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1 kilogram per second [kg/s] = 3.6 ton (metric) per hour [t/h]
Initial value
Converted value
kilogram per second gram per second gram per minute gram per hour gram per day milligram per minute milligram per hour milligram per day kilogram per minute kilogram per hour kilogram per day exagram per second petagram per second teragram per second gigagram per second megagram per second hectogram in second decagrams per second decigrams per second centigrams per second milligrams per second micrograms per second ton (metric) per second ton (metric) per minute ton (metric) per hour ton (metric) per day ton (short) per hour pound per second pound per minute pound per hour pound per day
More about mass flow
General information
The amount of liquid or gas that passes through a certain area in a certain amount of time can be measured in different ways, such as mass or volume. In this article we will look at calculation by mass. Mass flow depends on the speed of movement of the medium, the cross-sectional area through which the substance passes, the density of the medium, and the total volume of the substance passing through this area per unit time. If we know the mass and we know either the density or the volume, we can know the other quantity because it can be expressed using mass and the quantity we know.
Mass flow measurement
There are many ways to measure mass flow and there are many different models flowmeters that measure mass. Below we will look at some of them.
Calorimetric flow meters
Calorimetric flowmeters use temperature differences to measure mass flow. There are two types of such flow meters. In both, the liquid or gas cools the thermal element it flows past, but the difference is what each flow meter measures. The first type of flowmeter measures the amount of energy required to maintain a constant temperature on a thermal element. The higher the mass flow, the more energy it requires. In the second type, the difference in flow temperatures is measured between two points: near the thermal element and at a certain distance downstream. The higher the mass flow, the higher the temperature difference. Calorimetric flow meters are used to measure mass flow in liquids and gases. Flow meters used in liquids or gases that are corrosive are made from materials that resist corrosion, such as special alloys. Moreover, only parts that have direct contact with the substance are made from such material.
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Variable differential pressure flowmeters
Variable pressure flow meters create a pressure difference within the pipe through which the fluid flows. One of the most common methods is to partially block the flow of liquid or gas. The greater the measured pressure difference, the higher the mass flow. An example of such a flow meter is diaphragm based flow meter. The diaphragm, that is, a ring installed inside the pipe perpendicular to the flow of liquid, limits the flow of liquid through the pipe. As a result, the pressure of this fluid in the place where the diaphragm is located is different from the pressure in other parts of the pipe. Flowmeters with restriction devices, for example, with nozzles, they work in a similar way, only the narrowing in the nozzles occurs gradually, and the return to normal width occurs instantly, as in the case of a diaphragm. The third type of variable pressure flow meters, called Venturi flow meter in honor of the Italian scientist Venturi, it narrows and expands gradually. A tube of this shape is often called a Venturi tube. You can imagine what it looks like if you place two funnels with narrow parts facing each other. The pressure in the constricted part of the tube is lower than the pressure in the rest of the tube. It should be noted that flowmeters with a diaphragm or restriction device operate more accurately at high pressure, but their readings become inaccurate if the liquid pressure is weak. Their ability to partially retain water flow deteriorates when long-term operation, therefore, as they are used, they must be regularly maintained and, if necessary, calibrated. Despite the fact that such flowmeters are easily damaged during operation, especially due to corrosion, they are popular due to their low price.
Rotameter
Rotameters, or variable area flowmeters- these are flow meters that measure mass flow by pressure difference, that is, they are differential pressure flow meters. Their design is usually a vertical tube that connects horizontal inlet and outlet pipes. In this case, the inlet pipe is located below the outlet pipe. At the bottom, the vertical tube narrows - that is why such flow meters are called flow meters with a variable cross-section. The difference in cross-sectional diameter creates a pressure difference - just like with other differential pressure flowmeters. A float is placed in a vertical tube. On one side, the float tends upward, since it is acted upon by a lifting force, as well as by liquid moving up the pipe. On the other hand, gravity pulls it down. In the narrow part of the pipe, the total sum of forces acting on the float pushes it upward. With height, the sum of these forces gradually decreases until at a certain height it becomes zero. This is the height at which the float will stop moving up and stop. This height depends on constant variables such as the weight of the float, the taper of the tube, and the viscosity and density of the liquid. The height also depends on the variable mass flow rate. Since we know all the constants, or we can easily find them, then, knowing them, we can easily calculate the mass flow if we determine at what height the float stopped. Flow meters that use this mechanism are very accurate, with an error of up to 1%.
Coriolis flow meters
The operation of Coriolis flow meters is based on the measurement of Coriolis forces arising in oscillating tubes through which the medium flows, the flow of which is measured. The most popular design consists of two curved tubes. Sometimes these tubes are straight. They oscillate with a certain amplitude, and when there is no fluid flowing through them, these oscillations are phase-locked, as in Figures 1 and 2 in the illustration. If liquid is passed through these tubes, the amplitude and phase of the oscillations change, and the oscillations of the pipes become asynchronous. The change in phase of the oscillations depends on the mass flow rate, so we can calculate it if we have information about how the oscillations changed when the liquid was released through the pipes.
To better understand what happens to pipes in a Coriolis flow meter, let's imagine a similar situation with a hose. Take the hose attached to the faucet so that it is bent and begin to pump it from side to side. The vibrations will be uniform as long as no water flows through it. As soon as we turn on the water, the vibrations will change and the movement will become serpentine. This movement is caused by the Coriolis effect - the same thing that acts on the pipes in a Coriolis flow meter.
Ultrasonic flow meters
Ultrasonic or acoustic flowmeters transmit ultrasonic signals through liquids. There are two main types of ultrasonic flowmeters: Doppler and time-pulse flowmeters. IN Doppler flow meters The ultrasonic signal sent by the sensor through the liquid is reflected and received by the transmitter. The difference in frequency of the sent and received signals determines the mass flow. The higher this difference, the higher the mass flow.
Time-pulse flow meters compare the time it takes for a sound wave to reach a receiver downstream with the time taken upstream. The difference between these two quantities is determined by the mass flow rate - the larger it is, the higher the mass flow rate.
These flowmeters do not require the devices that emit the ultrasonic wave, the reflectors (if used), and the receiving sensors to be in contact with the liquid, so they are convenient for use with liquids that are corrosive. On the other hand, the liquid must pass ultrasonic waves, otherwise the ultrasonic flow meter will not work in it.
Ultrasonic flowmeters are widely used to measure the mass flow of open streams, such as in rivers and canals. These flowmeters can also measure mass flow in sewage drains and pipes. The information obtained from the measurements is used to determine the ecological state of the water stream, in agriculture and fish farming, in the treatment of liquid waste, and in many other industries.
