Recovery of vanadium from carbonaceous materials

A carbonaceous material containing vanadium is reacted with an oxidizing gas in a molten salt pool containing an alkali metal carbonate. Vanadium values present in the carbonaceous material are converted to water-soluble vanadium compounds which are recovered from the melt and reacted with a strong acid to precipitate the vanadium values as insoluble vanadates. The vanadates are recovered as product or optionally further converted to vanadium pentoxide.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for the recovery of vanadium from 
carbonaceous materials. In one of its more particular aspects, this 
invention relates to using a molten salt treatment for recovering vanadium 
values from carbonaceous materials derived from petroleum. 
2. Prior Art 
Vanadium is the most abundant trace metal present in petroleum, occurring 
in crude petroleum in the range of about 0.001% by weight to about 0.15% 
or more depending upon the source of petroleum. The petroleum containing 
the highest concentrations of vanadium occurs in Venezuela. Some processed 
Venezuelan petroleum residues, such as coke, for example, have been found 
to have a vanadium concentration of as high as about 5% by weight. Because 
of the economic value of vanadium, attempts have been made in the past to 
recover the vanadium present in petroleum. 
U.S. Pat. No. 2,383,972 discloses a process for recovering vanadium from 
petroleum during the course of a cracking operation which comprises 
reacting the metallic constituents of petroleum oil, including vanadium, 
with a solid hydrated sodium aluminum silicate of the zeolite type. 
Vanadium is recovered from the zeolite by means of solvent treating the 
zeolite with a strong mineral acid, precipitating the vanadium as ammonium 
vanadate by evaporating the acid solution with an excess of ammonium 
chloride, roasting the ammonium vanadate to produce the oxide, and 
reducing the oxide in an electric furnace. 
Removal of traces of vanadium and other metals has also been of interest in 
processing hydrocarbon feedstocks. U.S. Pat. No. 2,990,365 discloses a 
process for demetallizing hydrocarbon oils by modifying the properties of 
complex organometallic compounds, including vanadium organometallics 
occurring in the oils, by contacting the hydrocarbon oils in the liquid 
phase with a fused alkali metal hydroxide. The organometallic compounds 
present are thereby converted to alkali metal salts which have greater 
water solubility and can be more easily removed from the hydrocarbon oils 
than the organometallic compounds. 
U.S. Pat. No. 3,936,371 discloses a process for the removal of metal 
contaminants from heavy hydrocarbon oils by means of treatment with "red 
mud," a residue which occurs when bauxite is dissolved at high 
temperatures to produce alumina as a raw material for the electrolytic 
production of aluminum. Contacting the hydrocarbon oil with the "red mud" 
at temperatures in the range of about 350.degree. to 500.degree. C. in the 
presence of hydrogen at a pressure of about 1 to 300 atmospheres is said 
to be highly effective in removing the vanadium and other contaminants 
from the hydrocarbon oil. 
U.S. Pat. No. 4,003,823 discloses a process for simultaneously 
desulfurizing and demetallizing heavy hydrocarbon feedstocks by a 
hydroconversion process utilizing an alkali metal hydroxide and hydrogen 
at a pressure of about 500 to 5000 psig and a temperature in the range of 
about 500.degree. to 2000.degree. F. (260.degree. to 1093.degree. C.). 
U.S. Pat. No. 4,119,528 discloses a process in which simultaneous 
desulfurization, demetallization, and hydroconversion of heavy 
carbonaceous feeds is accomplished by treatment with potassium sulfide and 
hydrogen. The process is carried out at a temperature in the range of 
about 500.degree. to 2000.degree. F. (260.degree. to 1093.degree. C.) and 
a hydrogen pressure of about 500 to 5000 psig. 
These prior art processes are generally designed to remove metallic 
impurities from hydrocarbonaceous feedstocks and do not result in 
rendering vanadium values readily recoverable from such processed 
feedstocks. 
Recently, the use of molten salts for processing carbonaceous materials and 
for conducting a variety of chemical reactions has been suggested. U.S. 
