Multi-stage continuous processes

In the activated sludge process, single- or multi-stage continuous-flow aerated reactors are used (Fig. 4). Effluent from the bioreactor is separated in a settling tank and a portion of sedimented sludge is usually recycled to the reactor providing a continuous sludge inoculation. 

The extract contains, in addition to the sucrose, further solved or colloidally dispersed components, which in the juice purification stage must be - as far as possible - precipitated or destroyed under alkaline conditions by adding calcium oxide. This is carried out by a multi-stage, continuous treatment with, first, calcium oxide and, second, carbon dioxide. Both processing aids are produced in a separate calcining process in parallel. The excess calcium oxide is precipitated in so-called carbonation vessels with carbon dioxide from the calcining process. All precipitates and deposits are separated in a multi-step filtration. The sludge... 

Consideration of the basic differences between these scenarii lead to the present proposition that for a multi-stage continuous PHA-production process, the use of a plug-flow tubular reactor, or PFTR (in which Reynolds numbers are large), brings substantial increases in productivity when compared to a system consisting of CSTRs only. Support of this assertion comes firom the works of Levenspiel (29), where mean residence times for the two types of reactors are compared under the restriction of a desired goal ... 

Commercial production of PAO using a BF3 catalyst generally involves a multi-stage, continuous stirred tank reactor (CSTR) process . In early production technology, the catalyst was destroyed with diluted aqueous alkali after polymerization. More recent patents disclosed improved processes using BF3 catalyst recycle to reduce catalyst usage, minimize process waste and improve process economics. ... 

Tekmaheat Oy manufacture three kiln systems a compact chamber of 15-25m per batch, having an annual production capability of 1600-3000 m a drive-through chamber having a volume of 40-60 m, with an annual capacity of 5000-10 000 m and a multi-stage production line, in which the timber is pre-heated, dried, heat-treated and conditioned in a continuous throughput process, which has a capacity of 30 000-50 000 m per annum. 

Assess results Several methods can be applied to minimize the ozone consumption in combined processes of ozonation and biodegradation. For example, the different operational behavior of batch and continuous-flow systems, with the resulting differences in oxidation products, etc. has to be considered, as well as the fact that multi-stage systems for each treatment process may be of advantage over single stage systems. 

Plant requirements. Is it a single stage, multi stage batch, continuous process or any combination of these Will it use the existing plant or is a new plant required If it is the latter, chemical engineers and a design team will be involved. 

The basis of the process is to use activated carbon to recover SO2 in a salable form. The process flowsheet and chemistry are summarized in Figure 1. All steps of this dry, cyclic process are performed in continuous, countercurrent, multi-stage fiuidized-bed equipment. In the S02-removal step the carbon catalyzes the reaction of the SO2 with oxygen in the flue gas to form SO3, which is hydrolyzed to sulfuric acid that remains sorbed... 

In the laboratory, a multi-stage liquid-liquid extraction can be performed by a simultaneous distillation-extraction process according to Likens-Nickerson [29] (Fig. 2.10). Here, the liquid matrix with the solute in one flask is evaporated together with an immiscible solvent in a second flask. Extraction takes place in the vapour phase where an intensive distribution of both phases is ensured. The condensed vapours from the two phases are separated via a siphon using their different densities and their reintroduction into the original flasks. As the distillation process is continued, extraction is repeated until the solute is exhausted in the original matrix. This method is very useful when traces of non-volatile solutes are present, which are only partly miscible... 

J, A. Brodie, A Continuous Multi-Stage Melt Purification Process, p. 37, The Mechanical and... 

Sulphate (46% of production, and declining) a multi-stage wet chemical process, batch or continuous. Titanium dioxide is dissolved in the raw materials by concentrated sulphuric acid, precipitating the hydrous salt. This is then calcined to produce one of the two crystalline forms, anatase or rutile. 

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