JP2012246184A - Carbon dioxide circulation type lime burning facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide circulation type lime burning facility having high energy efficiency, capable of returning carbon dioxide into a lime burning furnace and using it as a heat medium without requiring a special blower fan.SOLUTION: This facility includes: a blower 3 for introducing a part of carbon dioxide to be served for preheating a raw material limestone inputted into a lime burning furnace, which is carbon dioxide cooled by preheating; an ejector device 4 having on a nozzle a driving gas supply port for supplying carbon dioxide having a pressure raised by the blower 3 as driving gas and a driven gas supply port for supplying a part of carbon dioxide generated by pyrolysis as driven gas, for sucking driven gas by driving gas flowing in the nozzle and discharging both gasses; and a main heat exchanger 9 into which carbon dioxide discharged from the ejector device 4, for performing heat exchange with a high-temperature heat medium. Further, the facility is constituted so that carbon dioxide having a temperature raised by heat exchange in the main heat exchanger 9 is supplied into the lime burning furnace as pyrolysis gas for the limestone.

Description

  The present invention relates to a carbon dioxide circulating lime firing facility that circulates carbon dioxide generated in a lime firing furnace and uses it as a heating medium.

  FIG. 3 shows a flow chart of a conventional quicklime manufacturing facility.

  The equipment shown in the figure includes an indirect heating lime furnace 100, a combustion furnace 102 with a combustion air fan 101 for supplying high-temperature combustion gas thereto, and an air preheater 103 for recovering heat from exhaust gas after lime firing. The exhaust gas treatment device 104 removes harmful substances in the combustion exhaust gas, and the chimney 105 that releases the combustion exhaust gas from which the harmful substances have been removed to the atmosphere.

  The combustion gas is guided to the lime baking furnace 100, and heat exchange is performed with the carbon dioxide gas flowing in the heat transfer tube 106 installed in the furnace. That is, a heat exchanger is placed in the lime furnace.

  The carbon dioxide circulation device 107 includes a carbon dioxide cooler 110 provided in the middle of a pipe connecting the pre-tropical zone 108 and the cooling zone 109 of the lime baking furnace 100, and a carbon dioxide circulation fan 111 that pressurizes the cooled carbon dioxide. And a carbon dioxide storage tank 112 for extracting and storing carbon dioxide (see, for example, Patent Document 1).

  Although the carbon dioxide circulation path in the quick lime production facility is simple, the carbon dioxide cooler 110 cools the carbon dioxide gas to near room temperature, and then the cooling zone 109 has a sufficient amount to cool the quick lime. Supply. That is, since the entire amount of the high-temperature carbon dioxide generated by the thermal decomposition is cooled to near normal temperature by the carbon dioxide cooler 110, a large amount of heat is discarded without being used.

  The circulating carbon dioxide gas is again heated by the sensible heat of the product quicklime and the combustion gas.

The endotherm of thermal decomposition (CaCO ₃ → CaO + CO ₂ ), which is an endothermic reaction, is 3.15 MJ / kg-CaO, and the unit energy consumption of quick lime production in a normal direct heating lime kiln is 3.8 MJ / kg. The heat discarded here is about twice that of 6MJ / kg-CaO.

  In this case, it must be said that it is advantageous from the viewpoint of overall energy consumption to separate and recover the carbon dioxide gas from the mixed exhaust gas of the direct heating lime baking furnace.

  Further, as shown in FIG. 4, a carbon dioxide circulating lime calciner that collects a large amount of carbon dioxide discharged from the lime calciner is also known.

  In the figure, limestone mixed with coke is supplied to the packed bed from the upper part of the lime baking furnace 120. By supplying the circulating carbon dioxide gas heated to 1,100 ° C. by the electric heater 121 to the lime baking furnace 120, the limestone is baked in the upper calcination zone 122, and further descends to reduce the combustion heat of the coke in the lower calcination zone 123. Thus, the calcined product is completed, and the quicklime of the product is discharged from the discharge valve 124 to the outside of the furnace (for example, see Patent Document 2).

