U.S. patent application number 12/736039 was filed with the patent office on 2011-05-05 for continuous fuel supply for a coal gasification reactor.
This patent application is currently assigned to UHDE GMBH. Invention is credited to Stefan Hamel, Eberhard Kuske.
Application Number | 20110100274 12/736039 |
Document ID | / |
Family ID | 41056397 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110100274 |
Kind Code |
A1 |
Kuske; Eberhard ; et
al. |
May 5, 2011 |
CONTINUOUS FUEL SUPPLY FOR A COAL GASIFICATION REACTOR
Abstract
A facility for the continuous supply of a coal gasification
plant with finely ground fuel material is disclosed. The fuel is
first stored in a storage tank and then fed to a lock hopper
system, where it is supplied with gas for the coal gasification
reaction. The lock hopper system consists of at least two lock
hoppers to achieve that the gas is injected quasi-continuously, and
the fuel is then passed to a feed tank in which a constant filling
level prevails over a given period of time, so that the fuel is
conveyed in a constant, smooth and pressurised flow from this feed
tank to the burners. The transfer from at least two lock hoppers to
a least one feed tank is carried out by pneumatic dense-flow
conveying at solid material densities of at least 100 kg/m.sup.3
and a differential pressure of at least 0.5 bar so that it is
possible to arrange the facility components at the same geodetic
height or different geodetic heights so as to achieve a space
saving and flexible plant construction. The invention also relates
to a process for the continuous and uniform supply of finely ground
fuel to a coal gasification reactor.
Inventors: |
Kuske; Eberhard; (Soest,
DE) ; Hamel; Stefan; (Wenden, DE) |
Assignee: |
UHDE GMBH
|
Family ID: |
41056397 |
Appl. No.: |
12/736039 |
Filed: |
February 18, 2009 |
PCT Filed: |
February 18, 2009 |
PCT NO: |
PCT/EP2009/001146 |
371 Date: |
December 9, 2010 |
Current U.S.
Class: |
110/347 ;
48/210 |
Current CPC
Class: |
C10J 2300/0903 20130101;
B01J 8/0015 20130101; C10J 2200/156 20130101; B01J 2208/00752
20130101; B01J 2208/00769 20130101; C10J 3/50 20130101 |
Class at
Publication: |
110/347 ;
48/210 |
International
Class: |
F23D 1/00 20060101
F23D001/00; C10J 3/00 20060101 C10J003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2008 |
DE |
10 2008 012 733 7 |
Oct 22, 2008 |
DE |
10 2008 052 673.8 |
Claims
1-36. (canceled)
37. A facility for supplying solid fuel materials to a reactor for
the gasification of solid fuel materials, comprising a grinding
device; a dust separator; a storage tank; at least two lock
hoppers; a connection device for dense-flow conveying; a feed tank;
a gasification reactor; and a device for pressure increase which
returns conveying gas from the feed tank to the lock hoppers;
wherein the grinding device is connected to the storage tank by
means of connection devices; the dust separator is installed
between the grinding device and the storage tank; the storage tank
is connected to the lock hoppers via the connection devices which
are suited for gravity flow or dense-flow conveying, and the lock
hoppers are connected to a feed tank by means of jointly used
connection devices which are suited as continuous supply line for
dense-flow conveying, and this feed tank is connected to the
gasification reactor via further fuel lines.
38. The facility according to claim 37, wherein the transfer of the
fuel material from lock hoppers to feed tank or tanks is
implemented via at least one connection device and at least one
unifying element, and the transfer from the unifying element to the
feed tank via individual continuous supply lines for dense-flow
conveying or via other unifying elements with transferring
connection devices.
39. The facility according to claim 38, wherein the facility
includes three lock hoppers and a unifying element, wherein each
lock hopper is connected to unifying element via a connection
device, and the unifying element is connected to feed tank via a
further connection device.
40. The facility according to claim 38, wherein the facility
includes three lock hoppers and two unifying elements, wherein two
lock hoppers are connected to the first unifying element via
connection devices, and the first unifying element is connected to
the second unifying element via another connection device, and the
third lock hopper is directly connected to the second unifying
element via a connection device, and the second unifying element is
connected to feed tank via a further connection device.
41. The facility according to claim 38, wherein the facility
includes four lock hoppers and three unifying elements, wherein two
lock hoppers each are connected to one unifying element each via
connection devices, these unifying elements being connected to the
third unifying element via further connection elements, and the
third unifying element being connected to feed tank via a further
connection device.
42. The facility according to claim 38, wherein the facility
includes six lock hoppers and two unifying elements, wherein three
lock hoppers each are connected to one unifying element each via
connection devices, these unifying elements being connected to feed
tank via separate connection devices.
43. The facility according to claim 38, wherein the facility
includes eight lock hoppers and two unifying elements, wherein four
lock hoppers each are connected to one unifying element each via
connection devices, these unifying elements being connected to feed
tank via separate connection devices.
44. The facility according to claim 38, wherein the facility
includes eight lock hoppers and three unifying elements, wherein
four lock hoppers each are connected to one unifying element each
via connection devices, these unifying elements being connected to
the third unifying element via further connection devices, and the
third unifying element being connected to feed tank via a further
connection device.
45. The facility according to claim 37, wherein the lock hoppers
are spatially integrated into grinding unit and are loaded from at
least one storage tank for finely ground dried fuel material.
46. The facility according to claim 37, wherein the lock hopper
system consists of two or more lock hoppers which may be
pressurised from outside.
47. The facility according to claim 37, wherein the lock hopper
system is connected to a downstream storage tank which supplies the
lock hopper system by gravity conveyance with finely ground fuel
material.
48. The facility according to 37, wherein the gas side of lock
hoppers and feed tank is connected by at least one connection
line.
