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Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation
 

Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation

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Plant Analytical Techniques ...

Plant Analytical Techniques

Gas Analysis: Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation

SCOPE AND FIELD OF APPLICATION
This method is suitable for the in situ determination of hydrogen sulfide in ammonia plant gas streams when testing is required during catalyst reduction.

PRINCIPLE
Hydrogen sulfide present in the gas precipitates cadmium sulfide from a cadmium solution. The precipitate is filtered then reacted with iodine; the excess iodine is then titrated with sodium thiosulfate.

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    Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation Document Transcript

    • GBH Enterprises, Ltd. Plant Analytical Techniques Gas Analysis: Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation 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
    • GAS ANALYSIS: 1 Determination of Hydrogen Sulfide by Cadmium Sulfide Precipitation SCOPE AND FIELD OF APPLICATION This method is suitable for the in situ determination of hydrogen sulfide in ammonia plant gas streams when testing is required during catalyst reduction. 2 PRINCIPLE Hydrogen sulfide present in the gas precipitates cadmium sulfide from a cadmium solution. The precipitate is filtered then reacted with iodine; the excess iodine is then titrated with sodium thiosulfate. 3 REAGENTS During the analysis, use only reagents of analytical reagent grade, unless otherwise specified, and water which has been deionized and then distilled from an all glass apparatus, or water of equivalent purity. 3.1 Cadmium acetate solution, 2% m/v solution in 5% v/v acetic acid: Dissolve 2g of cadmium acetate dihydrate in 100 mL of 5% v/v acetic acid. CADMIUM ACETATE IS POISONOUS AND SHOULD BE REGARDED AS A CANCER SUSPECT AGENT (CARCIONOGEN). 3.2 Iodine, standard volumetric solution, C(I,)-0.10 mol/L. 3.3 Sodium thiosulfate, standard volumetric solution, C(Na2S2O3) = 0.10 mol/L. Hydrochloric acid (SG 1.18). 3.4 THIS REAGENT IS CORROSIVE AND CAUSES BURNS 3.5 Hydrochloric acid, 5 mol/L solution in water: Add 44.5 mL of hydrochloric acid (3.4) to 55.5 mL of water, mixing thoroughly. 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
    • 3.6 Starch indicator solution, 0.2% m/v: Add 40 mg of mercuric iodide to approximately 800 mL of water, and heat to dissolve. Mix 2.0 g of soluble starch to a thin cream with a small quantity of water and pour into the boiling mercuric iodide solution. Boil for two minutes, cool and dilute to 1L with water. THIS REAGENT SHOULD BE STABLE FOR SEVERAL WEEKS. 4 APPARATUS 4.1 Standard volumetric glassware, class A. 4.2 Absorption train consisting of two Dreschel bottles and a rotary gas meter. 5 PROCEDURE 5.1 Measure 30 mL of cadmium acetate solution (3.1) into one of the Dreschel bottles, and dilute to 100 mL with water. The second Dreschel bottle is employed as a moisture trap. 5.2 Purge the sample line and connect it to the Dreschel bottles. Allow the gas to pass through the cadmium acetate solution until a suitable quantity of precipitate has been formed. Pass approximately 100 L of gas. 5.3 Disconnect the apparatus and filter the precipitate through a No 31 filter paper, washing all the precipitate from the bottle onto the filter paper with cold water. Ensure that all the precipitate is transferred to the filter, then wash thoroughly with cold water. 5.4 Place in a 500 mL conical flask, 50.0 mL of iodine solution (3.2). 10 mL of hydrochloric acid solution (3.5) and 50 mL of water. 5.5 Transfer the filter paper retaining the precipitate of calcium sulfide to the conical flask and shake well until dispersion is complete. 5.6 Wash down the inside of the conical flask with water and titrate the excess iodine with sodium thiosulfate solution (3.3), adding a few drops of starch indicator solution (3.6) near the end point, indicated by the pale-straw color of the solution. 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
    • 6 EXPRESSION OF RESULTS 6.1 The hydrogen sulfide, expressed as ppm v/v, is given by the expression where V1 is the volume of iodine solution used for the determination (in mL; ie 50); V2 is the titre of sodium thiosulfate solution used in the determination (in mL); 1.2 is the volume (in mL) of hydrogen sulfide gas, at normal temperature and pressure, which corresponds to 1 ml, of a 0.1 mol/L solution of iodine: V3 is the volume of gas sample passed (in L). 7 NOTES 7.1 During sampling, the gas sample should not be hot as it comes into contact with the absorption system; a cooling coil (condenser) should therefore be incorporated into the sampling process. 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