Indian Patents. 270009:"A METHOD AND APPARATUS FOR PRODUCING AERONAUTICAL GRADE TITANIUM SPONGE FROM TITANIUM TETRACHLORIDE"

Title of Invention	"A METHOD AND APPARATUS FOR PRODUCING AERONAUTICAL GRADE TITANIUM SPONGE FROM TITANIUM TETRACHLORIDE"
Abstract	A present invention relates to a method and apparatus for producing aeronautical grade titanium sponge from titanium tetrachloride by magnesiothermic reduction of titanium tetrachloride (TiCl4) followed by the vaccum distillation of sponge.

Full Text	A METHOD AND APPARATUS FOR PRODUCING AERONAUTICAL GRADE TITANIUM SPONGE FROM TITANIUM TETRACHLORIDE FIELD OF THE INVENTION The present invention relates to method and apparatus for producing aeronautical grade titanium sponge from titanium tetrachloride (which is produced by high temperature carbo chlorination of titanium mineral concentrates) by magnesiothermic reduction (Kroll process) followed by vacuum distillation of sponge to remove entrapped reactan/byproduct and development of apparatus for conducting the metal production process and its processing to a finished size suitable for subsequent ingot melting. BACKGROUND ART Titanium extraction is carried out by first preparing titanium tetrachloride from the oxide mineral concentrates by high temperature chlorination in the presence of carbon. The titanium tetrachloride is then purified and reduced to form titanium powder/sponge which is subsequently melted in inert gas/vacuum to prepare metal ingot. Magnesium reduction of TiCl4 (Kroll process) is widely practiced world over by many titanium sponge manufacturers for industrial production of titanium sponge with their own individual design of equipment/process. This invention brings out the methodologies and equipment specifically developed at the Defence Metallurgical Research Laboratory, Hyderabad for industrial production of titanium sponge. This work differs from the existing patents in terms of equipment design, process understanding and methodologies evolved for conducting the process operations. U.S. Patent 3,684,264 discloses reactor consisting of three sections which resulting in choking of nozzles during reduction and vacuum distillation. Further, reaction temperature is controlled by monitoring temperatures on the reactor's outer surface which may be erraraneous due to air cooling imparted during reduction. Also, in the prior art, MgCl2 is tapped through a nozzle at the bottom. Bottom tapping of molten salt is prone to hazards in case of leak and there will not be any control over the tapping. Further, the vacuum distillation is carried out by placing one reactor over another one which also leads to clogging of nozzles and the top flanges. Another design of equipment/process to form titanium sponge is disclosed in U.S. 4,441,925. The said patent teaches a reactor consisting of two vessels to carry out entire process. Transfer of reaction mass to another furnace causes exposure to an inert gas atmosphere. Further, reaction temperature is controlled by monitoring temperatures on the reactor outer surface which may be erraraneous as thermocouples are atmosphere, followed by cooling by external means and eventually spoiling the quality of the sponge produced. Yet another design of equipment/process to form titanium sponge is disclosed in U.S. 6,989,041. In the said patent, MgCl2 tapping pipe is located outside the reactor as a result a material is likely to get solidified due to top reactor cooling and cause tapping problems. Further, reaction surface is maintained by immersing a block like component inside the reactor. Thus to overcome drawbacks of the prior art such as clogging, temperature control an improved apparatus has been designed for conducting the process operations. OBJECTS OF THE INVENTION (i) The primary objective of the present invention is to provide a method of preparing titanium sponge of aeronautical grade purity. (ii) Another objective of the present invention provides a method for estimating oxy-chloride and carbon content in TiCl4. (iii) Still another object of the invention is to provide an improved purification procedure to minimize carbon content in titanium tetrachloride. (iv)Yet another objective of the invention is the use of an improved apparatus for ejection of titanium sponge cake from the reactor and its quality evaluation and size reduction to a finished size of 2-25 mm. (v) Still another object of the present invention is use of a 'heated interconnecting pipe assembly with a asset of inner sleeves to prevent condensation of vapors within the pipe. (vi) Yet another object invention of the is to monitor the temperatures inside the reactor at various levels. (vii) Still another object of the present invention is monitoring and control of back pressure in the tapping pipe. (viii) Yet another object invention of the present invention is to control heating of reactor zones and interconnecting pipe in order to minimize the vapours generation and to eliminate the condensation of material at the joints of inter-connecting pipe. SUMMARY OF THE INVENTION The present invention relates to a design and development of process apparatus and its allied accessories and methodologies for conducting the process operations of (i) TiCl4 purification by fractional distillation, (ii) magnesium reduction of pure TiCl4 to titanium sponge (iii) vacuum separation of reduced mass to drive out the entrapped Mg/MgCl2 from titanium sponge and (iv) mechanical processing of titanium sponge block for preparing homogeneous sponge lots of aeronautical grade quality in the size range of 2-25 mm which is suitable for melting and manufacture of titanium & titanium alloys. (1) The crude titanium tetrachloride have impurities such as dissolved gases (O, N, HCI, COCl2, COS etc), volatile impurities (SiCl4, SnCU, etc) and high boiling impurities (iron chlorides, titanium oxy-chloride etc). By a two stage fractional distillation conducted in two packed bed distillation columns the raw tetrachloride is purified into 'metal grade' tetrachloride. After extensive experimentation conducted in both the columns, the process parameters such as reflux ratio, vaporization rate and top product rate could be standardized for generating pure tetrachloride with all the impurity levels well below the specified limits, at a rate of 150 kg/h. (2) Though the magnesio-thermic reduction of titanium tetrachloride to prepare titanium sponge is very old and well studied, the methodology and operating practices and design of equipment to carry out the metal production usually vary from one manufacturer to the other and the technological features are unique and proprietary. Based on the pilot plant experiences over a prolonged period of technology development involving stage wise scale up of operations, the process equipment comprising twin reactor assembly, tapping pipe for MgCl2 tapping, Interconnecting pipe for the passage of Mg/MgCl2 vapors into the condenser retort during vacuum distillation process and other sub assemblies with innovative design parameters have been evolved at DMRL The performance of all the equipment have been extensively tested and found to be very much satisfactory for conducting the sponge production process. (3) As a result of repeated experimentation, the operation of reduction and vacuum distillation processes by optimal selection of the parameters such as temperature control in accordance with the liquid levels in the reactor, tetrachloride feed rate and addition scheme, the magnesium chloride tapping scheme, vacuum distillation temperature and heating methods has been standardized. (4) Titanium sponge cake produced is taken out for further processing by employing an 'ejection press', the design of which was evolved for smooth transfer of cake into a closed container without fire hazards. The sponge cake is skinned off the outer impurity rich layers and is graded into several quality fractions by another hydraulic press and tooling. Lumps of about 100 mm size so obtained are further cut to about 60 mm using another cutting tool and a press. A new shredder system innovatively designed and developed is employed for final size reduction to 2-25 mm size. Finished sponges of individual fractions are blended in a double cone blender for homogeneity. (5) As