United States Patent [19]
Reynolds et a1.
[11]
[45]
4,428,912
Jan. 31, 1984
[54] REGENERATION OF CHLORIDIZING
AGENT FROM CHLORINATION RESIDUE
[75] Inventors: James E. Reynolds, Golden; Alan R.
Williams, Denver, both of Colo.
[73] Assignee: Public Service Company of New
Mexico, Albuquerque, N. Mex.
[21] Appl. No.: 287,219
[22] Filed: Jul. 27, 1981
[63]
[51]
[52]
[58]
[56]
Related U.S. Application Data
Continuation-in-part of Ser. No. 50,549, Jun. 20, 1979,
Pat. No. 4,288,414, which is a continuation·in-part of
Ser. No. 873,400, Jan. 30, 1978, Pat. No. 4,159,310.
Int. C1.3 COIF 7/22
U.S. C1 423/132; 423/135;
423/136;423/155;423/202; 423/482
Field of Search 423/135, 136, 149,482,
423/132
References Cited
U.S. PATENT DOCUMENTS
1,581,436 4/1926 Galt 423/482
2,040,867 5/1936 Mitchell et aI 423/482
3,864,458 2/1975 Roberts 423/482
4,120,737 10/1978 Berrie et al. 423/482
4,237,102 12/1980 Cohen et al. 423/126
4,239,735 12/1980 Eisele et aI 423/126
FOREIGN PATENT DOCUMENTS
9198 of 1891 United Kingdom 423/482
Primary Examiner-Herbert T. Carter
[57] ABSTRACf
Alkali and alkaline earth metal chlorides contained in a
residue of a chlorination process of a feed material of
bauxite or clay associated with coal are removed by the
addition of sulfuric acid which causes their conversion
to their sulfate form, and the simultaneous production
of hydrochloric' acid. The residue, which has been rendered
environmentally acceptable, can be disposed of
readily, for example, to an ash pond or disposal area for
flue gas desulfurization sludges. The hydrochloric acid
is then recycled to the chlorination process. The hydrochloric
acid may be utilized, for example, as a binder of
the feed material, to prechloridize the feed material or
as a portion of the leach solution when the chlorination
process is a hydrochloric acid leach.
11 Claims, No Drawings
PREFERRED MODES FOR CARRYING OUT
THE INVENTION
2
(FGD) sludges. The hydrochloric acid which is produced
can be used in the chlorination process. For example,
it can be utilized as a binder of the feed material
and/or to prechloridize the feed material, e.g., convert
5 a portion ofthe chlorine consuming constituents to their
respective chlorides, or it may be utilized as a portion of
the leach solution if the chlorination process utilized is
a hydrochloric acid leach.
The process of the present invention is applicable to
any chlorination processes of feed materials which produce
a residue containing alkali or alkaline earth chlo-
15 rides. It is especially useful in those chlorination processes
for the recovery of aluminum from the feed material
and is particularly beneficial in the chlorination of
bauxite ~nd clays associated with coals wherein the
residue produced therefrom contains alkali or alkaline
20 earth metals.
Clays are generally fine-grained earthy material made
up of minerals which are essentially hydrous aluminum
silicates. The specific mineral content of the clay depends
upon the area in which the clay is found. The
clays on which the present process is operable are ones
found associated with coal, for example, parting clays
which .are found between seams of coal. Additional
examples include top and bottom contact clays, which
are found at the top and bottom, respectively, of the
coal reserve, clays in' the overburden of the coal and
clays found in coal refuse, i.e" the washings of coal to
remove ash forming minerals from the coal.
The particular chlorination process of the bauxite or
clay associated with coal is not critical to the process of
the present inventic)D as long as the residue from the
process contains alkali or alkaline earth metal chlorides.
For example, the chlorination process can be two stages
with both chlorination steps being conducted in the
presence of a reducing agent and chlorine, for example,
that disclosed in V.S. Pat. Nos. 1,605,098 and 1,600,216.
