COMPOSITION AND PHYSICO-CHEMICAL PROPERTIES OF NATURAL GASES
Natural gases are substances that are gaseous under normal (n.o.) and standard (d.u.) conditions. Depending on the conditions, gases can be in free, adsorbed or dissolved states.
In reservoir conditions, gases, depending on their composition, pressure and temperature (thermobaric regime in the reservoir), can be in different aggregate states - gaseous, liquid, in the form of gas-liquid mixtures.
Free gas usually located in an elevated part of the formation and located in the gas cap. If there is no gas cap in the oil reservoir, then all the gas in the reservoir is dissolved in oil.
The pressure at which the gas in the reservoir begins to separate from the oil is called saturation pressure... The saturation pressure of oil with gas in reservoir conditions is determined by the composition, amount of oil and gas, reservoir temperature.
Dissolved gas, as the pressure decreases during production, is released from the oil. It be called associated gas... In reservoir conditions, all oils contain dissolved gas. The higher the pressure in the formation, the more gas can be dissolved in the oil. In 1 m 3 of oil, the content of dissolved gas can reach 1000 m 3.
Natural gases produced from gas, gas condensate and oil fields consist of hydrocarbons (HC) of the methane series CH 4 –C 4 H 10: methane, ethane, propane, isobutane and n-butane, as well as non-hydrocarbon components: H 2 S, N 2, CO, CO 2, H 2, Ar, He, Kr, Xe and others.
Under normal and standard conditions, thermodynamically in the gaseous state, only hydrocarbons with the composition C 1 –C 4 exist. Under these conditions, alkane hydrocarbons, starting with pentane and higher, are in a liquid state, the boiling point for iso-C 5 is 28 o C, and for n-C 5 → 36 o C. However, hydrocarbons C are sometimes observed in associated gases 5 due to thermobaric conditions, phase transitions and other phenomena.
The qualitative composition of gases of petroleum origin is always the same (which cannot be said about the gases of volcanic eruptions). The quantitative distribution of components is almost always different.
The composition of gas mixtures is expressed as massor volume concentration of componentsin percents and mole fractionx.
where Wi is the mass of the i-th component; ΣWi is the total mass of the mixture.
, (2.16)
where Vi is the volume of the i-th component in the mixture; Σ Vi - total gas volume.
where ni is the number of moles of the i-th component in the mixture; Σпi is the total number of gas moles in the system.
The relationship between the volumetric and molar concentrations of the components follows from avogadro's law... Since equal volumes of any gases at the same temperature and pressure contain the same number of molecules, the volume of the i-th component of the mixture will be proportional to the number of moles of the i-th component:
where K is the coefficient of proportionality. Consequently
, (2.19)
that is, the concentration of a component in percent by mol (% mol.) in a gas mixture at atmospheric pressure practically coincides with the volumetric concentration of this component in percent (% vol.).
At high pressures, liquid hydrocarbons dissolve in the gas phase (gas solutions, gas condensates). Therefore, at high pressures, the density of the gas can approach the density of light hydrocarbon liquids.
Depending on the prevalence of light (methane, ethane) or heavy (propane and higher) hydrocarbons in petroleum gases, the gases are separated into dry and greasy.
Drynatural gas is called gas, which does not contain heavy hydrocarbons or contains them in small quantities.
Bold gas is a gas containing heavy hydrocarbons in such quantities when it is advisable to obtain from it liquefied gases or natural gasoline.
Gases extracted from purely gas deposits, contain more than 95% methane (Table 2.2) and represent the so-called dry gases.
INTRODUCTION
1.1.1 The course project (gas supply to the village of Kinzebulatovo) was developed on the basis of the general plan of the settlement.
1.1.2 When developing a project, the requirements of the main regulatory documents are taken into account:
- updated edition of SNiP 42-01 2002 "Gas distribution networks".
- SP 42-101 2003 "General provisions for the design and construction of gas distribution systems from metal and polyethylene pipes."
- GOST R 54-960-2012 “Gas control block stations. Cabinet-type gas reduction points ”.
