U.S. patent application number 11/595742 was filed with the patent office on 2007-03-15 for process for production of hydrogen from anaerobically deomposed organic materials.
This patent application is currently assigned to World Hydrogen Energy, LLC.. Invention is credited to Sukomal Roychowdhury.
Application Number | 20070056842 11/595742 |
Document ID | / |
Family ID | 29273209 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070056842 |
Kind Code |
A1 |
Roychowdhury; Sukomal |
March 15, 2007 |
Process for production of hydrogen from anaerobically deomposed
organic materials
Abstract
A process for the production of hydrogen from anaerobically
decomposed organic materials by applying an electric potential to
the anaerobically decomposed organic materials, including landfill
materials and sewage, to form hydrogen, and for decreasing the time
required to treat these anaerobically decomposed organic materials.
The organic materials decompose to volatile acids such as acetic
acid, which may be hydrolyzed by electric current to form hydrogen.
The process may be continuously run in sewage digestion tanks with
the continuous feed of sewage, at landfill sites, or at any site
having a supply of anaerobically decomposed or decomposable organic
materials.
Inventors: |
Roychowdhury; Sukomal; (San
Diego, CA) |
Correspondence
Address: |
KRAMER LEVIN NAFTALIS & FRANKEL LLP;INTELLECTUAL PROPERTY DEPARTMENT
1177 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Assignee: |
World Hydrogen Energy, LLC.
|
Family ID: |
29273209 |
Appl. No.: |
11/595742 |
Filed: |
November 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09932014 |
Aug 17, 2001 |
7138046 |
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11595742 |
Nov 10, 2006 |
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09472274 |
Dec 27, 1999 |
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09932014 |
Aug 17, 2001 |
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08659644 |
Jun 6, 1996 |
6090266 |
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09472274 |
Dec 27, 1999 |
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Current U.S.
Class: |
204/164 |
Current CPC
Class: |
C01B 3/342 20130101;
Y02E 60/36 20130101; Y02P 20/134 20151101; C01B 3/32 20130101; C25B
1/04 20130101; Y02P 20/133 20151101; C25B 1/02 20130101; C12P 3/00
20130101; Y02E 50/343 20130101; Y02E 60/366 20130101; Y02E 50/30
20130101 |
Class at
Publication: |
204/164 |
International
Class: |
H05F 3/00 20060101
H05F003/00 |
Claims
1. A process for producing hydrogen from anaerobically digested
organic materials comprising the steps of: placing said materials
in a reaction zone; and applying an electric potential across said
materials; thereby producing hydrogen and carbon dioxide whereby
said electric potential is applied occasionally after periods
without application of said electric potential.
2-22. (canceled)
Description
[0001] This application is a Continuation-In-Part of patent
application Ser. No. 08/659,644 now U.S. Pat. No. 6,090,266.
BACKGROUND OF THE INVENTION
[0002] It is recognized that additional sources of energy are
needed for sustained industrial growth. There exists an ever
present danger in depending too heavily on fossil fuels. Fossil
fuels (hydrocarbons) represent a limited supply of stored energy
which are typically released during a combustion process. By
burning hydrocarbons mankind has spewed billions of tons of toxic
pollutants into the atmosphere. It therefore makes sense from both
an environmental and economic standpoint to develop alternative
sources of renewable fuels.
[0003] Hydrogen is a fuel which does not produce pollutants, water
being its only combustion product. Hydrogen has many industrial
uses in the production of fertilizers, dyes, drugs, plastics,
hydrogenated oils and fats and methanol and is used in many
industries. It is also used as a rocket fuel and in this invention
as a minus-emissions fuel that allows ordinary engines to clean the
air.
[0004] 1. Field of the Invention
[0005] This invention relates to a process for the production of
hydrogen from anaerobically decomposed organic materials, including
materials such as those found in landfill materials and sewage
sludge, by applying an electric potential to and thereby creating a
current through the anaerobically decomposed organic material and
thereby forming hydrogen.
[0006] 2. Description of Related Art
[0007] The established processes for producing commercially
significant amounts of hydrogen are: (1) steam reforming of
hydrocarbons, (2) partial oxidation of coal, (3) electrolysis of
water, and (4) direct use of solar radiation (photovoltaic
method).
[0008] Steam-reformation of hydrocarbons and partial oxidation of
coal are disadvantageous in that fossil hydrocarbon fuels are
consumed. Production of hydrogen by electrolysis of water, a
relatively simple and non-polluting process, is costly and
therefore economically disadvantageous for most industrial
applications because the amount of energy needed for electrolysis
of water exceeds the energy obtained from the combustion of the
resulting hydrogen. Photovoltaic methods of hydrogen production
have inherent inadequacy related to access to solar radiation for
much of the world's population.
