Note: Descriptions are shown in the official language in which they were submitted.
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A Hydrogenation Gas Routing in Coal Liquefaction Plants
The present invention relates to a hydrogenation gas
routing in coal liquefaction plants, whereby the light and medium
oil that is obtained is being refined after hydrogenation.
orally, dried coal is mashed with solvent and hydra-
jointed by the addition of hydrogen. The products are separated
in the separators that follow the hydrogenation reactors. In hot
separators, the gases and vapors are drawn off at the head,
form a sup a liquid phase that contains the solids is drawn off
to a vacuum distillation.
The head product of the hot separator is passed to a
subsequent cold separator after cooling. In addition to the coal
oil water occurs here as the liquid phase from which valuable
contents (ammonia, phenol) are extracted in the subsequent stages
of the process.
The gas phase of the cold separator, which exits at the
head, is divide dafter oil washing that is conducted at process
pressure into circulating and output gas. The circulating gas is
returned to the hydrogenation after compensation for pressure loss
with a circulation-gas compressor. The output is cleaned in a gas
washer and broken down in a low temperature decomposition unit
into hydrogen, heating gas, SAG, and LUG. The hydrogen fraction
is mixed with the newly generated hydrogen of the hydrogenation.
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The coal oil is broken down into light, medium and heavy
oil in atmospheric distillation. The heavy oil is returned to the
mashing stage as solvent.
The light and medium oil fractions are in each instance
subjected to hydrogenating refinement for purposes of removing
sulfur, nitrogen, and similar undesirable components. To this
end, after the addition of hydrogen the crude light or crude
medium oil is vaporized and passed to solid-bed reactors. The
refinement is carried out on the Comma or Nemo catalyst layers.
In order to limit the temperature increase that is governed by the
reaction heat of the hydrogenation, quenching hydrogen is
channeled into the hydrogenation reactors. The emerging, refined
products are cooled in heat exchangers and by the injection of
quench water, and separated into refined product, water and gas in
separators. The state of the art is to return a part of the
H2-rich excess gas to the newly generated hydrogen of the
refinement as circulating gas after compensation for the pressure
loss with a circulating gas compressor, and to tap off the other
excess amounts of gas for cleaning and extraction of the hydrogen
and the gaseous hydrocarbons and return them to the appropriate
stages of the process.
The residue from the hot separator, which contains the
solids, is topped in a vacuum distillation. The heavy oil that is
extracted is returned, together with heavy and medium oil from the
atmosphere distillation, as a solvent, where it is used in the
mashing process.
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Synthesis gas (C0 + Ho) or, after hydrogenation and gas
washing, hydrogenating hydrogen is obtained in a gasification
stage.
If the hydrogen that is either returned or obtained
through residual gasification, low temperature fractionation or
circulation gas is insufficient for hydrogenation and stubbles-
lion, the shortfall can be made up by coal gasification with
subsequent conversion and gas cleaning, or by external procure-
mint.
It is the task of the present invention to simplify
hydrogenating gas supply and improve it from the point of view of
economy.
According to the present invention, the total quantity
of the gases resulting in the refining stages is supplied to the
newly generated hydrogen of the hydrogenation stage. That is to
say, there is no division of the hydrogen-rich gases coming from
the refining stages into circulating and excess gas, the total
quantity being passed to hydrogenation. The organic (Of- C4) and
inorganic (C0, C02, HIS) gaseous compounds that occur during
refining and are contained in the gas in addition to hydrogen have
no effect on the hydrogenation of the coal in the concentrations
that exist here.
According to the present invention there is further
provided a method of coal liquefaction comprising the steps of:
a) mashing incoming coal with solvent;
b) hydrogenating the mashed coal from step a) with
hydrogen to produce products of hydrogenation;
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c) refining said products of hydrogenation in a
plurality of stages to obtain hydrogen-rich gases and other
products comprising coal oil; and
d) recycling substantially all of said hydrogen-rich
gases, from at least a predetermined one of said plurality of
stages, produced in step c) back to the said hydrogenation step
for hydrogenation of said incoming coal.
Preferably step c) includes distilling of oil into
fractions and recycling substantially all of the hydrogen-rich
gases obtained back from said distilling to said hydrogenation
step. Also, preferably step c) includes hot separating the
products of hydrogenation, and then cold separating output
products from said hot separating step, and then at least
collecting a portion of gases collected from an output of said
cold separating step back to said hydrogenation step.
Particularly preferred in step c) is distilling of oil into
fractions and recycling substantially all of the hydrogen-rich
gases obtained from said distilling back to said hydrogenation
step.
Preferably when distilling oil into fractions and light
oil and medium oil are produced. These oils are then refined
further in separate stages for the light and medium oils
(particular preferred in each case is atmospheric distilling) and
substantially all the hydrogen rich gases from each separate
refining stage are recycled back to the hydrogenation step.
A preferred embodiment of the invention comprises a
method of coal liquefaction comprising the steps of:
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a) mashing incoming coal;
b) hydrogenating the mashed coal from step a) with
hydrogen to produce products of hydrogenation:
c) refining said products of hydrogenation in a
plurality of stages to obtain coal oil whereby hydrogen-rich gases
are produced;
d) said refining including distilling said coal oil into
at least a light oil fraction and a medium oil fraction which oil
fractions are refined further in a separate stage for the light
oil and a separate stage for the medium oil; and
e) recycling back substantially all of said
hydrogen-rich gases from said light oil refining stage and said
: medium oil refining stage to said hydrogenation step.
