No abstract

Laboratory and field tests have shown that electrostatic precharging can lead to a substantial decrease in the flow resistance of fabric filters. For lead smelter dust, the effectiveness of the precharger is dependent on the relative humidity of the suspending gas. For relative humidities below 5%, severe back corona occurs in the precharger, which results in poor particle charging and little improvement in filter performance. For relative humidities between 5% and 40%, little or no back corona occurs, precharging is effective and results in a reduction of up to 60% in the flow resistance of the fabric filter. The operational range of the precharger can be extended to lower relative humidities by cooling the earthed electrode. The improvement in filter performance can be achieved without the precipitation of large quantities of dust in the precharger.

Experiments on a high velocity pulse jet filter used to control emissions from a wool carbonizing process have shown that it is necessary to use filter cloths with a surface skin to prevent premature blinding of the fabric. The skin partially prevents dust and wool fiber from penetrating into the depth of the fabric and, subsequently, the dust is more easily dislodged during cleaning. Although both Goretex® and a calendered needlefelt have given satisfactory performance at a filtration velocity of 65 mm/s, there is a gradual increase in the resistance to airflow through the fabrics with time. This is due to the accumulation of dust on the fabric, which is not removed by the normal cleaning pulse. After eight months service, 56% of the resistance of the Goretex cloth was due to dust that was not dislodged from the fabric during cleaning, 38% to dust which was dislodged during cleaning but immediately redeposited on the bag, and 6% to dust added during the filtration cycle and cleaned from the fabric by the cleaning pulse. The efficiency of the cleaning process can be improved by cleaning the filter off-line rather than the more normal on-line cleaning. Under these conditions the dust that is usually redeposited on the bag is allowed to reach the hopper.

No abstract

The Shepherd of Hermas was one of the most widely circulated early Christian texts. Contemporary estimations of the text, however, are far from praiseworthy, and many regard the Shepherd to be so imprecise and poorly written as to lend itself to heterodox interpretation, especially in regard to its Christology and the infamous parable of “The Servant and the Vineyard.” This essay will argue that this negative evaluation of the Shepherd is misguided, and that not only does this specific parable avoid heterodox implications, but that it displays a thoroughly biblical understanding of Christ as the servant-messiah sent into the world by the Father to redeem the world, as witnessed by the apostolic preaching and the authors of the New Testament. This essay will demonstrate that the Shepherd presents the reader with a coherent narrative with which to understand the basic themes of the Christ event by weaving together a creative and original parable rooted firmly in the scriptural and interpretive tradition of both the Old and New Testaments.