosion of the heat exchanger. For example, when the moisture in the combustion gas is 15% and the SO ₃ concentration is 10 ppm, the sulfuric acid dew point temperature is about 140 ° C. (Patent Document 5). (SO ₃ ) combines with moisture to form sulfuric acid (H ₂ SO ₄ ), which condenses and adheres to the metal, thereby causing low-temperature corrosion of the metal.

Japanese Patent Laid-Open No. 9-4420 Japanese Patent Laid-Open No. 11-148316 JP-A-8-105305 JP 2012-13062 A JP 2011-185500 A

  The present invention has the above-mentioned problems in a low-temperature waste heat recovery power generation system using a low-boiling-point heat medium, that is, a binary power generation system that uses two heat mediums (heat cycles) until power generation. When the power of machinery such as the heat medium circulation pump is larger than the generated power, the substantial utilization rate of the generated output is low, and when using a heat exchanger that uses incinerator exhaust gas as a heat source, Low heat transfer efficiency due to low heat transfer rate, and when heating low boiling point heat medium with waste incinerator exhaust gas, etc., low temperature corrosion occurs in heat exchangers and equipment life is shortened, etc. While effectively preventing the occurrence of low-temperature corrosion in the heat exchanger by utilizing the characteristics of the component distribution of the combustion gas in the upper space of the primary combustion chamber of the stoker-type waste incinerator, Radiant energy in the primary combustion chamber A stoker system that can heat a low-boiling point heat medium through heat exchange as the main heat source, improve waste heat recovery rate and power generation efficiency, and can be applied to waste incineration facilities easily and economically. The main object of the invention is to provide a small-scale power generation system in a combustion furnace.

In order to achieve the above object, a small-scale power generation system in a stoker-type incinerator according to the present invention includes, as a first means , a heat exchanger that uses combustion heat in a primary combustion chamber of a stoker-type incinerator as a heating source, A heat medium circulation path is formed from the steam turbine generator, the condenser, and the heat medium circulation pump, and a low boiling point heat medium having a lower boiling point than water is circulated through the heat medium circulation path by the heat medium circulation pump. the generated in the heat exchanger and configured to drive a steam turbine generator with steam of low-boiling heat transfer medium, the heat transfer tubes of the heat exchanger in which the lower boiling point heat medium flows, after said primary combustion chamber the combustion It is placed in the zone.

In addition, the small-scale power generation system in the stoker type incinerator according to the present invention includes, as a second means, a heat exchanger that uses combustion heat in the primary combustion chamber of the stoker type incinerator as a heat source, a steam turbine generator, A heat medium circulation path is formed from the condenser and the heat medium circulation pump, and a low boiling point heat medium having a boiling point lower than that of water is circulated through the heat medium circulation path by the heat medium circulation pump, and the heat exchanger The steam turbine generator is driven by the steam of the low-boiling-point heat medium generated in step 1, the heat exchanger is provided outside the primary combustion chamber, and is led out of the furnace from the post-combustion zone of the primary combustion chamber. The low boiling point heat medium flowing through the heat exchanger is heated by combustion gas.

In the first means, it may be configured to support and fix the heat exchanger to either the top wall or sidewalls or the rear wall to form the combustion zone after the primary combustion chamber.

In the present invention, the heat medium is a low-boiling point heat medium, and a heat exchanger for heating and evaporating the low-boiling point heat medium is disposed in the post-combustion zone of the primary combustion chamber of the stoker type incinerator, and corrosive gas In the post-combustion zone containing almost no methane, the heat of the combustion is recovered to the low boiling point heat medium by the heat exchanger mainly using the radiant heat energy, and the steam turbine generator is It is configured to drive and generate power.
As a result, a higher heat transfer rate can be obtained than in the case of heat exchange by contact heat transfer of combustion gas, combustion heat can be recovered efficiently, and the power for catching power generation equipment such as a heat medium circulation pump can be greatly increased. It can be reduced and the power generation efficiency is improved.

