Gas separation: processes – Solid sorption – Soluble or deliquescent material used
Reexamination Certificate
2001-03-09
2002-04-09
Simmons, David A. (Department: 1724)
Gas separation: processes
Solid sorption
Soluble or deliquescent material used
C095S092000, C095S117000, C095S231000, C096S118000, C252S194000
Reexamination Certificate
active
06368384
ABSTRACT:
TECHNICAL FIELD
Tablets containing potassium formate are useful for drying gases because of their deliquescent properties.
BACKGROUND OF THE INVENTION
In the past, desiccants have been commonly used to dry gases such as natural gas, particularly for its transmission through pipelines. Typically the pipelines carry natural gas over hundreds of miles, and it is necessary and desirable to remove whatever moisture is present in the gas and/or in the pipeline. To this end, the art has employed common desiccant salts such as calcium chloride, made into tablets which tend to absorb the moisture.
An early patent to Hutchinson, U.S. Pat. No. 2,804,940, suggests passing a partially dehydrated natural gas upwards through a bed of solid particulate deliquescent material such as calcium, magnesium, or lithium chloride, or mixtures of them. Certain molar ratios of chlorides and bromides are suggested by Heath in U.S. Pat. No. 2,143,008 and by Thomas in U.S. Pat. No. 5,733,841; see also Thomas U.S. Pat. No. 5,766,309. for a good illustration of the placement of the solid deliquescent materials in a contemporary drying vessel; this patent (U.S. Pat. No. 5,766,309) is incorporated by reference herein in its entirety.
A solution of 40-70% potassium formate is suggested for use as a moisture absorbent in dehumidifiers and similar devices by Atkinson in U.S. Pat. No. 5,846,450.
SUMMARY OF THE INVENTION
Tablets are made of powdered or crystalline potassium formate and used to remove moisture from gases such as natural gas. The tablets may contain from 0.5% to 100% by weight potassium formate, the balance being alkali or alkaline earth metal formates (preferably sodium, calcium, cesium and/or magnesium formate), chlorides and/or bromides (preferably calcium chloride, potassium chloride, cesium chloride, lithium chloride, or mixtures thereof). The tablet is preferably made under compression and, for use in gas dryers in natural gas transmission lines, preferably weighs about 7 to 15 grams so it can conveniently form a bed in a more or less conventional gas dryer. A pillow shape is convenient, but no particular shape is required for this invention. Preferred tablets comprise 97.5% calcium chloride and 2.5% potassium formate. An additional 0.5% of a binder, which is preferably sodium lauryl sulfonate, may also be used.
The preferred tablets need not use these exact proportions, however—they may comprise 0.5% to 100% potassium formate, an additional 0.01% by weight to 1% by weight of a surfactant used as a lubricant, and the balance one or more alkali metal or alkaline earth metal halides.
REFERENCES:
patent: 2804940 (1957-09-01), Hutchinson
patent: 3050920 (1962-08-01), Norton
patent: 3246454 (1966-04-01), Norton
patent: 3740966 (1973-06-01), Pravda
patent: 3898166 (1975-08-01), Cooney
patent: 5104562 (1992-04-01), Kardos et al.
patent: 5725636 (1998-03-01), Gavlin et al.
patent: 5733841 (1998-03-01), Thomas
patent: 5766309 (1998-06-01), Thomas
patent: 5846450 (1998-12-01), Atkinson
patent: 5922109 (1999-07-01), Rooney et al.
patent: 6221276 (2001-04-01), Sarin
Clearwater, Inc.
Krayer William L.
Lawrence Frank M.
Simmons David A.
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