Humidification-dehumidification systems and methods at low top brine temperatures
Embodiments described generally relate to systems comprising a humidifier (e.g., a bubble column humidifier) and a heating device (e.g. a heat exchanger), and associated methods. In certain embodiments, the heating device heats a first liquid stream comprising a condensable fluid in liquid phase (e.g., water) and a dissolved salt (e.g., NaCl) to a relatively low temperature (e.g., about 90° C. or less) prior to the first liquid stream entering the humidifier through a main humidifier liquid inlet. In some cases, the system comprising the humidifier and the heating device requires only low-grade heat to operate, which may be advantageous due to the low cost and high availability of such heat.
1. A method of operating a humidifier, comprising:
flowing a first liquid stream comprising a condensable fluid in liquid phase and a dissolved salt through a first fluidic pathway of a first heating device, wherein the first liquid stream is heated within the first heating device to form a heated first liquid stream;
injecting the heated first liquid stream into a main liquid inlet of a humidifier comprising a plurality of stages, wherein the plurality of stages comprises a first stage, a last stage, and one or more intermediate stages positioned between the first stage and the last stage;
injecting a gas stream comprising a non-condensable gas into a main gas inlet of the humidifier;
flowing the heated first liquid stream through the humidifier in a first direction from the first stage to the last stage and simultaneously flowing the gas stream through the humidifier in a second direction from the last stage to the first stage, wherein heat and mass are transferred from the heated first liquid stream to the gas stream to produce a vapor-containing humidifier gas outlet stream and a concentrated liquid stream; and
flowing an extracted liquid stream comprising at least a portion of the concentrated liquid stream from an intermediate liquid outlet of the humidifier to the first heating device, wherein the intermediate liquid outlet of the humidifier is a liquid outlet of the first stage or one of the one or more intermediate stages of the humidifier;
wherein the method further comprises flowing the first liquid stream through a second heating device.
2. The method according to claim 1 , wherein the temperature of the heated first liquid stream at the main liquid inlet of the humidifier is about 90° C. or less.
3. The method according to claim 1 , wherein a flow rate of the extracted liquid stream at the intermediate liquid outlet of the humidifier is about 5% to about 50% of a flow rate of the concentrated liquid stream at a main liquid outlet of the humidifier.
4. The method according to claim 1 , wherein a flow rate of the extracted liquid stream at the intermediate liquid outlet of the humidifier is about 105% to about 150% of a flow rate of the concentrated liquid stream at a main liquid outlet of the humidifier.
5. The method according to claim 1 , wherein the humidifier is a bubble column humidifier.
6. The method according to claim 1 , wherein at least one stage of the plurality of stages of the humidifier comprises a bubble generator.
7. The method according to claim 6 , wherein the bubble generator comprises a sparger plate comprising a plurality of holes.
8. The method according to claim 1 , wherein at least one stage of the plurality of stages of the humidifier comprises a liquid layer comprising an amount of the heated first liquid stream and a vapor distribution region positioned adjacent the liquid layer.
9. The method according to claim 1 , further comprising flowing the vapor-containing humidifier gas outlet stream from a main gas outlet of the humidifier to a main gas inlet of a dehumidifier configured to remove at least a portion of the condensable fluid in vapor phase from the vapor-containing humidifier gas outlet stream to produce a dehumidifier liquid outlet stream and a dehumidifier gas outlet stream.
10. The method according to claim 9 , wherein the dehumidifier is a bubble column condenser.
11. The method according to claim 1 , wherein the first heating device is a first heat exchanger, a heat collection device, an electric heater, or a furnace.
12. The method according to claim 11 , further comprising flowing a heating fluid stream through a second fluidic pathway of the first heating device.
13. The method according to claim 1 , wherein:
the first heating device is a first heat exchanger,
the second heating device is a second heat exchanger, and
flowing the first liquid stream through the second heating device comprises flowing the first liquid stream through a first fluidic pathway of the second heat exchanger, and simultaneously flowing the dehumidifier liquid outlet stream through a second fluidic pathway of the second heat exchanger, such that heat is transferred from the dehumidifier liquid outlet stream to the first liquid stream to form a pre-heated first liquid stream.
14. The method according to claim 13 , further comprising flowing the pre-heated first liquid stream to the first heating device to form the heated first liquid stream.
15. The method according to claim 1 , further comprising flowing the heated first liquid stream to an intermediate humidifier liquid inlet, wherein the intermediate humidifier liquid inlet is a liquid inlet of the last stage or one of the one or more intermediate stages of the humidifier.
16. The method according to claim 1 , further comprising flowing the extracted liquid stream from the intermediate liquid outlet of the humidifier to a first tank prior to flowing the extracted liquid stream to the first heating device.
17. The method according to claim 1 , wherein the condensable fluid is water.
18. The method according to claim 1 , wherein the dissolved salt comprises NaCl.
19. A method of operating a humidifier, comprising:
flowing a first liquid stream comprising a condensable fluid in liquid phase and a dissolved salt through a first fluidic pathway of a first heating device, wherein the first liquid stream is heated within the first heating device to form a heated first liquid stream;
injecting the heated first liquid stream into a main liquid inlet of a humidifier comprising a plurality of stages, wherein the plurality of stages comprises a first stage, a last stage, and one or more intermediate stages positioned between the first stage and the last stage;
injecting a gas stream comprising a non-condensable gas into a main gas inlet of the humidifier;
flowing the heated first liquid stream through the humidifier in a first direction from the first stage to the last stage and simultaneously flowing the gas stream through the humidifier in a second direction from the last stage to the first stage, wherein heat and mass are transferred from the heated first liquid stream to the gas stream to produce a vapor-containing humidifier gas outlet stream and a concentrated liquid stream;
flowing an extracted liquid stream comprising at least a portion of the concentrated liquid stream from an intermediate liquid outlet of the humidifier to a first tank; and
after flowing the extracted liquid stream to the first tank, flowing the extracted liquid stream to the first heating device,
wherein the intermediate liquid outlet of the humidifier is a liquid outlet of the first stage or one of the one or more intermediate stages of the humidifier.
20. The method according to claim 19 , wherein the temperature of the heated first liquid stream at the main liquid inlet of the humidifier is about 90° C. or less.