Note: Descriptions are shown in the official language in which they were submitted.
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Treatment of recycling gas for direct thermochemical conversion of high
molecular weight organic substances into low viscosity liquid raw materials,
combustibles and fuels
The invention relates to a method for the direct thermochemical conversion of
high
molecular weight organic substances into low molecular weight organic products
that
are liquid with a low viscosity at ambient temperature. Furthermore, the
invention
relates to a device for carrying out the method according to the invention.
Carbon-containing materials and material mixtures of preferably long-chain or
cross-
linked molecules are called high molecular weight organic substances, such as
occur, especially, in renewable raw materials and in materials from the waste
economy, such as, for example, biomass, wood waste, plants, plant oils, animal
fats,
bone meal, waste oils, plastic waste and effluent sludge. These materials or
material
mixtures form the preferred starting materials or raw materials for the method
according to the invention.
The aimed for low molecular weight products or target products, which are
present in
the form of low viscosity liquids at ambient temperature and can be combusted,
are
in particular high-grade, as far as possible pure hydrocarbons, such as
petrochemical combustibles and fuels, with only a small heteroatom fraction
(oxygen,
sulphur, nitrogen, halogens, phosphorus, etc), the intrinsic value of the
target
products being determined by the hydrocarbon fraction and increasing with it.
Methods for direct thermochemical conversion of high molecular weight organic
substances into low molecular weight products and devices suitable for this
are
known from the prior art. In these methods, also called direct liquefaction,
organic
solid material macro molecules are cracked or shortened at relatively low
temperatures to about 500 C until the molecule lengths are present in the
range of
the respectively desired low-viscosity liquid, the so-called product oil, as
the target
product.
Compared to conventional cracking processes in the vapour phase of a
conversion
reactor, it has proven accordingly to be especially advantageous if the
cracking
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reactions take place with preheating of the starting materials, optionally
including
required solid material catalysts, and with intensive intermixing of the
reaction
components in the sump phase of the reactor. In this case, the preheating
temperature depends on the cracking temperature or reaction temperature and is
preferably selected to be lower than this.
In combination with this conduct of the method, the reaction mixture is heated
by
shock heating in the range of seconds to the reaction temperature, which is
made
possible by the direct provision of the preheated starting materials in
crushed form in
the sump phase of the reactor and the intensive intermixing.
The poorly volatile product fractions being produced as reaction products in
the
reactor and the inorganic constituents of the starting materials have an
autocatalytic
effect, which has an advantageous effect on the reaction parameters of
duration,
pressure and temperature. The maintenance of the autocatalytic effect while
saving
additional catalysts is ensured by a return, provided according to the prior
art, of
these poorly volatile product fractions present as liquid heavy oils to the
reactor.
A method of this type is described in the patent application DE-A1-102 15 679,
which
was carried out with the cooperation of one of the inventors here. According
to this,
the thermochemical conversion or direct liquefaction of the high molecular
weight
organic starting materials into the high-grade low molecular weight target
products
mentioned takes place by a sump phase reaction at temperatures between 350 C
and 500 C utilising the autocatalytic effects mentioned of the poorly volatile
product
fractions guided in the circuit and furthermore utilising a selective, product-
oriented
residence time control, namely with immediate and targeted removal of the
cracking
products from the reaction zone, as soon as the molecular lengths thereof have
reached the area of the desired target product. This selective product-
oriented
residence time control is realised by the distillation and stripping
simultaneously
occurring in the reactor at the boiling temperature of the reaction mixture,
in that
components which can be evaporated or are volatile are removed from the
reaction
mixture, on the one hand, by means of transition using distillation into the
vapour
phase and, on the other hand, are transferred from the liquid phase into the
gas
phase by means of a carrier gas flow.
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In the case of starting materials with a lack of hydrogen and/or an increased
heteroatom fraction, a hydrogenating and/or reducing gas, preferably hydrogen
and/or carbon monoxide as the carrier gas flow, is guided through the liquid
phase in
the reactor, which is accompanied by a reduction in the reaction gas pressure
and by
a reduction in the hydrogenating catalyst requirement. The hydrogen is used
here to
stabilise the cracking products and improve the quality of the product oil.
