Is there a method for analyzing liquid ammonia projects?
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The company needs to purchase a batch of liquid ammonia, and it is necessary to conduct analyses for ammonia content, moisture, oils, and residues. I have no experience in conducting such analyses at all; could anyone who is familiar with this process offer some guidance? !
Liquid ammonia – 1. Scope of application: This method is applicable to the testing of liquid anhydrous ammonia that is directly synthesized by the catalytic combination of hydrogen and nitrogen under high temperature and pressure. II. Appearance, Properties, Molecular Formula: This product is a colorless liquid at low temperatures; it has a strong pungent odor and is volatile. Its molecular formula is NH3. III. Technical Requirements: Parameter | Specification NH3 content % ≥ 99.9 Moisture % ≤ 0.10 Oil content, mg/kg ≤ 5 IV. Testing Methods 1. Determination of moisture content – volumetric method 1.1 Principle of the method: Liquid ammonia is allowed to volatilize naturally at room temperature. A standard sulfuric acid titrant is then used to react with the remaining NH3 in the residue. The moisture content is determined by subtracting the amount of ammonia remaining in the residue from the total amount of residue present. 1.2 Reagents 1.2.1 Standard sulfuric acid titration solution: C(1/2H2SO4) = 0.1 mol/L or C(1/2H2SO4) = 1.0 mol/L 1.3 Instruments 1.3.1 Lysenko container: total volume of not less than 200 ml, with a scale division of 10 ml in the upper part and a volume of 1.0 ml in the lower tube, and a minimum scale division of 0.05 ml. 1.4 Analysis steps 1.4.1 Open the sampling valve, release a portion of the liquid ammonia first, then place the Lysenko container at the sampling valve and quickly collect 200 ml of sample (this should be completed within 1 minute). 1.4.2 Place the sample in a fume hood, cover the mouth of the container with a rubber stopper having a hole in it (to prevent dust from contaminating the sample as the liquid ammonia evaporates), and allow the liquid ammonia to evaporate at room temperature. Once evaporation is complete (i.e., when no more bubbles appear in the container), hold the bottom of the container by hand until no gas escapes from the remaining liquid. Record the volume V1 of the remaining liquid in the Lysenko container; then pour all of it into a 250 ml beaker. Wash the container several times with water until the wash water becomes neutral, and add this wash water to the beaker. Add 2–3 drops of methyl red indicator, and titrate with standard sulfuric acid solution until the solution changes from yellow to slightly pink. Record the volume V2 of the standard sulfuric acid solution used in the titration. 1.5 Calculation of results: The moisture content X1 (%) is calculated using the following formula: X1 = 0.72 × V1 – 0.00167 × V2. Here, V1 represents the volume of residual liquid in the Lysenko container, in ml; V2 represents the volume of the standard sulfuric acid solution used, also in ml. The values 0.72 and 0.00167 are coefficients determined by the laboratory. (When using a standard sulfuric acid titrant with C(1/2H2SO4) = 1.0 mol/L, the value 0.00167 in the experimental coefficients should actually be 0.0167.)
1.6 Allowable deviation: The analytical result is taken as the arithmetic mean of the results of two parallel measurements, and the absolute difference between these two results should be less than 0.02%.
1.7 Notes: 1.7.1 No open flames should be present in the vicinity when liquid ammonia is evaporating, to avoid explosions. 1.7.2 Safety protective equipment should be worn when sampling, including a gas mask and cotton gloves. 2 Determination of ammonia content-----Calculation method 2.1 Principle of the method The ammonia content is obtained by subtracting the percentage of moisture in the liquid ammonia residue from 100. 2.2 Calculation of results The ammonia content X2 (%) is calculated using the following formula: X2 = 100 – X1, where X1 represents the residue (water) content, in %. 3 Determination of oil content – Gravimetric method 3.1 Principle of the method After evaporating the liquid ammonia, carbon tetrachloride is used to extract the oil from the residue; the mass of the remaining residue is then measured to determine the oil content. 3.2 Reagents 3.2.1 Carbon tetrachloride (CCl4): AR 3.2.2 Salt acid solution: 10% 3.2.3 Methyl red indicator: 1 g/L 3.3 Instruments: 3.3.1 Constant temperature water bath: capable of maintaining a temperature of 80–90°C 3.3.2 Constant temperature drying oven: capable of maintaining a temperature of 110°C 3.3.3 Lysenko container: 500 ml 3.4 Procedure: Take 500 ml of the sample into a Lysenko container, place it in a fume hood, and cover it with a rubber stopper having holes. Wait until the liquid ammonia has evaporated completely so that no gas is released anymore. Then use 10 ml of CCl4 to transfer the gasoline adhering to the walls of the container into a beaker that has been dried at 110°C until its weight remains constant. Wash the container twice more using 20 ml of CCl4 each time; combine the wash liquids in the beaker. Heat the beaker in an 80–90°C water bath until all the liquid has evaporated, then place it in an oven at 110°C for 30 minutes. After that, take it out and let it cool in a desiccator for 30 minutes before weighing it. Repeat this process until the weight of the beaker remains constant, with the accuracy reaching 0.0002 g. Result calculation: The oil content X3 (mg/kg) is calculated using the following formula: (m2 – m1) × 10^6 / X3 = V0 × 0.682. Where: m1 is the mass of the empty beaker, in g; m2 is the mass of the beaker together with the oil, in g; V0 is the volume of the sample, in ml; 0.682 is the density of liquid ammonia at its boiling point (-33.5°C), in g/cm3. The allowable tolerance is such that the arithmetic mean of the results of two parallel measurements shall be used as the analytical result, with the absolute difference between the two results not exceeding 0.5 mg/kg. 3.7 Notes 3.7.1 If obvious impurities remain after extracting the oil using carbon tetrachloride, it must be filtered through filter paper before evaporation. 3.7.2 If there are iron filings in the sample, 15 ml of 10% hydrochloric acid solution should be added first before adding carbon tetrachloride. The mixture is then transferred to a separatory funnel, shaken and allowed to settle so that the layers separate; subsequently, the carbon tetrachloride is poured into a beaker that has reached a constant weight. 3.7.3 Take another 30 ml of carbon tetrachloride in a beaker, and determine its residue content using the same procedure as for the sample; then subtract this residue content from the analysis results. 3.7.4 When sampling, care should be taken to wipe clean the oil residue at the sampling valve opening, and to drain it thoroughly before sampling.
