Study On Ion-exchange Adsorption Of Scaling Ion By Clinoptibolite In Thermal Power System Industry

The scale in thermal system is mainly caused by hardness ions. Because of the deform of pipe where scale formed, there is the hidden trouble of safe. And the thick layer of scale affects the normal heat transfer, which would cause a waste of energy, low down the economy in thermal system. The main anti-scaling methods include adding chemical scale inhibitor and using ion exchange resin, but the chemical composition would cause secondary pollution and ion exchange resin can't work at high temperature. Clinoptilolite, one of nature zeolite, has been found steady at high temperature, acid resistance. Utilization of clinoptilolite as cation exchangers in water treatment has increasing interest due to their availability and low cost. The research described here was designed to test the properties of actived clinoptilolite as an adsorbent for removing Ca²⁺ from thermal system. The comprehensive studies on the adsorption were conducted in static and mobile adsorption methods.The thermodynamics and kinetics of adsorptive process were investigated. The influential factors, such as adsorbent dose, pH value, salt concentration contact time, temperature etc. and competitive effects between 4A zeolite and clinoptilolite were studied also. The pseudo-second-order model was the best choice to describe the adsorption behavior of Ca²⁺, Ea is 41.89KJ/mol. The adsorption proceeds faster and reaches its equilibrium at higher temperature. Adsorption behavior of clinoptilolite can be approximately described with Langmuir equation, temperature has a little influence on the the maximum adsorbing capacity, which is 60.976mg/g. The results indicated that high temperature and concentration were benefial to adsorption property. The positive value ofâ–³H and AS suggest the endothermic entropy increase nature of the adsorption, the negative values of AG at various temperatures indicates the feasibility of the process and spontaneous nature of the adsorption. The changing trend of pH at different temperatures is roughly the same, the adsorption property in alkaline is superior to acid solution, the adsorption quantity approximately constant with the pH value increasing at the range from 4-8. The adsorption rate of 4A zeolite is smaller than clinoptilolite especially when the concentration <400mg/L.The adsorption of Ca²⁺ onto clinoptilolite in aqueou solution were also studied with fixed-bed column. The effects of experimental conditions such as column length, flow rate, concentration on the sorption capability were discussed. We also used Thomas BDST Adams Yoon model to fit for the breakthrough curve. The adsorption percent increases with the increase of temperature depth and decrease of concentration flow rate. All adsorption model could fit very well the breakthrough curves of Ca²⁺ in clinoptilolite column. The linear correlation coefficients at different conditions are all above 0.9. The adsorption capacity t and breakthrough time were calculated and forecasted by yoon Thomas and BDST mode, a good agreement was found between model predictions and experimental data. The breakthrough coefficient, increases with temperature and decreases with concentration depth flow rate, relative to the resistance.The experimental results show that actived clinoptilolite is suitable for the removal of Ca²⁺ in thermal system and with good prospects for industrial application.