State-of-the-art hardware combined with a touch-screen software platform and rugged design provides accurate, high-precision thermogravimetric constituent analysis—moisture, ash, volatile content, and LOI in various organic, inorganic, and synthetic materials. Complying with ASTM standardized methods, the TGA is applicable to many industries and applications including coal, cement, catalyst, foods, and feeds. Macro thermogravimetric analysis nominal 1 g replaces the often slow, labor-intensive, traditional manual gravimetric techniques that require multiple sample weighing and transfer steps involving ovens, muffle furnaces, and desiccator equipment. Flexible method settings, automation, and hardware capabilities deliver an automated analysis process while requiring only the manual measurement of the initial sample mass, for maximum productivity in your lab.
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CEM Corp. Fisher Scientific Co. A proximate analyzer as defined in claim 1 wherein said support means comprises a generally planar plate. A proximate analyzer as defined in claim 2 wherein said plate includes an aperture for receiving each of the crucibles. A proximate analyzer as defined in claim 1 further comprising nitrogen line means for selectively flooding said furnace with nitrogen to prevent oxidation of the samples during analysis, said nitrogen line means including a first end to be coupled to a nitrogen source, a second end communicating with said furnace, and a valve means between said first and second ends for controlling the flow of nitrogen through said line means.
A proximate analyzer as defined in claim 1 wherein said furnace comprises a container with an upper open end and a cover, and further wherein said elevator means includes means for elevating said support means to a position proximate said upper open end to facilitate loading and unloading of the samples.
A device as defined in claim 6 further comprising gas line means for selectively flooding said furnace with a gas devoid of oxygen to prevent oxidation of the samples during analysis, said gas line means including a first end to be coupled to a gas source, a second end communicating with said furnace chamber, and a valve means between said first and second ends for controlling the flow of gas through said line means.
A device as defined in claim 6 wherein said furnace comprises a lower container having an upper open end and a cover for selectively closing said container, said cover movable between open and closed positions, and wherein said transport means includes means for elevating said sample-holding means to a position proximate said upper end when said cover is in said open position to facilitate loading of the crucibles.
The proximate analysis of a material to determine the content of at least some of its constituent components provides important information regarding the material. This is particularly true with coal and coke, which are composed primarily of the four components moisture, volatiles, fixed carbon, and ash. Coal and coke proximate analysis results are useful in predicting energy content, potential pollution problems, and the ash which will remain after burning.
The ASTM standards for determining the moisture, volatiles, fixed carbon, and ash content of coal and coke are relatively complex. Each of the moisture, volatiles, and ash content determinations are made by first weighing a sample to be analyzed, second subjecting the sample to elevated temperatures in a controlled atmosphere for a standard period of time, and third weighing the sample to determine sample weight loss.
Well-known mathematical formulas are then utilized to calculate the moisture, volatiles, fixed carbon, and ash content of the material. The samples must be repeatedly handled and weighed during testing. The handling is time consuming and can be dangerous because of the high temperatures involved.
Further, because the sample must be left in the furnace for a fixed period of time, the tests are relatively time-consuming with no provision made for rapidly analyzing a sample analyzable in less then the standard time periods. Although analyzers have been developed for facilitating the proximate analysis of coal and coke, these analyzers are not without their drawbacks.
One such analyzer includes a furnace and a balance having a weigh platform positioned in the furnace. Consequently, a sample, or sample-containing crucible, may be placed on the balance to provide a constant readout of sample weight during the heating period. However, only one sample may be analyzed during each analyzer cycle. Another device includes a rack containing a plurality of samples, or sample-containing crucibles, and a furnace in which the rack is positioned.
Although this analyzer is capable of heating a plurality of samples simultaneously, the individual samples must be handled and weighed outside of the furnace both before and after heating. Essentially, a proximate analyzer is provided including a furnace chamber, an electronic balance having a weigh platform within the furnace chamber, a sample rack within the furnace chamber adapted to support a plurality of sample-containing crucibles, and means for continuously and individually depositing the crucibles in a predetermined sequence on the weigh platform.
Additionally, a circuit means is operatively coupled to the balance for receiving weight interpretation signals therefrom for monitoring the individual weights of the crucibles to determine the weight loss of the samples during heating and to calculate proximate analysis results.
Consequently, the analyzer is capable of analyzing a plurality of samples during one analyzer cycle. The samples are not handled after being loaded into the furnace because all weighing is conducted automatically within the furnace chamber. This improves accuracy of measurement and eliminates the danger of handling the heated crucibles.
Third, because the weights of the samples are continually monitored, the circuit means can analyze the weighings to determine when analysis is complete, for example when the weights of the samples attain a relatively constant value or constant rate of change indicating that the constituent component driven from the samples during the particular temperature and environmental conditions has been eliminated from the sample.
