US2723903A - Production of titanium tetrachloride - Google Patents

Description

United States Patent- PRODUCTION OF TITANIUM TETRACHLORIDE Howard M. Cyr and Frank S. Grifiith, Palmerton, and Charles lVL'McFarland, Lehighton, Pa., assignors to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey No Drawing. Application July 26, 1955, Serial No. 524,614

2 Claims. (Cl. 2387) This invention relates to the production of titanium tetrachloride and, more particularly, to the production of titanium tetrachloride from titaniferous raw materials by a continuous and autogenous chlorination process.

Years of research have been expended on the problem of producing titanium tetrachloride by the chlorination of titaniferous material such as ilmenite. The early' chlorination procedures favored the use of finely divided titaniferous material and carbon in order to permit access of chlorine gas to the solid components of the reaction mass. But it was found that even a finely divided mass of titaniferous material and carbon was not readily penetrable by the chlorine, so L. E. Barton proposed, as described in his United States Patent No. 1,179,394, the use of a large amount of coking coal as the source of carbon and the coking of an uncompressed mixture of this coal and titaniferous material in order to form a porous cinder. This cinder was sufliciently porous to promote greater access of the chlorine to the titaniferous material when the chlorination was carried out in the then-conventional chlorination apparatus which, as pointed out by Barton, usually consisted of a multiplicity of horizontal trays in Whichthe solid reactants were heated to redness. The amount of carbon used by Barton was sufliciently great to permit the cinder to retain its original form and structure even after substantially complete exhaustion of its original titanium component. More recently, I. E. Muskat et al., in their United States Patent No. 2,184,887, pointed out that the chlorination of titaniferous material in admixture with carbon could be carried out without use of external heating, i. e. autogenously, by using not more than about 35% of carbon by weight of the titaniferous material. Muskat et al. further found that such a mixture of titaniferous material and carbon could be chlorinated autogenously in briquetted form, but, they pointed out an increase in carbon content beyond their 35% limit exerted a quenching eifect upon the chlorination reaction, thus making temperature maintenance very difficult. Unlike the Barton cinder, the Muskat et al. briquettes, asthey are chlorinated, disintegrate into an ash which is withdrawn from the chlorinating furnace.

The Barton procedure is one in which the cinder, resembling What is now known as coke fingers, is relatively immovable in the chlorinating reaction zone because of the interlocking of the sharp-edged fingers. Accordingly, the Barton cinder resists moving or settling through a chlorination zone, and consequently the Barton procedure is normally a batch operation. Experience has shown, as described on page 735 of the June 1954 issue of the Journal of Metals, in the article entitled Titanium metal production expanded at Henderson plant, and on page 86 of the March 19, 1955, issue of Chemical Week, in the article entitled Fluid route bypasses problems, that the type of operation proposed by Muskat et al. is interrupted by the accumulation of fine ash in the bottom of the chlorinating furnace and is therefore discontinuous.

ICC

Contrary to Bartons teaching that the mixture of titaniferous material with a large amount of carbon should be uncompressed in order that it be porous and penetrable by chlorine, and contrary to the Muskat et al. statement that amounts of carbon in excess of about 35% by weight of the titaniferous material quench the chlorination reaction so as to make it difiicult or impossible to maintain autogenous reaction conditions, we have discovered that a densified, briquetted mixture of titaniferous material and at least by weight of at least partially cokable carbonaceous material canbe chlorinated under completely autogenous reaction conditions and, moreover, that this autogenous reaction can be maintained under continuous operating conditions wherein the briquettes are charged to one end of the chlorinating zone and the resulting titanium-depleted briquettes are withdrawn from the other end of the chlorinating zone without significant interruption of the chlorination reaction. I e

