Approximate physical characteristics (depending on composition; under normal conditions, unless otherwise stated):

Density:

· from 0.68 to 0.85 kg/m³ (dry gaseous);

· 400 kg/m³ (liquid).

· Auto-ignition temperature: 650 °C;

· Explosive concentrations of a mixture of gas and air from 5% to 15% by volume;

· Specific heat of combustion: 28-46 MJ/m³ (6.7-11.0 Mcal/m³) (i.e. it is 8-12 kW-h/m³);

Octane number when used in engines internal combustion: 120-130.

· 1.8 times lighter than air, so when there is a leak, it does not collect in the lowlands, but rises [

Chemical composition

The main part of natural gas is methane (CH 4) - from 92 to 98%. Natural gas may also contain heavier hydrocarbons - homologues of methane:

· ethane (C 2 H 6),

· propane (C 3 H 8),

· butane (C 4 H 10).

as well as other non-hydrocarbon substances:

· hydrogen (H 2),

hydrogen sulfide (H 2 S),

carbon dioxide (CO 2),

nitrogen (N 2),

· helium (He).

Pure natural gas is colorless and odorless. To make it easier to detect a gas leak, odorants are added to it in small quantities - substances that have a strong unpleasant odor (rotten cabbage, rotten hay, rotten eggs). Most often, thiols are used as an 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)=0 – equation of state of the gas.

Composition of natural gas:

4. Isobutane

5. n Butane

6. n Pentane

µ - molecular weight

ρ – normal density

– gas density in air

P cr – critical pressure

T cr – critical temperature.

Equation of state of natural gas; features of gas isotherms. Critical condition. Critical state of methane and its homologues. Liquefaction of gases.

- equation of gas state.

As the pressure increases and the temperature decreases, the gas turns into a liquid state.

Perfect gas. Clapeyron-Mendeleev equation. Real gas. Compressibility. Supercompressibility coefficient. The given parameters. Formula for calculating the supercompressibility coefficient.

,

- equation of state of a perfect gas.

R0 = 8314

for real gas:

,

z – compressibility coefficient.

Equation of gas state.

Gas equation of state – 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 a family of isotherms.

Above the critical temperature, the gas always remains in the gaseous state at any pressure. At a temperature below the critical one, when the gas is compressed, if a certain specific volume is reached, condensation of the gas begins and it goes into a two-phase state. When a certain specific volume is reached, the condensation of the gas stops and it acquires the properties of a liquid.

The equation of state of an ideal gas is described by the Mendeleev-Clapeyron equation: , or , Where .

Gas constant , .

For methane having a molar mass , the gas constant is .

At high pressures and temperatures characteristic of main gas pipelines, they are used various models real gases, which has the phenomenon of supercompressibility. These models are described by the adjusted Mendeleev-Clayperon equation: , where is the supercompressibility coefficient, which for real gases is always less than unity; - reduced pressure; - reduced pressure.

To calculate the supercompressibility coefficient, 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 found 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. Gas mixtures and calculation of their parameters. Calculation of critical parameters of a gas mixture.

Physicochemical characteristics natural gases. Calculation of gas mixture.

Gases are divided into natural and artificial. Currently, natural gases are mainly used for gas supply. They have a complex multicomponent composition. Depending on their origin, natural gases are divided into three groups:

1. Gases extracted from pure gas fields, consisting of 82...98% methane;

2. Gases from gas condensate fields containing 80...95% methane;

3. Gases from oil fields (associated petroleum gases), containing 30...70% methane and a significant amount of heavy hydrocarbons. Gases with a content of heavy hydrocarbons (from propane and above) less than 50 g/m 3 are usually called dry or “lean”, and those with a high content of hydrocarbons are called “fat”.

Recently, people have often started talking about the fourth group of natural gases – shale gas and coalbed methane. Shale gas is natural gas produced from shale, consisting primarily of methane. Shale gas is formed as a result of the degradation of kerogen, which is contained in oil shale; gas is there in microcracks. Large-scale industrial production shale gas development began in the United States in the early 2000s at the Barnett Shale field. Thanks to sharp growth its production, called the “gas revolution” in the media, in 2009 the United States became the world leader in gas production, with more than 40% coming from unconventional sources (coalbed methane and shale gas). Coalbed methane is found in coal-bearing sediments. Causes explosions in coal mines. Coal bed methane is a cleaner and more efficient fuel than coal.

Natural gases are colorless, odorless and in their normal state they come in different forms. states of aggregation. Methane, ethane and ethylene gases, propane, butane, butylene and propylene - in the form of liquid vapor, and under high pressure - liquid substances. Heavy hydrocarbons, starting with isopentane, are liquids in their normal state; they are part of the gasoline fraction. In order for natural gases to have an odor for safety purposes, special substances - odorants - are specially added to them.

Gases are usually considered under two conditions:

1. Normal condition - R n =0.1013 MPa (normal Atmosphere pressure), T n =273.16K (0 0 C);

2. Standard condition - R st =0.1013 MPa (normal atmospheric pressure), T st =293.16K (20 0 C – room temperature).

To perform hydraulic and thermal calculations of gas pipelines and calculate operating modes compressor stations it is necessary to know the basic properties of natural gases: density, viscosity, gas constant, pseudocritical values ​​of temperature and pressure, heat capacity, thermal conductivity, compressibility and Joule - Thomson coefficients.