  In the lime baking furnace 120, an electric heater 121 for heating the circulating carbon dioxide gas is placed outside the furnace, and the carbon dioxide cooler as shown in FIG. 2 is not provided.

  Then, the carbon dioxide gas at the outlet of the lime firing furnace whose temperature is lowered to 700 ° C. to 800 ° C. by the thermal decomposition of limestone and the preheating of the limestone is circulated using the carbon dioxide circulation fan 125.

  The carbon dioxide circulation fan 125 must be able to handle a high-temperature fluid that exceeds the operating temperature range of a normal fan. For example, a special fan using a ceramic material such as silicon carbide is required. Such blowers are limited in type and amount of air flow, and in particular, there are no models that can be used on the scale of a lime factory in an ironworks.

JP 2004-231424 A JP 2009-161391 A

  In the conventional quick lime production facility shown in FIG. 3, as described above, since energy efficiency is poor, it is more comprehensive energy consumption (cost) to separate and recover the carbon dioxide gas from the mixed exhaust gas of the direct heating lime baking furnace. Then there is a problem that it becomes advantageous.

  Also, in the carbon dioxide circulating lime firing furnace shown in FIG. 4, since a blower fan must be used in a high temperature range that does not hold unless a special ceramic blower is used, such a special ceramic blower can be used. This design has a problem that the scale and configuration of the apparatus are restricted.

  The present invention has been made in consideration of the problems in the conventional lime firing furnace as described above, has high energy efficiency, and returns carbon dioxide to the lime firing furnace without requiring a special blower fan. A carbon dioxide circulating lime firing facility that can be used as a medium is provided.

In the process of pyrolyzing limestone (CaCO ₃ ) to produce quick lime (CaO), a large amount of carbon dioxide (CO ₂ ) is generated from the inside of the limestone, and this carbon dioxide has an adverse effect on global warming.

  The present invention has been made in consideration of the above problems, and is an indirect heating type that makes it possible to recover carbon dioxide generated in the production process of quicklime in the state of high-concentration carbon dioxide so as to be stored in the ground or the ocean. This is a carbon dioxide circulating lime firing facility.

  The indirect heating type indicates that high-temperature combustion gas does not directly contact limestone to transfer heat.

  In the present invention, the path through which combustion gas flows and the path through which carbon dioxide gas generated by pyrolysis of limestone is separated, so that the latter path through which carbon dioxide gas flows contains only about 3% of water. High purity carbon dioxide that does not require a process is produced as exhaust gas.

  The path through which the former combustion gas flows contains a large amount of nitrogen derived from air, and in a normal case, the carbon dioxide concentration is 20% or less. However, since the amount of carbon dioxide gas generated by pyrolysis is about three times that of carbon dioxide gas generated by combustion, it is significant to separate the path of carbon dioxide gas generated by pyrolysis.

The present invention is a carbon dioxide circulating lime firing facility that circulates carbon dioxide generated by thermal decomposition of limestone into a lime firing furnace and uses it as a heating medium.
A blower that is a part of the carbon dioxide gas used for preheating raw limestone charged into the lime firing furnace and that is guided by the carbon dioxide gas cooled by the preheating,
The nozzle has a driving gas supply port for supplying the carbon dioxide gas boosted by the blower as a driving gas, and a driven gas supply port for supplying a part of the carbon dioxide gas generated by thermal decomposition as the driven gas. An ejector device for sucking the driven gas by the driving gas flowing in the nozzle and discharging both gases;
A carbon dioxide gas discharged from the ejector device is guided, and includes a main heat exchanger that performs heat exchange with a high-temperature heat source,
The gist is that the carbon dioxide gas heated by the heat exchange of the main heat exchanger is supplied to the lime baking furnace as a pyrolysis gas of limestone.

  In this invention, a 2nd heat exchanger is provided in the flow path which connects the said air blower and the said ejector apparatus, and this 2nd heat exchanger is from the said lime baking furnace in a high temperature state without passing through the preheating of raw material limestone. If a part of the discharged carbon dioxide gas is introduced, the driving gas supplied to the ejector device can be heated.

