JP2008190830A - Boiler system, power generation system and operation method of boiler system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler system, a power generation system and an operation method of the boiler system, capable of using concentrated sludge generated in a sewage treatment facility as fuel. <P>SOLUTION: This boiler system has a pressurizing fluidized bed boiler 20, a kneader 31 mixing CWP composed of coal, water and limestone, and a slurry tank 37 storing the concentrated sludge generated in a sewage treatment plant 40, and supplies the concentrated sludge to the kneader 31 from the slurry tank 37. The kneader 31 manufactures and supplies mixed fuel to the pressurizing fluidized bed boiler 20 by mixing the CWP and the concentrated sludge. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a boiler system, a power generation system, and an operation method of the boiler system, and is particularly useful when applied to the case where concentrated sludge generated in a sewage treatment facility is included in fuel and effectively used.

  In the sewage treatment facility, a large amount of organic sludge is generated in the process of treating domestic sewage such as domestic wastewater and rainwater. In such a sewage treatment facility, various treatments for purifying sewage are performed, and such sludge treatment is also performed. Such sludge treatment generally reduces sludge in a sanitary manner by concentrating and dewatering the sludge.

  In the sludge treatment, about 98% of the composition of the sludge after concentration is moisture, and after dehydration, the moisture is about 80% of the sludge. This concentrated sludge is also called concentrated sludge, and the dewatered sludge is also called dehydrated sludge. Since dehydrated sludge is in a wet mud, it is easy to transport, so it is transported from sewage treatment facilities and used as cement and brick materials and compost. In addition, dehydrated sludge is used in incineration systems as boiler fuel (see, for example, Patent Document 1).

  However, even with dewatered sludge, the water accounts for about 80% of the total, and a sufficient amount of heat cannot be obtained during combustion. Furthermore, considering that the dehydrated sludge may be dried before incineration, the dehydrated sludge could not be efficiently used as fuel for the incineration system.

  Further, for example, a sewage treatment facility such as a small-scale sewage treatment plant or a septic tank does not have a dehydration treatment apparatus, and dehydrated sludge may not be generated in the first place. Although it is conceivable to provide a new dewatering apparatus in such a sewage treatment facility, such an apparatus is very expensive and difficult to realize.

JP-A-2005-323131

  In view of such circumstances, an object of the present invention is to provide a boiler system and a power generation system that can use concentrated sludge generated in a sewage treatment facility as a fuel, and a method for operating the boiler system.

  In order to achieve the above object, a first aspect of the present invention is a boiler system including a furnace that burns a mixed fuel containing fuel and water, and is concentrated from sewage by sewage treatment in a sewage treatment facility. A boiler system comprising mixed fuel supply means for mixing sludge with the fuel and water to produce a mixed fuel and supplying the mixed fuel to the furnace.

  In the first aspect, the concentrated sludge from the sewage treatment facility and the fuel containing water are mixed to produce a mixed fuel. The furnace then burns the supplied mixed fuel. That is, the concentrated sludge, most of which is composed of moisture, is used as a substitute or supplement for water that has been mixed with conventional fuel. Thereby, the quantity of the water currently mixed with the fuel can be reduced. Moreover, the sludge content in the concentrated sludge can also be used for combustion, and the amount of fuel used can be reduced.

  On the other hand, even in a sewage treatment plant, the concentrated sludge can be disposed of without dewatering the sludge into dehydrated sludge. For this reason, it is not necessary to provide an expensive apparatus such as a dehydration apparatus, and it is not necessary to bear the cost for such capital investment. Conventionally, concentrated sludge is dehydrated to generate dehydrated sludge, and dehydrated sludge is incinerated with a fuel oil or other auxiliary combustor. However, the time and cost of such incineration can be reduced. .

  According to a second aspect of the present invention, in the boiler system according to the first aspect, the mixed fuel supply means has the fuel, the water, and the water so as to have a predetermined viscosity based on the viscosity of the manufactured mixed fuel. And a viscosity adjusting means for adjusting a mixing ratio of the concentrated sludge.

  In the second aspect, the mixed fuel adjusted to a predetermined viscosity is supplied to the furnace.

  According to a third aspect of the present invention, in the boiler system according to the second aspect, the mixed fuel supply means mixes the fuel, the water, and the concentrated sludge, and supplies water to the mixing device. Water supply means for supplying, concentrated sludge supply means for supplying the concentrated sludge to the mixing device at a constant rate, and fuel supply means for supplying fuel to the mixing device, the viscosity adjusting means, The boiler system is characterized in that the amount of water injected by the water injection means is adjusted so as to have a predetermined viscosity based on the viscosity of the mixed fuel produced by a mixing device.

