Green Dairy Plant: Process Simulation and Economic Analysis of Biogas Use in Milk Drying

Abstract

A project of a new milk drying unit processing 4800 kg/h of fresh milk into milk powder with expected steam consumption of 1000 kg/h (equivalent to ca. 2.6 GJ/h) was assessed. In this paper, investment profitability of this project was analyzed combining mathematical modeling, market analysis, and parametric sensitivity study. Aspen Plus was used as the simulation environment to determine values of key process variables—major streams, mass flows, and energy consumption. Co-digestion of cattle manure in an adjacent biogas plant was considered to provide biogas to partially or completely substitute natural gas as an energy source. As biogas composition from potential co-digestion was unknown, variable methane content from 45 to 60 mol.% was considered. In the next step, thorough economic analysis was conducted. Diverse effects of biogas addition depending on market prices, biogas treatment costs, and biogas methane content were simulated and evaluated. In a market situation closest to reality, biogas mixing to boiler fuel decreased simple payback period from 11.2 years to 5.1 years. However, if biogas treatment costs were high (final biogas price equal to or above 0.175 EUR/m3), the simple payback period was increased two- to sixfold, making the analyzed project practically unfeasible.

A review of commercial process simulators applied to food processing

“…For example, Quintero et al (2013) used Excel and MATLAB subroutines to reproduce detoxification and sugar fermentation reactions; Madoumier et al (2017) applied generic built‐in unit operation coupled with short‐cut models to represent pre‐heaters and pasteurizers with pre‐established heat exchangers. In Janošovský et al (2020), the burner was simulated as a stoichiometric reactor with defined 100% conversion of combustible components, the furnace as a shell‐and‐tube heat exchanger, and the feed water preheater as a mixer. All these works are detailed and listed in Table 2, among other relevant cases of study in the food process field, found in literature, in line with this review.…”

“…With the main objective of analyzing energy consumption and costs, Janošovský et al (2020) simulated the whole production line to obtain powder milk using Aspen Plus. Milk was simulated as an aqueous solution of six chemicals representing fat (palmitic and oleic acid), carbohydrates (lactose), minerals (calcium and potassium), and proteins (proline).…”

“…As a start point Ribeiro and Caño (2003) (also applied by Madoumier et al, 2017) approximated the thermophysical changes in the product considering separately the evaporated water (available Aspen models) and incorporating literature equations for milk thermophysical properties. On the other hand, several approaches prompted modeling milk as hypothetical or non‐conventional component (Bon et al, 2010; Janošovský et al, 2020; Munir et al, 2016; Zhang et al, 2014). As a missing point we notice that, despite all these studies involved industrial thermal processing of milk (evaporation, concentration, pasteurization), none of them analyzed the damages that temperature could produce in critical nutrients such as vitamins or flavor components.…”

“…The authors also analyze the influence of total solid contents in the predicted properties, assuming typical values found in different dairy processes, including whole, skim and concentrated milk. This way, these results enable predicting material and energy balances for milk as a collection of pseudo-components varying total solids, in a wide range of milk process simulation on the bases of temperature ranges from 4 to 75 C.With the main objective of analyzing energy consumption and costs,Janošovský et al (2020) simulated the whole production line to obtain powder milk using Aspen Plus. Milk was simulated as an aqueous solution of six chemicals representing fat (palmitic and oleic acid), carbohydrates (lactose), minerals (calcium and potassium), and proteins (proline).…”

Anaerobic Digestion for Producing Renewable Energy—The Evolution of This Technology in a New Uncertain Scenario

“…Eliminating these contaminants is of great relevance and this is particularly true for the removal of H 2 S. This compound may cause serious corrosion problems and give rise to operability issues associated with its oxidation products. In the case of CO 2 , the importance of removing this compound is based on the quality standard of biogas and the type of valorization technology this gas will be destined to [ 8 , 9 , 10 ].…”