  In the present invention, an auxiliary ejector device is connected to the main heat exchanger, the air boosted by the second blower is supplied to the driving gas supply port of the auxiliary ejector device, and the lime is supplied to the driven gas supply port. Exhaust discharged from the lime firing furnace that is used for cooling quick lime discharged as a product from the bottom of the firing furnace can be supplied.

  In the present invention, if a combustor is provided between the main heat exchanger and the auxiliary ejector device, the exhaust discharged from the auxiliary ejector device is burned and supplied to the main heat exchanger as a high-temperature heat source. be able to.

  In this invention, the 3rd heat exchanger is provided in the flow path which connects the said 2nd heat exchanger and the said ejector apparatus, and heat exchange with the carbon dioxide gas discharged | emitted from the said ejector apparatus is provided in this 3rd heat exchanger. If the exhaust gas that is supplied to and discharged from the main heat exchanger is guided, the driving gas supplied to the ejector device can be further heated.

  In this invention, a 4th heat exchanger is provided in the flow path which connects said 2nd air blower and the drive gas supply port of the said auxiliary ejector apparatus, The carbonic acid discharged | emitted from the said ejector apparatus in this 4th heat exchanger If the exhaust gas that is used for heat exchange with the gas and discharged from the main heat exchanger is guided, the driving gas supplied to the auxiliary ejector device can be further heated.

  In the present invention, a fifth heat exchanger is provided in a flow path for supplying fuel to the combustor, and the fifth heat exchanger is used for heat exchange with the carbon dioxide gas discharged from the ejector device. The carbon dioxide circulating lime baking facility according to claim 3, wherein exhaust gas discharged from the main heat exchanger is guided and the fuel supplied to the combustor is heated.

  In the present invention, at least one carbon dioxide concentration meter for measuring the concentration of carbon dioxide gas used as a heat medium is installed in the carbon dioxide gas flow path, and the carbon dioxide concentration information output from the carbon dioxide concentration meter If the controller for controlling the blast amount of the drive gas supplied to the auxiliary ejector device based on the above is provided, the concentration of carbon dioxide released to the outside of the carbon dioxide circulating lime baking facility can be maintained at a specified value. .

  According to the carbon dioxide circulating lime firing facility of the present invention, carbon dioxide can be efficiently separated and recovered, and a special blower fan is not required, and the carbon dioxide is returned to the lime firing furnace to be used as a heating medium. Has the advantage of being able to.

It is a flowchart of the carbon dioxide circulation type lime baking equipment concerning the present invention. It is explanatory drawing which shows the operation principle of the ejector apparatus shown in FIG. It is a flowchart of the conventional quicklime manufacturing equipment. It is a flowchart of another conventional carbon dioxide circulating lime baking furnace.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a flow diagram of a carbon dioxide circulating lime baking facility according to the present invention.

  The carbon dioxide circulating lime firing facility in FIG. 1 uses a Beckenbach lime firing furnace (hereinafter abbreviated as a firing furnace) 1. This firing furnace 1 uses a part of carbon dioxide gas (circulation gas) after lime firing to preheat and remove moisture from the raw limestone supplied to the firing furnace 1.

  In the present invention, by using a main ejector device (ejector device) 4 to be described later, the high-temperature carbon dioxide gas from the firing furnace 1 is circulated as a pyrolysis gas to the firing furnace without cooling.

  FIG. 2 is an explanatory diagram showing the operating principle of the main ejector device 4.

  The main ejector device 4 has a nozzle structure, in which a fluid f is ejected at a high speed from the ejection portion 4a having a throat portion to the center portion of the nozzle, and negative pressure is generated in the nozzle by the fluid f that jumps into the inlet portion of the diffuser 4b. The gas around the injection unit 4a is drawn and injected from the exhaust port 4c.

  In the present invention, the carbon dioxide gas that has been cooled to about 200 ° C. by preheating limestone and can be blown by a high-temperature blower fan is used as a drive gas for the main ejector device 4 as a drive gas supply port (primary flow side) 4d. In addition, a part of the carbon dioxide gas generated by the thermal decomposition is supplied as a driven gas to the driven gas supply port (secondary flow side) 4e.

