CA1139702A - Method and apparatus for on-line monitoring of bitumen content in tar sand - Google Patents
Method and apparatus for on-line monitoring of bitumen content in tar sandInfo
- Publication number
- CA1139702A CA1139702A CA000370382A CA370382A CA1139702A CA 1139702 A CA1139702 A CA 1139702A CA 000370382 A CA000370382 A CA 000370382A CA 370382 A CA370382 A CA 370382A CA 1139702 A CA1139702 A CA 1139702A
- Authority
- CA
- Canada
- Prior art keywords
- tar sand
- radiation
- filter
- bitumen
- pass
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000011275 tar sand Substances 0.000 title claims abstract description 58
- 239000010426 asphalt Substances 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000012544 monitoring process Methods 0.000 title claims abstract description 8
- 230000005855 radiation Effects 0.000 claims description 44
- 238000001914 filtration Methods 0.000 claims description 6
- 238000012545 processing Methods 0.000 abstract description 3
- 238000000605 extraction Methods 0.000 abstract description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 230000008569 process Effects 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- 230000009102 absorption Effects 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 4
- 239000003921 oil Substances 0.000 description 4
- 230000001360 synchronised effect Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 239000011269 tar Substances 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000004576 sand Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- UKUVVAMSXXBMRX-UHFFFAOYSA-N 2,4,5-trithia-1,3-diarsabicyclo[1.1.1]pentane Chemical compound S1[As]2S[As]1S2 UKUVVAMSXXBMRX-UHFFFAOYSA-N 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 101150087426 Gnal gene Proteins 0.000 description 1
- 229910000673 Indium arsenide Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229940052288 arsenic trisulfide Drugs 0.000 description 1
- 239000011365 complex material Substances 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000005188 flotation Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Substances [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/008—Controlling or regulating of liquefaction processes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3563—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
Landscapes
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Wood Science & Technology (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Remote Sensing (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
"METHOD AND APPARATUS FOR ON-LINE MONITORING OF
BITUMEN CONTENT IN TAR SAND"
ABSTRACT OF THE DISCLOSURE
An improvement in the processing of bituminous sands is described, whereby the concentration of bitumen in tar sand feed is measured by infrared light reflected from the tar sand surface. Near infrared is shone onto the surface of the incoming tar sand and reflected light is collected and passed through two parallel filters, one being a measuring filter having a wavelength range of 2180 to 2260 nm and the other being a reference filter having a wavelength range of 2270 to 2350 nm.
The beams emerging from the filters are measured electronically and the resulting signals are separately integrated and amplified by electronic means. The ratio of the amplified signals is used to provide a read-out signal responsive to the bitumen concentration. The results may be used to adjust processing conditions in the extraction process to allow for the variations of bitumen in the feed.
BITUMEN CONTENT IN TAR SAND"
ABSTRACT OF THE DISCLOSURE
An improvement in the processing of bituminous sands is described, whereby the concentration of bitumen in tar sand feed is measured by infrared light reflected from the tar sand surface. Near infrared is shone onto the surface of the incoming tar sand and reflected light is collected and passed through two parallel filters, one being a measuring filter having a wavelength range of 2180 to 2260 nm and the other being a reference filter having a wavelength range of 2270 to 2350 nm.
The beams emerging from the filters are measured electronically and the resulting signals are separately integrated and amplified by electronic means. The ratio of the amplified signals is used to provide a read-out signal responsive to the bitumen concentration. The results may be used to adjust processing conditions in the extraction process to allow for the variations of bitumen in the feed.
Description
~39~
FIELD OF T~IE INVENTION
This invention relates to an infrared reflectance monitor for indicating the bitumen content trend in tar sand feed~
BACKGROUND OF T~E INVENTION
Bitumen is today being commercially extracted from tar sand using a recovery process commonly known as the hot water process.
In general, this process involves: mixing the mined tar sand with hot water, steam and sodium hydroxide in a tumbler; diluting the produced slurry with additional hot wateri retaining the diluted slurry under quiescent conditions in an open-topped primary separation vessel having an outlet in its conical base, whereby aerated bitumen rises to form a primary froth, which is collected~ and solids settle and are re-moved through the outlet; withdrawing a dragstream from the middle of the vessel, said dragstream containing non-rising bitumen and clay particles; and subjecting said dragstream to induced air flotation to recover a secondary froth.
The tar sand is a complex material. More particularly, it comprises: sand-size solid grains; connate water sheathing the grains;
fine clay-like solids (-325 mesh) which appear to be concentrated in the water; and bitumen filling the interstices between the water-sheathed sand grains.
The concentrations of these various components, which make up the tar sand, vary throughout the deposit and hence in the feed led to the extraction plant. These variations in concentration have a marked effect on the efficiency of the recovery process.
