Note: Descriptions are shown in the official language in which they were submitted.
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1 BACKGROUND OE' T~IE INVENTION
_
1. Prior Art
Among the prior art known to the inventors is United
States Patent No. 3,451,769 issued June 2~, 196~, to Kishitaka,
et al, which is not concerned with desulfurizing coal, but is
nevertheless considered of some pertinency. This patent teaches
the concept of oxidation of ferrous ions to ferric ions by
employment of NO2 as a catalyst in the presence of oxygen. The
invention thereafter achieves a simplification of processing by
mixing the oxidized solution with a concentrated amount of un-
oxidized solution and subsequently neu-tralizes the mixture with
ammonia. This entire process involves the treating of waste
pickling liquors. The present invention, on the other hand, -~
involves the use of NO2 to electively oxidize the sulfur in coal
in the presence of both carbon and hydrocarbon. Unli~e Kishitaka,
in the present invention the sulfur is in a solid (not liquid)
phase. Kishitaka has water present and depends upon the solution
of NO2 to form nitric acid which is the oxidizinq agent. The
use of an alkali metal hydroxide in the present invention method
is an added step to remove sulfur not previously removed, while
Kishitaka uses ammonia as an integral reagent.
United States Patent No. 3,387,941 issued June 11, 196
to Murphy, involves desulfurizing coal with steam and alkali
metal hydroxides at 500-850C. The present invention, on the
other hand, operates at lower temperatures of 100-500F and
hydroxides are used only to hydrolyze and dissolve previously
oxidized organic sulfur compounds. Water is only used to mechan-
ically extract previously oxidized iron-sulfur compounds in the
coal (iron and sulfites and sulfates).
United States Patent No. 3,607,718 issued September 21,
7~ `
1 1971 to Leaders, also -teaches a sulfur removing method for coal--
involving the dissolution and hydrogenation of the coal to
remove ash and inorganic and organic sulfur by the use of a ~`
partially hydrogenated hydrocarbon solvent. This is a process -
clearly totally different from that of this invention.
United States Patent No. 3,375,188 issued March 26, 1968
to Bloomer, teaches a method for deashing coal by dissolving
pulverized coal at 600-850F in a boiling aromatic hydrocarbon
mixture. The present invention method is carried out at a lower
temperature without hydrocarbons being present, and the coal
itsel is not dissolved by the sulfur bearing components are oxi-
dized and subsequently leached out.
United States Patent No. 3,723,291 issued to Thakker on
March 27, 1973 involves adding an alkali metal ca~bonate to the ~`
coker feed stack prior to coking and then after coking, treating
the coke with hydrogen at a temperature of from 1000F to 2000F.
This is a toaally different and much higher temperature process
than that of the present invention.
SUMMARY OF THE INVENTION
The pre~ent invention method provides an improved
method for desulfurizing coal while producing concentrated
sulfuric acid as a commercially useful by-product.
The preferred embodiment of the present invention in- ~;
volves the following steps: Coal is first converted into particu-
lates. We prefer to use pulverized coal in which no particulate
is lar~er than approximately 1/4" in diameter. Although the
process can be made to work on larger particles the sulfur removal ~ `
efficiency is reduced. The pulverized coal is placed into a
reaction chamber into which is passed a combination of four gases
with the interior of the chamber being maintained at a temperature
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1 in the range from 100 to 500F, for from 1 to 30 minutes, for
continuous reactions or for Erom O.S to 5 hours for batch reaction,
at a pressure in the range from 1 to 20 atmospheres. The prccess
can be either on a batch or continuous basis as desired.
