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Green Energy Series
SPM-4100 Ethanol Distillation

Click to viewh scematic display A Click to view schematic display B Click to view schematic display C Click to view schematic display D
        

Process Description

The Simtronics Ethanol Distillation simulator enables comprehensive training for fuel ethanol distillation unit operators. The simulated process is representative of the basic two-stage distillation process used to conventionally concentrate the ethanol in a beer feed to approximately 95 liquid volume %. To make a fuel-grade ethanol product, the distillation section is followed by a drying unit to eliminate most of the remaining water in the product ethanol produced by distillation of the feed beer. The simulated process includes the following main equipment:

- Beer Column (performs primary separation of ethanol from the beer)
- Rectification Column (eliminates most of the water from the ethanol)
- Stillage Flash Drum (removes ethanol from produced stillage)
- Ethanol Drying Unit (eliminates water from the ethanol)
- Fusel Oil Decanter Unit (removes byproduct fusel oils)

The conventional two-column distillation process allows operators to develop a good understanding of ethanol distillation principles and operations that would be applicable to commercial ethanol production facilities. This includes developing an understanding of the thermodynamic limit of ethanol concentration using conventional distillation.

A full range of operations can be learned and practiced on the Ethanol Distillation simulator. These include normal, startup, shutdown, and emergency shutdown procedures.


Instrumentation

Beer Column Instruments & Controls
The beer feed to the unit from battery limits is controlled by FIC-501. The beer ethanol concentration is indicated on AI-501 and the temperature is indicated on TI-501. After passing through E-502 and E-501, the preheated beer temperature is indicated on TI-503 prior to entering the Beer Column T-501.

The top pressure of T-501 is indicated on PI-501 and the overhead vapor temperature is indicated TI-504. Tray 20 temperature is indicated on TI-505. The differential pressure across the trays of the Beer Column is indicated on PDI-503. The bottom level of stillage in T-501 is controlled by LIC-501 which adjusts the flow of stillage to the Stillage Flash Drum D-501. The stillage temperature from T-501 is indicated on TI-506. Direct Low Pressure (LP) steam flow to the bottom of T-501 is controlled by FIC-503. The supply pressure of LP steam is indicated on PI-503.

The level of stillage in the Stillage Flash Drum D-501 is controlled by LIC-502 which adjusts the flow of stillage to storage at battery limits. The flow rate of Medium Pressure (MP) steam to the Stillage Flash Ejector EJ-501 is controlled by FIC-504. The supply pressure of MP steam is indicated on PI-504. The pressure of the Stillage Flash Drum is indicated on PI-502. This pressure is affected by the net vapor compression capacity of EJ-501 which is, in turn, affected by the MP steam flow to the ejector. Therefore, adjustments to the MP steam flow will affect the pressure in D-501. Keep in mind that any MP steam flow adjustments will also affect the performance of the distillation columns. More steam will eventually increase the ethanol concentration in the vapor to the drying unit and will increase the reflux in the two columns.

The motors for Stillage Pumps P-501A/B are operated by switches HS-501A/B, respectively. The warm stillage temperature leaving P-501A/B is indicated on TI-507. The temperature of stillage after cooling in E-501 is indicated on TI-508. The flow rate of stillage to storage at battery limits is indicated on FI-502.

Rectification Column Instruments & Controls
The ethanol concentration of the vapor feed to the Rectification Column T-502 from the Beer Column T-501 is indicated on AI-502. The level of the bottom of T-501 is controlled by LIC-511 which adjusts the setpoint of the column bottoms liquid flow controller FIC-511. Rectification Column bottoms is reflux for the Beer Column T-501. The T-502 bottoms liquid temperature is indicated on TI-515. The ethanol composition of the bottoms liquid is indicated on AI-511.

The motors for Rectification Column Bottoms Pumps P-502A/B are operated by switches HS-502A/B, respectively. The flow of column bottoms from P-502A/B to Beer Column T-501 is controlled by FIC-511.

Rectification Column Instruments & Controls
The differential pressure across the trays of T-502 is indicated on PDI-512. The flow of the upper side draw to the Fusel Oil Decanter X-502 is controlled by HIC-511. The upper draw tray temperature is indicated on TI-513. The flow of the lower side draw to the Fusel Oil Decanter X-502 is controlled by HIC-512. The lower draw tray temperature is indicated on TI-514. The wash water flow to X-502 is controlled by FIC-512. The net produced fusel oil product flow to battery limits is indicated on FI-513.

The temperature of tray 28 is controlled by TIC-512 which adjusts the cooling water flow through Condenser E-503. Increasing the cooling water flow will produce more condensate from E-503 which, in turn, will cause the reflux flow to the top of T-502 to increase. As the reflux flow increases, the temperature of tray 28 will decrease because the tray’s ethanol concentration will increase at the expense of the water concentration.

The pressure at the top of T-502 is indicated on PI-511. The overhead vapor temperature entering Beer Preheater No. 1 E-502 is indicated on TI-511. The temperature of the partially condensed vapor leaving E-502 is indicated on TI-516. The beer feed temperature leaving E-502 is indicated on TI-502.

Condenser & Drying Section Instruments & Controls
The process side outlet temperature of Rectification Column Condenser E-503 is indicated on TI-521. The cooling water flow through E-503 is controlled by tray 28 temperature controller TIC-512. Note that TV-512 has a minimum stop of 10% to prevent complete stoppage of cooling water flow through E-503.

The pressure of Reflux Drum D-502 is normally controlled by PIC-521B which controls the flow of concentrated ethanol vapor to the Ethanol Drying Unit X-501. The flow of vapor to X-501 is indicated on FI-523 and the ethanol content of the vapor is indicated on AI-521. PIC-521A will automatically vent the ethanol vapor from D-502 if the pressure gets too high. Its setpoint is 20 PSIA.

The flow of product ethanol from X-502 is indicated on FI-524. The flow of recycle ethanol is indicated on FI-525.

The level of D-502 is normally controlled by LIC-521A which adjusts the setpoint of the Rectification Column reflux flow controller FIC-521. In case the level in D-502 gets too high, LIC-521B will divert wet ethanol from D-502 to storage at battery limits. The setpoint of LIC-521B is 90%.

The motors for Reflux Pumps P-503A/B are operated by switches HS-503A/B, respectively. The flow of reflux (wet ethanol) P-503A/B to Rectification Column T-502 is controlled by FIC-521. The concentration of ethanol in the reflux is indicated on AI-522 and the temperature of the reflux is indicated on TI-522. The flow rate of wet ethanol to storage at battery limits is controlled by FIC-522.