With rising energy costs and mounting pressure to reduce emissions, the petroleum refining and petrochemicals industries are increasingly focused on optimising plant performance to increase energy efficiency. The two main players in this arena are the Owner Operators and the engineering and construction companies that serve these refineries and chemical plants. Engineering and construction companies are faced with generating process designs optimised for capital and operating expenditures with quick turn-around times. Owner Operators are pressed to increase product yields while maintaining product quality and strict safety standards. The challenges faced by both parties force them to evaluate and study heat exchange equipment in the context of the process because heat exchangers are critical to the overall process performance.

Heat exchangers are associated with up to 80% of the primary energy consumed in a process and make up almost 30% of the capital investment. Heat exchange equipment has direct ties to process profitability – both in greenfield and brownfield projects. Essentially, the heat exchanger is the backbone in chemical plants, requiring regular assessment of mechanical integrity to optimise plant production needs. Therefore, processors downstream of the ‘cheap’ refinery energy will view energy cost with greater scrutiny.

To achieve optimal process design and performance, engineering and construction companies are forced to take a holistic approach to process optimisation using high fidelity simulations – an approach only achievable with the incorporation of rigorous exchanger designs in simulation to accurately model thermal and hydraulic performance in the context of the entire process. This strategy forms best practice for plants striving to optimise profitability.

Increased Pressure on Performance and Products

Process plants remain under continuous and intense pressure to improve throughput and reduce production costs. This begins the moment a new plant goes on-line. Increasing throughput brings economy of scale and improves return on investment. Overall, it is predominantly financial pressures that drive the need for process engineers to upgrade existing equipment or modify the process for a major upgrade. In addition, changing demand from refineries in terms of product output is another key factor when considering process improvements. Examples of this include deeper cracking of crude to meet higher value feedstock requirements to petrochemical plants or growing regulatory pressure to produce low sulphur diesel. Transitioning plants to produce low sulphur diesel requires major capital investment and significant modifications to existing operations. These industries are also feeling the costly impact of greater volatility of energy prices.

Empowering Process Engineers

The simplest energy reduction strategy involves recovering heat and then recycling it to provide a greater throughput per unit of energy consumed, thus increasing operational profit and reducing emissions. The traditional workflow for designing heat exchangers requires manual data transfer from process engineer to thermal and mechanical experts and ultimately to a cost estimator. The design cycle is slow, involves several iterations and is prone to data transcription errors. All of these limitations inhibit the evaluation of additional design scenarios. In addition, with this approach exchanger design is taken out context to the process, resulting in lost opportunities for further optimisation of the exchanger and the process as a whole.

The challenges with the existing workflow can be resolved by providing process engineers with the industry leading, comprehensive engineering software suite, which creates a seamless, integrated engineering workflow. These software applications help to optimise design and operational performance and create a powerful and collaborative environment across departments within the organisation. Many leading global refineries and petrochemical companies utilise the Aspen Exchanger Design and Rating (EDR) product family, which covers the principle types of heat exchange equipment and utilises proprietary methods – backed up by more than forty years of industry focused, in-house research. AspenTech’s process simulators change the workflow by integrating simulation, economic evaluation, basic engineering, energy optimisation and Aspen EDR tools into a single environment for the process engineer. This enables process engineers, thermal equipment specialists and mechanical engineers to collaborate in producing cost effective process designs for minimum capital and operating cost in fewer engineering man hours, thus reducing project timescales.

AspenTech recently introduced Activated Analysis in Aspen HYSYS and Aspen Plus, which displays energy efficiency, heat exchanger details and capital and operating economics while modelling is being performed. The process engineer can optimise based on these key performance indicators without needing to consult specialists. This industry first in process optimisation allows process engineers to find energy and capital cost savings faster. Through Activated Energy, process engineers can quickly identify ways to improve designs to reduce energy costs, saving design time and future operating cost. By employing Activated Economics, process engineers can apply science rather than intuition to ensuring the best use of capital. Activated Exchanger Design & Rating is the newest addition to Activated Analysis in Aspen Plus and Aspen HYSYS. This new, intuitive feature allows engineers with minimal heat transfer experience to produce rigorous exchanger models more easily and more efficiently. With rigorous exchanger models, operational risks and warnings are revealed. This provides for a more effective optimisation of the entire process, while making efficient use of premium value process and specialist engineering effort to evaluate more process alternatives within tight project deadlines.

The Aspen EDR product suite covers shell and tube, air cooled, plate-fin, and plate exchangers. AspenTech is unique in providing a single environment for optimisation of shell & tube heat exchangers for both thermal and mechanical design constraints. All six products in the Aspen EDR product family operate within a common user interface, which automates data transfer from one programme to another, allowing engineers to compare the advantages of different exchanger types in the context of the process simulation.

In a recent case study, Petrofac was asked to determine a feasible way to increase the capacity of a gas plant with minimal changes to plant hardware. Using the above described workflow, Petrofac was able to validate the technical and economic feasibility of multiple process improvement schemes. For modeling the process, Aspen HYSYS, a process simulator for Oil & Gas applications, was utilised. The possibility of quickly and efficiently incorporating Aspen Exchanger Design & Rating (EDR) models was essential to the preparation of the optimum revamp process design. In a self-refrigerated gas process both thermal and the hydraulic performance of exchangers have a major impact on operating economics. The resulting re-vamp plan demonstrated a one month payback period. Petrofac integrated rigorous heat exchanger models into Aspen HYSYS process flowsheets to debottleneck a gas plant and achieved 20% increased capacity requirements.

Petrofac engineers obtained exchanger designs quickly and easily during conceptual process design phase. Rigorous models provided more accurate capital operating cost estimates allowing better selection of the most optimum process configuration, both for green-field process designs and, in this case, a plant re-vamp. In the optimisation of process operations, rigorous models within simulation provide precise identification of process bottlenecks and improved validation of remedial measures. Lakshmi Venkatesh, Petrofac, commented, “The rigorous Aspen Exchanger Design & Rating models available within Aspen HYSYS have enabled us to solve debottlenecking problems in a way not otherwise achievable.”

Integrated Solutions Deliver Proven Results

New discoveries in the integration of process simulation models with Activation energy analysis and Heat Exchanger Design and Rating have provided engineers with the tools to achieve millions of dollars of benefit through increased capacity and energy savings. Integration reduces project errors and re-works, makes use of specialist engineering manpower and reduces project timescales. It is a proven enabler in reducing capital equipment and process operating costs.

Many global engineering and construction companies and refining, chemical and petrochemical owner operators have achieved benefits from rigorous exchanger modeling in simulation, including:

·         Reduced exchanger costs by up to 30%

·         Improved reliability and increased process uptime

·         Improved engineering efficiency by up to 30%

·         Superior technology backed by over 40 years of Aspen HTFS research

Bringing together Exchanger Design and Rating and process simulation software provides companies designing and operating processes with integrated lifecycle solution. This encompasses conceptual design, detailed design and plant start-up through to operations decision support. Essentially, fully integrated process simulation empowers engineers to build and operate safer, more efficient and more competitive process plants.