  In addition, a heat exchanger is installed in the atmosphere containing almost no corrosive gas such as SOx or HCl in the combustion gas of the stoker-type combustion furnace, that is, in the post-combustion zone of the stoker-type combustion furnace. Even if the combustion gas is in direct contact with the heat exchanger tube of the vessel, the risk of low temperature corrosion is not high. As a result, it is possible to significantly reduce the total cost of installing the waste power generation facility without reducing the life of the heat exchanger and increasing the repair cost.

  Furthermore, since the heat exchanger can be easily installed in the rear combustion zone, etc. of the stoker-type combustion furnace, the power generation system can be easily applied even to an existing stoker-type combustion furnace, and waste heat recovery is possible. The rate and power generation efficiency can be improved.

It is a systematic diagram which shows the basic composition of embodiment of this invention. It is explanatory drawing which shows the installation possible range of the heat exchanger in a stoker type combustion furnace. It is a systematic diagram of a binary power generation system using a conventional low boiling point heat medium.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram showing a basic configuration of a small-scale power generation system according to an embodiment of the present invention. In FIG. 1, 1 is a stoker-type combustion furnace, 2 is a combustion gas (combustion waste) of a stoker-type combustion furnace. (Heat) as a heat source, 3 is a low boiling point heat medium circulating in the heat exchanger 2, 4 is a steam turbine generator, 5 is a low boiling point heat medium steam condenser, and 6 is a low boiling point heat medium. A circulation pump, 7 is a low boiling point heat medium circulation path, 8 is a cooler, 9 is cooling water, 10 is a cooling water circulation pump, 11a and 11b are cooling water circulation paths, 12 is cooling air, and 13 is a blower.

As shown in FIG. 2, the stoker-type combustion furnace 1 includes a furnace body 14, a waste hopper 15, a supply pusher 1 6 , a stalker 17, a hopper lower hopper 18, a primary combustion chamber 19, a secondary combustion chamber 20, a primary Composed of combustion air A1a to A1d, secondary combustion air A2, ash outlet 21, ash containers 21a to 21d, ash conveyor 23, and the like. The stoker 17 is composed of a dry stoker 17a, a combustion stoker 17b, and a post-combustion stoker 17c, and the primary combustion air A1 is supplied to the stokers 17a, 17b, and 17c from below the stoker 17. Further, the primary combustion chamber 19 has a combustion zone 19a substantially corresponding to the lower position of the secondary combustion chamber 20, and a rear portion having substantially the same length as the combustion zone 19a substantially corresponding to the upper portion of the post-combustion stoker 17c. And a combustion zone 19b.

Referring to FIG. 2, waste W in waste hopper 15, the feed pusher 16 is supplied onto the dried stoker 17a, the width of the primary combustion air A ₁ and the primary combustion chamber 19 and the like which is supplied from the lower elevation By heating and drying with heat, moisture and volatile components in the waste W evaporate, and unburned gas (reducing gas) such as CO (carbon monoxide) and HC (hydrocarbon) is released.

The dried waste W is fed onto the combustion stoker 17b, with combusted by raising the flame by the primary combustion air A ₁ from below, reached a burnout point at the downstream end of the combustion stoker 17b, subsequently It is sent to the post-combustion stoker 17c, after being called every combustion by the primary combustion air a ₁ from below, is dropped discharged from ash removal opening 2b.
Further, the unburned gas and unburned substances generated by the incineration of the waste W are completely caused by the primary combustion air A ₁ supplied from under the stoker 17 and the secondary combustion air A ₂ supplied to the secondary combustion chamber 20. After being combusted, it is discharged out of the furnace body 14 from an exhaust gas outlet (not shown).
In addition, since the stoker type incinerator 1 itself is well-known, the detailed description is abbreviate | omitted here.

