Energy recovery methodology in industrial processes

International audienceThrough the CERES -2 project, supported by the French Research National Agency (ANR), we have developed an open source software platform, called CERES, to optimize heat recovery in continuous industrial processes. This platform is based on a multi-scale and multi critera methodology for heat recovery optimisation. This methodology is based on the following calculation steps:1. Minimum Energy Requirement identification2. Minimum Exergy Requirement and utilities identification3. Exchanger network constructionAt each step we solve a linear mono-objective problem. The first step allows, from a set of heat flows, to build the composite curves and to determine the minimum heating and cooling energy requirements. With the set of heat flows and a solution of the first step, the second step proposes the introduction of utilities, such as heat pumps or organic Rankine cycle (ORC), to minimize the exergy destruction. The last step is based on an algorithm of heat exchanger network design (HEN) including utilities and heat recovery technologies sizing, based on economic criteria. The set of heat flows are constructed in the platform CERES from industrial processes Modelica models. CERES has been validated with 3 industrial case studies

A Multi-Objective Optimization Method to integrate Heat Pumps in Industrial Processes

Aim of process integration methods is to increase the efficiency of industrial processes by using pinch analysis combined with process design methods. In this context, appropriate integrated utilities offer promising opportunities to reduce energy consumption, operating costs and pollutants emissions. Energy integration methods are able to integrate any type of predefined utility, but so far there is no systematic approach to generate potential utilities models based on their technology limits. This work focusses on the integration of industrial heat pumps and the development of a corresponding heat pump data base. This latter offers the possibility to integrate different heat pump types to any process, in a flexible and systematic way. A methodology, integrating the heat pump data base in an energy integration problem, and using multi objective optimization in order to identify optimal solutions, is presented. The results of a brewery process are presented and analyzed

Heat pump integration for total site waste heat recovery

Total Site Heat Integration (TSHI) promotes energy recovery between processes to enhance overall energy efficiency of an industrial complex. Various industrial waste heat utilisation technologies have been studied to improve the energy efficiency of energy system. Vapour compression as an open loop heat pump system has good potential to be used to upgrade the waste heat to useful heat in Total Site systems. Vapour compression systems upgrade low grade waste heat by supplying a low quantity of high pressure steam (thermocompressor) or mechanical work (mechanical-compressor) to generate higher pressure steam, as is common with evaporation systems. The vapour compression system recovers the latent heat content of the industrial waste heat, which reduces cooling demand, decreasing the demand for high quality steam and reducing boiler load. This paper introduces an effective Total Site targeting methodology to integrate open cycle heat pump systems, i.e. vapour compression technologies, into an integrated industrial energy system for enhancing overall site energy efficiency. Industrial waste heat and high quality steam demand are able to be reduced simultaneously though this integration. The energy reduction and cost-benefit of thermo-compressor and mechanical-compressor installations are compared through a literature case study. The case study showed a deficit of heat at the MPS and a surplus of heat the LPS, which was identified as a candidate for compression according to the appropriate placement principle for heat pumps. For the case study, a four-stage mechanical vapour compression system and two-stage thermal vapour compression system resulted in an energy cost reductions of 343,859 USD/y and 168,829 USD/y

Heat Pump Integration in Industrial Processes -II

This semester project follows a previous project at LENI-EPFL ad aims at finding the best optimization approach in terms of heat pump integration in industrial processes. The multi-objective optimization method chosen seeks the minimum of both operating and investment costs related to heat pump purchase

Optimal heat pump integration in industrial processes

Among the options for industrial waste heat recovery and reuse which are currently discussed, heat pumping receives far less attention than other technologies (e.g. organic rankine cycles). This, in particular, can be linked to a lack of comprehensive methods for optimal design of industrial heat pump and refrigeration systems, which must take into account technical insights, mathematical principles and state-of-the-art features. Such methods could serve in a twofold manner: (1) in providing a foundation for analysis of heat pump economic and energetic saving potentials in different industries, and further (2) in giving directions for experimentalists and equipment manufacturers to adapt and develop heat pump equipment to better fit the process needs. This work presents a novel heat pump synthesis method embedded in a computational framework to provide a basis for such analysis. The superstructure-based approach is solved in a decomposition solution strategy based on mathematical programming. Heat pump features are incorporated in a comprehensive way while considering technical limitations and providing a set of solutions to allow expert-based decision making at the final stage. Benchmarking is completed by applying the method on a set of literature cases which yields improved-cost solutions between 5% and 30% compared to those reported previously. An extended version of one case is presented considering fluid selection, heat exchanger network (HEN) cost estimations, and technical constraints. The extended case highlights a trade-off between energy efficiency and system complexity expressed in number of compression stages, gas- and sub-cooling. This is especially evident when comparing the solutions with 3 and 5 compression stages causing an increase of the COP from 2.9 to 3.1 at 3% increase in total annualized costs (TAC)

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

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