Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a process for the generation
of electric power.
Electric power can be generatled by burning fossil
fuels and directly utilizing the gases liberated thereb~
to drive a power-gsnerating turbin~, or utilizing the
said gases for producing steam with whioh a turbine for
the said object can be driven. When fuels are used whlch
contain considerable quantities of sulphur (and this will
generally be the case), large quantities of sulphur
oxides are formed. Before the combustion gases are
discharged to the atmQsphere, at least most of the sulphur
oxides must be removed therefrom in order to minimize
environmental pollution. Although such a removal is
possible per se, for example as described in the ~K
patent application No, 1,089,716, in a number of cases,
removal of sulphur dioxides from the combustion gases will
for economic reasons not be attra¢tive. If the sulphur
oxides-containing gases are directly utilized to drive a
power-generating turbine, they will moreover at a certain
temperature have an unaoceptable corrosive effe¢t on the
materials of the said turbine, whioh restricts the
temperature range in which the gaaes can be utilized to `~
drive a turbine.
It is also possible to burn the fuel partially, i.e.
by burning with a deficiency of oxygen or air largsly to
; ` convert it into ¢arbon monoxide and hydrogen. This
combustion is generally carried out under pressure. In
this process the bound sulphur present in the fuel will
be largely converted into hydrogen sulphide. This
hydrogen sulphide can be removed from the resultant gas
mixture, after which the gases can be burnt completely and
the essflntially S02-free combustion gases utilized to drive
a power-generating turbine. ~he gases formed during the
partial combustion of the fuel will generally also ¢ontain
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not inconsiderable quantitie~ of carbon dioxide. In the
removal of hydrogen sulphide with liquid basic absorbents
the problem now arises that carbon dioxide is absorbed
into the said absorbents together with hydrogen sulphide.
After desorption of the gases from the said absorbents,
mixture6 of carbon dioxide and hydrogsn sulphide are
obtained which contain relatively large quantities of
carbon dioxide. If it is desired to convert the hydrogen
sulphide present in these mixtures into elemental sulphur
(for example by means of a Claus process), the objection
is encountered that the carbon dioxide present, which
behaves as an inert gas in the Claus process, neces6itates
the u6e of large (and therefore expensive) Claus plants,
and moreover has an adverse effect on the heat balance
of the Claus plant.
~oreover, it is preferred to remove the smallest
possible quantity ~ carbon dioxide from the gas mixture ~ -
obtained during the partial combustion of the fuel,
because the said carbon dioxide also contributes to the
supply of energy to the power-generating turbine. ~hi~
contribution can be very considerable; the difference in ;i
the total output of the power station may be 0.3~,
depending on whether substantially no or substantially all
carbon dioxide is removed from the gas mixture obtained
during the partial combustion of the fuel.
The invention provides a process in which the said
problems are obviated and a power-generating turbine is
driven with the energy from a sulphur-free gas, and in
which hydrogen sulphide i6 obtained in such a concentrated
form that it can readily be processed into elemental
sulphur (preferably by means of a Claus process).
The invention therefore relates to a prooess for
the generation of electric power, characterized in that
a heavy liquid or a solid sulphur-containing fuel is
partially burnt, the combu~tion gases are cooled, the
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hydrogen sulphide is removed from the combustion gaees by
absorption in an aqueous solution of a tertiary amine, the
absorbed hydrogen sulphide is liberated and converted into
elemental sulphur, the gases obtained after the absorption
of hydrogen ~ulphide in the aqueous solution of a tertiary
amine are burnt and a power generating turbine is driven
with the resultant energy.
Use may very suitably be made of a distillate fraction
of a mineral oil as liquid sulphur-containing fueln
Preference is given to heavy fuel oils consisting entirely
or partially of a distillate residue of a mineral oil or
asphalts. Lignite and coke~ and in particular coal, are
very suitable as solid sulphur-containing fuel. It is
also possible to use fuels in which solid constituents
(e.g. coal) are dispersed in liquid constituents (e.g.
a residual fuel oil).
The partial combustion of the fuel may be carried
out by burning in the presence of a quantity of air or
oxygen which is at least sufficient to convert all the
boun-d~carbon and hydrogen present in the fuel into carbon
monoxide and hydrogen. If desired, water or steam is also
added to the fuel prior to the partial combustion.
