GOST 25720-83

UDC 001.4.621.039.8:006.354 Group E00

001.4.621.56:006.354

621.039.5:001.4:006.354

621.452.3.6:006.354

INTERSTATE STANDARD

WATER BOILERS

Terms and Definitions

Heat water boilers. Terms and definitions

ISS 01.040.27

Date of introduction 01/01/84

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of Energy Engineering

2. APPROVED AND ENTERED INTO EFFECT by Resolution of the USSR State Committee for Standards dated April 14, 1983 No. 1837

3. The standard fully complies with ST SEV 3244-81

4. INTRODUCED FOR THE FIRST TIME

5. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS

6. REPUBLICATION. 2005

This standard establishes the terms and definitions of basic concepts of hot water boilers used in science, technology and production.

The terms established by the standard are mandatory for use in all types of documentation, scientific, technical, educational and reference literature.

There is one standardized term for each concept.

The use of synonymous terms of a standardized term is not allowed.

Synonyms that are unacceptable for use are given in the standard as reference and are designated “NDP”.

Established definitions can, if necessary, be changed in the form of presentation, without violating the boundaries of concepts.

The standard provides an alphabetical index of the terms it contains.

Standardized terms are in bold, invalid synonyms are in italics.

	Definition
1. Boiler NDP. Steam generator	According to GOST 23172
2. Hot water boiler	Boiler for heating water under pressure
3. Hot water waste heat boiler NDP. Recovery hot water boiler	A hot water boiler that uses the heat of hot lawns technological process or engines
4. Hot water boiler with natural circulation	A hot water boiler in which water circulation is carried out due to the difference in water density
5. Hot water boiler with forced circulation	A hot water boiler in which water is circulated by a pump
6. Direct-flow hot water boiler	Hot water boiler with sequential single forced movement of water
7. Hot water boiler with combined circulation	A hot water boiler that has circuits with natural and forced water circulation
8. Electric hot water boiler	A hot water boiler that uses electrical energy to heat water
9. Stationary hot water boiler	Hot water boiler installed on a fixed foundation
10. Mobile hot water boiler	Hot water boiler mounted on a vehicle or on a movable foundation
11. Gas-tube hot water boiler	A hot water boiler in which the products of fuel combustion pass inside the heating surface pipes, and water passes outside the pipes Note. There are fire-tube, smoke-fired and fire-tube-smoke-fired water heating boilers
12. Water tube boiler	A hot water boiler in which water moves inside the heating surface pipes, and fuel combustion products move outside the pipes
13. Heat output of water heating boiler	The amount of heat received by water in a hot water boiler per unit time
14. Nominal heating output of the hot water boiler	The highest heating output that a water heating boiler must provide during long-term operation at nominal values ​​of water parameters, taking into account permissible deviations
15. Design water pressure in the hot water boiler	Water pressure taken when calculating the strength of a water heating boiler element
16. Operating water pressure in the hot water boiler	The maximum permissible water pressure at the outlet of the hot water boiler during normal operation
17. Minimum operating water pressure in a hot water boiler	Minimum permissible water pressure at the outlet of a hot water boiler, at which the nominal value of subheating of water to boiling is ensured
18. Design temperature of the metal walls of the hot water boiler elements	The temperature at which the physical and mechanical characteristics and permissible stresses of the metal walls of the elements of a hot water boiler are determined and their strength is calculated
19. Nominal water temperature at the inlet to the hot water boiler	Water temperature, which must be provided at the inlet to the hot water boiler at rated heating output, taking into account permissible deviations
20. Minimum water temperature at the inlet to the hot water boiler	The water temperature at the inlet to the hot water boiler, providing an acceptable level of low-temperature corrosion of heating surface pipes
21. Nominal water temperature at the outlet of the hot water boiler	The water temperature that must be ensured at the outlet of the hot water boiler at rated heating output, taking into account permissible deviations
22. Maximum water temperature at the outlet of the hot water boiler	The water temperature at the outlet of the hot water boiler, at which the nominal value of subcooling of water to boiling at operating pressure is ensured
23. Nominal water flow through the hot water boiler	Water flow through the hot water boiler at rated heating output and at rated values ​​of water parameters
24. Minimum water flow through the hot water boiler	Water flow through a hot water boiler, providing the nominal value of subcooling of water to boiling at operating pressure and nominal water temperature at the boiler outlet
25. Subheating water to boiling	The difference between the boiling temperature of water corresponding to the operating water pressure and the temperature of the water at the outlet of the hot water boiler, ensuring that water does not boil in the pipes of the boiler heating surfaces
26. Nominal hydraulic resistance of the water heating boiler	Water pressure drop measured behind the inlet and in front of the outlet fittings, at the rated heating output of the water heating boiler and at the rated values ​​of water parameters
27. Temperature gradient of water in a hot water boiler	The difference in water temperature at the outlet of the hot water boiler and the inlet to the boiler
28 Main operating mode of the hot water boiler	Operating mode of a water heating boiler, in which the water heating boiler is the main source of heat for the heating system
29. Peak operating mode of a hot water boiler	Operating mode of a water heating boiler, in which the water heating boiler is a source of heat to cover peak loads of the heating system

