鼓风对城市污泥好氧堆肥温度变化的影响

第22卷第5期2002年5月生 态 学 报A CTA ECOLO G I CA S I N I CA V o l .22,N o.5M ay,2002鼓风对城市污泥好氧堆肥温度变化的影响黄启飞,高　定,黄泽春,郑玉琪,李艳霞,陈同斌3

(中国科学院地理科学与资源研究所环境修复室,北京100101)

基金项目:国家“九五”科技攻关资助项目(962909201205);北京中科博联环保高新技术有限公司资助项目

收稿日期:2001209207;修订日期:2002202205

作者简介:黄启飞(1973～),男,湖北宜昌人,博士。主要从事废弃物资源化研究。

本研究工作得到西北农林科技大学张增强同志的协助,特此致谢。

3通讯联系人A utho r fo r co rrespondence E 2m ail :chentb @igsnrr .ac .cn

摘要:采用强制通风静态垛和温度反馈自动测控堆肥工艺,研究了鼓风过程对城市污泥好氧堆肥温度的影响。当城市污泥和调理剂比例为1∶1时(体积比),处于鼓风口远端(风向远点)各个层次的堆体温度基本上不会随鼓风过程而变化;处于鼓风方向中部(风向中点)、鼓风口近端(风向近点)的堆体,其中层、上层的温度将会下降,平均下降速率分别为0105℃ m in 、0104℃ m in ,但是温度下降的速率在整个鼓风过程中并不均匀,温度下降速率在0～10m in 较快,在10～40m in 较慢;当混合堆料中调理剂含量较低时(3∶2),堆体上层温度在鼓风过程中将会上升,上升速率约为01022～0105℃ m in ,中层温度下降,在鼓风开始阶段(0～10m in ),下降速率较快,约为0112℃ m in ,随后变化速率较小,约为0101℃ m in 。对于不同调理剂比例的堆体,处于风向远点、

中点的下层温度基本不受鼓风作用的影响;处于风向近点的堆体,其下层温度会随着鼓风过程而下降,平均下降速率约为01025～0103℃ m in 。

关键词:城市污泥;堆肥;静态垛;温度;鼓风

Tem pera ture Changes D ur i ng Sewage Sludge Com posti ng a s I nf lu -enced by Aera ti ng

HUAN G Q i 2Fei ,GAO D ing ,HUAN G Ze 2Chun ,ZH EN G Yu 2Q i ,L I Yan 2X ia ,CH EN

Tong 2B in 3　(L abora tory of E nv ironm en ta l R e m ed ia tion ,Institu te of Geog rap h ic S ciences and N a tu ra l R esou rces R e 2

sea rch ,Ch inese A cad e my of S ciences ,B eij ing 100101,Ch ina ).A cta Ecolog ica S in ica ,2002,22(5):742

～746Abstract :It w as w ell recognized that m any facto rs affected the compo sting p rocess and the resulting p rod 2

uct ,and temperature w as the mo st i m po rtant eco logical deter m inant fo r compo sing m aterial

.T he ach ieve 2m ent of m ini m um temperature layers w as i m po rtant to an effective compo sting p rocess and contributed substantially to the h igh rates of decompo siti on ach ieved during p rocessing .A s the compo sting began ,temperature increase occurred th roughout the p ile and the w ell insulated regi ons of the inner zones of the p ile passed th rough the m esoph ilic ther moph ilic boundary ,w h ich w as in the range of 44℃to 52℃.H igh temperatures (e .g 55℃)had been p roved to eli m inate po tential pathogenic m icroo rganis m s in the compo st substrate .H eat generati on w as p ropo rti onal to the vo lum e of the p ile and heat lo ss w as p ropo rti onal to the surface area of the compo st p ile .T he larger the p ile ,the less heat lo ss and the greater the temperature .

T emperatures above 60℃began to i m pact on the activity of the m icrobial comm unity .U lti m ately ,the temperature m igh t reach above 80℃at w h ich stage the bi o logical comm unity w as severely destroyed .T he op ti m um compo sting temperatures ,based on the mo st efficient decompo siti on ,w ere in the range of 52℃to 60℃.T he temperature of a p ile depended largely on airflow .T he temperature betw een the center and the surface of the p ile varied greatly in static p iles largely because of airflow .T urning of stack s o r fo rced aerati on ,as in environm entally contro lled compo sting ,could contro l temperature effectively .T er m inati on

of such p ractices resulted in the temperature soon returning to the range of 70℃to 80℃.So airflow p ro 2cess w as i m po rtant to contro l the compo sting temperature .T he ai m s of th is study w ere to investigate :(i )How did aerating p rocess influence the compo sting temperature in the aerated static p ile system ?(ii )to w hat degree aerating p rocess influenced the compo sting temperature ?

