PRESENTED BY RICHARD WERMUTH OF KARBON SERVICES

Transcription

1 PRESENTED BY RICHARD WERMUTH OF KARBON SERVICES

2 IN ORDER TO UNDERSTAND HOW COAL QUALITY EFFECTS EFFICIENCY WE FIRST NEED TO LOOK AT COAL S PROPERTIES.

3 IT S BLACK IT S DIRTY IT S DUSTY IT BURNS SOMETIMES NOT SO BRIGHTLY!

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5 Generally, only a basic coal analysis is performed by both the mine and the user. So what it the basic analysis of coal and what does it mean? BASIC ANALYSIS = PROXIMATE, C.V., SULPHUR {S} PROXIMATE ANALYSIS THIS CONSISTS OF: INHERENT MOISTURE VOLATILE MATTER ASH FIXED CARBON

6 INHERENT MOISTURE Inherent moisture is moisture that will remain in coal even after it has been air dried This moisture varies and will always be present in coal VOLATILE MATTER Volatile matter refers to a number of oils, tars & gases in the coal that will be released when the coal is heated to a specific temperature. Volatiles are released as a gas and are vital for ignition. Volatiles will be release at approx c ASH This is the portion of the coal that is ash. If you were able to burn your coal to the best possible level you would produce this % of ash. FIXED CARBON This is a calculated figure! Fixed carbon excludes carbon found in volatiles. It is not a measurement of carbon. Simply subtract the above 3 from 100 and this will give you your fixed carbon.

7 PROXIMATE March April June Sept april Inh Moisture Volatile % Ash % Fixed Carb on Calorific Value Mj/kg

8 C.V. is the measurement of the energy value in the coal. GENERALLY EXPRESSED AS MJ/KG. UNDERSTANDING that majority of boilers & furnaces in south Africa were designed to burn a grade coal, makes C.V. VERY IMPORTANT! In order to get the MCR of steam out of the boiler you will need to burn the C.V. that the boiler was designed to burn. Burning LOWER C.V S will result in an inability to attain maximum production

9 Originally, coals were divided into 4 grades based only on C.V. A GRADE - B GRADE - C GRADE - D GRADE Mj/kg Mj/kg Mj/kg - 25 Mj/kg THE ABOVE IS THE ORGINAL SABS APPROVED GRADING OF COAL

10 UNFORTUNATELY THESE DAYS, THE GRADES ACCORDING TO C.V. DO NOT APPLY. VERY FEW PRODUCERS ARE PRODUCING MJ COALS, AND MANY MERCHANTS AND MINES ARE SELLING COALS WITH LOWER C.V S AS A GRADE COALS. THERE ARE 2 MAIN REASONS FOR THIS: 1. THE LACK OF GOOD COAL LEFT IN SOUTH AFRICA many of the high C.V coals have been mined out, or in the old days mines would only remove the sweet spot of the seam giving the best C.V and leaving lower quality underground. mines have been reopened to mine this lower quality out. 2. THE EXPORT MARKET the export market only requires a C.V of 26.5 Mj/kg. this means that producers will not wash/beneficiate coal to a higher C.V as this would reduce the yield.

11 HOW DO YOU KNOW WHAT C.V TO PROCURE??? Every boiler was designed to burn a specific C.V of coal. Majority of installed boilers were designed to burn an A grade coal { Mj/kg } The aim regarding C.V would be to get a coal with as close to the boiler specification as possible. Burning a coal with a lower C.V will result in less steam being produced / more coal being used. It is important to weigh up the pro s and cons of burning a lower C.V coal to ensure that you are not increasing the cost of production.

12 ALMOST ALL COAL HAS SULPHUR IN IT, AND THEREFORE BURNING COAL WILL LEAD TO SO2 (SULPHUR DIOXIDE) EMMISSIONS It is important to know the percentage of sulphur in coal for environmental issues, and to control the firing process to eliminate the excess production of SO2. Total moisture is often not measured. This analysis would have to be done on coal in the yard/silo etc. as rain and weather conditions will effect the amount of moisture. Depending on how much rain etc. the coal is exposed to the total moisture content can be as high as 20% This can reduce the C.V of coal dramatically Knowing this can assist the operator to fire the boiler as efficiently as possible

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14 ULTIMATE ANALYSIS CONSISTS OF : ASH TOTAL SULPHUR TOTAL CARBON HYDROGEN NITROGEN OXYGEN We have already discussed ash & sulphur. Ash is done in both Proximate and Ultimate analysis and Sulphur forms part of Ultimate analysis but can be done separately to the other analyses.

