U.S. patent number 3,871,172 [Application Number 05/430,543] was granted by the patent office on 1975-03-18 for process with fluidized combustor and fluidized heat exchanger for air.
This patent grant is currently assigned to Chemical Construction Corporation. Invention is credited to Edward T. Coles, John F. Villiers-Fisher.
United States Patent |
3,871,172 |
Villiers-Fisher , et
al. |
March 18, 1975 |
Process with fluidized combustor and fluidized heat exchanger for
air
Abstract
Carbonaceous fuels are burned in a high pressure fluidized bed
combustor to produce a hot sinter or ash which is passed to a
fluidized bed heat exchanger for direct contact with pressurized
air. The resultant heated pressurized air is expanded through a gas
turbine which drives an electrical generator.
Inventors: |
Villiers-Fisher; John F.
(Kendall Park, NJ), Coles; Edward T. (Brooklyn, NY) |
Assignee: |
Chemical Construction
Corporation (New York, NY)
|
Family
ID: |
23707980 |
Appl.
No.: |
05/430,543 |
Filed: |
January 3, 1974 |
Current U.S.
Class: |
60/781; 48/210;
60/39.464; 110/245; 60/39.12; 60/682; 122/4D |
Current CPC
Class: |
F28C
3/16 (20130101); F02C 1/04 (20130101); F02C
3/205 (20130101) |
Current International
Class: |
F28C
3/16 (20060101); F28C 3/00 (20060101); F02C
3/20 (20060101); F02C 1/00 (20060101); F02C
1/04 (20060101); F02c 007/02 (); F02g 005/00 () |
Field of
Search: |
;60/39.46,39.12,39.02,682,39.18A,39.18C ;48/210 ;23/288E,288S |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Olsen; Warren
Attorney, Agent or Firm: Chaboty; J. L.
Claims
We claim:
1. A process for producing electrical power by the combustion of a
carbonaceous fuel which comprises
a. introducing said carbonaceous fuel into an elevated pressure
fluidized combustion zone, said fluidized combustion zone
containing at least one bed of fluidized ash particles,
b. passing a first compressed air stream into said combustion zone,
whereby said bed is fluidized and said fuel is burned in said
fluidized bed to produce a substantially solids-free hot gas
containing combustion products, and whereby ash from fuel
combustion is agglomerated and added to said bed,
c. withdrawing said hot gas from said combustion zone,
d. passing hot solids from said fluidized combustion zone to a
fluidized heat exchange zone,
e. passing a second compressed air stream into said fluidized heat
exchange zone, whereby said second air stream is heated and said
hot solids are cooled,
f. recycling the cooled solids produced by step (e) to said
combustion zone,
g. expanding the heated second air stream through mechanical power
recovery means, said mechanical power recovery means being
connected with and driving an electrical generator, and
h. withdrawing electrical power from said electrical generator.
2. The process of claim 1, in which said carbonaceous fuel is an
ash-containing liquid fuel selected from the group consisting of
crude oil, liquid asphalt, petroleum refining residual oil, fuel
oil, and gas oil.
3. The process of claim 1, in which said carbonaceous fuel is a
solid fuel selected from the group consisting of coal, lignite,
coke, slack, anthracite, solid asphalt, and pitch.
4. The process of claim 1, in which said fluidized combustion zone
and said fluidized heat exchange zone are maintained at a pressure
in the range of about 5 kg./sq. cm. to 20 kg./sq. cm.
5. The process of claim 1, in which said fluidized combustion zone
is at a temperature in the range of about 1000.degree.C to
1300.degree.C, said second air stream is heated from an initial
temperature in the range of about 100.degree.C to 300.degree.C to a
higher temperature in the range of about 900.degree.C to
1200.degree.C, and said cooled solids are recycled at a temperature
in the range of about 150.degree.C to 350.degree.C.
6. The process of claim 1, in which said hot gas withdrawn from
said combustion zone is cooled by indirect heat exchange with a
fluid selected from the group consisting of compressed air, steam
and water.
7. The process of claim 6, in which said fluid is compressed air,
and the heated compressed air is passed to said fluidized
combustion zone to fluidize said bed and support combustion.
8. The process of claim 1, in which said mechanical power recovery
means is a gas turbine.
9. The process of claim 1, in which said mechanical power recovery
means is connected with a drives a compressor, the input fiuid to
said compressor being ambient air which is compressed to form said
second compressed air stream.