  In FIG. 1, the firing furnace 1 has a tower-like furnace cylinder 1a, and an upper middle cylinder 1b is provided above the central part in the furnace cylinder 1a, and a lower middle cylinder 1c is provided below the upper middle cylinder 1b.

  From a raw material charging device (not shown) provided at the upper portion of the furnace tube 1a, raw material limestone and fuel coke are charged into the furnace.

  A plurality of upper gas supply ports 1e are provided in the circumferential direction on the outer peripheral wall of the furnace upper part 1d, and a plurality of lower gas supply ports 1g are provided in the circumferential direction on the outer peripheral wall of the furnace lower part 1f. The supplied limestone is fired by the supplied circulating carbon dioxide gas rg heated to 1,200 ° C., which will be described later, and the product quicklime is deposited on the fixed table 1h located at the bottom of the furnace, and the hopper 1i. It has come to be collected through.

  The circulating carbon dioxide rg rises in the furnace tube 1a and thermally decomposes limestone in the furnace, and about 70% of the generated carbon dioxide enters the inside from the lower part of the upper middle tube 1b, and the furnace is heated at a temperature of 860 ° C. It is discharged outside (see carbon dioxide gas cg1). On the other hand, about 30% of the remaining carbon dioxide gas cg2 passes through the preheating section 1j and is deprived of heat by preheating the limestone introduced from the upper part of the furnace tube 1a, and the temperature is lowered to about 200 ° C. 2 is led.

  The carbon dioxide gas cg2 removed by the cyclone 2 is pressurized by the blower 3 and sent to the primary flow side of the main ejector device 4 as a driving gas og. Further, 860 ° C. carbon dioxide gas cg <b> 1 is supplied to the secondary flow side of the main ejector device 4 through the circulation channel 5.

  The carbon dioxide gas cg2 serving as the driving gas og is heated from 200 ° C. to 600 ° C. by passing through the second heat exchanger 7 and the third heat exchanger 8. In addition, operation | movement of the 2nd heat exchanger 7 and the 3rd heat exchanger 8 is mentioned later.

  The circulating carbon dioxide rg of about 700 ° C. discharged from the main ejector device 4 when the carbon dioxide gas cg1 and the driving gas og join together is then introduced into the main heat exchanger 9 and heated to about 1200 ° C., The gas is supplied to the upper gas supply port 1e and the lower gas supply port 1g, respectively.

  The main heat exchanger 9 is supplied with combustion heat from the combustor 10, and the air necessary for the combustion of the combustor 10 has low combustion efficiency at room temperature, so it is used to cool quick lime and is heated. Air is supplied through the auxiliary ejector device 11.

  Specifically, the primary flow side of the auxiliary ejector device 11 is supplied with air whose pressure has been increased from a new air source via the blower 12 and supplied as a driving gas for the auxiliary ejector device 11. Thereby, the air introduced into the hopper 1i is extracted from the upper part of the lower middle cylinder 1c, and the extracted exhaust 750 ° C. is drawn into the secondary flow side of the auxiliary ejector device 11. Yes.

  Further, a fourth heat exchanger 14 is provided in the flow path 13 leading to the primary flow side of the auxiliary ejector device 11, and a flow path 15 is further branched from the flow path 13, and the flow path 15 is the auxiliary ejector device. 11 discharge-side flow paths 21. The flow path 15 is provided with a damper 16 for adjusting the gas flow rate.

The damper 16 is controlled by a controller 17, and the controller 17 measures carbon dioxide measured by a carbon dioxide concentration meter 19 provided in a CO ₂ extraction flow path 18 leading to a CO ₂ storage container (not shown). The degree of opening and closing is commanded to the damper 16 according to the gas concentration.

  Further, the exhaust gas discharged from the auxiliary ejector device 11 is dust-removed by the cyclone 20 and then supplied to the combustor 10 through the discharge-side flow channel 21. A carbon dioxide concentration meter 22 is provided.