  The heat exchanger 2 has the same structure as a known heat exchanger, and the low boiling point heat medium 3 flowing in the heat transfer tube is heated by the heat of the combustion gas from the post-combustion zone 19b, thereby reducing the low boiling point. Heat carrier vapor is generated. Moreover, the normal heat exchanger carbon steel pipe is used for the heat exchanger tube of the said heat exchanger 2, and the special corrosion-resistant steel pipe is not used.

  The heat exchanger 2 is installed in the post-combustion zone 19b of the primary combustion chamber 19, and the radiant energy of the combustion heat in the post-combustion zone 19b is converted into a heat transfer tube with a high heat transfer rate by so-called radiant heat transfer ( As a result, the high boiling point heat medium 3 is efficiently heated and vaporized. Needless to say, the heat exchanger 2 may be provided outside the primary combustion chamber 19 and heated by the combustion gas led out from the post-combustion zone 19b to the outside of the furnace body.

  As shown in FIG. 2, the position where the heat exchanger 2 is installed is located on the ceiling wall surface or the side wall surface downstream of the approximate center of the length L in the flow direction of the waste W in the primary combustion chamber 19 or above the rear combustion stoker 17c. It may be a space portion, or may be a rear wall surface on the end side of the primary combustion chamber 19.

The reason why the heat exchanger 2 is installed in the rear combustion zone 19b region of the primary combustion chamber 19 is to prevent the occurrence of low-temperature corrosion of a so-called heat transfer tube (heat exchange tube). That is, the use of low-boiling heat medium 3 as a heat recovery medium, the corrosive gases such as SO _X or HCl is present in the combustion gases directly into contact with the as described above the heat transfer tube (heat exchanger tube), inevitably This is because the risk of low temperature corrosion increases.

However, in a stoker-type incinerator, particularly a step-type stoker incinerator for municipal waste incineration, the content of corrosive gases such as SO _X and HCl in the combustion gas in the post-combustion zone 19b is reduced to the combustion zone. It has been confirmed that it is significantly reduced compared to the combustion gas in 19a.

  This is because corrosive gases such as HCl and SOx in the combustion gas are generated by combustion of plastics such as vinyl chloride contained in the waste W, and these plastics are 350 ° C to 500 ° C. Since it decomposes and burns at 0 ° C. and its combustion speed is high, it burns on the combustion stoker 17b. Therefore, corrosive gas is mainly generated on the combustion stokers 17a and 17b, and is present in a large amount in the main combustion exhaust gas in the combustion zone 19a above the combustion stoker 17b and the dry stoker 17a. As a result, above the post-combustion stoker 11c. The corrosive gas and dust hardly remain in the combustion gas in the post-combustion zone 19b.

Also, in the measurement in industrial waste incinerators (stepped stoker incinerator, only two stages of combustion stoker and post-combustion stoker), in the exhaust gas discharged from the secondary combustion chamber 20 to the outside of the furnace When SO ₂ is 300 ppm and HCl is 950 ppm, the results are obtained that SO ₂ in the combustion gas derived from the post-combustion zone 19b is 8 ppm and HCl is 50 ppm.

  That is, in a stoker incinerator, particularly a staircase type stoker incinerator, there is almost no corrosive gas such as SOx or HCl in the combustion gas in the post-combustion zone 19b, and as a result, in the post-combustion zone 19b. Even if the heat exchanger 2 is installed, the risk of low-temperature corrosion is not particularly increased.

  The low boiling point heat medium 3 is selected by comprehensively judging steam pressure, heat capacity, heat transfer coefficient, corrosivity, stability, etc., and a low boiling point heat medium having a boiling point other than water of 100 ° C. or less is desirable. In this embodiment, alternative chlorofluorocarbon (HFE, boiling point 34 ° C.) is used as the low boiling point heat medium, but in addition to inert gas such as alternative chlorofluorocarbon, ammonia, hydrocarbon-based butane, It is also possible to use a combustible gas such as pentane.

