Natural Gas Compressor Stations Research Articles

Mobile measurements of climate forcing agents: Application to methane emissions from landfill and natural gas compression

Measuring greenhouse gas (GHG) source emissions provides data for validation of GHG inventories, which provide the foundation for climate change mitigation. Two Toyota RAV4 electric vehicles were outfitted with high-precision instrumentation to determine spatial and temporal resolution of GHGs (e.g., nitrous oxide, methane [CH4], and carbon dioxide [CO2]), and other gaseous species and particulate metrics found near emission sources. Mobile measurement platform (MMP) analytical performance was determined over relevant measurement time scales. Pollutant residence times through the sampling configuration were measured, ranging from 3 to 11 sec, enabling proper time alignment for spatial measurement of each respective analyte. Linear response range for GHG analytes was assessed across expected mixing ratio ranges, showing minimal regression and standard error differences between 5, 10, 30, and 60 sec sampling intervals and negligible differences between the two MMPs. GHG instrument drift shows deviation of less than 0.8% over a 24-hr measurement period. These MMPs were utilized in tracer-dilution experiments at a California landfill and natural gas compressor station (NGCS) to quantify CH4 emissions. Replicate landfill measurements during October 2009 yielded annual CH4 emissions estimates of 0.10 ± 0.01, 0.11 ± 0.01, and 0.12 ± 0.02 million tonnes of CO2 equivalent (MTCO2E). These values compare favorably to California GHG Emissions Inventory figures for 2007, 2008, and 2009 of 0.123, 0.125, and 0.126 MTCO2E/yr, respectively, for this facility. Measurements to quantify NGCS boosting facility-wide emissions, during June 2010 yielded an equivalent of 5400 ± 100 TCO2E/yr under steady-state operation. However, measurements during condensate transfer without operational vapor recovery yield an instantaneous emission rate of 2–4 times greater, but was estimated to only add 12 TCO2E/yr overall. This work displays the utility for mobile GHG measurements to validate existing measurement and modeling approaches, so emission inventory values can be confirmed and associated uncertainties reduced.Implications: Measuring greenhouse gas (GHG) source emissions provides data and validation for GHG inventories, the foundation for climate change mitigation. Mobile measurement platforms with robust analytical instrumentation completed tracer-dilution experiments in California at a landfill and natural gas compressor station (NGCS) to quantify CH4 emissions. Data collected for landfill CH4 agree with the current California emissions inventory, while NGCS data show the possible variability from this type of facility. This work displays the utility of mobile GHG measurements to validate existing measurement and modeling approaches, such that emission inventory values can be confirmed, associated uncertainties reduced, and mitigation efforts quantified.

An Algebraic Approach to Fault Detection for Surge Avoidance in Turbo Compressor

This paper presents an innovative algebraic sensor fault detection approach for surge avoidance in turbo compressors (TC) in the natural gas compressor stations (GCS). The main objective is surge avoidance in the presence of sensor faults in TC. In this way, the robust parity space approach for fault detection is extended to highly nonlinear dynamic of TC based on Groebner basis and elimination technique. No work has been previously reported on the use of this technique for nonlinear dynamic systems with parametric uncertainties. This algebraic approach is simulated on the Moore–Greitzer control oriented model in the presence of parametric uncertainties, disturbances, and sensor faults. Simulation results are presented to demonstrate the effectiveness of the proposed fault detection approach.

Compressed natural gas behavior in a natural gas vehicle fuel tank during fast filling process: Mathematical modeling, thermodynamic analysis, and optimization

Every CNG station includes two main parts: a compressor equipped with inter- and after-coolers and a fast filling process (FFP). In this study, both processes were simulated in a FORTRAN based computer program. To model the compression process of real natural gas, the polytropic work of a three-stage compressor was considered. Moreover, the FFP was modeled based on mass conservation and first law of thermodynamics for a non-adiabatic cylinder. Due to high operating pressure, AGA-8 equation of state (EOS) was utilized for accurate computation of necessary thermodynamic properties. Both applied models for compression and FFP were compared with the real data. In particular, the FFP model was evaluated using experimental data obtained from an operating compressed natural gas (CNG) station in Sanandaj, Iran. The comparison showed a good agreement between model and experimental data. In the last part of this paper, the best operating condition for attaining either the minimum energy consumption in compressors and coolers or the maximum final accumulated mass of gas within NGV cylinders was determined using particle swarm optimization (PSO) algorithm.

