Title of Invention

PROCESS FOR TREATING SOUR NAPHTHA SOUR NAPHTHA OBTAINED AS A BY-PRODUCT DURING HYDRO-PROCESSING OF DIESEL STREAMS AND A SYSTEM FOR PERFORMING THE SAME

Abstract

A process for preparing sweet naphtha from sour naphtha containing upto 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams, said process comprising the steps of: (a) mixing the sour naphtha containing upto 1.9 wt. % H2S and lean DEA in a wt/wt ratio of 1:1 to 2:1 at a temperature range of 45°C to 50°C; (b) optionally passing the mixture of step (a) through a funnel filled with asbestos wool or glass wool to obtain a clear mixture containing sweet naphtha and DEA rich in H2S, and (c) allowing the clear mixture of step (b) to stand for a time period ranging between 1 to 5 minutes thereby separating sweet naphtha from DEA rich in H2S.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See section 10, Rule 13) PROCESS FOR PREPARING SWEET NAPHTHA FROM SOUR NAPHTHA" BHARAT PETROLEUM CORPORATION LIJVUTED, a Government of India Enterprise having its registered office at Bharat Bhavan 4 and 6, Currimbhoy Road Ballard Estate Mumbai Maharashtra-400 001, India, Tel # (022) 271 3000/4000; FAX # (022) 271 3688. The following specification (particularly) describes the nature of the invention and the manner in which it is to be performed. ORIGINAL 844/MUMNP/2003 GRANTED 3-1-2005 PROCESS F0R TREATING OF SOUR NAPHTHA OBTAINED AS A BY PRODUCT DURING HYDROPROCESSINGOF DIESEL STREAMS AND A SYSTEM FOR PERFORMING THE SAME 5 Field of the Invention The present invention relates to a process for treatment of sour naphtha containing about 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams. The present invention also provides a system for performing the aforesaid process. 10 Background and Prior Art to the Invention Bharat Petroleum Corporation Limited (BPCL) had built a diesel hydro desulphurisation (DHDS) plant at BPCL refinery in 1999 to reduce the sulfur content in diesel from 2.0 wt. % to 0.05 wt. %. 15 After commissioning the plant, it was observed that during the process of diesel hydro desulphurisation sour naphtha containing 1.9 wt. % hydrogen sulfide was generated as a by-product. Initially, the naphtha stream coming from diesel striper unit of the DHDS Plant was 20 diverted to Motor Spirit Pool without any treatment. It was discovered that four tanks of gasoline failed on copper corrosion (approx. 40,000 tonnes). To correct the situation, lot of caustic was added to the tanks. The Applicants found when caustic is added to the tank, a sludge gets formed at the bottom of the tank. Hence, process was adding caustic to the tank was stopped. To overcome the problem, H2S scavenger was added which had 25 costed 10 lacks rupees. Subsequently, it was decided to stop the diversion of the naphtha to the MS Pool. As a second attempt, the naphtha stream obtained was diverted to Fluidized Catalytic Cracking Unit Fractionator. The Applicants experienced the same problem of copper 30 corrosion. The Applicants also tried adding caustic at this point. However noticed that consumption of caustic was drastically increased in LPG and Gasoline Merox due to high H2S content. Diversion of the sour naphtha stream to FCCU unit also necessitated correction of Gasoline by adding H2S scavenger, which was an additional cost. The Applicants then tried diverting the sour naphtha stream to Heavy crude Processing (HCP) stabilizer. Due to the diversion of the sour naphtha stream, the LPG failed in H2S due to this naphtha addition and the caustic consumption had increased. In this case also the Applicants had to re-process the LPG which resulted in additional operating cost. 5 Finally the Applicants tried diverting the sour naphtha stream to crude tank. However, to their dismay, this also resulted in heavy corrosion in HCP distillation column over head system. Here also the caustic consumption has increased. 10 Finally, the diesel stripper was being operated at total reflux to overcome the problem. However, running the diesel stripper at total reflux resulted in withdrawing of cycle oils (low flash) from DHDS feed and therefore due to low exothermicity in the reactor, the DHDS feed heater posed a limitation on increasing DHDS feed. 15 The Applicants contacted M/S Universal Oil Products (UOP) whom suggested providing a separate treatment plant which included a naphtha stabilizer. The treatment plant consisted of a stripping column that would strip the H2S from the naphtha. The gas rich in H2S thus stripped was supposed to be processed in an Amine treating unit. The cost for setting up this unit was very high and hence, it was dropped. 20 As part of the DHDS plant, a separate treatment facility was not provided to treat the high H2S content naphtha stream coming from diesel stripper of the DHDS plant. The Applicants later leamt that the DHDS units designed by M/S Institute of Fmcieus Pertoleum (IFP) had Naphtha treatment as a part of their design and hence, these 25 refineries did not face any problem due to the quality of naphtha. The Applicants found that the cost for setting up a naphtha treatment plant in accordance with the design of IFP was also very high. The Applicants found that the cost for setting up the plant suggested by UOP as well as 30 that being used by IFP were well over 2.9 crore rupees. When the Applicants conducted a search, they noticed that H2S present in LPG and FG were removed by treating the LPG / FG with Diethanol amine (DEA). However, there does not exist any single citation which teaches a process of removing the H2S from naphtha stream using DEA. Hence, the Applicants contacted Engineers India Limited and M/S Koch-Glitch with their query. However, both the organizations were not aware of a process for removing H2S from naphtha stream using DEA and were unable to give any 5 references or guarantee on the outcome of the process. Hence, the Applicants felt a grave need to provide a simple and economical process for treating the sour naphtha containing high content of H2S obtained as a by-product during hydroprocessing of diesel streams. 