  In the third aspect, a certain amount of concentrated sludge is supplied from the concentrated sludge supply means to the mixing device. That is, a certain amount of water is supplied to the mixing device. Thus, when adjusting the amount of water supplied to the mixing device, the viscosity adjusting unit can control only the amount of water supplied from the water injection unit to the mixing device without controlling the amount of concentrated sludge supplied from the concentrated sludge supply unit. Good.

  According to a fourth aspect of the present invention, in the boiler system according to any one of the first to third aspects, the fuel is coal, and the mixed fuel is water, coal, concentrated sludge, and limestone. In the boiler system, the furnace is a pressurized fluidized bed boiler.

  In the fourth aspect, concentrated fuel sludge is mixed with CWP (Coal Water Paste) made of water, coal, and limestone to produce a mixed fuel, and this mixed fuel can be burned in a pressurized fluidized bed boiler.

  In order to achieve the above object, a fifth aspect of the present invention resides in a power generation system including the boiler system described in any one of the first to fourth aspects.

  In the fifth aspect, it is possible to generate power by driving the gas turbine generator or the steam turbine generator of the power generation system with the thermal energy generated in the furnace of the boiler system.

  A sixth aspect of the present invention for achieving the above object is an operation method of a boiler system including a furnace for burning a mixed fuel containing fuel and water, and is separated from sewage by sewage treatment in a sewage treatment facility. A mixed fuel sludge is mixed with the fuel and the water to produce a mixed fuel, the mixed fuel is supplied to the furnace, and the mixed fuel is burned in the boiler. It is in.

  In the sixth aspect, when the fuel containing water is produced, the moisture of the concentrated sludge from the sewage treatment facility can be used. Thereby, the quantity of the water currently mixed with the fuel can be reduced. Moreover, the sludge content in the concentrated sludge can also be used for combustion, and the amount of fuel used can be reduced.

  According to the present invention, fuel containing water is mixed with concentrated sludge generated at a sewage treatment facility to produce a mixed fuel, and the mixed fuel is burned in a furnace. That is, the concentrated sludge, most of which is composed of water, is used as a substitute or supplement for water that has been mixed with conventional fuel. Thereby, the quantity of the water currently mixed with the fuel can be reduced. In addition, the sludge content in the concentrated sludge can be used as fuel, and the amount of fuel used can be reduced.

  On the other hand, even in a sewage treatment plant, the concentrated sludge can be disposed of without dewatering the sludge into dehydrated sludge. For this reason, it is not necessary to provide an expensive apparatus such as a dehydration apparatus, and it is not necessary to bear the cost for such capital investment. Conventionally, concentrated sludge was dehydrated to produce dehydrated sludge, and the dehydrated sludge was incinerated with fuel oil and other auxiliary combustors, but this was also reduced in time and costs for incineration. can do.

  Hereinafter, the best mode for carrying out the present invention will be described. The description of the present embodiment is an exemplification, and the present invention is not limited to the following description.

  Prior to describing a power generation system including a boiler system according to the present embodiment, concentrated sludge and dewatered sludge generated by sewage treatment in a sewage treatment facility will be described. FIG. 1 is a schematic diagram showing a flow of sludge treatment in a sewage treatment facility.

  First, in a sewage treatment facility, domestic sewage and rainwater collected via the sewer are stored in a sedimentation basin, and substances contained in the sewage are precipitated, and various water treatments such as aeration are performed (steps). S1). As a result of such treatment, sludge is separated from sewage in a sedimentation basin or the like, and such sludge is sent to a sludge treatment apparatus. In the sludge treatment apparatus, the sludge is concentrated to produce concentrated sludge (step S2). Concentration treatment includes gravity concentration in which sludge stays in the sedimentation tank and concentrates due to the difference in specific gravity and gravity, and floating concentration that causes fine bubbles to adhere to solids, reverses the specific gravity difference, and floats on the water surface to concentrate. It is processing. The concentrated sludge thus produced is composed of about 2% organic matter and the like, and about 98% moisture. Further, in a sewage treatment facility provided with a device for dewatering the concentrated sludge, a flocculant is added to the concentrated sludge to generate dehydrated sludge having a reduced moisture content (step S3).

  Concentrated sludge, for example, has a dry heat per kg of about 2000 kcal, while dehydrated sludge has a dry heat per kg of about 4000 kcal. Here, the amount of heat for drying means the amount of heat for the dried portion after water is evaporated from the sludge. In the past, this dewatered sludge was transported to an incineration system or the like and used as fuel. On the other hand, the boiler system according to the present embodiment uses this concentrated sludge to burn fuel.

  Here, a power generation system including a boiler system using a pressurized fluidized bed boiler which is an example of a furnace will be described. FIG. 2 is a schematic configuration diagram of a power generation system including the boiler system according to the present embodiment. This power generation system includes a boiler system 10 that generates steam by burning fuel, and a steam turbine generator 70 that is driven by the steam.

