Apparatus and method to intermittently manufacture and dispense nitrogen gas

The invention produces essentially pure nitrogen from air by an intermittent, automatic, and unattended process. Air is filtered, compressed and enters a nitrogen module containing a permeable membrane that selectively separates nitrogen from the air and discharges oxygen and other gases. Automated temperature and pressure controls allow the permeable membrane to separate air components. A discharge hose allows use of the nitrogen product for a variety of intermittent applications including vending for inflation of tires, filling portable nitrogen vessels, and use in manufacturing processes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is generally directed to an improved apparatus and 
method for intermittent manufacturing nitrogen gas, separated from air, 
using a permeable membrane in an automatic and unattended process. 
Particularly, the improved method and apparatus eliminates a need for a 
nitrogen storage vessel and incorporates improved methods of maintaining 
membrane temperature while preventing moisture in air from forming liquid 
water that affects the air separation process. For very high purity 
nitrogen from the intermittent operation, an optional brief purge start-up 
period improves the purity. The nitrogen may be used in product 
manufacturing processes, inflating tires, vending to customers for tire 
inflation, filling portable nitrogen vessels, and other applications by 
people needing nitrogen. 
2. Description of the Prior Art 
Nitrogen manufacture from air by separating the oxygen and nitrogen has 
been accomplished by selective absorbent materials, distillation of liquid 
air, and membrane separation. These processes produce nitrogen for 
industrial uses such as chemical manufacture, inert gas welding, purging 
of explosive environments prior to electric arc cutting or welding, and 
food preservation. Also these processes are mostly continuous nitrogen 
production to the industrial process or to continually fill large storage 
containers. U.S. Pat. Nos. 5,302,189; 5,004,482; 4,810,265; 4,348,213; and 
3,140,931 describe these manufacturing processes and industrial uses. The 
absorbent materials, although efficient, require regeneration of absorbent 
materials. 
U.S. Pat. No. 5,388,413 describes a portable nitrogen source for 
continuously producing nitrogen at various sites with flow rates 
controlled by restrictor assembly (item 60, col. 3 line 67) adjusted 
manually to control operation. This patent uses a membrane for gas 
separation with air cooling and then air heating to provide proper 
temperatures to control the membrane temperature for gas separation. 
Although these provisions may be sufficient for continuous generation of 
nitrogen gas, the patent is not adequate to provide proper separation on 
start up or intermittent operation. Pressure controls are manually 
adjusted and temperatures are inadequate for proper gas separation until 
steady state production of nitrogen occurs. For intermittent and 
unattended production, immediate separation of nitrogen from air is needed 
when starting or oxygen will dilute the nitrogen. The prior art processes 
also require operators to produce the nitrogen gas. 
U.S. Pat. Nos. 4,452,341; 4,289,225; 4,236,622; 3,208,574; and 1,427,529 
relate to the intermittent supply of air. These patents supply air for 
inflating tires. 
Publications such as Goodyear Application Bulletin no. 17 (09-85), Longer 
Tires, (01-95) describe the advantages of using nitrogen rather than air 
for safety, longer life, and therefore less cost. However, there is no 
system found in the prior art that provides compact, intermittent, and 
automatic production of essentially pure nitrogen for manufacturing, 
consumers, or tire inflation. Recently, improvements in permeable membrane 
designs permit improved nitrogen separation capacities that eliminates the 
need for nitrogen storage vessels in the invention. 
SUMMARY OF THE INVENTION 
The invention produces essentially pure nitrogen gas from air by an 
intermittent, automatic, and unattended process. Air is first filtered, 
compressed, and may be dehydrated or heated to prevent moisture 
condensation during the separation process. The air then enters a nitrogen 
module containing a permeable membrane that selectively separates nitrogen 
from the air and discharges oxygen and other gases. A discharge hose 
allows use of the nitrogen product for a variety of intermittent 
applications including inflation of tires, packaging of items in an inert 
atmosphere, making special mixtures of air with nitrogen, and allowing 
filling of portable vessels for use at other sites. 
The membrane requires temperature control for ideal separation. The 
continuous temperature control of the module allows instantaneous and 
intermittent separation of the air's gaseous components through the 
permeable membrane. Heating the air and the module also prevents formation 
of moisture, or freezing of any moisture that may condense from the air. 
For proper separation of nitrogen from air, both air and nitrogen 
pressures must also be controlled. The combined pressure and temperature 
control at all times permits intermittent, immediate, and unattended 
manufacturing of nitrogen gas for consumer use or vending. A signal means 
for sensing a need to manufacture nitrogen from air automatically starts, 
produces, and ejects a desired amount of nitrogen gas. 