Pat. No. 3,708,270 discloses a process in which carbonaceous materials are 
pyrolyzed by contact with a hot sulfate- or sulfide-containing melt under 
nonoxidizing conditions to produce valuable effluent combustible gases and 
char. 
In U.S. Pat. No. 3,916,617, there is disclosed a process for gasification 
of a carbonaceous material to produce a combustible gas containing a high 
proportion of carbon monoxide to carbon dioxide. The resulting low Btu gas 
can be used as an energy source for conventional boilers, for example. 
U.S. Pat. No. 3,899,322 discloses a process for recovering valuable metals 
from scrap containing metal values by means of a molten salt treatment 
using an alkali metal carbonate and optionally an alkali metal sulfate. A 
molten salt pool is maintained at a temperature in the range of about 
400.degree. to 1800.degree. C. Excess air is passed into the pool, and the 
molten metal is removed from below the molten salt pool. The process is 
said to be particularly useful for recovering noble-type metals such as 
copper, silver, gold, palladium, and platinum, and also aluminum, from 
scrap containing such metal values. 
In U.S. Pat. No. 4,164,416, there is disclosed a process for recovering 
metallic copper or lead from a sulfide ore containing the same by reacting 
the sulfide ore with a carbonaceous material and gaseous oxygen in a 
molten alkali metal carbonate pool. Temperatures in the range of about 
600.degree. to 1350.degree. C. are utilized to cause reduction of the 
metal sulfide to metallic copper or lead. 
None of the foregoing processes, however, can be used to recover vanadium 
values from carbonaceous materials. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to recover at least 90% of the 
vanadium present in carbonaceous materials. It is another object of this 
invention to provide a process for recovering vanadium values from various 
petroleum feedstocks by converting the vanadium compounds present in such 
petroleum feedstocks to readily recoverable vanadates. It is another 
object of the present invention to recover the vanadium values present in 
a petroleum residue utilizing a gasification process. It is yet another 
object of this invention to provide such a process which requires a 
minimum number of processing steps. Other objects and advantages of this 
invention will become apparent in the course of the following detailed 
description. 
SUMMARY OF THE INVENTION 
In accordance with the broad aspects of the present invention, a 
carbonaceous material containing vanadium is treated with an 
oxygen-containing gas in a molten salt pool comprising an alkali metal 
carbonate. During the course of the gasification of the carbonaceous 
material, the vanadium values present are converted to water soluble 
vanadium compounds, such as alkali metal metavanadates. The water soluble 
vanadium compounds are reacted with a strong acid, such as sulfuric acid, 
to form insoluble alkali metal vanadates which, if desired, can be further 
converted to vanadium pentoxide, V.sub.2 O.sub.5, the commercially 
available form of vanadium, sometimes known as "black cake." 
The invention will be more clearly understood by reference to the detailed 
description of certain preferred embodiments which follows, taken in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The process of the present invention can be used to recover vanadium values 
from a wide variety of carbonaceous materials. In general, it is preferred 
to use as feedstocks petroleum residues, that is, materials from which at 
least some of the lower boiling petroleum fractions have been removed. In 
this respect, a preferred starting material is petroleum coke, such as 
fluidized coke, delayed coke, or Flexicoker coke. Other petroleum 
residues, such as asphalt and heavy petroleum oils, can be used similarly. 
Tar sands coke or other carbonaceous materials containing vanadium can 
also be used, if desired. It should, of course, be appreciated that the 
more concentrated the vanadium is in the feedstock, the more economical 
will be the recovery of vanadium values from such feedstock. In general, 
concentrations of vanadium in the range of about 0.001% to 5% are known to 
occur in various kinds of crude petroleum and petroleum residues. In 
particular, Venezuelan residues contain a relatively high percentage of 
vanadium which is recoverable by the process of the present invention. For 
example, a Venezuelan petroleum containing 0.013% by weight of vanadium 
may be found to contain 0.06% vanadium in a residual oil and 0.4% vanadium 
in fluid coke made from the residual oil. 
Vanadium occurs in petroleum and other carbonaceous materials in various 
forms. The most common form present in petroleum is vanadium porphyrin. It 
is also known that vanadium occurs in petroleum in nonporphyrinic forms. 
