Physico-chemical properties of natural gases. Calculation of gas mixture
Introduction
1.1 General
1.1.1 Currency project (gas supply of the village of Kinshebulatovo) 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:
- Actualized edition 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 "Points of gas regulatory blocks. Reducing items of the Cabinet gas. "
1.2 General information about the settlement
1.2.1 There are no 1.2.1 in the territory of the settlement of industrial and utilities.
1.2.2 The settlement is built up with one storey houses. There is no centralized heating and centralized hot water in the settlement.
1.2.3 Gas distribution systems on the territory of the settlement are carried out underground steel pipes. Modern distribution systems of gas supply are a complex complex of structures consisting of the following basic elements of gas ring, dead-end and mixed networks of low, medium, high pressure, laid in the city or other settlement within the quarters and inside buildings, on highways - on highways of gas management stations (GRS).
Characteristics of the construction district
2.1 General information about the settlement
Kinzebulatovo, Kinzebulat (Bashka. Kinyәbulat) - Village in Ishimbay district of the Republic of Bashkortostan, Russia.
Administrative center of the rural settlement "Bayguzinsky village council".
The population is about 1 thousand people. Kinshebulatovo is 15 km from the nearest city - Ishimbaya - and 165 km from the capital Bashkortostan - Ufa.
It consists of two parts - the Bashkir village and the former settlement village.
Toruk river flows.
There is also a Kinsebulatovskaya oil field.
Agrobusiness - Association of Peasant Farm "Drikher"
Calculation of the characteristics of the composition of natural gas
3.1 Features of gas fuel
3.1.1 Natural gas has a number of advantages compared with other types of fuel:
- low cost;
- high heat of combustion;
- transportation of gas mains gas pipelines for long distances;
- Full combustion makes it easy to the condition of the staff, maintenance of gas equipment and networks,
- the absence of carbon oxide gas in the composition, which makes it possible to avoid poisoning when leakage;
- gas supply of cities and settlements significantly improves the state of their air basin;
- the ability to automate the combustion processes of the achievement of high efficiency;
- Less release when burning harmful substances than when burning solid or liquid fuel.
3.1.2. Natural gas fuel consists of combustible and non-combustible components. The greater the fuel part of the fuel, the greater the specific heat of its combustion. The combustible part or organic mass includes organic compounds, which includes carbon, hydrogen, oxygen, nitrogen, sulfur. The non-combustible part of CO is from the hall and moisture. The main components of natural hectares for is methane CH 4 from 86 to 95%, severe hydrocarbons with M H n (4-9%), ballast impurities are nitrogen and carbon dioxide. The content of methane in natural gases reaches 98%. Gas has no color, no smell, so it is odoring it. Natural combustible gases according to GOST 5542-87 and GOST 22667-87 consists mainly of hydrocarbons of the methane row.
3.2 Combustible gases used by gas supply. Physical properties of gas.
3.2.1 For gas supply, natural artificial gases are used according to GOST 5542-87. The content of harmful impurities in 1 g / 100 m 3 gas should not exceed:
- hydrogen sulfide - 2g;
- ammonia - 2g;
- cyanide compounds - 5;
- resins and dust- 0.1g;
- Naphthalene - 10g. in summer and 5g. in winter.
- Gases of pure gas deposits. Consist mainly of methane, are dry or torshi (no more than 50 g / m 3 propane and higher);
- associated gases of petroleum fields, contain a large amount of hydrocarbons, usually 150 g / m 3, are fatty gases, this is a mixture of dry gas, propane - butan fraction and gas gasoline.
- Gaza condensate deposits, this is a mixture of dry gas and condensate. Condensate pairs are a mixture of heavy hydrocarbon steam (gasoline, ligroin, kerosene).
3.2.3. The calorific value of the gas, pure gas fields, from 31,000 to 38,000 kJ / m 3, and the passing gas of oil fields from 38,000 to 63,000 kJ / m 3.
3.3 Calculation of the composition of Natural Gas Deposit Proletarian
Table 1-composition gas field Proletarian
3.3.1 Lowest heat combustion and density of natural gas components.
3.3.2 Calculation of heat combustion 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 gas fuel density:
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 gas fuel density:
where the remuneration is 1.21-1.35 kg / m 3;
ρ relative 
, (3)
3.3.5 Definitions of the amount of air required for incineration 1 m 3 of gas Theoretically:
[(0.5 o + 0.5 n 2 + 1.5H 2 S + σ (M +) with 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 calculation of gas fuel defined by the calculation will be reduced to Table 2.
Table 2 - Gas Fuel Characteristics
| Q mj / m 3 | P gas kg / n 3 | P rel. kg / m 3 | V m 3 / m 3 | V m 3 / m 3 |
| 41,34 | 1,08 | 0,89 | 10,9 | 11,45 |
Tracing gas pipeline
4.1 Classification of gas pipelines
4.1.1 Gas pipelines deployed in cities and settlements are classified according to the following indicators:
- view of the transported gas of natural, associated, oil, liquefied hydrocarbon, artificial, mixed;
- pressure of low, medium and high gas gas (I category I and II); - Deposit relative to the Earth: underground (underwater), overhead (surface);
-The location in the system of planning cities and settlements is external and internal;
- By the principle of construction (distribution gas pipelines): flakes, dead-end, mixed;
- Metal pipe materials, non-metallic pipes.
4.2 Choosing a gas pipeline
4.2.1 The gas distribution system may be reliable and economical with the right choice of routes for laying gas pipelines. The following conditions are influenced by the following conditions: distance to consumers of gas, direction and travel width, view of the road surface, presence along the route of various structures and obstacles, terrain, planning
quarters. The routes of gas pipelines are chosen taking into account the gas transportation by the shortest way.
4.2.2 From street gas pipelines in each building, put inputs. In urban areas with a new layout, gas pipelines are located within the quarters. When tracing gas pipelines it is necessary to observe the distance of gas pipelines from other structures. A laying of two or more gas pipelines in one trench at one or different levels (steps) is allowed. At the same time, the distance between gas pipelines in the light should be provided sufficient for the installation and repair of pipelines.
