Natural Gas Pressure Research Articles

Combustion optimization in gas burners of reverberatory furnaces during the melting of nickel alloys

In recent years, due to climate change environmental sustainability programs have been created that require the search for alternatives to reduce air emissions and reduce fuel consumption. The combustion industry is looking for an effective solution to increase the life cycle of its equipment and improve combustion efficiency without neglecting safety or savings. The efficiency of the medium pressure natural gas burners associated with chemical energy, which is converted into heat, that is, the hotter the gaseous products of combustion, the more efficient the burner. The work analyzes the combustion process and their chemical reactions; combustion products obtained in accordance with various conditions; combustion characteristics and factors that influence; and measurement methods needed to optimize combustion and their equipment. In the metallurgical production of nickel, optimization of the burners is very important due to the high temperature used in the reverberatory furnace. That is, the use of a large excess of air would be unfavorably energetic, and the use of a very low excess would result in small intimate mixtures of air and fuel, followed by the release of unreacted reagents and the formation of toxic gases arising at high temperatures. For this reason, the results of this work are an important source of information. The innovation is to automate the use of non-invasive sensors to control the combustion process. The sensors play a fundamental role in the industry, because the information they provide supports the enhanced use of data in the enterprise, increase productivity, efficiency and safety.

Techno-economic analysis of power generation by turboexpanders in natural gas pressure reduction stations

The objective of this paper is to perform a techno-economic feasibility study of recovering pressure energy of natural gas stream through installing turboexpanders in a pressure reduction station and selling the generated electrical power to the national grid. As a case study, the operating and real conditions of a major pressure reduction station in Iran is collected throughout the years 2015, 2016 and 2017. To account for the effects of the inherently variable operating conditions, a thermodynamic model based on exergy analysis estimates off-design turboexpander isentropic efficiency, size and cost estimate as well as minimum preheating temperature required to avoid hydrate formation due to the expansion process. The detailed economic analysis shows that for the project to be economically feasible, an electricity purchase price of > $0.08/kWh is required. Furthermore, the results of this study are useful for designing automatic preheating temperature control system.

Techno-economic analysis of power generation by turboexpanders in natural gas pressure reduction stations

The objective of this paper is to perform a techno-economic feasibility study of recovering pressure energy of natural gas stream through installing turboexpanders in a pressure reduction station and selling the generated electrical power to the national grid. As a case study, the operating and real conditions of a major pressure reduction station in Iran is collected throughout the years 2015, 2016 and 2017. To account for the effects of the inherently variable operating conditions, a thermodynamic model based on exergy analysis estimates off-design turboexpander isentropic efficiency, size and cost estimate as well as minimum preheating temperature required to avoid hydrate formation due to the expansion process. The detailed economic analysis shows that for the project to be economically feasible, an electricity purchase price of > $0.08/kWh is required. Furthermore, the results of this study are useful for designing automatic preheating temperature control system.

Employing enhanced geometries in water bath heating system of natural gas pressure drop stations: Comparative study

In pressure drop stations (PDSs), the natural gas (NG) is heated before its pressure is reduced. It is commonly performed in a water bath heating system equipped with a serpentine-shaped pipe-line and a fire tube. A part of NG is burned in the fire tube, and the produced heat is transferred to water as heat transfer media. Then, the NG following through the pipe-line achieves the heat, and its temperature goes up. In this study, three enhanced geometries, namely twisted-insert (TI), twisted-tube (TT), and corrugated-tube (CT), are proposed to enhance thermal performance of the pipe-line and reduce fuel consumption of the heating system. Firstly, the obtained results are validated with data collected from a real PDS with the capacity of 1000 m3/h. It is found that the mean deviation between the current results and the real data is less than 1%. Then, the enhanced models are examined at three different levels of the specific design factor, i.e. ratio of 360° twist-pitch (or wave-length) to straight-section. It is found that replacing an enhanced model with the reference model can noticeably affect both thermal and hydraulic characteristics of the pipe-line. For given operating conditions, the use of the TI, TT, and CT models can enhance the NG temperature by about 6, 2, and 3 K compared to the reference model. At the same time, the pressure drop of the NG increases about 10, 7, and 12 times higher than the reference model. As a rule of thumb, the TI, TT, and CT models can reduce the length of the pipe-line by about 50%, 25%, and 37.5%, respectively.