1.2 General information about the locality
1.2.1 There are no industrial and public utility companies on the territory of the settlement.
1.2.2 The settlement is built up with one-storey buildings. The village does not have centralized heating and centralized hot water supply.
1.2.3 Gas distribution systems in the territory of the settlement are made underground from steel pipes. Modern gas distribution systems are a complex complex of structures, consisting of the following main elements of gas ring, dead-end and mixed networks of low, medium, high pressure, laid on the territory of a city or other settlement within blocks and inside buildings, on highways - on the highways of gas control stations (GRS).
DESCRIPTION OF THE CONSTRUCTION AREA
2.1 General information about the settlement
Kinzebulatovo, Kinzebulat (head. Kinyәbulat) - a village in the Ishimbay region of the Republic of Bashkortostan, Russia.
Administrative center of the rural settlement "Baiguzinsky village council".
The population is about 1,000 people. Kinzebulatovo is located 15 km from the nearest city - Ishimbay - and 165 km from the capital of Bashkortostan - Ufa.
Consists of two parts - a Bashkir village and a former oil industry settlement.
The Tyruk River flows.
There is also the Kinzebulatovskoye oil field.
Agribusiness - Association of Peasant Farms "Udarnik"
CALCULATION OF NATURAL GAS COMPOSITION
3.1 Features gas fuel
3.1.1 Natural gas has a number of advantages over other fuels:
- low cost;
- high heat of combustion;
- long-distance transportation of gas through main gas pipelines;
- complete combustion facilitates the working conditions of personnel, maintenance gas equipment and networks,
- the absence of carbon monoxide in the gas, which makes it possible to avoid poisoning in the event of a leak;
- gas supply to cities and towns significantly improves the condition of their air basin;
- the ability to automate combustion processes to achieve high efficiency;
- less emission when burning harmful substances than when burning solid or liquid fuels.
3.1.2. Natural gas fuels are composed of combustible and non-combustible components. The more combustible part of the fuel, the greater the specific heat of combustion. The combustible part or organic mass includes organic compounds, which include carbon, hydrogen, oxygen, nitrogen, sulfur. The non-combustible part consists of the hall and moisture. The main components of natural gas are methane СН 4 from 86 to 95%, heavy hydrocarbons С m Н n (4-9%), ballast impurities are nitrogen and carbon dioxide. The methane content in natural gases reaches 98%. The gas is colorless and odorless, so it is odorized. Natural combustible gases according to GOST 5542-87 and GOST 22667-87 consist mainly of methane hydrocarbons.
3.2 Combustible gases used for gas supply. Physical properties of gas.
3.2.1 Natural artificial gases are used for gas supply in accordance with GOST 5542-87, the content of harmful impurities in 1 g / 100m 3 of gas should not exceed:
- hydrogen sulfide - 2g;
- ammonia - 2g;
- cyanide compounds - 5;
- resin and dust - 0.1g;
- naphthalene - 10g. summer and 5y. in winter.
- gases from purely gas fields. They consist mainly of methane, are dry or lean (no more than 50 g / m 3 propane and above);
- associated gases of oil fields, contain a large amount of hydrocarbons, usually 150 g / m 3, are fat gases, it is a mixture of dry gas, propane-butane fraction and gasoline.
- gases from condensate fields, it is a mixture of dry gas and condensate. Condensate vapors are a mixture of heavy hydrocarbon vapors (gasoline, naphtha, kerosene).
3.2.3. Calorific value of gas, purely gas fields, from 31000 to 38000 kJ / m 3, and associated gases of oil fields from 38000 to 63000 kJ / m 3.
3.3 Calculation of the composition of natural gas from the Proletarskoye field
Table 1-Gas composition of the Proletarskoye field
3.3.1 Net calorific value and density of natural gas components.
3.3.2 Calculation of the calorific value of natural gas:
0.01 (35.84 * CH 4 + 63.37 * C 2 H 6 + 93.37 * C 3 H 8 + 123.77 * C 4 H 10 + 146.37 * C 5 H 12), (1 )
0.01 * (35.84 * 86.7+ 63.37 * 5.3+ 93.37 * 2.4 + 123.77 * 2.0+ 146.37 * 1.5) \u003d 41.34 MJ / m 3.
