U.S. patent application number 12/450323 was filed with the patent office on 2010-04-29 for method for the wet-chemical transformation of biomass by hydrothermal carbonization.
This patent application is currently assigned to Fraunhofer=Gellschaft zur Forderung der angewandten Forschung e. V. Invention is credited to Markus Antonietti, Peter Eisner, Andreas Malberg, Michael Menner, Andreas Stabler.
Application Number | 20100101142 12/450323 |
Document ID | / |
Family ID | 39400476 |
Filed Date | 2010-04-29 |
United States Patent
Application |
20100101142 |
Kind Code |
A1 |
Eisner; Peter ; et
al. |
April 29, 2010 |
METHOD FOR THE WET-CHEMICAL TRANSFORMATION OF BIOMASS BY
HYDROTHERMAL CARBONIZATION
Abstract
A method for converting biomass into higher-energy-density
solids, in particular carbon, humus or peat, is described. In the
method, organic substances from the biomass are suspended in water
to form a suspension and at least a part of the suspension to be
converted is heated to a reaction temperature and is converted into
higher-energy-density solids by hydrothermal carbonization at
elevated pressure. The conversion is carried out in a reaction
volume which is located underneath the Earth's surface. Uniformity
of the product quality and an increase in the economic efficiency
of the process are achieved by the method.
Inventors: |
Eisner; Peter; (Freising,
DE) ; Malberg; Andreas; (Munchen, DE) ;
Stabler; Andreas; (Munchen, DE) ; Menner;
Michael; (Eichenau, DE) ; Antonietti; Markus;
(Nuthetal, DE) |
Correspondence
Address: |
BREINER & BREINER, L.L.C.
P.O. BOX 320160
ALEXANDRIA
VA
22320-0160
US
|
Assignee: |
Fraunhofer=Gellschaft zur Forderung
der angewandten Forschung e. V
Munchen
DE
|
Family ID: |
39400476 |
Appl. No.: |
12/450323 |
Filed: |
December 11, 2007 |
PCT Filed: |
December 11, 2007 |
PCT NO: |
PCT/DE2007/002227 |
371 Date: |
October 8, 2009 |
Current U.S.
Class: |
44/607 |
Current CPC
Class: |
C10L 9/02 20130101; Y02E
50/30 20130101; C10L 5/44 20130101; Y02E 50/10 20130101; C10L 9/086
20130101; C10L 9/08 20130101; C10L 9/00 20130101 |
Class at
Publication: |
44/607 |
International
Class: |
C10L 5/00 20060101
C10L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2007 |
DE |
102007014429.8 |
Claims
1-22. (canceled)
23. A method for converting biomass into higher-energy-density
solids, comprising suspending organic substances from the biomass
in water to form a suspension, heating at least a part of the
suspension to be converted to a reaction temperature and converting
into higher-energy-density solids by hydrothermal carbonization at
elevated pressure, wherein said converting is carried out in a
reaction volume that is located underneath the Earth's surface.
24. The method according to claim 23, further comprising buffering
released reaction heat of the reaction volume in a surrounding area
corresponding to at least four times a mean diameter of the
reaction volume by surrounding the reaction volume with a mass of
compact liquid and/or solid material which is greater than eight
times the biomass contained in the reaction volume.
25. The method according to claim 23, wherein the converting is
carried out at a process pressure which is higher than an
equilibrium pressure which would be established at the reaction
temperature in a gastight reactor filled with the suspension.
26. The method according to claim 24, wherein the converting is
carried out at a process pressure which is higher than an
equilibrium pressure which would be established at the reaction
temperature in a gastight reactor filled with the suspension.
27. The method according to claim 25, further comprising generating
the process pressure hydrostatically by introducing the at least a
part of the suspension to be converted into a volume region of a
volume filled with water or the suspension up to an upper filling
level, wherein a height difference of at least 100 m exists between
an upper filling level and the volume region forming the reaction
volume.
28. The method according to claim 23, wherein a cavity in the
Earth's surface serves as the reaction volume and is filled with
water or the suspension.
29. The method according to claim 23, wherein a region below a
water surface of a sea or a lake serves as the reaction volume.
30. The method according to claim 28, further comprising inserting
at least one reactor in the cavity and filling said at least one
reactor with water or the suspension.
