U.S. patent application number 14/027265 was filed with the patent office on 2014-01-09 for heating system for heating heat-transfer oil usingboiler flue gas.
This patent application is currently assigned to SHANGHAI FUBO EP EQUIPMENT CO., LTD.. The applicant listed for this patent is SHANGHAI FUBO EP EQUIPMENT CO., LTD.. Invention is credited to Bing LIU, Xuelve QIAN.
Application Number | 20140007823 14/027265 |
Document ID | / |
Family ID | 44895035 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140007823 |
Kind Code |
A1 |
QIAN; Xuelve ; et
al. |
January 9, 2014 |
HEATING SYSTEM FOR HEATING HEAT-TRANSFER OIL USINGBOILER FLUE
GAS
Abstract
A heating system for heating heat-transfer oil using exhaust
heat of boiler flue gas. The system includes: a flue, an
economizer, an air preheater, and a heat-transfer oil heater. The
economizer and the air preheater are disposed in the flue along the
flow direction of the flue gas. The heat-transfer oil heater is
disposed inside the flue in front of the economizer and is
connected to a heat consumption device via a first circulating
pipe. The circulating pipe is equipped with a circulating pump.
Inventors: |
QIAN; Xuelve; (Shanghai,
CN) ; LIU; Bing; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHANGHAI FUBO EP EQUIPMENT CO., LTD. |
Shanghai |
|
CN |
|
|
Assignee: |
SHANGHAI FUBO EP EQUIPMENT CO.,
LTD.
Shanghai
CN
|
Family ID: |
44895035 |
Appl. No.: |
14/027265 |
Filed: |
September 16, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/CN2011/080030 |
Sep 22, 2011 |
|
|
|
14027265 |
|
|
|
|
Current U.S.
Class: |
122/20B ;
122/421; 122/451.1 |
Current CPC
Class: |
F22D 1/36 20130101; F22D
5/00 20130101; F22D 1/38 20130101; F24D 7/00 20130101; F22D 1/50
20130101; F24H 1/125 20130101 |
Class at
Publication: |
122/20.B ;
122/421; 122/451.1 |
International
Class: |
F24H 1/12 20060101
F24H001/12; F24D 7/00 20060101 F24D007/00; F22D 5/00 20060101
F22D005/00; F22D 1/38 20060101 F22D001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2011 |
CN |
201120069052.6 |
Claims
1. A heating system for heating heat-transfer oil using exhaust
heat of boiler flue gas, the system comprising: a) a flue (1); b)
an economizer (3); c) an air preheater (4); and d) a heat-transfer
oil heater (2); wherein the economizer (3) and the air preheater
(4) are disposed in the flue along a flow direction of the flue
gas; the heat-transfer oil heater (2) is disposed inside the flue
(1) in front of the economizer (3) and is connected to a heat
consumption device (19) via a first circulating pipe; and the
circulating pipe is equipped with a circulating pump (12).
2. The system of claim 1 further comprising an exhaust heat
utilization device, wherein the exhaust heat utilization device
comprises a heat absorption member (5) and a heat release member
(6) communicating with each other through a second circulating
pipe; the heat absorption member (5) is disposed inside the flue
behind the air preheater (4); and the heat release member (6) is
arranged on a water inlet pipe of the economizer (3) or inside an
air inlet channel of the air preheater (4).
3. The system of claim 2, wherein the heat release member (6) is
arranged on the water inlet pipe of the economizer (3), the water
inlet pipe of the economizer is provided with a deaerator (14) and
a high pressure heater (11) for allowing boiler feedwater to pass
through the heat release member (6), the deaerator (14), and the
high pressure heater (11), respectively, to enter the economizer
(3).
4. The system of claim 3, wherein a feedwater pump (7) is arranged
on a water pipe by which the deaerator (14) and the high pressure
heater (11) are connected.
5. The system of claim 3, wherein a steam inlet pipe of the high
pressure heater (11) and a steam inlet pipe of the deaerator (14)
communicate; and a condensate drainage pipe of the high pressure
heater (11) is connected to the deaerator (14).