The clays can be chlorinated in the presence of carbon
monoxide and chlorine at a temperature of 600·_900· C.
to chlorinate the aluminum, iron and titanium. Thereafter,
the residue can be treated with carbon, and chlorine
at an elevated temperature to chlorinate the silica and
aluminum silicates contained in the clay, for example,
the process disclosed in U.S. Pat. No. 1,875,105. The
chlorination process can be comprised of treating the
feed material containing aluminum and silicic acid with
a carbonaceous materia! and equal parts of chlorine and
silicon tetrachloride in· order to chlorinate the aluminum
and not the silica contained in the material, for
example, as described in U.S. Pat. No. 1,866,731. The
chlorination process can utilize a reductive chlorination
followed by an oxidative chlorination. Alternatively,
the chlorination process can be a leaching process, for
example, leaching with hydrochloric acid.
Essentially, the process of the present invention is
useful in all chlorination processes of bauxite and clay
associated with coal which contain aluminum wherein
the chlorination process produces a residue containing
alkali or alkaline earth metal chlorides. The process is
particularly beneficial when the residue contains calcium
chloride. The residue is treated with sulfuric acid
in an amount which is sufficient to convert the chloride
values. to their sulfate forms. It is generally preferred
that the sulfuric acid be supplied in an amount which is
4,428,912
1
BACKGROUND ART
PRIOR ART STATEMENT
DISCLOSURE OF THE INVENTION
DESCRIPTION
CROSS RELATED PATENT APPLICATIONS
REGENERATION OF CHLORIDIZING AGENT
FROM CHLORINATION .RESIDUE
60
Alkali and alkaline earth metal chlorides contained in
a residue of a chlorination process of a feed material
containing aluminum are rendered environmentally
inert by the addition of sulfuric acid which causes the
conversion of the metals to their sulfate form and the 65
simultaneous production of· hydrochloric acid. The
residue can be disposed of readily, for example, to an
ash pond or disposal area for flue gas desulfurization
Many processes have been taught for the chlorination
of aluminum bearing ores and clays and examples of
such processes can be found in U.S. Pat. Nos. 1,605,098;
1,600,216; 1,875,105; 1,866,731; and 3,244,509. Many of 25
these processes do not address the removal of alkali or
alkaline earth metals from any residue which may be
produced by the process. U.S. Pat. Nos. 3,244,509 and
3,466,169 both utilize electrolysis to remove alkali chlorides
and alkaline earth chlorides from the residues 30
produced in their processes.
U.S. Pat. No. 4,237,102 discloses an intricate cyclic
process for obtaining very pure alumina by a hydro- 35
chloric acid attack of a silico-aluminous material. After
the aluminum containing feed material has been leached
with hydrochloric acid and the aluminum chloride separated,
then the oxide impurities contained in the liquor
are extracted by the addition of sulfuric acid, in the 40
presence of hydrochloric acid, to form a sulfohydrochloric
leach which precipitates the impurities as their
sulfates. That leach is then degassed to obtain hydrochloric
acid and sulfuric acid which are recycled to the
process. 45
U.S. Pat. No. 4,239,735 discloses the removal ofmetal
oxide impurities from kaolin clay by the use of a dilute
mineral acid, e.g., 2 N-6 N hydrochloric, nitric acid or
sulfuric acid, as a preleach of kaolin clay prior to subjecting
the clay to a 26 percent hydrochloric acid and 50
HzSiF61each to recover aluminum chloride.
None of the prior art recognizes or suggests the utilization
of sulfuric acid as a means for removing alkali
and alkaline earth metal chlorides from the residue
produced by a chlorination process of bauxite or a clay 55
associated with coal and to produce a dilute hydrochloric
acid for use in a pretreatment of the feed material or
in the chlorination process.
TECHNICAL FIELD
The process of the invention relates to a method for
the disposal of alkali and alkaline earth metal chlorides
which remain in the final residue resulting from the
chlorination of feed materials containing aluminum,
particularly the chlorination of bauxite anq clays associated
with coal.
This application is a continuation-in-part application
of Ser. No. 050,549, filed June 20, 1979 now U.S. Pat.