The method of our present invention is therefore directed to the continuous and autogenous chlorination of the titanium component of titaniferous material containing at least 20% titanium oxide calculated as TiOz, and comprises initially preparing a charge consisting essentially of the aforesaid titaniferous material and solid carbonaceous material, both in finely divided form, in which the carbonaceous material contains about 50% to coking coal and the balance, if any, non-coking coal. The total amount of this carbonaceous material admixed with the titaniferous material ranges from about 75% to by Weight of the titaniferous material. This charge is then simultaneously mixed and compressed to eifect intimate contact. between the titaniferous and carbonaceous materials. Thereafter, the mixture is briquetted. The density of the briquette is at least 25% and usually 70% greater than the bulk density of the original mix. The briquetted mixture is coked at a temperature. of at least about 600 C. for a period of time sufficient to drive oif substantially all of those volatile components of the coking coal which can be evolved at that temperature. The resulting coked briquettes are charged to one end of a chlorinating zone. Chlorine gas is passed substantially continuously through a body of the coked briquettes which are maintained at a chlorination reaction temperature within the range of about 600 to 1000 C. by the exothermic heat of the chlorination reaction resulting from contact between the chlorine gas and the hot briquettes. The chlorination of the titanium component of the briquettes is thus eifected without substantially destroying the coherent structure of the briquettes and While permitting the briquettes to move substantially continuously through the chlorinating zone from the charging end thereof toward a. discharge end of said zone as their titanium content is being depleted by chlorination. The titanium-depleted briquettes are withdrawn from the discharge end of the chlorinating zone while the chlorination reaction is continued, whereby an uninterrupted autogenous reaction in the chlorinating zone is maintained. The titanium tetrachloride evolved in the chlorinating zone is recovered by conventional means. Although we have found that when relatively small cold briquettes are delivered directly to the reactor, the heat generated by the chlorination reaction is sufficient to maintain autogenous chlorinating conditions, the conservation of heat by charging the coked briquettes while still hot increases the length of the chlorination reaction period while the briquettes pass through the reactor and thus promotes substantially complete chlorination of even the largest briquettes.

The titaniferous material which may be chlorinated by the method of our invention includes titanium ores and titanium concentrates. For example, rutile and ilmenite are representative of such titanium ores and the slags produced as described in United States Patent No. 2,476,453' are representative of titanium concentrates which may be'used in practicing our invention. Ilmenites generally contain from about to or more of titanium dioxide (with an iron oxide content which is generally greater with lower titanium oxide contents), and native rutiles contain as high as 95% titanium dioxide (and generally nearly free of iron oxide). The aforementioned slag concentrates contain at least and generally at least 70%, titanium oxide calculated as TiOz. These slag concentrates further contain varying amounts of iron oxide up to 20%, calculated as Fe. and may contain up to 18% of lime and magnesia calculated as CaO and MgO. In general, slag concentrates containing amounts of iron oxide approaching the aforesaid upper limit of 20% contain relatively small amounts of lime, and conversely the slag concentrates containing amounts of lime approaching the upper limit of 18% are generally characterized by the presence of only a small amount of iron oxide. Although either of these two extremes of slag concentrate composition as well as compositions of intermediate iron oxide and lime contents may be used in practicing our invention, the method of our invention is of particular value in the chlorination of those slag concentrates which are relatively low in iron oxide and relatively high in lime. The lime and magnesia present as gangue constituents in titanium slag concentrates become chlorinated to some extent and the resulting calcium and magnesium chlorides form melts which have lower freezing points than either of the individual chlorides. Thus, these chlorides tend to form a liquid mixture at the normal operating temperature in the practice of our invention, but the porosity of our briquettc structure is such that this melt is largely adsorbed and is to this extent sequestered by the briquettes so as not to interfere with the chlorination of the titaniferous material. Moreover, this sequestering of the molten calcium and magnesium chlorides precludes the possibility of the briquettes being stuck together by an outer film or coating of the molten chlorides.

