Continuous Countercurrent Ion Exchange Research Articles

Observer Design for a Bilinear Model of a Continuous Countercurrent ION Exchange Process

The paper describes a method and proposes an algorithm for a bilinear observer design as part of a state estimation solution for a Continuous Countercurrent Ion Exchange (CCIX) process used for desalination of water. The aim of the design is to determine immeasurable process state variables using real CCIX measurement data obtained from a different study. The solution requires determination of the observer gain matrix and it is formulated on the basis of the pole placement method. The contribution of the paper is in the developed bilinear dynamic models of the process and the observer and in the extending of the pole placement method for the special matrices of the bilinear observer. An analytical procedure is developed and implemented for calculation of the characteristic equation of the observer as part of calculation of the observer gain matrix. Matlab and SIMULINK software programs for determining the estimated states are developed. Investigation of the performance of the bilinear observer and the closed loop system under various constant values of the control input and different state initial conditions is performed. The results are presented and discussed.

ChemInform Abstract: Decontamination of Low-Level Radioactive Wastewaters by Continuous Countercurrent Ion Exchange

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

OPTIMAL CLOSED-LOOP CONTROLLER DESIGN FOR AN ION EXCHANGE PROCESS USED FOR DESALINATION OF WATER

A personal computer based control system for the countercurrent multistage ion exchange process for desalination of water is built. The developed control system is part of an optimization strategy of the continuous countercurrent ion exchange (CCIX) process. The paper focuses on the design of an optimal nonlinear controller as a part of a two layer control strategy with layers of optimization and direct control. The design involves two stages, nonlinear linearizing the closed loop system controller and linear quadratic controller for the linearized system. The controller is realized in LabVIEW software environment. Algorithm and programs for implementation of the design method are developed.

Counter-current ion exchange for the removal of organically bound sodium from low-rank coals

South Australian low-rank coals contain high levels of water-soluble and ion-exchangeable ions that can be deleterious to coal combustion and gasification. The presence of sodium causes the formation of low melting point bonded deposits that can produce severe fouling and slagging in many processes using these coals. Approximately 70% of the sodium present in Bowmans coal is water-soluble and can therefore be removed by simple water leaching, however the remaining 30% is organically bound, predominantly to carboxyl groups. Ion exchange using sulphuric acid at pH 2 is necessary to remove this sodium, but this can generate large volumes of acidic wastewater if multiple washing stages are used with fresh water each time. Using a simple laboratory procedure, the continuous counter-current ion exchange leaching of sodium from this coal was simulated which reduced the sodium level from 1.30% on a dry basis (db) to 0.15% (db) after three stages of counter-current washing at a total coal:water ratio of 1:2. The effectiveness of interstage dewatering on the efficiency of sodium removal was highlighted. The agreement between predicted and measured values of moisture and sodium in coal was excellent.

CSA Continuous Countercurrent Ion Exchange (CCIX) Technology

Abstract The CSA-CCIX concept started at ORNL in 1951. It has been adapted to a wide variety of applications worldwide, in water and waste water treatment, fertilizers, hydrometallurgy, and general chemical processing. Unique features and how it works are described. Two extreme applications are described in detail. One is for the extraction of trace amounts of uranium from a copper leach, at 37.85m3/min (10,000 gpm) where very high throughput rates are emphasized. The other is for Acid Retardation, where a strong acid waste is purified and recovered. The feed processing rate here is much lower than the resin rate.

Continuous Countercurrent Ion Exchange for Desalination and Tertiary Treatment of Effluents and Other Brackish Waters

A continuous countercurrent ion exchange (CCIX) process has been developed for desalination of mineralized effluents and brackish water. The process utilizes macroporous resins in a strong cation/weak anion sequence. Removal of organic matter by the anion resin results in colour and odour removal and approximately 70% reduction of the COD of humus tank effluent. No pretreatment is required and resin has been in use over the equivalent of more than two years of continuous operation without significant fouling or loss of capacity. Any required degree of desalination is attinable. The basic four-colunn system (cation load and regeneration pair and anion load and regeneration pair) of countercurrent fluidized bed multistage contactors attains greater than 80% water recovery using up to 1,0 N sulphuric acid and 0,2 N lime slurry as regenerants. Low solubility of CaSO4, in the cation waste liquid and column operating problems if high lime concentrations are used set limits on the water recovery. Calcium content of the feed water affects water recovery. New techniques using five-column systems permit byproduct recovery and/or reuse of spent regenerants and result in over 90% water recovery. The capital cost estimate for a 10 000 kℓ/day plant is R5 million while unit costs of water are 30 to 40 c/kℓ. for removal of 500 mg/ℓ TDS. Present work involves lime contacting improvements and evaluation of carbon adsorption polishing of the ion exchange product to produce potable water.

Note on a continuous counter current ion exchange with two step regeneration for zinc recovery from synthetic fibre plant waste water

Note on a continuous counter current ion exchange with two step regeneration for zinc recovery from synthetic fibre plant waste water

Separation of stable isotopes by chemical and ion-exchange methods

Methods of separating stable isotopes by the use of various types of molecular compounds. The use of molecular compounds for separating isotopes of boron, sulphur and oxygen. Isotopic exchange reactions in the electric discharges. Calculation of single stage separation factors for exchange reactions. Potentialities of the isotope separation process using ion exchange. The use of ion exchange for separating lithium isotopes. Combination of ion chromatography with electromigration of ion. Synthetic zeolites (molecular sieves) used as ion exchangers. Principles and applications of the continuous countercurrent ion exchange method.

Studies on Continuous Countercurrent Ion Exchange of the System of Magnesium and Hydrogen Ion

Continuous countercurrent ion exchange was studied with the cationic system of magnesium and hydrogen ion, using an exchange column, 2cm in internal diameter and 5 to 30cm in height, where the bed of resin particles moved downward.The data were correlated by an equation so as to relate the overall volumetric coefficient of mass transfer based on fluid film to operating variables and the properties of the ionic system.The results indicated that film resistance of each phase was of the same order of magnitude. Overall volumetric coefficient based on the fluid film was found to be about 0.03 [1/sec].Non-dimensional constants, α and β, appearing in the correlation equation, and related to film resistance of each phase, were 2.4 and 0.2, respectively. These values were smaller than those, 4.7 and 0.9, respcctively, obtained by Hiester et al., for the monovalent system of lithium, potassium and hydrogen ion. These differences may be attributable to the colum diameter differences, i.e., 9cm diameter in the Hiester's equipment and 2cm diameter in the authors'. More studies will be required, however, to know what factors participate in this phenomenon. Some considerations were made on the mutual relation between the degree of the exchange adsorption of magnesium in the solution and the ratio of the fluid flow rate to the resin particles flow rate.