Minimization of energy use in multipurpose batch plants using heat storage: an aspect of cleaner production

Abstract

a b s t r a c tA mathematical technique for optimization of energy use through the exploitation of heat storage in heat integrated multipurpose batch plants is presented in this document. Storage of heat is effected through the use of a heat transfer fluid. The resultant mathematical formulation exhibits a mixed integer linear programming (MILP) structure, which yields a globally optimal solution for a predefined storage size. The concept of heat integration in batch plants with the objective of minimising energy use is indeed an aspect of cleaner production that has received very limited attention in published literature. This is largely because batch plants are perceived to be less energy-intensive compared to their continuous production counterparts which is untrue for some batch operations, like dairy and brewing processes; hence the need for dedicated techniques. Application of the proposed method to an agrochemical facility has shown savings of more than 75% in external utility steam consumption.

The green brewery concept – Energy efficiency and the use of renewable energy sources in breweries

“…For breweries where rescheduling is a delicate issue due to the biological processes the adaptation or integration of storage tanks into the hot water management is a favorable option. Approaches for heat integration for batch processes including heat storage systems have been reported by several authors; however they are still not extensively studied [1][2][3][4]. The ideal choice of renewable energy resources for specific applications has been lately discussed by a number of researchers.…”

Optimum heat storage design for heat integrated multipurpose batch plants

“…Using both direct heat integration and indirect heat integration, via heat storage, may significantly reduce utility needs in a batch processing plant [1]. Optimising the size of the heat storage vessel as well as the initial temperature of the heat storage fluid decreased the requirement for external hot utility for an industrial case study by 33% compared to using suboptimal parameters.…”

“…Both direct and indirect heat integration are considered. The formulation is based on previous models in the literature [14,1]. These models could not adequately address multipurpose facilities, but were ideal for multiproduct cases.…”

“…For non-optimal values for the heat storage capacity and initial heat storage temperature, heat was stored, but not reused over the time horizon [1]. The results for different scenarios are summarised in Table 6.…”

“…Some batch industries do, however, have a much higher utility requirement than others. For example, utility requirements in the food industry, breweries, dairies, meat processing facilities, biochemical plants and agrochemical facilities contribute largely to the total cost [6,7,8,9,10,11,12,1]. Although the energy savings obtainable through heat integration may not be as large in magnitude as in the continuous case, energy savings have often been neglected in batch processes in the past and large percentage savings are possible.…”