Continuous process of sodium bicarbonate production by Solvay method

Transcription

1 Continuous process of sodium bicarbonate production by Solvay method Manual to experiment nr 10 Instructor: Dr Tomasz S. Pawłowski 1

2 Goal of the experiment The goal of the experiment is introduction of industrial, continuous process of sodium bicarbonate production by Solvay method. Experiment description Chemical, laboratory installation to sodium bicarbonate production by Solvay method is the model of industrial installation. It consists of two, main units: the tower where the brine (water saturated with sodium chloride) is being saturated by ammonia and the tower (carbonating column) where ammoniated brine is being saturated by carbon dioxide. Both reactors are connected to each other. During the sodium bicarbonate production process reactors are being fed continuously by: carbon dioxide, ammonia and brine. Continuous process demands the substrates feeding rate and the carbonating column temperature keeping on the stable level. Sodium bicarbonate suspension is periodically being collected, then filtrated and the chloride as well as ammonia concentrations in the filtrate have to be stable. Chloride and ammonia concentrations are controlling by means of the titration analysis. Experiment execution Before experiment execution put the protective apron, glasses (unless the correction glasses are worn) and the latex gloves on. Read the material safety data sheets (MSDS) of the substances used during experiment. Check the equipment status up, turn the lifts and electric slats on. 2

3 The numbering of the apparatus of the chemical installation describing in the manual is based on the scheme presented below: Legend: 1. Carbon dioxide cylinder, 2. Ammonia cylinder, 3. Carbon dioxide rotameter, 4. Ammonia rotameter, 5. Carbon dioxide manostat, 6. Ammonia manostat, 7. Peristaltic pump, 8. Graduated cylinder with brine, 9. Valve, 10. Valve, 11. Absorption column, 12. Valve, 13. Valve, 14. Carbonating column, 15. Motor stirrer, 16. Thermostat, 17. Valve, 18. Vessel with ammoniated brine. 3

4 1. Fill the both towers (nr 11 and 14) with the ammoniated brine from the vessel nr 18 to specified level. Use the peristaltic pump (nr 8) and rubber hose. During filling turn the water thermostat on (nr 16). 2. Prepare the burettes to all titration analysis (with NaOH, HNO3 and AgNO3 standard solutions), indicators (potassium chromate, methyl orange, phenolphthalein) and formaldehyde. Determine sodium chloride concentration in the brine according to the receipt below: Pipette 10 ml brine solution to 250 ml volumetric flask and fill up to the mark with distilled water. Then, from the solution obtained, take 5 ml to Erlenmeyer flask and add a little bit distilled water and a few drops of potassium chromate solution as indicator. The solution prepared titrate by 0.1 M AgNO3 to get brown colour of the precipitation. NaCl (G N C ) concentration calculate according to the formula: G N C v p g/l where: volume in ml of 0.1 M AgNO3 used to titration, correction with regard to indicator = 0.2 ml, 0.2 volume in ml of origin solution used to analysis ( 1/50 from 10 ml), amount in g of NaCl correspond with 1 ml of 0.1 M AgNO3. 3. After filling of both reactor columns by ammoniated brine turn the peristaltic pump and motor stirrer (nr 15) of carbonating column on. 4. Open the valve nr 10. Open valves (main and reducer valve) of the CO2 cylinder (nr 1). The value of CO2 flow should be defined, controlled on rotameter nr 3 and kept on the stable level. Write the hour of starting the carbonating process. 5. Prepare, label and weight three Erlenmeyer flasks and Petri dishes. Fit the kit to filter under low pressure. 6. After about one hour of carbonating process, when the white suspension of sodium bicarbonate is appeared in the carbonating column, put the labeled flask under tap, down of the carbonating column, open the valve nr 17 and let the suspension up to defined (marked) level. 7. Open valves (main and reducer valve) of the NH3 cylinder (nr 2). The value of NH3 flow should be defined, controlled on rotameter nr 4 and kept on the stable level. Turn the peristaltic pump on and start brine feeding of absorption column. Write to the table attached (see below on the pattern): the hour when the process has started and the brine volume in the graduated cylinder (nr 8). 4

