Slurry pretreatment

The same conditions also resulted in the maximum glucose yield, 17.2 g/ 100 g of SFF. At the pretreatment conditions used, the formation of fermentation-inhibiting compounds was very low (results not shown) (16). The concentration of furfural in the slurry pretreated at 190°C for 10 min was about 0.3 g/L. No HMF was detected. 

Conventional mechanical flotation cells have been widely used in the industry for many years and remain the primary means of cleaning coal particles smaller than 100 mesh. These units consist of a number of cells (usually 4-6) connected in series, each cell containing a mechanical agitator and aerator. The feed slurry, pretreated with frother and, usually, collector reagents, passes from one cell to the next with the most floatable coal being recovered in the first cell and the least floatable coal in the last cell. 

Filtration is often referred to as mechanical separation because the separation is accompHshed by physical means. This does not preclude chemical or thermal pretreatment used to enhance filtration. Although some slurries separate well without chemical conditioning, most pulps of a widely varying nature can benefit from pretreatment (see Flocculating agents). 

Pretreatment Chemicals Even though the suspended solids concentration of the slurry to be tested may be correct, it is frequently necessary to modify the sluriy in order to provide an acceptable filtration rate, washing rate, or final cake moisture content. The most common treatment, and one which may provide improvement in all three of these categories, is the addition of flocculating agents, either inorganic chemicals or natural or synthetic polymers. The main task at this point is to determine which is the most effective chemical and the quantity of chemical which should be used. 

Hydrolysis, although a simple method in theory, yields terephthalic acid (TPA), which must be purified by several recrystallizations. The TPA must be specially pretreated to blend with ethylene glycol to form premixes and slurries of the right viscosities to be handled and conveyed in modern direct polyesterification plants. Hie product of the alkaline hydrolysis of PET includes TPA salts, which must be neutralized with a mineral acid in order to collect the TPA. That results in the formation of large amounts of inorganic salts for which commercial markets must be found in order to make the process economically feasible. There is also the possibility that the TPA will be contaminated with alkali metal ions. Hydrolysis of PET is also slow compared to methanolysis and glycolysis.1... 

For pastes and slurries, some form of pretreatment equipment will normally be needed, such as extrusion or granulation. 

When deciding on the type of the reactor required for a particular chemical or physical transformation, the first question that needs to be addresses is whether the cavitation enhancement is the result of an improved mechanical process (due to enhanced mixing). If this is the case, then cavitation pretreatment of a slurry may be all that is required before the system is subjected to conventional type transformation scheme and the scale up of the pretreatment vessel would be a relatively simpler task. 

Products Company and Davison (W.R. Grace) Catalysts) and Hydrocarbon Technologies, Inc. ART provides non-zeolitic catalysts for ebullating residue hydrocracking and fixed bed pretreating HDT [140], A nanoscale iron based, slurry catalyst is recommended for coal liquefaction, while a molecule-sized and chemically in situ generated catalyst is employed for the high conversion of asphaltenic fractions or heavy oils [141],... 

When rare earth Y-zeolite (REY) was added to the PILC or to the parent clay, the dried PILC or "as received" clay was reslurried in water and the calcined REY added to the 10 wt % level. This slurry was then mixed, filtered, dried, and calcined at 500 C for 2 hours in air. The calcined REY was obtained from Union Carbide and contained 14.1 wt % rare earth elements, primarily lanthanum and cerium. Portions of the PILC were pretreated by one of the methods listed below prior to the microactivity testing. 

Pretreatment is often necessary to obtain the proper percentage of organics and to render solids into a liquid or slurry form that can be pumped. 

Set-up for Ethylene Glycol Lignin Production. A process development unit (PDU), previously described by Chornet and co-workers (11), was used for the experiments. A typical preparation consists of initially mixing 1-1.2 kg of wood meal with 10 1 of ethylene glycol. The mixture is allowed to stand overnight for imbibition to take place. To enhance solvent to substrate penetration, the slurry is homogenized at 200°C in the pretreatment section of the PDU. It is then pumped through the treatment section which consists of a tubular reactor at 220°C. The product slurry is collected in a receiver. The detailed procedure and choice of conditions above have been published elsewhere (11,12). 

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