Calculation of heat supply of industrial area

Contents

Introduction

1 Organizational - technical section

1.1 Design Input

1.2 Characteristics of the heat supply object

1.3 Selection of coolant and its parameters

1.4 Method of heat network laying

1.5 Thermal Insulation Design Selection

2 Design section

2.1 Determination of design heat flow rate

2.2 Annual Heat Consumption

2.3 Schedule of heat load duration

2.4 Characterization and calculation of heat release control

2.5 Hydraulic calculation of heat network

2.6 Thermal calculation

3 Economic section

3.1 Heat Transport Economics

Conclusion

List of sources used

List of drawings

Introduction

Heat supply is a large branch of the national economy. Suffice it to say that for the needs of heat supply, 25% of all produced and generated fuel is spent annually. In the context of limited fuel resources, the rational and economical use of fuel resources is a task of great national importance. A significant role in solving this problem is given to centralized heat supply and heating, which are closely related to electrification and energy. Centralized heat supply is based on the use of large district boiler houses, characterized by significantly higher efficiency than small heating plants. Heating, that is, centralized heat supply based on combined heat and electricity generation, is the highest form of district heat supply. It reduces fuel consumption by 20-25%. In addition to fuel economy, the centralization of heat supply is of great social importance, contributing to increased labor productivity, displacing low-skilled professions, improving working conditions and improving the culture of production. Centralized heat supply systems significantly improve the living conditions of the population. With centralized heat supply, small heating plants that are sources of air basin pollution are eliminated, and large heat sources are used instead, the gas emissions of which contain minimum concentrations of toxic substances. Thus, the centralization of heat supply contributes to solving the major problem of our time - the protection of the natural environment .

Currently, as a result of advances in the use of nuclear fuel, a new direction is developing - centralized heat supply based on nuclear power plants and nuclear boiler houses. The use of nuclear fuel for heat supply reduces the consumption of scarce organic fuel and facilitates solving the problem of the country's fuel and energy balance.

For district heating, two types of heat sources are used: thermal power plants (CHP) and district boiler houses (PK). Combined heat and electric power generation is carried out at the CHPP, which provides a significant reduction in specific fuel consumption during electricity generation. At the same time, first, the heat of the working medium - water vapor - is used to obtain electricity during steam expansion in turbines, and then the remaining heat of the spent steam is used to heat water in heat exchangers that make up the heating equipment of the CHP. Hot water is used for heat supply. Thus, at the CHP, high-potential heat is used to generate electricity, and low-potential heat is used for heat supply. This is the energy sense of combined heat and electricity generation. With their separate generation, electricity is obtained at condensing stations (CES), and heat in boiler houses. In condensers of steam turbines at CES, a deep vacuum is maintained, which corresponds to low temperatures, and cooling water is not used. As a result, additional fuel is used for heat supply. Therefore, separate production is less cost effective than combined production.

The advantages of heating and district heating are most pronounced in the concentration of heat loads, which is typical for modern developing cities. It should be borne in mind that when heating, capital investments in CHP and heat networks turn out to be more than in CES and centralized heat supply systems from PK, so it is economically advisable to build a CHP only under high thermal loads.

Hot water is used as heat carrier for heat supply to cities, and water steam is used for heat supply to industrial enterprises. Heat carrier from heat sources is transported via heat conductors. Hot water is supplied to consumers via heat supply lines, gives its heat in heat exchangers and after cooling it is returned via return heat lines to the heat source. Thus, the heat carrier continuously circulates between the heat source and the consumers. Coolant circulation is provided by heat source pump station. Water steam is supplied to industrial consumers through steam pipelines under its own pressure, condenses in heat exchangers and gives off its heat. The resulting condensate is returned to the heat source by overpressure or by means of condensate pumps.

Modern heat networks of urban heat supply systems are complex engineering structures. The length of the heating networks from the source to the extreme consumers is tens of kilometers, and the diameter of the highways reaches 1400 mm. Heat networks include heat pipelines; compensators that perceive temperature elongations; disconnecting, regulating and safety equipment installed in special chambers or pavilions; pump stations; district thermal points (RTP) and thermal points (TP).

Heat conductors are laid underground in non-passing and semi-passing channels, in headers and without channels. Heat insulation is used to reduce heat losses when heat carrier moves through heat conductors.

To control the hydraulic and thermal modes of the heat supply system, it is automated, and the amount of heat supplied is controlled in accordance with the requirements of consumers. The largest amount of heat is spent on heating buildings. The heating load changes as the outside temperature changes. To keep the heat supply consistent with the needs, it uses central control at the heat sources. It is not possible to achieve high quality of heat supply, using only central regulation, therefore, additional automatic control is used at heat stations and consumers. Water consumption for hot water supply continuously changes, and to maintain stable heat supply hydraulic mode of heating networks automatically

and the temperature of the hot water is kept constant.

