# US 4,398,476 A · Method for incinerating sewage sludge

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- Number: US 4,398,476 A
- Document ID: US4398476A
- Status: Granted
- Kind: A
- Application number: 06/303,988
- Filed: 1981-09-21
- Granted: 1983-08-16
- Earliest claimed: 1980-09-19
- Assignees: Shinryo Air Conditioning Co., Ltd.
- Inventors: Akira Suzuki; Yasumi Shioya; Keiichi Kimura
- Web page: https://patentgrep.com/patent/US4398476A

## CPC

- C02F 11/12: by de-watering, drying or thickening
- C02F 11/10: by pyrolysis
- C02F 11/13: by heating
- F23G 7/001: {for sludges or waste products from water treatment installations (F23G5/008 takes precedence)}
- Y02W 10/40: Valorisation of by-products of wastewater, sewage or sludge processing
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- F23G: CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

A method and an apparatus of incinerating dewatered sludge without using an auxiliary fuel comprising pelletizing the partially dewatered sludge having a water content of 70 to 75%, drying the pellets with a heat source obtained by burning gases formed by dry-distillation and gasification, using part of the resulting dry-distilled gas in said drying step, dry-distilling the pellets by the sensible heat of a gas formed by gasification, gasifying the dry-distillation residues with air, water vapor and the remainder of said dry-distilled gas.

## Claims

### Claim 1

A method of incinerating sewage sludge which comprises the steps of:
(a) pelletizing dewatered sludge having a water content of 70 to 75% which is obtained by dewatering excess sludge from sewage treatment,
(b) drying the pellets with a heat source obtained by burning gases described hereunder which are formed by dry-distillation and gasification,
(c) dry-distilling the pellets by the sensible heat of the gas described hereunder which is formed by gasification,
(d) using part of the resulting dry-distilled gas in said drying step,
(e) burning the remainder of the resulting dry-distilled gas in the presence of air and water vapor,
(f) gasifying the residue from the dry-distillation step with the gas resulting from said burning step,
(g) using the gas resulting from said gasification step in said drying step and said dry-distillation step, and
(h) discharging the residue in the form of ash resulting from said gasification step, to thereby achieve incineration of the dewatered sludge without an auxiliary fuel.

### Claim 2 (depends on 1)

The process of claim 1 in which said pellets are about 1 mm to about 10 mm in size.

### Claim 3 (depends on 1)

The process of claim 1 in which said pellets are cylindrical forms about 5 mm to about 10 mm in diameter and about 10 mm to about 20 mm long.

### Claim 4 (depends on 1)

The process of claim 1 in which said dry-distillation is carried out at a temperature of from about 400.degree. C. to about 600.degree. C.

### Claim 5 (depends on 1)

The process of claim 1 in which said dry-distillation is carried out at about 450.degree. C. for about 20 minutes.