U.S. patent application number 12/390508 was filed with the patent office on 2009-07-09 for feed system.
Invention is credited to Oliver Neumann.
Application Number | 20090173005 12/390508 |
Document ID | / |
Family ID | 38924507 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090173005 |
Kind Code |
A1 |
Neumann; Oliver |
July 9, 2009 |
Feed System
Abstract
Transport system for the introduction of biomass into a gasifier
comprising: a plug screw that forces the biomass into the gasifier,
wherein the plug screw is formed such that the biomass is
compressed in order on the one hand for it to be conveyed against a
pressure in the gasifier and, on the other hand, to leave the gas
and bed material in the gasifier, having a gate valve adjacent to
the plug screw and which closes when the plug screw stops so that
heat, vapour and gas cannot escape.
Inventors: |
Neumann; Oliver; (Offenbach,
DE) |
Correspondence
Address: |
Nixon Peabody LLP
200 Page Mill Road, Suite 200
Palo Alto
CA
94306
US
|
Family ID: |
38924507 |
Appl. No.: |
12/390508 |
Filed: |
February 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP2007/058034 |
Aug 2, 2007 |
|
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12390508 |
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Current U.S.
Class: |
48/86R ;
48/197R |
Current CPC
Class: |
C10J 3/503 20130101;
C10J 3/723 20130101; C10J 2300/1261 20130101; C10J 2200/158
20130101 |
Class at
Publication: |
48/86.R ;
48/197.R |
International
Class: |
C10J 3/30 20060101
C10J003/30; C10J 3/46 20060101 C10J003/46 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2006 |
DE |
10 2006 039 622.7 |
Claims
1. Transport system for the introduction of biomass into a gasifier
comprising: a plug screw that forces the biomass into the gasifier,
wherein the plug screw is formed such that the biomass is
compressed in order on the one hand for it to be conveyed against a
pressure in the gasifier and, on the other hand, to leave the gas
and bed material in the gasifier, having a gate valve adjacent to
the plug screw and which closes when the plug screw stops so that
heat, vapour and gas cannot escape.
2. The transport system according claim 1, wherein a cooling system
cools the plug screw from the inside or the outside.
3. The transport system according claim 1, wherein one gate valve
is arranged upstream of the plug screw and one gate valve is
arranged downstream of it.
4. The transport system according claim 1, whereby a cellular wheel
feeder is mounted before the plug screw onto which a feed chute
abuts.
5. The transport system according claim 1, whereby the plug screw
is equipped in its forward area with a system of nozzles that
operates in a similar fashion to a jet pulse system.
6. The transport system according claim 1, whereby a sealing gas
may be introduced into the casing of the plug screw, more
particularly N2 (nitrogen) or CO2 (carbon dioxide) is supplied to
the injection tube.
7. The transport system according claim 1, whereby a buffer that
operates with a regulated discharge unit, is connected upstream of
the plug screw.
8. The transport system according claim 1, whereby the discharge
system comprises a screw mounted centrally in the buffer silo and
regulated by a controller.
9. The transport system according claim 8, whereby the entire screw
can be moved over the floor of the bunker, also by means of a
speed-regulated rotary drive.
10. The transport system in accordance with claim 1, whereby one or
more metering screw(s) meter the biomass that is fetched from the
buffer bunker and, where necessary a transport screw transports the
biomass to the plug screw.
11. The transport system i according claim 1, whereby a control
unit that calculates the volume of gas produced proportionally to
the feedstock so that this physical dependence can be used as a
control for the volume of material fed so that the measurement of
the synthesis gas volume, or the comparison between the specified
value and the measured volume of syngas produced may be used as the
managing control for the volume of feedstock.
12. Method for the introduction of biomass into a gasifier
comprising: introducing of the biomass by way of a plug screw
whereby the plug screw is regulated such that the biomass is
compressed in order on the one hand for it to be conveyed against a
pressure in the gasifier and, on the other hand, to leave the gas
and bed material in the gasifier, Closing of a gate valve adjacent
to the plug screw and which closes if the plug screw stops so that
heat, vapour and gas cannot escape.
