Heat pump integration in a cheese factory

The aim of process integration is to increase the efficiency and to reduce the energy consumption, operating costs and CO 2 emissions of an industrial process. The proposed methodology is applied to a real case study of a cheese factory with non-simultaneous process operations and uses the time average approach combined with restricted matches. This work focuses on appropriate heat pump integration and two different integration strategies are proposed. In the first option, process modifications and direct heat exchange between the process and heat pump streams are not allowed, which means that the integration of heat pumps has to be realized through intermediate heat transfer networks. On the contrary, in the second option, direct heat exchange and process modifications are possible. The results of both options are analyzed and compared for the French and German context. Depending on the industrial constraints and the location, it is shown that the final choice of new heat pump installations may be different. Saving potential in operating costs is higher for option 2 where the cost savings can be higher than 40% for both countries. Furthermore the potential CO 2 emissions and primary energy savings are compared. © 2011 Elsevier Ltd. All rights reserved.

Process integration and opportunities for heat pumps in industrial processes

Helen Carla Becker, François Maréchal

Process integration methods allow one optimizing industrial processes. The main goals are decreasing energy demand and operating costs as well as reducing pollutants emissions. High fuel costs promote installations of heat pumps. In a heat pump, process waste heat is valorized by electrical power to produce higher quality heat. This energy is used to satisfy a part of the process demand so that less fuel is required and CO2 emission will decrease. Based on pinch analysis, this paper presents a methodology to identify heat pump opportunities in industrial processes. The method considers the whole process including utilities and the energy conversion system. A combined analysis which considers thermal and material streams in the process is realized to optimize the heat recovery and the integration of energy conversion units. By analogy, all water streams are listed and the potential of water recuperation is also calculated. The combination of appropriate refrigeration and heat pump cycles leads to an important energy saving potential. The respective flow rates are defined by optimization. The application case of a typical dairy process is used to calculate the energy and operating cost savings potential as well as its corresponding investment costs and payback rates.

2011

Methodology and Thermo-Economic Optimization for Integration of Industrial Heat Pumps

Helen Carla Becker

This thesis presents a systematic methodology, based on pinch analysis and process integration techniques, to integrate heat pumps into industrial processes. The main goals are to decrease the energy consumption and the corresponding operating costs, and therefore to increase the energy efficiency of an industrial process. The objective of this thesis is to identify heat pump opportunities, and to optimize simultaneously the energy conversion and utility system of a process. The process and utility integration is realized, using mixed integer linear programming (MILP). In order to find systematically the optimal operating conditions of heat pumps, an optimization framework combining linear and non-linear optimization methods is presented. Technologically feasible heat pumps are collected in a data base and proposed to the process. A multi-objective optimization, combined with process integration methods, gives the possibility to systematically identify optimal heat pump sizing and positioning solutions. Pinch analysis is a promising tool, however several limits have been discovered, and the basic methodology has been extended to obtain more realistic solutions. The first extension gives the possibility to integrate heat exchange restrictions due to industrial constraints (e.g. safety reasons, or long distances). A methodology, based on the decomposition into sub-systems, is developed to include heat exchange restrictions. The penalty of these heat exchange restrictions can be decreased by integrating intermediate heat recovery loops, which transfer heat indirectly between two sub-systems. A further developed extension, which enables to define subsystems at different levels, makes the approach very flexible and useful for many different application cases. The second extension is realized to integrate multi-period and multi-time slice problems. The main focus is the integration of storage units, to enable the heat recovery between different time slices. The interest in heat pumps can be increased when integrating storage units, because their working hours and profitability increase. The methodology and its extensions are tested and validated with several real industrial case studies. It is shown that there is a great potential for industrial heat pumps.

EPFL2012

Methodology and Thermo-Economic Optimization for Integration of Industrial Heat Pumps

Helen Carla Becker

EPFL2012