Recycling types

What can you tell about the influencing resistances for the porous catalyst from the data of Table P18.27 obtained in a recycle type mixed flow reactor. In all runs the leaving stream has the same composition, and conditions are isothermal throughout. 

The second reactor of the Berty, recycle type is shown in the upper left center of Figure 1. It was also used to explore the effect of periodic operation. 

Some comments are made in the following on the different recycling types and possible allocation solutions to be applied ... 

Recycled type (nutrient-like) Many others, e.g., Ni, Cd, Zn, Ge, and Ba, show a gradual increase in their concentration from the surface to deep water, much like nutrients (nitrate, phosphate, and silicate or alkalinity), suggesting their involvement in the biogeochemical cycle of biological uptake in the surface water and regeneration in deep waters. As a result of global ocean circulation, the deep-water... 

This example provides many aspects of the application of the recycle-type model. It is probably the most flexible model that has been successfully utilized to help describe large scale mixing patterns in actual chemical reactors. 

Type ID Annual production (some recycled) Type ID Annual production (some recycled) ... 

The model reaction of p-xylene hydrogenation was chosen in order to provide the mild conditions of the experiments in both gas and capillary condensed phases, and to avoid the influence of side reaction and catalyst deactivation. The recycle type of gradientless reactor was used that provides uniform temperature and concentration profiles within all the catalyst packing. The catalyst particles (0.25-0.50 mm) provide a negligible intraparticle limitation of mass- and heat-transfer. 

R = recycled type. S = scavenged type, C = conservative type ° SIO Pier sample ... 

The lowest recycling-type step of the resource cascade for nanocomposites is usually incineration with energy recovery [69,79]. To the extent that nanocomposites are incinerated that contain nanopartides serving as fire retardants, it is to be expected that the calorific value of the nanocomposite will turn out to be lower than the corresponding value of the neat polymer [61]. 

Fig. 13.3.5. A Burgess-Manning separator vessel (top frame) equipped with type A-X recycling type multicyclones (bottom frame). Courtesy Burgess-Manning, Inc.

Gasoline engine equipment such as carburetors, injectors, intake manifolds, valve systems and combustion chambers, are subject to fouling by the fuel itself, the gases recycled from the crankcase, or even dust and particulates arriving with poorly filtered air. Three types of problems then result ... 

Chiral 2-oxazolidones are useful recyclable auxiliaries for carboxylic acids in highly enantioselective aldol type reactions via the boron enolates derived from N-propionyl-2-oxazolidones (D.A. Evans, 1981). Two reagents exhibiting opposite enantioselectivity ate prepared from (S)-valinol and from (lS,2R)-norephedrine by cyclization with COClj or diethyl carbonate and subsequent lithiation and acylation with propionyl chloride at — 78°C. En-olization with dibutylboryl triflate forms the (Z)-enolates (>99% Z) which react with aldehydes at low temperature. The pure (2S,3R) and (2R,3S) acids or methyl esters are isolated in a 70% yield after mild solvolysis. 

Compounds having low vapor pressures at room temperature are treated in water-cooled or air-cooled condensers, but more volatile materials often requite two-stage condensation, usually water cooling followed by refrigeration. Minimising noncondensable gases reduces the need to cool to extremely low dew points. Partial condensation may suffice if the carrier gas can be recycled to the process. Condensation can be especially helpful for primary recovery before another method such as adsorption or gas incineration. Both surface condensers, often of the finned coil type, and direct-contact condensers are used. Direct-contact condensers usually atomize a cooled, recirculated, low vapor pressure Hquid such as water into the gas. The recycle hquid is often cooled in an external exchanger. 

Because an excess of ammonia is fed to the reactor, and because the reactions ate reversible, ammonia and carbon dioxide exit the reactor along with the carbamate and urea. Several process variations have been developed to deal with the efficiency of the conversion and with serious corrosion problems. The three main types of ammonia handling ate once through, partial recycle, and total recycle. Urea plants having capacity up to 1800 t/d ate available. Most advances have dealt with reduction of energy requirements in the total recycle process. The economics of urea production ate most strongly influenced by the cost of the taw material ammonia. When the ammonia cost is representative of production cost in a new plant it can amount to more than 50% of urea cost. 

The natural process of bringing particles and polyelectrolytes together by Brownian motion, ie, perikinetic flocculation, often is assisted by orthokinetic flocculation which increases particle coUisions through the motion of the fluid and velocity gradients in the flow. This is the idea behind the use of in-line mixers or paddle-type flocculators in front of some separation equipment like gravity clarifiers. The rate of flocculation in clarifiers is also increased by recycling the floes to increase the rate of particle—particle coUisions through the increase in soUds concentration. 

Waste Treatment. Environmental concerns have increased the need to treat Hquid discharges from all types of industrial processes, as well as mnoffs where toxic substances appear as a result of leaks or following solubilization (see Wastes, industrial). One method of treatment consists of an ion-exchange system to remove the objectionable components only. Another involves complete or partial elimination of Hquid discharges by recycling streams within the plant. This method is unacceptable unless a cycHc increase in the impurities is eliminated by removing all constituents prior to recycling. 

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