Patent Application
20100058963
The present invention relates to a method for disposing of an organic waste of high water content and a disposal apparatus therefor, and more specifically relates to a method for disposing of an organic waste of high water content and a disposal apparatus therefor, with which effective utilization of the organic waste of high water content as fuel can be attained by drying the organic waste of high water content with the use of a cement burning facility, and with which the operation efficiency of cement burning facility can be enhanced without the possibility of adversely affecting the operation of the cement burning facility in spite of the use of the gas extracted inside the cement burning facility.
Priority is claimed on Japanese Patent Application No. 2006-300605, filed Nov. 6, 2006, the content of which is incorporated herein by reference.
In a rotary kiln of a cement burning facility, the combustible wastes such as scrap tires and waste plastics among organic wastes, have been used conventionally as a partial substitution of fuel.
In addition, in recent years, a method is also carried out in which the organic wastes of high water content that are ultimately combustible are disposed of through an incineration disposal by directly loading the wastes in a rotary kiln.
Examples of such organic wastes of high water content include organic aqueous (or dewatered) sludge such as sewage sludge, and a sludge treatment process has been proposed in which the aqueous sludge is directly introduced to the bottom portion of a rotary kiln or a precalcining furnace without subjecting the sludge to a pretreatment, such as drying and addition of additives, followed by incineration (Patent Document 1).
In general, since the organic aqueous sludge is mostly composed of water and organic matter, only a trace amount of ash is produced as a residue due to the incineration. Accordingly, even when the organic aqueous sludge is directly loaded in a rotary kiln, the incineration disposal of the sludge inside the rotary kiln is possible without adversely affecting the components of cement clinker.
Meanwhile, in the above method where the organic aqueous sludge is directly introduced to a rotary kiln and incinerated, there has been a problem of dramatic reduction in the capability of cement clinker burning of cement burning facilities, which is associated with the evaporation of water in the aqueous sludge and which is due to the decline in material temperatures in the bottom portion of a rotary kiln, the decline of sensible heat in the materials that are heated and decarboxylated in a suspension preheater or a precalcining furnace, the decline of temperature in a zone where a cement material is sintered into a clinker form (that is, kiln burning zone), or the like. Moreover, since the quantity of heat or electricity usage per unit clinker at the time of cement clinker burning increases, there was also a possibility of difficult operation due to the economic reasons.
Accordingly, in order to minimize the adverse effects such organic wastes of high water content impose on the operation of cement burning facilities, an attempt has also been made to directly dry the organic wastes of high water content by using the gas extracted from a clinker cooler in the cement burning facility and to effectively use the dried organic wastes as a fuel (Patent Document 2).
In the drawing, 1 represents a rotary kiln, 2 represents a suspension preheater, 2a to 2d represent cyclones on the respective stages within the suspension preheater 2, 3 represents a precalcining furnace, 4 represents a clinker cooler, 5 represents an electric dust collector, 6 represents a suction fan, 7 represents an exhaust chimney, 8a to 8d represent cooling air fans of the clinker cooler 4, 9 represents an induced draft fan (IDF) which is a suction fan that sucks in the exhaust gas from the suspension preheater 2, 10 represents a secondary air duct of the precalcining furnace 3, 11 represents an exhaust duct of the clinker cooler 4, 12 represents an exhaust duct of the suspension preheater 2, and 13 represents a material supply line to the suspension preheater 2.
In addition, the reference symbol 14 represents a drying apparatus and the drying apparatus 14 is constituted of an extraction duct 15 which extracts a portion of the exhaust gas discharged from the clinker cooler 4, a dryer 16 which dries an organic waste of high water content using the extracted exhaust gas, a dust collector 17 which collects dust from the exhaust gas containing the dried organic waste of high water content, and an exhaust duct 18 and an exhaust gas introducing fan 19 for reusing the exhaust gas, after collecting the dust therefrom, as a cooling air of the clinker cooler 4.
The dried organic wastes obtained with this drying apparatus 14 are used effectively as a fuel for a cement burning facility.
Meanwhile, although a large amount of odor components or the like is contained in the exhaust gas after drying, these odor components or the like is completely combusted and decomposed by introducing the exhaust gas to a clinker cooler in the cement burning facility as an air for cooling clinkers of high temperatures and then using the cooled exhaust gas as a secondary air for combusting fuels in a rotary kiln or a precalcining furnace.
Accordingly, even when a large amount of odor components or the like is contained in the exhaust gas, no special equipment is required for deodorization in order to remove the odor components or the like which are contained in the exhaust gas.
In addition, as an apparatus for drying the organic wastes of high water content which does not involve the above direct drying method using high temperature gas, an apparatus for drying the organic wastes of high water content which employs a superheated steam circulation method and which is installed in a cement burning facility has been proposed (Patent Document 3).
