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Determination of Oxygen in Anhydrous Ammonia
 

Determination of Oxygen in Anhydrous Ammonia

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Determination of Oxygen in Anhydrous Ammonia

SCOPE AND FIELD OF APPLICATION
This method is suitable for the determination of trace amounts of oxygen in Liquefied anhydrous ammonia.

The trace oxygen analyzer provides for trace oxygen analysis in decade steps ranging from 0 - 10 to 0 - 10,000 ppm v/v (full scale).

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    Determination of Oxygen in Anhydrous Ammonia Determination of Oxygen in Anhydrous Ammonia Document Transcript

    • GBH Enterprises, Ltd. Plant Analytical Techniques ANHYDROUS AMMONIA: DETERMINATION OF OXYGEN 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 information for its own particular purpose. GBHE gives no warranty as to the fitness of this information 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 personnel injury caused by or resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. 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
    • ANHYDROUS AMMONIA: 1 DETERMINATION OF OXYGEN SCOPE AND FIELD OF APPLICATION This method is suitable for the determination of trace amounts of oxygen in Liquefied anhydrous ammonia. The trace oxygen analyzer provides for trace oxygen analysis in decade steps ranging from 0 - 10 to 0 - 10,000 ppm v/v (full scale). 2 PRINCIPLE Liquid ammonia is vaporized by passing it through a stainless steel coil immersed in warm water. Oxygen diffusing into the fuel cell of the analyzer reacts chemically to produce an electric current which is proportional to the oxygen concentration in the gas phase immediately adjacent to the sensing surface of the fuel cell. The signal produced by the fuel cell from the trace oxygen is amplified by a two-stage solid state amplifier. 3 APPARATUS 3.1 Trace oxygen analyzer: a Teledyne Analytical Instruments, model 311-1, or similar, is suitable. This instrument is marketed in the UK by Analysis Automation Limited, and adapted for use with anhydrous ammonia. 3.2 Stainless steel coil: a minimum of 20' of 1/8" O.D. coiled to approximately 6” diameter is suitable. This coil is to be fitted at one end with Swagelok quick connect QC4-S-400 (1/4”) single end shut-off). The other connection to the coil should be a stainless steel compression fitting suitable for connection to the sample line. 3.3 Sample line: stainless steel reduced to 3/8” outside diameter, with a purge line and double isolation valves. 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
    • 4 CALIBRATION 4.1 Stand the analyzer (3.1) upright on a level surface, and with the range switch in the "OFF" position, check the alignment of the meter pointer with the zero mark on the scale. If necessary, make any adjustment using the screw on the face of the meter. 4.2 Set the range switch to the "CAL" position 4.3 Install the plastic tube equipped male disconnect fitting to either of the analyzer's sample ports and a blank disconnect fitting in the other port. 4.4 Gently suck air through the plastic tube using a hand aspirator and observe the meter reading. Continue to suck air through the tube until the reading is stable. 4.5 Unlock and adjust the span control until the meter pointer is in coincidence with the "CAL" mark on the meter scale. 4.6 Immediately after stage 4.5 has been accomplished, connect a source of inert gas, containing only a trace amount of oxygen, and allow to purge at 5L/min until the reading obtained is at a very low level (~10 ppm v/v). An overnight purge may be required to obtain this low level. 5 Procedure 5.1 Purging 5.1.1 Before proceeding with a determination of oxygen in ammonia, purge with an inert gas down to at least 1.0 ppm v/v, using a purge rate of 5L/min 5.1.2 When a satisfactorily low oxygen level is achieved, withdraw the disconnect fittings rapidly, ensuring that the purge gas supply line is the first to be removed. The fuel cell should not be subject to excessive pressure since leaks in the cell manifold may result. 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
    • 5.2 Analysis 5.2.1 Connect the coil (3.2) to the sample point with a suitable stainless steel compression fitting, and immerse in a container of warm water. 5.2.2 Carefully open the isolation valve, and purge the sample line (3.3) and coil (3.2) free of air. 5.2.3 Establish a flow rate of approximately 5L/min, using a suitable flow-meter such as a rotameter, and continue the purging for a few minutes to ensure that the system is delivering a representative sample of vaporized ammonia. 5.2.4 Connect the disconnect fittings to the analyzer, and ensure that the vent line is fitted before the ammonia line, but with a minimum time elapsing between the two connections. 5.2.5 A satisfactory result can be expected within 15 minutes of starting to pass ammonia, if all connections have been made correctly. Periodically change the warm water in which the coil (3.2) is immersed, such that an effective temperature for the vaporization of ammonia is maintained. The response of the fuel cell to oxygen is likely to be very slow at these low levels of oxygen A direct reading for oxygen in ppm v/v will ultimately be obtained. 5.2.6 When the determination is complete, ammonia should be purged from the instrument using an inert gas. 6 Expression of Results The oxygen in anhydrous ammonia, expressed as ppm m/m is given by the expression 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
    • Where C is the reading for oxygen concentration, obtained directly from the analyzer (in ppm v/v); 32 is the relative molecular mass of oxygen; 17 is the relative molecular mass of ammonia. 7 Notes 7.1 An 3/8” Ermeto coupling is suitable for the connection from the coil to The sample line. 7.2 Nitrogen is generally used as the inert gas for purging purposes. 7.3 Carbon dioxide should never be used for purging the analyzer, since the fuel cell life would be drastically reduced. 7.4 The rapid withdrawal of the disconnect fittings may be assisted if the operator wears a pair of rubber gloves, which ensures a better grip in the confined space around the connections. 7.5 During the ammonia analysis, it is advisable to ensure that a supply of warm water is situated close to the sample point. Longer periods of effective sampling may then be employed. 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
    • 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