In order to increase the reaction rate in the formation of humic acid by air-oxidation of brown coal with the purpose of seeking a scientific as well as technical basis to see whether it is possible to adopt a continuous process in stead of the ordinary batch one, the oxidation of Tza-Lai-Nor brown coal in air-fluidized bed under pressure has been studied. Experiments were carried out in a simple fluidized-bed reactor made from alloyed steel. Effects of both pressure from 0 to 20 gauge atmospheres and temperatures from 150 to 1901-, on the rate of formation of humic acid were investigated. Experimental results have shown that the former has a more significant effect under which the time required for the oxidation process as the humic acid content of oxidized coal has attained a value of about 80% is in reverse proportion to absolute pressure of the system. On the other hand, effect of temperature has been shown playing also an important rule in the increase of rate of oxidation reaction. Owing to the constructional restriction of the reactor it is rather difficult to dissipate the huge amount of heat of reaction at some particular moment in the early period of oxidation, so that the seemingly maximum temperatures at corresponding pressures can hardly be further raised. Under the conditions of our experiments the most favorable technical data have been found to be. 20 atmospheres and 170℃, oxidation period 1.5 hrs. or alternately 5 atmospheres and 190℃, oxidation period 2.5~3 hrs. In both cases the humic acid contents of oxidized coals are in the range of 85~87% , and the carboxylic radical values are about 2.1~2.4 milliequivalents per gram of moisture-ash-free oxidized coal.

The flow characteristics of the liquid and solid phase in a multi-stage flui-dized bed with down comers was studied systematically in the following aspects: (1) the longitudinal back-mixing of the liquid phase, (2) the pressure drop of the liquid flowing through the perforated distribution plate, (3) the gravity flow of the solid particles through the bottom aperture of the downcomer pipe, and (4) the working characteristics of the downcomer pipe. The main results obtained are summarized as follows. (1) The longitudinal back-mixing of the liquid phase does not follow the Danckwerts diffusion model, but can be described by a simple combined model of piston flow and backmix flow in series. (2) The pressure drop of the liquid flowing through the perforated distribution plate can be calculated by the following equation, (3) The gravity flow rate of the granular particles through the bottom aperture of the downcomer is given by, (4) The influence of the back-pressure drop upon the flow rate of the solid particles through the downcomer has been observed, and the limiting working condition can be expressed as,

In this paper the type "B" multi-stage fluidized bed for the gas-solid system has been studied. The apparatus used was a 180 mm. I. D. 3-stage bed. The first section of this paper deals with the working characteristics of the downcomer pipe. The influence of pressure drop through the distribution plate upon solid flow in the downcomer pipe has been examined. The authors suggest the use of reduced flow rate G/G0 and reduced pressure-drop gradient (P/L)/ (P/L)kp to correlate all the factors affecting solid flow. Data with the same value of d0/dT can be correlated satisfactorily with this method, but no simple relation seems to exist for data having different values of d0/dT. In the second section of this paper, a method of heat transfer calculation for the multi-stage fluidized bed has been proposed based on the assumption that the gas and solid leaving the fluidized bed are kept in thermal equilibrium. The equation derived is similar to the Kremsers[6,7] equation for absorption.