Calculation of the thermal scheme of a boiler house with hot water boilers operating on a closed heat supply system for three operating modes of the boiler house. Circuitry for hot water boilers
Thermal schemes of boiler houses
According to their purpose, small and medium-sized boiler houses are divided into the following groups: heating, designed for heat supply of heating, ventilation, hot water supply systems for residential, public and other buildings; production, providing steam and hot water technological processes industrial enterprises; production and heating, providing steam and hot water to various consumers. Depending on the type of heat carrier produced, boiler houses are divided into hot water, steam and steam water heating.
In general, a boiler plant is a combination of a boiler (boilers) and equipment, including the following devices. Fuel supply and combustion; purification, chemical treatment and deaeration of water; heat exchangers for various purposes; source (raw) water pumps, network or circulation pumps - for circulating water in the heat supply system, make-up pumps - to compensate for water consumed by the consumer and leaks in networks, feed pumps for supplying water to steam boilers, recirculating (mixing); nutrient tanks, condensing tanks, accumulator tanks hot water; blow fans and air path; smoke exhausters, gas path and chimney; ventilation devices; systems automatic regulation and fuel combustion safety; heat shield or control panel.
The thermal scheme of the boiler room depends on the type of heat carrier produced and on the scheme of heat networks connecting the boiler room with consumers of steam or hot water, on the quality of the source water. Water heating networks are of two types: closed and open. With a closed system, water (or steam) gives off its heat in local systems and is completely returned to the boiler room. With an open system, water (or steam) is partially, and in rare cases completely taken off in local installations. The heat network scheme determines the performance of water treatment equipment, as well as the capacity of storage tanks.
As an example, the fundamental thermal scheme hot water boiler for open system heat supply with calculated temperature regime 150-70°C. The network (circulation) pump installed on the return line ensures the supply of feed water to the boiler and then to the heating system. The return and supply lines are interconnected by jumpers - bypass and recirculation. Through the first of them, in all operating modes, except for the maximum winter one, part of the water is bypassed from the return to the supply line to maintain the set temperature.
Principal thermal diagram of a hot water boiler house
According to the conditions for preventing metal corrosion, the temperature of the water at the inlet to the boiler when operating at gas fuel must be at least 60 °C to avoid condensation of water vapor contained in the flue gases. Since the temperature return water almost always below this value, then in boiler houses with steel boilers part of the hot water is supplied to the return line by a recirculation pump.
Make-up water enters the collector of the network pump from the tank (a pump that compensates for the consumption of water by consumers). The initial water supplied by the pump passes through the heater, chemical water treatment filters and, after softening, through the second heater, where it is heated to 75-80 °C. Next, the water enters the column vacuum deaerator. The vacuum in the deaerator is maintained by suction of the vapor-air mixture from the deaerator column using a water-jet ejector. working fluid The ejector is water supplied by a pump from the tank of the ejector installation. The steam-water mixture removed from the deaerator head passes through a heat exchanger - a vapor cooler. In this heat exchanger, water vapor condenses, and the condensate flows back into the deaerator column. Deaerated water flows by gravity to the make-up pump, which supplies it to the suction manifold network pumps or in the make-up water tank.
Heating in the heat exchangers of chemically treated and source water is carried out by water coming from the boilers. In many cases, the pump installed on this pipeline (shown by a dashed line) is also used as a recirculation pump.
If the heating boiler is equipped steam boilers, then hot water for the heat supply system is obtained in surface steam-water heaters. Steam water heaters are most often free-standing, but in some cases heaters are used that are included in the boiler circulation circuit, as well as built on top of the boilers or built into the boilers.
A schematic thermal diagram of a production and heating boiler house with steam boilers supplying steam and hot water to closed two-pipe water and steam systems heat supply. One deaerator is provided for the preparation of feed water of boilers and make-up water of the heating network. The scheme provides for heating the source and chemically treated water in steam-water heaters. The blowdown water from all boilers enters the continuous blowdown steam separator, which is maintained at the same pressure as the deaerator. The steam from the separator is discharged into the steam space of the deaerator, and hot water enters the water-to-water heater for preliminary heating of the source water. Next, the purge water is discharged into the sewer or enters the make-up water tank.
Steam network condensate returned from consumers is pumped from the condensate tank to the deaerator. The deaerator receives chemically purified water and condensate from the steam-water heater of chemically purified water. Network water is heated sequentially in the condensate cooler of the steam-water heater and in the steam-water heater.
In many cases, hot water boilers are also installed in steam boilers for the preparation of hot water, which fully meet the demand for hot water or are peak. The boilers are installed behind the steam-water heater along the water course as the second stage of heating. If the steam boiler serves open water networks, the thermal scheme provides for the installation of two deaerators - for feed and make-up water. To equalize the mode of preparation of hot water, as well as to limit and equalize pressure in hot and cold water supply systems in heating boilers, installation of storage tanks is provided.
Schematic diagram of a steam boiler house with closed networks.
BOILER FITTINGS AND HEADSET
Boiler fittings
Devices and instruments used to control the operation of parts of the boiler unit under pressure, to turn on, off and regulate pipelines for water and steam, the main safety devices are called armatures.