Converting mass flow to volumetric flow
If the density of the liquid is known, then the mass flow rate can be easily converted to volumetric flow, and vice versa. Mass is found by multiplying density by volume, and mass flow can be found by multiplying volume flow by density. It is worth remembering that volume and volumetric flow change with changes in temperature and pressure.
Application
Mass flow is used in many industries and in everyday life. One application is to measure water flow in private homes. As we discussed earlier, mass flow is also used to measure open flows in rivers and canals. Coriolis and variable area flowmeters are often used in waste treatment, mining, paper and pulp production, power generation, and petrochemical extraction. Some types of flow meters, such as transition flow meters, are used in complex systems for assessing various profiles. In addition, information about mass flow is used in aerodynamics. There are four main forces acting on an airplane: lift (B), directed upward; thrust (A), parallel to the direction of movement; weight (C) directed towards the Earth; and drag (D), directed opposite to the movement.
Air mass flow affects the movement of an airplane in several ways, and we'll look at two of them below: the first is the overall flow of air past the airplane, which helps the airplane stay in the air, and the second is the flow of air through the turbines, which helps the airplane move forward. Let's consider the first case first.
Let's consider what forces influence the plane during flight. It is not easy to explain the action of some of them within the framework of this article, so we will talk about them in general, using a simplified model, without explaining small details. The force that pushes the plane upward and is labeled B in the illustration is - lift.
The force that, due to the gravity of our planet, pulls the plane towards the Earth is its weight, indicated in the figure by the letter C. In order for the plane to remain in the air, the lift force must overcome the weight of the plane. Drag- the third force that acts on the plane in the direction opposite to the movement. That is, drag resists forward movement. This force can be compared to the force of friction, which slows down the movement of a body on a solid surface. Drag is indicated in our illustration by the letter D. The fourth force that acts on an airplane is traction. It occurs as the engines operate and pushes the plane forward, that is, it is directed opposite to the drag. In the illustration it is indicated by the letter A.
The mass flow of air that moves relative to the aircraft affects all of these forces except weight. If we try to derive a formula for calculating mass flow using force, we will notice that if all other variables are constant, then the force is directly proportional to the square of the speed. This means that if you double the speed, the force will quadruple, and if you triple the speed, the force will increase nine times, and so on. This relationship is widely used in aerodynamics, since this knowledge allows us to increase or decrease speed by changing force, and vice versa. For example, to increase lift we can increase the speed. You can also increase the speed of the air that is forced through the engines to increase thrust. Instead of speed, you can change the mass flow.
Don't forget that lift is affected not only by speed and mass flow, but also by other variables. For example, decreasing air density reduces lift. The higher the plane rises, the lower the air density, therefore, in order to use fuel most economically, the route is calculated so that the altitude does not exceed the norm, that is, so that the air density is optimal for movement.
Now consider an example where mass flow is used by turbines through which air passes to create thrust. In order for the aircraft to overcome drag and weight and be able to not only stay in the air at the desired altitude, but also move forward at a certain speed, the thrust must be high enough. Airplane engines create thrust by passing a large flow of air through turbines and pushing it out with great force, but over a short distance. The air moves away from the airplane in the opposite direction to its motion, and the airplane, according to Newton's third law, moves in the opposite direction to the air's motion. By increasing mass flow, we increase thrust.
To increase thrust, instead of increasing mass flow, you can also increase the speed at which air exits the turbines. In airplanes, this consumes more fuel than increasing mass flow, so this method is not used.
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Steam boiler low pressure Viessmann with a capacity of 25 t/h, can be used in thermal power plants as a backup source of steam.
Fuel
For given characteristics of natural gas:
- CH4 - 98%
- C2H6 - 0.72%
- C3H8 - 0.23%
- C4H10 - 0.10%
- N2 - 0.79%
- O2 - 0.00%
- CO2 - 0.06%
- other - 0.02%
Fuel gas consumption for the backup boiler - 1936 Nm3/hour
Operating overpressure 300 kPa
Oil
Fuel oil consumption – 1236 kg/h
Operating excess oil pressure in front of the burner 400 – 500 kPa
Ambient temperature 5-35 C
Main characteristics of the boiler
| Parameter | Magnitude |
| Nominal steam output of the boiler at gas fuel | 25 t/h |
| Nominal steam output of an oil fuel boiler | 18 t/h |
| Length | 8670 mm |
| Height | 4450 mm |
| Width | 4000 mm |
| total weight | 50,000 kg |
| Excessive pressure, no more | 1.0 MPa |
| Test overpressure, no more | 1.65 MPa |
| Nominal steam pressure | 0.8 MPa |
| Nominal steam temperature | 170°C |
| Supply water temperature | 102°C |
| Fuel | natural gas/fuel oil |
| Boiler efficiency in the regulation range (natural gas) | not less than 90±1% |
| Boiler efficiency in the regulation range (fuel oil) | not less than 90±1% |
| Natural gas consumption at rated power | 1936 Nm3/hour |
| Fuel oil consumption at rated power | 1239 kg/hour |
| Emissions | |
| Natural gas NOx | no more than 100 mg/Nm3 |
| Natural gas CO | no more than 100 mg/Nm3 |
| Natural gas solid waste content | no more than 5 mg/Nm3 |
| Fuel oil NOx | no more than 500 mg/Nm3 |
| Fuel oil CO | no more than 100 mg/Nm3 |
| Fuel oil solid waste content | no more than 100 mg/Nm3 |
The specified waste values refer to dry flue gases, pressure 101,325 Pa, temperature 0°C and O 2 content 3% by volume.
Description of the Viessmann boiler
Steel three-pass boiler with a cylindrical combustion chamber and controlled convection heated panels.
The boiler is designed with wide water walls and a large pitch between the flame tubes to ensure safety during operation.
The boiler design takes into account a large volume of water, a large space for steam and big square evaporation mirrors, as well as a built-in drop separator to improve steam quality. Losses due to radiation are not large; this is achieved through water cooling of the rotating chambers of the wall without lining.
The boiler is placed on longitudinal profiles, which are mounted on concrete foundation. Sound insulation is installed between the profile supports and the foundation. The boiler is manufactured and tested in accordance with Instruction TRD 604. After 1 year of operation, it is necessary to carry out an internal inspection of the boiler.
Read also: Powerful steam boilers Red Boilermaker
To ensure safety, the boiler room must be ventilated. The minimum hole for ventilation should have a diameter of 150 cm 2, in addition, for each kW of rated power exceeding 50 kW, it is necessary to provide an increase in the diameter of the hole by 2 cm 2, and the air flow speed should be 0.5 m/s.
Shut-off valves with actuators on the steam line are included in the delivery of the boiler.
In order to prevent an unacceptable increase in pressure, the boiler is equipped with a safety valve. Sludge removal is carried out periodically in automatic mode.
