Experimental Study on the Circulating Characteristics of the Return Particles in CFB and the Validity of the Particles to Desulphurization
The cold-model experimental system that particles flow from the top of CFB reactor is set up to study the circulating characteristics of the particles in the reactor. In order to get further information about the particles distribution and interaction with air flow, the two-phase gas-particle flow and particle concentration in the tower are studied with the use of phase-Doppler particle dynamic analyzer (PDA) system. The effects of the operating parameters including the mass flow rate and the superficial gas velocity on the process of the particles return to the main flow were investigated. The definition of valid internal circulation is put forward in this paper to describe the contribution of the particle to the SO 2 removal reaction. The results showed that the concentration distribution tends to be right high and left low in the radial direction. In axial, more particles concentrated in the upper of the reactor, especially in the case of high superficial gas velocity. With the decrease of the superficial gas velocity, the maximum fallback length of particle and the average particle concentration increase quickly. While the valid particle concentration increases slowly. The quantity of valid particles increases a little. Sending the particle from the top of the reactor has little contribution to the SO 2 removal reaction.
Material Balance Calculation and Experimental Research of Dry FGD Process
During the desulphurization process, the equilibrium concentration of particulates and the time of reaching it can be calculated by the material balance law. Comparison was then made between the stoichiometric concentration and the experimental results. Based on a dry flue gas desulphurization system, the effects of paniculate circulation on the efficiency, resistance profile and operational stability of the system were analyzed and studied. The results show that particulate circulation enhances the desulphurization efficiency by 10%-15%. It takes about 30 min to reach the equilibrium concentration. The experimental results, indicate that the concentration of particulates should be controlled between 600 g/m3 and 1 000 g/m3.
Gambling and Problem Gambling in Sweden: Changes Between 1998 and 2009
Gambling participation and rates of problem gambling change over time in response to a variety of factors including gambling availability, demographic changes and adaptation at individual and societal levels. These relationship are complex and only partially understood. The major aim of the present study was to provide general population estimates of gambling participation and problem gambling for Sweden and compare these estimates with estimates from a previous national study. The study was also designed to identify risk factors for problem gambling including change in these factors over time. Data are from the first phase of the Swedish Longitudinal Gambling Study (Swelogs) in which a representative sample of 8,165 people was assessed using validated problem gambling and other measures to facilitate comparison with findings from the 1997/1998 Swedish Gambling Study (Swegs). Overall, it was found that gambling participation reduced markedly, although in some population sectors increases were evident for some forms including poker and electronic gaming machines. Lifetime prevalence of probable pathological gambling increased; however, past 12 months probable pathological and problem gambling prevalence did not. Males, younger adults and people born outside Sweden were at high risk in both studies. Significant prevalence increases were evident for people aged 18–24 and those with low levels of education. The results indicate that relationships between gambling exposure, participation and problems are dynamic with shifting implications for public health and social policy.