15 TOTAL CARBON: Total carbon is a true measurement of the carbon present in the coal ( as opposed to fixed carbon which is a calculated measurement) and accounts for all carbon present, including carbon in volatiles HYDROGEN: This analysis can give you an insight into the reactivity of the coal, as hydrogen is highly reactive. Too much hydrogen in the coal can result in loss in efficiency due to the formation of water in flue gases. NITROGEN: Nitrogen is found in small quantities. The presence of this Nitrogen can affect the production of NOX emissions. OXYGEN: Oxygen in coal should be taken into account when firing coal, as the release of this oxygen when the coal is fired can affect air-fuel ratios.

16 ULTIMATE Ash Total Sulphur Total Carbon Hydrogen Nitrogen Oxygen

17 UNDERSTANDING PHOS IN COAL AND THE POTENTIAL FOULING EFFECTS OF P2O5 (PHOS IN ASH) IS VERY IMPORTANT. HIGH PHOS IN COAL WILL RESULT IN HIGH PHOS IN ASH AND PHOS FOULING CAN SHUT A BOILER DOWN IN LESS THAN 24HOURS 24 HOURS OF BURNING HIGH PHOS COAL

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20 FREE SWELL INDEX: Free swell index (FSI) is an analysis of the how the coal expands and swells once it is heated past approx. 400 c. This can affect bed depth, burnout, carbon is ash, and can lead to damage of arch s etc. It is important to remember that a coal with an FSI of 1 (one) will double is size. HARD GROVE INDEX: Hard grove index refers to the hardness of coal. This is valuable information, as handling of coal will result in degradation. Greater care, and less handling should be applied to coals with higher HGI s as these will degrade and result in fines. If a coal has low HGI it could effect ignition as volatiles will not be liberated as fast. Harder coals can also cause feeder problems if sizing is not correct, and if the coal is to be milled/crushed then there will be greater wear and tear on the machinery performing this task.

21 ASH ANALYSIS/CONSTITUENTS IS ONE OF THE MOST IMPORTANT ANALYSIS A USER CAN DO ON HIS COAL. UNDERSTANDING THE MAKE UP OF THE ASH AND HOW THIS DIRECTLY RELATES TO SLAGGING AND FOULING CAN HAVE MASSIVE SAVINGS. KARBON SERVICES LIKES TO REFER TO ASH CONSTITUENTS AS THE BLOOD LINE OF THE COAL Ash Analysis Total Silica as Si02 % Aluminum as Al203 % Total Iron as Fe203 % Titanium as Ti Phosphorus as P205 % Calcium as CaO % Magnesium as MgO % Sodium as Na20 % Potassium as k20 % Sulphur as S03 %

22 THE MOST IMPROTANT FACTORS IN ASH CONSTITUENTS ARE IRON AS Fe2O3 CALCIUM AS CaO MAGNESIUM AS MgO These 3 constituents are the 3 main culprits of slagging and fouling in a boiler/ furnace. Slagging and fouling can greatly reduce efficiency and cause damage to all parts of the boiler/furnace. Grate damage, side seal damage, tube leaks, sheet clinker, side wall clinker, economiser fouling. The list could go on. All can be reduced/ minimised by firing a coal that has a good Blood Line! Looking at ash constituents is like having a blood test done to find out what is wrong with you! Phos as P2O5 is also important. Sulphur as SO3, can help in an understanding of how much S in coal is being converted into SO2.

23 A.F.T s provide vital information about temperatures within the boiler/furnace and the temperature that the ash begins to melt, becomes vicious, and adhesive. There are generally 4 temperature recorded: INITIAL DEFORMATION TEMPERATURE: is the temperature at which the prepared cone of ash just begins t fuse or show evidence of deformation at the top of the cone as it is being heated in a standard furnace test. At the corresponding temperature in a boiler / furnace ash particles will retain a SLIGHT tendency to stick together or slowly build up on heat transfer surfaces. SOFTENING (SPHERE) TEMPERATURE: corresponds to an observed condition between initial deformation and fluidity. Visually in the lab, softening temperature will be observed when the cone has deformed to a spherical form where the height = width

24 HEMISPHERICAL TEMPERATURE: the hemispherical temperature is when the cone has further deformed to the point where it assumes a hemispherical shape and its height equals half its width {H = ½ W } FLUID TEMPERATURE: This is reached when the test cone flattens out to a pancake shape on the plaque. The fluid temperature is where one could expect the ash to flow in streams or drip off heat surfaces. Heavy clinker forms on the grates Under a fuel bed. BOTH SOFTENING & HEMISPHERICAL TEMPERATURE ARE RELATED TO A POINT AT WHICH THE FUEL SHOWS A GREATLY ACCELERATED TENDENCY TO MASS TOGETHER AND STICK IN LARGE QUANTITIES TO HEAT ABSORBING SURFACES.

