热解温度和时间对马弗炉制备生物炭的影响

Effect of Pyrolysis Temperature and Time on Biochar Production in a Muffle Furnace

为总结马弗炉制备生物炭的经验和明晰热解温度和时间对生物炭性质的影响,以玉米秸秆为原料,在不同热解温度(400,500,600℃)和时间(2,3,4,6,8h)交叉条件下,在实验室用马弗炉烧制生物炭,计算生物炭的产率,测定其碳和氮含量,并总结利用马弗炉制备生物炭的经验。结果表明:不同热解条件下,生物炭的产率为11.2%~32.1%,生物炭的碳含量为60.9%~77.3%,全氮含量为1.1%~2.8%,C/N为23.5~71.6。随着热解温度的升高,生物炭的产率降低,400℃时为20.5%~32.1%,500℃时为12.6%~19.4%,600℃时为11.4%~16.8%。随着热解时间的延长,生物炭的产率有降低的趋势。生物炭的碳含量随热解温度升高而增加(400℃时为60.9%~63.2%,500℃时为62.6%~71.8%,600℃时为66.3%~77.3%),随热解时间呈无规律变化。生物炭的全氮含量及C/N随热解时间和温度的变化没有明显的规律。对马弗炉制备生物炭的建议为:(1)烧制生物炭时,使用锡箔纸包裹坩埚外壁,可以防止秸秆被烧成灰,使生物炭的产率保持稳定,但是锡箔纸不可重复使用;(2)热解温度不要超过700℃,当超过700℃时,部分秸秆会被烧成灰,生物炭的产率很低;(3)烧制结束后,关闭马弗炉电源,待炉内温度降低后,再打开炉门,这样可以避免高温生物炭与冷空气的接触。综上所述,马弗炉热解是实验室较低温度下(小于700℃)制备生物炭的一种有效方法。

In order to summarize the experience of producing biochar using muffle furnace and reveal the effect of pyrolysis temperature and time on biochar properties,we conducted a pyrolysis of maize straw under different temperatures(400,500,600℃)and holding times(2,3,4,6,8 hour)to study the technical essentials for biochar production in muffle furnace.The yield of biochar production was calculated and the contents of carbon and nitrogen in biochar were measured.The results showed that biochar yields(biochar mass/straw mass)were 11.2%-32.1%under different pyrolysis conditions,and that carbon(C)and total nitrogen(N)contents and C/N ratios of biochar were 60.9%-77.3%,1.1%-2.8%,and 23.5-71.6,respectively.Biochar yield decreased with rising pyrolysis temperature(400℃:20.5%-32.1%,500℃:12.6%-19.4%,600℃:11.4%-16.8%),but biochar C contents increased with temperature(400℃:60.9%-63.2%,500℃:62.6%-71.8%,600℃:66.3%-77.3%).Biochar yield had a decreasing trend with pyrolysis holding time.Biochar N contents and C/N ratios did not have a regular change with pyrolysis temperature or holding time.We have the following suggestions for the production of biochar using muffle furnace:(1)Packaging the crucible using tin foil paper can avoid straw becoming ash and make a stable yield of biochar production,but the tin foil paper cannot be used repeatedly;(2)The pyrolysis temperature is no more than 700℃,in case that some residue would become ash;(3)When the pyrolysis is finished,open the muffle furnace until the temperature in muffle furnace goes down.These results suggested that muffle furnace pyrolysis is an effective method of biochar production below 700℃in the laboratory.