Tw o aerated static p iles w ere designed in a building in tw o 116m ×110m bays w ith cem ent floo rs and w alls

.A erati on boards w ere laid on the bo ttom of the bays .T he p iles contained sew age sludge (dry m at 2ter =1511percent )and bulk ing agent w ith tw o p ropo rti ons :1∶1(M ix 1)and 3∶2(M ix 2)by vo lum e .A bulk ing agent layer on the aerati on boards dispersed air th rough the 110m h igh m ix layer .Tw o p iles w ere covered w ith a 20c m insulating layer of recycled compo st .Each bay had a aerato r to supp ly am bient air .Senso rs w ere inserted into the different po siti ons of the p iles to detect the compo sting temperatures ,and the detected data w as fed back to the computerized contro l system .A th ree 2stage contro l algo rithm

contro lled the damper duty cycle of aerato rs .T he p ri m ary compo sting p rocess had been undertaken fo r 16

days

.W hen the compo sting p rocess w as during the h igh temperature peri od (>55℃),the aerating p ro 2cess kep t fo r 40m inutes ,and a computer w ith a autom atic contro l softw are (Comp soft )logged tempera 2tures of all po siti ons every 5m inutes and generated repo rts .

T he varying pattern and degree of temperature w ere different w hen m ixing rati o of feedstock and monito red spo ts w ere different .T he monito red spo ts w ere located at upper layer 、m iddle layer and under layer of p iles fo llow ing to the aerating directi on .W hen the m ixing rati o of sew age sludge and bulk ing agent w as 1:1,the temperature decreasing speed of m iddle 2layer and upper 2layer located at m iddle po siti on and upper po siti on fo llow ing to the aerating directi on w as about 0104～0105℃ m in .W hen the m ixing rati o

w as 3∶2,the temperature of upper 2layer increased at the speed of 01022～0105℃ m in .T he temperature

of m iddle 2layer decreased at the speed of 0112℃ m in in the early stage of aerating (0

～10m ins ),then at the speed of 0101℃ m in during the peri od of 10

～40m ins .T he temperature of under layer located at m id 2dle po siti on and backw ard po siti on w as no t influenced by aerating ,but the under layer temperature of up 2

per po siti on decreased at the speed of 01025～0103℃ m in .

Key words :sew age sludge ;compo sting ;static p ile ;temperature ;aerating

文章编号:100020933(2002)0520742205　中图分类号:X 705　文献标识码:A

堆体温度是城市污泥好氧堆肥过程中的关键参数[1,2]。好氧堆肥的理想温度范围是52～60℃,在这一温度范围内持续一定时间则可杀灭病原微生物及杂草种子,有机物降解的速率较快[3],Bach 、M ck inley 等学者陆续证明了这一结论[4,5]。但是,如果不加以控制,则堆体温度最高能升至82℃[6],因此需要对其进行有效地控制。

堆体和外界环境进行能量交换主要通过3种方式:传导、对流、辐射[7],但是只有很少的热量是通过辐射和传导方式散失的,无论采用负压引风还是正压鼓风工艺,大部分的热量都将通过蒸发冷却的方式(对流)散失[8,9],所以各种堆肥工艺的堆体温度在很大程度上要依靠鼓风过程来控制[8],鼓风作用使得堆体中心和表面温度差异极大[8,10,11]。M iller 、H arper 等研究认为,翻堆和鼓风是控制堆体温度的有效措施[12,13],如果不采取这些措施,堆体温度很快就将达到70～80℃[10,14]。

鼓风不仅是调控堆肥温度的重要手段,而且可以调节堆体中的氧气、水分含量[15],但是对于鼓风过程影响堆肥温度的方式和程度还鲜见报道。堆肥是一个复杂的系统,对于不同混料比例、堆体的不同部位,鼓风过程对堆温的影响范围和程度都会随之变化。本研究的目的就是探讨鼓风过程对城市污泥堆肥温度的影响,为利用鼓风过程控制堆肥温度提供理论依据。

