FR2512518A1 - Method of vaporising liquid gas - has heat passed externally to tank by pipes containing mixture freezing at predetermined temperature - Google Patents

Abstract

The method vapourises liq. gas held in a tank. Vapourisation takes place in one or more vessels external to the tank. These are heated by an intermediate fluid which is a mixture which freezes at a predetermined temp. When this fluid freezes on gas vapourisation, an extra source of heat is given. The vessels are pipes (3) connected top and bottom to the tank (1). The pipes are held in covers (4) which receive ambient heat and are filled with fluid (5). Heat is passed to the pipes from the intermediate fluid.

Description

 Liquefied gases are stored in the liquid phase in pressurized tanks. In a large number of cases the use is made in gas phase. The transition from the liquid phase to the gas phase requires a calorific contribution.

This calorific contribution can come from the atmosphere if lton lowers the vapor pressure of liquefied gases by gaseous sampling.

 This is called "natural vaporization". When the 1, natural vaporization is insufficient it must be supplemented by means of a vaporizer. The latter mainly consists of an exchanger receiving a calorific contribution thus allowing an artificial vaporization. The calorific contribution can be produced by a flame, an electrical resistance or a hot fluid (water, vapor or gas). This calorific intake must be regulated, depending on the desired flow and pressure conditions.

 The present invention aims to ensure sufficient vaporization while avoiding the production of a calorific contribution, and rendering regulation unnecessary.

 To this end, the subject of the invention is a method for vaporizing liquefied gases stored in a storage tank and used in the gas phase, characterized in that a vaporization complementary to that of the tank, takes place in one or more enclosures outside the tank, these enclosures receiving the necessary heat input from the atmosphere through a transfer fluid into which the enclosures are immersed.

 According to a characteristic that this process can have, the transfer fluid is a mixture which can be frozen at a predetermined temperature, allowing during the freezing due to the vaporization of the liquefied gases, an additional calorific contribution.

 The subject of the invention is also a vaporization installation for implementing the above-mentioned process, characterized in that the enclosures are tubes connected to the upper part and to the lower part of the storage tank allowing their complete filling with liquefied gas, and the tubes are contained in envelopes receiving a calorific contribution from the environment, and filled with a transfer and accumulation fluid so that the calorific contribution is made to the vaporization tubes by thermal sampling with the transfer fluid.

 According to a characteristic which this installation can have, the transfer fluid is a mixture which can be frozen at a predetermined temperature allowing during its freezing due to the vaporization of the liquefied gases an additional calorific contribution.

 In order to better understand the invention, an embodiment will be described below with reference to the accompanying drawing.

 It can be seen in this drawing that the installation mainly consists of a storage tank 1, a pressure reducer 2, vaporization tubes 3 and heat input casings 4, containing a transfer and accumulation fluid calorific 5.

 At rest, the installation is at a temperature equal to that of the environment 6, and at a pressure resulting from the vapor pressure of the stored liquefied gas.

 When there is a demand for gas, the sample is taken from the stored gas mass. The resulting reduction in pressure causes the liquid phase to vaporize, with a calorific drawdown on the transfer fluid 5. The latter in turn draws heat from the atmosphere 6.

 To obtain the desired gas flow through the regulator 2, it is sufficient to size the vaporization tubes 3 and the heat supply envelopes 4 according to the gas flow and the atmosphere 6. The system is self-regulating.

 The vaporization tubes 3 must be subjected to the same resistance specifications as the storage tank 1. On the other hand, the heat supply envelopes 4 have no constraint to respect and in particular they are practically not subjected to any pressure. They may be of economical material and of small thickness.

 All of elements 3, 4 and 5 thus constitute a complete vaporizer, of more economical construction than conventional models. Additional equipment for the production and regulation of heat intake is useless, the latter being provided automatically and free of charge by the atmosphere.

The low coefficient of exchange between the atmosphere 6 and the heat input envelopes 4 requires a large area, but which can be produced with economical materials.

The spray tubes 3 of a more expensive construction have a much smaller surface area given the higher exchange coefficient provided by the transfer fluid 5.

 Generally the flow rates requested from the uses are very variable. In conventional vaporization systems, the calorific intake must be calculated according to the maximum instantaneous flow that can be requested. In the present invention, the peak flow rates can be capped by heat sampling on the transfer fluid 5 forming a heat accumulator as a function of its volume.

In addition, by using a judiciously dose freezing mixture, depending on the minimum ambient temperature, and the vapor pressure of the liquefied gas, it is possible to recover the freezing heat of the mixture, which considerably increases the available thermal flywheel. .

 The thermal flywheel rebuilds when the requested gas flow rate becomes lower than the nominal installation flow rate.

 The installation is easily expandable, vaporization tubes 3 can be added, or their lengths increased. It is the same with regard to the diameter and the lengths of the heat supply envelopes 4, conditioning the surface of heat supply by the atmosphere, and the volume of thermal accumulation.

 Level 7 of the vaporization assembly, relative to the storage tank, must allow complete filling of the vaporization tubes 3 as a function of the minimum level of liquefied gases from the storage tank 1.

Claims (4)

 1. Method for vaporizing liquefied gases stored in a storage tank and used in the gaseous phase characterized in that the vaporization takes place in one or more enclosures external to the reservoir, these enclosures receiving the necessary heat input from the atmosphere by 'through a transfer fluid where the speakers are immersed.  2. Method according to claim 1 characterized in that the transfer fluid is a mixture freezable at a predetermined temperature, allowing during its freezing due to the vaporization of the liquefied gases, an additional calorific contribution.  3. vaporization installation for liquefied gases to implement the method according to claim 1, characterized in that the enclosures are tubes (3) connected to the upper part and to the lower part of the storage tank (1) allowing their complete filling in liquefied gas by level difference (7), and the tubes (3) are contained in envelopes (4) receiving a calorific contribution of the atmosphere, and filled with a fluid (5) for transfer and accumulation in such a way that the heat input is made to the vaporization tubes by thermal sampling with the transfer fluid.  4. vaporization installation for implementing the method according to claim 3, characterized in that said transfer fluid (5) is a mixture freezable at a predetermined temperature allowing during its freezing due to the vaporization of liquefied gases a calorific contribution additional.