In this apparatus for drying the organic wastes of high water content, a sludge cake formed of the organic wastes of high water content is mixed by stirring with a circulation dried powder, which is obtained by flush drying sludge, and thereby adjusting water content, and the resulting mixed powder is milled with a milling machine located inside a dryer. Then the powder is dried inside a drying duct, followed by the collection of dried power with a cyclone. A constant amount of the obtained dried powder is blown into a rotary kiln in the cement burning facility and is used as a portion of fuel for burning cement clinkers.
In this apparatus, the following process is employed. That is, the exhaust gas (water vapor) generated by the drying of a sludge cake is used as a heating medium for drying, and a hot section in the cement burning facility is serving as an exhaust gas heating section which indirectly heats the above exhaust gas. The above exhaust gas is introduced to this exhaust gas heating section and is heated and deodorized. A portion of the heated and deodorized exhaust gas is circulated to the above milling machine, and the increment of the exhaust gas is extracted to the outside of the system. At the same time, a heat exchange is conducted between the remaining of the heated and deodorized exhaust gas and the exhaust gas from the cyclone of the aforementioned dryer using a heat exchanger, and thereby preheating the exhaust gas from the cyclone.
In addition, as a method for disposing of wastes other than the organic wastes of high water content, a method is proposed in which cement is produced by employing a system for waste to fuel conversion, where a waste containing halogen is disposed of using high temperature gas inside a cement burning facility (Patent Document 4).
In this disposal method, the waste containing halogen is thermally decomposed through indirect heating using the high temperature gas extracted from the suspension preheater in the cement burning facility, and a produced halogen compound is removed while the combustible gas, from which the halogen compound is removed, as well as the residual materials are used effectively as a fuel in the cement burning facility.
In this system for the waste to fuel conversion, a high temperature gas extracted from the suspension preheater is used as a heat source.
A high temperature air extracted from a clinker cooler or a high temperature gas extracted from the bottom section of a rotary kiln is usually used as the high temperature gas within the cement burning facility. However, as in this system for the waste to fuel conversion, when the high temperature gas extracted from a suspension preheater is used as a heat source, the operation of the cement burning facility is adversely affected to a relatively lesser extent, and the heat source in the cement burning facility can be used effectively.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. Hei 8-276199
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. Sho 63-151650
[Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2002-273492
[Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2006-206386
Meanwhile, in the above method disclosed in Patent Document 2 for directly drying organic wastes of high water content by using the gas extracted from a clinker cooler, since a large amount of water vapor is contained in the exhaust gas after drying, if the gas is treated with the clinker cooler, the water vapor contained in the exhaust gas is introduced to a rotary kiln or a precalcining furnace. As a result, there has been a problem of the increase in the amount of high temperature gas required for burning a unit cement clinker (gas unit requirement).
This increase in the gas unit requirement may impose adverse effects on the operation of the cement burning facility, such as the reduction in the amount of burning of cement clinkers and the increase in the amount of heat for burning (heat quantity unit requirement).
Although the extent of adverse effects imposed on the facility operation, due to the reduction in the amount of burning of cement clinkers or the increase in the heat quantity unit requirement, remains at 20 to 40%, as compared to the conventional cases where the wastes are directly loaded in the bottom section of a rotary kiln, the adverse effects imposed on the facility operation is still great, and thus there has been a concern that the required amount of cement production cannot be achieved with the increase in the disposal of organic wastes of high water content.
In addition, since the hot section in the main body of a cement burning facility is used as a heating section (heat exchange section) that heats a heating medium for drying in the drying method disclosed in Patent Document 3, a hot section which can serve as a heating section is limited to the lower region of a suspension preheater, the region of a hot section in the upstream part of a clinker cooler, and the like. Hence, when this region of the hot section is selected as the heating section, for example, a large amount of sensible heat contained in the gas or heating material inside the cement burning facility is lost to the heating medium. Accordingly, there has been a problem of deterioration in the heat quantity unit requirement for the clinker burning in the cement burning facility, as well as a possible decline in the capacity of clinker burning.
Similarly, in term of the reduction in the amount of burning of cement clinkers and the increase in the heat quantity unit requirement in the cement burning facility, although the extent of reduction in the amount of clinker burning remains at 40 to 50%, as compared to the cases where the wastes are directly loaded in the bottom section of a rotary kiln, the heat quantity unit requirement may increase up to 80%. In other words, since the bulk of the heat source for drying is obtained by depriving of the amount of heat useful in the cement burning facility in this method, when compared to the other methods that use the exhaust gas or the like in the cement burning facility, not only there has been a problem of greatly worsening the situation in terms of the heat consumption in the cement burning facility, but also there has been a problem of concerns raised in that the amount of cement production required cannot be achieved with the increase in the disposal of organic wastes of high water content.
In addition, in order to carry out thermal decomposition and separation of a waste containing halogen in the system for the waste to fuel conversion disclosed in Patent Document 4, the waste containing halogen needs to be heated to a high temperature up to the maximum of 650° C. For this reason, the temperature of the high temperature gas introduced to an indirect heater for thermally decomposing this waste containing halogen also needs to be increased to an even higher temperature, which has been a problem.
