FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2006 COMPLETE Specification (See Section 10 and Rule 13) A METHOD FOR REMOVING CHLORIDES FROM HYDROCARBON STREAM RELIANCE INDUSTRIES LIMITED an Indian Company of 3rd Floor, Maker Chamber - IV, 222, Nariman Point, Mumbai-400 021, Maharashtra, India The following specification particularly describes the invention and the manner in which it is to be performed. FIELD OF DISCLOSURE The present disclosure relates to a method for removing chlorides from a hydrocarbon stream. Particularly, the present disclosure relates to a method for removing chlorides from a heavy hydrocarbon stream such as naphtha, diesel, light vacuum gas oil, light coker gas oil, heavy atmospheric gas oil, heavy vacuum gas oil, heavy coker gas oil, vacuum gas oil or mixtures thereof. BACKGROUND Inorganic and organic chlorides present in even small quantities in hydrocarbon streams can upset the process conditions either by poisoning the catalyst or by causing corrosion of the equipment. For example: severe corrosion is observed in crude top column, hydrotreater reactor top and downstream circuit including surge drum, high temperature exchangers and transfer lines especially along the elbow/joint sections. Generally pitting type of corrosion is observed in these equipments, suggesting that chlorides are the main cause of corrosion. Among chlorides, hydrogen chloride and ammonium chloride have the highest potential to cause corrosion. In the hydrotreaters, the organic chlorides also get converted to inorganic chloride i.e. hydrogen chloride, thereby worsening the corrosion problem. The hydrocarbon stream coming from crude distillation unit has significant amounts of inorganic and organic chlorides. For example: the gas oil produced in atmospheric distillation may contain up to 25 ppm chlorides while the light vacuum gas oil produced in the top section of vacuum distillation unit may contain up to 50 ppm chlorides. These chlorides are mainly produced by hydrolysis of chloride salts of magnesium and calcium metals. These metal salts are present in the crude oil and carried to the distillation unit due to insufficient desalting. Thus, both the inorganic and organic chlorides are detrimental to the hydrocarbon processing units, especially the hydrotreaters, and must be removed from the hydrocarbon stream prior to processing. Commonly, an adsorbent or a catalyst is used to remove the chlorides from the hydrocarbon streams. US3864243 discloses use of bauxite as a chloride adsorbent, where the adsorbent is dehydrated at 425 - 650 °C before use. US3935295 discloses the use of calcium and zinc oxide adsorbent for removal of inorganic chlorides. US4713413 discloses the use of alumina adsorbent at 20 °C for removing organic chlorides. US5107061 discloses the use of crystalline molecular sieve Zeolite X in soda form for removal of organic chlorides from a hydrocarbon stream. US5595648 and US5645713 disclose the use of low surface area solid caustic bed for removing chlorides from hydrocarbon streams. US5614644 discloses the use of copper containing scavenger material for removing organic chlorides from hydrocarbon streams and US6060033 discloses the use of alkali metal oxide loaded on alumina for removing inorganic chlorides from hydrocarbon streams. Use of the afore-mentioned chloride adsorbents for removing chlorides from heavy hydrocarbon streams such as vacuum gas oil or coker gas oil is unfeasible due to their high viscosities and high pour points and presence of small amounts of asphaltenic materials. These properties of the heavy hydrocarbon streams cause following problems when an adsorbent is used: high delta pressure is required across the adsorbent bed, higher temperature conditions are required for adsorption, difficulty in regeneration of the adsorbent, lower chloride loading capacity and lower chloride removal efficiency. Also, catalysts have been used in the past for converting the organic chlorides to inorganic chlorides. US3892818 uses rhodium catalyst to convert pure organic chlorides to hydrogen chloride, where the catalyst contains 0.1 wt% rhodium and the reaction is carried out at about 250 °C. US4721824 discloses the use of magnesium oxide and binder for catalytic removal of organic chlorides from hydrocarbon streams. US5371313 discloses the use of calcium oxide at 130 - 170 °C for removal of tert butyl chloride. The above-mentioned processes are suitable for light hydrocarbon streams (80% less moisture. In the process, light hydrocarbons from the heavy hydrocarbon stream are separated along with the chlorides and moisture as a vapor stream. In accordance with one of the embodiments of the present disclosure, the amount of light hydrocarbon present isolated vapor stream is less than 3 wt% with respect to the weight of the heavy hydrocarbon stream. The temperature and