The
hydrogenating effect of the hydrogen only occurs, however, at an increased
reaction
pressure, which is in turn dependent on the starting product. In starting
products
with a low heteroatom fraction, therefore with a great chemical similarity
between the
starting material and target product, both the process guidance under excess
pressure and the hydrogen component in the reaction gas can be dispensed with.
In
cases such as this, the thermochemical conversion preferably takes place at a
reduced reaction pressure or at negative pressure in the reactor.
The reaction mixture is generally present in the reactor in a gas-vapour
phase, a
liquid phase and a solid phase. The gas-vapour phase is composed here of the
reaction gas and the vaporous reaction products. The reaction gas comprises by-
products of the cracking reactions and optionally further components, for
example
the hydrogenating gas hydrogen. The vaporous reaction products are in the form
of
evaporated product oil hydrocarbons and - depending on the starting materials
used
- optionally water vapour. The liquid phase is formed by the poorly volatile
product
fractions present as heavy oils, while the solid phase, in addition to solid
reaction
residues, also has added solid material catalysts and non-volatile starting
materials.
According to DE-A1-102 15 679, the gas-vapour phase is separated by means of
phase separation from the liquid phase with the solid phase suspended therein.
This
liquid phase is then transferred by further phase separation into the poorly
volatile
product fractions, which are in turn returned to the reactor. The separated
gas-
vapour phase is split by means of condensation under reaction pressure into
the
reaction gas with reducing and hydrogenating fractions and into the vaporous
reaction products with condensable oil and water fractions. By separation, in
addition to the product gas, product oil, product water and aerosol are
obtained in
this manner. The hydrogen fraction is isolated by means of gas separation from
the
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reaction gas thus obtained and returned in its entirety to the reactor as
hydrogenating gas. The remaining reaction gas fraction is thus necessarily
also
returned as stripping gas to the reactor and/or used as combustion gas to
obtain
process energy, optionally after pressure compensation or relief in the case
of a
process conduct at excess pressure. If the conversion takes place under
increased
reaction pressure, this also supplies the preliminary pressure required for
the gas
separation and also contributes to a reduction in the compression energy
required to
return the hydrogen to the reactor.
Poorly volatile product fractions still present are isolated by distillation
from the
vaporous reaction products according to the teaching of DE-A1-102 15 679,
optionally after pressure relief in the case of a process conduct at excess
pressure,
said product fractions being in turn returned to the reactor. Owing to the
optionally
required pressure relief, gas fractions released in the liquid phase are
released and
are separated following the distillation by means of a further condensation
step and
used for the process energy supply. The liquid reaction products remaining
here
only still contain product oil and, depending on the raw material, water. The
latter is
optionally separated in a further phase separation step, so only the product
oil
desired as the target product remains.
To obtain additional hydrogen for return to the reactor as hydrogenating gas,
synthesis gas with components carbon monoxide and hydrogen is optionally
formed
from the water separated in this phase separation and from solid fractions of
the
poorly volatile product fractions returned to the reactor with the addition of
external
water by means of water vapour gasification according to DE-A1-102 15 679.
This is
then directly introduced into the reactor as a reducing and hydrogenating gas.
Optionally, alternatively or additionally to this, the synthesis gas, also
together with
the water obtained from the phase separation, in a carbon monoxide conversion,
is
completely transferred into hydrogen and carbon dioxide. The hydrogen obtained
in
this manner is then released from the carbon dioxide in a further gas
separation
process and introduced as the hydrogenating gas component into the reactor.
This
further gas separation is used to provide hydrogen from the reaction gas to
return to
the reactor and, by means of the separated reaction gas, to ensure the energy
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supply of the total thermochemical conversion and/or to also supply this as
stripping
gas to the reactor.
It is desirable from certain points of view to aim for improvements here.