a result of the present invention production of titanium sponge of aeronautical grade purity from raw TiCl4 has been put into practice by employing specifically designed process equipment and allied accessories and presses and tooling using methodologies evolved for the same. The sponge produced in the technology demonstration has been found to be of excellent quality and meets not only all the international standards specified for the aeronautical applications but also the stringent specifications of other customers. BRIEF DESCRIPTION OF FIGURES: Fig 1 shows a schematic of Reactor Fig.2 illustrates a schematic of temperature probes location along the reactor wall Fig.3 shows a mechanism of sponge formation Fig.4 shows a schematic of titanium sponge block formation in a Kroll reactor Fig.5 explains a calibration curves for the determination of oxychloride in TiCl4 Fig.6 shows a calibration curves for the determination of carbon content in TiCl4 Fig.7 indicates a schematic location of temperature and vacuum probes during vacuum distillation Fig.8. shows a zone wise energy consumption during vacuum distillation process Fig.9 shows a schematic of ejection press Fig. 10 explain a schematic of sponge grading press Fig.l 1 illustrates different fractions of sponge cake Fig. 12 shows a schematic of the shredder system for sponge crushing DETAILED DESCRIPTION OF THE INVENTION In the present invention design and development of apparatus/process control strategies for the production of titanium sponge from TiCl4 by magnesium reduction is evolved by improving operation methodologies, apparatus, process control and product quality. The reactor design (Fig.l) takes into account the stringent considerations of the process, compatibility with reactants/ byproducts, pressure tightness, vacuum tightness and high temperature oxidation resistance required for the outer surface and high temperature strength requirements. The reactor is a cladded stainless steel pressure vessel approximately measuring 1.5 m diameter and 6 m long designed to conduct the magnesiothermic reduction and vacuum distillation processes in a single furnace station. To the reactor inner wall a stainless steel fabricated dip pipe with specific design objectives is welded to carry out draining of liquid byproduct periodically during the reduction process by applying pressure. The inner and outer surface of the tapping pipe is made compatible with reactants/byproducts and to eliminate transfer of certain impurities to titanium sponge produced. The lid of the reactor is also constructed with stainless steel and provided with necessary nozzles to conduct the reduction process and the vacuum distillation operation wherein the vapors of the excess reactant and entrapped byproduct are removed from the reduced mass and are collected in an identical reactor which can be used for subsequent batch operation with negligible loss of reductant/byproduct. At the bottom of the reactor, an opening is provided to which a cap is specially welded before the start up of the process operation and the cap is de-welded with special care at the end of the process for ejecting the sponge cake at room temperature. The heating requirements for conducting the reduction and vacuum distillation process are met by employing a multi-zone pit type electrical resistance furnace. With the help of a network of steel pipes connected to an air blower, the reactor outer surface temperature is controlled during the reduction process. The furnace is maintained vacuum-tight during the vacuum separation process to safeguard the reactor. For the measurement of temperatures inside the reactor, a stainless steel pipe housing (Fig.2) is welded to the reactor inner surface to accommodate a set of thermocouples to measure temperatures at various levels. A set of ribs welded to the inner surface of the retort at the bottom which supports the sponge on a perforated steel plate. The reduction process is managed by appropriate selection of TiCl4 feed rate & a predetermined addition scheme; reaction temperature control, periodic withdrawal of MgCl2 from the reactor as per a predetermined schedule so as to control the reaction height. During the entire reduction process, the reactor pressure is maintained within 0.07-0.27 bar g by argon gas admission and automatic pressure release as and when required. However, the by-product MgCl2, is removed periodically by pressurizing the reactor. The pressure controls in the reactor/tapping pipe are critical during the reduction process. A number of reactions are possible in the magnesio-thermic reduction of TiCl4 involving formation of lower chlorides of titanium viz TiCl3 and TiCl2. As the reactions taking place in more than two phases are kinetically improbable, magnesium reduction of TiCl4 to titanium has to take place in steps involving one or two phase reactions. When the solubility of TiCl4 and Mg in MgCl2 is considered, the reactions leading to formation of TiCl3 and the reactions leading to formation of TiCl2 which are probable from the kinetic point of view have to be considered to explain the reaction mechanism. Therefore the major paths for the titanium reduction could be the following: (Formula Removed) The reduction mechanism can then be explained as follows: As TiCl4 is fed into the reactor containing molten magnesium, it vaporizes and is transported to the liquid magnesium surface. Reaction of TiCl4 (g) with magnesium liquid gives rise to the formation of tiny droplets consisting of MgCl2 or MgCl2/TiCl2. Further significant reduction of TiCl4 can only take place by the dissolution of magnesium in the salt droplets, and its transport to the salt/gas interface, and the reduction reaction (2) (Fig. 3 a). Formation of titanium from TiCl2/ MgCl2 salt does not need the presence of the gas phase and can take place at any location where the supply of magnesium can be ensured. At the Mg/salt interface, formation of titanium sponge again involves three phase reactions. Kinetically, therefore, titanium forms when the MgCl2 droplet reaches a surface where the nucleation and growth of titanium sponge is favored. Sponge formation proceeds by the dissolution of magnesium in the salt, its diffusion through the salt and the chemical reaction (3) at the titanium surface or crucible wall (Fig. 3 (b) and (c). This reaction can also take place by an electrochemical mechanism of charge transfer through magnesium metal as proposed by Waseda and Okabe [17]. Initially, TiCl4 is reduced to TiCl2 and MgCl2 on the liquid magnesium surface, forming tiny droplets as explained earlier. These droplets may be continuously swept towards the reactor wall due to convection currents set up by the buoyancy and surface tension forces due to temperature differences in the bath. These droplets can then get further reduced to titanium at the reactor wall/already formed sponge. The reduction of TiCl4 to TiCl2 can also continue to take place on the liquid magnesium surface near the wall/sponge deposit at the gas-droplet interface which also involves release of exothermic heat. Thus it is possible that occurrence of both the reactions viz. reactions 2 and 3 can cause increased heat release near the wall/sponge deposit. This can explain the observed high temperatures on the magnesium surface near the reactor wall/sponge deposit. As the sponge layer at the crucible wall widens (Fig.4), the surface area available for TiCl4 reduction progressively decreases. This can result in decreased consumption of TiCl4 and pressure build up. On the contrary, pieces of sponge periodically break-off and settle down exposing fresh surface of magnesium. This may explain the erratic behavior observed in the reactor where" periods of relatively constant pressure is interspersed with periods of a number of bleed-offs. Towards the end of the process, the level of sponge accumulated fills the crucible up to the level of liquid magnesium surface. Availability of liquid magnesium and surface area for TiCl4 reduction therefore becomes seriously limited, leading to frequent bleed-offs and forcing the termination of the batch. Vacuum distillation of the reduced mass is carried out in the same reactor assembly using the same furnace. For this operation the reactor is