DIESEL HYDRODESULPHURISATION UNIT CHAPTER-1 DESIGN BASIS

Transcription

1 CHAPTER GENERAL DESIGN BASIS Panipat refinery is designed to cater the demand of the petroleum products in the northern region of India.The Panipat refinery consists of the following units: 1. Atmospheric and Vacuum Unit. 2. Once Through Hydrocracker Unit 3. Catalytic Reformer Unit 4. Resid Fluid Catalytic Cracking Unit 5. Hydrogen Generation Unit 6. Visbreaking Unit 7. Bitumen Blowing Unit 8. Amine Regeneration Unit 9. Sour Water Stripper 1.2 PURPOSE OF THE DHDS PROCESS The DHDS unit is set up to reduce sulfur content in the diesel and produce diesel with 0.25% Sulphur. The unit treats the following gas-oils fractions. 1. S.R.Gas oil 2. Vacuum Diesel 3. Vis-Breaker Gas Oil 4. Total Cycle Oil Hydrodesulfurisation Section The purpose of the section is to reduce 90% Sulphur in feed diesel using hydrogen from Catalytic Reformer or Hydrogen Generation Units. In addition to the deep desulfurisation, the diolefin and olefins will be saturated and a denitrification will also occur. The choice of catalysts and operating conditions is made in order to avoid hydrogenation of the aromatics. Feedstocks are blended from various sources, straight run or cracked products Sulfur and nitrogen contents are depending upon the crude. Cracked products are characterized by the presence of unsaturated hydrocarbons (olefins, diolefins and aromatics) Nowadays, more and more stringent specifications are imposed upon sulfur content of diesel delivered by refineries. CHAPTER-1 DESIGN BASIS 1/27

2 Denitrification improves the product stability. The required level of desulfurisation is achieved by hydrotreating over a specially selected catalyst. The presence of olefins or diolefins calls for additional bed installed in upstream of the desulfurisation bed. In the present case, no aromatic hydrogenation is aimed at. The unit is able to produce treated Diesel Oil with maximum sulfur content of 500 ppm by providing an additional second Reactor in series Amine Treatment Section The Amine Treatment Section is designed to remove Hydrogen Sulfide (H2S) from gaseous hydrocarbons effluents. H2S removal from gaseous hydrocarbons effluents is achieved by means of a continuous absorption/regeneration process using a 25% wt. Di-Ethanol Amine (DEA) for H2S removal. This section includes the following main equipments - HP Amine Absorber - LP Amine Absorber 1.3 CAPACITY AND TURNDOWN RATIO The DHDS unit is designed to hydrodesulfurise the two feedstock blends as in the table named as Feed 1 and Feed 2 in section and respectively. The characteristics of Feed 3 used as check feed is given in The unit nameplate capacity is 700,000 MTPA with a stream factor of 8000 hours per year. The design capacity is 770,000 MTPA. The unit turndown rate is 50% of the design capacity The design covers 2 cases: In the case 1, 90% of the feed sulphur is converted to H2S. In the case 2 with the installation of second reactor the sulphur in the feed is reduced to 500 wt. ppm for the feeds 1 and 2. CHAPTER-1 DESIGN BASIS 2/27

3 The hydrogen required for the reactions is supplied either from the Catalytic Reforming Unit or Hydrogen Generation Unit. Lean Amine is supplied from the Amine Regeneration Unit Nitrogen/air facilities for HR and HR-348 catalyst in-situ regeneration are also provided. The two feedstock blends are a mixture of: Feed 1 : 87% wt. of SRGO and 13% wt. of SRVD Feed 2 : 70% wt. of SRGO, 10% wt. of SRVD, 3% wt. of VBGO and 17% wt. of CGO Check Feed : 65% wt. of SRGO, 10% wt. of SRVD and 25% wt of Total Cycle Oil CHAPTER-1 DESIGN BASIS 3/27

4 1.4 FEED SPECIFICATIONS Feed 1 The characteristics of the feed 1 to be treated is as follows ((value)=estimated) DESCRIPTION SRGO SRVD FEED 1 % on feed mix (wt) Sp. Gr % S. wt Nitrogen ppm wt Cetane number Flash point, o C (81) Dist. ASTM. o C - IBP % % % % % % % EP Metal content, wt ppm - Nickel Vanadium Name plate capacity Design capacity : 7,00,000 T/y : 7,70,000 T/y CHAPTER-1 DESIGN BASIS 4/27

