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In this work, a two-stage packed bed scrubber was designed and optimized for purification of industrial waste gas containing ammonia at a concentration of 1400 mg m-3. Basic material balance equations, equilibrium data, and the generalized pressure drop correlation were used for the calculation. For the analysis of different configurations, Katmar software was utilized, which uses the generalized pressure drop correlation in order to calculate the scrubber diameter based on the allowable pressure drop and proximity to flooding conditions. It was found that optimal results are achieved in a two-stage device, using 70 vol.% sulfuric acid for chemisorption of ammonia. Pall rings, 50 mm in size and made of polypropylene, were selected as a column packing. Performances of scrubbers of three column diameters (i.e., Dc=2; 2.1 and 2.2 m) were analyzed. From the aspect of the liquid phase flow, the column diameter of 2 m provides satisfactory results. According to the packing specifications, the pressure drop through the packing layer would be about 900 Pa. It was found that the pressure gradient, and therefore the total pressure drop in the column decreases with increasing the column diameter. However, as the diameter of the column increases, the minimum flow rate of the liquid phase required to wet the packed bed increases, so the required liquid flow rate increases. Taking into account all of the analyzed process parameters, as well as the required purification degree of the waste gas, the optimal configuration of the device was proposed.

In this paper the influence of process parameters on the material hold-up in a fluidized bed dryer with inert particles was investigated. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 m height, with glass spheres of diameters dp = 1.20 mm and 1.94 mm as inert particles. The material used for drying was NaHCO3 slurry of two different concentrations, 10 and 20 wt.%. Dynamics of the material hold-up was determined for four different drying temperatures, in the range from 60 to 120°C by taking the samples of coated particles during the drying process and measuring the mass with and without the coated material film. The obtained results showed strong positive dependence of the material hold-up on the initial slurry concentration as well as on the drying temperature. The rate of the material film coating formation is quicker at higher drying temperatures.

In this paper, an innovative fluidized bed dryer with inert particles is presented. The system can be used for drying of solutions, suspensions and pastes in order to obtain a powdered product. The experiments were performed in a pilot-scale dryer with a cylindrical column 0.215 m in diameter and 1.2 mm height, with glass spheres as inert particles. The material used for drying was CuSO4 solution. The effects of operating conditions on the dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Nearly isothermal conditions were found due to thorough mixing of the particles. The energy efficiency of the dryer was also assessed. Simple heat and mass balances predicted the dryer performance quite well. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172022]

Ethylene oxide (EtO) is an organic compound, which is used as starting material in the production of polymers and as sterilizing agent for thermolabile materials. Although ethylene oxide is not common as an organic pollutant, its removal from numerous emission sources (e.g. ethylene oxide production plants or food and pharmaceutical sterilizing units) is of the crucial importance because of its mutagenic, teratogenic and cancerogenic effect on human health. The objective of this paper is the experimental investigation of ethylene oxide (EtO) absorption in diluted aqueous solution of sulfuric acid in order to evaluate the applicability of this procedure as well as to obtain project parameters for industrial plant realization. It was found that absorption is suitable as the fist step in the purification treatment of high EtO concentrations in the emission gases. According to the literature data, the basic parameter that defines the scrubber efficiency is the contact time, i.e. the ratio of packing height in scrubber and velocity of gas mixture. To investigate the characteristics of wet treatment in a broad range of contact time, part of experimental studies were conducted in the system with two and with three scrubbers in series. The obtained experimental results show that the high degree of EtO removal can be achieved (>98%) when the contact time is sufficiently long (about 25 s). The process is effective until the concentration of formed glycol in the solution reaches value of about 20%. The process is safe and there is no danger of ignition and explosion of air and EtO mixture, although at the entrance to the scrubber EtO concentrations are significantly above the lower explosive limit.

The dynamics of ethylene oxide sorption and desorption on Al2O3 sorbent were investigated. The investigations of ethylene oxide sorption on Al2O3 show that significant sorption appeared above 125°C. The removal of sorbed ethylene oxide from Al2O3 was achieved by continuous increasing of the temperature up to 450°C in air stream. The analysis of desorbed products show that 90% of adsorbed ethylene oxide is converted to CO2 and the rest consists of the three derivatives of ethylene oxide. The exact composition of desorbed organic products will be determined in further investigation. The desorption temperature profiles point out the presence of two exothermic picks, as was confirmed by detection of CO2 and derivates of ethylene oxide at these temperatures. Investigation of textural characteristics and thermal stability of Al2O3 sorbent show that there are no changes of any characteristics of Al2O3 in sorption/desorption operating temperatures regimes. Only at 700°C the specific surface area of Al2O3 decreases of about 10%. This indicates that the investigated Al2O3 is convenient material for removal of ethylene oxide by sorption.

A fluid bed dryer with inert particles represents a very attractive alternative to other drying technologies according to the main efficiency criteria, i.e. specific water evaporation rate, specific heat consumption and speci­fic air consumption. A high drying efficiency results from the large con­tact area and from the large temperature difference between the inlet and outlet air. A rapid mixing of the particles leads to nearly isothermal conditions throughout the bed. A fluid bed dryer with inert particles was used for drying of slurries. Experiments were performed in a cylindrical column 215 mm in diameter with glass spheres as inert particles. In this paper, results of drying experi­ments with slurries of Zineb fungicide, copper hydroxide, calcium carbo­nate and pure water used as the feed material are presented. In our fluidized bed we successfully dried a number of other materials such as: fungicides and pesticides (Ziram, Propineb, Mangozeb, copper oxy-chloride, copper oxy-sulphate, Bordeaux mixture), other inorganic compounds (calcium sulphate, cobalt carbonate, electrolytic copper, sodium chloride), and a complex compound (organo-bentonite). The effects of operating conditions on dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Temperature profile along the bed was mapped, and nearly isothermal conditions were found due to thorough mixing of the particles. Analysis of drying and energy efficiencies as a function of inlet and outlet air temperature difference was performed for deeper insight in dryer behavior and for optimizing dryer design and operation from an energy point of view. A simple mathematical model based on an overall heat balance predicts the dryer performance quite well. The industrial prototype with fluid bed of 0.8 m in diameter and capacity 650 kg of evaporated moisture per hour was realized on the basis of presented investigations on pilot unit. The most important results are 50% decrease in energy consumption and no-additional grinding of dried product in comparison with old tunnel drying technology.