5 8. At 10 minutes intervals through the valve nr 17, collect, by dropping the suspension up to marked level on carbonating column, three portions of it to Erlenmeyer flasks. Each portion cool in cold water, weight and then filter under low pressure. 9. Measure the filtrate volume and the mass of the wet sodium bicarbonate. All results write to the table. 10. From the filtrate of the last portion prepare basic solution which will be used to titration in order to determine the chloride and ammonia concentrations: Pipette 10 ml of filtrate to 250 ml volumetric flask and fill up to the mark with distilled water such prepared solution is basic solution to carry out all titrations described below. 11. Carry out three types of titrations: Determination of chloride and free and weakly bounded ammonia: Place 5 ml of the basic solution in Erlenmeyer flask and dilute with small amount of distilled water. Then titrate with 0.1 M HNO3 solution in the presence of the methyl orange (to the first change of colour) in order to determine free and weakly bounded ammonia. Then, to the same solution add a few drops of K2CrO4 solution and titrate with 0.1 M AgNO3 to get brown colour of the precipitation. Concentrations of the free and weakly bounded ammonia and chloride anions calculate from the below formulas. 5

6 Concentration of the free and weakly bounded ammonia (G NH, ): G NH, v g/l where: v volume in ml of 0.1 M HNO3 used to titration, amount in g of NH3 correspond to 1 ml of 0.1 M HNO3, 0.2 volume in ml of origin solution used to analysis ( 1/50 from 10 ml). Chloride concentration (G C ): v p G C 0.2 g/l where: v volume in ml of 0.1 M AgNO3 used to titration, p correction with regard to indicator = 0.2 ml, 0.2 volume in ml of origin solution used to analysis ( 1/50 from 10 ml), amount in g of chloride correspond with 1 ml of 0.1 M AgNO3. Determination the total concentration of ammonia: Pipette 5 ml Basic solution to Erlenmeyer flask. Neutralize with 0.1 M HNO3 in the presence of the metyl orange. Add 4 ml of 40% formaldehyde (before neutralized in the presence of the phenolphthalein) and leave for 1 minute to react. Then titrate the educed acid with 0.1 M NaOH in the presence of phenolphthalein to the pink color. Total concentration of ammonia (G NH,. ): G NH,. v g/l where: v volume in ml of 0.1 M NaOH used to titration, amount in g of NH3 correspond to 1 ml of 0.1 M NaOH, 0.2 volume in ml of origin solution used to analysis ( 1/50 from 10 ml). 12. After collection the last portion of sodium bicarbonate suspension turn the all cylinder valves (with CO2 and NH3) off. Empty and clean carbonating column. 13. Clean the laboratory equipment and make the laboratory stand ready to the next experiment. 14. On the basis of approved and signed table with results prepare the report of the experiment according to requirements below. 6

7 Report of the experiment should include 1. Goal of the experiment, 2. Experiment description: a) scheme of the apparatus, b) description of the operations performed and the conditions and parameters of the process, c) measurement results (results sheet). 3. Elaboration of the results: a) chemical equations, b) mathematical elaboration of the results obtained: Extent of sodium intake in two methods: a) as the ratio of number of NH4Cl moles in the final solution (filtrate) to initial number of NaCl moles (exist in the brine, in graduated cylinder): U N I G NH, G C 100 % where: G Cl chloride concentration in the filtrate, i 17 molar mass of chloride and ammonia, G NH3,zw bounded ammonia in the filtrate: G NH, G NH,. G NH, g/l 7

8 b) calculated from the weight efficiency of sodium bicarbonate (W): U N II G N HCO W 100 % where: G N HCO weight of dry sodium bicarbonate in [g/h], theoretical efficiency of sodium bicarbonate calculated by means of the formula: W S g/h where: NaCl amount introduced into the carbonization with the brine solution in [g/h], 84 and 58.5 molar mass of sodium bicarbonate and sodium chloride. Extent of utilization of ammonia ( ):,,. 100 % 4. Discussion of the results, 5. Conclusions. 8