However, little is known of the structure of the vanadium compounds, other 
than vanadium porphyrins, in which vanadium naturally occurs in crude 
petroleum. Regardless of the form in which vanadium occurs in the 
carbonaceous materials which are used as feedstocks for the process of the 
present invention, treatment of such feedstocks in the molten salt pool of 
a molten salt gasification plant has been found to convert the vanadium 
values present to soluble vanadium compounds. For example, where molten 
sodium carbonate is utilized as a principle component of the molten salt 
pool, the vanadium is converted to sodium metavanadate, NaVO.sub.3. 
It is a unique feature of the present invention that the vanadium values 
present in a carbonaceous feedstock can be isolated and recovered in such 
a molten salt plant during gasification of such feedstock to produce low 
or medium Btu heating fuels. This is accomplished by continuously 
withdrawing a stream from the molten salt pool, recovering the vanadium 
values from such stream, and regenerating and recycling the spent salts 
withdrawn from the molten salt pool. Vanadium recovery is thus achieved 
simultaneously with the production of such heating fuels. 
Reference will now be had to FIG. 1 of the drawings in order to set forth 
in greater detail the utilization of a molten salt gasification plant in 
recovering vanadium values from petroleum and other carbonaceous 
feedstocks and to better appreciate the advantages of the present 
invention. In FIG. 1, a gasifier 10 contains a molten pool of an alkali 
metal carbonate and may additionally contain alkali metal sulfates, 
sulfides, or other salts. The sulfate, sulfide, or other salt, if present, 
decreases the temperature necessary to provide the requisite molten salt 
pool by lowering the melting point of the mixture of salts constituting 
the pool. The alkali metal carbonate may be, for example, sodium 
carbonate; or it may be a mixture of alkali metal carbonates such as a 
ternary mixture of lithium carbonate, sodium carbonate, and potassium 
carbonate, consisting of about 43.5 mole % lithium carbonate, 31.5 mole % 
sodium carbonate, and 25.0 mole % potassium carbonate, which forms a 
eutectic having a melting point of about 397.degree. C. If an alkali metal 
sulfate, sulfide, or other salt is used in addition to the carbonate, it 
may be present initially in a concentration of about 1% to 25% by weight 
of the mixture of salts used to form the molten salt pool. 
In the following description, the composition of the molten salt pool will, 
for the sake of convenience, be exemplified as sodium carbonate, Na.sub.2 
CO.sub.3. The feedstock exemplified will be petroleum coke. Temperatures 
in the range of about 700.degree. to 1000.degree. C., and preferably about 
800.degree. to 950.degree. C., are maintained in the molten salt pool by 
controlling the rate at which an oxygen-containing gas is fed to the 
gasifier 10. Superatmospheric pressures in the range of about 2 to 50 
atmospheres, and preferably about 5 to 30 atmospheres, are maintained in 
gasifier 10. Coke is introduced into gasifier 10 below the surface of the 
melt by means of a conduit 12. The oxygen-containing gas is similarly 
introduced via a conduit 14, and sodium carbonate is introduced via a 
conduit 16. Air, enriched air, or oxygen is most commonly used as the 
oxygen-containing gas. If oxygen or enriched air is used, steam is 
preferably mixed with the oxygen to moderate the temperature and provide a 
thermal balance for the system. The oxygen-containing gas is exemplified 
herein as a mixture of oxygen and steam, O.sub.2 /H.sub.2 O. 
The operation of gasifier 10 is described with some degree of particularity 
in U.S. Pat. No. 3,916,617, the disclosure of which is hereby incorporated 
by reference. In the gasification step of the process of this invention, 
treatment of the feedstock in gasifier 10 results in the production of a 
low or medium Btu gas which is removed from gasifier 10 through a conduit 
18 to be utilized in a conventional steam boiler, gas turbine, or other 
heating means. Where the oxygen-containing gas is air, a low Btu gas is 
produced, since the oxygen in the effluent from the gasifier 10 is diluted 
with nitrogen. Where oxygen is used, as exemplified herein, a medium Btu 
gas is produced. Vanadium present in the feedstock is converted to soluble 
vanadium compounds, here exemplified as sodium metavanadate. Sulfates are 
converted to sulfides in the gasifier 10. 