Thus, the
reductions of hydrogenating components of the reaction gas required for the
thermochemical conversion in the reactor are already fixed with regard to the
quantity and composition with the selection of the starting material and
therefore not
accessible to further adjustment. This has the consequence that an optimal
utilisation of the gas fractions contained in the reaction gas is not
provided, which
has a limiting effect on the efficiency of the method and the quality and
yield of the
target products and leads to increased method costs.
In addition, the return of the reaction gas to the reactor is directly and
exclusively
determined by the reaction pressure prevailing there. To this extent, possible
pressure fluctuations in the reactor and inside the reaction gas circuit
therefore have
an effect on the reaction gas feed into the reactor such that the reducing,
hydrogenating and stripping effect of the reaction gas in the reactor likewise
fluctuates and the aimed for removal of the cracking products from the
reaction zone,
in other words, the method-specific selective product-oriented residence time
control,
can be disturbed, so ultimately the quality and yield of the target products
decrease.
Moreover, the reaction gas guided in the circuit purely caused by the large
number of
method steps to be run through, is subject to a considerable loss, which leads
to a
reduction in the efficiency of the method and therefore likewise to a smaller
target
product yield.
The present invention is based on the object of developing the method which is
very
advantageous and already described in DE-A1-102 15 679 taking into account the
above described facts in such a way that a method conduct is made possible, in
which the direct thermochemical conversion of high molecular weight organic
starting
materials in low molecular weight organic target products takes place with
improved
quality and a higher yield with overall lower method costs. It is furthermore
the
object of the invention to disclose a device for carrying out the method
according to
the invention.
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This aim is achieved by a method with the features of claim 1:
The invention is based on the concept of disclosing a method for the direct
thermochemical conversion of at least one high molecular weight organic
starting
material into low molecular weight organic products, which are liquid with a
low
viscosity at ambient temperature and can be combusted, comprising the method
steps:
(1) providing the starting material, poorly volatile product fractions and at
least one
reducing gas in a reactor,
(2) shock heating the starting material to the reaction temperature,
(3) converting the starting material at elevated temperature using the reduced
effect
of the gas and/or autocatalytic effects of the product fractions in vaporous
reaction
products and reaction gas,
(4) separating the reaction gas by means of condensation by removing the
condensed reaction products, the separated reaction gas
a) comprising hydrogen, methane and optionally further hydrocarbon products,
carbon monoxide and carbon dioxide in the case of oxygen-containing starting
materials and
b) comprising hydrogen, methane and optionally further hydrocarbons in the
case
of oxygen-free starting materials,
characterised by the further method steps of
(5) conditioning the separated reaction gas by means of
o discharging at least one part of the gas mixture and/or
o removing at least one part of the carbon dioxide or
o reforming at least one part of the carbon dioxide, the methane and/or
further
hydrocarbons or
o removing one part of the carbon dioxide and parallel reforming of at least a
further part of the carbon dioxide and at least one part of the methane and/or
further hydrocarbons or
o removing one part of the carbon dioxide and subsequent reforming of at least
a further part of the carbon dioxide and at least one part of the methane
and/or further hydrocarbons or
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o reforming one part of the carbon dioxide and at least one part of the
methane
and/or further hydrocarbons and subsequent removal of at least one further
part of the carbon dioxide and
optionally, additionally by means of the feeding of hydrogen and/or another
reducing
material, especially in the form of carbon monoxide and/ or tetralin,
(6) returning the conditioned reaction gas to the reactor to simultaneously
produce a
reducing, especially hydrogenating effect to convert the starting material
and/or a
stripping effect to discharge the product.
The alternatively disclosed method steps of conditioning the separated
reaction gas
in combination with the optional feeding of additional hydrogen therefore
allow an
adjustment of the components of the reaction gas effective for the method
according
to the quantity and composition and therefore also an adjustment of the total
gas
quantity returned to the reactor. Consequently, the simultaneous
hydrogenating,
reducing and stripping effect of the reaction gas in the reactor during the
conversion
of the starting materials can be controlled by means of the reaction gas
conditioning
according to the invention.