31. The method according to claim 29, further comprising inserting
at least one reactor in the sea or the lake and filling said at
least one reactor with water or the suspension.
32. The method according to claim 30, wherein the at least one
reactor is formed with a flexible outer wall.
33. The method according to claim 30, wherein the at least one
reactor is inserted in a horizontal or inclined shaft and is
surrounded by water, which exhibits a hydrostatic pressure whereby
a wall of the reactor is at least partially relieved of pressure in
the reactor.
34. The method according to claim 30, wherein the at least one
reactor is at least partially perforated to allow passage of
gases.
35. The method according to claim 28, further comprising supplying
cold water, for slowing conversion of the biomass, in a controlled
manner to the reactor or cavity at different heights via cooling
water supply lines to avoid overheating.
36. The method according to claim 23, further comprising pumping
said at least a part of the suspension to be converted in a pumping
direction through the reaction volume, to produce a pulsating flow
of the at least a part of the suspension to be converted through
the reaction volume by repeated brief reversal of the pumping
direction.
37. The method according to claim 23, further comprising generating
turbulence in the reaction volume to counter any sedimentation of
solids in the reaction volume.
38. The method according to claim 23, further comprising pumping
the suspension water or another cooling medium for cooling and
using the heat dissipated by the cooling to generate electrical
energy.
39. The method according to claim 23, further comprising providing
the Earth's heat in the reaction volume sufficient to contribute
towards increasing the temperature of the suspension to be
converted.
40. The method according to claim 23, further comprising forming a
circuit in which the higher-energy-density solids are removed from
the suspension after conversion and supplying an added part of the
suspension anew to the reaction volume.
41. The method according to claim 23, further comprising separating
heavy substances from the suspension before introducing the
suspension into the reaction volume.
42. The method according to claim 23, wherein the water contains at
least one conversion-promoting substance or at least one
conversion-promoting substance is added to the water or the
suspension.
43. The method according to claim 23, further comprising adjusting
viscosity of the suspension supplied to the reaction volume so that
the viscosity is at least 20 mPas.
44. The method according to claim 23, further comprising adjusting
viscosity of the suspension supplied to the reaction volume so that
a liquid phase extracted from the reaction volume does not exceed a
viscosity of 5 mPas.
45. The method according to claim 23, further comprising providing
the suspension to be converted in a container which allows pressure
exerted on the container to be transferred to contents of the
container, wherein the suspension to be converted remains in the
container during said converting.
46. Higher-energy-density solids produced by the method according
to claim 23 comprising fuel or a starting material for a fuel.
47. Higher-energy-density solids produced by the method according
to claim 23 comprising hydrocarbon-rich liquid fuel.
Description
TECHNICAL FIELD OF APPLICATION
[0001] The present invention relates to a method for converting
biomass into higher-energy-density solids, in particular carbon,
humus or peat, wherein organic substances from the biomass are
suspended in water to form a suspension and wherein at least a part
of the suspension to be converted is heated to a reaction
temperature and is converted into higher-energy-density solids by
hydrothermal carbonisation at elevated pressure. The organic
substances can be plant parts, other biomass or organic waste.
PRIOR ART
[0002] The conversion of biomass into products having a higher
mass-specific energy content compared with the biomass used such
as, for example, oil, gas or coal, is becoming increasingly
important.
[0003] Known inter alia are methods for obtaining gas and/or oil
and carbon at high temperatures, for example, by pyrolysis,
gasification or sulphurisation. In this connection catalysts are
frequently used to accelerate the reaction and positively influence
the product composition.
[0004] Recently wet-chemical methods such as hydrothermal
carbonisation have also been discussed for obtaining products
having a higher mass-specific energy content compared with the
biomass used. In this case, plant parts or other organic substances
are comminuted, suspended in water and usually reacted with at
least one conversion-promoting substance, for example, with acid
and/or an additional organic and/or inorganic catalyst. The
suspension is poured into a reactor and the reactor is closed. The
suspension is then heated to temperatures between 170.degree. and
250.degree.. Since the reactor is closed, as a result of the water
vapour partial pressure, the pressure increases with increasing
temperature. Depending on the temperature, the pressure increases
to values of 10*10.sup.5 to 20*10.sup.5 Pa (10 to 20 bar) or
higher. In the course of the hydrothermal carbonisation reaction,
hydrogen and oxygen are separated in the form of water from the
carbohydrates contained in the biomass, whereby energy is released.