` In general, the combustion will be carried out under
pressure; pressures from 5 to 50 kg/cm2 are very suitable.
The gas obtained during the partial combustion, which
gas contains largely ~2 and also C0, H2, C02 and H2S, is
cooled, generally to a temperature between room temperature
and 100C, in partioular between 20 and 70C, and if
desired, solid oonstituents such as coal and metal oxides
~30 are removed therefrom, for example by washing with water.
The heat resulting from the cooling i8 very suitably
utilized for the production of steam, for example in a
waste heat boiler.
The H2S i6 removed from the gas obtained during the
partial combustion by absorption in an aqueous solution
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of a tertisry amine and this treatment is preferably oarried
out without reducing the pressure of the gas mixture. In~
order to keep the absorption of C02 in this solution as
low aQ pos~ible, it is preferred to use a tertiary amine
containing at least one hydroxy alkyl group, such as tri-
ethanol amine. Most preference i9 given to tertiary amines
containing one alkyl group a~d two hydroxy alkyl groups, in
particular to methyl diethanol amine. ~se i~ very auitably
made of an aqueous solution containing 1-5 mol/l of the
tertiary amine.
If desirèd, physical solvents for H2S may also be
incorporated in the aqueo~s solution of a tertiary amine,
which solvents may be, for example, sulfolane, N-methyl ~ -
p~rolidone, dimethyl formamide.
The gases are very suitably contacted counter-
currently with the absorbent in an absorption tower
which is filled with filling elements, such as Raschig
rings and/or contains a number of contact tray~.
The gases absorbed in the aqueous solution of the
tertiary amine are suitably removed therefrom by heating
and/or stripping with steam. As a result of the fact that
in the process acoording to the invention only a small
quantity of carbon dioxide is absorbed in the aqueous
solution of the tertiary amine, the quantity of steam ~;-
required for stripping is smaller than when use is made
of other absorbents for acid gase~ which ab~orb more
carbon dioxide. Moreover, the quantities of liquid
absorbents can be much smaller in the former case than in
the latter case, 80 that the plants for the absorption of
~0 the acid gases and those for the steam stripping of the
absorbent loaded with acid gases can be of smaller
dimensions.
The resultant gases, which consist predominantly
of E2S and C02, can be passed to a Claus plant, where the
~5 ~2S is converted to elemental sulphur. If the C02 content
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of the aforementioned resultant gases is still too high
to be able to readily process these gases in a Claus
plant9 they are very suitably treated once again with an
aqueous solution of a tertiary amine, for example in a
separate absorption tower and preferably at atmospheric
pressure. The gas not abaorbed in this second absorption
step (which consists predominantly of C02) can (if desired,
after combustion of the traces of ~2S present therein)
be discharged to the atmosphere. ~he gases absorbed
in the second absorption step are (if desired partially)
liberated from the loaded aqueous solution of a tertiary
amine by means of heating and/or stripping with steam
- a~d the resultant gases, which consist entirely or
substantially entirely of H2S, oan readily serve as feed
for a Claus plant.
~he gases obtained after the treatment with an
aqueous solution of a tertiary amine, which gases are now
entirely or substantially entirely free of sulphur compounds,
are subsequently burnt further. The resultant energy can
be used for the production of steam, with whioh a turbine
is driven-for the generation of current.
It is preferred that the resultant combustion gases
themselves are used for driving a turbine for the generation
of electric power, i.e. that use is made of an expansion
turbine. As has been expounded above, the absence of
sulphur oxides in the gases allows higher gas temperatures
to be used for the turbinej which improved the efficiency
of the power~~enerating prooess. These inoreases in efficienoy
~; are approx. 1~o per 100C inorease in inlet temperature.
The gases leaying the turbine are oooled with water, - -
as a result of whioh steam is obtained with whioh, if
desired, a steam turbine for the generation of eleotrio
power is driven, and subsequently discharged to the abmo-
sphere. ~ere a~ain, the absenoe of sulphur oxides is found
to be an advanbage~ since the gases oan be cooled to a
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274 ::
temperature below the dewpoint of ~ulphur oxiaes (and thus
more heat can be withdrawn therefrom) before they are
discharged to the atmosphere.
