DIESEL HYDRODESULPHURISATION UNIT CHAPTER-9 CATALYST AND REGENERATION

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1 CHAPTER-9 CATALYST AND REGENERATION 9.1 MANUFACTURER: HR 945 and HR-348 are manufactured by PROCATALYSE : In their facilities located at Salindres France. PROCATALYSE Head Office Address : 212/216 Av. Paul Doumer RUEIL MALMANISON FRANCE TEL. (1) FAX (1) CATALYSTS SPECIFICATIONS HR-945 HR 945 is a NiMo type catalyst to be used in front of hydro treatment 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 m 2 /g Total pore volume 0.4 cm 3 /g Tapped bulk density 0.88 kg/l CHAPTER-9 CATALYST AND REGENERATION 1/10

2 9.2.2 HR-348: HR-348 is a NiMo type catalyst used for the hydrodesulfurization, dearomatization and hydrodenitrification of hydrocarbons cuts including gasolines, naphthas, kerosenes, gas-oils and vacuum gas-oils. HR-348 has a very high hydrodesulfurization activity and stability which makes it attractive for deep desulfurization. HR-348 can be used in association with NiMo or CoMo type catalyst where specific objectives are required. HR-348 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. Cylindrical extrudates Diameter 1.2 mm Nickel (NiO) 3.3 wt % Molybdenum (MoO3) 16.5 wt % Total pore volume Sock loading density Dense loading density Bulk crushing strength 0.42 cm3/g 0.72 kg/l 0.82 kg/l 1.49 Mpa 9.3 PACKAGING, HANDLING AND STORAGE HR 945 Delivered in steel drums 217L net 130 kg HR 348 Delivered in steel drums 217 L net 130 kg Or in 1500L big bags (net 800 kg) CHAPTER-9 CATALYST AND REGENERATION 2/10

3 Handling Recommendations : Drums must be handled with care to avoid catalyst breakage. The drums must not be rolled and must not be allowed to fall. Rain, snow, sand can damage the catalyst and its containers. Therefore, adequate shelter for the catalyst during storage, transport and loading must be arranged. Before loading operation, the catalyst loading equipment must be safely installed and checked ready for operation. Reactors and internals must be previously inspected for dimension conformity and cleanliness. During catalyst loading and unloading operations personnel must take the following precautions: Outside the reactors, wear dust mask, protective clothing, goggles, gloves and helmet. Inside the reactors for a short period, wear a safely harness. A second man must be in attendance near the top of the reactor. As a general, man entry is given into a vessel when the atmosphere has been proven suitable and all vessel nozzles are blinded. In addition person working in the reactor during the catalyst loading must wear air mask covering the face and other safety harnesses. 9.4 SULPHURIZATION OF CATALYSTS Sulphurization Reactions The metals of the catalyst are in the oxide form, thus, they must undergo a treatment to recover the active sulfide form. This is the purpose of the sulfurization. This operation consists in sweeping the catalyst with a stream, which contains enough DMDS (dimethyl disulfide) or other sulfiding agent to sulfurize the catalyst. DMDS decomposes into H2S which sulfurizes the catalyst metals according to the following reactions : DMDS decomposition (dimethyldisulfide) CH3-S-S-CH3+2H2 2CH4+2H2S CHAPTER-9 CATALYST AND REGENERATION 3/10

4 Sulfurization of molybdenum oxide MoO3 +2H2S + H2 - MoS2 + 3 H2O Sulfurization of the nickel oxide 3 NiO + 2 H2S + H2 - Ni3S2 + 3 H2O The total amount of DHDS required is 6000 kg Sulfurization Procedure : The sulfurization procedure is already described (Refer to section First startup/catalysts sulfurization start-up of reaction section/sulfurization of catalysts.) The total amount of DMDS is injected in about 16 hours. However this period can be longer if the DMDS injection flow rate has to be reduced for any reason. The main steps are: - Injection of DMDS in the inert start-up feed. The minimum temperature required for the thermal decomposition of dimethyldisulfide, to produce the sulfurization agent (H2S) is 150 C. It is recommend to start the DMDS injection at C. - A temperature step at C till a significant amount of H2S appears in the recycle gas (> 0.1% volume) - A high temperature step maintained at 350 C during 12 hours at least. - The reactor temperature is then decreased to the SOR temperature. Note that hot hydrogen must never be circulated without hydrogen sulfide on the catalyst. If it occurs the catalyst could be desulphurized. Should such a situation arise, decrease the reactor inlet temperature down to 200C. 9.5 CATALYST REGENERATION During the run, catalyst deactivates and the End of Run conditions are achieved when, at maximum temperature on the reactor, the product specification are not met or when the pressure drop on the reactor does not CHAPTER-9 CATALYST AND REGENERATION 4/10