The longer the reaction lasts, the more water is separated and the
energy density of the products increases further. Solids such as,
inter alia, peat, humus, lignite, low-grade anthracite or other
substances having a significantly higher mass-specific energy
content compared to the biomass used are produced.
[0005] The reaction proceeds faster or slower depending on the
concentration and structure of the contents, primarily the
carbohydrates (e.g. sugar, starch, cellulose, hemicellulose or
others) in various raw materials, various plants and plant parts,
residue from food production, sewage sludge or other biogenic
materials and waste. Depending on the properties and the
concentration of the biogenic raw materials used, more or less heat
is released per unit time, the temperature and the pressure in the
reactor increase more rapidly or more slowly and different absolute
values are achieved for pressure and temperature. In the course of
the reaction when increasingly less biogenic material is available
for the reaction, the reaction is slowed considerably. The
temperature drops again until the reaction is terminated after a
certain time because the temperature is too low. This possibly
leads to incomplete conversion of the material used, for which a
reaction time of several hours up to several days or longer may be
necessary. However, external after-heating of the reactor to
lengthen reaction times requires an additional energy input which
can make the carbonisation uneconomical.
[0006] The coupling of temperature and pressure in this reaction
and the different reaction rates of different raw materials used
have the result that the temperature and pressure profiles during
the reaction are very different depending on the composition and
concentration of the biomass in the input stream of the
hydrothermal carbonisation. The products obtained can thus differ
very substantially in their composition. This can have the result
that the products have no constant quality and do not give high
yields which can make the hydrothermal carbonisation
uneconomical.
[0007] The object of the present invention is to provide a method
for converting biomass into higher-energy-density solids by
hydrothermal carbonisation whereby a more uniform product quality
is achieved and the economic efficiency of the process is
increased.
DESCRIPTION OF THE INVENTION
[0008] The object is achieved by a method according to claim 1.
Advantageous embodiments of the method are the subject matter of
the dependent claims or can be deduced from the following
description or the exemplary embodiment.
[0009] In the method for converting biomass into
higher-energy-density solids, in particular carbon, humus or peat,
organic substances from the biomass are suspended in water to form
a suspension. In a preferred embodiment a conversion-promoting
substance is present in the water or is added to the water or the
suspension. The conversion-promoting substance can, for example, be
an acid and/or an organic or inorganic substance which accelerates
the reaction. The biomass can comprise, for example, organic waste,
plant parts, wood, algae or other carbon-containing organic
products. At least a part of the suspension to be converted is
heated to a reaction temperature and is converted into
higher-energy-density solids by means of hydrothermal carbonisation
at elevated pressure. The method is characterised in that the
conversion is carried out in a reaction volume that is located
underneath the Earth's surface.
[0010] The reaction volume for buffering released reaction heat in
a surrounding area corresponding to at least four times the mean
diameter of the reaction volume is preferably surrounded by a mass
of compact liquid and/or solid material which is greater than eight
times the mass contained in the reaction volume. Good
homogenisation of the product properties is already observed above
this mass.
[0011] In the proposed method the reaction therefore takes place
underneath the Earth's surface. The Earth's surface is understood
in this context as the boundary layer between the solid Earth's
crust or the oceans on the one side and the atmosphere on the other
side. By carrying out the process underneath the Earth's surface
with a sufficient quantity of compact, liquid and/or solid material
around the reaction volume, even with fluctuating biomass
concentration and composition it is possible to produce energy- and
carbon-rich products which have a significantly more uniform
composition than products produced in the known manner in a reactor
above the Earth's surface.
[0012] By moving the reaction chamber below the Earth's surface
with the surrounding material such as, for example, rock, sand,
water or soil, this material can absorb a large part of the energy
released in the form of heat at the initial stage of the reaction.
As a result of the heat exchange taking place with the surrounding
mass, the temperature in the reaction volume or reaction mixture
increases more slowly and not so far as in a reactor above the
Earth's surface, and the pressure likewise does not fluctuate so
strongly. In consequence at the beginning, the reaction does not
proceed so rapidly and is more uniform. However, as the
concentration of convertible biomass contents decreases with time,
the temperature in the reaction does not fall so rapidly as in the
hitherto known process. Rather, the surrounding material then
slowly delivers the stored heat back to the reaction volume. The
reaction volume thus remains warm for much longer and the reaction
can be continued without additional heating of the suspension for
many hours or even days until different raw materials have been
converted to comparable products having a higher energy density.
