Pumps – Processes – Of pumping one fluid by contact or entrainment with another
Reexamination Certificate
1998-01-23
2001-05-15
Yuen, Henry C. (Department: 3747)
Pumps
Processes
Of pumping one fluid by contact or entrainment with another
C138S034000
Reexamination Certificate
active
06231313
ABSTRACT:
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
The present invention relates to de-icing systems, and particularly to systems which prevent either water vapor or entrained water droplets in compressed air from freezing and clogging up compressed air lines or devices which use compressed air, or both, in low temperature environments. The invention also relates to a novel turbine which is particularly well suited for the de-icing system.
Many mechanical devices use compressed air as a source of power. Other devices use compressed air in other ways for their operation. For example, artificial snow making devices use compressed air to atomize water and distribute the artificial snow over a ski area. Many compressed air systems are designed to be operated in low temperature environments. For example, a sawmill may use compressed air as a power supply source, and the machinery may be located in unheated buildings and used during the winter. Many other outdoor operations, including construction sites, quarries, railroads and marine applications, use compressed air. Air naturally contains water vapor, measured by the term “humidity”. When the air is compressed, the water vapor is also compressed. As the compressed air is cooled while under pressure, some of the water vapor condenses into water droplets. If the compressed air is moving, the water droplets often remain entrained or suspended in the moving air stream. As a result, the compressed air thus includes water vapor and entrained water droplets.
There are a number of systems and processes for removing water from compressed air, either using an after-cooler and a separator to remove entrained water droplets, or desiccant dryer to remove water vapor, or both. However, it is usually not cost efficient to remove all of the moisture from the air. This remaining moisture (water vapor or entrained water droplets or both) can then freeze up in the air supply lines, when operating below 32° F., or in the devices that use compressed air when the expansion of the compressed air causes the temperature of the air to fall below freezing.
One solution to preventing water in compressed air lines from freezing is to add a de-iceant to the air. The de-iceant combines with the water and lowers the freezing point of the resulting mixture, much as antifreeze works in a cooling system. Most de-iceants are alcohol-based. However, these cannot be used in some situations, such as in underground mining operations or other confined areas, because the alcohol is combustible and toxic. Other less frequently used de-iceants are propylene glycol-based which are less toxic and non-combustible. One problem with these de-iceants, however, is that they are more viscose, and thus harder to effectively add to compressed air.
One procedure for adding de-iceants is to have a container filled with de-iceant connected to the compressed air line with a venturi system that draws the de-iceant from the container as the compressed air flows past. This system does not atomize the de-iceant. Venturi systems work well on small air lines, up to two inches in diameter or less than 1000 cfm air flow. However, they require repeated refilling of small storage containers. If there are numerous air lines, such venturi systems require the containers filled with de-iceant to be scattered around the compressed air system, with the associated labor-intensive requirement of replenishing the contents of the containers. For larger systems, a larger de-iceant storage tank is desirable, with a controllable valve for introducing de-iceant into the air stream. For instance, a vaporizer may be used to heat the de-iceant to a vapor state, in which it is injected into the compressed air lines. However, a heated vaporizer is not suitable for propylene glycol-based de-iceants.
Another consideration in adding de-iceant is control over the amount of de-iceant added to the compressed air. The optimum amount of de-iceant is dependent on a number of variables, including the moisture content of the compressed air, the flow rate of the compressed air and the ambient temperature. Since these variables can and do change, particularly the flow rate of the compressed air, the optimum amount of de-iceant to add changes. Venturi and other tank systems are generally provided with some control features, and inherently change the feed rate as the flow rate changes. However, for larger compressed air systems using a vaporizer, typical vaporization units do not have a way of automatically changing supply rates as the compressed air flow rate changes. Thus, one adding de-iceant at a constant rate must either add an amount to meet the highest air usage, which would be wasteful when not operating at peak demand, or face potential freeze ups if an insufficient amount is added and the air usage rate goes up. Since the cost of unclogging frozen air lines and the associated down time of operating equipment is so great, operators tend to use more de-iceant than is needed.
Thus, there is a need for a de-icing system which can controllably add a de-iceant to a high volume compressed air stream, preferably a de-iceant that is non-combustible and less toxic than alcohol based de-iceants. It would also be beneficial if the system were capable of monitoring the flow rate of compressed air and automatically changing the rate of addition of de-iceant.
SUMMARY OF THE INVENTION
A de-icing system has been invented that adds a de-iceant to a high volume compressed air stream in a controllable fashion, with the rate of addition being automatically controlled so that the rate of de-iceant addition can match changes in the flow rate of air in the system. In the preferred embodiment of the invention, a turbine is used to both measure the air flow rate and disperse the de-iceant.
In a first aspect, the invention is a method of dispersing de-iceant into a stream of air flowing through an air supply line comprising the steps of: a) placing a turbine in the air supply line; b) forcing at least a portion of the stream of compressed air to pass through the turbine, thus causing the turbine to spin; and c) using the spinning turbine to atomize the de-iceant.
In a second aspect, the invention is a method of adding de-iceant to compressed air comprising the steps of: a) detecting the rate of flow of compressed air through an air supply line; and b) pumping de-iceant from a de-iceant supply source and dispersing the de-iceant into the air flowing through the air supply line at a rate proportional to the detected rate of flow of compressed air through the air supply line.
In a third aspect, the invention is a method of preventing water in compressed air from freezing up inside of a compressed air supply line or a compressed air usage device comprising the steps of: a) forcing compressed air through the air supply line to one or more compressed air usage devices; b) causing a turbine to spin at a rate proportional to the rate of air flow through the air supply line; and c) dispersing de-iceant into the compressed air flowing through the air supply line at a rate proportional to the turbine spin rate.
In a fourth aspect, the invention is a system of injecting de-iceant into a flowing stream of compressed air comprising: a) a turbine within the flowing air stream; b) a source of liquid de-iceant; c) a de-iceant supply device in fluid communication with the source of de-iceant for injecting de-iceant into the stream of compressed air; and d) a controller which controls the rate of de-iceant injection and is connected to the turbine and the de-iceant supply device.
In a fifth aspect, the invention is a compressed air system comprising: a) one or more compressors; b) an air supply line into which compressed air is
Heitmann Arnold M.
Littlefield Robert G.
Brinks Hofer Gilson & Lione
Gimie Mahmoud M
Shurtz Steven P.
Tanner Systems, Inc.
Yuen Henry C.
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