The yases used are preferably 2 (0-5 to 20 volume %),
NO (0.25 to 10 volume ~), NO2 (0.25 to 10 volume ~) and N2 the
remainder. The resulting sulfur containing products from this -
O
step will typically be Fe SO4, SO3 or SO2 gas and R~ - R2 and
1 0 11
Rl - S - R2. Fe SO4 is removed by water extraction as *his salt
is soluble in water. The SO3 is converted into concentrated
H2SO~ by being passed into a condenser containing a solution of
H2SO4. The SO2 is recycled to the reactor where it is subsequent-
ly oxidized to S03. It is within the scope of our invention to
convert the SO2 or other sulfur containing compounds to SO3 by
exposure of the SO2 to oxygen within the reactor by further
reacting the reactOr effluent gas before contacting the gas with
sulfuric acid. It is also within the scope of our invention to
react the SO3 gas with compounds such as calcium oxide or sodium
hydroxide t form calcium sulfate or sodium sulfate instead of
sul~uric acid. These latter two variations are not discussed in
dètail herein. In addition to calcium oxide or sodium hydroxide,
any other alkali metal or alkaline earth oxide or hydroxide may
he employed. If it is deslred to remove the sulfur from the above
two indicated hydrocarbon sulfur containing radicals, a subsequent
exposure thereof to sodium hydroxide heated to a temperature of
from 200-220F at a pressure of from 1 to 20 atmosphere for 1 to ~;
30 minutes is required. `~
: .
It is therefore an object of the present invention to ;
provide an improved and simplified method for the desulfurization
of coal.
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1 Another object of the present invention is to provide
an improved coal desulfurizing method which provides ~2SO~ acid
as a by-product at a cost which renders the same commercially
saleable.
These and other objects o~ this invention may be had
by referring to the following description taken in conjunction
with the accompanying drawings.
DESCRIPTION OF THE DRA~INGS
In the drawings: `
FIGURE 1 is a block diagram representing the process
for removing sulfur from coal in accordance with the presently
preferred embodiment of ~he invention;
FIGURE 2 is a diagrammatical illustration, in section, ;~
of the condenser of FIGURE l;
FIGU~E 3 is a diagrammatical illustration, in section,
o~ the reactor of FIGURE 1, suitable for continuous processing;
and
` FIGURE 4 is a diagrammatical view,;in section, of a
reactor for the present invention suited for batch processing. `~
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and more particularly to
FIGURE 1, there is shown a representative continuous process
arrangement for carrying out the present inventinn. A batch
processing arrangement is also understood to be within the scope
of this inventinn.
Coal in crushed or raw form is initially fed into a
pulverizer 10 which serves to convert the raw coal into particles `
to be processed, the size of which will range from 200 mesh to as
large as 1/4" in diameter. Pulverizers for accomplishing this
commutation are well known and are commercially available, and
thus pulverizer 10 will not be described in detail.
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1 The converted coal is then fed into a reactor 18.
Reactor 18 will be more fully described hereinafter in combination
with FIGURE 2. Reactor 18 receives the coal particles from
pulverizer 10, together with a predetermined quantity of a combin-
ation of the following four gases in the below listed relative
quantities.
2 ~ 0-5 to 20 volume %
NO - 0.25 to 10 volume ~
NO2 ~ 0.25 to 10 volume %
N2 balance
The chemical reaction which occurs both in reactor 18
and in subsequent steps in accordance with this invention will
be described hereinafter. The physical steps only will first be
considered. Upon being heated for a period of time of from 1 to
30 minutes at a pressure in the range from 1 to 20 atmospheres
at a temperature of from 100 to 500F in reactor 18, the output
from reactor 18 will typically be a combinatlon of materials,
some solid, some gaseous, including Fe SO4, desulfurized coal and
some additional hydrocarbons containing some sulfur. The solid
portion of the output from the reactor 18 is directed to an
extractor 26.
Water is added to the reactor products in extractor 26
and the inorganic sulfur present as sulfates or sulfites dissolves
and passes to separa~or 24 with the liquid stream. This soluble
portion includes the sulfur initially present as iron pyrites
which is converted to sulfates and sulfites in the reactor. To
aid in the removal of the sulfates and sulfites in the extractor,
a soluble caustic such as sodium hydroxide may be added to the
water in extractor 26. The water may also be kept warm to
facilitate solubility.