3.3.3 Determination of the density of gas fuel:
Gas \u003d 0.01 (0.72 * CH 4 + 1.35 * C 2 H 6 + 2.02 * C 3 H 8 + 2.7 * C 4 H 10 + 3.2 * C 5 H 12 +1.997 * C0 2 + 1.25 * N 2); (2)
Gas \u003d 0.01 * (0.72 * 86.7 + 1.35 * 5.3 + 2.02 * 2.4 + 2.7 * 2.0 + 3.2 * 1.5 + 1.997 * 0 , 6 +1.25 * 1.5) \u003d 1.08 kg / N 3
3.3.4 Determination of the relative density of gaseous fuel:
where air is 1.21-1.35 kg / m 3;
ρ rel 
, (3)
3.3.5 Determination of the amount of air required for combustion of 1 m 3 of gas theoretically:
[(0.5CO + 0.5H 2 + 1.5H 2 S + ∑ (m +) C m H n) - 0 2]; (four)
V \u003d ((1 +) 86.7 + (2 +) 5.3 + (3 +) 2.4 + (4 +) 2.0 + (5 +) 1.5 \u003d 10.9 m 3 / m 3;
V \u003d \u003d 1.05 * 10.9 \u003d 11.45 m 3 / m 3.
3.3.6 The characteristics of gaseous fuel determined by the calculation are summarized in Table 2.
Table 2 - Gas fuel characteristics
| Q MJ / m 3 | R gas kg / N 3 | R rel. kg / m 3 | V m 3 / m 3 | V m 3 / m 3 |
| 41,34 | 1,08 | 0,89 | 10,9 | 11,45 |
GAS PIPELINE ROUTING
4.1 Classification of gas pipelines
4.1.1 Gas pipelines laid in cities and towns are classified according to the following indicators:
–By the type of transported natural gas, associated gas, petroleum gas, liquefied hydrocarbon gas, artificial gas, mixed gas;
- by gas pressure of low, medium and high (I category and II category); –For the deposit relative to the ground: underground (underwater), aboveground (above water);
- by location in the planning system of cities and settlements, external and internal;
–On the principle of construction (distribution gas pipelines): loopback, dead-end, mixed;
- according to the pipe material, metal, non-metal.
4.2 Selection of the gas pipeline route
4.2.1 The gas distribution system can be reliable and economical with the right choice of routes for laying gas pipelines. The choice of the route is influenced by the following conditions: distance to gas consumers, direction and width of passages, type of road surface, presence of various structures and obstacles along the route, terrain, layout
quarters. Gas pipelines are selected taking into account the transportation of gas by the shortest route.
4.2.2 From street gas pipelines, inlets are laid into each building. In urban areas with a new layout, gas pipelines are located within blocks. When routing gas pipelines, it is necessary to observe the distance of gas pipelines from other structures. It is allowed to lay two or more gas pipelines in one trench at the same or different levels (steps). In this case, the distance between the gas pipelines in the light should be sufficient for the installation and repair of pipelines.
4.3 Basic provisions for laying gas pipelines
4.3.1 Laying of gas pipelines should be carried out at a depth of at least 0.8 m to the top of the gas pipeline or case. In places where the movement of vehicles and agricultural machinery is not foreseen, the depth of laying steel gas pipelines is allowed at least 0.6 m.On landslide and erosion-prone areas, laying gas pipelines should be provided for a depth of at least 0.5 m below the sliding surface and below the predicted boundary. area of \u200b\u200bdestruction. In justified cases, it is allowed to lay gas pipelines on the ground along the walls of buildings inside residential yards and quarters, as well as on bleaching sections of the route, including on sections of transitions through artificial and natural barriers when crossing underground utilities.