The component whose concentration variations can most deleteriously affect the hot water process is the fine solids (hereinafter termed "Fines"). The solids component of a low fines tar sand may ~ontain in the order of 5% by weight fines, while the solids component of a high fines tar sand may contain in the order of 2Q~ by weight fines.
~397~;~
Operators of the process can react to the presence of higher levels of fines in the ~eed by -increasing the sodium hydroxide and water additions to the process; these increases will reduce the deleterious effects of the high fines on the eff;ciency of the bitumen recovery process.
To date, the practice used for monitoring the tar sand composition has involved sampling the feed and subjecting the samples to laboratory analysis. However, this is a t;me-consuming process and thus the implementation of changes in water and sodium hydroxide addition is late, with the result that the hot water process is rarely operated at optimum conditions.
There has thus existed a long-standing need for an on-line analysing means which would monitor and indicate tar sand feed grade trends accurately and quickly.
It needs to be noted that there is an inverse proportional relationship between bitumen and fines concentrations in tar sand. There-fore the development of an accurate indicator of bitumen content would provide the industry with a means for monitoring fines content.
SUMMARY OF THE INVENTION
In accordance with the invention, tar sand feed grade trends are monitored by:
(a) shining near infrared radiation onto the surface of advancing tar sand;
(b) filtering a first portion of reflected radiation through a first filter which is adapted to pass only radiation of a wavelength range absorbed to a significant extent by bitumen alone among the components of tar sand;
(c) filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the tar sand and which has a wavelength close to the first wavelength rangej g~
(d) sensin~ the radi.ation passed by the first filter and producing an electrical si.gnal indicative of its intensity;
(e) sens;ng the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
(f) establishing a ratio of said signals and producing an electrical output indicative of said ratio and which is indicative of the bitumen content of the tar sand;
(g) continuing the foregoin~ steps sufficiently frequently to give a reading representative oF the bitumen content of the tar sand.
In a preferred embodiment of the invention, the fi.rs.t filter is adapted to pass only radiation havi.ng a wavelength oF about 21~Q to about 2260 nm and the second filter is adapted to pass only radia~i:on havi.ng a wavelength of about 2270 to about 2350 nm.
It is necessary to have two filters, adapted to pass different wavelengths (a measure and a reference)~ due to variations in intensity of the incident radiation and to variati.ons i.n the nature of the reflecti.ve surface. Inci.dent radiation can be affected by extraneous sources of light, alterations in electrical supply to th.e near i.nfrared lamps, or deterioration of those lamps... At the same ti:me, the tar sand reflecti.ve surface may vary according to its. roughnes.s. or smoothnes:s, the quanti:ty of b;tumen, or such properties. as dryness and degree of oxi:dati'on~ Before.
absorption of the near infrared due to bitumen can be. determi:ned~ it i:s necessary to compensate for the extent to which the reflected rays. are affected by the other properties of the tar sand or th.e inci`dent radi`ati'on.
It is thus the purpose of the reference filter to determi'ne those effects on the reflected radiation due to vari.ations. of tar sand or inci:dent radi':ationwhi.ch are disti.nct from absorption by bi'tumenO W.i`th th.i:s compensati.ng means-present, absorption due to bitumen alone is successfully is-olate.d from ancil-lary variati.ons.in reflected radiationA ThR wavelength range of the refer~n.ce.filter should be close to that of the meas.ure fi.lter? b.ecause th~e extent tQ
which ancillary variati.ons. affect reflectance i's wavelength-dependent~
~ ~3~7~
The development of the present invention involved some surprising discoveries. Previous uses of reflexive infrared in connection with oil monitoring had been limited to recording oil layers having a thickness in the order of 10~. This is the thickness of~ for instance, oil spills on bodies oF water. However, penetration to this order of depth would not be useful in tar sand monitoring, as the individual sand particles are commonly thicker than 10~. It Follows that one would question whether the infrared would reach interior bitumen. Surprisingly9 the infrared appears to penetrate between 1 and 3 mm. into the tar sand.
Also, tar sand contains variations in concentration oF bitumen and there was concern that these localized rich and lean zones would deleteriously affect the desired performance of the instrument. It was found that manageable absorptions were obtained in both low and high bitumen content zones. Finally9 the bituminous component, at the surface of the tar sand mass (such as a layer of tar sand on a conveyor belt), quickly becomes dry and oxidized. Its chemical nature changes significantly from the bitumen present further into the layer. There was therefore concern that this surface effect would affect the reliability of the measurement. However, bitumen readings taken at the surface of a pile have been found to be essentially the same as those obtained after the surface layer is removed.
In addition, the present inventor had to conduct extensive experimentation involving over 130 spectra and many analyses to discover the proper wavelength requirements of the filters.