4.3 Basic provisions when laying gas pipelines
4.3.1 Gas pipeline laying should be carried out at a depth of at least 0.8 m to the top of the gas pipeline or case. In those places where the movement of transport and agricultural machinery is not envisaged, the depth of steel gas pipelines is allowed at least 0.6 m. On landslide and erosion exposed areas of gas pipelines should be provided for a depth of at least 0.5 m below the sliding mirror and below the projected border Section of destruction. Based on the ground-based gas pipelines on the walls of the buildings inside the residential courtyards and quarters, as well as on the whitening areas of the route, including in the sections of transitions through artificial and natural barriers when crossing underground communications.
4.3.2 Overhead and terrestrial gas pipelines with fading can be laid in rock, multi-nesting grounds, in wetlands and with other complex primer conditions. Material and disbelief dimensions should be taken on the basis of the heat engineering calculation, as well as ensuring the sustainability of the gas pipeline and obmissions.
4.3.3 Laying gas pipelines in tunnels, manifolds and channels is not allowed. Exceptions make up the laying of steel gas pipelines by pressing up to 0.6 MPa in the territory of industrial enterprises, as well as the channels of multi-neuroprous soils under road and railways.
4.3.4 Pond compounds should be provided with all-in-disposal. Connectors can be connections from steel pipes with polyethylene and in places of installation of fittings, equipment and instrumentation (instrumentation). The detachable compounds of polyethylene pipes with steel in the ground can only be provided with a case of a case with a control tube.
4.3.5 Gas pipelines in the entrance and exit places, as well as the inputs of gas pipelines in the building should be included in the case. In the space between the wall and the case, it is necessary to close the entire thickness of the crossed design of the case of the case, one should be sealed with an elastic material. The inputs of gas pipelines in the building should be provided directly to the room where gas-wide equipment is installed, or adjacent rooms connected from the indoor opening. Gas pipelines are not allowed into the premises of basement and basement floors of buildings, except for the introductions of gas pipelines of natural gas into single-welter and blocked houses.
4.3.6 A disconnecting device on gas pipelines should be provided:
- Before detached blocking buildings;
- to disable residential buildings above five floors;
- in front of the outer gas - exploratory equipment;
- Before gas regulatory points, with the exception of the enterprise in the enterprise, on the branch of the gas pipeline to which there is a disconnecting device at a distance less than 100m o T GRP;
- at the exit of gas regulatory items, chased gas pipelines;
- on the branches of the gas pipelines to settlements, individual neighborhoods, quarters, groups of residential buildings, and with the number of apartments more than 400 and to a separate house, as well as on branches of industrial consumers and boiler houses;
- when crossing water obstacles with two threads and more, as well as one thread with the width of the water barrier during the meal horizon 75m and more;
- When crossing the railways of the total network and highways 1-2, if the disconnecting device, which ensures the cessation of gas supply on the transition site located at a distance from the roads of more than 1000 m.
4.3.7 Disconnecting devices on overhead gas pipelines,
passed along the walls of the buildings and on the supports, one should be placed at a distance (within the radius) from the door and opening window openings at least:
- for gas pipelines of the bottom of the pressure - 0.5 m;
- for medium pressure gas pipelines - 1 m;
- for high pressure gas pipelines of the second category - 3 m;
- For high pressure gas pipelines of the first category - 5 m.
In the sections of the transit gas pipeline of gas pipelines on the walls of the buildings, the installation of non-shut-off devices is not allowed.
4.3.8 The vertical distance (in light) between the gas pipeline (case) and underground engineering communications and structures in the places of 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 In places intersection of gas pipelines with underground communications, manifolds and channels of various purposes, as well as in places of passage of gas pipelines through the walls of gas wells, the gas pipeline should be laid in a case. The ends of the case should be excreted at least 2 m. In both sides of the outer walls of intersected structures and communication, when the walls of gas wells are crossing the walls - at a distance of at least 2 cm. The ends of the case must be taken by waterproofing material. At one end of the case in the upper points of the slope (with the exception of the places of intersection of the walls of the wells), it is necessary to provide a control tube exiting a protective device. In the interlock space of the case and the gas pipeline, the operational cable (communication, telemechanics and electrobatic) lines (communications, telemechanics and electrobatic) is allowed to 60V, the maintenance of gas distribution systems is intended.
4.3.10 Polyethylene pipes used by the construction of gas pipelines must have a strength factor at GOST R 50838 at least 2.5.
4.3.11 Polyethylene pipe gas pipelines are not allowed:
- in the territory of the settlements at a pressure of over 0.3 MPa;
- beyond the territory of the settlements at a pressure of over 0.6 MPa;
- for transporting gases containing aromatic and chlorinated hydrocarbons, as well as the liquid phase of the SUG;
- at the wall temperature of the gas pipeline under operating conditions below -15 ° C.
When using pipes with a strength factor of at least 2.8, laying of polyethylene gas pipelines with pressure over 0.3 to 0.6 MPa in the territories of settlement with a predominantly one - two-story and cottage residential buildings. On the territory of small rural settlements, the laying of polyethylene gas pipelines is allowed to 0.6 MPa with a reserve ratio of a strength of at least 2.5. At the same time, the depth of the gasket must be at least 0.8 m to the top of the pipe.
4.3.12 Calculation of gas pipelines for strength should include determining the thickness of the walls of pipes and connecting parts and stresses in them. At the same time, for underground and ground steel gas pipelines, pipes and connecting parts with a wall thickness of at least 3 mm should be applied, for overhead and internal gas pipelines - at least 2 mm.
4.3.13 Characteristics of limit states, reliability coefficients by responsibility, regulatory and calculated values \u200b\u200bof loads and impacts and their combination, as well as the normative and calculated values \u200b\u200bof the characteristics of materials should be taken in the calculations, taking into account the requirements of GOST 27751.
4.3.14 In constructing in areas with complex geological conditions and seismic impacts, special requirements should be taken into account and measures ensuring the strength, stability and tightness of gas pipelines. Steel gas pipelines must be protected from corrosion.