A small stream of melt is continuously removed from the gasifier and 
replaced by the addition of dry sodium carbonate preferably mixed with the 
coke in order to prevent excessive build-up of ash and sodium sulfide, 
which are produced in the gasification reaction. The ash concentration is 
normally controlling when coal is gasified; but for high-sulfur petroleum 
coke, the sodium sulfide concentration controls, and the sodium carbonate 
recycle rate is adjusted to maintain a steady-state sodium sulfide 
concentration of about 5% to 60% by weight and preferably about 35% to 40% 
in the gasifier melt pool. Melt is removed from the gasifier, by a simple 
overflow arrangement, through a conduit 20 to a quench tank 22, which 
contains an aqueous quench liquor at a much lower temperature than that of 
the melt. For example, quench tank 22 may be operated at a temperature in 
the range of about 100.degree. to 300.degree. C., preferably about 
150.degree. to 200.degree. C. The quench liquor may consist of water or 
preferably may consist of salt solutions, produced in later steps in the 
process of this invention, which are recirculated to make up the quench 
liquor. 
The quenched melt is then conducted from quench tank 22 through a conduit 
24 to a filter 26 wherein any ash which may be present is separated. Ash 
is removed through a conduit 28, and the filtrate is fed via a conduit 30 
to a carbonator 32. 
Carbonator 32 serves several purposes. Any sodium silicate, derived from 
silicates present in the feedstock, which is present in the filtrate is 
converted to silica, sodium bicarbonate and sodium carbonate by reaction 
with carbon dioxide, as illustrated in Equations 1 and 2. 
EQU Na.sub.2 SiO.sub.3 +2CO.sub.2 +H.sub.2 O.fwdarw.SiO.sub.2 +2NaHCO.sub.3 (1) 
EQU Na.sub.2 SiO.sub.3 +CO.sub.2 .fwdarw.SiO.sub.2 +Na.sub.2 CO.sub.3 (2) 
Sodium sulfide produced in the gasification reaction is converted to sodium 
bicarbonate, sodium carbonate and hydrogen sulfide as illustrated in 
Equations 3 and 4. 
EQU Na.sub.2 S+2CO.sub.2 +2H.sub.2 O.fwdarw.2NaHCO.sub.3 +H.sub.2 S (3) 
EQU Na.sub.2 S+CO.sub.2 +H.sub.2 O.fwdarw.Na.sub.2 CO.sub.3 +H.sub.2 S (4) 
Sodium bicarbonate is also produced by carbonation of sodium carbonate as 
illustrated in Equation 5. 
EQU Na.sub.2 CO.sub.3 +CO.sub.2 +H.sub.2 O.fwdarw.2NaHCO.sub.3 (5) 
The alkalinity of the solution fed to the carbonator is reduced from about 
pH 13.0 to pH 8.0. Carbon dioxide is fed to carbonator 32 from a calciner 
44 via a conduit 34. Hydrogen sulfide is removed from carbonator 32 
through a conduit 36 and may be conveyed to a processing plant for further 
utilization, such as to a Claus plant for the recovery of elemental 
sulfur. 
A slurry containing the precipitated sodium bicarbonate and various soluble 
materials including the vanadium values, which have been converted to 
sodium metavanadate in gasifier 10, is removed from carbonator 32 via a 
conduit 38 and fed to a centrifuge 40. The solids separated in centrifuge 
40, principally precipitated sodium bicarbonate, are removed via a conduit 
42 and fed to calciner 44, in which the sodium bicarbonate is converted to 
solid sodium carbonate as illustrated in Equation 6. The sodium carbonate 
is recycled to gasifier 10 through conduits 46 and 16. 
##STR1## 
Carbon dioxide formed in the reaction in calciner 44 is fed to carbonator 
32 via conduit 34. 