Heat points are central (CTP) and individual (ITP). Heat supply from CTP is provided for several buildings, and from ITP - one building. CTP is located in separate one-story buildings, and ITP is located in the building room. Heat stations provide the necessary amount of heat to the buildings for their heating and ventilation with automatic maintenance of the necessary hydraulic and thermal modes in the heating systems. In heat exchangers, tap water is heated to 65 ° C, and then it is supplied to residential and public buildings for hot water supply. The hot water temperature is controlled automatically .

Organizational and Technical Section

1.3 Selection of coolant and its parameters

In a centralized heat supply system, water and steam are used as a coolant, in connection with which water and steam systems are distinguished.

The advantage of water as a coolant:

a) easily regulated;

b) less heat loss per 1 km of heat line;

c) high efficiency of heat supply system;

d) increased accumulation of water system;

e) minimum cost of connection to heat networks.

Disadvantages of water as coolant:

a) high consumption of electric power for pumping compared to the consumption of electric power for pumping condensate in steam systems;

b) high sensitivity to accidents, because coolant leakage from steam networks due to significant specific volumes of steam is many (about 20-40) times less than in water systems (in case of small damage, steam networks can remain in operation for a long time, while water systems require stopping);

c) high density of coolant and rigid hydraulic communication between all points of the system.

1.3.1 Selection of coolant parameters

Parameters in steam heat supply systems are determined by process requirements. Increasing the temperature of water in heat supply systems leads to a decrease in pipe diameters and a decrease in pumping costs. The "water" coolant is used for heating, ventilation, hot water supply with a temperature in the supply pipeline of 150 ° С, in the reverse - 70 ° С.

1.3.2 Selection of coolant type

If the heat load of the district consists only of heating, ventilation and hot water supply, then water is used as the coolant. In cases where there is also a small process load in the area requiring increased potential (steam), and the seasonal load is not large, steam is used as a coolant. In complex cases, the coolant is determined by technological calculation.

In this course design, we select a coolant - water.

1.4 Method of heat network laying

When designing the heat supply of new areas at the first stage, it is required to select the direction (route) of the heat networks from the heat source to the consumers. This is done according to the heat map of the district, taking into account the materials of geodetic survey of the area, the plan of existing and planned above-ground and underground structures and communications, data on the characteristics of soils and the height of the state of groundwater, etc.

When choosing a heat network route, the following basic conditions are taken into account: reliability of heat supply, quick elimination of possible malfunctions and accidents, safety of maintenance personnel, the smallest length of the heat network and the minimum amount of work on its construction. At the same time, the possibility of joint laying of heat pipelines with other engineering networks (water pipelines, gas pipelines, sewers, etc.) is also taken into account if this is allowed according to the conditions of reliability of all networks and safety of their maintenance. Joint laying can be carried out both underground (in impassable and through channels, urban and intra-quarter headers) and above-ground (multi-level supports, masts, racks). Such solutions usually lead to a reduction in the total cost of building utilities.

In residential areas of cities, the thermal pipeline route is laid, as a rule, in technical lanes separate for engineering networks parallel to the red lines of streets, roads and driveways outside the roadway and the strip of green spaces. During justification it is allowed to lay heat lines under the roadway and sidewalks.

In order to reduce corrosion of underground heat pipelines during route laying, crossings and approach to sources of wandering currents (tram tracks, DC suction cables, etc.) by wetlands, areas undergoing flooding, contaminated territories should be avoided.

In the territory not subject to development, as a rule, above-ground laying of heat conductors on low supports is used. At the same time, the route of heat networks should be planned along roads or taking into account the construction of roads for the construction and maintenance of heat networks. According to the reliability conditions, it is not allowed to lay thermal conductors along the eyebrows of ravines, terraces and artificial excavations during planting soils. To reduce the cost of building and operating heating networks, crossings of rivers, ravines and wetlands should be avoided .

At plant sites, heat networks are usually laid in specially designated technical lanes outside the roadway together with process pipelines, regardless of the parameters of the coolant and the medium, both above-ground and underground.

Pipelines are crossed with utility networks and various structures at different levels with certain distances between them, as well as with the implementation of measures that eliminate their harmful mutual influence. At the same time, in order to reduce the costs of building heat networks and to increase the reliability of heat supply, it is desirable to intersect them with complex communications (railways and roads, tram tracks, metro lines, rivers, etc.) buildings and structures at an angle of 90 °; for the metro line, this angle can be reduced to 60 °, for the rest - 45 °.

The slope of heat networks in the sections shall be accepted at least 0.002 regardless of the direction of movement of the coolant and the method of laying, with the exception of individual sections: at intersections, gaskets in places, etc., where laying without a slope is allowed. On the route of heat networks in the lower points, descent devices are indicated, and in the higher ones - airbags that are placed in chambers. Water is lowered from pipelines to discharge

wells with water discharge from them by gravity or pumps (directly from pipelines) in the sewage system (with water temperature not exceeding 40 ° С) and in absorbing wells.