The reaction volume is preferably in direct contact with the
surrounding compact material, at least in some places.
[0013] Another advantage of the proposed method is that by
returning heat from the surrounding material into the reaction
volume even after removal of the products, new biomass can be
supplied again and brought to reaction without external heating or
at least without strong additional heating. In many cases, this
allows several batches to be carbonised successively without any
external supply of heat. In principle, the method therefore allows
both a continuous supply of biomass and also batch operation. As a
result, the throughput in the method according to the invention can
be varied very substantially as a result of the thermal buffering
of the surrounding soil or water without any losses of uniformity
in the product quality.
[0014] At the same time, the method must be carried out in a region
underneath the Earth's surface in which a sufficient mass of
surrounding material is available for thermal buffering. The
material should preferably have such a compact structure that in
the surrounding area of four times the mean diameter of the
reaction volume, it should have a total mass which corresponds to
eight times the mass contained in the reaction volume. Relative to
a cylindrical reaction volume of diameter D and height H, this
means that a cylindrical volume having the same height and four
times the diameter minus the cylindrical reaction volume should
contain at least eight times the mass contained by the reaction
volume filled with the suspension in order to achieve particularly
good buffering for the proposed method.
[0015] As a result of the pressure prevailing underneath the
Earth's surface, the surrounding material such as, for example,
soil, loam, sand or water is capable of at least partly
compensating for and absorbing the pressure coming from the
reaction. A reactor used for hydrothermal carbonisation underneath
the Earth's surface can therefore be designed as considerably
thinner-walled compared with that for use above the Earth's
surface. This additionally saves costs. In a particularly simple
reactor design, this reactor can, for example, consist of steel
which is embedded in concrete or -reinforced concrete in a cavity
under the Earth's surface. Very good heat transfer to the
surrounding material takes place through the concrete cladding. The
wall of this reactor can be very thin-walled.
[0016] Furthermore, the wall of the cavity can be used as the
reactor wall. If necessary, this wall can be additionally lined
with watertight materials. Such a lining can also be achieved by
synthetic additives in the water. Automatic sealing by the reaction
products of the process such as, for example, coal particles can
possibly take place with respect to the surrounding rock.
[0017] The product composition can additionally be homogenised if
the pressure is increased above the pressure corresponding to the
reaction temperature. As a result of the additional application of
pressure in the reaction volume, the pressure certainly increases
during the entire reaction and then falls again but the percentage
relative pressure fluctuations are smaller. It is particularly
advantageous if the pressure in the reaction volume is kept
constant or at least largely constant by means of technical
measures. By means of these measures temperature and pressure are
decoupled from one another. The operator of the hydrothermal
carbonisation is therefore in a position to select the pressure
according to the composition of the input so that the
homogenisation of the product quality is improved. Application of
an additional pressure can not only homogenise the composition of
the end product. Rather, depending on the input material, the yield
of solid products having high energy density can be increased by
the elevated pressure so that the process can be operated even more
economically. With the additional build-up of pressure, the
operator has a valuable instrument at his disposal that can
specifically vary and thereby optimise the product quality or the
yield depending on the requirement and composition.
[0018] In addition to various other mechanical methods, for
example, the pressure build-up can be achieved by moving the
reaction volume sufficiently deep into the ground. The location of
the reaction volume is selected to be sufficiently deep that a
water column located above the reaction volume which is required to
supply and remove the suspension, produces a hydrostatic pressure
in the reaction volume which is higher than the equilibrium
pressure which would be established at the reaction temperature in
a gastight reactor filled with the suspension. During the build-up
of such a hydrostatic pressure it is additionally very simple to
maintain a constant pressure. In this case, it is merely necessary
to ensure that liquid can enter or exit at the surface of the water
column. This can be made possible, for example, by openings or by
using non-sealing pumps such as, for example, rotary pumps. During
a temperature rise in the reaction volume, liquid can then exit at
the surface and the pressure in the reaction volume remains largely
constant. The water column is thereby used as a pressure buffer.
The reaction conditions are thereby homogenised and the solid
material yield can be additionally increased.
