FIELD OF INVENTION

The present invention is in the field of an Automation System for facilitating optimum coal blending at Coal Handling Plant of Coke Oven Batteries using on-line measurement of ash content in in-coal from mines as well as in blend coal. The Automation System also involves Level-II automation based process monitoring, PLC & Weigh feeder based control & monitoring of blending operation at Coal Handling Plant. The invention has been implemented at Coal Handling Plant within Coke Oven Complex of Bokaro Steel Plant.
BACKGROUND ART
The coal demand of Coke Ovens are catered by Coal Handling Plant (CHP). Like other integrated steel plants, Coal to Bokaro Steel Plant is supplied by various coal mines both indigenous as well as foreign. The major Indigenous coals coming to Bokaro are Dugda, Bhojudih, Sudamdih, Munidih, Madhuban, Mahuda (Prime Coking Coal), Mahuda (Medium Coking Coal), Belatand, Chasnala, Patherdih, Rajrappa, Kathara, Swang, Kedla, Jamadoba etc. The major foreign coal resources are from countries like Australia (Hard and soft Coal), USA (Hard and soft Coal), Mozambique, Canada, Indonesia etc. Due to these diverse coal suppliers, the quality of incoming coal varies between a wide range. The incoming coals with divergent properties are stored in different silos or stockpiles in CHP. In Bokaro steel Plant, Coal is stored in 81 nos. vertical concrete Silos. Each silo is designated for a particular source and mixing of coal from various sources in one silo is generally not allowed. Before dispatching to Coke Oven, coal from different silos are blended at different proportions to make a blend coal with desired quality.
Coal handling circuit of Bokaro Steel Plant comprises two nos. wagon tipplers, two stream of conveyors (900 TPH each) and 81nos. RCC silos. Coal Storage capacity of each silo is 2500 ton. The silos are in three rows i.e. 27 silos in each row. Each silo is provided with weigh feeder for controlling the coal discharge. The Silo and Path selection is done from a central control room called Dispatcher through a PLC
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system. The coal is weighed in both the tracks through belt weighers. The blend coal from each row is sent to coal crusher unit in three rows of conveyor. After coal crusher the blend coal is transported to Mixer station in a single row conveyor. After mixer the coal is distributed in four Coal Towers before charging to Coke Oven Batteries.
Ash content in coal is one of the crucial parameter considered in iron making operation because it directly influences the blast furnace performance. Ash content in coke is directly related with ash content in coal. Due to the above mentioned reasons, ash content in coal is one of the prime factors considered in coal blending. Coal, as received at CHP from various sources have divergent ash content property. Based on the observation from laboratory coal sample analysis, it has been found that the average Ash % variation from major Indian resources varies from 19 to 30%. The average Ash % variation from major Foreign resources varies from 7 to 13 %. So the average ash variation in incoming coal varies between 7 to 30%. Coals from these divergent sources are stored in different silos and are blended in different proportions to obtain coal of desired quality. The blend coal is delivered to Coke Ovens for carbonization. One of the prime objectives of CHP is to work out an optimum solution for coal blending with these wide ranging incoming coals to achieve a consistent quality coal charge for Coke Ovens. However, the greatest impediment in deciding optimum coal blending is unavailability of real time measurement of input and output ash content and other elemental analysis. These values are generally known after laboratory analysis of samples taken, after a significant delay, which makes the blending operation very difficult.
