Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROCESS FOR HYDROGENATION OF COAL
The invention relates to a process for hydrogenation of coal,
in which the coal is mixed with an emulsifier oil to form a slurry.
The slurry is pumped to reaction pressure, heated and is then
subjected to catalytically accelerated hydrogenation in the pres-
ence of hydrogen.
A process for the hydrogenation of coal is known in which the
coal is dried and in pulverized form is mixed with emulsifier oil,
and the coal slurry obtained is then pumped to reaction pressure,
and is heat exchanged with a portion-of the subsequent reaction
products. The slurry is then heated in a preliminary heater to a
temperature closa to that of the reaction by bringing in outside
heat, and is subsequently hydrogenated in a reactor, in the
presence of hydrogen and a suitable catalyst. The product frac-
tion leaving the reactor is fractionated in a subsequent heat
exchanger into a vaporous main fraction comprising gases, benzenes,
and distillation oils, and a liquid base fraction comprising un-
rea~ted coal, ashes, catalyst particles, as well as other high-
molecular substances which are difficult to hydrogenize, such asasphaltenes, in particular, as well as bitumen and heavy oil.
While the main fraction is cooled by heat exchange with the
coal slurry and is being drawn off by the charge, the heavy oil is
separated from the base fraction and is utilized as an emulsifier
~5 oil for the incoming coal.
Disadvantages of this known process are its high energy
consumption as well as its considerable equipment expense.
Thus the entire coal charge must be dried in a special drier
using outside heat. For example, if the charge consists of bitum-
inous coal with an average water content of about 8~, the dryingo~ a ton of coal requires an energy output of about 0.1 Gcal Igram
calories). Moreover, the coal has to be pulverized in an expensive
process to a particle size of <0.1 mm.
In the known process hydrogenation occurs at relatively high
pressure, which is due to the fact that in the process of preheat-
ing the coal slurry to the hydrogenation start-up temperature of
approximately 410C. gas, separating as physically and chemically
bound water and lower hydrocarbons ~methane, ethane, etc.) reaches
the reactor. This causes a lowering of
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the partial pressure of the hydrocarbon which only can be compen-
sated for by increased total pressure in the reactor resulting in
turn in a requirement for increased pump energy and increased
equipment expense for reinforcing the reactor and other pressure
equipment.
A disadvantage of the known process is that heat exchange
for heating the coal slurry has proven to be difficult. As the
coal slurry has high viscosity, a uniform introduction of the coal
slurry into the areas of the heat exchanger is hard to achieve,
and additionally, the further heating of the coal slurry in the
preheater presents difficulties since the coal suspended in the
slurry greatly expands as a result of the prevailing high tempera-
tures. This results in a further increase in viscosity so that in
the end, only a pulsating passage of the coal slurry through the
preheater is possible, which causes considerable abrasion and wear
to the equipment. In this connection, pressure shocks of up to 10
bar can occur.
The objective of the present invention is directed to a pro-
cess for the hydrogenation of coal mentioned above, wherein there
are improved economics in energy consumption and equipment expense.
The invention achieves this objective in that at least a
portion of the hot product gases, resulting from the hydrogenation,
are intimately mixed with the coal slurry under pressure, and that
the gases can be separated from the resultant mixture of gases,
liquids and solids, and the remaining mixture, consisting of solids
and liquids, can be hydrogenated.
The intimate mixing of the incoming coal slurry, already
pumped to pressure, with the hot gases occurring as a reaction pro-
duct at the top of the hydrogenation reactor, or at the top of the
heat separator - if there is one subsequent to the reactor -
greatl~ enhances heating of the coal slurry Thereby all of the
physically bound, and a portion of the chemically bound water
contained in the coal is withdrawn. In the course of this heat
exchange, the coal is completely dried, and a significant feature
is that the usual costly drying step in the coal preparation
process, can be dispensed with.
Another important advantage is that due to the high tempera-
ture attained by the coal in direct heat exchange with the hot
product gases from the hydrogenation, other gases contained in the
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coal, like methane, ethane and others, are released. The
coal entering the hydrogenation process following heat exchange
thus is already essentially free of gas, reducing formation of
gases in the hydrogenation reactor itself. This in turn leads to
an increased hydrogen partial pressure in the reactor, enhancing
hydrogenation effectiveness. In comparison to known processes,
hydrogenation can now be carried out at a lower total pressure,
thereby making it more economical in both initial investment and
operating costs.