Broadly stated, the invention is a method for monitoring tar sand feed bitumen content trends, comprising: shining near infrared radiation onto the surface of advancing tar sand; filtering a flrst portion of the reflected radiation through a first filter which is adapted to pass only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of tar sand, filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the ~39~2 tar sand and which has a wavelength close to the first wavelength range;
sensing the radiation passed by the first filter and producing an electrical signal indicate of its in-tens:ity; sensing the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
establishing a ratio of said signals and producing an electrical output indicative of said ratio, and which is indicative of the bitumen content of the tar sandi and continuing the foregoing steps sufficiently frequently to give a reading representative of the bitumen content of the tar sand, In another aspect of the invention, there is provided an infrared reflectance monitor for indicating the bitumen content trend in tar sand feed, said monitor comprising: a source of infrared radiation adapted to be directed at the tar sand; means for focusing radiation reflected by the tar sand; first and second filters that may be alternately positioned in the path of the focused reflected radiation, the First such filter being adapted to pass only radiation having a wavelength absorbed by bitumen alone among the components of the tar sand, the second such Filter being adapted to pass only radiation having a wavelength not absorbed by any of the tar sand components; and means for sensing the intensity of each passed radiation species and producing a signal indicative of the bitumen content.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic showing the interrelationship of the principal elements of the instrument;
Figure 2 is a schematic showing a known instrument incorporated into the invention;
Figure 3 is a plot showing the infrared spectrum of typical bitumen such as is contained in tar sand;
~39~Z
Figure 4 is a plot ~howing the infrared spectrum of typical solids in tar sandi and Figure 5 is a plot showiny a typical relationship between bitumen content in tar sand as determined by reflective infrared and as determined by laboratory analysis.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present tar sand monitor is an instrument which, when suspended about 40 to 60 inches above the tar sand, provides a remote indication of the bitumen concentration (weight percent) in the surface layer of said tar sand. When the tar sand is on a moving conveyor belt, the instrument continuously produces a measurement which is an averaging of the bitumen content of a strip observed over a period of approximately 30 seconds. The strip typically has a width of approximately 6 inches and a length of approximately 250 feet.
A greatly simplified layout is given in Figure l to show the interrelationship of the optical and electronic elements. For greater detail, refer to Figure 2. The monitor comprises a source of infrared radiation, more particularly a Tungsten-halogen lamp l, mounted at the focal point of an aluminum parabolic reflector la. The lamp l is used in conjunction with a focusing lens lb. Preferably, dual transmitters (not shown) are used, to ensure continuous operation if one lamp burns Gut. As stated, the lamp l beams radiation at the tar sand surface, which radiation is partly reflected.
A receiver lens 2 is suitably mounted in the path of the reflected radiation. The lens 2 functions to focus the incoming radiation to a small point. An arsenic trisulfide lens is suitable -for this purpose.
A filter wheel 3, driven by filter wheel motor 4, is positioned between the lens 2 and the latter's focal point. The wheel 3 carries a pair of filters of the following specification:
~L3 9~7 Filter No. 1 -centre wavelength 2.22~m + 0.01 ~m half-band width O.OB~m + 0.11 ~m transmission on wavelength 50% peak or greater transmission off 0.1% absolute or less at all wavelength wavelengths out of band to 5~m Filter No. 2 Centre wavelength 2.33~m + 0.02~m half-band width 0.08~m + O.ll~m transmission on 50% peak or greater wavelength transmission off 0.1% absolute or less at all wavelength wavelengths out of band to 5~m Filter No. 1 passes only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of the tar sand. The beam passed by this filter is termed the measure beam.
Filter No. 2 passes only radiation of a wavelength not absorbed by any of the components of tar sand9 this radiation has a wavelength close to the measuring wavelength. The beam passed by filter No. 2 is termed the reference beam.
The lamp 1, receiver lens 2, filter wheel 3, motor 4, and most of the electronic equipment shown schematically in Figure 2 and briefly described below are commercially available from Wright and Wright Inc., Oak Bluffs, Massachusetts, in the form of a monitor designated Model E
250.
Continuing now with such description, a photodetector 5 is provided at the focal point of the receiver lens 2. This photodetector senses each of the alternately passed measure and reference beams and emits electrical signals proportional to their intensities. An indium arsenide photodetector is suitable for this purpose.
The photodetector signals are transmitted to and amplified by a preamplifier 6. The preamplifier output is fed to an AGC amplifier 16 and thence to a multiplexer 7.
~3~
A sync pick-off 8 is provided to sense and indicate when each filter is directing a beam at the photodetector 5~ This sync pick-off 8 comprises a U-shaped optical switch straddling the filter wheel 3 and employing a liyht source and a silicon photodetector at opposite ends oF
the switch. Light emitted by the sync pick-off passes through slots in the outer edge of the Filter wheel and thus periodically transmits a signal determined by the filter wheel position.