Moreover, in absence of any on-line analysis of blend coal for ash content measurement, it is extremely difficult to verify the accuracy of ongoing blending operation or taking any corrective action. The laboratory analysis of blend coal is also available after a significant delay. The consistency in blend coal quality is directly reflected in consistency of coke after carbonization in coke ovens. Hence, due to the wide variation of input coal quality and delayed availability of laboratory analysis, optimum coal blending at CHP is very difficult. In absence of on-line measurement of coal ash in blend coal, timely corrective action is also very difficult. Un-availability of real time measurement of coal ash content in in-coming and blend coal is one of the major problem in coal blending operation, which results in variation
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in blend coal ash content from the norm. Another issue related to optimum coal blending is inadequate control of coal discharge through weigh feeders. A centralized and efficient control of all the weigh feeders is imperative for effective coal blending. It accentuates the need of PLC based control and monitoring of entire weigh feeder operation. Further, to achieve optimum coal blending, a Level-II automation tier supervision and control is required. The above involves application of hierarchical automation concept, wherein Level-0 tier comprise different sensors, weigh feeders and elemental analyzers. Level-I comprise of a PLC system and weigh feeder controllers. All the weigh feeder controllers, sensors and driving mechanism need to be integrated with a PLC for centralized blending operation. Level-II automation system comprises of a server computer, which is seamlessly connected with PLC through data network. The Level-II software keeps track of entire blending operation.
The sequence followed in coal blending is manual sample collection of coal from conveyor belt once or twice in a day and send the same to laboratory for analysis of ash %. The coals from the mines are stored in bunkers or stockpiles. In case of Silo type storage, based on the ash % requirement in blend coal and throughput rate (Ton / Hour (TPH)), coal is discharged at various rates from the different Silos at a time. The Silos selected for discharge are based on the source (characterized by ash %) of the coal stored inside the silos. The blend composition is prepared by manual calculation which is primarily based on available coal sources (characterized by ash %) and coal stock in silos, keeping the target ash % in blend coal and TPH in mind. The throughput i.e. coal flow rate from silos are generally regulated by weigh feeder mechanism. The coal flow rate are manually fed to weigh feeder controllers for flow regulation. The ash % in blend coal is also confirmed by same process of manual sample collection of coal from conveyor belt once / twice in a day and sends the same to laboratory for analysis of ash %.
Drawbacks of the Known Art:
The aforesaid known art suffers from following major drawbacks:
1. Manual sample collection by scooping coal from conveyor is not statistical representative of coal for ash % analysis. Hence the laboratory analysis of coal ash % based on manual coal sampling is statistically inaccurate.
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2. As laboratory analysis takes significant time, the blending operation is generally completed before availability of laboratory results for in-coming coal. The blend composition is prepared on the basis of representative ash % value designated to each coal mines, which is not accurate. This is one of the major problems in coal blending operation.
3. As the laboratory analysis of blend coal also takes significant time, efficacy of blending operation cannot be checked and no regulatory control action is possible by adjusting blending operation. This is one of the major reason for variation of ash % in blend coal.
4. Optimum blending of coal is very difficult, in absence of any centralized supervisory monitoring & control of entire coal blending operation by regulating coal discharge from silos (81 silos in case of Bokaro Steel) through an integrated automation system.
5. Coal hanging i.e. sticking of coal inside silos is a major problem in achieving optimum coal blending. In absence of any automation system, such coal hanging is generally not detected and cause variation in blend composition. Such variation leads to inconsistency of ash content inblend coal.
OBJECT OF INVENTION:
The objective of the invention is to develop an automation system for optimum coal blending and to improve consistency of ash variation in blend coal through following major interventions:
1) Real time measurement of coal ash and moisture content through On-Line Cross Belt Elemental Analyzers in in-coming coal from mines right on the conveyor belt.
2) Real time measurement of coal ash and moisture content through On-Line Cross Belt Elemental Analyzers in blend coal right on the conveyor belt.
3) Level-II automation based software for supervisory monitoring of blending operation
4) PLC based centralized control of entire coal blending operation
5) Weigh feeder based control of coal silo discharge
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6) Integration of entire automation system following the concepts of hierarchical automation.
SUMMARY OF INVENTION
Therefore such as herein described there is provided a method for optimum coal blending at Coal Handling Plant of Coke Oven Batteries comprising the steps of-
a) measuring of ash and moisture percentage in real time on incoming coal on the conveyor belt at Coal Handling Plant through elemental and moisture analyzers;
b) calculating coal stock in the silos based on the belt weigher data from incoming conveyors and weigh feeder discharge data and blend composition w.r.t. coal source, tonnage and percentage using Level-II system including keeping track of silo weigh feeder operation and calculates total discharge and runtime of silos in operation;
c) interfacing Elemental Analyzers, PLC & Weigh Feeders to a common Level-II based Automation System through customized OPC protocol based driver; and
d) integrating the coal blending operation through Level-II, PLC and Weigh Feeders.