[0009] Unlike the methods for production of hydrogen outlined
above, the process of the present invention does not depend on
fossil fuels or the somewhat random appearance of sunlight to
produce hydrogen. The present process converts what are typically
waste materials into hydrogen, while simultaneously reducing the
mass of said materials and/or reducing the treatment time of such
materials by application of a relatively small and/or intermittent
electric potential to said materials. The process of this invention
uses raw materials typically found in, among other places,
municipal waste sites and sewage treatment plants and produces more
energy, in the form of the chemically stored potential energy of
hydrogen, than the electric energy required to produce the
hydrogen.
[0010] A method of producing hydrogen from sugars is discussed in
Energy and the Environment, Proceedings of the 1st World Renewable
Energy Congress, Reading, UK 23-28 Sep. 1990. S. Roychowdhury and
D. Cox ("Roychowdhury"). This method involves the production of
hydrogen from pure sugars such as glucose or maltose.
[0011] Roychowdhury reports the initial production of hydrogen upon
inoculation of a sugar solution with so-called "landfill inocula".
To obtain landfill inocula, materials were obtained from various
depths in a landfill, dried, ground (to obtain "landfill powder")
and then incubated in situ. The incubated culture medium was
observed to produce carbon dioxide and methane, primarily, and
little else, indicating the presence of highly methanogenic flora
in the inoculum. The supernatant from this culture medium, or in
some cases the landfill powder, were used as inocula.
[0012] Previously, Roychowdhury disclosed that upon inoculation of
various sugar solutions with the landfill supernatant or landfill
powder, the sugar solution produced hydrogen and carbon dioxide,
and no methane or oxygen; indicating the presence of
hydrogen-producing bacteria present in the landfill inoculum and/or
landfill hydrogen. Hydrogen production decreased with increasing
acidity.
[0013] It is another object of this invention to provide a method
of hydrogen production which does not require the use of fossil
fuels.
[0014] It is an object of the invention to serve communities that
have relatively undeveloped electricity distribution and other
energy infrastructures with a system that provides useful energy
from collected wastes.
[0015] It is an object of the present invention to separate carbon
dioxide, nitrogen and other gases from produced hydrogen.
SUMMARY OF THE INVENTION
[0016] This invention relates generally to a process which produces
hydrogen from anaerobically decomposed organic materials such as
anaerobically composted cellulosic materials and anaerobically
digested sewage sludge. This process decreases the time required to
treat anaerobically composed cellulosic materials and anaerobically
digested sewage sludge. More specifically, the invention relates to
an embodiment wherein a relatively low electric potential is
applied to anaerobically decomposed organic materials such as
anaerobically composted cellulosic waste materials and
anaerobically digested sewage sludge which, as a result of
anaerobic decomposition, have been fermented into "volatile"
carboxylic acids such as acetic acid and bicarbonates of ammonia.
The electric current resulting from the application of an electric
potential is believed to hydrolyze the acetic acids, other volatile
carboxylic acids, and bicarbonates of ammonia within the decomposed
materials, thereby producing hydrogen. Formation of methane is
suppressed, Organic mass, such as solids contained within sewage
sludge is reduced at an increased rate, and the time required to
treat waste materials such as sewage sludge is thereby reduced.
[0017] In another embodiment the time of application of
electropotential is intermittent and the duty cycle of voltage
application is adaptively adjusted to minimize electric power
consumption while maximizing hydrogen production. In application it
is believed that the activities of microorganisms that produce
enzymes that release hydrogen from the ferment is greatly
encouraged and that activities of microorganisms that produce
enzymes favoring methane production are depressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a flow chart showing both production of hydrogen
and suppression of methaneogenesis from anaerobically decomposed
organic materials in the presence of an applied electropotential,
and methanogenesis from anaerobically decomposed organic materials
in the absence of an applied electropotential.
[0019] FIG. 2 is a flow chart showing a process for production of
hydrogen which includes on-site anaerobic decomposition of organic
material.
[0020] FIG. 3 is a bar graph representation of the information in
Table 1.
[0021] FIG. 4 is a bar graph representation of the information in
Table 3.
[0022] FIG. 5 is a bar graph representation of the information in
Table 3.
[0023] FIG. 6 is a bar graph representation of the information in
Table 5.
[0024] FIG. 7 is a bar graph representation of the information in
Table 6.
[0025] FIG. 8 is a bar graph representation of the information in
Table 8.
[0026] FIG. 9 is a bar graph representation of the information in
Table 9.
[0027] FIG. 10 is a bar graph representation of the information in
Table 10.