Reliability Assessment Based on Multisource Information Fusion Method for High Pressure Natural Gas Compressors

Abstract Compressor units used for long-distance transportation natural gas pipeline pressurization have high-pressure and high-risk characteristics. Hence, the scientific reliability assessment is important for high-pressure compressor units, to evaluate the reliability standard, find the performance deficiency, and provide references for operation and maintenance. The classical reliability assessment method is not suitable for the complex and high-reliability equipment, like high-pressure compressor units and pipelines. The reliability assessment of the high-reliability equipment is faced with the challenge of the multisource information. A reliability assessment method based on the multisource information fusion is proposed in this work. The fusion resources consist of design information, component test information, and trial operation information. The reliability of high-pressure compressor units can be assessed by fusing the characteristic parameters, from component-based assessment, function-based assessment, quality evaluation, and life model, by D–S evidence theory. A case study is conducted to verify the proposed reliability assessment method in a 20 MW-class high-pressure compressor. There are four information resources in the case, i.e., component test data, design information, operation data, and simulation data. The compressor reliability is assessed as 99.32%, validated by the statistical assessment result based on long-term shutdown reports. This application points out the existing weakness in the high-pressure compressor units and indicates the directions for improving the design, analysis, operation, and failure prevention technologies. It reveals that the reliability assessment based on multisource information can provide a guarantee for the operation and maintenance of high-pressure compressor units. Meanwhile, the proposed method has good expansibility, which may be used in more fields.

MCDM Model for Natural Gas Pressure Reducing Station Site Selection

Considering the increasing scenario of natural gas consumption, it is necessary that all agents in the chain use methods that structure decision-making and problem-solving processes. This paper proposes a multicriteria decision model to solve a site selection problem for a pressure reducing station. A natural gas distribution company was selected to test the model and the preference modeling was conducted through the flexible interactive tradeoff (FITradeoff) approach, according to the preferences of the decision maker (DM). FITradeoff's decision support system was used to assess the alternatives of the model, through the inference of the criteria scale constants. The results proved the robustness of the model and the DM evidenced consistency in its preferences. Also, the FITradeoff method demonstrated to be intuitive to apply, since a smaller effort is required from the DM and this is because the procedure does not require complete information in the scale constants elicitation process.

Microstructure Design and Properties of X100 Gas Line Pipe

The microstructure evolution process of X100 pipeline steel is analysed, and the influence of different alloy composition and accelerated cooling process on microstructure evolution is studied in this article. It is obtained that acicular ferrite microstructure can make the yield strength of steel reach 650 MPa through micro alloying and thermo-mechanical control process(TMCP) with the comprehensive reinforcement effect of grain refinement, micro-alloying element precipitates and dislocation substructure. Acicular ferrite has the characteristics of fine grain, cross distribution, large angle grain boundary and presence of sub structure and high density movable dislocation. Test results of product quality also show that X100 pipeline steel which adopts Mn-Nb-Ti component system with a small amount of Ni (V), Mo alloy addition and TMCP process has obvious characteristics of fine grain. The Matrix is consisted of granular bainite and appropriate amount of MA as dispersion phase, which makes the tensile strength reach more than 800 Mpa. At the same time, the X100 pipeline steel has the characteristics of high toughness and good weldability, which is beneficial to ensure the safe operation of high pressure natural gas pipeline.