Such monitoring reduces analysis time since the samples need not be left in the furnace any longer than necessary to conduct the analysis. These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the written specification and appended drawings.
As seen in FIG. Sample rack 18 is a disc having a plurality of apertures 22 positioned evenly about the periphery of the platter see also FIG. A plurality of sample-containing crucibles 24 may be positioned on platter 18 with one of the crucibles generally aligned with each one of apertures 22 and supported by the peripheral edge of the aperture. Mechanism 20 is then actuated to continuously and individually deposit crucibles 24 on weigh platform 16 by rotating platter 18 so that one of apertures 22 is aligned with weigh platform 16 and then lowering platter 18 to deposit the associated crucible on the weigh platform.
After weighing is complete, platter 18 is shifted upwardly to lift the weighed crucible off of weigh platform 16, and the next adjacent crucible is weighed in a similar manner. Consequently, crucibles 24 may be weighed within furnace 12 without opening the furnace. Referring more specifically to the construction of furnace 12 FIG. Lower member 26 includes a generally cylindrical side wall 30 integrally joined to generally horizontal, planar furnace floor 32 see also FIG.
The upper end of member 26 is open with wall 30 terminating with an annular top surface Cover 28 is a generally planar member having a circular shape and, when closed, rests on the upper surface 33 of wall Both lower member 26 and cover 28 are fabricated from well-known refractory ceramic materials such as alumina.
Cover 28 is hingedly secured to member 26 by a hinge 36 for movement between a closed position resting on surface 33 of lower member 26 as indicated in FIG.
A pair of conventional pneumatic cylinders 38 are mounted on opposite sides of furnace 12 see also FIG. When cover 28 is in its fully open position 28", cylinders 38 are positioned as indicated in FIG. The electronic balance 14 includes a weigh platform 16 supported on shaft Shaft 46 extends vertically and is located within a generally cylindrical bore 48 formed in furnace floor The inside diameter of bore 48 is somewhat larger than the outer diameter of shaft 46 so that the shaft is freely movable within the bore.
Sample platter 18 FIGS. Plate 50 includes twenty evenly spaced circular apertures 22 extending therethrough near the outer periphery of the platter. One aperture 22a is designated the zero-position aperture, and each of apertures 22 has generally the same diameter. The circular configuration of apertures 22 and plates 50 has a common axis 54 about which sample platter 18 rotates.
Since the center of each aperture is the same distance from axis 54, by rotating platter 18, any one of apertures 22 may be vertically aligned with weigh platform Elevation and rotation means 20 are provided to selectively raise platter 18, rotate the platter, and subsequently lower the platter to sequentially place a sample-holding crucible 24 on weigh platform Means 20 FIG. Means 20 further includes lifting means 60 which includes horizontal support plate 64, rod block 66 fixedly secured to the underside of plate 64, and a pneumatic cylinder 68 having shaft 70 fixedly secured to block Consequently, when pneumatic pressure is applied to cylinder 68, shaft 70 extends from the cylinder upwardly shifting rod block 66 and support plate 64 to which the platter-rotating means, including motor 58, is mounted.
When the pneumatic pressure is released from cylinder 68, shaft 70, block 66, and support plate 64 move downwardly. Guide block 76 is fixedly secured to leg 77 of rod block 66 and includes an aperture 78 for receiving guide 74 extending upwardly from base 76 of analyzer A second guide rod 72 extends slidably through an aperture in plate 64 such that the plate 64 and platter 18 rotatably coupled thereto are held in precise rotational alignment when the platter is raised and lowered by the actuation of cylinder By controlling pneumatic cylinder 68, support plate 64 may be vertically shifted between a raised load position shown in solid lines in FIG.
Because rotation device or motor 58 travels vertically with plate 64, it also moves vertically between a load position shown in FIG. Finally, because shaft 56 removes vertically with rotation device 58, platter 18 is vertically shiftable between a load position shown in FIG. In the load position, rack 18 is proximate the upper open end of furnace 12 to facilitate the positioning of crucibles 24 on apertures A latch 94 FIG. Latch 94 includes a locking edge which does not interfere with the movement of plate 64 when latch 94 is in its unlocked position.
Motor 58 rotates rack 18 until one of the apertures 22 and crucible 24 thereon is generally vertically concentrically aligned with weigh platform Device 58 then stops to maintain platter 18 in the desired angular orientation.
