Modelling and Optimization of a Brewery Plant from Starch Sources using Aspen Plus

Abstract

The brewing industry faces challenges with the use of malted barley as the primary starch source in Nigeria including quality control and standards, local production and demand, market competition, and price. The challenges of developing new product designs using pilot plants include inherent drawbacks and significant time constraints. This research explores the potential of sorghum as a valuable addition to barley in the brewing industry, especially in semi-arid regions like Africa. This study developed and optimised a model simulated using Aspen Plus for the brewing process, incorporating both malted barley and raw sorghum. Process parameters from a Brewery Plant formed the basis for the model to simulate the entire process from grain to fermented beverage. 1417.5Kg of raw sorghum grist was mashed in the mash copper vessel with 4800Kg of process water at 50℃ to observe protein rest and heated up to 93℃. The mash is cooled down to 75℃ via the mash cooler. At heating to 93℃ of the mash copper, 937.2kg of malted barley grist was mashed in the mash tun vessel with 3500Kg of process water at 50℃ to obverse protein rest. The cooled mash in the mash copper was transferred to the mash tun to achieve saccharification at 66℃ yielding 2460.658 kg/hr of wort after wort separation using a mash filter in the wort kettle. The wort was boiled to 100oC for concentration and sterilization. The boiled wort is pitched with brewer’s yeast (Saccharomyces cerevisiae) after chilling down to 9oC via a plate heat exchanger to commence fermentation. 1321.781 kg/hr of ethanol is produced in the fermentation storage tank during fermentation. Optimisation efforts focused on varying the barley to sorghum ratio, optimizing barley feed resulted in statistically significant improvements in ethanol yield (p<0.0001). The model's accuracy was confirmed through Box-behnken design and ANOVA, demonstrating strong agreement between actual and simulated ethanol yields. Additionally, pinch analysis facilitated heat exchanger optimization, enhancing energy efficiency and sustainability during the brewing process. Heat gained via the water side of the plate heat exchanger during wort cooling was charged into the system for sparging process amounting to energy cost saving of 0.34%. The economic analysis underscored the financial viability of the brewing process, with a total capital cost of $1,133,600.00 and annual operating expenses of $16,831,800.00. Raw material costs totaled $14,738,400.00 annually, while product sales generated $251,082,000.00 per year. Moreover, energy savings were achieved, with low pressure (LP) steam utilization saving $91 per year and refrigerant use contributing $46 annually. The desired rate of return for the project is set at 20% per year, with a payback period of 1.5 years. The findings from this study will contribute to the growing body of knowledge in the field of brewing process simulation and modeling and have practical implications for the brewing industry.