Optimal design of solar-assisted industrial processes considering heat pumping: Case study of a dairy

Abstract

Pinch analysis and Mixed Integer Linear Programming (MILP) have been extensively studied for optimization of industrial processes addressing heat recovery, utility selection and sizing. Analysis of renewable utility integration, such as solar thermal or photovoltaics, introduces several obstacles for established methods: the time-dependency of resources, storage inertia and losses, and intrinsic non-linearities of the system performance are difficult to represent by linearized, time-invariant MILP equations. Moreover, waste heat recovery options such as heat pumping cannot be neglected as a potential competitor to solar heat. This work presents a set of multi-period MILP equations for solar technologies as well as a superstructure for optimization of heat pump cycles. Additionally, a methodology is proposed and applied to simultaneously optimize the process' refrigeration and renewable utility system using ε-constrained parametric optimization. The proposed methodology is illustrated on the basis of a dairy plant for which the different utility technologies are compared and evaluated based on economic and environmental criteria. It is illustrated that integration of solar energy can contribute to strongly reduce the environmental impact of the process (65-75% reduction in CO 2 equivalent emissions), but only in combination with heat recovery (27%) and an improved heat pump system (33%). Heat recovery and heat pump placement for industrial processes are hereby shown to reduce exergy destruction and total costs and increase energy efficiency in the system by means of thermo-economic optimization. The solutions show that investment in solar energy can be economically and environmentally attractive for industrial processes by considering the whole system and ensuring that solar energy is optimally integrated and utilized.

Optimal heat pump integration in industrial processes

“…This paper addresses the gaps denoted (2) and (3) by presenting a novel comprehensive superstructure synthesis method which is solved using mathematical programming for optimal integration of industrial heat pump systems. Preliminary versions of this heat pump superstructure (HPS) [32,33] were generalized and extended to incorporate fluid selection, HEN [34] 2016 AHP MINLP -contin. 1 TAC G Oluleye et al [35] 2016 HP/AHP/HE/AHT TP HYSYS 10 K 2 Fuel S TP Oluleye et al [36] 2016 HP/AHP/HE/AHT MILP HYSYS 10 K 2 TAC S Binary Dinh et al [37] 2015 HP MILP PR fixed 3 Power S ( ) Flowrates Kamalinejad et al [29] 2015 HP MINLP RP contin.…”

Critical Analysis of Process Integration Options for Joule-Cycle and Conventional Heat Pumps

“…The first process is a spray drying process of milk powder in a dairy factory [35], and its GCC is shown in Figure 8. The second process is also from dairy product processing [36], which uses raw milk to produce concentrated milk, pasteurised milk, cream, yoghurt and dessert. The GCC for that is shown in Figure 9.…”

“…The stream data are taken from Wallerand et al [36], as shown in the Appendix A (Table A1). The ∆T min of the process is 4 • C. As can be seen from the GCC in Figure 9, the Pinch Temperature of this process is 66.9 • C. The hot utility required is 2.34 MW and the cold utility required is 0.94 MW.…”

A Systematisation of Methods for Heat Integration of Solar Thermal Energy in Production Processes: A Review

“…Milk chilling, fruit cleaning, milk pasteurisation and fruit drying are included in use of solar heat. Moreover, Wallerand et al [39] analysed a dairy plant in Switzerland. Production of concentrated milk, yogurt and other dairy products is integrated with a combination of solar heating, photovoltaics and heat pumps.…”