[0028] FIG. 11 is a schematic illustration of an embodiment that
adaptively controls application of intermittently applied voltage
to maximize hydrogen production while minimizing methane
production.
[0029] FIG. 12 is a schematically illustrated embodiment showing
generation of voltage for practicing the principles of the
invention.
[0030] FIG. 13 is a schematic illustrating the principles of
another embodiment of the invention.
[0031] FIG. 14 is a schematic illustrating the principles of
another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The process of the present invention may typically be
practiced at any large municipal landfill or sewage treatment
facility, but can be practiced on a smaller scale wherever
anaerobically decomposed organics such as anaerobically composted
cellulosic materials or anaerobically digested sewage sludge are
found or may be generated.
[0033] Anaerobically composted cellulosic materials are typically
found in landfill materials. Anaerobically digested sewage sludge
typically comprises sludge found at municipal sewage treatment
plants. Landfill materials generally consist of approximately 70%
cellulosic materials and have a moisture content of 36% to 46%.
Sewage sludge is primarily liquid, contains volatile acids such as
acetic acid, and includes 2-3% solids. Both landfill materials and
sewage sludge naturally contain methane-producing abacterial
species and hydrogen-producing bacterial species.
[0034] The invention may be practiced by applying an electric
potential of between 1 and 7 volts, preferably between 3 and 6
volts, most preferably between 3.0 and 4.5 volts to, and thereby
passing an electric current through, anaerobically decomposed
organic materials such as landfill materials or sewage sludge. This
electric potential is applied through electrodes which are
preferably made from lead, copper, steel, brass or carbon, more
preferably from cast iron bars, and most preferable from metal
impregnated or otherwise electrically conductive graphite.
[0035] Anaerobic decomposition, specifically anaerobic composting
and anaerobic digestion, refers to a process where organic
compounds, typically but not limited to compounds of the general
formula C.sub.nH.sub.2nO.sub.n, decompose in the absence of an
oxygen-donor environment. Volatile acids such as acetic acid are
typically formed by such anaerobic decomposition. Although
anaerobic decomposition may in some instances be preceded by
aerobic decomposition, aerobic decomposition is not a prerequisite
to anaerobic decomposition and electrodes can be placed within the
organic materials prior to the commencement of anaerobic
decomposition.
[0036] As described above, both landfill materials comprising
anaerobically composted cellulosic materials and anaerobically
digested sewage sludge contain relatively high amounts of volatile
acids such as acetic acid. These acids are known to act as
electrolytes. In practicing the invention, one or more sets of
electrodes may be placed within landfill material or sewage sludge
in such a way that an electric potential is applied, and according
to the principles of the invention resulting in an electrical
current with low polarization and ohmic losses. Electrode distance
and placement along with the program of voltage control including
occasional reversal of polarity may be adjusted to achieve these
conditions. The voltage, average spacing of electrodes and number
of electrodes will vary depending upon the size and composition of
the landfill material or sewage sludge sought to be used to produce
hydrogen. Electrode sets, may be of any suitable shape, e.g.
plates, bars, grids, etc.
[0037] In a preferred embodiment of the invention, each individual
electrode is placed into landfill materials and is surrounded by an
inert "cage" which effectively ensures that the moisture component
of the landfill materials, and not a component which might
interfere with electrical activity, is immediately adjacent each
electrode. Place of the electrodes in a suitable position within
the landfill material may require some trial and error.
[0038] When an electric potential is applied, hydrogen production
begins and production of hydrogen increases to from 70% to 75% by
volume of the total gases produced. The level of methane produced
decreases from a high of approximately 70% by volume of the total
gases produced, when the electric current is first applied, to
greatly diminished trace levels. Carbon dioxide and nitrogen
production remain relatively constant and do not vary significantly
with methane or hydrogen production.
[0039] Without being bound by theory, it is believed that the
essence of the electrochemistry of this invention is the enzyme
facilitated production and decomposition of low molecular weight
volatile acids such as acetic acid produced by bacterial breakdown
of carbohydrates and other nutrients. Because oxygen production is
not observed, it is believed that electrolysis of water is not a
source of hydrogen. It is further believed that hydrogen gas
produced by the electrolysis of volatiles present in the sludge and
in landfill materials, inhibits the subdivision, growth, and
activity of methanogenic species.
[0040] In a preferred embodiment, cellulosic materials and/or
sewage sludge are made to decompose "on-site", i.e. in a localized
bin or chamber, rather than at a centralized landfill or sewage
treatment facility. The anaerobically composted cellulosic waste
materials and/or the anaerobically digested sewage sludge are then
optionally taken to a transfer station equipped with electrodes as
previously described to produce hydrogen, or alternatively made to
produce hydrogen "on-site" by application of electric potential at
or near the on-site bin or chamber. In this alternate embodiment,
hydrogen could then be stored or used on-sites as a energy source
to produce useful forms of energy including the relatively minor
amount used to practice the principles of the invention.
