Abstract
Agroindustrial biomass residues are considered potential feedstocks for renewable fuels and chemical production through processes such as thermal conversion. In this regard, thermal conversion characteristics of molasses, a byproduct from sugar production, have not been investigated. In this study, thermal conversion properties of molasses at temperatures of 700–900 °C have been studied using a single-particle reactor. Fuel swelling, combustion times, CO gas yields and gasification reactivities, and NO emissions and release of K and Cl during combustion and gasification were the thermal conversion characteristics of the molasses studied. In addition, the melting behavior of molasses ash produced at 500 °C was assessed using FactSage thermodynamic modeling and differential scanning calorimetry–thermogravimetric analysis measurements. Results of the molasses thermal conversion properties were compared with those of vinasse and black liquor samples from the integrated sugar–ethanol mill and soda pulping of hardwood, respectively. The results show that the molasses droplets had the least swelling tendency and the longest combustion time in the temperature range used, suggesting a lower conversion rate of molasses in an industrial boiler than the vinasse and black liquor. Moreover, at temperatures relevant for industrial gasification processes, that is, ≥800 °C, the gasification rates of molasses were lower than those of the vinasse and black liquor, probably owing to the lower total concentration of catalytic alkali and alkaline earth metals in the molasses. The release of K and Cl to a high degree from molasses during combustion and gasification and the low melting temperature of molasses ash make it a challenging fuel to utilize using the current thermal conversion technologies. Nevertheless, a black liquor recovery boiler type with a simpler (or an oxidizing) lower furnace than that of a black liquor recovery boiler and an entrained flow gasifier of the type demonstrated for black liquor may be potential options for the production of energy and recovery of inorganic chemicals from molasses.
Highlights
Agroindustrial biomass residues, forest residues, and waste streams containing biomass, including municipal solid waste, are increasingly gaining attention as sustainable feedstocks for the production of renewable fuels and chemicals. The utilization of these feedstocks for the production of energy and chemicals contributes to curbing CO2 emissions, reduces the burden on the environment and economy arising from their treatment and disposal, and promotes a circular economy
The volatile matter (VM) contents of the fuels given in the table were obtained after recalculating the VM results obtained from the proximate analysis to a wt % dry fuel basis by excluding the moisture contents
The melting behavior of molasses ash produced at 500 °C was assessed using FactSage thermodynamic modeling and differential scanning calorimetry (DSC) measurements
Summary
Agroindustrial biomass residues, forest residues, and waste streams containing biomass, including municipal solid waste, are increasingly gaining attention as sustainable feedstocks for the production of renewable fuels and chemicals. The utilization of these feedstocks for the production of energy and chemicals contributes to curbing CO2 emissions, reduces the burden on the environment and economy arising from their treatment and disposal, and promotes a circular economy. One of the agroindustrial processes where biomass residues have not been fully utilized is the integrated sugar and ethanol production.[2] Figure 1 shows a simplified version of the integrated process/mill.
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