The solid carbonaceous material with which the titaniferous material is mixed in practicing our invention is characterized by the presence of coking coal either with or without a minor amount of non-coking coal. The presence of the coking coal promotes the development of structural stability'in the resulting coked briquettes by virtue of the fusion (and hence binding eifect) of the coking coal during the coking operation. In order to assure this result, we have found it advantageous to use coking (bituminous) coals of high fluidity, that is, coals having a fluidity of about 10,000 units or more on the Giesler fluidity scale (a plastometric test procedure described in Appendix III of the A. S. T. M. Standards on Coal and Coke, 1948). In general, we have found that the carbonaceous material should comprise at least about 50% by weight of coking coal and may consist exclusively of such coking coal. If less than all of the carbonaceous material is provided in the form of coking coal, the balance may be provided by the use of noncoking coal,such as anthracite, coke breeze or petroleum coke, or mixtures of these substantially non-coking coals (as they are referred to collectively herein and in the claims).

The amount of such carbonaceous material admixed with the titaniferous material in the practice of our invention ranges between 75% and 135% by weight of the titaniferous material. In the case of ilmenites, regardless of their titanium oxide content, the same range of carbonaceous material is required because, when the titanium oxide content of the ilmenite is relatively low, its iron oxide content is relatively high and the chlorination of this iron consumes a considerable amount of available carbon. The aforementioned titanium slag concentrates correspond to a relatively high titanium oxide ilmenite and thus require the same amount of carbonaceous material for chlorination. In the case of rutile, the same range of carbonaceous material is required for chlorination of the high titanium oxide content of the rutile. Amounts of carbonaceous material below about do not form coked briquettes containing an adequate residual structure to support the briquettes after substantially all of the titanium component of the titaniferous material (regardless of its nature) has been chlorinated. Amounts of carbonaceous material above the upper limit of the aforementioned range may be used but tend to lower the capacity of the furnace. Therefore, the aforementioned range for'the proportion of carbonaceous material to titaniferous material represents the most advantageous condition for obtaining a coked briquette having the optimum combination of structural stability, ability to absorb molten residual chlorides and accessibility of the titanium for chlorination.

Both the titaniferous material and the coking coal component of the carbonaceous material should be finely divided inasmuch as a fine degree of subdivision of the titaniferous material promotes its chlorination and a fine degree of subdivision of the coking coal contributes significantly to the formation of structurally stable briquettes. Thus, both of these components should be ground to all minus 20 mesh (Tyler Standard) and 30% minus 200 mesh either separately before mixing or together after mixing. However, we have found it advantageous to use the non-coking component'of the carbonaceous material in a coarser condition, nominally through 6 and on mesh.

The titaniferous material and carbonaceous material are brought into intimate contact with one another by a mixing and compression treatment which can be readily achieved in a pug mill or in the type of device known as an edge runner, chaser or Chilean mill. The resulting mixture forms a more coherent and stable briquette structure which, after coking, is nevertheless sufficiently porous to promote effective chlorination of its titaniferous component.

The resulting intimate mixture of titaniferous material and solid carbonaceous material is then briquetted. For this purpose, moistening with water will produce a sufficiently plastic and coherent mass to retain a subsequently applied briquetted shape. However, in order to impart greater structural strength to the uncoked briquette, we have found it advantageous to introduce a small amount, generally about 3 to 8% by weight, of a carbonaceous binding agent such as sulfite liquor, pitch, or the like, as distinguished from argillaceous binders, such as bentonite and other clays, which tend to impair the porosity of the resultingbriquettes and also introduce impurities into the titanium tetrachloride. Conventional briquetting equipment, such for example as that which forms pillow-block briquettes 2 inches by 2 inches by 1% inches, will produce from such moistened mixtures briquettes having adequate strength to withstand subsequent coking.

