Biomass Economiser Coil Industrial Exhaust Heat Exchange H Fin Tube Economizer
H Fin Tube Economizer Application
1. The use of Industrial Biomass Boilers in heating systems is beneficial because it uses agricultural, forest, urban and industrial residues and waste to produce heat and electricity with less effect on the environment than fossil fuels.
2. This type of energy production has a limited long term effect on the environment because the carbon in biomass is part of the natural carbon cycle; while the carbon in fossil fuels is not, and permanently adds carbon to the environment when burned for fuel (carbon footprint).
3. Historically, before the use of fossil fuels in significant quantities, biomass in the form of wood fuel provided most of humanity’s heating.
Exhaust Heat Exchange for Boilers
1. Cain Industries offers an extensive selection of boiler economizers specifically designed to recover BTU exiting the exhaust stack and transferring it back into a desired heat sink.
2. Our broad line of economizers cover the spectrum of boiler sizes, ranging from very small hot water boilers with burner inputs of 200,000 BTU/hr to large boilers delivering steam at 250,000 lb/hr.
3. Cain also produces boiler feedwater systems, condensate tank and pump systems, exclusive sootblower assemblies and unique modulating internal exhaust gas bypass systems.
Energy Savings Potential
1. The available heat in a boiler’s exhaust gases is dependent upon the hydrogen content of the fuel, the fuel firing rate, the percent of excess oxygen in the flue gases, and the stack gas temperature.
2. Consider a natural gas-fired boiler that produces 100,000 lb/hr of 100-psig saturated steam. At 83% efficiency, the boiler firing rate is about 116 MMBtu/hr. At its full firing rate, the boiler consumes over 4,860 lb of natural gas each hour while exhausting 10,938 lb of high temperature water vapor each hour. The water vapor in the flue gas contains over 10.6 MMBtu/hr of latent heat. As shown in Table 2, the total heat actually available for recovery is strongly dependent upon the stack gas temperature at the condensing economizer outlet.
3. Assume that an indirect contact condensing economizer is retrofitted onto this 100,000 lb/hr steam boiler to heat 50% of the makeup water from 55°F to 200°F and flue gases are cooled to 100°F. At these conditions, 12.75MMBtu/hr of total energy is available in the exhaust, of which 7.55 MMBtu/hr will be recovered to heat makeup water in the condensing economizer. More energy could be recovered if additional heat sinks are available.
Combustion Efficiency @4%Excess O2(%)
Stack Gas Temperature F
78 to 83%
350 to 550
With Feedwater Economizer
84 to 86%
250 to 300
With FW and Condensing Economizer
92 to 95%
75 to 150
Flue Gas Temperature Leaving Condensing Economizer