4.3.2 Aboveground and aboveground gas pipelines with embankment can be laid in rocky, permafrost soils, in swampy areas and under other difficult soil conditions. The material and dimensions of the embankment should be taken based on the heat engineering calculation, as well as ensuring the stability of the gas pipeline and the embankment.
4.3.3 Laying gas pipelines in tunnels, collectors and channels is not allowed. Exceptions are the laying of steel gas pipelines with a pressure of up to 0.6 MPa on the territory of industrial enterprises, as well as in channels of permafrost soils under roads and railways.
4.3.4 Pipe connections should be provided as one-piece. Connections of steel pipes with polyethylene pipes can be detachable and in places where fittings, equipment and instrumentation are installed. Detachable joints of polyethylene pipes with steel pipes in the ground can only be provided if a case with a control tube is installed.
4.3.5 Gas pipelines at the points of entry and exit from the ground, as well as gas pipelines inlets to buildings should be enclosed in a case. In the space between the wall and the case, the entire thickness of the structure to be crossed should be sealed. The ends of the case should be sealed with an elastic material. Entries of gas pipelines into buildings should be provided directly for the room where the gas-using equipment is installed, or adjacent rooms connected by a covered opening. It is not allowed to enter gas pipelines into the premises of the basement and basement floors of buildings, except for the entries of natural gas pipelines into single-family and blocked houses.
4.3.6 The disconnecting device on gas pipelines should be provided for:
- in front of detached blocked buildings;
- to disconnect risers of residential buildings above five floors;
- in front of outdoor gas-using equipment;
- in front of gas control points, except for the hydraulic fracturing of the enterprise, at the branch of the gas pipeline to which there is a disconnecting device at a distance of less than 100 m from the hydraulic fracturing;
- at the exit from gas control points, looped gas pipelines;
- on branches from gas pipelines to settlements, separate microdistricts, quarters, groups of residential buildings, and with more than 400 apartments, to a separate house, as well as on branches to industrial consumers and boiler houses;
- when crossing water barriers with two or more lines, as well as one line with a water barrier width with a low water level of 75 m or more;
- at the intersection of railways of the general network and highways of 1–2 categories, if a disconnecting device ensuring the cessation of gas supply at the crossing section located at a distance of more than 1000 m from the roads.
4.3.7 Disconnecting devices on overground gas pipelines,
laid along the walls of buildings and on supports should be placed at a distance (within a radius) from door and opening window openings at least:
- for low pressure gas pipelines - 0.5 m;
- for gas pipelines of medium pressure - 1 m;
- for high-pressure gas pipelines of the second category - 3 m;
- for high-pressure gas pipelines of the first category - 5 m.
Installation of disconnecting devices on the sections of transit laying of gas pipelines along the walls of buildings is not allowed.
4.3.8 The vertical distance (in the light) between the gas pipeline (case) and underground utilities and structures at their intersection should be taken taking into account the requirements of the relevant regulatory documents, but not less than 0.2 m.
4.3.9 At the intersection of gas pipelines with underground utilities, collectors and channels for various purposes, as well as at the places where gas pipelines pass through the walls of gas wells, the gas pipeline should be laid in a case. The ends of the case should be brought out at a distance of at least 2 m in both directions from the outer walls of the structures and communications being crossed, when crossing the walls of gas wells - at a distance of at least 2 cm. The ends of the case should be sealed with waterproofing material. At one end of the case, at the upper points of the slope (with the exception of the intersections of the walls of the wells), a control tube should be provided that goes under the protective device. In the annular space of the case and the gas pipeline, it is allowed to lay a service cable (communication, telemechanics and electrical protection) with a voltage of up to 60V, intended for servicing gas distribution systems.
4.3.10 Polyethylene pipes used for the construction of gas pipelines must have a safety factor for GOST R 50838 of at least 2.5.
4.3.11 Laying of gas pipelines from polyethylene pipes is not allowed:
- on the territory of settlements at a pressure of over 0.3 MPa;
- outside the territory of settlements at a pressure of over 0.6 MPa;
- for transportation of gases containing aromatic and chlorinated hydrocarbons, as well as the liquid phase of LPG;
- at a gas pipeline wall temperature under operating conditions below –15 ° С.
