Heat Recovery Opportunities Research Articles

Opportunities for Low Value Heat Recovery at Wastewater Treatment Plants

Opportunities for Low Value Heat Recovery at Wastewater Treatment Plants

Heat recovery and heat pumping opportunities in a slaughterhouse

Pinch analysis was employed to recover and reuse a part of the waste energy during the production and cleaning periods of a slaughterhouse in Canada. The INTEGRATION software was used to find possible options for HR (heat recovery). Several HR opportunities were identified in various systems of the slaughterhouse including boilers, hot water production, singeing, refrigeration, and barn air heating. A recommendation was also made to store more energy in the form of hot water. Opportunities for using heat pumps for additional HR were also investigated. The proposed projects can significantly reduce natural gas consumption in the steam and hot water boilers as well as in the air heating systems. It is shown that the proposed projects can reduce natural gas use by approximately half a million dollars per year.

Waste heat and water recovery opportunities in California tomato paste processing

Water and energy efficiency are important for the vitality of the food processing industry as demand for these limited resources continues to increase. Tomato processing, which is dominated by paste production, is a major industry in California – where the majority of tomatoes are processed in the United States. Paste processing generates large amounts of condensate as moisture is removed from the fruit. Recovery of the waste heat in this condensate and reuse of the water may provide avenues to decrease net energy and water use at processing facilities. However, new processing methods are needed to create demand for the condensate waste heat. In this study, the potential to recover condensate waste heat and apply it to the tomato enzyme thermal inactivation processing step (the hot break) is assessed as a novel application. A modeling framework is established to predict heat transfer to tomatoes during the hot break. Heat recovery and reuse of the condensate water are related to energy and monetary savings gained through decreased use of steam, groundwater pumping, cooling towers, and wastewater processing. This analysis is informed by water and energy usage data from relevant unit operations at a commercial paste production facility. The case study indicates potential facility seasonal energy and monetary savings of 7.3 GWh and $166,000, respectively, with most savings gained through reduced natural gas use. The sensitivity of heat recovery to various process variables associated with heat exchanger design and processing conditions is presented to identify factors that affect waste heat recovery.

Heat integration in processes with diverse production lines: A comprehensive framework and an application in food industry

Heat integration is a key measure to improving energy efficiency and maximising heat recovery. Since the advent of Pinch analysis in the 1980s, direct and indirect integration approaches have developed in separate domains with very few examples where both approaches are utilised together to maximise heat recovery. This paper presents a novel decision-making framework for heat integration in complex and diverse production lines, with the aim to provide the user with a step-by-step guide to evaluate all heat recovery opportunities through a combination of direct and indirect heat integration. This framework involves analysis at both the zonal level and the factory level. The proposed framework was applied to a case study based on a confectionery factory in the UK that manufactured multiple products across a diverse range of food technologies. It demonstrates that the framework can effectively identify the significant streams to be considered in the heat integration analysis, and address practical factors such as diverse production times, geographical proximity, and potential of compromise to product quality when the direct and indirect heat integration opportunities are proposed and assessed both within and between production zones. This practical framework has the potential to benefit the wider food industry and beyond.

Biomass Gasification-Based Syngas Production for a Conventional Oxo Synthesis Plant—Process Modeling, Integration Opportunities, and Thermodynamic Performance

This work investigates the energy performance consequences of replacing conventional natural gas-based syngas production with biomass gasification-based production as a supply of feedstock for a conventional oxo synthesis plant. The investigation is conducted for a plant currently processing 175 MW [higher heating value (HHV) basis] of natural gas (NG) annually. Two concepts based on the same gasification technology are considered: (i) replacing the NG feedstock with biomass-derived synthetic NG (bio-SNG); (ii) replacing syngas with biomass-derived syngas. The work is based upon process models established in Aspen Plus in order to obtain mass and energy balances. Heat recovery opportunities by means of production of useful thermal heat and integration of a steam network for combined heat and power production are investigated using pinch analysis tools. Two different ways of harnessing the high-temperature excess heat are investigated: (i) maximization of the power production; (ii) low-pressure (LP) steam ...

A review of data center cooling technology, operating conditions and the corresponding low-grade waste heat recovery opportunities

Abstract The depletion of the world's limited reservoirs of fossil fuels, the worldwide impact of global warming and the high cost of energy are among the primary issues driving a renewed interest in the capture and reuse of waste energy. A major source of waste energy is being created by data centers through the increasing demand for cloud based connectivity and performance. In fact, recent figures show that data centers are responsible for more than 2% of the US total electricity usage. Almost half of this power is used for cooling the electronics, creating a significant stream of waste heat. The difficulty associated with recovering and reusing this stream of waste heat is that the heat is of low quality. In this paper, the most promising methods and technologies for recovering data center low-grade waste heat in an effective and economically reasonable way are identified and discussed. A number of currently available and developmental low-grade waste heat recovery techniques including district/plant/water heating, absorption cooling, direct power generation (piezoelectric and thermoelectric), indirect power generation (steam and organic Rankine cycle), biomass co-location, and desalination/clean water are reviewed along with their operational requirements in order to assess the suitability and effectiveness of each technology for data center applications. Based on a comparison between data centers' operational thermodynamic conditions and the operational requirements of the discussed waste heat recovery techniques, absorption cooling and organic Rankine cycle are found to be among the most promising technologies for data center waste heat reuse.