ALPHABETIC INDEX OF TERMS

Temperature gradient of water in a hot water boiler
Working water pressure in the hot water boiler
Minimum operating water pressure in the hot water boiler
Design water pressure in the hot water boiler
Boiler
Water heating boiler
Water tube boiler
Water-heating gas-tube boiler
Mobile water heating boiler
Direct flow hot water boiler
Water heating boiler with natural circulation
Water heating boiler with combined circulation
Water heating boiler with forced circulation
Stationary hot water boiler
Utilization hot water boiler
Electric hot water boiler
Water heat recovery boiler
Subheating water to boiling
Steam generator
Water consumption through the hot water boiler is minimal
Nominal water flow through the hot water boiler
Main operating mode of the hot water boiler
Peak operating mode of the water heating boiler
Hydraulic boiler nominal resistance
Minimum water temperature at the inlet to the hot water boiler
The water temperature at the inlet to the hot water boiler is nominal
Maximum water temperature at the outlet of the hot water boiler
The water temperature at the outlet of the hot water boiler is nominal
Calculated temperature of the metal walls of the water heating boiler elements
Heat output of hot water boiler
Nominal heating output of the hot water boiler

hot water

The boiler is an important component of the heating system, on which the efficiency of its operation depends. Today, one of the most common types of heating is water, which explains the growing popularity of using hot water boilers.

You can see a variety of units on sale, the difference between which is the coolant used, design, installation technology, etc.

Purpose

The hot water boiler is used for heating small buildings, cottages and town houses. Typically, such units are used in the absence of a central heating system or in a situation where it is not practical to build a boiler house. In addition to heating, they are used in hot water supply systems.

A hot water boiler is a device for heating water under pressure, i.e. without the possibility of boiling.

Specifications

The main characteristics of hot water boilers include:

Heating capacity (thermal power)

This is the amount of thermal energy that can be transferred to the coolant per unit of time. The unit of measurement for heat output is kilowatt. This indicator can be found in the product data sheet.

Depending on the thermal power, boilers are of low, medium and high power.

Coolant temperature

The nominal and minimum water temperatures at the boiler inlet are distinguished. The nominal temperature is the temperature that the device should provide under normal operating conditions. Typically it ranges from 60 to 110°C.

The minimum temperature must be observed to avoid low-temperature corrosion of the pipeline due to the formation of condensate in it.

The maximum temperature at the boiler outlet is the level at which the coolant does not boil. Usually it is 110-115°C.

The unit with this indicator is intended for individual use. But there are also products with a higher value maximum temperature. They are used to equip thermal power plants.

Gradient. This is the temperature difference between the water entering and leaving the boiler. Usually its value is 50-55 °C. The gradient indicator is influenced by the material from which the equipment is made.

Varieties

Modern hot water boilers are designed approximately the same. They may differ in manufacturer (domestic and foreign) and in power characteristics.

Speaking about structural design, all boilers are divided into:

Fire tube

A feature of such models is the presence of special tubes through which the heated products of fuel combustion occur. The operating principle of a fire tube boiler is to use automatic burners equipped with blower fans.

Water tube

The design of such water heating boilers is distinguished by the presence of special boiling tubes through which water moves. Heating occurs by burning energy. This type of boiler heats up quite quickly and is easy to regulate.

There is also the possibility of serious overloads. The undeniable advantage of water tube heating devices lies in the low probability of their explosion.

Regarding the number of circuits, most boilers have two circuits. But there are also single-circuit products. If the boiler is double-circuit, then the coolant will be supplied to both the heating system and the water supply network.

In addition, some models can be equipped with circulators to provide more intensive water circulation. The boiler design may also include an expansion tank.

According to the type of fuel used, hot water boilers are divided into:

Boilers for solid fuel. The energy source can be coal, wood or sawdust. Units of this type are used in bathhouses, saunas, and cottages, as they require significant space for placement.

Liquid fuel boilers. This could be diesel fuel, fuel oil, machine oil. Area of ​​application: heating of private houses and cottages.

Gas boilers. The fuel is natural or liquefied gas. Installation of water heating boilers of this type is typical for houses, town houses and even apartments.

Electric boilers. Electric hot water boilers are installed in small cottage buildings and apartments.

The photo of hot water boilers shows that, depending on the installation method, they can be:

• Floor-standing.
• Wall-mounted.

There are the following operating rules for hot water boilers:

• A hot water boiler requires systematic checks and adjustments, and this must be done by a specialist.
• A professional should install and operate boiler equipment.
• The boiler needs routine adjustments every three years.

Photo of a hot water boiler

1. Define hot water and energy boilers. Define the following elements of a steam generator: heating surfaces, superheaters, drum, air heater, economizer and lining.

