Introduction to the exchange rate on gas supply of the city district

Contents

Contents 

Introduction

2. Calculation and explanatory part

2.1 Characteristics of gas-supplied territory

2.2 Main characteristics of gas fuel

2.3 Estimated Gas Consumption by City District

2.4 Description of the gas distribution system of the city district 

2.5 Number of network gas control points (GRP) and their location in the area 20 

2.6 Hydraulic calculation of LPC distribution gas pipelines

2.7 Hydraulic calculation of SHP distribution gas pipelines

2.8 Construction of in-house gas pipelines.............................................................................................................................................................  

2.9 Selection of gas pipeline material, type of gas pipeline laying and their corrosion protection 

     3. Conclusion

     4. List of sources used

Introduction

Modern city  gas supply distribution systems are a complex complex of structures, consisting of the following main elements of low, medium and high pressure gas networks, gas distribution stations (GRS), gas control points (GRS) and plants (GRU). To control the operation of this system, there is a special service with appropriate means to ensure the possibility of uninterrupted gas supply.

 Gas supply projects of regions, cities and towns are developed on the basis of schemes of promising gas flows, schemes for the development and placement of sectors of the national economy and projects of district plans, master plans of cities taking into account their development for the future. The gas supply system shall ensure uninterrupted gas supply to consumers, be safe in operation, simple and convenient to maintain, shall provide for the possibility of disconnecting individual elements or sections of the gas pipeline for repair and emergency work.

The main element of urban gas supply systems are gas pipelines, which are classified by gas pressure and purpose. Depending on the maximum gas pressure, city gas pipelines are divided into the following groups:

- low-pressure gas pipelines with gas pressure up to 5 kPa;

- medium pressure gas pipelines with pressure from 5 kPa to 0.3 MPa;

- high-pressure pipelines of category II with pressure from 0.3 to 0.6 MPa;

- high-pressure pipelines of category I with gas pressure from 0.6 to 1.2 MPa.

Low-pressure gas pipelines serve to transport gas to residential, public buildings and consumer services.

Medium and high (II category) pressure pipelines are used to supply urban low and medium pressure distribution networks through FRG.

City gas pipelines of high (I category) pressure are the main arteries feeding a large city, they are made in the form of a ring, a half-ring or in the form of rays.

In this course project, it is necessary to select and calculate the city, quarter and house  gas supply system, as well as the selection of GRU equipment and the calculation of the burner for the boiler of the quarterly boiler room according to the initial data.

Technical and economic advantages of gas use:

- Gas is a versatile, high-quality fuel that can satisfy all the needs of production and eliminates the need to use other types of fuel and electricity.

- Ease of transportation and no need for storage provide a high economic effect of replacing other types of fuel with gas.

- The use of gas improves the sanitary and hygienic conditions of work at work and living conditions of the population. It contributes to the growth of labor productivity, allows you to improve the air pool in cities and industrial centers.

- Natural gas is a valuable chemical raw material of the industry for the production of alcohol, rubber, plastics, etc.

- Gas has the following advantages over solid fuel:

- easy transportation to consumption objects;

- ignition speed and combustion cessation;

- possibility of complete combustion in case of slight excess air with achievement of high temperatures in furnace devices;

- ease of maintaining the required process atmosphere (oxidative, reducing, neutral)

Natural gas supply to cities and settlements aims to:

improving the living conditions of the population;

replacing more expensive solid fuel or electricity in thermal processes at industrial enterprises, thermal power plants, at municipal enterprises, in medical institutions, catering enterprises, etc.;

improving the ecological situation in cities and settlements, since natural gas during combustion practically does not emit harmful gases into the atmosphere.

Natural gas is supplied to cities and towns through main gas pipelines starting from gas production sites (gas fields) and ending at gas distribution stations (GRS) located near cities and towns.

To supply gas to all consumers, a gas distribution network is being built in the cities, gas control points or installations (GRP and GRU) are being equipped, control points and other equipment necessary for the operation of gas pipelines are being built.

On the territory of cities and villages, gas pipelines are laid only underground.

On the territory of industrial enterprises and thermal power plants, gas pipelines are laid above the ground on separate supports, on overpasses, as well as on the walls and roofs of production buildings.

Gas pipelines shall be laid in accordance with the requirements of SNiP [1].

Natural gas is used by the population for burning in domestic gas appliances: stoves, water gas heaters, in heating boilers

At public utilities, gas is used to obtain hot water and steam, baking bread, cooking in canteens and restaurants, and heating rooms.

