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

Abstract

List of symbolsA Area (m 2 ) C Carbon content (%) c Specific heat (kJ/kg K) h Enthalpy (kJ/kg) H Heat transfer coefficient (kW/m 2 °C) HV Heat value HHV Higher heating value (kJ/kg) L Energy loss (%) LHV Lower heating value (kJ/kg) m Proportion of material flow per kilogramme of fuel (kg/kg) m Mass flow rate (kg/s) Q Available heat (kJ/kg) Q Heat flow (kW) T Temperature (°C) U Uncertainty x Mass fraction (kg/kg) Greek letters λ Water vaporisation heat (kJ/kg) η First law efficiency Subscripts ash Ashes ah Drum ashes amb Ambient b Bagasse bd Blowdown in the boiler conv Convection C, CO, Co 2 Carbon, carbon monoxide, carbon dioxide db Dry bagasse Abstract This work presents an experimental efficiency analysis of sugar cane bagasse boilers performed according to the first law of thermodynamics. The methodology employed to determine efficiency regarding the first law is the indirect or energy losses method, based on the energy balance method established in the most recent standards, ASME PTC 4-2008 and EN 12952-15:2003. Experimental data were obtained from boilers installed in sugar and ethanol mills in the state of São Paulo, Brazil. Calculation of heat losses through the boiler walls is presented in detail and compared with a previous calculation method recommended in an older standard (ASME PTC 4.1 1964). Moreover, calculation of the uncertainty of the efficiency determination is presented and discussed. On the basis of the obtained results, the main causes of energy losses are identified, and suggestions aimed at improving boiler efficiency are made.

Techno‐economic sustainability analysis of biomass fired industrial boiler: biomass evolution as heat and power generation source

“…It will also reduce the per unit cost of electricity linked with biomass-based power plants and will attract the investors to invest in the biomass-based power plants. [10,17,20,44]…”

“…Edgar et al analysed sugarcane bagasse boiler using the first law of thermodynamics and based upon the results, they concluded that moisture content in the biomass is the major cause of low efficiency. Other losses they described were due to hydrogen conversion into water and losses through stack [17]. Modern technologies like organic Rankine cycle (ORC) are better for burning of biomass.…”

Assessment of energy and exergy efficiencies in steam generators

“…These are the five most common losses present in regular steam generators. Cortes-Rodríguez et al [5] indicated that use of fuel HHV (high heating value) revealed important energy losses related to fuel moisture (usually relevant when biomass is used as fuel). Furthermore, they highlighted that the term related to fuel energy input, which is difficult to obtain when some solid fuels are used, should be calculated as in Eq.…”

“…Equation 1, also referred to as "the indirect method" or "stack loss method", is usually preferable in detriment of the direct efficiency equation ("direct method"), η = (ṁ steam .�h)/(ṁ fuel .LHV) [5,20]. Propagation of measurement errors is usually reduced using the indirect method since the magnitude of measured losses is smaller than the magnitude of useful product.…”

“…The work presented herein follows the steps of Cortes-Rodríguez et al [5], who assessed the efficiency of steam generators, based on the first law of thermodynamics, using the losses method [2]. The objective of this study is to analyze a large water tube steam generator, including blowdown, incomplete combustion, ashes, surface heat losses, and exhaust gases energy losses.…”