Hot water boiler- boiler for heating water under pressure. “Under pressure” means that boiling water in the boiler is not allowed: its pressure at all points is higher than the saturation pressure at the temperature reached there (almost always it is higher than atmospheric pressure).

Steam boiler- a boiler designed to generate saturated or superheated steam. Can use the energy of the fuel burned in its firebox, electrical energy(electric steam boiler) or utilize heat generated in other installations (recovery boilers).

Boiler heating surface- the surface of the walls separating flue gases from the heated media through which heat is transferred from the flue gases.

Superheater- a device designed to superheat steam, that is, increase its temperature above the saturation point. The use of superheated steam can significantly increase the efficiency of a steam plant.

Boiler drum- an element of a stationary boiler designed to collect and distribute the working fluid, to separate steam from water, purify steam, and ensure a supply of water in the boiler

Air heater- a device designed to heat the air directed into the furnace boiler unit in order to increase the efficiency of fuel combustion due to the heat of exhaust gases.

Economizer(English) Economizer, from the English word economize- “save”) - an element of a boiler unit, a heat exchanger in which feed water is heated by gases leaving the boiler before being supplied to the boiler. The device increases the efficiency of the installation.

Brickwork - a system of fencing for the regatta boiler, separating its firebox and gas ducts from the environment. Boiler lining is used in boilers that do not have all-welded gas-tight screens

2. Give an example of an RCD circuit that responds to ground fault current (show the choice of setting, list the advantages and disadvantages).

An RCD that responds to ground fault current is designed to eliminate the danger of electric shock when people touch the housing during a phase fault by quickly disconnecting the damaged electrical installation from the network. Here with the device protective shutdown is a current relay KST (Fig. 5.4, b), connected to the grounding conductor cut directly or through a current transformer TA. KST relay operating current

3. Operation of power transformers: main tasks, directions, activities.

Before turning on the transformer to the network from reserve or after repair is carried out inspection both the transformer itself and all equipment connected to it.

Wherein are being checked:

oil level in the conservator and transformer inputs;

serviceability and starting position of the cooling system equipment;

correct position of voltage switch indicators;

position of the grounding disconnector and state of the arresters in the neutral;

whether the arc suppression reactor is turned off;

condition of porcelain insulators and bushing covers, as well as bus ducts and shielded current ducts.

If the transformer has been repaired, then attention is paid to cleanliness of workplaces, absence of short circuits, protective grounding and foreign objects on the transformer and transformer equipment.

The transformer is connected to the network by pushing to full voltage from the supply side(mains transformers from the HV winding side). Switching on is often accompanied by a strong surge of magnetizing current. However, automatic shutdown of the transformer by differential current protection does not occur, since it is detuned from the magnetizing current when the transformer is first tested with voltage, which allows it to avoid false triggering during all subsequent switch-ons.

When the transformer is put into operation, it is possible that the rated load will immediately appear on it. Turn on full load allowed for any negative temperature air of transformers with cooling systems M and D and not lower than -25 ° C of transformers with cooling systems DC and C. If the temperature of the air, and therefore the oil in the transformer, is lower than specified, it is raised by turning the transformer on at idle speed or under load no more 50% nominal. In emergency situations, these restrictions are not adhered to and the transformers are turned on at any temperature (which, due to the temperature difference between the oil and the windings, naturally affects the wear of the winding insulation)

Increasing oil viscosity in winter time is taken into account when putting into operation not only the transformer itself, but also its cooling devices. Circulation pumps of the ETsT series operate reliably at a temperature of the pumped oil not lower than -25 °C, and of the ETsTE series - not lower than -20 °C. Therefore, when the transformers are put into operation, the circulation pumps of the cooling systems are turned on only after the oil has been preheated to the specified temperature values. In all other cases, forced oil circulation pumps must be automatically put into operation simultaneously with the transformer being connected to the network. Cooler fans at low oil temperatures should be switched on when the oil temperature reaches 45 °C.

in operation, is carried out using ammeters, on the scales of which red marks must be marked corresponding to the rated loads of the windings. Simultaneously with monitoring the current value, the uniformity of load across phases. In autotransformers, the current in the common winding is also controlled.

Hot water industrial boilers on a multi-fuel design they cope an order of magnitude better not only with heating large-scale premises, but also with solving other problems. Such installations are capable of achieving impressive power levels - up to 20 MW, which is much more than simple boilers, running on gas. Before choosing a specific model, you need to know the device, the operating principle of this equipment and the characteristics of energy carriers. Knowledge about the types of boilers, their advantages and disadvantages, as well as how much you can buy them for will also help in your choice.

Design, principle of operation of hot water boilers

Variations of industrial hot water boilers are designed in the same way in almost all cases. Differences are recorded in categories, energy carrier used, power and manufacturer (domestic brands or foreign ones).