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37~
1 The liquid phase, as men-tioned above, passes to separ-
ator 24 where it is cooled to precipate the inorganic sulfates
and sulfites, which are then removed by filtration. The water is
then heated and recycled through extractor 26.
The solid phase product of extractor 26 is then passed
to dryer 28 where it is dried. The drier is a standard commercial
product, known to the art, and need not be described in detail.
The dried output of drier 28 is coal having a substantially lower
sul~ur content than that entering the process.
The gaseous products from reactor 18 flow through trap
12 which removes volatile fuels and entrained coal particles
which are carried in the gas stream. Suitable traps are commer-
cially available and commonly known.
The clean gas from trap 12 which contains sulfur dioxide
.
and sulfur trioxide given up by the coal in reactor 18 is bubbled ;~
through a sulfuric acid solution in condenser 14 dissolving
sulfur trioxide ln the acid solution. As previously mentioned,
it is also within the scope of our invention to react with the ;
S03 to form other compounds instead of sulfuric acid ~i.e. with
ammonium hydroxide to form ammonium sul~ate, with sodiu~ hydroxide
to form sodium sulfate, with calcium oxide to make calcium su~fatej.
These compounds could also be made by reacting the sulfuric acid
with ~he appropriate basic compound.
A cross-sectional representation of the condenser 14
is shown in greater detail in FIGURE 2. Fed into inlet pipe 25
~are the outlet gases from reactor 18, including 2' N2~ N0, N02, ~ ~
S2 and S03. It should be noted that two other gases may also be ``
generated in reactor 18; these are C0 and C02. The la~ter two
gases will be produced, if at all, from an unavoidable minimal
3~ oxidation of some of the coal particles in the reactor in the
.
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1 pre~ence of oxygen. Any C0 produced will merely pass on through
the system without affecting the present invention process as C0
is basically inert. Any generated C02 on the other hand, should
be removed, and this is accomplished at a later stage in the
present invention method in a manner hereafter to be explained~
The incoming gases to condenser 14 are treated as
~ollows: The gases containing S03 are bubbled up under some
pressure through a porous disk 27 ~ituated within and near the
lower end of the condenser. This disk 27 permits the gases to
pass up therethrough while preventing liquid H2S04 previously
included within the condenser 14 from leaking through. Any
sulfur trioxide in the gas will dissolve in the acid covering ~ ;
porous disk 27. The acid with dissolved sulfur trioxide is passed
into tank 29 where water is added to make more sul~uric acid.
The withdrawal of concentrated acid from the vessel and its re-
placement by water keeps the acid concentration in the tank approx- -~
imately constant during operation.
The gas passing through condenser 14l having its acid
soluble sulfur compounds removed, consists primarily ~ 2~ N0,
20 N02, C0 and C02, N2 and acid insoluble sulfur compounds This ~ ~
gas is passed through purifier 16 where the C02 is removed. A - -
: -~.. :: -,
~raction of the gas leaving purifier 16 (about 0.1 to 1%~ is ~ ~ -
vented through scrubber 22 (which removes the noxious componenta).
This is necessary since the reactant gases are consumed by the
process, causing a buildup in the inert gas in the gas stream.
By venting a portion of the gas and providing makeup gas, as
indicated by gas mixer 20, the active gas proportions can be - -
maintained. ~ -
Since N0, 2 and N02 exist in an equilibrium at any
temperature, only N0 and 2 need be supplied, the required N02
being formed from the mixture.
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1 As shown in FIGU~E 1, the reconstituted gas mixture is
then recycled through reactor 18.
While most of the processing equipment required to
practice the invented process is standard equipment, the reactor
itself is not and therefore detailed descriptions of suitable
reactors for both continuous and batch processing follows:
Re~erring now to FIGURE 3 which illustrates a continuous
process reactor utilizing a so-called fluidized bed for the
handling of the coal.
