최소 유동화 속도 계산 목적(Object) 유동층 반응기(fluidization reactor)에서 고체입자의 최소 유동화 속도(minimum fluidization velocity)를 실험을 통해 측정하고, 이론적 방법으로 계산하여 실험값을 검증해본다. 물리화학실험2

다공층 - P Support 가스 또는 액체 유동화 현상(fluidization) 고체 입자의 다공층을 통하여 기체 또는 액체가 빠른 속도로 그 기체 또는 액체가 다공층을 유동화 시킴. 가스 또는 액체 다공층 Support - P 물리화학실험2

Various forms of contacting of a batch of solids by fluid 물리화학실험2

Q P - P B fixed bed (static) fluidized bed (boiling) Ut F A OA : 거의 직선임 : Ergun equation 성립 A : 고체입자가 위로 움직이려는 경향이 나타남. B : 다공층이 가장 느슨한 상태에 들어감. BF : 입자들이 서로 분리되는 경향이 나타남. F : 유동화가 시작됨. FP : - P=일정 P : 고체 입자가 쓸려나가기 시작함 (entrainment) PQ : bed의 형태가 없어짐. Q : 모든 입자가 다 쓸려나간 상태 물리화학실험2

유동층 반응기 : 200 g/hr 5 물리화학실험2

Advantages and disadvantages of Fluidized Beds for Industrial Operation The smooth, liquidlike flow of particles allows continuous automatically controlled operations with easy handling. The rapid mixing of solids leads to close to isothermal conditions throughout the reactor; hence the operation can be controlled simply and reliably. In addition, the whole vessel of well-mixed solids represents a large thermal flywheel that resists rapid temperature change, responds slowly to abrupt changes in operating conditions, and gives a large margin of safety in avoiding temperature runaways for highly exothermic reactions. The circulation of solids between two fluidized beds makes it possible to remove (or add) the vast quantities of heat produced (or needed) in large reactors. It is suitable for large-scale operations. Heat and mass transfer rates between gas and particles are high when compared with other modes of contacting. The rate of heat transfer between a fluidized bed and an immersed object is high; hence heat exchanges within fluidized beds require relatively small surface areas. 물리화학실험2

Disadvantages For bubbling beds of fine particles, the difficult-to-describe flow of gas, with its large deviation from plug flow, represents inefficient contacting. This becomes especially serious when high conversion of gaseous reactant or high selectivity of a reaction intermediate is required. The rapid mixing of solids in the bed leads to nonuniform residence times of solids in the reactor. For continuous treatment of solids, this gives a nonuniform product and poorer performance, especially at high conversion levels. For catalytic reaction, the movement of porous catalyst particles, which continually capture and release reactant gas molecules, contributes to the backmixing of gaseous reactant, thereby reducing yield and performance. Friable solids are pulverized and entrained by the gas and must be replaced. Erosion of pipes and vessels from abrasion by particles can be serious. For noncatalytic operations at high temperature, the agglomeration and sintering of fine particles can require a lowering in temperature of operations, therby reducing the reaction rate considerably. 물리화학실험2

유동층 반응기, 질소 실린더, 유량계, 모래(sand), 비이커, 저울(chemical balance) 등 실험 기구 및 시약 유동층 반응기, 질소 실린더, 유량계, 모래(sand), 비이커, 저울(chemical balance) 등 실험 방법 ① 실험 시료(모래)의 100g 무게를 측정한다. ② 모래를 유동층 반응기에 넣는다. ③ 유량계로 질소 유량을 서서히 증가시킨다. ④ 최소 유동화 속도를 측정한다. ⑤ 모래의 평균 입자크기를 계산한다. 결과 및 고찰 결론 물리화학실험2

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