주성분분석(PCA) 기법에 기반한 CNG 충전소의 이상감지 모니터링 및 진단 시스템 연구

Abstract - In this study, we suggest a system to build the monitoring model for compressed natural gas (CNG) stations, operated in only non-stationary mod es, and perform the real-time mon-itoring and the abnormality diagnosis using principal component analysis (PCA) that is suitable for processing large amounts of multi-dimensional data among mu ltivariate statistical analysis methods. We build the model by the calculation of the new characteristic variables, called as the major components, finding the factors representing the trend of process operation, or a combina-tion of variables among 7 pressure sensor data and 5 temperature sensor data collected from a CNG station at every second. The real-time monitoring is performed reflecting the data of process operation measured in real-time against the built model. As a r esult of conducting the test of mon-itoring in order to improve the accuracy of the system and verification, all data in the normal operation were distinguished as normal. The cause of abnormality could be refined, when abnor-mality was detected successfully, by tracking the variables out of the score plot.Key words : fault detection, monitoring, diagnosis, principal component analysis (PCA), CNG station

Selected Aspects of Safety Assurance at CNG Filling Stations

Aim: The aim of this paper is to present safety issues, including fire protection at Compressed Natural Gas (CNG) fueling stations, on the example of the technical standard developed under the auspices of The Chamber of the Natural Gas Industry ST-IGG 1601:2012 relating to the design, construction and operation of CNG stations in Poland. Introduction: There are nearly thirty CNG filling stations in Poland. But so far, technical standards concerning requirements for this kind of objects haven t been developed. To organize the requirements in this regard and facilitate appropriate services in designing, constructing, operating and supervising the aforementioned objects, the decision to develop the above-mentioned standard (finally 1 Akademia Gorniczo-Hutnicza w Krakowie, Wydzial Zarządzania, ul. Gramatyka 10, 30-067 Krakow, wklad procentowy w powstanie artykulu – 50% / AGH University of Science and Technology, Poland; percentage contribution – 50%; jsas@zarz.agh.edu.pl; 2 Komenda Glowna Panstwowej Strazy Pozarnej w Warszawie ul. Podchorązych 38 00-463 Warszawa; wklad procentowy w powstanie artykulu – 50% / National Headquarters of the State Fire Service of Poland (KG PSP), percentage contribution – 50%; sekretariat_ kgpsp@kgpsp.gov.pl; © by Wydawnictwo CNBOP-PIB Please cite as: BiTP Vol. 33 Issue 1, 2014, pp. 83-91 DOI:10.12845/bitp.33.1.2014.10

Evaluation of Gas Turbine Outboard Bleed Air on Overall Engine Efficiency and CO2e Emission in Natural Gas Compressor Stations

Gas turbine (GT) engines employed in natural gas compressor stations operate in different modes depending on the power, turbine inlet temperature, and shaft speeds. These modes apply different sequencing of bleed valve opening on the air compressor side of the engine. Improper selection of the GT and the driven centrifugal gas compressor operating conditions can lead to larger bleed losses due to wider bleed valve openings. The bleed loss inevitably manifests itself in the form of higher overall heat rate of the GT and greater engine emission. It is, therefore, imperative to determine and understand the engine and process conditions that drive the GT to operate in these different modes. The ultimate objective is to operate the engine away from the inefficient modes by adjusting the driven gas compressor parameters as well as the overall station operating conditions (i.e., load sharing, control set points, etc.). This paper describes a methodology to couple the operating conditions of the gas compressor to the modes of GT bleed valve opening (and the subsequent air bleed rates) leading to identification of the operating parameters for optimal performance (i.e., best overall efficiency and minimum CO2e emission). A predictive tool is developed to quantify the overall efficiency loss as a result of the different bleed opening modes and map out the condition on the gas compressor characteristics. One year's worth of operating data taken from two different compressor stations on TransCanada Pipelines' Alberta system were used to demonstrate the methodology. The first station employs a GE-LM1600 gas turbine driving a Cooper Rolls-RFBB-30 centrifugal compressor. The second station employs a GE-LM-2500+ gas turbine driving NP PCL-800/N compressor. The analysis conclusively indicates that there are operating regions on the gas compressor maps where losses due to bleed valves are reduced and, hence, CO2 emissions are lowered, which presents an opportunity for operation optimization.

