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Fuel Additive Training. Cost Factor in Oil Fired Plant.

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Presentation on theme: "Fuel Additive Training. Cost Factor in Oil Fired Plant."— Presentation transcript:

1 Fuel Additive Training

2 Cost Factor in Oil Fired Plant

3 Fireside Concerns of Solid and Liquid Firing  Preburner corrosion/fouling  Burner corrosion/fouling  Furnace slagging  High temperature corrosion  Cold end corrosion  Gaseous emissions  Poor combustion

4  nozzle pluggage  tank corrosion  sludge in oil (asphaltenes)  water in oil  MB growth Minimizing Preburner and Burner Fouling:  Adding dispersants to fuel to minimize fouling  Dispersants promote a homogeneous fuel mixture  Improves suspension of Asphaltenes and solids Preburner and Burner Fouling- MFO Case:

5 FUEL INJECTION SPRAY PATTERNS

6 Furnace Slagging Concerns of solid & Liquid Firing  Poor heat transfer  Gas path pluggage  Fireside damage  Inhibit ash removal

7 Typical Location of Fouling and Slagging in Coal Fired Boiler

8 Major Slagging Elements  Vanadium  Sodium  Nickel  Potassium  Calcium  Lead  Zinc  Iron

9 CHEMICAL NATURE OF PROBLEM (cont) Alkali oxides of Na & K adhere to metal surfaces through reaction with SO 3  S (usually present as iron pyrites) converted to SO 2  SO 2 + ½ O 2 -> SO 3  Na 2 O + SO 3 -> Na 2 SO 4  3 SO Na 2 SO 4 + Fe 2 O 3 -> 2 Na 3 Fe(SO 4 ) 3  Ash constituents adhere to molten film building in thickness

10 Minimizing Slagging in Furnace  Mechanically - retrofit boiler to burn different fuel - tune burner guns - tune grate speed - check for proper soot blower alignment  Operationally - change fuel - change load/firing rate - increase excess air - increase soot blow frequency

11 Minimizing Slagging in Furnace Chemically  Elevate melting point of impurities in fuel  Increase friability of slag  Promote passivation of boiler surfaces AdditiveMelting Temperature  Magnesium oxide3180 oF  Calcined Alumina3875 oF  Calcium Silicate3255 oF  Aluminum oxide5166 oF  Titanium oxide3659 oF

12 How Fuel Additive Works:  Fuel additives function by elevating the melting point of the compounds formed by the impurities in the fuel  The goal is to minimize the amount of sticky, slag forming material in the flue gas  If the compounds formed remain dry, they are more likely to fall out the bottom as ash or be collected in the precipitators.

13 Melting Temperature of Compounds after Treatment

14 Typical MFO Analysis

15 Typical Coal Analysis

16 COMBUSTION Combustion is the breakdown of the organics to a gas during the slow chemical reaction of oxidation Coal combustion &/or fouling problems determined by :

17 Combustion Reactions Generic Reaction HC Fuel + O2CO2 + H2O + SOx + NO x + Heat Specific Reaction:HC (BTU/lb)  C + O2CO214,100  CO + ½O2CO23,960  H2 + O2H2O + ½O261,100  S + O2SO23,980

18 Poor Combustion Concerns  Smoking stack  High carbon in ash (LOI)  Increased fuel usage  Particulate emissions  Poor boiler efficiency

19 Combustion Catalyst  improves boiler efficiency  reduces volume of ash produced  reduces carbon content in ash  reduces particulate in flue gas  lowers excess air requirements (lowering NOx and

20 COMBUSTION IMPROVEMENT  Continuous application of combustion catalyst  Reduced activation energy to accelerate combustion  Reduced carbon content in fly ash  Reduced % excess air requirement

21 FUEL + AIR FREE RADICALS EACT 1 Progress of Reaction EACT 2 Potential Energy HEAT OF COMBUSTION FLUE GAS POTENTIAL ENERGY DIAGRAM FOR COMBUSTION REACTIONS

22 HOT END PROBLEMS  Hot Section defined as operating temperature > 1000 F (535 C)  Furnace, convective zone, superheaters  Low viscosity ash formation  Slag deposits  Metal surface corrosion

23 FURNACE SLAG DEPOSITS

24 Untreated vs Treated Slagging 1000x SEM Highlighted area #2 -Treated: Larger pores Weaker and lighter deposits Easier to remove Highlighted area #1- Untreated: Small pores and packed Hard and tenacious deposits Create problems

25 COLD END PROBLEMS  Cold section defined as operating temperature < 1000 F (535 C)  Air preheaters, ID fans, economisers, boiler stack  Caused by sulphuric acid attack formed when flue gas cooled below the acid dew point  Metal sulphates formed result in fouling

26 Minimizing Cold End Corrosion  Can be minimized by adding magnesium and/or magnesium oxide to the fuel at the time of combustion.  The magnesium reacts with the sulfur to reduce the concentration of SO 3 compounds in the flue gas.  Reducing the amount of sulfur available to form sulfur dioxide compounds which result in the formation of H 2 SO 4  By minimizing the amount of sulfuric acid present in the flue gas, the magnesium oxide effectively elevates the acid dew point of the sulfuric acid that does form.

27 Neutralization Reaction  Mg + 2O2 + SMgSO4  MgO + 3/2O2 + SMgSO4  Mg + 1/2O2MgO  Mg + ClMgCl

28 Treatment Strategies

29 TREATMENT STRATEGIES  Neutralisation  Alkaline additive to neutralise sulphuric acid as formed  Catalyst Deactivation  Coating &/or reaction with catalysts (Cu, Fe)  Continuous application to coal prior to pulverisers  Often combined treatment with combustion catalyst

30 FIRESIDE ADDITIVES Raises fusion temperature of adherent deposits  Produces dry, friable, high mp compound  Weakens bonding of slag to metal surface  Reacts with complex sulphates & other slag components  Changes slag from a hard, dense material to soft, expanded, porous powder  Forms metallic film on metal surface  Protects surfaces from corrosive action  Minimises catalytic action of SO 2 to SO 3

31 Diffusion of Additive Throughout Slag Materials  Particle size of additive (MgO) in fireside gas is 0.3 – 0.03   The combustion gas diffuses throughout slag due to permeability of slag materials  This mechanism keeps the slag formed is lighter, softer, and easier to remove via shootblowing

32 Treatment Results

33

34 Fly Ash pH The easiest means to measure the efficacy of chemical treatment Sample taken from Air Heater outlet pH checking thru 1% slurry of fly ash (fly ash + demin water) Target fly ash pH:

35 IMPROVING COMBUSTION EFFICIENCY

36 ACID DEWPOINT & TEMPERATURE RELATIONSHIPS

37 Fuel Additive Products  Powder Products  FST 5370 Slag inhibitor with corrosion inhibitor  Drew 11-GFM Slag inhibitor & combustion catalyst  Drew 11-GFS Slag inhibitor ~ dosage 0.1 kg/Ton fuel  Liquid Product: Amergy 222N for MFO preburner ~ dosage 0.15 – 0.25 kg/Ton fuel

38 Questions?


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