When using pipes with a safety factor of at least 2.8, it is allowed to lay polyethylene gas pipelines with a pressure of more than 0.3 to 0.6 MPa in the territories of a settlement with mainly one-two-story and cottage residential buildings. On the territory of small rural settlements, it is allowed to lay polyethylene gas pipelines with a pressure of up to 0.6 MPa with a safety factor of at least 2.5. In this case, the laying depth should be at least 0.8 m to the top of the pipe.
4.3.12 The strength analysis of gas pipelines should include the determination of the wall thickness of pipes and fittings and the stresses in them. At the same time, pipes and fittings with a wall thickness of at least 3 mm should be used for underground and surface steel gas pipelines, for aboveground and internal gas pipelines - at least 2 mm.
4.3.13 Characteristics of limiting states, reliability factors for liability, standard and calculated values \u200b\u200bof loads and effects and their combinations, as well as standard and calculated values \u200b\u200bof characteristics of materials should be taken in calculations taking into account the requirements of GOST 27751.
4.3.14 During construction in areas with difficult geological conditions and seismic effects, special requirements must be taken into account and measures must be taken to ensure the strength, stability and tightness of gas pipelines. Steel gas pipelines must be protected against corrosion.
4.3.15 Underground and surface steel pipelines with embankments, LPG tanks, steel inserts for polyethylene gas pipelines and steel cases on gas pipelines (hereinafter referred to as gas pipelines) should be protected against soil corrosion and corrosion by stray currents in accordance with the requirements of GOST 9.602.
4.3.16 Steel cases of gas pipelines under roads, railways and tramways during trenchless laying (puncture, punching and other technologies permitted for use) must, as a rule, be protected by means of electrical protection (3X3), when laid in an open way - by insulating coatings and 3X3.
4.4 Selection of material for the gas pipeline
4.4.1 For underground gas pipelines, polyethylene and steel pipes... For aboveground and aboveground gas pipelines, steel pipes should be used. For internal low pressure gas pipelines, it is allowed to use steel and copper pipes.
4.4.2 Steel seamless, welded (longitudinal and spiral seam) pipes and fittings for gas distribution systems should be made of steel containing not more than 0.25% carbon, 0.056% sulfur and 0.04% phosphorus.
4.4.3 The choice of material for pipes, pipeline valves, fittings, welding materials, fasteners and others should be made taking into account the gas pressure, the diameter and thickness of the gas pipeline wall, the design temperature of the outside air in the construction area and the temperature of the pipe wall during operation, ground and natural conditions, the presence of vibration loads.
4.5 Overcoming natural obstacles with a gas pipeline
4.5.1 Overcoming natural obstacles by gas pipelines. Natural obstacles are water barriers, ravines, gorges, gullies. Gas pipelines at underwater crossings should be laid with deepening into the bottom of the crossed water barriers. If necessary, according to the results of calculations for ascent, it is necessary to ballast the pipeline. The elevation of the top of the gas pipeline (ballast, lining) should be at least 0.5 m, and at crossings through navigable and floatable rivers - 1.0 m lower than the predicted bottom profile for a period of 25 years. When performing works by the method of directional drilling - not less than 20 m below the predicted bottom profile.
4.5.2 At underwater crossings the following should be applied:
- steel pipes with a wall thickness of 2 mm more than the calculated one, but not less than 5 mm;
– polyethylene pipeshaving a standard dimensional ratio of the outer diameter of the pipe to the wall thickness (SDR) of no more than 11 (according to GOST R 50838) with a safety factor of at least 2.5.
4.5.3 The height of the laying of the above-water passage of the gas pipeline from the design level of the rise of water or ice drift (high water horizon - GVV or ice drift - GVL) to the bottom of the pipe or superstructure should be taken:
- at the intersection of ravines and beams - not less than 0.5 m and above the GVV 5% coverage;
- when crossing non-navigable and non-floating rivers - at least 0.2 m above the GWV and GVL of 2% supply, and if there is a grubber on the rivers - taking it into account, but not less than 1 m above the GWV of 1% supply;
- when crossing navigable and floating rivers - not less than the values \u200b\u200bestablished by the design standards for bridge crossings on navigable rivers.