[0019] Particular advantages are achieved if the reaction volume is
configured to have a greater width than height. During the
generation of hydrostatic pressure an approximately equal pressure
is thus generated at all points in the reaction volume, thereby
additionally promoting homogenisation of the reaction conditions.
The reaction volume can be formed by insertion into horizontal
shafts, for example coal shafts.
[0020] In a particularly advantageous embodiment for generating the
hydrostatic pressure, a height difference of at least 100 m is
selected between the upper filling level and the reaction volume. A
pressure higher than 10*10.sup.5 Pa (10 bar) is thus formed in the
reaction volume as a result of the water column located thereabove.
Larger height differences of 200 m or more allow higher pressures
to be established which can be very advantageous depending on the
requirement.
[0021] In a very advantageous embodiment, the reactor is designed
so that an inlet and outlet opening are located at the same height
or at least at a similar height compared to the total reactor
height so that the hydrostatic pressure difference between the
openings does not exceed 10% of the pressure. The pumps used then
do not need to overcome any high pressure differences and can thus
be designed very simply and cost effectively.
[0022] In addition to using a rigid reactor, it is also possible to
configure the outer wall of the reactor as flexible so that this
nestles against the inner wall of the cavity or at least serves as
a barrier towards the surrounding rock or water. Thin metal sheets
or metal films can be used particularly advantageously here, these
having a high temperature resistance compared to other
materials.
[0023] An advantage of the pressure build-up by the hydrostatic
pressure in the reactor is that the pressure increases uniformly
with increasing depth. The reaction therefore does not begin
abruptly and spontaneously but slowly and uniformly with increasing
pressure and increasing temperature. By varying the delivery rate
and the relative borehole diameter in the case of a borehole as the
cavity, the dwell time can be specifically adjusted and thereby
matched to the respective raw material. It is appropriate to attach
cooling water connections at regular intervals over the height and
volume of the reactor so that cold water can be introduced if
required to slow the reaction. This can avoid overheating of the
reaction and the heated water can thereby be used for energy. This
process can also take place via heat exchangers to be installed in
the reactor.
[0024] When adjusting long residence times in the reactor, it can
occur that the flow rate needs to be throttled to such an extent
that the particles in the suspension settle out more rapidly than
the suspension flow. Different strategies are possible to avoid
blockages in the reactor.
[0025] Thus, mixing elements, flow baffles, static mixers,
agitators or other devices which influence the flow can be
installed in the reactor to limit the sedimentation of solids.
Gases such as, for example, compressed air can be particularly
advantageously introduced into the reactor to effect thorough
mixing. It is also possible to achieve gas formation by making the
water in the suspension partially evaporate. The turbulence thereby
produced leads to thorough mixing and avoids blockages.
[0026] Specific evaporation of part of the water can also be used
to empty the reactor after the end of the reaction. For this, a
pressure reduction in the reaction volume can be achieved by
pumping away water located in the inlet or outlet and spontaneous
evaporation is achieved in the reaction volume. As a result of this
evaporation process which proceeds very similarly to delayed
boiling, so much mass is conveyed from the reaction chamber in a
very short time that as a result of the very high flow rates which
thereby occur, sedimented or deposited solids and smuts are
conveyed to the surface.
[0027] In order to increase the flow rate in the reactor, the flow
cross-sections can be reduced to such an extent that a critical
flow rate is exceeded. It is also possible to erect a cascade of
agitator reactors in tunnels underground and surround these with
soil, rock or water, through which flow takes place in series. In
this form, they can be manufactured very cost-effectively and allow
rapid flow.
[0028] Blockage of the reactor can also be avoided if the flow
direction is reversed at regular intervals and thus a type of
pulsation is achieved on which a constant flow rate is superposed.
This pulsation leads to turbulence in the reactor and thereby very
efficiently prevents deposits.
[0029] In order to largely avoid disturbing components in the
reaction chamber, it is advantageous to remove disturbing
components such as stones, metal, glass or similar inorganic
materials from the suspension before the reaction. This can
comprise gravitational separation such as a primary settling tank
in sewage treatment works or a hydrocyclone or another method known
from the prior art for separating solids from suspensions.