General device:

1. Pipes at the bottom (3 pcs.) - for water entry, including for cooling, so that the boiler does not overheat, for filling and draining.
2. Air valve - located at the very bottom of the structure.
3. The lower damper is a door that covers the firebox.
4. Compartment for cleaning from combustion products.
5. A cover near the chimney to make cleaning easier.
6. Chimney.
7. Upper flap.
8. Pipe at the top (2 pcs.) - for the outlet of water, including the one that protects against overheating.

Principle of operation:

1. Fuel is placed in the firebox.
2. Water flows through the receiving pipe.
3. Under the influence of high temperatures as a result of combustion, the water in the receiver heats up and rises further through the pipe “artery” to be supplied to the heating system.
4. The chimney performs a convection function - it draws out gas and smoke from the combustion of energy.
5. The air exchange valve supplies or blocks the supply of oxygen for combustion.

Typically, such boilers are made of strong but flexible steel that can withstand very high temperatures and pressure.

Coolant: water

Such installations use the cheapest natural coolant - water. They are quite suitable for heating a hangar, warehouse or other large-scale indoor space. But water can create scale inside the system, which improved boiler models can reduce or clean.

Such boilers are usually designed to heat:

• stock;
• residential buildings (utilities);
• production premises (workshop, covered platforms);
• premises of agricultural significance;
• vegetable stores or granaries;
• institutions and administrative buildings;
• other large objects and structures.

Proton water boiler

Types: fire tube, water tube

The special design advantages of hot water boilers are that you can choose any of two options: fire-tube (or gas-tube) or water-tube.

Characteristics:

1. The fire tube model is a special system of tubes supplying heated energy, automatic burners with blowing fan devices. IN living conditions these options are not used.
2. Water tube model - special boiling tubes move the coolant. Warm up quickly, overloads occur, but explosions are practically excluded.

Types: low temperature, high temperature

There are also boilers of varying levels of combustion and heat transfer. For example, there are options for long-term and short-term combustion, and there are also other types.

Characteristics:

1. Low temperature model – up to 115 degrees. Great savings in fuel consumption, but there is also an accumulation of condensate, so careful operation is required.
2. High temperature model – up to 150 degrees and above. Reliability is stable, the level of operation is high. Quiet operation, minimal waste emissions, and safety control systems.

Features of a single-circuit (heating) boiler and a double-circuit (+ hot water supply) water heating boiler

Features of boiler circuits:

1. Single-circuit – used for central heating premises.
2. Dual-circuit – used for central heating premises and heating of water supply for supply hot water.

Both options may differ in greater efficiency.

Fuel: firewood, pellets, gas, diesel, fuel oil

Models may also differ in the use of different coolants.

There are boilers:

• wood - medium-cost solid fuel;
• gas - cheap;
• diesel – medium-cost;
• fuel oil - medium-cost;
• pellets - expensive peat granules.

The most economical is a gas hot water heater. For floor-standing installations, solid fuel coolant options are more often used, but gas or diesel can also be used.

Advantages and disadvantages of water heating devices

Advantages of hot water units:

1. Easy floor or wall installation.
2. Arrangement of tubes in a circle to improve the aerodynamics of internal heating.
3. Optimal heating speed.
4. No condensation accumulation.
5. Production of saturated steam.
6. Using a cheap coolant - water.

Disadvantages of models:

1. Corrosion of metal.
2. Additional filtration of water is needed if it is of poor quality to avoid blockages in the pipes.
3. High price.

Additionally: automatic boiler control, automatic fuel filling

A modern device - a control unit, sensors and more - allows you to switch to automatic control equipment. During operation, automatic fuel loading can be achieved. And the built-in intelligent system with an innovative processor will also allow you to configure automation during control.

TOP hot water industrial boilers - description with characteristics and prices of three boilers for an area of ​​1000 sq.m.

There are different versions of the models, some of them can be considered as examples.

Gas production boiler Wolf GKS Eurotwin

Floor standing boiler VAILLANT atmoCRAFT VK INT 1454/9

1. Heat transfer – 92.5%.
2. Power – 143 kW.
3. Single-circuit type.
4. Heating area – 1430 sq.m.
5. The chimney diameter is 250 mm.
6. Dimensions: 1570x1145x960 mm.
7. Weight – 550 kg.
8. Manufacturer – Germany.
9. Price from 650,000 rubles

The design of such boilers is more complex than simple equipment - other units are used. Heated water moves very quickly through heating pipes and radiators, heating them, which produces heat. Also, industrial-grade water heating boilers are large in size, an order of magnitude smaller than domestic options. The use of boilers does not require special maintenance and care.

Boiler – a device in which the heat released during the combustion of organic fuel, as well as the heat of exhaust gases, is used to produce steam or heat water with a pressure above atmospheric, consumed outside this device. The boiler consists of a firebox, heating surfaces, frame, and lining. The boiler may also include: a superheater, a surface economizer and an air heater.

Boiler plant – combination of boiler and auxiliary equipment, including: draft machines, prefabricated flues, chimney, air ducts, pumps, heat exchangers, automation, water treatment equipment.

