Abstract
The main objective of this study was to evaluate the use of batch bubble column to produce high particle size (>300 micron) of sodium bicarbonate product to improve filtration and drying operations in the production process. Lab scale batch bubble column of 80 mm diameter and 0.5 m height was used to study the process for sodium bicarbonate production using 20% sodium carbonate solution as a starting solution. Three operating variables were considered, CO2 gas content (20-100 %), temperature (30-70 oC) and time (0.5-2.5 h). The bicarbonate yield and crystals size were considered to be the objective variables of the process. Response surface methodology (RSM) was used with central composite design (CCD) of experiments. Empirical polynomial multivariable equations were obtained. The reaction time was found to be the most effective operating condition on the yield of sodium bicarbonate, and temperature was found to be the most effective operating condition on crystal size of sodium bicarbonate. The optimum conditions achieved 400 microns particle size at temperature 70 oC and time 2.5 h. Kinetics study of the process showed that zero order reaction with both sodium carbonate and CO2 concentrations was approximately fitted the experimental data, useful for shortcut process design purposes.
Highlights
Sodium bicarbonate has many applications; animal feeds, paper industry, plastic foaming, water treatment, leather treatment, flue gas treatment, detergent and cleaning products, drilling mud to improve fluidity, fire extinguisher powder, human food products and domestic uses, and pharmaceutical applications.Sodium bicarbonate (NaHCO3) appears as an intermediate product in soda ash production, Solvay process
The main objective of this study was to evaluate the use of batch bubble column to produce high particle size (>300 micron) of sodium bicarbonate product to improve filtration and drying operations in the production process
It is produced from purified sodium carbonate rather than from purifying the intermediate, because of several reasons: the difficulty in drying the intermediate bicarbonate; the presence of a small amount of ammonia lead to be unfit for many uses; and containing many impurities in addition to ammonia [1]
Summary
Sodium bicarbonate (NaHCO3) appears as an intermediate product in soda ash (sodium carbonate) production, Solvay process. The production process of purified sodium bicarbonate is by the dispersion of a CO2 gas in a solution of purified soda ash (Na2CO3) with the following reaction equations [2]; CO2 (g) ↔ CO2 (l) (1) CO2 (l) + OH- ↔ HCO3- (2) HCO3- + OH- ↔ CO3-2 (3). The equilibrium between NaHCO3, Na2CO3 and CO2 depends on temperature, concentrations of carbonate and bicarbonate, and CO2 partial pressure over the solution. The process of production of the bicarbonate has a large number of complex physical and chemical phenomena; gas-liquid mass transfer, reaction, solid crystallization in two-component (sodium carbonate and sodium bicarbonate) solution in equilibrium, and three phase gas-liquid-solid hydrodynamics. Bubble column is the commonly used unit operations equipment for sodium bicarbonate production
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