Key Indicators Represent Operation Opportunities

The intention of defining key indicators is to describe the process and energy performance with a small number of operating parameters. A key indicator can be simply an operation parameter. Some examples of key indicators are reaction temperature, distillation temperature and pressure, column overhead (ovhd) reflux ratio, column overflash, spillback of a pump, heat exchanger U value, and so on. The parameter identified as a key indicator is important due to its significant effect on process and energy performance. 

Reaction condition optimization considers reaction severity in terms of temperature and pressure profiles in accordance with catalyst performance in the entire run length. Optimizing reaction conditions, selecting better catalysts, and maintaining catalyst performance in operation have significant effects on both yields and energy efficiency. Consider reaction temperature as an example. In the catalyst cycle, the catalyst performance deteriorates, which affects the reaction conversion. To compensate, the reaction temperature may be increased. However, more severe reaction conditions require more heat from hot utilities such as fired heaters, while severe conditions also produce more desirable products as well as undesirable by-products. The question is how to determine the optimal reaction temperature, which is a function of reaction conversion, production rate, and energy use. 

Minimizing recycle is another optimization example in separation. A common observation in a process plant is that unconverted streams or off-specification streams are recycled back to the front of a process. Reeyele streams undo separation. Minimizing recycle presents a significant opportunity for process plants to smartly reduce energy consumption. However, minimizing recycle requires proper operation of separation columns across the whole plant from upstream to downstream. 

Fired heaters provide a major part of heat source for reaction and separation. Reliability is the major concern for furnace operation with heat flux for large heaters and tube wall temperature (TWT) for small heaters as the most important reliability parameters. Increasing either heat flux or TWT could increase furnace efficiency. When operating heat flux is much lower than the maximum limit, this is an indication of the furnace being underutilized and thus presents an opportunity for increased feed rate. Increase feed rate is a win-win operation since more feed also results in reduced energy intensity. 

Rotating equipment used in the process industry includes pumps, compressors, motors and turbines. For pumps and compressors with fixed speed motors, minimizing spill backs could result in significant power savings. Optimizing steam turbine operation and maintenance could save steam. The selection of process drivers, namely, motors versus steam turbines, could save energy costs. 

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