Alkalinization occurs continuously and is ensured by a control valve with a servomotor, which is regulated depending on the level of water conductivity in the boiler.
The boiler body is insulated with continuous insulation 120 mm thick.
Exploitation
The first start-up of the boiler is carried out by a service organization or a person authorized by it. The value settings must be reflected in the measurement report and confirmed at the manufacturer and with the future customer. The boiler can be operated without the constant presence of personnel.
The reserve boiler must be mothballed, like a boiler that is taken out of service for a long period.
When the boiler is idle for a long time, it is necessary to thoroughly clean its surface on the flue gas side. Then preserve the surfaces with preservative oil mixed with graphite.
On the water side, it is recommended to fill the boiler with water purified from gas impurities, with a low salt content and the addition of additives to combine with oxygen. After this, it is necessary to close the shut-off valve on the steam side. The concentration of oxygen sorbents must be monitored at least once a year, and if necessary, more.
It is necessary to inspect the outside annually, and every three years, inspect its internal parts. Hydraulic strength tests must be carried out every nine years. Once every six months, inspect all safety and regulatory equipment.
Boiler technical equipment
The boiler also includes:
- pressure regulator with range 0 - 1.6 MPa
- safety valve, DN100/150 in an angular design with an opening pressure of 1.0 MPa with a throughput capacity of 29.15 t/hour.
- feed pump, high-pressure centrifugal pump GRUNDFOS type CR 32-8K with electric motor. Water consumption 28.8 m3/hour, lifting height 107 m. Minimum height pressure 4.5 m. Feed water temperature no more than 105 °C. Electric motor power 15 kW.
- check valve DN 80, PN16
- water indicator PN 40 with holder, two shut-off valves and one release valve
- boiler level regulator. A level regulator is integrated into the electrical control cabinet of the Viessmann-Control boiler for continuous regulation of the boiler feed water with maximum level limitation and a level switch for limiting the minimum boiler water level.
- shut-off steam valves DN 300, PN 16
- Feed water shut-off valves DN 80, PN16
- feed water control valve
- automatic desalting equipment consisting of a conductivity electrode, a sampling valve and a desalting regulator.
- pressure gauge with a range of 0 – 1.6 MPa
- cooler of selected steam samples with an excess pressure of no more than 2.8 MPa with a valve for the test sample and a valve for cooling the sample.
- pressure limiter in the range 0 – 1.6 MPa
- air vent DN 15, PN 16
Read also: double-circuit waste gas recovery boiler
Feed water
Boiler feedwater parameters:
Water should be colorless, clean, without soluble substances
burner
Double gas burner WEISHAUPT with O2 regulation for combustion liquid fuel in accordance with the requirements of DIN 51603 or gas in accordance with the requirements of the DVGW work table G 260. The burner operates on a rotary atomization principle for high-intensity fuels.
Weishaupt industrial combined burner type WКГMS 80/3-A, ZM-NR with reduced NOx and CO emissions. Version with separate fan, burner body made of light alloys with sectional air valve. Power regulation is two-stage, sliding when using a step regulator and smooth when using a stepper power regulator.
Electronic general control of gas-air combustion with individual servomotors and automatic tightness control gas fittings integrated into the digital burner control unit. The microprocessor-controlled digital burner automation W-FM 100 is designed to control and monitor all burner functions.
A dual fuel gas/fuel oil burner must be tested in accordance with the instructions for gas and oil burners. The oil burner must be tested and marked in accordance with EN 267 and TRD 411. The gas burner must be tested in accordance with EN 676 and marked in accordance with Directive 90/396/EWG with the CE mark and TRD 412.
The connection of the burner to the boiler will be carried out at the manufacturer's factory.
The fuel oil or gas flow setting must be such that the maximum thermal output of the boiler is not exceeded.
air fan
The combustion air is equipped with an air fan with a noise suppressor, a fan-air duct compensator, and a protective mesh on the suction side. The fan is installed in an anti-noise box, which reduces general noise from fan operation to a level of 80 dB. The air duct is routed to the burner through a channel. An integral part The burner valve is a control valve connected to the burner inlet flange.
Exercise
1. Characteristics of the boiler unit
1.1 Technical characteristics of the boiler KE-25-14S
2. Calculation of fuel by air
2.1 Determination of the amount of combustion products
2.2 Determination of enthalpy of combustion products
3. Verification thermal calculation
3.1 Preliminary heat balance
3.2 Calculation of heat transfer in the furnace
3.3 Calculation of heat transfer in a convective surface
3.4 Economizer calculation
4. Final heat balance
Bibliography
Exercise
Complete the design of a stationary steam boiler in accordance with the following data:
boiler type KE-25-14S
full saturated steam output, D, kg/s 6,94
working pressure (excessive), R, MPa 1,5
feed water temperature:
to the economizer, t pv1, ºС 90
behind the economizer, t pv2, ºС 170
temperature of air entering the furnace:
to the air heater, t v1, ºС 25
behind the air heater, tВ2, ºС 180
fuel KU-DO
fuel composition: C g = 76.9%
N g = 5.4% g = 0.6%
O g = 16.0% g = 1.1%
Fuel ash content A c = 23%
fuel moisture W p = 7.5%
excess air coefficient α = 1.28.
stationary thermal steam boiler
1. Characteristics of the boiler unit
Steam boiler KE-25-14S, with natural circulation with layered mechanical fireboxes, is designed to produce saturated or superheated steam used for the technological needs of industrial enterprises, in heating, ventilation and hot water supply systems.
The combustion chamber of KE series boilers is formed by side screens, front and back walls. Combustion chamber of KE boilers with steam output from 2.5 to 25 t/h divided by a brick wall into a firebox with a depth of 1605÷2105 mm and an afterburning chamber with a depth of 360÷745 mm, which allows you to increase the efficiency of the boiler by reducing mechanical underburning. The entry of gases from the furnace into the afterburning chamber and the exit of gases from the boiler are asymmetrical. It is tilted under the afterburning chamber in such a way that the bulk of the pieces of fuel falling into the chamber roll onto the grate.
The KE-25-14S boiler uses a single-stage evaporation scheme. The water circulates as follows: feed water from the economizer is supplied to the upper drum under the water level through a perforated pipe. Water is drained into the lower drum through the rear heated pipes of the boiler bundle. The front part of the beam (from the front of the boiler) is lifting. From the lower drum, water flows through overflow pipes into the chambers of the left and right screens. The screens are also fed from the upper drum via lower risers located at the front of the boiler.
The boiler block KE-25-14S is supported by the chambers of the side screens on longitudinal channels. The chambers are welded to the channels along the entire length. In the area of the convection beam, the boiler block rests on the rear and front transverse beams. The transverse beams are attached to the longitudinal channels. The front beam is fixed, the rear beam is movable.