According to their purpose, valves are divided into shut-off, control, purge and safety valves.
The fittings are made with forced drive and self-acting.
By design, actuator valves are divided into valves, gate valves and taps, and self-acting - into safety and check valves and steam traps.
The fittings also conditionally include water-gauge glasses and other water-indicating devices.
Valves and gate valves
Valves are used as control and shut-off devices (Fig. 3). how stop valves they are used for passage diameters up to 109-150 mm.
a - shut-off flange; b - regulating:
1 - body; 2 - shutter; 3 - flange; 4 - joint seal;
5 - spindle; 6 - shtl rvach (flywheel); 7 - traverse; 8 - cover;
9 - valve seat
In a shut-off valve, the sealing surface of the valve is tightly adjacent to the surface of the seat. The valve consists of a body, a cover, a spindle on which the valve hangs. The body contains a valve seat. A gland seal is installed at the point where the spindle passes through the cover.
In a control valve, the valve has a variable section. This makes it possible to change the flow area. The control valve is made in the form of a profiled needle, a hollow spool, etc. In a fully closed state, they do not provide full tightness. Typically, control valves are designed to operate with a pressure drop of 1.0 MPa.
The main indicator of the operation of a control valve is its characteristic (dependence of the relative flow rate of the medium on the degree of opening of the valve) (Fig. 3 b).
For the purposes of regulation, the most favorable linear characteristic, which requires the implementation of regulatory bodies with a complex profile of opening windows for the flow of the medium. The spool type control valve has a hollow spool with profiled windows, which is driven by a spindle in translational motion. When the spool is moved relative to the two seats, the degree of opening of the windows changes.
In rock control valves, the regulating body is made in the form of a rolling pin having a conical shape near the seats. When moving the rolling pin, the annular gap between it and the valve seats changes.
In needle control valves, adjustment is achieved by moving a shaped needle.
Gate valves are mainly used as shut-off devices (Fig. 4), although there are also special designs of control valves. In gate valves, the closing element (wedge, disks) moves in the direction perpendicular to the flow. According to the principle of pressing the locking body, the gate valves are divided into wedge, with a parallel-forced gate and self-sealing.
In wedge gate valves, the locking body is made of a whole or split wedge.
The coefficient of hydraulic resistance of valves b = 0.25-0.8, and y shut-off valves b = 2.5-5.
gate valves
a - wedge flangeless with a drive; b - parallel flange
1- sealing discs; 2 - spacer device; 3 - body;
4 - cover; 5 - remote drive lever; 6 - flywheel; 7 - gear wheel; 8 - traverse; 9 - stitch seal;
10 - spindle; 11 - earring ring.
valves
A valve is a shut-off or regulating body of automatic action.
Steam boilers have check, feed, pressure reducing and safety valves.
check valve prevents the movement of the working medium in the opposite direction. So, for example, check valves on the feed lines close in case of an emergency pressure drop in the feed pipes and prevent the release of water from the boiler.
By design, check valves are divided into lifting and rotary.
In lift valves (Fig. 5, a), the valve (spool) 2 is the shut-off element, the shank of which enters the guide channel of the cover tide 1.
In rotary valves (Fig. 5, b), plate 6 rotates around axis 7 and blocks the passage.
check valves installed in boiler rooms, usually on pressure lines centrifugal pumps, on feed lines upstream of the boiler to allow water to pass in only one direction and in other places where there is a danger of backflow of the medium.
 |
a - lifting; b - rotary:
1 - cover; 2 - spool; 3 - body; 4 - valve axis; 5 - lever;
6 - plate; 7 - axis of the lever.
Feed valve serves for automatic regulation of the boiler supply in accordance with the steam consumption.
In valves installed on modern boilers, the water presses the vertical gate against the seat.
Safety valve is a shut-off device that automatically opens when the pressure rises. It is installed on drum boilers, steam pipelines, tanks, etc. When the valve is opened, the medium is discharged into the atmosphere. Safety valves can be lever (Fig. 7 a), spring (Fig. 7 b) and impulse (Fig. 8).
a - single-lever; b - spring:
1 - body; 2 - shutter; 3 - spindle;
4 - cover; 5 - lever; 6 - cargo; 7 - spring
AT lever valve the locking body (plate) is held closed by the load. In a spring-loaded safety valve, the pressure of the medium on the disc is counteracted by the preload force of the spring.
Safety valves are available as single or double. Depending on the lifting height of the plate, the valves are divided into low-lift and full-lift. In fully lifted valves, the area open to the passage of the medium when the valve is lifted exceeds the passage of the seat. They have more capacity than low-lift ones.
In accordance with the rules, each boiler with a steam capacity of more than 100 kg / h must be equipped with at least two safety valves, one of which must be a control valve. On boilers with a capacity of 100 kg/h or less, one safety valve may be installed.
The total capacity of the valves must be at least the hourly capacity of the boiler. If the boiler has a non-switchable superheater, part safety valves with a throughput of at least 50% of the total bandwidth must be installed on the outlet manifold.