Firebox (combustion chamber ) – a device designed to convert the chemical energy of fuel into physical heat of high-temperature gases with the subsequent transfer of the heat of these gases to heating surfaces (working fluid).

Heating surface – a boiler element for transferring heat from the torch and combustion products to the coolant (water, steam, air).

Radiation surface– the heating surface of the boiler, which receives heat mainly by radiation.

Convective surface– the heating surface of the boiler, which receives heat mainly by convection.

Screens – boiler heating surfaces located on the walls of the firebox and flues and protecting these walls from the effects of high temperatures.

Festoon – an evaporative heating surface located in the outlet window of the furnace and formed, as a rule, by rear screen pipes separated over considerable distances by forming multi-row bundles. The purpose of the festoon is to organize the free exit of flue gases from the furnace into a rotary horizontal gas duct.

Drum - a device in which collection and distribution is carried out working environment, ensuring a supply of water in the boiler, dividing the steam-water mixture into steam and water. For this purpose, steam separation devices located in it are used.

Boiler beam – convective heating surface of the boiler, which is a group of pipes connected by common collectors or drums.

Superheater b– a device for increasing the steam temperature above the saturation temperature corresponding to the pressure in the boiler.

Economizer – a device for preheating water by combustion products before feeding it into the boiler drum.

Air heater b– a device for heating air by combustion products before feeding it to the burners.

1. 
   GENERAL DIAGRAM OF A BOILER INSTALLATION WITH NATURAL CIRCULATION, OPERATING

ON PUMPED SOLID FUEL

Fig.1. General scheme boiler plant with natural circulation,

running on solid fuel:

fuel path:

1 – dust preparation system; 2 – pulverized coal burner;

gas path:

3 – combustion chamber; 4 – cold funnel; 5 – horizontal gas duct; 6 – convective shaft; 7 – gas duct; 8 – ash catcher; 9 – smoke exhauster; 10 – chimney;

air path:

11 – air intake shaft; 12 – fan; 13 – heater; 14 – 1st stage air heater; 15 – 2nd stage air heater; 16 – hot air ducts; 17 – primary air; 18 – secondary air;

steam-water path:

19 – supply feed water; 20 – water economizer of the 1st stage; 21 – water economizer of the 2nd stage; 22 – feed water pipeline; 23 – drum; 24 – lowering pipes; 25 – lower collectors; 26 – screen (lifting) pipes; 27 – scallop; 28 – steam line for dry saturated steam; 29 – steam superheater; 30 – desuperheater; 31 – main steam valve (MSV)

1. 
   Air path .

Cold air from the upper part of the boiler shop room with a temperature of 20-30 °C is taken by fan 12 through the air intake shaft 11 and sent to the 1st stage air heater 14. In some cases, cold air can be heated to a temperature of 50-90 °C. In this case, the air is heated to 50 °C by recirculating part of the hot air into the suction pipe of the fan, and to a temperature of 85-90 °C - in a steam or water heater 13. Passing sequentially through the 1st and 2nd stages of the air heater (14, 15), the air is heated to a temperature of 300-350 °C. After the 2nd stage air heater, the air enters the hot air duct 16 and part of it (primary air) is sent through the air duct 17 to the mill for drying and transportation coal dust. The other part (secondary air) is directed through air duct 18 to the pulverized coal burners.

1. 
   Steam-water path.

Feed water after preliminary preparation (softening, deaeration) feed pump supplied to the 1st stage economizer manifold. Its temperature after the regenerative heater is 145-220 °C. If a surface desuperheater 30 is installed to regulate the steam temperature, then part of the water is first directed there to ensure regulation of the temperature of the superheated steam. Passing sequentially through the 1st and 2nd stages of the water economizer 20, 21, the water is heated either to the boiling temperature (t pv = t boil) - a boiling-type economizer, or to a temperature below the boiling point (t pv by natural circulation and occurs due to the difference densities of water in the lowering pipes and the steam-water mixture in the screen (lifting) pipes.

In the boiler drum, the steam-water mixture is separated into steam and water. Separation devices are installed in the steam space of the drum, with the help of which moisture droplets are captured from the steam flow. The dry saturated steam obtained in the drum through the steam line 28 enters the superheater 29, first into its counterflow part, then into the direct flow part, where the steam is superheated to a given temperature. A desuperheater 30 is installed between the counter-flow and direct-flow parts of the superheater, which serves to regulate the steam temperature. Steam with specified parameters enters the steam pipeline through the main steam valve 31 and then to the consumer (steam turbines, process consumers).

Boiler with outside has an external fencing - lining, which includes cladding made of 3-4 mm steel sheet on the side of the boiler room, an auxiliary frame, and the fireproof lining itself - thermal insulation thickness 50-200 mm. The main purpose of lining and cladding is to reduce heat losses in environment and ensuring gas density.