The pick-off signals are transmitted to a logic circuit 9 which functions to switch the multiplexer 7 to transmit the detected and ampliFied signal to either the measuring signal amplifier 10 or reference signal amplifier 11, depending on which filter is sensed to be in front of the photodetector 5.
There are provided measure and reference signal processing means comprising amplifiers 10, 11, synchronous demodulators 12, 13 and integrators 1~, 15. The multiplexer 7 alternately shorts to ground that amplifier 12 or 13 not passing the detected and amplified signal. The synchronous demodulators 12,13 allow only signals of the frequency corresponding to the rotational speed of the filter wheel to be passed, with other frequencies being rejected. They thus reduce the electronic 20 noise in the signal.
Each amplifier 10~ 11 has adjustable gain from approximately xl.O to xlO.O, as well as zero adjustment. The amplified measure or reference signals are detected by the synchronous demodulators 12, 13 respectively . The demodulators 12, 13 are operative to pass signals 25 at exactly the same frequency as the chopped frequency of light detected by the photodetector 5. The chopped frequency is of course set by the rotational frequency of the filter wheel 3. The sync pick-off 8 senses this chopped Frequency and feeds this frequency to each of the synchronous demodulators 12, 13 through the logic circuit 9. The demodulators 12, 13 30 reject all detected analog signals other than this chopped frequency to thereby increase the signal-to-noise ratio.
~3~
The de-tected signals from demodulators 12, 13 are fed to integrators 14, 15 respectively. The integrators 14, 15 average the signal strength over a preset interval of t-ime to compensate for signal variations due to rocks, clay lumps and variations in the tar sand oil content. A 30-second time constant has been found suitable.
An automatic gain control circuit 16 reFerred to as the AGC
amplifier is provided to control the strength of the signals -fed to the amplifiers 10, 11. The gain control circuit 16 senses the output voltage from the integrator 14, and if low, increases the gain of the AGC
amplifier. Conversely, when the output voltage of the integrator 14 is high, the gain control circuit 16 reduces the gain of the AGC amplifier to prevent saturation of the amplifiers 10, 11.
The averaged signals from the integrators 14, 15 (vjnte9rator 14 and vjnte9rator 15) respectively are fed to a ratiometer 17. The ratiometer 17 calculates a voltage output ratio (vOut) of the two signal strengths according to the equation 1 below.
vOut = 2-0 x ~ egrator 15 Volts (1) Vintegrator 14 The ratiometer 17 operates with a conventional logrithm, summation, antilog method to obtain the ratio (vOut).
The output (vOut) from the ratiometer 17 is fed through an output amplifier 18 and a current driver 19, and finally to an output meter (not shown). The output signal IoUt is also run to an external potentiometer (not shown) which returns an adjustable feedback signal to the input of the output amplifier 18 to provide current gain control.
Also provided externally is a zero control (not shown). The zero and current gain controls allow adjustment such that a standard 4 to 20 mA
current signal represents the desired range of bitumen content (5 to 15% bitumen).
~5L3~
The output signals from the integrators 14, 15 are also fed to threshold detectors 20, 21 respectively. Each of the threshold detectors 20, 21 is in turn connected to an instrument status alarm relay 22~ 23 respectively. The threshold detector 20, 21 activates when the voltage level of integrator 14 or 15 output approaches zero. Activation causes the contacts of the alarm relay 22 or 23 to open, thereby indicating a monitor malfunction. Further, loss of power to the monitor de-energizes and opens the alarm relays 22,23 to indicate failure. Opening of the relay 22 or 23 forces the current output of the current driver 19 to zero.
The output meter (not shown) is a digital voltmeter which displays the amplified output signal from the current driver 19.
The monitor as described above operates oFf 115 V AC (60 ~Iz) line power and thus is provided with a low voltage power supply 24 to convert this power to ~ 15 V DC. The + 15 V DC is Further converted to 5 V DC through a zener network 25. The monitor components operate from the 5 V or + 15 V DC power supply.
The AC input to the monitor is internally fused at 26 to prevent short circuit damage to the monitor. The AC input is also passed through a voltage transient suppressor 27 to suppress high voltage spikes.
While the present invention has been disclosed in connection with the preferred embodiment thereof, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention as defined by the following claims.
FIELD OF T~IE INVENTION
This invention relates to an infrared reflectance monitor for indicating the bitumen content trend in tar sand feed~
BACKGROUND OF T~E INVENTION
Bitumen is today being commercially extracted from tar sand using a recovery process commonly known as the hot water process.
