IE83635B1 - A process and apparatus for treating waste material - Google Patents
A process and apparatus for treating waste materialInfo
- Publication number
- IE83635B1 IE83635B1 IE1999/0903A IE990903A IE83635B1 IE 83635 B1 IE83635 B1 IE 83635B1 IE 1999/0903 A IE1999/0903 A IE 1999/0903A IE 990903 A IE990903 A IE 990903A IE 83635 B1 IE83635 B1 IE 83635B1
- Authority
- IE
- Ireland
- Prior art keywords
- mixture
- causing
- waste material
- raising
- additive
- Prior art date
Links
- 239000002699 waste material Substances 0.000 title claims description 64
- 238000000034 method Methods 0.000 title claims description 63
- 239000000203 mixture Substances 0.000 claims description 183
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium monoxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 108
- 238000001035 drying Methods 0.000 claims description 57
- 239000000292 calcium oxide Substances 0.000 claims description 54
- 235000012255 calcium oxide Nutrition 0.000 claims description 54
- 239000000654 additive Substances 0.000 claims description 45
- 230000000996 additive Effects 0.000 claims description 44
- 238000006243 chemical reaction Methods 0.000 claims description 39
- 239000000463 material Substances 0.000 claims description 33
- 238000011144 upstream manufacturing Methods 0.000 claims description 31
- 239000010802 sludge Substances 0.000 claims description 27
- 229920002456 HOTAIR Polymers 0.000 claims description 25
- 239000002245 particle Substances 0.000 claims description 18
- 239000000969 carrier Substances 0.000 claims description 14
- 239000010865 sewage Substances 0.000 claims description 10
- 238000006297 dehydration reaction Methods 0.000 claims description 9
- 239000000428 dust Substances 0.000 claims description 8
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 6
- 235000015450 Tilia cordata Nutrition 0.000 claims description 6
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 6
- 239000004571 lime Substances 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- YLUIKWVQCKSMCF-UHFFFAOYSA-N calcium;magnesium;oxygen(2-) Chemical compound [O-2].[O-2].[Mg+2].[Ca+2] YLUIKWVQCKSMCF-UHFFFAOYSA-N 0.000 claims description 3
- 239000004568 cement Substances 0.000 claims description 3
- 230000004323 axial length Effects 0.000 claims description 2
- 230000002093 peripheral Effects 0.000 claims description 2
- 239000010801 sewage sludge Substances 0.000 description 71
- 230000001717 pathogenic Effects 0.000 description 11
- 244000052769 pathogens Species 0.000 description 11
- 239000007787 solid Substances 0.000 description 9
- 239000007788 liquid Substances 0.000 description 7
- 238000009928 pasteurization Methods 0.000 description 6
- 230000010006 flight Effects 0.000 description 5
- 241001438449 Silo Species 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 4
- 239000000383 hazardous chemical Substances 0.000 description 4
- 230000001264 neutralization Effects 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000002708 enhancing Effects 0.000 description 3
- 238000005273 aeration Methods 0.000 description 2
- 230000036633 rest Effects 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L Calcium hydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 230000037250 Clearance Effects 0.000 description 1
- 235000019749 Dry matter Nutrition 0.000 description 1
- 241000238631 Hexapoda Species 0.000 description 1
- 241000700159 Rattus Species 0.000 description 1
- 241000258242 Siphonaptera Species 0.000 description 1
- -1 and in particular Substances 0.000 description 1
- 235000012970 cakes Nutrition 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 235000011116 calcium hydroxide Nutrition 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 229910052570 clay Inorganic materials 0.000 description 1
- 230000035512 clearance Effects 0.000 description 1
- 230000001419 dependent Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003028 elevating Effects 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000003415 peat Substances 0.000 description 1
- 239000003516 soil conditioner Substances 0.000 description 1
- 230000003019 stabilising Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
- C02F11/145—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances using calcium compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/0418—Wet materials, e.g. slurries
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/02—Lime
- C04B2/04—Slaking
- C04B2/06—Slaking with addition of substances, e.g. hydrophobic agents ; Slaking in the presence of other compounds
- C04B2/066—Making use of the hydration reaction, e.g. the reaction heat for dehydrating gypsum; Chemical drying by using unslaked lime
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B1/00—Preliminary treatment of solid materials or objects to facilitate drying, e.g. mixing or backmixing the materials to be dried with predominantly dry solids
- F26B1/005—Preliminary treatment of solid materials or objects to facilitate drying, e.g. mixing or backmixing the materials to be dried with predominantly dry solids by means of disintegrating, e.g. crushing, shredding, milling the materials to be dried
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/028—Arrangements for the supply or exhaust of gaseous drying medium for direct heat transfer, e.g. perforated tubes, annular passages, burner arrangements, dust separation, combined direct and indirect heating
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B11/00—Machines or apparatus for drying solid materials or objects with movement which is non-progressive
- F26B11/02—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles
- F26B11/04—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis
- F26B11/0463—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having internal elements, e.g. which are being moved or rotated by means other than the rotating drum wall
- F26B11/0477—Machines or apparatus for drying solid materials or objects with movement which is non-progressive in moving drums or other mainly-closed receptacles rotating about a horizontal or slightly-inclined axis having internal elements, e.g. which are being moved or rotated by means other than the rotating drum wall for mixing, stirring or conveying the materials to be dried, e.g. mounted to the wall, rotating with the drum
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
- F26B2200/18—Sludges, e.g. sewage, waste, industrial processes, cooling towers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Description
A process and apparatus for treating waste material
The present invention relates to a process and apparatus for treating waste material,
and in particular, though not limited to a process and apparatus for treating sewage
waste in sludge form.
