First and Second Law to Analyze the Performance of Bagasse Boilers

Abstract

The performance of sugar cane bagasse boilers is commonly analyzed through the first law of thermodynamics, using the energy balance method and the fuel lower heating value as calculation base. This work presents a first law analysis using two different methods: the input/output and the energy balance. The employment of the fuel higher and lower heating values as calculation base are presented and discussed. Moreover, a second law analysis is showed, based on two methods: input/output and exergy balance. The methods based on exergy concept permits to observe the main irreversibilities that happen during the steam production in a bagasse boiler.

Experimental efficiency analysis of sugarcane bagasse boilers based on the first law of thermodynamics

“…The methodology adopted for the determination of bagasse boiler efficiency involved the use of two currently applied reference standards: ASME PTC 4-2008 [3] (a revised version of a previous standard [13]) and BS EN 12952-15: 2003 [4], with the necessary adaptations, because bagasse is a solid fuel that is burned with a high moisture content [14]. Besides these standards, methodologies previously developed elsewhere were also used [11,15]. This work was carried out using data collected from real performance testing of bagasse boilers which form part of sugar mill cogeneration systems operating in the state of São Paulo, Brazil.…”

“…2 illustrates the application of thermodynamic analysis to a boiler. First law analyses can be applied via two methods: (1) the input/output method and (2) the energy balance method (losses method), both of which can be formulated based on either the lower or the higher calorific value [11,18]. In alternative works, second law analysis can be applied using the input/output method and also the energy balance using data previously obtained by first law analysis.…”

“…where m mb is the ratio between the water vapour mass flow rate formed from fuel moisture content and the fuel flow rate; h mb,out and h mb,r are the specific enthalpies of the water vapour formed from fuel moisture content at the boiler outlet and in the reference state, respectively [11,15].…”

“…An adaptation of the indirect method for the particular case of bagasse boilers was proposed by Silva-Lora and Zampieri [9] and Barroso et al [10], with these authors adopting an efficiency definition based on the fuel lower heating value (LHV). Discussing this choice, Sosa-Arnao and Nebra [11] point out that it is, in fact, more correct to employ the higher heating value (HHV), as per Acosta [12], as it is required by the current ASME standard [3]. These two methods are presented and discussed in the present paper.…”

Combined production of sugar, ethanol and electricity: Thermoeconomic and environmental analysis and optimization

“…In order to improve the exergy efficiency of this piece of equipment, higher temperatures and pressures should be considered as well as better combustion systems. Furthermore, the use of exhaust gases to dry bagasse also increases the efficiency [40]. Actually, bagasse drying may be accomplished by different technologies, each of them with an associated improvement in the exergy performance of the mill [41].…”