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Oxygen and carbon dioxide mass transfer and the aerobic, autotrophic cultivation of moderate and extreme thermophiles: A case study related to the microbial desulfurization of coal
Author(s) -
Boogerd F. C.,
Bos P.,
Kuenen J. G.,
Heijnen J. J.,
van der Lans R. G. J. M.
Publication year - 1990
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260351106
Subject(s) - autotroph , thermophile , flue gas desulfurization , carbon dioxide , oxygen , heterotroph , chemistry , carbon fibers , coal , environmental chemistry , environmental science , biology , bacteria , biochemistry , materials science , organic chemistry , composite number , composite material , enzyme , genetics
Abstract Mass transfers of O 2 , CO 2 , and water vapor are among the key processes in the aerobic, autotrophic cultivation of moderate and extreme thermophiles. The dynamics and kinetics of these processes are, in addition to the obvious microbial kinetics, of crucial importance for the industrial desulfurization of high‐pyritic coal by such thermophiles. To evaluate the role of the temperature on the gas mass transfer, k L a measurements have been used to supplement the existing published data. Oxygen mass transfer from gas (air) to liquid (5 m M H 2 SO 4 in water) phase as a function of the temperature has been studied in a laboratory‐scale fermentor. At 15, 30, 45, and 70°C, ( k L a ) o values (for oxygen) were determined under three different energy input conditions by the dynamic gassing in/out method. The ( k L a ) o was shown to increase under these conditions with increasing temperature, and straight lines were obtained when the logarithm of ( k L a ) o was plotted against the temperature. By multiplying the equilibrium concentration of O 2 in water with ( k L a ) o maximal, O 2 transfer capacities were calculated. It appeared that in finite of a decreased solubility of O 2 at elevated temperature in mechanically mixed fermentors the calculated transfer capacities showed only minor changes for the range between 15 and 70°C. However, in an air‐mixed fermentor the transfer capacity of O 2 decreased slowly but steadily. Carbon dioxide mass transfer was predicted by calculations on the basis of the data for oxygen transfer. The maximal CO 2 transfer capacity, calculated as the product of the equilibrium CO 2 concentration times ( k L a ) c , decreased slowly as the temperature increased over the range 15–70°C under all three energy input conditions. Subsequent process design calculations showed that for aerobic, autotrophic cultures, CO 2 limitation is more likely to occur than O 2 limitation.