analyzersinthecoalindustry.pdf

7/27/2019 AnalyzersintheCoalIndustry.pdf

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The History and Future of Nuclear Elemental Analyzers for Product

Optimization in the U.S. Coal Industry

Steve Foster

Vice President Product Development; SABIA, Inc.

Abstract

This paper takes a critical look at the use of nuclear elemental analyzers** in coal - past, presentand future. The paper begins with a brief historical tour of analyzers and then discusses in detailthe strengths and trade-offs of current equipment, where they work, the value they deliver, andwhere they failed, concluding with a look at latest developments in the technology, and howthese developments impact future coal product optimization and cost reduction.

** Nuclear Elemental Analyzers as defined for the purposes of this paper includes those analyzers that measure the individual elements of the

periodic table. For example, Ash is determined by adding the sum of the individually measured constituents of Ash, i.e., Silicon, Iron, Calcium,

Aluminum, Potassium, Titanium, etc…

Introduction

Coal commerce in the United States is based on proper characterization of the shipped coal.Coal contracts specify the volume, timing, and the quality of the shipped coal, using specificlimits for such things as ash, sulfur, BTU, and SO2/MBTU. The need to monitor these parameters has necessitated widespread use of material sampling systems and lab analysis.

Although nuclear elemental analyzers have yet to qualify as the basis for conducting commercein coal they are now an accepted approach for real-time monitoring and control of processes tooptimize delivered coal to specific contractual quality parameters.

The value of real-time monitoring and control as made available through nuclear elementalanalyzers is that it provides an accurate method for coal producers to optimize the value of their product. Parameters such as ash or sulfur content can be optimized for pile construction, or through real time blending while loading a train. In both cases, coal producers can lengthen thelife of reserves, optimize the use of existing coal types, avoid penalties and reduce operatingcosts. Real-time monitoring can thus be of great value to many coal producers, adding profitdirectly to the bottom line. At times the economic justification for real-time on-line analysis can

be compelling, with some analyzers paying for themselves within a few weeks.

Despite the value provided by real-time elemental analysis, nuclear elemental coal analyzers arenot universally used. The use of real-time monitoring has been limited by the high cost of theequipment, implementation difficulties, long-term cost of ownership, and issues with the performance of the equipment.



This paper will briefly review the use of nuclear elemental analyzers in the coal industry. Thearticle will discuss the strengths and trade-offs of the current equipment, the latest developmentsin the technology, and how these developments will have an impact on coal product optimizationand cost reduction in the future.

A Brief History

The Nuclear Beginning – Dual Gamma Ash Gauges

Beginning in the 70’s instrument manufacturers began to make nuclear gauges available to coal producers for the on-line, real-time determination of total ash. Most of these instruments usedthe attenuation of a dual gamma-ray energy source to determine the percent of ash in a movingstream of coal. These instruments are still available today and range in price from about $60K to$100K+. Industry experts have noted that a large percentage of these units have not performedthe function for which they were purchased, although there are many very satisfied customers.Several hundred of these instruments have been purchased and installed in the coal industry over

the years, serving as a testimony to the industries’ need for on-line determination of the qualityof coal.

Enter - the True Nuclear Elemental Analyzer

At about the same time dual gamma ash gauges were appearing in the market significantresearch was going on that would lead to a true nuclear elemental analyzer. As a result of the pioneering work of Bob Stewart at the Bureau of Mines in the 1970’s and further research under grants from the federal government and from EPRI in the 1970’s and 1980’s it became possibleto introduce a commercially viable PGNAA analyzer in the mid-1980’s. The first successfulversion of these instruments was “chute-type” analyzers that required a gravity-feed of the

customer’s coal from the top of the unit onto an exit conveyor underneath the unit. The basicsticker price for these units was as much as $500K. With the costs of mounting the unit andgetting the coal into and out of the unit taken into consideration, the total cost of ownership oftentopped $1M.



