Compression Energy Requirement Research Articles

A Pinch Analysis approach for minimizing compression energy and capital investment in gas allocation network

Transportation of fluid is a very important aspect of process industries, especially for oil and gas industries. Pipelines have been considered as the most effective and safest way of transporting fluids. Transportation of gas through a pipeline is an energy-intensive process; hence, energy optimization in gas transportation networks is an important issue to be considered while framing the environmental policies. In this paper, a novel graphical methodology based on pinch analysis approach for simultaneous minimization of capital investment and compression energy requirement in gas allocation network with the aid of thermodynamic relations is developed. The results of the proposed methodology are expressed as a Pareto optimal front. The e-constraint method is used to generate Pareto optimal front for the two objectives. Identifying the relationship between capital investment and energy requirement gives the opportunity to the decision-maker for choosing the suitable optimal operating point based on the operating and economic conditions of the process. This result allows the planner to calculate the effects via increasing or decreasing energy requirement or capital investment. The applicability of the proposed methodology is demonstrated through two illustrative examples.

Double-cone ignition scheme for inertial confinement fusion.

While major progress has been made in the research of inertial confinement fusion, significant challenges remain in the pursuit of ignition. To tackle the challenges, we propose a double-cone ignition (DCI) scheme, in which two head-on gold cones are used to confine deuterium–tritium (DT) shells imploded by high-power laser pulses. The scheme is composed of four progressive controllable processes: quasi-isentropic compression, acceleration, head-on collision and fast heating of the compressed fuel. The quasi-isentropic compression is performed inside two head-on cones. At the later stage of the compression, the DT shells in the cones are accelerated to forward velocities of hundreds of km s–1. The head-on collision of the compressed and accelerated fuels from the cone tips transfer the forward kinetic energy to the thermal energy of the colliding fuel with an increased density. The preheated high-density fuel can keep its status for a period of approximately 200 ps. Within this period, MeV electrons generated by ps heating laser pulses, guided by a ns laser-produced strong magnetic field further heat the fuel efficiently. Our simulations show that the implosion inside the head-on cones can greatly mitigate the energy requirement for compression; the collision can preheat the compressed fuel of approximately 300 g cm−3 to a temperature above keV. The fuel can then reach an ignition temperature of greater than 5 keV with magnetically assisted heating of MeV electrons generated by the heating laser pulses. Experimental campaigns to demonstrate the scheme have already begun.This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.

Economic Optimization of Dual Mixed Refrigerant Liquefied Natural Gas Plant Considering Natural Gas Extraction Rate

This study mainly focuses on the profit optimization of the natural gas liquefaction process considering extraction rate. The target process is the dual mixed refrigerant (DMR) process with 1 million tons per annum (MTPA) capacity. The liquefaction ratio and the amount of boil-off gas (BOG) varies according to the natural gas extraction rate to meet the liquefaction capacity. Therefore, utilizing produced BOG and minimizing wasted BOG is key from an economic point of view. This study performed profit optimization with various extraction rates. Moreover, the energy and cost optimizations are performed to analyze the extraction rate effect. As results for the profit maximization, the total compression energy requirement and the plant cost show optimum values between the energy and cost optimization results. The profit increases by 22.5% with 93.2% liquefaction ratio through the optimization. The result shows that producing BOG as the amount of the fuel requirement for the compression energy supply is the op...

Total Cost Optimization of a Single Mixed Refrigerant Process Based on Equipment Cost and Life Expectancy

This study mainly focuses on minimizing the total cost of the single mixed refrigerant (SMR) process based on the equipment cost equations considering equipment life expectancy. Moreover, the energy and cost analyses are performed by comparing optimization results with two different objectives. The objective functions to be minimized include the total compression energy and the total annual cost, which is the sum of the annual capital cost and annual operating cost. By the compression energy minimization, the operating cost is significantly reduced by 16.2% because the largest part of this cost is taken by electricity for the compression energy requirement. In addition, a 14.0% capital cost saving is realized by the energy minimization. The results of total cost minimization show a 16.0% operating cost reduction from the base case, which is a little lower compared to energy minimization, but the capital cost saving is dramatically higher at 28.3%. Through the cost analyses, it is found that the compressor...

Enhancement of single mixed refrigerant natural gas liquefaction process through process knowledge inspired optimization and modification

This study examined the enhancement of the single mixed refrigerant (SMR) natural gas liquefaction process. The effects of the main parameters, such as mixed refrigerant (MR) composition and operating pressures on the compression energy requirement were investigated. A process knowledge inspired decision-making method was exploited for liquefied natural gas process optimization. The results showed that the proposed optimization methodology is simple and effective in determining the optimal operating conditions and could save up to 30.6% in terms of the compressor duty compared to the base case. In addition, the proposed optimization methodology provides process understanding, which is essential to process engineers. Another benefit of the proposed methodology is that it can be applied to any MR liquefaction cycle. The use of heavier refrigerants, such as isobutane and isopentane, and the addition of a NG compressor were examined to improve the energy efficiency of the SMR process. The effect of the intercooler outlet temperature on energy saving was also considered. The synergistic effects of those modifications on improving the performance of the liquefaction process were investigated.

