A Holistic Methodology for Optimizing Industrial Resource Efficiency

Efficient consumption of energy and material resources, including water, is the primary focus for process industries to reduce their environmental impact. The Conference of Parties in Paris (COP21) highlighted the prominent role of industrial energy efficiency in combating climate change by reducing greenhouse gas emissions. Consumption of energy and material resources, especially water, are strongly interconnected and, therefore, must be treated simultaneously using a holistic approach to identify optimal solutions for efficient processing. Such approaches must consider energy and water recovery within a comprehensive process integration framework which includes options such as organic Rankine cycles for electricity generation from low–medium-temperature heat. This work addresses the importance of holistic approaches by proposing a methodology for simultaneous consideration of heat, mass, and power in industrial processes. The methodology is applied to a kraft pulp mill. In doing so, freshwater consumption is reduced by more than 60%, while net power output is increased by a factor of up to six (from 3.2 MW to between 10–26 MW). The results show that interactions among these elements are complex and therefore underline the necessity of such comprehensive methods to explore their optimal integration with industrial processes. The potential applications of this work are vast, extending from total site resource integration to addressing synergies in the context of industrial symbiosis.

Conventional and advanced district energy systems

Daniel Favrat, Céline Weber

District energy systems have the potential to decrease the CO2 emissions linked to energy services (heating, hot water, cooling and electricity), thanks to the implementation of large polygeneration energy conversion technologies, connected to a group of buildings over a network. To transfer the energy from the large polygeneration energy conversion technologies to the users, conventional district energy systems use water as energy transfer medium with often two independent supply and return piping systems for heat and cold. However, sharing energy or interacting with decentralized heat pump units often results in relatively large heat transfer exergy losses due to the large temperature differences that are economically required from the water network. Using refrigerants as a district heating or cooling fluid at an intermediate temperature could alleviate some of these drawbacks. Because of the environmental concerns about conventional refrigerants, CO2, which is a natural refrigerant, used under its critical point, could be an interesting candidate. Pipe sizing of a multiservices superstructure, based on a two pipe CO2 network at 18°C is compared with a standard 4 pipes water network for heating and cooling.

Universita degli Studi di Padova2007

Energy efficiency and conversion in complex integrated industrial sites

Zoé Périn-Levasseur

This thesis presents a methodology to analyse the integration of heat recovery energy conversion technologies and biorefinery concepts in existing pulp and paper facilities. By using innovative process integration techniques and thermo-economic optimisation tools, efficient energy saving opportunities can be obtained and guidelines can be applied to implement energy efficiency enhancing measures. The objective is to provide engineers a decision support tool for the design of heat exchangers networks. The system approach used in this work is based on the development of a framework that implements existing simulation tools and process integration methods. The first contribution of this work resides in the establishment of a reconciled model of a complex pulping facility where utility and process measurements are studied simultaneously. Derived operating nominal conditions are validated through a complete sensitivity analysis. The resulting base case model is considered to be representative of the original process and constitutes the basis of the process energy integration definition problem. The core of the methodology consists in the application of two successive approaches: the top-down and the bottom-up approach. The top-down approach allows to identify which sub-systems of the facility consume more energy and could eventually lead to large energy savings. Conversion technologies used to produce utilities and their distribution to the process are also identified. The bottom-up approach benefits from the results of the top-down approach in order to evaluate the energy saving potentials. Systematic definition of the process heat transfer requirement defined as hot and cold streams is obtained according to different heat-temperature profiles. The exergy concept is employed to explain how using different heat-temperature profiles of the same energy requirement is changing the perspective of the energy use in the facility and therefore make possible the identification of energy saving opportunities with different levels of process modifications. An innovative way of considering the steam producers using as a main feed process materials in the definition of the process integration problem is also presented. The development of scenarios using systematically all energy requirement definitions is done and allows the elaboration of a decision support tool that point out the critical process modifications necessary to achieve interesting energy savings. A detailed example of the complete methodology developed in this thesis is illustrated using the multi-effect evaporator. The optimal integration of combined heat and power production and heat pumps is also presented. Finally, the interest of using this methodology is demonstrated in the case of a biorefinery integration by the development of a trade-off between the conversion of lignocellulosic materials into bio-materials and energy.

EPFL2009

Methodology for the identification of promising integrated biorefineries

Ayse Dilan Celebi

Steady increase in global energy consumption, greenhouse gas emissions, and depletion of fossil energy resources, together with increased attention towards sustainable development has prompted researchers to discover economical and environmentally competitive non-petroleum alternatives and biomass is considered to be one of the most promising renewable sources of energy and carbon of this matter to address the aforementioned issues within a biorefinery platform. A biorefinery is an integrated processing facility that converts biomass into transportation fuels, value-added chemicals, heat, and electricity via biochemical and thermochemical conversion routes. Integrated biorefineries are capable of mimicking petroleum refineries via application of advanced process synthesis methods including modeling, simulation, integration and optimization techniques. This thesis presents a comprehensive synthesis methodology for the integration of bioprocessing technologies in biorefineries by addressing techno-economic and environmental sustainability analysis. The proposed systematic design approach combines advanced process modeling approaches, process integration techniques, and multi-objective optimization algorithms to assess the performance of the overall system with respect to economic, environmental, and energetic indicators. The design strategy is applied based on different case studies. Results indicate that multi-product processes can yield significant cost and environmental benefits. Additionally, the integration of biochemical and catalytic processes with thermochemical conversion pathways results in increased carbon efficiency and economic and environmental competitiveness. Synergies between biorefineries and energy system are assessed by integrating industrial plants with a cogeneration system producing biofuels and process heat. In doing so, system efficiency is increased by coupling the proposed cogeneration system with carbon capture and sequestration (CCS) and power-to-gas technologies to store the renewable intermittent electricity in the form of biofuels. The results exhibit that through system expansion, integrated biorefinery systems allow us to imitate fossil refineries with a large spectrum of bio-based products. This further increases the resource efficiency while offering a promising solution to mitigate CO2 emissions and hence reaching the longer-term decarbonization target set by the Paris Agreement.