In medical institutions, natural gas is used for sanitary treatment, preparation of hot water, for cooking.

At industrial enterprises, gas is burned primarily in boilers and industrial furnaces. It is also used in technological processes for heat treatment of products manufactured by the enterprise.

In agriculture, natural gas is used to prepare feed for animals, to heat agricultural buildings, and in production workshops.

When designing gas networks of cities and towns, the following issues have to be solved:

identify all gas consumers in the gasified area;

determine the gas flow rate for each consumer;

Determine where distribution gas pipelines are laid;

determine the diameters of all gas pipelines;

select equipment for all GRP and GRU and determine their locations;

to pick up all shutoff valves (latches, cranes, gates);

determine the places of installation of control tubes and electrodes for monitoring the state of gas pipelines during their operation;

develop methods of laying gas pipelines at their intersection with other communications (roads. heat tracts, rivers, ravines, etc.);

determine the estimated cost of construction of gas pipelines and all structures on them;

disassemble measures for safe operation of gas pipelines.

The volume of issues to be resolved from the listed list is determined by the assignment on the course or diploma project.

The initial data for gas supply network design are:

composition and characteristics of natural gas or gas field;

climatic characteristics of the construction area;

development plan of a city or settlement;

data on the coverage of gas supply to the population;

characteristics of heat supply sources of the population and industrial enterprises;

data on production by industrial enterprises and heat consumption standards per unit of these products;

population of the city or population density per hectare;

list of all gas consumers for the period of gasification and prospects for the development of the city or village for the next 25 years;

list and type of gas-using equipment at industrial and municipal enterprises;

storey of residential areas.

II Calculated - Explanatory Part

2.1 Characteristics of gas-supplied territory

Argengelsk is a city in the north of the European part of Russia. The administrative center of the Arkhangelsk region and the Primorsky municipal district forms the urban district of Arkhangelsk. The population is 350,985 people. (estimate as of January 1, 2013). It is located on both banks of the Northern Dvina and the delta islands 3035 km from the confluence of the river in the White Sea. The climate is temperate, marine.

The city is located at the mouth of the Northern Dvina, 3035 kilometers from its confluence with the White Sea. Arkhangelsk is located on a flat area. Altitude - 7 meters. The territory of the urban district of Arkhangelsk is 29442 hectares (294.42 km ²). The city embankments stretched along the river sleeves for 35 km.

Arkhangelsk is equated with the regions of the Far North.

The climate of the city is temperate, marine with long moderately cold winters and short cool summers. It is formed under the influence of the northern seas and transfers of air masses from the Atlantic in conditions of small amounts of solar radiation. The average January temperature is − 12.8 °, July - + 16.3 °. 607 mm of precipitation falls per year .

Arkhangelsk is characterized by frequent weather changes, high humidity and a large number of days with precipitation. During the invasion of cold air from Siberia in winter, frosts periodically up to − 45 ° C (the last time − 45 ° was noted on January 21, 2010), at the same time there are sometimes thaws. In summer, with the invasion of a hot air mass from the steppes of Kazakhstan, heat is possible, while in summer at night frosts are possible.

The maximum temperature in Arkhangelsk + 34.4 ° was recorded on July 13, 1972. The minimum temperature of − 45.2 ° was recorded on January 8, 1885.

Climatological data:

The estimated temperature of the coldest five-day period, with a security of 0.92: 21 ° С.

Average annual temperature: + 1.3 ° С.

Heating period: 

          duration: 273 days,

          average outside air temperature -8 ° С,

2.2 Main characteristics of gaseous fuel

To determine the composition of natural gas, it is necessary to know its lower combustion heat Qnr. It is determined based on the composition of the gas and lies in the range of 35... 40 MJ/m3.

2.4 Description of the gas distribution system of the city district 

Gas supply systems are a complex complex of structures. The choice of the gas supply system of the city is influenced by a number of factors. This is primarily: the size of the gasified territory, the features of its layout, population density, the number and nature of gas consumers, the presence of natural and artificial obstacles to the laying of gas pipelines (rivers, dams, ravines, railway tracks, underground structures, etc.). When designing the gas supply system, they develop a number of options and make a technical and economic comparison. For construction, the best option is used.