The supernatant liquor from centrifuge 40, containing the vanadium values 
in the form of sodium metavanadate in solution, is drained and the liquid 
stream removed through a conduit 48 . The stream from conduit 48 divides, 
a part of the stream being recycled to quench tank 22 through a conduit 
50, with the remaining portion being fed through a conduit 52 to a 
precipitator 54. Depending upon the vanadium concentration, about 10% to 
nearly 100% of the stream from centrifuge 40 may be processed for vanadium 
recovery. A strong acid, here exemplified as sulfuric acid, is fed to 
precipitator 54 through a conduit 56. Precipitator 54 is operated at 
elevated temperatures, usually at temperatures above the boiling point of 
the sulfuric acid solution and preferably at a temperature in the range of 
about 75.degree. to 125.degree. C. Sulfuric acid of about 15% to 98% 
concentration, and preferably about 35% to 50%, is used for the acid feed 
to the precipitator. Waste acids from vanadium demetallizing plants may 
furnish a suitable feed for the precipitator and may provide an additional 
source of vanadium. Other acids may be used if desired. Insoluble "red 
cake," a product sometimes characterized as sodium hexavanadate, Na.sub.4 
V.sub.6 O.sub.17 and sometimes characterized as sodium dihydrogen 
hexavanadate, Na.sub.2 H.sub.2 V.sub.6 O.sub.17, is precipitated from an 
acid solution of about pH 1.0 to pH 3.5, preferably about pH 2.0 to pH 
2.8. The formation of "red cake" is illustrated in Equations 7 and 8. 
EQU 6NaVO.sub.3 +H.sub.2 SO.sub.4 .fwdarw.Na.sub.4 V.sub.6 O.sub.17 +Na.sub.2 
SO.sub.4 +H.sub.2 O (7) 
EQU 6NaVO.sub.3 +2H.sub.2 SO.sub.4 .fwdarw.Na.sub.2 H.sub.2 V.sub.6 O.sub.17 
+2Na.sub.2 SO.sub.4 +H.sub.2 O (8) 
A slurry containing the insoluble "red cake" from precipitator 54 is 
removed through a conduit 58 to a filter 60. Following filtration of the 
slurry in filter 60, the "red cake" is fed via a conduit 62 to a "red 
cake" fuser 64. The filtrate containing sodium sulfate is removed via a 
conduit 66 to a dryer 68 and recycled via conduits 70, 46, and 16 to 
gasifier 10 where it is used as make-up salt for the molten salt pool in 
the gasifier. If desired, a portion of the "red cake" may be removed as a 
product via a conduit 72. In fuser 64, the "red cake" is converted to 
"black cake" by heating at a temperature in the range of about 700.degree. 
to 1000.degree. C., and preferably about 800.degree. to 900.degree. C. The 
conversion of "red cake" to "black cake" is illustrated in Equations 9 and 
10. 
##STR2## 
The "black cake" is removed to storage through a conduit 74. "Black cake," 
a commercially available vanadium pentoxide concentrate, contains about 
86% to 90% vanadium pentoxide and about 6% to 10% sodium oxide. 
In the embodiment of the present invention illustrated in FIG. 2, wherein 
parts similar to those in FIG. 1 are designated by corresponding numerals, 
operation of gasifier 10' is as indicated above in the description of FIG. 
1. Melt from gasifier 10' is removed via conduit 20' to quench tank 22'. 
The quenched melt is withdrawn via conduit 102 to a precarbonator 104. 