10 Objective of the Present Invention The main objective of the present invention is to provide a process for treatment of sour naphtha containing about 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams. 15 Another object of the present invention is to provide an economical process for converting sour naphtha containing about 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams to sweet naphtha by treating with Diethanol amine. 20 Still another object of the present invention is to provide a system for performing the aforesaid process. Summary of the Present Invention Accordingly, the present invention provides an economical process for converting sour 25 naphtha containing about 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams to sweet naphtha, the said process comprising the step of mixing lean DEA and the sour naphtha stream in a static mixer for a time period sufficient for the reaction between H2S and DEA to occur, sending the mixture of naphtha stream and DEA to a gravity settler to separate sweet naphtha and DEA rich in H2S. The present invention 30 also provides a system for performing the aforesaid process. Brief Description of the Accompanying Drawings Tn the drawings accompanying the specification, Figure 1 represents the upstream process for hydroprocessing of diesel stream Figure 2 represents the device system of the present invention used to convert the sour 5 naphtha containing about 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams to sweet naphtha. Figure 3 represents the downstream process. Detailed Description of the Present Invention 10 The present invention provides a process for converting sour naphtha containing upto 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams to sweet naphtha, the said process comprising the steps of: (a) mixing the sour naphtha containing upto 1.9 wt. % H2S and lean DEA in a wt./wt. ratio of 1:1 to 2:1 at a temperature range of 45°C to 50°C; 15 (b) optionally passing the mixture of step (a) through a funnel filled with asbestos wool to obtain a clear mixture containing sweet naphtha and DEA rich in H2S, and (c) allowing the clear mixture of step (b) to stand for a time period ranging between 10 seconds to 10 minutes thereby separating sweet naphtha from REA rich in 20 H2S. In an embodiment of the present invention wherein in step (a), the sour naphtha and lean DEA are mixed in a static mixer. 25 In another embodiment of the present invention wherein in step (a), the wt./wt. ratio of sour naphtha to lean DEA is 1:1. In yet another embodiment of the present invention wherein in step (a), the DEA is mixed with sour naphtha till H2S in sour naphtha reacts with DEA. 30 In still another embodiment of the present invention wherein in step (b), the DEA / naphtha mixture is passed through a funnel filled with asbestos wool to avoid formation of an emulsion. In still another embodiment of the present invention wherein in step (c), the mixture of naphtha and DEA is allowed to stand in a gravity settler for a time period ranging between 30 seconds to 3 minutes to separate sweet naphtha from DEA rich in H2S. 5 In one more embodiment of the present invention wherein DEA rich in H2S being heavier than sweet naphtha settles down in the gravity settler. In one another embodiment of the present invention wherein the DEA rich in H2S is 10 drawn from the bottom of the gravity settler while the sweet naphtha is drawn from the top of the gravity settler. In a further embodiment of the present invention wherein the DEA rich in H2S is sent to amine regeneration unit for recycling the DEA. 15 In an embodiment of the present invention wherein the sweet naphtha thus obtained has H2S content less than 50 ppm. In another embodiment of the present invention, the steps (a) to (c) can be repeated to 20 further decrease the H2S level in the sweet naphtha. In yet another embodiment of the present invention wherein the sweet naphtha thus obtained has H2S content preferably less than 5 ppm. 25 The present invention also provides a system for converting sour naphtha containing upto 1.9 wt. % H2S obtained as a byproduct during hydroprocessing of diesel streams to sweet naphtha, said system comprising a static mixer provided with at least two inlet means for receiving lean DEA and sour naphtha respectively, said static mixer being connected to a gravity settler and said gravity settler bring provided with at least two 30 outlet means for drawing rich DEA and sweet naphtha. In an embodiment of the present invention, the inlet means are provided with control valves for controlling the amount of lean DEA and sour naphtha being supplied to the static mixer. In another embodiment of the present invention, a funnel filled with asbestos wool is optionally provided between the static mixer and the gravity settler. 5 The present invention is further described with reference to the following example which is given by way of illustration and hence, the examples should not be construed to limit the scope of the present invention in any manner. Example 1 10 The Applicants have first carried out a plant test wherein they mixed the sour Naphtha obtained from the diesel stripper unit was mixed with lean DEA in a wt./ wt. ratio of 1:1 in a small bottle and mixed thoroughly. The Applicants noticed that the pungent smell in sour naphtha disappeared. The Applicants further discovered that when the mixture was allowed to stand for a maximum time period of 45 seconds, sweet naphtha gets separated 15 from DEA rich in H2S. This plant level experiment gave the Applicants the clue that H2S present in naphtha can be reduced substantially by using a good mixing system and also that number of transfer units required for this purpose will be minimum. Example 2 20 A pilot project was then taken up by the Applicants wherein the sour naphtha obtained from the diesel stripper of the DHDS unit (figure 1) was pumped to a static mixer through pipes and lean DEA was mixed to the sour naphtha in the static mixer (figure 2). The rate of flow of sour naphtha was maintained between 20-40 MT/D. The static mixer was run for a time period in the range of 30 seconds to 10 minutes. During this period, the 25 following reaction takes in the static mixer. R2NH + H2S ► R2NH3S Wherein R represents CH2-CH2-OH and R2NH3S represents DEA rich in H2S. This reaction is exothermic. 