49. The facility according to claim 37, wherein one or more gas
introduction devices may be installed in any place of the lock
hopper system, the dense-flow conveying lines, the gas-sided
connection lines or the feed tank, by which it is possible to
influence the conveyance or transport of solid material.
50. The facility according to claim 49, wherein at least one of the
devices for the introduction of gas is an injector.
51. The facility according to claim 37, wherein devices may be
installed in any place of the lock hopper system, the expansion
lines, the recycle lines or the excess gas lines by which the gas
flow can be separated from solid material or dust.
52. A process for supplying finely ground fuel materials to a
cooled reactor for gasification with oxygen-containing gasifying
agents under pressure, wherein: the gasifier outlet temperatures
are above the slag melting point in the range between 1200 and
2000.degree. C. and the pressure is between 0.3 and 8 MPa; and the
finely ground fuel material is pressurised via a lock hopper system
to a pressure level above the gasifier pressure, transferred to at
least one feed tank and from there dosed in dense flow via at least
one fuel line to one or more gasification burners of one or several
gasifiers; wherein the conveying gas volume supplied at the
discharge of lock hopper is recovered in feed tank and returned to
lock hopper by means of a device for pressure increase; and the
transfer from at least two lock hoppers to at least one feed tank
is carried out by using a pneumatic continuous supply line jointly,
simultaneously or successively at solid material densities of at
least 100 kg/m.sup.3 and a differential pressure of at least 0.5
bar.
53. The process for supplying finely ground fuel materials
according to claim 52, wherein the expansion gases from lock
hoppers are at least partially used for blanketing the grinding
circuit with inert gas.
54. The process for supplying finely ground fuel materials
according to claim 52, wherein the dust separator of the grinding
unit is also used for dedusting expansion gases from lock
hoppers.
55. The process for supplying finely ground fuel materials
according to claim 52, wherein pressurising by supplied gas is
preceded by a mutual partial pressurisation of lock hoppers.
56. The process for supplying finely ground fuel materials
according to claim 52, wherein the fuel material is conveyed from
lock hoppers to feed tanks via a number of continuous supply lines
which is smaller than the number of lock hoppers.
57. The process for supplying finely ground fuel materials
according to claim 52, wherein the solid material from the outlet
of each lock hopper is passed to unifying elements via a connection
device and then into the continuous supply line, the number of
unifying elements being smaller than the number of lock hoppers and
at least identical with the number of continuous supply lines.
58. The process for supplying finely ground fuel materials
according to claim 52, wherein the unifying elements are provided
as closely to and preferably symmetrically to the outlet nozzles of
lock hoppers.
59. The process for supplying finely ground fuel materials
according to claim 52, wherein temporarily at least two lock
hoppers discharge solid material simultaneously into continuous
supply line.
60. The process for supplying finely ground fuel materials
according to claim 52, wherein the feed tank is spatially
integrated into the building of the grinding unit.
61. The process for supplying finely ground fuel materials
according to claim 52, wherein the geodetic installation height of
lock hoppers is smaller than the installation height of feed
tank.
62. The process for supplying finely ground fuel materials
according to claim 52, wherein the continuous supply line enters
feed tank below the solid material level.
63. The process for supplying finely ground fuel materials
according to claim 52, wherein the particle size of the solid
fine-grain fuel materials is smaller than 0.5 mm.
64. The process for supplying finely ground fuel materials
according to claim 52, wherein continuous supply from lock hoppers
is controlled by adjusting the pressure difference between lock
hopper and feed tank such that the filling level of feed tank is
kept constant.
65. The process for supplying finely ground fuel materials
according to claim 52, wherein the gas inlet or outlet into the
free space of the lock hoppers influences the pressure difference
between lock hopper and feed tank and is used as control parameter
for the transport of solid material.
66. The process for supplying finely ground fuel materials
according to claim 52, wherein the discharge of solid material is
facilitated by the addition of gas into the lock hopper in
immediate vicinity to the discharge nozzle.
67. The process for supplying finely ground fuel materials
according to claim 52, wherein the density in continuous supply
line is adjusted by adding gas into continuous supply line and/or
unifying element.
68. The process for supplying finely ground fuel materials
according to claim 52, wherein the continuous supply line can be
purged by adding gas into continuous supply line itself and/or into
unifying element.
69. The process for supplying finely ground fuel materials
according to claim 52, wherein the connection elements between lock
hopper and unifying element are supplied with gas.
70. The process for supplying finely ground fuel materials
according to claim 52, wherein the conveying gas volume supplied at
the discharge of lock hopper is recovered in feed tank and returned
to lock hopper by means of an injector.
71. The process for supplying finely ground fuel materials
according to claim 69, wherein the propellant gas which serves to
control the pressure of lock hopper is used to operate injector.
Description
[0001] The invention relates to a process for the controlled
continuous supply of fine-grain to pulverised fuel materials into a
pressurised feed tank in a pressure gasification process in which
finely ground or pulverised (<0.5 mm) fuel materials such as
coal, petrol coke, biological waste or fuels are converted in
suspension with low particle load (<50 kg/m.sup.3; no fluidised
bed) by reaction with gasifying agents containing oxygen, under
elevated pressure at temperatures above the slag melting point.
[0002] In the course of pressure gasification processes a
carbon-containing fuel material is converted by means of an
oxygen-containing gas, wherein the oxygen-containing gas is
supplied in a substoichiometric ratio so that a carbon monoxide
containing product gas is obtained. If the reaction gas contains
water vapour, the product gas is of synthesis gas character and
contains major portions of hydrogen. To achieve a conversion that
is as complete as possible under substoichiometric conditions, the
fuel material must be fed to the reactor in finely ground
condition. The reaction normally takes place under elevated
pressure.