EXAMPLES
Electrodes
[0041] Electrodes were cast iron bars, 300 mm long, 25 mm wide and
2.5 mm thick. Other metallic electrodes were used including lead,
copper, steel, brass and others. pair of copper impregnated
graphite electrodes of the same size was used. Degradation of the
graphite electrode was not very noticeable.
Landfill Materials
[0042] Samples of landfill material were obtained from a sanitary
landfill at Staten Island N.Y. from a depth of between 30 to 50
feet. The landfill materials naturally produce methane and carbon
dioxide as primary gases (in 55:35 proportions) through
methanogenesis.
Sludge
[0043] Sludge samples were taken from a primary digester of a
sewage treatment plant at Brooklyn, N.Y. Sewage sludge produces
methane and carbon dioxide (in 65:30 proportions) by
methanogenesis.
Special Apparatus
[0044] A series of experiments were set up to determine whether the
production of hydrogen would take place when voltage was applied
through either sewage sludge or through landfill materials. The pH
of the sludge was 7.0-7.5 and the pH of the landfill material was
6.5-7.0. Apparatus included on 800 ml flask with a three hole
rubber stopper. Two of those holes were fitted with electrodes and
the third hole had a glass delivery tube. The electrodes and the
third hole had a glass delivery tube. The electrodes were connected
across two 1.5 volt batteries in series, resulting in an applied
potential of about 3.0 volts. The apparatus was placed in an
incubator set either at 37.degree. C. and later at 55.degree. C.
Other apparatus included a New Brunswick Fermenter using a 6-8
liter glass vessel where the temperature, and rotating stirrer and
a cooling system could be controlled at a desired setting.
Experimental Data
Example 1
[0045] As an experimental control, freshly obtained sewage sludge
in an 800 ml flask was placed at 37.degree. C. in an incubator
gases, including primarily methane, were produced as described at
Table 1 and depicted at FIG. 3. TABLE-US-00001 TABLE 1 Production
of CH.sub.4 and CO.sub.2 DAYS % CH.sub.4 % CO.sub.2 % N.sub.2 1 65
30 5 2 70 25 5 3 70 25 5 4 65 30 4 5 60 35 4 6 55 40 5
Example 2
[0046] Sewage sludge from the primary digester was placed in an 800
ml flask which was then placed in a preheated incubator at
37.degree. C. Methane gas was generated. As soon as optimum
production of methane was achieved, a current was passed through
the liquid in the flask. The production of methane gas declined
gradually and hydrogen and carbon dioxide were produced. Methane
was completely suppressed when production of hydrogen reached its
peak, as described at Table 2 and depicted at FIG. 4.
TABLE-US-00002 TABLE 2 Production of H.sub.2 and Suppression of
CH.sub.4 DAYS % CH.sub.4 % CO.sub.2 % H.sub.2 1 60 35 -- 2 70 25 --
3* 45 25 20 4 25 28 46 5 5 30 60 6 TR 30 68 *As and when current
was passed.
Example 3
[0047] Sewage sludge from the primary digester was placed in an 800
ml flask which was then placed in an incubator at 37.degree. C. A
current was passed through the sludge, applying 3 volts, using the
two 1.5 volt batteries in series. Very little methane was produced
at the beginning. Within 3 days, production of hydrogen reached its
peak and methane gas was virtually totally suppressed, as described
at Table 3 and depicted at FIG. 5. TABLE-US-00003 TABLE 3
Production of H.sub.2 and CO.sub.2 When Voltage Was Applied From
the Start DAYS % H.sub.2 % CO.sub.2 % N.sub.2 % CH.sub.4 1 65 25 2
8 2 70 25 2 TR 3 70 18 8 TR 4 70 20 8 -- 5 68 25 4 --
Example 4
[0048] A sewage sludge sample was placed in a five liter flask in
the New Brunswick Fermenter and 4 electrodes were introduced.
Electrical current was passed through (2.5 volts and 0.05 to 0.07
Amps). In the beginning only methane and carbon dioxide were
produced with very little hydrogen. As soon as the voltage was
increased to 4.0-4.5, and current to 0.11-0.15 Amps, methane was
gradually suppressed and hydrogen was produced as described at
Table 4. TABLE-US-00004 TABLE 4 Production of H.sub.2 and CO.sub.2,
From Sludge in 5 liter Container DAYS % H.sub.2 % CO.sub.2 %
N.sub.2 % CH.sub.4 1 -- 30 12 50 2 5 35 8 46 3 4 30 6 60 5 25 30 5
40 6 48 25 5 20 7 60 20 2 8 9 70 25 4 TR
Example 5
[0049] It is of particular interest to treat landfill materials
because these materials present municipalities around the world
with ubiquitous problems of vector (rodents, roaches, and
communicable disease germs) breeding places along with sources of
greenhouse gases and groundwater contamination due to production of
poisonous leachate. The present invention provides for carbon
sequestration from landfills including those that are depositories
for sewage sludge.