The gas conditioning is accordingly carried out in such a way that the
hydrogen
content of the reaction gas is sufficient to ensure, in the reactor, a
hydrogenating
atmosphere or the partial hydrogen pressure necessary for the thermochemical
conversion. The reducing atmosphere necessary for the oxygen degradation in
the
conversion reaction in the reactor is provided by the reducing effect of the
carbon
monoxide, methane and optionally further hydrocarbon components of the
conditioned reaction gas and advantageously assisted by the hydrogen
component.
The stripping effect of the conditioned reaction gas returned to the reactor
is ensured
by the returned total gas quantity. A possible deficit of hydrogen in the
separated
reaction gas, which can occur, for example, caused by the starting material,
is
compensated by means of the additional feeding of hydrogen during the
conditioning.
The advantageous effect of the method according to the invention, namely the
optimised conversion of the starting material in the reactor with simultaneous
cracking, distillation and/or stripping, is therefore produced from the direct
sequence
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of the method steps disclosed individually and is, to this extent, based on
the special
type of reaction gas guidance or circulating gas treatment.
The conditioning alternative disclosed to achieve the object according to the
invention to the separated reaction gas advantageously takes into account the
large
spectrum of starting products which can be used according to the method.
Depending on the respective starting material or the material components of
the raw
material used, the conditioning alternative is selected, with which an optimal
composition of the individual effective reaction components and total gas
quantity is
to be ensured with regard to the simultaneous hydrogenating, reducing and
stripping
effect for the conversion of the starting material in the reactor.
The removal of the carbon dioxide from the separated reaction gas or the
reduction
of the carbon dioxide fraction contained according to the first conditioning
alternative
may, for example, take place by means of a diaphragm separation process.
Carbon
monoxide, at least methane and optionally further hydrocarbons and hydrogen
remain as the important components in the reaction gas thus being produced, so
the
quantity of the effective gas fractions and the fraction thereof of the total
flow are
advantageously increased.
During the reforming of the carbon dioxide and the methane and/or the further
hydrocarbons disclosed as the second conditioning alternative, these
components of
the reaction gas are converted into carbon monoxide and hydrogen, so the
fraction
thereof in the total gas flow and the quantity of the effective gas fractions
are still
further increased compared to the first method alternative. A conversion of
this type
may, for example, take place in fixed bed reactors on platinum catalysts.
A still greater adjustability or optimisation of the effective gas fractions
and their
fraction in the total gas flow, therefore a further increase in quality of the
reaction
gas, is possible by combining the first two method alternatives.
According to the third conditioning alternative, the reaction gas separated
during the
condensation is subjected in two parallel method steps to a carbon dioxide
removal
and a reforming of the carbon dioxide, methane and/or the further
hydrocarbons.
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According to the fourth conditioning alternative, the removal of the carbon
dioxide
fraction firstly takes place in a first method step and immediately following
this, the
reforming of the separated reaction gas and optionally then still present
carbon
dioxide fractions and the fractions of methane and further hydrocarbons takes
place
in a second method step.
A serial sequence of the method steps also has the fifth conditioning
alternative,
according to which, however, the reforming of the fractions present in the
reaction
gas of carbon dioxide, methane and/or further hydrocarbons takes place as the
first
method step and immediately thereafter in a second method step, the removal of
the
optionally still present carbon dioxide fractions takes place.
Each conditioning alternative also comprises the feeding of hydrogen, to be
carried
out if necessary, into the separated reaction gas. This feeding preferably
takes
place immediately following the carbon dioxide removal and/or the reforming of
the
carbon dioxide, the methane and/or the further hydrocarbons.
According to the method of the invention, the quantity of the effective gas
fractions
and the fraction thereof in the total flow of the reaction gas can therefore
be modified
in an advantageous manner. Compared to the method known from DE-A1-102 15
679, the optimisation thus possible in the utilisation of the gas fractions
obtained in
the reaction gas leads to an increase in the efficiency of the method and to
an
improvement in the target product quality and yield with overall lower method
costs.
The further hydrocarbon may, for example, be ethane, propane and/or butane
without being limited thereto. The poorly volatile product fractions may
comprise
hydrocarbons with at least 18 carbon atoms, preferably with 20 to 40 carbon
atoms.