[0003] Since gasification reactions are operated economically only
if operated continuously for an extended period of time, the amount
of finely ground fuel material supplied per time unit should be as
constant as possible to ensure trouble-free operation. The transfer
of the fuel material to the required pressure level and the supply
of the fuel material under pressure are problems yet to be solved
in coal gasification reactions. For this reason, coal gasification
plants always include plant equipment which serve to ensure
trouble-free supply of fuel to the reactor. Such equipment usually
consists in special dosing tanks and lock hopper assemblies
operated by gravity flow.
[0004] Using dosing tanks is not always a means to completely
eliminate the pressure variations occurring when loading the
reactor. This may result in pressure variations during the carbon
gasification reaction which will temporarily change the composition
of the synthesis gas. Especially the discontinuous filling of the
dosing tank from the pressure locks generates pressure variations
which are of unfavourable effect on the pressure difference which
serves as driving force for the conveyance between dosing tank and
burner.
[0005] Introducing the fuel material by gravity flow as done when
supplying the coal gasification reactors with fuel material is also
a potential source of error. As the finely ground fuel material may
clog or plug depending on its quality and degree of drying,
conveyance will sometimes proceed batchwise only or with unexpected
periodic interruptions. In addition, lock hopper systems based on
gravity flow frequently require sophisticated design solutions
since tanks between which conveyance is to be achieved must be
arranged on top of each other.
[0006] Fuel feed systems according to the state of the art are
expenditure-intensive and not always reliable in operation. In the
case of large-capacity plants, the spatial separation of grinding
and gasification units involves considerable additional expenditure
as regards the transport of finely ground fuel materials from the
grinding unit to the fuel feed system. This makes it necessary to
provide additional equipment (conveying vessels or pneumatic pumps,
filters, buffer tanks above the feed systems). In addition,
considerable expenditure is incurred by piping, instrumentation and
construction work, the latter especially because of the exposed
position of the buffer tanks at the highest elevation of the
gasification unit. Furthermore, lock hopper systems which operate
according to the gravity flow principle have proven to be
inadequately reliable in operation. Additional equipment will at
any rate increase the risk of failure.
[0007] Apart from this commonly known fact, the principle of lock
hopper gravity feed involves specific functional risks. Despite
many very diverse approaches, it has proven to be extremely
difficult to carry out the process of vessel pressurising carefully
enough to keep the internal stress of the bulk material
sufficiently low. In many cases, the bulk material is locally
compacted to such a degree that the gravity flow to the feed tank
is subsequently not induced at all or only to an inadequate extent.
The solid material inventory of the feed tank hence diminishes,
which frequently causes a limited output or may even cause the
failure of the gasification unit.
[0008] The problem aggravates if oversizing owing to a high plant
capacity comes up against the construction limits and if the
gasification unit is to be designed for a higher pressure
(typically 4 MPa) than that of the units which have been in
operation for many years (typically 2.5 MPa).
[0009] Lock hopper gravity feed from the lock hopper into the feed
tank will produce very high transfer mass flow rates, provided the
desired gravity flow is achieved, and thus comparatively short
transfer periods. The transfer of solids during lock-hopper feeding
will raise the filling level in the feed tank. The filling level
will then continuously decrease again by the amounts of fuel
supplied to the burners and increase again by the next lock hopper
transfer operation. In this way, the feed tank is subjected to
temporarily changing conditions which may even affect the steady
delivery from the feed tank. It is considerably more advantageous
to keep the pressure conditions, the filling level and the pulsed
feed into the bulk fill by dropping-in material, for instance, as
constant as possible with regard to time.
[0010] The present invention solves these problems by a dosing tank
which contains the finely ground fuel material under pressure and,
according to the invention, has a nearly constant fuel filling
level. Such almost constant filling level in the feed tank is
ensured according to the invention by supplying solid material
continuously from at least two lock hoppers via at least one
jointly used continuous supply line which is suited for dense-flow
conveying. As the continuous supply line is not operated by
gravity, it is further possible to install the feed tank and the
supplying lock hoppers at different geodetic elevations and, in
addition, at a greater distance from one another, as may be, for
example, in a different building.
[0011] Known are dosing devices for fuel materials that feed the
fuel material to the reactor via a dosing tank with upstream lock
hopper system. U.S. Pat. No. 5,143,521 A describes a system for the
feeding of fuel material into a feed tank which stores pressurised
fuel material and is supplied continuously with finely ground fuel
material by a system of lock hoppers. The lock hoppers are
connected by a line and pressurised alternately. The pressure of
the expansion gas of the one lock hopper may be used via a system
of expansion turbines, Venturi tubes and compressors to pressurise
the other lock hopper. In this way, it is possible to adjust the
pressure of finely ground coal at atmospheric conditions to a level
suited for coal gasification. Nitrogen is used as pressurising
gas.
[0012] DE 102005047583 A1 describes a process and a facility for
dosing and feeding pulverised fuel materials under pressure to a
coal gasification reactor. To ensure a constant the feed of fuel
material to the coal gasification reactor over a given period of
time, the fuel is stored intermediately in a dosing tank, in the
lower part of which a dense fluid bed is generated above the tank
bottom by feeding in gas, through which the pulverised fuel
material is supplied continuously via burners to a pressurised
gasification reactor. Actual feeding to the burners is here
implemented by the so-called high-speed conveyance, wherein the
supply of auxiliary gas to the feed line downstream of the burner
is used to generate a pressure difference by which the fuel
material is then transported to the burners. The dosing tank is
supplied with fuel material from two locks which transport the fuel
material by means of gravity and a star feeder into the dosing
tank. This is, however, susceptible to failures and requires
structures of high altitudes. A use of grinding devices is not
mentioned.
