Recovering heat,
By Chris Giron
losing emissions
Transport membrane condenser
ups efficiency by 95 percent
Heat recovery systems
work to recover both sensible and latent heat, as
well as water from the exhaust stream. A transport
membrane condenser can
increase fuel-to-steam energy efficiency by as much
as 15 percent compared
to earlier heat recovery
systems.
Glossary
BTU: British thermal unit of energy equal to about 1055.05585 joules.
Sensible heat: Thermal energy that when transferred to or from a
substance results in a change of temperature.
Latent heat: Heat given off or absorbed in a process other than a
change of temperature.
Nanoporous: Porous at a nano level.
NOx: Nitrogen oxide.
Boiler-generated steam remains an effective method of heat ransfer for most process and
discrete manufacturing applications;
however, a tremendous amount of energy and water can be lost. In natural
gas combustion products, approximately 18 percent is water vapor, and if it
is left to escape with the exhaust, it
carries about 10 percent of the input
energy with it. So a system can never
exceed 90 percent efficiency if this
moisture escapes.
This same condition exists in your
home furnace or hot water tank, except
that they send the condensed water to
the drain instead of reusing it.
Fuel costs and environmental regu-latory mandates have created a strong
need for cost-effective solutions to enhance boiler performance to reduce
use of fuel and other energy forms, decrease water consumption, and lower
greenhouse gas (GHG) emissions.
Although the basic boiler itself has
not changed much, a number of technological advances over the last 20
years provide a way for manufacturers
using steam boilers to reduce variable
fuel consumption through higher energy
efficiencies and to operate in a more
sustainable way.
One of these technological advances is heat recovery. Heat recovery systems work to recover both sensible and
latent heat, as well as water from the
exhaust stream (see Figure 1). This enhances boiler efficiency and preheats
boiler feed water, which can be reallocated to other facility processes.
A boiler heat recovery technology
that addresses these issues is a condensing economizer. Water passes
through a condensing economizer on
its way to the boiler. Sensible heat is
recovered from the maximum boiler
exhaust temperature, starting in the
range of 400 degrees F, down to the
