Calculating Oxygen Transfer Rates in Biochemical Reactors: a Step-by-step Approach

Understanding oxygen transfer rates in biochemical reactors is essential for optimizing microbial growth and product formation. Accurate calculations help in designing efficient systems that meet oxygen demands without excessive energy consumption.

Basics of Oxygen Transfer in Reactors

Oxygen transfer rate (OTR) refers to the amount of oxygen transferred from the gas phase to the liquid phase per unit time. It depends on factors such as aeration rate, agitation speed, and reactor design.

Key Parameters for Calculation

Several parameters are necessary for calculating OTR, including the volumetric mass transfer coefficient (k_La), the saturation concentration of oxygen (C_sat), and the actual dissolved oxygen concentration (C_DO). The basic formula is:

OTR = k_La × (C_sat – C_DO)

Step-by-Step Calculation Process

First, determine the saturation concentration of oxygen in the liquid, which depends on temperature and pressure. Next, measure the dissolved oxygen concentration during operation. Then, find the volumetric mass transfer coefficient through experimental methods or correlations based on agitation and aeration conditions. Finally, apply the formula to calculate the oxygen transfer rate.

Example Calculation

Suppose the saturation concentration (C_sat) is 8 mg/L, the current dissolved oxygen (C_DO) is 4 mg/L, and the k_La is 20 1/h. The OTR is calculated as:

OTR = 20 × (8 – 4) = 80 mg/h

This indicates that 80 milligrams of oxygen are transferred to the liquid per hour under these conditions.