Molar mass of gas ( M), it is the mass of 1 mole of gas. One mole of a substance consists of approximately 6 billion trillion. number of any molecules (equal to Avogadro’s number: N A =6.02·10 23). Its dimension [ M]= kg/mol, or [ M]= g/mol. The molar mass of a gas is found through its molecular mass. For example, molecular mass hydrogen is approximately equal to 2, then its molar mass M≈2g/mol=2·10 -3 kg/mol. For oxygen M≈32g/mol, for nitrogen M≈28g/mol, for propane (C 3 H 8) M≈12·3+1·8=44g/mol, etc. The density of a gas is the mass of a unit volume:

The relative density of gas in air Δ is the ratio of gas density to air density. For all gas states the following expression holds:

Here [ M]= g/mol, 28.96 g/mol – molar mass of air. For standard condition

here ρ is the gas density under standard conditions (air density under standard conditions is 1.205 kg/m 3, for normal conditions 1.29 kg/m 3).

Any gas in an amount of 1 mole in the normal state occupies a volume of approximately 22.4 × 10 -3 m3, so the density of the gas under normal conditions is

Here [ M]= g/mol, but this expression is not valid for the standard state.

Viscosity (dynamic) of gas μ , A [ μ ]=Pa·s. The viscosity of a gas is determined by the transfer of momentum (from one layer to another) by a gas molecule during its transition from one flow layer to another. Therefore, gas viscosity strongly depends on temperature and is almost independent of gas pressure (up to 4 MPa). Dynamic μ and kinematic ν The gas viscosity of the gas is related by the relation:

Specific heat capacity of gas at constant pressure With, A [ With]=J/(kg K). It is equal to the amount of heat required to heat 1 kg of gas by 1K at constant pressure. Gas pressure R shows the force acting normal to a unit area of ​​the wall of a vessel from gas molecules. [ R]= atm, [ R]=Pa, or [ M]= MPa. 1 MPa= 10 6 Pa≈10 Atm. The gas temperature is determined on the Kelvin and Celsius scales, they are related by the ratios:

In many cases, compression can turn a gas into a liquid. However, the gas temperature must be below critical ( T cr). If it is equal to or higher critical temperature, then the gas does not turn into liquid at any pressure. And also, if the gas pressure is equal to or higher than the critical pressure ( R cr), then subsequently, at no temperature, the gas does not turn into liquid.

The main types of gas transport include railway transport, sea transport and pipeline transport. Each mode of transport has its strengths and weaknesses.

To calculate the gas mixture, it is necessary to know the equation of state of the gas. The equation of state of a gas relates the basic parameters of a gas, such as its quantity, volume, pressure and temperature. From school and higher physics courses, you know the equations of state of Mendeleev-Clapeyron, van der Waals, and for gas pipelines the equation of state of a gas, written in terms of gas compressibility, is convenient:

Where R- gas constant defined for a particular gas or gas mixture. It is found through the universal gas constant (8.314 J/(mol K)):

units of measurement in expression (8): [ m]= kg, [ M]= kg/mol, ([ R]= Pa). z in expression (128) is called gas compressibility (compressibility coefficient) for a specific gas or gas mixture. The compressibility coefficient depends on the state of the gas. It is usually determined using special nomograms depending on the given temperatures and pressures, or in analytical form using a formula recommended by industry design standards. The quantities are called reduced gas parameters:

. (129)

The compressibility coefficient takes into account the deviation of the properties of natural gas from the laws of ideal gas. There are 2 formulas recommended by industry design codes for compressibility factor. But both of them are approximate and give almost identical results for the real parameters of the main gas pipeline. The first of the formulas:

And the other formula is:

. (131)

In these formulas for the main gas pipeline, the average values ​​of pressure and temperature are taken:

. (132)

The first formula is convenient for calculation.

Typically, the amount of gas mixture (or gas) is transferred through its volume. But the volume depends on the actual state of the gas, that is, if for a given state the working volume of the gas is known V, then in other states the corresponding volumes of gas will be different. For clarity, volumes are taken for normal and standard conditions. In technical calculations, and in calculations for gas storage and transportation, as well as in commercial calculations, the volume of gas is reduced to a standard condition.

The formula for bringing the working volume of gas to normal conditions (normal volume) is as follows:

. (133)

Formula for reducing the working volume of gas to standard conditions (commercial volume):

. (134)

Here [ R]= MPa.

The necessary physical and chemical properties of the gas mixture include the following parameters: molar mass M, pseudocritical temperature T kr, pseudocritical pressure R kr, pseudocritical volume V cr, specific heat gas at constant pressure, dynamic viscosity and thermal conductivity λ . They are determined through the properties of each component of the mixture.

The composition of the gas mixture is characterized by the mass, or volume, or mole fractions of each component. The volume fractions of each component of the mixture are equal to the corresponding mole fractions and are easier to calculate with. Let the volume fractions of each component of the mixture at 1 , at 2 , at 3, etc. Then the following formula is always valid for the entire gas mixture:

The remaining parameters of the mixture are defined differently in different sources. The simplest method is the method of determination using the rule of additivity (proportional addition). This method is easy to use, but not very accurate. It is used when approximate calculations and gives a very good result when the proportion of methane in the mixture is at least 96% (especially when calculating viscosity). So.