5 1.4.2 Feed 2 The characteristics of the feed 2 to be treated is as follows ((value)=estimated) DESCRIPTION SRGO SRVD VBGO CGO FEED 2 % on feed mix (wt) Sp. Gr % S. wt Nitrogen ppm wt Bromine number Cetane number Flash point, o C (67) Dist. ASTM. o C - IBP (178.6) 172-5% % (202.6) % (228) % (252.6) % (279.5) % (313) % EP (349.1) 403 Metal content.wt ppm - Nickel Vanadium Name plate capacity : 700,000 T/y Design capacity : 770,000 T/y Feed 3 CHAPTER-1 DESIGN BASIS 5/27

6 The characteristics of the feed 3 used as check feed are as follows ((value)=estimated) DESCRIPTION SRGO SRVD TCO FEED 3 % on feed mix (wt) Sp. Gr % S. wt Nitrogen ppm wt Bromine number Cetane number Flash point, o C (36) Dist. ASTM. o C - IBP % % % % % % % EP Metal content.wt ppm - Nickel Vanadium Name plate capacity: 690,000 T/Y 1.5 MAKE-UP HYDROGEN SPECIFICATIONS CHAPTER-1 DESIGN BASIS 6/27

7 The hydrogen make-up is available at the battery limit with the following composition: a. Hydrogen from Catalytic Reforming Unit Molar Composition Vol. % H Cl 6.2 C2 1.6 C3 0.8 C4 0.7 C Impurities Chlorine & Chloride ppm v 2 max. b. Hydrogen from Hydrogen Generation Unit Molar Composition Vol. % H Cl 0.1 Impurities CO + CO2 ppm v 50 max. CHAPTER-1 DESIGN BASIS 7/27

8 1.6 ESTIMATED PRODUCT SPECIFICATIONS Desulfurised Diesel The Desulfurised diesel is produced at the stripper bottom and dried in the coalescer before being sent to storage. Description Feed 1 Feed 2 Case 1 Case 2 Case 1 Case 2 SPGR Sulfur content, wt. ppm Nitrogen content, wt. ppm Water content, wt. ppm <500 <500 <500 <500 Bromine Number <1 <1 <1 <1 Cetane index Pour Point o C Same as feed Same as feed Same as feed Same as feed Flash point o C Same as feed Same as feed Same as feed Same as feed Color Same as feed Same as feed Same as feed Same as feed Stabilized Naphtha The naphtha recovered as liquid distillate from the stabilizer bottom is sent to the naphtha storage. Description Feed 1 Feed 2 Case 1 Case 2 Case 1 Case 2 SPGR H 2 S content wt ppm Nitrogen wt ppm max RON 72 to to to to 74 RVP CHAPTER-1 DESIGN BASIS 8/27

9 1.6.3 Sweet Fuel Gas from LP Amine Absorber Sweet Fuel gas from LP amine is routed to FCC fuel gas header. Feed 1 Feed 2 Description Case 1 Case 2 Case 1 Case 2 H 2 content, mol% 35 to to to to 23 H 2 S content, ppm vol H 2 O content, mol% HC content, mol% 63 to to to to 75 MW 19.3 to to to to Purge Gas from HP Amine Absorber Normally this flow is zero Sour Water from Cold Separator Feed 1 Feed 2 Description Case 1 Case 2 Case 1 Case 2 NH 4 SH, wt% This sour water is oversaturated with hydrocarbon and excess of H 2 S : HC content : 600 wt. ppm H 2 S content : 150 to 300 wt. ppm CHAPTER-1 DESIGN BASIS 9/27

10 1.7 CHEMICALS, CATALYSTS AND OTHER ITEMS Anhydrous Ammonia During in-situ catalyst regeneration under nitrogen/air atmosphere anhydrous ammonia is injected at the reactor bottom at a rate of 100 wt ppm (compare to gas at reactor inlet). Properties: Density, kg/m 3 : 636 Viscosity, cp : 0.14 Molecular weight : Dimethyl Disulfide(DMDS) The Dimethyl Disulfide is injected at the feed pump suction at 1 wt % rate in the recirculating gas oil, during catalyst sulfiding Estimated DMDS consumption per catalyst sulfiding is about 3500 kg (Provision for dense loading included) Antifouling Agent The antifouling agent is injected at the feed pump suction diluted at 10% in straight run gasoil at the rate of 10 ppm of pure product compared to the feed. Type : CHIMEC 3033 or equivalent Antifoaming Estimated Annual consumption = 7700 kg The antifoaming is injected at the 52-PA-CF-107 suction, 52-CC feed and 52-CC feed, diluted at 10% in demineralised water at the rate of 20 wt. ppm of pure product compared to each stream. Type : CHIMEC 8039 or equivalent Estimated annual consumption = 2400 kg CHAPTER-1 DESIGN BASIS 10/27