Alternatives of integrated processes for coproduction of LNG and NGLs recovery

In this paper, integrated schemes for production of LNG and NGLs recovery are presented and DMR liquefaction cycle serves as a base process to which separation process of NGLs is integrated at. Main highlight of integration is a split of demethanizer into rectifying and stripping sections whereby light components of liquid stream from natural gas flashed throughout phase separator are stripped via stripping column while vapor stream is rectified into rectifier. To reach operating pressure of demethanizer requires to reduce pressure of flashed natural gas which gives an option of reusing the released power to recompress lean methane from NGLs recovery process. As for heat integration, rectifier is operated at low temperature and direct heat integration between both sections of demethanizer is not likely; thus heat of the final products in NGLs recovery train is retrieved by interreboiling stripping section. After all integration, mixed refrigerant cycle is optimized for compression energy requirement by varying the refrigerant composition and operating pressure levels through knowledge-based optimization methodology. The integrated schemes minimize the overall energy requirements.

Knowledge inspired investigation of selected parameters on energy consumption in nitrogen single and dual expander processes of natural gas liquefaction

Nitrogen based single and dual expander processes were analyzed for efficiency improvement considering compression energy minimization as objective. The significant parameters of nitrogen single and dual expander processes were investigated for their effect on the compression energy requirement. Thereafter optimization of single expander process was performed using process knowledge and for dual nitrogen expander process a customized algorithm inspired by the knowledge of design variables process is devised. The optimization results, in the specific energy requirement of 0.7449 kWh/kg LNG for single and 0.5007 kWh/kg LNG for dual nitrogen expander processes. The optimization results comparison with previous published studies show a significant energy savings. Furthermore, the proposed optimization methodology is flexible to be extended for any kind of single and dual expander process.

Waste heat recovery in CO2 compression

Carbon capture and storage (CCS) is a strategically important approach for achieving significant reductions in greenhouse gas emissions from large stationary emission sources, and ensures the availability of a reliable global energy supply for the future. Carbon dioxide (CO2) compression accounts for a significant amount of the capital and operating costs, and energy penalties associated with the CCS system. In this paper, different CO2 compression strategies were reviewed, and the opportunities of recovering waste heat as an effort to reduce their energy consumption were examined. Models of an intercooling compression chain and a 2-stage shockwave compression chain were built to investigate their respective energy consumption and potential waste heat recovery. An organic Rankine cycle (ORC) model was employed to recover waste heat. An exergy analysis was applied to assess the performance of the system. The results indicated that, without waste heat recovery, the shockwave compression chain had a higher specific energy requirement than the intercooling option. With waste heat recovery, the compression energy requirement in both cases dropped as expected, and the shockwave option required a lower specific compression energy with respect to the intercooling option. Within the ORC system, thermal efficiency, exergy efficiency, and exergy destruction rates decreased as turbine inlet temperature (TIT) increased. The ORC's evaporator was found to be the largest contributor to exergy destruction. These results demonstrate opportunities to optimize the CCS configuration and improve the overall economics of the plant.

Energy saving opportunities in integrated NGL/LNG schemes exploiting: Thermal-coupling common-utilities and process knowledge

Novel integrated and optimization schemes for natural gas (NG) liquid recovery and liquefaction step are presented. The liquefaction of NG was carried out using the newly developed KSMR liquefaction cycle while the separation of NG liquids was performed using energy efficient thermally coupled distillation schemes. The main highlight of integration are, (i) feed splitting to provide reboiler duty in the methane scrubber, (ii) common refrigeration utilities required all over the plant; and (iii) flexibility of integrated plant for easy transition between ethane recovery or ethane rejection. These integration steps minimize the overall plant-specific power requirements and the duplication of processing equipment. After successful integration, the MR cycle was optimized for the compression energy requirement by varying the refrigerant composition and operating pressure levels with the aid of an in-house established knowledge-based optimization (KBO) methodology. The KBO approach is robust in application and gives consistent results. Compared to the base case, 9% improvement in plant compression energy requirement was obtained.

Design optimization of single mixed refrigerant natural gas liquefaction process using the particle swarm paradigm with nonlinear constraints

The particle swarm paradigm is employed to optimize single mixed refrigerant natural gas liquefaction process. Liquefaction design involves multivariable problem solving and non-optimal execution of these variables can waste energy and contribute to process irreversibilities. Design optimization requires these variables to be optimized simultaneously; minimizing the compression energy requirement is selected as the optimization objective. Liquefaction is modeled using Honeywell UniSim Design™ and the resulting rigorous model is connected with the particle swarm paradigm coded in MATLAB. Design constraints are folded into the objective function using the penalty function method. Optimization successfully improved efficiency by reducing the compression energy requirement by ca. 10% compared with the base case.

Membrane Systems for the Recovery of Hydrogen from Multicomponent Gas Mixtures Obtained in Biomass Gasification

This work first generally reviews possible membrane materials for the hydrogen enrichment of biomass gasification producer gas mixture. Subsequently two permeator arrangements (single stage and two-stage with sweep) equipped with a glassy membrane material are evaluated through numerical modelling. The evaluation of the permeator systems focuses on critical hydrogen upgrading parameters like achievable hydrogen purity, hydrogen recovery and compression energy requirement. It is shown that the two-stage arrangement with sweep allows production of hydrogen with relatively high purity (above 98 % v/v) and recovery.