pressure are critical parameters during the drying process, in which, maximum chloride removal is to be attained with minimum or no distillation of the hydrocarbon feed. The preferred temperature range for drying is between 90 - 350 °C and the drying is done for a time period between 10 -120 minutes. Typically, the temperature and pressure of the vacuum dryer coumn is controlled by controlling the reflux ratio and ejector steam flow. The heavy hydrocarbon stream can be heated in a single step by exchanging heat with HHP steam or can be heated in two steps, by first exchanging heat with the vacuum dryer bottom stream and then exchanging heat with the HHP steam and the HP steam. In one of the embodiments, the hydrocarbon stream is heated with HP stream at a pressure ranging between 40 to 44/Kg/cm (g), preferably 43/Kg/cm (g) and at a temperature ranging between 380°C to 390°C, preferably 385°C after exchanging the heat with vacuum dryer bottom stream. In accordance with one embodiment, the heavy hydrocarbon stream is heated in a single step with HHP stream at a at pressure ranging between 110 to 120 /Kg/cm (g), preferably 115/Kg/cm (g) and at a temperature ranging between 500 to 520°C, preferably 510°C The distillation of hydrocarbon stream is not desired in the process since it will generate a light hydrocarbon fraction having more chlorides than the primary hydrocarbon stream. Hence, corrosivity of the distilled fraction will be higher than the primary feed. Thus, the distillation of the hydrocarbon feed is minimized by accurate control of the temperature and pressure during drying in the vacuum dryer column. Referring to Figure 1, there is disclosed a schematic of the process configuration for treatment oflight vacuum gas oil (LVGO) in accordance with the present disclosure. The various heavy hydrocarbons streams and hydrocarbon residues can be treated similarly with modifications in the process conditions based on the boiling range of the hydrocarbon stream. The process is suitable for hydrocarbons having an initial boiling point ranging between 180 - 600 °C. In accordance with an exemplary embodiment, the process comprises heating the LVGO up to the drying temperature at atmospheric pressure, prior to drying, in a single step (130 - 300 °C) or in two steps viz., i) 130 - 250 °C by exchanging heat with vacuum dryer bottom stream (marked by A, B and C in Figure 1); ii) 250 - 300 °C by using HHP steam (marked by label D in Figure 1). 5 wt% vaporization of the hydrocarbon stream can be achieved by using higher vacuum and lower temperature (<250 °C) which can be achieved by using HP steam. The heated LVGO is received in the vacuum drying column 100, where the drying column is a packed column or a tray column. The vacuum is maintained in the vacuum drying column 100 by means of steam ejectors 104. The chloride impurities get evaporated along with the moisture and light hydrocarbons and are separated through a vapor stream leaving the top of the vacuum dryer column. The vapor stream (marked by label E) containing chlorides, moisture and some light LVGO are condensed in a pre-condenser 102 and a condenser 106 and removed through a receiver 108 at H. The vacuum dryer bottom stream (marked by label F) is used for heating the incoming hydrocarbon stream. The small quantity of light LVGO separated with the impurities is recovered (marked by I) and can be sent to crude desalter for further chloride removal. The vacuum dried LVGO is routed for further processing. The treated product contains 1-10 ppm chlorides. This process can be carried out continuously in the same vacuum drying column. The disclosure will now be described with reference to the following examples which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration. An automated TBP apparatus having a 10L feed vessel capacity was used for vacuum drying the heavy hydrocarbon stream. The TBP apparatus was provided with accurate temperature, vacuum, and stirrer speed control. 3-6 liters of heavy hydrocarbon stream was heated at temperatures between 90 -350 °C under vacuum pressure of 20 - 700 torr for time intervals between 10 -120 minutes. A cold trap was kept at - 50 °C to collect any condensed hydrocarbon, moisture and chloride species. Chloride analysis of the hydrocarbon stream was done before and after the vacuum drying. Example 1: 100 mL light vacuum gas oil (LVGO) having total chloride content of 6.2 ppm was heated in an open container at 160 °C and atmospheric pressure for 60 minutes. Chloride content of the heated LVGO was 2.2 ppm showing a 64 % reduction. Example 2: 5 liter LVGO having a total chloride content of 7 ppm was heated in a TBP apparatus at 120 °C and 380 torr pressure for 120 minutes. No chloride reduction was observed. Example 3: 5 liter LVGO having a total chloride content of 5.7 ppm was heated in a TBP apparatus at 180 °C and 