Carbon dioxide is introduced into precarbonator 104 via conduits 106 and 
108 from a calciner 136. In precarbonator 104, sodium silicate is 
converted to silica, sodium bicarbonate, and sodium carbonate by reaction 
with carbon dioxide as illustrated in Equations 1 and 2; sodium sulfide is 
converted to sodium bicarbonate, sodium carbonate and hydrogen sulfide as 
illustrated in Equations 3 and 4; sodium carbonate is carbonated to 
produce sodium bicarbonate as illustrated in Equation 5; and the 
alkalinity of the solution is reduced from about pH 13.0 to a pH in the 
range of about pH 9.0 to pH 10.0 and preferably to about pH 9.5. The 
resulting slurry is removed from precarbonator 104 through a conduit 110 
to a filter 112, wherein ash and silica are removed as waste via a conduit 
114. The filtrate is conducted via a conduit 116 to a stripper 118. In 
stripper 118, hydrogen sulfide is stripped from the filtrate by means of 
steam introduced via a conduit 120. Hydrogen sulfide gas exits through a 
conduit 122 and may be further treated as previously explained. The 
filtrate from stripper 118 is fed via a conduit 124 to a carbonator 126 
wherein carbon dioxide introduced via a conduit 128 causes the remaining 
sodium sulfide and sodium carbonate to be converted to sodium bicarbonate 
crystals and the alkalinity of the solution to be further reduced from 
about pH 9.5 to a pH in the range of about pH 8.0 to pH 8.2. The 
precipitated sodium bicarbonate, in the form of a slurry, is removed 
through a conduit 130 to a centrifuge 132. Solids are removed from 
centrifuge 132 via a conduit 134 to a calciner 136. The remaining liquids 
are drained from centrifuge 132 via a conduit 138. At this point, the 
liquid stream is divided, part of the stream passing via a conduit 140 to 
vanadium recovery stages as previously described with respect to FIG. 1, 
the remainder of the stream being fed via a conduit 142 to quench tank 22' 
and used as quench liquor therein. The solids fed from centrifuge 132 to 
calciner 136 are heated to a temperature in the range of about 250.degree. 
to 750.degree. C., and preferably about 400.degree. to 650.degree. C., and 
the carbon dioxide thereby released is removed from calciner 136 via 
conduit 106 and introduced to precarbonator 104 via conduit 108 and to 
carbonator 126 via conduit 128. The solids remaining in calciner 136 are 
conducted via conduits 144 and 16' to gasifier 10' wherein they are 
introduced below the surface of the melt and used as additional make-up to 
form the molten salt pool in gasifier 10'. 
The embodiment shown in FIG. 2 has the advantages of reducing the quantity 
of solids which are required to be removed in the carbonation stage, of 
facilitating the separation of bicarbonate crystals in the carbonator, and 
of providing a relatively pure hydrogen sulfide product. By removing the 
hydrogen sulfide from the filtrate in a separate stage in stripper 118 by 
the use of steam prior to feeding it to the carbonator, the hydrogen 
sulfide is uncontaminated by carbon dioxide. Also, silicate removal is 
facilitated. This advantage is particularly important where the 
carbonaceous material being gasified is material containing a relatively 
high proportion of silicates. 
In the embodiment illustrated in FIG. 3, wherein parts similar to those in 
FIG. 1 or FIG. 2 are designated by corresponding numerals, provision is 
made for recycling sulfates as well as for recovering vanadium values. 
Following precipitation of "red cake" in precipitator 54' and filtration 
thereof in filter 60', the filtrate is fed from filter 60' via a conduit 
202 to a neutralizer 204, wherein an alkali metal base is used to 
neutralize excess sulfuric acid. Sodium carbonate, for example, is 
introduced into neutralizer 204 through a conduit 206. The excess sulfuric 
acid is thereby neutralized as illustrated in Equation 11. 
EQU H.sub.2 SO.sub.4 +Na.sub.2 CO.sub.3 .fwdarw.Na.sub.2 SO.sub.4 +CO.sub.2 
+H.sub.2 O (11) 
The neutralized filtrate containing sodium sulfate is fed via a conduit 208 
to a crystallizer 210 which is cooled to a temperature in the range of 
about 15.degree. to -5.degree. C., and preferably about 0.degree. to 
-2.degree. C. In crystallizer 210, part of the sodium sulfate crystallizes 
out as Glauber's salt, sodium sulfate decahydrate, Na.sub.2 
SO.sub.4.10H.sub.2 O. The resulting slurry is removed from crystallizer 
210 through a conduit 212 to filter 214, where the precipitated Glauber's 
salt is removed via conduit 216 to calciner 218, converted to anhydrous 
sodium sulfate and recycled to gasifier 10" via conduits 220, 46' and 16", 
where it is used as make-up salt for the molten salt pool in the gasifier. 