Measurement and verification of transient injection flow rate of high pressure natural gas pulse injector

A high-pressure natural gas direct injection engine can achieve lean combustion and diffusion combustion of natural gas, which can reduce the emission level and improve power performance. However, the transient gas injection rate of the injector directly affects the combustion rate. In order to optimize engine performance, it is essential to focus on the technology used to measure the transient injection rate. Therefore, in this study, a method is developed to measure the transient flow rate of a high-pressure natural gas pulse injector. First, experiments were conducted to locate the optimum position for sensor installation, thereby ensuring the quality of the signal. Subsequently, a mass flow meter and schlieren imaging method was used to verify the injection mass and injection start/end timing. Finally, the common working conditions of a certain type of injector are measured. Results indicated that the test error of the cycle injection mass and injection start/end timing did not exceed 4% and 2.1%, respectively. As the injector energizing time increased, the injection rate curve changed from triangle to trapezoid. As the injection pressure increased, the injection start delay time decreased and end delay time increased. Measurement of the main and post injection strategy indicates that the main injection has a significant impact on the injection mass and injection rate curve for post injection. When the interval between the two injections is short, the injection rate curves merge. This increases the injection duration. The total injection mass of the main injection and post injection mass is found to be significantly higher than the sum of the two independent injections.

Effect of geometrical parameters on thermal efficiency and fuel consumption of heaters of a natural gas pressure reduction station using Sobol statistical sensitivity analysis

AbstractThe main objective of natural gas pressure reduction station or city gate stations (CGSs) is to adjust gas pressure within a standard range for home usage. CGSs usually utilize heaters for pressure tuning, which generally consume a considerable amount of energy. In this paper, the effect of six influential parameters, namely, the length of gas‐coil, the diameter of gas‐coil, the radius of heater shell, length of heater shell, fire tube diameter, and length, on the amount of fuel consumption and thermal efficiency is investigated using Sobol statistical sensitivity analysis. The results show that gas‐coil length and diameter are not effective in fuel consumption and thermal efficiency. In contrast, increasing the heater shell radius, heater shell length, and fire tube radius has the same effect as they cause a linear increase in fuel consumption. According to results taken from Sobol analysis, they similarly have an influence of 19%–23% on fuel consumption and 21%–22% on thermal efficiency. Finally, it was revealed that the effect of fire tube length on fuel consumption and thermal efficiency of the heater was 37% and 35%, respectively.

Comparative experimental investigation on combustion pressure of pure methane and natural gas with elevated initial pressure

In this study, the combustion pressure of pure methane-air mixture, with 99.99% purity, and a mixture of air with Natural Gas (NG) consisted of 84.2% Methane, 9.5% Ethane, and 3.7% Propane was investigated, while both mixtures had an initial pressure of 10 bar. In this study, the combined effect of initial turbulence, pressure, and ignition energy on the combustion characteristics of each mixture was investigated. The fuel concentration in the methane-air and NG-air mixture varied between 4.98% and 17.3%. The flammability limits of the NG were 4.41% and 14.47%, whereas they were 5% and 15% for pure methane. To investigate the effect of rich or lean mixture on the combustion pressure, experiments were conducted with equivalence ratios of 0.50, 0.75, 1.00, 1.50, and 2.00. For both sets of experiments, the maximum combustion pressure occurred at the equivalence ratio of 1.00. The results showed that the lower methane concentration and the presence of other hydrocarbons such as Ethane and Propane in NG, do not cause the maximum combustion pressure to occur in a ratio other than the equivalence ratio of 1.00. Also, the study showed that the igniter energy had a significant effect on the combustion pressure, where an increase in the spark energy dramatically increased the combustion pressure for both pure methane and NG. The experiments were expended to demonstrate the effect of initial turbulence created via the mixer, on the combustion pressure for both fuels. The results suggest that the use of the mixer has a significant effect on the combustion pressure, so that experiments performed with the mixer significantly increased the combustion pressure in both fuels. Also, the study showed that the combustion pressure is influenced more than initial turbulence rather than ignition energy. The results of this study can be used in different fields from preventing unwanted combustion and detonation in engines or at places with High-risk environments such as mines and storage facilities for these gases.

