Novel reactors

A continuous centrifugal bioreactor, in which cells are fluidized in balance with centrifugal forces, has been designed to allow high density cell cultivation and superior aeration without elutriation of the suspended cells (van Wie et al., 1991). Reactor performance was hampered by elutriation of biomass by evolved gas in an anaerobic fermentation, indicating that it may not be suitable in its present state for three-phase fermentations. Immobilization of the cells on denser particles may overcome this problem. 

Naouri et al. (1991) described another contained fluidized bed, the so-called high compacting multiphasic reactor (HCMR), which they used for malic and lactic acid fermentations for wine improvement. Bioparticles were contained within a tapered region and liquid was rapidly recycled through this region by pumping improved liquid/solid contact was cited as the advantage of this reactor. 

Gas logging, the adherence of small bubbles to particles, causing them to rise to the surface in the reactor and form an inefficient packed bed with poor mass transfer properties, can be a problem in various fermentations and in wastewater treatment. A double entry fluidized bed reactor has been developed with simultaneous top (inverse) and bottom (conventional) inlets to overcome this problem (Gilson and Thomas, 1993). 

Effluent is drawn off from a side port. Under conditions in which a conventional three-phase fluidized bed bioreactor operated in an unstable manner because of gas logging, the new bioreactor converted glucose to ethanol at a 27% higher rate. Saccharomyces cerevisiae was grown in alginate beads for this reaction. 

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Tubular reactors often offer the greatest potential for inventory reduction. They are usually simple, have no moving parts, and a minimum number of joints and connections that can leak. Mass transfer is often the rate-limiting step in gas-liquid reactions. Novel reactor designs that increase mass transfer can reduce reactor size and may also improve process yields. 

A novel reactor for pyrolysis of a PE melt stirred by bubbles of flowing nitrogen gas at atmospheric pressure permits uniform temperature depolymerisation. Sweep-gas experiments at temperatures 370-410 C allowed pyrolysis products to be collected separately as reactor residue (solidified PE melt), condensed vapour, and uncondensed gas products. MWDs determined by GPC indicated that random scission and repolymerisation (crosslinking) broadened the polymer-melt MWD. 19 refs. USA... 

C. (1997) Synthesis of nano-particles of CaC03 in a novel reactor, in Process Intensification in Practice Applications and Opportunities (ed. J. Semel), Mechanical... 

The chemical route a potential decrease in manufacturing costs is roughly proportional to the reduction in number of processing steps. B2C is therefore attractive if it is an enabler for a chemistry that carmot be carried out in classic batch equipment. This is the opportunity for novel reactor technologies. The economic impact is, however, hard to define quantitatively [34, 60]. 

Modeling, Simulation and Control of Chemical Reaction Systems Nano Materials Synthesis and Application Novel Reactors and Processes Polymer Reaction Engineering... 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

Figure 7.9 Complex patterns can be interpreted as novel reactor designs.

Hendershot, R.J., Lasko, S.S., Fellmann, M.-F. et al. (2003) A novel reactor system for high throughput catalyst testing under realistic conditions. Appl. Catal. A Gen., 254, 107. 

New applications and novel reactor configurations or operational modes for three-phase systems are continually being reported. These include the operation of a three-phase fluidized bed in a circulatory mode (Liang et al., 1995), similar to the commonly applied gas-solid circulating fluidized bed the application of a three-phase fluidized bed electrode that can be used as a fuel cell (Tanaka et al., 1990) magnetically stabilized three-phase fluidized beds centrifugal three-phase reactors and airlift reactors. 

Novel nonnucleoside reverse transcriptase (NNRT) inhibitor, 18 722 Novel reactor systems, design of, 20 742-744... 

The simulated countercurrent moving bed chromatographic reactor A novel reactor-separator (with A.K. Ray and R.W. Carr). Chem. Eng. Sci. 49, 69-480 (1994). 