The binding frame of the KE-25-14S boiler is installed on corners welded along the chambers of the side screens along the entire length.
To make it possible to move the elements of the KE-25-14S boiler blocks in a given direction, some of the supports are made movable. They have oval holes for bolts that secure them to the frame.
KE boilers with grate and economizer are delivered to the customer in one transportable unit. They are equipped with an entrainment return system and a sharp blast. The entrainment, settling in four ash pans of the boiler, is returned to the furnace using ejectors and introduced into the combustion chamber at a height of 400 mm from the grate. The mixing pipes for entrainment return are made straight, without turns, which ensures reliable operation of the systems. Access to the entrainment return ejectors for inspection and repair is possible through hatches located on the side walls. In places where hatches are installed, the pipes of the outermost row of the bundle are inserted not into the collector, but into the lower drum.
The KE-25-14S steam boiler is equipped with a stationary device for cleaning heating surfaces according to the plant design.
The KE-25-14S steam boiler is equipped with a firebox of the ZP-RPK type with pneumomechanical throwers and a grate with rotary grates.
Behind boiler units in case of combustion of hard and brown coals with reduced humidity W< 8 устанавливаются водяные экономайзеры.
Boiler platforms of the KE type are located in places necessary for servicing boiler fittings. Main boiler platforms: side platform for servicing water indicating devices; side platform for servicing safety valves and shut-off valves on the boiler drum; a platform on the rear wall of the boiler for servicing the purge line from the upper drum and for access to the upper drum when repairing the boiler.
There are stairs leading to the side landings, and a descent (short staircase) from the upper side landing to the back landing.
The KE-25-14 C boiler is equipped with two safety valves, one of which is a control valve. For boilers with superheaters, the control safety valve is installed on the outlet manifold of the superheater. A pressure gauge is installed on the upper drum of each boiler; If there is a superheater, the pressure gauge is also installed on the outlet manifold of the superheater.
The following fittings are installed on the upper drum: the main steam valve or valve (for boilers without a superheater), valves for sampling steam, sampling steam for auxiliary needs. A shut-off valve with a nominal size of 50 is installed on the elbow for draining water. mm.
In the KE-25-14S boiler, periodic and continuous blowing. Shut-off valves are installed on the periodic purge lines from all lower chambers of the screens. The blower steam line is equipped with drain valves to remove condensate when the line is heated and shut-off valves for supplying steam to the blower. Instead of steam blowing, a gas pulse or shock wave generator (SHW) can be installed.
Check valves and shut-off valves are installed on the supply pipelines in front of the economizer; A power control valve is installed in front of the check valve, which is connected to the boiler automation actuator.
The KE-25-14S steam boiler provides stable operation in the range from 25 to 100% of the nominal steam output. Tests and operating experience of a large number of KE type boilers have confirmed their reliable operation at a lower pressure than the nominal pressure. With a decrease in operating pressure, the efficiency of the boiler unit does not decrease, which is confirmed by comparative thermal calculations of boilers at nominal and reduced pressure. In boiler houses intended for the production of saturated steam, boilers of the KE type are reduced to 0.7 MPa pressure provide the same performance as at pressure 1.4 MPa.
For KE type boilers, the throughput of the safety valves corresponds to the rated steam output at an absolute pressure of 1.0 MPa.
When operating at reduced pressure safety valves on the boiler and additional safety valves installed on the equipment must be adjusted to the actual operating pressure.
With a decrease in pressure in boilers to 0.7 MPa The equipment of boilers with economizers does not change, since in this case the underheating of water in feed economizers to the steam saturation temperature in the boiler is 20°C, which meets the requirements of the Gosgortekhnadzor rules.
1.1 Technical characteristics of the boiler KE-25-14S
Steam capacity D = 25 t/h.
Pressure R = 24 kgf/cm 2 .
Steam temperature t= (194÷225) ºС.
Radiation (beam-receiving) heating surface N l = 92.1 m 2 .
Convective heating surface N k = 418 m 2 .
Type of combustion device TCHZ-2700/5600.
Combustion mirror area 13.4 m 2 .
Overall dimensions of the boiler (with platforms and stairs):
length 13.6 m;
width 6.0 m;
height 6.0 m.
Boiler weight 39212 kg.
2. Calculation of fuel by air
2.1 Determination of the amount of combustion products
The calculation of the amount of combustion products is based on stoichiometric ratios and is performed with the aim of determining the amount of gases formed during the combustion of fuel of a given composition at a given excess air ratio. All calculations of the volume of air and combustion products are carried out on 1 kg fuel.
Since the task indicates the ash content of the dry mass of the fuel, we will determine the ash content of the working mass of the fuel.
A r = A s (100 - W r) / 100,
A p = 2.3∙ (100 - 7.5) /100 = 21.3%.
Conversion factor of combustible mass into working mass
(100 - W р - А р) /100 = (100 - 7.5 - 21.3) /100 = 0.71.
Operating mass of fuel components
C p = 76.9 ∙ 0.71 = 54.6%, H p = 5.4 ∙ 0.71 = 3.9%, p = 0.6 ∙ 0.71 = 0.5%,
О р = 16.0 ∙ 0.71 = 11.4%, р = 1.1 ∙ 0.71 = 0.8%.
Examination:
р + Н р + S р + О р + N р + А р + W р = 100%,
6 + 3,9 + 0,5 + 11,4 + 0,8 + 21,3 + 7,5 = 100%.
In theory required amount dry air
o = 0.089 (C p + 0.375S p) + 0.267H p - 0.033O p; o = 0.089∙ (54.6 + 0.375 ∙ 0.5) + 0.267 ∙ 3.9 - 0.033 ∙ 11.4 = 5.54 m 3 /kg.
Volume of triatomic gases
V = 0.01866 (C p + 0.375S p); = 0.01866∙ (54.6 + 0.375 ∙ 0.5) = 1.02 m 3 /kg.
Theoretical nitrogen volume
0.79V o + 0.008N p; V = 0.79 ∙ 5.54 + 0.008 ∙ 0.8 = 4.38 m 3 /kg.
Theoretical volume of water vapor
0.112Н р + 0.0124W р + 0.016V о; = 0.112 ∙ 3.9 + 0.0124 ∙ 7.5 + 0.016 ∙ 5.54 = 0.61 m 3 /kg.
Theoretical amount of humid air
o vl = V + 0.016V o; (2.8), V = 0.61 + 0.016 ∙ 5.54 = 0.70 m 3 /kg.
Excessive air volume
and = (α - 1) V o; u = 0.28 ∙ 5.54 = 1.55 m 3 /kg.
Total volume of combustion products
r = V+ V + V+ V and; g = 1.02 + 4.38 + 0.61 + 1.55 = 7.56 m 3 /kg.