4.3.15 Underground and terrestrial steel gas pipelines, sug reservoirs, steel inserts Polyethylene gas pipelines and steel cases on gas pipelines (hereinafter - gas pipelines) should be protected by soil corrosion and corrosion of wandering currents in accordance with the requirements of GOST 9.602.
4.3.16 Steel gas pipelines under roads, railway and tramways with a trenchless gasket (puncture, jurisdiction and other technologies allowed by use) should, as a rule, are protected by means of electrical protection (3x3), when laying in an open method - insulating coatings and 3x3.
4.4 Selecting a gas pipeline material
4.4.1 For underground gas pipelines, polyethylene and steel pipes should be applied. For terrestrial and overhead gas pipelines, steel pipes should be applied. For internal gas pipelines, the bottom of the pressure is allowed to apply steel and copper pipes.
4.4.2 Steel seamless, welded (straight and spiral suture) pipes and connecting parts for gas distribution systems should be made of steel containing no more than 0.25% carbon, 0.056% sulfur and 0.04% phosphorus.
4.4.3 Selection of pipe material, pipeline shut-off valves, connecting parts, welding materials, fasteners and others should be made taking into account the pressure of the gas, diameter and thickness of the wall of the gas pipeline, the calculated outdoor air temperature in the construction area and the temperature of the pipe wall during operation, soil and Natural conditions, presence of vibratory loads.
4.5 Overcoming natural obstacles to the gas pipeline
4.5.1 Overcoming natural obstacles to gas pipelines. Natural obstacles are water barriers, ravines, gorges, beams. Gas pipelines on underwater transitions should be pasted with gluke in the bottom intersected water obstacles. If necessary, according to the results of calculations, it is necessary to make the piping ballasting. Mark of the top of the gas pipeline (ballast, lining) must be at least 0.5 m, and on the transitions through shipping and alloys rivers - by 1.0 m below the predicted bottom profile for a period of 25 years. In the production of work by the method of obliquely directional drilling - at least 20m below the predicted bottom profile.
4.5.2 On the underwater transitions should be applied:
- steel pipes with a wall thickness of 2 mm more calculated, but not less than 5 mm;
- polyethylene pipes having a standard dimensional ratio of the outer diameter of the pipe to the wall thickness (SDR) not more than 11 (according to GOST R 50838) with a strength factor of at least 2.5.
4.5.3 The height of the laying of the surface transition of the gas pipeline from the calculated level of water lifting or ice drift (High Water Horizon - GVV or Ice Age - GVL) to the bottom of the pipe or the span structure should be taken:
- when crossing ravines and beams - not lower than 0.5 m and over GWV 5% security;
- with the intersection of non-good and non-local rivers - not less than 0.2 m above GVV and GBL 2% security, and if there is a Courthouse, with its account, but not less than 1 m above GVV 1% security;
- When crossing navigable and alloys rivers - no less values \u200b\u200bestablished by the designations of the bloveture of bridge transitions on shipping rivers.
4.5.4 Plate valves should be placed at a distance of at least 10m from the transition boundaries. Abroves the intersection of high water horizon with 10% security.
4.6 Crossing artificial obstacles to the gas pipeline
4.6.1 Crossing artificial obstacles gas pipelines. Artificial obstacles are highways, iron and tram roads, as well as various mounds.
4.6.2 The distance horizontally from the places of intersection by the underground gas pipelines of tram and railway tracks and roads must be, not less:
- to bridges and tunnels on public railways, tramways, roads 1 - 3 categories, as well as to pedestrian bridges, tunnels through them - 30m, and for railways not general use, roads 4 - 5 categories and pipes - 15m;
- before the zone of the direction of the arrow (start of pests, the tail of the cross, the places of joining the rails of suction cables and other intersections of the path) - 4M for tram tracks and 20m for railways;
- Before supporting the contact network - 3m.
4.6.3 There is a reduction in the specified distances in coordination with organizations, in which intersected structures are located.
4.6.4 Underground gas pipelines for all pressures in places of intersections with railway and tramways, roads 1 - 4 categories, as well as the main streets of the citywide, should be laid in cases. In other cases, the issue of the need for a device of cases is solved by the project organization.
4.7 cases
4.7.1 Cases must satisfy the conditions of strength and durability. At one end of the case, it is necessary to provide a control tube leaving for a 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 under the condition of installation at one end of the exhaust candle case with a sampling device, derived from a distance of at least 50m from the edge of the Earthly Love (the axis of the extreme Rail at zero marks). In other cases, the ends of cases should be located at a distance:
- not less than 2nd of the far rail of the tramway and railways, the potassium is 750 mm, as well as from the edge of the carriageway of the streets;
- Not less than 3m onds of the edge of the drainage of roads (cuvette, ditch, reserve) and from the extreme rail of railways not general use, but not less than 2M oh soles of embankments.
4.7.3 Depth of laying a gas pipeline from the rail sole or the top of the road coating, and in the presence of an embankment - from its soles to the top of the case must meet the security requirements, be at least:
- in the work of work in the open method - 1.0 m;
- in the production of works by the method of priming or inclined drilling and panel laying - 1.5 m;
- in the production of works by the method of puncture - 2.5 m.
4.8. Crossing pipes with roads
4.8.1 The walls of the walls of the steel gas pipeline pipes When crossing it, the general use railways should be 2 - 3 mm more calculated, but not less than 5 mm at distances 50 m per side from the edge of the earthen canvase (the axis of the extreme rail on zero marks).
4.8.2. Polyethylene gas pipelines in these areas and at the intersections of roads 1 - 3, polyethylene pipes are not more than SDR 11 with a reserve ratio of a strength of at least 2.8.
4.9 Anticorrosive Pipeline Protection
4.9.1 Pipelines used in gas supply systems are usually carbon and low-alloyed steels. The service life and reliability of pipelines are largely determined by the degree of protection against destruction when contacting the environment.