10. The process of claim 6 in which the cooled gas produced by said
indirect heat exchange is expanded through a gas turbine, said gas
turbine being connected with and driving a compressor, the input
fluid to said compressor being ambient air which is compressed to
form said first compressed air stream.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The invention relates to the production of electrical power by the
combustion of ash-containing carbonaceous fuels.
2. Description of the Prior Art:
The production of electrical power by burning carbonaceous fuels
such as coal to generate steam, which is expanded through steam
turbines which drive electrical generators and thereby produce
electrical power, is a well established commercial procedure widely
practiced in steam power plants. The combustion of carbonaceous
solids in a fluidized bed is described in U.S. Pat. No.
3,171,369.
SUMMARY OF THE INVENTION
In the present invention, a carbonaceous fuel such as coal is
burned in a pressurized fluid bed combustor, under conditions which
produce agglomeration of the ash particles which join the fluidized
bed. A portion of the hot ash or sinter is withdrawn from the fluid
bed combustor and passed in direct heat exchange fluid bed contact
with compressed air which is thereby heated. The heated compressed
air is expanded through a gas turbine which drives an electrical
generator to produce power.
The combustion of coal in an agglomerating bed under pressure
produces a combustion effluent gas containing a minimum of fly ash,
but the ash loadings are still above the levels allowable for
existing gas turbines. In the present invention, a modification of
this approach gives a clean gas which can be used to run a turbine.
The hot sinter from the combustor moves to a fluid bed direct
contact heat exchanger, and the hot sinter cascades through the
exchanger. Compressed air fluidizes the sinter and is heated
towards 1100.degree.C. The hot air is expanded through a gas
turbine which drives an electrical generator to produce power. The
gas turbine may also drive one or more air compressors. The hot
expander or gas turbine outlet gas may be passed in indirect heat
exchange with water to make steam, or may be used to superheat the
compressed air. The hot sinter from the combustor can be dedusted
by flowing against a portion of the combustor feed air if
necessary. This may be necessary as a general rule as a guard
against combustor upset and poor ash agglomeration.
The net result and advantage of the invention is that the heat
liberated from coal combustion produces very hot clean pressurized
air using a very cheap fluid bed direct contact heat exchanger, and
the hot air is usefully employed by expansion through a gas turbine
to drive an electrical generator and thereby produce electric
power.
It is an object of the present invention to provide an improved
process for producing electrical power by the combustion of a
carbonaceous fuel.
Another object is to provide clean hot compressed air in an
improved manner for the actuation of a gas turbine.
A further object is to heat compressed air in an improved manner
using combustion of an ash-containing carbonaceous fuel as a heat
source.
Another object is to generate heat for the elevation of the
temperature of compressed air in an improved manner.
Still another object is to effectively utilize hot sinter from a
fluid bed combustor in which carbonaceous fuel is burned to produce
an agglomerate sinter or ash.
These and other objects and advantages of the present invention
will become evident from the description which follows.
DESCRIPTION OF THE DRAWING AND PREFERRED EMBODIMENTS
Referring now to the drawing, a flowsheet of a preferred embodiment
of the invention is presented. Carbonaceous fuel stream 1 is passed
into a fluid bed consisting essentially of agglomerated ash within
the fluid bed combustor 2. Stream 1 may consist of an
ash-containing liquid fuel such as crude oil, liquid asphalt, a
residual oil derived from petroleum refining, a fuel oil or gas
oil. In other instances stream 1 may consist of a solid fuel such
as various types of coal including anthracite, bituminous,
sub-bituminous or lignite or the like, or coke, slack, solid
asphalt or pitch. In any case, stream 1 is passed into the fluid
bed within unit 2 above lower foraminous grate 3. The fluid bed
consisting of a fluidized combustion zone within unit 2 is
generally maintained at an elevated pressure, typically in the
range of about 5 kg./sq. cm. to 20 kg./sq. cm., and an elevated
temperature, generally in the range of about 1000.degree.C to
1300.degree.C, is maintained within unit 2 by the combustion of
stream 1 with compressed air stream 4, which is admitted into unit
2 below grate 3 at a pressure typically in the range of about 5
kg./sq. cm. to 20 kg./sq. cm.