Moreover, since the heating is conducted through indirect heating, the extent of heat transfer is also unsatisfactory. Furthermore, the exhaust gas after the heat exchange is returned to a suspension preheater while its temperature is kept high, and in particular, when the exhaust gas of a high temperature is flown to the exhaust duct of the suspension preheater, the temperature of exhaust gas in the suspension preheater increases, which may lead to the decline of gas processing capacity of a suction fan (IDF), and may further lead to the decline of the production capacity of the cement burning facility. In addition, since the extracted high temperature gas is discharged from the suspension preheater without reusing the sensible heat thereof, the heat quantity unit requirement for the clinker burning is also exacerbated.
As described so far, in the disposal method or the system disclosed in Patent Documents 2 to 4, when the organic wastes of high water content are subjected to a combustion treatment using a cement burning facility, it is possible that the operation of the cement burning facility is adversely affected. Accordingly, a method for disposing of organic wastes of high water content has been desired, in which the dried organic wastes obtained by drying the organic wastes of high water content can be effectively used as a fuel in a cement burning facility, and in which the operation of the cement burning facility is not adversely affected at all even when the drying is carried out using a heat source extracted from the cement burning facility.
The present invention is made in order to solve the above problems and its object is to provide a method for disposing of an organic waste of high water content and a disposal unit therefor, with which effective utilization of the organic waste of high water content as fuel can be attained by drying the organic waste of high water content, such as sewage sludge, with the use of a cement burning facility, and with which the operation efficiency of cement burning facility can be enhanced without the possibility of adversely affecting the operation of the cement burning facility.
The present inventors conducted intensive and extensive studies in order to solve the above problems and discovered the following to complete the present invention as a result. That is, by drying an organic waste of high water content to produce a dried organic waste through the use of a heating medium, which exchanged heat with the high temperature gas extracted from the cement burning facility, followed by another heat exchange between this heating medium after being subjected to a drying process and the high temperature gas, and thereby recycling the heating medium for drying the organic waste of high water content, and by supplying this dried organic waste to a cement burning facility or a combustion apparatus for combustion, this dried organic waste can be used effectively as a fuel in the cement burning facility and the residual material after the combustion can be used as a cement clinker material without adversely affecting the operation of the cement burning facility or the cement quality.
That is, a first aspect of the present invention is a method for disposing of an organic waste of high water content, which uses a cement burning facility to convert the organic waste of high water content into fuel and to subject the resultant to a combustion treatment, the method being characterized by having: a drying step in which the organic waste of high water content is dried to produce a dried organic waste through the use of a heating medium that was subjected to a heat exchange with a high temperature gas extracted from the cement burning facility, and in which the heating medium used for the drying is subjected to another heat exchange with the high temperature gas, thereby recycling the heating medium for drying the organic waste of high water content; and a combustion step in which this dried organic waste is supplied to the cement burning facility or a combustion apparatus and combusted.
In this method for disposing of an organic waste of high water content, since the organic waste of high water content is dried to produce a dried organic waste through the use of a heating medium, which has exchanged heat with a high temperature gas extracted from the cement burning facility, the only exhaust gas generated through this drying process is water vapor, and thus the operation of the cement burning facility is not adversely affected even when this exhaust gas is disposed of in the cement burning facility, and the dried organic waste can be effectively used as a fuel in the cement burning facility.
In addition, since another heat exchange between the heating medium after being subjected to a drying process and the high temperature gas is conducted and thereby recycling the heating medium for drying the organic waste of high water content, the heating medium can be reused efficiently and effectively, and thus it is economical.
A second aspect of the present invention is a method for disposing of an organic waste of high water content, the method characterized in that the combustion step is a step in which the dried organic waste is supplied to at least one of a rotary kiln, a precalcining furnace, and a suspension preheater in the cement burning facility, and combusted.
In this method for disposing of an organic waste of high water content, since the dried organic waste is supplied to at least one of a rotary kiln, a precalcining furnace, and a suspension preheater in the cement burning facility and is combusted therein, the obtained dried organic waste can be used effectively as a fuel for the burning of cement clinkers, and the operation of the cement burning facility is not adversely affected because the waste is dried.
A third aspect of the present invention is a method for disposing of an organic waste of high water content, the method characterized in that the high temperature gas is a gas extracted from at least one of cyclone gas outlet sections on the respective stages of the suspension preheater in the cement burning facility, and the heating medium used for the drying is superheated steam generated due to the drying of the organic waste of high water content.
In this method for disposing of an organic waste of high water content, by making the high temperature gas extracted from at least one of cyclone gas outlet sections on the respective stages of the suspension preheater in the cement burning facility to serve as the high temperature gas extracted from the cement burning facility, the amount of gas flowing through a cement burning apparatus is increased, as a result of which the clinker burning capacity of the cement burning apparatus can be improved.
In addition, by making the superheated steam generated due to the drying of the organic waste of high water content to serve as the heating medium after the drying process, the amount of the heating medium which is directly used for the drying process can be suppressed to a minimum level without adversely affecting the operation of the cement burning facility.