1.6 Allowable deviation: The analytical result is taken as the arithmetic mean of the results of two parallel measurements, and the absolute difference between these two results should be less than 0.02%.
1.7 Notes: 1.7.1 No open flames should be present in the vicinity when liquid ammonia is evaporating, to avoid explosions. 1.7.2 Safety protective equipment should be worn when sampling, including a gas mask and cotton gloves. 2 Determination of ammonia content-----Calculation method 2.1 Principle of the method The ammonia content is obtained by subtracting the percentage of moisture in the liquid ammonia residue from 100. 2.2 Calculation of results The ammonia content X2 (%) is calculated using the following formula: X2 = 100 – X1, where X1 represents the residue (water) content, in %. 3 Determination of oil content – Gravimetric method 3.1 Principle of the method After evaporating the liquid ammonia, carbon tetrachloride is used to extract the oil from the residue; the mass of the remaining residue is then measured to determine the oil content. 3.2 Reagents 3.2.1 Carbon tetrachloride (CCl4): AR 3.2.2 Salt acid solution: 10% 3.2.3 Methyl red indicator: 1 g/L 3.3 Instruments: 3.3.1 Constant temperature water bath: capable of maintaining a temperature of 80–90°C 3.3.2 Constant temperature drying oven: capable of maintaining a temperature of 110°C 3.3.3 Lysenko container: 500 ml 3.4 Procedure: Take 500 ml of the sample into a Lysenko container, place it in a fume hood, and cover it with a rubber stopper having holes. Wait until the liquid ammonia has evaporated completely so that no gas is released anymore. Then use 10 ml of CCl4 to transfer the gasoline adhering to the walls of the container into a beaker that has been dried at 110°C until its weight remains constant. Wash the container twice more using 20 ml of CCl4 each time; combine the wash liquids in the beaker. Heat the beaker in an 80–90°C water bath until all the liquid has evaporated, then place it in an oven at 110°C for 30 minutes. After that, take it out and let it cool in a desiccator for 30 minutes before weighing it. Repeat this process until the weight of the beaker remains constant, with the accuracy reaching 0.0002 g. Result calculation: The oil content X3 (mg/kg) is calculated using the following formula: (m2 – m1) × 10^6 / X3 = V0 × 0.682. Where: m1 is the mass of the empty beaker, in g; m2 is the mass of the beaker together with the oil, in g; V0 is the volume of the sample, in ml; 0.682 is the density of liquid ammonia at its boiling point (-33.5°C), in g/cm3. The allowable tolerance is such that the arithmetic mean of the results of two parallel measurements shall be used as the analytical result, with the absolute difference between the two results not exceeding 0.5 mg/kg. 3.7 Notes 3.7.1 If obvious impurities remain after extracting the oil using carbon tetrachloride, it must be filtered through filter paper before evaporation. 3.7.2 If there are iron filings in the sample, 15 ml of 10% hydrochloric acid solution should be added first before adding carbon tetrachloride. The mixture is then transferred to a separatory funnel, shaken and allowed to settle so that the layers separate; subsequently, the carbon tetrachloride is poured into a beaker that has reached a constant weight. 3.7.3 Take another 30 ml of carbon tetrachloride in a beaker, and determine its residue content using the same procedure as for the sample; then subtract this residue content from the analysis results. 3.7.4 When sampling, care should be taken to wipe clean the oil residue at the sampling valve opening, and to drain it thoroughly before sampling.
I have conducted impurity analysis in 6N-grade high-purity ammonia for Suzhou Linde.