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

Ján Janošovský,Eva Marková,Adriána Kačmárová,Miroslav Variny

doi:10.3390/pr8101262

Ján Janošovský, Eva Marková + Show 2 more

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https://doi.org/10.3390/pr8101262

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Journal: Processes	Publication Date: Oct 7, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Slovak University of Technology in Bratislava

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.

Highlights

Increasing depletion of fossil fuels and emission of greenhouse gases have motivated significant advances in renewable energy use in the last decade
In the second part of the process simulation, the verified Aspen Plus model was used to predict steam consumption of the new milk drying unit with the fresh whole milk capacity of 4800 kg/h which corresponded to approximately 25% of total milk processing rate in the analyzed dairy plant
The presented approach consisted of mathematical modeling and economic analysis based on a parametric sensitivity study

Summary

Introduction

Increasing depletion of fossil fuels and emission of greenhouse gases have motivated significant advances in renewable energy use in the last decade. Biogas is used mainly as fuel in steam boilers and in combined heat and power generation, as a biomethane for injection into the natural gas grid and as transportation fuel [2,3]. The first common biogas treatment step is desulphurization to avoid excessive corrosion and other operability problems associated with the presence of H2 S and its oxidation products. It can be carried out physicochemically or biologically, inside the digester or in a separate unit [5]. In order to inject biogas into the natural gas grid in European countries, methane volumetric content from at least 85% to more than 97% is required [3]

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