Energy Assessment for Grassroots Plant: A Comprehensive Checklist
Energy assessment studies are essential for optimising energy efficiency in any grassroots plant. An effective assessment should consider multiple factors, from process and utility systems to CHP optimisation, to ensure maximum energy savings. This article outlines a comprehensive checklist of the key steps involved in an energy assessment study.
Process and Utility Systems
The first step in an energy assessment study is to consider process and utility systems simultaneously. This can be done through process integration techniques such as pinch analysis and mathematical programming. This can help to identify areas where energy efficiency can be improved and aid in the optimisation of the CHP system.
Cogeneration
Another important step is to assess the potential for cogeneration. This involves examining the power-to-heat ratio to determine if cogeneration is a more efficient option than central power generation plants.
Tri-Generation and Quadra-Generation
If water desalination is part of the total-site, then tri-generation and even quadra-generation may be possible.
Mechanical Energy Integration
Mechanical energy integration is also important to consider. This can include power generation from high pressure liquids or pressure exchangers.
Load Management
Conducting major equipment load management for several demand scenarios is also beneficial. This can help identify areas where energy efficiency can be improved.
Variable Speed Drivers
The use of variable speed drivers can also help to optimise energy efficiency.
Optimising CCP Systems
Optimising combined cooling and power/refrigeration systems (CCP systems) is another key step in an energy assessment study. This can help to reduce energy consumption and improve efficiency.
Air Pre-Heaters
Using air pre-heaters for combustion air can also improve energy efficiency.
Integrating Flue Gases
Integrating flue gases with the rest of the process using grand composite curve of pinch technology can help to reduce energy consumption.
Compressor Systems
Optimising air and nitrogen compressors system design can also help to reduce energy consumption.
Economisers and Pre-Heaters
Using economisers and pre-heaters in boilers can help to reduce energy consumption.
Turbines
Using turbo-expanders instead of JT valves, and to drive gas compressors, can help to reduce energy consumption. Gas turbines are more efficient than steam turbines, so it is important to consider this when undertaking an energy assessment study.
Boiler Steam Pressure and Temperature
Optimising boiler steam pressure and temperature to match process needs, unless electricity generation is the controlling factor, is also beneficial.
Auxiliary Turbines
Using auxiliary turbines can help to minimise steam let downs, reducing energy consumption.
Steam Utilisation
Optimising steam utilisation can help to save capital cost and reduce energy consumption.
Recovering Valuable Gases
Recovering valuable gases from fuel gases and fully utilising streams pressure can help improve energy efficiency.
Minimising H2
Minimising the use of H2 and any other utility wheel in the plant can help to reduce energy consumption.
Cooling Medium Return Temperature
Reducing cooling medium return temperature in refrigeration cycles can improve energy efficiency.
Sub-Cooling
Using sub-cooling in refrigeration cycles, using water first and cold process streams second, can help to reduce energy consumption.
Heat Rejection
Heat rejection from refrigeration systems to process cold or hot section, to the ambient, and to another refrigerant should be considered.
Highest Efficiency Turbines
Using highest efficiency turbines in the CHP system can help to reduce energy consumption.
Stripper Optimisation
Optimising steam use in strippers through optimal pressure design and minimising live steam utilisation can help to improve energy efficiency.
Separating H2
Separating H2 from fuel gas systems and recovering C2 and C3+ can help to reduce energy consumption.
Processing Wastes
Avoiding unnecessary processing of wastes and inert (off-gas) can help to reduce energy consumption.
Pressure Adjustment
Adjusting operating pressures and optimal pressure interaction can help to improve energy efficiency.
Piping System
Optimising piping system to minimise excessive pressure drops can also help to reduce energy consumption.
Reusing Lowest Quality Water
Reusing lowest quality water can help to reduce energy consumption.
Multi-Objective Process Units
Using multi-objective process units, if applicable, can help to improve energy efficiency.
Stripped Sour Water
Maximising the use of stripped sour water and minimising generation of wastewater can help to reduce energy consumption.
Water Injection
Eliminating direct water injection for cooling purposes can help to reduce energy consumption.
Boiler Blow-Down
Extracting the low pressure steam from the boiler blow-down can help to improve energy efficiency.
Process Water Effluent
Using process water effluent as a source for the next lower water quality level can help to reduce energy consumption.
Waste Heat Steam Generation
Increasing waste heat steam generation can help to improve energy efficiency.