A means for vending an amount of nitrogen for personal use may be added to 
the apparatus. 
Accordingly, an object of the invention is to provide an apparatus and 
method for producing nitrogen from air by intermittent and immediate 
manufacturing, using a permeable membrane in an automatic and unattended 
process. 
Another object of the invention is to eliminate the possibility of liquid 
water forming on the permeable membrane by moisture removal from air or 
air and/or heating apparatus components. 
Another object of the invention is to provide an automatic means for 
maintaining proper pressures and temperatures during the nitrogen gas 
manufacturing operation and standby readiness. 
Another object of the invention is to provide a means for vending of 
nitrogen to consumers for inflating tires and filling portable vessels. 
Another object of the invention is to provide an automatic means for 
intermittent nitrogen supply for manufacturing processes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention method and apparatus shown in FIG. 1 includes an air 
compressor 20, preferably an oilless and reciprocating type, having an 
integral or attached electric motor 21 drawing atmospheric air 10 through 
a filter 22. If an oil type compressor is used, the filter should be 
downstream of the compressor to remove any contamination. The compressor 
is sized to produce the correct amount of air flow and to deliver desired 
nitrogen product quantities at a pressure required to separate nitrogen 
from air. The compressed air flows through conduit 23, constructed from 
plastic and/or metal tubing or pipe, either rigid or flexible, to an 
optional means for separating excessive moisture from the air 24. This 
moisture separating means includes a coalescing filter or similar device 
that removes the moisture with a means for draining liquid water 25. 
Moisture may also be removed from air by inducing centrifugal flow, 
selective absorbent or adsorbent, selective membrane separation, or other 
devices. In a coalescing filter moisture and other particles coalesce on a 
filter and fall to the coalescing filter bottom. The means for liquid 
water purging may be manual or preferably accomplished with an automatic 
valve 25 automatically activated by the intermittent cycles of operation 
or other time related device. 
The compressed air then enters a permeable membrane module 27. This module 
comprises a membrane means 28 for essentially separating nitrogen from 
other air components 29. The membrane means for separating may be arranged 
singularly, parallel, or series constructed in hollow fiber form, or in 
spiral wound, pleated sheet or in any other desired configuration. The air 
enters the module and oxygen, carbon dioxide, moisture and other gases 29 
pass through the membrane means for separating and are purged from the 
container while the nitrogen 30, enriches to desired purity by the removal 
of other air components, flows out of the module through a conduit 23. The 
materials used in the construction of membranes are described in U.S. Pat. 
No. 5,388,413. A manufacturer of the membrane is Medal.sub..TM. in 
Newport, Del. For larger production capacities of nitrogen, a plurality of 
modules 27 may be added in parallel. For increased nitrogen purity, the 
modules may be added in series. 
The separation process of nitrogen from air may be affected by the 
formation of liquid water on the membrane, the temperature of the 
membrane, and the pressure differential across the membrane means 28 for 
separating nitrogen from air. One method to lessen water formation is a 
means 24 for removing water. The water formation possibility may also be 
reduced by a means for controlling temperature in the module that includes 
heating the air prior to entrance into the compressor as explained below, 
using heaters such as electrical resistance conductive heaters 33, radiant 
heaters, or convection heaters, controlled by thermostats and positioned 
to heat the air in the apparatus and/or the module containing the 
permeable membrane. Heating the air in the conduit and the module by an 
electric resistance heater as shown in FIG. 1 is preferred. In warm 
environments, the heat necessary for apparatus operation may be provided 
by the environment surrounding the apparatus that warms the air and the 
module to the proper temperatures. Freezing temperatures of water are 
destructive to the apparatus operation. 
An automatic back pressure control valve or a safety valve 26 is used to 
prevent over pressure of the system including the permeable membrane in 
the permeable membrane module. A valve setting in the range of 150 psig 
pressure is preferred although other pressures may also be set. 
The nitrogen gas flows from the module through conduit 23 to a check valve 
34 and to a means for automatic controlling nitrogen pressure in the 
module such as a back pressure valve 31. The purity of the nitrogen gas 
depends upon the pressures and temperature maintained in the module. 
Preferably, a back pressure valve that automatically controls the module 
pressure is recommended. However orifices, venturi restrictions, flow 
control valves, or other automatic means for controlling pressure may also 
be used. The back pressure controls the differential pressure between the 
nitrogen side and the exhaust gas side of the permeable membrane and the 
dwell time of the gas stream within the permeable membrane module 27. For 
example, a back pressure setting of 90 psig results in about 20 standard 
cubic feet of nitrogen gas per hour having a purity of 98%-99%. For this 
gas production rate, the compressor 20 is sized to be 21/2 times larger 
capacity. 
