Semicontinuous Discharge of Non‐Newtonian Filter Cakes in Electrofiltration

A novel mode of operation for electrofiltration is presented. The newly developed operation procedure allows for cake removal without disassembling the chamber. Highly viscous filter cakes are discharged from the filtration chamber by inserting air which permits a rapid restart of the process. The cleaning time could be reduced from about 10 min to a few seconds. The semicontinuous operation is liable to full automation and allows for cake discharge and filtration in a short period of time. In successive cycles was proved that the process efficiency is maintained using the same membrane. A fully continuous system can be accomplished by assembling several units in parallel in a single filtration press.     

Determination of the overall migration from silicone baking moulds into simulants and food using 1H-NMR techniques

Different silicone baking moulds (37 samples) were characterized with respect to potential migrating substances using ¹H-NMR, RP-HPLC–UV/ELSD and GC techniques. In all cases cyclic organosiloxane oligomers with the formula [Si(CH₃)₂–O] _n were identified (n = 6 … 50). Additionally, linear, partly hydroxyl-terminated organosiloxanes HO–[Si(CH₃)₂–O] _n –H (n = 7 … 20) were found in 13 samples. No substances other than siloxanes could be detected, meaning the migrants mainly consist of organopolysiloxanes. Based on this knowledge, a ¹H-NMR quantification method for siloxanes was established for the analysis of both simulants and foodstuffs. Validation of the ¹H-NMR method gave suitable performance characteristics: limit of detection 8.7 mg kg^–1 oil, coefficient of variation 7.8% (at a level of 1.0 mg kg^–1 food). Migration studies were carried out with simulants (olive oil, isooctane, ethanol (95%), Tenax) as well as preparation of different cakes. From the 1st to 10th experiment, siloxane migration into cakes only slightly decreased, with a significant dependence on fat content. Migration never exceeded a level of 21 mg kg^–1 (3 mg dm^–2) and was, therefore, well below the overall migration limit of 60 mg kg^–1 (10 mg dm^–2). However, migration behaviour into simulants differed completely from these results.     

电子布氏硬度计在电池锌饼检测中的应用

锌饼的硬度与铅、镉、铁等金属杂质含量有关。采用金属布氏硬度法检测锌饼硬度,能快速间接地判定杂质以及添加的金属含量是否异常。介绍了电子布氏硬度计的工作原理和使用条件;对常见的故障及排除方法进行了探讨。     

Intramuscular fatty acid profile of longissimus dorsi and semitendinosus muscle from Kundi steers fed on pasture with cottonseed cake supplement

The present study was accomplished to evaluate the intramuscular fatty acid (FA) composition of different muscles taken from Kundi steers (n = 15), which were approximately 24 months old, fed on a cottonseed cake supplement, and were made to graze on alfalfa pasture for 95 days prior to slaughter. The samples were taken from longissimus dorsi region (loin and ribeye portion) and distal region of semitendinosus muscle for intramuscular FA analysis. Saturated FA, comprising 49.48–52.09% of total FA composition, in all the muscles were studied. Ribeye portion of longissimus dorsi muscle contain relatively higher (P > 0.05) amount of trans FA (3.37%) as compared with loin portion of longissimus dorsi muscle (3.1%) and distal region of semitendinosus muscle (2.84%). The sum of monounsaturated FA in all the muscles studied was estimated in the range of 32.21–34.64%, while polyunsaturated FA contribute 11.39–12.39% of total FA. The mean conjugated linoleic acid was found to be 0.28, 0.35 and 0.41 in ribeye and loin portion of longissimus dorsi muscle and distal region of semitendinosus muscle, respectively.     

降低114m^2立盘过滤机滤饼附液率的改进措施

针对立盘过滤机滤饼附液率较高的问题，主要从年心轴、分配头、扇形板及滤布选用等方面进行了深入探讨，分析了反吹风、进料分配器、滤液的排放方式等对立盘过滤机滤饼附液率的影响，提出了相应的改进措施。     

浅析离心过滤过程恒浓度问题

通过离心过滤过程平均浓度和瞬时浓度两种情况的理论分析，对该过程恒浓度的判别公式进行了推导，并结合盐硝生产实验作了讨论。     

从“月饼”看食品安全问题

该文从月饼的起源、演变和发展的角度着眼,分析了月饼目前存在主要问题,以及产生这些问题的主要原因。根据目前食品行业新出台的政策,笔者提出了一些解决的方法和措施。     

泥水盾构泥浆渗透试验及成膜规律研究进展

泥水盾构维持开挖面稳定的关键在于及时形成致密的微透水或不透水泥膜,但泥膜在开挖面上的形成机理尚不明确。为了进一步弄清泥膜的形成机理,有必要针对泥水盾构开挖面泥膜形成规律的研究进展进行总结与分析。通过总结国内外学者关于泥膜形成机理的研究成果,分析泥膜形成的一般规律,指出目前研究中存在的不足并给出建议。研究得出,泥浆渗透试验主要有竖向和横向两种形式,但试验方案以及试验装置还有待改进;泥浆性质和地层特性是影响泥膜形成的主要因素;泥浆性质可以通过添加物进行调整;通过总结泥浆颗粒与砂土地层颗粒的匹配关系获得泥膜形成的一般规律。     

地铁列车振动荷载对穿越泥水盾构泥膜渗透系数的影响

泥水盾构穿越饱和砂土地层中的运营地铁时,在地铁列车振动荷载的作用下,开挖面前方土体中会产生超孔隙水压力,从而降低泥膜承受的压力差,使泥膜回弹,渗透系数增大,进而影响开挖面稳定。通过动三轴试验,研究了不同类型砂土在地铁列车振动荷载的作用下的超孔隙水压力增长规律,并利用改进的Kozeny-Carman公式分析了其对泥膜渗透系数的影响。研究表明:地铁列车振动荷载振幅与在其作用下产生的砂土最大超孔隙水压力之间的关系可用指数函数表示;砂土中粗颗粒间的孔隙起控制作用时的最大动孔压比和泥膜最大渗透系数增大比约为细颗粒间的孔隙起控制作用时的最大动孔压比和泥膜最大渗透系数增大比的50%和60%;当动应力比不大于0.15时,振动荷载振幅的增大对最大动孔压比的增加影响并不明显;相对密实度对最大动孔压比的影响并不明显;卸荷程度相同时,轴向卸荷比水平卸荷对最大动孔压比的影响约大一倍;一般情况下,地铁列车振动荷载最大可使泥膜渗透系数增大约15倍;当泥膜渗透系数不大于7.73×10-8 cm/s时,可不必考虑运营地铁列车振动荷载对泥膜渗透系数的影响。     

Gravitational drainage of compressible organic materials

A model was developed to simulate drainage of compressible particle suspensions, and study how cake compression and volumetric load influence the process. The input parameters were settling velocity, cake resistance and compressibility. These parameters were found using a new experimental method. Dextran‐MnO₂ particle suspensions were drained as these resemble organic waste slurries with respect to settling and compressibility. It was demonstrated that cake compressibility must be taken into account to obtain adequate simulations. This implies that pressurized filtration resistances cannot be used for drainage simulations. In the filtration step, a distinct increase of dry matter from top to bottom of the cake was observed. During the subsequent consolidation, the cake compressed and a uniform dry matter profile was found. The final dry matter content of the cake increased with feed concentration and volumetric load. The drainage time increased proportionally with feed concentration and, more importantly, proportionally with squared volumetric load. © 2010 American Institute of Chemical Engineers AIChE J, 2010