Each steam boiler is supplied with fittings and fittings. TO headset includes all devices and devices - hatches, manholes, gates, blowing devices, etc.; To fittings- all instruments and devices related to the measurement of parameters and regulation of the working fluid (pressure gauges, water indicators, gate valves, valves, safety and check valves etc.), ensuring the possibility and safety of servicing the unit.

The boiler structures are supported by a load-bearing steel frame, the main elements of which are steel beams and columns.

5.Gas path .

Coal dust from the dust preparation system 1 enters the combustion chamber 3 through burner 2, burns in suspension, forming a torch whose temperature is 1600-2200 °C (depending on the type of fuel burned). The slag formed during the combustion of fuel enters a special bunker through the so-called cold funnel 4, from there it is washed off with water into the slag pipes, and then the slag is sent to the ash dump using bagger pumps. From the torch, heat is transferred by radiation to the combustion screens, while the flue gases are cooled and their temperature at the exit from the furnace is 900-1100 ° C. Passing sequentially through the heating surfaces (festoon 27, steam superheater 29 located in the horizontal flue 5, water economizers 20, 21 and air heaters 14, 15 located in the convective shaft 6), the flue gases give up their heat to the working fluid (steam, water, air) and are cooled to a temperature of 120-170 °C behind the first stage of the air heater. Then the flue gases through the flue 7 enter the ash catcher 8, where ash particles are collected from the flue gas flow. Ash collected from flue gases in an ash catcher by air or water is transported to an ash dump. The flue gases, cleared of ash, are directed by the smoke exhauster 9 into the chimney 10. With the help of the chimney, harmful dust and gas emissions are dissipated in the atmosphere.

(7) 4. HEAT BALANCE OF A BOILER UNIT (better from the lecture)

When compiling the heat balance of a boiler unit, equality is established between the amount of heat entering the unit, called available heat, and the sum usefully used heat Q 1 and heat losses Q 2-6.

Based on the heat balance, the efficiency of the boiler unit and the required fuel consumption are calculated. The heat balance is compiled for 1 kg of solid (liquid) or 1 m 3 of gaseous fuel at steady state thermal state

boiler unit.

The general heat balance equation has the form

Q 1 + Q 2 + Q 3 + Q 4 + Q 5 + Q 6, kJ/kg or kJ/m 3.

The available heat of 1 kg of solid (liquid) fuel is determined by the formula

For most types of fairly dry and low-sulfur solid fuels, Q p = is taken, and for gas fuels it is taken. For very wet solid fuels and liquid fuels, the physical heat of the fuel i t is taken into account, which depends on the temperature and heat capacity of the fuel supplied for combustion

i tl = c tl t tl.

For solid fuels in summer period time, tt = 20 °C is taken, and the heat capacity of the fuel is calculated using the formula

KJ/(kg K) .

The heat capacity of the dry mass of the fuel is:

For brown coals - 1.13 kJ/(kg∙K);

For hard coals - 1.09 kJ/(kg K);

For coals A, PA, T - 0.92 kJ/(kg K).

IN winter period take t t =0 °C and physical heat is not taken into account.

The temperature of the liquid fuel (fuel oil) must be high enough to ensure a fine spray in the nozzles of the boiler unit. Usually it is = 90-140 °C.

Heat capacity of fuel oil

, kJ/(kg K) .

In the case of preliminary (external) heating of air in air heaters before it enters the air heater of the boiler unit, the heat of such heating Q in.in is included in the available heat of the fuel and is calculated using the formula

where  gv is the ratio of the amount of hot air to the theoretically necessary; Δα VP – air suction in air heaters; - enthalpy of the theoretical volume of cold air; - enthalpy of the theoretical volume of air at the inlet to the air heater.

When using steam-mechanical nozzles to spray fuel oil, steam from the station's general mains enters the furnace of the boiler unit along with the heated fuel oil. It introduces additional heat Qf into the firebox, determined by the formula

Q f = G f (i f – 2380), kJ/kg,

where G f – specific consumption steam per 1 kg of fuel oil, kg/kg; i f - enthalpy of steam entering the nozzle, kJ/kg.

The parameters of the steam supplied to the fuel oil spray are usually 0.3-0.6 MPa and 280-350 °C; the specific steam consumption at rated load is in the range G f = 0.03 - 0.05 kg/kg.

The total amount of heat usefully used in the boiler:

- for hot water boiler

Q = D in, kW,

where D in is the water flow through the boiler, kg/s; , - enthalpy of water at the inlet and outlet of the boiler, kJ/kg;

- for a steam boiler

where D pe is the consumption of superheated steam, kg/s; D pr - consumption of blowing water (by continuous blowing we mean that part of the water that is removed from the boiler drum to reduce the salt content of the boiler water), kg/s; i pe - enthalpy of superheated steam, kJ/kg; i pv - enthalpy of feed water, kJ/kg; i kip - enthalpy of boiling water, kJ/kg.

Enthalpies are determined by the corresponding temperatures of steam and water, taking into account the change in pressure in the steam-water path of the boiler unit.

