Fine particle separation in a riser with flow modifications

Fine particle separation is of great interest in industry. Coal and mineral processing industries are currently very interested in particle separation for its potential in cleaning coal matter. A circulating fluidized bed riser system has been constructed to investigate possible separation of coal containing pyrite from clean coal. The system was constructed to operate using compressed air in which an air-solid mixture would pass through the riser and the solids would enter in to a dense, product, or filter collection bin. Several different variables were investigated during the project such as the collection ring wall height, particle entrance size into the riser, and mass flux of particles into the riser. By changing the particle entrance into the riser, and changing the ratio of nozzle flow and particle mass flux, a jet style flow could be achieved. The objective of this investigation was to observe how changing the flow field in a circulating fluidized bed would affect particle separation.;The first experiment was conducted using a mixture of sand and steel shot with particles sizes between 250 and 500 micron. Results from using the sand and steel shot proved to be very promising as more than 90% of the steel shot could be collected from the sand. The results were then used to determine the experimental conditions that were to be used while separating pyrite laden coal particles from clean coal. There was approximately 1% initial pyrite in the mixture and size ranges for the particles were between 105 and 210 micron. The results using the run-of-mine coal were not as promising as those of the sand and steel shot as a maximum of 25% of the pyritic laden coal could be separated from the cleaner coal. A third experiment was then performed in which chunks of pure pyrite were crushed and then added into clean coal and run through similar separation conditions to the run-of-mine coal. The mixture contained 4% pyrite, and both the pure pyrite and clean coal size ranges were between 105 and 210 micron. The results from this test proved to be very good as up to 77% of the pure pyrite could be recovered from the clean coal

Application of Polyethylene Air-Bubble Cushions to Improve the Shock Absorption Performance of Type I Construction Helmets for Repeated Impacts

BACKGROUND: The use of helmets was considered to be one of the important prevention strategies employed on construction sites. The shock absorption performance of a construction (or industrial) helmet is its most important performance parameter. Industrial helmets will experience cumulative structural damage when being impacted repeatedly with impact magnitudes greater than its endurance limit. OBJECTIVE: The current study is to test if the shock absorption performance of Type I construction helmets subjected to repeated impacts can be improved by applying polyethylene air-bubble cushions to the helmet suspension system. METHODS: Drop impact tests were performed using a commercial drop tower test machine following the ANSI Z89.1 Type I drop impact protocol. Typical off-the-shelf Type I construction helmets were evaluated in the study. A 5 mm thick air-bubble cushioning liner was placed between the headform and the helmet to be tested. Helmets were impacted ten times at different drop heights from 0.61 to 1.73 m. The effects of the air-bubble cushioning liner on the helmets’ shock absorption performance were evaluated by comparing the peak transmitted forces collected from the original off-the-shelf helmet samples to the helmets equipped with air-bubble cushioning liners. RESULTS: Our results showed that a typical Type I construction helmet can be subjected to repeated impacts with a magnitude less than 22 J (corresponding to a drop height 0.61 m) without compromising its shock absorption performance. In comparison, the same construction helmet, when equipped with an air-bubble cushioning liner, can be subjected to repeated impacts of a magnitude of 54 J (corresponding to a drop height 1.52 m) without compromising its shock absorption performance. CONCLUSIONS: The results indicate that the helmet’s shock absorbing endurance limit has been increased by 145% with addition of an air-bubble cushioning liner

Application of Air-Bubble Cushioning to Improve the Shock Absorption Performance of Type I Industrial Helmets

The industrial helmet is the most used and effective personal protective equipment to reduce work-related traumatic brain injuries. The Type I industrial helmet is a basic helmet model that is commonly used in construction sites and manufacturers. The purpose of the current study was to investigate if shock absorption performance of these helmets could be improved by using an air-bubble cushioning liner to augment the helmet’s suspension system. Drop impact tests were performed using a commercial drop tower test machine according to the ANSI Z89.1 Type I drop impact protocol. Typical off-the-shelf Type I industrial helmets were utilized in the study. The effects of the air-bubble cushioning on the helmets’ shock absorption performance were evaluated by comparing the original off-the-shelf helmet samples to the helmets equipped with an air-bubble cushioning liner. The air-bubble cushioning liner (thickness 5 mm) was placed between the headform and the helmet when being tested. The impactor had a mass of 3.6 kg and was free-dropped from different heights. The maximal peak transmitted forces for each of the tests have been evaluated and compared. Our results show that the shock absorption effectiveness of the air-bubble cushioning is dependent on the magnitude of the impact force. At lower drop heights (h \u3c 1.63m), the air-bubble cushioning liner has little effect on the transmitted impact forces, however, at higher drop heights (h ≥ 1.73m) the air-bubble cushioning liner effectively reduced the peak transmitted forces. At a drop height of 1.93 m (the highest drop height tested), the air-bubble cushioning liner reduced the peak transmitted force by over 80%. Our results indicate that adding an air-bubble cushioning liner into a basic Type I industrial helmet will substantially increase shock absorption performance for large impact forces