Recovery specific

A hydrocarbon feed gas is to he treated in an existing foiir-theoretical-tray ahsorher to remove hiitane and heavier components. The recovery specification for the key component, hiitane, is 75 percent. The composition of the exit gas from the ahsorher and the required liqiiid-to-gas ratio are to he estimated. The feed-gas composition and the eqiiilihriiim K values for each component at the temperature of the (soliite-free) lean oil are presented in the following table ... 

In some cases, wastewater can be substantially reduced by substituting an organic solvent for water in the synthesis and separation steps of the production process, with subsequent solvent recovery. Specific pollutants can be eliminated by requesting specification changes from raw material suppliers in cases when impurities are present and known to be discharged in process... 

Stage Recovery (%) Specific activity units" per mg of protein9... 

Table 6.9. Recoveries and Product Specifications in Each Distillation Task in Figures 6.10 and 6.11. [Adopted from Mujtaba and Macchietto, 1994] Purities in bold face indicate the desired product specifications. Other purity and recovery specifications (decision variables of type (b are set at typical values.

Product rate specification. The product rate specification can be expressed simply as a flow rate. Alternatively, it can be expressed as a recovery." Some examples of the use of recovery specification are... 

A double-recovery specification is equivalent to specifying one product rate and one product purity. For instance, 95 percent of the light key in the feed is to be recovered in the distillate, and 90 percent of the heavy key in the feed is to be recovered in the bottom. This sets both the distillate rate to (zLNK + 0.95zLK + 0,10zhk)F, and the heavy key concentration of the distillate at... 

Section 3.1.1 states that in a process design, a separation is specified in terms of purities and product flows. For a simple column, two specifications are made and at least one must be a purity. Section 3.1.1 also states that the purity specification can be substituted by a physical property which is a function of the purity or composition, while a product flow can be substituted by a recovery specification. 

More than one product purity or recovery specification Not all methods will accept or solve. Replace one purity specification with some other such as reflux rate or a product rate. The methods best suited to solve multiple purity specifications are the inside-out methods (Sec. 4.3.1). 

LC-MS/MS methods are usually subjected to a validation procedure before they are used for routine analysis. In case of GLP studies or clinical studies, a validation is considered to be mandatory. During the validation procedure, the assay is evaluated with respect to the overall performance. Parameters tested are the limit of quantification (5 1 signal/noise ratio), within batch and inter batch reproducibility (accuracy and precision), recovery, specificity and long-term sample stability in matrix (Shah 2000, EEC Guidance on validation 1994, EEC Guidance on validation 1996, FDA Guidance for Industry 2001). 

Step 8. Several control valves now remain unassigned. Steam flow to the trim heater controls reactor inlet temperature. Cooling water flow to the trim cooler is used to control the exit process temperature and provide the required condensation in the reactor effluent stream. Liquid recirculation in the absorber is flow-controlled to achieve product recovery, while the cooling water flow to the absorber cooler controls the recirculating liquid temperature. Acetic acid flow to the top of the absorber is flow-controlled to meet recovery specifications on the overhead gas stream. Cooling water flow to the cooler on this acetic acid feed to the absorber is regulated to control the stream temperature. Cooling water flow in the column condenser controls decanter temperature. 

If one or more unit operations have been given infeasible specifications, then the flowsheet will never converge. This problem also occurs with multicomponent distillation columns, particularly when purity specifications or flow rate specifications are used, or when nonadjacent key components are chosen. A quick manual mass balance around the column can usually determine whether the specifications are feasible. Remember that all the components in the feed must exit the column somewhere. The use of recovery specifications is usually more robust, but care is still needed to make sure that the reflux ratio and number of trays are greater than the minimum required. A similar problem is encountered in recycle loops if a component accumulates because of the separation specifications that have been set. Adding a purge stream usually solves this problem. 

The recovery specifications are converted to product component rate specifications ... 

Since the system is binary, the two recovery specifications determine the total product rates by overall material balance. With the total number of stages fixed, the reflux ratio required to achieve the desired separation depends on the feed locations. It is desirable to operate the column at the lowest possible reflux ratio in order to minimize the condenser and reboiler duties. 

Simple flash is suitable in a large number of cases, when the difference in K-values between light and heavies is quite large, over 10 (Fig. 7.16a). Pressure and temperature are optimisation variables against recovery specifications. Better separation can be obtained in more stages with intermediate heating/cooling, in which the temperatures and pressures are also subject to optimisation (Fig. 7.16b). 

The design of multistage separation operations involves solving the variable relationships for output variables after selecting values of design variables to satisfy the degrees of freedom. Two cases are commonly encountered. In Case I, recovery specifications are made for one or two key components and the number of required equilibrium stages is determined. In Case II, the number of equiiib-... 

The first step in the selection of a separation process is to define the problem. Usually, this entails establishing product purity and recovery specifications. Product purity specifications are established ultimately... 

Behaviour to Behaviour Variables Recovery specification for separation units. 

In addition to being independent, the specifications must be feasible. The obvious feasible limits for component product rate specifications are D, < FZ- and fi, < FZ-. For component recovery specifications the feasible limits are < 1 and r < 1. 

The fourth column of Table E13.7 gives the reflux ratio required to meet both the DME purity and recovery specifications. The variation of this ratio from 0.47 to 0.77 is significant, because it is direcdy related to the required condenser and reboiler duties. If the NRTL w/correction calculation is closest to the truth, the reboiler duty required is 80% greater than that obtained in the baseline shortcut simulation. Ironically, this is the thermodynamics option suggested by the CHEMCAD expert system. 

A review of the potential specifications is warranted at this point. The goal is to remove any specifications that do not map onto typical instrumentation measurements. For example, flow meters work in volume units, not in molar units. Because the specifications of boil-up, reflux, distillate, and bottoms product rate given in Figure 8.16 are all molar flow specifications, they should not be used as control objectives. The reflux ratio and component recovery specifications are also expressed in molar units and, therefore, cannot be used. In fact, the only specifications that can be used directly from the design simulation are ... 

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