11 1.7.5 Corrosion Inhibitor Solution The corrosion inhibitor is injected in the stripper and stabilizer overheads diluted at 1% in stabilized naphtha at the rate of 6 wt. ppm of pure product compared to the total column overhead. Type : CHIMEC 1044 or equivalent Estimated annual consumption = 600 kg Caustic Soda Solution During in-situ Catalyst regeneration under nitrogen/air atmosphere, a 10% wt. Caustic soda solution is injected downstream of reactor effluent water cooler 52- EE at a rate of 0.7 wt.% of pure caustic (compare to gas at reactor inlet). Estimated pure NaOH consumption per catalyst regeneration = 71,000 kg Catalysts Type : HR HR-945 Manufacturer : PROCATALYSE PROCATALYSE Quantity : Case 1 : 26.5 m m 3 Case 2 : 61.1 m m Catalyst HR Deep Hydrorefining of Petroleum Cuts HR presents very high denitrification and aromatic hydrogenation activities as well as desulfurization activity better than common NiMo catalysts. These features are particularly interesting in the treatment of feedstocks coming from thermal and catalytic conversion processes. It can be used in association with other NiMo type or CoMo type catalysts where specific objectives are required. HR is either delivered under oxide form to be sulfided in-situ, or presulfurized ex-situ by SULFICAT process. CHAPTER-1 DESIGN BASIS 11/27

12 TYPICAL PROPERTIES Nickel and molybdenum oxides on very high purity alumina Cylindrical extrudates Diameter 1.2 mm Nickel (NiO) 3.3 Wt% Molybdenum (MoO3) 16.5 Wt% Total pore volume 0.42 Cm3/g Sock loading density 0.72 Kg/l Dense loading density 0.82 Kg/l Bulk crushing strength 1.49 MPa Catalyst HR 945 Hydrotreatment of Cuts Containing Olefins HR 945 is a NiMo type catalyst to be used in front of hydrotreatment catalysts to protect them against deactivation by unsaturated compounds generally contained in cracked stocks. HR 945 special design limits the polymerization of olefins and diolefins and thus, the coke formation, even at low hydrogen partial pressure. The resulting advantage is longer cycle operation. It can be used in combination with any HR series catalysts. HR 945 is either delivered under oxide form to be sulfided in-situ, or presulfurized ex-situ by SULFICAT process. TYPICAL PROPERTIES Nickel and molybdenum oxides on very high purity alumina Spheres Diameter 2 to 4 mm Surface area 140 m2/g Total pore volume 0.4 cm3/g Tapped bulk density 0.88 kg/l Bulk crushing strength 1.55 mini. MPa Other Items CHAPTER-1 DESIGN BASIS 12/27

13 Absorbent Type : Puraspec 2110 Puraspec 2240 Manufacturer : ICI-Katalco ICI-Katalco Quantity : 1.9 m m Alumina Balls Type : Mullite or equivalent Quantity : 1/4 diameter Case 1 : 1.56 m 3 Case 2 : 2.02 m 3 3/4 diameter Case 1 : 2.08 m 3 Case 2 : 3.27 m Ceramic Balls Type : 1 ½ or 50 mm Quantity : 0.3 m BATTERY LIMIT CONDITIONS - PROCESS Operating Design Temp.( o C) Pressure (kg/cm 2 g) Temp.( o C) Pressure (kg/cm 2 g) Feed from storage Feed from CDU Feed from VDU Feed from VBU Feed from FCCU Make-up H2 (HGU) Makeup H2 (CRU) Sour Water Rich Amine Lean Amine Diesel to Storage Offspec Diesel Stabilized Naphtha Naphtha to Slop Spent Caustic Caustic Solution Sweet FG to RFCCU FO Supply FO Return Flare Header AMB ATM BATTERY LIMIT CONDITIONS - UTILITIES CHAPTER-1 DESIGN BASIS 13/27

14 1.9.1 Steam and Condensate Low Pressure Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature Medium Pressure o C Pressure Kg/cm 2 g Temperature o C Condensate Pressure Kg/cm 2 g Temperature o C Cooling Water Supply Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C Return Pressure Kg/cm 2 g Temperature o C CHAPTER-1 DESIGN BASIS 14/27