The boiling point at atmospheric pressure may preferably be between 350 C and
500 C.
Further advantageous embodiments of the method according to the invention
emerge from the dependant claims 2 to 16 and are described below:
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In the method of the invention, carbon-containing materials and/or material
mixtures
of long-chain and/or cross-linked macro molecules, especially in the form of
renewable raw materials as well as residual and waste materials, are
advantageously used as the starting materials. These include, especially,
biomass,
wood waste, plants, plant oils, animal fats, bone meal, used oils, plastics
material
waste and effluent sludge.
In view of the quality and yield of the target products, it is especially
advantageous if
the starting material and the reaction gas are provided in the liquid heavy
oil phase
of the reactor gas. However, provision of the reaction components in the
vapour
phase of the reactor is basically also possible.
The reaction temperatures and reaction pressures which are optimal for the
thermochemical conversion depend on the respective starting materials. For the
conversion of the raw materials preferably used in the method according to the
invention into the preferred target products, namely product oils, reaction
temperatures of 200 C to 600 C, especially 300 C to 500 C, at absolute
reaction
pressures of 0.1 bar to 300 bar, especially from 0.5 bar to 200 bar, are
preferably
required. Especially, it is advantageous in the preferred starting materials
with
elevated oxygen, sulphur or nitrogen fractions, if a reducing excess pressure
atmosphere prevails during the conversion in the reactor. This is preferably
formed
by the feeding of reducing gases such as, for example, carbon monoxide and/or
hydrogen at elevated pressure to about 200 bar.
To stabilise the method conduct, the starting materials are continuously fed
to the
reactor and the vaporous reaction products and the reaction gas are
expediently
continuously removed from the reactor.
The vapour phase removed continuously from the reactor and liquefied by
condensation forms the condensed reaction products removed from the reaction
gas
circuit with the petrochemical combustibles and fuels preferred as the target
products
with a high hydrocarbon content and low viscosity. Liquid heavy oil fractions
and
reaction water still present are optionally separated by distillation,
condensation
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and/or phase separation by a further treatment of the condensed reaction
products
according to the prior art.
The conditioned reaction gas is expediently compressed before its return to
the
reactor. Compressing the reaction gas ensures that possible pressure
fluctuations in
the reactor or pressure losses within the reaction gas circuit are compensated
and
therefore the reaction gas feed into the reactor is decoupled from the
reaction
pressure prevailing therein, so the simultaneous reducing, hydrogenating and
stripping effect of the reaction gas in the reactor can be constantly
maintained. This
ensures that the targeted removal of the crack products from the reaction
zone, in
other words the method-specific selective, product-oriented residence time
control
can proceed undisturbed, and in that to this extent, quality and yield
fluctuations in
the target products are avoided.
Moreover, the compression of the reaction gas also has a stabilising effect in
a
process conduct under excess pressure, such as is necessary, for example, in
the
case of the conversion of starting products with a shortage of hydrogen and/or
with
an increased heteroatom fraction. In this case, it is especially advantageous
with
regard to the quality and yield of the target product if the reducing excess
pressure
atmosphere is formed by hydrogen and/or carbon monoxide.
In a preferred embodiment of the invention, condensed reaction products
removed
from the reaction gas circuit are converted to hydrogen, which is then in turn
mixed
as a hydrogenating gas fraction with the reaction gas, to control the
hydrogenating
effect of the reaction gas in the reactor. This return preferably takes place
during the
compression of the reaction gas.
In the case of a hydrogen excess in the reaction gas circuit, the hydrogen
thus
obtained can either be temporarily stored or supplied for an external use.
In a further preferred embodiment of the invention, the conditioned reaction
gas is
preheated before its return to the reactor. A method step of this type
supplements
the preheating of the starting materials known from the prior art before the
feeding
thereof into the reactor and further advantageously shortens the heating
period of
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the reaction mixture in the reactor. The aforementioned compression of the
conditioned reaction gas expediently takes place before the heating thereof.
