Dryer moisture indicator

Information

  • Patent Grant
  • 6655043
  • Patent Number
    6,655,043
  • Date Filed
    Friday, September 21, 2001
    23 years ago
  • Date Issued
    Tuesday, December 2, 2003
    21 years ago
Abstract
A moisture indicator in an air flow drying process where hot gas is circulated over and around a granular material having an undesirable amount of moisture includes a detector located in the path of the exhaust gas to determine exhaust flow temperature, a valve control device associated with the temperature detector to control the percentage of hydrocarbon gas in the hot gas intake and an indicator connected to the valve control device. A display is associated with the indicator to display the percentage of hydrocarbon gas in the gas intake which indicates the amount of moisture in the granular material. The percentage of hydrocarbon gas needed in the intake is inversely proportional to the amount of moisture in the granular material. The percentage signals the loader operator whether the granular material loaded has an acceptable amount of moisture for successful operation of the drying process.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention pertains to indicators and more particularly to indicators that display the condition of the contents of containers where knowledge of the condition of the contents of the container is necessary for the performance of supporting activities.




2. Related Prior Art




In the area of material drying, such as sand drying, the relative moisture content of material to be dried must be known. The relative moisture content is often critical to the speed with which a subsequent dependent process may be accomplished. In some processes, such as drying sand, a high moisture content may prevent the drying process from being accomplished or completed efficiently or satisfactorily.




For example, in a sand drying plant where the sand is to be added to aggregates and oil derivatives to form asphalt, the moisture content of sand must be decreased to a predetermined level. Sand is scooped up from an outdoor pile and placed in a large tumbler. The sand is put through a drying procedure where hot gas is circulated over the wet sand, run through a dryer transition stage to a dust collector and then exhausted through the use of a large exhaust fan. The temperature of the exhaust is low when moisture is present in the sand and increases as the moisture content decreases or the sand is dried. When more sand having a significant moisture content is placed in the drying area, the temperature of the exhaust gas drops again, depending on the amount of moisture in the sand.




Although all the sand is taken from the same mound, in most cases taking sand from higher on the mound will result in loading sand with a lower moisture content. This is due primarily to the effect of gravity (moisture, i.e. water, is heavier than air and will tend to leach to the lower areas of the mound) and the drying effect of the sun and wind which will be most noticeable on the top and exposed sides of the mound. The drying effect of the sun and wind can be very rapid and significant and can aid in the drying process. In general, dropping the height of the bucket into which sand is loaded by a mere four inches, that is, taking the sand from deeper on the mound where it has a higher moisture content, can produce a significant change in the drying operation. The resulting change can be so significant that it can mean the difference between an efficient successful drying operation and one which operates too slowly and inefficiently, causing costs to increase because of increased man hours and increased gas consumption.




Unfortunately, the person who has the most control over the amount of moisture in the sand being loaded, and as a result, the gas consumption, has the least knowledge of the amount of moisture in that sand and the amount of gas being consumed. The dryer operator located in the control room is the only person who has the information concerning the moisture content through the knowledge of the amount of gas being consumed to dry the sand.




There are many types of moisture indicators in the art. Some detect the amount of moisture contained in a substance directly by insertion of a probe into the material, measure the moisture content and provide a digital readout of the actual moisture content. One such type is the “AQUA-SPEAR” moisture meter manufactured Mastrad Company.




U.S. Pat. No. 4,047,105, titled “Method and Apparatus for Providing an Output Indication Proportional to the Moisture Content of Particulate Material”, issued to Bruce Olen Anderson relates to method and apparatus for providing an output indication proportional to the moisture content of particulate material where a probe drive signal having a predetermined frequency and amplitude is inserted and applied to the particulate material. A current indicator signal proportional to the current applied to the particulate material is provided. The current signal is proportional to the moisture content of the particulate material.