A fourth aspect of the present invention is a method for disposing of an organic waste of high water content, the method characterized in that the high temperature gas is any one or both of an exhaust gas discharged from the suspension preheater in the cement burning facility, and an extraction gas extracted from a clinker cooler in the cement burning facility, and the heating medium used for the drying is superheated steam generated due to the drying of the organic waste of high water content.
In this method for disposing of an organic waste of high water content, by making at least one of an exhaust gas discharged from a suspension preheater in the cement burning facility and an extracted gas extracted from a clinker cooler in the cement burning facility to serve as the high temperature gas extracted from the cement burning facility, the possibility of adversely affecting the operation of the cement burning facility due to the use of a high temperature gas can be eliminated.
In addition, by making the superheated steam generated due to the drying of the organic waste of high water content to serve as the heating medium after the drying process, the amount of gas that is used for the drying process can be suppressed to a minimum level without adversely affecting the operation of the cement burning facility.
A fifth aspect of the present invention is a method for disposing of an organic waste of high water content, the method characterized in that a portion of the superheated steam is extracted and subjected to a deodorization treatment, and thereafter, introduced to the cement burning facility.
In this method for disposing of an organic waste of high water content, by extracting a portion of the superheated steam and subjecting it to a deodorization treatment, followed by its introduction to the cement burning facility, when the introduction is made to an exhaust gas line of a suspension preheater, for example, the adverse effects on the operation of the cement burning facility due to the introduction can be completely eliminated, as a result of which a marked improvement in the clinker burning capacity in the operation of the cement burning facility due to the aforementioned extracting from the cyclone gas outlet section on each of the stages will become apparent.
A sixth aspect of the present invention is a method for disposing of an organic waste of high water content, the method characterized in that a portion of the superheated steam is directly introduced to a section having a temperature of 800° C. or more in the cement burning facility.
In this method for disposing of an organic waste of high water content, since a portion of the superheated steam is directly introduced to a section having a temperature of 800° C. or more in the cement burning facility, the only introduced superheated steam is a portion generated by drying, and thus the resulting adverse effects on the operation of the cement burning facility is extremely small, and they can be cancelled out sufficiently by the improvement in the cement clinker burning capacity due to the aforementioned extracting from the cyclone gas outlet section on each of the stages.
A seventh aspect of the present invention is an apparatus for disposing of an organic waste of high water content, which used a cement burning facility to convert the organic waste of high water content into fuel and to subject the resultant to a combustion treatment, the apparatus characterized by having: a heat exchange unit that carries out a heat exchange between a heating medium and a high temperature gas extracted from the cement burning facility; a drying treatment unit that dries the organic waste of high water content to produce a dried organic waste through the use of the heating medium that was subjected to the heat exchange; a circulation line that circulates the heating medium used for the drying process between the heat exchange unit and the drying treatment unit; and a supply line that supplies the dried organic waste to the cement burning facility or a combustion apparatus.
In this apparatus for disposing of an organic waste of high water content, a heat exchange between a high temperature gas extracted from the cement burning facility and a heating medium is carried out by the heat exchange unit, an organic waste of high water content is dried by the drying treatment unit to produce a dried organic waste through the use of the heating medium which has exchanged heat, and the dried organic waste is supplied to the cement burning facility or a combustion apparatus by the supply line to carry out a combustion treatment.
Due to this configuration, there is no possibility of adverse effects on the operation of the cement burning facility, and the cement clinker burning capacity is improved.
Moreover, the dried organic waste obtained by effectively using the sensible heat contained in the exhaust gas discharged from a cement burning apparatus is used effectively as a fuel in the cement burning facility.
Furthermore, by carrying out another heat exchange between the heating medium after being subjected to a drying process and the high temperature gas and thereby recycling the heating medium for drying the organic waste of high water content through the circulation line, the heating medium can be reused efficiently and effectively.
An eighth aspect of the present invention is an apparatus for disposing of an organic waste of high water content, the apparatus characterized by further including a deodorization treatment unit that extracts a portion of superheated steam generated in the drying treatment unit and subjects the extracted superheated steam to a deodorization treatment.
In this apparatus for disposing of an organic waste of high water content, a portion of the superheated steam generated in the drying treatment unit is extracted and this extracted superheated steam is subjected to a deodorization treatment by the deodorization treatment unit. Due to this configuration, it is possible to supply only hot water vapor, from which odor components are removed, to an exhaust gas line of a suspension preheater in the cement burning facility or the like with no adverse effects imposed on the operation of the cement burning facility which is associated with the above process.
A ninth aspect of the present invention is an apparatus for disposing of an organic waste of high water content, the apparatus characterized by further including a deodorization treatment line that extracts a portion of superheated steam generated in the drying treatment unit, introduces the extracted superheated steam directly to a section having a temperature of 800° C. or more in the cement burning facility, and carries out a deodorization treatment.
In this apparatus for disposing of an organic waste of high water content, by extracting a portion of superheated steam generated in the drying treatment unit and carrying out a deodorization treatment by directly introducing this extracted superheated steam to a section having a temperature of 800° C. or more in the cement burning facility through the deodorization treatment line, the organic waste of high water content can be efficiently disposed of, in spite of a simple deodorization treatment conducted on the superheated steam.