Minimization of Fuel Consumption of Natural Gas Compressor Stations with Similar and Dissimilar Turbo-Compressor Units

AbstractThis paper studies and compares the results of a simple and fast heuristic method, genetic algorithm (GA), and the exhaustive search method (ES) concerning the minimization of fuel consumption of a natural gas compressor station (CS). The results, obtained for an input data set [natural gas flow rate of 150 million standard cubic meters per day (MMSCMD), suction pressure of 5.45 MPa, and discharge pressure of 6.9 MPa], showed that for a CS with similar turbo-compressor (TC) units, all of the applied methods achieved the same solution (fuel consumption rate of 3.620 kg/s). By contrast, for a CS with dissimilar TC units, the GA and ES methods attained a lower fuel consumption rate (3.738 kg/s) than that obtained by the heuristic method (3.753 kg/s). The effect of changing the CS flow rate, suction, and discharge pressures on optimal fuel consumption rate was also investigated. In the first case study, a 100 MMSCMD (or 100%) increase in the flow rate, 8.3 bar (or 13%) increase in discharge pressur...

Failure Analysis of Induction Motors: Magnetic Wedges in Compression Stations

This article presents the failure analysis and field measurements of five 7,500-hp induction motors driving reciprocating compressors for a natural gas compression station. The failure analysis examined fan design, vibration, motor-operating temperature, compressor loading profile, number of motor starts, and ambient temperature. A comparison between direct online motor starting and soft starting using an adjustable speed drive (ASD) and the impact on motor performance are presented. The settings and historical data gathered from the microprocessor protection relay for the motors are also covered and discussed.

Cover Chem. Eng. Technol. 4/2012

AbstractLippe Natural Gas Compressor Station. Courtesy of WINGAS GmbH & Co. KG.

Single Versus Dual Recycle System Dynamics of High Pressure Ratio, Low Inertia Centrifugal Compressor Stations

Compression systems are designed and operated in a manner to eliminate or minimize the potential for surge, which is a dynamic instability that is very detrimental to the integrity of the compressor unit. Compressor surge can occur when compressors are subjected to rapid transients such as those occurring following an emergency shutdown (ESD) or a power failure, which in turn, requires fast reaction. To prevent this from occurring, compressor stations are designed with single or dual recycle systems with recycle valves, which are required to open upon ESD. There has been extensive debate and confusion as to whether a single recycle or a dual recycle system is required and the circumstances and the conditions under which one system or the other must be used. This paper discusses this crucial design issue in detail and highlights the parameters affecting the decision to employ either system, particularly for high pressure ratio, low inertia compressors. Parameters such as gas volume capacitance (V) in the recycle path, compressor power train inertia, compressor performance characteristics, the recycle valve coefficient (Cv), prestroke and stroke time, and check valve dynamic characteristic are crucial in determining the conditions for dynamic instabilities. A simple analytical methodology based on the perturbation theory is developed that provides a first-cut analysis to determine if a single recycle system is adequate for a given compression system. The concept of an inertia number is then introduced with a threshold value that determines which recycle system to use. Techniques to circumvent compressor surge following ESD are discussed and their respective effectiveness are highlighted including when and if a delay in the fuel cutoff will be effective. An example of a case study with actual field data of a high pressure ratio centrifugal compressor employed in a natural gas compressor station is presented to illustrate the fundamental concept of single versus dual recycle systems.

Development of Korean hydrogen fueling station codes through risk analysis

When hydrogen fueling stations were constructed first time in Korea in 2006, there were no standards for hydrogen fueling stations. Hence the CNG (Compressed Natural Gas) station codes were temporarily adopted. In last three years, from 2006 to 2009, the studies for the development of hydrogen fueling station standards were carried out, with the support of the Korean government. In this study, three research groups cooperated to develop optimized hydrogen fueling station codes through risk analysis of hydrogen production and filling systems. Its results were integrated to develop the codes. In the first step to develop the codes, the standards for CNG stations and hydrogen fueling station were compared with each other and analyzed. By referring to foreign hydrogen fueling station standards, we investigated the potential problems in developing hydrogen fueling station codes based on the CNG station standards. In the second, the results of the high-pressure hydrogen leakage experiment were analyzed, and a numerical analysis was performed to establish the safety distance from the main facilities of a hydrogen fueling station to the protection facilities. In the third, HAZOP (Hazard and Operability) and FTA (Fault Tree Analysis) safety assessments were carried out for the on-site and off-site hydrogen fueling stations—currently being operated in Korea— to analyze the risks in existing hydrogen fueling stations. Based on the study results of the above three groups, we developed one codes for off-site type hydrogen fueling stations and another codes for on-site type hydrogen fueling stations. These were applied from September 2010.