[0013] The present invention describes an integrated process for
comminuting a carbonaceous fuel material, pressurising the fuel by
means of a suitable gas, distributing and transporting the fuel to
a feed tank and feeding it to the reactor. Transport, distribution
of the fuel and feeding to the reactor are implemented by
dense-flow conveying in a so-called continuous supply line. In this
way, the complete fuel supply chain of the reactor can be carried
out without gravity flow. The gasification reactor outlet
temperatures are preferably above the slag melting point in a range
between 1200 and 2000.degree. C. and the pressure is preferably
between 0.3 and 8 MPa.
[0014] Dense-flow conveying in this context signifies a pneumatic
conveying which does not transport the fuel material particles as
individual particles but in a dense flow in the form of dense
packings or plugs which fill in the entire cross-sectional area of
the pipe. The dense-flow conveying flow rates are generally between
4 and 5 m/s, wherein a high transport volume is achieved despite
the high solid load of the gas flow. Dense-flow conveying is
characterised by gentle transport of the material and is especially
little susceptible to failures by adhering or moist conveying
material. The present pneumatic dense-flow conveying process is
carried out preferably with solid densities of at least 100
kg/m.sup.3 and at a differential pressure of at least 0.5 bar.
[0015] Special claim is laid to a process for supplying finely
ground fuel materials to a cooled reactor (15) for gasification by
means of oxygen-bearing gasifying agents under pressure, wherein
[0016] the gasifier outlet temperatures are above the slag melting
point in the range between 1200 and 2000.degree. C. and the
pressure is between 0.3 and 8 MPa, [0017] and the finely ground
fuel material is pressurised via a lock system to a pressure level
above the gasifier pressure, transferred to at least one feed tank
and from there dosed in dense flow via at least one fuel line to
one or more gasification burners of one or several gasifiers, and
[0018] the transfer from at least two lock hoppers to at least one
feed tank is carried out by using a pneumatic continuous supply
line jointly, simultaneously or successively at solid material
densities of at least 100 kg/m.sup.3 and a differential pressure of
at least 0.5 bar.
[0019] In an embodiment of the process, the transfer from the lock
hoppers to the feed tank or tanks is controlled by at least one
connection device and at least one unifying element and the
transfer from the unifying element to the feed tank is implemented
by means of individual connection devices or by means of additional
unifying elements with transferring connection devices.
[0020] The transferring connection devices are designed in an
exemplary fashion as continuous supply lines suited for dense-flow
conveying. By installing unifying elements downstream of the lock
hoppers, the fuel material is conveyed from the lock hoppers to the
feed tanks via a number of continuous supply lines which is,
smaller than the number of lock hoppers. It is also possible to
direct the solid material from the outlets of the lock hoppers not
directly into the unifying elements but via connection elements so
that it is passed via lines into the unifying elements first and
then into the continuous supply line. Here, the number of unifying
elements is smaller than the number of lock hoppers and it may be
identical with the number of continuous supply lines. The unifying
elements are provided as closely to the outlet nozzles as possible
and arranged as symmetrically to them as possible to ensure a
smooth solid flow.
[0021] In a preferred embodiment of the process, the fuel material
is processed into a finely ground form by mean of a mill or a
suitable grinding device. For this purpose, the fuel material can
be made available in any form. It is possible to deliver fuel
material that has already been finely ground. In such case, claim
is only laid to the pressurisation of the fuel material and the
transport into the reactor. Usually, however, the grinding process
is an integral part of the process according to the invention,
especially if the grinding device is arranged in local proximity to
the reactor. In a preferred embodiment of the invention, the coal
milling and drying (CMD) unit is an integral part of the coal
gasification plant.
[0022] To carry out the transfer function, the lock hoppers are
pressurised with a gas. Recycled process gas may be used, for
example. It is also possible to use an inert gas. Pressurising is
performed advantageously with inert gases (e.g. nitrogen, carbon
dioxide) or by means of process gases or recycle gases. To
configure the transfer process in an advantageous way, pressurising
of the lock hoppers by supplied gas is preceded by a mutual partial
pressurisation of the lock hoppers. To keep the process conditions
as constant as possible, the lock hoppers are pressurised and
depressurised alternately.
[0023] In an additional embodiment of the process, the grinding
circuit is blanketed with inert gas and for blanketing the grinding
circuit with inert gas, the expansion gases from the lock hoppers
are used. The latter are depressurised at regular intervals for
carrying out the transfer process, wherein the discharged gas can
be recycled to the grinding devices. This will make the process
reliable in operation and keep the plant operating cost at a
reasonable level. The gas of the grinding circuit is additionally
dedusted. For this purpose a dust separator is used which may also
be used to dedust the expansion gases from the lock hoppers. The
pressurisation or expansion gas may be dedusted by means of a dust
separator in basically any place of the process.
[0024] The finely ground fuel material is then preferably fed to a
feed tank. In this way it is possible to store the fuel material in
accordance with the availability and to temporarily buffer the raw
material flow. It is thus possible to adjust bottlenecks which are
compensated by refilling at a later date.
[0025] To run the process according to the invention, all solid,
carbonaceous fuel materials that can be divided into small
particles by milling or grinding may be used. These may especially
be all kinds of carbon, wherein hard coal, brown coal and basically
coals of all carbonization kinds are suitable. Suitable as fuel
materials are also biological fuel materials such as wood,
biomasses and other fuel materials such as plastic waste and petrol
coke or mixtures of these. To run the process according to the
invention, it should merely be possible to crush the fuel materials
into a finely ground form which is suitable for dense-flow
conveying.
