Design parameters for fixed bed reactors of activated carbon developed from fertilizer waste for the removal of some heavy metal ions

Activated carbon, developed from fertilizer waste, has been used for the removal of Hg²⁺, Cr⁶⁺, Pb²⁺, and Cu²⁺. Mass transfer kinetic approach has been successfully applied for the determination of various parameters necessary for designing a fixed-bed absorber. Parameters selected are the length of the (PAZ) primary adsorption zone (δ), total time involved for the establishment of primary adsorption zone (t_x), mass rate of flow to the absorber (F_m), time for primary adsorption zone to move down its length (t_δ), amount of adsorbate adsorbed in PAZ from breakpoint to exhaustion (M_s), fractional capacity (f), time of initial formation of PAZ (t_f) and per cent saturation of column at break point. Chemical regeneration has been achieved with 1 M HNO₃.     

Groundwater Remediation and Aquifer Clean-Up: A Case Study

Groundwater was being remediated with pump and treat technology at a facility where the groundwater was contaminated with commonly used degreaser solvents. Hydraulic conductivity of the heterogeneous residuum was beneficiated by applying pneumatic fracturing technology. The remedial system was controlled and monitored by a sophisticated remote telemetry system. A case history follows.     

The role of relationships in understanding telecommuter satisfaction

Relationships are fundamental to organizational functioning, yet as telecommuting and other forms of virtual work become increasingly popular, research has not yet focused on how the virtual context might alter relationships so as to impact important work outcomes. This study therefore examines the role relationships play in mediating the link between the extent of telecommuting and job satisfaction. In doing so three fundamental types of relationships maintained by employees are investigated—those with managers, coworkers, and family. Regression analysis of field data from 294 telecommuting employees in a large telecommunications company revealed the anticipated inverted U‐shaped relationship, mediated by leader‐member exchange quality, team‐member exchange quality, and work‐family conflict. Copyright © 2006 John Wiley & Sons, Ltd.     

Characteristics of large cooking oil pool fires and their extinguishment by water mist

Large cooking oil pool fires, occurring in industrial oil cookers, present a severe hazard to food processing plants due to their size and the large amount of hot oil involved. This paper reports a series of full-scale fire experiments conducted in a large industrial oil cooker mock-up. The characteristics of large cooking oil pool fires and the effect of oil depth and hood position in the oil cooker on fire growth were studied. The use of water mist for extinguishing large oil pool fires and their extinguishing performance under different discharge pressure and with different types of water mist systems were investigated. Experimental results showed that the cooking oil underwent a substantial expansion in volume during heating. The fires developed quickly once the oil auto-ignited. The fire growth rate was affected by the oil depth in the pan and the hood position in the oil cooker. The water mist fire suppression systems effectively extinguished large cooking oil fires and prevented them from re-igniting. Their extinguishing performance was determined by the type of water mist system, discharge pressure and hood position in the oil cooker.     

On the response of 500 gal propane tanks to a 25% engulfing fire

This paper presents detailed data on the thermal response of two 500 gal ASME code propane tanks that were 25% engulfed in a hydrocarbon fire. These tests were done as part of an overall test programme to study thermal protection systems for propane-filled railway tank-cars.

The fire was generated using an array of 25 liquid propane-fuelled burners. This provided a luminous fire that engulfed 25% of the tank surface on one side. The intent of these tests was to model a severe partially engulfing fire situation.

The paper presents data on the tank wall and lading temperatures and tank internal pressure. In the first test the wind reduced the fire heating and resulted in a late failure of the tank at 46 min. This tank failed catastrophically with a powerful boiling liquid expanding vapour explosion (BLEVE). In the other test, the fire heating was very severe and steady and this tank failed very quickly in 8 min as a finite rupture with massive two-phase jet release. The reasons for these different outcomes are discussed. The different failures provide a range of realistic outcomes for the subject tank and fire condition.     

On the thermal rupture of 1.9 m propane pressure vessels with defects in their thermal protection system

This paper describes the results from a series of fire tests that were carried out to measure the effect of defects in thermal protection systems on fire engulfed propane pressure vessels.

In North America thermal protection is used to protect dangerous goods rail tank-cars from accidental fire impingement. They are designed so that a tank-car will not rupture for 100 min in a defined engulfing fire, or 30 min in a defined torching fire. One common system includes a 13 mm blanket of high-temperature ceramic fibre thermal insulation covered with a 3 mm steel jacket. Recent inspections have shown that some tanks have significant defects in these thermal protection systems. This work was done to establish what levels of defect are acceptable from a safety standpoint.

The tests were conducted using 1890 l (500 US gallon) ASME code propane pressure vessels (commonly called tanks in the propane industry). The defects tested covered 8% and 15% of the tank surface. The tanks were 25% engulfed in a fire that simulated a hydrocarbon pool fire with an effective blackbody temperature of 870 °C.

The fire testing showed that even relatively small defects can result in tank rupture if the defect area is engulfed in a severe fire, and the defect area is not wetted by liquid from the inside. A wall failure prediction technique based on uniaxial high-temperature stress rupture test data has been developed and agrees well with the observed failure times.     

Application of tracer ratio and inverse dispersion methods with boat-based plume measurements to estimate ammonia emissions from seabird colonies

Ammonia emissions from two contrasting seabird colonies in Scotland were measured, based on the determination of atmospheric concentrations downwind of the colonies. Atmospheric concentrations of ammonia (NH₃) across the downwind plume were compared with the inverse application of a Gaussian dispersion model (ID) to calculate the modelled NH₃ emission that would generate the measured cross-wind-integrated plume concentration. In parallel, a tracer gas (sulphur hexafluoride, SF₆) was released from the colonies with air samples taken to allow determination of SF₆ concentrations. On the basis of the known emission rate of SF₆, the magnitude of ammonia emissions was estimated by the cross-wind-integrated tracer ratio (TR) of NH₃/SF₆ concentrations. Coupled with data on annual bird attendance, the measurements indicate annual emissions from the Isle of May and the Bass Rock of 18 and 132 tonnes NH₃-N year^–1, respectively. The measured NH₃ emissions were compared with estimates of seabird nitrogen excretion to estimate the proportion of excreted N that is volatilised as NH₃ (F_Nr). The emission estimates of the two methods compared favourably, giving 4 and 6 kg NH₃-N h^–1 (F_Nr = 15%) for the Isle of May for the ID and TR methods, respectively, and 21 and 25 kg NH₃-N h^–1 (F_Nr = 50%) for the Bass Rock for the ID and TR methods, respectively. The results provide the first measurement-based estimates to allow regional up scaling of ammonia emissions from seabirds.