No. 4,288,414 which is a continuation-in-part applica- 10
tion of Ser. No. 873,400, filed Jan. 30, 1978 which is
now U.S. Pat. No. 4,159,310.
3
slightly in excess of the stoichiometric amount required
for the reaction of the alkali or alkaline earth metals
sought to be converted. Generally, the sulfuric acid will
be utilized in an amount of from about 250 percent to
about 350 percent and preferably from about 275 per- 5
cent to about 325 percent based on the weight of contained
calcium in the residue being treated. To improve
gypsum precipitation conditions and extract thechlorides
of alkali metals with high yield, preferably lcl diluted
sulfuric acid, containing approximately 50 weight 10
percent or less sulfuric acid, is utilized. For example, the
sulfuric acid can be obtained from a sulfur dioxide
scrub-regeneration system utilized on stack gas. The
sulfuric acid will cause the precipitation of calcium, if
present, as gypsum and will leach out water-soluble 15
chlorides and a small amount of acid soluble chlorides.
Generally, the sulfuric acid leach is conducted for a
time of from about 10 minutes to about I hour and
preferably from about 15 minutes to about 30 minutes.
Shorter leach times may result in incomplete solubiliza- 20
tion of metal chlorides, while longer leach times unnecessarily
increase the cost ofleach equipment and energy
to suspend the leach pulp. Generally, a temperature of
from about 30· C. to about 70· C. and preferably from
about 40· C. to about 60· C. produces a rapid filtering 25
residue.
After the leaching, the residue is subj~cted to a solidliquid
separation and liquor recovered therefrom,
which contains dilute hydrochloric acid, sulfuric acid
and some small amounts of metal chlorides, isrecycled 30
back to the chlorination process preferably for use as a
binder for pelletizing the feed material and/or to prechloridize
the feed material. The hydrochloric acid is a
preferred binder for the feed material as it apparently
chemically reacts with the feed material to fo"rm hy-35
drates which aid in the binding process. The use of the
hydrochloric acid as a binder will also prechloridize the
feed material since it will convert at least a portion of
the chlorine consuming alkali and alkaline earth metals
contained in the feed material to their respective chlo-40
ride salts. The prechlorination of the feed material is
particularly beneficial when it contains high levels of
calcium or magnesium.
If the chlorination process utilizes a hydrochloric
acid leach, then the hydrochloric acid liquor may form 45
a part of the leach or may be used as a preleach to
prechloridize at least a portion of the chlorine consuming
alkali and alkaline earth metals contained in the feed
material.
The process of the present invention is particularly 50
useful in an oxidative, reductive chlorination such as
that disclosed in U.S. Ser. No. 050,549, filed June 20,
1979 and incorporated herein by reference. In such a
process, generally the clay or bauxite is first pelletized
with a hydrochloric acid binder solution. The pellets 55
are high-density, high strength pellets. Following pelletizing,
the pellets are dried, for example, at about 300·
C. in a direct fire dryer. Dry pellets are inventoried for
feed to the shaft chlorinator furnace. The clay or bauxite
may be ground before pelletizing; however, this does 60
not affect the recovery of the metal values.
Shaft chlorinations require a high-crush, strong pellet
feed which does not lose strength during chlorination.
Pelletization of clay or bauxite without any binder produces
a weak pellet when sintered at 300· C. Various 65
binders can be utilized, for example, sulfuric acid, hydrochloric
acid, sodium chloride and bentonite. When
bentonite is utilized the sintering should be done at a
4
temperature of about 1,000· C. Hydrochloric acid is the
preferred binder, particularly hydrochloric acid produced
in accordance with the process of the present
invention.
The feed material whether or not pelletized, is then
subjected to an oxidative chlorination step wherein the
iron is first removed by selective chlorination. In this
step, about 90 Percent of the iron is converted and volatilized
as ferric chloride with substantially no chlorination
or volatilization of the other metal values present.