As the reaction gas conditioning, supplemented by compression and preheating,
requires no further method steps, the total number of method steps forming the
reaction circuit is significantly smaller that in the prior art. Accordingly,
the loss of
reaction gas during the method conduct is substantially smaller than is the
case in
the closest prior art, which, in comparison, leads to an improvement in
efficiency and
ultimately to lower method costs.
In a further advantageous development of the method according to the
invention, the
conditioned reaction gas is used for the pneumatic feeding of starting
materials into
the reactor. In this case, the crushed and preheated starting materials
present as
solid materials in a known manner are introduced by means of the reaction gas
under excess pressure, in particular directly into the sump phase of the
reactor, with
intensive intermixing of all the reaction components. It is likewise possible
for one
part of the conditioned reaction gas flow for the pneumatic feeding of
starting
materials to be branched off in a targeted manner as a partial gas flow and
used in
parallel with the main gas flow as a carrier gas for the feeding of starting
materials
into the reactor.
In addition to this, a further advantageous method conduct comprises in that
the
reaction gas is used as an inertisation gas for the starting materials in the
reactor to
improve the quality of the target products. The air oxygen present in the
reactor
and/or gases capable of reaction or explosion or gas mixtures are thus
displaced by
the reaction gas.
In a further embodiment of the invention, with a surprisingly advantageous
effect on
the target product quality and yield, the carbon dioxide fraction present in
the
reaction gas is at least partially removed from the reaction gas circuit to
increase the
partial hydrogen pressure in the reactor. This proves to be advantageous,
especially
if sufficient reaction gas for the stripping effect is present in the reactor.
It may also
be necessary here for additional carbon dioxide to be isolated by suitable
separation
from the reaction gas in order to be able to be likewise discharged from the
reaction
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gas circuit. This separation may, for example, take place by gas washes, such
as
pressure water washes (absorption method with water or alkaline washing
agents) or
pressure change absorption on activated carbon.
An advantageous embodiment of the method according to the invention also
comprises in that the carbon dioxide and methane and further hydrocarbon
fractions
present in the separated and/or conditioned reaction gas have to be removed
from
the reaction circuit in order to be used as the reaction media for reforming
for
synthesis gas production.
In a last embodiment of the method according to the invention, the separated
and/or
conditioned reaction gas is partly removed from the reaction gas circuit and
used to
cover the thermal energy requirement during the conversion of the starting
material,
so a significant improvement in efficiency of the method is made possible.
The aim of the invention is further achieved by a device with the features of
claim 16.
The invention is based on the concept of disclosing a device, having a
reaction gas
circuit to guide gaseous reaction products with at least
- one reactor for carrying out thermochemical conversion reactions of a
reaction
mixture in the reactor,
- a means for liquefying vaporous reaction products,
- a means for separating liquid reaction products and reaction gas,
characterised in that furthermore
- means for conditioning the separated reaction gas to adjust a reducing, in
especially hydrogenating and/or stripping effect of the reaction gas are
provided in
the reactor, comprising
o means for discharging one part of the gas mixture and/or
o means for removing carbon dioxide or
o means for reforming carbon dioxide, methane and optionally further
hydrocarbons or
o means for removing carbon dioxide and means for reforming carbon dioxide,
methane and optionally further hydrocarbons in a parallel arrangement or
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o means for reforming carbon dioxide, methane and/or further hydrocarbons as
well as, arranged upstream thereof in the flow direction in the reaction gas
circuit, means for removing carbon dioxide or
o means for removing carbon dioxide as well as, arranged upstream thereof in
the flow direction in the reaction gas circuit, means for reforming carbon
dioxide, methane and/or further hydrocarbons and
- optionally additionally arranged upstream or downstream thereof in the flow
direction in the reaction gas circuit, means for feeding hydrogen and/or
another
reducing material.
Advantageous configurations of the device according to the invention emerge
from
the dependent claims 17 and 18.
***
The invention will be described with more details below, by way of example,
with
reference to the accompanying schematic figures, in which:
Fig. 1 shows a flow diagram of a preferred embodiment of the device
according to the invention with means for removing carbon dioxide and
means for reforming carbon dioxide, methane and further
hydrocarbons in a parallel arrangement according to a method
alternative and
Fig. 2 shows a flow diagram of a further preferred embodiment of the device
according to the invention with means for removing carbon dioxide and
means for reforming carbon dioxide, methane and further
hydrocarbons in an arrangement connected one behind the other
according to a further method alternative.