Characteristics of methane

§ Colorless;

§ Non-toxic (non-poisonous);

§ Odorless and tasteless.

§ Methane consists of 75% carbon, 25% hydrogen.

§ Specific gravity is 0.717 kg/m 3 (2 times lighter than air).

§ Flash point is the minimum initial temperature at which combustion begins. For methane it is 645 o.

§ Combustion temperature- This Maximum temperature, which can be achieved with complete combustion gas, if the amount of air required for combustion exactly corresponds to the chemical formulas of combustion. For methane it is 1100-1400 o and depends on the combustion conditions.

§ Heat of combustion– this is the amount of heat that is released during the complete combustion of 1 m 3 of gas and it is equal to 8500 kcal/m 3.

§ Flame propagation speed equal to 0.67 m/sec.

Gas-air mixture

Which gas contains:

Up to 5% does not burn;

From 5 to 15% explodes;

Over 15% burns when additional air is supplied (all this depends on the ratio of the volume of gas in the air and is called explosive limits)

Combustible gases are odorless; in order to timely detect them in the air and quickly and accurately detect leaks, the gas is odorized, i.e. give off a smell. For this purpose, ETHYLMERCOPTAN is used. The odorization rate is 16 g per 1000 m 3. If there is 1% natural gas in the air, you should smell it.

Gas used as fuel must comply with GOST requirements and contain harmful impurities per 100m 3 no more than:

Hydrogen sulfide 0.0 2 G /m.cube

Ammonia 2 gr.

Hydrocyanic acid 5 g.

Resin and dust 0.001 g/m3

Naphthalene 10 gr.

Oxygen 1%.

Using natural gas has a number of advantages:

· absence of ash and dust and removal of solid particles into the atmosphere;

· high heat of combustion;

· ease of transportation and combustion;

· the work of service personnel is facilitated;

· sanitary and hygienic conditions in boiler houses and surrounding areas are improved;

· wide range of automatic control.

When using natural gas, special precautions are required because... leakage is possible through leaks at the junction of the gas pipeline and fittings. The presence of more than 20% of gas in a room causes suffocation; its accumulation in a closed volume of more than 5% to 15% leads to an explosion gas-air mixture. In case of incomplete combustion it is released carbon monoxide, which even at low concentrations (0.15%) is poisonous.

Natural gas combustion

Burning called fast chemical compound combustible parts of fuel with air oxygen, occurs when high temperature, is accompanied by the release of heat with the formation of flame and combustion products. Combustion happens complete and incomplete.

Full combustion– Occurs when there is sufficient oxygen. Lack of oxygen causes incomplete combustion, in which less heat is released than with full carbon monoxide (has a poisonous effect on operating personnel), soot is formed on the surface of the boiler and heat loss increases, which leads to excessive fuel consumption, a decrease in boiler efficiency, and air pollution.

The products of natural gas combustion are– carbon dioxide, water vapor, some excess oxygen and nitrogen. Excess oxygen is contained in combustion products only in cases where combustion occurs with excess air, and nitrogen is always contained in combustion products, because is integral part air and does not take part in combustion.

Products incomplete combustion gas may be carbon monoxide, unburned hydrogen and methane, heavy hydrocarbons, soot.

Methane reaction:

CH 4 + 2O 2 = CO 2 + 2H 2 O

According to the formula For the combustion of 1 m 3 of methane, 10 m 3 of air is required, which contains 2 m 3 of oxygen. In practice, to burn 1 m 3 of methane, more air is needed, taking into account all kinds of losses; for this, a coefficient is used TO excess air, which = 1.05-1.1.

Theoretical air volume = 10 m3

Practical air volume = 10*1.05=10.5 or 10*1.1=11

Completeness of combustion fuel can be determined visually by the color and nature of the flame, as well as using a gas analyzer.

Transparent blue flame - complete combustion of gas;

Red or yellow with smoky streaks – combustion is incomplete.

Combustion is regulated by increasing the air supply to the firebox or decreasing the gas supply. This process uses primary and secondary air.

Secondary air– 40-50% (mixed with gas in the boiler furnace during combustion)

Primary air– 50-60% (mixed with gas in the burner before combustion) a gas-air mixture is used for combustion

Combustion characterizes flame distribution speed is the speed at which the flame front element distributed by relatively fresh stream of gas-air mixture.

The rate of combustion and flame propagation depends on:

· on the composition of the mixture;

· on temperature;

· from pressure;

· on the ratio of gas and air.

The burning rate determines one of the main conditions for the reliable operation of the boiler room and characterizes it flame separation and breakthrough.

Flame break– occurs if the speed of the gas-air mixture at the burner outlet is greater than the combustion speed.

Reasons for separation: excessive increase in gas supply or excessive vacuum in the firebox (draft). Flame separation is observed during ignition and when the burners are turned on. The separation of the flame leads to gas contamination of the furnace and gas ducts of the boiler and to an explosion.