[0030] Furthermore, particles which tend to sediment can be
specifically removed from the reactor. For this purpose apparatus
can be incorporated in the reactor which discontinuously or
continuously conveys sedimented solids from the reactor using
systems according to the prior art (e.g. conveyor belts, scrapers,
chains, screws, pumps). These solids can be fractionated outside
the reactor so that coarse organic materials can be returned to the
reaction chamber following appropriate comminution.
[0031] It can be desirable to remove from the reactor gases or
vapour formed as a result of the pressure drop in the part of the
reactor through which upward flow takes place. This can be
achieved, for example, by perforating the reactor wall, for example
in the part of the reactor through which upward flow takes place.
These holes can be provided to the surroundings or to the in the
part of the reactor through which downward flow takes place.
Pressure compensation is thus ensured. Fissured or karst rock
formations can also be used to remove the gas.
[0032] If a rapid escape of gases or liquid volumes due to
temperature-density differences (geyser effect) is to be avoided,
appropriate pressure valves or check valves should be incorporated
which close when a defined pressure or a defined flow rate is
exceeded, thereby briefly effecting a pressure rise and terminating
the outgassing process. Convection flows can be specifically
prevented by this means.
[0033] In a particularly simple design the reactor merely consists
of a cavity present in deeper layers of rock where the supply of
reaction mixture is conveyed through a supply line to a sufficient
depth for the reaction. It is particularly advantageous, for
example, to use old conveyor shafts from mining, disused tunnels or
other underground structures. In this case, the existing lining of
the shafts or tunnels can be used as the "reactor wall" and the
entire volume of the shaft can be used as the reactor. In addition
to lining the shaft with watertight materials, the system can be
sealed by additives in waters or the system can seal itself with
respect to the surrounding rock by reaction products such as coal
particles.
[0034] When using bores in the ground, an inlet or outlet must be
provided in the lower region of the reactor. By providing an inlet
or outlet channel in the lower region of the shaft or the bore
whose cross-sectional area and pump capacity can be variably
adjusted, an upward flow is established over the remaining shaft
cross section. Depending on the requirement, the area ratio of
reactor space through which upward flow takes place and reactor
space through which downward flow takes place can be 0.01% to
99.99%. Heat exchangers for cooling or heating, which can be
arranged in the shaft, are used to control the temperature and the
reaction and thereby ensure the product quality and the energy
removal and consequently the energy utilisation outside the
reactor.
[0035] It can be desirable to convey the product flow upwards from
the depths at another location from that at which the raw material
was introduced, similar to the use of geothermal energy. For
example, horizontally running coal shafts which were previously
used as underground mining areas and are now disused, can be used
as reaction volumes. Thus, the raw material suspension can be
introduced into the shaft via externally located regions and all
input flows from the conveyor shaft can be conveyed centrally out
from the depths or the other way round. Thus, existing shaft
installations can be almost completely used as "reactors" for the
production of biogenic fuels. Many tens of thousands of cubic
metres of volume are available there as reactor so that very high
throughputs can be achieved despite the long dwell time of the
reaction. It is also possible to use other underground cavities
with gas or water, caverns, caves, karst and porous rock formations
or water-filled tunnels as reactors, The person skilled in the art
from the field of geology will be able to identify suitable
cavities which can be flooded with water and used for the method
described.
[0036] In this case it is always particularly advantageous to use
the Earth's heat at greater depths to promote the reaction. It can
also be appropriate to use residual deposits of coal or oil. Here
in parallel with the biomass reaction, it is also possible to
extract the residual reserves from oil deposits which have already
become uneconomical to extract as a by-product, so to speak. Thus,
the volume of the deposit can be used as the reactor and remaining
residual deposits of fossil raw materials can be appropriately
utilised. As a result of the high reaction temperature, oil in the
rocks is thin so that the residual deposits can be conveyed very
efficiently from the depths.
[0037] It is advantageous to cycle the water used for the
suspension completely or partially in the cycle to completely
utilise the raw material. For this purpose it is necessary to
separate the desired reaction products such as, for example coal
particles, from the suspension and to convey the remaining
substrates, unreacted raw materials and reaction products such as,
for example, phenols or other secondary products together with new
comminuted biogenic raw material back into the reaction chamber. It
is known to the person skilled in the art that a concentration of
minerals or non-convertible fractions is to be avoided. This can be
achieved by a suitably dimensioned bleed flow.
[0038] Process-technology solution approaches such as secondary
sedimentation basins, decanters, filter presses or briquetting
installations can be used to separate coal particles.