Volume fraction of triatomic gases
V/V g; = 1.02/7.56 = 0.135.
Volume fraction of water vapor
V/V g; r = 0.70/7.56 = 0.093.
Total fraction of water vapor and triatomic gases
n = r+ r, n = 0.093 + 0.135 = 0.228.
The pressure in the boiler furnace is taken equal to P t = 0.1 MPa.
Partial pressure of triatomic gases
Р= 0.135 ∙ 0.1 = 0.014 MPa.
Partial pressure of water vapor
P = 0.093 ∙ 0.1 = 0.009 MPa.
Total partial pressure
P p = P + P; R p = 0.014 + 0.009 = 0.023 MPa.
2.2 Determination of enthalpy of combustion products
Flue gases formed as a result of fuel combustion act as a coolant in the working process of a steam boiler. The amount of heat given off by gases can be conveniently calculated by the change in enthalpy flue gases.
The enthalpy of flue gases at any temperature is the amount of heat spent on heating the gases obtained from the combustion of one kilogram of fuel from 0º to this temperature at constant gas pressure in the firebox.
The enthalpy of combustion products is determined in the temperature range 0…2200ºС with an interval of 100ºС. We carry out the calculations in tabular form (Table 2.1).
The initial data for the calculation are the volumes of gases that make up the combustion products, their volumetric isobaric heat capacities, excess air coefficient and gas temperature.
We take the average isobaric heat capacities of gases from reference tables.
The theoretical amount of gases is determined by the formula
I = ΣV c t=
VC+ VC + VC) t.
The theoretical enthalpy of moist air is determined by the formula
V o C cc t.
r = I + (α - 1) I.
Table 2.1 Calculation of enthalpy of combustion products
V= 1.02 m 3 /kg V= 4.38 m 3 /kg V= 0.61 m 3 /kg Io, kJ/kg Humid air (α - 1) I o vv, kJ/kg I g, kJ/kg With RO2, kJ/ (m 3 ∙K) V RO2 C RO2, kJ/ (m 3 ∙K) With N, kJ/ (m 3 ∙K) V o N C N , kJ/ (m 3 ∙K) With H2O, kJ/ (m 3 ∙K) V o H2O C H2O, kJ/ (m 3 ∙K) With vv, kJ/ (m 3 ∙K) I o centuries, kJ/kg 0 100 200 300
400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900
2000 2100 2200 1,599 1,700
1,787 1,822 1,929 1,988 2,041 2,088 2,131 2,169 2, 203 2,234 2,263 2,289
2,313 2,335 2,355 2,374 2,391 2,407 2,422 2,435 2,448 1,631 1,734
1,823 1,920 1,968 2,028 2,082 2,130 2,174 2,212 2,247 2,279 2,308 2,335 2,359
2,382 2,402 2,421 2,439 2,455 2,470 2,484 2,497 1,294 1,295
1,299 1,306 1,316 1,327 1,340 1,353 1,367 1,379 1,391 1,403 1,414 1,425 1,434
1,444 1,452 1,461 1,469 1,475 1,482 1,489 1,495 5,668 5,672
5,690 5,720 5,764 5,812 5,869 5,926 5,987 6,040 6,093 6,145 6, 193 6,242
6,281 6,325 6,360 6,399 6,434 6,461 6,491 6,522 6,548 1,494 1,505
1,522 1,542 1,566 1,589 1,614 1,641 1,668 1,695 1,722 1,750 1,776 1,802 1,828
1,852 1,876 1,899 1,921 1,942 1,962 1,982 2,000 0,911 0,918
0,928 0,941 0,955 0,969 0,985 1,001 1,017 1,034 1,050 1,068 1,083 1,099 1,115
1,130 1,144 1,158 1,182 1,185 1, 197 1, 209 1,220 0 832 1688 2574
3475 4405 5362 6340 7342 8357 9390 10441 11501 12579 13657 14756 15850 16963
18081 19192 20316 21452 22583 1,318 1,324
1,331 1,342 1,354 1,368 1,382 1,397 1,414 1,424 1,437 1,449 1,461 1,472 1,483
1,492 1,501 1,510 1,517 1,525 1,532 1,539 1,546 0 733 1475 2230
3000 3789 4594 5418 6267 7100 7961 8830 9713 10601 11502 12399 13305 14221
15128 16052 16975 17905 18843 0 205 413 624
840 1061 1286 1517 1755 1988 2229 2472 2720 2968 3221 3472 3725 3982 4236
4495 4753 5013 5276 The theoretical enthalpy of moist air is determined by the formula I = V o C inc t.
The enthalpy of gases is determined by the formula r = I + (α - 1) I. Based on the calculation results (Table 2.1), we construct a diagram of the dependence of the enthalpy of gases I 1 from their temperature t(Fig. 2.1). Fig. 2.1 - Diagram of the dependence of the enthalpy of gases on their temperature When a steam boiler operates, all the heat entering it is spent on generating useful heat contained in the steam and covering various heat losses. The total amount of heat entering the boiler is called available heat. There must be equality (balance) between the heat entering the boiler and leaving it. The heat leaving the boiler is the sum of useful heat and heat losses associated with the technological process of generating steam of specified parameters. The heat balance of the boiler is compiled in relation to one kilogram of fuel under steady-state (stationary) boiler operation. The lower calorific value of the working mass of fuel is determined using the Mendeleev formula: n r = 339C r + 1030H r - 109 (O r - S r) - 25W r, n r = 339 ∙ 54.6 + 1030 ∙ 3.9 - 109 ∙ (11.4 - 0.5) - 25 ∙ 7.5 = 21151 kJ/kg.
Boiler efficiency (accepted according to the prototype) Heat loss: from chemical incomplete combustion (p.15) 3 = (0.5÷1.5) = 0.5%; from mechanical underburning (Table 4.4) 4 = 0.5%; V environment(, Fig. 4.2) 5 = 0.5%; with flue gases 2 = 100 - (η" + q 3 + q 4 + q 5), 2 = 100 - (92 + 0.5 + 0.5 + 0.5) = 6.5%. Average isobaric volumetric heat capacities of moist air cold, at a temperature t v1 (Table 1.4.5) With b1 = 1.32 kJ/kg; heated, at a temperature t v2 (Table 1.4.5) With b1 = 1.33 kJ/kg. The amount of heat introduced into the furnace with air: cold xv = 1.016αV o With in 1 t b1, xb = 1.016 ∙ 1.28 ∙ 5.54 ∙ 1.32 ∙ 25 = 238 kJ/kg;
warmed up gv = 1.016αV o With at 2 t v2, gv = 1.016 ∙ 1.28 ∙ 5.54 ∙ 1.33 ∙ 180 = 1725 kJ/kg.