30 The Applicants observed that during the aforesaid process, an emulsion was being formed. Formation of the emulsion did not allow separation of the sweet naphtha from DEA rich in H2S. To overcome this problem of formation of the emulsion, the naphtha/DEA mixture was passed through a funnel containing asbestos wool. It was observed that by passing the Naphtha / DEA mixture through the funnel containing asbestos wool a clear solution was obtained. This clear solution was then transferred to a gravity settler. The solution was allowed to stand in the gravity settler for a time period ranging between 1 to 5 minutes and more preferably for a time period ranging between 2 5 to 3 minutes. DEA rich in H2S being heavier than sweet naphtha settled at the bottom of the gravity settler. Existing redundant vessel was used as gravity settler. The gravity settler was provided with at least two outlets one near a top end of the gravity settler and the other at a bottom of the gravity settler. The sweet naphtha was drawn from the outlet near the top end of the gravity settler while the DEA rich in H2S was drawn from the 10 outlet at the bottom of the gravity settler. The rich amine thus drawn is further processed in the down stream process (figure 3). In order to regenerate the DEA for reuse, the DEA rich in H2S drawn from the gravity settler was sent to an amine regeneration unit wherein the H2S was stripped from the 15 DEA and lean DEA was regenerated. The lean DEA thus regenerated is recycled back to the static mixer. The sour naphtha obtained from the diesel stripper unit contained H2S content in the range of 0.4 to 1.0 wt. %. The sweet naphtha obtained by following the process described 20 above contained H2S content in the range of 20-50ppm. Due to the improved quality of naphtha thus being produced, the sweet naphtha thus obtained from the gravity settler is directed to slops tank. It was also found that aforesaid process can be repeated in order to further decrease the 25 amount of H2S in the naphtha. More particularly, the Applicants found that if the process is repeated once more, the level of H2S in the naphtha is less than 5 ppm. The pilot project was commenced during November 2001 and the same is running successfully till date. 30 Advantages of the Present Invention 1. The net benefit on capital cost is approximately Rs. 2.5 crores as the devices required for treatment of sour naphtha are very cheap and are readily available. In We Claim: 1. A process for preparing sweet naphtha from sour naphtha containing upto 1.9wt. % H2S obtained as a by-product during hydroprocessing of diesel streams, said process comprising the steps of: (a) mixing the sour naphtha containing upto 1.9 wt. % H2S and lean DEA in a wt/wt ratio of 1:1 to 2:1 at a temperature range of 45°C to 50°C; (b) optionally passing the mixture of step (a) through a funnel filled with asbestos wool or glass wool to obtain a clear mixture containing sweet naphtha and DEA rich in H2S, and (c) allowing the clear mixture of step (b) to stand for a time period ranging between 1 to 5 minutes thereby separating sweet naphtha from DEA rich in H2S. 2. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein in step (a), the sour naphtha and lean DEA are mixed in a static mixer. 3. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein in step (a), the DEA is mixed with sour naphtha till H2S in sour naphtha reacts with DEA. 4. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein in step (c), the clear mixture of step (b) is allowed to stand in a gravity settler for a time period ranging between 10 seconds to 10 minutes to separate sweet naphtha from DEA rich in H2S. 5. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein in step (c), the clear mixture of step (b) is allowed to stand in a gravity settler for a time period ranging between 2 to 3 minutes to separate sweet naphtha from DEA rich in H2S. 6. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein the DEA rich in H2S is drawn from the bottom of the gravity settler while the sweet naphtha is drawn from the top of the gravity settler. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein the DEA rich in H2S is sent to amine regeneration unit for recycling the DEA. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein the sweet naphtha thus obtained has H2S content less than 50 ppm. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein the steps (a) to (c) may be optionally repeated to further decrease the H2S content in the naphtha. A process for preparing sweet naphtha from sour naphtha as claimed in claim 1, wherein the sweet naphtha thus obtained has H2S content less than 5 ppm. A system for preparing sweet naphtha from sour naphtha containing upto 1.9 wt. % H2S obtained as a by-product during hydroprocessing of diesel streams as claimed in claim 1, said system comprising a static mixer provided with at least two inlet means for receiving lean DEA and sour naphtha respectively, said static mixer being connected to a gravity settler and said gravity settler bring provided with at least two outlet means for drawing rich DEA and sweet naphtha. A system for preparing sweet naphtha from sour naphtha as claimed in claim 12, wherein the inlet means are provided with control valves for controlling the amount of lean DEA and sour naphtha being supplied to the static mixer. A system for preparing sweet naphtha from sour naphtha as claimed in claim 12, wherein a funnel filled with asbestos wool is optionally provided between the static mixer and the gravity settler. Dated this 25th day of August, 2003. G. Deepak Sriniwas Of K & S Partners Agent for the Applicants

