A loop reactor is regarded as a new type of reactor for bulk polymerization of olefins. Several approaches to evaluate its performance are madeherein. A simple model of discharge flow is proposed and related with the results obtained by measurement of average circulation velocity. The average circulation velocity is proportional to impeller speed and the sine of the impeller blade angle. It depends upon Reynolds numberand dimensions of the impeller. Flow pattern was measured and the influence of baffles and impeller geometry is discussed qualitatively. In the case of unbaffled conditions, fluid flows in a helical motion. Intensity of this motion increases with impeller speed and pitched angle. In the case of baffled conditions, tangential velocity component is suppressed and normalized distribution of axial velocity is independent of impeller geometry. Pressure distribution was measured and pressure loss was obtained. Total pressure loss shows good agreement with the value calculated by superposition of frictional loss in straight parts and bend loss in bends obtained from established correlations. Intro ductionThe loop reactor was proposed by Norwoodet alZ) in a slurry polymerization of olefins. The recent development of highly active catalysts enable the olefins polymerization to proceed towards a bulk polymerization.As discussed very often, some difficulties have been pointed out, such as deposition of polymer on the reactor wall and impeller and insufficient heat transfer capacity, in a conventional stirred-tank reactor process. Furthermore, the loop reactor has potential applications to liquid-phase bulk polymerization, processing of highly viscous liquid and biochemical reaction.The advantages of the loop reactor are summarized as follows.

Measurements of power consumption in a loop reactor of 10 cm i.d. with pitched paddle impellers were carried out in the range of mixing Reynolds number Re,,, = lo2 to 2 X io5 using water and corn syrup solution (p = 1-60 mPa*s) as working fluid. The effect of pitched angle of the impeller blade, I #J , upon power consumption is expressed by the equation N P a (sin $)2 at Re,,, > 200 where flow is turbulent. There exists no influence of baffle condition and no difference between batch and continuous operations. The circulation velocity was controlled by changing the opening size of throttle rings and length of tubing loop as well as changing the impeller speed. The results were rearranged into the pumping characteristic curves based on the idea that the impeller region and the tubing loop behave independently. The characteristics of the impellers tested are similar to that of the axial-flow pump. By use of the resultant characteristic curves, an approach to estimated power consumption is proposed.

Mixing process under batch operation was investigated by the impulse response method. A series solution of the dispersion model for recirculation flow is given and a simple procedure to determine the model parameter, Bodenstein number Bo, is proposed. Dimensions of the loop reactor used in most experiments are: inner diameter=10 cm, whole pipe length=280 cm and reactor volume=22 /. The impellers used are: pitched paddles of three different pitched angles and three different diameters, an axial flow pump-type impeller and a marine screw. Bodenstein number was converted into Peclet number, Pe, which in turn is correlated with the pipe Reynolds number, Rep. For the experimental range of i?^=2.5 x l03-2 x l05, Pe ranges over 3-16, which is 2-3 times that in a straight pipe. Geometry of the impeller does not affect the value of Pe for a given value of Rep. Pe in unbaffled condition is larger than that in baffled condition because of helical motion of fluid. The numberof circulations before the fluctuation decays below 1 % of average concentration is analytically found to be 0.134 Bo.

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A gas production system by injecting hot water into a methane hydrate layers with lower aquifer under the sea bottom has been studied using with horizontal wells in radial arrangements. In order to overcome extremely low permeability and large dissociation heat of the MH layer, the system forming dissociated chamber with high permeability and communication to lower aquifer has been proposed and evaluated by physical and numerical models. The numerical simulations were successfully matched with experiments using the physical model. Moreover, numerical simulations of gas production by the hot water injection into a field of methane hydrate sediment using dual horizontal wells 500 m in length were carried out for a methane hydrate reservoir of 15m in layer thickness, 60% of hydrate saturation, 100 and 25 md in horizontal and vertical absolute permeabilities, respectively. In this study, after getting communication between hot water chamber and lower aquifer, a gas production scheme for the area of 1km×1km has been proposed by using radial flow between different horizontal well pair through lower aquifer. At the beginning, dual horizontal wells was preheated by hot water circulation in the wells for 90 days to get communication of area between two horizontal wells. After gas production with four pairs of dual wells for one year, radial hot water flow can be used to make the chamber expand in horizontal section of the reservoir. The simulations were performed under the following conditions: hot water temperature of 85°C, injection rate of 2000 ton/day, horizontal wells 500 m in length, and a hydrate layer 15m in thickness with vertical absolute permeability of 25 md horizontal one of 100 md and methane hydrate saturation of 60%. The cumulative gas production during 15 years, it was estimated as 1.3×108 std-m3 during 15 years by using with the injection scheme with radial hot water flow between different wells pair after one year.