Initial data for calculation …..………………………………………………….3
1. Analytical calculation of the principle thermal diagram of a hot water boiler house …………..……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
2. Calculation of the basic thermal diagram of a water-heating boiler house using a computer ………………………………………………………….12
2.1 Initial data file ……………………………………………...12
2.2 Calculation results …………………………………………………...14
Conclusion …….……………………………………………………………………………15
List of used literature ………….…………………………………….15
Initial data for calculation
The calculation is performed for the schematic diagram of the boiler room shown in Figure 1. The boiler house is designed to supply hot water to residential and public buildings for the needs of heating, ventilation and hot water supply.
The heat loads of the boiler house, taking into account losses in external networks in the maximum winter mode, are as follows: for heating 6.84 Gcal/h; for ventilation 0 Gcal/h and for hot water supply 2.16 Gcal/h. The total heat output of the boiler house is 9.0 Gcal/h.
Heating network work on temperature chart 150-70 °С, accepted for hot water supply mixed scheme heating water for subscribers. Estimated minimum temperature outside air -55 °С. Heating raw water before chemical water treatment, it is taken up to 20 ° С from 5 ° С in winter and 15 ° С in summer. Water deaeration is carried out in a deaerator at atmospheric pressure.
For convenience, table 1 "Initial data" is given, for calculating the thermal scheme of a boiler house operating on closed system heat supply. This table is compiled on the basis of the design of the heat supply system or the calculation of heat consumption by various consumers according to aggregated indicators. The calculation is made for three typical regimes: maximum winter, coldest month and summer.
Rice. 4.3. Schematic diagram of the boiler house with hot water boilers
1 - hot water boiler; 2 – network pump; 3 - recirculation pump; 4 – raw water pump;
5 – make-up water pump; 6 – make-up water tank; 7 – raw water heater; 8 - heater
chemically purified water; 9 – make-up water cooler; 10 - deaerator; 11 - vapor cooler
Table 1 "Initial data"
| Name | Dimension | Designation | The value of the value for the characteristic modes of operation of the boiler house | ||
| maximum winter | coldest month | summer | |||
| Location of the boiler room | - | Khabarovsk | |||
| Maximum expenses heat: | MW | ||||
| for heating residential and public buildings | MW | - | - | ||
| for ventilation of public buildings | MW | - | - | ||
| for hot water supply | MW | 2,5 | 2,5 | ||
| Estimated outdoor temperature for heating | °С | -55 | -43,2 | - | |
| Estimated outdoor temperature for ventilation | °С | -45 | - | - | |
| Indoor air temperature | °С | - | |||
| Raw water temperature | °С | ||||
| Temperature of heated raw water before chemical water treatment | °С | ||||
| Make-up water temperature after deaerated water cooler | °С | ||||
| Coefficient of auxiliary needs of chemical water treatment | - | 1,25 | 1,25 | 1,25 | |
| Water temperature at the outlet of hot water boilers | °С | ||||
| Water temperature at the inlet to hot water boilers | °С | ||||
| Estimated hot water temperature after local hot water heat exchangers | °С | ||||
| Preliminary consumption of chemically treated water | t/h | 0,7 | |||
| Preliminarily accepted water consumption for heating chemically treated water | t/h | 0,15 | |||
| Heating water temperature after the chemically treated water heater | °С | ||||
| Efficiency of heaters | - | 0,98 | 0,98 | 0,98 |
Analytical calculation of the principle thermal scheme of a hot water boiler house
Calculation of the thermal scheme of a boiler house with hot water boilers operating on a closed heat supply system is recommended to be carried out in the following sequence.
1. The coefficient of reduction of heat consumption for heating and ventilation is determined for the mode of the coldest month:
2. Water temperature in the supply line for heating and ventilation needs for the coldest month mode:
where is the temperature inside the room; - temperature head in the heating device; - estimated temperature difference of network water; - Estimated temperature difference in the heating system.
It follows from the initial data: ; ;
3. Return network water temperature after heating and ventilation systems for the coldest month mode:
4. Heat supply for heating and ventilation:
5. Total heat supply for the needs of heating, ventilation and hot water supply:
For the maximum winter regime
For the coldest month
6. Water consumption in the supply line of the hot water supply system for consumers for the maximum winter mode:
t/h
7. Thermal load heater of the first stage (on the return line of the network water) for the mode of the coldest month:
8. Heat load of the second stage heater for the coldest month mode:
9. Flow rate of network water to the local heat exchanger of the second stage, i.е. for hot water supply, for the coldest month mode:
t/h
10. Flow of network water to the local heat exchanger for summer mode:
t/h
11. Consumption of network water for heating and ventilation:
For the maximum winter regime
t/h;
For the coldest month
t/h
12. Consumption of network water for heating, ventilation and hot water supply:
For the maximum winter regime
For the coldest month
For summer mode
13. Return network water temperature after external consumers
°C;
For the coldest month
°C;
For summer mode
°C.