The combination of gases, liquids and solids, which result
from the intimate mixing of the hot product gases and the coal
slurry, is fractionated in a heat separator downstream to the
mixing device. The heated base product from the separator, now
comprising distillation oils condensed from product gases in
addition to the coal slurry, is directly carried to the hydrogena-
tion reactor. The gases formed at the top of the s~parator are
further cooled by the hydrogenation of hydrocarbon. The distilla-
tion oils, condensed during cooling, are processed in a distilla-
tion facility, while the remaining gases are washed and the
hydrocarbon recovered in the process is recycled. Further treat-
ment of the recovered distillation oils can be carried out in a
distillation facility without difficulty because all non-distilla-
ble components, like entrained asphaltenes, and others, which
originally were part of the hot product gases in the hydrogenation
reactor, have already been washed out in the process of the direct
heat exchange with the coal slurry, and together with the slurry,
are returned to the hydrogenation reactor.
Another essential advantage of this process is that the heat-
ing of the incoming coal slurry to hydrogenation start-up tempera-
ture does not require heat exchangers charged with the coal slurry.The largest portion of the heat required is introduced in the
form of exothermic reaction heat in the process of mixing the hot
product gases. In a further feature of the invention, additional
heat which may-be required can be obtained either by heating of
the hydrogenation hydrocarbon and/or by mixing the coal slurry
- ~ith a heated distillation fraction from the distillation plantr
mentioned above.
Moreover, the costly pulverizing of the coal to an average
size of ~ 0.1 mm becomes unnecessary as the coal, on its way to
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the hydrogenation reactor, only passes through pipes, instead of
passing through heat exchangers, where it could cause deposits.
A device for carrying out the process is characterized in that
the exit of the high-pressure pump for the incoming coal slurry and
the top of the hydrogenation reactor are in communication with the
inlet of a mixing device, the exit of the mixing device is in comm-
unication with a se~arator, and the bottom of the separator is in
communication with the inlet of the hydrogenation reactor. Further
details of the invention are depicted by way of a schematic.
The drawing shows schematically a process for the hydrogenatlon
of coal, in which the coal to be processed, without previous drying
and having a water content of about 6% and a particle size of up to
2 mm, is fed to an emulsifier vessel 4 via line l and is mixed with
emulsifier oil which is entering via line 2. The catalysts required
for the hydrogenation, e.g. alloys of metals of Groups IV, VI and
-~III of the Periodic System, or combinations thereof, are supplied
via line 3 and mixed with the coal or sprayed onto it, respectively.
In the emulsifier vessel 4, the slurry has a ratio of 70~ by weight
coal to approximately 30% by weight oil.
The coal slurry is pumped to a pressure o~ approximately
200 bar by pump 5 and is carried directly to the lower region of
mixing device 8. At the same time, mixing device 8 is supplied
with hot product gases from the top of hydrogenation reactor 22
via line 7. These gases, which in addition to hydrogen, water
vapor and low-boiling hydrocarbons like methane! ethane, etc.
essentially contain distillation oils in the naphtha-, medium-
and heavy oil range, have a temperature of approximately 470C.
and are intimately mixed with the incoming coal slurry in mixing
device 8. Mixing device 8 advantageously consists of a simple,
vertical pipe.
Due to the rapid mixing, the temperature at the exit of
mixing device 8 is approximately 400C., which aids in the removal
of all water contained in the coal, and even a portion of the
shemically bound water, as well as highly volatile gases, like
methane, ethane, etc.
The contents of mixing device 8, having been thoroughly
mixed, is directed to separator 9, where it is separated into
a gaseous and a solids-liquid phase. The solids-liquid phase,
now consisting of dried coal and partially degassed coal, in
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addition to emulsifier oil, heavy oil and entrained asphaltenes
from the product gases, which have been condensed and washed out
during the mixing process, are now fed directly to hydrogenation
reactor 22 by pump 19 via line 20.
The gaseous phase of separator 9 is further cooled and there-
by partially condensed in heat exchanger 10, and directed to
separator 11. The top product of separator 11 reaches a wash
facility 12 and is subjected there to an oil wash. Hydrogen-free
residual gas is withdrawn via line 13, while the remaining hydro-
gen is mixed with fresh hydrogen entering via line 14, is then
carried to heat exchanger 10 via line 17, then to furnace 18 for
further heating and finally is returned to the hydrogenation
reactor via line 21.
The bottom product of separator 11, essentially a fraction
consisting of naptha-, medium-, and heavy oil, as well as water,
is directed via line 15 to distillation plant 16, where it is
separated into the different product fractions.
If additional heat is required for heating of the fresh coal
slurry, a heavy oil fraction is extracted from distillation plant
16, heated in a heat exchanger 26 by an outside heat supply and is
then added to the incoming coal slurry, vi-a line 6.
The liquid portion of the product occurring in the hydrogena-
tion reactor is directed to vacuum distillation facility 24 via
line 23. The heavy oil thus recovered flows in the form of
emulsifying oil towards container 4 via line 2, while the solids-
containing distillation residue is with drawn from the facility
via line 25. The residue can be further processed in a gasifica-
tion plant (not depicted) for the production of hydrogen.
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