5 allow a sufficient recycle gas flow rate. This deactivation is the result of coke deposition. The activity of catalyst is recovered by burning the coke. It can be done. In situ by means of air nitrogen mixture at controlled oxygen concentration and temperature. Ex situ after catalyst unloading under inert atmosphere In Situ Regeneration : Once unit is shutdown, the status of unit is : Reaction section under nitrogen. Reactor RB-101 temperature <40C Recycle gas compressor KA-102 and make-up compressor KA-101 A/B under nitrogen and isolated. Feed surge drum V-101 & feed pump P-101 A/B isolated. Stripper C-101 isolated from reaction section. The line-up the regeneration circuit, the following actions have to be taken: Disconnect stripper feed preheater E-103 A/B (tube side) and E-101 A/B/C/D/E using dedicated regeneration line and by-passing the exchangers. Connect ammonia injection line to reactor effluent. Install the regeneration static mixer JA-103 Fit one wash water pump P-102 A/B suction to the caustic tank T-105 and related discharge to the static mixer, the other wash water pump shall be in wash water circuit which could be used for possible deplugging of the air cooler EA-101 A/B/C/D. Turn the flare header which releases from reaction section to safe atmosphere or to furnace stack., to avoid possible oxygen presence into the flare header. air to make-up compressor KA-101 A/B suction which is able to work with nitrogen or plant air. Connect plant air to make-up compressor KA-101A/B suction, which is able to work with nitrogen or plant air. CHAPTER-9 CATALYST AND REGENERATION 5/10

6 The regeneration circuit is ready, all regeneration steps here below explained: a) Follow procedure of air freeing and make sure that the circuit is free of oxygen. b) Start make-up compressor KA-101 A/B with nitrogen and pressurize the reaction system up to 5 kg/cm 2 g. Circulate nitrogen with the recycle gas compressor KA-102. Collect samples to be sure that circulating gas contains less than 0.2% hydrogen and hydrocarbons and is oxygen free. c) Increase pressure at recycle compressor KA-102 suction up to 17 kg/cm 2 g, attention should be provided to the temperature increasing through the make-up compressor KA-101 A/B. If its discharge temperature increases beyond 150C reduce discharge pressure by reducing the operating pressure at the separator. Maintain this pressure throughout the regeneration by bleeding to atmosphere the excess of the flue gas or adding nitrogen as required. Circulate nitrogen at maximum possible rate. d) Put in service the oxygen analyzer to monitor the oxygen concentration at reactor inlet. e) Light the furnace F-101 and raise the reactor RB-101 inlet temperature up to 315C. Do not exceed a heating rate of 20C/h f) When the reactor RB-101 inlet temperature is 315 C and all bed temperatures are at least 260C, switch the make-up compressor KA- 101 A/B suction from nitrogen to air. Since this is the first introduction of air, it should be slow and all temperatures in the reactor are observed closely. Air rate should be slowly increased until a concentration of 0.5% oxygen by volume in the reactor inlet gas is reached. g) As soon as air is introduced in the system, acid gas will be formed. To protect against trace quantities of SO3, which may be formed, ammonia should be injected into the exchanger E-102 A/B near the reactor outlet. Ammonia injection rate should be set at 100ppm wt. (about 3 kg/h). At this stage the caustic scrubbing of the effluent gas to remove SO2 is started caustic scrubbing should be done on a oncethrough basis using a 10% sodium hydroxide solution at a rate of about 2200 kg/h. The caustic scrubbing rate has been set so as to wash all the SO2 and part of CO2 gases out of the effluent stream. Adjust CHAPTER-9 CATALYST AND REGENERATION 6/10

7 caustic injection flow rate checking SO2 absence in the recycle gas. Resulting spent caustic ph should be in the range of To avoid the possibility of caustic embrittlement, the caustic solution injection is made downstream the effluent air cooler EA-101 A/B/C/D and good contact with the reactor effluent gas is ensured by the static mixer JA-103. Regulate effluent air cooler performance to have a maximum Cold separator V-103 temperature of 55C. h) Control the reactor RB-101 inlet temperature by-passing of E-102 A/B, check that the temperature at air cooler inlet is >180C, otherwise control this temperature by increasing E-102 A/B by-pass flow rate and control the inlet temperature increasing the heater firing rate. i) Caustic scrubbing and ammonia injection are continued as long as SO2 is detected in the reactor RB-101 effluent and for an additional 8 h after SO2 concentration drops to zero. Evolution of SO2 may stop until the second or third burn. The recycle gas should be checked for SO2 at regular intervals to confirm that a complete removal has been achieved. j) Watch for possible pressure drop building-up in the exchangers (mainly in the air cooler) due to ammonium bicarbonate deposition. If any pressure drop increase is noted, start injecting wash water as required to dissolve the salts from the system. k) At 315C reactor inlet temperature and 0.5C volume of oxygen, maximum catalyst temperature should not cross 370C. Watch temperature closely. During this time; make analysis of the oxygen content of the inlet gas. Also, make sure that the maximum volume of recycle gas is being circulated. l) Slowly increase air rate until the oxygen content at the reactor RB-101 inlet reaches 0.7% volume. At 330C reactor inlet temperature and 0.7% volume of oxygen, maximum catalyst temperature should not cross 410C. If temperature goes beyond over 430C, reduce air rate. If 450C reached, cut out air completely until all temperatures are below 410C. Check the oxygen content and analyzer reliability because a temperature rise of over 120C with only 0.7% volume of oxygen probably indicates a faulty analysis result. m) Hold the reactor RB-101 inlet temperature at 330C-355C until the first burning wave has passed through all the catalyst beds. This is indicated by all bed temperatures having passed through peaks and by decreasing temperatures at outlet of the Reactor RB-101. CHAPTER-9 CATALYST AND REGENERATION 7/10

