Patent Application
20050284538
The present invention relates to design and construction of a liquefied gas-carrying adaptation of the principle mode and mechanism of an in prior art disclosed “Bulk Material Conveyor”, U.S. Pat. No. 4,024,947. More specifically it relates to container design, method of filling, emptying and transporting liquefied gas (LNG) safely and without undue re-gasification or boil-off loss in transit. Furthermore, container design and attached piping feature recovery and recycling of in transit re-gasified fluid and other emitted gas.
In general, a liquefaction plant liquefies gas by cooling it to below −260° F. (−160° C.). Elongated containers are then dynamically filled with LNG while in side-by-side upright position, similar to filling bottles by conventional bottling machines. Thereafter, containers are sealed, rotated into horizontal end-to-end position and rapidly transported by the conveyor to their destination where they are returned into the same side-by-side upright position and siphoned empty. Any in transit re-gasified LNG, which may occur during extended conveyor stoppage, as well as other residual gas, is recovered and returned in returning empty containers and by a gas return pipe to the filling end of the conveyor for re-liquefaction, or it is made available for other use at both ends and alongside of the conveyor.
The present invention provides the ability to carry LNG by a conveyor of a type having in a closed loop an endless string of elongated containers traveling at relatively high rate of speed between a filling end and a discharge end, containers being folded into vertical side-by-side relationship at relatively low rate of speed for filling at filling end and for discharge by means of siphoning at discharge end. Containers have two walls separated by insulating or vacuum space, an outer wall to provide physical strength, propulsion, guidance and connection to adjacent containers, and an inner wall to contain LNG, normally un-pressurized but when necessary under high pressure. When in folded upright relationship, upper ends of containers reveal two access ports, one for fluid filling and discharge, and the other for gas release. Containers are equipped with safety gas-only pressure release valves, which are connected to an attached endless flexible gas return pipe. Discharge of gas from containers is transmitted by the gas return pipe back to the liquefaction plant or it is made available for other use. The flexibility of the gas return pipe allows it to bend with containers as they fold and unfold at filling and discharge ends. Said LNG transporting conveyor comprising:
The present invention is intended to enable transportation overland of LNG in large quantities, similar to what is already commonly done by ship at sea. The advantage of liquefaction is that gas volume is thereby reduced by a ratio of about 620 to one. While LNG ships take many days for a single delivery, they have on board refrigeration machines to prevent re-gasification of their cargo. Re-gasification expands LNG back to its original volume, except when it is confined in pressure containers. The present invention has no refrigeration machines traveling with its containers. Instead it relies on delivering un-pressurized LNG at high rate of speed, thereby leaving very little time for temperature increase and re-gasification in transit. To enable high speed, wheels as means of suspension are replaced with permanent magnets in repulsion, and gears as means for propulsion are replaced with linear induction motors. Due to the use of siphoning as unloading means, turning containers upside down between loading and unloading ends of conveyor, as described in prior art, is eliminated.
Large quantities of stranded natural gas in remote regions could be brought as LNG to market with this invention, for example, from the North Slope of Alaska for a distance of 800 miles (1,300 Km) to a shipping port in the south of Alaska. With a line speed of 200 miles/hour (320 Km/hour), containers would be exposed for four hours to re-gasification inducing surroundings, which with pre-cooling of LNG to lower than re-gasification temperature and with good insulation or vacuum, as used in vacuum flasks, would keep heat intrusion and re-gasification to a minimum. However, the present invention provides that any emitted gas due to re-gasification and excessive container pressure would be recovered and returned for re-liquefaction by the endless gas return pipe to which all containers are connected. No gas would be released to the outside. In case of an accident, only directly affected containers could break open. Spilled contents would quickly evaporate. The gas return pipe attached to the sides of containers is fitted at intervals with pressure surge shutoff valves, which would limit gas loss in case of pipe fracture.
For a shorter application, the present invention could also be used as an LNG land bridge across Panama similar to what already exists for crude oil. Many new LNG ships are now also too large to fit through the Panama Canal. LNG re-gasification boil-off while in transit may be reduced or even totally avoided by (1) pre-cooling containers before filling, (2) filling containers only partially and (3) replace long conveyors with shorter ones interspaced with liquefaction booster plants.
