Measuring and testing – Gas content of a liquid or a solid – Particular separator
Patent
1997-02-18
1998-12-01
Brock, Michael
Measuring and testing
Gas content of a liquid or a solid
Particular separator
73 3107, 7386312, G01N 122
Patent
active
058441239
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a gas sensing system and was primarily developed for measuring gas concentrations, in solution, in gas mixtures, liquids and other fluid mediums, for example foodstuffs such as jams and other preserves, and for carrying out such measurements in-situ, preferably during the continuous flow of the medium. The system also has applications for gas sensing in other media, such as wine, beer, cider, sugar solutions, flowable solid material such as sugar, food granules and agglomerates together with non-foodstuffs such as pharmaceutical preparations and oils.
It is often important to know the concentrations of certain gases in certain mediums, and one of the most important applications is in determining the acceptability of foodstuffs. A prime example arises in the preserves industry where sulphur dioxide gas, SO.sub.2, is frequently employed during storage and transportation as a preservative for the raw materials (for example, pulped fruit) from which the preserve is made. Once the preserve has been manufactured the sulphur dioxide may no longer be required in the finished product and, in fact, European Community Regulations are in force requiring that sulphur dioxide concentrations in preserves be less than thirty parts per million (ppm). In other foodstuffs and beverages (such as beer), legislation world-wide is becoming stricter and present U.S. requirements limit the SO.sub.2 concentrations in beer to less than 10 ppm. However, in certain products such as wine, the sulphur dioxide is required, in known concentrations, to act as a preservative during storage. In both cases, it is highly desirable to know the concentration level of the sulphur dioxide.
The conventional procedure for regulating gas concentrations in preserves is by "boiling off" the gas by heating, or by vacuum processing the preserve sufficiently to cause the gas to evolve from solution until its concentration falls to a desired level. The conditions under which the boiling off procedure is effective will vary depending on the concentrations of the gas in the preserve and how it is chemically bound with the preserve (it is known that sulphur dioxide forms weak complexes with certain naturally occurring organic materials, particularly aldehydes and ketones, and such complexes are generally broken down at temperatures in excess of 60.degree. C.) and therefore it is inevitable that the residual gas concentration in the finished product will vary.
Therefore, quality control checks are necessary at frequent intervals whereby samples of the preserve are taken and tested, using standard laboratory procedures, to determine the gas concentrations in the preserve product. In the production environment, known gas sensors are neither sufficiently rugged or suitable for use at the high temperatures and pressures generally required. Quality control regulations may require that certain gas concentrations, such as sulphur dioxide, in a foodstuff product may not exceed a permitted level. Furthermore, if following a quality control check on sulphur dioxide concentration it is found that the gas concentration level is too great, a continuous production line of the foodstuff may be stopped to determine the origin of the problem while the gas removal procedure is revised. Typically, the known method of gas concentration measurements (such as SO.sub.2) is off-line, whereby a production sample is taken and gas concentration measurements are achieved by wet chemical means, a destructive test, taking between 30-60 minutes. During this period, production continues at the rate of several tonnes per hour. Therefore, if an unacceptable gas concentration is found then several tonnes of the product will have been produced which will be suspect and require further processing. Furthermore, simply increasing the boiling off time of the preserve to ensure that more gas will be removed, without control, would likely result in an unacceptable increase in production costs.
In addition, existing tests, even using the most accurate commercially avail
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Marsh Robert Anthony
Scarott John Wilfred
Smith Rodney Edward
Starnes Roger Kevin
Turner Colin Edwin
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