Fig. 1 shows a schematic view of the arrangement in principle of the device
components of a preferred embodiment of the invention and the flow course of
the
reaction gas during operation of this device. Accordingly, the reaction
products
produced during the thermochemical conversion of the starting material are
removed
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in the form of hot vapours of gases from the reactor 1 and supplied to a
condenser 2
to liquefy the vaporous reaction products with cooling. In a downstream
separator 3,
the liquid reaction products are separated from the reaction gas. The
separated
liquid reaction products are separated from the reaction gas circuit and
transferred in
further treatment stages (not shown) into the target products (product oil).
The
separated reaction gas, which is now present as a dry mixture and
substantially
comprises the components carbon dioxide, carbon monoxide, methane, further
hydrocarbons (for example ethane, propane or butane) and hydrogen, is now fed,
in
a first stage, for gas conditioning, having the carbon dioxide removal 4 and,
in
parallel with this, the reformer 5 for carbon dioxide, methane and further
hydrocarbons in order to remove carbon dioxide or convert it to hydrogen and
carbon
monoxide. The reaction gas leaving the first conditioning stage now also
substantially has the components carbon monoxide, methane and further
hydrocarbons and hydrogen. The reaction gas thus conditioned is fed to a
second
stage of gas conditioning, which has the compression 6 and a hydrogen supply
to
feed additional hydrogen into the reaction gas circuit. In a subsequent third
conditioning stage, the modified and compressed reaction gas is heated in gas
preheating 7 and then returned directly to the reactor 1.
***
The invention will be further described below with the aid of application
examples:
Example 1:
A loop reactor (volume = 100 I) is filled with a poorly volatile oil,
preloaded with a gas
mixture of 65 vol.% H2, 20 vol.% CO and 15 vol.% CH4 to a pressure of 100 bar
and
heated to a reaction temperature of 500 C.
The starting materials preheated to 200 C are continuously metered by means of
a
suitable feed system into the hot oil of the reactor with a mass flow of 50
kg/h plus 10
% water content. As a result, a shock heating of the starting materials which
is
advantageous for the reaction is achieved. In parallel with the starting
material
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addition, a reaction gas flow at a volume flow of 75 Nm3/h is guided through
the
reactor, composition: 65 vol.% H2, 20 vol.% CO and 15 vol.% CH4.
Owing to the ideal intermixing of the two reaction phases, gas and starting
material,
in the catalytically acting, poorly volatile reaction oil, the starting
materials are
converted into vapours and gases which, owing to the stripping effect of the
reaction
gas flow, are continuously discharged therewith. The gases and vapours leaving
the
reactor have a temperature of 500 C and a pressure of 100 bar, the volume flow
is
100 Nm3/h with a composition: 20 vol.% H2, 30 vol.% CO2, 15 vol.% CO, 10 vol.%
CH4 and 20 vol.% water, 3 vol.% diesel and 2 vol.% petrol vapour.
This flow is cooled to 20 C in a downstream condenser, which is designed as a
pipe
coil condenser. The components water, diesel and petrol condense and are
separated in a subsequent gravity separator under 100 bar pressure from the
gas
phase. The liquid phase is relieved of pressure and supplied for a further
use.
The gas phase is supplied to a high pressure washing column (packed column, D
=
150 mm, H = 2.5 m): under 100 bar pressure, the gas (75 Nm3/h) is introduced
from
below and water (m = 500 kg/h) is trickled from above as a washing liquid in a
counter-flow. The waste water is regenerated by pressure relief and then again
used
for CO2 absorption. The fresh water consumption in this concept is about 5 to
10 %
of the washing water flow.
