Rate of production

Example 4.5 Given that a low rate of production is required, convert the continuous process from Example 4.4 into a batch process. Preliminary sizing of the equipment indicates that the duration of the processing steps are given in Table 4.7. ... 

To evaluate design options and carry out preliminary process optimization, simple economic criteria are required. What happens to the revenue from product sales after the process has been commissioned The sales revenue first pays for fixed costs which are independent of the rate of production. Variable costs, which do depend on the rate of production, also must be met. After this, taxes are deducted to leave the net profit. 

There can be an element of maintenance costs that is fixed and an element which is variable. Fixed maintenance costs cover routine maintenance such as regular maintenance on safety valves which must be carried out irrespective of the rate of production. There also can be an element of maintenance costs which is variable. This arises from the fact that certain items of equipment can need more maintenance as the production rate increases. Also, royalties which cover the cost of purchasing another company s process technology may have different bases. Royalties may be a variable cost, since they can sometimes be paid in proportion to the rate of production. Alternatively, the royalty might be a single-sum payment at the beginning of the project. In this case, the single-sum payment will become part of the project s capital investment. As such, it will be included in the annual capital repayment, and this becomes part of the fixed cost. 

The product Ha r then represents the total rate of production of substance s by chemical reaction within the micropore, while represents the flux... 

Nitration at a rate independent of the concentration of the compound being nitrated had previously been observed in reactions in organic solvents ( 3.2.1). Such kinetics would be observed if the bulk reactivity of the aromatic towards the nitrating species exceeded that of water, and the measured rate would then be the rate of production of the nitrating species. The identification of the slow reaction with the formation of the nitronium ion followed from the fact that the initial rate under zeroth-order conditions was the same, to within experimental error, as the rate of 0-exchange in a similar solution. It was inferred that the exchange of oxygen occurred via heterolysis to the nitronium ion, and that it was the rate of this heterolysis which limited the rates of nitration of reactive aromatic compounds. 

Even without a rapid gas flow, the droplets produced are very small, at about 1-pm diameter or less, and they are produced at a rate of about 10 per second, similar to the rate of production of droplets in an ultrasonic device. 

Ca.ta.lysts, Catalyst performance is the most important factor in the economics of an oxidation process. It is measured by activity (conversion of reactant), selectivity (conversion of reactant to desked product), rate of production (production of desked product per unit of reactor volume per unit of time), and catalyst life (effective time on-stream before significant loss of activity or selectivity). 

The world s largest producers are Perstorp AB (Sweden, United States, Italy), Hoechst Celanese Corporation (United States, Canada), Degussa (Germany), and Hercules (United States) with estimated 1989 plant capacities of 65,000, 59,000, 30,000, and 22,000 t/yr, respectively. Worldwide capacity for pentaerythritol production was 316,000 t in 1989, about half of which was from the big four companies. Most of the remainder was produced in Asia (Japan, China, India, Korea, and Taiwan), Europe (Italy, Spain), or South America (Brazil, Chile). The estimated rate of production for 1989 was about 253,000 t or about 80% of nameplate capacity. 

Energy in the form of injected water or CO2 may be suppHed to increase the rate of production of light cmde oils. AppHcation of heat to the reservoirs, eg, using hot water, steam, heated CO2, fireflood, or in situ combustion, however, is generally associated with the production of heavier, viscid cmdes. 

Rates of production of lignite have continued to increase since 1960. In 1980 374 x 10 tons of coal equivalent (tee) were produced. One tee is the amount of energy available from combustion of a metric ton of coal having a heat content of 29.3 GJ, ie, 29.3 MJ/kg (12, 600 Btu/lb) (3). In 1989 this figure had risen to 460 x 10 tee. This 23% increase is somewhat less than the 28% increase in hard coal production during this period (see Coal). In 1990 the 1130 X 10 metric tons of lignite produced worldwide represented 24% of the total coal production. 

Enzyme Immunosensors. Enzyme immunosensors are enzyme immunoassays coupled with electrochemical sensors. These sensors (qv) require multiple steps for analyte determination, and either sandwich assays or competitive binding assays maybe used. Both of these assays use antibodies for the analyte of interest attached to a membrane on the surface of an electrochemical sensor. In the sandwich assay type, the membrane-bound antibody binds the sample antigen, which in turn binds another antibody that is enzyme-labeled. This immunosensor is then placed in a solution containing the substrate for the labeling enzyme and the rate of product formation is measured electrochemically. The rate of the reaction is proportional to the amount of bound enzyme and thus to the amount of the analyte antigen. The sandwich assay can be used only with antigens capable of binding two different antibodies simultaneously (53). 

The part of the resource that is economically recoverable varies by country. The estimates made in the survey show that the proven recoverable reserves would last about 1200 years at the 1988 annual rate of production and that the estimated additional amount in place represent almost 1700 years at 1988 annual consumption. 

A variable expense is considered to be one which is directly proportional to the rate of production Rp or of sales Rs as is most appropriate to the case under consideration. Unless the variation in finished-product inventoiy is large when compared with the total production over the period in question, it is usu ly sufficiently accurate to consider Rp and Rs to be represented by the same-numerical-value R units of sale or production per year. A fixed expense is then considered to be one whiai is not directly proportional to R, such as overhead charges. Fixed expenses are not necessarily constant but may be sub-... 

Product concentration can be controlled by any property of the solution that can be measured with the requisite accuracy and reh-ability. The preferred method is to impose control on rate of product... 

These cut points are shown as vertical lines on the crude-oil TBP plot of Fig. 13-91, from which the following volume fractions and flow rates of product cuts are readily obtained. ... 

The differential equation of batch grinding is deduced from a balance on the material in the size range k. The rate of accumulation of material of size k equals the rate of production from all larger sizes minus the rate of bre age of material of size k ... 

Rate of change = rate in — rate out -t- rate of production... 

Film manufacture also requires special considerations in the case of polypropylene in order to ensure small crystal structures and hence high clarity. Chill-roll casting processes may be used and these give films of high clarity and minimal thickness variations at high rates of production. Blown film processes can, however, give superior mechanical properties and in addition equipment costs are lower, and in consequence the process is more economic for lower tonnage production. 

Write the rate law that would describe the rate of product formation for each of the following systems ... 

The ion-pair return phenomenon can also be demonstrated by comparing the rate of loss of enantiomeric purity of reactant with the rate of product formation. For a number of systems, including 1-aiylethyl tosylates, ftie rate of decrease of optical rotation is greater than the rate of product formation. This indicates the existence of an intermediate that can re-form racemic reactant. The solvent-separated ion pair is the most likely intermediate in the Winstein scheme to pl this role. 

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