14. Consumption of make-up water to replenish leaks in the heating network of external consumers:
For the maximum winter regime
For the coldest month
For summer mode
15. Consumption of raw water entering the chemical water treatment:
For the maximum winter regime
For the coldest month
For summer mode
16. Temperature of chemically treated water after deaerated water cooler:
For the maximum winter regime
For the coldest month
For summer mode
17. Temperature of chemically treated water entering the deaerator
For the maximum winter regime:
For the coldest month
For summer mode
18. Raw water temperature is checked before chemical water treatment:
For summer mode
19. Heating water consumption for deaerator:
For the maximum winter regime and the coldest month
For summer mode
20. The consumption of chemically purified water for feeding the heating system is checked:
For the maximum winter regime and the coldest month
For summer mode
21. Heat consumption for raw water heating:
For the maximum winter regime and the coldest month
For summer mode
22. Heat consumption for heating chemically treated water:
For the maximum winter regime and the coldest month
For summer mode
MW<0, значит, подогрев химически очищенной воды в летний период не требуется.
23. Heat consumption for the deaerator:
For the maximum winter regime and the coldest month
For summer mode
24. Heat consumption for heating chemically treated water in the deaerated water cooler:
For the maximum winter regime and the coldest month
For summer mode
25. Total heat consumption required in hot water boilers:
For the maximum winter regime
For the coldest month
For summer mode
26. Water flow through hot water boilers:
For the maximum winter regime
t/h;
For the coldest month
t/h;
For summer mode
t/h
The choice of a heat supply system (open or closed) is made on the basis of technical and economic calculations. Using the data received from the customer and the methodology set out in § 5.1, they begin to draw up, then calculate the schemes, which are called thermal schemes of boiler rooms with hot water boilers for closed heat supply systems, since the maximum heat output of cast iron boilers does not exceed 1.0 - 1, 5 Gcal/h.
Since it is more convenient to consider thermal schemes using practical examples, the following are schematic and detailed diagrams of boiler houses with hot water boilers. Schematic diagrams of boiler rooms with hot water boilers for closed heat supply systems operating on a closed heat supply system are shown in fig. 5.7.
Rice. 5.7. Principal thermal diagrams of boiler rooms with hot water boilers for closed heat supply systems.
1 - hot water boiler; 2 - network pump; 3 - recirculation pump; 4 - raw water pump; 5 - make-up water pump; 6 - make-up water tank; 7 - raw water heater; 8 - heater for the chemistry of purified water; 9 - make-up water cooler; 10 - deaerator; 11 - vapor cooler.
Water from the return line of heating networks with a small pressure (20 - 40 m of water column) enters the network pumps 2. Water is also supplied there from make-up pumps 5, which compensates for water leaks in the heating networks. Hot network water is also supplied to pumps 1 and 2, the heat of which is partially used in heat exchangers for heating chemically treated 8 and raw water 7.
To ensure the water temperature in front of the boilers, set according to the conditions for preventing corrosion, the required amount of hot water from the hot water boilers 1 is supplied to the pipeline behind the network pump 2. The line through which hot water is supplied is called recirculation. Water is supplied by a recirculation pump 3, which pumps heated water. In all operating modes of the heating network, except for the maximum winter one, part of the water from the return line after the network pumps 2, bypassing the boilers, is supplied through the bypass line in the amount of G lane to the supply line, where water, mixing with hot water from the boilers, provides the specified design temperature in the supply line of heating networks. The addition of chemically treated water is heated in heat exchangers 9, 8 11 and deaerated in deaerator 10. Water for feeding heating networks from tanks 6 is taken by make-up pump 5 and fed into the return line.
Even in powerful hot water boilers operating for closed heat supply systems, one make-up water deaerator with low productivity can be dispensed with. The capacity of make-up pumps is also reduced, the equipment of the water treatment plant is also reduced, and the requirements for the quality of make-up water are reduced compared to boilers for open systems. The disadvantage of closed systems is some increase in the cost of equipment for subscriber hot water supply units.
To reduce water consumption for recirculation, its temperature at the outlet of the boilers is maintained, as a rule, higher than the temperature of the water in the supply line of heating networks. Only with the calculated maximum winter mode, the water temperatures at the outlet of the boilers and in the supply line of the heating networks will be the same. To ensure the calculated temperature of the water at the inlet to the heating networks, the water leaving the boilers is mixed with network water from the return pipeline. To do this, a bypass line is installed between the pipelines of the return and supply lines, after the network pumps.
The presence of mixing and recirculation of water leads to operating modes of steel hot water boilers that differ from the mode of heating networks. Hot water boilers work reliably only if the amount of water passing through them is maintained constant. The water flow must be maintained within the specified limits, regardless of fluctuations in thermal loads. Therefore, the regulation of the supply of thermal energy to the network must be carried out by changing the temperature of the water at the outlet of the boilers.
To reduce the intensity of external corrosion of pipes on the surfaces of steel hot water boilers, it is necessary to maintain the temperature of the water at the inlet to the boilers above the flue gas dew point temperature. The minimum allowable water temperature at the inlet to the boilers is recommended as follows:
- when working on natural gas - not lower than 60°С;
- when working on low-sulphur fuel oil - not lower than 70°С;
- when working on high-sulphur fuel oil - not lower than 110°С.
Due to the fact that the water temperature in the return lines of heating networks is almost always below 60 ° C, thermal schemes of boiler houses with hot water boilers for closed heat supply systems provide, as noted earlier, recirculation pumps and corresponding pipelines. To determine the required water temperature behind steel hot water boilers, the operating modes of heating networks must be known, which differ from schedules or regime boilers.
