METHOD AND DEVICE FOR THE TREATMENT OF ORGANIC MATTER USING THICKENING AND THERMAL TREATMENT

Abstract

The present invention relates to a method for the treatment of organic matter, in particular sewage sludge, comprising the following steps: The organic matter is first thickened to increase the solids concentration. The thickened organic matter is supplied directly into a digester. The organic matter is then removed from the digester by way of a recirculation line, thermally treated and returned to the digester. The invention further relates to a device for the treatment of organic matter, in particular sewage sludge, comprising a digester, a thickener and a recirculation line, where the thickener is arranged upstream of the digester, and the recirculation line is designed to supply organic matter from the digester directly to the thermal treatment device, and to return the treated organic matter to the digester.

Claims

1. A method for treatment of organic matter, the method comprising: thickening the organic matter to increase solids concentration, directly feeding the thickened organic matter into a digester, removing organic matter from the digester by way of a recirculation line, thermally treating the removed organic matter, and returning the thermally treated organic matter back to the digester.

2. The method according to claim 1 wherein the thermal treatment comprises thermal hydrolysis.

3. The method according to claim 1 wherein the organic matter is during the thermal treatment heated to a temperature in the range of 120° C. to 170° C.

4. The method according to claim 3 wherein the organic matter is during the thermal treatment maintained for 20 to 60 minutes in the temperature range.

5. The method according to claim 1 wherein the organic matter is after completion of the thermal treatment cooled before the thermally treated organic matter is returned to the digester.

6. The method according to claim 1 wherein the organic matter is thickened to a solids concentration in the range from 7% to 20%.

7. The method according to claim 1 wherein the ratio of volume flows of supply to the digester and return via the thermal treatment is in the range from 0.5 to 5.

8. The method according to claim 1 wherein the organic matter is for the thermal treatment introduced by way of the recirculation line directly from the digester into a heat exchanger system.

9. The method according to claim 1 wherein the organic matter comprises sludge from a biological wastewater treatment plant.

10. The method according to claim 1 wherein the thickening is effected by way of addition of polymers to the organic matter, which are at least in part decomposed in the digestion process.

11. The method according to claim 1 wherein the entire thermally treated organic matter is returned into the digester.

12. The method according to claim 1 wherein only a partial flow of the organic matter is removed from the digester by way of the recirculation line.

13. A device for treatment of organic matter, the device comprising: a digester; a thickener arranged upstream of the digester; a thermal treatment device configured to thermally treat the organic matter; and a recirculation line designed to supply organic matter from the digester directly to the thermal treatment device and to return the treated organic matter to the digester.

14. The device according to claim 13, where said wherein the thickener is arranged directly upstream of the digester.

15. The device according to claim 13 wherein the digester comprises an outlet through which digested organic matter is removed.

16. The device according to claim 1 wherein the digester comprises a digestion tower.

17. The device according to claim 13 wherein the thermal treatment device comprises an indirect heat exchanger.

18. The method according to claim 1 wherein the organic matter is thickened to a solids concentration in the range of 10% to 15%.

19. The method according to claim 1 wherein ratio of volume flows of supply to the digester and return via the thermal treatment is in the range of 0.5 to 1.5.

Description

[0039] The invention shall now be explained in more detail with reference to a preferred embodiment:

[0040] FIG. 1 shows a schematic representation of an embodiment of the device according to the invention.

[0041] Organic matter 1 to be treated is in the form of sewage sludge therein first supplied to a thickener 2 in which an increase in the solids concentration to more than 7% and preferably to more than 10% is achieved mechanically and/or by the addition of flocculation aids.

[0042] The thickened organic matter is then supplied directly via a thickened sludge line 3 to a digester 4 in the form of a digestion tower. The organic matter is in digestion tower 4 maintained preferably within a temperature range of between 25° C. and 60° C., more preferably in the mesophilic range between 33° C. and 39° C. This temperature is monitored and controlled by sensors.

[0043] Efficient digestion occurs due to the increased viscosity of the organic matter by the thickening, where it can additionally be optimized with bacteria retention. A recirculation line 5, 6, first section 5 of which leads from a lower region of digestion tower 4 to a thermal treatment device 7 in the form of a disintegration system, is provided in order to nevertheless allow for sufficient intermixing in the digester and furthermore the digestion of the organic matter by way of thermal treatment. Thermal treatment device 7 can be actuated as an actuator for controlling the temperature in the digester. The thermal treatment device can in particular be provided as the sole heat source for controlling the temperature in the digester.

[0044] Thermal disintegration unit 7 is designed as an indirect heat exchanger in which the organic matter is heated to a temperature range of approximately 120° C. to 170° C. The retention time of the organic matter in the disintegration system is between 10 and 60 minutes. A second section 6 of the recirculation line leads from thermal disintegration system 7 back into digestion tower 4. i.e. digested sludge is by way of recirculation line 5, 6 supplied to the thermal disintegration system and again returned to digestion tower 7 after the thermal treatment has been performed.

[0045] A significant reduction in the viscosity of the organic matter can be effected as a result of the thermal treatment, and it is thereby possible to thicken the organic matter in the supply to the digestion tower, i.e. in thickened sludge line 3, not only to a solids concentration of approximately 5% to 7% like in prior art, but to values above 7% and up to 20%. Since the viscosity of the organic matter can be significantly reduced by thermal treatment device 7 provided in the recirculation line, the maximum permissible solids concentration at the inlet of the digestion stage is significantly increased. Given the same solid mass in the supply and the same hydraulic retention time in the digestion, the digestion tower can therefore be selected to be considerably smaller without this having to fear a negative effect on the outcome of the digestion.

[0046] The digested sludge 8 is removed from the digestion tower and supplied to subsequent stages.