  Further, the by-product gas generated in the factory facility is also supplied to the combustor 10 as a fuel gas, and a fifth heat exchanger 24 is provided in the fuel supply passage 23 for supplying the by-product gas. In addition, each said flow path is comprised with the pipe line.

  Next, the operation of the carbon dioxide circulating lime baking facility having the above-described configuration will be described.

  When the pressure of some carbon dioxide gas is increased to a relatively high pressure of about 0.15 MPa_abs by the blower 3 and supplied to the primary flow side of the main ejector device 4 as a driving gas and the main ejector device 4 is operated, the limestone is preheated. Without being discharged, the carbon dioxide gas cg1 is drawn into the secondary flow side of the main ejector device 4 and supplied again to the lime firing furnace 1 as the circulating carbon dioxide gas rg.

  Here, the flow rate of the carbon dioxide gas cg1 discharged without preheating the limestone is increased by the amount of carbon dioxide newly generated by thermal decomposition in the firing furnace 1 in addition to the circulating carbon dioxide gas rg. For this reason, when the entire amount is supplied to the secondary flow side of the main ejector device 4, the flow rate of carbon dioxide gas circulating in the firing furnace 1 increases as it is operated. Therefore, it is necessary to discharge the carbon dioxide gas generated by thermal decomposition out of the system.

  Therefore, a discharge flow path 25 that discharges the carbon dioxide gas path discharged without preheating the limestone to the outside of the system under atmospheric pressure, and a circulation flow path 5 that supplies the secondary eject side of the main ejector device 4 The flow rate of the driving gas og supplied to the main ejector device 4 is adjusted by the blower 3 and kept constant, so that the flow rate of the carbon dioxide gas flowing through the circulation passage 5 is kept constant, and the carbon dioxide generated by the thermal decomposition is maintained. The flow rate corresponding to the gas is pushed out of the system under atmospheric pressure.

  By the way, the carbon dioxide gas cg1 pushed out of the system under atmospheric pressure has a temperature of about 860 ° C. On the other hand, since the drive gas og of the main ejector device 4 is only sent out from the blower 3, it is a relatively low temperature of about 200 ° C.

  It is the momentum conservation that is established between the high-pressure driving gas, the low-pressure secondary flow gas, and the mixed gas after mixing the two that govern the performance of the ejector device. The gas is changed to a mixed gas with a kinetic force intermediate between the two. The momentum of the fluid is expressed by the following equation.

Here, p: pressure, A: flow path cross-sectional area, m dots: mass flow rate (= Aρv), ρ: density, v: flow velocity.

  Therefore, even if the pressure p remains constant, if the density ρ is decreased, the flow velocity v increases and the momentum increases. For this purpose, it is necessary to increase the temperature of the driving gas og.

  Therefore, the carbon dioxide gas cg1 pushed out of the system under atmospheric pressure is supplied to the second heat exchanger 7, and the driving gas og of the main ejector device 4 is heated using the temperature of the carbon dioxide gas cg1 of about 860 ° C. Yes. Thereby, the temperature of the carbon dioxide gas cg1 flowing through the primary flow side flow path 6 is increased to about 410 ° C. The operation of the third heat exchanger 8 will be described later.

  On the other hand, paying attention to quick lime as a product, raw limestone is supplied from the upper part of the firing furnace 1, and after preheating and moisture removal, it is heated by a circulating carbon dioxide gas rg of about 1,200 ° C. and thermally decomposed to about 900 ° C. It flows down the firing furnace 1 as it is. If the quick lime product is discharged at a high temperature of 900 ° C., it cannot be handled as it is, and if it is dissipated, the energy intensity is deteriorated by about 0.6 MJ / kg-CaO.

  Therefore, it is conceivable to apply the heat generated when cooling the product quick lime by heat exchange to the heat required in the system, but when carbon dioxide is used as the cooling heat medium, it is 600 to 900 ° C. In the temperature range, the product quick lime reacts with carbon dioxide, which causes re-carbonation, causing a problem that hard calcium carbonate adheres to the wall surface of the apparatus.

