Mechanisms Involved in Fly Ash Precipitation in the Presence of Conditioning Agents - A Review
Conditioning agents are usually used to improve the collection efficiency of electrostatic precipitators by causing a reduction in the resistivity of the fly ash. However, certain conditioning agents may have other effects including changing the electrical breakdown strength of the flue gas, space charge enhancement of the collecting field, increasing the mean particle size, changing the adhesion and cohesion properties of the ash, and changing the acid dew point of the flue gas. These mechanisms are reviewed and related to results reported in the literature for ammonia and triethylamine, two conditioning agents which appear able to affect one or more of the mechanisms mentioned above, in addition to the resistivity.
Ammonia/flyash interactions and their impact on flue gas treatment technologies
Abstract Ammonia/flyash interactions were investigated to assess their importance in flue gas treatment processes. Theoretical calculations are presented for the upper bound of ammonia uptake by flyash during selective catalytic reduction. Assuming diffusion-controlled uptake, significant ammonia loss to flyash is predicted; this is not supported by industrial experience. Thus, experiments were conducted to measure ammonia adsorption and reaction on flyash as a function of temperature. Based on the experimental results, ammonia/flyash interactions are not expected to interfere with either current or proposed low-temperature (110–160°C) operation. When adding ammonia as an electrostatic precipitator (ESP) conditioning agent, however, the extent of adsorption onto flyash will be very sensitive to operating conditions. This may explain the erratic performance of ammonia in ESP conditioning reported in the literature. Finally, the saturation capacity for ammonia adsorption onto flyash exceeds the maximum threshold established for flyash reuse as a cement additive and thus could limit this large-volume opportunity for mitigating flyash disposal.
From student to therapist: exploring the first year of practice.
OBJECTIVES
The transition from classroom to clinical practice challenges many health professional students. This study used a phenomenological approach to explore the lived experience of rehabilitation students during their final placement and first year of practice.


METHOD
Students (n = 6) in occupational therapy and physical therapy wrote reflective journals every 2 weeks during their final fieldwork placement and first year of practice. The researchers independently analyzed the journals for common themes. An independent peer completed a blind analysis of two journals. Data were also compared with published first-person accounts of novice practitioners.


RESULTS
The lived experience of the first year of practice included four consecutive stages: Transition, Euphoria and Angst, Reality of Practice, and Adaptation. Themes from the journals included great expectations, competence, politics, shock, education, and strategies.


CONCLUSION
Recognizing the stages in the process of transition from student to therapist may assist in educational curriculum development and clinical support and supervision for new graduates. Educators need to continue to make education practice relevant while maintaining a theoretical perspective.