Modeling of the flow comparator as calibration device for high pressure natural gas flow metering in Modelica

The German national metrological institute, Physikalisch-Technische Bundesanstalt, is developing a new concept a for a volumetric primary standard to calibrate high pressure gas flow meters. The TUHH is supporting these Research & Development activities with its competence to elaborate computational models for detailed analysis of complex electromechanical systems including fluid flow aspects. The new primary standard is called Flow Comparator and uses an actively driven piston prover to measure the gas flow rate using the time the piston needs to displace a defined enclosed volume of gas in a cylinder. A computational model is developed in Modelica® to investigate the Flow Comparator’s dynamic behavior and interaction with other components in the loop. The validation of the developed model shows good compliance with measured piston velocity and differential pressure at the piston. The model is used to optimize the frequency inverter’s control voltage trajectory to increase the available calibration time.

Impact of twisting tapes with various pitch lengths on the exergy and entropy performances of line heaters

Water bath fire tube heaters, so-called line heaters, are commonly used for industrial applications from small scales to large scales. The main problem of such heaters is the very low effectiveness of the heater due to the inefficient heat transfer within the heater (mainly between the fire tube and gas flow). The effects of using a specific type of twisting tape on the performance of these heaters, a typical heater used in natural gas pressure reductions points, were recently investigated. This study assesses the impacts of twisting tapes with different styles placed in the gas coil of the heater on the entropy generation and exergy performance of these heaters via computational fluid dynamic methods. For this, a typical gas mixture and typical line heater were considered. The results show that twisting tapes with larger numbers of twists and shorter twist pitch better enhance the exergy efficiency of the heater and decrease the rate of entropy generation over the gas heating process. Based on the obtained results, twisting tapes with the 17 and 68 twists decrease the rate of entropy generation by 16.8% and 27.1% and decrease the Bejan number for, respectively, over 36% and 77%.

A comprehensive assessment of low-temperature preheating process in natural gas pressure reduction stations to better benefit from solar energy

In this study, a thermodynamic model is developed for a natural gas pressure reduction station, which uses solar energy as an auxiliary energy source for preheating the natural gas. To increase the duration of solar energy usage per day and the consequent decrease in the fuel consumption of the heater, a novel design is presented in which preheating the gas to lower temperatures becomes possible through the use of multi-stage preheating and pressure reduction. Through this novel design, it becomes possible to utilize a single heater to preheat all stages, which reduces the costs dramatically. To investigate the effectiveness of the proposed design in different climate conditions, a comprehensive economic analysis is conducted based on fuel saving and carbon dioxide emission reduction. The results show that the return of capital is within 1–10 years considering different parameters, including: 1- daily time duration of solar energy usage by the station before implementation of the new design, 2- additional daily time duration of solar energy usage after implementation of the new design, and 3- number of preheating and pressure reduction stages. Finally, the effects of different parameters on the return of capital are discussed.

Design and optimization of integrated single mixed refrigerant processes for coproduction of LNG and high-purity ethane

Abstract In this study, two novel integrated single mixed refrigerant (SMR) processes are proposed to coproduce liquefied natural gas (LNG) and high-purity liquid ethane, which are suitable for improving the economic benefits of high ethane-containing natural gas. In Process 1, cryogenic distillation and conventional SMR process are integrated to separate ethane while producing LNG. Since the distillation pressure is below the critical pressure of methane, heat transfer temperature difference in the low temperature section may be relatively large. Therefore, in Process 2, the pressure of natural gas is increased by adding a compressor after the distillation column. Aspen HYSYS is used to simulate the proposed processes, and the key parameters of the refrigeration cycles are optimized by genetic algorithms. Based on the comprehensive consideration of initial investment and operating cost, Process 2 is recommended for large-scale plant, while Process 1 for small-scale plant and situations with requirement of simple system, for example floating LNG production (FLNG). Furthermore, a simplified Process 1, with propane eliminated from the mixed refrigerant, is presented for better adaption to FLNG conditions.

