U.S. patent application number 12/668577 was filed with the patent office on 2010-08-19 for process to produce a methane rich gas mixture from gasification derived sulphur containing synthesis gases.
This patent application is currently assigned to PAUL SCHERRER INSTITUT. Invention is credited to Serge Biollaz, Tilman J. Schildhauer, Martin Seeman.
Application Number | 20100205863 12/668577 |
Document ID | / |
Family ID | 39745214 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100205863 |
Kind Code |
A1 |
Biollaz; Serge ; et
al. |
August 19, 2010 |
Process to Produce a Methane Rich Gas Mixture From Gasification
Derived Sulphur Containing Synthesis Gases
Abstract
A method for converting a raw gas into a methane-rich and/or
hydrogen-rich gas includes the following steps: a) providing the
raw gas stemming from a coal and/or biomass gasification process,
thereby the raw gas comprising beside a methane and hydrogen
content carbon monoxide, carbon dioxide, alkanes, alkenes, alkynes,
tar, especially benzole and naphthalene, COS, hydrogen sulfide and
organic sulfur compounds, especially thiophenes; thereby the ratio
of hydrogen to carbon monoxide ranges from 0.3 to 4; b) bringing
this raw gas into contact with a catalyst in a fluidized bed
reactor at temperatures above 200.degree. C. and at pressures equal
or greater than 1 bar in order to convert the raw gas into a first
product gas, thereby simultaneously converting organic sulfur
components into hydrogen sulfide, reform tars, generate water/gas
shift reaction and generate methane from the hydrogen/carbon
monoxide content; c) bringing the first product gas into a sulfur
absorption process to generate a second product gas, thereby
reducing the content of hydrogen sulfur and COS from 100 to 1000
ppm down to 1000 ppb or less; d) optionally bringing the second
product gas into a carbon dioxide removal process to generate a
third product gas at least almost free of carbon dioxide; e)
bringing the third product gas into a second methanation process to
generate a fourth product gas having a methane content above 5 vol
%; f) optionally bringing the fourth product gas into a carbon
dioxide removal process to generate a fifth product gas at least
almost free of carbon dioxide g) bringing the fifth product gas
into an hydrogen separation process in order to separate a hydrogen
rich gas from a remaining methane-rich gas, called substitute
natural gas.
Inventors: |
Biollaz; Serge; (Waldshut,
DE) ; Schildhauer; Tilman J.; (Brugg, CH) ;
Seeman; Martin; (Wettingen, CH) |
Correspondence
Address: |
LERNER GREENBERG STEMER LLP
P O BOX 2480
HOLLYWOOD
FL
33022-2480
US
|
Assignee: |
PAUL SCHERRER INSTITUT
Villigen PSI
CH
|
Family ID: |
39745214 |
Appl. No.: |
12/668577 |
Filed: |
July 3, 2008 |
PCT Filed: |
July 3, 2008 |
PCT NO: |
PCT/EP2008/005464 |
371 Date: |
January 11, 2010 |
Current U.S.
Class: |
48/127.7 ;
48/197R |
Current CPC
Class: |
C10G 67/02 20130101;
C10G 45/34 20130101; C10G 2/30 20130101; C10G 2/33 20130101; C10L
3/102 20130101; C10G 47/00 20130101; C10J 3/00 20130101; C10G 67/14
20130101; C10G 45/04 20130101; C10J 2300/1807 20130101; C10G 67/06
20130101; C10J 2300/1665 20130101; C10G 47/02 20130101; C10G 45/00
20130101; C10L 3/08 20130101 |
Class at
Publication: |
48/127.7 ;
48/197.R |
International
Class: |
C10L 3/06 20060101
C10L003/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2007 |
EP |
070 13 482.0 |
Claims
1-15. (canceled)
16. A process for producing a methane-rich gas mixture for further
application in high temperature fuel cells or for manufacturing
synthetic natural gas (SNG) from gasification-derived synthesis gas
mixtures that contain at least some compounds problematic to
conventional methanation units, the process which comprises. at
least one unit allowing for methanation, water gas shift reaction,
and for converting most or parts of the problematic compounds to
less problematic compounds by one or more of the following.
hydrodesulphurization of organic sulfur species;
hydrodenitrogenation of organic nitrogen species; hydrogenation or
reformation of alkanes, alkenes, and alkynes; and hydrogenation,
reforming or cracking of hydrocarbons; the unit being operated at
temperatures between 200.degree. C. and 900.degree. C. and at
pressures between 0.8 bara and 70 bara; and the unit including a
catalyst containing metals forming an active phase selected from
the group consisting of molybdenum, cobalt, ruthenium, nickel,
tungsten or sulfides thereof, and the active phase metals being
supported on materials containing one or more materials selected
from the group consisting of aluminum, silicon, titanium,
zirconium, cerium, gadolinium, manganese, vanadium, lanthanum,
chromium, or oxides thereof.
