A software for simulation of fermentation processes

CO23_edited
A SOFTWARE FOR SIMULATION OF FERMENTATION PROCESSES

By

M. RIBAS, R. HURTADO, F. DOMENECH, R. SABADI, N. GARRIDO

Cuban Research Institute on Sugar Cane Derivatives (ICIDCA)

mauricio.ribas@icidca.edu.cu

KEYWORDS: Fermentation processes, mathematical modelling, ethanol production, software simulation
Abstract

Fermentation is a key process stage in ethanolproduction and has a high incidence in the overall process efficiency in distillery. For improving this efficiency, a rigorous analysis for defining the best choice in operation variables is needed. Simulation of the process is a recognised way for doing such an analysis. In this paper, the software tool FERMENTA® for simulation of fermentation processes is presented. This software tool allowssimulation of continuous and discontinuous modes of fermentation. In the continuous mode of operation, several stages can be considered. In the batch mode, alternatives for feeding (batch, fed batch with different politics) can be analysed. The mathematical model includes non-stationary balances for biomass, substrate, ethanol, oxygen, energy. The kinetic expression can be selected by the user among morethan 30 possibilities, taking or not into account inhibition factors in the process. Parameters in this equation can be estimated from experimental data. The result is a useful software tool that can be used for analysis of fermentation processes in industry and also for academic purposes. In this paper, the software is described and some case studies used for showing its possibilities.Introduction

The technology of ethanol production by anaerobic fermentation of sugarcane molasses is well known. This process, used initially in the production of alcoholic drinks, reached high generalisation grade during the Second World War with the purpose of having an alternative source of fuel. Nowadays, ethanol with different purity grades is still produced from molasses and sugar juices.Their uses go from the pharmaceutical and cosmetics industry to the production of alcohol used as fuels by vehicles.

Keeping in mind the multiple uses of ethanol, there is an intensified interest in the study of all steps involved in ethanol production in order to reduce costs. Mathematical modelling reduces research costs by eliminating part of the experimental work, because it allows the studyof process parameter interactions through simulation. Besides, it provides understanding of the process, which is helpful for operational policy definitions and can be applied for later optimisation and control.

In this paper, the mathematical model of alcohol fermentation process and FERMENTA 4.0 software, designed for simulating this process, is presented. This software could be useful inother fermentative processes because it reduces costs by eliminating part of the experimental work and allows the study of process parameter interactions through simulation. Besides, it provides understanding of the process, which is helpful for operational policy definitions and can be applied for later optimisation and control.

Finally, we present a case study where the influence of someoperational conditions on the yield and productivity of fermentation processes was assessed. We compare the simulation results with typical industrial data.

Process Description

The conversion of sugar to ethanol is an anaerobic biological reaction by Saccharomyces cerevisiae yeast cells. This yeast is used commercially and classified as heterotrophics, the necessities of coal and energyare satisfied by monosaccharides (simple sugars) like glucose. Disaccharides like sucrose can also be used after the hydrolysis of the yeast in fructose and glucose (inverted sugar).

Raw materials used for ethanol production include sugary ones: juices of different fruits, beet juices, juices of cane sugar, intermediate streams of the process like molasses, etc. Sugarcane is a raw...