High efficiencies with low fuel utilization and thermally integrated fuel reforming in a hybrid solid oxide fuel cell gas turbine system

Solid oxide fuel cell (SOFC) - gas turbine (GT) systems have a potential to achieve 70% efficiency, which with high fuel flexibility and high part load efficiency, makes this hybrid a promising technology for the next power generation systems. To realize the high efficiency and reduce the capital cost, most studies focus on high fuel utilization SOFC stack design with internal fuel reforming configuration in SOFC-GT hybrids. None of them have considered low fuel utilization SOFC design in the hybrid system, which could extend the SOFC lifetime and also decrease the capital cost from fuel cells, accelerating the commercialization of fuel cell technologies. To fill this research gap, this work examined the system performance of a pressurized natural gas hybrid SOFC-GT system with a thermally integrated fuel reforming process. Specifically, system cycle analysis was performed in this work to explore the feasibility of achieving high efficiencies with low SOFC fuel utilizations. An equilibrium reformer model and a one-dimensional SOFC model were employed to represent the SOFC system, while balance of plant model was built in Ebsilon® to simulate the associated performance of recuperated gas turbine cycle. With the thermally integrated system configuration, 70% efficiency could be reached at 50% SOFC fuel utilization with a high fuel pre-reforming rate (only ~ 5 mol% CH4 at anode inlet). Low fuel utilization operations with high fuel pre-reforming rates provided higher design flexibility without violating any operational constraints while maintaining a high system efficiency as compared to on-anode reforming.

Design and Experiment of Low-Pressure Gas Supply System for Dual Fuel Engine

Abstract A low-pressure gas supply system for dual fuel engines was designed to transport liquid natural gas from a storage tank to a dual fuel engine and gasify it during transportation. The heat exchange area and pressure drop in the spiral- wound heat exchanger, the volume of the buffer tank and the pressure drop in the pipeline of the gas supply system were calculated by programming using Python. Experiments were carried out during the process of starting and running the dual fuel engine using this gas supply system. Experimental data show that the gas supply system can supply gas stably during the process and ensure the stable operation of the dual fuel engine. The effects of the parameters of natural gas and ethylene glycol solution on the heat exchange area of the spiral-wound heat exchanger and the volume of the buffer tank in the gas supply system were studied. The results show that the heat exchange area calculated according to pure methane can adapt to the case of non-pure methane. The temperature difference between natural gas and ethylene glycol solution should be increased in order to reduce the heat exchange area. The heat exchange area selected according to the high pressure of natural gas can adapt to the low pressure of natural gas. The volume of the buffer tank should be selected according to the situation of the minimum methane content to adapt to the situation of high methane content. The main influencing factor in selecting the volume of the buffer tank is the natural gas flow. The results can provide guidance for the design of the gas supply system for dual fuel engines.

AN ALTERNATIVE METHOD FOR CONTROLLING HYDRATE FORMATION IN NATURAL GAS REDUCTION UNIT WITH LIQUEFIED NATURAL GAS PRODUCTION

Background The article is devoted to the problem of controlling gas hydrates formation at a gas pressure reduction station due to the process of natural gas pressure reduction. Aims and Objectives The main aim of the study is to propose the use of fiberglass pipes as a method of controlling gas hydrates formation in the gas reduction line of a natural gas reduction plant with liquefied natural gas production. Comparison of the developed technology for hydrate formation controlling with the control method, originally laid down in the reduction unit under consideration. Ensuring safe work of service personnel, reducing economic costs for the construction and operation of the gas distribution station due to the use of the developed technology controlling gas hydrate formation in the gas reduction line of the reduction unit. Results Modern trends in the introduction of lowtonnage production of liquefied hydrocarbons on the basis of a gas distribution station are considered. The method of hydrate formation controlling in the line of gas reduction unit, originally laid down by the author of the patent, is analyzed, and the conclusion is made that the use of this technology to control gas hydrates is inappropriate from the point of view of the safety of gas distribution station workers. The advantages of fiberglass pipes made of composite materials over steel pipes are established. It is proved that the use of composite gas pipelines as a method of controlling hydrate formation in a reduction unit provides a positive economic effect in the construction and operation of a gas distribution station due to certain advantages of fiberglass pipes over steel pipes. It has been proved that to ensure the safety of the work of the personnel of a gas distribution station operating a natural gas reduction unit with the production of liquefied natural gas, it is advisable to replace steel pipes with fiberglass pipes made of composite materials, instead of using an increase in the energy flow rate and its turbulization to control gas hydrates formation. The percentage of reduction of friction pressure losses in the technological gas pipeline of the unit was calculated when replacing steel pipes with composite ones. It is proved that the use of the developed technology to hydrate formation control in the reduction gas line of the reduction unit provides a more rational use of the energy of the natural gas stream. The preservation of the temperature of the transported energy carrier in the future will allow the use of the stored heat for the needs of the station or for the needs of consumers.