The process air stream 4 rises through the fluid bed within unit 2
and maintains fluidization of the bed. In addition, the combustion
of stream 1 within the bed serves to generate heat and maintain
elevated temperature within the bed, as well as forming an ash
which becomes sticky or tacky and at least partially agglomerated
in the fluid bed within unit 2. The agglomeration of the ash within
unit 2 serves to effectively curtail or prevent the entrainment of
fine ash particles in the hot gas containing gaseous combustion
products such as carbon dioxide and sulfur dioxide, which rises
from the bed within unit 2 and is withdrawn via upper hot product
gas stream 5.
Stream 5 is withdrawn from the top of unit 2 at an elevated
temperature typically in the range of about 1000.degree.C to
1300.degree.C, and stream 5 contains only a very minor proportion
of entrained fine ash particles. In some instances, stream 5 may be
essentially devoid of ash. In any case, stream 5 is also at an
elevated pressure typically in the range of 5 kg./sq. cm to 20
kg./sq. cm., and stream 5 is now processed for heat and power
recover as well as sulfur dioxide removal.
Stream 5 passes through indirect heat exchanger 6, which is
typically of shell and tube configuration or the like, and stream 5
is cooled by heat exchange with compressed process air, which is
discharged from unit 6 via stream 4 at an elevated temperature
typically in the range of 200.degree.C to 500.degree.C. The
partially cooled gas stream 7 which is also discharged from unit 6
is passed into boiler or steam generator 8, and is further cooled
by indirect heat exchange with liquid water stream 9, which is
thereby heated and vaporized to form steam stream 10.
The further cooled gas stream 11 discharged from unit 8 now passes
through gas-to-gas heat exchanger 12 and is fully cooled by heat
exchange with gas which has been treated for sulfur dioxide
removal, as will appear infra. The fully cooled gas stream 13
discharged from unit 12 is now at a reduced temperature typically
in the range of 50.degree.C to 200.degree.C, and stream 13 is
passed into sulfur dioxide removal unit 14, which is provided in
order to remove sulfur dioxide from the gas stream and thereby
prevent air pollution. Unit 14 is typically a scrubbing tower or
venturi scrubber or the like in which the gas stream is contacted
with an aqueous alkaline solution or slurry, containing an alkaline
compound of sodium, potassium, calcium, magnesium, barrium or the
like, which absorbs sulfur dioxide from the gas stream in the form
of an alkali sulfite or bisulfite. Typical procedures of this
nature are described in U.S. Pat. Nos. 3,653,823; 3,650,692;
3,632,306; 3,622,270; 3,617,212; 3,607,033; 3,607,001; 3,600,131;
3,577,219; 3,542,511 and 3,533,748. Typical types of venturi
apparatus configurations for attaining contact of the gas stream 13
with a scrubbing liquid or slurry in unit 14 are described in U.S.
Pat. Nos. 3,638,925; 3,584,440; 3,567,194; 3,544,086; 3,440,803 and
3,085,793. The operation of sulfur dioxide removal in unit 14 will
also serve to remove substantially all of the fly ash or dust
particles from the gas stream.
Separated sulfur dioxide is passed to product utilization or sales
via stream 15. In some instances, sulfur dioxide-containing stream
15 may be passed to a sulfuric acid production facility for
conversion to sulfuric acid. In other instances, stream 15 may be
cooled via refrigeration to condense product liquid sulfur dioxide
for sales.
The resulting cooled and substantially sulfur dioxide-free gas
stream 16 produced by unit 15 is at elevated pressure, and stream
16 is now reheated and expanded through mechanical power recovery
means to generate usable power. Stream 16 is reheated in unit 12 by
indirect heat exchange with stream 11, and the resulting reheated
clean gas stream 17 is expanded to atmospheric pressure through gas
turbine 18 and is then discharged to atmosphere via stream 19.
Turbine 18 is connected via shaft 20 with air compressor 21, which
compresses ambient air stream 22 to from compressed air stream 23
which is passed through unit 6 and heated to form stream 4.
Returning to unit 2, a hot solids stream 24 consisting of
agglomerated ash particles at an elevated temperature typically in
the range of about 1000.degree.C to 1300.degree.C is withdrawn from
the fluid bed within unit 2 and utilized in accordance with the
present invention. Stream 24 is passed into a fluidized bed of ash
particles within the fluidized heat exchange zone 25, which is
provided with a lower support grate 26. The hot ash particles are
cooled in the fluid bed within unit 25 by direct contact heat
exchange with air, as will appear infra. Cooled ash particles are
withdrawn from the fluid bed within unit 25 via lower outlet stream
27, which is typically at a temperature in the range of about
150.degree.C to 350.degree.C. stream 27 is divided into bleed
stream 28, which is removed from the system and passed to disposal
to prevent buildup of excessive solid ash in the system, and stream
29 which is recycled to the fluid bed within unit 2.