MDH places Ad for PGNAA chute-type Analyzer IEA Survey shows 30 PGNAA chute-type units sold

Slurry Analyzer Introduced in rock Hybrid chute/belt unit introduced

SABIA introduces low-cost belt version for coal

‘85 ‘86 ‘87 ‘88 ‘89 ‘90 ‘91 ‘92 ‘93 ‘94 ‘95 ‘96 ‘97 ‘98 ‘99 ‘00 ‘01 ‘02 ‘0

Belt versionfor coal

Over 100 units soldLab version of PGNAA announced

Chute-type vendors include MDH, Gamma-Metrics, SAIC, and Coalscan

Gamma-Metrics Announces PGNAA chute-type Analyzer

Figure 1. PGNAA Timeline in Coal

The technology utilized in these analyzers to determine the elemental composition of the coal became known as PGNAA (Prompt Gamma Neutron Activation Analysis – see IEA Coal

Research On-Line Analysis of Coal, 1991). As the timeline shows above the first commerciallyviable units were introduced in the mid 80’s although the basic research was done in the 70’s.This delay was in part because instrument manufacturers had to wait for the signal processing

technologies to catch up. It took time for other technologies to advance enough to make it practical for instrument companies to utilize the technique for on-line, real-time determination of elements in a moving stream of material. In order for analyzers to acquire enough statistics inthe measurement process they needed to convert incoming pulses into digital signals at the rateof several hundred thousand per second. Not until the mid 80’s did computers and A/Dconverters exist that had the speed and capacity to process the incredible quantities of datainvolved in PGNAA.

How They Work

Basic PrinciplesWhen a bulk material such as coal is bombarded with thermal neutrons, (<1 electron volt neutronenergy), from a Californium 252 nuclear source, many of the neutrons are captured by elementalatoms within the coal. When this happens the atom becomes temporarily unstable. In order tore-stabilize the atom sheds a spectrum of high-energy gamma rays. The specific energies of gamma rays given off are a unique set for each of the elements within the periodic table. This principle makes it possible to create a signal to enable the on-line elemental analysis of coal possible with PGNAA.



Obtaining and Processing the Signal In order to create an electronic signal used for the determination of the weight percent of theelements of interest within the coal the unique elemental signature gamma rays resulting from

the capture of neutrons by elemental atoms are detected by a scintillating crystal such as SodiumIodide (NaI). As the gamma rays penetrate the detector they deposit their energy as high-speedelectrons within the crystal. These electrons create ionization, which can be detected as UV light pulses. The light pulses are in turn detected by photo-multiplier tubes ( a vacuum tube electroniccomponent operating at a high voltage, typically 500 to 1000 VDC) and turned into electrical pulses which are immediately amplified, shaped and then converted into digital signals, andcollected into a spectrum over some predetermined period of time (typically one minute) whichcan then be processed by a computer at very high speeds.

Nucleus of Nucleus of Nucleus of ElementalThermal Stable Elemental Excited Elemental Atom Stabilized by Neutron Atom Atom with Captured Release of Gamma Spectrum

Neutron Neutron still captured inside

γ

Figure 2. The Nuclear Physics of PGNAA



Processing the Spectrum

The resulting gamma-ray spectrum collected over a one-minute period is actually a histogram of all the incoming gamma-ray energy levels ranging from zero to ten Mev (Million electron volts).In coal anywhere from five to fifteen elements are represented in the spectrum. A typicalspectrum is shown below which over in one minute collects several million pulses.

