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Authors
Abstract(s)
No trabalho desenvolvido, realizaram-se ensaios de pirólise, em leito fixo, para duas
biomassas lenhocelulósicas residuais: a casca de noz (Juglans regia) e a casca de amêndoa
(Prunus dulcis). O objetivo principal foi a produção de carbonizados e o estudo do efeito da
temperatura de pirólise nas características dos mesmos, com vista à sua aplicação para
remediação de solos. Fez-se variar a temperatura de pirólise entre 474 e 756 ºC, fixando a rampa
de aquecimento a 20 ºC/min, o tempo de pirólise a 40 min, o caudal de azoto a 2,1 g/min e o
tamanho de partícula a 1-4 mm. Foram avaliados os rendimentos de cada produto e o poder
calorífico superior (PCS) do gás produzido. O rendimento do carbonizado diminuiu com o
aumento da temperatura para ambas as biomassas, tendo-se obtido valores entre 32,15% e
28,12% para a casca de noz, e entre 31,24% e 27,72% na casca de amêndoa.
O PCS do gás foi crescente com a temperatura, com os valores obtidos situados entre
2,26 e 4,14 MJ/Nm3 para a casca de noz e entre 2,88 e 5,25 MJ/Nm3 para a casca de amêndoa.
Na análise próxima dos carbonizados, para ambas as cascas, verificou-se um aumento
quer no teor de cinzas quer no carbono fixo, com a temperatura. O teor de cinzas situou-se entre
2,82% e 3,43% para a casca de noz e entre 3,20% e 4,15% para a casca de amêndoa. O carbono
fixo subiu de 80,92% para 91,10% na casca de noz e de 81,77% para 91,18% na casca de
amêndoa. Já o teor de voláteis foi decrescente com o aumento da temperatura, com valores entre
16,26% e 5,47% para a casca de noz e entre 15,03% e 4,67% para a casca de amêndoa. Os
valores do PCS dos carbonizados foram praticamente constantes, entre 31,11 e 32,23 MJ/kg.
Os carbonizados eram todos alcalinos e o seu pH subiu com o aumento da temperatura
de pirólise. Obteve-se valores para a casca de noz entre 8,10 e 9,45 e, para a casca de amêndoa,
entre 8,48 e 10,25. Quanto à condutividade elétrica os valores variaram de 421 até 1114 μS/cm
na casca de noz e de 470 até 1743 μS/cm na casca de amêndoa. Relativamente ao potencial de
calagem, os carbonizados foram todos classificados como classe 1.
Desta forma, concluiu-se que tanto o carbonizado como o gás de pirólise provenientes
destas biomassas podem ser utilizados como combustíveis. Para além disto, e tendo em vista a
remediação de solos, os carbonizados apresentaram valores interessantes para este âmbito.
Estes podem ser úteis no tratamento de solos ácidos, pelo seu pH alcalino e, tendo em conta o
potencial de calagem e a condutividade elétrica, estes poderão ter alguma ação de melhoria na
capacidade de troca de catiões dos solos, o que poderá favorecer a manutenção e reposição de
minerais e nutrientes no solo.