Depending on the maximum gas pressure, city gas pipelines are divided into the following groups:

high pressure category 1 with pressure from 0.6 to 1.2 MPa;

high pressure category 2 with pressure from 0.3 to 0.6 MPa;

average pressure from 5 kPa to 0.3 MPa;

low pressure up to 5 kPa;

High and medium pressure gas pipelines serve to supply medium and low pressure urban distribution networks. They are the bulk of the gas to all consumers of the city. These gas pipelines are the main arteries supplying the city with gas. They are made in the form of rings, the floor of rings or rays. Gas is supplied to high and medium pressure gas pipelines from gas distribution stations.

Modern systems of urban gas networks have a hierarchical construction system, which is associated with the above classification of gas pipelines by pressure. The upper level consists of high-pressure gas pipelines of the first and second categories, and lower low-pressure gas pipelines. The gas pressure during the transition from a high level to a lower level gradually decreases. This is done using pressure regulators installed on the FRG.

According to the number of pressure stages used in urban gas networks, they are divided into:

two-stage, consisting of high or medium pressure and low pressure networks;

three-stage, including high, medium and low pressure gas pipelines;

multi-stage, in which gas is supplied through gas pipelines of high (1 and 2 categories) pressure, medium and low pressure.

The choice of the gas supply system in the city depends on the nature of gas consumers who need gas of the appropriate pressure, as well as on the length and load of gas pipelines. The more diverse gas consumers and the greater the length and load of gas pipelines, the more difficult the gas supply system will be.

In most cases, for cities with a population of up to 500 thousand people, the most economically feasible is a two-stage system. For large cities with a population of more than 1,000,000 people and the presence of large industrial enterprises, a three or multi-stage system is preferable.

Since the city is medium-sized and has consumers that require different pressures, we accept a two-stage gas supply scheme with a gas pipeline of low (up to 0.005 MPa) and high (up to 0.6 MPa) pressure. In this case, the high-pressure gas pipeline is designed as a dead end, since it is the main artery supplying gas to the city area. Large gas consumers join the high-pressure network: an industrial enterprise, a quarterly boiler room, public catering enterprises, and a network GRP. 

Low pressure networks consist of ring gas pipelines.

The connection between the high and low pressure gas pipelines is carried out through the network FRG, where the pressure decreases to the required value and is kept constant automatically.

The gas distribution station is located in the southeast of the city district at a distance of 1200 m.

2.9 Selection of gas pipeline material, type of gas pipeline laying and their corrosion protection.

Materials and technical products used in gas supply systems must first of all be reliable and meet the requirements of state standards or technical conditions approved in accordance with the established procedure and passed state registration. Steel pipes are used for gas pipelines. 

For underground inter-settlement gas pipelines with a pressure of up to 0.6 MPa and underground gas pipelines with a pressure of up to 0.3 MPa laid in the settlements, steel pipes are used in accordance with the Safety Rules of the State City Technical Supervision of the Russian Federation PB 1252903. On the territory of cities and industrial enterprises saturated with engineering communications, gas pipelines from non-metallic pipes are not built, so we choose steel pipes.

The laying of external gas pipelines in the territory of settlements should be provided, as a rule, underground. Above-ground and ground laying of external gas pipelines is allowed inside residential quarters and courtyards, as well as on other separate sections of the route.

There are 2 methods of protecting gas pipelines from corrosion - active and passive.

Passive consists in the isolation of gas pipelines (bitumen mineral and bitumen rubber mastic). To enhance insulation, reinforcing wrappers made of waterproofing brizole and glass fiber are used. Plastic film materials coated with an adhesive layer are also used for protection.

Active methods include cathodic and tread protection and drainage.

III Conclusion

This course project is the basis for the development of the course of the discipline "Gas Supply," studied in the specialty "Heat and Gas Supply and Ventilation."

This exchange rate project defines the physical characteristics of natural gas used for gas supply to a residential microdistrict in the city of Arkhangelsk:

Qnr = 36,884 * 0,993 = 36,626 (MJ/m3), αg = 0,7994 kg/m3, W0 = 40964

The annual gas demand of a residential microdistrict with a population of 7,790 people is calculated using specific gas consumption standards. The estimated hour gas flow rate by the microdistrict, to which the corresponding equipment of the network gas control station was selected: pressure regulator RDNK-400M, safety shutoff valve of the PKK 40MN type, gas filters of the FG-506 type, safety relief valve PSK50S/50, was also determined.

Designed a low-pressure internal supply network and an internal house network of a one-story residential building, which has as gas devices a 4-fold gas stove used for cooking. Using hydraulic calculation, diameters of gas pipelines are determined, which provide pressure losses in the gas network, which do not exceed 200 Pa for the internal supply network and 400 Pa for the internal house network.