[0050] Landfill materials collected by random borings were provided
for determination of the least energy expenditures per energy
production. Experiments were set up with landfill materials
(composted municipal solid wastes) in two 800 ml flasks, (1) with
landfill materials only, (2) with landfill materials where
electrodes were dipped in. The results are described at Tables 5
and 6, and depicted at FIGS. 6 and 7. TABLE-US-00005 TABLE 5
Production of Gases From Landfill Materials DAYS % H.sub.2 %
CO.sub.2 % N.sub.2 % CH.sub.4 1 -- -- -- -- 2 -- 3 10 -- 3 -- 20 8
10 5 -- 40 6 50 6 -- 30 5 63 7 -- 30 5 60 8 -- 35 4 60 9 -- 35 5
62
[0051] TABLE-US-00006 TABLE 6 Production of Gases From Landfill
Materials in Presence of Applied Voltage DAYS % H.sub.2 % CO.sub.2
% N.sub.2 % CH.sub.4 Total CC 1 53 -- All -- 95 2 72 8 13 -- 302 3
76 17 6 -- 500 4 75 18 6 -- 600 5 72 18 6 -- 450 7 79 18 6 -- 600 9
65 18 14 -- 500
Example 6
[0052] Example 5 was repeated: (1) with sludge only, (2) with
sludge having operating electrodes. The results are described at
Tables 7 and 8, and depicted FIG. 8. TABLE-US-00007 TABLE 7
Production of Gases From Sludge in Absence of Applied Voltage DAYS
% H.sub.2 % CO.sub.2 % N.sub.2 % CH.sub.4 Total CC 2 -- 20 14 65 50
3 -- 14 10 70 125 4 -- 19 4 72 225 5 -- 22 4 66 258 6 -- 18 8 70
200
[0053] TABLE-US-00008 TABLE 8 Production of Gases From Sludge in
Presence of Applied Voltage DAYS % H.sub.2 % CO.sub.2 % N.sub.2 %
CH.sub.4 Total CC 2 65 28 4 8 85 3 70 20 2 TR 200 4 70 18 8 TR 310
5 70 20 2 -- 330 6 68 22 4 -- 258
Example 7
[0054] An experiment was set up with landfill materials in a 6
liter vessel with electrodes. A current was created through the
landfill materials by applying an electric potential of 3.5 V. The
results are described at Table 9 and depicted at FIG. 9.
TABLE-US-00009 TABLE 9 Production of Gases From Landfill Materials
in 6 Liter Vessel With Applied Voltage DAYS % H.sub.2 % CO.sub.2 %
N.sub.2 % CH.sub.4 TOTAL 1 75 TR 12 -- 100 2 70 5 10 -- 1020 4 75 7
15 -- 850 6 75 8 17 -- 750 8 70 5 20 -- 600
Example 8
[0055] Landfill materials in a 6 liter vessel were placed in a
preheated incubator at 55.degree. C. After 4 days electrodes were
connected to 3.5 volt terminals. The results are described at Table
10, and depicted at FIG. 10.
[0056] Similar results are achieved by mixing a relatively small
amount of inoculum of human sewage sludge with farm manure and/or
crop wastes. After an incubation period in which anaerobic
conditions were established, methane and carbon dioxide were
produced with very little hydrogen. Upon presentation of voltage at
2.0 to 5.0 volts to cause current to reach 0.10 to 0.20 Amps,
methane production was depressed and hydrogen was again produced as
summarized in Table 10. Similar results are achieved by use of
inoculum from previous runs of Example 4 and provide improvements
in the efficiency of conversion of chemical energy potential of
organic substances 25 into hydrogen. TABLE-US-00010 TABLE 10
Production of Gas from landfill Materials in Two Different
Environments In the Same Set-Up DAYS % H.sub.2 % CO.sub.2 % N.sub.2
% CH.sub.4 TOTAL 1 -- 5 All -- 20 2 -- 20 35 125 3 -- 35 55 200 4
5* -- 30 20 150 7 25 31 7 150 8 60 35 TR 250 9 68 31 -- 285 10 65
30 -- 200
[0057] FIG. 11 shows an embodiment 200 in which suitable electrodes
such as concentric electrodes 202 and 204 receive intermittently
applied voltage to influence the solvated organic waste between the
electrodes to produce hydrogen more or less according to the data
shown in Tables 8, 9, and 10. In operation, voltage is applied by
voltage source 216 according to a duty cycle controlled by relay
212 that is constantly adjusted by controller 210 to facilitate
hydrogen generation and to prevent substantial methane
production.
