Ralph G. Scurlock

The solubilities of nitrous oxide, carbon dioxide, Aliphatic ethers and alcohols, and water in cryogenic liquids

Abstract Experimental investigations using IR spectroscopy and a variable pressure cell (up to 30 bar) have shown that nitrous oxide, carbon dioxide and some aliphatic ethers are considerably soluble in liquid nitrogen, liquid oxygen and liquid argon between 77 K and 135 K, with solubilities ranging from 10 −4 mole fraction for nitrous oxide to 10 −8 mole fraction for di-isopropyl ether. The solubility data have been found to be dependent on the temperature of the cryogenic liquid and the molecular structures and properties of the solute and solvent molecules. The solubilities of water, hydrogen sulphide, methanol and ethanol have been found experimentally to be very low, i.e. less than 10 −8 mole fraction in liquid nitrogen, liquid oxygen and liquid argon. These values are considerably lower than those measured previously using gravimetric methods (10 −7 - 10 −5 ). The experimental solubilities are compared with the predicted values based on the “ideal” and “regular solution” theories. Both theories failed to predict solubilities comparable with the experimental values.

Design of a variable pressure infrared absorption cell

A variable pressure infrared absorption cell of 62 mm pathlength operating at pressures up to 3 MN m-2 and between 4 and 300 K is described. A brief account is given concerning the selection of optical windows and body materials, stress calculations and techniques for sealing the optical windows.

THE SOLUBILITY OF SOLUTES IN CRYOGENIC LIQUIDS

The solubilities of a number of compounds have been experimentally measured in cryogenic liquids between 77 and 135K using infrared spectroscopy in a variable pressure (up to 3 MNm−2) infrared absorption cell. Nitrous oxide, carbon dioxide and some aliphatic ethers have been found to be considerably soluble in cryogenic liquids with solubilities ranging from 10−4 to 10−8 mole fraction. The solubility data have been found to be dependent on temperature of the cryogenic liquid and the molecular structures and properties of the solute and solvent molecules The solubilities of water, hydrogen sulphide, methanol and ethanol have been found to be very low i.e. less than 10−10 mole fraction in liquid nitrogen, liquid oxygen and liquid argon. These values are considerably lower than those measured previously using gravimetric methods (10−7 to 10−5 mole fraction).

Insulation: The Reduction of ‘A’ and ‘B’ Heat In-flows

There are two important properties of all cryogenic fluids which can be used to help insulate both A and B heat inflows, and reduce liquid boil-off to a minimum. These are (1) the significant ratio of sensible heat between NBP and ambient temperature of the cold vapour, divided by the latent heat of vaporization (75 for helium, 7.9 for hydrogen, 3.3 for neon, 1.0 for oxygen and nitrogen, 0.8 for LNG). (2) The natural convective heat transfer between cold vapour and container wall is magnified 10-fold or more in vertical temperature gradients at the lowest temperature of any cryogenic vapour column. This chapter describes in detail how these insulation properties may be used advantageously to reduce both A and B heat inflows, by radiation, conduction and convection, in the design of all cryogenic systems.

Liquid Transfers Avoiding 2-Phase Flow

The transfer of cryogenic liquids like LNG down pipes is not as simple as pumping water. The difference is that cryogenic liquids are stored at their boiling points, whilst water is stored at ambient temperature, which is a long way from its boiling point at 100 °C.

Vacuum Insulated Tanks for Pressurised LNG

The rise of LNG as a green fuel, in the face of global warming, is leading to the use of relatively small, vacuum insulated VI tanks for 1–100 m3 capacity of pressurised LNG. Such tanks have been widely used over many years for the supply of nitrogen, oxygen and argon as cryogenic liquids. They are called ‘zero-boil-off Liquid Gas Cylinders’, and they have never been a problem for unstable evaporation of the cryogenic liquid contents. This chapter describes how this handling behaviour also applies to LNG.

The Rollover Sequence of Events, Starting with Stratification

The chapter concentrates on the sequence to be expected if stratification in LNG or LPG cannot be prevented. The natural convective heat flows into the stratified layers will lead to density equilibration between the layers, when spontaneous mixing or roll-over may lead to a large rise in BOR.

Surface Evaporation of Cryogenic Liquids, Including LNG and LPG

Surface evaporation of the boil-off gas is the key to understanding how stratification and rollover can take place.

Factors Creating Stratification: Management of LNG Rollover

Stratification or the creation of two convectively stable layers of liquids with different densities is the beginning of events leading to possible roll-over.

Heat Flows in LNG and LPG Cryogenic Storage Systems at 1 Bar

In a cryogenic storage system, all the A heat inflows through the insulation, are into the stored liquid. The B heat inflows are absorbed by the “cold” in the boil-off vapour.