Processes for starting up and operating deep tank anaerobic fermentation reactors for making oxygenated organic compound from carbon monoxide and hydrogen

A process for anaerobic bioconversion of a gas substrate comprising carbon monoxide, hydrogen, and carbon dioxide in a reactor by contact of the gas substrate with an aqueous menstruum containing microorganisms suitable for converting the gas substrate to an oxygenated organic compound in the reactor, the reactor being a deep tank bubble column bioreactor, the process further comprising:

• (a) blanketing the reactor above the aqueous menstruum to the essential exclusion of oxygen with a head space gas comprising at least one of carbon monoxide, hydrogen, carbon dioxide, nitrogen, and a lower alkane;
• (b) continuously supplying a feed gas comprising at least a portion of the gas substrate to the aqueous menstruum in the reactor:
• (c) injecting the gas substrate and a motive liquid into a bottom portion of the reactor to form a dispersion of the motive liquid and microbubbles, the microbubbles having a non-zero diameter of less than about 500 microns, the motive liquid being a recycled portion of the aqueous menstruum;
• and,
• (d) maintaining sufficient height of the aqueous menstruum in the reactor to permit the process to convert at least 80% of the carbon monoxide and the hydrogen to an oxygenated organic compound wherein:
• the mass transfer of carbon monoxide to the aqueous menstruum in the reactor is modulated to maintain the carbon monoxide concentration below that amount which results in carbon monoxide inhibition by at least one of:
• (i) adjusting gas to liquid flow ratio in the injecting the gas substrate and the motive liquid into the reactor,
• (ii) changing rate of motive liquid flow in the injecting the gas substrate and the motive liquid into the reactor, and
• (iii) adjusting carbon monoxide mole fraction in the feed gas by admixture of the gas substrate with at least one other gas to maintain stable operation of the dispersion.

A process for anaerobic bioconversion of a gas substrate comprising carbon monoxide, hydrogen, and carbon dioxide in a reactor by contact of the gas substrate with an aqueous menstruum containing microorganisms suitable for converting the gas substrate to an oxygenated organic compound in the reactor, the process further comprising:

• (a) blanketing the reactor above the aqueous menstruum to the essential exclusion of oxygen with a head space gas comprising at least one of carbon monoxide, hydrogen, carbon dioxide, nitrogen, and a lower alkane;
• (b) continuously supplying a feed gas comprising at least a portion of the gas substrate to the aqueous menstruum in the reactor:
• (c) injecting the gas substrate and a motive liquid into the reactor to form a dispersion of the motive liquid and microbubbles, the microbubbles having a non-zero diameter of less than about 500 microns;
• and,
• (d) maintaining sufficient height of the aqueous menstruum in the reactor to permit the process to convert at least 80% of the carbon monoxide and the hydrogen to an oxygenated organic compound wherein:
• the mass transfer of carbon monoxide to the aqueous menstruum in the reactor is modulated to maintain the carbon monoxide concentration below that amount which results in carbon monoxide inhibition by at least one of:
• (i) adjusting gas to liquid flow ratio in the injecting the gas substrate and the motive liquid into the reactor,
• (ii) changing rate of motive liquid flow in the injecting the gas substrate and the motive liquid into the reactor, and
• (iii) adjusting carbon monoxide mole fraction in the feed gas by admixture of the gas substrate with at least one other gas to maintain stable operation of the dispersion.