Flame breakthrough– occurs if the speed of flame propagation (burning speed) is greater than the speed of outflow of the gas-air mixture from the burner. The breakthrough is accompanied by combustion of the gas-air mixture inside the burner, the burner becomes hot and fails. Sometimes a breakthrough is accompanied by a pop or explosion inside the burner. In this case, not only the burner, but also the front wall of the boiler can be destroyed. A slip occurs when there is a sharp decrease in gas supply.

If the flame comes off and breaks through, the maintenance personnel must stop supplying fuel, find out and eliminate the cause, ventilate the firebox and flue ducts for 10-15 minutes and re-ignite the fire.

The combustion process of gaseous fuel can be divided into 4 stages:

1. Gas leaking from the burner nozzle into the burner device under pressure at an increased speed.

2. Formation of a mixture of gas and air.

3. Ignition of the resulting combustible mixture.

4. Combustion of a flammable mixture.

Gas pipelines

Gas is supplied to the consumer through gas pipelines - external and internal– to gas distribution stations located outside the city, and from them via gas pipelines to gas regulatory points hydraulic fracturing or gas control device GRU industrial enterprises.

Gas pipelines are:

· high pressure first category over 0.6 MPa up to 1.2 MPa inclusive;

· high pressure of the second category over 0.3 MPa to 0.6 MPa;

· average pressure of the third category over 0.005 MPa to 0.3 MPa;

· low pressure fourth category up to 0.005 MPa inclusive.

MPa - means Mega Pascal

Only medium and low pressure gas pipelines are laid in the boiler room. The section from the network gas distribution pipeline (city) to the premises together with the disconnecting device is called input.

The inlet gas pipeline is considered to be the section from the disconnecting device at the inlet if it is installed outside the room to the internal gas pipeline.

There should be a valve at the gas inlet into the boiler room in a lighted and convenient place for maintenance. There must be an insulating flange in front of the valve to protect against stray currents. At each branch from the gas distribution pipeline to the boiler, at least 2 shut-off devices are provided, one of which is installed directly in front of the burner. In addition to fittings and instrumentation on the gas pipeline, in front of each boiler, it is necessary to install automatic device, providing safe work boiler To prevent gases from entering the boiler furnace in the event of faulty shut-off devices, purge candles and safety gas pipelines with shut-off devices are required, which must be open when the boilers are idle. Low pressure gas pipelines are painted in boiler rooms in yellow, and medium pressure in yellow with red rings.

Gas-burners

Gas-burners- a gas burner device designed to be supplied to the combustion site, depending on technological requirements, a prepared gas-air mixture or separated gas and air, as well as to ensure stable combustion of gaseous fuel and regulate the combustion process.

The burners are presented the following requirements:

· the main types of burners must be mass-produced in factories;

· burners must ensure the passage of a given amount of gas and the completeness of its combustion;

· provide minimal amount harmful emissions in atmosphere;

· must operate without noise, flame separation or breakthrough;

· must be easy to maintain, convenient for inspection and repair;

· if necessary, could be used for reserve fuel;

· samples of newly created and existing burners are subject to GOST testing;

The main characteristic of burners is its thermal power, which is understood as the amount of heat that can be released during complete combustion of the fuel supplied through the burner. All these characteristics can be found in the burner data sheet.

INTRODUCTION

1.1 General provisions

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 the project, the requirements of the main regulatory documents:

– updated version of SNiP 42-01 2002 “Gas distribution networks”.

– SP 42-101 2003 “General provisions for the design and construction of gas distribution systems made of metal and polyethylene pipes.”

– GOST R 54-960-2012 “Block gas control points. Gas reduction points are cabinet-mounted.”

1.2 General information O locality

1.2.1 There are no industrial or municipal enterprises on the territory of the settlement.

1.2.2 The settlement is built up one storey buildings. Not available in the locality central heating and centralized hot water supply.

1.2.3 Gas distribution systems throughout the territory of the populated area are made underground from steel pipes. Modern gas distribution systems are a complex set of structures consisting of the following main elements of gas ring, dead-end and mixed networks of low, medium, high pressure, laid in the territory of a city or other populated area inside blocks and inside buildings, on mainlines - on mainlines of gas control stations (GRS).

CHARACTERISTICS OF THE CONSTRUCTION AREA

2.1 General information about the locality

Kinzebulatovo, Kinzebulat(bashk. Kinyebulat) - a village in the Ishimbaysky district of the Republic of Bashkortostan, Russia.

Administrative center rural settlement "Bayguzinsky Village Council".

The population is about 1 thousand people. Kinzebulatovo is located 15 km from the nearest city - Ishimbay - and 165 km from the capital of Bashkortostan - Ufa.

It consists of two parts - a Bashkir village and a former oil workers’ village.

The Tairuk River flows.

There is also the Kinzebulatovskoye oil field.

Agribusiness - Association of Peasant Farms "Udarnik"

CALCULATION OF CHARACTERISTICS OF NATURAL GAS COMPOSITION

3.1 Features gas fuel

3.1.1 Natural gas has a number of advantages compared to other types of fuel:

– low cost;

– high heat of combustion;

– transportation by main gas pipelines gas over long distances;

– complete combustion facilitates the working conditions of personnel and 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 of harmful substances during combustion than when burning solid or liquid fuels.