The reactor comprises an outer casing 30 and an inner
shell 31 spaced there~rom. The inner shell ,must be capable of
withstanding the process pressure and temperature contemplated! `~
and the outer casing is preferably theremally insulated. Heating
,D
fluid, for example steam or hot oil, is introduced into the space
between casing 30 and shell 31 throu~h inlet pipe 32. After ~ -
passing through the annular space 34 between the casing 30 and
. . .
shell 31, thereby heating shell 31 and its contents, the heating
fluid flows out of outlet 33. An inlet 37 is provided at the '- ~'
bottom of shell 31 for the purpose of introducing the oxidizing
gas into the reactor. As will be presently di,scussed, the
oxidizing gas is blown through the recctor at high velocity. It
will therefore be desirable that the~gas be preheated to prevent
the gas from cooling the contents o~ the reactor.
. ~ :
Coal is conveniently introduced into the reactor at ~ ,
the bottom o~ the reac~or and from the side at inlet 36. A , ~
porous disk 35 below the coal inlet spreads the inlet gas across ~ '
the area of the reactor so that its vertical velocity is relatively
uniform over the entire area.
The gas stream flowing upward through the particles of
coal causes the particles to be agitated and thus the coal in the
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', .. .. ~ . :. : .
: .. : ... . , .. - .. . ..
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1 reactor acts as a fluid. Coal en-tering at inlet 36 flows upward
through the reactor and eventually out of the top of the reactor
through outlet 38. Coarse pieces of coal which are too large to
flow upward under the influence of the oxidizing gas and other
particles of coal flow out of the coarse coal outlet 39.
Oxidized coal flowiny out of outlet 38 is separated
from the oxidizing gas by a cyclone separator 40, a standard item,
well known in the art.
As previously described, the coal output is fed to the
extractor while the gas is fed to a condenser through a trap.
The batch type reactor illustrated in FIGURE 4 includes 5
an outer casing 50 and inner shell 51 similar to the casing 30
and shell 31 of FIGURE 3, except that in the case of casing 50 ~ ~
and shell 51, removable tops 50' and 51' are provided to allow ~ -
charging of the shell with coal. Alternatively, hatches could - ~-
be provided for this purpose. -, ~
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The heating jacket 54 is supplied with heating f1Uid ~-
through inlet 52, the outlet being indicated as 53.
A porous disk 55 spxeads the flow o~ gas entering
through inlet 57 in a manner identical to that previously
described ~or the continuous process reactor. Gas outlet 58
directs the spent oxidizing gas to the trap and condenser.
In operation, the batch reactor is disassembled, re-
moving casing cover 50' and shell cover 51', and a charge of
pulverized coal is loaded into the reactor. The reactor is then
covered, heating fluid is started heating up the vessel and
oxidizing gas is blown through the charge. After sufficient
time to oxidize the sulfur compounds in the coal has passed, the
fluid and gas flows are stopped, the reactor disassembled, and
the charge removed and placed in the extractor for the next step
in the process.
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1 ~ representative empirical formula for coal is ClooH80NS
which also includes FeS and FeS0~. This coal may, when including
these typical sulfur compounds, be depicted by the formula
C10OH80NS FeS FeS04. of these three S's in this highly
empirical and genralized ~ormula, the sulfur content will typically
divide as follows:
FeS04 - 5%
FeS - 47-l/2~
Rl-S-R2 - 47-l/2%
The S in the Rl-S-R2 formula is considered as the
organic sulfur included in the coal while FeS (Pyrites) and FeS04
is the inorganic iron bearing sulfur. The R would in turn refer-
ence the ClooH80 of the above noted general formula.
- The chemical reaction steps of the presently invented
method may generally be explained as follows:
N02 gas reacts in the coal reac-tor 18 with FeS contained ~;
in accordance with this equation.