Untreated waste material, in particular, sewage waste may contain, and indeed in
general contains substances which are hazardous to humans and the environment,
these substances may include organic and inorganic compounds, pathogens and
particulate solids. Thus, it is desirable to treat such waste materials, and in
particular, sewage prior to disposal. Various processes and apparatus are known for
the treatment of such waste sludge materials. In one known process to kill
pathogens in sewage sludge, the sludge is heated to a high temperature for an
extended period of time. The heating process is generally referred to as
pasteurisation and the degree to which the pathogens within the sludge are killed or
neutralised is largely dependent upon the temperature levels employed and the
residence time of the waste material at the elevated temperature. In general, in the
pasteurisation process the sewage sludge is heated to a temperature of
approximately 70°C for periods of two and a half hours and upwards. indeed, in
many cases time periods considerably in excess of two and a half hours are
required, and thus, pasteurisation tends to be a relatively time consuming process.
However, pasteurisation alone in general, is ineffective in neutralising the odours
which may emanate from waste materials, and in particular, from sewage sludge.
Unfortunately, the odours from sewage sludge have a tendency to attract vectors,
such as vermin, namely, rats, mice and the like, and insects, such as flies, fleas and
the like which in turn can pose a health risk by acting as carriers for any remaining
pathogens and other hazardous substances remaining in the sewage sludge after it
has been pasteurised. Apart from the health risks which residual odours in sewage
sludge can lead to, for example, the attraction of vectors and the like, residual
odours in pasteurised sewage sludge are also objectionable.
It is well known that sewage sludge is high in minerals and other substances which
have beneficial effects as fertilisers in the growing of crops, plants and the like when
spread on land. However, because of the objectionable odour, it is not feasible to
spread pasteurised sludge on land. Deodorising processes for treating sewage
sludge are known, however, they tend to suffer from disadvantages. One process for
deodorising sewage sludge is to add quicklime to the sludge for elevating the pH of
the sludge which tends to stabilise the sludge and reduce the odour. However, such
known methods of treating sludge whereby the sludge is pasteurised and treated
with quicklime tend to be relatively time consuming and costly, and in general, do not
satisfactorily remove the odour.
A further difficulty in the treatment of sewage sludge is that the consistency of the
sludge can vary vastly, from a relatively liquid consistency to a substantially solid
consistency. Furthermore, the sewage typically is made up of solid and liquid
components, and in general, the solid components comprise a bound liquid, typically
water, and thus, where the sewage sludge comprises a high degree of water, the
water may be made up a free liquid component as well as the bound liquid
component. While the free liquid component in general, can be removed by a
dewatering step in the process, nevertheless dewatered sludge may have varied
solids content and the solids may be of varying sizes. Accordingly, even dewatered
sludge may have vastly different physical characteristics which may vary from a
viscous, colloidal liquid to a dry cake or clay. Because of this, known processes and
apparatus for treating sewage sludge in general, are unsatisfactory due to the fact
that they tend to be relatively time consuming processes, and in general, have a
relatively high energy requirement and do not adequately remove odours.
There is therefore a need for a process and apparatus for treating sewage sludge for
reducing pathogen and odour levels of the sludge. Indeed, there is a need for a
process and apparatus for treating many waste materials for reducing the pathogen
and odour levels thereof.
The present invention is directed towards providing such a process and apparatus.
According to the invention there is provided a process for treating waste material in
sludge form comprising the steps of:
mixing the waste material with an additive for causing an exothermic reaction
in the mixture and for raising the pH of the mixture, and aerating the mixture during
mixing thereof,
subjecting the mixture of waste material and additive to chopping for reducing
the particle size of the mixture, and
dehydrating the chopped mixture in a rotary dryer.
In one embodiment of the invention the additive for causing the exothermic reaction
and for raising the pH of the mixture comprises substances containing calcium oxide.
in another embodiment of the invention the additive for causing the exothermic
reaction in the mixture and for raising the pH of the mixture is selected from a group
comprising lime, quicklime, dolomitic lime, cement kiln dust and lime kiln dust.
in a further embodiment of the invention the additive for causing the exothermic
reaction in the mixture and for raising the pH of the mixture is added to the waste
material in an amount sufficient for causing the temperature of the mixture to rise to
at least 70°C, and preferably to 75°C, and advantageously to at least 80°C, and
ideally to at least 90°C.
In one embodiment of the invention the additive for causing the exothermic reaction
in the mixture and for raising the pH of the mixture is added to the waste material in
an amount sufficient for raising the pH of the mixture to a pH of at least 8, and
preferably to a pH of at least 10, and advantageously to a pH of at least 12.
In another embodiment of the invention the additive for causing the exothermic
reaction in the mixture and for raising the pH of the mixture is mixed with the waste
material for a time sufficient for causing the temperature of the mixture to raise to at
least 70"C, and preferably to at least 75°C, and advantageously to at least 80°C, and
ideally to at least 90°C.
In a still further embodiment of the invention the additive for causing the exothermic
reaction in the mixture and for raising the pH of the mixture is mixed with the waste
material for a time sufficient for raising the pH of the mixture to a pH of at least 8,
and preferably, to a pH of at least 10, and ideally to a pH of at least 12.
In one embodiment of the invention the mixture is mixed for a time period of at least
minute, and preferably for a time period of approximately 2 minutes.
In one embodiment of the invention the mixture is mixed in an auger mixer.
Preferably, the chopping operation is carried out by subjecting the mixture to the
action of chopping blades.
Advantageously, the mixture is subjected to the chopping action on exiting the mixer.
in another embodiment of the invention a hot air stream is directed through the
rotary dryer, and the temperature of the hot air stream is at least 120°C. Preferably,
the temperature of the hot air stream through the rotary dryer is in the range of
120°C to 600°C. Advantageously, the temperature of the hot air stream through the
rotary dryer is in the range of 300°C to 550°C. Preferably, the temperature of the hot
air stream through the rotary dryer is in the range of 300°C to 400°C, and ideally the
temperature of the hot air stream through the rotary dryer is in the order of 400°C.
