Integrating cogeneration and intermittent waste-heat recovery in food processing: Microturbines vs. ORC systems in the coffee roasting industry
File(s)
Published version
Author(s)
Pantaleo, AM
de palma, pietro
Fordham, Julia
Oyewumni, Oyeniyi
Markides, Christos N
Type
Journal Article
Abstract
Coffee roasting is a highly energy intensive process wherein a large quantity of heat is discharged from the stack at medium-to-high temperatures. Much of the heat is released from the afterburner, which is required to remove volatile organic compounds and other pollutants from the flue gases. In this work, intermittent waste-heat recovery via thermal energy storage (TES) and organic Rankine cycles (ORCs) is compared to combined heat and power (CHP) based on micro gas-turbines (MGTs) for a coffee roasting plant. With regard to the former, a promising solution is proposed that involves recovering waste heat from the flue gas stream by partial hot-gas recycling at the rotating drum coffee roaster, and coupling this to a thermal store and an ORC engine for power generation. The two solutions (CHP + MGT prime mover vs. waste-heat recovery + ORC engine) are investigated based on mass and energy balances, and a cost assessment methodology is adopted to compare the profitability of three system configurations integrated into the selected roasting process. The case study involves a major Italian roasting plant with a 500 kg per hour coffee production capacity. Three options are investigated: (i) intermittent waste-heat recovery from the hot flue-gases with an ORC engine coupled to a TES system; (ii) regenerative topping MGT coupled to the existing modulating gas burner to generate hot air for the roasting process; and (iii) non-regenerative topping MGT with direct recovery of the turbine outlet air for the roasting process. The results show that the profitability of these investments is highly influenced by the natural gas and electricity prices and by the coffee roasting production capacity. The CHP solution via an MGT appears as a more profitable option than waste-heat recovery via an ORC engine primarily due to the intermittency of the heat-source availability and the high electricity cost relative to the cost of natural gas.
Date Issued
2018-09-01
Date Acceptance
2018-04-29
Citation
Applied Energy, 2018, 225, pp.782-796
ISSN
0306-2619
Publisher
Elsevier
Start Page
782
End Page
796
Journal / Book Title
Applied Energy
Volume
225
Copyright Statement
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/)
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Grant Number
EP/J006041/1
EP/P004709/1
Subjects
Science & Technology
Technology
Energy & Fuels
Engineering, Chemical
Engineering
Coffee roasting
Intermittent heat recovery
Micro gas turbine
Organic Rankine cycle
Waste heat recovery
RANKINE-CYCLE SYSTEMS
WORKING FLUID SELECTION
SAFT-VR MIE
BATCH PROCESSES
THERMOECONOMIC ANALYSIS
ENERGY RECOVERY
GAS-TURBINE
PC-SAFT
OPTIMIZATION
EFFICIENCY
09 Engineering
14 Economics
Energy
Publication Status
Published
Date Publish Online
2018-05-26