Refrigeration – Cryogenic treatment of gas or gas mixture – Liquefaction
Reexamination Certificate
2002-08-21
2004-09-07
Doerrler, William C. (Department: 3743)
Refrigeration
Cryogenic treatment of gas or gas mixture
Liquefaction
C165S111000, C165SDIG001, C062S048200
Reexamination Certificate
active
06786063
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a device arranged to condense gas/vapour, for example hydrocarbons in gas phase, from volatile liquids, for example hydrocarbons in liquid phase, the device hereinafter and simplistically denoted as a gas condenser.
BACKGROUND OF THE INVENTION
Upon storage and transport of volatile liquids, for example crude oil or crude oil products in liquid state, a portion of the liquid normally evaporates, so that gas/vapour, for example hydrocarbon gas, is collected above the liquid surface of the container or tank in which the liquid is stored. Within an enclosed container/tank, the evaporation results in pressure build-up, so that the pressure, upon a given maximum pressure, must be reduced by venting out the gas/vapour, for example through suitable valves, the gas/vapour normally being released to the surrounding atmosphere.
Upon loading a hydrocarbon liquid, for example, to a storage tank, the storage tank possibly being partially filled with an equivalent or similar liquid, the liquid filled thereto will displace gas/vapour present in the storage tank together with potential gas/vapour evaporating from the storage tank liquid, the gas/vapour normally being released to the surrounding atmosphere.
PRIOR ART
Upon transport, storage or loading of, for example, crude oil, possibly crude oil products, which, at atmospheric or close to atmospheric normalcy, exist(s) in liquid phase, it is common practice to release, at a given maximum pressure, evaporation gasses/vapours directly into the surrounding atmosphere, the container/tank of the liquid/gas being provided with one or more pressure valves, so-called snifting valves, which, at a given maximum pressure, open and release the gas/vapour.
Moreover, and in connection with storage and transport of refrigerated liquid gas, several methods, devices and/or systems for condensing gas exist, including:
NO 305525 concerns a “method and device for storing and transport of liquidised natural gas”;
U.S. Pat. No. 2,784,560 concerns a “method and device for the storing and handling of liquid gas”; while
U.S. Pat. No. 3,733,838 concerns a “system for repeatedly liquefying the extract of a liquid gas”.
The above-mentioned methods, devices and/or system comprise, among other things, suction and condensing devices for the handling of gas which has evaporated from refrigerated liquid gas.
Furthermore, the prior art represented by U.S. Pat. No. 3,921,412 concerns a “vapour recovery device utilising a condensing dispenser nozzle”, the dispenser nozzle condensing vapour/gas which is being displaced when filling of liquid into a container, where the dispenser nozzle is placed in the filler opening of the container.
DISADVANTAGES OF THE PRIOR ART
A substantial disadvantage of releasing a hydrocarbon gas, for example, into the surrounding atmosphere, consists in the effluent/discharge potentially being harmful to the surrounding environment. Also, it is of economic interest to retain as much as possible of the hydrocarbon gas within the container or the tank, and preferably within the hydrocarbon liquid, inasmuch as the hydrocarbon gas is valuable and may be used for industrial purposes.
Disadvantageously, prior art according to NO 305525, U.S. Pat. Nos. 2,784,560 and 3,733,838 concern methods, devices and/or systems for condensing gas/vapour in connection with storage and transport of refrigerated liquid gas, and thus are not arranged to condense gas/vapour in connection with storing, transport, loading and unloading of, for example, crude oil or crude oil products which, at atmospheric or near-atmospheric normalcy, exist in liquid phase. Furthermore, the technical solutions described in NO 305525, U.S. Pat. Nos. 2,784,560 and 3,733,838 are comprehensive, complicated and expensive.
The technical solution described in U.S. Pat. No. 3,921,412 is limited to the condensing of gas/vapour being displaced during the filling of liquid into a container and does not concern condensing of gas/vapour evaporating from a liquid during transport or storage thereof.
Hence, no prior art technical solutions seem to exist to condense gas/vapour, for example hydrocarbons in gas phase, from volatile liquids, for example hydrocarbons in liquid phase, and which are arranged to enable simple and efficient condensing of larger volumes of such gases/vapours.
THE OBJECTIVE OF THE INVENTION
The objective of the invention is to provide a gas condenser arranged to condense gas/vapour, for example hydrocarbons in gas phase, from volatile liquids, for example hydrocarbons in liquid phase, the gas condenser being arranged to provide a simple and efficient condensing of larger volumes of such gases/vapours.
Another objective of the invention is to provide a gas condenser which, if desired, directly or indirectly may be adapted to the current gas/vapour condensing need, considering that the need may increase/decrease relative to increasing/decreasing evaporation and/or displacement of such a gas/vapour, and the gas condenser possibly may be connected to other necessary equipment, devices and/or appliances in order to, for example, control/adjust flow parameters of the fluids which, during use of the gas condenser, flow through it, possibly also in order to pre-treat and/or after-treat, for example remove air or air components within, said fluids flowing through the gas condenser.
How to Achieve the Objective
The objective is achieved by using one or several gas condensers according to the invention, the following description specifying in a simplified version, however, the utilisation of only one gas condenser, the utilisation of several gas condensers only providing a greater gas/vapour condensing capacity and no different mode of operation than that of utilising one gas condenser only.
The volatility of a liquid indicates the degree of ease at which a liquid will evaporate. A liquid possessing a low boiling point and a high vapour pressure (relative to the ambient condition) indicates volatility in a liquid. Concerning this, a liquid, for example a hydrocarbon liquid, may consist of several liquid components, the liquid components being more or less volatile relative to one another, and especially relative to an overlying gas volume within a tank/container. At a certain pressure- and temperature condition, each of the liquid components possesses an individual boiling point and vapour pressure, the liquid components possessing the lowest boiling point and the highest vapour pressure evaporating first. Thus, a mixture of various gas components may gradually emerge within, for example, a storage tank.
Upon evaporation of a volatile liquid, for example a hydrocarbon liquid, being stored within a tank, the evaporation normally, but not always, will be influenced by the following parameters and in the following way:
The evaporation increases when the gas-exposed surface area of the liquid (liquid surface area) increases; the evaporation increases when the liquid volume increases (provided the liquid surface area increases simultaneously); the evaporation increases when the gas volume/liquid volume ratio within the tank increases; the evaporation decreases when the liquid ambient pressure increases; the evaporation increases when the liquid ambient temperature increases; the evaporation increases when the liquid storage time within the tank increases; the evaporation varies dependent on the liquid component composition, and in such a way that the evaporation decreases when the boiling point of a liquid component increases, while the evaporation increases when the vapour pressure of a liquid component increases.
During transport of, for example, crude oil in a tanker, stirring devices, so-called agitators, are often used to stir the crude oil in the bottom layer of the tank(s). This is done in order to prevent extensive segregation of the crude oil, thereby preventing the heaviest and most viscous crude oil components from sinking to the bottom of the tank(s) and, by so doing, impeding the subsequent unloading of the crude oil. This stirring of the crud
Andrus Sceales Starke & Sawall LLP
Doerrler William C.
Venturie AS
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