Solid waste treatment with conversion to gas and anaerobic digestion

• US 9,868,964 B2
• Filed: 02/04/2016
• Issued: 01/16/2018
• Est. Priority Date: 02/06/2015
• Status: Active Grant

• Current Assignee: Anaergia Inc.
• Original Assignee: Anaergia Inc.
• Inventors: Josse, Juan Carlos, Scherson, Yaniv D.
• Primary Examiner(s): Prince, Fred
• Application Number:
  US15/015,479
• Publication Number:
  US 20160230193A1
• Time in Patent Office: 712 Days
• Field of Search: 210603, 210609
• CPC Class Codes: B01F 23/20 Mixing gases with liquids
• CPC Class Codes: B01L 3/56 Labware specially adapted for transferring fluids
• CPC Class Codes: C02F 11/04 Anaerobic treatment; Production of methane by such processes
• CPC Class Codes: C02F 11/10 by pyrolysis
• CPC Class Codes: C02F 11/12 by de-watering, drying or thickening
• CPC Class Codes: C02F 11/13 by heating
• CPC Class Codes: C02F 2303/06 Sludge reduction, e.g. by lysis
• CPC Class Codes: C02F 9/00 Multistage treatment of water, waste water or sewage
• CPC Class Codes: C12P 5/023 Methane
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

Waste solids are treated by pyrolysis at a temperature over 700 degrees C. to produce char and a gas. The gas is treated in an anaerobic digester. In one system, gas and digestate are brought into contact in a diffusion cone. In another option, headspace gas above the digestate is re-circulated through the digestate, for example by way of an eductor downstream of the diffusion cone.

Claims

1. A process comprising steps of,

a) producing a gas containing hydrogen and carbon monoxide from pyrolysis of a feedstock at a temperature of over 750 degrees C.;

and,

b) adding the gas to an anaerobic digester,

wherein the feedstock comprises plastic.

2. The process of claim 1 wherein the feedstock comprises a mixture of biogenic and non-biogenic material.

3. The process of claim 1 wherein the anaerobic digester is coupled with or part of a municipal wastewater treatment plant.

4. The process of claim 1 comprising producing a gas containing hydrogen and carbon monoxide from pyrolysis of a feedstock at a temperature of 800 degrees C. or more.

5. An apparatus for transferring syngas to digestate comprising a diffusion cone in a sidestream loop wherein the diffusion cone defines an outer surface of part of the sidestream loop with a downwardly increasing cross sectional area.

6. The apparatus of claim 5 having an eductor in the sidestream loop downstream of the diffusion cone and connected to a headspace of the digester.

7. A process for treating wastewater comprising,

a) treating the wastewater to generate a sludge;

b) feeding the sludge to an anaerobic digester to produce biogas and digestate;

c) dewatering the digestate to produce a cake;

d) thermally drying the cake to produce a dried cake;

e) pyrolysing the dried cake at a temperature of over 700 degrees C. or more to produce char and syngas;

f) feeding the syngas to the anaerobic digester;

g) monitoring one or more indicators of carbon monoxide inhibition in the anaerobic digester.

8. The process of claim 7 comprising pyrolysing the dried cake at a temperature of over 800 degrees C. or more.