[0039] Another possibility for implementing this invention can be
seen in the submarine area. Here, for example, simple thin-walled
conduits can be guided into the sea at great depths as reactors.
However, it can also be advantageous to introduce the reaction
mixtures directly into deep layers of lakes or deep sea layers and
therefore use large areas of the sea such as, for example, coastal
areas with great sea depths as reactors. In this case, it can be
particularly advantageous to use regions in the ocean which are
particularly hot due to volcanic activity such as, for example,
some regions in the Pacific. The upward flow of hot submarine
springs can then be used to convey the reaction products such as,
for example, coal.
[0040] The method described brings additional advantages when used
in combination with geothermal energy. Thus, energy is supplied to
the reaction mixture in warmer regions of the Earth, the reaction
mixture is additionally heated and the reaction thereby
accelerated. The additionally released energy can then be used
according to the prior art by removing the heat or by converting
into electrical current or hydrogen.
[0041] The carbon-rich reaction products are present in many cases
as finely dispersed nanospheres. This circumstance can be used very
advantageously for conveying the solid energy carriers. Thus, after
the energy carrier suspension emerges from the reactor, mechanical
separation of the solids from the liquid can initially be carried
out, for example, by centrifugal separation methods. The liquid
fraction containing the amino acids and minerals from the organic
raw material can be used as manure directly or after concentrating
by partial separation of the water. The nanoparticle solids which
predominantly consist of carbon are again mixed with water and
adjusted to a dry substance content of 40 to 60 mass %. An energy
density of up to 18 gigajoules per tonne can thus be established in
the suspension, which corresponds to approximately half the energy
density of crude oil. Transporting nanoparticle energy carriers
over large distances in this form is completely economical by
pipelines known from the prior art.
[0042] The viscosity plays a decisive role in avoiding
sedimentation effects and for the separation of coal from the
liquid phase. In order to avoid too-rapid sedimentation of the
biogenic raw materials, the viscosity of the suspension in the
reactor inlet should be at least 20 mPas (measured in a rotary
viscosimeter at a shear rate of 10 m/s). In the reactor outlet,
values of 5 mPas should not be exceeded for improved separation of
particulate solids.
[0043] Various methods are known to the person skilled in the art
for adjusting the viscosity in the inlet. Thus, an elevated
viscosity can be set by specifically using different biomasses,
biomass having defined carbohydrates (cellulose, starch, oligo- or
monosaccharides), their degree of comminution, concentration and
via the swelling time of the carbohydrates. In this case, the
parameters described and the choice of raw material should be
varied in such a manner that after the reaction, the liquid has a
correspondingly low viscosity as a result of the degradation and
conversion of the biomass.
[0044] In a further advantageous embodiment of the method according
to the invention, the biomass or the reaction suspension is
conveyed into the depths in vessels or drums such as containers,
barrels, baskets, sacks, cylindrical or rectangular vessels made of
different materials or in similar spatially defined volumes, into
the interior of the reactor accommodated underground.
[0045] As a result of the high thermal capacity of the ground and
the liquid in the reactor, the containers or the vessels in the
reactor are sufficiently heated so that the reaction can take place
inside the container without removing the biomass from the
containers.
[0046] This measure can very efficiently avoid particles from the
suspension sedimenting on the bottom of the reactor and no longer
being able to be removed therefrom. In the embodiment of the closed
or half open container, the particle size can be variably adjusted
or fine comminution can be dispensed with before carrying out the
reaction. Thus, larger particles such as, for example, pieces of
wood can be conveyed into the reactor. Coal particles having an
edge length of several centimetres can thus be obtained, making it
easier to separate the water from the coal after completion of the
reaction.
[0047] It is important for the embodiment using containers that
provision is made for pressure equalisation with the surrounding
water. It must be ensured by providing openings or valves in the
containers that according to the depth, the pressure in the reactor
can be transferred to the interior of the container.
[0048] It can also be advantageous to allow an exchange of liquid
from the container with the surrounding liquid through suitable
openings in the container. The heat transport into the interior of
the container is thereby improved and the transfer of liquid
reaction products and non-suspended extremely fine particles from
the containers into the surrounding liquid and therefore also into
other container is made possible. Thus, despite very efficient
avoidance of sedimentation effects and blockages in the reactor,
exchange of temperature, liquid and reaction products can take
place between the containers, resulting in a faster reaction and
homogenisation of the product composition.
