Grassroots Plant Energy Assessment: Essential Concepts and Execution Steps
Introduction
Plant energy assessment is an important process for ensuring that a facility is operating optimally and efficiently. This assessment takes into account all of the processes and utilities involved in a project, and evaluates the best way to optimize efficiency. This article will provide an overview of the essential concepts and execution steps of a grassroots plant energy assessment.
Process Integration/Optimization Techniques
Process integration/optimization techniques are essential for simultaneous process and utility systems optimization. These techniques allow engineers to evaluate the process movers optimal allocation and the use of adjustable speed drives. They also provide the optimum practical utility consumption targets to compare with the utility requirements for the base case design.
Main Task in Plants’ Energy Assessment
The main tasks for plants’ energy assessment include a thorough review of all process design, licensors schemes, systems drawings, and data analysis documents to form the total-site big picture. This review should also include understanding the process energy needs and utility systems preferences of both the new plant and the existing one, if applicable. It is also important to understand the interaction between the site and beyond the fence site(s).
Once these tasks have been completed, it is necessary to identify all opportunities for energy savings in the base case design. This includes challenging every process step in the base case design to generate new process alternatives for the sake of lower energy system operating and capital cost. From available data, engineers can then establish different process-utility design schemes that can render better energy consumption, less number of units, and lower process-utility systems capital cost.
Execution Steps
The next step is to propose scope for definitive assessment for the new process-utility systems scheme(s). This includes the most accurate economic analysis and presenting the plant-wide energy utility systems synthesis. After discussing the findings with engineering contractors and project teams, it is necessary to address the power and heat supply decision. This includes determining whether to use cogeneration or not to satisfy the process heat and power supply.
The execution steps of a plant energy assessment include data extraction for the study to be done for each stream that needs to be heated or vaporized and any stream that needs to be cooled or condensed in the “base design case”. Calculating targets for energy utility to be calculated for the process with integration and without integration is also essential. The grand composite curve (GCC) should be utilized to show the potential cogeneration opportunities and best drivers for the process, if any. Constructing the site-source and sink composite curves and listing all possible design and operational modifications to be investigated to explore its impact on the utility consumption and other process units is also important.
The execution steps should be done for several ∆Tmin., before selecting the optimal. A preliminary evaluation of the HENs capital cost will be needed, or whatever targeting method is used, to reach the close-to-optimum ∆Tmin. A trade-off between the energy saving impact “$” and for instance the control/operability impact $ should be calculated, documented and shown in the energy assessment study. Other subjective decisions need to be mentioned and documented clearly with enough techno-economical support as much as possible to support the decisions of accepting or rejecting process initiatives for the sake of energy efficiency optimization.
Conclusion
Grassroots plant energy assessment is an essential process for ensuring that a facility is operating efficiently and optimally. It requires an understanding of the process integration/optimization techniques, the main tasks in plants energy assessment, and the execution steps involved. This article provides an overview of these essential concepts and execution steps.
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