[0058] Feedback information from gas detector 206/208 is provided
to controller 210. If trace amounts of methane are detected a
voltage is applied between electrodes 202 and 204 for a recorded
time period until methane production is depressed. The time until
methane traces are detected again is noted by controller 210 and a
duty cycle of applying voltage across electrodes 202 and 204 for a
time interval slightly longer than the time noted for depressing
methane production followed by neutral electrode operation for a
time period slightly less than the time noted previously for traces
of methane to be detected.
[0059] This duty cycle is adaptively changed to shorten the time of
voltage application and to extend the time between voltage
application for purposes of minimizing methane production while
maximizing hydrogen production with least application of voltage to
electrodes 202 and 204. Voltage level is reduced to provide another
variable and adaptively adjusted with respect to the time of
voltage application to minimize energy expenditure. This adaptive
control algorithm rapidly adjusts for changes in organic waste
composition, moisture content, temperature, and other
variables.
[0060] FIG. 12 shows an embodiment in which the fuel gas produced
by the process of the invention in the presence of electrodes 230
and 232 is in part made available for energy conversion in 240 to
electricity by a fuel cell or engine-generator set. Adaptively
controlled application of voltage to electrodes 230 and 232 is
provided by controller 236 and relay 234 as shown for purposes of
minimizing energy consumption per therm of hydrogen produced.
[0061] Moreover, adaptive controller 236 provides a control
algorithm to minimize methane production while facilitating maximum
hydrogen production. Solenoid operated valve 238 controls delivery
of fuel gas by line 242 to energy conversion unit 240 as needed to
meet adaptively adjusted duty cycle and to meet other demands for
electricity as delivered by insulated cables 244. Suitable power
for pumping water, providing a heat-pump cycle, or production of
electricity at 240 may be by a heat engine and generator, a fuel
cell, a thermoelectric generator, or other devices that convert
fuel potential energy into electricity.
[0062] In many applications, it is preferred to utilize a piston
engine and generator in which the engine is fueled with a SmartPlug
combination fuel injector and ignition system to facilitate
extremely robust operation. SmartPlug operation is disclosed in
U.S. Pat. Nos. 5,394,852 and 5,343,699. This enables the raw
mixture of hydrogen and carbon dioxide to be used as a very low
grade fuel without further conditioning while producing very high
thermal efficiency and full rated power in comparison with engine
operation on gasoline or diesel fuel. This is a particularly
important advantage for remote operation and to bring fuel and
power to depressed economies where it is prohibitive to import
fossil-based fuels.
[0063] Preferential production of hydrogen provides thermodynamic
advantages based on faster fuel combustion, wider air/fuel ratio
combustion limits, and with SmartPlug operation the engine operates
essentially without throttle losses. These thermodynamic advantages
provide much higher brake mean effective pressure or "BMEP" for the
same heat release in comparisons with gasoline or diesel fuel.
[0064] As shown in Table 11, it is possible to actually clean the
air with an engine generator running on hydrogen-characterized fuel
produced from landfill or sewage organic wastes. The ambient air
was cleaned by operation of an engine that is compared in operation
between hydrogen and gasoline. TABLE-US-00011 TABLE 11 TEST RESULTS
AMBIENT 0.00 ppm CO 1.0 ppm NO AIR 29 ppm HC (Carbon (Nitrogen
TEST: (hydrocarbons) Monoxide) Monoxide) ENGINE WITH HYDROGEN
OPERATION Idle: 18 ppm HC 0.00 ppm CO 1.0 ppm NO Full Power: 6 ppm
HC 0.00 ppm CO 2.0 ppm NO USING GASOLINE AS FUEL IN THE SAME
ENGINE: Idle: 190 ppm HC 25,000 ppm CO 390 ppm NO.sup. Full Power:
196 ppm HC 7,000 ppm CO 95 ppm NO
[0065] Substantial amounts of carbon dioxide are produced along
with hydrogen by operation of electro-conditioned anaerobic
digestion of organic wastes. Economical separation of hydrogen from
the carbon dioxide is needed for fuel cell applications, for
increasing the storage density of hydrogen, and for increasing the
value of hydrogen produced. Such separation is provided by the
embodiment of FIG. 13. This embodiment also serves the purpose of
providing for utilization 25 of the carbon dioxide for various
purposes including use in greenhouses or hydroponics and is an
important aspect of the invention.