[0049] The containers can be conveyed through the reaction space
similar to the situation with tower heaters in the food industry
which are used for heating tins in a displacement conveyance
system, i.e. each container pushes the next container further in
the tubular reaction space. It is also possible to use conveyor
systems for containers according to the prior art such as, for
example, chain conveyors, conveyor screws, cables and other devices
for transporting vessels through conduits. The containers can also
be transported through the shaft or reaction space in like manner
to other transport systems in mining by cables or on rails in a
type of "underground railway".
[0050] It is also possible to produce spatially defined reaction
volumes by separating individual reactor regions by using locks,
metal sheets or other internal parts or by so-called scrapers which
largely seal the reactor cross section and can be entrained with
the flow as dividing walls between individual reactor sections. As
a result of this multichamber design of the reaction space,
different process conditions such as temperature, for example, can
be established in each segment, making it easier to control the
process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] The proposed method is explained briefly hereinafter with
reference to an exemplary embodiment in conjunction with the
drawings. In the figures:
[0052] FIG. 1 is an example of the arrangement of the reaction
volume underneath the Earth's surface; and
[0053] FIG. 2 is a schematic diagram of the process sequence in the
proposed method.
WAYS FOR IMPLEMENTING THE INVENTION
[0054] FIG. 1 schematically shows an example of an embodiment of a
reactor for carrying out the present method, which in this example
is inserted in a shaft 1 underneath the Earth's surface. The shaft
1 lies at a depth of 200 m. The reactor 2 has an inlet 3 to the
reaction volume which in this case occupies the entire volume of
the horizontally arranged reactor. The suspended biomass is pumped
via this inlet 3 into the reaction volume. The reaction products
are pumped upwards again via the outlet 4. The wall of the reactor
2 can be relative thin since the hydrostatically generated pressure
in this case is absorbed by the surrounding soil 5. The reactor 2
is surrounded in an area of soil 5 which corresponds to at least
four times the diameter D of the reaction volume. No larger
cavities can be present in this surrounding area so that the total
mass in a volume occupied by the material in this surrounding area
corresponds to at least eight times the mass of the reaction
mixture in the reaction volume. The suspended biomass is initially
brought to a temperature of about 80.degree. C. in the reactor 2.
As a result of the very violent exothermic reaction in the reaction
volume at the beginning of the process, the suspension is heated
above 200.degree. C. As a result of the large mass of the
surrounding material, the heat absorption and storage has the
result that no rapid overheating takes place. In a subsequent
course of the reaction when substantially less heat is produced,
the reaction temperature is achieved by the heat released by the
surrounding material, so that the reaction can be maintained for a
fairly long time without any external supply of energy.
[0055] FIG. 2 schematically shows the process sequence again in a
flow diagram. The biomass 6 supplied from a farm, which can be in
the dry or wet state, is initially comminuted in a comminution and
suspension step 7 and suspended in water. Acids, organic and
inorganic catalysts can be used as additives. After heating the
suspension thus obtained to about 80.degree. C., this is conveyed
by means of a suitable pump into the deep shaft reactor 8 as shown
schematically, for example, in FIG. 1. The exothermic reaction
takes place in the reaction volume of this reactor whereby in the
first time interval of the process, a hot suspension at about
200.degree. C. containing water and coal particles is removed from
the reactor. The heat of this suspension is used in a conversion
step 9 to produce electrical energy. In a separation step 10 the
water and coal are separated so that finally pure coal 11 is
available for energy production. The coal can be used, for example,
as raw material for liquid hydrocarbon-rich fuels. In the
separation step 10 a fraction comprising water with minerals and
amino acids dissolved therein is obtained. The minerals and amino
acids are separated in step 12 and transported back to the fields
again as manure. The water is reused in the comminution and
suspension step 7.
REFERENCE LIST
[0056] 1 Shaft [0057] 2 Reactor [0058] 3 Inlet [0059] 4 Outlet
[0060] 5 Surrounding soil [0061] 6 Biomass [0062] 7 Comminution and
suspension step [0063] 8 Reactor [0064] 9 Conversion into
electrical energy [0065] 10 Separation step [0066] 11 Coal [0067]
12 Separation of minerals and amino acids from water [0068] 13
Manure
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