In one embodiment of the invention the hot air stream is passed through the rotary
dryer in contra flow relative to the flow of mixture through the rotary dryer.
In one embodiment of the invention the mixture is subjected to dehydration until the
moisture content of the dehydrated mixture is in the range of 5% to 45% by weight of
the mixture. Typically, the mixture is subjected to dehydration until the moisture
content of the dehydrated mixture is in the range of 5% to 35% by weight of the
mixture.
In one embodiment of the invention the mixture is subjected to dehydration for a time
period in the range of 5 minutes to 15 minutes, and advantageously, for a time
period in the range of 7 minutes to 10 minutes.
in one embodiment of the invention the moisture content of the waste material prior
to mixing with the additive for causing the exothermic reaction in the mixture and for
raising the pH of the mixture is in the range of 75% to 95%.
In another embodiment of the invention the moisture content of the waste material
prior to mixing with the additive for causing the exothermic reaction in the mixture
and for raising the pH of the mixture is in the range of 80% to 90%.
In another embodiment of the invention the moisture content of the waste material
prior to mixing with the additive for causing the exothermic reaction in the mixture
and for raising the pH of the mixture is in the range of 85% to 88%.
In another embodiment of the invention the waste material is sewage.
Additionally, the invention provides apparatus comprising a mixing means for mixing
the waste material with an additive for causing an exothermic reaction in the mixture
and for raising the pH of the mixture, a means for reducing the particle size of the
mixture, and a means for dehydrating the mixture.
In one embodiment of the invention the mixing means comprises an elongated auger
mixer. Preferably, the auger mixer comprises an elongated cylindrical housing.
Advantageously, the auger mixer comprises an auger screw which defines a
rotational axis, and which is located within the housing.
in one embodiment of the invention the auger screw is formed by a ribbon auger
carried on and extending around a main carrier shaft, and spaced apart therefrom.
Preferably, the ribbon auger is carried on the main carrier shaft by a plurality of
spaced apart radially extending spokes extending radially from the main carrier shaft
to the ribbon auger.
In another embodiment of the invention a plurality of mixing paddles are provided
along the auger screw, each mixing paddle extending from one 360" segment of the
auger screw to an adjacent 360° segment.
Advantageously, each mixing paddle presents a radially and axially extending face
to the mixture as the auger screw is being rotated.
Preferably, each mixing paddle extends substantially axially between the respective
adjacent 360" segments of the auger screw, and is located towards the peripheral
edges thereof.
In one embodiment of the invention the mixing means is inclined upwardly from an
upstream end for receiving the waste material and the additive to a downstream end
from which the mixed material is discharged.
in another embodiment of the invention a dispensing means is provided for
dispensing the additive for causing the exothermic reaction in the mixture and for
raising the pH of the mixture into the waste material. Preferably, the dispensing
means comprises a metering means for metering the additive into the waste material
as the waste material is being fed to the mixing means.
Advantageously, the dispensing means is located at the upstream end of the mixing
means.
Advantageously, the rotary dryer comprises an elongated rotatable drying drum
within which the mixture is dried, the drying drum defining a main rotational axis and
having an upstream end for receiving the mixture of additive and waste material and
a downstream end from which the dehydrated mixture is discharged.
Ideally, a tumbling means is located within the drying drum for tumbling the mixture
within the drying drum as the drying drum rotates.
In one embodiment of the invention the tumbling means comprises at least one
panel of mesh material extending radially from an inner surface of the drying drum.
Preferably, each panel of mesh material extends to a position adjacent the main
rotational axis of the drying drum.
Advantageously, the panels of mesh material are joined along the main rotational
axis of the drum.
Preferably, three panels of mesh material are located equi-spaced circumferentially
around the drum.
ldeally, each panel of mesh material extends in an axial direction along the inner
surface of the drying drum.
Preferably, each panel of mesh material is located adjacent the upstream end of the
drying drum.
in one embodiment of the invention each panel of mesh material extends
substantially along half the axial length of the drum.
in one embodiment of the invention each panel of mesh material defines a plurality
of perforations, and each perforation is of size such that its minimum dimension lies
in the range of 1cm to 10cms. Preferably, the minimum dimension of each
perforation in each panel lies in the range of 3cms to 7cms, and ideally is
approximately 5cms.
In one embodiment of the invention the tumbling means comprises a plurality of
axially extending blades extending inwardly from the inner surface of the drying
drum.
Preferably, the tumbling blades are spaced apart circumferentially around the drum.
Advantageously, the tumbling blades extend radially from the inner surface of the
drying drum.
Ideally, the tumbling blades are located in a downstream portion of the drying drum.
In one embodiment of the invention the tumbling blades are located in the
downstream half of the drying drum.
In another embodiment of the invention the tumbling means comprises a plurality of
tumbling members extending from a main support shaft of the drying drum disposed
within the drying drum and co-axial with the drying drum.
Preferably, the tumbling members are spaced apart circumferentially and axially
along the main support shaft.
Advantageously, the tumbling members extend radially from the main support shaft.
Ideally, each tumbling member is of rectangular cross-section and is arranged to
have an auger type action on the mixture within the drying drum.
In a further embodiment of the invention the auger type action of the tumbling
members acts in a direction for urging the mixture in a direction towards the
downstream end of the drum.
in another embodiment of the invention the tumbling blades and the tumbling
members co-operate for tumbling the mixture in the drying drum.
