Solids process

PHASE CONTACTING AND LIQUID-SOLID PROCESSING AGITATION OF LOW-VISCOSITY PARTICLE SUSPENSIONS... 

Loop Reactors For some gas-hquid-solid processes, a recirculating loop can be an effective reactor. These involve a relatively high horsepower pumping system and various kinds of nozzles, baffles, and turbulence generators in the loop system. These have power levels... 

Solids processes clearly differ from vapour liquid systems in two main ways. Firstly and most obviously, solid systems have a particle size or size distribution added to their specification. Secondly, solids processing systems use different... 

As mentioned above, the solids process synthesis approach (Rossiter and Douglas, 1986) has been applied to the optimization of a continuous salt crystallization plant similar to that depicted in Figure 9.2 (Rossiter, 1986). In... 

Gruhn, G., Rosenkranz, J., Werther, J. and Toebemiann, J.C., 1997. Development of an object-oriented simulation system for complex solids processes. Computers and chemical engineering, 21, S187. 

Hill, P.J. and Ng, K.M., 1997. Simulation of solids processes accounting for particle size distribution. American Institute of Chemical Engineers Journal, 43, 715. 

Jones, G.L., 1984. Simulating the effects of changing particle characteristics in solids processing. Computers and Chemical Engineering, 8, 329. 

Rajagopal, S., Ng, K.M. and Douglas, J.M., 1988. Design of solids processes Production of potash. Industrial and Engineering Chemistry Research, 27, 2071. 

Rossitter, A.P., 1986. Design and optimisation of solids processes Part III. Chemical Engineering Research and Design, 64, 191-196. 

Only a small fraction of faecal contaminants contributed to the enviromnent through human and animal faeces reach new hosts to infect them. Many of the defecated microorganisms never reach the soil and/or water bodies, since faecal wastes are submitted to purification (water) and hygienization (solids) processes, which remove a fraction of the pathogens and indicators. An important fraction of those that reach either the soil or water are removed (adsorption to soil particles and suspended solids, followed by sedimentation) and/or inactivated by natural stressors (physical, chemical and biological) in soil and water bodies. 

As the zeolite catalyst preparation is not trivial, a catalyzed epoxidation reaction serves to demonstrate the feasibility of gas/liquid/solid processing using this industrially well-applied catalyst class [30]. 

In liquid-solid processes reaction takes place between a liquid reactant and an insoluble or sparingly soluble solid which must be finely divided to speed up the process. Another measure to accelerate the process is to use an aqueous solution of a phase-transfer agent (typically a quaternary ammonium salt). The solid can also be a catalyst for reactions between liquid components, e.g. in acylations, carried out both conventionally in the presence of metal chlorides (mostly AICI3) or catalysed by zeolites and Grignard reactions. 

Semibatch reactors are often used to mn highly exothermic reactions isothermally, to run gas-liquid(-solid) processes isobarically, and to prevent dangerous accumulation of some reactants in the reaction mixture. Contrary to batch of)eration, temperature and pressure in semibatch reactors can be varied independently. The liquid reaction mixture can be considered as ideally mixed, while it is assumed that the introduced gas flows up like a piston (certainly this is not entirely true). Kinetic modelling of semibatch experiments is as difficult as that of batch, non-isotherma experiments. 

Laboratory reactors for studying gas-liquid processes can be classified as (1) reactors for which the hydrodynamics is well known or can easily be determined, i.e. reactors for which the interfacial area, a, and mass-transfer coefficients, ki and kc, are known (e.g. the laminar jet reactor, wetted wall-column, and rotating drum, see Fig. 5.4-21), and (2) those with a well-defined interfacial area and ill-determined hydrodynamics (e.g. the stirred-cell reactor, see Fig. 5.4-22). Reactors of these two types can be successfully used for studying intrinsic kinetics of gas-liquid processes. They can also be used for studying liquid-liquid and liquid-solid processes. 

For the factored estimate a list is made of all pieces of equipment, and the delivered cost of each item is obtained. This could be determined by inquiring from manufacturers, from past records, or from published data. The delivered cost of all the equipment is summed and multiplied by an appropriate factor. According to Lang this factor would be 3.10 for a solids process plant, 3.63 for a solid-fluid plant, and 4.74 for a fluid plant. These factors are referred to as Lang factors. This estimate is often used in the preliminary stages of engineering, but is not extremely accurate. 

To use the Lang factors the engineer must define what type of plant is being built. This is important, since the largest factor is 50% greater than the smallest. It is sometimes difficult, however, because there is a continuum of chemical plants between the two extremes. A coal-briquetting plant is obviously a solids processing plant. Methanol and ammonia plants are fluids plants. Plants that extract chemicals from solids fall between. 

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