Efficient use of adsorbents for indoor air scrubbing

1. A method for reducing the level of at least one pollutant contained in indoor air from a human-occupied, enclosed environment, the method comprising:

providing an air treatment assembly including at least one type of adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow from the enclosed environment during an adsorption phase and regenerating the adsorbent during a regeneration phase upon exposure to a regenerating gas flow;

cycling between the adsorption phase and the regeneration phase,

wherein:

during the adsorption phase, the method comprises streaming the indoor air flow over and/or through the adsorbent in a first direction such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, wherein after being flowed over and/or through the adsorbent, the air flow comprises a scrubbed air flow;

during the regeneration phase, the method comprises streaming the regeneration gas flow over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration gas flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent;

terminating a respective adsorption phase when an adsorption efficiency value is less than or equal to a fraction of an initial adsorption efficiency value of the adsorbent; and

terminating a respective regeneration phase when a regeneration rate is within a predetermined range of a productivity of a complete regeneration phase of the adsorbent.

2. The method of claim 1 where there are at least two adsorbents such that the streaming indoor air flows through a first adsorbent and subsequently through a second adsorbent, and that as a result of the reversal of the flow direction during regeneration, substances purged from the first adsorbent do not flow across the second adsorbent.

3. The method of claim 1 , wherein:

pollutants which are released from the adsorbent during regeneration accumulate in the air treatment assembly or air conduits attached to it, and as a result of the reversal of the flow direction during regeneration, the released pollutants are substantially prevented from accumulating downstream from the adsorbent and accumulate substantially in sections of the air treatment assembly that are upstream from the adsorbent,

the air treatment assembly comprising an inlet for indoor air flowing through the adsorbent; and

upstream the adsorbent being in greater proximity to the inlet than downstream the adsorbent.

4. The method of claim 1 , wherein the pollutant is selected from the group consisting of: carbon dioxide, volatile organic compounds, sulfur oxides, radon, nitrous oxides and carbon monoxide.

5. The method of claim 1 , wherein the adsorbent comprises at least one of an amine supported by a solid, activated carbon, clay, carbon fibers, silica, alumina, zeolites, molecular sieves, titanium oxide, polymer, porous polymers, polymer fibers and metal organic framework.

6. The method of claim 5 , wherein the supporting solid is at least one of silica, carbon, clay or metal oxide.

7. The method of claim 1 , wherein the adsorbent comprises granular solids or pelleted shaped solids.

8. A system for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the system comprising:

an air treatment assembly including an adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow during an adsorption phase and regenerating the adsorbent during a regeneration phase upon exposure to a regenerating gas flow; and

a controller for cycling between the adsorption phase and the regeneration phase;

streaming means for:

streaming the indoor air flow over and/or through the adsorbent in a first direction during a respective adsorption phase, such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, and

streaming the regeneration air flow over and/or through the adsorbent in a second direction opposite to the first direction during a respective adsorption phase, such that the regeneration gas flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent,

wherein the controller is configured such that:

a respective adsorption phase is terminated when an adsorption efficiency value is less than or equal to a fraction of an initial adsorption efficiency value; and

a respective regeneration phase is terminated when a regeneration rate that is within a predetermined range of a productivity of a complete regeneration phase of the adsorbent.

9. A method for reducing the level of at least one pollutant contained in indoor air from an enclosed, human-occupied environment, the method comprising:

providing an air treatment assembly including an adsorbent, the adsorbent configured for capturing at least one pollutant entrained in an indoor air flow from the enclosed environment and regenerating upon exposure to a regenerating gas flow;

streaming the indoor air flow over and/or through the adsorbent in a first direction such that the adsorbent captures at least some of the at least one pollutant from the indoor air flow, wherein the streaming of the indoor air flow over and/or through the adsorbent comprises an adsorption phase; and

streaming the regeneration gas flow over and/or through the adsorbent in a second direction opposite to the first direction, such that the regeneration air flow regenerates at least some of the adsorbent and purges at least some of the at least one pollutant from the adsorbent, wherein the streaming of the regeneration gas flow over and/or through the adsorbent comprises a regeneration phase,

cycling between the adsorption phase and the regeneration phase, wherein

one cycle comprises an adsorption phase followed by a regeneration phase, one cycle period comprises the total time elapsed during one cycle;

the at least one pollutant purged from the adsorbent is carried away by the regeneration gas flow, and

a complete regeneration phase comprises a first time period for removing substantially all of the at least one pollutant from the adsorbent during the regeneration phase, and

and

a complete adsorption phase comprises a second time period for substantially saturating all the adsorbent during the adsorption; and

limiting at least one of:

the duration of the first time period to a period of time which is less than the complete adsorption phase, and

the duration of the second time period to a period of time which is less than the complete regeneration phase.

10. The method of claim 9 , wherein prior to streaming the regeneration gas flow the method further includes determining a level of an adsorption efficiency, wherein the adsorption efficiency at any point in time during the one cycle has a value of 1−Cin/Cout, wherein Cin is the concentration of the pollutant in the incoming air flow and Cout is the concentration of the pollutant in an outgoing air flow, and wherein an initial adsorption efficiency value is the adsorption efficiency value at the beginning of the adsorption phase, wherein when the adsorption efficiency value is less than the initial adsorption efficiency value, streaming of the regeneration gas flow over and/or through the adsorbent is performed.

11. The method of claim 10 , wherein the adsorption efficiency value is at least about 20% less than the initial adsorption efficiency value.

12. The method of claim 10 , wherein the adsorption efficiency value is at least about 30% less than the initial adsorption efficiency value.

13. The method of claim 10 , wherein the adsorption efficiency value is at least about 50% less than the initial adsorption efficiency value.

14. The method of claim 10 , wherein the adsorption efficiency value is at least about 80% less than the initial adsorption efficiency value.