[0026] Subsequent to the comminuting process and the storage in the
feed tank, the solid material is passed to the lock hopper system
in which the solid material is pressurised with supplied gas to
carry out the gasification reaction. In a preferred embodiment of
the invention the feed tank is atmospheric. Conveyance of the solid
material into the lock hoppers is advantageously performed by
gravity.
[0027] To run the process according to the invention, the lock
hopper system consists of at least two lock hoppers. In this way,
it is possible to connect the discharging operations in series and
to ensure a nearly continuous material flow. In an advantageous
embodiment the lock hoppers are pressurised individually.
[0028] In an embodiment of the process according to the invention
two lock hoppers are used to ensure a continuous material flow. The
investment cost for the plant is thus low. In a further embodiment
of the invention, it is also possible to use three or more lock
hoppers. This is especially recommended in the case of high plant
throughputs.
[0029] It is possible to use a plurality of lock hoppers and a
plurality of unifying elements. In principle, the facility
according to the invention may consist of lock hoppers and unifying
elements of any number. The number of lock hoppers is determined by
the throughput of the plant. The number of unifying elements is
determined by the number of lock hoppers and the number of
continuous supply lines. Different arrangements of theoretically
any number are possible. The interconnection of the lock hoppers
and the unifying elements may basically also be carried out as
desired. For this, any number of connection devices may be used.
Preferred connection devices are pipelines. Possible as well are
hoses or flanges, for example. The mode of spatial interconnection
may also be selected as desired.
[0030] Subsequent to pressurising the tanks, the contained fuel
material is discharged in dosed quantities and the pressure in the
tanks is then expanded. In an advantageous embodiment of the
invention the expansion gas is used to partially pressurise the
next lock hopper in the cycle. In order to improve the efficiency,
this may be implemented by introducing the expansion gas directly
into the tank to be pressurised.
[0031] To reduce the dust load of the expansion gas, the expansion
gas is advantageously introduced into the dust separator which is
also used to dedust the gas from the storage tank or from the
grinding process. In principle, it is also possible to clean the
gas from solid material dusts by means of several independent dust
separators. To keep the investment cost low, it is advantageous to
use only one dust separator.
[0032] The material flow from the lock hoppers is routed to the
feed tank via at least one unifying element and the continuous
supply line. To utilise the advantage of the invention, the lock
hoppers are emptied one after the other in such a way that a nearly
continuous fuel material flow to the feed tank is achieved. In this
way, the subsequent feed tank for the gasification reactor can be
supplied with a continuous material flow of a pressure that is
suitable for the gasification reaction, wherein the filling level
of the feed tank remains nearly constant. The filling level of fuel
material in the feed tank can be adjusted according to the
advantageous embodiment of the process such that it does not vary
by more than .+-.30% over a given period of time. If the process
according to the invention is run by specialists, it is easily
possible to keep the filling level variations of the feed tank in a
range of not more than .+-.10% over an extended period of time.
[0033] The filling level of the feed tank may also be kept constant
by controlling the continuous supply of finely ground fuel material
from the lock hoppers by adjusting the pressure difference between
lock hopper and feed tank. The inlet or outlet of gas into the free
space of the lock hoppers influences the pressure difference
between lock hopper and feed tank and is used as control parameter
for the solid material transport.
[0034] To run the process, the finely ground fuel materials are
preferably of a particle size which is smaller than 0.5 mm. This is
achieved in a grinding and comminuting process. The discharge of
solid material from the lock hopper may be facilitated by the
addition of gas into the lock hopper in the immediate vicinity of
the discharge nozzle. The density in the continuous supply line is
adjusted advantageously by adding gas into the continuous supply
line or into the unifying element or into both. The addition of gas
at this point may also be used to purge the continuous supply line
or the unifying element. The connection elements between lock
hopper and unifying element may also be supplied with gas.
[0035] The conveying gas volume supplied at the discharge of the
lock hopper is recovered in the feed tank in an advantageous
embodiment of the invention and returned into the lock hopper by
means of an injector. The returned conveying gas and the propellant
gas of the injector are jointly used as replacement gas for the
emptying lock hopper and thus also for maintaining the pressure of
the lock hopper during the conveying process.
[0036] To suit certain requirements, it may be of advantage that
two or more lock hoppers discharge solid material simultaneously or
temporarily simultaneously into a conveying line. Gas balancing
between the feed hoppers may advantageously be achieved by a gas
connection line between the lock hoppers.
[0037] The process according to the invention may also include
processes which are subsequent processes of the coal gasification
process according to the invention. Also included in the process
according to the invention are process steps which are required for
a routine operation of the reactor. These may, for instance, be
cleaning steps. These may as well be supporting process steps such
as the supply of gas for loosening plugs. Possible as well are
process steps for measuring parameters such as filling levels, flow
rates, pressures or temperature. The invention especially also
describes a facility to run this process. The facility according to
the invention may include all plant units that are required for
operating a coal gasification plant according to the process of the
present invention.
[0038] Claim is also laid to a facility used to supply solid fuel
materials to a reactor for the gasification of solid fuel
materials, comprising [0039] a grinding device, [0040] a dust
separator, [0041] a storage tank, [0042] at least two lock hoppers,
[0043] at least one connection device for dense-flow conveying,
[0044] a feed tank, [0045] a gasification reactor, wherein [0046]
the grinding device is connected to a storage vessel by means of
connection devices, wherein a dust separator is installed between
the grinding device and the storage tank, and [0047] the storage
vessel is connected to the lock hoppers via connection devices
which are suited for gravity flow or dense-flow conveying, and
[0048] the lock hoppers are connected to a feed tank by means of
jointly used connection devices which are suited as continuous
supply line for dense-flow conveying, and this feed tank is
connected to the gasification reactor via further fuel material
lines.