(A) Fe S + 4 N02~ FeS04 + 4 N0 ~ ~ -
The organic sulfur on the other hand reacts as follows
with the N02 gas, also within reactor 18 in accordance with the
following equation: 0
1 Rl ~ S - R2 + N2-~ R1 - S - R2 + N0
The partially oxidized organic sulfur compound again
reacts with the N02 gas in the reactor, thusly:
(B2) Rl - S - R2 + N02 Rl ~ 11 ~ R2 + N0
The organic sulfur compound which now contains two
doubling bonded oxygen atoms further reacts with N02 gas within
the reactor 18 as follows:
O
ll
(C) 1 ~ R2 + N02 ~ l + R2 ~ S03 ~ or So
--1 0 ~
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1 The reactions represented by equa-tions (A), (Bl) and
(B2) all result in the production of NO gas. This NO combines
with oxygen as indicated by equation (D) to produce N02; this N02
is used again in equations (A), (Bl), (s2) and (C). - ~
(D) NO + 1/2 2~ ~ 2 : :
Thus without water, without hydrogen, without a
hydrogenated organic solvent and without an alkali soak, most of r
the organic sulfur is freed from the coal.
The reactor products produced by the reactor as depicted ~ : :
in equation (Bl) and (B2) to the extent that they do not react
further with N02 to totaIly free the organic sulfur, may further
be treated in accordance with an additional process as-follows~
~- ~
Each of these reaction products may be exposed in the
extractor 26 to NaOH or some other alkali metal hydroxide, thus
the following will occur~
O
11 . '
Rl S R2
Ol - :
20 . 1 I R2 ;~
H2- + NaOH --- ~Rl + R2 + Na2S03 in solutio~
or Na2S04 in solution.
The above-described reaction which is intended to
remove additional.organic sulfur not totally removed in reactor
18 is carried out in the extractor 26.
It will be understood that in lieu of sodium hydroxide,
there may be used potassium hydroxide or any other alkali metal
hydroxide for the indicated purpose. This step when employed is ; ~- ;
preferably ~arried out at from 1 to 10 atmospheres, at a tempera~
ture in the range of from 180F to 230F.
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1 It will be observed that in the above reac-tions, the
active gas which reacts with the sulfur compounds present in the
coal is N02. Neither NO nor 2 is directly invalved in the re-
action, however, both NO and 2 are unavoidably present since NO,
2 and N02 react in an equilibrium reaction as follows:
NO ~ 1/2 2~ N02
Thus as N02 is consumed by the reaction with sulfur, additional
N02 is formed by the equilibrium reaction. Similarly, N02 is
formed as NO and 2 are supplied in the make-up gas.
Any FeS04 contained within the coal in the reactor 18
(or produced as a result of reaction (A)), will not further
react therein as it is already fully oxidized. It will later
be precipitated out in the extractor 26 where water is added to
the coal. Thus, the FeS04 is removed baslcally by mechanical as
opposed to chemical means.
It will, of course, be apparent from an examinatio~ of
the chamical reactions occurring in reactor 18 that the oxidized
sulfur compounds there formed, if they are further to be reduced
are soluble in caustic and not in waker -- thus encouraging use
2~ of the additional but not necessary step previously described.
A further note regarding the oxidation step in reactor
18 for the removal of sulfur in the organic form is considered
significant. The oxidation reaction product
..
Rl - R2 in equation (Bl) combined with additional
N02 at step (B2) resulting in a further oxidized state of the
sulfur in the organic radical, permitting the substantial
removal of the organic sulfur at step (C) by the still further ;
exposure of the radical O
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1 to N02 gas freein~ the Rl and R2 (coal) radicals from the organic
sulfur without the employment of the caustic step previously
described.
While both of the reactor products of the organic sulfur
containing radicals will react with caustic as employed above, it -
should further be noted that only the reaction product producea by --
equation (B2) will react with NO2 to free the sulfer [equation ~C)].
A further study of equations (A), (Bl) and (B2) indicate
the formation of NO whichis required for equation D to go forward
and the reaction product of equation D is NO2 which is required
for the reaction of (A), (Bl), (B2) and (C) to occur.