Euro 2 기준 LNG-경유 혼소엔진의 배출가스 특성에 관한 연구

Heavy duty diesel engine has relatively small portion of whole vehicles due to long drive distance and large engine displacement, but largely influences atmosphere environment. City buses changed to CNG (Compressed Natural Gas) bus with Korea-Japan Worldcup. Heavy duty truck and intercity bus, however, were impossible to use CNG because those kinds of vehicles had long drive distance and CNG station was installed mainly at the around of the bus garage of city. Insulation container storing the natural gas as a liquid makes heavy duty truck and intercity bus possible to use the natural gas. Drive using diesel is possible where is hard to recharge the gas. With LNG (Liquefied Natural Gas), the dependence on oil is largely decreased, PM (Particulate Matter) and NOx which is chronic disadvantage of diesel is remarkably reduced and finally , the representative green house gas, is reduced over 10%.

Thermodynamic Optimization of Organic Rankine Cycles at Several Condensing Temperatures: Case Study of Waste Heat Recovery in a Natural Gas Compressor Station

In this article, the authors performed the thermodynamic optimization of organic Rankine cycles (ORCs) using several working fluids and considered the effect of three heat rejection media in the condenser: cooling water, ambient air, and hot water at high temperature for co- or trigeneration applications. The ORC system was modelled and optimized using the Aspen Hysys process simulator. The objective function is the maximization of turbine power output. Most natural gas compression stations use no heat recovery system. In this study, they applied the optimization procedure to the recovery of waste heat from gas turbines used to drive natural gas compressors in natural gas pumping stations. They used operational data from an existing pumping station to illustrate the potential benefits of ORC systems for this application, taking into account also non-thermodynamic aspects such as toxicity, flammability, and investment cost return. The highest ORC turbine output powers were obtained with aromatic hydrocarbons, then with aromatic fluorocarbons, n-hydrocarbons, and siloxanes (in that order). For the case studied here — a gas turbine of 2.6 MW of mechanical power— the proposed ORC can produce around 1 MWe, with a thermal efficiency of up to 24 per cent depending on the working fluid and condensing temperature.

Experimental and numerical simulation investigations on particle sampling for high-pressure natural gas

A novel Null-type sampling nozzle with six sampling holes was developed to measure the particle concentrations and size distributions in high-pressure natural gas flows under isokinetic sampling conditions. The isokinetic sampling performances of sampling nozzles were investigated by experiments and numerical simulations with standard κ– ε turbulent model. The maximum deviation between the experimental and numerical data was less than 4%. In order to ensure reliability and stability, sampling nozzles were calibrated in standard wind tunnel. Furthermore, this novel Null-type sampling nozzle was used to measure the separation efficiency of filter with an operation pressure of 6.0 MPa in a natural gas compressor station. The results of experiment and numerical simulation show that the new Null-type sampling nozzles have relatively smaller isokinetic sampling errors and reliable sampling efficiencies, which enable it competent to sample high-pressure natural gas.

Transient Optimization in Natural Gas Compressor Stations for Linepack Operation

One of the key factors in the operation of a natural gas pipeline network is the linepack in the network. The desired operation of the network as derived from estimated receipts and deliveries is expressed in terms of the desired linepack profile that must be maintained. The compressor stations in the pipeline network are then operated in a manner that generates this linepack profile. Generally, the operating points selected for the units in the compressor stations are based on experience and experimentation and are therefore not optimal. In this paper, we present a systematic approach for operating the units of a compressor station to meet a specified linepack profile. The first step in developing this approach is the derivation of a numerical method for analyzing the flow through the pipeline under transient nonisothermal conditions. We have developed and verified a fully implicit finite difference formulation that provides this analysis capability. Next, the optimization of the compressor stations is formulated as a standard nonlinear programing problem in the following form: Find the values in the design variable vector denoted by b=[b1,b2,…,bn]T, to minimize a given objective function F(b), subject to the constraints gj(b)⩽0, j=1,…,m. Here, n is the number of operational parameters whose optimal value is to be determined, while m is the number of operational constraints that must be enforced. In our formulation, the design variables are chosen to be the operating speeds of the units in the compressor stations, while the objective function is taken to be the average fuel consumption rate over the interval of interest, summed over all units. The constraint functions gj(b) are formulated suitably to ensure that operational limits are met at the final solution that is obtained. The optimization problem is then solved using a sequential unconstrained minimization technique (SUMT), in conjunction with a directed grid search method for solving the unconstrained subproblems that are encountered in the SUMT formulation. The evaluation of the objective function and constraint functions at each step of the optimization is done by using the fully implicit analysis method mentioned above. A representative numerical example has been solved by the proposed approach. The results obtained indicate that the method is very effective in finding operating points that are optimal with respect to fuel consumption. The optimization can be done at the level of a single unit, a single compressor station, a set of compressor stations, or an entire network. It should also be noted that the proposed solution approach is fully automated and requires no user involvement in the solution process.