17. The process according to claim 16, wherein the problematic
compounds are compounds selected from the group consisting of
organic sulfur or nitrogen compounds, alkanes, alkenes, alkynes,
aromatic hydrocarbons or non-aromatic hydrocarbons
18. The process according to claim 17, wherein the aromatic
hydrocarbons are selected from the group consisting of naphthalene,
toluene, benzene, and phenols.
19. The process according to claim 16, which comprises carrying out
the process in a fluidized bed reactor with catalyst particles
having a size in a range from 20 to 2000 .mu.m.
20. The process according to claim 19, which comprises controlling
a temperature with heat transfer means.
21. The process according to claim 19, which comprises controlling
a temperature of the process with heat transfer means in the
fluidized bed reactor.
22. The process according to claim 16, which comprises feeding
additional hydrogen into the process.
23. The process according to claim 22, which comprises feeding the
additional hydrogen from a recycle stream at the top of the
reactor, at the bottom of the reactor, and/or in between.
24. The process according to claim 22, which comprises feeding the
additional hydrogen into the process as secondary injection into a
fluidized bed.
25. The process according to claim 16, which comprises feeding
additional steam into the process, by feeding at the top of the
reactor, at the bottom of the reactor, and/or in between.
26. The process according to claim 25, which comprises feeding the
additional steam into the process as secondary injection into a
fluidized bed.
27. The process according to claim 16, which comprises processing
in an additional bed of active carbon, ZnO, or other metal oxides
for removing undesired species including H.sub.2S and COS.
28. The process according to claim 27, which comprises effecting a
water removal process prior to the bed of active carbon, ZnO or
other metal oxides to enhance a separation efficiency (e.g., by
means of a membrane).
29. The process according to claim 16, which comprises additionally
removing carbon dioxide.
30. The process according to claim 16, which comprises additionally
feeding in steam, followed by a second methanation step.
31. The process according to claim 16, which comprises additionally
feeding in steam, followed by a second methanation step carried out
in a fluidized bed reactor.
32. The process according to claim 30, which comprises additionally
removing carbon dioxide.
33. The process according to claim 16, which comprises additionally
removing water.
34. The process according to claim 16, which comprises additionally
removing hydrogen.
35. The process according to claim 34, which comprises returning
the hydrogen removed in the additional removal step in a recycle
stream fed into the first methanation unit.
36. A method for converting a raw gas into a methane-rich and/or
hydrogen-rich gas, which comprises the following steps. a)
providing raw gas originating from a coal and/or biomass
gasification process, the raw gas including a content of methane
and hydrogen and a content of carbon monoxide, carbon dioxide,
alkanes, alkenes, alkynes, tar, COS, hydrogen sulfide, and organic
sulfur compounds; wherein a ratio of hydrogen to carbon monoxide
ranges from 0.2 to 5; b) bringing the raw gas into contact with a
catalyst arranged as a fluidized bed reactor at temperatures above
200.degree. C. and at pressures equal or larger than 1 bar in order
to convert the raw gas into a first product gas, thereby
simultaneously converting organic sulfur components into hydrogen
sulfide, reform tars, generating water/gas shift reaction, and
generating methane from the hydrogen/carbon monoxide content; c)
introducing the first product gas into a sulfur absorption process
to generate a second product gas, thereby reducing a content of
hydrogen sulfur and COS from 100 to 1000 ppm down to 1000 ppb or
less; d) optionally bringing the second product gas into a carbon
dioxide removal process to generate a third product gas
substantially or completely free of carbon dioxide; e) introducing
the third product gas into a second methanation process to generate
a fourth product gas having a methane content above 5 vol %; f)
optionally bringing the fourth product gas into a carbon dioxide
removal process to generate a fifth product gas substantially or
completely free of carbon dioxide; and g) introducing the fifth
product gas into an hydrogen separation process in order to
separate a hydrogen rich gas from a remaining methane-rich gas
(substitute natural gas).
