The Measurement Of Fluid Flow Parameters And Mass Transfer Coefficient In Bubble Columns

Purified terephthalic acid (PTA), one of the important feedstocks of polyester, is produced by p-xylene (PX) liquid phase oxidation. Industry processes of PTA are all controlled by foreign companies, so domestic companies import all of the existing technology and equipment from them. For improve the market competitive power of domestic companies and break through the patent barrier of foreign companies, it is nessessary to develop domestic industry techonology.Compared with traditional agitated tank, the patent on bubble column as the main reactor of PX oxidation is rare. Further more, Bubble column reactor has its own strong points such as simple structure, low construction and operating cost. So bubble column has been chose as main reactor of new-type industry process.The paper included the following aspects:1. Conductivity probe, Pavlov tube and oxidation of sodium sulfite has been used to measure the parameters about flow field and mass transfer in gas-liquid and gas-liquid-solid bubble columns with different diameters. Experiments are based on the feature of PX oxidation, such as high superficial velocity, high solid content and large equipment. The results are as follows(1).With the increasing of superficial gas velocity, local gas holdup remark increases. The radial distribution of local gas holdup becomes flatter with the increasing of column diameter; the addition of solid makes local gas holdup decrease.(2) . With the increasing of gas velocity and column diameter, the radial distribution of liquid velocity become steeper; the addition of solid disturbs the movement of gas-liquid phase. In the inversion point of liquid flow, root-mean-square fluctuation velocity is maximum value. Turbulent intensity increases with superficial gas velocity, column diameter and solid content.(3). The biggest eddy size approaches to column diameter. Eddy size increases with column diameter, while gas velocity almost has almost no influence on it. Power distribution for varying wavelet scale that fine scale and large scale power became larger with the increasing of gas velocity and column diameter.(4). With increasing of gas velocity and column diameter, liquid phase mass transfer coefficient increases. The addition of solid has no influence on mass transfer coefficient.2. The damping internal had been placed in bubble column reactor to solving the problem caused by the scaling up of equipment, for example the ununiformity distribution of liquid velocity and gas hold-up caused gas short pass in the centre of column, then influenced mass transfer and reaction. The results are summarized as follows(1). The damped internal could effectively improve the radial distribution of axial liquid velocity. In small bubble column, the liquid velocity distribution curve is flatter. Quasi- homogeneous model could indicate the effects of internal well.(2). The radial distribution of local gas holdup is flatter when internal is placed in the column.(3). The relating formula about the influence of gas velocity, column diameter and internal front face area on mass transfer coefficient is presented.