4.9.2 Corrosion is the destruction of metals caused by chemical or electrochemical processes when interacting with the environment. The medium in which the metal is subject to corrosion is called corrosion or aggressive.
4.9.3 The most relevant for underground pipelines is electrochemical corrosion, which is subject to the laws of electrochemical kinetics, is the oxidation of the metal in electrically conductive media, accompanied by the formation and flow of electric current. In this case, the interaction with the environment is characterized by cathode and anode processes flowing on various parts of the metal surface.
4.9.4 All underground steel pipelines stacked directly into the ground are protected in accordance with GOST 9.602-2005.
4.9.5 In the grounds of medium corrosion activity in the absence of wandering currents, steel pipelines are protected by insulating coatings "very reinforced type", in the soils of high corrosion aggressivity of the dangerous effect of wandering currents - protective coatings "very reinforced type" with mandatory use of 3x3.
4.9.6 All stipulated corrosion protection are introduced into operation of the distribution of underground pipelines into operation. For underground steel pipelines in the zones of the dangerous influence of the 3x3 wandering currents, it is introduced no later than 1 month, and in other cases later than 6 months after laying the pipeline into the ground.
4.9.7 The corrosion aggressiveness of the soil in relation to steel is characterized by three ways:
- specific electrical resistance of the soil, determined in the field;
- Specific electrical soil resistance, defined in laboratory conditions,
- the average density of the cathode current (J k), which is necessary to shift the potential of steel in the soil by 100 mV, negatively inpatient (corrosion potential).
4.9.8 If one of the indicators indicates a high soil aggressiveness, then the soil is considered aggressive, and the definition of other indicators is not required.
4.9.9 The dangerous influence of the wandering DC on underground steel pipelines is the presence of a sign-changing and largely displacement of the pipeline potential relative to its stationary potential (alternating zone) or the presence of only positive offset of the potential, as a rule, varying in magnitude (anodic zone) . For designed pipelines, the presence of wandering currents in the ground is read.
4.9.10 Hazardous effects of AC on steel pipelines is characterized by a displacement of the average potential of the pipeline in a negative side of at least 10 mV, with respect to the stationary potential, or the presence of an AC density of more than 1 mA / cm 2. (10 a / m 2.) On auxiliary electrode.
4.9.11 Application 3x3 Required:
- when laying pipelines in soils with high corrosion aggressiveness (protection against soil corrosion),
- with the hazardous effect of constant wandering and variable currents.
4.9.12 When protecting against soil corrosion, the cathode polarization of underground steel pipelines is carried out in such a way that the average value of the polarization potentials of the metal was in the range from -0.85v. Up to 1.15V on the saturated copper-sulfany electrode in comparison (MSE).
4.9.13 Insulating operation in the tracks are carried out by manually in the insulation of the bogs and small shaped parts, the corrections of the coating damage (no more than 10% of the pipe area) arising from the transportation of pipes, as well as during the repair of pipelines.
4.9.14 When eliminating damage to the factory isolation in place, laying the gas pipeline should be ensured by the technologies and technical capabilities of coating and controlling its quality. All operations on the repair of the insulating coating are reflected in the passport of the gas pipeline.
4.9.15 Polyethylene, polyethylene ribbons, bitumen and bitumen and polymer mastic, weathered polymer materials, rolled assulsive materials, compositions based on chloride polyethylene, polyester resins and polyurethane compositions are recommended as the main materials for the formation of protective coatings.
Determination of Gaza expenses
5.1 Gas consumption
5.1.1 Gas spending on the network sites can be divided into:
running, transit and dispersed.
5.1.2 By road consumption is called consumption that is evenly distributed along the length of the site or the entire gas pipeline is equal to or very close in magnitude. It can be selected through the same in size and for the convenience of calculation it is evenly distributed. Typically, this consumption is consumed by the same type of gas appliances, for example, capacitive or flowing water heaters, gas stoves, etc. Concentrated are called expenses that pass through the pipeline without changing, throughout the length and are selected at certain points. Consumers of these expenses are: industrial enterprises, boiler rooms with constant flow rate for a long time. Transit calls the costs that pass on a specific area of \u200b\u200bthe network without changing, and provide gas consumption, to the next area being a way or concentrated.
5.1.2 Gas costs in the settlement are travel or transit. There are no focused gas costs, since there are no industrial enterprises. Travel expenses consist of gas devices installed in consumers, and depends on the season of the year. The apartment has four burner plates of the GLEM UN6613RX brand with a gas consumption of 1.2 m 3 / h., Flowing water heater of type "Vaillant" for hot consumption with a flow rate of 2 m 3 / h, capacitive water heaters "VIESSMANN VITOCELL-V 100 CVA- 300 "with a flow rate of 2.2 m 3 / h.
5.2 Consumption of Gaza
5.2.1 Gas consumption varies by the hour, day, days of the week, months of the year. Depending on the period of the period for which, gas consumption takes permanent distinguishes: seasonal non-uniformity or unevenness of the months of the year, daily unevenness or unevenness of the days of the week, hour unevenness or uneven hours of day.
5.2.2 The uneven gas consumption is associated with seasonal climatic changes, the mode of operation of the enterprises of the season, weeks and day, the characteristic of the gas equipment of various consumers of unevenness of unevenness is built by step-by-time gas costs. To regulate the seasonal unevenness of gas consumption, the following methods are applied:
- underground gas storage;
- the use of consumers of regulators, which dump surplus in the summer;
- reserve crafts and gas pipelines.
5.2.3 To regulate the uneven gas consumption of gas in the winter months, gas selection is used from underground storage facilities, and in a small period of the year, downloading to underground storage facilities. To cover the daily peak loads of the use of underground storages is not economical. In this case, gas supply limitations are introduced to industrial enterprises and the peak coating stations are used, in which gas liquefaction occurs.
Natural gas is the most common fuel today. Natural gas is called natural, because it is mined from the very beginning of the Earth.
The gas combustion process is a chemical reaction at which natural gas interacts with oxygen, which is contained in the air.
In the gaseous fuel there is a combustible part and non-combustible.