Coking of the briquetted mixture may be carried out In general, coking a body of the coked briquettes while maintaining the.

briquettes at a temperature advantageously within the range of 600 to 1000 C. Within this temperature range, the chlorine readily permeates the briquette structure and reacts with the titanium oxide component of the titaniferous material with the resulting formation of titanium tetrachloride vapor as the primary product and carbon monoxide and carbon dioxide as the main by-products. In addition, the chlorine reacts with the iron, magnesium, calcium, aluminum and silicon oxides to varying extents depending upon the temperature and composition of the briquettes. After the chlorination reaction has been initiated, the exothermic heat of reaction is sufiicient to maintain the chlorination temperature range without the application of external heat. Thus, completely autogenous reaction conditions prevail in the practice of our invention. The chlorine gas is substantially continuously passed through the body of coked briquettes which are maintained at reaction temperature by the exothermic heat of reaction, and the coked briquettes charged to one end of the chlorination reaction zone move substantially continuously through and toward a discharge end of the chlorinating zone as their titanium content is being depleted by chlorination. The titanium-depleted briquettes are withdrawn from the discharge end of the chlorinating zone in such manner as to maintain uninterrupted autogenous reaction conditions in the chlorinating zone; that is, the titanium-depleted briquettes are withdrawn either continuously or intermittently, but in either event they are withdrawn at an average rate substantially equal to the rate at which they are produced by the chlorination reaction. Thus, by substantially continuously passing chlorine gas through the body of hot titanium-containing briquettes in the reaction zone, and by charging fresh briquettes to one end of this zone and discharging spent 1.6 before, the briquettes of our invention promote a degree of selectivity in the chlorination of the titaniferous slag concentrate which has not been achievable heretofore. Moreover, the fact that these briquettes make it possible to chlorinate the charge in the form of a long slender column works to the advantage of our method inasmuch as a slender reaction column eifectively radiates the exothermic heat of reaction and promotes substantially uniform temperatures throughout the cross section of the column. Actual control of the reaction temperature may be achieved by various expedients, such as by dilution of the chlorine with an inert gas, by dilution of the briquettes with non-reactive materials, by spreading or contracting the reaction zone by increasing or decreasing the size of the ore or slag particles, by varying the size of the briquettes, by diffusion of the distribution of the chlorine in the reactor (i. e., by introducing it into vertically spaced portions of the briquette charge), by varying the rates of charging the briquettes and chlorine, by varying the relative proportions of preheated and cold briquettes in the charge, by choice of furnace insulation, or by a combination of these expedients. The resulting facility for Titanium Source Coking Coal Non-Coking Coal Binder Sorel Slag Bituminous Goal 1 Metallurgical Coke Sulfite Liquor Comp. Percent Comp. Percent Comp. Percent Comp. Percent 70. Volatile. 37. 1 Fixed 0... Fixed 0... 54. 2 Ash Ash .i

High fluidity coal, Giesler fluidometer rating to 14,000 R. P. M. compared with very low R. P. M. for coals used in metallurgical coke.

briquettes from the other end of the reaction zone, sub stantially continuous chlorination of the titanium-containing briquettes is achieved without interruption in the autogenous reaction conditions which prevail in the chlorination reaction zone.

Inasmuch as the degree of reactivity of the magnesium, aluminum and silicon components of the briquettes increases with the chlorination temperature, there is an economic advantage in conducting the reaction at a temperature sufiiciently high to effect chlorination of the titanium while sufliciently low to minify chlorination of the other components of the briquettes. The high structural strength of the briquettes of our invention makes possible their chlorination in a deep but narrow bed, as in a long slender column, and the resulting deep bed ofiers a longer reaction period for the ascending chlorine. This prolonged reaction opportunity permits the use of a lower chlorination temperature while nevertheless insuring complete chlorination reaction. Inasmuch as lower reaction temperatures minify the chlorination of the non-titaniferous components of the charge as pointed out herein- A mix composed of 50 parts of the slag, 40 parts of the bituminous coal, 10 parts of the coke, 7 parts of the binder, and water as required, was blended and had a bulk density of about 55 pounds per cubic foot. The

lended mixture wasthcn treated in a Chilean type mill (also known as a chaser). The mix was discharged from the chaser and briquetted on a commercially available roll press which form 2" by 2" by 1%" pillow block briquettes with a density of about pounds per cubic foot measured by determining the volume displaced by a briquette of known weight. These briquettes were broken inhalf for a more effective size in the subsequent chlorination operation. These briquettes were placed in a steam dryer for 2 hours to eliminate moisture which would otherwise cause them to crack badly in the heat of the coking furnace. The dried briquettes were hard and could be handled without breakage.