[0066] The solubility of carbon dioxide in water is about 21.6
volumes of gas per volume of water at 25 atmospheres pressure and
12.degree. C. (54.degree. F.). Increasing the pressure or
decreasing the temperature increases the amount of carbon dioxide
dissolved per volume of water. Lowering the pressure or increasing
the temperature releases dissolved carbon dioxide. In most areas of
the Earth, the ground water is maintained at a temperature that is
equal to the mean annual air temperature plus one degree (F) for
each 80' of overburden to the saturated zone.
[0067] FIG. 13 shows a system for separating carbon dioxide from
hydrogen by differential absorption of carbon dioxide within a
suitable medium such as water or a hindered amine. In operation,
mixed gases consisting of hydrogen, carbon dioxide, and lesser
amounts of nitrogen and other gases are forced into the bottom of a
column of water 302 approximately 1,000' or higher.
[0068] It is generally preferred to use a column of water that is
developed by placing a well approximately 1000' below the saturated
zone of the local groundwater. This provides the extremely large
heat sink benefit of the sub soil including the ground water in the
saturated zone where the temperature is generally constant at the
desired temperature of 4.degree. C. to 16.degree. C. (40.degree. F.
to 60.degree. F.) for most climate zones throughout the year. Water
columns that are elevated along mountain slopes are also feasible
but may suffer freezing conditions in the winter and unfavorable
warming in the summer season.
[0069] Mixed gases are delivered to the bottom of tube 304 by a
suitable pump (not shown). Mixed gases enter into a suitable
scrubber zone such as the helical fin 306 that is attached to tube
304 with a higher elevation at the point of attachment than any
other point on the element of rotation that describes the helical
surface as shown. Gases thus tend to be buoyed towards tube 304 as
they are scrubbed by the absorbing fluid. Carbon dioxide readily
enters into solution at the pressure and temperature conditions
maintained. Hydrogen exits at the top of the helix into tube 308
and is delivered to the surface for various uses.
[0070] Carbon-dioxide rich water is ducted to the surface by
coaxial tube 310 as shown. As the head pressure lessens, carbon
dioxide bubbles develop and escape upward and create a lower
density mixture that is buoyantly lifted to the gas separator
section 312 where denser water 25 that has lost the ability to
retain carbon dioxide is returned to annular space 302 and sinks
the bottom to replace the upward travelling inventory of water that
is lifted within tube 310. Carbon dioxide is collected at the top
of 310 by tube 314 for various useful purposes.
[0071] FIG. 14 shows an embodiment in which energy used to
pressurize the hydrogen and carbon dioxide is regeneratively
recovered by an expansion engine. Embodiment 400 shows an extremely
rugged and simple energy conversion system that combines various
renewable resources such as sewage, garbage, and farm wastes with
solar energy to supply electricity, hydrogen, and carbon
dioxide.
[0072] In many situations and applications it is preferred to
pressurize water in a suitable vessel 402 to provide for the
separation by solubility differences as desired to purify hydrogen.
In operation, mixtures of hydrogen and carbon dioxide are forced
through tube 404 into pressure vessel 402 at the nominal pressure
of 450 PSI. It is preferred to utilize a spiral mixer consisting of
a helical fin 406 that causes the mixture of gases to scrub along
the surface and form high surface-to-volume ratios. The mixed gases
follow an extended path through the water as carbon dioxide is
absorbed to allow the hydrogen to be collected at the top of spiral
scrubber 406 by tube 408 as shown. Carbon dioxide is absorbed into
the water while hydrogen is collected at the top of separator 406
as shown.
[0073] Hydrogen is delivered by conduit 408 for immediate use in an
engine or fuel cell or it may be stored for future use as needed.
Carbon dioxide saturated water is taken from absorber vessel 402 by
tube 410 to valve manifold 426 which provides control valves to
time the flow of carbon dioxide rich water into each of a group of
heat exchangers such as 414, 416, 418, 420, 422, and 424 as shown.
Each heat exchanger is provided with an exit a nozzle that is aimed
at the blades or buckets of an adjacent fluid motor rotor such as
430, 432, 434, 436, 438, and 440 which deliver work to a common
output shaft as shown.
[0074] An inventory of water and carbon dioxide solution under
pressure is suddenly forced into a preheated heat exchanger such as
414 by briefly opening the control valve that serves 414. As the
fluid is heated the temperature and pressure of the fluid increases
and it vaporizes and is expelled with very high momentum to power
motor 430. Each of the other heat exchanger chambers receives a
charge of fluid on a timed basis so that the shaft power from the
group of motors shown can be considered to have multiple phase
torquing such as six phase if each heat exchanger receives flow at
a different times or three phase if two heat exchangers are filled
simultaneously. A suitable application of the output of the fluid
motor is generator 428 or other useful loads as needed.