Heat recovery opportunities in UK industry

A database of the heat demand, and surplus heat available, at United Kingdom industrial sites involved in the European Union Emissions Trading System, was used to estimate the technical potential of various heat recovery technologies. The options considered were recovery for use on-site, using heat exchangers; upgrading the heat to a higher temperature, using heat pumps; conversion of the heat energy to fulfill a chilling demand, using absorption chillers; conversion of the heat energy to electrical energy, using Rankine cycles; and transport of the heat to fulfill an off-site heat demand. A broad analysis of this type, which investigates a large number of sites, cannot accurately identify site level opportunities. However the analysis can provide an indicative assessment of the overall potential for different technologies. The greatest potential for reusing this surplus heat was found to be recovery at low temperatures, utilising heat exchangers; and in conversion to electricity, mostly using organic Rankine cycle technology. Both these technologies exist in commercial applications, but are not well established, support for their development and installation could increase their use. The overall surplus heat that was technically recoverable using a combination of these technologies was estimated at 52PJ/yr, saving 2.2MtCO2e/yr in comparison to supplying the energy outputs in a conventional manner. It is thought that a network and market for trading in heat and the wider use of district heating systems could open considerable potential for exporting heat from industrial sites to other users.

Innovative visualization technique for energy flow analysis: Waste heat recovery and energy savings opportunities

Improving the performance of existing industrial plants through new technologies and innovative eco-energy solutions is raising a lot of challenges for researchers and practitioners. In the search for new sustainable designs, understanding the current energy distribution within a plant in regards to its energy requirements is essential for the decision-making process. The technique of Composite Curves is commonly employed to evaluate the scope for energy savings. However, it is seldom self-explanatory. In the present work, an alternative to the energy Composite Curves representation is proposed to complement the visualization of energy integration opportunities. A novel energy management assessment based on mapping of the overall process energy is introduced as a practical illustration to support the thermal energy integration.

An Overview of Opportunities for Waste Heat Recovery and Thermal Integration in the Primary Aluminum Industry

Efficient smelters currently consume roughly 13 MWh of electricity per ton of aluminum, while roughly half of that energy is lost as thermal waste. Although waste heat is abundant, current thermal integration in primary aluminum facilities remains limited. This is due to both the low quality of waste heat available and the shortage of potential uses within reasonable distance of identified waste heat sources. In this article, we present a mapping of both heat dissipation processes and heat demands around a sample facility (Alcoa Deschambault Quebec smelter). Our primary aim is to report opportunities for heat recovery and integration in the primary aluminum industry. We consider potential heat-to-sink pairings individually and assess their thermodynamic potential for producing energy savings.

Opportunities for low-grade heat recovery in the UK food processing industry

Energy efficiency in the process industry is becoming an increasingly important issue due to the rising costs of both electricity and fossil fuel resources, as well as the tough targets for the reduction in greenhouse gas emissions outlined in the Climate Change Act 2008. Utilisation of waste heat sources is key to improving industrial energy efficiency, with an estimated 11.4 TWh of recoverable heat being wasted each year, a quarter of which is from the food and drinks processing sector.This paper examines the low-grade waste heat sources common to the food and drinks processing sector and the various opportunities for the use of this heat. A review of the best available technologies for recovery of waste heat is provided, ranging from heat transfer between source and sink, to novel technologies for the generation of electricity and refrigeration.Generally, the most economic option for waste heat recovery is heat exchange between nearby/same process source and sink, with a number of well-developed heat exchangers widely available for purchase. More novel options, such as the use of organic Rankine cycles for electricity generation prove to be less economical due to high capital outlays. However, with additional funding provision for demonstration of such projects and development of modular units, such technologies would become more common.

Energetic and exergetic assessments of a cement rotary kiln system

The cement production is one of the most energy consuming processes, typically accounting for 50 to 60% of the production costs. However, there are several ways of heat recovery opportunities to achieve better energetic and exergetic efficiencies for the whole system. In this paper, energetic and exergetic analyses of an existing rotary kiln system are presented, and first and second law efficiencies are calculated. Two distinct cogeneration systems which use the waste heat from both pre-heater and clinker cooler exhaust gases to produce either electricity and/or to preheat the raw material before entering the kiln system. The effect of these two heat recovery systems on the overall efficiency of the system is also discussed. The results showed that the energy and exergy efficiencies of the existing system are 54.9 and 28.1%, respectively. With the cogeneration, these exergy efficiencies have been obtained to be 70.6% for the use of waste heat recovery steam generator (WHRSG) and 81.5% for the use of heat to pre-heat the raw material, respectively, which dictates a remarkable improvement over the existing system. Key words: Cement process, rotary kiln system, energy and exergy audit, cogeneration.