The dried briquettes were then coked at 900 C. for 1 hour. During the coking most of the volatile matter in the coal and the binder was driven oh, and the resulting hard coke structure had the following analysis.

7 TiOa 45.8% FeO 7.2 CaO 1.7 MgO 4.0 SiOz 5.7 A1203 6.1 Bulk density 44 lb./cu.ft. Apparent briquette density 90 lb./cu.ft. 1 ilriquette porosity 40% Measured by determining the volume displaced by a hriquette of known weight.

For the chlorination operation, a vertically disposed retort was filled to a depth of 2 ft. with lump coal (although it has been found that coke or residue briquettes from a previous chlorination operation could similarly be used), and then hot briquettes coked as described hereinbefore were added to a depth totaling 7 ft. (approximately 160 lb. of the hot briquettes were used for this change). Air was introduced near the bottom of the retort at the rate of about 50 cubic feet per minute in order to burn the coal and preheat the retort. When the thermocouples inside the retort recorded about 700 C. (and this temperature was attained in about 1 /2 hrs.), the air supply was turned off. The burning coal charge was quickly lowered in the retort and the hot coked slag briquettes were charged at the top to bring the charge level above the gas exit level at which the effiuent gases were withdrawn '(at a height about '8 feet above the bottom of the retort).

Chlorine was then introduced into the bottom of the retort at a flow rate of 5 to 6 cubic feet per minute, and thereafter the chlorination reaction proceeded autogenously. Thereafter, hot coked briquettes were charged intermittently to the retort at a rate of 60 pounds an hour. These charging rates provided an excess of chlorine to insure the formation of FCl3 which is more volatile than FeClz while nevertheless holding the excess chlorine in the exit gas to 2% or less. A reaction zone temperature of 800 C. to 900 C. was maintained autogenously by the heat of the chlorination reaction in the retort, and the chlorides volatile at these temperatures, to wit, SiC14, TiCh, FeCls, and AlCls, were withdrawn from the retort through the efiiuent gas outlet along .with CO and C02. The vapors were cooled with a jet of cold TiCl4 and the resultant titanium tetrachloride slurry was collected in a storage tank. The less volatile CaClz and MgClz remained in the residue briquettes which were discharged from the retort at regular intervals. The charge of'briquettes kept their shape and did not form excessive fines in spite of the fact that they moved progressively downwardly through the retort as their titanium content was being depleted by the chlorination reaction. The downward movement of the body of briquettes through the chlorinating zone was efiected by intermittently discharging the spent briquettes through a star valve at the lower end of the retort at a rate sufiicient to make room in the upper portion of the retort for the charge of fresh briquettes. in spite of this discharging of spent briquettes from the chlorinating retort, the delivery of chlorine gas to the retort was continued so as to maintain the autogenous reaction conditions prevailing within the retort.

it should be noted that temperature control for the chlorination operation was achieved simply by adjusting the sensible heat in the coked briquettes charged to the retort. in the operation described herein, the chlorination reaction zone temperature of 800-900 C. was maintained by charging approximately half of the briquettes directly from the coking operation and the other half in the form of coked briquettes which had cooled to ambient temperature.

The aforementioned titanium tetrachloride-containing slurry was red in color, clue to the presence of solid iron chlorides in the liquid titanium tetrachloride, but after filtering this slurry the resulting liquid phase comprised a clear straw-yellow liquor, Removal of the vanadium c 8 content of this liquor by conventional procedure and its subsequent distillation resulted in a water-white liquid titanium tetrachloride of high degree of purity and suitable for use as a raw material from which ductile metallic titanium was produced.