connected to another reactor of identical design which is placed in a water cooled condenser station. The connection is accomplished through a heated stainless steel pipe. The mating flanges of the interconnecting pipe were designed to have good thermal distribution within the entire pipe so as to eliminate any condensation of species inside the pipe affecting the process thereby. Leak tightness of the equipment and all the joints, selection of heating procedure to achieve controlled vapours generation, final distillation temperature and soak and vacuum level influence greatly the efficiency of the distillation operation and eventually contribute to the quality of the product. Poor heat transfer through titanium sponge which controls the overall rate of the distillation process, is considered while evolving the operating schedule. Optimal selection of temperature and cycle time minimizes the contamination of sponge by the reactor material. After cooling down to room temperature, the titanium sponge cake is ejected out of the reactor carefully employing a custom-built hydraulic press under a slight argon gas purge. The impurity laden outer layer of the sponge cake is carefully skinned out and the cake is graded into different fractions by employing a tailor made slicing press. The sponge then has to undergo several size reduction processes for preparing aeronautical grade quality sponge lots. In each of these operations, the challenges for the design of equipment & tooling are safeguarding the quality and structure of sponge, minimization of fines generation and elimination of fire hazards. Purification of titanium tetrachloride to bring down the total impurity content from about 2000 ppm to about 100 ppm is carried out in two stages in two packed bed distillation columns. All the volatile impurities such as SnCl4 are removed from the top of the first column and the non-volatiles and solids are stripped off from the TiCl4 in the second column. The distillation columns were provided with necessary heat exchangers and re-boilers and equipped with suitable instrumentation to monitor the parameters such as column pressure, vaporization rate, chloride feed rate, temperature etc. Repeated experimentation over a period of time led to establishment of trouble-free column operation and optimal control of reflux ratio, vaporization rate, product rate etc. Compared to the conventional purification techniques, innovative distillation. procedures are evolved to remove impurities from the tetrachloride especially the titanium oxy-chloride impurity and carbon. Development of improved analytical techniques for TiCl4 to estimate the oxy-chloride and total carbon contents followed by extensive laboratory scale experiments led to evolution of improved distillation procedures to tackle the impurities: oxy-chloride and carbon in the tetrachloride. Based on extensive laboratory scale experimental work, an Infra Red spectroscopic method was developed for quantitative estimation of titanium oxy-chloride in TiCl4 in the range 50-1500 ppm. TiCLt samples with varied concentrations of the oxy-chloride were generated for this study by spiking tetrachloride with varied amounts of water carried out in a glove box arrangement. IR spectras for dissolved TiOCl2 are recorded and the peak at 1182.7 cm-1 corresponding to the oxy-chloride was envisaged for the quantitative estimation based on the absorbance. Calibration curves (Fig.5) could be generated for the estimation of the oxy-chloride content in the tetrachloride sample with an error not exceeding 10%. Experimentation on determination of total carbon content of TiCl4 employing TOC analyzers involving oxidation of sample at high temperature in presence of a catalyst to convert all the carbon into CO2 which is estimated by non-dispersive infrared gas analyzer was extensively conducted. Samples preparation in 0.5-5% HC1 and study of IR response led to a new method of analysis of total carbon of TiCl4 (Fig 6) shows calibration curve derived for estimating carbon content of tetrachloride from the IR counts. By employing this method total carbon in TiCl4 in the range 20-1000 ppm could be estimated with good accuracy and excellent repeatability. Experimentation on magnesiothermic reduction of TiCl4 and vacuum distillation of the reduced mass was carried out in a twin reactor assembly on a batch scale of 3000 kg of sponge. Initially solid magnesium ingots are taken into the reactor and heated to a temperature of about 800°C in argon gas atmosphere. TiCl4 is pumped into the reactor through a nozzle fitted to the reactor lid. The tetrachloride addition is monitored to maintain desired reaction temperature and level inside the reactor. Exothermic heat is removed in a controlled manner by supplying air to the areas of over heating through a buzzle pipe assembly provided inside the furnace and connected to a blower. MgCl2 is tapped out periodically from the reactor at a predetermined schedule by a 'valve less system' by pressurizing the reactor up to about 0.7 bar g (6 psig). The reaction progress is monitored by constant observation of reactor pressure and inner temperatures at various heights along the wall. Increase in wall temperatures at the reaction site followed by lowering of temperatures (possibly due to burying of temperature probe location by sponge) is periodically noticed which is in line with the proposed reaction mechanism described in section III 5. Inert gas cover is provided during the tapping time by supplying argon gas through a nozzle mounted on the tapping pipe to eliminate air ingress. During the reaction period; adequate 'pressure' in the tapping pipe is maintained ensuring elimination of tapping line choking due to solidification of mass. Final tapping of MgCl2 is carried out after completing the addition of required quantity of tetrachloride. Subsequently the reduced mass is cooled to about 500°C after which the reactor is connected to another reactor placed in the condenser station through 'inter connecting pipe' to carry out vacuum distillation operation. The vacuum distillation process is conducted by heating the reaction mass in stages to a temperature of about 1000°C under a dynamic vacuum of the order of 10"3 torr. Efficient distillation practice could be achieved by evolving suitable design of 'heated inter connecting pipe assembly with a set of inner sleeves to obtain desired thermal distribution necessary to prevent condensation of vapors within the pipe which otherwise leads to forced termination of the operation. An innovative dust trap system with refrigeration cooling for trapping any carry over condensable mass such as lower chlorides of titanium, had been introduced in the vacuum pumping line for protecting the front end high vacuum pumps which had been found working satisfactorily. Throughout the distillation process, temperatures as indicated by the temperatures probes TPI- TP13 and vacuum levels as recorded by the vacuum probes VPI--VPIV (Fig 7) are continuously monitored to monitor the rate and status of the distillation. Intensive distillation is found to be indicated by steep rise in TP13 and fall in VPI-VPIII. Similarly the distillation progress could be tracked by continuous monitoring of energy consumptions of the zones corresponding to the level of reaction mass, as the energy requirement reduces after the entrapped material vaporizes and leaves the mass (Fig 8). Combined monitoring of TIP 13, VPIII and energy consumption could enable to arrive at optimal distillation soak for achieving complete elimination of entrappants and minimize pickup of impurity elements from the reactor wall. Temperature and Pressure control by Distributed Control System: The temperature signals measured at various locations along the inner wall of the reactor using simplex thermocouples are wired through analog multiplexer as input to a software based PID temperature controller in the Distributed Control System (DCS). The controller generates output signal based on the difference between the set point and the measured temperatures at desired location. The controller output signals are wired to a I/P converter for conversion to pneumatic signals. This signal is fed to an air damper for throttling the air flow rate at