1　材料与方法

111　供试材料性质　供试城市污泥为北京市方庄污水厂的脱水污泥,该厂处理的主要是生活污水,污泥

3475期黄启飞等:鼓风对城市污泥好氧堆肥温度变化的影响　

的含水率8419%,挥发性有机物含量为7413%。

本试验采用CTB 调理剂作为填充料[16],其含水率和饱和吸水率分别为2.70%、65.7%。

112　试验装置　将城市污泥与调理剂按照设定比例混合,然后堆置于116m ×110m ×111m 的堆肥池中。堆肥池底部为布气板,通风系统采用鼓风机,试验装置见文献[17]。

113　试验方法　混料比例为1∶1和3∶2(污泥∶CTB 调理剂,体积比),将堆料充分混匀后上堆。在离鼓风口(堆体纵轴方向)的近、中、远的位置选定3个点(分别称为风向近点、风向中点和风向远点),每个点011m 、015m 、017m 的深度位置上各设一个温度传感器,测定值代表该点上、中、下3个层次的温度。

采用中国科学院地理科学与资源研究所环境修复研究室研制的温度变送器以及自动测控程序(Comp soft 软件)集成系统(CTB 堆肥自动测控系统)对堆温进行监测。

堆肥试验时间为4月,当两个处理的堆温进入高温期(>55℃),4月11日12:00～13:00(此段时间气温变化不大,可以忽略其影响),持续鼓风40m in ,每5m in 通过传感器采集温度数据进行分析。2　结果与讨论

211　鼓风对高比例堆体温度的效应

图1为混料比例1∶1时风向远点、中点、近点堆体温度随鼓风过程的变化曲线。风向远点堆体3个层次的温度基本上对鼓风过程不响应,这主要是由堆肥原料的结构和风量决定的(图12a )。通过鼓风过程对堆体温度进行控制时,堆体的结构和通风量都会对堆体温度的变化产生影响[15]。根据以往的试验结果,当混料比例为1∶1时,堆肥物料中调理剂比例高,堆体通气性好,鼓风过程对于堆温影响比较明显。但是当堆温与气温相差不大时,通气性好的堆体(或某些部位)有可能对鼓风作用不响应。同时,根据流体力学原理,在堆体底部的风室中,沿着风向设定的3个点中,风向远点堆体的得到的风量最多,风向近点堆体得到的风量最少[7],因此在同一个堆肥仓中,好氧发酵的速度存在差异,风向远点堆体物料的好氧发酵过程进行较快。在本试验条件下,远点堆体物料3个层次的温度为21～23℃,而气温为20℃左右,与堆温差别不大。鼓风过程持续40m in ,除了上层堆体温度在鼓风开始阶段0～10m in 呈现微弱下降趋势(下降速率为0102℃ m in )外,其他各点的堆温在持续鼓风过程中基本没有变化

。

图1　1∶1混料比例的堆体风向远点(a )、中点(b )、近点(c )各层次温度变化

F ig .1　T emperature changing of different layers at the backw ard po siti on (a )、the m iddle po siti on (b )and the upper po siti on (c )fo llow ing to the aerating directi on w hen the vo lum e rati o of sew age sludge to bulk agent w as 1∶1随着鼓风过程的持续进行,风向中点堆体各层次的温度都呈现下降趋势,下层、中层、上层的温度下降幅度分别为0163℃、2110℃、1153℃(图12b ),但是这种下降趋势在整个鼓风过程中并不均匀。在鼓风的0～10m in 段内,各层次的温度下降速率最快,下层、中层、上层分别为0106℃ m in 、0109 m in 、0107℃ m in ;在鼓风的10～40m in 时间范围内,下层的温度基本没有变化,中层、上层的温度变化速率分别为0104℃

447　生　态　学　报22卷

m in 、0103℃ m in 。堆体下层温度较低,所以鼓风过程对于下层物料的温度影响在鼓风开始阶段较明显(0～10m in ),随后则影响不大。在整个鼓风过程中,中层的温度变化最为明显,主要是由于堆体温度的高低和热量平衡过程决定的[7]。上层的温度最高,但是上层与中层的温差(3℃)小于中层与下层的温差(10℃),所以上层与中层的热量交换过程也较弱[7],中层对于上层的冷却效应弱于下层对中层的冷却效应。持续鼓风40m in ,中层的温度平均下降速率约为0105℃ m in ,上层则为0.04℃ m in 。在堆温控制过程中,这一参数对于设定风机鼓风时间具有参考意义。