The main combustible component of natural gas is methane - CH4. Its content in natural gas reaches 98%. Methane does not smell, does not taste and is non-toxic. The limit of its flammability is from 5 to 15%. It is these qualities that made it possible to use natural gas, as one of the main types of fuel. The concentration of methane is life threatening more than 10%, so may suffice, due to the lack of oxygen.
To detect gas leakage, gas is subjected to odorization, in other words, a hazardous substance is added (ethyl mercaptan). At the same time, the gas can be detected at a concentration of 1%.
In addition to methane in natural gas, combustible gases may be present - propane, butane and ethane.
To ensure high-quality combustion of gas, it is necessary in sufficient amounts to bring air into the combustion zone and achieve good gas mixing with air. The optimal is considered to be the ratio of 1: 10. That is, one part of the gas accounts for ten parts of the air. In addition, it is necessary to create the desired temperature regime. In order for gas to ignore it, it is necessary to heat it up to the temperature of its ignition and in the future the temperature should not fall below the ignition temperature.
It is necessary to organize the removal of combustion products into the atmosphere.
Full burning is achieved if there are no combustible substances in the combustion products of the exit to the atmosphere. At the same time, carbon and hydrogen are combined together and form carbon dioxide and water pair.
Visually with full combustion flames light blue or bluish purple.
Full combustion of gas.
methane + oxygen \u003d carbon dioxide + water
CH 4 + 2O 2 \u003d CO 2 + 2N 2
In addition to these gases, nitrogen and remaining oxygen comes to a combustible gas. N 2 + O 2
If the combustion of gas is not completely, the fuel substances are ejected into the atmosphere - carbon monoxide, hydrogen, soot.
Incomplete gas combustion occurs due to insufficient air. At the same time, the Scoot languages \u200b\u200bappear visually in the flame.
The risk of incomplete combustion of gas is that carbon monoxide can cause poisoning boiler room. The content of CO in air 0.01-0.02% may cause light poisoning. Higher concentration can lead to severe poisoning and death.
The resulting soot settles on the walls of boilers worsening the heat transmission to the heat carrier reduces the efficiency of the boiler room. Soot carries out warmly worse than methane 200 times.
Theoretically, the combustion of 1m3 gas is needed 9m3 air. In real air conditions, it takes more.
That is, an excessive amount of air is necessary. This magnitude denoted alpha shows how many times the air is spent more than theoretically, theoretically.
The alpha coefficient depends on the type of the specific burner and is usually prescribed in the duct passport or in line with the recommendations of the organization produced commissioning.
With increasing amount of excess air above the recommended, heat losses are growing. With a significant increase in the amount of air, the flame may occur by creating an emergency. If the amount of air is less than recommended, the burning will be incomplete, thereby creating a threat to poisoning the boiler room.
For more accurate control of the quality of the combustion of fuel, there are gas analyzers, which measure the content of certain substances in the composition of the outgoing gases.
Gas analyzers can be included with boilers. In case there are no, the corresponding measurements conducts a commissioning organization with portable gas analyzers. A modest card is compiled in which the required control parameters are prescribed. By adhering to them, it is possible to ensure normal full combustion of fuel.
The main parameters for regulating fuel combustion are:
- the ratio of gas and air served on the burner.
- camerage of an excess air.
- diffix in the furnace.
- The usefulness of the boiler.
At the same time, under the coefficient of the useful effect of the boiler, the ratio of useful heat to the value of all the expended heat is implied.
The composition of the air
| Gas name | Chemical element | Contents in air |
| Nitrogen | N2. | 78 % |
| Oxygen | O2. | 21 % |
| Argon | AR | 1 % |
| Carbon dioxide | CO2. | 0.03 % |
| Helium | He. | less than 0.001% |
| Hydrogen | H2. | less than 0.001% |
| Neon | Ne | less than 0.001% |
| Methane | CH4 | less than 0.001% |
| Krypton | Kr. | less than 0.001% |
| Xenon | Xe. | less than 0.001% |
Definition
Natural gas - This is a mineral in a gaseous state. It is used in very wide limits as fuel. But natural gas itself is not used as fuel, it is distinguished from it components for individual use.
Composition of natural gas
Up to 98% of natural gas is methane, it also includes methane homologs - ethane, propane and butane. Sometimes carbon dioxide, hydrogen sosement and helium can be present. This is the composition of natural gas.
Physical properties
Natural gas is bluntless and has no smell (if it does not have hydrogen sulfide), it is easier air. Gulf and explosive.
Below are more detailed properties of natural gas components.
Properties of individual components of natural gas (consider the detailed composition of natural gas)
Methane (CH4) is a colorless gas without smell, lighter than air. Gulf, but still it can be stored with sufficient ease.
Ethane (C2H6) is a colorless gas without smell and color, a little heavier than air. Also fuel, but not used as fuel.
Propane (C3H8) - colorless gas without smell, poisonous. It has a useful property: propane is liquefied with a slight pressure, which makes it easy to separate it from impurities and transport.
Butane (C4H10) - by properties close to propane, but has a higher density. Twice as heavy air.
Carbon dioxide (CO2) is a colorless gas without smell, but with sour taste. Unlike other components of natural gas (with the exception of helium), carbon dioxide does not burn. Carbon dioxide is one of the most low-toxic gases.
Helium (HE) - colorless, very easy (the second of the easiest gases, after hydrogen) without color and smell. Extremely inert, under normal conditions does not react with any substances. Does not burn. Not toxic, but at elevated pressure may cause anesthesia, like other inert gases.
Hydrogen sulfide (H2S) - colorless heavy gas with a smell of rotten eggs. Very poisonous, even with a very small concentration causes a paralysis of an olfactory nerve.
Properties of some other gases that are not part of natural gas, but having a use close to the use of natural gas
Ethylene (C2H4) - colorless gas with a pleasant smell. According to the properties of close to the ethane, but differs from it less density and flammability.
Acetylene (C2H2) - Extremely combustible and explosive colorless gas. With strong compression, it is capable of exploding. It is not used in everyday life due to the very large risk of fire or explosion. Basic use - in welding work.