A tenth aspect of the present invention is an apparatus for disposing of an organic waste of high water content, the apparatus characterized by further including a line that introduces an extraction gas, which is extracted from at least one of cyclone gas outlet sections on the respective stages of a suspension preheater in the cement burning facility, to the heat exchange unit as a high temperature gas.
In this apparatus for disposing of an organic waste of high water content, by extracting a high temperature gas from at least one of cyclone gas outlet sections on the respective stages of a suspension preheater in the cement burning facility through the line that introduces the high temperature gas to the heat exchange unit, the ventilation capacity of the cement burning facility is improved. Accordingly, the possible adverse effects imposed on the cement clinker burning capacity or the like which are caused by running this apparatus for disposing of an organic waste of high water content can be eliminated, and the organic waste of high water content can be efficiently disposed of.
An eleventh aspect of the present invention is an apparatus for disposing of an organic waste of high water content, the apparatus characterized by further including any one or both of a line that introduces an exhaust gas from a suspension preheater in the cement burning facility to the heat exchange unit as a high temperature gas; and a line that introduces an extraction gas, which is extracted from a clinker cooler in the cement burning facility, to the heat exchange unit as a high temperature gas.
In this apparatus for disposing of an organic waste of high water content, at least one of a line that introduces an exhaust gas, which is extracted from a suspension preheater, as a high temperature gas to the heat exchange unit and a line that introduces an extraction gas, which is extracted from a clinker cooler, as a high temperature gas to the heat exchange unit is included. Accordingly, it is possible to use the exhaust gas extracted from the suspension preheater or the extraction gas extracted from the clinker cooler, and the high temperature gas after the heat exchange can be used efficiently and effectively through its reuse for drying cement materials or the like without adversely affecting the operation of the cement burning facility.
According to the method of the present invention for disposing of an organic waste of high water content, since the organic waste of high water content is dried to produce a dried organic waste through the use of a heating medium, which has exchanged heat with a high temperature gas extracted from the cement burning facility, the operation of the cement burning facility is not adversely affected, and the obtained dried organic waste can be effectively used as a fuel in the cement burning facility.
In addition, since another heat exchange between the heating medium after being subjected to a drying process and the high temperature gas is conducted and thereby recycling the heating medium for drying the organic waste of high water content, the heating medium can be reused efficiently and effectively.
According to the apparatus of the present invention for disposing of an organic waste of high water content, since the apparatus includes a heat exchange unit that carries out a heat exchange between a high temperature gas extracted from the cement burning facility and a heating medium; a drying treatment unit that dries the organic waste of high water content to produce a dried organic waste by using the heating medium which has exchanged heat; a circulation line that circulates the heating medium after being subjected to a drying process between the heat exchange unit and the drying treatment unit; and a supply line that supplies the dried organic waste to the cement burning facility or a combustion apparatus, the sensible heat contained in the exhaust gas discharged from the cement burning facility can be used effectively, and the cement clinker burning capacity of the cement burning facility can be improved without adversely affecting the operation of the cement burning facility.
In addition, since another heat exchange between the heating medium after being subjected to a drying process and the high temperature gas is conducted and thereby recycling the heating medium for drying the organic waste of high water content, the heating medium can be reused efficiently and effectively.
1: Rotary kiln; 2: Suspension preheater; 2a to 2d: Cyclone; 3: Precalcining furnace; 4: Clinker cooler; 5: Electric dust collector; 6: Suction fan; 7: Exhaust chimney; 8a to 8d: Cooling air fan; 9: Suction fan (induced draft fan (IDF)); 10: Secondary air duct; 11: Exhaust duct; 12: Exhaust duct; 13: Material supply line; 21: Treatment apparatus of organic sludge; 22: Heat exchanger; 23: Dryer; 24: Deodorization equipment; 25: Hopper; 26: High temperature gas extraction duct; 27: Exhaust duct; 28: Superheated steam line; 29: Superheated steam line; 30: Organic sludge supply line; 31: Supply line; 41: Treatment apparatus of organic sludge; 42: High temperature gas extraction line; 43: High temperature gas exhaust line.
Preferred embodiments of the method and apparatus of the present invention for disposing of an organic waste of high water content will be described with reference to the attached drawings.
Note that each of the embodiments are provided in order to specifically describe the present invention for a better understanding of the scope and spirit thereof, and thus the embodiments do not limit the present invention unless otherwise specified.
In the drawing, the reference symbol 21 represents an apparatus for disposing of organic sludge, and the apparatus is constituted of a heat exchanger (heat exchange unit) 22 that carries out a heat exchange between the exhaust gas (high temperature gas), which is extracted from a suspension preheater 2 in the cement burning facility, and steam (heating medium); a dryer (drying treatment unit) 23 that dries organic sludge to produce dried organic sludge by using this superheated steam (heating medium) which has exchanged heat; deodorization equipment (deodorization treatment unit) 24 that conducts a deodorization treatment on the superheated steam; a hopper 25 that stores the dried organic sludge; a high temperature gas extraction duct (line) 26; an exhaust duct (line) 27; a superheated steam line (circulation line) 28; a superheated steam line (extraction line) 29; an organic sludge supply line 30 that supplies the organic sludge to the dryer 23; and a supply line 31 that supplies the dried organic sludge to the precalcining furnace 3.
