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Design
The design process is divided into the following steps:
1. Burner Model Selection
• Determine net input required for the tank or process
• Select tube efficiency
• Calculate gross input required
• Select burner model
2. Tube Design
3. Control Methodology
4. Ignition System
5. Flame Monitoring System
6. Combustion Air System: blower and air pressure
switch
7. Main Gas Shut-Off Valve Train
8. Process Temperature Control System
Step 1: Burner Model Selection
Determine the Net Input Required to the Tank
The net input to the tank is determined from heat balance
calculations. These calculations are based on the heatup
and steady-state requirements of the process, and take
into account surface losses, tank wall losses and tank
heat storage. Detailed guidelines for heat balance
calculations are in the Eclipse Combustion Engineering
Guide (EFE 825).
Select Tube Efficiency
The efficiency of the tube is the net heat input to the tank
divided by the heat input to the tube. Efficiency is
determined by the effective tube length. The diameter of
the tube has little influence on the efficiency. At a given
burner input, the net input to the tank is higher for a longer
tube than for a relatively short tube.
It is customary to size conventional immersion tubes for
70% efficiency, a reasonable compromise between fuel
economy and tube length. Small diameter tubes occupy
less tank space than conventional tubes, however, so
their length can easily be increased to provide efficiencies
of 80% or more.
Calculate the Gross Burner Input
Use this formula to calculate gross burner input in Btu/h:
Fuel Type
If using an alternative fuel supply, contact Eclipse with an
accurate breakdown of the fuel components.
Applications Requiring Special Consideration
ImmersoJet burners are used for firing spray wash tanks,
dip tanks, and storage tanks such as those used for fire
sprinkler systems. Generally, the small bore system can
be used wherever conventional immersion burner
systems are used, except where high heat flux off the
small bore tube can break down the contents of the tank.
Zinc Phosphate Solutions
High heat fluxes break down the phosphate, forming a
heavy insulating sludge, which deposits on tube surfaces
and causes rapid tube burnout. To reduce early tube
failure, make the immersion tube with electro-polished
stainless steel, and limit the burner to the capacity shown
in the limited capacity portion of Table 3.2 where capacity
is based on tube size.
net output to tank
= gross burner input
tube efficiency
Table 3.1 Fuel Type
Fuel
Symbol
Gross
Heating Value
Specific
Gravity
WOBBE
Index
Natural
Gas
CH
4
90%+
1000 Btu/ft
3
(40.1 MJ/m
3
)
0.60
1290
Btu/ft
3
Propane
C
3
H
8
2525 Btu/ft
3
(101.2 MJ/m
3
)
1.55
2028
Btu/ft
3
Butane
C
4
H
10
3330 Btu/ft
3
(133.7 MJ/m
3
)
2.09
2303
Btu/ft
3
Btu/ft
3
at standard conditions (MJ/m3 at normal
conditions)
System Design
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