Successful conversion to natural gas firing • FCT Combustion • Ricardo Costa • Adriano Greco
Natural Gas – Pros and Cons Natural gas flame needs to be hotter to have the same lengh 3
Natural Gas – Pros and Cons 4
Accessories – Safe operation • Natural gas Valve train Automatic shut off valves Pressure regulator Flow control valve Flowmeter Safety devices and features according local regulations • Flame sensor • BMS • Control of all fuels • From cooler to the stack – “No short -cuts ”
Combustion in Rotary Kilns Factors Affecting Burner Operation Type of fuel Oxygen in the kiln Momentum ratio between the burner jets and secondary air Kiln, cooler and hood aerodynamics and What to get from a good burner relative burner position Reduced Energy Costs Burner tip Design (Atomizer, Gas Nozzle Increased Production etc.) Improved Safety & Reliability Reduced Maintenance Costs Reduced Emissions Improved Product Quality Reduce Rings 6
Turbulence vs Jet Excitation • Turbulent Burner Uses the energy contained in the fuel and/or oxidant stream to promote the mixing. This concept is based on steady-state, constant jet streams interfering with each other and with the surrounding secondary air, creating the necessary turbulence. This principle is applied in the design of most current kiln burners. • Jet Excitation Phenomenon that a fluid passing at high speed through a nozzle into a larger chamber, with certain geometric characteristics, would precess around the chamber’s longitudinal axis. This was called “Jet Excitation”. 7
Burner technology types high momentum jet (Hawthorne & Hottel, 1950’s, generic public domain technology available to all) - incorporated by FCT and others in burner designs Swirl (Leuckel, Beer, 1960’s, public domain technology available to all ) - incorporated by FCT in Turbulent Jet Burner Swirl 0 0.2 0.25 0.5 1.1 8
Classic Turbulent Burner Flame 9
Gyro-Therm Burners • Use patented “ Precessing Jet” technology – no moving parts in a hot and dusty environment. • Produce a naturally staged combustion regime • Causes natural gas to crack to soot, giving high luminosity comparable to oil firing • Suppresses NOx formation due to fuel rich combustion within flame envelope • Short bulbous flame with high radiant heat transfer properties - controllable heat flux profile • No Primary Air Required 10
Thermal Profile Comparison How Significant is the Difference in the Mixing? 120 100 Oil Gas: TDJF Gas: Gyro-Therm 80 Wall Heat Flux (kW/m^2) 60 40 20 0 0 5 10 15 20 25 30 35 40 45 -20 -40 Distance from Burner Nozzle (m) 11
Burner Characteristics • To help understand the Gyro-Therm burner flame a little better it is worth considering the Bunsen burner you may have used during science experiments at school. Adjustable openings for entrainment of air to mix with the gas prior to igniting Gas supply 12
Burner Characteristics [1] If the air hole is closed then the gas burns only with air that is entrained as the gas exits the nozzle. Due to the low gas velocity air and fuel mixing is poor. This reduced mixing results in incomplete combustion, producing a cooler but brighter yellow flame referred to as the “luminous flame”. The yellow flame is luminous due to small soot particles in the flame which are heated to incandescence. The yellow flame is considered "dirty" because it leaves a layer of carbon on whatever it is heating. [2] Air hole slightly open, [3] Air hole half open, [4] Air hole fully open (very hot almost invisible blue flame). 13
Burner Characteristics • A turbulent jet gas burner has high momentum to ensure sufficient air is entrained into the flame for complete combustion. • The high momentum means that fuel and air mix very quickly as the gas leaves the burner tip resulting in low soot formation in the flame, a low flame luminousity (low radiation heat transfer to the bed and walls) and therefore high flame temperature. • The high flame temperature and air levels in the flame results in high NOx production. 14
Burner Characteristics • Due to the jet of gas precessing around the Gyro-Therm chamber, at any moment in time the gas leaving the burner is burning fuel rich. • The fuel rich combustion results in high soot formation in the flame, a high flame luminousity (high radiation heat transfer to the bed and walls) and therefore low flame temperature • The low flame temperature and initial low air levels in the flame results in low NOx production. 15
. Gyro-Therm Nozzle 16
Precessing Jet behavior 17
Precessing Jet behavior 18
Precessing Jet behavior 19
Flame difference Gyro-Therm Flame Turbulent Jet Diffusion Burner 20
Results From Cement Plant Installations • Client location: USA • Sattelite kiln with riser duct • Burner installation: Jan 2017 • Results to date: • 18% NOx reduction • 4% Specific heat reduction • More stable operation = higher productivity • Direct ROI – Save $ 1 mi in SNCR installation 21
Results From Cement Plant Installations • Client location: USA • Kiln with ILC Calciner • Burner installation: May 2017 • Results to date: • Production increase - + 100 tpd • Improved fuel consumption • Decreased ammonia usage • Improved burning zone coating stability • Elimination of need for oxygen injection 22
Gyro-Therm Burners For Gas or Gas/Coal Fired Rotary Kilns • Higher Output • Lower Fuel Consumption • Lower NOx Emissions • Longer Refractory Life • No Primary Air required • Flame Shaping Capability • Stable Flame with High Turndown Ratio 23
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