In order to subject the organic sludge to drying/combustion treatments using this apparatus 21 for disposing of organic sludge, a high temperature gas extracted from a gas outlet section of a cyclone 2b on a second stage of the suspension preheater 2 and steam (heating medium) that circulates within the superheated steam line 28 are introduced to the heat exchanger 22, and the steam is heated with this high temperature gas to produce superheated steam (heating medium).
This superheated steam is introduced into the dryer 23 via the superheated steam line 28, and the organic sludge which is introduced by the organic sludge supply line 30 is dried inside this dryer 23 to produce dried organic sludge. The dried organic sludge is temporarily stored in the hopper 25, and thereafter, supplied to the precalcining furnace 3 as a fuel by the supply line 31, followed by the combustion treatment thereof.
In this apparatus 21 for disposing of organic sludge, by using a high temperature gas obtained by extracting an outlet gas from the cyclone 2b on the second stage below the cyclone 2a, which is at the highest level in the suspension preheater 2, and by adopting a drying method involving the steam which has exchanged heat, that is, a drying method involving the superheated steam circulation method, the effective utilization of the high temperature gas within the cement burning facility and the streamlining of the cement burning facility are achieved.
A procedure for selecting positions for extracting in the cyclones 2a to 2d will be described herein.
For example, when extracting exhaust gas from the outlet of the cyclone 2b on the second stage, the degree of effective utilization of this exhaust gas from the outlet of the cyclone 2b is low. Or rather, due to the extraction, the temperature of the exhaust gas from the suspension preheater 2 reduces, the loss in terms of the amount of heat due to the extracted exhaust gas is compensated, and the problem of increase in the heat quantity unit requirement is also solved.
At the same time, the temperature of the extracted exhaust gas also reduces due to the heat exchange in the dryer 23, as a result of which the ventilation capacity of the suction fan (IDF) 9 that sucks in the gas mixed with the exhaust gas from the suspension preheater 2 is increased.
Accordingly, the clinker burning capacity of the cement burning facility is improved as a result. There is also a case where the heat quantity unit requirement is improved due to this improvement in the clinker burning capacity.
Although the effects of improvements in terms of the clinker burning capacity get higher as the position for extracting exhaust gas gets to the cyclones on lower stages, the amount of heat loss due to the exhaust gas increases in the cyclones on lower stages and the adverse effects on the heat quantity unit requirement also gradually increases, and thus the increase rate of the clinker burning capacity of the cement burning facility reduces as a result. Therefore, the cyclone from which gas is extracted is most preferably the cyclone 2b on the second stage, and a cyclone 2c on a third stage is the second best.
Note that the above effects can be achieved even when the exhaust gas from the outlet of the cyclone 2a on the highest level is used. In this case, it is required to configure a extraction apparatus that extracts an exhaust gas from the cyclone 2a not to increase the ventilation resistance against the exhaust gas from the suspension preheater 2, and the countermeasure therefor includes the installation of a heat exchanger to the exhaust duct 12 of the suspension preheater 2.
The temperature of the high temperature gas extracted from the gas outlet section of the cyclone 2b on the second stage is usually within a range of 550 and 650° C. This high temperature gas is obtained by extracting from a position where a powder material that is loaded by the material supply line 13 for supplying cement powder materials is not mixed. Since the organic sludge to be dried has a water content of about 80% by weight, the amount of the extracted high temperature gas needs to be sufficient enough to meet the heat quantity required for evaporating the water contained in this organic sludge and producing the superheated steam. In other words, it is usually required to extract a gas volume of 4 to 8 Nm3 for 1 kg of organic sludge.
In addition, in a case where the concentration of dust in the exhaust gas to be extracted is high or in a case where a large amount of volatile component is contained which may cause the cement deposition in the subsequent heat exchanger 22, it is preferable to install a dust collector such as a cyclone to the high temperature gas extraction duct 26.
Moreover, it is also possible to prevent the attachment of volatile components onto the subsequent suction fan (IDF) 9 or the like by installing a dust collector such as a cyclone to the exhaust duct 27 and collecting the dust in the exhaust gas, which is cooled by the heat exchanger 22, with the dust collector.
The high temperature gas extracted from the suspension preheater 2 further heats the superheated steam, which is a circulating dried heating medium discharged from the dryer 23 and having a temperature of 130 to 200° C., in the heat exchanger 22 up to a temperature of 300 to 400° C.
The temperature of the high temperature gas reduces down to 300 to 350° C. due to this heat exchange, and the high temperature gas mixes with the exhaust gas from the suspension preheater 2 in the exhaust duct 12.