25 SIZING OR SCREENING OF COAL IS OF VITAL IMPORTANCE. ONE OF THE BIGGEST ISSUES THAT NEEDS TO BE OVERCOME IN ORDER TO FIRE COAL EFFICIENTLY IS BED PROFILE. THIS IS DIRECTLY RELATED TO THE SIZE DISTRIBUTION OF THE COAL. FIRING THE CORRECT SIZE / EVEN SIZE DISTRIBUTION OF COAL WHILE ELIMINATING SEGREGATION CAN IMPROVE EFFICIENCY DRAMATICALLY AND DECREASE SLAGGING AND FOULING, ESPECIALLY CLINKER FORMATION ON THE GRATE. WHAT IS THE CORRECT SIZING?

26 SIZING AND SIZE DISTRIBUTIONS VARY WITH BOILER MAKE, DESIGN, FEED SYSTEM ETC SO THERE IS NO SIMPLE ANSWER TO THE QUESTION. UNFORTUNATELY, THERE IS NOT A GREAT DEAL OF OPTION WHEN IS COMES TO COAL SIZING DUE TO SUPPLIERS NOT NEEDING TO MEET THE INDUSTRIAL USERS REQUIREMENTS DUE TO THE EXPORT MARKET. MOST BOILERS / FURNACES WILL USE A PEA PRODUCT, WHICH IS DEFINED AS A 6mm X 25mm GETTING AN EVEN DISTRIBUTION THROUGH THE SIZES SHOULD BE AN AIM FOR THE USER. THIS WOULD ENTAIL VISITING THE MINE AND DISCUSSING EXACTLY WHAT YOU WANT AND CHALLENGING THEM TO GIVE IT TO YOU!

27 KARBON SERVICES LOOKS AT A NUMBER OF SIZES WHEN LOOKING AT THE DISTRIBUTION {MINES OFTEN ONLY LOOK AT A FEW} THESE SIZE S ARE: mm 3.35 mm X 6.3 mm 6.3 mm X 10 mm 10 mm X 16 mm 16 mm X 20 mm 20 mm X 25 mm +25 mm It is IMPORTANT to remember that most mines use LONG slotted screens and therefore there sizing will be different form the actual sizes that are delivered to the user. SQUARE slotted screens should be used for sizing analysis.

28 KARBON SERVICES RECOMMENDS THE FOLLOWING DISTRIBUTION THROUGH THE SIZE S SIZE DISTRIBUTION: mm < 5 % 3.35 mm x 6.3 mm 5 % 6.3 mm x 10 mm 25 % 10 mm x 16 mm 30 % 16 mm x 20 mm 25 % 20 mm x 25 mm 5 % +25 mm < 5 % { preferably 0 % } If sizing can be delivered as close to the above breakdown as possible, and segregation can be minimised, bed profiles will improve dramatically!

29 THE PURPOSE OF THIS SIZING IS TO HAVE THE ABILITY TO CREATE A SITUATION WHERE ALL THE VARIOUS COAL PRODUCT SIZES ARE EQUALLY DISTRIBUTED OVER THE ENTIRE GRATE AREA

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32 THE NEXT STEP IN UNDERSTANDING THE PROPERTIES OF COAL AS A FUEL IS PETROGRAPHIC ANALYSIS. THIS IS AN IN DEPTH LOOK INTO THE FORMATION OF THE COAL, AND PROVIDES US WITH INFORMATION ABOUT THE REACTIVITY OF THE COAL. EVERY SEAM OF COAL WAS FORMED FROM A DIFFERENT COMBINATION OF CARBON MATTER (DEAD TREES) UNDER DIFFERENT CONDITIONS (HEAT, PRESSURE, ETC) AND THIS HAS GIVEN COAL CHARACTER! THE CHARACTER OF THE COAL GIVES US AN UNDERSTANDING OF HOW THE COAL WILL BEHAVE AND REACT IN THE BOILER/FURNACE. THIS INFORMATION CAN PROVIDE HUGE INSIGHT INTO COMBUSTION PROBLEMS AND POOR EFFICIENCYS

33 PETROGRAPHIC ANALYSIS REQUIRES A MICROSCOPIC ANALYSIS OF THE ORGANIC COMPOSITION OF THE COAL ORGANIC COMPOSITION: This relates to the microscopically discernible organic components of coal that are termed "maceral" and which are analogous to minerals in inorganic rocks. THREE MACERAL GROUPS ARE RECOGNIZED VITRINITE LIPTINITE INERTINITE These are distinguished from one another under the petrographic microscope by differences in reflectance, morphology, colour, shape, size, polishing hardness and fluorescence. their optical, physical, chemical and technological characteristics alter as the coal matures.