[0049] The dense-flow conveying from the lock hopper system to the
feed tank allows to install the feed tank at the same or different
geodetic height as the lock hopper system. In the case of the
gravity lock hopper systems known to date it is indispensable to
install the lock hoppers above the feed tank. By this measure it is
possible to reduce the constructional height of the overall plant
to a considerable degree. It is also possible to locate the lock
hopper system and the feed tank and the reactor in separate
buildings. The invention also involves the advantage that lower
constructional heights may be selected for the respective units.
The various plant components may be arranged as desired so that the
spatial layout of the plant can be done in a flexible way.
[0050] The transfer of the fuel material from the lock hoppers to
the feed tank or tanks is implemented via at least one connection
device and at least one unifying element, and the transfer from the
unifying element to the feed tank via individual continuous supply
lines for dense-flow conveying. The transfer from the lock hopper
to the feed tank may be implemented via further unifying elements
with transferring connection devices.
[0051] Depending on the embodiment of the process, 2 or more lock
hoppers are used to pressurise the fuel material. This is
especially recommended for plants with high fuel material
throughputs or if the lock hopper system is to be pressurised to
higher pressures. The inlet sides of the lock hoppers are connected
to a feed tank which conveys the fuel material into the lock
hoppers by the aid of both dense-flow conveying and gravity
conveying. For this purpose, a star feeder or a material manifold
may be installed in a suitable place between the storage tank and
the lock hoppers. It is also possible to install intermediate
vessels, bulb-shaped vessels or gas feeding devices between the
storage tank and the lock hoppers.
[0052] The fuel material supply system of the coal gasification
plant may also include a grinding device or a mill which may be of
any type desired. The mill in turn may also include additional
comminuting devices such as shredders for wood or crushers for
coal. The mill or crusher may also be supplied with gas or
blanketed with inert gas. In a preferred embodiment of the facility
according to the invention the lock hoppers are spatially
integrated into the grinding unit and are filled by gravity flow
from at least one storage vessel for finely ground fuel.
[0053] To run the process according to the invention, the lock
hopper system consists of two or more lock hoppers which may be
pressurised from outside. The lock hopper system is connected to an
upstream storage tank which supplies the lock hopper system by
gravity conveyance with finely ground fuel material. The conveying
or transport of the solid material is influenced advantageously by
introducing gas so that gas introduction devices which influence
the conveying or transport of solid material may be installed in
any place of the lock hopper system, the dense-flow conveying lines
or the feed tank.
[0054] The lock hoppers may be of any design desired. They may be
provided in the form of cylinders or as spheres. Preferably they
are provided with a downward discharge cone, the angle of which is
determined by the properties of the bulk material to counteract
arching and to ensure a uniform material flow. For this reason,
they are tapered towards the bottom in the ideal case. The fuel
material hence exits downwards in gravity direction. The storage
tanks as well as the downstream feed tanks are also of this
preferred design. The lock hoppers are fitted with inlet valves via
which the lock hoppers may be pressurised. The lock hoppers are
equipped with nozzles, shutoff and control valves according to the
state of the art which serve to control the flow of solid material,
to depressurise and pressurise or carry out pressure
compensation.
[0055] In an advantageous embodiment of the invention the expanded
gases may be recycled to the grinding device and/or the fuel
storage tank. To separate the gas from dust before it is discharged
from the system or recycled for being used in the plant, the lines
are preferably routed via dust separators. The latter separate the
dust and pass it to a proper disposal or recycle it to the storage
tank, for example. It is theoretically possible to install devices
by which the gas flow can be separated from solid material or dust
in any place of the lock hopper system, the dense-flow conveying
line, the fuel lines or the expansion lines. It is therefore of
advantage to provide for a gas-sided connection of the lock hoppers
with the feed tank.
[0056] The lines may be provided with gas introduction devices in
any place desired. These may be so-called "boosters", for example.
Especially the discharge devices for solid material, however, which
are prone to caking, plugging or arching, may include additional
gas introduction devices by which the solid material can be
loosened. The lock hoppers as well may be provided with gas
introduction devices in any place desired.
[0057] In such case, the material discharge of the lock hoppers is
fitted with a connection element via which the material flow from
the lock hoppers is passed to the unifying element. These elements
shall be designed for high pressures as the fuel is at a pressure
level above that of the gasification reactor during the whole
conveying process from the lock hopper to the feed tank. To ensure
controlled material flow, the lock hoppers are mounted
advantageously such that they are arranged symmetrically to the
unifying element so that the connection elements between the lock
hoppers and the unifying element are preferably of the same
length.
[0058] The unifying elements may be of any type desired. Preferably
these are devices which assume the function of mixing elements.
These may be, for example, pipe manifolds or Y-manifolds but also
so-called "pipe headers". Examples of suitable unifying elements
are given in EP 340 419 B1; here the elements described are
reversed in their function and used as unifying elements. The
connection devices as well may be of any type desired. Preferably
used are pipes. Possible as well are hoses or flanges.
[0059] The connection devices or the unifying element may also be
supplied advantageously with gas for material distribution. If a
plurality of unifying elements is provided, they may be supplied
with gas individually. For this purpose, the unifying element is
preferably provided with a gas introduction device. The feed tank
as well is provided with gas injection devices or gas introduction
devices in an embodiment of the invention.
[0060] The pipeline for supplying solid material to the feed tank
normally ends above the solid material filling level and, depending
on the properties of the bulk material, it may also enter the feed
tank below the solid material level in an embodiment of the
invention. As the solid material level is subject to only slight
variations if the process is run advantageously, this may be at a
lower or central height position of the feed tank. In this way it
is possible to achieve a low bulk density in the feed tank if the
solid material shows good gas-retaining properties, which reduces
the additional amount of gas required for conveyance to the
burners.