In another aspect of the present invention, the said real time Cross Belt Elemental Analysers facilitates real time analysis of elements (like N, P, Cl, S, Si, Al, Ti, Fe, Ca, Mg, Na, K etc.) present in coal right on the conveyor belt and once the elements present are known, the corresponding oxides are calculated from chemical equation using the molecular mass and thereafter the ash content in coal is calculated from summation of all the oxides present in the coal.
In yet another aspect of the present invention, for dry basis calculation, the real time moisture content in coal is measured by Microwave type Moisture Analyzer, and compensation is applied on as received basis calculation to derive dry basis measurement of Ash percentage.
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BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 illustrates the Architecture of Integrated Automation system in accordance with the present invention;
Fig. 2 illustrates the conveyor passing through analyzer tunnel in accordance with the present invention;
Fig. 3 illustrates the elemental Analyzer for Blend Coal in accordance with the present invention;
Fig. 4 illustrates the schematic of Level – II Data Integration in accordance with the present invention;
Fig. 5 illustrates the architecture of Level – II Software in accordance with the present invention;
Fig. 6 illustrates the HMI Screen depicting Overview of CHP Silos in accordance with the present invention;
Fig. 7 illustrates the HMI Screen depicting Blend Percentage in accordance with the present invention.
DETAILED DESCRIPTION
The present disclosure is based on concepts of hierarchical automation. The automation system functions as a single integrated system with vertical data flow approach. Level-0 tier of automation hierarchy comprises of different sensors, instruments, on-line cross belt elemental analyzers, drives etc. Level-0 will be seamlessly integrated with Level-I tier of automation, which comprise of Programmable Logic Controllers (PLC) and silo weigh feeder controllers. The basic blending operation is controlled by Level-I automation system. A Level-II tier automation system monitors the blending operation in supervisory mode and guides the operation with various reports, analysis and alarms. The schematic of the automation system is illustrated in Fig. 1.
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REAL TIME MEASUREMENT OF ASH CONTENT IN IN-COMING AND BLEND COAL
One of the greatest impediments in optimum coal blending is unavailability of real time measurement of ash content in in-coming coal from mines as well as in blend coal from CHP. Hence real time measurement of coal ash content using state-of-the-art On-line Cross Belt Elemental Analyzers in both incoming as well as blend coal can definitely contribute in optimum coal blending. These analyzers facilitate minute-by-minute measurement of ash content in coal right on the conveyor belt. The incoming coal analyzer is installed over Conveyor # Y37 (indicated in Fig. 2) between wagon tippler and silo top. It facilitates on-line measurement of Ash %, elemental analysis and moisture of incoming coal to CHP. The second analyzer is installed over conveyor # Y18 (indicated in Fig. 3). This is used for on-line measurement of Ash %, elemental analysis and moisture of blend coal from CHP.
The On-line Cross Belt Elemental Analysers facilitates real time analysis of elements (like N, P, Cl, S, Si, Al, Ti, Fe, Ca, Mg, Na, K etc.) present in coal right on the conveyor belt. The ash content is derived from the elements present. The Cross belt analyzers used at CHP, BSL are based on Prompt Gamma Neutron Activation Analysis (PGNAA) technology. The elemental analyzer following PGNAA technology uses Californium-252 (Cf-252) radioactive source, which emits thermal neutron of average energy around 2.5 Million electron Volt (MeV). The conveyor belt carrying coal is passed through the elemental analyzer as shown in Fig. 2. During the passage many nuclei of atoms present in different elements of coal captures the thermal neutrons (with energy less than 1 Million electron Volt (MeV)) emitted by Californium-252 radioactive source. When this happens, those atoms become temporarily unstable and excited to higher energy levels. In order to re-stabilize, the atoms immediately returns back to their original energy level by shedding spectrum of high energy Gamma rays. The specific energies of Gamma rays given off characterizes unique signature representing the each of the elements present in coal. Each element present in coal emits its own unique gamma-ray spectrum, which makes it possible to calculate the chemical composition coal. Once the elements present are known, the corresponding oxides are calculated from chemical equation using the molecular mass. The ash content in coal is calculated from summation of all the oxides present in the coal. The above mentioned, ash measurement is basically on as received basis. For dry basis calculation, the on-line moisture content
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in coal is measured by Microwave type Moisture Analyzer, and compensation is applied on as received basis calculation to derive dry basis measurement of Ash %.