In a further embodiment of the invention the drying drum is inclined downwardly to
the horizontal from the upstream end to the downstream end. Preferably, the angle
of inclination of the drying drum to the horizontal from the upstream end to the
downstream end is in the range of 1° to 10°. Advantageously, the angle of inclination
of the drying drum to the horizontal from the upstream end to the downstream end is
in the range of 3° to 7°. ldeally, the angle of inclination of the drying drum to the
horizontal from the upstream end to the downstream end is in the range of
approximately 5°.
In one embodiment of the invention a hot air stream generating means is provided
for directing a hot air stream through the drying drum for drying of the mixture
therein.
Preferably, the hot air stream generating means is located relative to the drying drum
for directing the hot air stream in contra flow to the direction of flow of mixture
through the drum.
Advantageously, the hot air stream generating means comprises a burner unit
located at the downstream end of the drying drum.
In one embodiment of the invention the chopping means comprises a plurality of
chopping blades located at the downstream end of the mixing means for chopping
the mixture prior to delivery into the dehydrating means. Advantageously, the
chopping means comprises a plurality of chopping blades mounted on the
downstream end of the main carrier shaft of the auger mixer.
In another embodiment of the invention the apparatus is suitable for treating sewage
material in sludge form.
The advantages of the invention are many. One of the most important advantages of
the invention is that it provides an apparatus and process for treating waste material
such that the treated material is effectively free of pathogens and other hazardous
substances, and is virtually free of odour. This is a particularly important advantage
in the treatment of sewage sludge. Another advantage of the invention is that the
treatment time required for treating the waste material is relatively short. The mixing
of the sewage sludge with quicklime takes approximately one to two minutes, while
the drying takes approximately seven to ten minutes. Accordingly, the total
processing time ranges from eight minutes to twelve minutes. This is a significantly
important advantage in that it leads to an effective efficient and relatively low energy
process for the treatment of sewage sludge. The relatively short processing time
required for treating sewage sludge, and other waste materials using the process
according to the invention is achieved, it is believed by a number of factors. Firstly,
by breaking up the sewage sludge into particles of relatively small size facilitates in
drying of the particles, and furthermore, it enhances the exothermic reaction
between the quicklime and the sewage sludge. This, also reduces the time and the
heat required for raising the temperature of the mixture of sewage sludge and
quicklime since more efficient use is made of the exothermic action of the quicklime.
Furthermore, by breaking up the particles of sewage into relatively small particles
enhances aeration of the particles during the dehydration part of the process which
further facilitates in the killing off and neutralising of pathogens and other hazardous
substances in the sewage sludge. it has been found that the treated sewage sludge
treated by the process and apparatus according to the invention is relatively stable,
and remains so. Indeed, it has been found that the pH of the treated material
remained at 12 for approximately seven days after processing. It is believed that the
combination of the use of quicklime and the dehydration of the mixture of sewage
sludge and quicklime at a relatively high temperature range of 300°C to 550°C, and
in particular at approximately 400°C plays a significant part in the stabilisation of the
treated material, and thus in its deodorisation.
The invention will be more clearly understood from the following description of a
preferred embodiment thereof which is given by way of example only with reference
to the accompanying drawings, in which:
Fig. 1 is a diagrammatic representation of apparatus according to the
invention for treating waste material,
Fig. 2 is a side elevational view of a portion of the apparatus of Fig. 1,
Fig. 3 is a cross-sectional end elevational view of the portion of the apparatus
of Fig. 2 on the line Ill-lll of Fig. 2,
Fig. 4 is an end elevational view of another portion of the apparatus of Fig. 1,
Fig. 5 is a cutaway perspective view of the portion of the apparatus of Fig. 4,
and
Fig. 6 is a front perspective view of the portion of the apparatus of Fig. 4
illustrating the outer part of the portion in broken lines.
Referring to the drawings there is illustrated apparatus according to the invention
indicated generally by the reference numeral 1 for continuously treating waste
material, and in this embodiment of the invention for treating sewage sludge for
killing or neutralising pathogens in the sewage sludge and for reducing or eliminating
odours in the sewage sludge. The apparatus 1 comprises a mixing means, namely,
an auger mixer 2 for mixing an additive, in this embodiment of the invention
quicklime as will be described below with the sewage sludge for causing an
exothermic reaction in the mixture of sludge and quicklime for raising the
temperature of the mixture and for raising the pH of the mixture, preferably, to a pH
of 12, as will also be described below. A means for dehydrating the mixture of
sewage sludge and quicklime after it has been thoroughly mixed in the mixer 2
comprises a rotary dryer 3 in which the temperature of the mixture is raised to
approximately 400°C for a residence time in the range of seven to ten minutes as will
be described below. The mixer 2 feeds the mixture of sludge and quicklime into the
rotary dryer 3 at the upstream end 4 thereof, and the treated dehydrated material is
delivered from the rotary dryer 3 at a downstream end 5. It has been found that the
moisture content of the treated material lies between 5% and 35% by weight, and in
general, is in the order of 20% by weight, the pathogens in the treated material have
been neutrallsed and the odour virtually entirely removed.
The sewage sludge with a moisture content in the range of 85% to 88% is fed to the
apparatus on an auger conveyor 8. An outlet 9 from the auger conveyor 8 delivers
the sewage sludge into an upstream hopper 10 of the auger mixer 2. Quicklime is
stored in a vertical silo 11 and is dispensed through a metering means, namely, a
volumetric metering auger 12 from the silo 11 to the hopper 10. The metering auger
12 from the silo 11 is set to meter the quicklime into the sewage sludge at a rate to
provide a mix of sewage sludge and quicklime in the ratio of approximately 20%
quicklime to 80% sewage sludge by volume.