风向近点堆体各层的温度变化如图12c 。各层次温度变化在鼓风0～10m in 时间段内最为明显,下层、中层、上层的温度变化速率分别为0107℃ m in 、0112℃ m in 、0108℃ m in ;在10～40m in 时间范围内,为0101℃ m in 、0103℃ m in 、0102℃ m in 。鼓风对中层的温度影响最大,对下层的温度影响最小,与中点的堆体温度变化规律类似。持续鼓风40m in 时,下层、中层、上层温度的平均下降速率约为0103℃ m in 、0105℃ m in ,0104℃ m in 。

综合上述讨论,对于高调理剂比例的堆体,鼓风过程对风向远点堆体各层次的温度影响不大。对于风向中点、近点的堆体,鼓风使得中层、上层的温度下降,平均下降速率为0105℃ m in 、0104℃ m in 。堆体的下层温度基本不受鼓风作用的影响,但是风向近点堆体的下层温度会随着鼓风过程而下降,速率约为0103℃ m in 。

212　鼓风对低比例堆体温度的效应

相对1∶1的混料比例而言,3∶2比例中调理剂含量较低。以往的试验结果表明,此种比例的堆体通气性较差,,压实现象明显,堆体温度较低。图2是各层次的堆温随鼓风过程的变化曲线

。

图2　3∶2混料比例的堆体风向远点(a )、中点(b )、近点(c )各层次温度变化

F ig .2　T emperature changing of different layers at the backw ard po siti on (a )、the m iddle po siti on (b )and the upper po siti on (c )fo llow ing to the aerating directi on w hen the vo lum e rati o of sew age sludge to bulk agent w as 3∶2

当鼓风过程持续进行40m in ,风向远点堆体的上层温度呈现上升趋势(图22a ),幅度为018℃。因为中层温度比上层温度高2～3℃。随着鼓风过程的持续进行,中层热空气上行,导致上层堆温上升。这是一个动态平衡,热空气上升带入热量,同时上层热空气排入外界带走热量,堆温的上升或下降取决于这两种过程的迭加效应[7]。本试验条件下,上层温度上升的速率为01022℃ m in 。中层温度在40m in 下降幅度为116℃,在0～10m in 下降速率约为0112℃ m in ,在10～40m in 下降速率约为0101℃ m in 。下层温度随着鼓风过程基本没有变化,主要是因为下层温度较低,与气温基本接近。

风向中点堆体的上层温度的变化速率为0105℃ m in (图22b )。中层的温度变化也呈现不均衡趋势,在0～10m in 下降速率约为0112℃ m in ,在10～40m in 下降速率约为0101℃ m in 。下层温度对于鼓风过程没有响应。

5475期黄启飞等:鼓风对城市污泥好氧堆肥温度变化的影响　

风向近点堆体上层、中层的温度随着鼓风过程变化的趋势和程度与远点、中点堆体类似(图22c )。下层温度变化约019℃,且变化速率在整个过程中较为均衡,速率约为01025℃ m in 。

因此,对于低调理剂比例的堆体,持续鼓风将会使上层堆温上升,上升速率约为01022～0105℃ m in 。在本试验条件下,主要是中层温度较高引起的,但是这一现象是否具有普遍意义,有待深入研究。鼓风过程将会使得中层温度下降,在鼓风开始阶段(0～10m in ),下降速率较快,约为0112℃ m in ,随后变化速率较小,约为0101℃ m in 。下层因温度较低,除了风向近点堆体,其它部位的下层温度则对鼓风过程没有响应。3　结论

鼓风是实现高温好氧堆肥过程控制的重要手段。在城市污泥堆肥过程中,鼓风对堆体温度的影响与调理剂的混合比例有关。当高调理剂的比例较高时,堆体风向远点各层次温度对于鼓风过程基本没有响应。风向中点、近点堆体的中层、上层的温度将会下降,下降幅度为0105℃ m in 、0104℃ m in 。风向中点堆体的下层温度基本不受鼓风作用的影响,但是风向近点堆体下层温度会随着鼓风过程而下降,速率约为0103℃ m in 。

低调理剂比例的堆体,在鼓风作用下,上层堆温将会上升,上升速率约为01022～0105℃ m in ;堆体中层温度在鼓风开始阶段(0～10m in )下降速率较快,约为0112℃ m in ,随后变化速率较小,约为0101℃ m in ,表明堆肥温度的变化在鼓风过程中是不均匀。除了风向近点会随着鼓风过程而下降外,其它部位的堆体下层温度对于鼓风过程则没有响应。

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