U.S. Pat. No. 4,621,229, titled “Instrument for Measuring the Moisture Content of Solids”, issued to Friedrich Hirth, relates to an Instrument for measuring the moisture content of solids that has probes which are placed in contact with the material which is to have its moisture content measured. The probes are used to measure the electrical resistance of the material. A d.c. voltage is connected with the probes and generates the voltage required for measurement of electrical resistance. The characteristic line representing the electrical resistance of the material as a function of its moisture content is logarithmic in nature and, in order to generate a straight characteristic line, the signals from the probes are fed to a logarithmic amplifier. The amplified signals are converted to a moisture content which may be read from an indicator constituting part of the instrument. A calibrating unit is interposed between the logarithmic amplifier and the indicator and functions to adjust the characteristic line of the instrument so that this at least approximates the characteristic line of the material undergoing moisture determination.




Other types of moisture indicators may provide a reading by color change. Humidity Indicators manufactured by AGM Container Controls, Inc. are of this type. In general, these indicate the amount of humidity in a specific area. For example, this type of moisture indicator is placed in a closed area such as a room or section of a building. The ambient air humidity is indicated by the color of the indicator. When dealing with a large area such as a room, the color change will be slow to indicate a gradual change in humidity and not an instantaneous change for a small area.




SUMMARY OF THE INVENTION




The present invention provides a moisture indicator in an air flow drying process where hot gas is circulated over and around a granular material. Typically, this granular material has an undesirable amount of moisture content. In this process, the temperature of the gas after it has been circulated over the wet or damp sand provides an indication of the moisture content of the sand. The greater the moisture content in the sand, the cooler the exhaust gas and conversely, the dryer the sand, the hotter the exhaust gas temperature. The moisture indicator of the present invention includes a detector located in the path of the exhaust gas to determine exhaust flow temperature. A detector is placed in the gas flow process after it has been circulated over the sand to detect temperature of the exhaust gas. A valve control device is either electrically or mechanically associated with the temperature detector. This valve control device is used to control the flow percentage of hydrocarbon gas in the hot gas intake. When the temperature of the gas in the exhaust section drops below a predetermined level, a signal is sent to the valves that control the amount of flammable gas (hydrocarbon heating gas) in the intake flow. This signal causes the valves to open, increasing the percentage of heating gas in the gas flow, increasing the temperature of the hot gas intake. An indicator is connected or linked with the valve control device. The indicator is associated with a display showing the percent of hydrocarbon gas that is currently being fed to the hot gas intake in order to maintain a predetermined temperature in the exhaust gas. This in turn provides an indication of the amount of moisture in the granular material that has just been loaded into the moisture dryer. The percentage of hydrocarbon gas in the intake gas flow is directly proportional to the percentage of moisture in the granular material being dried. The indicator is operated in conjunction with the valve control for the intake hydrocarbon gas and is indicative of the amount of moisture in the granular material as a function of the percentage of gas needed to maintain a predetermined temperature in the exhaust gas. This provides a signal to the loader operator as to whether the granular material loaded has an acceptable amount of moisture for successful, efficient operation of the drying process or whether he should take sand or other granular material from another location.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a schematic view of a granular material drying operation.





FIG. 2

is a front view of the display illustrated in connection with the granular drying operation of FIG.


1


.





FIG. 3

is a back view of the display of FIG.


2


.











DESCRIPTION OF THE PREFERRED EMBODIMENT




Referring now to

FIG. 1

, a schematic diagram of a granular material drying operation


12


is illustrated. A container


14


is shown as containing granular material


16


in its lower portion. In this embodiment the granular material used may be sand or other aggregates that require moisture removal. A hot air intake


18


is illustrated as connected to one end of container


14


which provides hot gas for the drying process. A hydrocarbon gas source


20


is connected to hot air intake


18


through a gas line


22


.




Intake pipe


18


is preferably approximately thirty inches in diameter with gas line


22


preferably being approximately one inch in diameter. Other sizes may be used as long as it permits adequate intake air flow and proper mixing of hydrocarbon or other flammable gas.




Valve assembly


24


with valves


24


A, . . . , etc. is used in gas line


22


to control the amount of hydrocarbon gas which is mixed with outside air within hot gas intake


18


. The hot gas mixture enters container


14


at an opening


26


, which connects to hot gas intake


18


. A hot gas


28


circulates throughout container


14


heating granular material


16


to remove any moisture that it may have. As hot gas


28


contacts moisture laden granular material


16


, it provides heat calories to permit moisture to change states from water to water vapor by absorbing heat. The absorption of heat to vaporize the moisture in granular material


16


causes a reduction in the temperature of hot gas


28


.