A Study on Risk and Expense Evaluation of Agility Supply Management of Machinery

We provide a technical assessment and critique of the existing literature via highlighting problems associated with conceptualization and technical improvement of agility practices. By presenting a narrative evaluation of the technical review, we underscore the nature of the SC hazard in addition to agility practices and furnish a synthesis for future studies. The purpose is to examine the relationship between identifying and ranking the elements affecting supply management for SC agility in compressed natural gas pressure vessels. This study is applied research and data are collected based on descriptive survey. The populace of the investigation is milled compressed natural gas pressure vessels. Survey data are amassed through interviews and questionnaires. Cronbach’s alpha has been utilized to evaluate the reliability of the values received 0.778, which shows that the questionnaire is of excellent reliability and the questionnaire has 27 questions. Also, because the volume of the statistical population is 270 people, the consequences show that there is a positive connection among the empowerment of SC agility. Driving agility is on a positive supply chain (SC) agility. The expense has a poagilitysitive impact on SC agility.

Investigation on using prospects of surplus pressure energy from natural gas transported through pipelines in Azerbaijan (in the order of discussion)

For transportation of natural gas through the pipelines of compressor stations, its pressure increases. Up to 10 percent of this energy is used for the slipping by the pipeline walls and the most to the gas pressure reduction. The paper reviews the issues of efficiency increase of gas provision network of our Republic due to the decrease of energy losses in transportation, distribution and regulation systems of natural gas. For this purpose, the energy losses associated with the decrease of natural gas pressure in gas distribution plants and gas control units have been studied, as well as using efficiency of this energy justified. It was defined that the pressure of natural gas being transported to the customers through the delivery main, reduces down to the set value via throttle valves in gas distribution plants at first and in gas control units subsequently, which leads to the loss of significant portion of initial energy delivered through compressor stations during gas compression. The studies showed that using special traditional throttling valves instead of expansion units, so-called detanders, enables obtaining electrical energy via environmentally-friendly method with minimum investments due to the surplus gas pressure.

Integrating Support Vector Regression with Genetic Algorithm for Hydrate Formation Condition Prediction

To predict the natural gas hydrate formation conditions quickly and accurately, a novel hybrid genetic algorithm–support vector machine (GA-SVM) model was developed. The input variables of the model are the relative molecular weight of the natural gas (M) and the hydrate formation pressure (P). The output variable is the hydrate formation temperature (T). Among 10 gas samples, 457 of 688 data points were used for training to identify the optimal support vector machine (SVM) model structure. The remaining 231 data points were used to evaluate the generalisation capability of the best trained SVM model. Comparisons with nine other models and analysis of the outlier detection revealed that the GA-SVM model had the smallest average absolute relative deviation (0.04%). Additionally, the proposed GA-SVM model had the smallest amount of outlier data and the best stability in predicting the gas hydrate formation conditions in the gas relative molecular weight range of 15.64–28.97 g/mol and the natural gas pressure range of 367.65–33,948.90 kPa. The present study provides a new approach for accurately predicting the gas hydrate formation conditions.