The gases which are introduced into reactor 18 are as
followS :,
N0 - lJ4 to 10~ by vclume
2 ~ 1/4 to 20% by volume
NO2 ~ 1/4 to 10% by volume
N2 ~ remainder.
While N2 is preferred, another inert gas or gases may
be substitutea in whole or in part therefor. The inert N2 gas
is required primarily for safety purposes (i~e., to prevent an
explosion) in the otherwise highly volatile atmosphere which would
be present in reactor 18, especially under conditions of elevated
temperature and pressure. The inert N2 is also present in the
selective reaction of the sulfur in the coal as opposed to the
combustion thereof.
~ -
of course some of the 2 and N0 is consumed during the
reactions which occur as above described in the reactor 18,
which must be replenished. NO2 exists in equilibrium with N0 and
2 at any temperature, and thus is spontaneously formed from a
mixture of N0 and 2 and need not be individually supplied.
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1 The following are examples of the sulfur reduction
which has been obtained by utilizing the process o this inven-
tion in accordance wi-th the batch process which takes place in a
period from 1 to 4 hours. The continuous process on the other
hand, will typically occur in from 1 to 30 minutes.
EXAMPLES
EX~PLE 1
.
Using the batch reactor process a sample of Lower
Kittanning coal previously pulverized and segreg~ted as to size
was treated. Coal of -14 t +28 ~esh-particle size was loaded into
the reactor, the reactor assembled and heated to 20QF. For
3 hours a ~as mixture consisting of air with 9 per cent nitrogen
oxide added was passed through the reactor and the bed of coal at
one atmosphere pressure. The flow rate was such that about 10
times the stoichiometric quantity of oxygen required to oxidize
the sulfur to sulfate forms was passed through the reactor.
The coal had an initial sulfur content of 4.3 per cent
(3.6~ pyritic, 0.7~ organic, a trace of sulfate). After treatment,
the coal was removed from the reactor, washed with water and
20 dried. The total sulfur content was 1.58 percent (i.e., 63% of
the sul~ur was removed). The coal was then washed with 10 per
cent aqueous sodium hydroxide ~ollowed by water and then dried. -
The total sulfur content was 0.47 per cent (i.e. 87~ of the sulfur
was removed).
EXAMPLE 2
Using the batch reactor process a sample of Lower
Kittanning coal previously pulverized and segregated as to size
was treated. Coal of -14 to +28 mesh size was loaded into the
reactor, the reactor assembled and heated to 200~F. For 3 houxs
a gas mixture consisting of air with 4.5 per cent nitrogen oxide ;
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1 added was passed through the reactor and the bed of coal at one
atmosphere pressure. The flow rate was such that about 10 times
the stoichiometric quantity of oxygen required to oxidize the
sulfur to sul~ate form was passed through the reactor. -
The coal had an initial sulfur content of 4.3 per cent.After treatment, the coal was removed from the reactor, washed
with water and dried. The total sulfur content was 2.5 per cent
(i e., 43 per cent of the sulfur was removed). The coal was then
washed with 10 per cent aqueous sodium hydroxide followed by -
lQ water and then dried. The total sulfur was 2.1 per cent (i.e~,
S0 per cent of the sulfur was removed). Approximately 95 per
cent of the initial coal sample was recovered after treatment and
before extraction.
EXAMPLE 3
.
Using the batch reactor process a sample of Illinois
#5 coal previously pulverized and seyregated as to size was
treated. Coal of -14 to +28 mesh size was loaded in~o the reactor,
the reactor assembled and heated to 200F. For 3 hours a gas
mixture consisting of air with 4.5 per cent nitrogen oxide adaed
was passed through the reactor and the bed of coal. The flow
rate was such that about 12 times the stoichiometric quantity of ` ~ -
oxygen required to oxidize the sulfur to sulfate forms was passed `
through the reactor.
