In most projects we typically identify 20 to 40 measures per plant marked as ' A' or ' B' (see Section 4.5.3) , that means they are likely profitable and feasible. B measures need further evaluation in order to finally categorize them as ' A ' or ' C ' . These investigations should be initiated now in dedicated projects, supported by members of the project team.
All ' A' measures will be then prioritized on the time scale. There are ' quick wins . . measures without or with very low investment like change of operational parameters (see Section 4.4.4). These will be realized as soon as possible in order to derive the benefit rapidly. Other measures like process modifications (see Section 4.4.5) or additional equipment are more costly and have to be adapted to the customer' s capital expenditure planning. The discussion on the customer' s side supported by the consultant on the basis of the documentation sheet, will result in an implementation plan shown in Figure 4.14.
Figure 4.14 Implementation plan.
Figure 4.14 Implementation plan.
The implementation plan is a roadmap for energy relevant investments for the next years. Every measure from this plan is a project on its own and will be realized following the project approval and execution procedure of the customer. That means for instance basic design, cost estimation, prove of profitability, project application followed by the project approval. After approval the project will continue with a safety study, detail design, procurement and construction. The consultant should then participate in the start-up of the modified plant in order to support the operators with his knowledge of the designed modification.
It is self-evident but important to mention that the implementation of measures has to be decided by the customer; nevertheless the consultant will support this process by his input.
Monitoring and Controlling
In our experience specific energy consumption in a plant varies widely with time, as illustrated in in Figure 4.15.
The graph shows firstly that the specific energy consumption decreases with the load. That is not surprising because there are a number of energy consumers independent of the actual load, for instance trace heating, fixed refluxes in columns, or coolants that are not controlled. Secondly, we see that the energy consumption scatters in a wide range. Every dot in the graph is a measured energy consumption value at a certain point in time. There is often no reason why the consumption should differ from one point to the other or from one shift to another. Furthermore, there is a best practice curve of the energy consumption that is a function of the load. This curve represents the best values achieved in the plant. The goal now will be to reduce the inconsistencies in the consumption values (for instance on the average curve shown in the graph) and to move the real consumption as close to the best practice curve as possible. A prerequisite for
Best Practice Level
reaching the best practice curve is to give the operators the ability to influence the energy consumption by showing them the actual consumption in the process control system and to compare that value with the best practice.
In order to do so, we implement performance monitoring in the plant. The idea is to depict the energy consumption or energy influencing parameters like concentrations or mass streams online and quantify the difference from calculated or best practice values. Thereby the operators will be given access to the data regarding actual energy consumption of their plant and to react accordingly, when the actual energy consumption is higher than expected.
The following elements are necessary for an online performance monitoring system:
• A distributed control system (DCS).
• Measuring devices for utilities like steam or electricity or measuring devices for energy influencing parameters; alternatively, some parameters can be calculated from a model.
• A mass and energy balance calculation (see Section 4.3.5) for the generation of calculated specific energy consumption values.
• Documented best practice values for energy consumption.
Now the consultant has to discuss the design of the performance monitoring screen in the DCS with the plant staff. An example of an implemented monitoring is shown in Figure 4.16 .
It is possible to illustrate the actual energy consumption qualitatively by a traffic light (red: highly above calculated value, yellow: above calculated value and green: near calculated value) or quantitatively by numbers (for instance expressed in kW or $ per hour above calculated value) or in form of a speedometer. The plant representatives and the consultant will discuss and design the interface of the DCS screen. Acceptance by the operators is crucial for the success of the monitoring tool. However, for reporting reasons (see Section 4.6.3) it is important to use common definitions of the energy consumption and its unit for the whole company ('$ per year' or 'MWh primary energy per year' or 'emitted tons of CO2 per year'). By doing so, it is possible to condense the consumption values for plant, site, business unit and company.
Was this article helpful?
Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.