Abstract: A tube-in-tube heat exchanger for exchanging heat between two fluids is provided. The heat exchanger has at least one tube pair; spaced apart first and second tube sheets; first and second annular flow chambers; and first and second inner tube flow chambers. A gasket surrounds each inner tube of each tube pair at each end, forming a seal between each annular flow chamber, each inner tube flow chamber, and each inner tube. Such configuration allows for modular construction and easy cleaning and replacement of fouled or damaged tubes.

Abstract: A method for introducing oxygen into a propagation zone of a fermentation process is provided. A propagation zone comprising a liquid ferment and microorganisms is provided. A portion of the liquid ferment is removed from the propagation zone and a molecular oxygen source is introduced into the removed liquid ferment to form a mixture comprising an oxygenated liquid ferment and non-dissolved gases. The oxygenated liquid ferment and the non-dissolved gases are separated and the non-dissolved gases are vented. The oxygenated liquid ferment is introduced to the propagation zone to be used by the microorganisms for reproduction and growth. In an additional step, carbon dioxide gas is recovered from the propagation zone.