Gas separation: processes – With control responsive to sensed condition – Pressure sensed
Reexamination Certificate
2002-01-18
2003-08-12
Smith, Duane (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Pressure sensed
C095S139000, C095S148000, C454S229000
Reexamination Certificate
active
06605132
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
This invention relates to a system for treating air for supply to an enclosed space in which it is to be breathed.
2. The Relevant Technology
It can be desirable to treat air that is to be breathed to remove contaminants and also to provide a suitable proportion of the individual components of an air mixture (oxygen, carbon dioxide, nitrogen etc). Contaminants that are to be removed might be solid (in particulate form), liquid (in aerosol form) or gaseous. The enclosed space in which the treated air is to be breathed might be a building or a vehicle. An example of an application for the system of the invention might be for example in an agricultural vehicle which can be exposed to an environment containing particulate and liquid or gaseous materials which preferably the driver of the vehicle should not be exposed to.
It is known to remove contaminants from a gas using regenerative adsorption apparatus. Such apparatus comprises at least two chambers, each containing a quantity of an adsorbent material. The gas is directed to flow through one of the chambers so that it can be treated while the adsorbent material in the other chamber is regenerated by displacement from it of the contaminant material which has previously been adsorbed while pressure in that chamber is reduced. The adsorbed component can be displaced by means of a purge stream of gas which might be taken from the outlet stream from the chamber in which adsorption is taking place. The regeneration of the adsorbent material can involve changes in one or both of the pressure and temperature in the chamber, especially a reduction in the pressure in the chamber and an increase in the temperature.
It is a disadvantage of known regenerative adsorption assemblies that large chambers can be required in order to provide sufficient adsorbent material to treat enough air adequately for it to be breathed, especially when the contaminants in the air only bond loosely to the adsorbent material
BRIEF SUMMARY OF THE INVENTION
According to the present invention, a system for treating air for supply to an enclosed space includes a regenerative adsorption assembly and a recirculation path for supplying breathed air from the enclosed space to be mixed with air from atmosphere before it is supplied to the enclosed space
Accordingly, in one aspect, the invention provides a system for treating air for supply to an enclosed space in which it is to be breathed, which comprises:
a. an inlet through which air can enter the system from atmosphere for supply to the enclosed space;
b. a regenerative adsorption assembly comprising at least two chambers which contain an adsorbent material, arranged so that air flowing in the inlet for supply to the enclosed space can pass through one of the chambers for adsorption of contaminants before supply to the enclosed space while adsorbent material in another of the chambers is purged of adsorbed contaminants;
c. a recirculation path for supplying air from the enclosed space to the inlet to be mixed with air from atmosphere before it is supplied to the enclosed space; and
d. means for adjusting the resistance to flow of air through the recirculation path according to the resistance that is provided to the flow of air from atmosphere into the enclosed space.
The system of the invention has the advantage that the load on the adsorbent material from contaminants in air which enters the system from the atmosphere is reduced so that adequate adsorption of the contaminants in air is possible with chambers for the adsorbent material in the pressure swing adsorption assembly which are smaller than are required conventionally without the recirculation path feature of the system.
The provision of means for adjusting the resistance to flow of gas through the recirculation path can ensure that the recirculated air and atmospheric air can be mixed in a desired ratio by allowing increased flow of recirculated air when the resistance to flow of atmospheric air is increased. Such an increase in the resistance to flow of atmospheric air can result from an increase in the air flow that is admitted to the enclosed space through one of the chambers which contain adsorbent material.
The resistance to flow of gas through the recirculation path can be adjusted by means of a variable flow restrictor. Such a component can be driven by an electrical motor in response to signals from control components. Preferably, however, the flow resistance is varied by provision of two or more recirculation paths which present different resistances to flow of gas through them, the system including means for changing the recirculation path through which the recirculated gas flows. For example, the system can provide two recirculation paths. One of them can provide little or no resistance to flow of air for use when air flows directly into the enclosed space and does not pass through the adsorption assembly. The other recirculation path provides greater resistance to flow of air for use when air flows into the enclosed space after flowing through the adsorption assembly. The selection of the recirculation path for the air can be made using appropriate valves which can be controlled by signals from control components.
In another aspect, the invention provides a method of treating air for supply to an enclosed space in which it is to be breathed, which comprises:
a. admitting air to an air treatment system from atmosphere;
b. mixing the air from atmosphere with recirculated air from the enclosed space;
c. passing the mixture through a chamber of a regenerative adsorption assembly comprising at least two such chambers, each containing an adsorbent material for adsorption of contaminants; and
d. supplying the air from the chamber after it has passed over the adsorbent material to the enclosed space.
Preferably, the system includes means for adjusting the relative proportions of the air from atmosphere and the air that is recirculated from the enclosed space that are mixed before supply to the enclosed space. This allows the extent of the treatment of the air that is supplied to the enclosed space to be adjusted according to the amount of contamination that is in the atmospheric air. For example, atmospheric air that is relatively clean and which only requires moderate treatment (if any) can be supplied to the enclosed space with little or no recirculated air. When the atmospheric air contains significant quantities of contaminant material, it will be supplied to the enclosed space with relatively more recirculated air, for example, so that the air that is supplied to the enclosed space comprises at least 40% recirculated air, and possibly at least 50% or at least 60% or more. The availability of recirculated air means that the load placed on the adsorbent material in the chambers need not become too high, even when atmospheric air contains high concentrations of contaminant material.
The means for adjusting the relative proportions of atmospheric and recirculated air can comprise a valve. The valve preferably provides constrictions against flow of the air from atmosphere and of the recirculated air, with the size of the at least one of the constrictions being variable. The valve makes it possible for the air from atmosphere and from the enclosed space to mix, notwithstanding the possibility that the air in the enclosed space is at a higher pressure than the air from atmosphere. Preferably, the valve considered as a whole amounts to a 3:2 valve with two inlet ports for the atmospheric and recirculated air, and an outlet port for the mixed air. Preferably, the valve is capable of closing completely the path for air to flow from atmosphere directly into the enclosed space, for example, in the event that there is an unexpected drop in air pressure within the enclosed space so that the pressure there is less than atmospheric pressure.
Preferably, the system includes a by-pass line for air from atmosphere to flow past the regenerative adsorption assembly when the air from atmosphere contains little
Domnick Hunter Limited
Lawrence Frank M.
Smith Duane
Workman & Nydegger & Seeley
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