3.1.2. Natural gas fuel consists of combustible and non-combustible components. The larger the combustible part of the fuel, the more specific heat its combustion. Combustible part or organic matter includes organic compounds, which includes carbon, hydrogen, oxygen, nitrogen, sulfur. The non-combustible part consists of the room and moisture. The main components of natural gas are methane CH 4 from 86 to 95%, heavy hydrocarbons C m H n (4-9%), ballast impurities are nitrogen and carbon dioxide. The methane content in natural gases reaches 98%. The gas has neither color nor odor, so it is odorized. Natural flammable 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/100 m 3 of gas should not exceed:

– hydrogen sulfide – 2g;

– ammonia – 2g;

– cyanide compounds – 5;

– resin and dust – 0.1g;

– naphthalene – 10g. in summer and 5g. in winter.

– gases from pure gas fields. Consist mainly of methane, are dry or lean (no more than 50 g/m3 of propane and above);

– associated gases from oil fields contain a large amount of hydrocarbons, usually 150 g/m 3, are rich gases, a mixture of dry gas, propane - butane fraction and gas gasoline.

– gases of condensate deposits, this is a mixture of dry gas and condensate. Condensate vapor is a mixture of heavy hydrocarbon vapors (gasoline, naphtha, kerosene).

3.2.3. The calorific value of gas, pure gas fields, is from 31,000 to 38,000 kJ/m 3 , and associated gases of oil fields are from 38,000 to 63,000 kJ/m 3 .

3.3 Calculation of the composition of natural gas from the Proletarskoye field

Table 1-Composition of gas from the Proletarskoye field

3.3.1 Lower 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) = 41.34 MJ /m 3 .

3.3.3 Determination of gas fuel density:

Gas = 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)

Gaza = 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)= 1.08 kg/N 3

3.3.4 Determination of the relative density of gas fuel:

where air is 1.21–1.35 kg/m3;

ρ rel , (3)

3.3.5 Determining the amount of air required for combustion of 1 m 3 of gas theoretically:

[(0.5СО + 0.5Н 2 + 1.5H 2 S + ∑ (m +) С m H n) – 0 2 ]; (4)

V = ((1 + )86.7 + (2 + )5.3 +(3 + )2.4 +(4 + )2.0 +(5 + )1.5 = 10.9 m 3 /m 3;

V = = 1.05 * 10.9 = 11.45 m 3 / m 3.

3.3.6 We summarize the characteristics of gas fuel determined by calculation in Table 2.

Table 2 - Characteristics of gas fuel

Q MJ/m 3	Gas P kg/N 3	R rel.	kg/m 3	kg/m 3
41,34	1,08	0,89	10,9	11,45

V m 3 / m 3

ROUTING OF GAS PIPELINE

4.1 Classification of gas pipelines

4.1.1 Gas pipelines laid in cities and towns are classified according to the following indicators:

– by type of transported natural, associated, petroleum, liquefied hydrocarbon, artificial, mixed gas;

– by gas pressure of low, medium and high (category I and category II); – by field relative to land: underground (underwater), aboveground (overwater);

– by location in the planning system of cities and towns, external and internal;

– according to the construction principle (gas distribution pipelines): looped, dead-end, mixed;

– according to the material of the pipes: metallic, non-metallic.

4.2 Selection of gas pipeline route 4.2.1 The gas distribution system can be reliable and economical when making the right choice

routes for laying gas pipelines. The choice of 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

blocks. Gas pipeline routes are selected taking into account the shortest route for gas transportation.

4.2.2 Inlets are laid from street gas pipelines into each building. In urban areas with a new layout, gas pipelines are located inside the blocks. When routing gas pipelines, it is necessary to maintain 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 (in steps). In this case, the clear distance between gas pipelines should be sufficient for installation and repair of pipelines.

4.3.1 Gas pipelines should be laid at a depth of at least 0.8 m to the top of the gas pipeline or casing. In those places where the movement of transport and agricultural machinery is not envisaged, the depth of laying steel gas pipelines is allowed to be at least 0.6 m. In landslide and erosion-prone areas, the laying of gas pipelines should be provided to a depth of at least 0.5 m below the slip surface and below the predicted boundary destruction site. In justified cases, it is allowed to lay gas pipelines on land along the walls of buildings inside residential courtyards and neighborhoods, as well as on white sections of the route, including sections of crossings through artificial and natural barriers when crossing underground communications.

4.3.2 Above-ground and above-ground gas pipelines with embankment can be laid in rocky, permafrost soils, in wetlands and other difficult soil conditions. The material and dimensions of the embankment should be taken based on thermotechnical calculation, as well as ensuring the stability of the gas pipeline and embankment.

4.3.3 Laying gas pipelines in tunnels, collectors and canals is not permitted. 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 channels in permafrost soils under roads and railways.

4.3.4 Pipe connections should be permanent. Connections between steel pipes and polyethylene pipes can also be detachable in places where fittings, equipment and instrumentation are installed. Detachable connections 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 pipeline entries into buildings should be enclosed in a case. The space between the wall and the case should be sealed to the full thickness of the structure being crossed. The ends of the case should be sealed with elastic material. Gas pipeline entries into buildings should be provided directly to the room where the gas-using equipment is installed, or to adjacent rooms connected by a covered opening. It is not allowed to enter gas pipelines into basement and ground floors buildings, except for the introduction of natural gas pipelines into single-family and semi-detached houses.