Figure 3. A Typical Gamma Ray Spectrum – High and Low Energies

Typical PGNAA Gamma-Ray Spectra

0

50000

100000

150000

200000

250000

300000

350000

400000

0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5

Mev

T o t a l C o u n t s

A l u m i n u m

S i l i c o n

C a l c i u m

I r o n

C a l c i u m

I r o n

S i l i c o n

Typical PGNAA Gamma-Ray Spectra

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

4500000

5000000

0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5

Mev

T o t a l C o u n t s

H y d r o g e n

@ 2 . 2 2 3 M e v

Figure 4. A Typical Gamma Ray High Energy Spectrum



Intuition says t accomplished with a

t

or

s

xpected Performance NAA the “rule of thumb” was that for most applications the “RMSD”

epending on the specific application, the performance verification of a PGNAA system can be

ws:

able 1. Hypothetical PGNAA Analyzer Guarantee

hat arriving at the weight percent of each element could besimple evaluation of the size of each of the peaks, which is not the case. Optimum use of theinformation in the gamma-ray spectrum requires a full spectrum analysis such as Library LeasSquares that utilizes the instrument response to pure elements used as a library against which theincoming spectral data can be compared on a minute-by-minute basis. Typically a multiplelinear regression technique is used which solves a linear matrix equation with matrix inverse

math. With the high speed and data capacity of computers available today the time required f this mathematical treatment (de-convolution of the spectra) of the data takes only seconds and becomes transparent to the end user. Prior to presentation of the final answers to the customer the results of the multiple linear regression are normalized with respect to each other. Thetechnology has made significant strides and now offers the marketplace impressive precisionand accuracies.

E In the early days of PGthat could be expected on a one-hour basis for Sulfur was 0.07% and for Ash was 0.7%. Even

though this early performance was good and added value to many operations, the units availabletoday are able to offer improved precision and accuracy. In some cases the “RMSD” possibleon a one-hour basis for Sulfur is less than 0.04% and for Ash less than 0.30%.

Dlabor intensive. In almost most cases the analyzer installation must be planned in such a waythat results from existing mechanical sampling systems can be compared in a meaningful waywith the results of the nuclear analyzer. Historically, guarantees by vendors have been made interms of “RMSD”, “Static Precision”, or more recently, “GRUBBS Estimator”. At issue, is theneed to quantify the performance of the instrument and to do it in such a way that it can be

related to existing sampling/lab systems. A coal analyzer guarantee might be stated as follo

T

Parameter Static Precision RMSD10 minute basis,30 points, 1σ,Wt. %

1 hour analysisComments

time, 20 points,Wt.%

0.10 0.07exceed 1.5%

not toexceed 3.0%

Sulfur Range not to

Ash 0.55 0.35 Range

tatic Precision = standard deviation of consecutive readings where;

S =

S

2

1

1

( )i

n

x xi

n

−∑=

−



S = Static Precision

he number of paired comparisonsxi = the analyzer value in the ith comparisonn = t

Root of the mean of the squared

= the average of the n analyzer values

e name implies, it is the squaredifferences between the analyzer and lab values,

where;

MSD =

RMSD = Root Mean Square Deviation, as th

R 1

i i

n

yi

−=

)

mber of paired comparisonsxi = the analyzer value in the ith comparison

i = the reference value in the ith

comparison

verification program on the Sulfur guarantee for

n = the nu

2

( xn

∑

y

Below are graphical examples of a performancethe PGNAA shown above:



Initial Sulfur Results Prior to Calibration

20 data points, 1 hour each

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3 3

PGNAA Wt. %

L a b W t %

r2 = RMSD =

std.error =

0.981

0.060

0.743

Note: The incorrect gain on

the instrument inflates the

RMSD.

.5

Figure 5. PGNAA Sulfur Data Prior to Calibration and Performance Verification Testing

Sulfur Performance Validation


0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3 3.5

PGNAA Wt. %

L a b W t %

r2 =RMSD =

std.error =

0.0560.997

0.059

Note: With a corrected gain

the instrument now passes the

RMSD guarantee of 0.07

Figure 6. PGNAA Sulfur Performance Validation Data after Calibration



Sulfur Performance Validation


0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3 3

PGNAA Wt. %

L a b W t %

r2 =RMSD =

std.error =

0.0890.997

0.059

Note: With only a few pointsfurther away from the "zero

bias" line the RMSD inflates

and is no longer acceptable.