In the present work, fixed-bed pyrolysis tests were carried out on two residual lignocellulosic biomasses: walnut (Juglans regia) shells, and almond (Prunus dulcis) shells. The main objective was to produce biochars and study the effect of pyrolysis temperature on their characteristics, with a view to their application for soil amendment. The pyrolysis temperature was varied between 474 and 756 ºC, setting the heating ramp at 20 ºC/min, the pyrolysis time at 40 min, the nitrogen flow rate at 2.1 g/min and the particle size at 1-4 mm. The yields of each product in the pyrolysis process and the higher heating value (HHV) of the produced gas were evaluated. The yield of the biochar decreased with increasing temperature for both biomasses, with values between 32.15% and 28.12% for walnut shells, and between 31.24% and 27.72% for almond shells. The HHV of the gas increased with the temperature, with values situated between 2.26 and 4.14 MJ/Nm3 for walnut shells and between 2.88 and 5.25 MJ/Nm3 for almond shells. In the proximate analysis of the biochars, for both shells, there was an increase in both the ash content and fixed carbon with temperature. The ash content was between 2.82% and 3.43% for the walnut shell and between 3.20% and 4.15% for the almond shell. Fixed carbon rose from 80.92% to 91.10% for walnut shells and from 81.77% to 91.18% for almond shells. The volatile matter content decreased with increasing temperature, with values ranging from 16.26% to 5.47% for walnut shells and from 15.03% to 4.67% for almond shells. The HHV of the biochars were practically constant, between 31.11 and 32.23 MJ/kg. The pH of the biochars generally increased in both cases as the temperature rose. Values were between 8.10 and 9.45 for the walnut shell and between 8.48 and 10.25 for the almond shell. As for electrical conductivity, the values ranged from 421 to 1114 μS/cm in the walnut shell and from 470 to 1743 μS/cm in the almond shell. In terms of liming potential, all the biochars were classified as class 1. It was therefore concluded that both the biochar and the pyrolysis gas from these biomasses can be used as fuels. In addition, and with a view to soil amendment, the biochars showed interesting values for this purpose. They could be useful in treating acidic soils, due to their alkaline pH and, considering their liming potential and electrical conductivity, they could have some improvement action the cation exchange capacity of soils, which could favor the maintenance and replacement of minerals and nutrients in the soil.
In the present work, fixed-bed pyrolysis tests were carried out on two residual lignocellulosic biomasses: walnut (Juglans regia) shells, and almond (Prunus dulcis) shells. The main objective was to produce biochars and study the effect of pyrolysis temperature on their characteristics, with a view to their application for soil amendment. The pyrolysis temperature was varied between 474 and 756 ºC, setting the heating ramp at 20 ºC/min, the pyrolysis time at 40 min, the nitrogen flow rate at 2.1 g/min and the particle size at 1-4 mm. The yields of each product in the pyrolysis process and the higher heating value (HHV) of the produced gas were evaluated. The yield of the biochar decreased with increasing temperature for both biomasses, with values between 32.15% and 28.12% for walnut shells, and between 31.24% and 27.72% for almond shells. The HHV of the gas increased with the temperature, with values situated between 2.26 and 4.14 MJ/Nm3 for walnut shells and between 2.88 and 5.25 MJ/Nm3 for almond shells. In the proximate analysis of the biochars, for both shells, there was an increase in both the ash content and fixed carbon with temperature. The ash content was between 2.82% and 3.43% for the walnut shell and between 3.20% and 4.15% for the almond shell. Fixed carbon rose from 80.92% to 91.10% for walnut shells and from 81.77% to 91.18% for almond shells. The volatile matter content decreased with increasing temperature, with values ranging from 16.26% to 5.47% for walnut shells and from 15.03% to 4.67% for almond shells. The HHV of the biochars were practically constant, between 31.11 and 32.23 MJ/kg. The pH of the biochars generally increased in both cases as the temperature rose. Values were between 8.10 and 9.45 for the walnut shell and between 8.48 and 10.25 for the almond shell. As for electrical conductivity, the values ranged from 421 to 1114 μS/cm in the walnut shell and from 470 to 1743 μS/cm in the almond shell. In terms of liming potential, all the biochars were classified as class 1. It was therefore concluded that both the biochar and the pyrolysis gas from these biomasses can be used as fuels. In addition, and with a view to soil amendment, the biochars showed interesting values for this purpose. They could be useful in treating acidic soils, due to their alkaline pH and, considering their liming potential and electrical conductivity, they could have some improvement action the cation exchange capacity of soils, which could favor the maintenance and replacement of minerals and nutrients in the soil.
Description
Keywords
Pyrolysis Biochar Biomass Soil Pirólise Carbonizado Biomassa Solos