Integration of Real Time Optimization with Model Predictive Control applied to a Gas-lift System: A comparative study.

Abstract

There is a rising need for more practical, efficient and sustainable techniques for improving industrial system operation in the face of a highly competitive market. The integration of real time optimization (RTO) and model predictive control (MPC) is a classical approach applied in the industry for improving processes. In this work, we analyze the application of the two most common RTO and MPC integration strategiesone-layer and two-layerto a gas-lifted system. We analyzed the performance of the economic cost function and efficiency in handling disturbance for each strategy, as well as consider practical industrial application. In the two-layer strategy, an upper economic optimization layer uses a rigorous nonlinear steady state model to compute the optimal process decision variables and send to the controller as an optimizing target which then computes the optimal control actions to achieve these targets. For this strategy, the hybrid RTO (HRTO) technique is implemented in the upper layer and an established controller-infinite horizon MPC with zone control-in the lower dynamic control layer. The hybrid RTO stems from the modification of the traditional static RTO found in the industry, to deal with the steady state wait time challenge. This is achieved by updating the optimizer with dynamic information rather than the static used in the traditional RTO. The zone control strategy allows the controller to focus on reaching a desired input target supplied by the optimization layer if the outputs are kept within their specified zones and constraints are respected. In the one-layer strategy, the gradient of the economic cost function is included in the controller cost function to be considered when computing the manipulated variable used to achieve optimal process operation. It was proposed with the main aim of practical industrial application. The two strategies were applied to a gas-lifted system and their results are compared and discussed considering economic objective. The results show that the IHMPC can reach the desired input targets despite abrupt disturbances of the uncertain parameter while keeping the outputs within the desired zone. Therefore, the HRTO can efficiently work with the IHMPC implemented in achieving optimal operation under uncertainties interfering as disturbance. It also shows that the onelayer strategy gives similar results to the two-layer strategy, implying that it can also achieve similar economic objective. However, the two-layer strategy using HRTO technique is more efficient in handling the disturbances.

Strategic Renewable Energy Resource Selection Using a Fuzzy Decision-Making Method

“…In their study, Sarpong et al [4] employed Decision Making Trial and Evaluation Laboratory (DEMATEL), ANP, and TOPSIS methodologies to analyse hesitant fuzzy linguistic term sets in order to properly calculate green supply chain management problems quantitatively. Shamaki et al [5] employed AHP and a Sequential Interactive Model for Urban Sustainability (SIMUS) to calculate each alternative source in terms of renewable energy. Authors suggested the use of SIMUS for estimation because it considers quantitative and qualitative assessment at a single time.…”

“…Dry rocks, lava, hot springs, and even firewood, animal excrement, crop remnants, and garbage can all be found. Biomass energy, solar energy, hydro energy, geothermal energy, and wind energy are the most common renewable energy sources [5].…”

“…Many densely populated countries, particularly energy-importing developing countries, rely substantially on petroleum imports now. Increases in international petroleum prices have had a negative impact on the economy and will continue to do so unless dependency on imported petroleum is reduced by switching to other resources [4,5]. Many countries with an oil-based economy, on the other hand, are considering alternatives to enhance their economies until 2050 [3][4][5].…”

“…Increases in international petroleum prices have had a negative impact on the economy and will continue to do so unless dependency on imported petroleum is reduced by switching to other resources [4,5]. Many countries with an oil-based economy, on the other hand, are considering alternatives to enhance their economies until 2050 [3][4][5]. In the long run, there are many different sorts of renewable energy that may be employed to make the planet a better place to live.…”