Paddle stirred reactor

At present our 6-m tank reactor gives 75% conversion for the first order reaction A R. However, since the reactor is stirred with an underpowered paddle turbine, we suspect incomplete mixing and poor flow patterns in the vessel. A pulse tracer shows that this is so and gives the flow model sketched in Fig. E12.2. What conversion can we expect if we replace the stirrer with one powerful enough to ensure mixed flow ... 

For further understanding the performance of the SCISR by comparison, the preparation experiments are also carried out simultaneously in a stirred tank reactor (STR) with an effective volume of 0.6x10 m3, the structure of which is indicated in Fig. 13.1. In order to mimic industrial conditions, the STR is equipped with three dampers distributed uniformly along the circle the stirrer is a flat paddle. 

Figure 4-20 shows a typical design of a stirred contained solids reactor. Here, the catalyst particles are mounted in the paddles that... 

Until now, bioreactors of various types have been developed. These include loop-fluidized bed [14], spin filter, continuously stirred turbine, hollow fiber, stirred tank, airlift, rotating drum, and photo bioreactors [1]. Bioreactor modifications include the substitution of a marine impeller in place of a flat-bladed turbine, and the use of a single, large, flat paddle or blade, and a newly designed membrane stirrer for bubble-free aeration [13, 15-18]. Kim et al. [19] developed a hybrid reactor with a cell-lift impeller and a sintered stainless steel sparger for Thalictrum rugosum cell cultures, and cell densities of up to 31 g L1 were obtained by perfusion without any problems with mixing or loss of cell viability the specific berberine productivity was comparable to that in shake flasks. Su and Humphrey [20] conducted a perfusion cultivation in a stirred tank bio-... 

Pitch-blade turbine (paddle stirrer with pitched blades) and propeller stirrers provide high mixing with an axial flow pattern. Both of these stirrers are normally used for low-viscosity liquids and in vessels with baffles. They are well suited for providing liquid homogenization and suspension of solids in slurry reactors. The stirrers can also be used in viscous fluids and for vessels with H/dT > 1, which are generally encountered in fermentation processes. For these situations, axial flow is increased with the use of multistage stirrers with pitched stirring surfaces. 

Stirred tank paddles power input suspend solids, 0.2 to 1.6 kW/m UD = 0.7 to 1.05/1. Baffle, four 90° baffle width = 0.08 x tank diameter off-the-wall distance = 0.015 x tank diameter. Minimum level of liquid = 0.15 x tank diameter for impeller tank diameter 0.28 1 and minimum level = 0.25 x tank diameter for impeller tank diameter = 0.4 1. Use a foot bearing plus a single, main axial hydrofoil impeller diameter = 0.28 x tank diameter located 0.2 x tank diameter from the bottom plus a pitched blade impeller diameter = 0.19 x tank diameter located 0.5 x tank diameter from the bottom. Liquid fluidized bed in general, particle diameter 0.5 to 5 mm with density and diameter of the particle dependent on the application. The superficial liquid velocity to fluidize the bed depends on both the diameter and the density difference between the liquid and the particle. Usually, the operation is particulate fluidization. Particle diameter 0.2 to 1 mm reactors superficial liquid velocity 2 to 200 mm/s. Fluidized adsorption bed expands 20 to 30% superficial liquid velocity for usual carbon adsorbent = 8 to 14 mm/s. Fluidized ion exchange bed expands 50 to 200% superficial liquid velocity for usual ion exchange resin = 40 mm/s. Backwash operations fixed-bed adsorption superficial liquid velocity = 8 to 14 mm/s fixed-bed ion exchange superficial backwash velocity = 3 mm/s. 

Wet explosion pretreatment [7] was perfonned batch-wise by suspending 350 g wheat straw pellets in 1.81 of deionized water in a 3.5-1 high-pressure reactor with a paddle stirrer with a maximum stirring speed of 2,000 rpm. The reactor was equipped with an injection device for injection of H2O2 solution, pure oxygen, or air. The reactor was heated by water jacket, which was coimected to a heat exchanger controlled by an oil heater. The highest temperature in the reactor was 190 C. The temperature and pressure inside the reactor were monitored by two temperature sensors (one in the bottom and one in the head space) and one pressure sensor. After the pretreatment, the material was flashed into a 5-1 container connected to the reactor. 

The catalyst can be mounted either in an annular basket or in a paddle-basket arrangement as shown in Figure 3. The paddle basket replaces the radial impeller, which is used only with the annular basket. For either arrangement the propellers remain in place. The cylindrical wall and the top and bottom of the reactor each have four 1/8-in. wide baffles. The wall baffles extend along the total height of the stirred chamber the top and bottom baffles extend radially to the cylindrical wall. 

Gas phase reactors Gaseous monomers, continuous heterogeneous solid cat. PE, PP fluidized beds horizontal with weirs rotating paddles helically stirred tanks. 

Mechanically agitated stirred tank reactors are preferentially used in food- and bio-technology or with smaller chemical productions where they are operated very often discontinuously. The gas phase is supplied either under pressure through a static gas feeder, by self-suction agitators or by surface aeration, sometimes assisted by an additional stirrer fitted just below the gas-liquid interface. Paddles with inclined or straight blades and turbines are the most common types of agitators. They are very effective with viscose liquids at low gas flow rates and large liquid volumes. 

The first is a continuous stirred tank reactor process [2]. The SPS polymerization is carried out with a continuous stirred tank reactor with a paddle-type agitator [3-5], a helix-type agitator [2,4], an anchor-type agitator [5], or a pipe blade [5]. TTie powder level is indicated by a driving radiant ray device [6]. 

Fresh styrene and catalyst components are fed to the jacketed stirred tank reactor with a multi-paddle agitator (V-300). In the reactor, styrene is polymerized to SPS in the presence of catalysts. The SPS powder is discharged from the bottom of the stirred tank reactor. The polymerization heat is removed only by the jacket coolant. 

In the polymerization process shown in Fig. Ic [3], a fresh feed of 8% polybutadiene rubber in styrene is added with antioxidant and recycled monomer to the first reactor operating at 124 C and about 18% conversion at about 40% fillage. The agitator is a horizontal shaft on which a set of paddles is mounted. Because the temperature in each compartment can be varied, it is claimed that the linear flow behavior provided by the reactor staging results in more favorable rubber-phase morphology than would be the case if the second reactor were operated as a single continuous stirred tank reactor. 

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