The flow rate of blowdown water from a drum steam boiler unit is

where p - continuous blowing boiler unit, %; at p Coefficient useful action of the designed steam boiler unit is determined from the reverse balance

 = 100 - (q 2 + q 3 + q 4 + q 5 + q 6), %.

The calculation problem comes down to determining the heat losses for the adopted type of steam boiler unit and the fuel burned.
8. Heat loss with flue gases

Heat loss with flue gases q 2 (5-12%) arise due to that physical heat (enthalpy) gases leaving the boiler exceeds the heat of the air entering the boiler and is determined by the formula

, % ,

where I ух is the enthalpy of exhaust gases, kJ/kg or kJ/m 3, determined by  ух with excess air in the combustion products behind the first stage air heater; I o xv - enthalpy of cold air.

Heat loss with flue gases depend on the selected flue gas temperature and excess air ratio, since an increase in excess air leads to an increase in the volume of flue gases and, consequently, an increase in losses.

One of the possible directions of reductionheat loss with flue gases is a decrease in the coefficient of excess air in the flue gases, the value of which depends on the coefficient of excess air in the furnace and air suction into the boiler flues

 х = + .

(9) Heat loss from chemical underburning of fuel q 3 (0 –2 %) occur when flammable gaseous components (CO, H) appear in combustion products 2, CH 4 ), which is associated with incomplete combustion of fuel within combustion chamber. The combustion of these combustible gases outside the combustion chamber is practically impossible due to their relatively low temperature.

Chemical incomplete combustion of fuel may result from:

General lack of air (α t),

Poor mixture formation (fuel combustion method, burner design),

Low or high values ​​of thermal stress of the furnace volume (in the first case - low temperature in the furnace; in the second - a decrease in the residence time of gases in the furnace volume and, therefore, the impossibility of completing the combustion reaction).

Heat loss with chemical underburning depends on the type of fuel, the method of its combustion and is adopted on the basis of operating experience of steam boiler units.

Heat losses with chemical underburning are determined by the total heat of combustion of the products of incomplete oxidation of the combustible mass of fuel

100, % .

(9) Heat loss from mechanical incomplete combustion q 4 (1-6 %) are associated with underburning of solid fuel in the combustion chamber. Part of it in the form of flammable particles containing carbon is carried away by gaseous combustion products, the other part isis removed along with the slag. During layer combustion, it is also possible for some of the fuel to fall through the gaps in the grate. Their size depends on the method of fuel combustion, the method of slag removal, the release of volatiles, the coarseness of grinding, and the ash content of the fuel and is calculated by the formula

Where A shl + pr, A un - the proportion of fuel ash in the slag, sinkhole and entrainment; G shl+pr, G un - content of combustibles in slag, failure and entrainment, %.

(11)optimal values ​​of the excess air coefficient in the furnace α t during combustion:

fuel oil 1,05 – 1,1;

natural gas 1,05 – 1,1;

solid fuel:

chamber combustion 1.15 – 1.2;

layer combustion 1.3 – 1.4.

Air suction along the gas path of the boiler can ideally be reduced to zero, however, complete sealing of various hatches and peepholes is difficult, and for boilers, suction is Δα = 0.15 – 0.3.

The most important factor influencing the loss of heat with flue gases is flue gas temperature . The temperature of the flue gases has a decisive influence on the efficiency of operation of a steam boiler unit, since the loss of heat with the flue gases is the greatest under normal operating conditions, even in comparison with the sum of other losses. A decrease in the flue gas temperature by 12-16 °C leads to an increase in the efficiency of the boiler unit by approximately 1.0%. The temperature of the flue gases is in the range of 120-170 °C. However, deep cooling of gases requires an increase in the size of convective heating surfaces and in many cases leads to increased low-temperature corrosion.

Choice optimal value coefficient of excess air in the furnace. For various fuels and methods of fuel combustion, it is recommended to take certain optimal values ​​of α t.

An increase in excess air (Fig. 2) leads to an increase in heat losses with exhaust gases (q 2), and a decrease leads to an increase in losses with chemical and mechanical underburning of fuel (q 3, q ​​4).

The optimal value of the excess air coefficient will correspond to the minimum value of the sum of losses q 2 + q 3 + q 4.

Rice. 2. To determine the optimal value of the coefficient

excess air

Table 1
Fuel consumption IN, kg/s supplied to the combustion chamber of the boiler unit can be determined from the balance between the useful heat release during fuel combustion and the heat absorption of the working environment in the steam boiler unit

Kg/s or m 3/s.

Estimated fuel consumption taking into account mechanical incomplete combustion

Boiler efficiency (gross) according to direct balance

Efficiency factor (net ) boiler plant

where Qсн is the energy consumption (in terms of heat) per own needs boiler plant, kW.

(15)5. CLASSIFICATION OF BOILERS AND THEIR MAIN PARAMETERS

Boilers are distinguished according to the following characteristics:

By purpose:

Energetically e– generating steam for steam turbines; They are distinguished by high productivity and increased steam parameters.