6. The system of claim 5 further comprising a control system, two
temperature sensors (8, 10), and a plurality of flow control valves
(9, 13, 21), wherein the temperature sensors and the flow control
valves are connected to the control system; a first temperature
sensor (8) is disposed on the heat absorption member (5), and a
second temperature sensor (10) is disposed on the flue between the
economizer (3) and the air preheater (4) or on a water outlet pipe
of the economizer (3); one branch of boiler feedwater passes
through a first flow control valve (21) and enters the deaerator,
and another branch of boiler feedwater passes through a second flow
control valve (9) and the heat release member (6) and enters the
deaerator; and a third flow control valve (13) is arranged on the
steam inlet pipe of the high pressure heater.
7. The system of claim 2, wherein the heat release member (6) is
arranged inside the air inlet channel of the air preheater (4); the
system further comprises a control system, a temperature sensor
(8), and a flow control damper (20); the temperature sensor (8) and
the flow control damper (20) are connected to the control system;
and the temperature sensor (8) is arranged on the heat absorption
member (5), and the flow control damper (20) is arranged inside the
air inlet channel of the air preheater in front of the heat release
member (6) along the flow direction of inlet air.
8. The system of claim 1, wherein the system further comprises an
oil-gas separator (18); and the oil-gas separator (18) is disposed
on the first circulating pipe between the heat-transfer oil heater
(2) and the heat consumption device (19).
9. The system of claim 8, wherein the oil-gas separator (18) is
connected to an expansion slot (17), and the expansion slot (17) is
connected to an oiling pump (16).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of International
Patent Application No. PCT/CN2011/080030 with an international
filing date of Sep. 22, 2011, designating the United States, now
pending, and further claims priority benefits to Chinese Patent
Application No. 201120069052.6 filed Mar. 16, 2011. The contents of
all of the aforementioned applications, including any intervening
amendments thereto, are incorporated herein by reference. Inquiries
from the public to applicants or assignees concerning this document
or the related applications should be directed to: Matthias Scholl
P.C., Attn.: Dr. Matthias Scholl Esq., 14781 Memorial Drive, Suite
1319, Houston, Tex. 77079.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to absorption and utilization of waste
heat from boiler flue gas, and more particularly to a heating
system of heat-transfer oil using boiler flue gas.
[0004] 2. Description of the Related Art
[0005] Organic heat carrier furnaces adopt an organic heat carrier
as a medium for transferring the heat energy. The heat energy
produced from the combustion is transferred to the organic heat
carrier through a furnace heating surface for heating the organic
heat carrier to a certain temperature. After that, the organic heat
carrier is transferred to a heat consumption device by using a
circulating oil pump to allow the organic heat carrier to release
the heat energy. Thereafter, a low temperature organic heat carrier
is returned to the furnace and heated again. The above processes
are repeated to realize the supply of heat to a heat consumption
device by using the organic heat carrier. The organic heat carrier
furnace has the following characteristics: 1. High temperature of
the heat carrier can be obtained at a relative low working
pressure; 2. The liquid phase is circulated for providing heat,
without heat loss resulting from condensation, so that the heat
supplying system has a high heat efficiency; 3. The organic heat
carrier furnace is capable of satisfying the requirement of
accurate process temperature on the heat utilization system because
of convenient operation control and uniform heat transfer. Thus,
the organic heat carrier furnace is widely applied in petroleum,
chemical, textile, printing and dyeing, rubber, leather, food, wood
processing and many other industries. Meanwhile, as described in
the former that the relatively high temperature heat carrier is
obtained in relatively low working pressure, the temperature of
such heat carrier is between 200 and 300.degree. C., or much
higher.
[0006] The flue gas produced from the combustion of the fuel of the
boiler contains acid gas. When the flue gas is at a high
temperature, the acid gas passes through various heating surfaces
in the form of gas until it is removed in a desulfurization tower.