In many cases, water heating networks are calculated to work according to the so-called heating temperature curve of the type shown in fig. 2.9. The calculation shows that the maximum hourly flow of water entering the heating networks from the boilers is obtained at a mode corresponding to the break point of the water temperature graph in the networks, i.e. at an outside air temperature that corresponds to the lowest water temperature in the supply line. This temperature is kept constant even if the outside temperature rises further.
Based on the foregoing, the fifth characteristic mode is introduced into the calculation of the thermal scheme of the boiler room, which corresponds to the break point of the water temperature graph in the networks. Such graphs are built for each area with the corresponding last calculated outdoor temperature according to the type shown in Fig. 2.9. With the help of such a graph, it is easy to find the required temperatures in the supply and return lines of heating networks and the required water temperatures at the outlet of the boilers. Similar charts for determining water temperatures in heating networks for various design outdoor air temperatures - from -13°С to -40°С were developed by Teploelektroproekt.
Water temperatures in the supply and return lines, ° С, of the heating network can be determined by the formulas:
where t vn is the air temperature inside the heated premises, ° С; t H - calculated outdoor air temperature for heating, ° С; t′ H - time-varying outdoor temperature, °С; π′ i - water temperature in the supply pipeline at t n °С; π 2 - water temperature in the return pipeline at t n ° С; tн - water temperature in the supply pipeline at t′ n, ° С; ∆t - calculated temperature difference, ∆t = π 1 - π 2, ° С; θ \u003d π c -π 2 - estimated temperature difference in the local system, ° С; π 3 \u003d π 1 + aπ 2 / 1+ a - the calculated temperature of the water entering the heater, ° С; π′ 2 is the temperature of the water going into the return pipeline from the device at t "H, ° С; a is the displacement coefficient equal to the ratio of the amount of return water sucked by the elevator to the amount of network water.
The complexity of the calculation formulas (5.40) and (5.41) for determining the water temperature in heat networks confirms the feasibility of using graphs of the type shown in fig. 2.9, built for an area with an estimated outdoor temperature of 26 °C. It can be seen from the graph that at outdoor temperatures of 3°C and above, until the end of the heating season, the water temperature in the supply pipeline of heating networks is constant and equal to 70°C.
The initial data for calculating the thermal schemes of boiler houses with steel hot water boilers for closed heat supply systems, as mentioned above, are heat consumption for heating, ventilation and hot water supply, taking into account heat losses in the boiler house, networks and heat consumption for the boiler house's own needs.
The ratio of heating and ventilation loads and hot water supply loads is specified depending on the local operating conditions of consumers. The practice of operating heating boiler houses shows that the average hourly heat consumption per day for hot water supply is about 20% of the total heat output of the boiler house. Heat losses in external heat networks are recommended to be taken in the amount of up to 3% of the total heat consumption. The maximum hourly calculated consumption of thermal energy for auxiliary needs of a boiler house with hot water boilers with a closed heat supply system can be taken according to the recommendation in the amount of up to 3% of the installed heat output of all boilers.
The total hourly water consumption in the supply line of the heating networks at the outlet of the boiler house is determined based on the temperature regime of the heating networks, and, in addition, depends on the leakage of water through leaks. Leakage from heat networks for closed heat supply systems should not exceed 0.25% of the volume of water in the pipes of heat networks.
It is allowed to take approximately the specific volume of water in local heating systems of buildings per 1 Gcal / h of the total estimated heat consumption for residential areas - 30 m 3 and for industrial enterprises - 15 m 3.
Taking into account the specific volume of water in the pipelines of heating networks and heating installations, the total volume of water in a closed system can approximately be taken equal to 45 - 50 m 3 for residential areas, for industrial enterprises - 25 - 35 MS per 1 Gcal / h of the total estimated heat consumption.
Rice. 5.8. Detailed thermal diagrams of boiler houses with hot water boilers for closed heat supply systems.
1 - hot water boiler; 2 - recirculation pump; 3 - network pump; 4 - network summer pump; 5 - raw water pump; 6 - condensate pump; 7 - condensate tank; 8 - raw water heater; 9 - heater of chemically purified water; 10 - deaerator; 11 - vapor cooler.
Sometimes, for a preliminary determination of the amount of network water leaking from a closed system, this value is taken up to 2% of the water flow in the supply line. Based on the calculation of the basic thermal diagram and after the selection of unit capacities of the main and auxiliary equipment of the boiler house, a complete detailed thermal diagram is drawn up. For each technological part of the boiler house, separate detailed schemes are usually drawn up, that is, for the equipment of the boiler house itself, chemical water treatment and fuel oil facilities. A detailed thermal diagram of a boiler house with three hot water boilers KV-TS - 20 for a closed heat supply system is shown in fig. 5.8.
In the upper right part of this diagram, there are hot water boilers 1, and in the left - deaerators 10 below the boilers there are recirculation pumps below the network, under the deaerators - heat exchangers (heaters) 9, a deaerated water tank 7, saw pumps 6, raw water pumps 5, drainage tanks and purge well. When performing detailed thermal schemes of boiler houses with hot water boilers, a general station or aggregate equipment layout scheme is used (Fig. 5.9).