Note that although the heating surface area of the heat exchanger 22 may be increased in order to increase the amount of heat exchange in the heat exchanger 22, when the exhaust gas after the heat exchange is used for drying the cement materials or used as a heat source for a boiler in an exhaust heat power generation apparatus, it is not necessary to increase the heating surface area so as to greatly reduce the gas temperature after the heat exchange. When considering these conditions, as a constitution of the heat exchanger 22, a multi-tubular heat exchanger, a plate heat exchanger, or the like is suitable.
The high temperature gas in which the temperature is reduced due to the heat exchange in the heat exchanger 22 is introduced to the exhaust duct 12 of the suspension preheater 2 and mixes with the exhaust gas from the suspension preheater 2.
When, for example, the heat exchange in the heat exchanger 22 is not sufficient and the temperature of the exhaust gas after the heat exchange is higher than the temperature of the exhaust gas of the suspension preheater 2 by 150° C. or more, the degree of rise in the exhaust gas temperature after the mixing is increased, and the blowing capacity reduces in conjunction with the rise in the temperature of the gas sucked by the suction fan (IDF) 9. As a result, there will be no room for the improvements in terms of the cement clinker burning capacity in the cement burning facility, and the amount of loss of sensible heat contained in the extracted high temperature gas increases, which may lead to the impairment of heat quantity unit requirement or the like.
The upper limit of the temperature of this high temperature gas after the heat exchange is preferably set, so as to be higher than the temperature of the exhaust gas from the suspension preheater 2 by 150° C., by securing a predetermined extent of area as the heating surface area of the heat exchanger 22. More preferably, the upper limit is set so as to be higher by 100° C. When the high temperature gas which is cooled down to a temperature of not greater than this upper limit is used, the gas temperature after the mixing with the exhaust gas from the suspension preheater declines.
For example, when the exhaust gas from the suspension preheater 2 in which the temperature is reduced by 20 to 30° C. due to the extraction of about 20% of the high temperature gas and the high temperature gas after the heat exchange are mixed, the temperature after mixing will be reduced, as compared to the case where extraction is not conducted, and thus the suction force of the suction fan (IDF) 9 can be enhanced even higher.
This means that when the temperature of the high temperature gas extracted from the gas outlet section of the cyclone 2b on the second stage (that is, 550 to 650° C.) is reduced to a temperature, which is higher than the exhaust gas temperature of the suspension preheater 2 (that is, about 350° C.) by up to 100 to 150° C. (that is, the upper limit is 450 to 500° C.), or to an even lower temperature, the gas temperature after mixing is lower than that before the extraction. Moreover, since the pressure loss due to the gas ventilation in the cyclone 2a on the uppermost stage is also reduced by extracting this high temperature gas, the suction force of the suction fan (IDF) 9 is enhanced even higher, and the cement clinker burning capacity can be improved.
When taking these points into account, since the temperature of the high temperature gas can easily be reduced to a predetermined temperature even if the performance of a heat exchanger is not high, it is possible to downsize and simplify an apparatus for disposing of organic sludge.
On the other hand, organic sludge of high water content which is supplied to the dryer 23 by the organic sludge supply line 30 is heated up to a water boiling point or thereabouts by the superheated steam circulating between the dryer 23 and the superheated steam line 28, thereby producing dried organic sludge with lower water content. Note that although it is necessary to increase the temperature until the drying of the organic sludge reaches the state of so-called “reduced rate of drying” in order to enhance the degree of dryness of the dried organic sludge, since dried organic sludge having a water content of about 5 to 10% is usually produced easily during a state of so-called “constant rate of drying” while the temperature of the organic sludge is kept at about 100° C. at the time of heating, the superheated steam having an excessively high temperature as a heating medium in a drying apparatus is not required.
In addition, the dried sludge to be combusted in the cement burning facility can function satisfactorily as a fuel even when the water content thereof is 5 to 10%.
Accordingly, the characteristic feature of the present embodiment is that it is possible to lower the temperature of the high temperature gas after the heat exchange in the heat exchanger 22 without making the temperature of a heating medium in a drying apparatus excessively high. In other words, it is easy to reduce the temperature of the high temperature gas to a lower level than the temperature of the exhaust gas from the suspension preheater 2, and the temperature of this gas after mixing with the exhaust gas from the suspension preheater 2 reduces, thereby making it possible to increase the amount of gas ventilation of the suction fan (IDF) 9.
Although a flash dryer, a fluid bed dryer, or the like can also be used as this dryer 23, a multi-stage dryer of a material transferring, and hot air type is preferable since the amount of dust contained in the exhaust gas after drying is low and the degree of dryness can be controlled relatively easily.
The dried organic sludge obtained in a manner described above is temporarily stored in the hopper 25, and thereafter, pneumatically transported by the supply line 31 and loaded to the precalcining furnace 3 as a fuel, followed by the combustion treatment thereof.