The oxidative chlorination is conducted in the presence
of chlorine and oxygen gases which are circulated for
up to three hours through the charge of feed material to
oxidatively chlorinate and v.olatilize about 90-95 percent
of the iron content. The oxygen is employed in an
amount of from about 20 percent to about 60 percent
and preferably from about 30 percent to about 50 percent
by volume of the total gas composition. The chlorine
is employed in an amount which is a small stoichiometric
excess of that needed to chlorinate the iron. The
oxidative chlorination is conducted at a temperature of
from about 650· to about 900· C. and preferably from
.about 750· to about .800· C. for a time period sufficient
to allow for the chlorination of most of the iron present.
Generally, the time period is from about 0.5 to about 2
hours.
Therefter, the material is subjected to a reductive
chlorination. The degree of chlorination of silica in the
reductive chlorination step is greatly reduced by using
only carbon monoxide as a reducing agent rather than a
carbonaceous material such as fuel oil or coke. Eliminating
solid carbonaceous materials as a reductant has
other advantages, such as, permitting initial oxidative
chlorination of the pellet charge, increasing the strength
of the pellets charged to the chlorinator as there is no
loss in pellet strength during the chlorination as there is
when coke, pitch or other carbonaceous material is
added. Ordinarily, an oxidative chlorination followed
by reductive chlorinationwould necessitate an intennediate
addition of coke to the feed,. which would be an
expensive process step. Surprisingly, this was found not
to be necessary in this process.
The carbon monoxide gas is added to the chlorinator
in an amount of from about 30 to about 70 percent and
preferably from about 40 to about 60 percentby volume
of the total gas composition. The chlorine is supplied in
slight excess of the stoichiometric amount needed to
chlorinate the aluminum present. Chlorine utilization is
related to the rate of gas flow, or space velocity, with
respect to bed volume of the reactor. The reaction rate
appears to be proportional to bed temperature with a
lesser dependence on chlorine-carbon monoxide ratio in
the reaction gas.
The injection of silicon tetrachloride into the reaction
gas mixture of chlorine and carbon monoxide is effective
in reducing the amount of chlorination of siliceous
material contained in bauxite, refuse, coal and clays
associated with coal. From about 3 to about 30 percent
silicon tetrachloride by volume of the total gas composition
may be injected during the reduction. For example,
six percent of silicon tetrachloride combined with
carbon monoxide, almost completely rejects silica chlorination
with only a small loss in alumina recovery. A
preferred method for introducing the silicon chloride is
to run the chlorine through the liquid silicon chloride
before it enters the reactor. The reaction of carbon
monoxide is sufficiently exothermic to be self-heating.
Generally, the temperature of the reductive chlorina*
* * * *
4,428,912
5 6
tion step is from about 600 to about 850· C. and prefera- is precipitated from a liquor comprising dilute hydrobly
from about 650· to about 750· C. The reductive chloric acid.
chlorinator is operated for a time period of from about 4. In a process for recovering aluminum from an
1 to about 3 hours to collect a small amount of residual aluminum-iron-containing clay associated with coal
iron chloride in a first stage condensor and a high purity 5 wherein the clay also contains at least one metal sealuminum
chloride in a second stage condensor. A lected from the group consisting of alkali and alkaline
third-stage condensor collects the chlorides of titanium earths and is subjected to a selective chlorination proand
silicon. The use of fractional distillation to recover cess for the recovery of said iron and aluminum as chlovolatilized
chlorides and noncondensables, e.g., chlo- rides thereof and wherein a residue containing a chlorine,
carbon monoxide and carbon dioxide, of the pro- 10 ride selected from the group consisting of alkali and
cess is described in Ser. No. 050,549, tiled June 20,1979. alkaline earth metals is formed, the improvement com-
The cooled, depleted pellets are conveyed to the prising leaching said residue with sulfuric acid to conleach
circuit where water soluble chlorides, if present, vert at least a portion of the alkali and alkaline earth
are removed and calcium chloride is precipitated as metal chlorides to their environmentally inert sulfates
gypsum with sulfuric acid. The residue solids are til- 15 and to form dilute hydrochloric acid and thereafter
tered, washed and sent to the disposal, while the hydro- recycling said dilute hydrochloric acid to the selective
chloric acid solution is evaporated as required for water chlorination process for use as a binder for pelletizing
balance control and recycled to the pelletization step said feed material prior to said chlorination.
