Gas release characteristics during carbonization of iron coke hot briquette and influence of heating rate

The release characteristics of CH_(4),H_(2),CO and CO_(2) from iron coke hot briquette(ICHB)during carbonization were studied.The results show that compared with briquette without iron ore,Fe_(3)O_(4) can inhibit the release rate of H2 and promote the production of CO and CO_(2).In addition,when the heating rate increases from 3 to 7℃/min,the release rates of CH4 and H2 increase,while the release rates of CO and CO_(2) first increase and then decrease.The carbonization process of ICHB was segmented,and corresponding kinetic analysis was carried out.The results show that the activation energy of StageⅡand StageⅣis higher in the carbonization process of ICHB,and the active pyrolysis of coal and the reduction of iron ore occur in these two stages.In addition,the effect of heating rate on the kinetic parameters of ICHB carbonization process was investigated.It was found that when the heating rate increased,the reaction activation energy of StageⅣdecreased first and then increased,which was consistent with the release law of CO and CO_(2).The analysis showed that the increase in heating rate leads to more reactions at higher temperatures,resulting in an increase in the release rate of some gases.In addition,thermal hysteresis can also cause some processes to fail to fully react at the end of heating.It is also found that the apparent activation energy and preexponential factor have kinetic compensation effect during the car-bonization of ICHB.

Combustion analysis of a hydrogen-diesel fuel operated DI diesel engine with exhaust gas recirculation

The rapid depletion of fossil fuel and growing demand necessitates researchers to find alternative fuels which are clean and sustainable. The need for finding renewable, low cost and environmentally friendly fuel resources can never be understated. An efficient method of generation and storage of hydrogen will enable automotive manufacturers to introduce hydrogen fuelled engine in the market. In this paper, a conventional DI diesel engine was modified to operate as gas engine. The intake manifold of the engine was supplied with hydrogen along with recirculated exhaust gas and air. The injection rates of hydrogen were maintained at three levels with 2 L/min, 4 L/min, 6 L/min and 8 L/min and 10 L/min with an injection pressure of 2 bar. Many of the combustion parameters like heat release rate （HRR）, ignition delay, combustion duration, rate of pressure rise （ROPR）, cumulative heat release rate （CHR）, and cyclic pressure fluctuations were measured. The HRR peak pressure decreased with the increase in EGR rate, while combustion duration increased with the EGR rate. The cyclic pressure variation also increased with the increase in EGR rate.

含水率不同的煤燃烧性能试验研究

为分析煤燃烧特性与水分含量之间的关系,以斜沟煤矿气煤为试验对象,借助锥形量热仪对含水率不同的煤样燃烧参数进行分析,同时研究煤样燃烧效率。试验结果发现:①伴随煤样含水率的升高,煤样点燃时间先下降后升高,含水率不同的煤样点燃时间由高到低的排序为18.73%>14.73%>2.73%>6.73%>10.73%;煤样热释放速率最大值、总热释放量、烟气生成率和总烟释放量先下降后升高再下降,煤样热释放速率最大值由高到低的排序为10.73%>2.73%>6.73%>14.73%>18.73%,总热释放量、烟气生成率和总烟释放量由高到低的顺序为2.73%>10.73%>6.73%>14.73%>18.73%;煤样燃烧效率由高到低排序为10.73%>6.73%>2.73%>14.73%>18.73%;②煤样中含有适当的水分,能有效增大煤的燃烧性能,根据试验结果选择6.73%~10.73%含水率的煤,能减少煤点燃时间,降低烟气生成率、CO生成速率及总烟释放量,增大热释放速率及燃烧效率。

地铁列车着火后在隧道内行驶的安全速度

地铁列车着火后在隧道内行驶的安全性对火灾应急救援具有重要意义，而行驶速度是决定着火列车安全性的关键因素．文中以热释放速率为0～10MW的火灾为原型，在1：8的隧道模型内进行列车火灾模型实验．经过相似变换的模型火灾的热释放速率为0—55kW．采用正庚烷为燃料，利用变频风机提供的流场模拟列车在隧道中的运动情况．通过测定不同行驶速度、着火部位及火源位置时，风速与火灾热释放速率的关系、列车周围的温度场以及火灾烟气蔓延规律，并以北京地铁为例，得到着火列车在隧道内行驶的最佳速度为41．83km／h．

基于聚氨酯海绵/棉织物的软体家具燃烧特性分析

为研究软体家具中不同软包材料对火灾现场的影响,利用锥形量热仪评估聚氨酯(PU)海绵/棉织物(CF)小尺寸试件燃烧性能,在35 kW/m^2的热辐射强度下,研究不同聚氨酯海绵和棉织物复合试件对点燃时间、热释放及烟气释放量等的影响。结果表明:采用阻燃棉织物能有效延长点燃时间、降低热释放;阻燃棉织物和阻燃聚氨酯海绵的复合软包材料阻燃效果体现有促进效应或累加效应,且会使烟气释放量增加;合理选择与搭配阻燃棉织物和聚氨酯海绵,能有效降低中等火灾的危险性。

蒸发吸热比例变化对700℃超超临界机组锅炉设计的影响

与600℃超超临界机组相比,700℃超超临界机组使锅炉蒸发段的吸热比例明显下降,其原因是炉侧烟气释放给水冷壁的纯辐射放热比例无法跟随700℃机组的锅内侧蒸汽吸热比例进行下调,锅内侧的过热度参数选择以及受热面的布置与现役600℃超超临界机组锅炉差异较大。因此,选择合适的过热度、布置蒸汽系统的受热面或设计新的过热器或再热器系统是700℃超超临界机组锅炉需要研究的重点课题。

地下换乘大厅火灾烟气温度分布研究

为合理设置城市综合交通枢纽地下换乘大厅排烟口高度,基于Froude准则,搭建比例为1∶10的地下换乘大厅机械排烟-补风试验平台。利用平台和数值模拟方法,试验研究地下换乘大厅火灾烟气在3种不同热释放速率（HRR）及4种不同排烟量条件下的温度分布,并探究排烟口高度的5个数值所对应的排烟效率。结果表明：HRR是影响地下换乘大厅烟气温度的主要因素,HRR越高,顶棚烟气温度越高;排烟口高度对大空间排烟效率影响较小;烟气竖向温度分布在6 m高度处出现明显分层现象,就净空高度为10 m的换乘大厅而言,排烟口宜设置于顶棚以下2~3 m处,此工况下排烟效率较高。