Nitrogen from the means for controlling back pressure flows through conduit 
23 to a means for controlling and dispensing nitrogen 32. The means may 
include a solenoid or other automatic valve 35 and/or a manual operated 
valve 36. The means for controlling the module pressure may be located in 
the means for dispensing nitrogen. The combination of an automatic valve 
and a manual valve may be a control use in vending applications. A flow 
meter 46 may be added to indicate, control, or record the amount of 
nitrogen flow. A factory needing intermittent and automatic production of 
nitrogen could elect to use only an automatic valve or only a manual valve 
for a means for dispensing nitrogen. For tire inflation, filling portable 
vessels, or other uses, the means for dispensing nitrogen could include 
flexible hoses 23 and an air chuck 38. 
A means for controlling and dispensing nitrogen 32 includes the operation 
of the electrical dispensing amounts and other components of the apparatus 
43 attached to the apparatus. This means is designed to initiate the 
compressor on demand and any appropriate controls to produce a desired 
amount of nitrogen gas. The indication and control parameters in this 
means may include temperatures, pressures, valve positions, flow 
indicators or recorders, compressor power, timing devices, electrical 
power, and gas analyzers. Appropriate controls include compressor 
operation, discharge pressure, flow valves, and/or timing devices for 
these controls to allow determined amounts of nitrogen to be vended. One 
method would be a timing device to power the compressor until a determined 
amount of nitrogen gas is produced. 
A means for vending nitrogen gas 44 allows customers to financially 
activate the invention apparatus to obtain a desired amount of nitrogen 
gas. The means for vending nitrogen gas includes activation by bills, 
coins, tokens, credit cards and codes such as numbers and or letters 45, 
to authorize the means to produce nitrogen gas. This device may be made 
tamper proof as described in prior art or other means. For applications 
where very pure nitrogen is needed, a means for venting the module, 
including vent 25 to bleed air from the module to atmosphere during 
starting for a few seconds until the module operating pressure is achieved 
may be added. This vent may be automated for a few seconds purge 
(depending upon the compressor size) and may increase purity about 1% of 
average amount for tire inflation. The means for venting may be achieved 
by opening the means for dispensing nitrogen to atmosphere for about 4 
seconds before use. 
FIG. 2 is perspective pictorial view of the apparatus with the means for 
enclosing, partially removed, to show one of the many possible enclosure 
methods of the apparatus. An upper compartment encloses some of the 
apparatus as shown. The apparatus components are identified identically to 
FIG. 1. 
The optional means for enclosing the apparatus 39 prevents tampering, 
allows access for maintenance, and aids in providing a temperature 
controlled environment. The enclosure is preferably constructed from metal 
surrounding the entire apparatus. The metals include aluminum, steel, and 
alloys of metals. Thermosetting plastics such as polyesters, nylons with 
or without reinforcing fibers may also be used. Some thermoplastic 
materials such as polypropylene, ABS, and PVC or other plastics with or 
without reinforcing may also be used. Where vandalism is not a problem, 
other materials such as wood may be used. The means for enclosing the 
apparatus may have compartments for various parts of the apparatus. 
Providing a constant warm temperature of about 110.degree. F. for the air 
and the permeable membrane module permits intermittent use with immediate 
production of nitrogen. Lower temperatures may also be possible. If the 
means for enclosing the apparatus 39 is used, the means for providing 
temperature control preferably uses electrical resistant heaters 40, 
thermostats 41, and insulation 42. Heat produced by the air compressor 
also aids in controlling the temperature of the nitrogen and components in 
the enclosure means. The inner surface of the means for enclosing the 
apparatus is insulated and the volume surrounding the apparatus is heated. 
The means for providing temperature control includes insulation made from 
inorganic materials including fiberglass and other fibers, organic 
materials including plastic foams, and wood products. Polyurethane foams 
and polystyrene foams are possible plastic foams. Biodegradable insulation 
may also be used. Plastic sheeting or layers are also included as 
insulation possibilities. A volume containing a vacuum may also provide 
the desired insulation. 
A plurality of modules having a membrane for separating nitrogen gas from 
air may be added in parallel to increase nitrogen manufacturing quantities 
or in series to increase nitrogen purity. 
From the above description of the invention, various changes and 
modifications to the apparatus will occur to those skilled in the art. All 
such modifications coming from within the scope of the appended claims are 
intended to be included therein.