The coal had an initial sulfur content of 3.5 per cent
(1.6% pyritic, 1.9% organic, a trace of sulfate). After treatment, -
the coal was removed from the reactor, washed with water and
dried. The total sulfur content was 1.9 per cent (i.e., 3~% of
the sulfur was removed). The coal was then washed with 10 per
cent aqueous sodium hydroxide followed by water and then dried.
The total sulfur content was 1.2 per cent (i.e., 60 per cent of
r;:
the sulfate was removed).
.'' `~ ~''.
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1 EXAMPLE 4
Vsing the batch reac-tor process, a sample of Illinois
#5 coal previously pulverized and segregated as to size was
treated. Coal of -14 to ~28 mesh ~article size was loaded into the
reactor, the reac-tor assembled and heated to 200F. For 3 hours
a gas mixture consistiny of air with 10% nitrogen oxide added
was passed through the reactor and the bed of coal at one atmos-
phere pressure. The flow rate was such that about 12 times the
stoichiometric quantity o~ oxygen required to oxidize the sulfur
to sulfate forms was passed thorugh the reactor.
The coal had an initial sulfur content of 3.5% (1.6%
pyritic, 1.9~ organic, a trace of sulfate). After treatment, the
coal was removed from the reactor, washed with water and dried.
The total sulfur content was 1.9% ~i.e., 46~ of the sulfur was
removed). The coal was then washed with 10~ aqueous sodium
hydroxide followed by water and then dried. The total sulfur
content was 1.0 per cent (i.e., 71% of the sulfur was removed).
EXAMPLE 5
Using the batch reactor process, a sample of Lower
~O Kittanning coal previously pulverized and segregated as to size
was treated. Coal of -80 to +100 mesh particle size was loaded into
the reactor, the reactor assembled and heated to 200F For 3
hours a gas mixture consisting of air with 5~ nitrogen oxide
added was passed through the reactor and the bed of coal at one
atmosphere pressure. The flow rate was such that about 10 times ~
the stoichiometric quantity of oxygen required to oxidize the ~ ;
sulfur to sulfate forms was passed through the reactor.
The coal had an initial sulfur content of 4.3~ (3.6%
pyritic, 0.7% organic, a trace of sulfate). After treatment, the
coal was removed from the ~eactor, washed with water, and dried.
~7~4
1 The total sulfur content was 2.9~ (i.e., 33~ of the sulfur was
removed). The coal was then washed with 10% aqueous sodium
hydroxide followed by water and then dried. The total sulfur
content was 1.9% (i.e., 56% of the sulfur was removed).
EXAMPLE 6
Using the ba-tch reactor process, a sample of Lower
Kittanning coal previously pulverized and segregated as to size
was treated. Coal of -14 to ~28 mesh particle ~ize was loaded i~nto
the reactor, the reactor assembled and heated to 200F. For 1.5
hours a gas mixture consisting of air with 10~ nitrogen oxide
added was passed through the reactor and the bed of coal at one
atmosphere pressure. The flow rate was such that about 5 times
the stoichiometric quantity of oxygen required to oxidize the
sulfur to sulfate forms was passed through the reactor.
The coal had an initial sulfur content of 4.3% ~3.6%
pyritic, 0.7~ organic, a trace of sulfate~. The coal was then
washed with 10~ aqueous sodium hydroxide followed by water and
then dried. l'he total sulfur content was 1.4% (i.e., 67% of the
sulfur was removed). ;
EXAMPLE 7
. .. .
Using the batch reaction process, a sample of Lower
Kittanning coal was treated as described above. The coal was -14 -~
to ~28 mesh size reacted ~or 5 hours at 200F using air with S
per cent nitrogen added. An excess of oxygen of 16 times was
passed through the reactor.
- The coal had an initial sulfur content of 4.3~. After ~-
oxidating and without any extraction (washing), the coal had a ~ -
sulfur content of 3.3% ~i.e., 23% of the sulfur was removed by
the oxidation treatment). ~-
There thus has been described a new and improved process
for desulfurizing coal and producing sulfuric acid in commerical
~ . . .
quantities as a valuable by-product. `~
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