Pinch analysis

 

Energy Conservation tools

 

Pinch analysis is a systematic methodology for energy saving based on thermodynamic principles developed by Linnhoff March in the late 70’s. It needs limited information about material (flowrate) and heat balance (temperature T, specific heat capacity Cp and enthalpy H). This method is useful to compare two networks, identify inefficient exchangers or assess the minimum energy (cold/hot utilities) required by the system and thus the maximum potential for improvement of a given scheme (the target). Pinch analysis never provides a direct solution but ways of improvement. Moreover, this methodology cannot take into account specific process requirements or operating constraints.

 

In order to get the best from Pinch analysis, AKEE associates it with a dedicated software named “CREO”, which enables imposing process flexibility constraints to optimize heat exchanger network.

 

CREO - Linear Programming model

 

CREO is a Linear Programming model developed by Axens/IFPEN, to determine the optimal heat exchanger network solutions for process flow schemes, but also taking into account operational and flexibility constraints. These constraints are specific to the process technology to allow operation of the plant with sufficient flexibility while achieving the target performance. As an example, some of these constraints are summarized below:

 

• Process heat exchange restrictions to avoid either contamination issues or safety issues

• Mandatory heat exchanges between two fluids

• Avoiding use of hot or cold utility on a given process fluid

• Fired heaters minimum duty requirement for either start-up or control considerations

• Heat exchangers bypass needs for operational flexibility

• Hydraulic limitations such as the head requirement for recycle compressors

 

Minimum temperature approach across specific exchangers

The CREO model objective is used to develop an energy conservation solution that offers the best compromise between CAPEX and OPEX, while affording customized operational flexibility.

 

Thanks to Pinch Analysis and CREO we have improved heat exchanger networks of our clients in CIS and worldwide. The Energy saving was systematically higher than 20% and the cost of implementation had a pay-out time from 1 to 5 years.

 

 

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