[0061] The facility according to the invention may be provided with
plant equipment required for the operation of a solid fuel supply
system in any place desired. This may be pumps but may also be
heating or cooling devices. Also included are valves or shutoff
devices. These may theoretically be installed in any place. The
integration of injectors is also possible. Here, so-called
"boosters" (gas injectors) may be used, for example, but also
possible are gas jet pumps. Finally the facility according to the
invention also includes thermometers or flow sensors for gases and
solid materials, pressure sensors, level meters or other measuring
devices.
[0062] The design type of dense-flow conveying from the lock
hoppers and from the feed tank allows to construct the whole plant
construction at low height. As the conveyance is independent of
gravity, the plant equipment may be installed in any place desired.
By this system, the space requirement can be reduced to a
considerable degree. The system of several lock hoppers and the
upstream storage tank as well as the constant-level feed tank
allows to achieve trouble-free and very constant conveying of fuel
to the feed tank over a given period of time, even for an extended
period of time. This contributes to the reliability of the plant
and ensures a constantly high product quality.
[0063] The facility according to the invention is illustrated in
more detail by means of two drawings, the embodiment not being
limited to these drawings.
[0064] FIG. 1 shows the process flow of a coal gasification
plant-which is equipped with a facility for the supply of fuel
material according to the invention. Fuel material 1 is supplied
and introduced into a mill or suitable grinding device 2. The
finely ground fuel material is then passed via a dust separator 3
and fuel line 3a into a storage tank 4, where the fuel is stored
intermediately. Subsequently the fuel is supplied to lock hoppers
5. The represented example shows two of them 5a, 5b. Lock hoppers 5
serve to pressurise the fuel batch by batch by supplying gas. For
this purpose, lock hoppers 5 are provided with gas introduction
devices 6a, 6b above the filling and gas introduction devices 6'a,
6'b into the filling. Between lock hoppers 5 there is a
compensation line 7 which may be opened in the case of need. An
expansion line 8 for depressurisation leaves lock hoppers 5, via
which the expanded gas may be used completely or only partially for
blanketing grinding device 2. The expanded gas, however, may also
be used for blanketing storage tank 4 with inert gas. To adjust
recycle gas 8c of grinding device 2 recycled by means of blower 8b
to adequate temperatures, the line may be provided with a heat
exchanger 8d or another suitable device for supplying heat.
Downstream of lock hoppers 5a, 5b the finely ground fuel material
is discharged via suitable connection devices 9a, 9b and passed to
unifying element 10. Unifying element 10 may be supplied with gas
via gas line 11. The finely ground material is then routed via
continuous supply line 12 to a feed tank 13.
[0065] In the exemplary variant shown in FIG. 1, two lock hoppers
5a, 5b make use of a continuous supply line 12 via unifying element
10. This is achieved advantageously in such a way that lock hoppers
5a, 5b feed the solid material alternately into dense-flow
conveying continuous supply line 12 via unifying element 10. To
minimise the interim time for switching from one lock hopper to the
other 5a, 5b and to ensure an almost uninterrupted conveying of
solid material, it is advantageous to couple both lock hoppers 5a,
5b in timely overlapping manner to unifying element 10. Helpful in
this respect is pressure compensation via compensation line 7
between that lock hopper that is almost empty already and the other
lock hopper that is still full 5a, 5b. It goes without saying that
it is also possible and advantageous to implement the described
procedure with more than two lock hoppers 5. If there are more than
two lock hoppers 5, it is also possible to use the expansion gas of
that lock hopper 5 that has just been emptied and shall now be
depressurised for being loaded with solid material from atmospheric
storage tank 4, for partial pressurisation of a lock hopper 5 which
is still under atmospheric condition. Connection device 9a, 9b is
provided with two valves (not shown), one close to the hopper
discharge, one close to unifying element 10. After a lock hopper 5
has been emptied to a minimum level and shut off from unifying
element 10 by the valve in proximity to unifying element 10, it is
recommended to purge or blow free by gas injection 9'a, 9'b at
connection device 9a, 9b, before the second valve is closed.
[0066] In the ideal case, a constant filling level 13a prevails in
feed tank 13. The pressure of feed tank 13 can be kept constant by
excess gas 21 or feed gas 22 by a gas compensation process. From
feed tank 13, the solid material is routed via fuel lines 14a, 14b
to coal gasification reactor 15 with one or more burners 16a, 16b.
In this case, the entire facility for the supply of solid fuel is
located in a separate plant unit, the building of grinding unit
17a. Coal gasification reactor 15 and feed tank 13 are located in
another building, the building of gas production unit 17b.
[0067] The advantages of the invention already mentioned which
especially involve a considerable reduction of the number of
equipment items, the construction height and hence the investment
cost as well as an increase in plant reliability, are obtained for
a moderate increase in the demand for pressurising gas. This is due
to the fact that that part of the gas used for dense-flow conveying
of the solid material in continuous supply line 12 which has been
used to reduce the solid material density to a value below the one
prevailing in feed tank 13, cannot be used as feed gas for coal
gasification reactor 15 since it is excess gas, see FIG. 2. If no
additional devices are available, this part is to be removed unused
as excess gas 21. At the same time, many times the amount of gas is
required in lock hopper 5, which is the active transferring hopper,
as a replacement for the discharged amount of solid material. It
therefore suggests itself to reduce the demand for gas by recycling
excess gas 21 from feed tank 13 as recycle gas 20 to the lock
hopper and using it for a partial substitution of the gas consumed
for replacement. This may be implemented by a blower or another
device for pressure increase. Owing to the low pressure difference
to be overcome between feed tank 13 and lock hopper 5 at
simultaneously high system pressure, an injector 18 suggests
itself, especially a gas jet pump. In addition, the pump is also
capable of conveying dust-bearing gas, dust separation is not
required. As propellant gas serves the pressurising gas used for
the purpose of replacement, which is available at significantly
higher pressure. The pressure side of injector 18 is switched over
to the currently active lock hopper 5. Under typical operating
conditions the portion of recycle gas amounts to about 25% of the
amount of replacement gas. At the same time the supply pressure of
propellant gas 23 is about 10 bar higher than the pressure of the
lock hopper, whereas the pressure of recycle gas 20 is only about
1-2 bar above the pressure of the lock hopper. These numerical
relationships make it obvious to the specialist that injector
system 18 is fully operative under the specified conditions.