The amount of heat transferred in the air heater vn = I gv - I hv, vn = 1725 - 238 = 1487 kJ/kg.
We take the temperature of the fuel entering the furnace equal to t tl = 30°C. Heat capacity of dry mass of fuel (Table 4.1) s s tl = 0.972 kJ/ (kg deg). Heat capacity of the working fuel mass c p tl = c c tl (100 - W p) /100 + cW p /100, Where With- heat capacity of water, With= 4,19 kJ/ (kg deg), s р tl = 0.972 · (100 - 7.5) /100 + 4.19 · 7.5/100 = 1.21 kJ/ (kg deg). Heat introduced into the furnace with fuel tl = c p tl t tl, i tl = 1.21 30 = 36 kJ/kg.
Available heat of fuel Q + Q int + i tl, = 21151 + 1487 + 36 = 22674 kJ/kg.
Flue gas enthalpy "ух = q 2 Q р р / (100 - q 4) + I хв," ух = 6.5 ∙ 22674/ (100 - 4.5) + 238 = 1719 kJ/kg.
Flue gas temperature (Table 1) t"uh = 164°C. We accept the degree of dryness of the resulting steam (p. 17) X =
(0,95…0,98) = 0,95.
Enthalpy of dry saturated steam (according to water vapor tables) at a given pressure i" =
2792 kJ/kg. Latent heat of vaporization r = 1948 kJ/kg. Enthalpy of wet steam i x = i" - (1 - x) r, i x= 2792 - (1 - 0.95) 1948 = 2695 kJ/
kg.
Enthalpy of feedwater before the economizer (at t at 2) i pv = 377 kJ/kg. Secondary fuel consumption B p = The purpose of the verification calculation of heat transfer in the firebox is to determine the temperature of the gases behind the firebox and the amount of heat transferred by the gases to the heating surface of the firebox. This heat can only be found with known geometric dimensions of the firebox: the size of the beam-receiving surface, N l, the full surface of the walls delimiting the combustion volume, F st, the volume of the combustion chamber, V T. Fig.3.1 - Sketch of the KE-25-14S steam boiler The beam-receiving surface of the firebox is found as the sum of the beam-receiving surfaces of the screens, i.e. Where N le - surface of the left side screen, N pe - surface of the right side screen; N z - surface of the rear screen; N le = N pe = L t l bae X bae; N ze = V ze l ze X bae; t - length of the firebox; l bе is the length of the side screen tubes; IN ze - width of the rear screen; X bе - angular coefficient of the side screen; l ze is the length of the rear screen tubes; X ze is the angular coefficient of the rear screen. Due to the difficulty of determining the lengths of the tubes, we take the size of the radiation-receiving heating surface from the technical characteristics of the boiler: N l = 92.1 m 2 . Full surface of the furnace walls, F st, is calculated from the dimensions of the surfaces limiting the volume of the combustion chamber. We reduce surfaces of complex configuration to an equal-sized simple geometric figure. Furnace wall surface area: boiler front fr = 2.75 ∙ 4.93 = 13.6 m 2 ;
back wall of the firebox zs = 2.75 ∙ 4.93 = 13.6 m 2 ;
firebox side wall bs = 4.80 ∙ 4.93 = 23.7 m 2 ;
under the firebox under = 2.75 ∙ 4.80 = 13.2 m 2 ;
firebox ceiling sweat = 2.75 ∙ 4.80 = 13.2 m 2 .
The full surface of the walls delimiting the combustion volume st = F fr + F zs + 2F bs + F under + F sweat, st = 13.6 + 13.6 + 2 ∙ 23.7 + 13.2 + 13.2 = 101.0 m 2 .
Combustion volume: t = 2.75 ∙ 4.80 ∙ 4.93 = 65.1 m 3 .
Furnace shielding degree Ψ = N l / F st, Ψ = 92.1/101.0 = 0.91. Heat retention coefficient φ = 1 - q 5 /100, φ = 1 - 0.5/100 = 1.00. Effective thickness of the radiating layer 3.6V t /F st, = 3.6 65.1/101.0 = 2.32 m.
Adiabatic (theoretical) enthalpy of combustion products a = Q (100 - q 3 - q 4) / (100 - q 4) + I gv - Q vn, a = 22674 (100 - 0.5 - 0.5) / (100 - 0.5) + 1725 - 1487 = 22798 kJ/kg.
Adiabatic (theoretical) temperature of gases (Table 1) T a = 1835°C = 2108 TO. We take the temperature of the gases at the outlet of the furnace T" t = 800°C = 1073 TO. Enthalpy of gases at the exit from the furnace (Table 1) at this temperature" t = 9097 kJ/kg. Average total heat capacity of combustion products (V g C av) = (I a - I "t) / ( t a- t" T), (V g C avg) = (22798 - 9097) / (1835 - 800) = 13.24 kJ/ (kg deg).
Conditional coefficient (Table 5.1) of heating surface contamination during layer combustion of fuel Thermal stress of the combustion volume v = BQ/V t, v = 0.77 22674/65.1 = 268 kW/m 3 .
Thermal efficiency coefficient Ψ e = 0.91 · 0.60 = 0.55. Coefficient of attenuation of rays by soot particles s = 0.3 (2 - α) (1.6T t /1000 - 0.5) C r /H r, s = 0.3 (2 - 1.28) (1.6 1073/1000 - 0.5) 54.6/3.9 = 3.68 ( m MPa) - 1 .
Part of the fuel ash carried away from the furnace into the convective flues (Table 5.2) Flue gas mass g = 1 - A p /100 + 1.306αV o, g = 1 - 21.3/100 + 1.306 1.28 5.54 = 10.0 kg/kg.
The coefficient of attenuation of rays by suspended particles of fly ash (Fig. 5.3) at accepted temperature t T k zł = 7.5 ( m ata) - 1 . Coefficient of attenuation of rays by particles of burning coke (p.29) k k = 0.5 ( m ata) - 1 . Concentration of ash particles in the gas stream μ zl = 0.01 A r a u n /G g, μ zl = 0.01 · 21.3 · 0.1/10.0 = 0.002. Coefficient of attenuation of rays by the combustion medium k t = 5.39 + 7.5 0.002 + 0.5 = 5.91 ( m ata)
- 1 .
Effective flame blackness and f = 1 - e -k tPtS, a f = 1 - 2.7 -5.91·0.1·2.32 = 0.74. The ratio of the combustion mirror to the total surface of the furnace walls during layer combustion ρ = F under /F st, ρ = 13.2/101.0 = 0.13. The degree of blackness of the furnace during layer combustion of fuel a t = a t = The value of the relative position of the maximum temperature for layered furnaces when burning fuel in thin layer(furnaces with pneumomechanical spreaders) is taken (p. 30) equal to: Parameter characterizing the temperature distribution along the height of the firebox (f.5.25) M = 0.59 - 0.5X t, M = 0.59 - 0.5 0.1 = 0.54. Estimated temperature of gases behind the furnace T t = T t = The discrepancy with the previously accepted value is ∆t t = t T - t" T, ∆t t = 817 - 800 = 17°C< ± 100°C.
