碳化温度对畜禽粪便水热炭燃烧特性的影响

Influence of hydrothermal carbonization temperature on combustion characteristics of livestock and poultry manures

大量、集中的畜禽粪便,若不加以合理处理利用极易引发严重的环境污染问题。该文选择了集约化程度较高的生猪、奶牛、肉牛、肉鸡和蛋鸡5种畜禽的粪便作为样本,研究了水热碳化温度对畜禽粪便水热处理的影响,通过元素分析、工业分析和热重试验,分析了水热炭的燃烧特性,并比较了不同畜禽粪便水热炭之间的差异。研究发现,水热碳化能够提高水热炭的碳元素、固定碳含量,提高高位热值,降低氢碳比、氧碳比和挥发分固定碳比的值,得到的水热炭类似于褐煤。热重试验发现,水热碳化能够减小不同畜禽粪便样品之间的性质差异。水热碳化温度为180和210℃时,除肉鸡粪便水热炭外,其他畜禽粪便水热炭的综合燃烧特性指数均得到提高,5种畜禽粪便中,奶牛和肉牛粪便水热炭具有更好的燃烧特性。

With the rapid development of livestock and poultry breeding,China has become the largest producer of animal manure worldwide.If the animal manure was not effectively utilized,it could cause serious environmental pollution.Hydrothermal carbonization(HTC)is a promising pretreatment method in disposing high moisture content bio-wastes,involving the decomposition and carbonization of biomass material in water medium at desired temperature(generally180-250℃)and autogenous pressure(2-10MPa).In this paper,5kinds of livestock and poultry manure,i.e.swine manure(SZ),dairy cattle manure(NN),beef cattle manure(RN),broiler manure(RJ),and layer chicken manure(DJ),were selected as samples.The effect of temperature on HTC of the livestock and poultry manures was studied.The hydrochar was produced in a laboratory scale semi-batch1L Parr autoclave reactor(Model4523,Parr Instrument Co.,USA).Approximately30g manure(in dry basis;solid-to-liquid ratio was1:12)was loaded into the reactor vessel,which was then sealed and purged with nitrogen5times to displace headspace gases,and the autoclave was heated to desired temperature(180,210,240℃).The uniformity of treatment throughout the manure sample was ensured by a rotor,which rotated inside the reactor at a constant speed of100rpm.The reactor was held at final temperature for60min and then quickly cooled down to room temperature.The hydrochar was recovered as solid residue by vacuum filtration and dried in an oven at105℃for24h.The produced hydrochars were characterized and their fuel qualities were evaluated,including proximate analysis,elemental analysis and combustion behaviors evaluation.The differences between different livestock and poultry manures were compared.The char yields were decreased with the increasing of reaction temperature,from67.34%±11.2%,64.55%±1.93%,65.9%±4.38%,54.61%±16.93%and58.05%±10.41%at180℃to54.30%±5.70%,49.33%±2.78%,50.70%±3.63%,45.83%±19.32%,and49.69%±9.77%at240℃for SZ,NN,RN,RJ and DJ,respectively.The hydrochar of NN and RN,got the maximum energy yields at180℃,which were71.07%±1.23%and71.93%±13.71%,respectively.The hydrochar of SZ,RJ and DJ,got the maximum energy yields at210℃,which were65.45%±3.22%,60.72%±10.77%and64.43%±10.42%,respectively.It was found that HTC can improve the content of carbon(C),fixed carbon(FC)and higher heating value(HHV),and decrease the molar ratios of oxygen and hydrogen to carbon(H/C and O/C)and the ratios of volatile matter to fixed carbon(VM/FC).In the van Krevelen diagram,the resulted hydrchars are similar to lignite.The thermogravimetric experiment found that the peak temperature at volatile devolatilization and combustion phase moves to higher temperature range,from284-308℃for manures to312-320℃for hydrochars.On the contrary,the peak temperature at FC combustion phase moves to lower temperature range,from435-483℃for manures to398-435℃for hydrochars.The HTC can narrow the difference between different livestock and poultry manures and make the hydrochars more similar.The hydrochars from cow and beef cattle manures have higher char yield,energy yield and composite combustion characteristic index compared with other manures.