380 torr pressure for 120 minutes. A minimal 9% reduction in chloride content was observed in the vacuum dried LVGO. Example 4: 5 liter LVGO having a total chloride content of 5.6 ppm was heated in a TBP apparatus at 300 °C and 380 torr pressure for 120 minutes. The chloride content of the vacuum dried LVGO was reduced to 0.8 ppm showing 85% reduction. Example 5: 5 liter LVGO having a total chloride content of 6.6 ppm was heated in a TBP apparatus at 300 °C and 380 torr pressure for 10 minutes. The chloride content of the vacuum dried LVGO was reduced to 2.2 ppm showing 66 % reduction. The results are summarized in Table 2. Table 32: Change in chloride concentration for Examples 1-5. Expt. Apparatus Temperature. °C Pressure, torr Tune, minutes LVGO Feed Cl, ppm Cl after heating, ppm % reduction 1 Open container 120 760 120 6.2 2.9 54 i TBP Unit 120 380 120 7.0 7.0 0 -i TBP Unit 180 380 120 5.7 5.2 9 4 TBP Unit 300 380 120 5.6 0.8 85 5 TBP Unit 300 380 10 6.6 2.2 66 It is observed from Table 32 that at optimum temperature and pressure conditions the time required to reduce the chloride concentration is very less. TECHNICAL ADVANTAGES A method for removing chlorides from a heavy hydrocarbon stream, as described in the present disclosure has several technical advantages including but not limited to the realization of: ■ it is a simple, effective and economical method for removing chlorides from heavy hydrocarbon streams such as naphtha, diesel, light vacuum gas oil, light coker gas oil, heavy atmospheric gas oil, heavy vacuum gas oil, heavy coker gas oil, vacuum gas oil or mixtures thereof; ■ the method removes inorganic impurities from the heavy hydrocarbon streams without the use of any adsorbent, additive or catalyst; and ■ the method also removes residual moisture from the heavy hydrocarbon streams. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. Any discussion of documents, acts, materials,, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary. In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. WE CLAIM 1. A method for removing chlorides from a heavy hydrocarbon stream, said method comprising the following steps: ■ subjecting the heavy hydrocarbon stream to drying by employing at least one heating means selected from the group consisting of vacuum dryer bottom stream, HP steam and HHP steam at a temperature that is lower than the Initial Boiling Point (IBP) of the hydrocarbon at a pressure ranging between 20 - 700 torr, wherein the vaporization of the hydrocarbon stream is maintained below 5wt%; and ■ isolating a vapor stream containing moisture, chlorides and light hydrocarbons from the heavy hydrocarbon stream. 2. The method as claimed in claim 1, wherein the amount of light hydrocarbon present in the isolated vapor stream is less than lwt% with respect to the total weight of the heavy hydrocarbon stream. 3. The method as claimed in claim 1, wherein the heavy hydrocarbon stream is at least one hydrocarbon fraction selected from naphtha, diesel, light vacuum gas oil, heavy vacuum gas oil, light coker gas oil, heavy coker gas oil, heavy atmospheric gas oil and vacuum gas oil. 4. The method as claimed in claim 1, wherein the drying is carried out at a temperature in the range of 90 - 350 °C. 5. The method as claimed in claim 1, further comprising condensing the vapor stream and recovering the light hydrocarbons from the condensed stream for further chloride removal. 6. The method as claimed in claim 1, wherein the heavy hydrocarbon stream contains moisture in the range of 100 - 2000 ppm and chlorides in the range of 1 - 100 ppm. 7. The method as claimed in claim 1, wherein the heavy hydrocarbon stream has an initial boiling point ranging between 180 - 600 °C. 8. The method as claimed in claim 1, wherein the step of drying is carried out for a time period ranging between 10 - 120 minutes. . 9. The method as claimed in claim 1, wherein the heavy hydrocarbon stream is heated in a single step by exchanging heat with HHP steam at pressure ranging between 110 to 120 /Kg/cm2(g) and at a temperature ranging between 500 to 520°C 10. The method as claimed in claim 1, wherein the heavy hydrocarbon stream is heated by exchanging heat with HP stream at a pressure ranging between 40 to 44 /Kg/cm (g) and at a temperature ranging between 380°C to 390°C 11. The method as claimed in claim 1, wherein the heavy hydrocarbon stream is heated in two steps comprising exchanging heat with the vacuum dryer bottom stream, followed by exchanging heat with at least one stream selected from HHP steam and HP steam. 12. The method as claimed in claim 1, wherein the temperature and pressure of the vacuum dryer column is controlled by controlling the reflux ratio and ejector steam flow. 13. The method as claimed in claim 1, wherein the drying is carried out in a column selected from a packed column and tray column.