Enthalpy of gases behind the furnace t = 9259 kJ/kg. The amount of heat transferred in the firebox t = φВ (I a - I t), t = 1.00 0.77 (22798 - 9259) = 10425 kW.
Direct return coefficient μ = (1 - I t /I a) 100, μ = (1 - 9259/22798) ·100 = 59.4%. Actual thermal stress of the combustion volume v = Q t /V t, q v = 10425/65.1 = 160 kW/m 3 .
Thermal calculation of the convective surface serves to determine the amount of heat transferred and comes down to solving a system of two equations - the equation heat balance and heat transfer equations. The calculation is performed for 1 kg burning fuel under normal conditions. From previous calculations we have: gas temperature in front of the gas duct in question t 1 = t t = 817°C; enthalpy of gases in front of the flue 1 = I t = 9259 kJ/kg; heat retention coefficient second fuel consumption B p = 0.77 kg/s. We first accept two values for the temperature of combustion products after the flue: t" 2 = 220ºC, t"" 2 = 240ºC. We carry out further calculations for two accepted temperatures. Enthalpy of combustion products after the convective beam: "2 = 2320 kJ/kg,"" 2 = 2540 kJ/kg. The amount of heat given off by gases in the beam: 1 = φВ р (I t - I 1); " 1 = 1.00 ∙ 0.77 (9259 - 2320) = 5343 kJ/kg,"" 1 = 1.00 · 0.77∙ (9259 - 2540) = 5174 kJ/kg.
Outer diameter of convective bundle pipes (according to drawing) d n = 51 mm. The number of rows along the flow of combustion products (according to the drawing) 1 = 35. Transverse pipe pitch (according to drawing) 1 = 90 mm. Longitudinal pitch of pipes (according to drawing) 2 = 110 mm. Pipe washing coefficient (Table 6.2) Relative transverse σ 1 and longitudinal σ 2 pipe pitches: σ 1 = 90/51 = 1.8; σ 2 = 110/51 = 2.2. Clear cross-sectional area for the passage of gases during cross-flushing of pipes f = ab- z 1 l d n, Where A And b- dimensions of the flue in the clear, m; l- length of the projection of the pipe onto the plane of the section under consideration, m; w = 2.5 ∙ 2.0 - 35 ∙ 2.0 ∙ 0.051 = 1.43 m 2 .
Effective thickness of the radiating layer of gases S eff = 0.9d n, eff = 0.9 0.051 Boiling point of water at operating pressure (according to tables of saturated water vapor) t" s = 198°C. Average gas flow temperature av1 = 0.5 ( t 1 + t); t" av1 = 0.5 (817 + 220) = 519ºC, t"" av1 = 0.5· (817 + 240) = 529ºC. Average gas consumption V"" cp1 = 0.77 7.56 (529 + 273) /273 = 17.10 m 3 /With.
Average gas speed ω g1 = V cp1 /F w, ω" g1 = 16.89/1.43 = 11.8 m/s, ω"" g1 = 17.10/1.43 = 12.0 m/s.
Heating surface contamination coefficient (p.43) ε = 0.0043 m 2 hail/Tue Average temperature of the contaminated wall (p.42) z = t" s + (60÷80), t h = (258÷278) = 270°C. Correction factors for determining the heat transfer coefficient by convection (Fig. 6.2): by the number of rows into relative steps to change physical characteristics Viscosity of combustion products (Table 6.1) ν" = 76·10 -6 m 2 /With, ν"" = 78·10 -6 m 2 /With.
Thermal conductivity coefficient of combustion products (Table 6.1) λ" = 6.72·10 -2 W/ (m°C), λ"" = 6.81·10 -2 W/ (m°C). Prandtl criterion for combustion products (f.6.7) Pr" = 0.62, Pr"" = 0.62. Heat transfer coefficient by convection (Table 6.1) α k1 = 0.233С z C f λР (ωd n /ν) 0.65 /d n, α" k1 = 0.233 1 1.05 6.72 10 -2 0.62 0.33 (11.8 0.051/76 10 -6) 0.65 /0.051.α" k1 = 94.18 W/ (m 2 · TO); α"" k1 = 0.233 1 1.05 6.81 10 -2 0.62 0.33 (12.0 0.051/78 10 -6) 0.65 /0.051,α"" k1 = 94.87 W/ (m 2 · TO).
Coefficient of attenuation of rays by triatomic gases 1, 1, Total partial pressure of triatomic gases (previously defined) R p = 0.023 MPa. Beam attenuation coefficient in a volume filled with ash at temperature t cf (Fig. 5.3) K"" zl = 9.0. Concentration of ash particles in the gas stream (previously determined) μ zl = 0.002. Blackness degree of dust-laden gas flow a = 1 - e-kgkzlRp μ zlSef, a" = 1 - e-23.30 9.0 0.002 0.023 0.177 = 0.002,a"" = 1 - e-23.18 9.0 0.002 0.023 0.177 = 0.002. Radiation heat transfer coefficient when burning coal a l = 5.67·10 -8 (a st + 1) aT 3 Where A st - degree of blackness of the wall, accepted (p.42) a st = 0.82; According to the accepted two temperature values t" 1 = 220ºC; t"" 1 = 240ºC and the obtained values " b1 = 5343 kJ/kg;"" b1 = 5174 kJ/kg;" k1 = 4649 kJ/kg;"" k1 = 5587 kJ/kg
We perform graphical interpolation to determine the temperature of combustion products after the convective heating surface. For graphical interpolation, we build a graph (Fig. 3.2) of the dependence Q = f (t). Fig.3.2 - Graph of dependence Q = f (t)
The point of intersection of the lines will indicate the temperature t p of gases escaping after the convective surface: t k = 232ºС. The amount of heat absorbed by the heating surface k1 = 5210 kW. Enthalpy of gases at this temperature I k1 = 2452 kJ/kg. Enthalpy of feedwater at the economizer inlet i xv = 377 kJ/kg. Enthalpy of feedwater leaving the economizer i gv = 719 kJ/kg. Heat retention coefficient (found earlier) The amount of heat given off by the flue gases in the economizer ek = D ( i gv - i xv); Q eq = 6.94∙ (719 - 377) = 2373 kJ.
Enthalpy of exhaust gases behind the economizer х = I к - Q eq /В р, ух = 2452 - 2373/0.77 = 103 kJ/kg.