4.3.6 A shut-off device on gas pipelines should be provided:

– in front of detached blocked buildings;

– to disconnect the risers of residential buildings above five floors;

– in front of outdoor gas-using equipment;

– in front of gas control points, with the exception of the gas distribution center of the enterprise, on the gas pipeline branch to which there is a shut-off device at a distance of less than 100 m from the gas distribution center;

– at the exit from gas control points, with looped gas pipelines;

– on branches of gas pipelines to settlements, individual microdistricts, blocks, groups of residential buildings, and when the number of apartments is more than 400, to individual houses, as well as on branches to industrial consumers and boiler houses;

– when crossing water barriers with two lines or more, as well as with one line when the width of the water barrier at a low-water horizon is 75 m or more;

– at the intersection of railways of the general network and highways of categories 1–2, if there is a shut-off device that ensures the cessation of gas supply at the crossing site, located at a distance from the roads of more than 1000 m.

4.3.7 Shut-off devices on above-ground gas pipelines,

laid along the walls of buildings and on supports, should be placed at a distance (in radius) from door and opening window openings of at least:

– for low pressure gas pipelines – 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 areas of transit laying of gas pipelines along the walls of buildings, the installation of disconnecting devices is not allowed.

4.3.8 Vertical distance (clear) between the gas pipeline (case) and underground engineering communications and structures at their intersections should be taken into account the requirements of the relevant regulatory documents, but not less than 0.2 m.

4.3.9 At places where gas pipelines intersect with underground communications, collectors and channels for various purposes, as well as at 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 must be brought out at a distance of at least 2 m on both sides from the outer walls of the crossed structures and communications, when crossing the walls of gas wells - at a distance of at least 2 cm. The ends of the case must be sealed waterproofing material. At one end of the case, at the upper points of the slope (with the exception of places where the walls of the wells intersect), a control tube should be provided, extending under protective device. In the interpipe space of the case and the gas pipeline, it is allowed to lay an operational cable (communications, 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 in accordance with GOST R 50838 of at least 2.5.

4.3.11 Laying gas pipelines from polyethylene pipes is not allowed:

– on the territory of settlements at pressure above 0.3 MPa;

– outside the territory of settlements at pressure above 0.6 MPa;

– for transporting gases containing aromatic and chlorinated hydrocarbons, as well as the liquid phase of LPG;

– when the temperature of the gas pipeline wall under operating conditions is below –15°C.

When using pipes with a safety factor of at least 2.8, it is permitted to lay polyethylene gas pipelines with pressures above 0.3 to 0.6 MPa in settlement areas with predominantly one- to two-story and cottage residential buildings. On the territory of small rural settlements It is permitted 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 must be at least 0.8 m to the top of the pipe.

4.3.12 Calculation of gas pipelines for strength should include determination of the thickness of the pipe walls and connecting parts and stresses in them. At the same time, for underground and above-ground steel gas pipelines, pipes and connecting parts with a wall thickness of at least 3 mm should be used, for above-ground and internal gas pipelines - at least 2 mm.

4.3.13 Characteristics limit states, reliability coefficients for responsibility, standard and design values ​​of loads and impacts and their combinations, as well as standard and design values ​​of material characteristics should be taken in calculations taking into account the requirements of GOST 27751.

4.3.14 When constructing in areas with complex geological conditions and seismic impacts, consideration should be given to special requirements and measures will be taken to ensure the strength, stability and tightness of gas pipelines. Steel gas pipelines must be protected from corrosion.

4.3.15 Underground and above-ground steel gas pipelines, LPG tanks, steel inserts of polyethylene gas pipelines and steel casings on gas pipelines (hereinafter referred to as gas pipelines) should be protected from soil corrosion and stray current corrosion in accordance with the requirements of GOST 9.602.

4.3.16 Steel casings of gas pipelines under roads, railways and tram tracks during trenchless installation (puncture, punching and other technologies permitted for use) should, as a rule, be protected by electrical protection means (3X3), during installation open method– insulating coatings and 3X3.

4.4 Selecting material for the gas pipeline

4.4.1 For underground gas pipelines, polyethylene and steel pipes. Steel pipes should be used for ground and above-ground gas pipelines. For internal low pressure gas pipelines, it is allowed to use steel and copper pipes.

4.4.2 Steel seamless, welded (straight seam and spiral seam) pipes and connecting parts for gas distribution systems must be made of steel containing no more than 0.25% carbon, 0.056% sulfur and 0.04% phosphorus.

4.4.3 The choice of pipe material, pipeline shut-off valves, connecting parts, welding materials, fasteners and others should be made taking into account the gas pressure, diameter and wall thickness of the gas pipeline, 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, and gullies. Gas pipelines at underwater crossings should be laid deep into the bottom of the water barriers being crossed. If necessary, based on the results of floating calculations, it is necessary to ballast the pipeline. The elevation of the top of the gas pipeline (ballast, lining) must be at least 0.5 m, and at crossings through navigable and floating rivers - 1.0 m below the predicted bottom profile for a period of 25 years. When carrying out work using directional drilling - no less than 20 m below the predicted bottom profile.