Industrial – generating steam both for steam turbines and for the technological needs of the enterprise.

Heating – producing steam for heating industrial, residential and public buildings. These include hot water boilers. A hot water boiler is a device designed to produce hot water at a pressure above atmospheric pressure.

Waste heat boilers - designed to produce steam or hot water by using secondary heat energy resources(VER) when processing waste chemical production, household waste, etc.

Energy technology – are intended to produce steam using water-recovery reactors and are an integral part of the technological process (for example, soda recovery units).

According to the design of the combustion device (Fig. 7):

There are fireboxes layered – for combustion of lump fuel and chamber – for burning gas and liquid fuels, as well as solid fuels in a dusty (or finely crushed) state.

In addition, by design they can be single-chamber or multi-chamber, and by aerodynamic mode - under vacuum And supercharged.

By type of coolant generated by the boiler: steam And hot water.

For the movement of gases and water (steam):

• 
  gas tubes (fire tubes and smoke tubes);
• 
  water tube;
• 
  combined.

(18) Diagram of a pressurized boiler. In these boilers, a high-pressure blowing installation provides an excess pressure in the combustion chamber of 4 - 5 kPa, which makes it possible to overcome the aerodynamic resistance of the gas path (Fig. 8). Therefore, in this scheme there is no smoke exhauster. The gas tightness of the gas path is ensured by installing membrane screens in the combustion chamber and on the walls of the boiler flue ducts.


Rice. 8. Boiler diagram under “supercharging”:

1 – air intake shaft; 2 – high-pressure fan;

3 – 1st stage air heater; 4 – water economizer

1st stage; 5 – 2nd stage air heater; 6 – air ducts

hot air; 7 – burner device; 8 – gas-tight

screens made of membrane pipes; 9 – gas duct

(19) Boiler diagram with multiple forced circulation

Rice. eleven. Structural diagram boiler with multiple forced circulation:

1 – economizer; 2 – drum;

3 – downward supply pipe; 4 - circulation pump; 5 – water distribution through circulation circuits;

6 – evaporative radiation heating surfaces;

7 – scallop; 8 – steam superheater;

9 – air heater

Circulation pump 4 operates with a pressure drop of 0.3 MPa and allows the use of small diameter pipes, which saves metal. The small diameter of the pipes and the low circulation rate (4 - 8) cause a relative decrease in the water volume of the unit, therefore, a decrease in the dimensions of the drum, a decrease in drilling in it, and hence a general decrease in the cost of the boiler.

The small volume and independence of the useful circulation pressure from the load make it possible to quickly melt and stop the unit, i.e. work in control and starting mode. The scope of application of boilers with multiple forced circulation is limited to relatively low pressures, at which the greatest economic effect can be obtained by reducing the cost of developed convective evaporation heating surfaces. Boilers with multiple forced circulation are widespread in heat recovery and combined cycle plants.
(20) Diagram of a fire tube boiler. The boilers are designed for closed heating, ventilation and hot water supply systems and are manufactured to operate at a permissible operating pressure of 6 bar and permissible temperature water up to 115 °C. The boilers are designed to operate on gaseous and liquid fuels, including fuel oil and crude oil, and provide an efficiency of 92% when operating on gas and 87% when operating on fuel oil.
Steel hot water boilers have a horizontal reversible combustion chamber with a concentric arrangement of smoke pipes (Fig. 9). To optimize the heat load, pressure in the combustion chamber and temperature of the exhaust gases, the smoke tubes are equipped with turbulators made of of stainless steel.

Rice. 9. Diagram of the combustion chamber of fire tube boilers:

1 – front cover;

2 – boiler furnace;

3 – smoke pipes;

4 – tube sheets;

5 – fireplace part of the boiler;

6 – fireplace hatch;

7 – burner device

(21)Fig. 12. Design diagram of Ramzin’s once-through boiler:

3 – lower distribution manifold water; 4 – screen

pipes; 5 – upper mixture manifold; 6 – extended

transition zone; 7 - wall part of the superheater;

8 – convective part of the superheater; 9 – air heater;

10 – burner
+lectures

(22) Boiler layout

The layout of the boiler refers to the relative position of the flues and heating surfaces (Fig. 13).

Rice. 13. Boiler layout diagrams:

a – U-shaped layout; b – two-way arrangement; c – layout with two convective shafts (T-shaped); d – layout with U-shaped convective shafts; d – layout with an inverter firebox; e – tower layout

Most common U-shaped layout (Fig. 13a - one-way, 13b – two-way). Its advantages are the supply of fuel to the lower part of the furnace and the removal of combustion products from the lower part of the convective shaft. The disadvantages of this arrangement are uneven filling of the combustion chamber with gases and uneven washing of heating surfaces located in the upper part of the unit by combustion products, as well as uneven concentration of ash across the cross-section of the convective shaft.