By way of illustration a diagrammatio example of an
embodiment of the invention is given with reference to
the accompanying Figure. Air supplied through line 1 is~
compres6ed in the compressor 2 and after having been
recompressed in the booster compressor 3 is mixed with
fuel, supplied through line 4. Partial combustion takes
place in the reactor 5 and a proportion of the heat
liberated i9 utilized for the production of steam in the
waste heat boiler 6. The ~ombustion gases are further
cooled in the cooler 7 and then, in order to remove carbon
and ash, scrubbed with water in the scrubbing tower 8 from
which carbon and ash are removed through line 9. ~he
combustion gases are then treated in the scrubbing tower 10
~ with an aqueous solution of methyl diethanol amine in order
; to remove H2S. The loaded methyl diethanol amine solution
is removed through line 11. ~y steam stripping in the
column 21 the H2S is liberated and passed through line 22
to the Claus plant 23, from which it becomes available
as sulphur through line 24. The gases freed of H2S are
subsequently mixed with compressed air (supplied through
line 12) and completely burnt in the reactor 13. The
resultant combustion gases are used to drive the turbine 14,
with which electric power is generated. ~he gases leaving
the turbine 14 are passed to the offgas boiler 15, in which
steam originating from the waste heat boiler 6 (supplied
through line 16) is heated further. ~his steam is used to
~ drive the steam turbine 17, with which electric power is
generated. ~he steam leaving this steam turbine is
conden~ed in the condenser 18 and the resultant water is
recyoled by means of the water pump 19 through line 20 to
the waste heat boiler 6 through the cooler 7.
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EXAMPLE
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An asphalt obtained by treating a mineral oil
distillation residue with liquid propane (known as a
propane asphalt~ was heated to 350C and partially
burnt at a temperature of 1400C and a pressure of
14 bar by means of air heated to 410C. ~he ~able shows
the composition of the propane asphalt and the gas
obtained therefrom (not taking water into account). ~he
resultant gas was cooled to 40C, and treated with an
aqueous solution of methyl diethano:L amine containin~ 24 g
of methyl diethanol amine per litre. ~he solution loaded
with acid gases was stripped with steam at atmospheric
pressure; the resultant gas mixture contained ~2S and
C2 in a weight ratio of 1.46 and was supplied to a Claus
plant in which the H2S wa~ converted to elemental sulphur.
~he combustion gas freed of ~2S had the oomposition,
not taking water into account, stated a~ "sulphur-free
MDEA gas" in the Table. A calculation was made of the
total output of the plant assuming that this gas wa
burnt with air at a pres~ure of 10 atm., a power-
generating turbine was driven with the oombustion gases
(inlet temperature of the gases 950C), and with the
-l~ gases leaving the turbine steam was prepared and used to
drive a steam turbine. ~his total output was 37.1%.
For purposes of comparison, the same experiment was
carried out but instead of an aqueous ~olution of methyl
diethanol amine, a solution of 27 g of di-isopropanol
amine per litre of water was used. ~he composition of the
. ~ ~
resultant gas is shown in the ~able as "sulphur-free ADIP
gas". A calculation was made of the total output if this
; gas had been further burnt in the manner a~ described
above, and used for the generatlon of power. The total
- output of the installation in this ca~e was 36~.
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.`~ g
~ A~LE
iPropane a8phalt Combustion~gas rulphur-free Sulphur-free
¦ I ~ M~ gaB ~ ADIP ~a~
composition i Composition l,¢omposition oomposition
~ . l . __ . _................. __
compo- j %w compo- ~w compo-I ~w compo- yOw
nents nent~ nents nent~
~, . . . . . . , __ __ _ ' ' .
C 83.6 C022-74 C02 2.24 C021.40
H 9-4 C023.04 C0 23.33 C023.53
S 6.56 H213.33 E2 13-50 X213~61 :- : -
N 0.29 H2S0.73 H2S 0.002 ~2S0.002
0 0.05 COS0.03 COS 0.02~ COS0.028
aB 0.10 CH4 '3C~4 -3 C~4 -3 .. .
H20 , _ H20_ E20 _
N259-39 N260.15 N2~ 60~67
0.71 A0.72 A0.73
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