LEVEL-II AUTOMATION BASED BLENDING OPERATION
A Level-II automation system has been developed for integrated supervision of blending operation. Following the concepts of hierarchical automation, the Level-II system comprise of Level-II server computer, which is connected to Level-I PLC network as well as both the elemental analyzers. All coal blending related data is stored in a relational database, which is also a part of Level-II system. One of the most significant interventions of this project is in-house software development. Being an integrated system, Level-II software has the access all the process data like conveyor running status, tripper positions, silo level indication, weigh feeder signals etc. Based on in-coming coal elemental analyzer data, the Level-II software calculates average ash content of coal in each silo. It also calculates coal stock in the silos based on the belt weigher data from incoming conveyors and weigh feeder discharge data. The system also display blend composition w.r.t. coal source, tonnage and percentage. The Level-II program also keeps track of silo weigh feeder operation and calculates total discharge and runtime of silos in operation. It calculates instantaneous blend composition and shift-wise cumulative actual blend composition. The software is intelligent enough to detect coal hanging inside silos as well as coal starvation situations.
For efficient operation of Level – II system, it is essential that all the necessary data from PLC and elemental analyzers are seamlessly transferred to Level – II system. Seamless data communication between Level – II and PLC as well as Level – II and both the elemental analyzers have been achieved through OPC protocol. OPC Server software has been provided by PLC manufacturer (Schneider) and Elemental analyzer manufacturer (Thermofisher). OPC client software has been developed as integral part of Level-II software. Special data acquisition software has been developed for integration of PLC and Elemental Analyzer and the same is a integral part of Level – II software. Data acquisition software receives data from PLC and elemental analyzer and saves them in various tables of a relational database. The database is Microsoft SQL Server. The different program modules of Level – II accesses these data whenever required. The schematic of Level – II data integration is depicted in Fig. 4.
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Level – II system keeps track of following salient operations of coal blending:
i. Conveyor Path Selection for unloading coal from tippler to Silo top from PLC
ii. Silo Number selection for coal unloading from PLC
iii. Silo-wise Coal Source selection from Level – II
iv. Totalized coal flow in Y-37 & Y-18 Conveyors
v. Silo-wise Weigh Feeder Selection from PLC
vi. Monitoring of Weigh feeder control operation
vii. Totalized coal flow in Y – 18 Conveyor
viii. Coal stock in individual silos
ix. In-coming coal elemental analyzer, moisture analyzer and belt weigher data monitoring
x. Blend coal elemental analyzer, moisture analyzer and belt weigher data monitoring
xi. Calculation of average ash content in silos
xii. Calculation of Actual, Cumulative and shift-wise Coal Blend Composition
PLC & WEIGH FEEDER BASED CONTROL & MONITORING OF BLENDING OPERATION
The developed system facilitates integrated blending operation through hierarchical automation system. The actual control operation is accomplished through Level-I automation tier PLC. The PLC system actually controls and monitors the entire conveyor operation. It also controls the Weigh Feeders. To accomplish integrated control all the weigh feeders needs have been integrated with PLC. The PLC and HMI software has been developed to cater all the communication and data related requirements of Level-II automation.