In general, this process involves: mixing the mined tar sand with hot water, steam and sodium hydroxide in a tumbler; diluting the produced slurry with additional hot wateri retaining the diluted slurry under quiescent conditions in an open-topped primary separation vessel having an outlet in its conical base, whereby aerated bitumen rises to form a primary froth, which is collected~ and solids settle and are re-moved through the outlet; withdrawing a dragstream from the middle of the vessel, said dragstream containing non-rising bitumen and clay particles; and subjecting said dragstream to induced air flotation to recover a secondary froth.
The tar sand is a complex material. More particularly, it comprises: sand-size solid grains; connate water sheathing the grains;
fine clay-like solids (-325 mesh) which appear to be concentrated in the water; and bitumen filling the interstices between the water-sheathed sand grains.
The concentrations of these various components, which make up the tar sand, vary throughout the deposit and hence in the feed led to the extraction plant. These variations in concentration have a marked effect on the efficiency of the recovery process.
The component whose concentration variations can most deleteriously affect the hot water process is the fine solids (hereinafter termed "Fines"). The solids component of a low fines tar sand may ~ontain in the order of 5% by weight fines, while the solids component of a high fines tar sand may contain in the order of 2Q~ by weight fines.
~397~;~
Operators of the process can react to the presence of higher levels of fines in the ~eed by -increasing the sodium hydroxide and water additions to the process; these increases will reduce the deleterious effects of the high fines on the eff;ciency of the bitumen recovery process.
To date, the practice used for monitoring the tar sand composition has involved sampling the feed and subjecting the samples to laboratory analysis. However, this is a t;me-consuming process and thus the implementation of changes in water and sodium hydroxide addition is late, with the result that the hot water process is rarely operated at optimum conditions.
There has thus existed a long-standing need for an on-line analysing means which would monitor and indicate tar sand feed grade trends accurately and quickly.
It needs to be noted that there is an inverse proportional relationship between bitumen and fines concentrations in tar sand. There-fore the development of an accurate indicator of bitumen content would provide the industry with a means for monitoring fines content.
SUMMARY OF THE INVENTION
In accordance with the invention, tar sand feed grade trends are monitored by:
(a) shining near infrared radiation onto the surface of advancing tar sand;
(b) filtering a first portion of reflected radiation through a first filter which is adapted to pass only radiation of a wavelength range absorbed to a significant extent by bitumen alone among the components of tar sand;
(c) filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the tar sand and which has a wavelength close to the first wavelength rangej g~
(d) sensin~ the radi.ation passed by the first filter and producing an electrical si.gnal indicative of its intensity;
(e) sens;ng the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
(f) establishing a ratio of said signals and producing an electrical output indicative of said ratio and which is indicative of the bitumen content of the tar sand;
(g) continuing the foregoin~ steps sufficiently frequently to give a reading representative oF the bitumen content of the tar sand.
In a preferred embodiment of the invention, the fi.rs.t filter is adapted to pass only radiation havi.ng a wavelength oF about 21~Q to about 2260 nm and the second filter is adapted to pass only radia~i:on havi.ng a wavelength of about 2270 to about 2350 nm.
It is necessary to have two filters, adapted to pass different wavelengths (a measure and a reference)~ due to variations in intensity of the incident radiation and to variati.ons i.n the nature of the reflecti.ve surface. Inci.dent radiation can be affected by extraneous sources of light, alterations in electrical supply to th.e near i.nfrared lamps, or deterioration of those lamps... At the same ti:me, the tar sand reflecti.ve surface may vary according to its. roughnes.s. or smoothnes:s, the quanti:ty of b;tumen, or such properties. as dryness and degree of oxi:dati'on~ Before.
absorption of the near infrared due to bitumen can be. determi:ned~ it i:s necessary to compensate for the extent to which the reflected rays. are affected by the other properties of the tar sand or th.e inci`dent radi`ati'on.
It is thus the purpose of the reference filter to determi'ne those effects on the reflected radiation due to vari.ations. of tar sand or inci:dent radi':ationwhi.ch are disti.nct from absorption by bi'tumenO W.i`th th.i:s compensati.ng means-present, absorption due to bitumen alone is successfully is-olate.d from ancil-lary variati.ons.in reflected radiationA ThR wavelength range of the refer~n.ce.filter should be close to that of the meas.ure fi.lter? b.ecause th~e extent tQ
which ancillary variati.ons. affect reflectance i's wavelength-dependent~
~ ~3~7~
The development of the present invention involved some surprising discoveries. Previous uses of reflexive infrared in connection with oil monitoring had been limited to recording oil layers having a thickness in the order of 10~. This is the thickness of~ for instance, oil spills on bodies oF water. However, penetration to this order of depth would not be useful in tar sand monitoring, as the individual sand particles are commonly thicker than 10~. It Follows that one would question whether the infrared would reach interior bitumen. Surprisingly9 the infrared appears to penetrate between 1 and 3 mm. into the tar sand.
