Study On The Application Of CO₂ In Chemical Crystallization Pellet Fluidized Bed System

With the continuous development of social economy,high hardness water has an increasing impact on people's production and life.The traditional high-hardness water treatment process can obtain better treatment results,but there are problems such as complex process conditions,low removal efficiency,and the generation of by-products.As a high-efficiency softening technology,chemical crystallization circulating granulation fluidized bed technology has achieved good results in practical engineering applications.The process does not produce by-products during the treatment process,can achieve zero emissions,has the advantages of large processing load,convenient operation and so on,and has broad application prospects.CO₂ is the main component of industrial production waste gas and the main pollutant of the greenhouse effect.Recovering CO₂ from industrial waste gas and combining it with chemical crystallization circulating granulation fluidized bed technology for water quality softening is an embodiment of the concept of green environmental protection,energy saving and emission reduction.This article examines the softening effect of CO₂ on high permanent hardness water and the pH adjustment effect of crystallization fluidized bed effluent in a chemical crystallization circulating granulation fluidized bed system through static tests and pilot tests,and explores the CO₂ softening high permanent hardness respectively The mechanism by which the water body and CO₂adjust the pH of the crystalline fluidized bed effluent and determine the relevant process conditions.Provide theoretical support and data support for the application of CO₂ in chemical crystallization circulating granulation fluidized bed system.The main research results are as follows:?1?CO₂-NaOH softening high permanent hardness water static test results show that:CO₂ and NaOH as a softener can obtain good treatment effect.When the reaction pressure is 2 bar,the dosage of NaOH is 3 mmol/L,and the dosage of CO₂ is 2 mmol/L,the pH of the water after softening is 9.56,and the removal rate of Ca²⁺is 88%.The dosage of the control agent is unchanged,and as the pressure of the reaction system gradually increases,the Ca²⁺removal rate gradually increases.When the reaction pressure is constant,with the addition of NaOH,the Ca²⁺removal rate increases significantly,while the addition of CO₂ has an effect on the improvement of Ca²⁺removal rate but is smaller than NaOH,but it has a greater effect on the CO₃^2-,HCO₃^-concentration and The pH has a significant effect.Therefore,when using CO₂ and NaOH as softeners,the dosage of NaOH should be determined according to the removal rate of Ca²⁺.The dosage of CO₂ should be determined based on Ca²⁺,alkalinity and pH in the effluent.?2?The pilot test results of CO₂-NaOH to soften groundwater with high permanent hardness show that CO₂ and NaOH are used as softeners in the chemical crystallization circulating granulation fluidized bed system.When the influent HCO₃^-concentration is 4.3 mmol/L When the Ca²⁺concentration is 8.6 mmol/L,the NaOH dosage is controlled to 10.75 mmol/L,the CO₂ dosage is 7.4 mmol/L,the system effluent pH is 9.5,the Ca²⁺concentration is 0.92 mmol/L,and the removal rate is 90%.When CO₂ and NaOH are used as softeners,a good softening effect can be obtained.By comparison with the NaOH-Na₂CO₃ method,it can be seen that the CO₂-NaOH method has the advantages of low system operating cost,low alkalinity and pH value of the softened water,and good chemical stability of the water quality.?3?The pilot test results of the CO₂ adjustment chemical crystallization circulating granulation fluidized bed effluent pH show that:three aeration pipes,five aeration pipes,and side-flow pipeline jets are used at normal pressure.The addition of CO₂ in the effluent of the fluidized bed reactor can achieve the effect of pH adjustment.Among them,the effect of the pH adjustment of the side-stream pipeline jet device is the best.CO₂ is added to the effluent of the chemical crystallization circulation granulation fluidized bed through the side-stream pipeline jet.The pH is adjusted from10.8 to 7.8,the dosage of CO₂ is 150mg/L,and the cost of the agent is 0.18 yuan/t.By measuring the pH at different positions from the aeration point,it can be seen that using a jet aeration,when the system flow rate is 130 m/h,the pH of the water has been adjusted to 7.8 at 30 cm from the aeration point.The hydraulic retention time is 8 s,so the rate of adjusting the pH of the water with CO₂ is higher.It can be seen from the pilot test results that,compared with the traditional inorganic acid to adjust the pH,the pH of the effluent of the CO₂ adjusting chemical crystallization circulation granulation fluidized bed has the advantages of fast adjustment rate,easy adjustment of the end point,simple system operation and other advantages.The recovered CO₂ is used in the process and can obtain good economic and ecological benefits.