Application
Methane Used as fuel in gas stoves.
Propane and Bhutan - as fuel in some cars. Also liquefied propane fill lighters.
Ethane It is rarely used as a fuel, its main application is to obtain ethylene.
Ethylene It is one of the most produced organic substances in the world. It is a raw material for polyethylene.
Acetylene Used to create a very high temperature in metallurgy (reconciliation and cutting of metals). Acetylene Very fuel, so it is not used as fuel in cars, and without this, the conditions for its storage should be strictly observed.
Hydrogen sulfidedespite its toxicity, in small quantities is used in the so-called. hydrogen sulfide baths. They use some antiseptic properties of hydrogen sulfide.
Basic useful feature helium It is its very small density (7 times lighter than air). Helium fill aerostats and airships. Hydrogen is even more lung than helium, but at the same time a fuel. High popularity among children have balloons inflounted by helium.
Toxicity
Carbon dioxide. Even large amounts of carbon dioxide do not affect human health. However, it prevents the absorption of oxygen when the content in the atmosphere is from 3% to 10% by volume. With such a concentration begins a suffocation and even death.
Helium. Helium is absolutely non-toxic under normal conditions due to its inertness. But at elevated pressure, the initial stage of anesthesia occurs, similar to the impact of the funny gas *.
Hydrogen sulfide. The toxic properties of this gas are large. With long-term exposure to the smell, dizziness occurs, vomiting. Also paralyzed the olfactory nerve, so the illusion of the absence of hydrogen sulfide arises, and in fact the body simply does not feel it. The poisoning of hydrogen sulfide occurs at a concentration of 0.2-0.3 mg / m3, the concentration is above 1 mg / m3 - mortal.
The process of burning
All hydrocarbons at full oxidation (excess oxygen) are isolated carbon dioxide and water. For example:
CH4 + 3O2 \u003d CO2 + 2H2O
In case of incomplete (lack of oxygen) - carbon monoxide and water:
2ch4 + 6O2 \u003d 2CO + 4H2O
With a smaller amount of oxygen, fine carbon (soot) is distinguished:
CH4 + O2 \u003d C + 2H2O.
Methane is burning with a blue flame, ethane - almost colorless, like alcohol, propane and butane - yellow, ethylene - luminous, carbon monoxide - light blue. Acetylene - yellowish, smoking. If you have a gas stove at home and instead of the usual blue flame you see yellow - know, this methane is diluted with propane.
Notes
HeliumUnlike any other gas, does not exist in solid state.
Laughing gas - This is the trivial name for nitrogen nitrogen N2O.
Comments and additions to the article - in the comments.
Introduction 2.
Composition and physical properties of natural gas 3
Chemical composition 3.
Physical properties 3.
Introduction
Natural gas is a mixture of gases formed in the bowels of the Earth with anaerobic decomposition of organic substances. Natural gas refers to minerals, one of the most important combustible fossils, which occupies key positions in the fuel and energy balances of many states. Natural gas is an important raw material for the chemical industry. In reservoir conditions (conditions of occurrence in earthly depths) is in a gaseous state - in the form of individual clusters (gas deposits) or in the form of gas caps of oil and gas fields, or in dissolved state in oil or water.
The energy and chemical value of natural gas is determined by the content in it of hydrocarbons. Very often in the fields it accompanies oil. The difference in natural and associated petroleum gas is available. In the latter, as a rule, more comparatively heavy hydrocarbons that are necessarily separated before using gas.
Composition and physical properties of natural gas
Chemical composition
Natural hydrocarbon gases are a mixture of limit hydrocarbons of the type of CNN2N + 2. The bulk of the natural gas is methane CH4 - up to 98%.
The composition of natural gas can also include more heavy hydrocarbons - methane homologs: - ethane (C2H6), is propane (C3H8), - butane (C4H10), as well as other inconspicure substances: - hydrogen (H2), - hydrogen sulfide (H2S), - carbon dioxide (CO2), - Nitrogen (N2), - helium (not)
Pure natural gas has no color and smell. In order to determine the leak of the smell, a small amount of substances that have a strong unpleasant smell, so-called odorants add to the gas. Most often, ethyl mercaptan is used as a odorant.
Physical properties
Approximate physical characteristics (depend on the composition; under normal conditions, unless otherwise indicated):
Density:
from 0.68 to 0.85 kg / m³ (dry gaseous);
400 kg / m³ (liquid).
Boiling point at atmospheric pressure: -162 ° C
Self-burning temperature: 650 ° C;
Explosive concentrations of gas mixture with air from 5% to 15% volume;
Specific heat combustion: 28-46 MJ / m³ (6.7-11.0 kcal / m³) (i.e. 8-12 kWh / m³);
Octane number when used in internal combustion engines: 120-130.
Easier air is 1.8 times, so when leakage is not going to lowers, but rises up.
Natural gases are divided into the following groups:
1. Gas produced from pure gas fields and is a dry gas free of heavy hydrocarbons.
2. Gases mined with oil (dissolved or associated gases). These are physical mixtures of dry gas, propane bunic fraction (fatty gas) and gas gasoline.
3. Gases extracted from gas condensate deposits - a mixture of dry gas and liquid hydrocarbon condensate. The hydrocarbon condensate consists of a large number of heavy hydrocarbons (C5 + Higher., C6 + Higher. Etc.), from which gasoline, ligroin, kerosene, and sometimes heavier oil fractions can be distinguished.
4. Gaza gas hydrate deposits.
The component composition and properties of individual components of natural gas are shown in Table 1.
Table 1. The main properties of the components of natural gases under standard conditions
|
Property |
Designation | |||||
|
Molecular mass | ||||||
|
Volume 1kg gas, m3 | ||||||
|
Air density | ||||||
|
Mass 1m3 gas, kg | ||||||
|
Critical pressure, MPa | ||||||
|
Critical temperature, to |
In many cases, the composition of natural hydrocarbon gases is not fully determined, but only to butane (C4H10) or hexane (C6H14) inclusive, and all other components are combined into the residue (or pseudocomponent).