Best Mode of Working the Invention :
As mentioned above, that the innovation envisages real time measurement of ash content in in-coming coal from mines as well as blend coal through On-Line Cross Belt Elemental Analyzers at Coal Handling Plant (CHP) of Bokaro Steel Plant. This is first installation of its kind for any Coke Ovens of Indian steel plant. In addition to ash content, the innovation also envisages real time measurement of moisture content in coal through On Line Microwave type Moisture Analyzers. Both the Elemental and
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Moisture analyzers use radioactive sources for measurement. Thermo fisher made ECA elemental analyzers has been used for elemental and ash content analysis. Berthold Moisture analyzers has been used for coal moisture analysis.
The developed automation system envisaged PLC and Weigh Feeder based blending operation. The weigh feeder system has been up-graded to enable remote control & monitoring by a centralized PLC system. The integrated automation system facilitated single window control of all the weigh feeders. The precision control through PLC and up-graded weigh feeders improved the blending efficiency. Schneider make PLC system has been used in the innovation. The multiple weigh feeder system made by IPA and ACME has been used for the automation system.
Further a Level-II tier automation system has been developed for supervisory monitoring of entire blending operation. Level –II system is integrated with Elemental / Moisture analyzers as well as PLC / Weigh feeder system. The Level – II system keeps track of silo feeding with in-coming coal as well as silo discharge through weigh feeders. It also keeps track of ash / moisture measurement of in-coming and blend coal. With the available data it calculates coal stock in silo and average ash content of coal in each silo. It also calculates the current and cumulative blend composition as well as coal source wise discharge. The availability of real time measurement of ash content in blend coal facilitates feedback signal for taking corrective action in weigh feeder control. All the aforesaid measures taken helps in achieving optimum coal blending. The results shows improvement in consistency of ash content in blend coal as elaborated in subsequent sections.
Level – II system has been implemented in Server grade computers. Following application programming software tools have been used for Level – II software development:
a. VC++ Programming Software and Windows Application Programming Interface (API). Both are achieved through Microsoft Visual Studio programming package
b. Microsoft SQL Server relational database
c. Schneider PLC OPC Server. OPC Client software is developed using VC++
d. Thermo fisher analyzer OPC Server. OPC Client software is developed using VC++
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Level – II system receives process related information from respective OPC and transfers the same to database. The integrated schematic of Level-II software implementation is depicted in Fig. 5.
Based on totalized coal flow from belt weighers installed in Y37 and Y18 analyzers, the Level-II program keeps track of coal flow input to silo. Similarly from totalized coal flow from weigh feeders, the coal discharge from individual silos are tracked by a different software module. Based on the aforesaid two data, level-II software calculates the exact coal stock present in the silos. However, there is a provision of manual correction of silo stock based on actual measurement. The Level-II software keeps track of in-coming coal minute-by-minute analysis of coal ash content. Based on silo selected for coal unloading, the level-II program calculates the weighted average of ash content of coal in each silo.
The Fig. 6 depicts HMI screen illustrating overview of all the Silos in the Coal Handling Plant (CHP). The screen gives information about silos selected for coal unloading, silo stock, average ash content in the silos, weigh feeders selected and TPH from the weigh feeders.
The Fig. 7 depicts HMI screen for display of current and cumulative blend percentage. The screen displays list of silos from which coal is being discharged for blend preparation through weigh feeders. It gives a comprehensive display of Silo No. and their respective Coal Mines, Weigh Feeder Set Points, actual TPH, total discharge from the beginning of respective shift and total silo runtime. The program is intelligent enough to detect the silo hanging problem. In addition to above the program gives current blend composition and cumulative blend composition from the beginning of shift. Tonnage discharge of individual coal source is also displayed in this screen. The program also facilitates display of actual blend composition for earlier shifts. Shift-wise blend composition of last two days can be seen through this HMI screen.
Inventive Step:
The novel features of the invention are explained below and protection shall be sought.
