Method and facility for stationary thermal hydrolysis of organic material with total energy recovery

Abstract

Procedure for the thermal hydrolysis of organic matter in steady state, with a double steam explosion and total energy recovery, which consists, as a minimum, of the 1) feeding stage, stepped pressurization and sequential injection of low, medium and high pressure level steam; 2) first stage of hydrolysis by consecutive steam explosion operations with the production of medium pressure level steam and thermal reaction; 3) second stage of hydrolysis consisting of steam explosion and production of low pressure steam. An installation for the implementation of the process, which consists of comprising pumps for stepped pressurization, fluid-steam mixers, valves, mixers, decompression elements, tanks, piping and instrumentation and control systems.

Claims

1. A process for continuous thermal hydrolysis of organic matter comprising: a first stage of a feeding of a first feedstock comprising organic matter mixed with an injection of a low pressure steam having a pressure of between −0.5 barg to 0.5 barg into a first hydrolysis tank; a second stage of a feeding of a second feedstock comprising organic matter mixed with an injection of a high pressure steam having a pressure of between 10 barg to 22 barg into a second hydrolysis tank, wherein a first stage of hydrolysis by a first steam explosion and a first thermal reaction takes place in the second hydrolysis tank resulting in a production of a mix of a third feedstock and a medium pressure steam having a pressure of between 3 barg and 9 barg, wherein further the third feedstock is fed into a third tank, wherein further a second stage of hydrolysis by a second steam explosion takes place in the third hydrolysis tank resulting in a production of the low pressure steam pressure level steam and a stream of hydrolyzed organic matter.

2. The process of claim 1, wherein a first hydrolysis tank effluent exiting from the first hydrolysis tank is circulated by a first pump, wherein further the first hydrolysis tank effluent comprises a temperature of 70° C. to 100° C., wherein a first portion of the first hydrolysis tank effluent is recirculated to a first mixer and a second portion of the first hydrolysis tank effluent is fed to a second mixer, wherein the first portion of the first hydrolysis tank effluent is mixed in the first mixer with the low pressure steam and subsequently fed into the first hydrolysis tank.

3. The process of claim 2, wherein the first pump comprises a non-Newtonian pump, a suspension pump or centrifugal pump.

4. The process of claim 1, wherein the second portion of the first hydrolysis tank effluent is mixed in a second mixer with the medium pressure steam to create the second feedstock, wherein the second feedstock is subsequently fed by a second pump to a third mixer, wherein the second feedstock is mixed in the third mixer with the high pressure steam and subsequently fed into the second hydrolysis tank.

5. The process of claim 4 wherein a temperature of the second feedstock exiting the second mixer does not exceed 170° C.

6. The process of claim 5 wherein the temperature of the second feedstock exiting the second mixer is between 120° C. and 160° C.

7. The process of claim 4 wherein the second feedstock is heated in the third mixer to a temperature between 160° C. and 220° C.

8. The process of claim 7 wherein the second feedstock is heated in the third mixer to a temperature of no more than 220° C. for less than 5 seconds.

9. The process of claim 4, wherein the second pump comprises a non-Newtonian pump, a suspension pump or centrifugal pump.

10. The process of claim 4 wherein the second feedstock that is mixed with the high pressure steam is fed into the second hydrolysis tank through a first decompression element.

11. The process of claim 10 wherein the maximum pressure of an outlet of the first decompression element is 8 barg.

12. The process of claim 10 wherein the second feedstock remains resident in the second hydrolysis tank for a time between 1 minute and 15 minutes.

13. The process of claim 12 wherein the temperature in the second hydrolysis tank is between 140° C. and 180° C.

14. The process of claim 13 wherein the second feedstock subsequently splits in the second hydrolysis tank to form the third feedstock and the medium pressure steam, wherein further the third feedstock has a pressure between 3 barg and 9 barg.

15. The process of claim 14 wherein the third feedstock that is fed into the third tank through a second decompression element.

16. The process of claim 15 wherein the temperature in the third tank is 97° C.

17. The process of claim 16 wherein the third feedstock subsequently splits in the third tank to form the hydrolyzed organic matter and the low pressure steam, wherein further the pressure in the third tank is between −0.5 barg and 0.5 barg.

18. The process according to any one of the preceding claims, wherein the organic matter comprises sewage sludge, domestic waste, industrial waste or combinations thereof.

19. The process according to any of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17, further comprising a pre-treatment for an anaerobic digestion of solids.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a diagram of the installation for the implementation according to the invention.

EXPLANATION OF AN EMBODIMENT

(2) Following FIG. 1 the procedure is described according to the invention claimed and the means used to perform an installation.

(3) The means used are: tanks or deposits (2), (3), (4); mechanical impulsion and fluid pressurization equipment (20), (21); fluid-steam mixers (17), (18), (19); expansion elements (22), (23).

(4) In the selected variant, sewage sludge is hydrolyzed, previously concentrated and at room temperature (5). In the ejector (17), the feed mixture (5) is produced, with low pressure steam (13) and with the recirculation stream (7). The output stream (8) of the ejector is returned to the deposits (2), in order to close a recirculation loop. All low steam (13) condenses in the system. Depending on the design conditions and the recirculation flow rates imposed, the stream (9) exiting the recirculation loop has a temperature between 70 and 100° C. and a pressure with values between 3 and 8 barg.

(5) The stream (9) after the first pressurization and heating stage receives the medium pressure vapor (15) in the mixer (18). According to the energy balances, in the operating conditions the temperature after the incorporation of medium and high-pressure steam streams moves between 120 and 160° C., without reaching the thermal level corresponding to the development of secondary reactions. This fluid (10) is pressurized by the pump (21), reaching pressures between 8 and 20 barg. In the ultra-fast mixer (19) the fluid receives a live steam injection (16) with a pressure between 10 and 22 barg, capable of raising its temperature to 160-220° C.

(6) After this ultra-rapid heating, the high temperature and pressure sludge (11) passes through the decompression element (22) and splits in the tank (3) in a medium pressure steam stream (15) which is conducted to the stage 1 and in a liquid stream (12). The liquid is kept in the tank (3), during a predetermined time, which varies between 1 and 15 minutes. With this sequence the organic matter is first subjected to a steam explosion process and then to a reaction process by thermal process. Consequently, the tank (3) fulfils the double function of flash tank and reactor. In the case described, the temperature inside the tank (3) is maintained at a pre-set and controlled setpoint value between 140 and 180° C.

(7) After remaining in the tank (3) during the pre-set reaction time, the pre-hydrolyzed organic material stream (12), with a pressure between 3 and 9 barg, passes through the decompression element (23) and into the tank (4), which acts as a flash chamber, splits in a low pressure steam stream (13) that is carried to stage 1 and in a stream (24) of hydrolyzed sludge that is brought to digestion. The tank pressure (4) can vary between −0.5 and 0.5 barg. In the variant described and with the ratio of liquid recirculating the pump (20) the pressure in the tank (4) is −0.1 barg and the outlet temperature of the stream (24) is 97° C.