Gas, as part of which heavy hydrocarbons make up no more than 75 g / m3, called dry. With the content of heavy hydrocarbons, more than 150 g / m3 gas is called fat.
Gas mixtures are characterized by mass or molar concentrations of components. To characterize the gas mixture, it is necessary to know its average molecular weight, the average density in kilograms per cubic meter or relative air density.
Molecular weight M of natural gas:
where M is the molecular weight of the i-th component; xi - the volumetric content of the i-th component, the share of the unit.
For real gases, usually m \u003d 16 - 20.
Gas density ρg is calculated by the formula:
where Vm is a volume of 1 praying gas under standard conditions.
Usually ρg is in the range of 0.73 - 1.0 kg / m3.
The gas density is largely dependent on pressure and temperature, and therefore this indicator is inconvenient for practical application. More often use the relative gas density through the air ρg.v. equal to the ratio of the gas density ρg to the density of air ρV, taken under the same pressure and temperature:
ρG.V. \u003d ρg / ρv,
If ρg and ρv are determined under standard conditions, then ρv \u003d 1.293 kg / m3 and ρg.v. \u003d ρg / 1,293.
The oil gases density ranges from 0.554 (for methane) to 2.006 (for butane) and above.
Gas viscosity characterizes the interaction force between gas molecules that are overcome during its movement. It increases with increasing temperature, pressure and content of hydrocarbon components. However, at pressures above 3MP, the temperature increases a decrease in gas viscosity.
The viscosity of oil gas is insignificant and at 0 ° C of 0.000131 PZ; Air viscosity at 0 ° C is 0.000172 PZ.
Gas state equations are used to determine many physical properties of natural gases. The equation of state is the analytical dependence between the gas parameters describing the behavior of the gas. These parameters are pressure, volume and temperature.
The state of the ideal gases under conditions of high pressure and temperature is determined by the Klapairone equation - Mendeleev:
where p - pressure; V is the volume of the ideal gas, N - the number of gas kilometers; R - Universal gas constant; T - Temperature.
The ideal is called gas, the interaction for the molecules of which is neglected. Real hydrocarbon gases are not subject to the laws of ideal gases. Therefore, the Clapieron Mendeleev equation for real gases is written in the form:
where Z is the coefficient of the superconductability of real gases, depending on the pressure, temperature and composition of the gas and characterizing the degree of rejection of the real gas from the law for ideal gases.
The ultra-superconductivity coefficient Z of real gases is the ratio of volumes of equal number of moles of the real V and the ideal V and gases with the same thermobaric conditions (i.e., at the same pressure and temperature):
The values \u200b\u200bof the supercondability coefficients can most reliably be determined on the basis of laboratory studies of the reservoir samples of gases. In the absence of such studies (as most often happens in practice), it is resorted to the calculated method of assessing Z according to the schedule of Brown (Fig. 1). To use the schedule, you need to know the so-called pseudocritical pressure and pseudocritical temperature.
Critical is called such a temperature, above which the gas cannot be turned into a liquid at no pressure. Critical pressure is called pressure corresponding to the critical point of gas transition into a liquid state.
With the approach of pressure and temperature values \u200b\u200bto the critical properties of gas and liquid phases, they become the same, the surface of the section between them disappears and they are equalized by their density.
With the advent of two or more components in the system in the patterns of phase changes, features arise that distinguish their behavior from the behavior of one-component gas. Without stopping in details, it should be noted that the critical temperature of the mixture is between the critical temperatures of the components, and the critical pressure of the mixture is always higher than the critical pressure of any component.
To determine the excessability coefficient z real gases, which are a multicomponent mixture, find the average of the values \u200b\u200bof critical pressures and temperatures of each component. These medium are called pseudocritical pressure PP.KR. and pseudocritical temperature TP.KR. They are determined from relations:
natural gas methane composition
where RKR. and TKR. - Critical pressure and temperature of the i-th component; Xi is the proportion of the i-th component in the volume of the mixture (in the fractions of the unit).
The above pseudo-critical pressure and temperature necessary for using brown graph are pseudo-critical values \u200b\u200bshown to specific pressure and temperature (to reservoir, standard or other conditions):
RPR. \u003d p / rp.kr.,
TPR. \u003d T / tp.kr.,
where P and T are specific pressure and temperature for which Z is defined.
The superticiency coefficient Z is necessarily used when calculating gas reserves to properly determine the change in the volume of gas during the transition from the reservoir conditions to the surface, when predicting the pressure change in the gas deposit and when solving other tasks.
ApplicationMethane is used as fuel in gas plates. Pour and butane - as fuel in some cars. Also liquefied propane fill lighters. It is rarely used as a fuel, its main application is to receive ethylene. Ethylene is one of the most produced organic substances in the world. It is a raw material for obtaining polyethylene. Aacetylene is used to create a very high temperature in metallurgy (reconciliation and cutting of metals). Acetylene is very fuel, therefore, it is not used as fuel in cars, and without this, its storage conditions should be strictly observed. Server hydrogen, despite its toxicity, in small quantities is used in the so-called. hydrogen sulfide baths. They use some antiseptic properties of hydrogen sulfide. The sourceful properties of helium is its very small density (7 times lighter than air). Helium fill aerostats and airships. Hydrogen is even more lung than helium, but at the same time a fuel. Great popularity among children have air balls, inflounted by helium. Califorgic gas. Even large amounts of carbon dioxide do not affect human health. However, it prevents the absorption of oxygen when the content in the atmosphere is from 3% to 10% by volume. With such a concentration, the suffocations begins and even death. Helium is absolutely non-toxic under normal conditions due to its inertness. But at elevated pressure, the initial stage of anesthesia occurs, similar to the impact of the funny gas. SERVICE. The toxic properties of this gas are large. With long-term exposure to the smell, dizziness occurs, vomiting. Also paralyzed the olfactory nerve, so the illusion of the absence of hydrogen sulfide arises, and in fact the body simply does not feel it. The hydrogen sulfide poisoning occurs at a concentration of 0.2-0.3 mg / m3, the concentration is above 1 mg / m3 is fatal. The combustion process of hydrocarbons with full oxidation (excess oxygen) is isolated carbon dioxide and water. For example: CH4 + 3O2 \u003d CO2 + 2H2PURS incomplete (disadvantage of oxygen) - carbon monoxide and water: 2ch4 + 6O2 \u003d 2CO + 4H2: a small amount of oxygen is released fine carbon (soot): CH4 + O2 \u003d C + 2H2O. Metan is burning with a blue flame Ethan is almost colorless, like alcohol, propane and butane - yellow, ethylene - luminous, carbon monoxide - light blue. Acetylene - yellowish, smoking. If you have a gas stove at home and instead of the usual blue flame you see yellow - know, this methane is diluted with propane.