Hot gas


28


is then withdrawn from container


14


through an exhaust pipe


30


. Exhaust pipe


30


carries hot air


28


through a dust collector


32


. Exhaust pipe


30


is also approximately thirty inches in diameter, but again, any size may be used as long as a proper air flow is permitted. Exhaust pipe


30


has an elbow


38


at point spaced apart from container


14


. The purpose of elbow


38


is to change direction of air flow to direct any dust particles into dust collector


32


. Temperature detector


40


is located outside of container


14


but before elbow


38


in order to obtain the temperature of hot gas


28


as it comes out of container


14


and before it cools further. Any further cooling of hot gas


28


will provide an erroneous reading and cause too high a percentage of hydrocarbon or flammable gas to be mixed with the intake air.




An exhaust line


34


is connected to dust collector


32


and contains a fan


36


which pulls hot air


28


from dust collector


32


. Contained within exhaust pipe


30


, near an elbow


38


which turns down to dust collector


32


, is a temperature sensor


40


.




Exhaust


34


is also preferably a pipe having a thirty inch diameter with fan


36


mounted therein. Fan


36


may be of any type currently in use in the art, as long as it is sized to fit within exhaust


34


and has the drawing ability to pull hot air out of the drying container.




Temperature sensor


40


is used to detect the temperature of hot gas


28


as it is exhausted from container


14


. Sensor


40


sends a signal indicative of the temperature of exhaust hot gas


28


through a line


42


. Line


42


is connected to a valve assembly


24


. Valve assembly


24


is used to control the amount or percentage of hydrocarbon gas being fed to intake line


18


. Valve assembly


24


is connected to an indicator


44


mounted on a display


46


through a mechanical linkage


48


. Indicator


44


is associated with display


48


which indicates the percentage of hydrocarbon gas being fed through intake


18


.




In operation hot air enters container


14


through opening


26


. Hot air


28


provides the additional calories to vaporize any moisture which may be contained within granular material


16


. The greater the moisture content in granular material


16


, the greater the number of calories provided by hot air


28


needed to vaporize the moisture in granular material


16


.




When hot air


28


is withdrawn from container


14


to dust collector


32


through the pulling action of fan


36


, it passes by temperature detector


40


. Temperature detector


40


compares the temperature of the exhaust gas


28


with a predetermined minimum. When the temperature of exhaust gas


28


is below this predetermined minimum, temperature detector


40


sends a signal to valve assembly


24


to open the valves


24


A, . . . , etc., allowing a greater percentage of hydrocarbon gas from container


20


to travel through gas line


22


to be mixed with intake air within intake pipe


18


. Thus, the lower the temperature of hot gas


28


when it reaches temperature detector


40


, the more hydrocarbon gas that gets mixed with ambient air in air intake


18


.




When the temperature drops and valve assembly


24


is told to open valves


24


A, . . . , etc. to permit more hydrocarbon gas to flow, mechanical linkage


48


moves indicator


44


to the right as valves


24


A, . . . , etc. open. Moving indicator


44


to the right indicates a greater percentage of hydrocarbon gas on display


46


.




Similarly, if the temperature of hot gas


28


as measured by temperature detector


40


exceeds a predetermined value, a signal is sent through connection


42


to valve assembly


24


to have it close valves


24


A, . . . , etc. and reduce the amount of hydrocarbon gas being fed to intake pipe


18


. As valve assembly


24


closes valves


24


A, . . . , etc., mechanical linkage


48


moves indicator


44


to the left, indicating on display


46


that the intake gas contains a lower percentage of hydrocarbon gas.