required regions of reactor outer surface for maintaining the desired reaction temperature. The pressure of argon in the reactor is measured using a pressure transmitter. The output of the pressure transmitter is wired to the software based ON/OFF pressure controller in the DCS system for monitoring and control of pressure. Whenever the pressure reaches the higher limit the DCS system generates output for opening/closing a electro- pneumatically operated bleeder valve for releasing the excess pressure. Similarly whenever the pressure falls to below the preset lower limit DCS system generates output for opening/closing a electro-pneumatically operated admittance valve for supplying argon gas to a preset pressure limit. Equipment for mechanical processing of titanium sponge block to a finished size of 2-25 mm mainly comprises (i) a custom built hydraulic ejection press, (ii) a grading press with a cutting tool for breaking down the cake into different quality fractions and (iii) a 'shredder system' for final size reduction of sponge from about 60mm to 2-25 mm size. Quality evaluation of titanium sponge block is carried out by a systematic and elaborate sampling method by which about 60 numbers of samples are collected from various locations of sponge block for enabling efficient grading of block and to segregate superior quality fractions for separate processing to prepare final sponge lots of aeronautical grade purity. The representative samples of crushed lets are obtained by an automatic riffle sampler as well as by coning & quartering of bulk crushed sponge. The sponge samples collected at various stages of sponge processing are assessed for their quality by melting into small buttons in an argon gas arc furnace and tested for hardness and analyzed for their impurity contents. The sponge cake ejection press (Fig.9) essentially consists of a main frame steel structure to hold the reactor firmly while load is applied on the bottom plate to dislodge the cake from the reactor walls and to push it into a container vessel. The ejection of the cake is accomplished by pushing the bottom plate with the help of a set of steel spacers/rams placed one over the other on the main ram of the press. Necessary interlocks and instrumentation is provided to the hydraulic system for carrying out ejection of cake carefully and with utmost safety. The cake container vessel into which the sponge cake is pushed in is initially evacuated and back filled with argon gas. Primary cutting of the sponge cake is carried out in an another hydraulic guillotine press (Fig 10) which consists of revolving table and a clamping slide to position the cake as required. With the help of a cutting tool fitted in the frame, the cake is divided into various quality fractions as illustrated in Fig 11. The press is also equipped with a moving shuttle for facilitating the grading process. Each fraction of sponge is separately processed to finished size and evaluated for quality. Final crushing of sponge is carried out in a custom built 'shredder system' exclusively developed for size reduction of titanium sponge pieces of about 50-70 mm into 2-25 mm size. The shredder system (Fig. 12) has unique design features to impart shear stresses on the sponge with minimal residence time to avoid compaction of pieces. The shredder system consists of a main steel shaft to which a set of toothed rings are fitted. The shaft rotates against a stationary comb structure housed in the shredder. Apart from size reduction the shredder system also ensures minimal generation of files without heating up of mass. As per customer demands titanium sponge lots of required purity are prepared and are blended in a double cone blender, stored and supplied in argon filled steel drums with chemical analysis certificate. Advantages 1. A titanium sponge of aeronautical sponge of high purity is obtained. 2. Optimal selection of temperature minimizes the contamination of sponge by the reactor material. 3. Titanium sponge is ejected out of the reactor by using a custom-built hydraulic press thereby safeguarding the quality and structure of sponge. We Claim; 1. A process for producing titanium sponge which comprises: (a) purifying titanium tetrachloride by fractional distillation; (b) magneisothermically reducing titanium tetrachloride obtained from step (a) in a reduction furnace containing molten magnesium and heating at a temperature of about 800°C in inert gas atmosphere; (c) cooling the reduced mass of step (b) at a temperature of about 500°C; (d) distillating the reduced mass in a condenser vessel which is connected to reduction furnace through interconnecting pipe, by heating in stages at a temperature of about 1000°C under a vacuum; (d) cooling the product of step (d) at a room temperature for obtaining desired sponge; (e) mechanical processing of the titanium sponge of aeronautical grade quality. 2. The process as claimed in claim 1, wherein the reduction pressure is in the range of 0.07 -0.27 bar. 3. The process as claimed in claiml, wherein the inert gas is argon. 4. The process as claimed in claim 1, wherein the interconnecting pipe is connected to an air blower for maintaining the temperature during the reduction process. 5. The process as claimed in claim 1, wherein the pure titanium tetrachloride contains 20-1000ppm of carbon and oxy-chloride content not more than 1500ppm. 6. The process as claimed in claim 1, wherein the purification is carried out in two packed distillation columns. 7. The process as claimed in any of the preceding claims, wherein magnesium reduction is achieved by heating solid magnesium ingots in the reduction furnace. 8. The process as claimed in any of the preceding claims, wherein the magnesium chloride is tapped periodically by pressurizing the furnace at about 0.7 bar g. 9. The process as claimed in claim 1, wherein the aeronautical grade size of titanium sponge is 2-25mm. 10. An apparatus for performing the process as claimed in any one of the preceding claims, the said apparatus comprising: a reduction furnace for magneisothermically reducing purified titanium tetrachloride; a condenser vessel for vaccum distilling the reduced mass obtained from reduction furnace; and a ejection press for mechanical processing of titanium sponge block obtained from the condenser vessel to a finished size in the range of 2-25 mm. wherein the reduction furnace and condenser vessel are interconnected through a pipe characterized in that the pipe is a heated interconnecting pipe assembly with an asset of inner sleeves to prevent condensation of vapors within the pipe. 11. An apparatus as claimed in claim 10, wherein the reduction furnace comprises a inlet for pumping the titanium chloride into the reactor; dip pipe fabricated to a reactor inner wall for draining liquid byproduct; tapping pipe at the outer and inner surface is made compatible with reactants byproducts to eliminate titanium sponge impurities; thermowel having a set of thermocouples welded to the reactor inner surface for maintaining temperature and pressure during the reduction process; and lid with nozzles for entrapping the vapours of the excess reactant 12. The apparatus as claimed in claim 10, wherein said condenser vessel comprises of: inner-connecting pipe with mating flanges for uniform thermal distribution within the entire pipe during vaccum distillation. 14. The apparatus as claimed in claim 10, wherein the said condenser vessel comprises of a cap for ejecting the sponge cake. 15. The apparatus as claimed in claim 10, wherein the ejection press comprises of: a custom built hydraulic ejection press for skinning off the outer impurity rich layers and grading into several quality fractions; a grading press with a cutting tool or breaking down the cake into different quality fractions; and a shredder system for reducing the size of sponge in the range of 2-25 mm. 16. The apparatus as claimed in claim 10, wherein the said apparatus is connected to a air blower to maintain temperature in the reduction furnace and vaccum tight in the condenser vessel. 17. A process for producing titanium sponge, and an apparatus for performing the process, substantially as herein described with reference to the foregoing examples and accompanying drawings.