Conclusion
Natural gas is widely used as fuel in residential, private and apartment buildings for heating, heating water and cooking; Like fuel for cars (car equipment of the car, gas engine), boiler rooms, CHP, etc. It is now used in the chemical industry as a starting raw material for obtaining various organic substances, such as plastics.
Environmental and natural gas is the cleanest type of organic fuel. With its combustion, a significantly smaller amount of harmful substances is formed compared to other types of fuel. However, the burning of humanity of a huge number of different types of fuel, including natural gas, over the past half century, led to an increase in carbon dioxide content in an atmosphere, which is greenhouse gas.
List of used literature
1. Korshak A.A., Shammazov A.M., Basics of Oil and Gas Business. Ed. "UGNTU. Ufa. 2005
2. Gimatudinov Shk.K., Shirkovsky A.I. Physics and gas reservoir. Ed. "Bosom". M. 1982
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Approximate physical characteristics (depend on the composition; under normal conditions, unless otherwise indicated):
· Density:
· From 0.68 to 0.85 kg / m³ (dry gaseous);
· 400 kg / m³ (liquid).
· Self-burning temperature: 650 ° C;
· Explosive concentrations of gas mixture with air from 5% to 15% volume;
· Specific heat combustion: 28-46 MJ / m³ (6.7-11.0 mcal / m³) (i.e., it is 8-12 kWh / m³);
· Octane number when used in internal combustion engines: 120-130.
· Easier air is 1.8 times, so when leakage is not going to lowers, but rises up [
Chemical composition
The bulk of natural gas is methane (CH 4) - from 92 to 98%. The composition of natural gas may also include more heavy hydrocarbons - methane homologs:
· Ethan (C 2 H 6),
· Propane (C 3 H 8),
· Butane (C 4 H 10).
as well as other inconspicuous substances:
· Hydrogen (H 2),
· Hydrogen sulfide (H 2 S),
· Carbon dioxide (CO 2),
· Nitrogen (N 2),
· Helium (not).
Pure natural gas has no color and smell. To facilitate the possibility of determining the leakage of gas, one in small quantities add odes - substances having a sharp unpleasant smell (rotten cabbage, heavy hay, rotten eggs). Most often, Tiol is used as a odorant, for example, ethyl mercaptan (16 g per 1000 m³ of natural gas).
[kg · m -3]; 
[M 3 · kg -1] - specific volume.
F (p, v, t) \u003d 0 - the equation of state state.
Composition of natural gas:
4. 
Isobutan
5. N Bhutan
6. N Pentan
μ - molecular weight
ρ - Normal density
- gas density by air
R KR - Critical pressure
T cr - critical temperature.
Equation of the state of natural gas; Features of gases isotherms. Critical situation. Critical state of methane and its homologues. Lengagement of gases.
- Gas state equation.
When the pressure increases and reduce the temperature, the gas goes into a liquid state.
Perfect gas. Clapieron Mendeleev equation. Real gas. Compressibility. The coefficient of superconductivity. Presented parameters. Formula for calculating the coefficient of supercondability.
,
- equation of the state of the perfect gas.
R 0 \u003d 8314 
for real gas:
,
z - compressibility coefficient.
Gas equation.
Gas state equation - functional dependence between pressure, specific volume and temperature, which exists for all gases in a state of thermodynamic equilibrium, that is 
.
Graphically, this dependence is depicted by the Isotherm family.
At a temperature of greater critical gas, always remains in a gaseous state at any pressure. At a temperature of a smaller critical, with a gas compression, if the gas condensation begins, and it moves into a two-phase state. When a certain specific volume is achieved, the condensation of the gas is stopped, and it acquires the properties of the liquid.
The equation of the state of the ideal gas is described by the Mendeleev-Klapairone equation: 
, 
or 
where 
.
Gas constant 
, 
.
For methane having a molar mass 
, gas constant is equal 
.
For high pressures and temperatures, various models of real gases are used characteristic of the main gas pipelines, which has a phenomenon of supercruitability. These models are described by the adjusted Mendeleev-Klaperon equation: 
, where - the coefficient of superconduct, which for real gases is always less than a unit; 
- reduced pressure; 
- Pressure given.
To calculate the coefficient of superconductivity, there are various empirical formulas, such as.
For a mixture of gases, the critical pressure is determined by the following formula: 
And the critical temperature is as follows: 
.
Characteristic parameters of natural gas components:
| Component name | ,  | , | ,  | ,  | , |
| Methane | 16.042 | 0.717 | 518.33 | 4.641 | 190.55 |
Ethane  | 30.068 | 1.356 | 276.50 | 4.913 | 305.50 |
Propane  | 44.094 | 2.019 | 188.60 | 4.264 | 369.80 |
| Nitrogen | 28.016 | 1.251 | 296.70 | 3.396 | 126.2 |
| Hydrogen sulfide | 34.900 | 1.539 | 238.20 | 8.721 | 378.56 |
| Carbon dioxide | 44.011 | 1.976 | 189.00 | 7.382 | 304.19 |
| Air | 28.956 | 1.293 | 287.18 | 3.180 | 132.46 |
45.Good mixtures and calculation of their parameters. Calculation of critical parameters of the gas mixture.