The counter current heat exchange between air and hot solids may be
achieved by several routes such as fluidized beds operating in
series, a single fluid bed operating just above minimum
fluidization velocity, a moving bed or combinations of the above.
The preferred mode is operation at just above minimum fluidization
velocities where the bed moves downward without mixing yet evenly
over its cross section because of its liquid like behavior.
Compressed air stream 30, which is at an elevated pressure
typically in the range of about 5 kg./sq. cm to 20 kg./sq. cm and a
temperature generally in the range of about 100.degree.C to
300.degree.C, is passed into unit 25 below grate 26 in accordance
with the present invention, and the air stream rises through unit
25 and is heated by contact with the hot agglomerated ash
particles. Essentially none of the ash is entrained in the air, and
a high temperature air stream 31 is withdrawn from the upper end of
unit 25 at a temperature typically in the range of about
900.degree.C to 1200.degree.C. Stream 31 is thus produced at high
temperature and pressure and is essentially devoid of entrained
solid particles, and stream 31 is eminently suitable for
utilization in a gas turbine for power generation.
Stream 31 is now passed through mechanical power recovery means,
which in this embodiment of the invention consists of the gas
turbine 32. The hot high pressure air expands within turbine 32 and
drives unit 32 which produces useful power. Unit 32 is also
preferably connected via shaft 33 to air compressor 34, which
compresses ambient air stream 35 to elevated pressure to form
stream 30.
Returning to unit 32, the resulting low pressure hot air stream 36
is discharged from gas turbine 32 and passed through heat exchanger
37 for the recovery of available heat. In this embodiment of the
invention unit 37 is a steam boiler, and water stream 38 is passed
into unit 37 for indirect heat exchanger with the hot air. The
water stream 38 is thus heated and vaporized to form steam stream
39. The cooled low pressure air stream 40 discharged from unit 37
may be passed to atmosphere discharge.
In accordance with the present invention, unit 32 is connected via
shaft 41 to electrical generator 42 and drives unit 42 to generate
usable electric power which is passed to utilization via power
lines or wire 43.
Numerous alternatives within the scope of the present invention
will occur to those skilled in the art. Streams 9 and/or 38 may
consist of steam which would be superheated in the respective units
8 or 37. The steam streams 10 and/or 39 may be expanded through a
steam turbine or turbines to generate power, or streams 10 or 39
may be employed for heating purposes, process usage or the like.
Streams 36 or 5 or both may be passed in indirect heat exchange
with stream 30 in order to superheat the compressed air stream 30.
The hot sinter stream 24 from the combustor can be dedusted by
flowing against a portion of the combustor feed air stream 4 if
necessary. This may be necessary as a general rule as a guard
against combustor upset and poor ash agglomeration. Unit 42
converts the energy in excess of the process requirements to
electric power. Alternate modes of interlocking the several
compressors and expanders will be obvious to those familiar with
combined cycle power applications.
An example of commercial application of the present invention will
now be described.
EXAMPLE
Following are point values for a typical installation. Heat fluxes
are thermal energy above 100.degree.F.
______________________________________ Stream Temp. Pressure Heat
Flow No. .degree.F psig. Flux Rate 10.sup.8 BTU/hr Tons/hr
______________________________________ 1 200 4 1000 180 11 154,000*
5 2000 170 23 7 1450 10 900 600 10.5 11 1100 13 320 150 15 6** 16
120 140 17 900 125 9.7 19 300 0 2.4 23 450 185 4 24 2000 5,000 27
600 28 18 30 450 185 8.5 335,000* 31 1950 170 45 36 1000 5 39 900
600 22 40 300 0 5 ______________________________________ *mols **as
elemental sulfur Note: In this design for a commercial facility,
compressor 21 was omitted and compressor 34 furnished both streams
28 and 30. Steam streams 10 and 39 were combined and expanded
through a steam turbine, not shown, which was connected with
generator 42 on a shaft linked with shafts 41 and 33.
* * * * *