  Therefore, air supplied to the combustor 10 is used as the cooling heat medium here. The temperature of the air rises as much as the quicklime is cooled, and if this heated air is used, a high-temperature combustion exhaust gas can be obtained with a small amount of fuel.

  The quick lime is cooled by sucking an atmosphere having an air ratio of about 1 (that is, equivalent air) with respect to the fuel charged into the combustor 10 from the product quick lime discharge port side in the firing furnace 1 and raising the inside of the furnace. Thereby, the quicklime temperature in a discharge port is cooled to about 250 degreeC.

  On the other hand, at the air outlet 1k of the firing furnace 1, the temperature of the exhaust is heated to 750 ° C. Since this exhaust gas is sucked from the atmosphere, a suction device is required. Since this temperature is also as high as 750 ° C., the auxiliary ejector device 11 is disposed downstream of the firing furnace 1. A blower 12 is used to produce the driving gas for the auxiliary ejector device 11 and is supplied at an air ratio of about 0.2.

  Note that it is conceivable to provide a blower fan upstream of the firing furnace 1 and push air into the furnace at a positive pressure, but in that case, it is inevitable that air will enter the path of the circulating carbon dioxide gas. The path of the circulating carbon dioxide gas and the path of the cooling air ca in the firing furnace 1 cannot be closed and divided, and are continuous with the same downflow path of the same limestone (heated and eventually becomes quick lime). Because it is connected to.

  An object of the present invention is to recover the pyrolysis gas as high-purity carbon dioxide gas that does not require separation, so that the pressure of the path of the cooling air ca → exhaust e is higher than the path of the circulating carbon dioxide gas (approximately atmospheric pressure). Do not. Conversely, in order to maintain the concentration of the released carbon dioxide gas cg1 with high purity, it is necessary to allow a certain amount of circulating carbon dioxide gas to enter the path of the cooling air ca → exhaust e.

  However, it is not preferable that a large amount of circulating carbon dioxide is mixed in the path of the cooling air ca → exhaust e and eventually included in the combustion exhaust gas and finally discharged, resulting in a decrease in the amount of carbon dioxide recovered. Therefore, the pipe is branched downstream of the blower 12, one flow path 13 is connected to the primary flow side of the auxiliary ejector device 11, and the other flow path 15 bypasses the auxiliary ejector device 11, and the auxiliary ejector via the damper 16. It connects with the discharge side flow path 21 of the apparatus 11 downstream.

Further, a carbon dioxide concentration meter 19 is installed in the CO ₂ extraction flow path 18 for releasing the carbon dioxide gas out of the system under the atmospheric pressure to monitor the carbon dioxide gas concentration. When this concentration falls below the specified concentration, the controller 17 operates the damper 16 to the closed side to increase the driving gas flow rate of the auxiliary ejector device 11 to increase the pressure (= cooling) of the secondary flow system of the auxiliary ejector device 11. Reduce air system pressure). Thereby, it is possible to reduce the flow rate of the cooling air mixed into the carbon dioxide gas discharged outside the system under atmospheric pressure.

Incidentally, carbon dioxide gas released from the system under atmospheric pressure is once stored as it is CO ₂ reservoir is underground reservoir. At present, the concentration of carbon dioxide gas stored in the seabed underlayer is set at 99.9% by the Marine Pollution Control Law. Therefore, in this embodiment, the specified concentration of carbon dioxide gas released outside the system under atmospheric pressure is set to 99.9% or more.

  If the damper 16 is closed too much, the flow rate of mixed cooling air becomes almost zero, but conversely, the suction effect of the auxiliary ejector device 11 works so much that the carbon dioxide gas to be recovered is contained in the combustion exhaust gas as described above. Will be discharged. Therefore, the controller 17 is programmed so that the damper 16 can be opened and closed without excess or deficiency.

  Next, focus on combustion exhaust gas.