The filtrate is recycled via conduit 222 to quench tank 22". 
The embodiment of FIG. 3 is advantageous in that the sulfate produced in 
the precipitation of vanadium "red cake" is eventually recycled to the 
molten salt make-up of gasifier 10", thereby utilizing not only the 
acidity of the sulfuric acid used in the precipitation but also the 
sulfate content thereof. 
The following example is intended to illustrate the process of the present 
invention but is not to be considered a limitation thereof. 
EXAMPLE 
A quantity of 0.900 lb sodium carbonate and 0.183 lb sodium sulfate was 
charged to a cold alumina tube, 13/4 in. ID by 2 in. OD by 18 in. high, 
disposed in a 21/2 in. diameter by 20 in. high electric furnace, the 
temperature of which was controlled by a saturable controller. The 
temperature of the tube was raised to 950.degree. C. over a 2-hour period. 
Then, 0.044 lb of petroleum coke was mixed into the molten salt bed in 
order to reduce the sodium sulfate to sodium sulfide. The bed was sparged 
with reducing gas containing 21% by volume of carbon monoxide, 12% 
hydrogen, and 67% nitrogen, at a rate of 3.25 liters per minute, 
corresponding to a superficial gas velocity of 0.5 fps, in order to 
exclude air and to simulate the steady state gas condition within the 
gasifier during operation, wherein, as pointed out above, a low Btu gas is 
produced by the use of air as the oxidizing gas fed to the gasifier. The 
coke was added gradually over a 15-minute period by pouring through a 
funnel. An additional 15 minutes were allowed for completion of the 
sulfate reduction. Then, over a 10-minute period, 0.1 lb vanadium 
pentoxide was added to the bed through the funnel. About 200 cc per minute 
of gas was used to stir the salt bed during this period. When all of the 
V.sub.2 O.sub.5 had been charged, the reducing gas was sparged through the 
molten salt for 2 hours while holding the salt temperature at 900.degree. 
C. After the 2-hour sparge period, the melt was poured into a stainless 
steel pan blanketed with nitrogen gas. A portion of the melt was dissolved 
in water and filtered, and filtrate and residue were analyzed for 
vanadium. It was found that 98.9 wt % of the vanadium charged to the melt 
was present in the filtrate as sodium metavanadate. 
A 100-gram sample of melt was dissolved in 500 grams water. The mixture was 
agitated on a hot plate, boiled for 10 minutes, and then suction filtered 
through a porous stainless steel filter. The dried residue was found to 
weigh 3.10 grams. The filtrate weighed 618.66 grams. A 200-gram portion of 
the filtrate was titrated with 15 wt % sulfuric acid at a temperature of 
92.degree. C. from pH 12.0 to pH 2.5 over a period of 20 minutes, and the 
solution was held at approximately the boiling temperature, 100.degree. 
C., for 1 hour. The red precipitate which formed was filtered and dried at 
125.degree. C. A quantity of 3.55 grams of precipitate formed was filtered 
and dried at 125.degree. C. A quantity of 3.55 grams of precipitate was 
collected. Analysis showed that 95.5% of the vanadium was present in the 
precipitate. 
Thus it can be seen that the present invention provides a process by which 
it is possible to recover at least 90% of the vanadium values present in 
carbonaceous feedstocks, at the same time producing useful products 
including a combustible gas and recovering substantially all of the sodium 
carbonate or other salt used in the gasification process. 
It will, of course, be realized that various modifications can be made in 
the design and operation of the present invention without departing from 
the spirit thereof. For example, the improved carbonate regeneration stage 
of FIG. 2 can be combined with the improved vanadium recovery stage of 
FIG. 3 to provide a process combining the advantages of both improvements. 
Thus, while the principle, preferred construction, and mode of operation 
of the invention have been explained and what is now considered to 
represent its best embodiment has been illustrated and described, it 
should be understood that within the scope of the appended claims, the 
invention can be practiced otherwise than as specifically illustrated and 
described.