4.5.2 At underwater crossings the following should be used:

– steel pipes with a wall thickness 2 mm greater than the calculated one, 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) 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 above-water passage of the gas pipeline from the calculated level of water rise or ice drift (horizon high waters– GVV or ice drift - GVL) to the bottom of the pipe or span should be taken:

– at the intersection of ravines and gullies - not lower than 0.5 m and above the GVV 5% security;

– when crossing non-navigable and non-raftable rivers - at least 0.2 m above the water supply and water supply line of 2% probability, and if there is a grub boat on the rivers - taking it into account, but not less than 1 m above the water supply line of 1% probability;

- when crossing navigable and raftable rivers - no less than the values ​​​​established 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 transition boundaries. The transition boundary is considered to be the place where the gas pipeline crosses the high water horizon with a 10% probability.

4.6 Crossing artificial obstacles by a gas pipeline

4.6.1 Gas pipelines crossing artificial obstacles. Artificial obstacles include roads, railways and trams, as well as various embankments.

4.6.2 The horizontal distance from the places where underground gas pipelines intersect tramways, railways and highways must be no less than:

– to bridges and tunnels on public railways, tram tracks, roads of categories 1–3, as well as to pedestrian bridges, tunnels through them - 30m, and for non-public railways, roads of 4 - 5 categories and pipes - 15m;

– to the switch transportation zone (the beginning of the points, the tail of the crosses, the points where suction cables are connected to the rails and other track intersections) – 4 m for tram tracks and 20 m for railways;

– to the supports contact network- 3m.

4.6.3 It is permitted 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, roads of categories 1 - 4, as well as main city streets should be laid in cases. In other cases, the issue of the need to install cases is decided by the design organization.

4.7 Cases

4.7.1 Cases must meet the conditions of strength and durability. At one end of the case there should be a control tube extending 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 candle with a sampling device is installed at one end of the case, placed at a distance of at least 50 m from the edge of the roadbed (the axis of the outermost rail at zero marks). In other cases, the ends of the cases should be located at a distance:

– at least 2 m from the outermost rail of tram tracks and railways, 750 mm potassium, as well as from the edge of the roadway of streets;

– at least 3 m from the edge of the drainage structure of roads (ditch, ditch, reserve) and from the outermost rail of non-public railways, but not less than 2 m from the bottom of the embankments.

4.7.3 The depth of laying the gas pipeline from the base of the rail or the top of the road surface, and if there is an embankment, from its base to the top of the casing must meet safety requirements and be no less than:

– when performing open-cut work - 1.0 m;

– when carrying out work using the method of punching or directional drilling and panel laying – 1.5 m;

– when performing work using the puncture method – 2.5 m.

4.8. Intersection of pipes with roads

4.8.1 The thickness of the walls of steel gas pipeline pipes when crossing public railways should be 2 - 3 mm greater 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 Anti-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 is largely determined by the degree of protection against destruction upon contact with environment.

4.9.2 Corrosion is the destruction of metals caused by chemical or electrochemical processes during interaction with the environment. The environment in which metal is subject to corrosion is called corrosive or aggressive.

4.9.3 Most relevant to underground pipelines is electrochemical corrosion, which obeys the laws of electrochemical kinetics, this is the oxidation of metal in electrically conductive environments, accompanied by the formation and occurrence of electric current. In this case, interaction with the environment is characterized by cathodic and anodic processes occurring in different areas of the 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 average corrosiveness in the absence of stray currents, steel pipelines are protected with insulating coatings of a “very reinforced type”; in soils of high corrosiveness and the dangerous influence of stray currents - by protective coatings of a “very reinforced type” with the mandatory use of 3X3.

4.9.6 All envisaged types Corrosion protection is put into operation for the distribution of underground pipelines into operation. For underground steel pipelines in areas dangerously influenced by stray currents, 3X3 is put into effect no later than 1 month, and in other cases later than 6 months after laying the pipeline in the ground.

4.9.7 The corrosive aggressiveness of soil towards steel is characterized in three ways:

– specific electrical resistivity of the soil, determined in field conditions;

– electrical resistivity of the soil, determined in laboratory conditions,

– the average density of the cathode current (j k), necessary to shift 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 high aggressiveness of the soil, then the soil is considered aggressive, and the determination of other indicators is not required.

4.9.9 Dangerous influence of wandering direct current on underground steel pipelines is the presence of a pipeline potential displacement varying in sign and magnitude relative to its stationary potential (alternating zone) or the presence of only a positive potential displacement, usually varying in magnitude (anodic zone). For the pipelines being designed, the presence of stray currents in the ground is considered dangerous.

4.9.10 Hazardous effects alternating current on steel pipelines is characterized by a shift in the average potential of the pipeline in the negative direction by at least 10 mV relative to the stationary potential, or the presence of an 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 corrosiveness (protection against soil corrosion),

– in the presence of the dangerous influence of direct 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 metal polarization potentials is within the range of –0.85V. up to 1.15V on a saturated copper sulfate electrode for comparison (m.s.e.).

4.9.13 Insulation work under route conditions is carried out manually when insulating prefabricated joints and small fittings, correcting damage to the coating (no more than 10% of the pipe area) that occurred during transportation of pipes, as well as when repairing pipelines.

4.9.14 When repairing damage to factory insulation on site and laying the gas pipeline, compliance with the technology and technical capabilities coating application and quality control. All repair work insulating coating reflected in the gas pipeline passport.