Next, the operation of the small-scale power generation system in the stoker type incinerator according to the present invention will be described.
1 and 2, a low boiling point medium (pentane / boiling point 36 ° C.) 3 having a temperature of about 30 to 32 ° C. is supplied to the heat transfer tube of the heat exchanger 2 by the low boiling point heat medium circulation pump 6. Here, it is heated by the combustion heat (combustion gas) in the post-combustion zone 19b, and heat medium vapor is generated.

  The steam turbine generator 4 is rotationally driven by the generated low-boiling-point medium steam, and necessary power generation is performed, and the low-boiling-point heat medium steam that has worked in the steam turbine / turbine generator is introduced into the condenser 5 and the cooling water 9 It cools and condenses.

  The condensed low boiling point heat medium 3 circulates and circulates in the low boiling point heat medium circulation path 7 including the heat exchanger 2 so that continuous power generation is performed. The cooling water 9 is cooled by the air-cooled cooler 8 and circulates in the cooling water circulation path 11.

  The small-scale power generation system according to the present invention is a large-scale stoker-type waste incinerator provided with a so-called waste power generation facility because the heat exchanger 2 is arranged in the post-combustion zone 19b of the stoker-type incinerator. In addition, even large or small stoker-type waste incinerators that do not have so-called waste power generation equipment can be easily installed without causing a significant increase in equipment costs, and improved waste heat recovery efficiency Economical high-efficiency power generation can be performed, and high practical utility can be obtained.

  The small-scale power generation system according to the present invention can be applied to any stoker-type incinerator regardless of whether the waste treatment capacity is large or small.

W Waste A ₁ Primary combustion air A ₂ Secondary combustion air 1 Stoker type combustion furnace 2 Heat exchanger 3 Low boiling point heat medium 4 Turbine generator 5 Condenser 6 Low boiling point heat medium circulation pump 7 Low boiling point heat medium circuit 8 Cooler 9 Cooling water 10 Cooling water circulation pump 11 Cooling water circulation path 12 Air 13 Blower 14 Furnace body 15 Waste hopper 16 Supply pusher 17 Stoker 17a Dry stoker 17b Combustion stoker 17c Post combustion stoker 18 Stoker hopper 19 Primary combustion chamber 19a Combustion zone 19b Post combustion zone 20 Secondary combustion chamber 21 Ash outlet

Claims (3)

A heat medium circulation path is formed from a heat exchanger that uses combustion heat in the primary combustion chamber of the stoker-type incinerator as a heat source, a steam turbine generator, a condenser, and a heat medium circulation pump, and the inside of the heat medium circulation path is with circulating flow of low-boiling heat transfer medium having a low boiling point than that of water by the heat medium circulation pump, and configured to drive a steam turbine generator by the steam of the low-boiling heat medium generated in the heat exchanger,
A small-scale power generation system in a stoker-type incinerator in which a heat transfer tube of the heat exchanger through which the low-boiling-point heat medium flows is arranged in a post-combustion zone of the primary combustion chamber . A heat medium circulation path is formed from a heat exchanger that uses combustion heat in the primary combustion chamber of the stoker-type incinerator as a heat source, a steam turbine generator, a condenser, and a heat medium circulation pump, and the inside of the heat medium circulation path is A low boiling point heat medium having a lower boiling point than water is circulated and circulated by a heat medium circulation pump, and a steam turbine generator is driven by steam of the low boiling point heat medium generated by the heat exchanger,
The heat exchanger is provided outside the primary combustion chamber, and the low-boiling point heat medium flowing through the heat exchanger is heated by the combustion gas led out of the furnace from the post-combustion zone of the primary combustion chamber. A small-scale power generation system in a stoker-type incinerator. The small-scale power generation system in a stoker-type incinerator according to claim 1, wherein the heat exchanger is supported and fixed to any one of a ceiling wall or a side wall or a rear wall forming a post-combustion zone of the primary combustion chamber.

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