For this city, we choose an underground method of laying pipelines in impassable channels, guided by the fact that wet soil conditions prevail in the city of Kursk.

The underground method is the main in residential areas, since the territory is not cluttered and the architectural appearance of the city does not deteriorate.

When laying in channels, heat conductors are protected from all sides from mechanical influences and loads and to some extent from ground and surface waters. Special movable supports are installed to perceive the self-weight of the heat line.

Channels are currently made, as a rule, from unified prefabricated reinforced concrete parts. For protection against ground and surface waters, external surface of channels is covered with bitumen with adhesive by means of hydro-protective roll material. To collect moisture that falls into the channels, their bottom should be given a transverse slope of at least 0.002 to one side, where sometimes closed (plates, grates) trays are made, along which water flows into the prefabricated pits, from where it is drained into the reservoir.

Impassable channels are usually used for heat conductors with a diameter of up to 500-700 mm. They are made rectangular, vaulted and cylindrical in shape from reinforced concrete slabs and arches, asbestos cement and metal pipes, etc. Air gap is usually left between surface of heat conductors and walls of channel, through which thermal insulation dries and moisture is removed from channels.

1.5 Thermal Insulation Design Selection

Thermal insulation is arranged on pipelines, valves, flange connections, compensators and supports for the following purposes: reduction of heat losses during its transportation, which reduces the installed capacity of the heat source and fuel consumption; reduction of coolant temperature drop supplied to consumers, which reduces required coolant flow rate and improves heat supply quality; lowering the temperature on the surface of the heat pipe and air in service places (chambers, channels), which eliminates the danger of burns and facilitates maintenance of heat pipes.

In addition, heat insulation coatings sometimes play the role of corrosion protection of the outer surface of steel pipes and equipment, which increases their durability and reliability of heat supply.

For thermal insulation, materials having low thermal conductivity and low corrosion activity coefficient, low water absorption, high electrical resistance and high mechanical strength are used. Materials subject to combustion and rotting, as well as substances capable of releasing acids, strong alkalis, harmful gases and sulfur, shall not be used.

The most difficult conditions for the operation of thermal conductors arise with underground channel and especially without channel laying due to moistening of thermal insulation with ground and surface waters and the presence of wandering currents in the soil. In this regard, the most important requirements for thermal insulation materials include low water permeability, high electrical resistance, and mechanical strength.

As thermal insulation in thermal networks, currently mainly inorganic materials (mineral and glass wool), lime-silica, sovelite, vulcanite, as well as compositions made of asbestos, concrete, asphalt, bitumen, cement, sand or other components are used.

Depending on the type of products used, thermal insulation is divided into wrapping (mats, strips, cords, bundles), piece (slabs, blocks, bricks, cylinders, semi-cylinders, segments, shells), pouring (monolithic, cast), mastic, backfilling.

Thermal insulation structures of steel pipelines during underground channel laying usually consist of three layers: anti-corrosion and cover. The anti-corrosion layer is superimposed on the outer surface of the steel pipe and is made of dressing and wrapping materials in not so many layers (lysol or brie ash on ash and ash mastic, epoxy or organosilicate enamels and paints, glass-ceramic, etc.). The main heat-insulating layer of wrapping, piece or monolithic products is laid on top of it. Behind it is a cover layer that protects the heat insulation layer from moisture and air from mechanical damage.

Conclusion

In this course project, a heat supply system was calculated for the city of Kursk. The course project consists of three sections.

1 The organizational and technical section considers the initial data for the design, describes the characteristics of the heat supply object, the route and the method of laying the heat network, as well as the selection of the thermal insulation structure.

2 Calculations are made in the Design section:

a) Estimated heat consumption from heat supply source, total annual heat consumption and losses in heat networks are determined. This is necessary in order to know how much heat needs to be generated, and at what temperature to supply the coolant to the system, in order to provide all areas with the necessary amount of heat for heating and hot water supply.

b) the heating load temperature control schedule was calculated and constructed, which is necessary to control the amount of heat generated at the CHP in accordance with the external air temperature.

c) hydraulic calculation was carried out, the task of which is to determine the diameters of the pipeline, the speed of the coolant, as well as determine pressure and head losses at any point of the thermal network. According to this calculation, a piezometric graph is built

d) Thermal calculation of the heat supply system was carried out, the task of which is to calculate the insulation thickness of pipelines, at which there will be minimum economic costs for materials and minimum heat losses to the environment.

3 In the economic section, the cost of heat losses in the network, the cost of electricity for pumping the coolant, the cost of annual operating costs and the amount of heat transportation costs was calculated, which amounted to 3.41 rubles/GJ .

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