This document discusses new technologies in process heating. It covers combustion technologies for fossil fuels and biomass, as well as biomass boiler designs. Challenges in biomass combustion include low density fuel with high moisture and emissions. New combustion technologies aim to improve efficiency, reduce emissions, and be compact and cost-effective. Computational tools like CFD and FEA are helping develop new products and solve design problems. Condensing technology allows recovering latent heat to boost efficiencies above 100%, but introduces material challenges.
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C&H Heating Technologies Guide
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Process heating :New Technology .
R. S. Jha
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Key drivers for the innovation.
• Efficiency
• Emission
• Reduction in carbon foot print
• Compactness
• Life cycle cost
• Serviceability & maintainability
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Fossil fuel : Combustion technology
• Classification of combustion technology-
*Grate combustion
- Stationary grate
- Travelling grate
- Reciprocating grate
*Fluidised bed combustion
*Dust combustion
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Biomass : An alternative fuel
• Challenges in biomass combustion-
*Fuel with low density, higher moisture level and
low calorific value- difficulty in handling.
*Inconsistent supply of fuel & seasonal variation
in fuel properties – Boiler should be designed
with fuel flexibility
*Higher level of emission
*Slagging & fouling
• Need of an appropriate combustion technology
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Thermax Lambion combustion technology
Inclined reciprocating grate
Horizontal reciprocating grate
Combined reciprocating grate is
being developed.
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Combloc- A packaged biomass
boiler
A Packaged
biomass boiler
with horizontal
reciprocating
grate
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CPRG- A biomass boiler with inclined
grate
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Future of combustion technology
• Gasification
• Oxyfuel combustion
• Unmixed combustion
• Chemical looping combustion
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Development in the boiler design
• Boiler development- Size, fuel flexibility,
emission & efficiency
• Development in combustion technology
• Heat transfer enhancement- Tube inserts
& special tubes
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Fluegas heat recovery
• Conventional heat recovery technology
*Feed water preheating
*Combustion air preheating
• Challenges
*Economics of heat recovery
*Low end corrosion
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Need for condensing technology.
• Flue gas still contains approximately 6-8 % heat of the net calorific value of the fuel.
• Natural gas has a significant portion of hydrogen, which gets converted in to water
vapour after the combustion. In the process of combustion, a significant portion of the
heat is lost to provide the required latent heat for the evaporation of water. If we
consider this heat, approximately 15-17 % heat is still left with the flue gas. This can
be easily explained by noting the difference of efficiency on the basis of GCV and
NCV. Even with conventional heat recovery system, the efficiency on the basis of
GCV is in the range of 83-85 %.
• If the condensation of water vapour of the flue gas is allowed, flue gas temperature
can be further reduced to maximise the boiler efficiency.
• This opens a significant opportunity for the flue gas heat recovery, as the latent heat
of condensation is recovered in the process of condensation. If the sufficient heat
sink is available and system is optimally designed, approximately 10-12 % heat can
be recovered higher than the sensible heat left with the flue gas (6-8 % of the NCV).
• If we consider efficiency on the basis of NCV, the efficiency of boiler can go beyond
100%. Using condensing technology, The latent heat of water vapour is received
back, which was considered as lost in the definition of Net calorific value.
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Challenges :Condensing technology.
• Criticality of material selection- Material selection is very
critical for the design and selection of the condensing
heat exchanger. The suitable material should be anti
corrosive to deal with acidic condensate. Material should
have higher thermal conductivity and non sticky.
• Chimney corrosion- Other challenge of the condensing
heat exchanger design is the problem of chimney
corrosion.
• Higher cost- Due to poor heat transfer performance and
the special metallurgy, the cost of condensing exchanger
system is normally high.
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Efficient method of steam utilisation
• Focus on system efficiency- Closed loop
system & open loop system
• Combined heat & power
• Process integration
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Aquaerotherm- Integral air heater
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Use of computational
technology for new
development
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CFD- Computational fluid dynamics
Higher stack temperature problem of
thermal oil heater has been analysed
and solved by using CFD.
Flowmaldistribution
identifiedand
correctedforoilfired
firetubeboiler.
CFD helped to develop new
correlation for the heat transfer
coefficient of the coil type heater.
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FEA- Finite element analysis.
*FEA has served as a major
tools for design and
development of many new
product,
*It has also helped to
identify and solve some of
the chronic problem.