37. The method according to claim 36, wherein the raw gas contains
at least one of benzole, naphthalene, and thiophenes.
Description
[0001] The present invention relates to a method for converting
coal or biomass to at least almost sulfur-free substitute natural
gas. Further, the invention relates to a process to produce a
methane rich gas mixture from gasification derived sulphur
containing synthesis gases.
[0002] In particular, the present invention relates to a continuous
production process of synthetic natural gas (SNG) from biomass,
coal or naphta. More specifically, the present invention relates to
the production of clean gaseous heating fuels from these less
valuable sulphur containing hydrocarbonaceous materials.
DESCRIPTION OF THE PRIOR ART
[0003] The production of SNG from biomass is the conversion of a
"dirty/difficult" fuel into a clean burning well known commodity.
The costumer has the freedom to use the SNG for power generation,
heating or mobility. A big plus is the already existing
infrastructure such as pipelines and compressed natural gas (NG)
cars. To insert the product gas of the methanation into the grid it
has to be cleaned of CO.sub.2 and compressed to 5 to 70 bars to
meet the standards of average natural gas.
[0004] The conversion of biomass to SNG is a complex process, which
can be structured roughly into four main units; gasification, raw
gas cleaning, fuel synthesis and gas sweetening. A solid feed is
thermally converted to a raw gas and subsequently cleaned of
particles, tars and sulphur. In the fuel synthesis, the raw gas is
converted into raw SNG (a CH.sub.4/CO.sub.2 mixture) that is
cleaned from CO.sub.2 and optionally H.sub.2 (gas sweetening)
before injection into the natural gas grid.
[0005] The presence of sulphur in the feedstocks leads to the
formation of H.sub.2S, COS or organic sulphur species, depending on
the temperature of the gasification. Low temperature (LT)
gasification promotes the formation of organic sulphur species such
like thiophenes, mercaptanes and thio-ethers, whereas high
temperature (HT) gasification leads to the formation of exclusively
H.sub.2S and COS.
[0006] The typical raw gas composition of HT and LT gasification is
shown in table 1.
TABLE-US-00001 TABLE 1 Low Temperature gasification High
Temperature (600-1000.degree. C.) gasification (1000-2000.degree.
C.) H.sub.2, CO, CO.sub.2, H.sub.2O H.sub.2, CO, CO.sub.2, H.sub.2O
CH.sub.4 a few ppm alkanes, alkenes, alkynes nil (especially
ethylene) Tars (Naphtalene, . . . ) nil H.sub.2S, COS H.sub.2S, COS
Org. S-species (mercaptanes, thio- nil ethers, thiophenes HCN,
NH.sub.3 HCN, NH.sub.3 Org. N-species (e.g. pyridine) nil
[0007] For the synthesis of SNG, LT-gasification is advantageous
(higher overall cold-gas efficiency), as the raw gas contains
already substantial amounts of CH.sub.4. Drawbacks of this kind of
raw gas are the high amount of poisonous components, such as
alkenes, alkynes, H.sub.2S, COS, organic S-species, HCN, NH.sub.3,
organic N-species.
[0008] For that reason, an efficient gas cleaning is required to
protect the catalysts applied in the fuel synthesis. An example of
a state of the art to produce synthesis gas for applications such
as Fischer-Tropsch-Synthesis or production of Methanol, DME, and
SNG is shown in FIG. 1a.
[0009] A scrubber at low temperatures is used to remove the tars
and the organic S-species and N-species. H.sub.2S, COS are absorbed
on solid absorbers available for this duty (active carbon, ZnO or
other metal oxides . . . ). In general, the gas cleaning is
followed by a Water-Gas-Shift reactor, CO.sub.2-seperation and
multiple methanation units. To increase the calorific value of the
gas to the quality limits of the gas grid, CO.sub.2 and H.sub.2 is
removed. The order of units 4-9 can be different.