4.5.4 Shut-off valves should be placed at a distance of at least 10 m from the border of the crossing. For the border of the crossing are taken the places where the gas pipeline crosses the high water horizon with 10% coverage.
4.6 Crossing artificial obstacles with a gas pipeline
4.6.1 Crossing artificial obstacles by gas pipelines. Artificial obstacles are highways, railways and tramways, as well as various embankments.
4.6.2 The horizontal distance from the intersection of underground gas pipelines tram and railway tracks and highways must be at least:
- to bridges and tunnels on public railways, tramways, highways of 1 - 3 categories, as well as to pedestrian bridges, tunnels through them - 30 m, and for non-public railways, highways of 4 - 5 categories and pipes - 15m;
- to the zone of the turnout transport (the beginning of the wits, the tail of the crosses, the points of connection to the rails of the suction cables and other crossings of the track) - 4m for tram tracks and 20m for the railways
- up to the overhead supports - 3m.
4.6.3 It is allowed to reduce the specified distances in agreement with the organizations in charge of the crossed structures.
4.6.4 Underground gas pipelines of all pressures at intersections with railway and tram tracks, highways of categories 1 - 4, as well as main streets of city-wide importance should be laid in cases. In other cases, the question of the need for the device of the cases is decided by the design organization.
4.7 Cases
4.7.1 Cases must meet the conditions of strength and durability. A test tube should be provided at one end of the case, which extends under the protective device.
4.7.2 When laying inter-settlement gas pipelines in cramped conditions and gas pipelines on the territory of settlements, it is allowed to reduce this distance to 10 m, provided that an exhaust plug with a sampling device is installed at one end of the case, brought out at a distance of at least 50 m from the edge of the roadbed (the axis of the extreme rail at zero marks). In other cases, the ends of the cases should be spaced at a distance:
- not less than 2 m from the end rail of the tramway and railways, potassium 750 mm, as well as from the edge of the carriageway of streets;
- not less than 3m from the edge of the drainage structure of roads (ditch, ditch, reserve) and from the extreme rail of non-public railways, but not less than 2m from the foot of the embankments.
4.7.3 The depth of laying the gas pipeline from the foot of the rail or the top of the road surface, and in the presence of an embankment, from its bottom to the top of the case, must meet safety requirements, be not less than:
- when performing work by an open method - 1.0 m;
- when performing work by punching shear or directional drilling and shield laying - 1.5 m;
- when performing work by the puncture method - 2.5 m.
4.8. Crossing pipes with roads
4.8.1 The thickness of the walls of the pipes of a steel gas pipeline when it crosses public railways should be 2 - 3 mm more than the calculated one, but not less than 5 mm at distances of 50 m in each direction from the edge of the roadbed (the axis of the outer rail at zero marks).
4.8.2 For polyethylene gas pipelines in these sections and at the intersections of highways of categories 1 - 3, polyethylene pipes of no more than SDR 11 with a safety factor of at least 2.8 should be used.
4.9 Corrosion protection of pipelines
4.9.1 Pipelines used in gas supply systems are usually made of carbon and low-alloy steels. The service life and reliability of pipelines are largely determined by the degree of protection against destruction upon contact with the environment.
4.9.2 Corrosion is the destruction of metals caused by chemical or electrochemical processes when interacting with the environment. The environment in which metal corrodes is called corrosive or corrosive.
4.9.3 The most relevant for underground pipelines is electrochemical corrosion, which obeys the laws of electrochemical kinetics, this is the oxidation of metal in conductive media, accompanied by the formation and flow of electric current. In this case, interaction with the environment is characterized by cathodic and anodic processes occurring on different sites metal surface.