Referring in particular to Fig. 2, the auger mixer 2 comprises a cylindrical housing 15
which defines an elongated auger accommodating bore 16 for accommodating an
auger screw 17. The housing 15 inclines upwardly from an upstream end 18 of the
auger mixer 2 to a raised downstream end 19 of the auger mixer 2 at an angle of
approximately 45° to the horizontal. The auger screw 17 comprises a main carrier
shaft 20 which is rotatable in bearings (not shown) in respective end caps 21 at the
axial opposite ends of the housing 15. A ribbon flight 22 of flat stock steel extends
around and is spaced apart from the main carrier shaft 20 and is carried on the shaft
by radiallly extending spokes 23. The ribbon flight as well as acting to urge the
mixture of quicklime and sewage sludge along the auger mixer 2 also acts to mix the
quicklime with the sewage sludge. A downstream outlet 24 feeds the mixture of
sewage sludge and quicklime into the upstream end 4 of the rotary dryer 3. A
plurality of mixing paddles 25 extend axially between respective adjacent 360‘
segments of the auger flight 22 for further enhancing mixing of the sewage sludge
and quicklime in the mixer 2. The mixing paddles 25 are of relatively flat stock steel
and are of radial width substantially similar to the radial width of the ribbon flight 22.
The mixing paddles 25 are arranged to present a radially and axially extending
abutment face 26 to the mixture for mixing thereof as the auger screw 17 is rotating.
An electrically powered motor 28 carried on the housing 15 by mounting brackets
(not shown) drives the auger screw 17.
A means for reducing the particle size of the mixture of sewage sludge and quicklime
prior to it being delivered into the rotary dryer 3 comprises a chopping means,
namely, a plurality of chopping blades 30 which are carried on the main carrier shaft
at the downstream end thereof and extend radially therefrom. The chopping
blades are of relatively flat stock steel welded to the main carrier shaft 20 and are
arranged at a helical angle to the shaft 20, as can be seen in Fig. 2. It has been
found that as the main carrier shaft 20 rotates the action of the chopping blades 30
on the mixture exiting from the auger screw 17 is sufficient for significantly reducing
the particle size of the particle matter in the mixture, and in this embodiment of the
invention reduces the particle size of the mixture such that the maximum dimension
of the particles does not exceed 5cms.
The rotary dryer 3 comprises an elongated drying drum 32 extending between the
upstream end 4 and the downstream end 5. A pair of spaced apart bearing rings 33
extend around the drum 32 for supporting the drum 32 on four rollers 35. One of the
bearing rings 33 rests on one pair of rollers 35, while the other bearing ring 33 rests
on the other pair of rollers 35. One roller 35 of each pair of rollers 35 is a driven roller
for rotating the drum 32, while the other roller of each pair of rollers 35 is an idler
roller. The rollers 35 are carried on shafts (not shown) which are rotatably carried in
a base frame 36. In this embodiment of the invention the base frame 36 mounts the
drum 32 so that the drum 32 inclines downwardly from the upstream end 4 to the
downstream end 5 at an angle of approximately 5° to the horizontal. Stationery end
caps (not shown) close the drum 32 at its respective axially opposite ends. An inlet
(not shown) is provided in the upstream end cap (not shown) for accommodating the
downstream outlet 24 of the auger mixer 2 for feeding the chopped mixture of
sewage sludge and quicklime into the drum 32 at the upstream end 4 thereof. A
downstream outlet (also not shown) at the lower end of the end cap (not shown) at
the downstream end 5 of the rotary dryer 3 delivers the treated material from the
drum 32.
A means for generating a stream of hot air, namely, a fan and burner unit 40 is
located at the downstream end of the rotary dryer 3, and delivers a heated stream of
air through the drum 32 from the downstream end 5 to the upstream end 4 in contra
flow to the direction of flow of the mixture of sewage sludge and quicklime. A dust
extractor filter unit 41 at the upstream end 4 of the rotary dryer 3 exhausts and filters
air and dust from the drum 32.
Referring now in particular to Figs. 4 to 6, the drum 32 comprises a tumbling means
which is provided in three forms, namely, three mesh panels 45, a plurality of
tumbling blades 46 located on an inner surface 47 of the drum 32, and a plurality of
tumbling members 48 extending radially from a main support shaft 49 of the drum 32
for tumbling the particulate mixture of sewage sludge and quicklime within the drum
32. The three mesh panels 45 extend radially from the main support shaft 49 and are
equi-spaced circumferentially around the main shaft 49 at 120° intervals for causing
initial tumbling of the mixture of sludge and quicklime in the drum 32. The mesh
panels 45 extend radially from the main shaft 49 to the inner surface 47 of the drum
32 and extend axially from a position approximately half way between the upstream
and downstream ends 4 and 5 of the drum 32 upstream towards the upstream end
4. However, although not illustrated in Figs. 5 and 6 the mesh panels 45 stop short
of the upstream end 4 a distance sufficient to provide clearance for the downstream
outlet 24 of the auger mixer 2. The mesh panels 45 are of expanded metal mesh
material with a minimum dimension of each perforation being approximately 5cms for
accommodating the largest size particle of the sewage sludge quicklime mixture.
The tumbling blades 46 are elongated blades and extend axially along and radially
inwardly from the inner surface 47, and are provided along the drum 32 between the
upstream and downstream ends 4 and 5. The tumbling blades 46 are equi-spaced
circumferentially around the inner surface 47 of the drum 32, and are spaced apart
axially, as well as being staggered circumferentially. For convenience only some of
the tumbling blades 46 are illustrated in Figs. 5 and 6. The tumbling members 48 are
of relatively flat stock steel, and extend radially outwardly from the main support
shaft 49 and stop short of the tumbling blades 46. The tumbling members 48 are
arranged helically and at an angle on the main support shaft 49 for urging the
particulate mixture in a downstream direction.
An output conveyor 50 feeds the treated material from the outlet (not sown) of the
rotary dryer 3 to a location where it may be bulk packed, bagged, pelletised or the
like.
