Recycle function

Particulate emissions can amount to as much as 0.25 tonne/tonne of pulp produced, particularly for an older pulp mill operating without controls (Table 15.13). Electrostatic precipitators, wet scrubbers, or occasionally both can achieve particulate containment of 95% or better [49]. The precipitator catch is returned to the black liquor stream for chemical recovery from the captured inorganic chemicals. Fumes lost from the dissolving tank vent are captured by demister pads or small low-energy scrubbers, which return the collected material to the green liquor circuit. Wet scrubbers are used for lime kiln dust containment. The waste liquor is used for slaking or other recycle functions in the lime circuit (Chap. 7), helping to decrease make-up chemical requirements and water emissions. 

The schematic shown in Figure 16.13 is quite complex since it involves two recycle streams. However, the RED for this system is much simpler, as shown in Figure 16.14, because there is no recycle function in the reliability flow. If any one of the items in the system fails (with the exception of either E-3A or E-3B), then the system fails. 

Scheme 2.19 Enantioselective Michael addition of cyclohexanone to nitroalkenes using recyclable functionalized ionic liquids as catalysts.

Most of the above responsibilities pertain to the recycling function. 

The recycling function controls the output flow control function, which is the ability to control the enclosure output gateways that force out of the SSR the raw materials, raw parts, and raw part fragments marked as refuse by the recycling function. 

Moitra, N., Kamei, T Kanamori, K., Nakanishi, K., Takeda, K and Shimada, T. (2013) Recyclable functionalization of silica with alcohols via dehydrogenative addition on hydrogen silsesquioxane. Langmuir, 29, 12243-12253. 

The recycling of material is an essential feature of most chemical processes. Therefore, it is necessary to consider the main factors which dictate the recycle structure of a process. We shall start by considering the function of process recycles and restrict consideration to continuous processes. Later the scope will be extended to include batch processes. 

MP-suspension by automated ASTM-bulb Magnetization current by Hall-Sensor Magnetization time UV-Light intensity All Liquids (fluorescence, contamination) Process times and temperatures Function of spraying nozzles, Level of tanks Flow rates (e.g. washing, water recycling) UV-Light intensity... 

The reactors were thick-waked stainless steel towers packed with a catalyst containing copper and bismuth oxides on a skiceous carrier. This was activated by formaldehyde and acetylene to give the copper acetyUde complex that functioned as the tme catalyst. Acetylene and an aqueous solution of formaldehyde were passed together through one or more reactors at about 90—100°C and an acetylene partial pressure of about 500—600 kPa (5—6 atm) with recycling as required. Yields of butynediol were over 90%, in addition to 4—5% propargyl alcohol. 

Tube-Cooled Converter. The tube-cooled converter functions as an interchanger, consisting of a tube-filled vessel with catalyst on the shell side (Fig. 7c). The combined synthesis and recycle gas enters the bottom of the reactor tubes, where it is heated by the reaction taking place in the surrounding catalyst bed. The gas turns at the top of the tubes and passes down through the catalyst bed. The principal advantage of this converter is in... 

Oxidation of cumene to cumene hydroperoxide is usually achieved in three to four oxidizers in series, where the fractional conversion is about the same for each reactor. Fresh cumene and recycled cumene are fed to the first reactor. Air is bubbled in at the bottom of the reactor and leaves at the top of each reactor. The oxidizers are operated at low to moderate pressure. Due to the exothermic nature of the oxidation reaction, heat is generated and must be removed by external cooling. A portion of cumene reacts to form dimethylbenzyl alcohol and acetophenone. Methanol is formed in the acetophenone reaction and is further oxidized to formaldehyde and formic acid. A small amount of water is also formed by the various reactions. The selectivity of the oxidation reaction is a function of oxidation conditions temperature, conversion level, residence time, and oxygen partial pressure. Typical commercial yield of cumene hydroperoxide is about 95 mol % in the oxidizers. The reaction effluent is stripped off unreacted cumene which is then recycled as feedstock. Spent air from the oxidizers is treated to recover 99.99% of the cumene and other volatile organic compounds. 

When two or more sections of the flow sheet perform similar functions, ie, both produce the same product using the same or similar unit operations, one section often can be eliminated by recycling the stream to the input of the remaining section. An MSA contaminated by other components in the mixture often functions as effectively as a pure MSA without the need for additional purification operations. 

The cost of various silver compounds is a function of the silver market price. In 1980, the estimated usage of silver ia the United States was 3730 metric tons (120 X 10 troy oz) (23). This silver is derived from silver mined within the United States silver recycled or reclaimed from secondary sources, eg, coiaage, flatware, jewelry, and photographic materials and imported silver. In 1980, Canada, Mexico, and Pern, the principal exporters of silver to the United States, shipped 1670 tons (53.8 x 10 troy oz) as silver buUion and silver compounds. U.S. imported 2799 t and exported 964 t ia 1988 (23). 

Typically, a baffle condenses a vapor flow to a Hquid in such a way that Hquid can drain off for recycle. A weU-designed and useful trap, on the other hand, catches and retains condensables such as water and the higher vapor pressure fraction of the working fluid of a pump. Although the terms baffle and trap seem to describe the same type of function, namely, to slow down but not prevent the rate at which some species of molecules pass through, traps can completely stop some molecular species (23). 

The carbon monoxide concentration of gas streams is a function of many parameters. In general, increased carbon monoxide concentration is found with an increase in the carbon-to-hydrogen ratio in the feed hydrocarbon a decrease in the steam-to-feed-carbon ratio increase in the synthesis gas exit temperature and avoidance of reequiUbration of the gas stream at a temperature lower than the synthesis temperature. Specific improvement in carbon monoxide production by steam reformers is made by recycling by-product carbon dioxide to the process feed inlet of the reformer (83,84). This increases the relative carbon-to-hydrogen ratio of the feed and raises the equiUbrium carbon monoxide concentration of the effluent. 

Oxidation and chlorination of the catalyst are then performed to ensure complete carbon removal, restore the catalyst chloride to its proper level, and maintain full platinum dispersion on the catalyst surface. Typically, the catalyst is oxidized in sufficient oxygen at about 510°C for a period of six hours or more. Sufficient chloride is added, usually as an organic chloride, to restore the chloride content and acid function of the catalyst and to provide redispersion of any platinum agglomeration that may have occurred. The catalyst is then reduced to return the metal components to their active form. This reduction is accompHshed by using a flow of electrolytic hydrogen or recycle gas from another Platforming unit at 400 to 480°C for a period of one to two hours. 

Carbon Conversion. Carbon conversion on a once-through basis is a function of the coal composition and is strongly influenced by the oxygen/coal ratio. For some coals, the conversion pattern is also affected by the level of steam in the blast. Another factor is fly slag recycle, which raises the carbon conversion by recycling the unconverted carbon, most of which resides on the fly slag. This results in an overall carbon conversion greater than 99%. 

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