for reuse as a pellet binder and/or for reuse as a pre- 5. The process of claim 2 or claim 4 wherein the
chloridizer. 20 sulfuric acid is utilized in an amount which is in excess
What is claimed is: of the stoichiometric amount required for reaction of
1. In a process for the chlorination of a feed material the sulfuric acid with the alkali and alkaline earth metal
selected from the group consisting of clay associated chlorides.
with coal and bauxite comprising leaching said feed 6. The process of claim 5 wherein the sulfuric acid is
material with a chlorinating agent to chlorinate said 25 utilized in an amount of from about 250 to about 350
aluminum and to produce a residue containing a chlo- weight percent based on the weight of alkaline earth
ride selected from the group consisting of alkali and metal chlorides.
alkaline earth metal chloride, the improvement com- 7. The process of claim 6 wherein the chlorination
prising adding sulfuric acid to the residue under condi- process is comprised of an oxidative chlorination of the
tions to cause the conversion of at least a portion of the 30 feed material followed by a reductive chlorination.
alkali or alkaline earth metal chlorides to their environ- 8. A method of treating an alkali metalore alkaline
mentally inert sulfate forms and to form a dilute hydro- earth metal-containing residue of a chlorination process
chIone acid and further comprising at least one step of for an aluminum-containing feed material selected from
(a) using said dilute hydrochloric acid as a pre-chlori- the group consisting of clay associated with coal and
dizing agent prior to said chlorination of (b) using said 35 bauxite comprising:
dilute hydrochloric acid as a binder for pelletizing said (a) leaching said residue with an amount of sulfuric
feed material prior to said chlorination. acid at least stoichiometrically equal to the amount
2. In a process for the chlorination of the metals con- of alkali and alkaline· earth metals present in said
tained in an aluminous feed material including at least feed for a time period of at least ten minutes to form
one metal selected from the group consisting of alkali 40 a second residue containing environmentally inert
and alkaline earths, said aluminous feed selected from sulfates of said alkali and alkaline earth metals and
the group consisting of bauxite and clay associated with a leach liquor comprising dilute hydrochloric acid;
coal wherein the chlorination process produces a resi- (b) recycling said dilute hydrochloric acid to said
due containing a chloride selected from the group con- chlorination process as a pre-chlorination agent
sisting of alkali and alkaline earth metal chlorides, the 45 prior to said chlorination; and
improvement comprising leaching said residue with (c) utilizing said dilute hydrochloric acid for use as a
sulfuric acid in an amount at least stoichiometrically binder for pelletizing said feed material prior to
equal to the amount of alkali and alkaline earth metals said chlorination.
present for at least about ten minutes at a temperature of 9. A method according to claim 8 wherein said chlofrom
about 30· C. to about 70· C. to produce a second 50 rination process utilizes a hydrochloric acid leach and
residue containing environmentally inert sulfate forms wherein said dilute hydrochloric acid may form a part
of said alkali and alkaline earths and to form a leach of said leach.
liquor comprising dilute hydrochloric acid for use in the 10. A method according to claim 8 wherein said chlochlorination
process and further comprising at least one rination is an oxidative, reductive chlorination.
step of (a) using said dilute hydrochloric acid to pre- 55 11. A method according to claim 10 wherein said
chloridize at least a portion of the chlorine-consuming pelletiZed feed undergoes oxidative chlorination at from
constituents contained in the feed material prior to the about 650· C. to about 900· C. and is thereafter subchlorination
process or (b) using said dilute hydrochlo- jected to a reductive chlorination in the presence of
ric acid as a binder to form the feed materials into pel- carbon monoxide at a temperature of from about 600·
lets suitable for use in the chlorination process. 60 C. to about 800· C. to produce depleted pellets contain-
3. The process of claim 1 or 2 wherein said residue ing water soluble chlorides which form the residue of
contains calcium chloride and wherein upon the addi- step (a).
tion ofsulfuric acid a gypsum-containing second residue
65