Discharge and Reduction Procedures for Methanation Catalyst

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Methanation Catalyst …

Methanation Catalyst
VULCAN Series VSG-N101/102
SHUTDOWN
CATALYST DISCHARGE
NICKEL CARBONYL HAZARD
REDUCTION PROCEDURE

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  • 1. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com GBH Enterprises, Ltd. DISCHARGE AND REDUCTION PROCEDURES FOR METHANATION CATALYST Process Information Disclaimer Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the Product for its own particular purpose. GBHE gives no warranty as to the fitness of the Product for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability for loss or damage resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.
  • 2. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com VULCAN Series VSG-N101/102 SHUTDOWN During a plant shutdown, VULCAN Series VSG-N101 catalyst may be left under process gas for short periods, so long as the temperature remains between about 300o F and 750o F. Below 300o F there is a danger of nickel carbonyl formation, and the reactor must be purged with a gas that does not contain carbon monoxide. CATALYST DISCHARGE The catalyst is usually discharged without stabilization and care must be taken to ensure that air does not enter the reactor. Normally, it is adequate to ensure that only the catalyst discharge manhole is open and that a positive pressure of nitrogen is maintained in the vessel. The pyrophoric catalyst is usually drenched with water on discharge to eliminate the danger associated with overheating of the catalyst on reaction with air. If preferred, the methanator may be filled with water as soon as the catalyst temperature is below 200o F and the whole discharge carried out with the catalyst under water. NICKEL CARBONYL HAZARD Catalysts containing metallic nickel must not be exposed to gases containing carbon monoxide at temperatures below 302o F. Observation of this rule avoids the risk of the formation of nickel tetracarbonyl, Ni(CO)4, an extremely toxic, almost odorless gas which is stable at low temperatures. It is most likely to be formed in methanation reactors when the plant is cooled down, unless the system has been thoroughly purged with nitrogen.
  • 3. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com REDUCTION PROCEDURE FOR VULCAN SERIES VSG-N101 METHANATION CATALYST Reduction of this catalyst is simple, because it reduces easily without causing a temperature rise. The whole operation may be carried out using process gas as soon as the shift converter(s) and CO2 removal plant have been commissioned and are lined out. Pressurization may take place at any convenient stage in the reduction. 1. Purge the methanator of air with process gas, nitrogen, or natural gas. 2. The catalyst may be heated with process gas, nitrogen, or natural gas. It is advantageous to keep the heating rate below 100o F per hour so that any water that has been absorbed on the catalyst during storage is slowly removed without placing the catalyst under stress. 3. Reduction starts between 390o F and 480o F, and any carbon oxides in the gas will methanate simultaneously. The methanation reaction is exothermic. In hydrogen and ammonia synthesis gas streams, the temperature rise will correspond to 108o F for each 1% CO2 and 133o F for each 1% CO that are methanated. The concentration of carbon oxides in the gas, usually process gas, for the next stage of reduction should be below 1%. The inlet temperature must be controlled with care. It is usually better to lower the heating rate to about 50o F per hour. 4. Heating is continued until the inlet temperature reaches 650o F, if possible. However, the maximum temperature of the catalyst should not exceed 750o F. At the end of reduction, the temperature may be raised so that as much of the bed as possible is at 650o F - 700o F to make absolutely sure that maximum activity is achieved. CARBON OXIDE CONTENT In some plants the initial start-up sequence is to commission the methanator before the low temperature shift converter and to use the methanator product gas as the hydrogen source for the low temperature shift reduction. If a new methanator catalyst must be reduced in this way, using gas that is not passed through the low temperature shifter converter, it may not be possible to reduce the carbon oxides content below 1%.
  • 4. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com A reduction may be undertaken with higher carbon oxide contents in the reducing gas, but more careful temperature control is required. Normally it should be possible to establish operation in an inlet temperature of about 450o F. With a maximum outlet temperature of 750o F - 800o F, this represents a carbon oxide level of about 2.5%, equivalent to about 2% carbon monoxide in the high temperature shift exit gas. If this carbon oxide level is not obtainable by either reducing the gas rate or increasing the steam ratio in the high temperature shift converter, the low temperature shift catalyst should be commissioned before the methanator. NICKEL CARBONYL HAZARD Catalysts containing metallic nickel must not be exposed to gases containing carbon monoxide at temperatures below 302o F. Observation of this rule avoids the risk of the formation of nickel tetracarbonyl, Ni(CO)4, an extremely toxic, almost odorless gas which is stable at low temperatures. It is most likely to be formed in methanation reactors when the plant is cooled down, unless the system has been thoroughly purged with nitrogen.
  • 5. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com