Gas distribution networks

Sales gas would be piped directly into the national gas distribution network (assuming one exists) and NGL products such as propane and butane can be stored locally in pressurised tanks. NGL products are often distributed by road or rail directly from the gathering station, although if ethane is recovered it is normally delivered by pipeline. 

Buried steel pipelines for the transport of gases (at pressures >4 bars) and of crude oil, brine and chemical products must be cathodically protected against corrosion according to technical regulations [1-4], The cathodic protection process is also used to improve the operational safety and economics of gas distribution networks and in long-distance steel pipelines for water and heat distribution. Special measures are necessary in the region of insulated connections in pipelines that transport electrolytically conducting media. 

By early 1990-ies the gas consumption in Azerbaijan totalled about 17 bcm. The Azeri gas distribution network covers around 85 % of the territory. The local gas production and the imports from Russia and Iran had significantly declined after the collapse of Soviet empire, and the supply to significant part of countries territory discontinued. 

Armenia owns some 1800 km high-pressure gas transmission and approximately 9000 km gas distribution network. In 1990 Armenia consumed some 4.5 bcm of gas, which declined to 1.5 bcm p.a. (2000), of which more than 75% is used for power generation. 

Traditionally, onshore gas is consumed on the gas markets, located in or near the production area. Onshore gas is typically fed into the local gas distribution network without any treatment other than separation. 

The fire and explosion hazards of chlorine-containing systems have been reviewed [1,3]. A rail tanker of chlorine was being emptied to a chlorine gas distribution network... 

Figure 2. Gas-distribution network with a tree structure...

Studies should be made of the economics of building biomass-fuelled district heating networks for new residentiaiycommercial communities, and in particular of the comparative costs of these and natural gas distribution networks for the supply of fuel for heating. 

The escape of natural gas from the gas distribution networks also exerts a considerable effect on physical, chemical and biological processes in the soil. The extent of the gas zone depends greatly on the rate of its escape, depth of the groundwater level, type of pipeline, the nature and moisture of the soil, treatment of its surface, etc. The composition of the gaseous phase in the soil is affected by the microbiological oxidation of methane. The rate of this depends on the soil temperature, presence of oxygen and the content of nutrients. At low temperatures, this microbial process is restricted, which also restricts the anaerobic zone. 

Figure 1.8 Top view of a. combinatorial reactor gas-distribution network. Copyright 2001-, Symyx Technologies, fnc., used with permission, ...

When the gas distribution network was planned, the number of pipe diameters was rationalised. For each pipe diameter, joints and couplings need to be made. Ideally, the pipe diameter should suit the planned flow, but a large number of pipe diameters increases the costs of manufacture and of stocks. Typical pipe dimensions are given in Table 14.3. 

As mentioned, gas distribution networks are usually located in highly populated areas. The influence of this situation ean be again studied from the database. This includes an information field on the population density of the areas where the accident took place. A qualitative value is used, with four possibilities high population (town), low population (vUlage), dispersed population (rural), and unknown. The results are shown in Table 41.9. 

Laura Carnevali, Marco Paolieri, Fabio Tarani, Emico Vicario and Ku-miko Tadano. Modeling and evaluation of maintenance procedures for gas distribution networks ... 

Modeling and Evaluation of Maintenance Procedures for Gas Distribution Networks with Time-Dependent Parameters... 

Keywords gas distribution networks, non time-homogeneous systems, performance evaluation, Markov regenerative processes, transient stochastic state classes. 

The gas distribution network comprises a kind of hybrid system combining continuous physical variables affecting fluid dynamics (pressure and flow rate) with the temporal behaviour of actions taken to recover from a failure. This duality is coped with by the interaction of two separate models a stochastic model is used to analyse the timings of the failure management procedure (Section 2.1), whereas a fluid-dynamics simulator is used to quantify the lack of service metrics associated with each possible set of boimdary conditions (Section 2.2). 

We illustrate here the gas distribution network considered in the experimental validation (Section 4.1) and we discuss the obtained results (Section 4.2). 

Figure 2 shows a topological representation of the sample gas distribution network analyzed in the experiments. The network has a double-loop topology and is made of a supply node marked as A, six load nodes marked as B through G, and fifteen pipelines. 

Table 1. Mass flow rates of the nodes of the gas distribution network shown in Figure 2 for three different load scenarios...

Fig. 2. Sample gas distribution network. The shaded nodes are supply nodes, while the others are load nodes. The dashed pipe is the one whose failure is considered.

Acknowledgments. We thank Terranova for help in gaining insight of the issues of gas distribution networks, and Regione Toscana for support within the programme FOR CRO FSE 2007-2013 under the specific project Ernesto. We also thank Massimo Nocentini for his contribution in the experimentation stage. 

Carnevali, L., Paoheri, M., Tarani, F., Vicario, E. Quantitative evaluation of availability measures of gas distribution networks. In VALUETOOLS (September 2013)... 

The activity of digging a slit trench at an urban site takes place in a day-work system to extend gas distribution network. The developer knows the working project as well as the detectable local restrictions. There is an almost total ignorance of the local buried infrastructures and from the sustainability conditions of the visible ones. 

Natural gas, liquefied petroleum gas (LPG), and carbon materials serving as the raw materials for cheap technical hydrogen usually contain marked amounts of sulfur compounds. In addition, sulfur-containing odorants (tetrahydrothiophene or ethylmercaptan) often are purposely added to the gas distribution network so that gas leaks may be detected in a timely manner, because natural gas is usually odorless. 

Gas purification to pipeline quality is yet another option. This option involves the conversion of landfill a medium heating value gas, into high heating value gas for local gas distribution networks (h, in compressed form, for vehicular fuel. In 1992, there were 7 sites that upgraded landfill gas to pipeline-quality gas. This option also remains uneconomical as Icmg as the prices of natural gas and fuel oil remain relatively low [16]. 

The steps after biogas generation differ according to the intended use. Direct combustion may be done in engines designed specifically for that purpose. If it is desired that the biogas be fed into the natural gas distribution network, then further purification is necessary. In addition to a few other requirements, the main criterion is that the purity of the methane must be at least 96% (Deublein and Steinhauser, 2008). 

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