The use of the apparatus 1 for carrying out the process according to the invention for
treating sewage sludge will now be described. The sewage sludge with a moisture
content of approximately 85% to 88% by weight and a solids content in the order of
12% to 16% is continuously fed on the auger conveyor 8 into the hopper 10, and
simultaneously the quicklime is continuously metered from the silo 11 by the
metering auger 12. The ratio of quicklime to sewage sludge depends on the moisture
content of the sludge, and is typically added in the ratio of 0.1 to 0.3 parts quicklime
to one part of sludge by volume. In practice, with a moisture content of the sewage
sludge of the order of 85% to 88%, the ratio of quicklime to sewage sludge is
approximately 0.2 parts quicklime to one part of sewage sludge. This, in general, is
sufficient for raising the pH of the mixture of sewage sludge and quicklime to
approximately 12. The quicklime is rapidly and thoroughly mixed with the sewage
sludge in the auger mixer 2, and typically, the resident time of the mixture in the
auger mixer 2 is between one minute and two minutes. The mixing of the quicklime
with the sludge as well as raising the pH of the sludge to a pH of 12 also causes an
exothermic reaction which rapidly raises the temperature of the mixture to 90°C, and
in cases where the temperature is not raised to 90°C, the temperature reaches at
least 70’, which is sufficient for subjecting the mixture to an initial brief pasteurisation
step. During mixing of the sewage sludge and quicklime in the auger mixer 2 air is
present for aeration of the mixture. Thus, the rate at which the sewage is fed into the
auger mixer 2 is controlled to ensure that an adequate supply of air is entrained in
the mixture of sewage sludge and quicklime.
The mixture of sewage sludge and quicklime is subjected to the chopping action of
the chopping blades 30 before being delivered through the downstream outlet 24 of
the auger mixer 2. The action of the chopping blades 30 on the solid matter of the
mixture is such as to reduce the particle size of the solid matter such that the
maximum dimension of any particle does not exceed 5cms.
The chopped mixture of sewage sludge and quicklime is delivered from the
downstream outlet 24 of the auger mixer 2 into the drum 32 of the rotary dryer 3
where it is tumbled and subjected to the heated air stream. The air is heated by the
fan burner unit 40 to a temperature of approximately 400°C and is delivered through
the drum 32 at a rate sufficient for raising the temperature of the mixture to
approximately 400°C. The residence time required of the sewage sludge and
quicklime mixture in the drum 32 in general, is in the order of seven minutes to ten
minutes. This, largely depends on the moisture content of the sewage sludge being
delivered into the hopper 10 of the auger mixer 2 and the final moisture content
required for the treated material. in general, with a starting moisture content of the
sewage sludge of the order of 85% to 88% it has been found that a residence time of
ten minutes of the sewage sludge and quicklime mixture in the drum 32 is sufficient
for producing treated material with a moisture content of approximately 15% to 20%
by weight of dry matter.
Additionally, it has been found that a residence time in the order of ten minutes of
the mixture of sewage sludge and quicklime in the drum 32 is sufficient for raising
the temperature of the mixture to 4000 for a time period of approximately ten
minutes. This, it has been found is sufficient for neutralising the pathogens and other
hazardous substances in the sewage sludge.
Typically, the auger mixer 2 and the rotary dryer 3 has a capacity of approximately
three to four tons of sewage sludge per hour on a continuous basis.
The exothermic reaction between the sewage sludge and the quicklime is caused as
follows:
CaO+H2O = Ca(OH)2 + heat
where the heat facilitates the pasteurisation and deodorising of the mixture.
The treated material delivered from the downstream outlet 39 of the rotary dryer 3
has been found to be virtually odourless, and is suitable for many uses, for example,
spreading on land as a fertiliser, as top soil, as a soil conditioner, for peat land
restoration, structural soil applications, land reclamation and use in reforestation.
While quicklime has been described as the additive for causing the exothermic
reaction and raising the pH of the sewage sludge, other suitable additives may be
used, for example, any other calcium oxide containing substances, such as, for
example, dolomitic lime, cement kiln dust, lime kiln dust, lime and the like. While the
proportion of quicklime to sewage sludge has been described as being
approximately 20% quicklime to 80% sewage sludge, it is envisaged that other
suitable proportions may be used, and the proportions in general, will depend on the
moisture content of the sewage sludge. A typical range of proportions of quicklime to
sewage sludge would be approximately 5% quicklime to 95% sewage sludge to 30%
quicklime to 70% sewage sludge.
Needless to say, while the apparatus and the process have been described for
treating sewage sludge, the apparatus and process may be used for treating many
other waste materials in sludge form.
While the tumbling members of the drying drum have been described as being
arranged in auger fashion, this is not necessary. It is also envisaged that the
tumbling members may be sequentially arranged on the shaft to define an auger.
Additionally, while the mixing auger has been described as being inclined at an
angle of approximately 45° to the horizontal, it is envisaged that the mixing auger
may be inclined at any suitable angle, and typically, may be inclined at an angle in
the range of 30° to 50°. It is also envisaged that the mixing paddles which extend
axially between adjacent 360° segments of the flights may be dispensed with.
Claims (84)
1. A process for treating waste material in sludge form comprising the steps of: mixing the waste material with an additive for causing an exothermic reaction in the mixture and for raising the pH of the mixture, and aerating the mixture during mixing thereof, subjecting the mixture of waste material and additive to chopping for reducing the particle size of the mixture, and dehydrating the chopped mixture in a rotary dryer.
2. A process as claimed in Claim 1 in which the additive for causing the exothermic reaction and for raising the pH of the mixture comprises substances containing calcium oxide.
3. A process as claimed in Claim 1 or 2 in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is selected from a group comprising lime, quicklime, dolomitic lime, cement kiln dust and lime kiln dust.
4. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for causing the temperature of the mixture to rise to at least 70°C.
5. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for causing the temperature of the mixture to rise to at least 75°C.
6. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for causing the temperature of the mixture to rise to at least 80°C.
7. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for causing the temperature of the mixture to rise to at least 90°C.
8. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for raising the pH of the mixture to a pH of at least 8.
9. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for raising the pH of the mixture to a pH of at least 10.
10. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is added to the waste material in an amount sufficient for raising the pH of the mixture to 12.
11. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for causing the temperature of the mixture to raise to at least 70°C.
12. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for causing the temperature of the mixture to raise to at least 75°C.
13. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed 21 with the waste material for a time sufficient for causing the temperature of the mixture to raise to at least 80°C.
14. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for causing the temperature of the mixture to raise to at least 90°C.
15. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for raising the pH of the mixture to a pH of at least 8.
16. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for raising the pH of the mixture to a pH of at least 10.
17. A process as claimed in any preceding claim in which the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is mixed with the waste material for a time sufficient for raising the pH of the mixture to a pH of 12.
18. A process as claimed in any preceding claim in which the mixture is mixed for a time period of at least 1 minute.
19. A process as claimed in any preceding claim in which the mixture is mixed for a time period of approximately 2 minutes.
20. A process as claimed in any preceding claim in which the mixture is mixed in an auger mixer.
21. A process as claimed in Claim 20 in which the chopping operation is carried out by subjecting the mixture to the action of chopping blades.
22. A process as claimed in Claim 21 in which the mixture is subjected to the chopping action on exiting the mixer.
23. A process as claimed in any preceding claim in which a hot air stream is directed through the rotary dryer, and the temperature of the hot air stream is at least 120”C.
24. A process as claimed in Claim 23 in which the temperature of the hot air stream through the rotary dryer is in the range of 120°C to 600°C.
25. A process as claimed in Claim 23 or 24 in which the temperature of the hot air stream through the rotary dryer is in the range of 300°C to 550°C.
26. A process as claimed in any of Claims 23 to 25 in which the temperature of the hot air stream through the rotary dryer is in the range of 300“C to 400°C.
27. A process as claimed in any of Claims 23 to 26 in which the temperature of the hot air stream through the rotary dryer is in the order of 400°C.
28. A process as claimed in any of Claims 23 to 27 in which the hot air stream is passed through the rotary dryer in contra flow relative to the flow of mixture through the rotary dryer.
29. A process as claimed in any preceding claim in which the mixture is subjected to dehydration until the moisture content of the dehydrated mixture is in the range of 5% to 45% by weight of the mixture. 23
30. A process as claimed in any preceding claim in which the mixture is subjected to dehydration until the moisture content of the dehydrated mixture is in the range of 5% to 35% by weight of the mixture.
31. A process as claimed in any preceding claim in which the mixture is subjected to dehydration for a time period in the range of 5 minutes to 15 minutes.
32. A process as claimed in any preceding claim in which the mixture is subjected to dehydration for a time period in the range of 7 minutes to 10 minutes.
33. A process as claimed in any preceding claim in which the moisture content of the waste material prior to mixing with the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is in the range of 75% to 95%.
34. A process as claimed in any preceding claim in which the moisture content of the waste material prior to mixing with the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is in the range of 80% to 90%.
35. A process as claimed in any preceding claim in which the moisture content of the waste material prior to mixing with the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture is in the range of 85% to 88%.
36. A process as claimed in any preceding claim in which the waste material is sewage.
37. A process for treating waste material, the process being substantially as described herein with reference to and as illustrated in the accompanying drawings. 24
38. Apparatus for treating waste material in sludge form, the apparatus comprising a mixing means for mixing the waste material with an additive for causing an exothermic reaction in the mixture and for raising the pH of the mixture and for aerating the mixture, a chopping means for reducing the particle size of the mixture, and a rotary dryer for drying the mixture of reduced particle size.
39. Apparatus as claimed in Claim 38 in which the mixing means comprises an elongated auger mixer.
40. Apparatus as claimed in Claim 39 in which the auger mixer comprises an elongated cylindrical housing.
41. Apparatus as claimed in Claim 39 or 40 in which the auger mixer comprises an auger screw which defines a rotational axis, and which is located within the housing.
42. Apparatus as claimed in Claim 41 in which the auger screw is formed by a ribbon auger carried on and extending around a main carrier shaft, and spaced apart therefrom.
43. Apparatus as claimed in Claim 42 in which the ribbon auger is carried on the main carrier shaft by a plurality of spaced apart radially extending spokes extending radially from the main carrier shaft to the ribbon auger.
44. Apparatus as claimed in any of Claims 41 to 43 in which a plurality of mixing paddles are provided along the auger screw, each mixing paddle extending from one 360” segment of the auger screw to an adjacent 360° segment.
45. Apparatus as claimed in Claim 44 in which each mixing paddle presents a radially and axially extending face to the mixture as the auger screw is being rotated.
46. Apparatus as claimed in Claim 44 or 45 in which each mixing paddle extends substantially axially between the respective adjacent 360° segments of the auger screw, and is located towards the peripheral edges thereof.
47. Apparatus as claimed in any of Claims 38 to 46 in which the mixing means is inclined upwardly from an upstream end for receiving the waste material and the additive to a downstream end from which the mixed material is discharged.
48. Apparatus as claimed in any of Claims 38 to 47 in which a dispensing means is provided for dispensing the additive for causing the exothermic reaction in the mixture and for raising the pH of the mixture into the waste material.
49. Apparatus as claimed in Claim 48 in which the dispensing means comprises a metering means for metering the additive into the waste material as the waste material is being fed to the mixing means.