Optimization of the distribution of compressed natural gas (CNG) refueling stations: Swiss case studies

To become a mass-market product, compressed natural gas (CNG) cars will need a dense network of filling stations. The Swiss natural gas industry plans to invest in 350 additional CNG stations to supplement the existing 50 sites. Cost–benefit analysis is used to define the optimal locations for these among the existing 3470 petrol filling stations. It is found using two simulations looking at equitable location of sites and socially optimal ones, that the investment in additional CNG infrastructure is unlikely to be socially advantageous.

Treatment of Wastewater Effluent from a Natural Gas Compressor Station

Florida Gas Transmission Company (FGTC), an Enron/Sonat affiliate, owns and operates a major interstate natural gas pipeline system that extends from South Texas to South Florida. At various locations along the pipeline are located compressor stations that boost the pressure of the natural gas flowing through the pipelines. As part of their normal operation, these stations generate small amounts of oily effluent as a result of cooling water blow-down, engine/parts wash-down, lube-oil-contaminated wastewater and rainwater from containment areas. In early 1997, economic considerations led FGTC to pursue alternative technologies to replace portions of the traditional treatment system. This paper reviews a trial effort undertaken by Wetland Sciences, Inc. to evaluate the technical feasibility of utilizing constructed wetlands to treat wastewater generated by the natural gas compressor station. The ultimate goal being the application of this technology to FGTC's other compressor stations.

Treatment of wastewater effluent from a natural gas compressor station

Florida Gas Transmission Company (FGTC), an Enron/Sonat affiliate, owns and operates a major interstate natural gas pipeline system that extends from South Texas to South Florida. At various locations along the pipeline are located compressor stations that boost the pressure of the natural gas flowing through the pipelines. As part of their normal operation, these stations generate small amounts of oily effluent as a result of cooling water blow-down, engine/parts wash-down, lube-oil-contaminated wastewater and rainwater from containment areas. In early 1997, economic considerations led FGTC to pursue alternative technologies to replace portions of the traditional treatment system. This paper reviews a trial effort undertaken by Wetland Sciences, Inc. to evaluate the technical feasibility of utilizing constructed wetlands to treat wastewater generated by the natural gas compressor station. The ultimate goal being the application of this technology to FGTC's other compressor stations.

都市部における低公害車普及のための燃料供給施設の整備に関する研究 : 駐車場併設型天然ガススタンドの提案と東京都区部における検討

都市部における低公害車普及のための燃料供給施設の整備に関する研究 : 駐車場併設型天然ガススタンドの提案と東京都区部における検討

An Indonesian Experience, Consumers’ Demand For Cng Compression Facilities Performance

Compressed Natural Gas (CNG) has been used to fuel vehicles in many countrie, including in Indonesia. However, there are many difficulties to overcome in CNG public acceptance. In Indonesia, one of these may be CNG consumer’s preference for certain CNG refuelling stations over others. Finding causes of this may help increase acceptance of CNG by Indonesian motorists and enable CNG to make a better contribution to achievingthe country’s energy diversification policy. It is hypothesized that the variation in intake pressures at CNG station to be a cause for preference by CNG consumers. This hypothesis is based on the variation in total energy of CNG delivered at the point of sale as a result of CNG compressor capacity. It is found that, when the gas system pressure was less than CNG station intel design pressure, the CNG produced in the fuel tank would not reach its design pressure. Consequently, its total energy per fuel tank and payback period of compression facilities investment was affected.The analysis of CNG acceptance and a correlation with CNG station intel design pressure and gas composition from the consumers’ point of view will examine the following factors:The effect of various intel pressure at CNG stations on the performance of existing CNG compressors and after-cooler.The effect of CNG compressor discharge conditions and after-cooler performance on the total energy of CNG delivered to the fuel tank which in turn affects the heating value of the fuel to the vehicle engines.Evaluation of CNG compressor discharge conditions effecting the payback period of CNG station investment and determination of potential significance to compression facilities acceptance.