.5

Figure 7. PGNAA Sulfur Performance With More Scatter about Zero Bias Line

Data Evaluation Techniques It can be seen that the use of RMSD as a measure for accepting or rejecting an analyzer can be tothe benefit of the customer inasmuch as this sample statistic includes the reference measurementerror (both the sampling and lab analysis error) and offers no means for distinguishing between

these sources of error that can sometimes be significant. For this reason one vendor hasdeveloped an acceptance technique that uses Grubb’s Estimators. With the Grubb’s Estimator method the customer can calculate an unbiased estimate of the precision of any of a number of measuring instruments used to replicate measurements of successive items, batches, or lots of materials. Typically the customer is asked to obtain dual independent lab analysis of the samesamples, with great care taken to ensure that all samples used are representative of the samesample population as seen by the PGNAA analyzer. The Grubb’s Estimator calculation is thenable to use these numbers to calculate an estimate of the precision of each participant in the test.Often this test is to the advantage of the vendor inasmuch as the system contributing data doesnot need to be calibrated to have the best precision. Additional approaches proposed in the pasthave included an ANOVA statistical approach, which attempts to measure the PGNAA

instrument precision independent of sampling and lab errors and a…………technique as proposed by Charles D. Rose. Unfortunately there is no standard approach for performanceverification of on-line PGNAA instruments. In the meantime the RMSD approach is the moststraightforward and effective from the customer point of view, even though use of it runs the risk of misjudgin

g the value of an analyzer to the operation.



The table below shows the theoretical range of sensitivity for each of the elements in the periodictable for a PGNAA instrument.

Table 2. Expected PGNAA Sensitivity to Elements of Interest*

Sensitivity in Weight % ** Elements

<0.01% Cl,Sc,Ti,Ni,Cd,Hg,Sm,Gd,Dy,Ho0.01-0.1% S,V,Cr,Mn,Fe,Co,Cu,Rh,Ag,In,Hf,Ir,Au,Nd,Eu,Er,Yb,H

0.1-0.3% N,Na,Al,Si,K,Ca,Ga,Se,Y,Cs,La,W,Re,Os,Pt,Pr,Tm

0.3-1.0% Li,Be,Mg,P,Zn,As,Mo,Te,I,Ta,Pb,Ce,Tb,Lu,Th,U

1.0-3.0% C,Ge,Br,Sr,Zr,Ru,Pd,Sb,Tl

>3.0% Other Elements* Note: Table taken from “On-Line Prompt Gamma Neutron Activation Analyzers, Published in the Process/Industrial

Instrument and Controls Handbook, Editor-Gregory K. McMillan, Fifth Edition, McGraw Hill, 1999.** Three sigma detection limit in 10 minutes within an elementary simple rock matrix, ≥150mm thick

Fre

igures 8 and 9 below show actual performance from an older chute-type analyzer that has beentrofit with new, state-of-the-art electronics.

Figure 8. Current Analyzer Sulfur Performance on PGNAA Analyzer

PGNAA Sulfur Permormance

R2 = 0.98 S

0.6

0.8

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

Analyzer

L a b

Loadi Trainsng Unit

tandard Error = 0.03

1

1.2

1.4



PGNAA Ash P

Figure 9. Current Analyzer Ash Performance on PGNAA Analyzer

erformance

Loading Unit Trains

R2 = 0.96 Standard Error = 0.18

5

6

7

8

9

10

3 4 5 6 7 8 9 10

Analyzer

L a b

3

4

Current Status of Nuclear Elemental Analyzers in Coal

There are currently four providers of PGNAA systems for the coal industry. Gamma-Metricshas been the industry leader for some time with over 100 PGNAA systems sold. The number-two provider is Scan Technologies in Australia. New vendors of PGNAA instruments includeAnalyzer Systems and SABIA, Inc. About 75% of the units sold in coal have been sold to minesfor blending and sorting of coal with only about 25% involved in installations associated directlywith the prep plant. Only a few systems have been installed at coal burning utilities. Price hasdictated that you had to choose one spot with the biggest payoff for installation.

