Sulphur dioxide (SO2) is one of a group of highly reactive gases known as “oxides of sulphur”. SO2 is linked with a number of adverse effects on the respiratory system and other environmental issues. It is an important industrial emission gas which causes several difficulties in the environment like acid rain. Sulphur dioxide is a ubiquitous component of fuel combustion exhausts and one of the first air pollutants to be regulated all over world. Several approaches have been adopted to reduce SO2 content in the environment. One of the most difficult environmental problems facing industry is how to economically control SO2 emissions. Conversion of H2SO4 from SO2, which could be a great impact on reducing pollution. Production of sulphuric acid is one of the best choice considering its economical values and utilities. This paper addresses the different processes to control SO2 and to use SO2 in most economic and productive way to reduce SO2 effect in environment. A review of various treatment methods has been provided and a brief description of each process has been included and their technical applicability is also compared.

Size enlargement of particles in fluidized bed granulation involves mixing of particles with a binder liquid to form larger wet granules and drying them to form dry granules. Identification of the time for completion of granulation process is critical as further fluidization of dry granules is providing extra energy for their attrition. Monitoring the bed pressure drop and bed temperature of a batch fluidized bed granulator with time can provide information on the time for completion of the granulation process. Experimental observations on granulation time and size of granules in a lab-scale batch fluidized bed granulator are presented. Model based equations are developed for the estimation of granulation time and size of granules.

Fluidized bed granulation is a process by which granules or coated particles are produced in a single piece of equipment by spraying a binder as solution. suspension, or melt on the fluidized powder bed. Heat and mass transfer correlation useful for designing a granulator has been derived based on the equivalence of evaporation rate of the liquid to the heat transferred from hot gas to particles:(m/A)D-p(2)lambda/L-mf(1 - epsilon(mf))(T-g - T-l)K-g = hD(p)/K-g.This equation is applied to data on granulation experiments by different workers to calculate Reynolds number and Nusselt number to obtain a relation between heat and mass transfer from gas to particles during granulation on a logarithmic scale from which the following empirical relation is obtained:Nu = 0.0205Re(1.3876)which is comparable to Kothari's correlationNu = 0.03Re(1.3).By using the heat and mass transfer correlation obtained, the entry length, that is the length of granulator up to which effective heat transfer from gas to bed particles takes place, is estimated, which is also validated with experimental study. The correct estimation of entry length is useful in optimal design of a granulator. (C) 2009 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

In granulation, fine particles combine to form a coarse granule in the form of a particle matrix partially or fully saturated with a binder liquid. The final product of granulation possesses a wide variety of granule size distributions with surface mean diameters which differ with operating conditions. The final granule size depends on the operating conditions, e.g. operating gas velocity, inlet air temperature, initial feed particle size, and viscosity of the binder. The objective of this paper is to find out the uniformity in the relation between the granule mass fraction in the final granule size distribution and the number of feed particles present in the granules. The total number of granules obtained depends on the experimental conditions but the granule mass fraction and the number of feed particles forming a single granule are independent of operating variables, feed material and method of granulation. The paper purports further to compare the uniform nature of mass fraction of the granules in final granule size distribution and the primary particles required to form that particular granule size irrespective of experimental conditions of granulation.

Granulation is a key process in several industries like pharmaceutical, food, fertilizer, agrochemicals, etc. Population balance modeling has been used extensively for modeling agglomeration in many systems such as crystallization, aerosols, pelletisation, etc. The key parameter is the coalescence kernel, β(i,j) which dictates the overall rate of coalescence as well as the effect of granule size on coalescence rate. Adetayo, Litster, Pratsinis, and Ennis (1995) studied fertilizer granulation with a broad size distribution and modeled it with a two-stage kernel. A constant kernel can be applied to those granules which coalesce successfully. The coalescence model gives conditions for two types of coalescence, Type I and II. A two-stage kernel, which is necessary to model granule size distribution over a wide size distribution, is applied in the present fluidized bed spray granulation process. The first stage is size-independent and non-inertial regime, and is followed by a size-dependent stage in which collisions between particles are non-random, i.e. inertial regime. The present work is focused on the second stage kernel where the feed particles of volume i and j collide and form final granule ij instead of i+j (Adetayo et al., 1995) which gives a wider particle size distribution of granules than proposed earlier.

Due to their polycationic nature, Spermidine (Spd3+) and Spermine (Spm4+) are known to interact with polyanionic compounds, e.g. negatively charged head group of phospholipid membrane components, thereby stabilizing salinity stress-induced damage of plasma membrane (PM). But to what extent polyamine-mediated restoration of activities of PM-bound enzymes occurs and differs within salt-sensitive and salt-tolerant rice cultivars is totally unknown. Therefore, PM was isolated from the roots of 3-day-old rice seedlings from two salt-tolerant (Nonabokra and Pokkali) and two salt-sensitive (M-1-48 and IR8) cultivars treated with none (control) or with NaCl (150mM, 16h) alone or with Spd (1mM, 16h). Vanadium sensitive but K+ stimulated H+-ATPase activity from equal amount of PM was measured by estimating released Pi. Results showed that nine-fold higher level of H+-ATPase (100% vanadium sensitive) was detected from PM of Nonabokra roots in comparison to M-1-48 roots. Salinity stress alone to the seedlings significantly reduces the activity of PM-bound H+-ATPase. The activity of H+-ATPase was restored to some extent in the roots treated with NaCl stress in presence of 1mM Spd. Analysis of PM-bound polyamine from untreated control roots showed only Putrescine from M-1-48 and IR8 cultivars, whereas roots of salt-tolerant plants, Nonabokra and Pokkali, have only Spermidine and Spermine. PM-bound H+-ATPase activity of control and treated plants, when measured by NADH oxidation (coupled reaction), 2.5–3.0-fold higher activity was detected from salt-tolerant cultivars. Salinity stress to the plants severely inhibits H+-ATPase activity and Spermidine co-treatment significantly recovers its activity in all four cultivars. Western Blot with equal amount of 5% SDS extracted protein from roots when analyzed by the polyclonal antibody raised against H+-ATPase (PM-bound) of Arabidopsis thaliana showed NaCl stress-induced decrease and Spermidine-induced recovery of 100kDa polypeptide (known MW of 100kDa H+-ATPase from rice). These results clearly demonstrate for the first time that the deficit of salt-sensitive rice cultivars, e.g. high accumulation of Na+, loss of K+ ion, salinity stress-induced sharp inhibition of PM-bound H+-ATPase activity, could be overcome by supplying Spermidine exogenously.