13. The method according claim 12, wherein a cooling system cools
the plug screw from the inside or the outside.
14. The method according claim 12 whereby one gate valve is mounted
upstream of the plug screw and one is mounted downstream of it and
these are closed as a function of the supply or removal of the
biomass.
15. The method according to claim 12 whereby a cellular wheel
feeder is mounted upstream of the plug screw onto which a feed
chute abuts wherein the feeder is controlled such that the plug
screw is continuously supplied with biomass.
16. The method according claim 12 whereby the plug screw is
equipped in its forward area with a system of nozzles that operates
in a similar fashion to a jet pulse system to inject into the
biomass.
17. The method according claim 12 whereby a sealing gas is
introduced into the jacket of the plug screw, more particularly N2
(nitrogen) or CO2 (carbon dioxide) is supplied under pressure to an
injection tube to prevent the occurrence of a drop in pressure.
18. The method according claim 12 whereby the plug screw is
supplied from a buffer by a regulated discharge unit.
19. The method according claim 12, whereby the discharge system
comprises a screw mounted centrally in the buffer silo and
regulated by a controller.
20. The method according claim 19, whereby the entire screw is
moved over the floor of the bunker, also by means of a
speed-regulated rotary drive.
21. The method system according claim 12, whereby one or more
metering screw(s) meter the volume that is fetched from the buffer
bunker and, where necessary a transport screw transports the
biomass to the plug screw.
22. The method according claim 12 whereby a control unit calculates
the volume of gas produced proportionally to the feedstock so that
this physical dependence can be used as a control for the volume of
material fed so that the measurement of the synthesis gas volume,
or the comparison between the specified value and the measured
volume of syngas produce may be used as the managing control for
the volume of feedstock.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT/EP2007/058034
filed Aug. 2, 2007, which claims priority of DE 10 2006 039 622.7
filed Aug. 24, 2006, both of which are incorporated by
reference.
FIELD OF THE INVENTION
[0002] The invention concerns a system for feeding biogenic
feedstock into a gasifier, more particularly into a pulse gasifier
in accordance with applications DE 10 2006 022 265.2, DE 10 2006
017 355.4, DE 10 2006 017 353.8.
BACKGROUND
[0003] The development of thermal gasification processes has
produced essentially three different types of gasifier, the
entrained flow gasifier, the fixed bed gasifier and the fluidized
bed gasifier.
[0004] Originally, the fixed bed gasifier and the fluidized bed
gasifier were developed for the commercial gasification of
biomasses.
[0005] The Carbo-V method will be illustrated here by way of an
example for the many different technical approaches to fixed bed
gasification.
[0006] Literature for fluidized bed gasification which is a
component of this application may be taken from the following
reference: "High-Temperature Winkler Gasification of Municipal
Solid Waste"; Wolfgang Adlhoch, Rheinbraun AG, Hisaaki Sumitomo
Heavy Industries, Ltd., Joachim Wolff, Karsten Radtke (Speaker),
Krupp Uhde GmbH; Gasification Technology Conference; San Francisco,
Calif., USA; Oct. 8-11, 2000; Conference Proceedings.
[0007] Literature for a circulating fluidized bed in a network
system may be taken from the following sources: "Decentralized heat
and power generation based on biomass gasification"; R. Rauch, H.
Hofbauer; Presentation at University of Leipzig 2004. "Circulating
fluidized bed, gasification using air,
[0008] Operation Experience with CfB-Technology for Waste,
Utilisation at a Cement Production Plant" R. Wirthwein, P. Scur,
K.-F. Scharf-Rudersdorfer Zement GmbH, H. Hirschfelder-Lurgi
Energie und Entsorgungs GmbH; 7th. International Conference on
Circulating Fluidized Bed Technologies; Niagara Falls, May
2002.