Although the technology is in widespread use, with over 100 units sold since 1985, much of themarket remains un-penetrated. In September, 1991, the IEA report on “On-line analysis of coal”stated that the number of on-line analyzers was expected to grow “substantially” in the coming

years. At that time, between 30 and 40 PGNAA systems had been sold in the US. In theintervening 12 years this number increased to over 100 units, falling short of the projected“substantial” increase, in effect selling only about 6 systems per year on average. Why hasn’tthe coal industry adopted the technology on a wider scale?



Perhaps the answer lies in some of the areas as shown in the table below:

Reasons for lack of PGNAA Market Penetration in Coal

Reason Comments Notes:

Sticker Price Still about $400K for chute-type

Associated

Construction Costs

Original Chute-type versions can have

construction costs equal to price of unit

Note: Gamma-Metrics ha

available in recent years achute/belt type unit to fit insampling systems that is sellinIn addition, a belt version of ttechnology is now availableseveral vend

s made

hybridto existin

g welhe

fromors, which nearly

eliminates associated constructioncosts.

Long-term cost of ownership

Expensive service contracts combinedwith cost of source replenishment

New competition in the servichas finally caused a decreas

e arene in pric

Customer Satisfaction

issues related to service

Although much of the marketplace is

satisfied with service there is room for improvement

The current list of suppliers to the coal industry is shown below:

The PGNAA Vendors

Vendor Offeri hnologyng Tec

Gamma-Metrics Sever includ1812Chute/ d

the FQM static sample analyzer.

Utilizes Cf252 neutronal PGNAA Models for Coal, which echute-type analyzer, CQM hybrid

belt analyzer, ECA belt type analyzer, ancsource with NaI crystaldetector.

CoalScan Two PGNAA Models for Coal, which include9500 chute-type analyzer, 9500X belt typeanalyzer.

Utilizes Cf252 neutronsource with NaI crystaldetector.

Analyzer Systems

One PGNAA Model for Coal, the ETI Full StreaAnalyzers FSEA made in conjunction with ETI.

tector.

m Utilizes Cf252 neutronsource with NaI crystalde

WKU One P

source with NaI crystaldetector.

GNAA Model for Coal, the Utilizes Neutrongenerator for neutron

SABIA, Inc. Several PGNAA Models for Coal, which includethe OnBelt belt type analyzer, the P3000 staticsample analyzer, the MSA3000 mechanicalsample analyzer, and the P3000S for slurry

Utilizes Cf252 neutronsource with NaI crystaldetector.



The technology has clearly proven itself in some very effective applications with payback ines being ac a few months. The body of evidence prove ingly that

h ss

more or less been u tor interven potential of the technology to reduce variance largely untapped. An ASTM standard has beenestablished but has yet to play a widespread role in adoption of the technology for use as a means

.

Some typical applications are listed below:

Open Loop Blending, manually adjusting to a targetClosed Loop l loop using twoachieve a target.

Pile BuildingRun of Mine

ed ProPrepPlant

Sort cleaned

e

he following list is an attempt to provide a comprehensive look at all the limitations to be

ter-element dependence. Because the extraction of the elemental information from thee

is

g, and P, which can be swamped by other elements. In addition, somets like Al can be strongly influenced by Fe.

2. xygen cannot be detected by a PGNAA system that uses thermal neutrons,the Cf252 neutron source. Please note that a nuclear coal

ental analyzer using a neutron generator with the associated fast neutrons canThese systems are usually more expensive because of the associated

generator.

some cas hieved in s overwhelmthey work althoug some producers continue to doubt their effectivene . The technology has

tion, leaving the truesed in open loop control modes with opera

of payment

Loadout

Blending, some type of PID contro or more sources to

Finish duct

coal

The Strengths and Weaknesses

WeaknessesAlthough PGNAA is a true elemental analysis technique capable of delivering minute-by-minutanalysis of a moving stream of coal it has some important limitations that should be taken intoconsideration before purchasing a system for use at a mine, prep plant, or coal burning utility.