  The boiler system 10 includes a pressurized fluidized bed boiler 20 which is an example of a furnace, and a mixed fuel supply means 30 for supplying mixed fuel to the pressurized fluidized bed boiler 20.

  The pressurized fluidized bed boiler 20 has a pressure vessel and a furnace main body provided therein (none of which is shown). A predetermined amount of a fluid medium containing limestone as a main component is contained in the furnace body. This fluidized medium is fluidized with pressurized air blown from the bottom of the furnace body by an air supply means (not shown) to form a fluidized bed. Then, the mixed fuel introduced into the fluidized bed by the mixed fuel supply means 30 is combusted in a pressurized state (for example, about 1 MPa).

  A heat transfer tube (not shown) connected to the steam turbine generator 70 is routed in the pressurized fluidized bed boiler 20, and heat generated by burning the mixed fuel in the pressurized fluidized bed boiler 20. Steam is generated in the heat transfer tube using the steam, and the steam turbine generator 70 is operated with this steam to generate power. Not only the steam turbine generator 70 but also a gas turbine generator that uses exhaust gas generated by combustion in the pressurized fluidized bed boiler 20 may be used.

  The mixed fuel supply means 30 produces mixed fuel and supplies it to the pressurized fluidized bed boiler 20. Here, the mixed fuel refers to a mixture of concentrated sludge mixed with CWP (Coal Water Paste) made of coal, water, and limestone as fuel. Specifically, the kneader 31 (mixing device) mixes coal, water, limestone, and concentrated sludge to produce a mixed fuel. On the other hand, a tank 32 for storing water, a coal bunker 33 for storing coal, and a limestone bunker 34 for storing limestone are provided, and these devices supply each raw material of the mixed fuel to the kneader 31. Yes. Further, a coarse pulverizer 35 and a fine pulverizer 36 for pulverizing coal are disposed between the kneader 31 and the coal bunker 33. The coal is supplied to the kneading machine 31 in a state of being roughly crushed by the coarse pulverizer 35, or is crushed by the coarse pulverizer 35 and then sent to the fine pulverizer 36 for further finely pulverizing and water. And supplied to the kneader 31 in a mixed state.

  Further, a slurry tank 37, a pump 38 and a flow rate control valve 39 are provided as concentrated sludge supply means for supplying concentrated sludge to the kneader 31. The slurry tank 37 is a tank that stores the concentrated sludge generated at the sewage treatment plant 40. In the present embodiment, the concentrated sludge is transported by the transport vehicle 41 and stored in the slurry tank 37, but is not limited to such a form, for example, a pipeline from the sewage treatment plant 40 to the slurry tank 37 is provided, Concentrated sludge may be supplied directly to the slurry tank 37 via this pipeline.

  The concentrated sludge stored in the slurry tank 37 is pressurized by a pump 38 and supplied to the kneader 31 through a pipe line disposed between the slurry tank 37 and the kneader 31. A flow rate control valve 39 is interposed in the pipeline, and the concentrated sludge is supplied to the kneader 31 at a constant rate by adjusting the opening degree of the flow rate control valve 39.

  The boiler system 10 is provided with a control device 50 (viscosity adjusting means). The control device 50 is an information processing device having a general function. Specifically, it includes a CPU, a storage device such as a ROM, a RAM, and a hard disk, and a display unit such as a liquid crystal screen and an input unit such as a keyboard (none of which are shown).

  The control device 50 supplies from the tank 32 to the kneading machine 31 from the sensor that detects the viscosity of the mixed fuel produced by the kneading machine 31 based on a signal indicating this viscosity so that the viscosity of the mixed fuel becomes a predetermined value. Control the amount of water injected.

  In the power generation system including the boiler system 10 having such a configuration, the concentrated sludge transported from the sewage treatment plant 40 and the water, coal, and limestone stored in the boiler system 10 are mixed by the kneader 31 so that the mixed fuel is obtained. Manufactured. The pressurized fluidized bed boiler 20 is supplied with the mixed fuel from the kneader 31 and burns the mixed fuel in the fluidized bed formed in the furnace body. And the steam turbine generator 70 is driven using the thermal energy generated by this combustion to generate electric power.

  As described above, the mixed fuel combusted in the pressurized fluidized bed boiler 20 is obtained by mixing concentrated sludge with CWP, which is a conventionally used fuel made of water, coal, and limestone. That is, the concentrated sludge, most of which is composed of moisture, is used as an alternative or supplement to the water previously mixed in CWP. Thereby, the quantity of the water conventionally utilized in order to manufacture CWP can be reduced. Moreover, the sludge content in the concentrated sludge can be used for combustion, and the amount of coal used can also be reduced.