Documents:

844-mum-2003-assignment(4-10-2005).pdf

844-mum-2003-cancelled pages(3-1-2005).pdf

844-mum-2003-claims(granted)-(3-1-2005).doc

844-mum-2003-claims(granted)-(3-1-2005).pdf

844-mum-2003-correspondece(14-12-2006).pdf

844-mum-2003-correspondece(ipo)-(11-9-2006).pdf

844-mum-2003-drawing(3-1-2005).pdf

844-mum-2003-form 1(24-10-2003).pdf

844-mum-2003-form 1(25-8-2003).pdf

844-mum-2003-form 1(3-1-2005).pdf

844-mum-2003-form 1(30-12-2004).pdf

844-mum-2003-form 1(4-10-2005).pdf

844-mum-2003-form 13(4-10-2005).pdf

844-mum-2003-form 19(25-8-2003).pdf

844-mum-2003-form 2(granted)-(3-1-2005).doc

844-mum-2003-form 2(granted)-(3-1-2005).pdf

844-mum-2003-form 26(30-12-2004).pdf

844-mum-2003-form 3(25-8-2003).pdf

844-mum-2003-form 5(30-12-2004).pdf

844-mum-2003-form 5(4-10-2005).pdf

844-mum-2003-form 8(15-9-2006).pdf

abstract1.jpg