Exergy analysis of heat exchangers in the copper-chlorine thermochemical cycle to enhance thermal effectiveness and cycle efficiency

Most existing nuclear power plants in North America are typically water-cooled and operate at 250–500°C. For this temperature level, the copper–chlorine (Cu–Cl) cycle is one of the most promising cycles that can be integrated with nuclear reactors for hydrogen production by decomposing water into its constituents. In this study, we analyze the heat exchangers in the Cu–Cl thermochemical cycle so as to enhance heat transfer effectiveness and thereby improve the cycle efficiency. The thermal management options for internal and external heat transfer are studied and heat recovery opportunities are investigated and compared. Each heat exchanger in the cycle is examined individually based on the chemical/physical behavior of the process, and the most appropriate options are recommended. A thermodynamic analysis and associated parametric studies are performed for various configurations to contrast their efficiencies and effectivenesses.

Energy Conservation Opportunities in Industrial Waste Heat Recovery Systems

ABSTRACT This article discusses waste heat recovery opportunities. Some of the opportunities are taken from energy audits and feasibility studies carried out in various plants located in Ontario, Canada. Opportunities discussed in the article include compressed air waste heat recovery, the application of a condensing economizer for heating boiler make-up water, waste heat recovery from coffee roasters, waste heat recovery from chemical reactor exhaust to preheat combustion air, steam boiler blowdown heat recovery, etc. The article also points out how some of the opportunities can be very attractive, depending on specific process and the existing system.

Energy Conservation Opportunities in an Industrial Refrigeration System

Industrial refrigeration can be found in many types of applications such as food processing, product preservation, and more. In many cases, it can represent one of the largest energy consumers in a facility. Studies show that it is possible to reduce energy consumption by up to 40 percent in industrial refrigeration systems. This article presents an analysis of the energy conservation opportunities identified in an ammonia-based industrial refrigeration system in a Canadian warehouse. Some of the energy conservation opportunities included in the analysis are: application of a floating head pressure control; application of variable-frequency drives in evaporator fans; optimization of hot gas defrost; heat recovery opportunities from the evaporative condensers; reduction of infiltration of air in cold storage; application of bi-level lighting control in the lamps in the cold storage; and application of screw compressor VFD controls.

Minimum energy consumption in sugar production by cooling crystallisation of concentrated raw juice

The sugar manufacturing process based on cooling crystallisation of concentrated raw juice is considered. Micro-filtration and softening of raw juice makes it possible to obtain white sugar by three-or four-stage cooling crystallisation. Prior to crystallisation, raw juice should be concentrated by multistage evaporation in a pressure range below the atmospheric pressure. The preferred evaporator arrangement is backward feed. As the temperature of vapours and condensates leaving the evaporator station is low, the opportunities for heat recovery are limited. In order to save energy, vapour recompression can be applied. For a given evaporator structure, the energy consumption depends on the parameters of the evaporation process. The minimum energy consumption of the novel process should thus be determined by simultaneously carrying out energy targeting and optimisation of evaporation. It is assumed that the consumption of utilities in the sugar factory is balanced with the supply of heat and power from the factory’s own power plant. Energy systems employing various CHP technologies and various evaporator stations optionally combined with vapour compressors are studied. A range of feasible solutions is defined in terms of minimum energy consumption and combined heat transfer area of the evaporator station and the heat exchanger network.

Integrated Design of a Conventional Crude Oil Distillation Tower Using Pinch Analysis

The substantial energy requirement of crude oil distillation columns is met partly by costly utilities, such as steam and fuel for fired heaters, and partly by heat recovered from the process, using process-to-process heat exchange. Energy savings, therefore, demand not only a distillation column that is energy-efficient, but also a heat exchanger network (HEN) which minimizes utility costs by maximizing heat recovery. A new crude oil distillation design procedure is presented which considers the column, the HEN and their interactions simultaneously, to minimize utility costs. Pinch analysis is used to determine minimum utility costs prior to the design of the HEN. In this method, the column is decomposed into a sequence of simple columns, which enables appropriate distribution of stages and simplifies analysis. Modifications, which further increase the efficiency of the process, are proposed: these are the installation of reboilers, rather than stripping steam, and the thermal coupling of column sections. The detrimental effects of these modifications on the heat recovery opportunities of the process are analysed for a distillation tower with side-strippers. A new step-by-step design procedure is derived from this analysis, and is applied to a case study. In the case study, the resulting design offers nearly 20% savings in utility costs over the base case design. The vapour flow in the column is reduced by a similar amount, offering capital savings, additional flexibility or the opportunity to increase throughput. The new integrated design procedure considers the column and its associated HEN simultaneously, aiming to minimize operating costs by obtaining the best fit between the process and the available utilities.