The ET Process® was developed to address common problems in enzymatic bio­diesel production. The process consists of primary and trim reactors. Typically, a reaction occurs at room temperature (25-30 °C) and ambient pressure.

The reaction time is in the range of 10-60 min, depending on the feedstock oil and alcohol reactant used. A well-mixed solution of oil, alcohol reactant, inert sol­vent and biodiesel is fed into a primary packed bed reactor or CSTR. The output of the primary reactor is separated into two liquid phases by evaporation of inert solvent, unreacted alcohol and water. The residue contains one phase composed of
crude biodiesel and another phase containing crude glycerol, which includes traces of solvent and alcohol. Crude biodiesel is re-mixed with inert solvent and make-up alcohol and allowed to proceed to completion. Evaporation again separates crude biodiesel from crude glycerol. Figure 11.2 shows the simplified flowsheet and photo of the mini-ET Process®.

Fig. 11.2 (continued)

At the end of the reaction, inert solvent and reactant alcohol are recovered, separated and reintroduced into the process. Trace water from oil, reactant alcohol and inert solvent or that produced from the reaction is discharged.

The final pure glycerol is obtained by removing residual solvent, alcohol and water through an evaporator. Pharma-grade glycerol can be obtained by decoloriza — tion of the glycerol product. Table 11.2 shows the typical product specifications.

The lipase source and immobilization process will affect the efficiency of the reaction. A good immobilization process can produce competitive catalyst perfor­mance, even when starting out from different lipase sources. The immobilized lipase can be used in the process for 12-18 months under normal operating condi­
tions, exhibiting steady activity within this period of time. The half-life of the bio­catalyst can reach more than 60 months. The amount required for the process is typically a few percent of a stream day capacity.