Full Text

A METHOD AND APPARATUS FOR PRODUCING AERONAUTICAL GRADE TITANIUM SPONGE FROM TITANIUM TETRACHLORIDE
FIELD OF THE INVENTION
The present invention relates to method and apparatus for producing aeronautical grade titanium sponge from titanium tetrachloride (which is produced by high temperature carbo chlorination of titanium mineral concentrates) by magnesiothermic reduction (Kroll process) followed by vacuum distillation of sponge to remove entrapped reactan/byproduct and development of apparatus for conducting the metal production process and its processing to a finished size suitable for subsequent ingot melting.
BACKGROUND ART
Titanium extraction is carried out by first preparing titanium tetrachloride from the oxide mineral concentrates by high temperature chlorination in the presence of carbon. The titanium tetrachloride is then purified and reduced to form titanium powder/sponge which is subsequently melted in inert gas/vacuum to prepare metal ingot. Magnesium reduction of TiCl4 (Kroll process) is widely practiced world over by many titanium sponge manufacturers for industrial production of titanium sponge with their own individual design of equipment/process. This invention brings out the methodologies and equipment specifically developed at the Defence Metallurgical Research Laboratory, Hyderabad for industrial production of titanium sponge. This work differs from the existing patents in terms of equipment design, process understanding and methodologies evolved for conducting the process operations.
U.S. Patent 3,684,264 discloses reactor consisting of three sections which resulting in choking of nozzles during reduction and vacuum distillation. Further, reaction temperature is controlled by monitoring temperatures on the reactor's outer surface which may be erraraneous due to air cooling imparted during reduction. Also, in the prior art, MgCl2 is tapped through a nozzle at the bottom. Bottom tapping of molten salt is prone to hazards in case of leak and there will not be any control over the tapping. Further, the vacuum distillation is carried out by placing one reactor over another one which also leads to clogging of nozzles and the top flanges.
Another design of equipment/process to form titanium sponge is disclosed in U.S. 4,441,925. The said patent teaches a reactor consisting of two vessels to carry out entire process. Transfer of reaction mass to another furnace causes exposure to an inert gas atmosphere.
Further, reaction temperature is controlled by monitoring temperatures on the reactor outer surface which may be erraraneous as thermocouples are atmosphere, followed by cooling by external means and eventually spoiling the quality of the sponge produced.
Yet another design of equipment/process to form titanium sponge is disclosed in U.S. 6,989,041. In the said patent, MgCl2 tapping pipe is located outside the reactor as a result a material is likely to get solidified due to top reactor cooling and cause tapping problems. Further, reaction surface is maintained by immersing a block like component inside the reactor.
Thus to overcome drawbacks of the prior art such as clogging, temperature control an improved apparatus has been designed for conducting the process operations.
OBJECTS OF THE INVENTION
(i) The primary objective of the present invention is to provide a method of preparing titanium sponge of aeronautical grade purity.
(ii) Another objective of the present invention provides a method for estimating oxy-chloride and carbon content in TiCl4.
(iii) Still another object of the invention is to provide an improved purification procedure to minimize carbon content in titanium tetrachloride.
(iv)Yet another objective of the invention is the use of an improved apparatus for ejection of titanium sponge cake from the reactor and its quality evaluation and size reduction to a finished size of 2-25 mm.
(v) Still another object of the present invention is use of a 'heated interconnecting pipe assembly with a asset of inner sleeves to prevent condensation of vapors within the pipe.
(vi) Yet another object invention of the is to monitor the temperatures inside the reactor at various levels.
(vii) Still another object of the present invention is monitoring and control of back pressure in the tapping pipe.
(viii) Yet another object invention of the present invention is to control heating of reactor zones and interconnecting pipe in order to minimize the vapours generation and to eliminate the condensation of material at the joints of inter-connecting pipe.
SUMMARY OF THE INVENTION
The present invention relates to a design and development of process apparatus and its allied accessories and methodologies for conducting the process operations of (i) TiCl4 purification by fractional distillation, (ii) magnesium reduction of pure TiCl4 to titanium sponge (iii) vacuum separation of reduced mass to drive out the entrapped Mg/MgCl2 from titanium sponge and (iv) mechanical processing of titanium sponge block for preparing homogeneous sponge lots of aeronautical grade quality in the size range of 2-25 mm which is suitable for melting and manufacture of titanium & titanium alloys.
(1) The crude titanium tetrachloride have impurities such as dissolved gases (O, N, HCI, COCl2, COS etc), volatile impurities (SiCl4, SnCU, etc) and high boiling impurities (iron chlorides, titanium oxy-chloride etc). By a two stage fractional distillation conducted in two packed bed distillation columns the raw tetrachloride is purified into 'metal grade' tetrachloride. After extensive experimentation conducted in both the columns, the process parameters such as reflux ratio, vaporization rate and top product rate could be standardized for generating pure tetrachloride with all the impurity levels well below the specified limits, at a rate of 150 kg/h.
(2) Though the magnesio-thermic reduction of titanium tetrachloride to prepare titanium sponge is very old and well studied, the methodology and operating practices and design of equipment to carry out the metal production usually vary from one manufacturer to the other and the technological features are unique and proprietary. Based on the pilot plant experiences over a prolonged period of technology development involving stage wise scale up of operations, the process equipment comprising twin reactor assembly, tapping pipe for MgCl2 tapping, Interconnecting pipe for the passage of Mg/MgCl2 vapors into the condenser retort during vacuum distillation process and other sub assemblies with innovative design parameters have been evolved at DMRL The performance of all the equipment have been extensively tested and found to be very much satisfactory for conducting the sponge production process.
(3) As a result of repeated experimentation, the operation of reduction and vacuum distillation processes by optimal selection of the parameters such as temperature control in accordance with the liquid levels in the reactor, tetrachloride feed rate
and addition scheme, the magnesium chloride tapping scheme, vacuum distillation temperature and heating methods has been standardized.
(4) Titanium sponge cake produced is taken out for further processing by employing an 'ejection press', the design of which was evolved for smooth transfer of cake into a closed container without fire hazards. The sponge cake is skinned off the outer impurity rich layers and is graded into several quality fractions by another hydraulic press and tooling. Lumps of about 100 mm size so obtained are further cut to about 60 mm using another cutting tool and a press. A new shredder system innovatively designed and developed is employed for final size reduction to 2-25 mm size. Finished sponges of individual fractions are blended in a double cone blender for homogeneity.
(5) As a result of the present invention production of titanium sponge of aeronautical grade purity from raw TiCl4 has been put into practice by employing specifically designed process equipment and allied accessories and presses and tooling using methodologies evolved for the same. The sponge produced in the technology demonstration has been found to be of excellent quality and meets not only all the international standards specified for the aeronautical applications but also the stringent specifications of other customers.
BRIEF DESCRIPTION OF FIGURES:
Fig 1 shows a schematic of Reactor
Fig.2 illustrates a schematic of temperature probes location along the reactor wall
Fig.3 shows a mechanism of sponge formation
Fig.4 shows a schematic of titanium sponge block formation in a Kroll reactor
Fig.5 explains a calibration curves for the determination of oxychloride in TiCl4
Fig.6 shows a calibration curves for the determination of carbon content in TiCl4
Fig.7 indicates a schematic location of temperature and vacuum probes during vacuum distillation
Fig.8. shows a zone wise energy consumption during vacuum distillation process
Fig.9 shows a schematic of ejection press
Fig. 10 explain a schematic of sponge grading press Fig.l 1 illustrates different fractions of sponge cake Fig. 12 shows a schematic of the shredder system for sponge crushing
DETAILED DESCRIPTION OF THE INVENTION
In the present invention design and development of apparatus/process control strategies for the production of titanium sponge from TiCl4 by magnesium reduction is evolved by improving operation methodologies, apparatus, process control and product quality.