The cleaned gas flow (45 Nm3/h) still contains negligible traces of CO2 and
substantially 42 vol.% H2, 33 vol.% CO and 25 vol.% CH4. This gas flow is
compressed by means of a piston compressor with the addition of 30 Nm3/h H2 to
110 bar and, preheated in a pipe coil heat exchanger to 300 C, guided back
into the
reactor, where the latter is again available as a reaction gas with a
composition of 65
vol.% H2, 20 vol.% CO and 15 vol.% CH4 and for stripping the reaction
products.
This modification of the circulating gas treatment is a simple concept in
terms of
apparatus. In order to keep the stripping gas volume flow and the partial
hydrogen
pressure constant, H2 is additionally fed in.
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Example 2:
A loop reactor (volume = 100 I) is filled with a poorly volatile oil,
preloaded with a gas
mixture of 53 vol.% H2 and 47 vol.% CO to a pressure of 80 bar and heated to a
reaction temperature of 450 C.
The starting materials preheated to 200 C are metered continuously by means of
a
suitable feed system into the hot oil of the reactor at a mass flow of 50 kg/h
plus 10
% water content. As a result, a shock heating of the starting materials that
is
advantageous for the reaction is achieved. In parallel with the starting
material
addition, a reaction gas flow with a volume flow of 78 Nm3/h is guided through
the
reactor, composition: 53 vol.% H2 and 47 vol.% CO.
Owing to the ideal intermixing of the two reaction phases, gas and starting
material,
in the catalytically acting, poorly volatile reaction oil, the starting
materials are
converted into vapours and gases, which are continuously discharged by the
stripping effect of the reaction gas flow with the latter. The gases and
vapours
leaving the reactor have a temperature of 450 C and a pressure of 80 bar and
the
volume flow is 100 Nm3/h with a composition: 20 vol.% H2, 30 vol.% CO2, 15
vol.%
CO, 10 vol.% CH4 and 20 vol.% water, 3 vol.% diesel and 2 vol.% petrol vapour.
This gas/vapour flow is relieved to 2 bar by means of a gas expansion turbine,
so the
mixture is cooled to 350 C. The expansion work of the gas is converted into
mechanical work here, which is removed as shaft power.
The mixture thus relieved is broken down in a conventional distillation column
at
atmospheric pressure into its fractions water, petrol, diesel and gas. The
liquid
fractions are removed as products for further use, while the gas flow (75
Nm3/h),
composition: 25 vol.% H2, 40 vol.% CO2, 20 vol.% CO and 15 vol.% CH4 is guided
into a reformer. The components CO2 and CH4 of the reaction gas are
selectively
converted on a fixed bed reactor with the aid of a platinum catalyst at 600 C
to CO
and H2. The CH4 is converted here almost completely according to the reaction
equation, see Example 2. After the reforming process, the gas is cooled, and
the
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volume flow is now 97.5 Nm3/h with a composition of 42 vol.% H2, 20 vol.% CO2
and
38 vol.% CO.
This gas flow is compressed by means of a piston compressor to 90 bar and
supplied to a high pressure washing column (packed column, D = 200 mm, H = 2.5
m): under 90 bar pressure, the gas (97.5 Nm3/h) is introduced from below and
water
(m = 380 kg/h) is trickled from above as washing liquid in a counter-flow. The
waste
water is regenerated by pressure relief and can then be used again for CO2
absorption. The fresh water consumption in this concept is about 5 to 10 % of
the
washing water flow.
The cleaned gas flow (78 Nm3/h) still contains negligible traces of CO2 and
substantially 53 vol.% H2 and 47 vol.% CO.
This is preheated to 400 C in a pipe coil heat exchanger. The hot gas flow is
guided
back into the reactor, where the latter is again available as a reaction gas
with a
composition of 53 vol.% H2 and 47 vol.% CO and is available for the stripping
of the
reaction products.
Especially advantageous here are the obtaining of energy from the compressed
gases, the production of finished products in the form of petrol and diesel
and the
operation of the process that is self sufficient in hydrogen.
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List of reference numerals
1 Reactor
2 Condenser
3 Separator
4 Carbon dioxide removal
Reformer for carbon dioxide, methane and further hydrocarbons
6 Compression
7 Gas preheating
***