4.9.15 Polyethylene, polyethylene tapes, bitumen and bitumen-polymer mastics, built-up bitumen-polymer materials, rolled mastics are recommended as the main materials for the formation of protective coatings. tape materials, compositions based on chlorosulfonated polyethylene, polyester resins and polyurethanes.

DETERMINATION OF GAS CONSUMPTION

5.1 Gas consumption

5.1.1 Gas consumption by network sections can be divided into:

travel, transit and dispersed.

5.1.2 Travel flow rate is a flow rate that is evenly distributed along the length of a section or the entire gas pipeline and is equal or very close in value. It can be selected through identical in size and for ease of calculation it is evenly distributed. Typically, this flow rate is consumed by gas appliances of the same type, for example, capacitive or instantaneous water heaters, gas stoves, etc. Concentrated flows are those that pass through the pipeline, without changing, along the entire length and are collected at certain points. The consumers of these expenses are: industrial enterprises, boiler houses with constant consumption over a long period of time. Transit costs are those that pass through a certain section of the network without changing and provide gas flow, being a route or concentrated flow to the next section.

5.1.2 Gas consumption in a populated area is travel or transit. There are no concentrated gas costs, since there are no industrial enterprises. Travel expenses are made up of expenses gas appliances installed by consumers, and depends on the season of the year. The apartment is equipped with four burner stoves of the Glem UN6613RX brand with a gas flow rate of 1.2 m 3 / h, a Vaillant type instantaneous water heater for hot flow with a flow rate of 2 m 3 / h, DHW water heaters"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 varies by hour, day, day of the week, month of the year. Depending on the period during which gas consumption is assumed to be constant, they are distinguished: seasonal unevenness or unevenness by month of the year, daily unevenness or unevenness by day of the week, hourly unevenness or unevenness by hour of the day.

5.2.2 The unevenness of gas consumption is associated with seasonal climatic changes, the operating mode of enterprises during the season, week and day, the characteristics of the gas equipment of various consumers, and to study the unevenness, stepwise gas consumption is built over time. To regulate seasonal unevenness in gas consumption, the following methods are used:

– underground gas storage;

– the use of consumers of regulators that dump excess into summer period;

– reserve fields and gas pipelines.

5.2.3 To regulate unevenness gas consumption gas in the winter months, they use gas extraction from underground storage facilities, and during short periods of the year, injection into underground storage facilities. To cover daily peak loads, using underground storage facilities is not economical. In this case, restrictions are imposed on the gas supply to industrial enterprises and peak coverage stations are used, in which gas liquefaction occurs.

For gas composition, determined from the average component composition of natural gas depending on the field, it is necessary to calculate the characteristics of the gaseous fuel. The characteristics of natural gas are given in Table 1.

Table 1 – Gas composition by volume for various fields

Gas component	CH 4	WITH 2 N 6	WITH 3 N 8	WITH 4 N 10	WITH 5 N 12	N 2	CO 2	N 2 S
Field	Severostavropolskoye, Stavropol Territory
Field	Bearish, Tyumen region
Field	Vaneiviskoe, Arkhangelsk region
Field	Zapolyarnoye, Tyumen region
Field	Layavozh, Arkhangelsk region
Field	Vasilkovskoe, Arkhangelsk region

Calorific value of gas– the amount of heat that can be obtained from the complete combustion of 1 m3 of gas under normal conditions.

There are higher and lower calorific values ​​of fuel.

Gross calorific value of gas– the amount of heat obtained from the complete combustion of 1 m3 of gas, including the heat released during the condensation of water vapor from combustion products.

Lower calorific value of gas- the amount of heat obtained during the combustion process, excluding the heat of condensation of water vapor - combustion products.

In practice, when gas is burned, water vapor does not condense, but is removed with other combustion products, so the calculation is based on the lower calorific value of the gas.

The calorific value (higher or lower) of dry gaseous fuel (gas) is determined by the formula

, (1)

where Q c is the heat of combustion of dry gas, kJ/m 3 ;

Q 1 , Q 2 , Q k – heat of combustion of the components that make up the gaseous fuel, kJ/m 3 ;

x 1 , x 2 , x 3 – volume fractions of the components that make up the gaseous fuel, %.

Table 2 – Heat of combustion of pure combustible gases

	Heat of combustion
	at 0 °C, and 101.3 kPa
Isobutane
Carbon monoxide
Hydrogen sulfide

The density of dry gas is determined as the sum of the products of the densities of the components that make up the gaseous fuel and their volume fractions:

, (2)

where p is the density of dry gas, kg/m3;

p 1 , p 2 , … , p k – densities of components, kg/m 3 .

Table 3 – physical characteristics gases

Gas composition	Density. kg/m 3 att = 0 0 C P=101.3 kPa	Relative density in air
Methane CH 4
Ethane C 2 H 6
Propane C 3 H 8
Butane C4H10
Isobutane C5H12
Carbon dioxide CO2
Hydrogen sulfide H 2 S

The relative density of dry gas in air is:

, (3)

where p in = 1.293 - air density under normal conditions, kg/m 3.

The gas characteristics are summarized in Table 4.

Table 4 - Characteristics of gaseous fuel under normal physical conditions (T=273.15 K, P=101.325 kPa)