Single-Solution-Based Vortex Search Strategy for Optimal Design of Offshore and Onshore Natural Gas Liquefaction Processes

Abstract

Propane-Precooled Mixed Refrigerant (C3MR) and Single Mixed Refrigerant (SMR) processes are considered as optimal choices for onshore and offshore natural gas liquefaction, respectively. However, from thermodynamics point of view, these processes are still far away from their maximum achievable energy efficiency due to nonoptimal execution of the design variables. Therefore, Liquefied Natural Gas (LNG) production is considered as one of the energy-intensive cryogenic industries. In this context, this study examines a single-solution-based Vortex Search (VS) approach to find the optimal design variables corresponding to minimal energy consumption for LNG processes, i.e., C3MR and SMR. The LNG processes are simulated using Aspen Hysys and then linked with VS algorithm, which is coded in MATLAB. The results indicated that the SMR process is a potential process for offshore sites that can liquefy natural gas with 16.1% less energy consumption compared with the published base case. Whereas, for onshore LNG production, the energy consumption for the C3MR process is reduced up to 27.8% when compared with the previously published base case. The optimal designs of the SMR and C3MR processes are also found via distinctive well-established optimization approaches (i.e., genetic algorithm and particle swarm optimization) and their performance is compared with that of the VS methodology. The authors believe this work will greatly help the process engineers overcome the challenges relating to the energy efficiency of LNG industry, as well as other mixed refrigerant-based cryogenic processes.

Optimal Selection and Location of Fixed-Step Capacitor Banks in Distribution Networks Using a Discrete Version of the Vortex Search Algorithm

“…Recently, a promissory metaheuristic optimization technique known as the vortex search algorithm (VSA) has emerged to solve complex nonlinear non-convex optimization problems in the continuous domain. Some of these approaches are optimal power flow in AC and DC networks [31][32][33], respectively; optimal selection of analog active filter components [34]; application of the VSA for numerical optimization [35][36][37]; optimal design of offshore and onshore natural gas liquefaction processes [38]; and optimal solution of the inverse kinematics problem of serial robot manipulators with offset wrist [39]; among others. It is worth mentioning that the main advantages of using the VSA in nonlinear optimization problems are the following: (i) its low standard deviation since it works with Gaussian distribution functions for exploring the solution space; (ii) its correct balance between exploration and exploitation of the solution space during the iteration procedure since the optimization search is guided by a variable radius applied on the Gaussian hypersphere that contains all the potential solutions of the current iteration; and (iii) its easy implementation for any programming language via sequential programming.…”

Performance Enhancement of Nitrogen Dual Expander and Single Mixed Refrigerant LNG Processes Using Jaya Optimization Approach

“…In simulation, keeping the outlet temperature of coolers at lower values decreases the specific energy consumption of that process. In addition, Qyyum et al [27] used the vortex search optimization (VSO) approach for process improvement of the SMR LNG process, obtaining energy consumption of 0.369 kWh per kilogram of LNG. It has been reported [14,28,29] that LNG processes, particularly SMR and N 2 dual expander-based processes, are still energy intensive, mainly due to the non-optimal design variables such as flowrates of refrigerant and condensation, and evaporation pressures of the refrigeration cycles.…”

“…The major reason behind the dual expander is that an expansion of nitrogen refrigerant takes place at two different (low and high) pressure levels, which ultimately reduces the generation of entropy within the multi-stream cryogenic LNG heat exchanger. Although dual expansion adds to the capital cost, it results in a significant reduction in operating cost [14,27]. In Figure 2, natural gas (stream-A) passes through the main cryogenic heat exchanger (LNG-1) at high pressure (50.0 bar) and ambient temperature.…”

A new optimization method of energy consumption for dynamic boil-off gas liquefaction

“…The previous researchers placed emphasis on research from the steady state minimization for BOG condensing system. The energy-saving of SMR and C3MR cycles is reduced 19 and the mixed refrigerant composition is optimized 20 . Energy conservation research also involves thermodynamic analysis of C3MR 21 .…”

“…Y1 is the energy consumption of Wk-3, Y2 is the energy consumption of Wk-4, x(1), x(2) and x(3) are the pressure, flow and temperature of the inlet BOG respectively, x(8) is the pre-cooled propane mass, x(9) is the mixed refrigerant mass, and hi(i=5, 7, C3, 26, MR,6,3,4,25,16,14,17,15,18,9,19) and ti(i=5, 7, C3, 26, MR, 6, 3, 4,25,16,14,17,15,18,9,19) are the enthalpy and temperature of control point i in the process respectively.…”