4.9.4 All underground steel pipelines laid directly into the ground are protected in accordance with GOST 9.602-2005.
4.9.5 In soils of medium corrosive activity in the absence of stray currents, steel pipelines are protected by insulating coatings of "very reinforced type", in soils of high corrosiveness of the dangerous influence of stray currents - by protective coatings of "very reinforced type" with the obligatory use of 3X3.
4.9.6 All envisaged types of corrosion protection are put into operation by distributing underground pipelines into operation. For underground steel pipelines in zones of hazardous influence of stray currents, 3X3 is put into operation no later than 1 month, and in other cases later than 6 months after laying the pipeline in the ground.
4.9.7 The corrosiveness of soil towards steel is characterized in three ways:
- the specific electrical resistance of the soil, determined in field conditions;
- specific electrical resistance of soil, determined in laboratory conditions,
- the average density of the cathodic current (j k) required to displace the potential of steel in the soil by 100 mV more negative than the stationary one (corrosion potential).
4.9.8 If one of the indicators indicates a high aggressiveness of the soil, then the soil is considered aggressive, and the determination of the remaining indicators is not required.
4.9.9 The dangerous influence of a stray direct current on underground steel pipelines is the presence of a changing in sign and in magnitude of the displacement of the pipeline potential in relation to its stationary potential (sign-alternating zone) or the presence of only a positive displacement of the potential, which, as a rule, varies in magnitude (anode zone) ... For the designed pipelines, the presence of stray currents in the ground is read as dangerous.
4.9.10 The dangerous effect of alternating current on steel pipelines is characterized by a displacement of the average potential of the pipeline in the negative direction by at least 10 mV in relation to the stationary potential, or the presence of alternating current with a density of more than 1 MA / cm 2. (10 A / m 2.) On the auxiliary electrode.
4.9.11 The use of 3X3 is mandatory:
- when laying pipelines in soils with high corrosive aggressiveness (protection against soil corrosion),
- in the presence of a dangerous influence of constant stray and alternating currents.
4.9.12 When protecting against soil corrosion, cathodic polarization of underground steel pipelines is carried out in such a way that the average value of the polarization potentials of the metal is within the range of –0.85V. up to 1.15V on a saturated copper-sulfate electrode in comparison (m.s.e.).
4.9.13 Insulation work in route conditions is performed manually when insulating prefabricated joints and small fittings, correcting damage to the coating (no more than 10% of the pipe area) that occurred during the transportation of pipes, as well as during the repair of pipelines.
4.9.14 When repairing damage to the factory insulation on site, laying the gas pipeline, it must be ensured that the technology and technical capabilities of coating and control of its quality are observed. All works on the repair of the insulating coating are reflected in the passport of the gas pipeline.
4.9.15 Polyethylene, polyethylene tapes, bitumen and bitumen-polymer mastics, fused bitumen-polymer materials, roll mastic-tape materials, compositions based on chlorosulfonated polyethylene, polyester resins and polyurethanes are recommended as the main materials for the formation of protective coatings.
DETERMINATION OF GAS FLOWS
5.1 Gas consumption
5.1.1 Gas consumption by network sections can be conditionally divided into:
track, transit and dispersed.
5.1.2 Path flow rate is a flow rate that is evenly distributed along the length of a section or the entire gas pipeline, equal or very close in magnitude. It can be selected through the same size and for ease of calculation, it is evenly distributed. Usually this consumption is consumed by the same type of gas appliances, for example, capacitive or instantaneous water heaters, gas stoves etc. Lumped flow rates are those that pass through the pipeline, without changing, along the entire length and are sampled at certain points. The consumers of these costs are: industrial enterprises, boiler houses with a constant consumption for a long time. Transit costs are those that pass through a certain section of the network without changing, and provide gas consumption, to the next section, being for it track or concentrated.
5.1.2 Gas consumption in the settlement is travel or transit. There are no concentrated gas expenditures, since there are no industrial enterprises. Travel costs are made up of the costs of gas appliances installed by consumers, and depends on the season of the year. The apartment has four Glem UN6613RX burner plates with a gas flow rate of 1.2 m 3 / h, a Vaillant instantaneous water heater for hot flow with a flow rate of 2 m 3 / h, Viessmann Vitocell-V 100 CVA- 300 "with a flow rate of 2.2 m 3 / h.