General station thermal schemes of boiler houses with hot water boilers for closed heat supply systems are characterized by the connection of network 2 and recirculation 3 pumps, in which water from the return line of heat networks can be supplied to any of the network pumps 2 and 4 connected to the main pipeline supplying water to all boilers of the boiler house. Recirculation pumps 3 supply hot water from the common line behind the boilers to the common line that supplies water to all hot water boilers.
With the aggregate layout of the boiler room equipment shown in fig. 5.10, for each boiler 1, network 2 and recirculation pumps 3 are installed.
Figure 5.9 General layout of boilers for network and recirculation pumps. 1 - hot water boiler, 2 - recirculation, 3 - network pump, 4 - network summer pump.
Rice. 5-10. Aggregate layout of boilers KV - GM - 100, network and recirculation pumps. 1 - hot water pump; 2 - network pump; 3 - recirculation pump.
Water from the return line flows in parallel to all network pumps, and the discharge pipe of each pump is connected to only one of the water heaters. Hot water is supplied to the recirculation pump from the pipeline behind each boiler until it is included in the common falling main and is sent to the feed line of the same boiler unit. When arranging with a modular scheme, it is envisaged to install one for all hot water boilers. Figure 5.10 does not show the make-up and hot water lines to the main pipelines and the heat exchanger.
The aggregate method of placing equipment is especially widely used in projects of hot water boilers with large boilers PTVM - 30M, KV - GM 100, etc. The choice of a general station or aggregate method of arranging boiler equipment with hot water boilers in each individual case is decided based on operational considerations. The most important of them from the layout of the aggregate scheme is to facilitate the accounting and regulation of the flow rate and the parameter of the coolant from each unit of large-diameter main heat pipelines and to simplify the commissioning of each unit.
Boiler plant Energia-SPB produces various models of hot water boilers. Transportation of boilers and other auxiliary boiler equipment is carried out by road, railway gondola cars and river transport. The boiler plant supplies products to all regions of Russia and Kazakhstan.
If a country house is used not just for summer holidays, but for year-round permanent residence, you should think about arranging a private boiler room. A properly designed and installed boiler plant will be able to serve all the necessary communications: heating systems, hot and cold water supply, ventilation. In order to avoid errors in the installation of equipment and correctly calculate the technical nuances, a thermal diagram of the boiler room must first be drawn up, indicating the main apparatus and materials.
General provisions for design
Each step in the installation of a boiler installation must be thought out, so you should not try to design communications and install equipment yourself, it is better to turn to specialists who have extensive experience in installing engineering systems for private cottages. They will give a number of valuable tips, for example, help you choose the most optimal model of the boiler and determine the location of its installation.
Suppose, for a small country house, a wall-mounted apparatus is enough, which can easily be located in the kitchen. A two-story cottage, accordingly, needs a specially allocated room, which must be equipped with ventilation, a separate exit and a window. There must be enough space to accommodate the remaining components: pumps, connecting elements, pipes, etc.
The process of designing a boiler room for a private house includes several points:
- preparation of a boiler room diagram regarding the location inside the house;
- equipment distribution scheme indicating the main technical characteristics;
- specification for the materials and equipment used.
In addition to the acquisition of system components and their installation, as well as graphic work, among which there should be a schematic diagram, professionals will help with the preparation of the necessary documents.
An example of a schematic diagram of a hot water boiler house: I - boiler; II - water evaporator; III - source water heater; IV - heat engine; V is a capacitor; VI - heater (additional); VII - battery tank
More about the schematic diagram of the boiler room
A well-designed graphic drawing should reflect, first of all, all the mechanisms, devices, apparatuses and pipes connecting them. Standard schemes for boiler houses in private houses include a set of boilers, recirculation, make-up and network pumps, storage and condensing tanks, fuel supply and combustion devices, water deaeration devices, heat exchangers, fans, control panels, heat shields. The choice and location of equipment is influenced by the type of coolant and thermal communications, as well as the quality of the water used.
In the process of drawing up a scheme for a hot water boiler, it is necessary to monitor the compliance with the technical characteristics of the equipment, which must meet the requirements of the selected temperature regime
Thermal networks operating on water can be divided into two groups:
- open, in which the liquid is taken in local installations;
- closed, in which water, having given off heat, returns to the boiler.
An example of a circuit diagram can serve as an example of an open-type hot-water boiler house. Installed on the return line circulation pump, which ensures the delivery of water to the boiler and further through the system. The design temperature regime of this scheme is 155-70°С. Two types of jumpers (recirculation and bypass) connect the two main lines - supply and return.
Schematic diagram of the boiler room: 1 - network pump; 2 – make-up pump; 3 – make-up water tank; 4 – source water pump; 5 - supply pump; 6 - supply tank; 7 - ejector; 8 - cooler; 9 - vacuum deaerator; 10 – purified water heater; 11 - cleaning filter; 12 – source water heater; 13 - hot water boiler; 14 - recirculation pump; 15 - bypass
Due to the occurrence of flue gases, corrosion of metal coatings of sulfuric acid or low-temperature origin may occur. To avoid its occurrence, you should control the temperature of the water. The optimal value at the inlet to the boiler is 60-70˚С. To increase the temperature to the required parameters, it is necessary to install a recirculation pump.