When the temperature of the flue gas is lower than a certain
degree, sulfur in the flue gas combines with the water vapor
therein and is transformed into sulfuric acid which is corrosive to
the heat transfer device. Low temperature corrosion generally
occurs in a cool end of the air pre-heat device and an economizer
having a low feedwater temperature. When the temperature of the
heating surfaces is lower than a dewpoint of the flue gas, sulfuric
acid resulting from the reaction between the water vapor in the
flue gas and sulfur trioxide (accounting for a very small part of
the sulfuric product produced from the combustion of the coal fuel)
is condensed on the heating surfaces, thereby being heavily
corrosive to the heating surfaces. In order to prevent the acid dew
corrosion on the heating surfaces of a rear part of the boiler, the
boiler is designed with a high exhaust temperature. The exhaust
temperature of a new boiler is generally 140.degree. C., and after
running for a certain period, the exhaust temperature achieves
160.degree. C. The direct discharge of the flue gas results in a
large waste of energy.
[0007] As the temperature of the flue gas is generally between 140
and 160.degree. C. and the temperature of the heat carrier is
between 200 and 300.degree. C., it is impossible to achieve the
heat transfer from the flue gas to the heat-transfer oil using the
direct heat transfer techniques. Thus, to recycle this part of low
temperature heat energy to heat the heat-transfer oil to a desired
temperature of between 200 and 300.degree. C., it is required to
rearrange the heating surface in the rear part of the furnace.
SUMMARY OF THE INVENTION
[0008] In view of the above-described problems, it is one objective
of the invention to provide a heating system of heat-transfer oil
using exhaust heat of boiler flue gas.
[0009] To achieve the above objectives, in accordance with one
embodiment of the invention, provided is a heating system of
heat-transfer oil using exhaust heat of boiler flue gas,
comprising: an economizer and an air preheater disposed inside a
flue along a flow direction of the flue gas. The heating system
further comprises a heat-transfer oil heater. The heat-transfer oil
heater is disposed inside the flue in front of the economizer; the
heat-transfer oil heater is connected to a heat consumption device
via a first circulating pipe; and a circulating pump is disposed on
the first circulating pipe.
[0010] In a class of this embodiment, the system further comprises
an exhaust heat utilization device. The exhaust heat utilization
device comprises a heat absorption member and a heat release member
communicating with each other through a second circulating pipe.
The heat absorption member is disposed inside the flue behind the
air preheater. The heat release member is arranged on a water inlet
pipe of the economizer or inside an air inlet channel of the air
preheater.
[0011] In a class of this embodiment, the exhaust heat utilization
device employs a high temperature forced circulating water or
naturally circulating steam having a heat transfer coefficient far
higher than the side close to the flue gas, so that the temperature
of the wall surface is determined by the side close to the working
medium. The automatic control device of the system is capable of
controlling the temperature of the wall surface according to the
variation of the boiler load to ensure the temperature of the wall
surface to be always higher than that of the acid dew point of the
flue gas, so that the exhaust heat of the flue gas is recycled to
the utmost on the basis of preventing the device from acid dew
corrosion.
[0012] In a class of this embodiment, when the heat release member
is arranged on the water inlet pipe of the economizer, the water
inlet pipe of the economizer is provided with a deaerator and a
high pressure heater for allowing the boiler feedwater to pass
through the heat release member, the deaerator, and the high
pressure heater, respectively, to enter the economizer.
[0013] In a class of this embodiment, a feedwater pump is arranged
on a water pipe by which the deaerator and the high pressure heater
are connected.
[0014] In a class of this embodiment, a steam inlet pipe of the
high pressure heater and a steam inlet pipe of the deaerator
communicate; a condensate drainage pipe of the high pressure heater
is connected to the deaerator.
[0015] In a class of this embodiment, the system further comprises
a control system, two temperature sensors, and a plurality of flow
control valves. The temperature sensors and the flow control valves
are connected to the control system, respectively. A first
temperature sensor is disposed on the heat absorption member, and a
second temperature sensor is disposed on the flue between the
economizer and the air preheater or on a water outlet pipe of the
economizer. One branch of boiler feedwater passes through a first
flow control valve and enters the deaerator, and another branch of
boiler feedwater passes through a second flow control valve and the
heat release member and enters the deaerator. A third flow control
valve is arranged on the steam inlet pipe of the high pressure
heater.
[0016] In a class of this embodiment, the heat release member is
arranged inside the air inlet channel of the air preheater, the
system further comprises a control system, a temperature sensor,
and a flow control damper. The temperature sensor and the flow
control damper are connected to the control system, respectively.