50. Apparatus as claimed in Claim 48 or 49 in which the dispensing means is located at the upstream end of the mixing means.
51. Apparatus as claimed in any of Claims 38 to 50 in which the rotary dryer comprises an elongated rotatable drying drum within which the mixture is dried, the drying drum defining a main rotational axis and having an upstream end for receiving the mixture of additive and waste material and a downstream end from which the dehydrated mixture is discharged.
52. Apparatus as claimed in Claim 51 in which a tumbling means is located within the drying drum for tumbling the mixture within the drying drum as the drying drum rotates.
53. Apparatus as claimed in Claim 52 in which the tumbling means comprises at least one panel of mesh material extending radially from an inner surface of the drying drum.
54. extends to a position adjacent the main rotational axis of the drying drum. Apparatus as claimed in Claim 53 in which each panel of mesh material
55. are joined along the main rotational axis of the drum. Apparatus as claimed in Claim 53 or 54 in which the panels of mesh material
56. mesh material are located equi-spaced clrcumferentially around the drum. Apparatus as claimed in any of Claims 53 to 55 in which three panels of
57. material extends in an axial direction along the inner surface of the drying drum. Apparatus as claimed in any of Claims 53 to 56 in which each panel of mesh
58. material is located adjacent the upstream end of the drying drum. Apparatus as claimed in any of Claims 53 to 57 in which each panel of mesh
59. material extends substantially along half the axial length of the drum. Apparatus as claimed in any of Claims 53 to 58 in which each panel of mesh
60. material defines a plurality of perforations, and each perforation is of size such that Apparatus as claimed in any of Claims 53 to 59 in which each panel of mesh its minimum dimension lies in the range of 1cm to 10cms.
61. Apparatus as claimed in Claim 60 in which the minimum dimension of each perforation in each panel lies in the range of 3cms to 7cms.
62. perforation in each panel is approximately 5cms. Apparatus as claimed in Claim 61 in which the minimum dimension of each
63. comprises a plurality of axially extending blades extending inwardly from the inner Apparatus as claimed in any of Claims 52 to 62 in which the tumbling means surface of the drying drum.
64. Apparatus as claimed in Claim 63 in which the tumbling blades are spaced apart circumferentially around the drum.
65. Apparatus as claimed in Claim 63 or 64 in which the tumbling blades extend radially from the inner surface of the drying drum.
66. Apparatus as claimed in any of Claims 63 to 65 in which the tumbling blades are located in a downstream portion of the drying drum.
67. Apparatus as claimed in any of Claims 63 to 66 in which the tumbling blades are located in the downstream half of the drying drum.
68. Apparatus as claimed in any of Claims 52 to 67 in which the tumbling means comprises a plurality of tumbling members extending from a main support shaft of the drying drum disposed within the drying drum and co-axial with the drying drum.
69. Apparatus as claimed in Claim 68 in which the tumbling members are spaced apart circumferentially and axially along the main support shaft.
70. Apparatus as claimed in Claim 68 or 69 in which the tumbling members extend radially from the main support shaft.
71. Apparatus as claimed in any of Claims 68 to 70 in which each tumbling member is of rectangular cross-section and is arranged to have an auger type action on the mixture within the drying drum.
72. Apparatus as claimed in Claim 71 in which the auger type action of the tumbling members acts in a direction for urging the mixture in a direction towards the downstream end of the drum.
73. Apparatus as claimed in any of Claims 68 to 72 in which the tumbling blades and the tumbling members co-operate for tumbling the mixture in the drying drum.
74. Apparatus as claimed in any of Claims 51 to 73 in which the drying drum is inclined downwardly to the horizontal from the upstream end to the downstream end.
75. Apparatus as claimed in Claim 74 in which the angle of inclination of the drying drum to the horizontal from the upstream end to the downstream end is in the range of 1° to 10°.
76. Apparatus as claimed in Claim 75 in which the angle of inclination of the drying drum to the horizontal from the upstream end to the downstream end is in the range of 3° to 7°.
77. Apparatus as claimed in Claim 76 in which the angle of inclination of the drying drum to the horizontal from the upstream end to the downstream end is in the range of approximately 5“.
78. Apparatus as claimed in any of Claims 51 to 77 in which a hot air stream generating means is provided for directing a hot air stream through the drying drum for drying of the mixture therein.
79. Apparatus as claimed in Claim 78 in which the hot air stream generating means is located relative to the drying drum for directing the hot air stream in contra flow to the direction of flow of mixture through the drum.
80. Apparatus as claimed in Claim 78 or 79 in which the hot air stream generating means comprises a burner unit located at the downstream end of the drying drum.
81. Apparatus as claimed in any of Claims 38 to 80 in which the chopping means comprises a plurality of chopping blades located at the downstream end of the mixing means for chopping the mixture prior to delivery into the dehydrating means.
82. Apparatus as claimed in any of Claims 38 to 81 in which the chopping means comprises a plurality of chopping blades mounted on the downstream end of the main carrier shaft of the auger mixer.
83. Apparatus as claimed in any of Claims 38 to 82 in which the apparatus is suitable for treating sewage material in sludge form.
84. Apparatus for treating waste material, the apparatus being substantially as described herein with reference to and as illustrated in the accompanying drawings. F.F. GORMAN & CO.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IE1999/0903A IE83635B1 (en) | 1999-10-29 | A process and apparatus for treating waste material |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IEIRELAND30/10/1998S1998/0900 | |||
IE980900 | 1998-10-30 | ||
IE1999/0903A IE83635B1 (en) | 1999-10-29 | A process and apparatus for treating waste material |
Publications (2)
Publication Number | Publication Date |
---|---|
IE990903A1 IE990903A1 (en) | 2000-11-15 |
IE83635B1 true IE83635B1 (en) | 2004-10-20 |
Family
ID=
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