In order for hot water boilers to serve for a long time, properly and economically, you should monitor the constancy of water consumption. The minimum flow rate is set by the equipment manufacturer.
For better operation of boiler plants, vacuum deaerators are used. The water jet ejector creates a vacuum, and the released steam is used for deaeration.
Automation of boiler equipment
It would be foolish not to take advantage of the opportunities that facilitate the operation of heating systems. Automation allows you to use a set of programs that control heat flows depending on the daily routine, weather conditions, and also help to additionally heat individual rooms, for example, a pool or a nursery.
An example of an automated circuit diagram: the automatic operation of the boiler house controls the operation of the water recirculation circuits, ventilation, water heating, heat exchanger, 2 underfloor heating circuits, 4 building heating circuits
There is a list of user functions that adapt the operation of the equipment depending on the lifestyle of the inhabitants of the house. For example, in addition to the standard program for providing hot water, there is a set of individual solutions that are more convenient and even economical for residents. For this reason, a boiler room automation scheme can be developed with the choice of one of the popular modes.
Good night program
It has been proven that the optimal night air temperature in the room should be several degrees lower than the daytime temperature, that is, the ideal option is to lower the temperature in the bedroom by about 4 ° C during sleep. At the same time, a person experiences discomfort when waking up in an unusually cool room, therefore, early in the morning the temperature regime must be restored. Inconveniences are easily solved by automatically switching the heating system to night mode and back. Night time controllers are operated by DE DIETRICH and BUDERUS.
Hot water priority system
Automatic regulation of hot water flows is also one of the functions of the general automation of equipment. It is divided into three types:
- priority, in which during the use of hot water the heating system is completely turned off;
- mixed, when the capacity of the boiler is divided into service for heating water and heating the house;
non-priority, in which both systems act together, but in the first place is the heating of the building.
Automated scheme: 1 - hot water boiler; 2 – network pump; 3 – source water pump; 4 - heater; 5 – HVO block; 6 – make-up pump; 7 - deaeration block; 8 - cooler; 9 - heater; 10 - deaerator; 11 – condensate cooler; 12 - recirculation pump
Low temperature operating modes
The transition to low-temperature programs is becoming the main direction of the latest developments of boiler manufacturers. The advantage of this approach is an economic nuance - a reduction in fuel consumption. Just automation allows you to adjust the temperature, choose the right mode and thereby reduce the level of heating. All of the above points must be taken into account at the stage of drawing up a thermal scheme for a hot water boiler.
The principal thermal diagram (PTS) of a boiler house with steam boilers for consumers of steam and hot water is shown in fig. eight.
Steam boilers are most often designed for the simultaneous release of steam and hot water, therefore, in their thermal schemes there are installations for heating hot water.
Usually, low-pressure steam boilers of 14 atm are installed, but not higher than 24 atm.
Raw water comes from a water supply system with a pressure of 30–40 m of water. Art. If the raw water pressure is insufficient, provide for the installation of raw water pumps 5.
Raw water is heated in the cooler of the continuous blowdown of steam boilers 11 and in the steam-water heater of raw water 12 to a temperature of 20-30 ºС. Next, the water passes through the water treatment plant (WTP), and part of it is sent to the chemically purified water heater 13, part passes through the deaerator vapor cooler 4 and enters the feed water deaerator (FW) 2. Condensate flows and steam after reduction are also directed to this deaerator. -cooling unit (ROU) 17 with a pressure of 1.5 atm for heating deaerated water up to 104 0 C. Deaerated water is supplied to the water economizers of the boiler and to the cooler of the DOU by means of a feed pump (PN) 6. Part of the steam generated by the boilers is reduced to the ROU and used for raw water heating and deaeration.
Rice. 8. Principal thermal diagram of a boiler room with steam boilers
1 - steam boiler, 2 - feed water deaerator (FW), 3 - make-up water deaerator, 4 - steam cooler, 5 - raw water pump, 6 - feed pump (PN), 7 - make-up pump, 8 - network pump (SN ), 9 - condensate pump (KN), 10 - condensate tank, 11 - blowdown water cooler (OPV), 12 - raw water heater, 13 - chemical heater. purified water (PHOV), 14 - make-up water cooler, 15 - condensate cooler, 16 - network water heater, 17 - reduction cooling unit (RDC), 18 - continuous blowdown separator, 19 - blowdown well, WTP - water treatment plant.
The second part of the chem. purified water is heated in the heater 14, partially in the vapor cooler 4 and is sent to the make-up water deaerator for heating networks 3. The water after this deaerator passes the water-to-water heat exchanger 14 and heats up the chemical. purified water. The make-up pump 7 supplies water to the pipeline in front of the network pumps 8, which pump the network water first through the condensate cooler 15 and then through the network water heater 16, from where the water goes to the heating network.
