Abstract
In this study, sewage sludge and mycelial waste from antibiotic production were pyrolyzed in a batch scale fixed-bed reactor as examples of two kinds of typical industrial biomass wastes with high nitrogen content. A series of experiments were conducted on the rapid pyrolysis and the slow pyrolysis of these wastes in the temperature range from 500–800 °C to investigate the Fuel-N transformation behavior among pyrolysis products. The results showed that Fuel-N conversion to Char-N intimately depended on the pyrolysis temperature and the yield of Char-N reduced with the increase of the pyrolysis temperature. Under the same pyrolysis conditions, Tar-N production mainly depended on complex properties of the different biomasses, including volatile matter, nitrogen content and biomass functional groups. HCN was the predominant NOx precursor in the rapid pyrolysis of biomass, whereas in the slow pyrolysis of mycelial waste, more NH3 was produced than HCN due to the additional NH3 formation through the hydrogenation reaction of Char-N, HCN and H radicals. At the same time, some part of the char was analyzed by Fourier Transform infrared spectroscopy (FTIR) to get more information on the nitrogen functionality changes and the tar was also characterized by Gas Chromatography and Mass Spectrometry (GCMS) to identify typical nitrogenous tar compounds. Finally, the whole nitrogen distribution in products was discussed.
Highlights
At present, with the sustained industrial growth, huge amounts of industrial wastes are produced that cause lots of serious environmental pollution problems
In particular the mycelial wastes from antibiotic production are already classified as dangerous solid wastes according to the current regulations in China, so it is urgent to develop some effective technologies to deal with these wastes
This study aims to understand the Fuel-N behavior or characteristics during the pyrolysis of industrial biomass wastes with high nitrogen content and achieve a better quantitative understanding of the separate effects of the temperature, the heating rate and the properties of biomass on pyrolysis reactions so as to develop novel combustion and gasification technologies with low NOx emissions
Summary
With the sustained industrial growth, huge amounts of industrial wastes are produced that cause lots of serious environmental pollution problems. Most of them are produced by pharmaceutical companies, food industries, beverage production and wastewater plants, such as 30 million tons of sewage sludge from wastewater plants and 2 million tons of mycelial waste produced annually from medicine manufacturing. Those typical industrial biomass wastes have similar properties with high nitrogen and water contents, causing a lot of environmental problems and until now they have no effective way of utilization. The thermal conversion technologies such as pyrolysis, gasification and combustion have been developed to alleviate the environmental load and are aimed to be applied in power generation due to the carbon-neutral nature of biomass resource and comparable heating value to low rank coals. During the thermal conversion of biomass, the nitrogen in biomass is released as nitrogen-containing volatiles (volatile-N) including
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