The reactor design (Fig.l) takes into account the stringent considerations of the process, compatibility with reactants/ byproducts, pressure tightness, vacuum tightness and high temperature oxidation resistance required for the outer surface and high temperature strength requirements. The reactor is a cladded stainless steel pressure vessel approximately measuring 1.5 m diameter and 6 m long designed to conduct the magnesiothermic reduction and vacuum distillation processes in a single furnace station. To the reactor inner wall a stainless steel fabricated dip pipe with specific design objectives is welded to carry out draining of liquid byproduct periodically during the reduction process by applying pressure. The inner and outer surface of the tapping pipe is made compatible with reactants/byproducts and to eliminate transfer of certain impurities to titanium sponge produced. The lid of the reactor is also constructed with stainless steel and provided with necessary nozzles to conduct the reduction process and the vacuum distillation operation wherein the vapors of the excess reactant and entrapped byproduct are removed from the reduced mass and are collected in an identical reactor which can be used for subsequent batch operation with negligible loss of reductant/byproduct. At the bottom of the reactor, an opening is provided to which a cap is specially welded before the start up of the process operation and the cap is de-welded with special care at the end of the process for ejecting the sponge cake at room temperature.
The heating requirements for conducting the reduction and vacuum distillation process are met by employing a multi-zone pit type electrical resistance furnace. With the help of a network of steel pipes connected to an air blower, the reactor outer surface temperature is controlled during the reduction process. The furnace is maintained vacuum-tight during the vacuum separation process to safeguard the reactor.
For the measurement of temperatures inside the reactor, a stainless steel pipe housing (Fig.2) is welded to the reactor inner surface to accommodate a set of thermocouples to measure
temperatures at various levels. A set of ribs welded to the inner surface of the retort at the bottom which supports the sponge on a perforated steel plate.
The reduction process is managed by appropriate selection of TiCl4 feed rate & a predetermined addition scheme; reaction temperature control, periodic withdrawal of MgCl2 from the reactor as per a predetermined schedule so as to control the reaction height. During the entire reduction process, the reactor pressure is maintained within 0.07-0.27 bar g by argon gas admission and automatic pressure release as and when required. However, the by-product MgCl2, is removed periodically by pressurizing the reactor. The pressure controls in the reactor/tapping pipe are critical during the reduction process.
A number of reactions are possible in the magnesio-thermic reduction of TiCl4 involving formation of lower chlorides of titanium viz TiCl3 and TiCl2.
As the reactions taking place in more than two phases are kinetically improbable, magnesium reduction of TiCl4 to titanium has to take place in steps involving one or two phase reactions. When the solubility of TiCl4 and Mg in MgCl2 is considered, the reactions leading to formation of TiCl3 and the reactions leading to formation of TiCl2 which are probable from the kinetic point of view have to be considered to explain the reaction mechanism. Therefore the major paths for the titanium reduction could be the following:
(Formula Removed)
The reduction mechanism can then be explained as follows:
As TiCl4 is fed into the reactor containing molten magnesium, it vaporizes and is transported to the liquid magnesium surface. Reaction of TiCl4 (g) with magnesium liquid gives rise to the formation of tiny droplets consisting of MgCl2 or MgCl2/TiCl2. Further significant reduction of TiCl4 can only take place by the dissolution of magnesium in the salt droplets, and its transport to the salt/gas interface, and the reduction reaction (2) (Fig. 3 a). Formation of titanium from TiCl2/ MgCl2 salt does not need the presence of the gas phase and can take place at any location where the supply of magnesium can be ensured. At the Mg/salt interface, formation of titanium sponge again involves three phase reactions. Kinetically, therefore, titanium forms when the MgCl2 droplet reaches a surface where the nucleation and
growth of titanium sponge is favored. Sponge formation proceeds by the dissolution of magnesium in the salt, its diffusion through the salt and the chemical reaction (3) at the titanium surface or crucible wall (Fig. 3 (b) and (c). This reaction can also take place by an electrochemical mechanism of charge transfer through magnesium metal as proposed by Waseda and Okabe [17].
Initially, TiCl4 is reduced to TiCl2 and MgCl2 on the liquid magnesium surface, forming tiny droplets as explained earlier. These droplets may be continuously swept towards the reactor wall due to convection currents set up by the buoyancy and surface tension forces due to temperature differences in the bath. These droplets can then get further reduced to titanium at the reactor wall/already formed sponge. The reduction of TiCl4 to TiCl2 can also continue to take place on the liquid magnesium surface near the wall/sponge deposit at the gas-droplet interface which also involves release of exothermic heat. Thus it is possible that occurrence of both the reactions viz. reactions 2 and 3 can cause increased heat release near the wall/sponge deposit. This can explain the observed high temperatures on the magnesium surface near the reactor wall/sponge deposit.
As the sponge layer at the crucible wall widens (Fig.4), the surface area available for TiCl4 reduction progressively decreases. This can result in decreased consumption of TiCl4 and pressure build up. On the contrary, pieces of sponge periodically break-off and settle down exposing fresh surface of magnesium. This may explain the erratic behavior observed in the reactor where" periods of relatively constant pressure is interspersed with periods of a number of bleed-offs. Towards the end of the process, the level of sponge accumulated fills the crucible up to the level of liquid magnesium surface. Availability of liquid magnesium and surface area for TiCl4 reduction therefore becomes seriously limited, leading to frequent bleed-offs and forcing the termination of the batch.
Vacuum distillation of the reduced mass is carried out in the same reactor assembly using the same furnace. For this operation the reactor is connected to another reactor of identical design which is placed in a water cooled condenser station. The connection is accomplished through a heated stainless steel pipe. The mating flanges of the interconnecting pipe were designed to have good thermal distribution within the entire pipe so as to eliminate any condensation of species inside the pipe affecting the process thereby. Leak tightness of the equipment and all the joints, selection of heating procedure to achieve controlled vapours generation, final distillation temperature and soak and vacuum level influence greatly the efficiency of the
distillation operation and eventually contribute to the quality of the product. Poor heat transfer through titanium sponge which controls the overall rate of the distillation process, is considered while evolving the operating schedule. Optimal selection of temperature and cycle time minimizes the contamination of sponge by the reactor material.
After cooling down to room temperature, the titanium sponge cake is ejected out of the reactor carefully employing a custom-built hydraulic press under a slight argon gas purge. The impurity laden outer layer of the sponge cake is carefully skinned out and the cake is graded into different fractions by employing a tailor made slicing press. The sponge then has to undergo several size reduction processes for preparing aeronautical grade quality sponge lots. In each of these operations, the challenges for the design of equipment & tooling are safeguarding the quality and structure of sponge, minimization of fines generation and elimination of fire hazards.
Purification of titanium tetrachloride to bring down the total impurity content from about 2000 ppm to about 100 ppm is carried out in two stages in two packed bed distillation columns. All the volatile impurities such as SnCl4 are removed from the top of the first column and the non-volatiles and solids are stripped off from the TiCl4 in the second column. The distillation columns were provided with necessary heat exchangers and re-boilers and equipped with suitable instrumentation to monitor the parameters such as column pressure, vaporization rate, chloride feed rate, temperature etc. Repeated experimentation over a period of time led to establishment of trouble-free column operation and optimal control of reflux ratio, vaporization rate, product rate etc. Compared to the conventional purification techniques, innovative distillation. procedures are evolved to remove impurities from the tetrachloride especially the titanium oxy-chloride impurity and carbon. Development of improved analytical techniques for TiCl4 to estimate the oxy-chloride and total carbon contents followed by extensive laboratory scale experiments led to evolution of improved distillation procedures to tackle the impurities: oxy-chloride and carbon in the tetrachloride.