The make-up water deaerator 3 also uses low pressure steam downstream of the ROW. With a closed heat supply system, the water consumption for feeding heating networks is usually negligible. In this case, quite often they do not allocate a separate deaerator for the preparation of make-up water for heating networks, but use a deaerator for the feed water of steam boilers.
The above scheme provides for the use of continuous blowdown heat from steam boilers. For this purpose, a continuous purge separator 18 is installed, in which water is partially evaporated by reducing its pressure from 14 to 1.5 atm. The resulting steam is discharged into the steam space of the deaerator, hot water is sent to the raw water water-to-water heat exchanger 11. The cooled blowdown water is discharged into the blowdown well.
Continuous blowing ensures uniform removal of accumulated dissolved salts from the boiler and is carried out from the place of their highest concentration in the upper drum of the boiler. Periodic blowdown is used to remove sludge that has settled in the boiler elements and is carried out from the lower drums and boiler collectors every 12-16 hours. Sometimes they provide for the supply of blowdown water to feed closed heating networks. Feeding of heating networks with purge water is allowed only if the total hardness of the network water does not exceed 0.05 meq/kg.
The PTS of a boiler house for open heat supply systems differs from the one given only by the installation of an additional deaerator for deaeration of make-up water of heating networks and the installation of storage tanks.
In all cases, the condensate from steam-water heaters under the pressure of heating steam should be directed to the DPV, bypassing the condensate tanks 10 and pumps 9. In open heat supply systems, atmospheric deaerators are usually installed to deaerate the make-up water. The use of boiler blowdown water as make-up water for open systems is not allowed. The feed water temperature after the deaerator is 104 °C. The temperature of the condensate returned from production is 80–95 °C.
Principal thermal diagram of a boiler room with hot water boilers for closed heat supply systems
PTS of boiler houses with hot water boilers for closed heat supply systems is shown in fig. nine.
Water from the return line of heating networks with a small pressure of 20–40 m. of water. Art. comes to the network pumps 2. Water is also supplied there from make-up pumps 5, which compensates for water leakage in heating networks. Hot network water is also supplied to pump 2, the heat of which is partially used in heat exchangers for heating chemical. purified water 8 and raw water 7.
To ensure the temperature of the water at the inlet to the boiler, set according to the conditions for preventing corrosion, the required amount of hot water from the hot water boilers 1 is supplied to the pipeline behind the network pump 2. Water is supplied by the recirculation pump 3.
In all operating modes of the heating network, except for the maximum winter one, part of the water from the return line after pumps 2, bypassing the boilers, is supplied through the bypass line in the amount G lane to the supply line, where water, mixing with hot water from boilers, provides the specified design temperature in the supply line of heating networks.
The addition of chem. purified water is heated in heat exchangers 9, 8, 11 and deaerated in deaerator 10. Water for feeding heating networks from tanks 6 is taken by make-up pump 5 and supplied to the return line.
To reduce water consumption for recirculation, its temperature at the outlet of the boilers is usually maintained above the temperature of the water in the heating supply line. Only with the calculated maximum winter mode, the water temperature at the outlet of the boilers and in the supply line will be the same.
For closed systems, even in powerful hot water boilers, one make-up water deaerator with low productivity can be dispensed with. The power of make-up pumps 5 and the equipment of the WLU also decrease, and the requirements for the quality of make-up water are reduced in comparison with open systems.
The disadvantage of closed systems is some increase in the cost of equipment for subscriber hot water supply units.
Hot water boilers work reliably only if the amount of water passing through them is maintained constant. The water flow must be constant, regardless of fluctuations in heat loads. Therefore, the regulation of the supply of thermal energy to the network must be carried out by changing the temperature of the water at the outlet of their boilers. G per.
To reduce the intensity of external corrosion of the pipe surfaces of steel hot water boilers, it is necessary to maintain the temperature of the water at the inlet to the boilers above the dew point temperature of the flue gases.
The minimum allowable temperature at the inlet to the boilers is recommended as follows: when operating on natural gas - not lower than 60 °C; when working on low-sulphur fuel oil - not lower than 70 °С; when working on high-sulphur fuel oil - not lower than 110°C. Since the temperature of the return network water is almost always below 60 ° C, a recirculation line is provided in the thermal schemes.
To determine the water temperature in heating networks for various calculated outdoor air temperatures, graphs developed by the heat and power project are built. For example, from such a graph it can be seen that at outdoor temperatures of +3 ºС and above, until the end of the heating season, the temperature of direct network water is constant and equal to 70 0 С.
The average hourly heat consumption per day for hot water supply is usually 20% of the total heat output of the boiler house:
3% - losses of external heating networks;
3% - expenses for own needs from the installed heating capacity of the boiler house;
0.25% - leakage from heat networks of closed systems;
0.25% - the volume of water in the pipes of heating networks.
Rice. 9. Schematic diagram of a boiler room with hot water boilers for a closed heat supply system
1 - hot water boiler, 2 - network pump (SN), 3 - recirculation pump, 4 - raw water pump (NSW), 5 - make-up water pump, 6 - make-up water tank, 7 - raw water heater, 8 - chemical heater. purified water (PHOV), 9 - make-up water cooler, 10 - deaerator, 11 - vapor cooler, 12 - water treatment plant (WTP).