5.2 Gas consumption
5.2.1 Gas consumption changes by hours, days, days of the week, months of the year. Depending on the t period during which, gas consumption is taken to be constant, they are distinguished: seasonal irregularity or irregularity in the months of the year, daily irregularity or irregularity in the days of the week, hourly irregularity or irregularity in the hours of the day.
5.2.2 Unevenness of gas consumption is associated with seasonal climatic changes, operating mode of enterprises during the season, week and day, characteristics of gas equipment of various consumers, studies of unevenness are built stepwise gas flow rates over time. To regulate the seasonal unevenness of gas consumption, the following methods are used:
- underground gas storage;
- the use of consumers of regulators that dump surpluses in the summer;
- reserve fields and gas pipelines.
5.2.3 To regulate the unevenness of gas consumption in the winter months, gas is taken from underground storage facilities, and in a short period of the year, it is pumped into underground storage facilities. To cover daily peak loads, the use of underground storage facilities is not economical. In this case, restrictions are imposed on gas supply to industrial enterprises and peak coverage stations are used, in which gas liquefaction occurs.
Page 1
Chemical composition natural gases heterogeneous and depends on the conditions of their formation and location in the sedimentary strata.
The chemical composition of natural gases is so simple that obtaining their substitutes, which have not only the appropriate characteristics, but also almost identical composition, does not require special technical solutions and excessive capital expenditures. An exception to this rule is hydrogen - a gas that can replace the depleting natural reserves of natural gas in the future. Since the goal of fossil fuel gasification is to produce methane, in the absence of hydrocarbon fuels, hydrogen could become an acceptable substitute for natural gas, which has a number of additional valuable characteristics, from which all natural gases mainly consist.
The chemical composition of natural gases is measured by an automatic gas chromatograph. The accuracy of these measurements is such that it makes it possible to calculate the basic physical characteristics with a small error, which, therefore, can be determined not directly, but by recalculation.
The chemical composition of natural gas obtained by cement plants from main gas pipelines may change not only for the indicated reasons, but also due to the fact that main gas pipelinescoming from different deposits are interconnected.
The chemical composition of natural gas is the same as shown on p.
The chemical composition of natural gases is not the same, but their main constituent is methane. Saratov gas contains 94 3%, Kuibyshevsky - 74 6%, Dashavsky - 98%; in gases from different regions of Dagestan, Kerch, Baku, Melitopol, Ukhta - from 80 to 98% of methane. The content of higher hydrocarbons is insignificant: from fractions of a percent to several percent. The composition of gases in some areas may be different in different layers, as, for example, in the gases of the Maikop and Dagestan fields.
The influence of the chemical composition of natural gas on its combustion temperature was described in Chapter I. An increase in the temperature of the air entering the rotary kiln significantly increases the flame temperature, but to a lesser extent than the amount of air heating.
If differences in the chemical composition of natural gases accumulated in different traps in a basin are mainly determined by the ability of each trap to retain more or less mobile components of gases, then determining the composition of carbon isotopes in methane from these gases can become a valuable tool for better assessing the conditions for trapping gases in different reservoirs. ...
The fractional composition of the limestone of the Yelenovskoye field and the chemical composition of natural gas are given on p.
Gas chromatography is one of the main methods for studying the chemical composition of natural gases, oils and condensates. The use of this effective and highly sensitive method allows not only to evaluate gas, oil, condensate as a chemical raw material, but also to obtain new geochemical indicators characterizing oil-producing rocks and oil-generating zones.
Gases containing more than 100 g of heavy hydrocarbon gases (ethane, propane, etc.) in 1 m3 are called rich, and less than 100 g are called dry. The chemical composition of natural gases depends on the type of field.
Natural gases, depending on the fields, can be dry and gas condensate. The chemical composition of natural gas from different fields is not the same.
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