Tconsidered by a potential buyer:

1. Ingamma-ray spectrum is done at once for all the elements an opportunity exists for somof the stronger elemental signals to influence or, dominate the weaker signals. Such

the case for Na, MelemenThe element Osuch as those supplied byelemmeasure Oxygen.neutron



3. Calibrations are typically site specific. This is due to a host of causes, but primarily tendsto be because a given site’s coal has more or less unique level of neutron absorbers suchas Chlorine or Boron. In addition, such things as coal-density, moisture levels, etc. canhelp define the calibration.

rically the analyzers require attention to ensure they are properly calibrated. This

moisture, calorific value, volatile matter, and ash fusion can only be estimated by

ble reading. For example, for BTU the result is derived from anempirical Ash, Moisture dilution equation that assumes a constant MAF BTU for the

6.

is

8.f about the same order of magnitude.

10. ,rately it must be assumed the remaining constituents are

e

11. mer

ication

Strengt Below y:

1.ermine the composition of the entire stream. For those elements

paybacks from reduced process variance and/or elimination of penalties or other costs associated with rejected trains.

4. Histodepends of course on the application and whether it is of a critical nature, but the

technology has not demonstrated that the units can be calibrated and then left alone.5. Because PGNAA is an elemental analysis technique, certain quality parameters such as

calculation. Empirical relations exist that do make it possible to provide the customer with an accurate and relia

coal. This assumption is not completely correct (more so at some sites than others), but itis not unusual to achieve a standard error on BTU of 150.To date the technology has not been able to measure trace levels of elements, so it doesnot add value to customers who are looking for trace levels of such things as Na, K,Mercury, Arsenic, etc..

7. Performance verification can be time consuming. Many customers never complete the prescribed performance verification testing because the unit begins adding value andused to aid in the operation.Historically the chute-type units have been expensive ($400K to $500K) with associatedconstruction costs o

9. Carbon does not activate well in a neutron flux, but because of its high level in coal it is areasonably good PGNAA element.The majority of ash constituents are analyzed well by PGNAA, such as Si, Al, Fe, Ca, Tiand K. To measure ash accuconstant and in bituminous coals this is valid. But in sub-bituminous and lignite coals thunaccounted for portion can be large and variable.

Accuracy and precision are difficult to define but it is necessary for vendor and custoto have a common understanding to effectively communicate needs and potential performance. This doesn’t happen most of the time. In spite of this poor communof needs vs. performance most customers end up happy because the technology workswell for most applications.

hsis a look at the impressive list of strengths for the technolog

PGNAA looks at the entire sample on an atomic level, with hundreds of thousands of events per second to det

it measures directly, PGNAA can do a much better job of telling you what is actually inthe coal. The technology has the potential to free the customer from sampling and laberrors.

2. PGNAA does a true elemental measurement of the coal, including the main componentsof ash, sulfur, etc.

3. With on-line, real-time information true dynamic process control can be achieved for Ashand Sulfur with some potential quick



4. With proper attention and maintenance the systems in many cases have delivered breathe-taking accuracy and precision, enabling customers to avoid penalties, take on newcontracts, extend mine life, increase profits, optimize use of sweet coal, etc..Depending on the application the technology can ha5. ve a dramatic payback. Return on

6. use

7.either conventional sampling and lab analysis or with dual

gamma ash gauges.

The list of weaknesses is not short and therefore cannot be ignored or treated lightly. Some

evidhinthe

dollars to the owner’s bottom line.

Rec

Recent The mo oal industry has beeinstalla oiceof locations that can add value to his operation. In addition, very affordable true PGNAAver placem greater visibility and control of his

totaquick r control of operations.