Based on extensive laboratory scale experimental work, an Infra Red spectroscopic method was developed for quantitative estimation of titanium oxy-chloride in TiCl4 in the range 50-1500 ppm. TiCLt samples with varied concentrations of the oxy-chloride were generated for this study by spiking tetrachloride with varied amounts of water carried out in a glove box arrangement. IR spectras for dissolved TiOCl2 are recorded and the peak at 1182.7 cm-1 corresponding to the oxy-chloride was envisaged for the quantitative estimation based on the
absorbance. Calibration curves (Fig.5) could be generated for the estimation of the oxy-chloride content in the tetrachloride sample with an error not exceeding 10%.
Experimentation on determination of total carbon content of TiCl4 employing TOC analyzers involving oxidation of sample at high temperature in presence of a catalyst to convert all the carbon into CO2 which is estimated by non-dispersive infrared gas analyzer was extensively conducted. Samples preparation in 0.5-5% HC1 and study of IR response led to a new method of analysis of total carbon of TiCl4 (Fig 6) shows calibration curve derived for estimating carbon content of tetrachloride from the IR counts. By employing this method total carbon in TiCl4 in the range 20-1000 ppm could be estimated with good accuracy and excellent repeatability.
Experimentation on magnesiothermic reduction of TiCl4 and vacuum distillation of the reduced mass was carried out in a twin reactor assembly on a batch scale of 3000 kg of sponge. Initially solid magnesium ingots are taken into the reactor and heated to a temperature of about 800°C in argon gas atmosphere. TiCl4 is pumped into the reactor through a nozzle fitted to the reactor lid. The tetrachloride addition is monitored to maintain desired reaction temperature and level inside the reactor.
Exothermic heat is removed in a controlled manner by supplying air to the areas of over heating through a buzzle pipe assembly provided inside the furnace and connected to a blower. MgCl2 is tapped out periodically from the reactor at a predetermined schedule by a 'valve less system' by pressurizing the reactor up to about 0.7 bar g (6 psig). The reaction progress is monitored by constant observation of reactor pressure and inner temperatures at various heights along the wall. Increase in wall temperatures at the reaction site followed by lowering of temperatures (possibly due to burying of temperature probe location by sponge) is periodically noticed which is in line with the proposed reaction mechanism described in section III 5. Inert gas cover is provided during the tapping time by supplying argon gas through a nozzle mounted on the tapping pipe to eliminate air ingress. During the reaction period; adequate 'pressure' in the tapping pipe is maintained ensuring elimination of tapping line choking due to solidification of mass. Final tapping of MgCl2 is carried out after completing the addition of required quantity of tetrachloride. Subsequently the reduced mass is cooled to about 500°C after which the reactor is connected to another reactor placed in the condenser station through 'inter connecting pipe' to carry out vacuum distillation operation.
The vacuum distillation process is conducted by heating the reaction mass in stages to a temperature of about 1000°C under a dynamic vacuum of the order of 10"3 torr. Efficient distillation practice could be achieved by evolving suitable design of 'heated inter connecting pipe assembly with a set of inner sleeves to obtain desired thermal distribution necessary to prevent condensation of vapors within the pipe which otherwise leads to forced termination of the operation. An innovative dust trap system with refrigeration cooling for trapping any carry over condensable mass such as lower chlorides of titanium, had been introduced in the vacuum pumping line for protecting the front end high vacuum pumps which had been found working satisfactorily. Throughout the distillation process, temperatures as indicated by the temperatures probes TPI- TP13 and vacuum levels as recorded by the vacuum probes VPI--VPIV (Fig 7) are continuously monitored to monitor the rate and status of the distillation. Intensive distillation is found to be indicated by steep rise in TP13 and fall in VPI-VPIII. Similarly the distillation progress could be tracked by continuous monitoring of energy consumptions of the zones corresponding to the level of reaction mass, as the energy requirement reduces after the entrapped material vaporizes and leaves the mass (Fig 8). Combined monitoring of TIP 13, VPIII and energy consumption could enable to arrive at optimal distillation soak for achieving complete elimination of entrappants and minimize pickup of impurity elements from the reactor wall.
Temperature and Pressure control by Distributed Control System: The temperature signals measured at various locations along the inner wall of the reactor using simplex thermocouples are wired through analog multiplexer as input to a software based PID temperature controller in the Distributed Control System (DCS). The controller generates output signal based on the difference between the set point and the measured temperatures at desired location. The controller output signals are wired to a I/P converter for conversion to pneumatic signals. This signal is fed to an air damper for throttling the air flow rate at required regions of reactor outer surface for maintaining the desired reaction temperature. The pressure of argon in the reactor is measured using a pressure transmitter. The output of the pressure transmitter is wired to the software based ON/OFF pressure controller in the DCS system for monitoring and control of pressure. Whenever the pressure reaches the higher limit the DCS system generates output for opening/closing a electro- pneumatically operated bleeder valve for releasing the excess pressure. Similarly whenever the pressure falls to below the preset lower limit DCS system generates output for opening/closing a
electro-pneumatically operated admittance valve for supplying argon gas to a preset pressure limit.
Equipment for mechanical processing of titanium sponge block to a finished size of 2-25 mm mainly comprises (i) a custom built hydraulic ejection press, (ii) a grading press with a cutting tool for breaking down the cake into different quality fractions and (iii) a 'shredder system' for final size reduction of sponge from about 60mm to 2-25 mm size. Quality evaluation of titanium sponge block is carried out by a systematic and elaborate sampling method by which about 60 numbers of samples are collected from various locations of sponge block for enabling efficient grading of block and to segregate superior quality fractions for separate processing to prepare final sponge lots of aeronautical grade purity. The representative samples of crushed lets are obtained by an automatic riffle sampler as well as by coning & quartering of bulk crushed sponge. The sponge samples collected at various stages of sponge processing are assessed for their quality by melting into small buttons in an argon gas arc furnace and tested for hardness and analyzed for their impurity contents.
The sponge cake ejection press (Fig.9) essentially consists of a main frame steel structure to hold the reactor firmly while load is applied on the bottom plate to dislodge the cake from the reactor walls and to push it into a container vessel. The ejection of the cake is accomplished by pushing the bottom plate with the help of a set of steel spacers/rams placed one over the other on the main ram of the press. Necessary interlocks and instrumentation is provided to the hydraulic system for carrying out ejection of cake carefully and with utmost safety. The cake container vessel into which the sponge cake is pushed in is initially evacuated and back filled with argon gas.
Primary cutting of the sponge cake is carried out in an another hydraulic guillotine press (Fig 10) which consists of revolving table and a clamping slide to position the cake as required. With the help of a cutting tool fitted in the frame, the cake is divided into various quality fractions as illustrated in Fig 11. The press is also equipped with a moving shuttle for facilitating the grading process. Each fraction of sponge is separately processed to finished size and evaluated for quality. Final crushing of sponge is carried out in a custom built 'shredder system' exclusively developed for size reduction of titanium sponge pieces of about 50-70 mm into 2-25 mm size. The shredder system (Fig. 12) has unique design features to impart shear stresses on the sponge with minimal residence time to avoid compaction of
pieces. The shredder system consists of a main steel shaft to which a set of toothed rings are fitted. The shaft rotates against a stationary comb structure housed in the shredder.
Apart from size reduction the shredder system also ensures minimal generation of files without heating up of mass.
As per customer demands titanium sponge lots of required purity are prepared and are blended in a double cone blender, stored and supplied in argon filled steel drums with chemical analysis certificate.
Advantages
1. A titanium sponge of aeronautical sponge of high purity is obtained.
2. Optimal selection of temperature minimizes the contamination of sponge by the reactor material.
3. Titanium sponge is ejected out of the reactor by using a custom-built hydraulic press thereby safeguarding the quality and structure of sponge.

