Fe + H2O = FeO + H2
The above equation tells us that with steam and hot or molten iron we can make H2 with rust being the byproduct. This rust can be converted back to iron. Check out the below links for more information.
A seven page pdf file called HYDROMAX - BRIDGE TO THE HYDROGEN ECONOMY
Alchemix home page: ALCHEMIX HOME PAGE
The above equation tells us that with steam and hot or molten iron we can make H2 with rust being the byproduct. This rust can be converted back to iron. Check out the below links for more information.
Abandoned Steel Mill
Alchemix first shows up in my extensive Hard Drive archives in Nov 2001 --
when they were proposing using molten zinc metal baths -- which I thought
was a very ingenious system indeed.
Ergo -- I researched it in much greater depth -- back "when"
Those other replies I posted are but a very few examples of where that
research led me.
My interest in this process comes from an old past "experience"
Around 1978 or so one of the industrial scrap yards I sourced "materials"
from was situated in an old abandoned steel mill near the Verdun Canal.
The plant was in full activity in the from the late 1800's to the early
1900's -- O believe the great depression was it's final death blow.
The "ruins" were fascinating and highly interesting.
The owner of this scrap yard became a close acquaintance -- and one day
supplied me with the address of the last plant engineer -- who still lived
about 3 miles from this site.
In 1978 he was 84 years of age -- but once I showed interested in the old
mill -- he became amazingly 'sharp'!
They had large underground "fire brick checker heat exchangers that could
be shifted in direction flow -- thus heated -- then heat recovered.
They also baked commercial construction bricks in the chambers.
They used the producer gas which was by product of the bessemer steel
making process in this manner.
It was burned in a tall vertical "kiln" -- which was the heart of a
reversible -- or two stage process.
The bottom part was where producer gas and air were encouraged to combust --
Directly above the combustion chamber were layers of heavy iron gratings --
above that were very high temperature (but less than 5 psi pressure!!)
steam super heaters -- and above that was a simple low pressure fire tube
boiler -- with a steam regulator -- max pressure was 100 psi -- and that
was reduced to feed the superheaters at 5 psi (A steam pressure regulator
is often simply a Tempering device -- where a little water is mixed in --
you end up with more volume -- lower pressures -- dry steam --
The exhaust from this kiln was in that mode ported in to the underground
checker heat exchanger/brick baking works.
They produced a lot of H2 -- had a good market for it -- though I never
asked more about that part (maybe Zeppelins though??)
Here is how the old engineer set up to make it "then" --
First they burned producer gas -- till the thick layer of iron grates
reached 2200 F or more -- and the boiler boiled hard. Balancing out (due to
it's design capacity -- with a good head of steam under 100 psi but with a
large waterr volume.
The hot exhaust gases went down to the heat exchangers --- giving up their
highest heat - -then being exhausted -- (Baking new brick also -- a little
Then the flow was reversed and switched -- the produce gas combustion and
air was shut down -- the heat exchanger direction was reversed -- ambient
air blown through it being heated and then fed into the bottom of the kiln
to be mixed with very super heated steam.
The low temperature low pressure super saturated steam was released into
the super heaters which were directly above the 2200 F plus thick cast iron
grates - -where radiant heat rose the temperatures of that steam to over
1800 F --
That steam was fed back into the bottom of the kiln with the super heated
air and rose up to impinge on the cast iron grates --
The reaction was steam -- hot iron -- iron Oxidizing to magnetic Oxide --
steam becoming H2 gas.
That off mixture then went into another underground complex where
relatively pure H2 was isolated from the air/H2 mix.
Once the iron grids cooled to much -- the system was reversed to run on the
producer gas to heat everything back up again.
The producer gas combustion produce much very hot CO2 which reduced the
magnetic oxide coatings on the iron grates back to iron -- and the process
then would flip again --
Another version they operated was when they got contract to make "black
iron piping" -- the black iron being iron with a layer of magnetic oxide -
-which resists all further corrosion.
Well -- if you replace the source of the producer gas from being the by
product of a bessemer furnace to a biomass gasifier --
And remember -- this all back turn of 1800's/1900's
Jeff -- you probably could build a small version of that process in your
own back yard!
Oh -- I did plumbing jobs in old Montreal where I took out steam for heat
delivery piping -- those old very low pressure systems (3 psi max) which
pipe was well over 100 years old -- and that same "Black" pipe described
above -- and totally not corroded at all -- just like new -- as the day it
Peter -- Belize
DETAILED DESCRIPTION OF THE INVENTION
The invention provides process and apparatus for producing simultaneously a
high-purity, high-pressure hydrogen-rich gas stream and a high-purity,
high-pressure carbon monoxide-rich gas stream separately and continuously
using a molten metal gasifier that contains at least two zones, a "feed
zone" and an "oxidation zone", (or in a saving embodiment, a feed mode and
an oxidization mode) together with necessary ancillary equipment. Each zone
(mode) preferably operates at a pressure above 5 atmospheres absolute and
contains a bath of comprising molten iron and, possibly, other molten
metals, such as copper, zinc, chromium, manganese, nickel or other meltable
metal in which carbon is soluble. Preferably the bath contains at least 30
percent iron by weight. Depending upon the feed, the bath may also contain
slag components which, if present, preferably form a separate phase.
In the feed zone, a hydrocarbon-containing feed in the form of a gas,
liquid, solid or mixed phase, e.g., a solid-liquid slurry or atomized solid
or liquid is introduced below the surface of the molten metal bath so that
the hydrocarbon feed comes into intimate contact with the molten metal. The
feed is introduced beneath the surface of the molten metal by a submerged
tuyere or lance or by high-velocity injection from a lance above the bath,
thereby ensuring that substantially complete chemical reactions and
substantially complete conversions to hydrogen and carbon are achieved. It
has been shown that high-purity hydrogen, defined as having a composition
very close to thermodynamic equilibrium, can be obtained in this manner.
The high-purity hydrogen thus formed leaves the feed zone as a
high-pressure hydrogen-rich gas, while the carbon dissolves in the molten
metal. Any nitrogen compounds present in the hydrocarbon feed will
decompose to form molecular nitrogen and leave as an impurity in the
hydrogen-rich gas. The hydrocarbon feed should contain a minimum of
moisture and other oxygen-containing compounds since these compounds will
decompose to form oxygen, which in turn will react with dissolved carbon to
form carbon monoxide, an undesirable impurity in the hydrogen-rich gas.
The molten metal from the feed zone containing higher levels of dissolved
carbon then enters the oxidation zone where oxygen, air, oxygen-enriched
air or other suitable oxygen-bearing stream is introduced. The
oxygen-bearing stream is introduced beneath the surface of the molten metal
by a submerged tuyere or lance or by high-velocity injection from a lance
from above the bath. A portion of the dissolved carbon reacts with the
oxygen to form carbon monoxide. It has been shown that high-purity carbon
monoxide, defined as having a composition very close to thermodynamic
equilibrium, can be obtained in this manner. The high-purity carbon
monoxide thus formed leaves the oxidation zone as a high-pressure carbon
monoxide-rich gas separate from the hydrogen-rich gas produced in the feed
zone. The molten metal from the oxidation zone which has a lower
concentration of carbon re-enters the feed zone where the carbon level is
Both molten metal zones are operated at elevated pressures, preferably
between 5 and 100 atmospheres absolute, which results in the production of
the hydrogen-rich and carbon monoxide-rich gases at elevated pressures,
thereby eliminating the need for costly compression of the gases to
industrial operating pressures, as mentioned earlier. By reducing gas
hourly space velocity (GHSV), elevated pressures also result in smaller
equipment and piping for the process including all downstream equipment and
in reduced dust carryover from the feed and oxidation zones and, by Stoke's
Law, elevated pressures reduce deleterious dust carry-over or "fuming".
A significant portion of the oxygen left in the molten iron as it re-enters
the feed zone will react with carbon from the hydrocarbon feed to form
carbon monoxide, which then becomes an impurity in the hydrogen-rich gas
stream. Thus, it is important to operate the process in such a manner that
there is a minimum of oxygen present in the molten iron when it re-enters
the feed zone. As a minimum, the molten metal will contain dissolved oxygen
based on the equilibrium with carbon monoxide gas. In addition, as an
oxygen-rich stream is introduced into molten metal, there is a tendency for
the oxygen solubility limit of the molten metal to be exceeded immediately
at the interface between the oxygen-rich stream and the molten metal, which
results in the formation of a separate iron oxide phase at the interface.
This iron oxide phase will be readily dissolved by surrounding molten metal
and not accumulate in the molten metal bath provided the overall oxygen
concentration of the molten metal bath is below the oxygen solubility
limit. If the overall equilibrium oxygen concentration of the molten metal
bath exceeds the solubility limit, however, the separate iron oxide phase
will tend to accumulate to significant levels. Then, when the molten metal
containing significant quantities of this iron oxide phase re-enters the
feed zone, much of this iron oxide phase will react with carbon from the
hydrocarbon feed to form a substantial quantity of carbon monoxide, which
will contaminate the hydrogen-rich gas being produced. Accumulation of
significant quantities of a separate iron oxide phase also substantially
increases the attack of the refractory walls in the vessels holding the
molten metal since a separate iron oxide phase can be very aggressive
toward refractory. Thus, the oxygen concentration in the molten metal must
be controlled so that it does not exceed its solubility limit.
When molten iron is in equilibrium with carbon monoxide gas (formed in the
oxidation zone), it has been shown that carbon and oxygen exist in the
molten iron at equilibrium concentrations which can be determined by the
equation: ##EQU1## where: K is an equilibrium constant that varies with
[C] is the concentration of carbon in molten iron, weight percent
[O] is the concentration of oxygen in molten iron, weight percent
P.sub.CO is the partial pressure of carbon monoxide, atmospheres absolute
T is the temperature, .degree. K.
The solubility limit of oxygen in molten iron can be described by:
log [O.sub.solubility limit ]=-6320/T+2.734 (2)
[O.sub.solubility limit ] is the concentration of oxygen in molten iron at
its solubility limit, weight percent
Thus, at a given temperature, T, the minimum concentration of carbon
required in the molten iron to ensure that the equilibrium oxygen
concentration in the molten iron does not exceed the oxygen solubility
limit can be described by the equation: ##EQU2##
At 1600.degree. C., for example, the solubility limit of oxygen based on
Equation (2) is 0.229 weight percent in molten iron. Using Equation (3) at
this temperature, the minimum carbon concentrations as a function of
pressure required to prevent the equilibrium oxygen concentration from
exceeding 0.229 weight percent are calculated as follows:
CO Partial Min. Carbon
Pressure, ata Conc., wt %
Similar relationships can be determined for different temperatures and for
molten metal baths which contain iron mixed with other metals.
In commercial steel-making practices, it is common to operate at a pressure
of one atmosphere and, in a few processes, under vacuum. As shown by data
above, when operating at carbon monoxide partial pressures of one
atmosphere or below, relatively low concentrations of carbon can be
achieved without reaching the oxygen solubility limit. For example, at
1600.degree. C. and one atmosphere, the carbon concentration must fall
below 0.0088 weight percent before the solubility limit of oxygen is
exceeded and a separate iron oxide phase starts to accumulate.
When operating at elevated pressures, on the other hand, control of minimum
carbon levels becomes much more critical. At 1600.degree. C. and 100
atmospheres of pressure, for instance, the oxygen solubility limit is
reached when the carbon level reaches about 0.88 weight percent, which is
100 times higher than for one atmosphere of pressure.
Thus, in the present invention, the carbon concentration in the molten iron
leaving the oxidation zone and entering the feed zone is controlled above
the value determined by Equation (3) at elevated pressures to prevent the
equilibrium oxygen level from exceeding its solubility limit and causing
the accumulation of a separate iron oxide phase, which would result in the
excessive formation of carbon monoxide in the feed zone and excessive
contamination of the hydrogen-rich gas.
The carbon concentration in the molten metal bath leaving the feed zone, on
the other hand, is controlled at a higher concentration in order to
minimize the quantity and circulation rate of molten metal required in the
system. The economics of the process are better when the differential in
the carbon concentrations between the feed zone and the oxidation zone are
higher. Thus, the carbon concentration in the molten metal leaving the feed
zone should be maximized, although the concentration must be kept below the
carbon solubility limit (which is in the range of 4-5 weight percent in
molten iron) in order to minimize unreacted carbon and hydrocarbon feed
from leaving the molten metal as dust and lower molecular weight
hydrocarbons in the effluent gas.
This invention also includes having the hydrogen-rich and carbon
monoxide-rich gases flow from the molten metal zones through separate
product gas lines and pass through successive downstream coolers and dust
removal systems to prepare the gases for use by industrial processes.
Suitable feeds for the process include hydrogen- and carbon-containing
materials selected from the group consisting of: light gaseous hydrocarbons
such as methane, ethane, propane, butane, natural gas, and refinery gas;
heavier liquid hydrocarbons such as naphtha, kerosene, asphalt, hydrocarbon
residua produced by distillation or other treatment of crude oil, fuel oil,
cycle oil, slurry oil, gas oil, heavy crude oil, pitch, coal tars, coal
distillates, natural tar, crude bottoms, and used crankcase oil; solid
hydrogen-and carbon-containing materials, such as coke, coal, rubber, tar
sand, oil shale, and hydrocarbon polymers; and mixtures of the foregoing.
A portion of the hydrogen-rich gas or carbon monoxide-rich gas may be
recycled in the process to facilitate feeding hydrocarbons to the feed zone
or feeding an oxygen source to the oxidation zone or to promote mixing or
movement of the molten metal.
When feeding a heavier liquid or solid hydrocarbon to the feed zone and
feeding oxygen to the oxidation zone, the overall process of converting the
feedstock to hydrogen-rich and carbon monoxide-rich gases is exothermic.
Thus, it becomes necessary to moderate the temperatures of the process. In
the present invention, this is accomplished by (a) adding light gaseous
hydrocarbons to the feed zone, (b) adding carbon dioxide to the oxidation
zone, (c) adding steam to the oxidation zone or (d) diluting the oxygen
with air. In each case, sufficient material is added to achieve an overall
adiabatic operation and stable operating temperatures. Case (a) or (b) is
preferred when the objective is produce two high-purity gas products. Case
(c) or (d) introduces impurities to the carbon monoxide-rich gas and is
practical only if the purity of the carbon monoxide-rich gas is not critical.
When a hydrocarbon feed containing sulfur compounds is fed to the feed
zone, the sulfur compounds will decompose and elemental sulfur thus formed
will dissolve in the molten metal. In conventional practice, a fluxing
agent, such as calcium oxide, is added to the bath to react with the
dissolved sulfur and produce a sulfide, which forms a slag phase which
tends to float on the top of the molten metal. The slag is removed
continuously or intermittently by tilting the vessel and pouring out the
slag or by allowing the slag to flow through a tap hole in the side of the
vessel. Pouring or tapping slag is difficult to practice in a vessel
operating at elevated pressures. To handle sulfur in hydrocarbon feeds
containing high levels of sulfur of up to 4 weight percent or more requires
the use of large amounts of fluxing agents and produces large amounts of
slag which must be disposed of safely. Thus, it is becomes very expensive
to handle hydrocarbon feeds containing high levels of sulfur using
As an added feature of the present invention, the sulfur in the hydrocarbon
feed is processed without the use of slag. Dissolved elemental sulfur (from
the hydrocarbon feed) is allowed to build up in the molten metal bath to an
equilibrium level and to react with hydrogen dissolved in the bath (also
from the hydrocarbon feed). Hydrogen sulfide is formed and leaves the
molten metal bath in the gaseous effluents, primarily the hydrogen-rich
gas. The concentration of elemental sulfur dissolved in the molten metal
bath will reach an equilibrium level such that the rate of sulfur leaving
the molten metal bath as hydrogen sulfide is equal to the rate of sulfur
entering the molten metal bath with the feed. The equilibrium concentration
of sulfur in the molten metal is a function of the carbon level present. By
achieving a relatively high level of carbon in the molten metal leaving the
feed zone, the equilibrium level of sulfur in the bath can be minimized.
Sulfur compounds other than hydrogen sulfide, such as carbonyl sulfide and
carbon disulfide, may also be formed and leave in the products gases,
especially in the carbon monoxide-rich gas. The product gases may be fed to
conventional scrubbers to remove the hydrogen sulfide and other gaseous
sulfur compounds, thereby recovering the sulfur for reuse in industry and
producing substantially sulfur-free product gases.
As another added feature of the present invention, a portion of the liquid
hydrocarbon feed, prior to its introduction to the molten metal feed zone,
may be used as a scrubbing medium to remove dust from the hydrogen-rich and
carbon monoxide-rich gases (6524AUS). The portion of the hydrocarbon feed
containing the removed dust is then joined with the remainder of the
hydrocarbon feed and introduced to the feed zone, thereby providing a
direct and inexpensive means of recovering and recycling the dust back to
the molten metal bath.
As still another added feature of the present invention, the liquid
hydrocarbon feed containing removed dust may be passed through a magnetic
separation device to preferentially separate out a portion of the low-iron
dust from the hydrocarbon feed before it is fed to the molten metal feed
zone. In this manner, a portion of the non-iron slag compounds which can
build up in the molten metal bath over time may be continuously removed
from the system.
Why not just make gasoline and diesel??
Why not just make gaoline and diesel??
United States Patent: 5,763,716
Benham , et al. June 9, 1998
Process for the production of hydrocarbons
A process of converting a feed of hydrocarbon-containing gases into liquid hydrocarbon products including a first reaction of converting the feed into one to 2.5 parts of hydrogen to one part carbon monoxide in the presence
of carbon dioxide and then secondly reacting the hydrogen and carbon monoxide in a Fischer-Tropsch synthesis reactor using a promoted iron oxide catalyst slurry to form liquid hydrocarbon products, wherein the carbon dioxide from the
first and second reactions is separated from the product streams and at least a portion of the separated carbon dioxide is recycled into the first reaction feed
and the hydrocarbon products are separated by distillation and a normally gaseous portion of the separated products are further reacted in another Fischer-Tropsch synthesis reactor to produce additional liquid hydrocarbon product.
There have only been a few instances wherein the Fischer-Tropsch reaction has been incorporated into a complete system, starting with a solid or gaseous feedstock. Germany placed several plants in operation during the 1930's
and 1940's using coal as the feed stock, referenced in Twenty-Five Years of Synthesis of Gasoline by Catalytic Conversion of Carbon Monoxide and Hydrogen, Helmut Pichler, Advances in Catalysis, 1952, Vol. 4, pp. 272-341. In
addition to the foregoing, South Africa has been using Fischer-Tropsch technology based upon this German work for the past 35 years to produce gasoline and a variety of ther products from coal, referenced in Sasol Upgrades Synfuels with Refining Technology, J. S. Swart, G. J. Czajkowski, and R. E. Conser, Oil & Gas Journal, Aug. 31, 1991, TECHNOLOGY. There was also a Fischer-Tropsch plant
built in the late 1940's to convert natural gas to gasoline and diesel fuel described in Carthage Hydrocol Project by G. Weber, Oil Gas Journal, 1949, Vol. 47, No. 47, pp. 248-250. These early efforts confirmed that commercial
application of the Fischer-Tropsch process for the synthesis of hydrocarbons from a hydrocarbon-containing feed stock gas requires solving, in an economical manner,
a set of complex problems associated with the complete system. For example, initially, it is important for the hydrocarbon-containing feed stock to be converted into a mixture consisting essentially of hydrogen and carbon monoxide before introduction of the mixture into the Fischer-Tropsch reactor.
Economic operation of specific sizes of Fischer-Tropsch reactors, generally requires the ratio of hydrogen to carbon monoxide to be within well established ranges. The
Hydrocol plant, referenced hereinbefore, used partial oxidation of natural gas to achieve a hydrogen to carbon monoxide ratio of about 2.0.
An alternative approach to partial oxidation uses steam reforming for converting light hydrocarbon-containing gases into a mixture of hydrogen and carbon monoxide. In this latter case, steam and carbon dioxide, methane and water are
employed as feed stocks and carbon dioxide can be recycled from the output of the reformer back to its inlet for the purpose of reducing the resultant hydrogen to carbon noxide ratio.
There are therefore, two primary methods for producing synthesis gas from methane: steam reforming and partial oxidation.
Steam reforming of methane takes place according to the following reaction:
H.sub.2 O+CH.sub.4 .apprxeq.3H.sub.2 +CO (1)
Since both steam and carbon monoxide are present, the water gas shift reaction also takes place:
142. H.sub.2 O+CO.apprxeq.H.sub.2 +CO.sub.2 ( 2)
Both of these reactions are reversible, i.e., the extent to which they proceed as written depends upon the conditions of temperature and pressure employed. High temperature and low pressure favor the production of synthesis gas.
Partial oxidation reactions utilize a limited amount of oxygen with hydrocarbon-containing gases, such as methane, to produce hydrogen and carbon monoxide, as shown in equation (3), instead of water and carbon dioxide in the
case of complete oxidation.
1/2 O.sub.2 +CH.sub.4 .fwdarw.2H.sub.2 +CO (3)
In actuality, this reaction is difficult to carry out as written. There will always be some production of water and carbon dioxide; therefore the water gas shift reaction (2) will also take place. As in the steam reforming case,
relatively high temperatures and relatively low pressures favor production of synthesis gas.
The primary advantage of partial oxidation over steam reforming is that once the reactants have been preheated, the reaction is self-sustaining without the need for the addition of heat.
Another advantage of partial oxidation is the lower ratios of hydrogen to carbon monoxide normally produced in the synthesis gas which ratios better match the desired ratio for use in the Fischer-Tropsch synthesis of hydrocarbon
liquids in the overall process.
A still further advantage of partial oxidation resides in the elimination of a need for the removal of carbon dioxide and/or hydrogen from the synthesis gas before being fed to the synthesis reactors.
While adjustment of the hydrogen to carbon monoxide ratio can be achieved by removal of excess hydrogen using a membrane separator, for example. This approach requires additional capital equipment and can result in lower oil or
liquid hyrdrocarbon yields due to a loss of hydrogen to the process.
In order for the overall process considerations to be used in a manner which can produce economical results whether employing either steam reforming or partial oxidation of a feed stock, the Fischer-Tropsch reactor must typically
be able to convert at least 90% of the incoming carbon monoxide. If a 90% conversion efficiency is to be achieved in single pass operation and hydrogen is not removed before introduction of the gas stream into the reactor, the
build up of unreacted hydrogen due to the excess of hydrogen will necessitate a larger reaction vessel to maintain a sufficiently long residence time in the
Recycle of unreacted hydrogen and carbon monoxide from the
outlet of the Fischer-Tropsch reactor back to its inlet is commonly employed to achieve the required conversion. However, when an excess of hydrogen is employed, an even
greater excess of unreacted hydrogen will build up under such a recycle operation. This condition, in turn, can necessitate an even larger reaction vessel or alternatively the hydrogen removal described must be employed.
Major drawbacks to the commercialization of many of the prior processes were the high cost of product specific catalysts, and when an inexpensive catalyst was utilized an unacceptable overall process conversion efficiency of the
carbon input into the hydrocarbon products produced.
The two catalyst types attracting the most serious attention for the Fischer-Tropsch reaction are either cobalt based or iron-based catalysts. In practice, a cobalt-based catalyst will favor the following reaction:
CO+2H.sub.2 .fwdarw.(--CH.sub.2 --)+H.sub.2 O (4)
While an iron catalyst will favor the following overall reaction (due to its high water gas shift activity):
2CO+H.sub.2 .fwdarw.(--CH.sub.2 --)+CO.sub.2 ( 5)
Theoretically, cobalt-based catalysts can produce higher conversion yields than iron-based catalysts since cobalt can approach 100% carbon conversion efficiency, whereas iron tends toward 50% carbon conversion efficiency during
the Fischer-Tropsch synthesis reaction since the reaction (5) favors the production of carbon in the form of CO.sub.2. The major drawbacks encountered are, first, that cobalt-based catalysts are very expensive compared to
iron-based catalysts and, further, if the Fischer-Tropsch technology was embraced worldwide on a large scale, the higher demand for relatively scarce cobalt might drive the cost even higher.
The use of cobalt-based catalysts has typically included recycle of tail effluent back to the inlet of the Fischer-Tropsch reactor to achieve 90% conversion primarily because cobalt favors formation of water. Too much water has been considered to be an inhibitor of either catalytic reaction
scheme. Thus, as the reaction proceeds in the presence of water, not only is the concentration of reactants less, but the concentration of inhibiting water vapor is greater. In practice, generally 70% carbon monoxide conversion is the maximum attainable in single-pass operation using a cobalt-based catalyst.
Iron-based catalysts, which favor carbon dioxide formation permit up to 90% of the theoretical conversion of carbon monoxide per pass without great difficulty, and without the formation of additional water, thereby eliminating the
necessity for effluent recycle back to the inlet of the Fischer-Tropsch reactor.
It has generally been considered undesirable to form CO.sub.2 in the Fischer-Tropsch synthesis reaction as happens using iron-based catalysts and therefore many process schemes use cobalt-based catalysts including
the recycle of some of the reactor effluent directly back into the Fischer-Tropsch reactor.
In summary, therefore, iron-based catalysts, while efficient in converting carbon monoxide into the products shown in equation (5), have previously been limited in overall carbon conversion efficiency since their use
favors the production of carbon dioxide, and therefore, they were not as efficient in overall carbon conversion efficiency to hydrocarbon products compared to the
process schemes utilizing cobalt based catalysts.
The Fischer-Tropsch synthesis has commercially therefore been used incombination with an up-stream steam reforming reactor which must then be followed by CO.sub.2 removal from the carbon monoxide and hydrogen reaction products before the CO and H.sub.2 synthesis gas produced by the
steam reforming reaction are subjected to a Fischer-Tropsch reaction using cobalt-based catalysts.
In selecting a suitable catalyst for use in a system which favors reaction (5), several considerations are important. In the Fischer-Tropsch synthesis using appropriately designed equipment, the hydrogen to carbon monoxide feed ratio to the Fischer-Tropsch reactor will optimally be in the range of from 0.6 to 2.5 parts of hydrogen for every part of carbon monoxide. This is necessary in order to obtain reasonably acceptable percent conversion of carbon monoxide into hydrocarbon per pass through the Fischer-Tropsch reactor without the undesirable formation of carbon in the catalyst bed.
In order to provide the H.sub.2 /CO ratio in the range of optimum ratios described hereinbefore for the catalyst selected, it is necessary and typical that an additional stage of hydrogen removal, by a membrane or the like, is
inserted into the product stream between the steam reformer and the Fischer-Tropsch reactor.
The present invention overcomes the foregoing difficulties, and provides a novel, unobvious and effective economically viable natural gas to oil conversion process using steam reforming or partial oxidation and a Fischer-Tropsch
synthesis using a promoted iron-based unsupported catalyst in a slurry reactor.
The present invention includes a solution to the problems of reducing the formation of excess hydrogen from the reformer or partial oxidation unit and increasing the overall carbon conversion efficiency for the entire
carbon input to the system when using specifically prepared promoted iron catalysts. As will be shown hereinafter, the carbon dioxide produced by such iron catalysts, contributes to the low carbon conversion efficiencies previously discussed, and can be used to solve both the excess hydrogen and low overall carbon conversion
Again jumping to:
The hydrogen and carbon monoxide-containing gas stream 12 is then introduced into a Fischer-Tropsch reactor which employs a catalyst slurry using an iron-based catalyst and preferably a precipitated iron catalyst and most
preferably a precipitated iron catalyst that is promoted with predetermined amounts of potassium and copper depending on the preselected probability of linear condensation polymerization, i.e. chain growth, and product
molecular weight distribution sought.
There are three fundamental aspects to producing a catalyst for a particular application: (1) composition, (2) method of preparation, and (3) procedure for its activation.
The preferred catalyst herein is an unsupported recipitated iron catalyst promoted with copper and potassium. The catalyst is made using elemental iron 473. and copper as starting materials.
The first step in the cataylst preparation process is dissolution of the starting metals in nitric acid to form a mixture of ferrous nitrate, ferric nitrate and cupric nitrate in appropriate proportions. The ratio of water to
acid is an important parameter and should be adjusted to give a weight ratio of about 6:1. The dissolution of the metals in nitric acid either by the addition of the metal to the acid or the acid to the metal produces an
evolution of nitrogen oxides, principally nitric oxide and nitrogen dioxide.
Nitric oxide has limited solubility in the acid, but can be readily oxidized to nitrogen dioxide by contact with air or oxygen. Nitrogen dioxide dissolves in water producing
nitric acid and nitric oxide, respectively. Therefore, in order to reduce nitrogen oxide emissions from the reaction vessel and, at the same time, to reduce the consumption of nitric acid needed for dissolution of the metals,
oxygen is bubbled through the solution while the metals are being dissolved. The small amount of nitrogen dioxide which escapes from the vessel is scrubbed using a potassium hydroxide or other basic solution such as of ammonium
hydroxide. The mixture is stirred until the metals are totally dissolved. The temperature of the solution increases as the metals dissolve, but is preferably
controlled to a maximum temperature of about 150.degree. C.
The next step in the catalyst process is precipitation of a catalyst precursor from the nitrate solution using ammonium hydroxide. Ammonium hydroxide is prepared by dissolving anhydrous ammonia in water. Ammonium hydroxide at ambient
temperature is added to the hot nitrate solution until the pH of the solution reaches 7.4. At this point, all of the metals have precipitated out as oxides.
The mixture is cooled to 80.degree. F. and the final pH is adjusted to 7.2. After precipitation, the catalyst recursor must be washed free of ammonium nitrate using high quality water which is free of chlorine. The slurry is first
pumped from the precipitation vessel into a holding tank located upstream of a vacuum drum filter.
The catalyst precursor is allowed to settle in
the holding tank, and a clear layer of concentrated ammonium nitrate solution forms above the solids. This layer is drawn off, such as by decantation or by centrifugation before the slurry is washed and filtered. A vacuum drum filter fitted with water spray bars is used for washing the catalyst precursor and concentrating the
The electrical conductivity of the filtrate is monitored to
ensure complete removal of ammonium nitrate from the slurry.
After the catalyst precursor has been washed, the last ingredient of the catalyst, potassium carbonate, is added in an amount appropriate for the quantity of iron contained in the batch. The potassium carbonate is dissolved in a small amount of water and this solution is mixed thoroughly into the slurry to distribute the potassium uniformly. At this point, catalyst present in the slurry should preferably be between about 8 to about 12% by weight.
Heat, such as from a spray dryer, is used to remove most of the water from the catalyst and at the same time to produce roughly spherical catalyst particles having diameters in the range of about 1 to about 5 up to about 40 to about 50
The last step in the process is annealing by heating the catalyst in air to about 600.degree. F. to remove residual moisture and to stabilize the catalyst. Chemically, the annealing step converts the hydrous iron oxide
Goethit Fe.sub.2 O.sub.3 H.sub.2 O, to Hematite, Fe.sub.2 O.sub.3. This step is carried out in a fluidized bed which can be electrically heated. The annealed catalyst is then
ready for induction or activation and use.
Determining the "best" activating procedure for a catalyst is difficult at best even if it is known what changes in the catalyst are needed to give the desired activity, selectivity and stability. Many different activating
procedures for making promoted Fischer Tropsch iron catalysts have been described in the literature. For example, one of the most definitive studies on
activating Fischer Tropsch iron catalysts for use in fixed-bed reactors was published by Pichler and Merkel. (United States Department of Interior Bureau of Mines, Technical Paper 718, By H. Pickler and H. Merkel, Translated by Ruth
Brinkley with Preface and Foreword by L. J. E. Hofer, United States Government Printing Office, Washington, D.C., 1949, Chemical and Thermomagnetic Studies on Iron Catalysts For Synthesis of Hydrocarbons). In this study, high activity of the catalyst was correlated with the presence of iron carbides after the activation
procedure. The most effective procedure used carbon monoxide at 325.degree. C. at 0.1 atm. pressure. The study also showed how the presence of copper and potassium in the catalyst affected activation of the catalyst.
The following equations show the stoichiometry for some of the reactions which can take place during activation:
Production of Cementite from Hematite using hydrogen-rich synthesis gas:
3Fe3.sub.2 O.sub.3 +11H.sub.2 +2CO.fwdarw.2Fe.sub.3 C+11H.sub.2 O(6)
Production of Cementite from Hematite using carbon monoxide alone:
3Fe.sub.2 O.sub.3 +13CO.fwdarw.2Fe.sub.3 C+11CO.sub.2 (7)
In the presence of an iron-based catalyst, the following reactions take place:
2nH.sub.2 +nCO.fwdarw.C.sub.n H.sub.2n --+nH.sub.2 O (olefin)(8)
Water gas shift reaction:
H.sub.2 O+CO.apprxeq.H.sub.2 +CO.sub.2 (10)
Jeff Davis replied on December 1, 2006 - 6:13pm Permalink
OK -- found the more exact reference:
United States Patent 5,537,940
Nagel , et al. July 23, 1996
Method for treating organic waste
Organic waste is treated in a molten metal bath to sequentially form
enriched hydrogen gas and carbon oxide gas streams. The method includes
introducing organic waste to a molten metal bath in the absence of a
separate oxidizing agent and under conditions that will decompose the
organic waste. As a consequence of this decomposition, an enriched hydrogen
gas stream is generated and the molten metal bath becomes carbonized.
Thereafter, an oxidizing agent is added to the carbonized molten metal bath
to oxidize the carbon contained in the carbonized molten metal bath.
Reaction of the oxidizing agent with the carbon causes formation of a
carbon oxide that escapes from the bath as an enriched carbon oxide gas
stream, thereby decarbonizing the molten metal bath.
BACKGROUND OF THE INVENTION
Disposal of organic wastes in landfills and by incineration has become an
increasingly difficult problem because of diminishing availability of
disposal space, strengthened governmental regulations, and the growing
public awareness of the impact of hazardous substance contamination upon
the environment. Release of hazardous organic wastes to the environment can
contaminate air and water supplies thereby diminishing the quality of life
in the affected populations.
To minimize the environmental effects of the disposal of organic wastes,
methods must be developed to convert these wastes into benign, and
preferably, useful substances. In response to this need, there has been a
substantial investment in the development of alternate methods for suitably
treating hazardous organic wastes. One of the most promising new methods is
described in U.S. Pat. Nos. 4,574,714 and 4,602,574, issued to Bach and
Nagel. The Bach/Nagel method for destroying organic material, including
toxic wastes, involves decomposition of the organic material to its atomic
constituents in a molten metal and reformation of these atomic constituents
into environmentally acceptable products, including hydrogen, carbon
monoxide and/or carbon dioxide gases.
SUMMARY OF THE INVENTION
The present invention relates to a method for treating organic waste in
molten metal contained in a vessel to sequentially form enriched hydrogen
gas and carbon oxide gas streams.
In one embodiment, an organic waste containing hydrogen and carbon is
introduced into molten metal, without the addition of a separate oxidizing
agent and under conditions sufficient to decompose the organic waste and to
generate an enriched hydrogen gas stream and to carbonize the molten metal.
The enriched hydrogen gas stream is substantially removed from the vessel.
Thereafter, a separate oxidizing agent is added into the carbonized molten
metal to oxidize carbon contained in the carbonized molten metal to form an
enriched carbon oxide gas stream. The enriched carbon oxide gas stream is
substantially removed from the vessel.
In another embodiment of the invention employed to increase the amount of
carbon dioxide to carbon monoxide in the enriched carbon oxide gas stream,
the organic waste is introduced into molten metal contained in a vessel
which comprises two immiscible metals wherein the first immiscible metal
has a free energy of oxidation, at the operating conditions, greater than
that for oxidation of carbon to carbon monoxide and the second immiscible
metal has a free energy of oxidation, at the operating conditions, greater
than that for oxidation of carbon monoxide to carbon dioxide, without the
addition of a separate oxidizing agent and under conditions sufficient to
decompose the organic waste and to generate an enriched hydrogen gas stream
and to carbonize at least one of the two immiscible metals. The enriched
hydrogen gas stream is substantially removed from the vessel. Thereafter, a
separate oxidizing agent is added into the carbonized molten metal to
oxidize carbon contained in the carbonized molten metal to generate an
enriched carbon monoxide and carbon dioxide gas stream having a
significantly increased ratio of carbon dioxide/carbon monoxide compared to
that produced in molten iron under the same conditions and decarbonizing
the molten metal. The enriched carbon oxide gas stream is substantially
removed from the vessel.
This invention has the advantage of treating organic waste to form an
enriched stream of hydrogen gas and a separate enriched stream of carbon
oxide gas, such as carbon monoxide or carbon dioxide or both. Enriched
hydrogen and/or carbon oxide gas streams are often desired. For example, an
enriched stream of hydrogen gas is particularly useful in the synthesis of
ammonia or oxoalcohol and in hydrogenation or desulfurization processes.
Hydrogen is also an excellent "clean" or "greenhouse gas free" fuel.
Molten Liquid Metal Bath Gasifiers
I also worked for a while in a cast iron foundry and remember the H2
evolved when stirring molten cast iron in the pot with a hard wood stick.
It was a very old fashioned operation.
But I simply loved pouring molten cast iron into a mold I had made up and
breaking it out later -- solid!!
by the way -- all those articles are archived under a folder titles:
Molten liquid metal bath gasifiers