  As a result of supplying high-temperature exhaust e of about 700 ° C. to the combustor 10 and burning it at a total air ratio of about 1.2, high-temperature combustion exhaust gas ce of about 3,600 ° C. is obtained. By supplying this to the main heat exchanger 9 provided downstream of the main ejector device 4 and exchanging heat with the circulating carbon dioxide rg, the circulating carbon dioxide rg of about 1,200 ° C. and about 930 ° C. The combustion exhaust gas ce is obtained.

  In the main heat exchanger 9, since it is allowed even if a small amount of brick fragments are mixed as impurities if it is lime for iron making, a hot blast furnace heating the blast furnace blast air to about 1,200 ° C. and Similarly, the use of a type consisting of a combustor and brick heat storage is proven and suitable.

  The combustion exhaust gas ce that has passed through the main heat exchanger 9 is still at a high temperature of about 930 ° C., and can be used for heat recovery. On the other hand, the heating target that requires heat in the system includes further heating of the driving gas of the main ejector device 4, heating of the driving gas of the auxiliary ejector device 11, and further, fuel gas supplied to the combustor 10. There are three types. The combustion exhaust gas ce at 930 ° C. has a sufficient amount of heat sufficient to heat these three types.

  Therefore, as described above, the temperature of the carbon dioxide gas cg1 flowing through the primary side flow path 6 is increased from about 200 ° C. to about 410 ° C., and further, the combustion exhaust gas flow path 26 → the third heat exchanger 8 The temperature of the driving gas og supplied to the main ejector device 4 through ce is heated to 600 ° C.

  Further, the combustion exhaust gas ce subjected to heat exchange in the third heat exchanger 8 is passed through another combustion exhaust gas flow path 27 connecting the third heat exchanger 8 and the fourth heat exchanger 14 to the fourth. By supplying to the heat exchanger 14, the drive gas of the auxiliary ejector apparatus 11 is heated to 500 degreeC.

  Further, the combustion exhaust gas ce subjected to heat exchange in the fourth heat exchanger 14 is passed through a further fuel exhaust gas flow path 28 that connects the fourth heat exchanger 14 and the fifth heat exchanger 24. 5 The fuel gas is heated to 300 ° C. by supplying it to the heat exchanger 24.

  As a result, the temperature of the combustion exhaust gas eg finally reaches about 470 ° C. and is released from the chimney 30 into the atmosphere. The amount of heat taken away by the combustion exhaust gas eg deteriorates the basic unit of quick lime production energy by about 0.7 MJ / kg-CaO. Since there is no more heat target in the system, the heat carried away by the combustion exhaust gas eg may be recovered as energy used outside the system by, for example, an exhaust heat recovery boiler.

  Table 1 shows the performance specifications when the carbon dioxide circulating lime baking facility having the above-described configuration is implemented.

  The basic unit of quick lime production energy in a normal direct heating lime baking furnace is about 3.8 MJ / kg-CaO, whereas the basic unit of quick lime production energy in the present invention is about 4.6 MJ / kg-CaO. Slightly increased. This is because the two systems of the carbon dioxide gas path generated by pyrolysis (see the flow path 29 in FIG. 1) and the combustion exhaust gas path (also the flow path 25) are independent, and exhaust heat is generated in each. Furthermore, there is currently no demand for heat to recover exhaust heat in order to circulate carbon dioxide in the system at a high temperature.

However, since the conventional method for separating carbon dioxide requires a process for separating and collecting carbon dioxide, considering the total cost, in the present invention, an additional fuel of 1,400 yen / t-CO ₂ must be input. However, since the separation / recovery process is not required, the separation / recovery cost of 2,500 yen / t-CO ₂ can be reduced, and eventually, the cost can be reduced by 1,100 yen / t-CO ₂ .

