1. Background
In
recent years, as people's awareness of environmental protection and energy
saving and consumption reduction has been continuously enhanced, the importance
of flue gas waste heat recovery in China has been increasing day by day. For
the flue gas of 80 ℃, there is no good waste heat extraction and dust removal
scheme
Waste heat extraction and dust removal
requirements in the temperature range of 80 ~ 130 ℃.
2. Characteristics
of ptfe heat exchanger
In the flue gas waste heat utilization
system, the selection of anti-flue gas corrosion materials generally goes
through the following stages:
(1) 316
stainless steel + nickel metal coating: this method was widely used in the
mid-1980s. After operation, it was proved that it could not meet the
requirements of anti-smoke corrosion, and the corrosion and blockage were
serious. The working time was less than two years, and it needed to be
replaced.
(2) Nickel
metal base material: this material was widely used in the 1990s. It was proved
by practice that it could not meet the requirements of anti-flue gas corrosion
and could only be used in the net flue gas reheater after desulfurization, with
high cost and poor economy.
(3) Superior
ash cleaning function: minimum surface tension in solid materials, very large
surface contact Angle, no adhesion to any material; The surface of tube wall is
smooth, and sometimes flexible, slightly vibration when using, so it is not
easy to scale; At the same time, the ash removal device is installed to solve
the problem of ash accumulation.
Through the operation practice of various
materials in the early stage, it is necessary to have a material itself with
unique anti-smoke corrosion ability, only in this way can the waste heat
utilization of flue gas make a difference. Based on the above analysis,
polytetrafluoroethylene heat exchanger made of fluoroplastics fits the market
demand and starts to stand out in the field of flue gas waste heat utilization,
mainly because of its performance as follows:
(1)
Strong corrosion resistance:
stable chemical performance, inert to almost all chemicals and solvents, and
almost no solvent or compound can dissolve it under 300 ℃, can be used in most
harsh working environment.
(2)
High and low temperature
resistance: non-metallic materials are not brittle at low temperature and not
softened at high temperature in the range of -190 ~ 260 ℃, and can be used
normally.
(3)
Superior ash cleaning
function: minimum surface tension in solid materials, very large surface
contact Angle, no adhesion to any material; The surface of tube wall is smooth,
and sometimes flexible, slightly vibration when using, so it is not easy to
scale; At the same time, the ash removal device is installed to solve the
problem of ash accumulation.
(4)
Excellent wear resistance:
non-metallic materials themselves have excellent wear resistance, and in the
design of low wear, low resistance gas velocity, so as to reduce the wear of
ptfe heat exchanger tube bundle.
(5)
Low resistance: non-metallic
material heat exchange tube itself has smooth surface, low friction
coefficient, and low resistance to flue gas; The design considers the
resistance of ptfe heat exchanger to flue gas and has the optimum structure
size.
(6)
Long service life:
non-metallic materials do not contain photosensitive genes, and are extremely
resistant to aging. They have the best aging life in plastics, strong wear
resistance, and are not easy to block ash. Non-metallic heat exchangers can be
used for 10 to 15 years under normal conditions.
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