34 KNOWING THE ORGANIC COMPOSITION OF THE COAL DIRECTLY RELATES TO THE REACTIVITY OF THE COAL THE MORE REACTIVE A COAL IS, THE GREATER THE HEAT TRANSFER WILL BE Golfview Landau 1 & 2 Grootgeluk Inyanda V4 V5 V6 V7 V.8 V.9 V1.0 V1.10 Golf V. INYANDA Landau 2 Landau 1 Grootgeluk

35 SLOW REACTING COAL WILL REQUIRE LONGER BURN OUT TIMES AND MAY NOT BE SUITABLE FOR BOILER USE. THIS A GRADE COAL RESULTED IN A HUGE DECREASE IN EFFICIENCY DUE TO ITS CHARACTER. THE BURN OUT CHARACTER RESLUTED IN EXTREAMLY HIGH UNBURNT CARBON IN ASH VALUES

36 COALS THAT ARE VERY SIMILAR IN TERMS OF PROX, C.V. ETC. CAN BE VERY DIFFERENT IN TERMS OF PETROGRAPHIC ANALYSIS AND THIS COULD RESULT IN HUGE DIFFERENCES IN FIRING AND EFFICIENCY. IT IS VERY IMPORTANT TO KNOW YOUR COAL!

37 THE FOLLOWING IS AN ACTUAL COAL TRIAL THAT WAS DONE TO ACSERTAIN WHEATHER OR NOT A NEW COAL WAS A VIALABLE OPTION TO REPLACE THE CURRENT COAL BEING USED.

38 PROXIMATE COAL 1 COAL 2 COAL 3 COAL 4 Inh Moisture Volatile % Ash % Fixed Carbon Calorific Value Mj/kg

39 ULTIMATE COAL 1 COAL 2 COAL 3 COAL 4 Ash Total Sulphur Total Carbon Hydrogen Nitrogen Oxygen Phos as P in COAL Free Swell Index H G I n.a. 56

40 Ash Analysis COAL 1 COAL 2 COAL 3 COAL 4 Total Silica as Si02 % Aluminium as Al203 % Total Iron as Fe203 % Titanium as Ti Phosphorus as P205 % Calcium as CaO % Magnesium as MgO % Sodium as Na20 % Potassium as k20 % Sulphur as S03 %

41 40 REFLECTANCE HISTOGRAM COAL 1 vs COAL 2 vs COAL3 vs COAL

42 COMBUSTION EFFICIENCY REPORT: Prepared by: Richard Wermuth of : Karbon Services Tel Date: 7TH January 2010 Customer: Location: Boiler No's Fuel: COAL TRIALS Analysis of Coal Fired: coal 1 coal 2 coal 3 coal 4 Total Moisture % Gross Calorific Value Mj/kg Inherent Moisture % Ash % Ultimate Analysis Carb on % {Air Dried} Hydrogen % Sulphur % Nitrogen % Oxygen %

43 Dry Flue Gas Analysis Carb on Dioxide % Oxygen % Carb on Monoxide % S02 By Calculation Sulphur Dioxide % N2 By Calculation Nitrogen % OPERATING CONDITIONS OF BOILER Flue gas temperature Degrees C Temperature of residue Ash C Amb ient temperature C Mass of Coal consumed Kgs Mass of Course Ash recovered Kgs Carb on content of ab ove % Mass of Fly Ash recovered Kgs Carb on content of ab ove % Estimated of Loss due to radiation & other %

44 BREAKDOWN OF BOILER LOSSES Read as coal 1 coal 2 coal 3 coal 4 Moisture in fuel % Water in flue gas from Hydrogen in fuel % Heat in Dry Flue Gasses % Incomplete combustion resulting in Carbon Monoxide in Flue Gas % Incomplete Combustion resulting in Unburned Carbon % Heat in Ash % Radiation & unaccounted losses % TOTAL OF ALL LOSSES % NETT BOILER EFFICIENCY % Excess Air RATIO % 115% 94% 103% 159.5%

45 40 REFLECTANCE HISTOGRAM COAL 1 vs COAL 2 vs COAL3 vs COAL

46 coal 1 coal 2 coal 3 coal 4 NETT BOILER EFFICIENCY % The boiler was operated under the same conditions for all 4 coals. Without making adjustments to the boiler, each coal can be assessed under the same conditions. The boiler can then be adjusted to suit the coal, and this can dramatically improve efficiency! A difference of almost 9% nett efficiency was noted between the coal 1 and 4.

47 HOPEFULLY THIS PROVIDES AN UNDERSTANDING OF HOW THE QUALITY OF COAL CAN EFFECT EFFICIENCY.. ANY QUESTIONS??? THANK YOU FOR YOUR TIME.