Another preferred embodiment of the invention comprises
a method of coal liquefaction comprising the steps of:
a) mashing incoming coal;
b) hydrogenating the mashed coal from step a) with
hydrogen to produce products of hydrogenation;
c) refining said products of hydrogenation in a
plurality of stages to obtain coal oil whereby hydrogen-rich gases
are produced;
d) said refining of said products of hydrogenation
including further refining of said coal oil into at least a first
oil fraction and a second oil fraction which oil fractions are
refined further in a separate stage for the first oil fraction and
a separate stage for the second oil fraction; and
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e) recycling back substantially all of said
hydrogen-rich gases from said first oil refining stage and said
second oil refining stage to said hydrogenation step.
According to the division of the gas phase from the cold
separator into circulation and output gas, it is either extracted
or channeled off through the gas wash and low-temperature
fractionation stage with the same gaseous compounds that result
additionally during hydrogenation of the coal.
The omission of dedicated circulating gas compressors,
gas washers and hydrogen reclamation stages for refining the light
and medium oil is a significant advantage vis-a-vis investment and
operation.
The invention will be further described with reference
to the accompanying drawing which is a flow diagram of a
hydrogenating gas system according to the invention.
Dried coal is mashed with solvent in a mashing stage (1)
and hydrogenated in a reactor (2) during the addition of hydrogen.
Phase separation takes place in a hot separator (3) that follows
the hydrogenation reactor (2). The gases and the vapors are
20 drawn off at the head. The liquid phase that contains the solids
is drawn off for vacuum distillation (5) from the sup.
After cooling, the head product from the hot separator
is passed to a cold separator (4). Water as well as COAL OIL
occur here, and the water is pumped off separately for
reextraction of the valuable contents such as ammonia and
phenol.
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The COAL OIL is drawn off and atmospherically distilled
during the addition of strip steam in an atmospheric distillation
stage (6). Light and medium oil from the atmospheric distillation
stage are in each instance passed separately to refining stages
(21, 22).
The gas phase that exits from the top of the cold
separator is divided in a oil washing stage (7) into returned
circulating gas and output gas is cleaned in a gas wash I and
broken down in a low temperature fractionating plant into
hydrogen, heating gas, SUNG and LUG.
The liquid phase formed in the hot separator contains
the solids and is topped in the vacuum distillation stage (5).
The heavy oil so extracted is returned to the mashing stage (1)
together with heavy and medium oil from the atmospheric
distillation as solvent.
Synthesis gas (CO + Ho) is obtained in a gasification
stage (10) or Hydrogenating hydrogen is obtained in a conversion
and gas wash stage (11) from the residue of the vacuum
distillation.
If the hydrogen that is returned through circulating
gas, low temperature fractionation (9) and residue gasification
(10) it insufficient for hydrogenation, the shortfall is made up
through additional coal gasification (12) with subsequent
conversion and gas wash stage (13).
The waste water from the cold separator, which contains
tar acid of the atmospheric distillation stage is passed to an
ammonia extraction stage (23) and a phenol extraction stage (24).
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After biological processing (25) the waste water is run off into
the public sewer system. The waste water that occurs during
gasification (12) is run off in the same manner, and the waste
water that occurs from gasification of the residue (10) is
run off into the public sewer system after it has been
neutralized (26).
The circulation gas that occurs from the oil wash (7) is
compressed to the required operating pressure by means of a
circulating-gas compressor (27). In addition to the circulating
gas and the freshly generated hydrogen from the low-temperature
fractionation the total quantity for the hydrogen-rich gases that
emerge from the refining stages (21, 22) are supplied once again.
A mixture of these gases is supplied to the hydrogenation stage
(2) and compressed to the pressure required for hydrogenation by
means of a compressor (28).
Example
In a coal liquification plant used for hydrogenation of
a gas flame coal in the Wrier, with a throughput of 5,000 t (way)
coal/day, some 31,833 kg/h crude light and 64,006 kg/h crude
medium oil occur in the atmospheric distillation, this
corresponding to an hourly output of approximately 208 t/h.
The refinement of the crude light oil takes place in two
stages with the addition of 3,138 kg/h (stage I) and 2,587 kg/h
(stage II) hydrogen at a purity of vowel at 60 bar. In the
; separators that follow the refining reactors the hydrogen-rich gas
phase (total quantity 5,629 kg/h) is separated from the
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hydrogenation product at 55 bar. The total quantity of gas is
passed directly to the hydrogenating gas.
Refinement of the crude medium oil takes place in one
stage with the addition of 9,873 kg/h hydrogen (vowel), also
at 60 bar. The gas that occurs in the subsequent separator (9,565
kg/h) is once again passed directly to the coal hydrogenation
stage.
By enrichment at Of - C4 - hydrocarbon gas fractions as
well as at C0 - C02 and HIS quantities the hydrogen content of the
hydrogenating gas flowing through the refining stages falls to
vowel in the case of light oil, or to vowel in the case of
medium oil.
These Ho partial pressures lie essentially above that of
the hydrogenating gas of the coal hydrogenation (216,252) kg/h,
vowel), so that the feed presents no problems.
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