  On the other hand, even in a sewage treatment plant, the concentrated sludge can be disposed of without dewatering the sludge into dehydrated sludge. For this reason, it is not necessary to provide an expensive apparatus such as a dehydration apparatus, and it is not necessary to bear the cost for such capital investment. Conventionally, concentrated sludge is dehydrated to generate dehydrated sludge, and dehydrated sludge is incinerated with a fuel oil or other auxiliary combustor. However, the time and cost of such incineration can be reduced. .

  Furthermore, the boiler system 10 according to the present embodiment can be easily applied to an existing boiler system or power generation system that includes the pressurized fluidized bed boiler 20. For example, if a portion surrounded by a broken line A is an existing portion as shown in FIG. 2, a portion surrounded by a broken line B may be newly added. That is, the boiler system 10 according to the present embodiment can be implemented simply by adding the slurry tank 37, the pump 38, and the flow rate control valve 39 to the existing boiler system.

  Further, a certain amount of concentrated sludge is supplied from the slurry tank 37 to the kneader 31 by adjusting the opening degree of the flow control valve 39. That is, a certain amount of water is supplied from the slurry tank 37 to the kneader 31. Thereby, in adjusting the amount of water supplied to the kneading machine 31, the control device 50 only needs to control the amount of water injected from the tank 32 to the kneading machine 31, and the viscosity adjustment can be easily realized. In particular, as described above, if such a control device 50 is provided in an existing boiler system, even if a slurry tank 37, a pump 38, and a flow rate control valve 39 are newly installed, the devices related to the control device 50, etc. There is no need to make any changes.

  In addition, although concentrated sludge was mixed with CWP which consists of water, coal, and limestone as a fuel, it is not limited to this. For example, concentrated sludge may be mixed with CWM (Coal Water Mixture) or emulsion fuel. CWM is a slurry fuel in which water is mixed with coal, and the emulsion fuel is a liquid fuel to which an additive that promotes emulsification (emulsification) by adding water to heavy oil, light oil or the like is added. Concentrated sludge can be used as a substitute or supplement for water, coal, heavy oil, etc. mixed with these CWM and emulsion fuel. And a furnace is not limited to a pressurized fluidized bed boiler, If it is a furnace which burns the fuel with which water was mixed, it can apply to the boiler system (power generation system) which concerns on this invention.

  INDUSTRIAL APPLICABILITY The present invention can be used in industries that use concentrated sludge produced in sewage treatment facilities as fuel.

It is the schematic which shows the flow of the sludge process in a sewage treatment facility. It is a schematic structure figure of a power generation system provided with the boiler system concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Boiler system 20 Pressure fluidized bed boiler 30 Mixed fuel supply means 31 Kneading machine 32 Tank 33 Coal bunker 34 Limestone bunker 35 Coarse pulverizer 36 Fine pulverizer 37 Slurry tank 38 Pump 39 Flow control valve 40 Sewage treatment plant 41 Transport vehicle 50 Control device 70 Steam turbine generator

Claims (6)

A boiler system comprising a furnace for burning a mixed fuel containing fuel and water,
A boiler system comprising mixed fuel supply means for mixing concentrated sludge separated from sewage by sewage treatment in a sewage treatment facility together with the fuel and water to produce a mixed fuel and supplying the mixed fuel to the furnace. In the boiler system according to claim 1,
The mixed fuel supply means includes viscosity adjusting means for adjusting a mixing ratio of the fuel, the water, and the concentrated sludge so as to obtain a predetermined viscosity based on the viscosity of the manufactured mixed fuel. Boiler system. In the boiler system according to claim 2,
The mixed fuel supply means mixes the fuel, the water and the concentrated sludge, a water injection means for supplying water to the mixing apparatus, and supplies the concentrated sludge to the mixing apparatus at a constant rate. Concentrated sludge supply means, comprising a fuel supply means for supplying fuel to the mixing device,
The boiler system characterized in that the viscosity adjusting means adjusts a water injection amount by the water injection means so as to have a predetermined viscosity based on a viscosity of the mixed fuel produced by the mixing device. In the boiler system as described in any one of Claims 1-3,
The fuel is coal;
The mixed fuel is produced by containing water, coal, concentrated sludge, and limestone,
The boiler system is a pressurized fluidized bed boiler.   A power generation system comprising the boiler system according to any one of claims 1 to 4. A method of operating a boiler system comprising a furnace for burning a mixed fuel containing fuel and water,
Concentrated sludge separated from sewage by sewage treatment in a sewage treatment facility is mixed with the fuel and the water to produce a mixed fuel, the mixed fuel is supplied to the furnace, and the mixed fuel is burned in the boiler. The operation method of the boiler system characterized by the above-mentioned.

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