We Claim;
1. A process for producing titanium sponge which comprises:
(a) purifying titanium tetrachloride by fractional distillation;
(b) magneisothermically reducing titanium tetrachloride obtained from step (a) in a reduction furnace containing molten magnesium and heating at a temperature of about 800°C in inert gas atmosphere;
(c) cooling the reduced mass of step (b) at a temperature of about 500°C;
(d) distillating the reduced mass in a condenser vessel which is connected to reduction furnace through interconnecting pipe, by heating in stages at a temperature of about 1000°C under a vacuum;

(d) cooling the product of step (d) at a room temperature for obtaining desired sponge;
(e) mechanical processing of the titanium sponge of aeronautical grade quality.

2. The process as claimed in claim 1, wherein the reduction pressure is in the range of 0.07 -0.27 bar.
3. The process as claimed in claiml, wherein the inert gas is argon.
4. The process as claimed in claim 1, wherein the interconnecting pipe is connected to an air blower for maintaining the temperature during the reduction process.
5. The process as claimed in claim 1, wherein the pure titanium tetrachloride contains 20-1000ppm of carbon and oxy-chloride content not more than 1500ppm.
6. The process as claimed in claim 1, wherein the purification is carried out in two packed distillation columns.
7. The process as claimed in any of the preceding claims, wherein magnesium reduction is achieved by heating solid magnesium ingots in the reduction furnace.
8. The process as claimed in any of the preceding claims, wherein the magnesium chloride is tapped periodically by pressurizing the furnace at about 0.7 bar g.
9. The process as claimed in claim 1, wherein the aeronautical grade size of titanium
sponge is 2-25mm. 10. An apparatus for performing the process as claimed in any one of the preceding claims, the said apparatus comprising:
a reduction furnace for magneisothermically reducing purified titanium tetrachloride;
a condenser vessel for vaccum distilling the reduced mass obtained from reduction
furnace;
and
a ejection press for mechanical processing of titanium sponge block obtained from the
condenser vessel to a finished size in the range of 2-25 mm.
wherein the reduction furnace and condenser vessel are interconnected through a pipe characterized in that the pipe is a heated interconnecting pipe assembly with an asset of inner sleeves to prevent condensation of vapors within the pipe.
11. An apparatus as claimed in claim 10, wherein the reduction furnace comprises
a inlet for pumping the titanium chloride into the reactor;
dip pipe fabricated to a reactor inner wall for draining liquid byproduct;
tapping pipe at the outer and inner surface is made compatible with reactants
byproducts to eliminate titanium sponge impurities;
thermowel having a set of thermocouples welded to the reactor inner surface for
maintaining temperature and pressure during the reduction process;
and
lid with nozzles for entrapping the vapours of the excess reactant
12. The apparatus as claimed in claim 10, wherein said condenser vessel comprises of:
inner-connecting pipe with mating flanges for uniform thermal distribution within the entire pipe during vaccum distillation.
14. The apparatus as claimed in claim 10, wherein the said condenser vessel comprises of a cap for ejecting the sponge cake.
15. The apparatus as claimed in claim 10, wherein the ejection press comprises of:
a custom built hydraulic ejection press for skinning off the outer impurity rich layers
and grading into several quality fractions;
a grading press with a cutting tool or breaking down the cake into different quality
fractions;
and
a shredder system for reducing the size of sponge in the range of 2-25 mm.
16. The apparatus as claimed in claim 10, wherein the said apparatus is connected to a air
blower to maintain temperature in the reduction furnace and vaccum tight in the
condenser vessel.
17. A process for producing titanium sponge, and an apparatus for performing the
process, substantially as herein described with reference to the foregoing examples
and accompanying drawings.

Documents:

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Patent Number

270009

Indian Patent Application Number

718/DEL/2007

PG Journal Number

48/2015

Publication Date

27-Nov-2015

Grant Date

24-Nov-2015

Date of Filing

30-Mar-2007

Name of Patentee

DEFENCE RESEARCH & DEVELOPMENT ORGANISATION

Applicant Address

MINISTRY OF DEFENCE, GOVT. OF INDIA, WEST BLOCK-VIII, WING-1, SECTOR-1, RK PURAM, NEW DELHI-110066, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHITTUR SREERAMAN RAMACHANDRAN	DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH, HYDERABAD-500 058
2	TIRUPPUDAIMURUDUR SUBRAMANIAN SITARAMAN	DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH, HYDERABAD-500 058
3	CHAGANTI RAJESHWAR VENKATA SATYA NAGESH	DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH, HYDERABAD-500 058
4	GUMMADI VEERA SIVA BRAHMENDRA KUMAR	DEFENCE METALLURGICAL RESEARCH LABORATORY, KANCHANBAGH, HYDERABAD-500 058

PCT International Classification Number

C22B34/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA