Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Destruction of hazardous or toxic waste
Reexamination Certificate
1999-12-15
2003-12-16
Naff, David M. (Department: 1651)
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Destruction of hazardous or toxic waste
C435S252100, C435S266000
Reexamination Certificate
active
06664101
ABSTRACT:
BACKGROUND OF THE INVENTION
Beside the methane emanating from technical installations and by a natural way from the soil, carbon dioxide is the most important greenhouse gas. It destructs the ozone belt which is protecting life on earth from to intensive ultraviolet radiation.
Since more than a decade technicians and scientists are seeking for methods and means in order to eliminate the noxious CO
2
from waste gases and to store it in the form of an insoluble chemical compound or outside of the atmosphere of the earth. There are technically feasible proposals (partly tested in pilot plants) in order to separate the CO
2
from combustion or other waste gases, to concentrate it (by liquefing), to use it industrially or to store it underground (in aquifers, deep sea or to stimulate poorly producing oil reservoirs). One of the practical ways to concentrate the CO
2
consists of reintroducing the combustion CO
2
by a secondary cycle in the combustion process after having made the combustion-air nitrogen-free by catalytic and/or cryogenic separation. Instead of the use in neighbouring chemical plants, the binding of CO
2
on sea weed as well as the bacterial fermentation of the CO
2
in special reactors have been technically examined in pilot plants. These latter processes need either large storing volumes for the CO
2
resp. CH
4
produced or an absolutely constant operation of the CO
2
producing installations, because these binding resp. fermentation processes are not flexible. Specially thermal power plants demand such flexibility in order to cover daily, weekly and seasonal peaks.
SUMMARY OF THE INVENTION
The present invention permits such flexible operation. The invention comprises the pumping of the separated, purified, liquefied and dryed CO
2
in a pipeline to a nearby aquifer, a natural gas reservoir or an oil bearing structure and injecting the CO
2
into it and treating the structures in the first two cases previously with bacteria cultures (and ev. suitable substrate). In the third case the methanogenic bacteria and the substrate will be already naturally present so that the conversion of the CO
2
to CH
4
may immediately begin. For that purpose the following conditions have to be naturally present or artificially created (see bibliography in the annex):
1. There has to be enough H
2
for reduction of the CO
2
(or as electron donor) in the structure (underground reservoir), either
in free form produced by metamorphic rock in the depth, or
by bacterial direct transmission from organic H
2
containing substrate, or
by bacterial splitting off of the pore water, or
by artificial feeding of H
2
in pure form of ammonia (NH
3
) which forms in the structure (underground reservoir), in contact with the pore water, partly ammoniumhydroxide NH
4
OH and with CO
2
urea (H
2
N)
2
CO which, by bacterial aided hydrolyzing, splits off free H
2
, or
e.g. by artificial feeding of formiates NaHCO
2
or Ca(HCO
2
)
2
.
2. The sulfate content of the sediment in the structure (underground reservoir) has to be either
enough poor that the sulfate no more can selectively bind the H
2
necessary for the CO
2
reduction, and/or
no H
2
S or other sulfide may act as methanogenic poison, or
the sulfate competing with the CO
2
reduction may be artificially blocked by an inhibitor (e.g. NA-molybdate or fluorlactate), or
by feeding H
2
in to the structure (underground reservoir) enough long before the CO
2
injection, so that the sulfate will be sufficiently reduced.
3. There must be present in the sediment a methanogenic bacterial population large enough (e.g. methanococcus, methanobacterium formicicum, methanobacterium thermoautotrophicum, methanosarcina barkerii, or other photosynthetic bacteria) which is able,
to split off free H
2
from the pore water or from H
2
S, and
to reduce the CO
2
to CH
4
sufficiently,
eventually by addition of catalysators like e.g. palladium,
adding, if necessary, the needed bacterial population and/or the substrate artificially.
The main condition to realize the CO
2
conversion is a drilling (in a aquifer, a natural gas reservoir or an oil bearing formation) across the gas or oil containing structure till in the aquatic phase thereunder, with cores from the interesting stratums and analyzing these cores in the laboratory.
The main aim is finding (or not) the necessary bacteria, the substrate whereon they live, the chemical composition of all sediment parts, the presence of H
2
, sulfate as well as the absence of Na—AL-silicates. With these results it will be further established under which conditions the found (or added) bacteria and the substrate are able to produce CH
4
from CO
2
and how much.
By adding other substrates (e.g. acetate, methanol, methylamine, dihydronicotinamide, dihydro-5-diazaflavine, 2-mercaptoethane-sulfonic acid and like) it will be established if the CO
2
reduction to CH
4
is intensified resp. accelerated. With a given substrate the addition of CO
2
, in the presence of H
2
, increases the CH
4
production normally by more than one magnitude. The same is the result when H
2
is added in presence of CO
2
. Consequently, both gases have to be present together for ensuring an optimal CH
4
production. In this connection it may be noted that the 4 H atoms needed for the CH
4
do not originate from the added H
2
gas (or NH
3
), but from the pore water. The H
2
gas serves only as electron donor. All research work hitherto existing shows that bacteria and substrate are only a transition station for the H
2
necessary for CO
2
reduction. Consequently, during the laboratory experiments the consumption of bacteria and substrate,as well naturally present as also artificially added matter, has to be established. Concerning the practical use of the invention, a consumption of bacteria and/or substrate to high could dictate an economic limit.
As soon as the different questions are resolved by the laboratory experiments, the same tests are following under in situ conditions of pressure and temperature (still in the laboratory). This clarifying by steps conducts to the optimum method which is than tryed out in a pilot test 1:1 after a second drilling (observation drilling) in relative vicinity to the first drilling. If there is a flow direction of the pore water, the testing has to be made on the low side and the CO
2
addition on the high side of the flow. An increasing CH
4
content signifies a positive conversion, which is confirmed by an also increasing H
2
content.
This is specially the case with the addition of ammonia gas instead of pure H
2
. The basic chemical transformation according to the formula CO
2
+4 H
2
=CH
4
+2 H
2
O becomes with ammonia in molecular writing 2 CO
2
+6 NH
3
=2 CH
4
+3 N
2
+4 H
2
O+H
2
, what means that the transformation yields a H
2
excess which passes over in the next step, so that, in constant operation, will be an equilibrium CO
2
: NH
3
of approx. 1:2,7. But this will only be the case if the H
2
procurement is not aided by bacterial assistance. Such bacterial assistance liberates practically always supplemental H
2
from organic substrates or from pore water, eventually supported by H
2
from metamorphic rock, what reduces the CO
2
/NH
3
proportion from 2,7 to 1 and less.
The CO
2
reduction produces in every case additional pore water. The use of NH
3
as H
2
donor has the special disadvantage of producing the double quantity of pore water compared to the use of pure H
2
and that 40% of the NH
3
gas remain as N
2
(ballast) in the structure and appear occasionally as pollution in the produced CH
4
and demand a separation (purification). Economically it could be better to inject pure H
2
under high pressure as emulsion in the liquid CO
2
(with or without emulgators). At the maximum possible proportion of volume CO
2
:H
2
of 1:4 the emulsion becomes foamy and at smaller H
2
requirements and higher pressure the H
2
is broken up in small gas bubbles in the liquid CO
2
.
The liquid medium CO
2
covers than the inner surface of the steel tube and not the H
Naff David M.
Ware Deborah K.
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