Referring to

FIG. 2

, display


46


is illustrated with indicator


44


, showing display


46


as a tractor operator (not shown) would view it from his operating position. As illustrated, display


46


contains a large green area


50


, a white area


52


and a large red area


54


. When the moisture content of granular material


16


is at an acceptable level, indicator


44


points to or is located in green area


50


. As the moisture content increases, indicator


44


will move to through white area


52


. When the moisture content reaches an unacceptable level, indicator


44


points to or is located in the red area


54


. Indicator


44


pointing to the red area


54


is a clear indication to the loader operator that the bucket on the tractor is digging too deep into the mound of sand. The loader operator should either raise his bucket or move to a different location on the sand mound or to a different sand mound. The operation of wind and sun on a sand mound can be such that a mere raising of the bucket four inches can bring the moisture content of granular material


16


down to a level that the moisture level is acceptable. This will move indicator


44


from red area


54


to green area


50


.




Referring now to

FIG. 3

, a back view of display


46


is illustrated. A base


56


of indicator


44


is illustrated as extending through display


46


. Base


56


is fastened to a slip linkage


58


. As mechanical linkage


48


moves to the right indicator


44


will move to the left. And conversely, as mechanical linkage


48


moves to the left moving the lower portion of slip linkage


58


to the left, indicator


44


will move to the right.




As can be seen, through the measurement of exhaust hot gas


28


using temperature detector


40


, the opening and closing of valves


24


A, . . . , etc. of valve assembly


24


can be controlled to regulate the flow of hydrocarbon gas from supply


20


through gas line


22


. The opening and closing of valves


24


A of valve assembly


24


will move indicator


44


using mechanical linkage


48


through slip linkage


58


and base


56


to indicate the percentage of hydrocarbon gas in intake gas


28


on display


46


. This percentage of hydrocarbon gas is the percentage which is needed to maintain the temperature of hot intake gas


28


within a predetermined temperature range. The exhaust temperature of hot gas


28


is inversely proportional to the amount of moisture within granular material


16


. As the moisture content of granular material


16


increases, the exhaust temperature of hot gas


28


decreases. Similarly, when the moisture content of granular material


16


decreases, the exhaust of hot gas


28


increases. The inverse proportionality is approximately linear so that an increase in temperature indicates a proportional decrease in moisture and a decrease in the exhaust temperature of hot gas


28


indicates a proportional increase in the moisture content of granular material


16


.




While there has been illustrated and described a particular embodiment of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and the present invention should not be limited thereto. It is intended that the present invention cover all those changes and modifications which fall within the true spirit and scope of the appended claims.



Claims
  • 1. A method of indicating the amount of moisture contained in a granular material in a drying operation having a hot gas intake and a gas exhaust including:measuring a temperature of gas in said gas exhaust; controlling the hot gas intake in response to said temperature of gas in said gas exhaust; associating a visual indicator with said controlling the hot gas intake; and using said indicator with a display to display an indication of moisture amount in the granular material.
  • 2. The method according to claim 1 wherein said controlling includes:opening valves providing flammable gas to said hot gas intake when said measured temperature is below a predetermined minimum; and closing said valves providing flammable gas to said hot gas intake when a measured temperature from said measuring a temperature exceeds a predetermined maximum.
  • 3. The method according to claim 2 wherein said associating an indicator includes:connecting said indicator with said valves providing flammable gas to said hot gas intake to provide an indication of moisture content of the granular material.
  • 4. A method of indicating an amount of moisture contained in a granular material in a drying container having a hot gas intake and a gas exhaust including:measuring a temperature of gas in said gas exhaust; controlling a temperature of the hot gas intake by controlling a percentage content of flammable gas in the hot gas intake in response to said temperature of gas in said gas exhaust; and using a visual indicator associated with a display to display an indication of said percentage content of flammable gas as a function of the amount of moisture in the granular material.
  • 5. The method according to claim 4 wherein said controlling a temperature of the hot gas intake by controlling a percentage content of flammable gas includes:opening valves providing said flammable gas to said hot gas intake when said measured temperature is below a predetermined minimum; and closing said valves providing said flammable gas to said hot gas intake when said measured temperature exceeds a predetermined maximum.
  • 6. The method according to claim 5 wherein said using an indicator includes:connecting said indicator with said valves providing flammable gas to said hot gas intake to provide an indication of moisture content of the granular material.
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4267643 Haried May 1981 A
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4509272 Gräff Apr 1985 A
4704805 Kaya et al. Nov 1987 A
4888885 Caughey Dec 1989 A
6079121 Khadkikar et al. Jun 2000 A
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