15 1.9.3 DM Water Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C Ambient Boiler Feed Water Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C Nitrogen Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C ambient Service/Plant Air Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C ambient 65 CHAPTER-1 DESIGN BASIS 15/27

16 1.9.7 Instrument Air Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C Dew Point at Atm. pressure = -40 o C Fuel Gas from B/L to Unit, from Unit to B/L Units Min. Normal Max. Mech. Design Pressure Kg/cm 2 g Temperature o C SITE DATA AND OTHER INFORMATION Reference Documents 1) Survey of India Maps 2) Meteorological Data Site Location 1 State where located Haryana 2 Nearest important town and distance Panipat 3 Nearest railway station and distance Panipat 4 Railway approach Gharonda 5 Nearest port - 6 Nearest airport and distance Delhi 7 Nearest highway milestone and distance NH-1 8 Approach road - Existing - Planned - From NH-1, 8 km CHAPTER-1 DESIGN BASIS 16/27

17 Geographical Data 1 Geographic bearing of site - 2 Height above mean sea level 238 M 3 Bench mark level and location Plate no.136, M.WL, Behind Canal Rest House at app. S and W co-ordinates 4 Site characteristics (Terrain Type) Flat land 5. Grade variation low point/high point m/ m Meteorological Data 1 Climate of area Moderate 2 Air Temperature Maximum/min. Dry bulb temperature Design dry bulb/wet bulb temperature Ambient Temperature max./min. 3 Rainfall Maximum recorded in 1 hour Maximum recorded in 24 hours Annual max./min./avg. Design intensity for surface 72 water drainage (MM/HR) 38.3 o C/6.8 o C 39 o C/27.5 o C 46.6 o C/(-)0.7 o C 72 mm 218 mm 705 mm/307 mm/ mm 4 Rainy season June - September 5 HFL data for last 20 years and maximum HFL recorded 6 Relative humidity Maximum 94% m Normal 19% CHAPTER-1 DESIGN BASIS 17/27

18 7 Wind velocity and direction - Wind velocity - Maximum 168 km/hr as a height of 30 mtr. - Wind direction and % age Mor. SE (28.4%) to NW (25.0 %), Eve. NW(35.5%)to SE (27.0 %) - Prevailing wind direction Mor SE to NW Eve NW to SE 8. Barometric Pressure - Maximum mb - Minimum mb - Average mb 9. Earthquake design As per IS:1893 Zone IV Site Grading Design HFL for grading : M Borrow area location/details : Across Western Jamuna Canal Proposed FGL : / / Roads and Pavements C.B.R. Value of soil: Drainage Storm water disposal point and distance : To main drain no. 2 at RD Approx. distance from refinery: 800M Water Supply Source of water : Munak head works Quality of water : Potable OPERATING CONDITIONS AND YIELDS CHAPTER-1 DESIGN BASIS 18/27

19 Estimated ex-reactor yields (% wt. of liquid HC feed) Feed 1 Description Case 1 Case 2 SOR MOR EOR SOR MOR EOR H 2 S NH C C C C C Total H 2 Chemical Consumption CHAPTER-1 DESIGN BASIS 19/27

20 Estimated ex-reactor yields (% wt. of liquid HC feed) (Contd.) Feed 2 Description Case 1 Case 2 SOR MOR EOR SOR MOR EOR H 2 S NH C C C C C Total H 2 Chemical Consumption CHAPTER-1 DESIGN BASIS 20/27

21 Operating conditions Reactor Feed 1 Description Case 1 Case 2 SOR MOR EOR SOR MOR EOR R01 inlet temperature, 0 C R01 outlet temperature, 0 C R01 WABT, 0 C Inlet pressure, kg/cm 2 g Outlet pressure, kg/cm 2 g R02 inlet temperature, 0 C R02 outlet temperature, 0 C R02 WABT, 0 C Inlet pressure, kg/cm 2 g Outlet pressure, kg/cm 2 g Space velocity H 2 recycle ratio, Sm 3 /m H 2 partial press., kg/cm 2 Minimum recommended CHAPTER-1 DESIGN BASIS 21/27