The temperature sensor is arranged on the heat absorption member,
and the flow control damper is arranged inside the air inlet
channel of the air preheater in front of the heat release member
along the flow direction of inlet air.
[0017] In a class of this embodiment, the system further comprises
an oil-gas separator; and the oil-gas separator is disposed on the
first circulating pipe between the heat-transfer oil heater and the
heat consumption device.
[0018] In a class of this embodiment, the oil-gas separator is
connected to an expansion slot, and the expansion slot is connected
to an oiling pump.
[0019] Advantages of the invention are summarized below: the
heating system of heat-transfer oil using the exhaust heat of
boiler flue gas fully utilizes the exhaust heat of the flue gas. By
changing the arrangement of the heating surfaces in the rear part
of the boiler, the efficiency and the output of the original boiler
are ensured, the exhaust gas temperature of the furnace is lowered,
part of the exhaust heat of the flue gas is recycled, and the
recycled heat energy is used to heat the heat carrier-heat-transfer
oil which can be widely applied in petroleum, chemical, textile,
printing and dyeing, rubber, leather, food, wood processing and
many other industries. Furthermore, on the basis of preventing the
devices where the flue gas passes through from dew-acid corrosion,
the exhaust heat of the flue gas is recycled to the utmost, the
utilization efficiency of the energy is improved, the efficiency of
flue gas discharging from the furnace is improved, and the
utilization types of the heat energy is various.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a structural diagram of a heating system of
heat-transfer oil using exhaust heat of flue gas from a boiler in
accordance with one embodiment of the invention; and
[0021] FIG. 2 is a structural diagram of a heating system of
heat-transfer oil using exhaust heat of flue gas from a boiler in
accordance with another embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0022] A heating system of heat-transfer oil using exhaust heat of
flue gas from a boiler, the system comprises an economizer 3 and an
air preheater 4 being disposed inside a flue 1 along a flow
direction of the flue gas. The system further comprises a
heat-transfer oil heater 2 disposed inside the flue 1 in front of
the economizer 3. The heat-transfer oil heater 2 is connected to a
heat consumption device 19 via a first circulating pipe. A
circulating pump 12 is disposed on the first circulating pipe.
[0023] As shown in FIG. 1, the heat-transfer oil heater 2, the
economizer 3, and the air preheater 4 are disposed inside the flue
1 along the flow direction of the flue gas. The heat-transfer oil
heater 2 is connected to the heat consumption device 19 via the
first circulating pipe. The circulating pump 12 is disposed on the
first circulating pipe for driving the circulation of a heat
carrier of the heat-transfer oil heater 2. In a rear part of the
flue 1, part of the heat energy of the flue gas is transferred to
the heat carrier of the heat-transfer oil heater 2 (the heat
carrier comprises but is not limited to heat-transfer oil). Driven
by the circulating pump 12, the heat carrier releases heat energy
inside the heat consumption device 19 and is circulated again, so
that the processes of heat absorption and heat release are
repeated. The heat consumption device 19 can be applied in
petroleum, chemical, textile, printing and dyeing, rubber, leather,
food, wood processing and many other industries. The heat-transfer
oil heater 2 is arranged in front of the economizer 2 inside the
flue 1 to absorb the exhaust heat of the flue gas entering to the
economizer 3. Thus, flue gas in the position of the heat-transfer
oil heater 2 has a high temperature and heat energy, and the
exhaust heat of the flue gas from the boiler is fully utilized.
[0024] An oil-gas separator 18 is disposed on the first circulating
pipe between the heat-transfer oil heater 2 and the heat
consumption device 19. An oil inlet pipe of the oil-gas separator
18 is connected to an oil outlet of an expansion slot 17, and an
oil inlet of the expansion slot 17 is connected to an oiling pump
16. The expansion slot 17 is further connected to an oil storage
tank 15. The oil storage tank 15 functions in storing the
heat-transfer oil when the device is stopped from running for
overhaul. The oiling pump 16 functions in injection of new oil and
discharge of old oil. The expansion slot 17 is used to buffer the
heated and expanded heat-transfer oil. The oil-gas separator is
used to separate the water mixed in the heat-transfer oil and
improve the heat transfer effect of the heat-transfer oil.
