Direct contact packed bed thermal gradient attenuators: Theoretical analysis and experimental observations

2003 ◽  
Vol 74 (5) ◽  
pp. 2886-2893 ◽  
Author(s):  
Kevin M. Lawton ◽  
Steven R. Patterson ◽  
Russell G. Keanini
Keyword(s):  
Theoretical Analysis ◽  
Thermal Gradient ◽  
Direct Contact ◽  
Packed Bed

Managing total reduced sulfur emissions at a Canadian kraft pulp mill

TAPPI Journal ◽  
2016 ◽  
Vol 15 (4) ◽  
pp. 265-272 ◽  
Author(s):  
ROHAN BANDEKAR ◽  
JIM FREDERICK ◽  
JAROSLAV STAVIK
Keyword(s):  
Direct Contact ◽  
Black Liquor ◽  
Pulp Mill ◽  
Packed Bed ◽  
Average Value ◽  
Emission Limit ◽  
Total Reduced Sulfur ◽  
Reduced Sulfur ◽  
Air Ingress ◽  
Solids Content

This study addresses the challenges a dissolving-grade pulp mill in Canada faced in 2014 in meeting its total reduced sulfur (TRS) gas emission limit. These emissions from the recovery boiler exit are controlled by passing the boiler exit gas through a TRS scrubber system. The mill employs a cyclonic direct contact evaporator to concentrate black liquor to firing solids content. The off-gases from the direct contact evaporator flow to the effluent gas control system that consists of a venturi scrubber, a packed bed scrubber, and a heat recovery unit. Emissions of TRS greater than the regulated limit of 15 ppm were observed for a 4-month period in 2014. The level of emissions measured during this period was significantly higher than about 12 ppm, the expected average value based on historic experience. The problem persisted from mid-June 2014 until the annual mill shutdown in October 2014. The main TRS components detected and the performance of the Teller scrubber in capturing them are examined. Other potential causes for these emissions are identified, including mechanical problems such as broken packing in the TRS packed bed scrubber, broken baffle plates in the scrubber, and cyclone evaporator leaks causing air ingress. Repairs were carried out during the mill shutdown, which eliminated the TRS emissions problem.

scholarly journals A Multi-Perspective Theoretical Analysis to Web Accessibility

2017 ◽  
pp. 117-139 ◽  
Author(s):  
Carlos Peixoto ◽  
Frederico Branco ◽  
José Martins ◽  
Ramiro Gonçalves
Keyword(s):  
Information Technology ◽  
Theoretical Analysis ◽  
Direct Contact ◽  
Public Services ◽  
Web Accessibility ◽  
End Users ◽  
The Past ◽  
Software Companies ◽  
Challenges And Opportunities ◽  
Work Done

Accessibility has become increasingly important in information technology, particularly due to legislation pressure to make affordable public services to all. Being end-users and software companies those who have direct contact with accessibility problems, other stakeholders are committed to defining methods and change mentalities in Web accessibility implementation. In addition to a conceptual definition, this chapter presents entities views with responsibilities in the area, taking into account their work done in the past and the prospects for future. The understanding of the interaction between all these perspectives will help to realize the way it will go, which carries with it great challenges and opportunities, widely explored in this work.

A theoretical analysis of direct contact evaporation in spray columns

1983 ◽  
Vol 10 (6) ◽  
pp. 533-543 ◽  
Author(s):  
P. Battya ◽  
V.R. Raghavan ◽  
K.N. Seetharamu
Keyword(s):  
Theoretical Analysis ◽  
Direct Contact

Size Dependent Orientation of Knudsen Force

2012 ◽  
Author(s):  
Taishan Zhu ◽  
Wenjing Ye ◽  
Jun Zhang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
Thermal Gradient ◽  
Rarefied Gas ◽  
Mechanical Force ◽  
Thermal Gradients ◽  
Free Molecule ◽  
Asymptotic Order ◽  
Size Dependent ◽  
Leading Term

Knudsen force acting on a heated microbeam adjacent to a cold substrate in a rarefied gas is a mechanical force created by unbalanced thermal gradients. The measured force has its direction pointing towards the side with a lower thermal gradient and its magnitude vanishes in both continuum and free-molecule limits. In our previous study, negative Knudsen forces were discovered at the high Knudsen regime before diminishing in the free-molecule limit. Such a phenomenon was however not observed in the experiment. In this paper, the existence of such a negative Knudsen force is further confirmed using both numerical simulation and theoretical analysis. The asymptotic order of the Knudsen force near the collisionless limit is analyzed and the analytical expression of its leading term is provided, from which approaches for the enhancement of negative Knudsen forces are proposed.

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