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a) On-line measurement of ash and moisture % in in-coming coal right on the conveyor belt at Coal Handling Plant through elemental and moisture analyzers for on-line estimation of average ash content in coal silos to facilitate optimum coal blending.
b) On-line measurement of ash and moisture % in blend coal right on the conveyor belt at Coal Handling Plant through elemental and moisture analyzers to improve the efficacy of coal blending control operation.
c) Interfacing Elemental Analyzers, PLC & Weigh Feeders to a common Level-II based Automation System through customized OPC based driver software
d) Integrated coal blending operation through Level-II, PLC and Weigh Feeders
e) Development of a Level-II automation system for supervisory monitoring of coal blending operation
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

WE CLAIM:

1. A method for optimum coal blending at Coal Handling Plant of Coke Oven Batteries comprising the steps of:-
a) measuring of ash and moisture percentage in real timeon incoming coal on the conveyor belt at Coal Handling Plant through elemental and moisture analyzers;
b) calculating coal stock in the silos based on the belt weigher data from incoming conveyors and weigh feeder discharge data and blend composition w.r.t. coal source, tonnage and percentage using Level-II system including keeping track of silo weigh feeder operation and calculates total discharge and runtime of silos in operation;
c) Interfacing Elemental Analyzers, PLC & Weigh Feeders to a common Level-II based Automation System through customized OPC protocol based driver; and
d) Integrating the coal blending operation through Level-II, PLC and Weigh Feeders.
2. The method for optimum coal blending as claimed in claim 1, wherein the said real time Cross Belt Elemental Analysers facilitates real time analysis of elements (like N, P, Cl, S, Si, Al, Ti, Fe, Ca, Mg, Na, K etc.) present in coal right on the conveyor belt.
3. The method for optimum coal blending as claimed in claim 2, wherein once the elements present are known, the corresponding oxides are calculated from chemical equation using the molecular mass and thereafter the ash content in coal is calculated from summation of all the oxides present in the coal.
4. The method for optimum coal blending as claimed in claim 2, wherein for dry basis calculation, the real time moisture content in coal is measured by Microwave type Moisture Analyzer, and compensation is applied on as received basis calculation to derive dry basis measurement of Ash percentage.
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5. The method for optimum coal blending as claimed in claim 1 wherein the said Level II system is configured for following operations of coal blending including:
i. Conveyor Path Selection for unloading coal from tippler to Silo top from PLC
ii. Silo Number selection for coal unloading from PLC
iii. Silo-wise Coal Source selection from Level – II
iv. Totalized coal flow in Y-37 & Y-18 Conveyors
v. Silo-wise Weigh Feeder Selection from PLC
vi. Monitoring of Weigh feeder control operation
vii. Totalized coal flow in Y – 18 Conveyor
viii. Coal stock in individual silos
ix. In-coming coal elemental analyzer, moisture analyzer and belt weigher data monitoring
x. Blend coal elemental analyzer, moisture analyzer and belt weigher data monitoring
xi. Calculation of average ash content in silos
xii. Calculation of Actual, Cumulative and shift-wise Coal Blend Composition.
6. The method for optimum coal blending as claimed in claim 1, wherein the said PLC system controls and monitors the entire conveyor operation and also controls the Weigh Feeders.
7. The method for optimum coal blending as claimed in claim 1, wherein said incoming coal analyzer is installed over Conveyor between wagon tippler and silo top, which facilitates on-line measurement of Ash percentage, elemental analysis and moisture of incoming coal to CHP.
8. The method for optimum coal blending as claimed in claim 2, wherein both the Elemental and Moisture analyzers use radioactive sources for measurement.
9. A system for optimum coal blendingat Coal Handling Plant of Coke Oven Batteries employing the method as claimed in any of the preceding claims.
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10. The system for optimum coal blending as claimed in claim 9,further includes :
a) real time measurement of coal ash and moisture content through On-Line Cross Belt Elemental Analyzers in in-coming coal from mines right on the conveyor belt; and
b) real time measurement of coal ash and moisture content through On-Line Cross Belt Elemental Analyzers in blend coal right on the conveyor belt.