[0009] Literature for the combination fixed bed (rotating tube) can
be taken from the following sources: 30 MV Carbo V Biomass Gasifier
for Municipal CHP; The CHP Project for the City of Aachen, Matthias
Rudloff; Presentation Paris, October 2005
[0010] Literature for combination fixed bed gasification (slagging
gasifier) can be taken from the following sources: Operation
Results of the BGL Gasifier at Schwarze Pumpe, Dr. Hans-Joachim
Sander SVZ, Dr. Georg Daradimos, Hansjobst Hirschfelder,
Envirotherm; Gasification Technologies 2003; San Francisco Calif.,
Oct. 12-15 2003; Conference Proceedings
[0011] Gasification takes place over two stages in the Carbo-V
process. First the biomass is split into its volatile and solid
constituents at 500.degree. C. This results in a gas containing tar
and also "char". The gas is burnt at temperatures in excess of
1200.degree. C., which breaks down the tars into CO2 and H2. A
synthesis gas containing CO and H2 is then generated from the hot
flue gas and the char.
[0012] These types of gasifier are completely unsuited to the
gasification of biomass (which occurs regionally and has a
significant influence on the costs in terms of logistics and
processing) because of the great technical effort and high economic
costs demanded by the high pressure level (up to 40 bar).
[0013] Fluidized bed gasifiers may be subdivided into two processes
which differ in the heating of the fluidized bed, the circulating
fluidized bed gasifier and the bubbling fluidized bed gasifier.
[0014] Literature relating to desulphurization in fluidized bed
gasification can be found in the following source: Gasification of
Lignite and Wood in the Lurgi Circulating Fluidized Bed Gasifier;
Research Project 2656-3; Final Report, August 1988, P. Mehrling, H.
Vierrath; LURGI GmbH; for Electric Power Research Institute, Palo
Alto, Calif.: ZWS-Druckvergasung im Kombiblock, Schlussbericht
(Circulating fluidized bed high-pressure gasification in a
combiblock, final report) BMFT FB 03 E 6384-A; P. Mehrling, LURGI
GmbH; Bewag
[0015] An allothermal circulating fluidized bed gasification plant
was brought on stream at the start of 2002 in Gussing (Austria).
The biomass is gasified in a fluidized bed using steam as the
oxidizing agent. A proportion of the char created in the fluidized
bed is burnt in a second fluidized bed to provide the heat for the
gasification process. A synthesis gas is generated by gasification
in steam. The disadvantages are the high acquisition costs for the
process engineering and excessive costs for process control.
[0016] The management of the fluidized bed material demands a
specific regulation and control system for steam circulation in the
form of an gas lift pump motion to enhance the exchange of heat and
material and to improve the reaction conditions by increasing the
effective reaction space. The gas lift pump is a materials handling
device in which solid matter/water mixtures are conveyed with the
help of compressed air (driving or conveying gas) for instance by
means of the injection of this gas through nozzles in pipework or
in a stirred tank. The injected gas causes a reduction in the
suspension density and hence an increase in buoyancy. Together with
the added kinetic energy, this results in conveyance.
[0017] A circulation flow results in the containers as the
flow.
[0018] This is thus transferred to the solids/gas suspension of the
fluidized bed.
[0019] This principle is transmitted in the present case to the
gas/solids suspension of the fluidized bed in the steam
converter.
[0020] All these systems require a transport system to deliver the
biogenic feedstock to the gasifier. The invention below describes a
system comprising the processes for delivering the biogenic
feedstock into a gasifier, in particular into a pulse gasifier.
[0021] The feedstock covers a broad palette. These may be extruded
material, round pellets such as are created by pelleting machines,
for instance, or biogenic media from agriculture (cereals).