It will be seen, accordingly, that the method, of our invention makes possible the effective and substantially complete chlorination of the titanium component of titaniferous materials of natural or artificial origin in a continuous and autogenous operation. The residual coherent briquette structure which is obtained as chlorination of the titanium component of the briquettes nears completion maintains a uniform physical distribution of the titanium component in the chlorinating atmosphere and thus assures substantially complete utilization of the titaniferous value of the starting material as well as continuity of the chlorination operation without interruption for the discharge of spent charge.

This is a continuation-in-part of our copending application Serial No. 504,124, filed April 26, 1955, which in turn was a continuation-in-part of our then pending application Serial No. 408,293, filed February 4, 1954, both applications Serial No. 504,134 and Serial No. 408,293 aforementioned having now been abandoned.

We claim:

1. The method of continuously and autogcnously chlorinating the titanium component of titaniferous material which comprises preparing a charge consisting essentially of finely divided titaniferous material and solid carbonaceous material, the titaniferous material containing at least 20% titanium oxide calculated as TiOz and the carbonaceous material containing about to 100% by weight of coking coal and the balance essentially non-coking coal, the total amount of said carbonaceous material ranging between about 75% and 135% by weight of the titaniferous material so as to provide a substantial carbonaceous residue after chlorination of the titanium content of the titaniferous material in contact therewith, simultaneously mixing and compressing the charge of said titaniferous material and carbonaceous material to effect intimate contact between these materials, thereafter forming briquettes having a density at least 25% higher than that of the charge, coking the briquettes at a temperature of at least about 600 C., charging the coked briquettes to one end of a chlorinating zone, passing chlorine gas substantially continuously through a body of the coked briquettes, maintaining said body of coked briquettes at a chlorination reaction temperature within the range of about 600 to 1000 C. by the exothermic heat of the chlorination reaction resulting from the contact between the chlorine gas and the hot briquettes, the chlorination of the tita nium component of the briquettes thus being effected without substantially destroying the coherent structure of said briquettes and while permitting the briquettes to move substantially continuously through the chlorinating zone from the charging end thereof toward a discharge end of said zone as their titanium content is being depleted by chlorination, withdrawing titaniumdepleted briquettes from the discharge end of the chlorinating zone while the chlorination reaction is continuing whereby uninterrupted autogenous reaction in the chlorinating zone is maintained, and recovering the resulting titanium tetrachloride evolved in the chlorinating zone.

2. The method of continuously and autogenously chlorinating the titanium component of titanium slag concentrate containing at least titanium oxide calculated as TiOz, up to 20% iron oxide calculated as Fe, and up to 18% lime calculated as CaO, which comprises preparing a charge consisting essentially of said slag and solid carbonaceous material both in finely divided form, said carbonaceous material containing about 50% to 100% by weight of coking coal and the balance essentially non-coking coal, the total amount of said carbtmaceous material ranging between about and 135% by weight of the slag concentrate so as to provide a substantial carbonaceous residue after chlorination of the titanium content of the slag concentrate in contact therewith, simultaneously mixing and compressing the charge of said slag concentrate and carbonaceous material to eifect intimate contact between these materials, thereafter forming briquettes having a density at least 25% higher than that of the charge, coking the briquettes at a temperature of at least about 600 C., charging the coked briquettes to one end of a chlorinating zone, passing chlorine gas substantially continuously through a body of the coked briquettes, maintaining said body of coked briquettes at a chlorination reaction temperature within the range of about 600 to 1000 C. by the exothermic heat of the chlorination reaction resulting from the contact between the chlorine gas andthe hot briquettes,

the chlorination of the titanium component of the briquettes thus being effected without substantially destroying the coherent structure of said briquettes and while permitting the briquettes to move substantially continuously through the chlorinating zone from the charging end thereof toward a discharge end of said zone as their titanium content is being depleted by chlorination, withdrawing titanium-depleted briquettes from the discharge end of the chlorinating zone while the chlorination reaction is continued whereby uninterrupted autogenous reaction in the chlorinating zone is maintained,'and recovering the resulting titanium tetrachloride evolved in the chlorinating zone.

