Method and apparatus for sewage treatment plants

Claim 2

In a sewage treatment plant including a plurality of sludge treatment stations including settling means, a lime furnace and a sludge furnace, the combination comprising means for delivering sludge from at least one of said settling means to said sludge furnace, a centrifuge for receiving lime mud precipitated by lime in said settling means and for discharging a semi-solid product rich in regenerable lime sludge that can be reburned to lime, means conveying said semi-solid product from said centrifuge to said lime furnace for reburning, said centifuge providing a centrate stream unsuitable for regeneration into lime, a spray dryer having a centrate inlet, a hot gas inlet and an outlet, means for conveying said centrate stream from said centrifuge to said spray dryer via its centrate inlet, means for conveying a portion of the hot exhaust gases and vapors from said sludge furnace to said spray dryer hot gas inlet, said sludge furnace having a sludge inlet feed line, means for conveying a centrate stream discharged from said spray dryer outlet to said sludge inlet feed line.

Claim 3

A sewage treatment plant according to claim 1, further including a wet type scrubber, means for conveying a second portion of said hot exhaust gas from said sludge furnace to said scrubber, means for conveying the centrate stream from said centrifuge to said scrubber for use as scrubbing liquid in said scrubber, and means for conveying the centrate stream from said scrubber to said spray dryer.

Claim 4

A sewage treatment system including a plurality of sludge treatment stations including settling means comprising means including a sludge furnace feed line for delivering sludge from at least one of said settling means to a sludge furnace, a centrifuge, an inlet in said centrifuge for admitting lime mud thereinto precipitated by lime in another of said settling means, a first outlet from said centrifuge, a lime furnace, means connecting said first outlet and said lime furnace for discharging regenerable lime sludge from said centrifuge into said lime furnace, a second outlet for discharging a centrate stream of non-regenerable sludge from said centrifuge, a spray dryer having a centrate inlet, a hot gas inlet and an outlet, outlet means in said sludge furnace for conveying hot exhaust gas from said sludge furnace to said spray dryer via its hot gas inlet, means for conveying said centrate stream from said second outlet in said centrifuge into said spray dryer via its centrate inlet for contact with said hot exhaust gases from said sludge furnace whereby said centrate stream is dried by said hot gases, and means for conveying a centrate stream discharged from the spray dryer outlet to said sludge furnace feed line.

Claim 5

A sewage treatment system including a plurality of sludge treatment stations including settling means comprising means including a sludge furnace feed line for delivering sludge from at least one of said settling means to a sludge furnace, a centrifuge, an inlet in said centrifuge for admitting lime mud thereinto precipitated by lime in another of said settling means, a first outlet from said centrifuge, a lime furnace, means connecting said first outlet and said lime furnace for discharging regenerable lime sludge from said centrifuge into said lime furnace, a second outlet for discharging a centrate stream of non-regenerable sludge from said centrifuge, a spray dryer having a centrate inlet, a hot gas inlet and an outlet, outlet means in said sludge furnace for conveying hot exhaust gas from said sludge furnace to said spray dryer via its hot gas inlet, means for conveying said centrate stream from said second outlet in said centrifuge into said spray dryer via its centrate inlet for contact with said hot exhaust gases from said sludge furnace whereby said centrate stream is dried by said hot gases, and means for conveying a centrate stream discharged from the spray dryer outlet to said sludge furnace feed line.

Claim 6

The invention as defined in claim 3, including a wet type scrubber, a second outlet in said sludge furnace, for said exhaust gas means connecting said scrubber to said second furnace outlet to pass said hot exhaust gas through the scrubber, means connecting the second outlet of the centrifuge to the scrubber to scrub said hot exhaust gas with said centrate steam, means for conveying the centrate stream from said scrubber to said spray dryer via its centrate inlet, said sludge furnace having a sludge feed line, and means for conveying the centrate stream dried in said spray dryer to said sludge feed line via said dryer outlet for burning in said sludge furnace.

Claim 7

In a sewage treatment system including a plurality of settling stations at least one of which produces a lime mud underflow and from at least one of which sludge is delivered to a sludge furnace, the process comprising passing the underflow lime mud precipitated by lime from at least one of said setting stations into a centrifuge, discharging from said centrifuge a first stream containing solids, the major constituent of which is calcium carbonate, passing said first stream to a lime furnace, passing a second stream from said centrifuge containing materials unsuitable for regeneration into lime to a spray dryer while simultaneously passing a portion of the hot exhaust gases and vapors from said sludge furnace to said spray dryer to dry said second stream, and passing the dried second stream containing solids from the spray dryer to a sludge feed line to said sludge furnace for burning.

Claim 8

In a sewage treatment system including a plurality of settling stations at least one of which produces a lime mud underflow and from at least one of which sludge is delivered to a sludge furnace, the process comprising passing the underflow lime mud precipitated by lime from at least one of said setting stations into a centrifuge, discharging from said centrifuge a first stream containing solids, the major constituent of which is calcium carbonate, passing said first stream to a lime furnace, passing a second stream from said centrifuge containing materials unsuitable for regeneration into lime to a spray dryer while simultaneously passing a portion of the hot exhaust gases and vapors from said sludge furnace to said spray dryer to dry said second stream, and passing the dried second stream containing solids from the spray dryer to a sludge feed line to said sludge furnace for burning.

Claim 9

In a sewage treatment system including a plurality of settling stations including settling tanks at least one of which produces a lime mud underflow and from at least one of which sludge is delivered to a sludge furnace, the process comprising passing the underflow lime mud precipitated by lime from at least one of said settling stations into a centrifuge, discharging from said centrifuge, a first stream containing solids, the major constituent of which is calcium carbonate, passing said first stream to a lime furance, passing a second stream from said centrifuge containing materials unsuitable for regeneration into lime to a wet scrubber associated with said sludge furnace, and using said second stream as the scrubbing liquid in said scrubber, and thence passing said second stream from said scrubber into a spray-type dryer while simultaneously passing a portion of the hot exhaust gases and vapors from said sludge furnace to said dryer to dry said second stream, and passing the dried second stream containing solids from the spray dryer to a sludge feed line to said sludge furnace for burning.

Claim 10

In a sewage treatment system including a plurality of settling stations including settling tanks at least one of which produces a lime mud underflow and from at least one of which sludge is delivered to a sludge furnace, the process comprising passing the underflow lime mud precipitated by lime from at least one of said settling stations into a centrifuge, discharging from said centrifuge, a first stream containing solids, the major constituent of which is calcium carbonate, passing said first stream to a lime furance, passing a second stream from said centrifuge containing materials unsuitable for regeneration into lime to a wet scrubber associated with said sludge furnace, and using said second stream as the scrubbing liquid in said scrubber, and thence passing said second stream from said scrubber into a spray-type dryer while simultaneously passing a portion of the hot exhaust gases and vapors from said sludge furnace to said dryer to dry said second stream, and passing the dried second stream containing solids from the spray dryer to a sludge feed line to said sludge furnace for burning.