Direct evaporator apparatus and energy recovery system

1. A direct evaporator apparatus for use in an organic Rankine cycle (orc) energy recovery system, comprising:

(a) a housing comprising a heat source gas inlet, and a heat source gas outlet, the housing defining a heat source gas flow path from the inlet to the outlet; and

(b) a heat exchange tube disposed within the heat source flow path, the heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, the heat exchange tube comprising a working fluid inlet and a working fluid outlet;

wherein the direct evaporator apparatus is configured such that at least a portion of a heat source gas having contacted at least a portion of the heat exchange tube is in thermal contact with a heat source gas entering the direct evaporator apparatus via the heat source gas inlet.

2. The direct evaporator apparatus according to claim 1 , configured such that the thermal contact is between the heat source gas exiting the direct evaporator apparatus and the heat source gas entering the direct evaporator apparatus.

3. The direct evaporator apparatus according to claim 1 , configured such that the thermal contact is between the heat source gas within the direct evaporator apparatus and the heat source gas entering the direct evaporator apparatus.

4. The direct evaporator apparatus according to claim 1 , further comprising a baffle and a return loop connecting the heat source gas outlet with the heat source gas inlet.

5. The direct evaporator apparatus according to claim 4 , wherein the baffle is adjustable to control a flow of the heat source gas exiting the direct evaporator apparatus and which passes through the return loop and is brought into thermal contact with the heat source gas entering the direct evaporator apparatus.

6. A direct evaporator apparatus for use in an organic Rankine cycle energy recovery system, comprising:

(a) a housing comprising a heat source gas inlet, and a heat source gas outlet, the housing defining a heat source gas flow path from the inlet to the outlet; and

(b) a heat exchange tube disposed within the heat source flow path, the heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, the heat exchange tube comprising a working fluid inlet and a working fluid outlet;

wherein the heat source gas inlet and the heat source gas outlet are configured such that at least a portion of a heat source gas exiting the heat source gas outlet is in thermal contact with a heat source gas entering the direct evaporator apparatus via the heat source gas inlet.

7. The direct evaporator apparatus according to claim 6 , wherein the heat exchange tube defines three zones, a first zone adjacent to the heat source gas outlet, a second zone adjacent to the heat source gas inlet, and a third zone disposed between the first zone and the second zone, the working fluid inlet being in direct fluid communication with the first zone, and the working fluid outlet being in direct fluid communication with the third zone; and wherein the first zone is not in direct fluid communication with the third zone.

8. The direct evaporator apparatus according to claim 6 , wherein the heat exchange tube is disposed entirely with the heat source gas flow path.

9. The direct evaporator apparatus according to claim 6 , wherein the heat exchange tube defines three zones, a first zone adjacent to the heat source gas outlet, a second zone disposed between the first zone and a third zone, said third zone being adjacent to the heat source gas inlet, the working fluid inlet being in direct fluid communication with the first zone, and the working fluid outlet being in direct fluid communication with the third zone.

10. The direct evaporator apparatus according to claim 6 , configured such that the thermal contact takes place across a barrier.

11. The direct evaporator apparatus according to claim 10 , wherein the barrier is a heat-transmissive barrier.

12. The direct evaporator apparatus according to claim 7 , further comprising a baffle and a return loop connecting the heat source gas outlet with the heat source gas inlet.

13. The direct evaporator apparatus according to claim 12 , wherein the baffle is adjustable to control a flow of the heat source gas exiting the direct evaporator apparatus and which passes through the return loop and is brought into thermal contact with the heat source gas entering the direct evaporator apparatus.

14. An organic Rankine cycle energy recovery system comprising:

(i) a direct evaporator apparatus comprising:

(a) a housing comprising a heat source gas inlet, and a heat source gas outlet, the housing defining a heat source gas flow path from the inlet to the outlet; and

(b) a heat exchange tube disposed within the heat source flow path, the heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, the heat exchange tube comprising a working fluid inlet and a working fluid outlet;

wherein the direct evaporator apparatus is configured such that at least a portion of a heat source gas having contacted at least a portion of the heat exchange tube is in thermal contact with a heat source gas entering the direct evaporator apparatus via the heat source gas inlet;

(ii) a work extraction device;

(iii) a condenser; and

(iv) a pump;

wherein the direct evaporator apparatus, work extraction device, condenser and pump are configured to operate as a closed loop.

15. The energy recovery system according to claim 14 , wherein the work extraction device comprises a turbine.

16. The energy recovery system according to claim 15 , wherein said turbine is configured to produce electrical energy.

17. A method of energy recovery comprising:

(a) introducing a heat source gas having a temperature into a direct evaporator apparatus containing a liquid working fluid;

(b) transferring heat from the heat source gas having a temperature T1 to the working fluid to produce a superheated gaseous working fluid and a heat source gas having temperature T2;

(c) expanding the superheated gaseous working fluid having a temperature T3 through a work extraction device to produce mechanical energy and a gaseous working fluid having a temperature T4;

(d) condensing the gaseous working fluid to provide a liquid state working fluid; and

(e) returning the liquid state working fluid to the direct evaporator apparatus;

wherein steps (a)-(e) are carried out in a closed loop; and

wherein the direct evaporator apparatus comprises (i) a housing comprising a heat source gas inlet, and a heat source gas outlet, the housing defining a heat source gas flow path from the inlet to the outlet; and

(ii) a heat exchange tube disposed within the heat source gas flow path, the heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, the heat exchange tube comprising a working fluid inlet and a working fluid outlet;

wherein the direct evaporator apparatus is configured such that at least a portion of a heat source gas having contacted at least a portion of the heat exchange tube is in thermal contact with a heat source gas entering the direct evaporator apparatus via the heat source gas inlet.

18. The method according to claim 17 , wherein the working fluid is a hydrocarbon.

19. The method according to claim 18 , wherein the working fluid is selected from the group consisting of methylcyclopentane, methylcyclobutane, cyclopentane, isopentane, and cyclohexane.

20. The method according to claim 17 , wherein the temperature of the heat source gas entering the direct evaporator apparatus is in a range from about 350° C. to about 600° C.

21. The method according to claim 17 , wherein the heat source gas is air.

22. The method according to claim 17 , wherein the heat source gas is flue gas.

23. The method according to claim 17 , wherein the heat source gas has a temperature T2 in a range from about 100° C. to about 250° C.

24. The method according to claim 17 , wherein the thermal contact is intimate mixing.