Metrics operational efficiency

These three steps will require work over many years. GSK is beginning the first step by determining how to optimally measure production and operational efficiency. A series of publications is available that describes GSK s efforts to develop appropriate metrics for its R D chemical development activities (Constable et al., 2001, 2002). 

Based on the individual half-cell reaction potentials, the theoretical electrochemical potential offered by a single Zn/Br cell should be approximately 1.828 V. This value is the Nemstian potential under zero current flow. However, the presence of internal inefficiencies and various resistance contributions seen in practice are expected to result in slightly lower cell voltage values. Another important performance metric for Zn/Br systems is current density, which is the amount of current passing through a unit area of an electrode surface. The current density, in turn, has a direct influence on the electrode capacity (i.e. energy per unit area) as well as the operating efficiency of the overall system. 

The three-step cumene process, including the liquid-phase reactions, is energyconsuming, environmentally unfavorable and disadvantageous for practical operation. The process also produces the unnecessary by-product acetone stoichio-metrically. Furthermore, the intermediate, cumene hydroperoxide, is explosive and cannot be concentrated in the final step, resulting in low phenol yield ( 5%, based on the amount of benzene initially used). Thus, direct phenol synthesis from benzene in a one-step reaction with high benzene conversion and high phenol selectivity is most desirable from the viewpoints of environment-friendly green process and economical efficiency. 

KPI system To speed up and anchor CIP in the organization, the companies that set the benchmark in this area establish a clear KPI system linking the operational performance metrics consistently and comprehensively to the overall objectives of the company - and these metrics have to be easily understood and reproduced within standard companywide reporting systems. For instance, at Clariant a number of different KPIs have been defined to track maintenance efficiency, but only a few (e.g., repair and maintenance costs/conversion costs) can really be tracked by the production team on the basis of standardized systems (Fig. 19.6). 

The selectivity of the sensor is determined by the efficiency of the coating material. Developing selective coatings is an ongoing research area. Figure 3 shows a useful metric for sensor performance called the receiver operating characteristic (ROC) curve [16]. 

For optimum operation, the cell temperature is maintained at 65-75°C with a pH of 6.9. Current efficiencies of over 90 percent have been reported with a power consumption of 4500-5800 kWhr per metric ton of sodium chlorate produced. Coated titanium metal anodes and steel cathodes are used, and small amounts of dichromate are added to the cell liquor to prevent the cathodic reduction of chlorate and hypochlorite. The cell liquor contains about 50 percent NaC103, which may be used as is, or evaporated to 75 percent... 

Success stories can show that improved process safety can contribute to increased productivity, cost efficiencies, and reliability. Using metrics to demonstrate the nexus between process safety performance and other organizational objectives only serves to reinforce individual and organizational commitments to process safety. A good process safety system, including appropriate metrics, can help prevent events such as unplanned shutdowns. Decreasing the number of unplanned shutdowns due to equipment failures or processing aberrations are examples of where process safety and other operational activities are linked. Unplanned shutdowns create extra cost and production problems as well as increase the probability of a process safety incident. 

Informed by the above efforts, eco-efficiency metrics were further refined for application at the operational level through the sustainability metrics work of the American Institute of Chemical Engineers (AIChE, www.aiche.org/cwrt/... 

Basic Eco-Efficiency Metrics. The above eco-efficiency categories can be captured by a small number of metrics. For illustration, let us consider the set of basic metrics adopted by BRIDGES to Sustainability (Schwarz et al., 2000, 2002), shown in Table 6.2. Informed by the work of NRTEE (1999) and WBCSD (Verfaillie and Bidwell, 2000), the metrics were chosen as ratios. Impacts are placed in the numerators and a measure of output is in the denominator. The denominator can be mass or other unit of product, functional unit, sales revenue, monetary value-added, or a certain measure of societal benefits. Expressing the metrics as ratios allow them to be compared and used in weighing decision alternatives and comparing operational units. Defined in this manner, the lower metrics are better as they reflect lower impacts per unit of value generation. 

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