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System and method to vaporize liquefied gases for delivery

IP.com Disclosure Number: IPCOM000028132D
Publication Date: 2004-Apr-27

Publishing Venue

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System and Method to Vaporize Liquefied

Gases for Delivery

Summary:

                    Provided is a novel system and method to vaporize liquefied gases and deliver the gases to point-of-use.  The system includes a liquefied gas reservoir, a heat exchanger, a vapor distributor, and related liquid and gas conduit and control devices.  Liquid from the liquefied gas reservoir flows under the gravitation and itself vapor pressure to the heat exchanger to be vaporized; the vapor flows through a vapor conduit back to the reservoir and out the vapor distributor to bubble through the liquid body inside the reservoir; gas is delivered from the vapor space inside the reservoir to point-of-use through a plurality of conduits.  Heat and mass exchanges between vapor and liquid phases during the vaporized gas bubbling through the liquid prevent from temperature and pressure fluctuation of gases for delivery and also condense any vaporized impurities to ensure the purity of gases.

           

BACKGROUND:

            The present invention relates to a system and method to vaporize liquefied gases for delivery.  In particular, the invention provides a system and method to vaporize liquefied gases at controlled rate for continuously delivering gases to point-of-use.

            In many applications, gases are stored in liquid form under their vapor pressure.  Upon the demand for gas in its utilization, gas is withdrawn from the upper region of the liquefied gas vessel.  The liquefied gas must absorb heat energy to sustain the gas withdrawal.  The heat energy needed for the liquid vaporization varies from gas to gas as listed in table 1.  For example, to vaporize 1 kilogram of ammonium (NH3) liquid at 20 oC needs 1163 kjoule energy, and to vaporize the same amount of sulfur hexafluride (SF6) at 20 oC needs only 67 kjoule.

There are different approaches to supply heat to liquefied gases for vaporization.  In the US patent 6,363,728 , an heating device is installed outside of gas vessel to heat the liquefied gas to produce vapor.  With a pressure monitory sensor and a PLC control device, gas pressure and vaporization can be automatically controlled and the gas supplying pressure can be maintained to some satisfactory.  Gas is supplied to users from the vapor section inside vessel.  In the operation, however, one may find that the heating device may not provide the heat to the liquid effectively.  The necessary heat exchanger surface area will change as the liquid level changes inside the vessel.  When the liquid level becomes low, the contact area between liquid and the wall of vessel is too small for liquid to receive sufficient heat energy for vaporization.  Also, The heating device is rather expensive.

In another method as stated in US patent 6,474,077, the liquefied gas cylinder is heated wi...