[0022] Characteristic for these biomasses are carbon contents in
the original material in the range of 40 to 50% by mass with
hydrogen contents in the range up to 6% by mass and oxygen contents
in the range from 40 to 50% by mass. The calorific values of the
feedstock are typically in the range up to 20 MJ/kg. The bulk
material densities vary over the range from 200 to 700 kg/h. In
addition to a certain proportion of fines, extruded materials have
a diameter between 5 and 10 mm with a length from 10 to 20 mm and
lump material has dimensions in the area of 20.times.30 mm with a
thickness of up to 10 mm.
SUMMARY OF THE INVENTION
[0023] An embodiment of the invention provides a transport system
which delivers the biomass to the reactor efficiently taking into
consideration the particular characteristics of the reactor.
[0024] The process sequence comprises the following steps that are
performed with the appropriate equipment.
a. Buffer:
[0025] Buffering in a silo (bunker) as a prior step to feeding and
metering. Feedstock from different stores may be conveyed to this
buffer.
b. Metering and Feeding to the Points of Delivery into the
Gasifier:
[0026] Taking the net gas production acting as a setpoint value as
a basis (result from the control regime for the steam reforming
gasifier), the feedstock is metered and distributed to one, two or
more points of delivery such that the gas production required
results. The system also provides the function of the plug screw
which acts as a pressure seal for the reactor system. The system
has the flexibility to fulfil these tasks while the broad range of
feedstock is being used.
c. Sealing the Reaction System Against the Atmosphere:
[0027] A pressure seal for the reactor provided by the material
plug formed in the plug screw and a multi-stage system of cellular
wheel feeder and gate valve before and after the plug screw and
pressurizing the feed tube with N2 (nitrogen) or CO2 (carbon
dioxide) may be necessary depending on the reactor type.
[0028] This material plug is continuously created in the plug screw
which acts as the feed device for the gasifier by adjustment of the
volumes. The feed screws are controlled so that the mass flow and
the permanent formation of the sealing plug is ensured.
[0029] This system is furthermore characterised in that the plug
screw(s) is/are equipped in their forward section with a system of
nozzles operating in a similar fashion to a jet pulse system, as is
known from filter technology.
[0030] The plug screw is further equipped with cooling devices for
the shaft and the jacket. (It is optionally possible to cool the
shaft vanes on this plug screw).
d. Prevention of the Return Flow of the Fluidized Bed Material into
the Feed and Metering System when the System is at a Standstill and
when the Feed and Metering System is not Operating:
[0031] When the gasifier is operating the material is fed into a
dense, fluidized bed. Measures are taken to prevent the backflow of
bed material into the plug screw when the feed screw is at a
standstill, particularly in the start up and shut down processes.
To this end, the system is equipped with a gate valve that operates
through the material being conveyed and shuts off the flow in a
suitable manner. This equipment also permits the plug screw(s) to
be drained through a drainage arrangement as a precaution against
the sort of backfires that cannot be excluded in the case of brief
shutdowns of the otherwise hot gasifier.
[0032] Thanks to these various aspects, the system is suited to
transporting into the reactor all feedstock coming into
consideration for gasification. Because of its particular
characteristics, the system is also capable of feeding into
internal pressures up to 5 bar.
[0033] It is clear from the above that the feed and metering system
comprises, in a preferred embodiment of the following elements:
[0034] a buffer with regulated discharge unit; [0035] a metering
screw(s) that doses the volume fetched from the buffer; [0036] a
transport screw to transport the material to the plug screw; [0037]
a cellular wheel feeder, gate valve before and after a plug screw
and a plug screw.
[0038] The volume of gas produced depends on (is proportional to)
the volume of feedstock. This physical dependency is used as a
control for the volume fed. Measurement of the volume of syngas, or
the comparison between the setpoint value specification and the
volume of syngas measured, is used as the managing closed loop
control for the volume of feedstock. As may be seen from the
drawings, these variables act directly on the metering screw
(single, parallel or multiple arrangement). This screw/these screws
is/are fed under the control of the discharge and metering screw
from the buffer bunker and these control elements too are
incorporated in the control loop together with a fill level monitor
in the feed chute to the metering screw(s).