[0010] Disadvantage of this process scheme is the high number of
operation units and the different temperature levels of the units
(especially cooling down to the scrubber temperature). To avoid
this kind of temperature gradients in the process, the use of raw
gas from a HT-gasification is common, an example of such process is
shown in FIG. 1b (U.S. Pat. No. 3,928,000, EP 0,120,590). The
different gas composition enables S-resistant Water-Gas-Shift (WGS)
and S-resistant Methanation and lowers the amount of operation
units. However, the raw gas composition is less favorable for the
SNG synthesis as the SNG composition results in higher energetic
losses.
[0011] First, the energetic effort in the gasification unit is
higher for the production of pure H.sub.2, CO, CO.sub.2-mixtures;
secondly the pure H.sub.2, CO, CO.sub.2-mixtures result in higher
thermal losses in the synthesis due to the exothermic enthalpy of
the methanation reaction.
DESCRIPTION OF THE INVENTION
[0012] By means of the subject process, the unfortunate temperature
level sequence and the number of operation units of the process
shown in FIG. 1a as well as the energetic losses of the process
shown in FIG. 1b can be avoided. A methane-rich stream can be
produced from sulphur containing feedstocks containing 10 to 95 mol
% of methane.
[0013] The first step following the Low-Temperature-gasification is
a multifunctional process unit featuring
hydrodesulphurization/denitrogenation, methanation, WGS, tar
reforming and cracking and the hydrogenation/reforming of alkenes
and alkynes simultaneously. The H.sub.2S produced from the organic
sulphur species by hydrolysis and the COS are removed by absorption
on common absorber materials such like ZnO, CuO. CO.sub.2 can be
removed before or after the 2.sup.nd methanation step. For the
adjustment of the calorific value excess H.sub.2 is separated and
may be recycled to unit 2.
[0014] The hydrodesulphurization unit (HDS) is a common process
step for the desulphurisation of feedstocks in the petrochemical
industry or of natural gas before steam reforming. The applied
catalysts for these units tend to catalyse both methanation and
watergas shift reaction which is unwanted as these exothermic
reactions may lead to a thermal runaway of the reactor. In the
subject process, however, the methanation and WGS-reactions are
desired.
[0015] To control the temperature rise due to exothermic reactions,
a fluidised bed reactor equipped with means for heat removal can be
applied. The catalyst fluidisation offers additionally the
potential for internal regeneration of the catalyst from carbon
deposits caused by compounds like ethylene or tars in the
LT-gasifier producer gas. Such an internal regeneration can be
found for fluidised bed methanation and can be enhanced by staged
addition of recycle H.sub.2 and/or steam in the upper part of the
fluidised bed.
[0016] Moreover, the raw gas stream leaving the unit can be
tailored to the requirements of a 2.sup.nd methanation unit to
minimise the total number of process units by the addition of
steam, H.sub.2 from the recycle and the proper choice of
temperature and pressure. alkenes and alkynes simultaneously. The
H.sub.2S produced from the organic sulphur species by hydrolysis
and the COS are removed by absorption on common absorber materials
such like ZnO, CuO. CO.sub.2 can be removed before or after the
2.sup.nd methanation step. For the adjustment of the calorific
value excess H.sub.2 is separated and may be recycled to unit
2.
[0017] The hydrodesulphurization unit (HDS) is a common process
step for the desulphurisation of feedstocks in the petrochemical
industry or of natural gas before steam reforming. The applied
catalysts for these units tend to catalyse both methanation and
watergas shift reaction which is unwanted as these exothermic
reactions may lead to a thermal runaway of the reactor. In the
subject process, however, the methanation and WGS-reactions are
desired.
[0018] To control the temperature rise due to exothermic reactions,
a fluidised bed reactor equipped with means for heat removal can be
applied. The catalyst fluidisation offers additionally the
potential for internal regeneration of the catalyst from carbon
deposits caused by compounds like ethylene or tars in the
LT-gasifier producer gas. Such an internal regeneration can be
found for fluidised bed methanation and can be enhanced by staged
addition of recycle H.sub.2 and/or steam in the upper part of the
fluidised bed.
[0019] Moreover, the raw gas stream leaving the unit can be
tailored to the requirements of a 2.sup.nd methanation unit to
minimise the total number of process units by the addition of
steam, H.sub.2 from the recycle and the proper choice of
temperature and pressure.
* * * * *