22 Reactor (Contd.) Feed 2 Description Case 1 Case 2 SOR MOR EOR SOR MOR EOR R01 inlet temperature, 0 C R01 outlet temperature, 0 C R01 WABT, 0 C Inlet pressure, kg/cm 2 g Outlet pressure, kg/cm 2 g R02 inlet temperature, 0 C R02 outlet temperature, 0 C R02 WABT, 0 C Inlet pressure, kg/cm 2 g Outlet pressure, kg/cm 2 g Space velocity H 2 recycle ratio, Sm 3 /m H 2 partial press., kg/cm 2 Minimum recommended Feed 3 (check Feed) : The operating conditions are the same as for Feed 2 except for space velocity which is increased by 10% due to the smaller flow rate. The Space velocity (LHSV) is the volume of liquid HC feed at 15 0 C in m 3 /hr divided by the volume of catalyst. The hydrogen recycle ratio is a measure of the hydrogen recycle through the furnace to the reactor entry. It is expressed as the standard m 3 /hr of pure H 2 recycled divided by the volume of HC liquid feed in m 3 /hr at 15 0 C. CHAPTER-1 DESIGN BASIS 22/27

23 The minimum hydrogen recycle ratio = 150 Sm 3 /m 3. The hydrogen partial pressure is measured at the reactor outlet. The minimum hydrogen partial pressure = 35 kg/cm Cold Separator Temperature, 0 C : 50 Pressure, kg/cm 2 g : Stripper Stripper feed temperature, 0 C : 262 to 265 Stripper reflux drum temperature, 0 C : 40 Stripper reflux drum Pressure, kg/cm 2 g : 5.0 Stripping ratio = Stripping steam (kg / h) : 22 to 24 Stripper feed (t / h) Reflux ratio: Feed 1 Feed 2 Description Case 1 Case 2 Case 1 Case 2 SOR EOR SOR EOR SOR EOR SOR EOR Reflux / feed (% wt) CHAPTER-1 DESIGN BASIS 23/27

24 ESTIMATED UTILITIES CONSUMPTION The following table gives estimated utility consumption for DHDS plant. S.No. UTILITY CONSUMPTION 1 Cooling Water, m3/hr Boiler Feed Water Unit, kg/hr D.M. Water, m3/hr. Intermittent use 4 Service Water, m3/hr Condensate flowrate(condensate pump) LP Steam consumed, kg/hr MP Steam Consumed, kg/hr Power Consumed, KW Fuel, MG Kcal./hr CHAPTER-1 DESIGN BASIS 24/27

25 1.13 ESTIMATED CATALYST, ALUMINA BALLS, CERAMIC BALLS, CONSUMPTION Catalysts Type : HR HR Manufacturer : PROCATALYSE PROCATALYSE Quantity : Case 1 : 26.5 m m 3 Case 2 : 61.1 m m Alumina balls Type : Mullite or equivalent Quantity : 1/4 diameter : Case 1 : 1.56 m 3 : Case 2 : 2.02 m 3 3/4 diameter : Case 1 : 2.08 m 3 : Case 2 : 3.27 m Ceramic Balls Type : 1½ OR 50 mm Quantity : 0.3 m 3 CHAPTER-1 DESIGN BASIS 25/27

26 ESTIMATED CHEMICALS CONSUMPTION Chemicals used during normal operation S. No CHEMICALS CONSUMPTION Kg/year REMARKS 1 Corrosion Inhibitor Antifouling 7,700 3 Antifoaming 2, Chemicals used during transient/catalyst regeneration operation S. No CHEMICALS CONSUMPTION Kg. REMARKS 1 DMDS 6,400 Consumption per catalyst sulfiding 2 Anhydrous Ammonia 580 Consumption per catalyst regeneration 3 NaOH (pure) 71,000 Consumption per Catalyst regeneration CHAPTER-1 DESIGN BASIS 26/27

27 WASTE EFFLUENTS Off-gases to Atmosphere Flue Gas from Fired Heater Continuous flow : About 4000 Sm3/h. H2S content depends on FG quality N2 Bleed during regeneration Once every 2 years. Duration : about 8 days Flow rate : Max. 615 kg/h Composition N2 : 91% wt. CO2: 7% wt Aqueous Effluent The sour water is the purge of the SWS unit Water from fired heater decoking Once every 4 years. Duration about 2 days. Content : Coke, SO2, H2S, NH Spent caustic during regeneration Once every 2 years. Duration about 8 days. Flowrate of water : 2440 kg/h content (NH4)2SO4 : 12 kg/h Na2CO3 : 210 Na2SO3 : 107 This spent caustic has to be sent to an oxidation plant with aeration by air in presence of catalyst to oxidize the sulfites in sulfates Waste Water during Sulfiding Once every 2 years. Duration about 8 hours. Flow rate : 270 kg/h, H2S content : Up to 0.2% wt. CHAPTER-1 DESIGN BASIS 27/27