[0039] The following transport screws, not regulated in one
possible embodiment, convey the feedstock to the actual feed
system.
[0040] The full control loop concept thus comprises feeding
biogenic feedstock into a gasifier for allothermal gasification
with the heat of reaction for the gasification reaction being
generated in special pulse burners.
DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows a schematic overview of the invention;
[0042] FIG. 2 shows the schematic structure of the metering screw
and the plug screw;
[0043] FIG. 3 shows the plug screw in detail.
PREFERRED EMBODIMENTS
[0044] The control concept comprises the specification by the
volume of synthesis gas for metering the feedstock through
regulated discharge from a buffer and speed-regulated metering
screws with monitoring of the fill level of the supply chutes,
distribution to the feed devices and formation of the shut-off
plugs in the speed-regulated feed screws, with their speed being
regulated by the master controller and the fill level monitoring in
the supply to the feed system. This feed system (for solids)
constitutes substantial progress in fluidized bed gasification.
[0045] The discharge system 1 (FIG. 1) comprises a screw 3, the
rotation speed of which is regulated by the master controller 2,
and which is mounted centrally in the buffer bunker 4. The entire
screw is moved over the silo base by means of a rotary drive 5,
itself also speed-regulated. Speed regulation is configured such
that the fill level of this screw is maintained at a constant level
by the screw turning into the material held in the silo. This means
that the delivery rate is directly proportional to the speed of
rotation of the screw and hence this discharge system is suitable
for feed regulation. The current consumption of the rotatably
mounted screw that is directly proportional with the torque of this
screw is used as the reference variable for the speed control.
[0046] The volume is determined by the master control as a function
of the setpoint value for the synthesis gas 7 by means of a
metering screw. The volume fetched from the buffer silo is metered
accordingly.
[0047] One or more transport screws 8 transport the volume to the
plug screws 9.
[0048] The feed system comprises a cellular wheel 10, gate valve 11
upstream of the screw for onwards conveying and simultaneously
shutting off both in start-up and shut-down operation and for
feeding the plug screw 9. The system is equipped with a system 12
(see FIG. 3) for pressurizing it with air as a sealing medium
and/or an inert gas such as N2 or CO2 or steam (the latter medium
also acting as an extinguishing and sealing medium). As is clear
from FIG. 2, the system comprises the plug screw itself, in which
the material plug is generated to plug the pressure. The screw is
designed such that this material plug remains stable across the
entire speed range and hence with variable volumes of feedstock.
This feedstock is conveyed directly into the hot fluidized bed via
the gate valve that remains open during operation through a smooth,
heat resistant pipe.
[0049] Furthermore, the screw includes cooling equipment 13, 14 for
cooling the screw shaft 14 and optionally the screw vanes and the
jacket 13 in which the screw is fitted. This can be shaft cooling
and jacket cooling.
[0050] One part of the system is the gate valve 15 directly between
the feed screw and the gasifier 16 that is closed when the screw is
shut down and prevents the inert bed material flowing back into the
screw.
[0051] This gate valve is made from heat resistant material as it
is located at the interface between the gasifier which is hot in
operation and the cooled screw. This measure also prevents backflow
during the operational phases in which the feedstock plug being fed
does not itself establish the isolation.
[0052] The feedstock is supplied to the feed screw by way of a
chute 17, cellular wheel feeder 10 and gate valve 11. The fill
level monitoring 18 in this feed line guarantees the necessary
permanent formation of a material plug for the feedstock throughput
configured through the main control system. The arrangement of the
cellular wheel feeder and gate valve upstream of the screw
furthermore permits the introduction of a sealing gas (air or inert
gases such as CO2, nitrogen or steam in exceptional cases).
[0053] Gate valve 11 permits an additional gas-tight seal.
[0054] A pressure range of the reaction system of up to 5 bar
overpressure, as a rule 1.5 bar overpressure, is hence
controllable.
* * * * *