[0068] Gas recycling is integrated into the pressure control system
of feed tank 13 in the following way: Based on the consideration
that, at constant operating conditions, excess gas 21 is to be
removed from feed tank 13, the pressure increase in feed tank 13 is
avoided by having injector 18 suck off the released amount of gas
and feed it to lock hopper 5. If the pressure in feed tank 13
continues to rise, the excessive pressure amount is removed as
excess gas 21. This gas as well can be used beneficially if
required, e.g. for substituting purge gases which are fed to the
gasification reactor in various places. Should a pressure increase
of feed tank 13 be required especially during the start-up
procedure, which cannot be achieved by excess gas 21, with closed
valves in the lines for recycle gas 20 and excess gas 21, the
shortage is compensated by fresh feed gas 22.
[0069] The pressurising gas used as propellant gas 23 for injector
18 is compensation-controlled by the pressure controller of lock
hopper 5. Depending on the position of the throttling valve in the
propellant gas line, the amount of propellant gas ranges between 70
and 100% of the gas amount required for replacement. The set value
of the lock hopper pressure is determined via a cascade (not shown)
from the level of feed tank 13 (or from its weight). With regard to
the level, a fixed set value (e.g. 50%) is given. If this set value
is exceeded, the value of pressure difference between lock hopper 5
and feed tank 13 controlled by the controller cascade is reduced so
that the subsequently fed solid mass flow decreases, and if the
level drops below the set value, the controllers operate vice
versa.
[0070] FIGS. 3 to 8 show, by way of example, arrangements with a
varying number of lock hoppers 5 and unifying elements 10. These
are connected by pipelines in different ways.
[0071] FIG. 3 shows a facility according to the invention which
includes three lock hoppers 5 and one unifying element 10, wherein
each lock hopper 5 is connected to unifying element 10 via a
connection device 9, and unifying element 10 is connected to feed
tank 13 via a continuous supply line 12. Unifying element 10 can be
supplied with gas via gas line 11.
[0072] FIG. 4 shows a facility according to the invention which
includes three lock hoppers 5 and two unifying elements 10, wherein
two lock hoppers 5 are connected to the first unifying element 10a
via connection devices 9a, 9b, and the first unifying element 10a
is connected to the second unifying element 10b via another
connection device, and the third lock hopper 5 is directly
connected to the second unifying element 10b via a connection
device 9c, and the second unifying element 10b is connected to feed
tank 13 via a continuous supply line 12.
[0073] FIG. 5 shows a facility according to the invention which
includes four lock hoppers 5 and three unifying elements 10,
wherein two lock hoppers 5 each are connected to one unifying
element 10 each via connection devices 9a-9d, these unifying
elements 10 being connected to the third unifying element 10c via
further connection elements 9e, 9f, and the third unifying element
10c being connected to feed tank 13 via a continuous supply line
12.
[0074] FIG. 6 shows a facility according to the invention which
includes six lock hoppers 5 and two unifying elements 10, wherein
three lock hoppers 5 each are connected to one unifying element 10
each via connection devices 9, these unifying elements 10 being
connected to feed tank 13 via separate continuous supply lines 12a,
12b.
[0075] FIG. 7 shows a facility according to the invention which
includes eight lock hoppers 5 and two unifying elements 10, wherein
four lock hoppers 5 each are connected to one unifying element 10
each via connection devices 9a, 9b, these unifying elements 10
being connected to feed tank 13 via separate continuous supply
lines 12.
[0076] FIG. 8 shows a facility according to the invention which
includes eight lock hoppers 5 and three unifying elements 10,
wherein four lock hoppers 5 each are connected to one unifying
element 10a, 10b via connection devices 9, these unifying elements
10a, 10b being connected to the third unifying element 10c via
further connection devices 9, and the third unifying element 10b
being connected to feed tank 13 via a continuous supply line
12.
LIST OF REFERENCES USED
[0077] 1 Fuel material [0078] 2 Grinding device [0079] 3 Dust
separator [0080] 3a Fuel line [0081] 4 Storage tank [0082] 5,5a,5b
Lock hoppers [0083] 6,6a,6b Gas introduction devices [0084] 6'a,6'b
Gas introduction devices [0085] 7 Compensation line [0086] 8
Expansion line [0087] 8a Expansion gas line [0088] 8b Blower [0089]
8c Recycle gas [0090] 8d Heat exchanger [0091] 9a-9f Connection
devices [0092] 9'a,9'b Gas injection [0093] 10, 10a-10c Unifying
elements [0094] 11 Gas line [0095] 12, 12a, 12b Continuous supply
line [0096] 13 Feed tank [0097] 13a Filling level [0098] 14a,14b
Fuel lines [0099] 15 Coal gasification reactor [0100] 16a,16b
Burners [0101] 17a Building of grinding unit [0102] 17b Building of
gas production unit [0103] 18 Injector [0104] 19 Gas [0105] 20
Recycle gas [0106] 21 Excess gas [0107] 22 Feed gas [0108] 23
Propellant gas [0109] .DELTA.p Pressure as control parameter [0110]
PC Pressure controllers
* * * * *