If mother liquor L is supplied

If mother liquor L is supplied to evaporator E without preheating, that is at t = t = 0 °C, consumption of heat in the evaporator is high and the bace inhibitors ratio of the compressor reaches very high values of n = 40–45 (Fig. 7a). Failure to preheat mother liquor leads to a significant increase in the power of the compressor per unit mass of solution (Fig. 7b). Lower than 70 °C, compression ratio rapidly decreases with increase in temperature of mother liquor and at higher temperatures the change in compression ratio with increase in temperature is small. Aybar (2002) concluded that the minimum temperature at which water should be fed into the evaporator is 75 °C as latent heat of condensation of steam does not give enough heat for evaporation at lower temperatures. Lower temperatures lead to a larger temperature difference between compressed superheated steam and mother liquor in the evaporator. According to Zhou et al. (2014), larger temperature difference leads to a higher compression ratio and subsequently higher energy consumption by the compressor. High power consumption reduces the energy efficiency of the process. At t below 10 °C, performance coefficient is extremely low, in the range ε = 1.5–1.7 (Fig. 8). Performance coefficient at temperatures of mother liquor above 70 °C rises rapidly with increase in temperature. For a 55% w/w concentrated solution, performance coefficient is double that of 75% w/w concentrated solution with t above 80 °C. An increase in concentration of concentrated waste steam leads to an increase in the pressure ratio. This is as a result of the effect of boiling point elevation (Han et al., 2015).
Conclusion Production of KNO3 through conventional methods with subsequent purification through recrystallization with solvent recovery and incorporation of mechanical vapor compressor is energy efficient and it presents good economic prospects. Analysis has shown that in the considered design, the performance coefficient, depending on the temperature of mother liquor, is between 1.5 and 7.5. Without pre-heating mother liquor, COP is very low. Above 80 °C, power consumption by the compressor is low and COP is higher than 4. Concentration of mother liquor influences solvent recovery through elevation of boiling point. A more concentrated mother liquor boils at a higher temperature than a pure solvent and thus consumes more power. As a result, other than preheating mother liquor, the rise in power consumption as a result of boiling point elevation should be minimized through other methods. In instances where KNO3 concentration is high and impurities are low, recirculation of mother liquor can be considered whereas if concentration of impurities is high, an additional crystallizer and separator to reduce concentration of impurities before solvent recovery can be installed.
Acknowledgement
Introduction Water pollution is a major problem in the world. As per the UN, approximately 40% of the world\'s population of more than two billion people face water shortage. In 2025, this may be increased to 5.5 billion or more than 2.5 times. Chemical industry, especially pharmaceutical industry is at the forefront of the water management task, because of growing government pressure on effluent discharge, raw water usage, increasing process water prices and in various places, general lack of available water. Recent progress in chemical analyses has resulted in the detection of a large number of pharmaceutical and personal care products in aquatic environments (Kaplan, 2006; Oulton et al., 2010). Pharmaceutical and personal care products are a varied group of synthetic trace organic compounds that have been received widespread attention, as they are worldwide, determined, and have endocrine disruption potential in aquatic organisms (Rahman et al., 2009). Among pharmaceutical and personal care products, antibiotics are of concern as of their possible effects on natural ecosystems and the development of pathogen resistance to antibiotics (Liu et al., 2015). After their use, these substances are usually excreted only partially metabolized and end up in the variety of pharmaceuticals have been reported to be existing in surface water and effluent of sewage treatment plants (STPs) showing their poor biodegradability in municipal sewage and STPs (Kümmerer, 2003). Because of their toxicity to various microorganisms, low microbial elimination effectiveness is particularly expected for antibiotics and many countries control the level of antibacterial residues in agricultural, veterinary, dairy, and meat based food products.