DESCRIPTION OF SYMBOLS 1 Firing furnace 1a Furnace 1b Upper middle cylinder 1c Lower middle cylinder 1d Furnace upper part 1e Upper gas supply port 1f Lower furnace 1g Lower gas supply port 1h Fixed table 1i Hopper 1j Preheating part 1k Air outlet 2 Cyclone 3 Blower 4 Main ejector device 5 Circulation flow path 6 Primary flow side flow path 7 Second heat exchanger 8 Third heat exchanger 9 Main heat exchanger 10 Combustor 11 Auxiliary ejector device 12 Blower 13 Flow path 14 Fourth heat exchanger 15 Flow path 16 Damper 17 Controller 18 CO ₂ extraction passage 19 Carbon dioxide concentration meter 20 Cyclone 21 Discharge side passage 22 Carbon dioxide concentration meter 23 Fuel supply passage 24 Fifth heat exchanger 25 Release passage cg1, cg2 Carbon dioxide ce Combustion exhaust gas e Exhaust og Driving gas rg Circulating carbon dioxide

Claims (8)

In the carbon dioxide circulation lime firing facility that circulates the carbon dioxide generated by the thermal decomposition of limestone into the lime firing furnace and uses it as a heating medium,
A blower that is a part of the carbon dioxide gas used for preheating raw limestone charged into the lime firing furnace and that is guided by the carbon dioxide gas cooled by the preheating,
The nozzle has a driving gas supply port for supplying the carbon dioxide gas boosted by the blower as a driving gas, and a driven gas supply port for supplying a part of the carbon dioxide gas generated by thermal decomposition as the driven gas. An ejector device for sucking the driven gas by the driving gas flowing in the nozzle and discharging both gases;
A carbon dioxide gas discharged from the ejector device is guided, and includes a main heat exchanger that performs heat exchange with a high-temperature heat source,
A carbon dioxide circulating lime baking facility characterized in that the carbon dioxide gas heated by heat exchange of the main heat exchanger is supplied to the lime baking furnace as a pyrolysis gas of limestone.   A second heat exchanger is provided in a flow path connecting the blower and the ejector device, and the second heat exchanger is discharged from the lime firing furnace in a high temperature state without preheating the raw limestone. The carbon dioxide circulating lime baking facility according to claim 1, wherein a part of the carbon dioxide gas is guided and the driving gas supplied to the ejector device is heated.   Auxiliary ejector device is connected to the main heat exchanger, air driven by a second blower is supplied to a driving gas supply port of the auxiliary ejector device, and a furnace of the lime firing furnace is supplied to a driven gas supply port. The carbon dioxide circulating lime baking facility according to claim 1, wherein exhaust gas discharged from the lime baking furnace is supplied for cooling of quick lime discharged as a product from the bottom.   A combustor is provided between the main heat exchanger and the auxiliary ejector device, and the combustor burns exhaust discharged from the auxiliary ejector device and supplies the main heat exchanger as a high-temperature heat source. The carbon dioxide circulating lime baking facility according to claim 3, which is configured as described above.   A third heat exchanger is provided in a flow path connecting the second heat exchanger and the ejector device, and the third heat exchanger is used for heat exchange with the carbon dioxide gas discharged from the ejector device. The exhaust gas discharged from the main heat exchanger is guided, and the driving gas supplied to the ejector device is further heated. The carbon dioxide circulating lime baking facility according to claim 2.   A fourth heat exchanger is provided in a flow path connecting the second blower and the driving gas supply port of the auxiliary ejector device, and the fourth heat exchanger is connected to the carbon dioxide gas discharged from the ejector device. The carbon dioxide circulation type according to claim 3, wherein exhaust gas that is supplied to the heat exchanger and discharged from the main heat exchanger is guided, and the driving gas supplied to the auxiliary ejector device is further heated. Lime baking equipment.   A fifth heat exchanger is provided in the flow path for supplying fuel to the combustor, and the main heat exchange is provided to the fifth heat exchanger for heat exchange with the carbon dioxide gas discharged from the ejector device. The carbon dioxide circulating lime firing facility according to claim 3, wherein exhaust gas discharged from the combustor is guided and the fuel supplied to the combustor is heated.   At least one carbon dioxide concentration meter for measuring the concentration of carbon dioxide gas used as a heating medium is installed in the carbon dioxide gas flow path, and based on the carbon dioxide concentration information output from the carbon dioxide concentration meter. The carbon dioxide circulation type lime baking facility according to claim 3, further comprising a controller that controls a blowing amount of driving gas supplied to the auxiliary ejector device.