Cylinder 68 is then deactuated to lower platform 64, device 58, and platter 18 into weigh positions 18", 58", and 64" as shown in FIG. As platter 18 moves downwardly to weigh position 18", crucible 24 is deposited on the weigh platform. Rack 18 is maintained in this position for a sufficient period allowing balance 14 to determine a steady weight and provide an electronical output signal representative thereof.
Crucible 24 is generally well known being a cup-shaped member preferably fabricated of porcelainized alumina. In the preferred embodiment, each crucible 24 weighs approximately 10 grams and is designed to contain a sample weighing approximately 1 gram. Consequently, the ratio of crucible weight to sample weight is approximately 10 to 1 although the sample weight may vary between 0. Oxygen source 80 and nitrogen source 82 provide oxygen and nitrogen under a pressure of approximately 30 p.
Sources 80 and 82 are controlled by valves 84 and 86, respectively, to introduce oxygen and nitrogen selectively into line 88 connected to nozzles 90 and 92, which extend through side wall 30 of lower member 26 and terminate in nozzle ends 90a and 92a, respectively.
Nozzles 90 and 92 are arranged within chamber 34 to prevent the introduced gases from being directed against weigh platform 16 and shaft 46 which might affect balance accuracy. An electrical control circuit which, in the preferred embodiment of the invention comprises a computer FIG.
The computer is electrically coupled by conventional interface circuits to oxygen valve 84, nitrogen valve 86, cover pistons 38, latch 94, balance 14, shifting assembly 60, rotation device 58, and temperature control Additionally, computer is operatively connected to an input keyboard and a printer Computer receives signals from keyboard , and balance 14 and generates signals to actuate the other devices connected thereto.
The computer is programmed to implement analyzer control as described herein, specifically with reference to FIGS. Temperature control is a commercially available device including a thermocouple not shown located in chamber 34 to control the temperature therein. Operation FIG. All control is conducted by computer which receives signals from keyboard and balance 14 and issues control signals to oxygen valve 84, nitrogen valve 86, cover pistons 38, latch 94, shifting assembly 60, rotation device 58, and temperature control To initiate a machine cycle, the operator pushes an "analyze" key on keyboard Computer then supplies signals to cover pistons 38 to raise cover 28 to an open position 28" and to shifting assembly 60 to raise platter 18 to load position as indicated by step The operator removes any crucibles 24 remaining on rack 18 from a previous analyzer cycle.
The operator then positions an empty crucible 24 on plate 18 in zero-position aperture 22a as indicated by step Additionally, an empty crucible 24 is positioned on platter 18 in a counter-clockwise direction from position zero 22a for each sample to be analyzed. For example, if three samples are to be analyzed, a total of four crucibles are placed on rack 18 and if seventeen samples are to be analyzed, eighteen crucibles are placed on rack Each crucible 24 is positioned and aligned with one of the apertures 22, so that a total of twenty crucibles may be positioned in the twenty apertures.
Crucible 24 in zero position 22a remains empty during the entire machine cycle, so that a maximum of nineteen samples may be analyzed during one analyzer cycle. After the empty crucibles are loaded, computer supplies signals to cover pistons 38 to lower cover 28 to its closed position as indicated by step Each of crucibles 24 on rack 18 is weighed beginning with the crucible in zero position 22a. Computer supplies control signals to shifting assembly 50 and rotation device 58 to sequentially, individually align each crucible 24 with weigh platform 16 and deposit the crucible on the weigh platform.
The computer records the empty crucible weights as "crucible weights", and determines which of apertures 22 do not contain crucibles. The individual crucibles are then individually presented for sample loading by positioning the crucible over weigh platform Shifting assembly 60 lowers plate 18 to weigh position 18", depositing the just-loaded crucible on weigh platform
CEM Corp. Fisher Scientific Co. A proximate analyzer as defined in claim 1 wherein said support means comprises a generally planar plate. A proximate analyzer as defined in claim 2 wherein said plate includes an aperture for receiving each of the crucibles. A proximate analyzer as defined in claim 1 further comprising nitrogen line means for selectively flooding said furnace with nitrogen to prevent oxidation of the samples during analysis, said nitrogen line means including a first end to be coupled to a nitrogen source, a second end communicating with said furnace, and a valve means between said first and second ends for controlling the flow of nitrogen through said line means. A proximate analyzer as defined in claim 1 wherein said furnace comprises a container with an upper open end and a cover, and further wherein said elevator means includes means for elevating said support means to a position proximate said upper open end to facilitate loading and unloading of the samples. A device as defined in claim 6 further comprising gas line means for selectively flooding said furnace with a gas devoid of oxygen to prevent oxidation of the samples during analysis, said gas line means including a first end to be coupled to a gas source, a second end communicating with said furnace chamber, and a valve means between said first and second ends for controlling the flow of gas through said line means.
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