The FuGreat advances have been made in PGNAA performance in the last 20 years but the best is yet tocom . In the past PGNAA analyzers have been large, expensive to buy, expensive to maintain,wit performance. In the future the units will be smaller, and moreaffoelem hgau chas N s

neetechnology continues to prove itself at more and more sites it is anticipated that it will be used inlosed loop software control applications more and more. In this area the coal industry isgging behind other industries like Cement that use closed loop control with almost all of the

ll be more software packages that work effectively withand pile building. It is anticipated that in the future units will

er

Investments range from a few weeks to a few months.The technology has proven to be robust, reliable and consistent. Some systems in

today have been in more or less constant use for over 15 years.PGNAA can give the customer visibility and the associated control of his operationheretofore not possible with

Weakness/Strength Summary

of the weaknesses preclude the use of the technology in some applications. However, asenced by the 100+ systems shipped to date, the vast majority of applications are not

dered by the weaknesses. In these cases the customer is able to play to the strengths of technology. Many of these applications have been great successes, adding significant

ent Developments and The Future

Important Developments

st important recent development in the application of PGNAA in the cn the advent of an on-belt version of the technology, which makes for much less expensive

tion costs and quicker installations. It also enables the customer to have a greater ch

sions of belt analyzers are available that actually make it possible for customers to consider ent of several units at a single site, giving the customer

l operation. Systems now have a feature, which makes them accessible via the Internet for eview of results, thus providing management with a tool for better

ture

eh some important limitations inrdable with further improvements to performance. Prices will be falling in the future for trueental analyzers and will eventually be comparable to prices in the past for dual gamma as

ges. Performance will continue to improve with increasing ability to do trace elements sua and K and possibly Hg and Arsenic at some point in the years ahead. The nuclear source

ded to deliver the necessary performance will become smaller and smaller. As the

claPGNAA analyzers. In the future there withe analyzers for on-line blending be developed that work effectively with coal slurries and begin to populate the prep plantsthemselves. The systems of the future will have better front-end electronics and therefore great



system stability and accuracy. Systems of the future will be less dependent on temperaturefluctuations and more amenable to harsh environments. It is anticipated that improvedtechniques for measuring BTU on-line will make their way into the marketplace in the comingyears. The size of the units are getting smaller and easier to install and will continue to do so.With regards to calibrations, the units still require calibration on site but the ultimate goal of some manufacturers is to create a universal calibration with the unit working right out of the box

when on site. This is an ambitious goal but there is at least a theoretical basis for such a dream.l calibration is probably several years away. Also, at least one vendor has leasing in

umberge, James F., “On-line Analysis Can Boost Profits from Blending”, Coal Age Magazine,

.48, June 1987.

The universamind for some point in the future. If the numbers are right, this could be the means to place thistechnology on a wide basis. It appears fairly certain at this point that the new on-belt PGNAAanalyzers will be gaining wide acceptance at a rapid rate throughout the industry due toaffordability and ease of installation. In summary, the PGNAA technology has proven itself andif it delivers on the promise of the future, it may eventually find its way into every place coal ishandled. This has been predicted before but with recent developments in technology it appearsonce again about to happen. Time will tell.

REFERENCES

Kirchner, A.T., “On-line analysis of coal”, IEA Coal Research report IEACR/40, September 1991.

Proctor, R.J., “On-line Prompt Gamma Neutron Activation Analyzers”, Process/Industrial andControls Handbook, Editor-Gregory K. McMillan, Fifth Edition, McGraw Hill, 1999.

Rose, Charles D., “Methods for Assessing the Accuracy of On-Line Coal Analyzers”, Journal of Coal Quality, p.19-28, January-March 1991.

Sanda, Arthur P., “On-line Analyzers Improve Coal Quality”, Coal Age Magazine, p.52, June1992.

Woodward, Richard C. & Lee, Brenda, “On-line Analysis Evolves”, Coal Age Magazine, p.22,March 1977.

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