Also, tar sand contains variations in concentration oF bitumen and there was concern that these localized rich and lean zones would deleteriously affect the desired performance of the instrument. It was found that manageable absorptions were obtained in both low and high bitumen content zones. Finally9 the bituminous component, at the surface of the tar sand mass (such as a layer of tar sand on a conveyor belt), quickly becomes dry and oxidized. Its chemical nature changes significantly from the bitumen present further into the layer. There was therefore concern that this surface effect would affect the reliability of the measurement. However, bitumen readings taken at the surface of a pile have been found to be essentially the same as those obtained after the surface layer is removed.
In addition, the present inventor had to conduct extensive experimentation involving over 130 spectra and many analyses to discover the proper wavelength requirements of the filters.
Broadly stated, the invention is a method for monitoring tar sand feed bitumen content trends, comprising: shining near infrared radiation onto the surface of advancing tar sand; filtering a flrst portion of the reflected radiation through a first filter which is adapted to pass only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of tar sand, filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the ~39~2 tar sand and which has a wavelength close to the first wavelength range;
sensing the radiation passed by the first filter and producing an electrical signal indicate of its in-tens:ity; sensing the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
establishing a ratio of said signals and producing an electrical output indicative of said ratio, and which is indicative of the bitumen content of the tar sandi and continuing the foregoing steps sufficiently frequently to give a reading representative of the bitumen content of the tar sand, In another aspect of the invention, there is provided an infrared reflectance monitor for indicating the bitumen content trend in tar sand feed, said monitor comprising: a source of infrared radiation adapted to be directed at the tar sand; means for focusing radiation reflected by the tar sand; first and second filters that may be alternately positioned in the path of the focused reflected radiation, the First such filter being adapted to pass only radiation having a wavelength absorbed by bitumen alone among the components of the tar sand, the second such Filter being adapted to pass only radiation having a wavelength not absorbed by any of the tar sand components; and means for sensing the intensity of each passed radiation species and producing a signal indicative of the bitumen content.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic showing the interrelationship of the principal elements of the instrument;
Figure 2 is a schematic showing a known instrument incorporated into the invention;
Figure 3 is a plot showing the infrared spectrum of typical bitumen such as is contained in tar sand;
~39~Z
Figure 4 is a plot ~howing the infrared spectrum of typical solids in tar sandi and Figure 5 is a plot showiny a typical relationship between bitumen content in tar sand as determined by reflective infrared and as determined by laboratory analysis.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present tar sand monitor is an instrument which, when suspended about 40 to 60 inches above the tar sand, provides a remote indication of the bitumen concentration (weight percent) in the surface layer of said tar sand. When the tar sand is on a moving conveyor belt, the instrument continuously produces a measurement which is an averaging of the bitumen content of a strip observed over a period of approximately 30 seconds. The strip typically has a width of approximately 6 inches and a length of approximately 250 feet.
A greatly simplified layout is given in Figure l to show the interrelationship of the optical and electronic elements. For greater detail, refer to Figure 2. The monitor comprises a source of infrared radiation, more particularly a Tungsten-halogen lamp l, mounted at the focal point of an aluminum parabolic reflector la. The lamp l is used in conjunction with a focusing lens lb. Preferably, dual transmitters (not shown) are used, to ensure continuous operation if one lamp burns Gut. As stated, the lamp l beams radiation at the tar sand surface, which radiation is partly reflected.
A receiver lens 2 is suitably mounted in the path of the reflected radiation. The lens 2 functions to focus the incoming radiation to a small point. An arsenic trisulfide lens is suitable -for this purpose.
A filter wheel 3, driven by filter wheel motor 4, is positioned between the lens 2 and the latter's focal point. The wheel 3 carries a pair of filters of the following specification:
~L3 9~7 Filter No. 1 -centre wavelength 2.22~m + 0.01 ~m half-band width O.OB~m + 0.11 ~m transmission on wavelength 50% peak or greater transmission off 0.1% absolute or less at all wavelength wavelengths out of band to 5~m Filter No. 2 Centre wavelength 2.33~m + 0.02~m half-band width 0.08~m + O.ll~m transmission on 50% peak or greater wavelength transmission off 0.1% absolute or less at all wavelength wavelengths out of band to 5~m Filter No. 1 passes only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of the tar sand. The beam passed by this filter is termed the measure beam.
Filter No. 2 passes only radiation of a wavelength not absorbed by any of the components of tar sand9 this radiation has a wavelength close to the measuring wavelength. The beam passed by filter No. 2 is termed the reference beam.
The lamp 1, receiver lens 2, filter wheel 3, motor 4, and most of the electronic equipment shown schematically in Figure 2 and briefly described below are commercially available from Wright and Wright Inc., Oak Bluffs, Massachusetts, in the form of a monitor designated Model E
250.