On the other hand, the superheated steam evaporated from the organic sludge inside the dryer 23 is mixed with the circulating superheated steam, and then a portion thereof is transferred to the deodorization equipment 24 via the superheated steam line 29 and is subjected to a deodorization treatment. Thereafter, the treated superheated steam joins the exhaust gas line 12 of the suspension preheater 2 again and is used for drying of cement materials or the like.
As described so far, according to the method of the present embodiment for disposing of the organic sludge, the operation of the cement burning facility is not adversely affected, and the obtained dried organic sludge can be effectively used as a fuel in the precalcining furnace 3 of the cement burning facility.
In addition, since another heat exchange between the superheated steam after drying and the exhaust gas is conducted and thereby recycling the superheated steam for drying the organic sludge, the superheated steam can be reused efficiently and effectively.
According to the apparatus of the present embodiment for disposing of the organic sludge, the sensible heat contained in the high temperature gas extracted from the suspension preheater 2 in the cement burning facility can be effectively used, and the cement clinker burning capacity of the cement burning facility can be improved without adversely affecting the operation of the cement burning facility.
In addition, since another heat exchange between the superheated steam after drying and the exhaust gas of a high temperature is conducted and thereby recycling the superheated steam for drying the organic sludge, the superheated steam can be reused efficiently and effectively.
Note that instead of transferring a portion of the superheated steam to the deodorization equipment 24, this portion of the superheated steam may be introduced between the gas outlet section of the cyclone 2d on the lowest stage of the suspension preheater 2 and the cyclone 2c, which is located on the stage above the lowest stage for the cyclone 2d, or may be directly introduced to an inlet for cooling air of the clinker cooler 4, and the odor components therein may be thermally decomposed by passing through a hot section inside the cement burning facility where the temperature is 800° C. or more, so that the operation of the cement burning facility can be kept unaffected adversely.
In other words, it is preferable to directly introduce a portion of the superheated steam to a section having a temperature of 800° C. or more in the cement burning facility. Due to this process, the only introduced superheated steam will be a portion generated by drying, and thus the resulting adverse effects on the operation of the cement burning facility is extremely small, and they can be cancelled out sufficiently by the improvement in the cement clinker burning capacity due to the aforementioned extraction from the cyclone gas outlet section on each of the stages.
Regarding the abovementioned section having a temperature of 800° C. or more in the cement burning facility, it depends on the form of the cement burning facility or the like, and the upper limit of the temperature thereof is not particularly limited, although it is usually 1,600° C. even in the section having the highest temperature. Accordingly, the above superheated steam may be directly introduced to a section in the cement burning facility where the temperature is within a range of 800° C. to 1,600° C.
In addition, instead of transferring a portion of the superheated steam to the deodorization equipment 24, this portion of the superheated steam may be cooled using a condenser or the like to recover as water, and the recovered water is subjected to a waste water treatment that decompose the odor components or the like contained therein and may be used again in the cement production facility.
In this apparatus 41 for disposing of organic sludge, the high temperature exhaust gas to serve as the heat source for drying is diverged from the exhaust duct 12 of the suspension preheater 2 and transferred to the heat exchanger 22 by the high temperature gas extraction line 42. In this exhaust gas, the chlorine gas, SOx, and other volatile components volatilized at the hot section in the cement burning facility are barely contained and the dust content therein is also relatively low, and thus there is no need to remove these components in advance before the exhaust gas is transferred to the heat exchanger 22.
This exhaust gas from the suspension preheater 2 is introduced to the heat exchanger 22 at a temperature of about 350 to 400° C., and then cooled down to about 200° C. after the heat exchange with the superheated steam. Thereafter, the resulting exhaust gas mixes again with the exhaust gas from the suspension preheater 2 in the exhaust duct 12 of the suspension preheater 2 in a similar manner to a portion of the superheated steam, in which the odor components are decomposed/removed in the deodorization equipment 24.
According to the apparatus 41 for disposing of organic sludge, since a high temperature exhaust gas diverged from the exhaust duct 12 in the downstream side of the suction fan (IDF) 9 of the suspension preheater 2 is employed as the high temperature gas for drying in the dryer 23, the exhaust gas can be introduced to the same position after the temperature thereof is lowered due to the heat exchange. In addition, since it is configured so that the superheated steam generated due to the drying of organic sludge is introduced to the exhaust duct 12 after being subjected to a deodorization treatment, the gas ventilation in the cement burning facility is not adversely affected in any way, as a result of which the disposing of organic sludge can be carried out without adversely affecting the operation of the cement burning facility.
The method and apparatus of the present invention for disposing of organic wastes of high water content can be employed in a cement burning facility, and can efficiently dispose of the organic wastes of high water content, such as sewage sludge, which are discharged in various industrial fields. In addition, the obtained dried organic waste can be used effectively as a fuel in the cement burning facility, the residual materials after the burning process are used as cement clinker materials, and the heating medium after the drying process can also be reused efficiently and effectively, and thus the present invention may contribute to the resource savings which may solve the problems in the industrial fields in general. Accordingly, the present invention has extremely high industrial applicability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-300605 | Nov 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/071554 | 11/6/2007 | WO | 00 | 5/4/2009 |