8 n) At about the time the first burning wave has passed through both catalyst beds, oxygen begins to appear in the reactor effluent gas. Reduce the air rate to prevent a build-up of oxygen concentration in recycle gas. o) After this first burning wave has passed through the Reactor RB-101, reduce the air injection and raise the reactor inlet temperature to about 15C/h according to the following schedule. If a second burning wave develops, stop raising temperature and stay below maximum temperature limits above. Reactor inlet temperature C Maximum inlet oxygen % volume p) When the Reactor RB-101 inlet temperature is 455C and all bed temperatures reach a minimum of 425C, slowly increase air rate until oxygen concentration is 0.7% volume at Reactor RB-101 inlet if any temperatures start to rise, reduce air promptly. q) Hold 455C as Reactor RB-101 inlet temperature and 0.7% volume oxygen concentration for about 6 hours. r) Then burning is completed if all the three following conditions are met. 1) Oxygen is no longer consumed. This is indicated by the progressive reduction of air injection down to zero to maintain the same oxygen concentration in the circuit. 2) CO2 is no longer produced. This is indicated by the progressive reduction of caustic injection to maintain the same temperature at separator. 3) There is no longer a temperature rise across any catalyst bed. s) Shut of ammonia, and caustic injection, switch the make-up compressor KA-102 suction to nitrogen which is used to maintain Reactor RB-101 pressure. t) Reduce Reactor RB-101 inlet temperature down to 260C reducing heater 52-FF firing rates. Continue to recycle the nitrogen flue gas mixture until all bed temperatures are C. This cool down rate should be set by mechanical design considerations for the Reactor CHAPTER-9 CATALYST AND REGENERATION 8/10

9 RB-101 and flanges. During this period, inject wash water into the Reactor RB-101 effluent stream upstream the effluent air cooler EA- 101 A/B/C/D to flush caustic from circuit. u) When all temperatures are below 230C stop the wash water injection and drain water from all low points of the circuit. v) Continue to cool down the Reactor RB-101 with nitrogen circulation until the Reactor RB-101 temperatures are lower than 40C. Depressurize the circuit, open it and disconnect all regeneration facilities. Follow the preliminary operation for new start-up Ex-situ Regenration Catalyst Unloading : The used catalyst is pyrophoric and contact with air should be avoided, the catalyst should be unloaded under nitrogen in drums (or bins) and sent to an outside company for regeneration. The unloading will be done by a specialized contractor able to work in inert atmosphere with air masks. Before unloading, the Reactor RB-101 should be cooled down to 40C. The unit is shutdown. The status of the unit is with reaction section under nitrogen. The recycle gas compressor KA-102 is used to circulate nitrogen and cool down the Reactor RB-101. This operation will take a long time using the normal circuit due to the recycle gas compressor discharge temperature and the exchangers. A solution to speed up this operation is to create a temporary bypass of this exchanger, straight from recycle gas compressor to the heater inlet. An alternate is to ask a special contractor to cool down the Reactor RB-101 between 100C and 50C by a subcooled nitrogen flow. When the temperature are down to <50C, connect nitrogen hoses to different points of the Reactor RB-101 to prevent any air entry and isolate the reactor form the rest of the unit by blinds. Catalyst is stored in steel drums (or bins) with a plastic bag liner after air freeing by a nitrogen sweep. During the catalyst unloading, the oxygen content of the reactor atmosphere is continuously checked and the operation is stopped if O2% vol. >5% CHAPTER-9 CATALYST AND REGENERATION 9/10

10 When the Reactor RB-101 is empty, to prevent any risk of polythonic corrosion some refiners wash the vessel with a sodium ash solution (2% wt. Na2CO3 in water containing less than 10ppm chlorine). This is not mandatory when stabilized material by Nobium Titanium is used Coke burning for waste disposal: When the catalyst is at end of life it has to be unloaded for waste disposal. To facilitate this unloading and manipulation, the coke is burnt on the catalyst. CHAPTER-9 CATALYST AND REGENERATION 10/10