Continuing now with such description, a photodetector 5 is provided at the focal point of the receiver lens 2. This photodetector senses each of the alternately passed measure and reference beams and emits electrical signals proportional to their intensities. An indium arsenide photodetector is suitable for this purpose.
The photodetector signals are transmitted to and amplified by a preamplifier 6. The preamplifier output is fed to an AGC amplifier 16 and thence to a multiplexer 7.
~3~
A sync pick-off 8 is provided to sense and indicate when each filter is directing a beam at the photodetector 5~ This sync pick-off 8 comprises a U-shaped optical switch straddling the filter wheel 3 and employing a liyht source and a silicon photodetector at opposite ends oF
the switch. Light emitted by the sync pick-off passes through slots in the outer edge of the Filter wheel and thus periodically transmits a signal determined by the filter wheel position.
The pick-off signals are transmitted to a logic circuit 9 which functions to switch the multiplexer 7 to transmit the detected and ampliFied signal to either the measuring signal amplifier 10 or reference signal amplifier 11, depending on which filter is sensed to be in front of the photodetector 5.
There are provided measure and reference signal processing means comprising amplifiers 10, 11, synchronous demodulators 12, 13 and integrators 1~, 15. The multiplexer 7 alternately shorts to ground that amplifier 12 or 13 not passing the detected and amplified signal. The synchronous demodulators 12,13 allow only signals of the frequency corresponding to the rotational speed of the filter wheel to be passed, with other frequencies being rejected. They thus reduce the electronic 20 noise in the signal.
Each amplifier 10~ 11 has adjustable gain from approximately xl.O to xlO.O, as well as zero adjustment. The amplified measure or reference signals are detected by the synchronous demodulators 12, 13 respectively . The demodulators 12, 13 are operative to pass signals 25 at exactly the same frequency as the chopped frequency of light detected by the photodetector 5. The chopped frequency is of course set by the rotational frequency of the filter wheel 3. The sync pick-off 8 senses this chopped Frequency and feeds this frequency to each of the synchronous demodulators 12, 13 through the logic circuit 9. The demodulators 12, 13 30 reject all detected analog signals other than this chopped frequency to thereby increase the signal-to-noise ratio.
~3~
The de-tected signals from demodulators 12, 13 are fed to integrators 14, 15 respectively. The integrators 14, 15 average the signal strength over a preset interval of t-ime to compensate for signal variations due to rocks, clay lumps and variations in the tar sand oil content. A 30-second time constant has been found suitable.
An automatic gain control circuit 16 reFerred to as the AGC
amplifier is provided to control the strength of the signals -fed to the amplifiers 10, 11. The gain control circuit 16 senses the output voltage from the integrator 14, and if low, increases the gain of the AGC
amplifier. Conversely, when the output voltage of the integrator 14 is high, the gain control circuit 16 reduces the gain of the AGC amplifier to prevent saturation of the amplifiers 10, 11.
The averaged signals from the integrators 14, 15 (vjnte9rator 14 and vjnte9rator 15) respectively are fed to a ratiometer 17. The ratiometer 17 calculates a voltage output ratio (vOut) of the two signal strengths according to the equation 1 below.
vOut = 2-0 x ~ egrator 15 Volts (1) Vintegrator 14 The ratiometer 17 operates with a conventional logrithm, summation, antilog method to obtain the ratio (vOut).
The output (vOut) from the ratiometer 17 is fed through an output amplifier 18 and a current driver 19, and finally to an output meter (not shown). The output signal IoUt is also run to an external potentiometer (not shown) which returns an adjustable feedback signal to the input of the output amplifier 18 to provide current gain control.
Also provided externally is a zero control (not shown). The zero and current gain controls allow adjustment such that a standard 4 to 20 mA
current signal represents the desired range of bitumen content (5 to 15% bitumen).
~5L3~
The output signals from the integrators 14, 15 are also fed to threshold detectors 20, 21 respectively. Each of the threshold detectors 20, 21 is in turn connected to an instrument status alarm relay 22~ 23 respectively. The threshold detector 20, 21 activates when the voltage level of integrator 14 or 15 output approaches zero. Activation causes the contacts of the alarm relay 22 or 23 to open, thereby indicating a monitor malfunction. Further, loss of power to the monitor de-energizes and opens the alarm relays 22,23 to indicate failure. Opening of the relay 22 or 23 forces the current output of the current driver 19 to zero.
The output meter (not shown) is a digital voltmeter which displays the amplified output signal from the current driver 19.
The monitor as described above operates oFf 115 V AC (60 ~Iz) line power and thus is provided with a low voltage power supply 24 to convert this power to ~ 15 V DC. The + 15 V DC is Further converted to 5 V DC through a zener network 25. The monitor components operate from the 5 V or + 15 V DC power supply.
