Heat treated waste sludge disposal

Claim 2

The invention defined in claim 1 in which said devices include a screw feed arrangement to feed cake into the fluidized bed.

Claim 3

The invention defined in claim 1 in which said devices include a mill for breaking up the cake into small pieces, and blower means for blowing the milled cake into said chamber.

Claim 4

The invention defined in claim 4 in which said blower means is arranged to blow the milled cake downwardly into the freeboard of said chamber.

Claim 5

The invention defined in claim 2 in which said mechanical dewaterer consIsts of a solid long bowl centrifuge arranged to receive the cooked decanted sludge and deliver it to said screw feed.

Claim 6

Apparatus for disposing of sewage or other organic waste sludge by combustion, comprising in combination a combustion chamber having an exhaust outlet and an inlet for material to be burned, a continuously operating centrifuge or filter type mechanical dewaterer, a throughput-type pressure cooker operative to heat sludge passed through it to a temperature of approximately 350* to 400* F. under sufficient pressure to prevent evaporation and for a period of 15 to 45 minutes sufficient to free cellular bound water in the sludge, a decanter for decanting at last part of the freed water, means for supplying thickened sludge and continuously feeding it under said pressure through the cooker during said period and to the decanter, and for feeding the underflow sludge from the decanter to the dewaterer wherein a friable readily crumbled cake having a solids content of 35 to 75 percent is formed, a mill arranged to mill said cake into small pieces, and a blower arranged to blow the milled cake through said inlet into the combustion chamber for maintaining autogenous combustion of the dewatered sludge, with the inert combustion gases and entrained finely divided ash passing through the exhaust outlet.

Claim 7

A process for disposal of secondary or mixed primary and secondary sewage sludge comprising subjecting the sludge to a sedimentary thickening operation producing a sludge having a solids concentration of over 5 percent, continuously pumping the thickened sludge under pressure through a pressurized heating zone in which the sludge is subjected to temperatures between 300 and 450* F., at pressures sufficient to avoid evaporation for a period between 15 and 60 minutes to free the cell water, decanting free liquid from the heat treated sludge, continuously feeding the remaining sludge into a solid bowl centrifuge to form cake having a solids content of over 35 percent, establishing a body of hot inert granular material at combustion temperature blowing combustion air at substantially room temperature into the body to fluidize the same, and feeding the dewatered sludge cake to said bed to disperse, finely divide and autogenously burn the same.

Claim 8

The invention defined in claim 8 including the steps of breaking up the cake into granular form and blowing it into contact with the fluidized body.

Claim 9

The invention defined in claim 8 including the step of screw feeding the cake into the fluidized body.

Claim 10

The invention defined in claim 8 including the steps of milling the cake into small particles, and blowing the particles directly into the fluidized bed.

Claim 11

The invention defined in claim 8 including milling the cake into small particles and blowing the particles into the freeboard above the fluidized bed.

Claim 13

The invention defined in claim 12 in which the centrifuging takes place in an elongated solid bowl centrifuge.

Claim 14

A process for disposing of sewage sludge at least in part biological in nature and containing cellular bound water comprising subjecting the sludge to a high degree of thickening by controlling the operation of a clarifier having an upper body of liquor for effluent and a lower bed of sluDge in which (a) the ratio of sludge volume in the bed compared with the sludge withdrawn in a day is in the range between 1/4 and 3, (b) the depth of the bed is maintained between 1 and 5 ft., (c) the dry weight of solids fed to the clarifier is between 4 and 40 pounds per square foot of sludge bed area, (d) the rate of feed is between 250 and 1,500 gallons per square foot of sludge bed area and (e) the dilution of the feed to the clarifier is between 1, 000 and 6,000 parts of solids per million parts of liquid, continuously pumping the thickened sludge under pressure through a pressurized heating zone in which the sludge is subjected to temperatures substantially above boiling, at pressures sufficiently above atmospheric to avoid evaporation for period sufficient in combination with said temperature and pressure to free the cellular water, decanting free liquid from the heat treated sludge, mechanical dewatering the sludge from decanting to form cake having a solids content of over 35 percent, providing a combustion chamber and feeding the dewatered sludge cake to said chamber to autogenously burn the same.

Claim 15

The invention defined in claim 15 in which the mechanical dewatering comprises centrifuging.

Claim 16

The invention defined in claim 15 in which said temperature is between 350 and 425* F. and said time is between 20 and 40 minutes.

Claim 17

The invention according to claim 15 in which said chamber is provided with a body of fluidized inert granular material at sludge combustion temperature, and the dewatered sludge cake is fed to the fluidized body.

Claim 18

A process for disposal of dilute sewage sludge containing cellular bound water comprising subjecting the sludge to a thickening operation producing a solids concentration of over 5 percent, continuously pumping the thickened sludge through a pressurized heating zone having in which the sludge is subjected to temperatures between 300 and 450* F., at pressures sufficient to avoid evaporation for a period between 20 and 40 minutes to free the cellular bound water, separating the freed water from the sludge, and thereafter subjecting the sludge to mechanical dewatering to produce a sludge having a solids content of 35 percent or more, establishing a body of hot granular inert material, blowing combustion air through said body to fluidize the same, and feeding the pressure cooked dewatered sludge cake to said bed, to disperse, finely divide, and autogenously burn the same.

Claim 19

The invention according to claim 19 in which said thickening operation comprises centrifuging in a nozzle-type centrifuge to provide a thickened underflow.