[0025] The arrangement of the heat-transfer oil heater results in a
lower temperature of flue gas entering the economizer and the
subsequent air preheater, which may influence the use of the
economizer and the air preheater. As an improvement of the
invention, an exhaust heat utilization device is arranged behind
the air preheater 4 along the flow direction of the flue gas. The
exhaust heat utilization device is capable of recycling part of the
exhaust heat of the flue gas for compensating the heat energy to
the economizer or the air preheater.
[0026] Preferably, the exhaust heat utilization device comprises a
heat absorption member 5 and a heat release member 6 communicating
with each other through a second circulating pipe. The heat
absorption member 5 is disposed inside the flue behind the air
preheater 4 for absorbing part of the exhaust heat of the flue gas.
The heat release member 6 is arranged on a water inlet pipe of the
economizer 3. The flue gas enters a desulfurization device for
treatment after passing through the heat absorption member 5.
[0027] The water inlet pipe of the economizer is provided with a
deaerator 14, a feedwater pump 7, and a high pressure heater 11.
Boiler feedwater enters the deaerator 14 through two branches. One
branch of the boiler feedwater passes through a first flow control
valve 21 and directly enters the deaerator 14, and the other branch
of the boiler feedwater passes through a second flow control valve
9 and the heat release member 6 for absorbing heat and enters the
deaerator 14. After being discharged from the deaerator 14, the
feedwater passes through the feedwater pump 7 and enters the high
pressure heater 11. The feedwater is heated in the high pressure
heater 11 and enters the economizer 3. Furthermore, a steam inlet
pipe of the high pressure heater 11 and a steam inlet pipe of the
deaerator 14 communicate. A third flow control valve 13 is arranged
on the steam inlet pipe of the high pressure heater 11. A
condensate drainage pipe of the high pressure heater 11 is
connected to the deaerator 14. The high pressure heater and the
deaerator share the same steam source. One part of the steam from
the steam source directly enters the deaerator 14, and another part
of the steam heats the boiler feedwater through the high pressure
heater 11. After releasing the heat energy, the stem is condensed
and transformed into condensed water that enters to the deaerator
through the condensate drainage pipe between the high pressure
heater 11 and the deaerator 14.
[0028] The system further comprises a control system, two
temperature sensors 8, 10, and a plurality of flow control valves
9, 13, 21. The temperature sensors and the flow control valves are
connected to the control system, respectively. A first temperature
sensor 8 is disposed on the heat absorption member 5 for measuring
a temperature of a wall surface of the device; and a second
temperature sensor 10 is disposed on the flue between the
economizer 3 and the air preheater 4 or on a water outlet pipe of
the economizer 3. By controlling the first flow control valve 9 and
the second flow control valve 21, the water content that enters the
deaerator 14 is maintained constant; the required heat is
controlled by adjusting the water content entering the heat release
member 6, so that the heat absorption member 5 of the exhaust heat
utilization device is prevented from the acid dew corrosion, and
the exhaust heat of the flue gas is recycled to the utmost.
[0029] The heat-transfer oil heater 2 absorbs exhaust heat in the
flue gas to heat the heat-transfer oil, and the heat absorption is
determined by the acid dew point of the flue gas. Supposing the
exhaust gas temperature at the preheater 4 of the original boiler
system is T.sub.1, and the acid dew point is T.sub.2; to prevent
the heat absorption member 5 of the exhaust heat utilization device
from the acid dew corrosion, the temperature of the wall surface of
the heat absorption member 5 contacting with the flue gas is
required to be at least 10.degree. C. (a safe margin) higher than
T.sub.2. Meanwhile, a heat transfer temperature difference is
required between the temperature of the flue gas and the
temperature of the wall surface of the heat absorption member 5 to
ensure an economically reasonable arrangement of the heat surfaces
of the exhaust heat utilization device. Thus, the exhaust gas
temperature of the exhaust heat utilization device is
T.sub.2+10.degree. C. of the safe margin+approximately 15.degree.
C. (the temperature difference for heat transfer), labeled as
T.sub.3. An energy saving temperature drop of the original boiler
system is calculated as T.sub.1-T.sub.3. As the exhaust heat
utilization device is used to indirectly compensate the heat
transfer loss of the economizer 3 and does not provide heat energy
to other devices, the recycled and saved heat energy is provided to
other heat consumption device by the heat-transfer oil heater 2.
Apparently, the temperature difference of the flue gas close to the
inlet and outlet of the heat-transfer oil heater is required to be
no larger than T.sub.1-T.sub.3 to lower the influence of the
addition of the heat-transfer oil heater on the thermal system of
the original boiler as much as possible.
[0030] The temperature difference between the heat-transfer oil in
the inlet and outlet of the heat-transfer oil heater 2 is generally
controlled at 30.degree. C., based on which an appropriate
circulation flow of the heat-transfer oil is selected to transfer
the absorbed heat energy to the heat consumption device 19. Part of
the heat energy of the flue gas is absorbed by the heat-transfer
oil heater 2 so that the heat energy absorbed by the economizer 3
and the air preheater 4 is lowered. As an improvement of the
invention, the high pressure heater 11 is arranged on the water
inlet pipe of the economizer 3. By thermodynamic calculation, the
boiler feedwater is adjusted to allow the flue gas temperature and
the water temperature at the outlet of the economizer 3 are close
to or higher than those of the original system, so that the
influence of the addition of the heat-transfer oil heater on the
economizer 3 and the air preheater 4 is decreased.
[0031] The heat source of the high pressure heater 11 is extracted
steam transported to the deaerator 14, which is originally used to
heat the boiler feedwater in the deaerator 14. When the part of
extracted steam is used as the heat source of the high pressure
heater 11, it is required a substituted heat source to heat the
feedwater in the deaerator 14 to maintain the total extracted steam
constant. An exhaust temperature of the boiler is between 140 and
160.degree. C., whereas a temperature of the heated feedwater of
the boiler or the condensed water is 20.degree. C. If the fume
directly transfers heat to the feedwater of the boiler or the
condensed water, a temperature of the wall surface of the heat
exchanger is close to an acid dew point of the fume, thereby
resulting in acid dew corrosion on the heat exchanger. In order to
prevent the problem, the waste heat utilization device is composed
of a heat absorption member 5 and a heat release member 6. The heat
absorption member 5 is disposed inside the boiler flue for
absorbing heat and transferring the heat to a working medium; and
in the heat release member 6, the working medium transfers the heat
to the make-up water or the condensed water. Working principle of
the working medium is that the working medium is generally high
temperature forced circulating water or naturally circulating steam
having a heat transfer coefficient far higher than the side close
to the fume, so that the temperature of the wall surface is
determined by the side close to the working medium. The temperature
of the working medium is controlled to prevent the heat absorption
member 5 from acid dew corrosion.
[0032] As shown in FIG. 2, as another embodiment of the heating
system of heat-transfer oil using the exhaust heat of the flue gas
of the invention, technical features thereof are the same as the
above except that the heat release member 6 of the exhaust heat
utilization device is arranged inside the air inlet channel of the
air preheater 4. The exhaust heat utilization device is primarily
used to heat the inlet air of the air preheater. The water inlet
pipe of the economizer is provided with a low pressure heater or
other devices. The control system is connected to a temperature
sensor 8 and a flow control damper 20. The temperature sensor 8 is
arranged on the heat absorption member 5 for testing the
temperature of the wall surface thereof. The flow control damper 20
is arranged inside the air inlet channel of the air preheater in
front of the heat release member 6 along the flow direction of
inlet air for adjusting the heat absorption of the heat absorption
member. The absorbed heat of the exhaust heat utilization device
herein is used to heat the air entering the air preheater, and the
compensation of the heat energy on the air preheater is
lowered.
[0033] While particular embodiments of the invention have been
shown and described, it will be obvious to those skilled in the art
that changes and modifications may be made without departing from
the invention in its broader aspects, and therefore, the aim in the
appended claims is to cover all such changes and modifications as
fall within the true spirit and scope of the invention.
* * * * *