The AC input to the monitor is internally fused at 26 to prevent short circuit damage to the monitor. The AC input is also passed through a voltage transient suppressor 27 to suppress high voltage spikes.
While the present invention has been disclosed in connection with the preferred embodiment thereof, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention as defined by the following claims.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for monitoring tar sand feed bitumen content trends, comprising:
shining near infrared radiation onto the surface of advancing tar sand;
filtering a first portion of the reflected radiation through a first filter which is adapted to pass only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of tar sand;
filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the tar sand and which has a wave-length close to the first wavelength range;
sensing the radiation passed by the first filter and producing an electrical signal indicative of its intensity;
sensing the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
establishing a ratio of said signals and producing an electrical output indicative of said ratio and which is indicative of the bitumen content of the tar sand; and continuing the foregoing steps sufficiently frequently to give a reading representative of the bitumen content of the tar sand.
shining near infrared radiation onto the surface of advancing tar sand;
filtering a first portion of the reflected radiation through a first filter which is adapted to pass only radiation of a wavelength absorbed to a significant extent by bitumen alone among the components of tar sand;
filtering a second portion of reflected radiation through a second filter which is adapted to pass only radiation not absorbed to a significant extent by any component of the tar sand and which has a wave-length close to the first wavelength range;
sensing the radiation passed by the first filter and producing an electrical signal indicative of its intensity;
sensing the radiation passed by the second filter and producing an electrical signal indicative of its intensity;
establishing a ratio of said signals and producing an electrical output indicative of said ratio and which is indicative of the bitumen content of the tar sand; and continuing the foregoing steps sufficiently frequently to give a reading representative of the bitumen content of the tar sand.
2. The method as set forth in claim 1 wherein:
the first filter is adapted to pass only wavelengths of about 2180 to about 2260 nm;
and the second filter is adapted to pass only wavelengths of about 2270 to about 2350 nm.
the first filter is adapted to pass only wavelengths of about 2180 to about 2260 nm;
and the second filter is adapted to pass only wavelengths of about 2270 to about 2350 nm.
3. An infrared reflectance monitor for indicating the bitumen content trend in tar sand feed, said monitor comprising:
a source of infrared radiation adapted to be directed at the tar sand;
means for focusing radiation reflected by the tar sand;
first and second filters that may be alternately positioned in the path of the focused reflected radiation, the first such filter being adapted to pass only radiation having a wavelength absorbed by bitumen alone among the components of the tar sand, the second such filter being adapted to pass only radiation having a wavelength not absorbed by any of the tar sand components and means for sensing the intensity of each passed radiation species and producing a signal indicative of the bitumen content.
a source of infrared radiation adapted to be directed at the tar sand;
means for focusing radiation reflected by the tar sand;
first and second filters that may be alternately positioned in the path of the focused reflected radiation, the first such filter being adapted to pass only radiation having a wavelength absorbed by bitumen alone among the components of the tar sand, the second such filter being adapted to pass only radiation having a wavelength not absorbed by any of the tar sand components and means for sensing the intensity of each passed radiation species and producing a signal indicative of the bitumen content.
4. The monitor as set forth in claim 3 wherein:
the first filter is adapted to pass only wavelengths of about 2180 to about 2260 nm; and the second filter is adapted to pass only wavelengths of about 2270 to about 2350 nm.
the first filter is adapted to pass only wavelengths of about 2180 to about 2260 nm; and the second filter is adapted to pass only wavelengths of about 2270 to about 2350 nm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000370382A CA1139702A (en) | 1981-02-09 | 1981-02-09 | Method and apparatus for on-line monitoring of bitumen content in tar sand |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000370382A CA1139702A (en) | 1981-02-09 | 1981-02-09 | Method and apparatus for on-line monitoring of bitumen content in tar sand |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139702A true CA1139702A (en) | 1983-01-18 |
Family
ID=4119119
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000370382A Expired CA1139702A (en) | 1981-02-09 | 1981-02-09 | Method and apparatus for on-line monitoring of bitumen content in tar sand |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1139702A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5376276A (en) * | 1992-04-29 | 1994-12-27 | Alberta Energy Company, Ltd. | In situ primary froth quality measurements using microwave monitor |
| WO2000054566A3 (en) * | 1999-03-15 | 2001-08-02 | Kumamoto Technopolis Foundatio | Soil survey device and system for precision agriculture |
-
1981
- 1981-02-09 CA CA000370382A patent/CA1139702A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5376276A (en) * | 1992-04-29 | 1994-12-27 | Alberta Energy Company, Ltd. | In situ primary froth quality measurements using microwave monitor |
| WO2000054566A3 (en) * | 1999-03-15 | 2001-08-02 | Kumamoto Technopolis Foundatio | Soil survey device and system for precision agriculture |
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