[0075] It is preferred to provide concentrated radiation to the
heat exchangers by a suitable solar collector such as a field of
heliostats or a parabolic dish 442 as shown. At times that solar
energy is insufficient to meet energy conversion needs,
supplemental heat may be applied by combustion from a suitable
burner 448. For such supplemental heating it is preferred to use
mixtures of carbon dioxide and hydrogen and/or other combustible
gases released by anaerobic digestion of organic matter.
[0076] After undergoing heating and expansion to a suitably low
pressure, carbon dioxide is collected by tube 458 and taken to a
suitable application. Water is condensed and collected in reservoir
450 which is cooled by countercurrent heat exchanger 456 by
circulation of a suitable heat exchange fluid from 446 to 456 and
then through 448 to a suitable cogeneration application. Cooled
water is pressurized by pump 454 and returned to pressure vessel
402 to complete the novel carbon dioxide removal and energy
conversion cycle.
SUMMARY OF THE INVENTION
[0077] Method and apparatus for utilization of intermittently
applied voltage for depression of methane production while
maximizing hydrogen generation from organic landfill and sewage
wastes is provided along with a rational control regime for
minimizing the energy expenditure to do so. Renewable biomass and
solar resources are combined in a unique energy conversion regime.
Production of electricity from an engine operated on hydrogen
sourced by the invention is integrated in a synergistic combination
that provides regenerative separation of carbon dioxide from fuel
gas air and cleaning with carbon sequestration.
[0078] The time to dispose of organic materials is preferably
reduced by anaerobically digesting such materials in a reaction
zone and applying art electric potential across the zone thereby
producing hydrogen and carbon dioxide. It is preferred to apply the
electric potential occasionally after periods without application
of said electric potential. It is preferred to apply the electric
potential at a frequency and for a period to maximize the quantity
of hydrogen produced per the amount of electricity consumed.
[0079] It is preferred to separate carbon dioxide and fuel produced
by pressurizing a fluid to a state that provides preferential
absorption of carbon dioxide, mixing the fuel and carbon dioxide
with the pressurized fluid, and collecting the fuel that remains
after preferential absorption of carbon dioxide. Energy conversion
efficiency is increased by adding heat to the fluid after
preferential absorption of carbon dioxide for the purpose of
increasing the amount of work produced by a motor that expands the
pressurized fluid, releasing the carbon dioxide in conjunction with
the expanding process, and cooling the fluid before the
pressurizing step.
[0080] The preferred source of such heat is selected from the group
including solar energy, heat released by combustion of a portion of
the fuel produced, concentrated solar energy, and a combination of
solar energy along with heat produced by combustion of a portion of
the hydrogen.
[0081] An energy conversion process is provided by the steps of
anaerobically digesting organic materials to produce carbon dioxide
and fuel selected from the group including hydrogen, methane, and
mixtures of hydrogen and methane, separating the carbon dioxide
from the fuel. The preferred method of separation is comprised of
pressurizing a fluid to a state that provides preferential
absorption of carbon dioxide, mixing the carbon dioxide and fuel
with the fluid, collecting the fuel that remains after said
preferential absorption of carbon dioxide, adding heat to the fluid
after preferential absorption of carbon dioxide for the purpose of
increasing the amount of work produced by a motor that expands
pressurized fluid, releasing carbon dioxide in conjunction with the
expanding process, and cooling the fluid before the pressurizing
step.
[0082] In instances that it is preferred to utilize anaerobic
digestion to produce hydrogen instead of methane, feedstock organic
materials are placed in a reaction zone and an electric potential
or voltage is applied across the materials thereby producing
hydrogen and carbon dioxide. It is preferred to provide application
of intermittent voltage for purposes selected from the group
including depression of microorganismal activity that produces
methane, enhancement of microorganismal activity that produces
hydrogen, and creation of an atmosphere within organic materials
that is maintained rich in hydrogen. The process intermittent
application of voltage is optimized by feedback information from a
gas detector as provided to a controller means. If trace amounts of
methane are detected, the voltage is applied for a recorded time
period until methane production is depressed, the time until
methane traces are detected again is noted by the controller and a
duty cycle is provided for applying voltage for a time interval
slightly longer than the time noted for depressing methane
production followed by neutral electrode operation for a time
period slightly less than the time noted previously for traces of
methane to be detected In this process, the voltage level is
variably reduced to provide an adaptively adjusted control with
respect to the time of said voltage application to minimize energy
expenditure.
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