No references cited.

Claims (1)

1. THE METHOD OF CONTINUOUSLY AND AUTOGENOUSLY CHLORINATING THE TITANIUM COMPONENT OF TITANIFEROUS MATERIAL WHICH COMPRISES PREPARING A CHARGE CONSISTING ESSENTIALLY OF FINELY DIVIDED TITANIFEROUS MATERIAL AND SOLID CARBONACEOUS MATERIAL, THE TITANIFEROUS MATERIAL CONTAINING AT LEAST 20% TITANIUM OXIDE CALCULATED AS TIO2 AND THE CARBONACEOUS MATERIAL CONTAINING ABOUT 50% TO 100% BY WEIGHT OF COKING COAL AND THE BALANCE ESSENTIALLY NON-COKING COAL, THE TOTAL AMOUNT OF SAID CARBONACEOUS MATERIAL RANGING BETWEEN ABOUT 75% AND 135% BY WEIGHT OF THE TITANIFEROUS MATERIAL SO AS TO PROVIDE A SUBSTANTIAL CARBONACEOUS RESIDUE AFTER CHLORINATION OF THE TITANIUM CONTENT OF THETITANIFEROUS MATERIAL IN CONTACT THEREWITH, SIMULTANEOUSLY MIXING AND COMPRESSING THE CHARGE OF SAID TITANIFEROUS MATERIAL AND CARBONACEOUS MATERIAL TO EFFECT INTIMATE CONTACT BETWEEN THESE MATERIALS, THEREAFTER FORMING BRIQUETTES HAVING A DENSITY AT LEAST 25% HIGHER THAN THAT OF THE CHARGE, COKING THE BRIQUETTES AT A TEMPERATURE OF AT LEAST ABOUT 600*C., CHARGING THE COKED BRIQUETTES TO ONE END OF A CHLORINATING ZONE, PASSING CHLORINE GAS SUBSTANTIALLY CONTINUOUSLY THROUGH A BODY OF THE COKED BRIQUETTES, MAINTAINING SAID BODY OF COKED BRIQUETTES AT A CHLORINATION REACTION TEMPERATURE WITHIN THE RANGE OF ABOUT 600* TO 1000* C. BY THE EXOTHERMIC HEAT OF THE CHLORINATION REACTION RESULTING FROM THE CONTACT BETWEEN THE CHLORINE GAS AND THE HOT BRIQUETTES, THE CHLORINATION OF THE TITANIUM COMPONENT OF THE BRIQUETTES THUS BEING EFFECTED WITHOUT SUBSTANTIALLY DESTROYING THE COHERENT STRUCTURE OF SAID BRIQUETTES AND WHILE PERMITTING THE BRIQUETTES TO MOVE SUBSTANTIALLY CONTINUOUSLY THROUGH THE CHLORINATING ZONE FROM THE CHARGING END THEREOF TOWARD A DISCHARGE END OF SAID ZONE AS THEIR TITANIUM CONTENT IS BEING DEPLETED BY CHLORINATION, WITHDRAWING TITANIUMDEPLETED BRIQUETTES FROM THE DISCHARGE END OF THE CHLORINATING ZONE WHILE THE CHLORINATION REACTION IS CONTINUING WHEREBY UNINTERRUPTED AUTOGENOUS REACTION IN THE CHLORINATING ZONE IS MAINTAINED, AND RECOVERING THE RESULTING TITANIUM TETRACHLORIDE EVOLVED IN THE CHLORINATING ZONE.