C. Wandrey, 1998, A novel reactor concept for the enzymatic reduction of poorly soluble ketones, J. Mol. Catal. B ... 

Chen J, Wang Y, Jia Z, Zheng C. Synthesis of nanoparticles of CaC03 in a novel reactor. In Semel J, ed. 2nd International Conference on Process Intensification in Practice. London BHR Group, 1997 157-164. 

Arakawa ST, Mulvaney RC, Felch DE, Petri JA, Vandenbussche K, Dandekar HW. Increase productivity with novel reactor design. Hydrocarbon Processing 1993 (March) 93-100. 

Dautzenberg FM. Novel reactor concepts in hydrotreating. Cattech 1999 3 54—63. 

Process intensification refers to a chemical process using significantly smaller equipment. Examples include novel reactors, intense mixing devices, heat and mass transfer devices that provide high surface area per unit of volume, devices... 

Novel reactor configurations as well as new process approaches to pretreat and saccharify biomass was the focus of this session. 

The field of chemical kinetics and reaction engineering has grown over the years. New experimental techniques have been developed to follow the progress of chemical reactions and these have aided study of the fundamentals and mechanisms of chemical reactions. The availability of personal computers has enhanced the simulation of complex chemical reactions and reactor stability analysis. These activities have resulted in improved designs of industrial reactors. An increased number of industrial patents now relate to new catalysts and catalytic processes, synthetic polymers, and novel reactor designs. Lin [1] has given a comprehensive review of chemical reactions involving kinetics and mechanisms. 

Mass transfer is often the rate-limiting step in gas-liquid reactions. Novel reactor designs that increase mass transfer can reduce reactor size and may also improve process yields. 

MODAR, Co (2) shipboard waste treatment using a novel reactor design [123,126] by Foster Wheeler and General Atomics, and (3) treatment of PCB waste streams containing very low levels to 100% concentration [125] by MHI. 

The environmental issues are providing an exciting opportunity for R D to make a significant contribution, not only to the health of the local community but also the financial health of the company. Some of the major areas for study by R D are catalytic solutions, solvent replacement, novel reactors, such as microreactors, as well as considering the product design carrying out life cycle assessments and the use of alternative feedstocks. This area has become known as Green Chemistry [D-6]. 

The novel reactor was used to study the deactivation of n-hexane cracking on an US-Y zeolite catalyst. These experiments showed that on a faujasite the coke formation deactivates the main reactions and not the coking reaction itself, in contrast with previous observations on pentasil zeolites. The coke deposition also modifies the product distribution of n-hexane cracking. This effect can be explained by the non-uniform strength of the acid sites in the Y-zeolite and the acid strength requirements of the various reactions. 

The deactivation of a Fischer-Tropsch precipitated iron catalyst has been investigated by means of a novel reactor study. After use of the catalyst in a single or dual pilot plant reactor, sections of the catalyst were transferred to microreactors for further activity studies. Microreactor activity studies revealed maximum activity for catalyst fractions removed from the region situated 20 - 30% from the top of the pilot plant reactor. Catalyst characterization by means of elemental analyses, XRD, surface area and pore size measurements revealed that (1 deactivation of the catalyst in the top 25% of the catalyst bed was mainly due to sulphur poisoning (2) deactivation of the catalyst in the middle and lower portions of the catalyst bed was due to catalyst sintering and conversion of the iron to Fe304, Both these latter phenomena were due to the action of water produced in the Fischer-Tropsch reaction. 

U Zardi et al, A Novel Reactor Design for Ammonia and Methanol Synthesis , IV Intern Conference Fertilizer Technology, London 1981, Hydrocarbon Process, 1982, 61 (No 8), 129-133... 

It is important to note that there is no global optimum reactor design that fits all purposes. There are always some trade-offs, and they should be evaluated on a case-by-case basis. Novel reactor designs have been constantly introduced to satisfy specific needs, some of which are outlined here. 

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