Flue gas temperature behind the economizer tх = 10ºС. After performing a thermal calculation, the final heat balance is established, the purpose of which is to determine the achieved steam production at a given fuel consumption and the efficiency of the boiler. Available heat Q = 22674 kJ/m 3 .
Fuel consumption B = 0.77 kg/s. The amount of heat transferred in the firebox pt = 10425 kW. The amount of heat transferred in the vapor-forming convective beam k = 5210 kW. Amount of heat transferred in the economizer eq = 2373 kW. The total amount of heat transferred to the water in the boiler 1 = Q pt + Q k + Q eq, 1 = 10425 + 5210 + 2373 = 18008 kW.
Feed water enthalpy i p.v = 377 kJ/kg. Enthalpy of wet steam i x
= 2695 kJ/kg. Full (maximum) steam output of the boiler Q 1 / ( i X - i item c); = 18008/ (2695 - 377) = 7.77 kg/s.
Boiler efficiency η = 100∙Q 1 / (V p Q); η = 100 18008/ (0.77 22674) = 100%. Balance discrepancy: in thermal units ΔQ = QηB p - Q 1 (100 - q 4) /100; ΔQ = 22673 1.00 0.77 - 18008 (100 - 0.5) /100 = 65 kJ;
in percentages δQ = 100∆Q/Q, δQ = 100 65/22674 = 0.29%< 0,5%.
1. Tomsky G.I. Thermal calculation of a stationary boiler. Murmansk. 2009. - 51 p. 2. Tomsky G.I. Fuel for stationary steam and hot water boilers. Murmansk. 2007. - 55 p. Esterkin R.I. Boiler installations. Coursework and diploma design. L.: Energoatomizdat. 1989. - 280 p. Esterkin R.I. Industrial boiler installations. L.: Energoatomizdat. 1985. - 400 p.
3. Verification thermal calculation
3.1 Preliminary heat balance
= 0,77 kg/s.3.2 Calculation of heat transfer in the furnace
,
∙0,228 = 5,39 (m MPa) - 1 .
,
= 0,86.
,
= 1090 TO= 817°C.
3.3 Calculation of heat transfer in a convective surface
= 0,177 m.
,
·0.228 = 23.30 ( m MPa) -
·0.228 = 23.18 ( m MPa) -
/2,
kJ/kg ;"" k = 62.46 · 418 · 214/1000 = 5587 kJ/kg.
3.4 Economizer calculation
4. Final heat balance
Bibliography
Saturated or superheated steam for the technological needs of enterprises. Boilers are available in three types:
E(KE) with productivity 2.5; 4; 6.5; 10 and 25 t/h with layer combustion devices;
E(DE) with productivity 4; 6.5; 10; 16 and 25 t/h with oil-gas burners;
DKVR with productivity 2.5; 4; 6.5 and 10 t/h with gas-oil furnaces.
Steam boilers type E(KE) with layer combustion devices.
Steam boilers of type E (KE) have the following versions: E-2.5-1.4R (KE-2.5-14S); E-4-1.4R (KE-4-14S); E-6.5-1.4R (KE-6.5-14S); E-10-1.4R (KE-10-14S).
The main elements of type E(KE) boilers (Fig. 73) are upper and lower drums with an internal diameter of 1000 mm, left and right side screens and a convective beam made of pipes
0 51 X 2.5 mm. In addition, the boiler is equipped with equipment, the list of which is given in table. 46 (for all types of boilers, blower fan VDN-9).
Boilers of type E (KE) (Table 47) are supplied to consumers in assembled blocks, with a frame, without lining or cladding.
Steam boiler type E-25-1.4R (KE-25S) with a layer combustion device. The boiler (Fig. 74) consists of two drums (upper and lower), having an internal diameter of 1000 mm and a wall thickness of 13 mm.
The combustion chamber of the boiler, 2710 mm wide, is completely shielded with pipes 0 51 X 2.5 mm (screening degree 0.8).
To burn hard and brown coals, a mechanical firebox ТЧЗМ-2.7/5.6 is placed under the boiler, which consists of a scaly chain grate reverse and two pneumomechanical spreaders with a plate feeder ZP-600. Active area of the combustion mirror
Rice. 73. Steam boiler E-2.5-1.4R: / - grate; 2 - side screen; 3 - upper drum; “/ - feed water supply pipeline; 5 - boiling pipes; 6 - lower drum; 7 - service area; 8 - lining; 9 - firebox
Rice. 74. Steam boiler E-25-1.4R:
/ - chain grille; 2 - fuel feeder; 3 - side screen; 4 - rear screen; 5 - upper drum; 6 - feed water supply pipe; 7 - lower drum; 8 - air heater; 9 - bypass pipes; 10 - service area
The tail surfaces consist of a single-pass air heater VP-228 with a heating surface of 228 m2, which provides air heating to approximately 145 °C and a cast iron economizer EP1-646 with a heating surface of 646 m installed after it along the gas flow.
The boiler kit includes a VDN-12.5 fan with a 55 kW (1000 min-1) electric motor, a DN-15 smoke exhauster with a 75 kW (1000 min-1) electric motor, and a BTs-2 X 6 X 7 ash collector for flue gas purification .
Convective superheater Volume, m3 water steam
Efficiency when burning coal, %
Coal consumption, kg/h
TOC o "1-5" h z stone 3080
Brown 5492
Overall dimensions (with platforms 12 640 X 5628 X 7660 and stairs), mm
Weight, kg 37,372
* Boilers of type E-25R are also available with an absolute steam pressure of 2.4 MPa (24 kgf/cmg). In boilers with superheaters. the temperature of the superheated steam is 250°C. In necessary and technically justified cases, it is allowed to manufacture boilers with a steam temperature of 350 °C.
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47. Technical characteristics of boilers E(KE)
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(DE-4-I4IM) |
(DE-6.5-14GM* |
E-І0-1.4GM (DE-10-14 GM) |
(DE-I6-14GM) |
E-25-1.4GM* (DE-25-14GM) |
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Radiation |
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Convective |
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Superheater |
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Boiler water volume, m3 |
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Drum inner diameter |
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Estimated efficiency. % |
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On fuel oil |
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Consumption, kg/h |
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Gaza (8620 kcal/m) |
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Fuel oil (9260 kcal/kg) Overall dimensions, mm |
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Weight, kg |
Steam gas-oil boilers type E(DE). Gas-oil boilers of type E(DE) (Table 48), depending on steam output, are produced in the following options: E-4-1.4GM (DE-4.0-14GM);
E-6.5-1.4GM (DE-6.5-14GM); E-10-1.4GM (DE-10-14GM); E-16-1.4GM (DE-16-14GM); E-25-1.4GM (DE-25-14GM).
The main components of the listed boilers (Fig. 75) are the upper and lower drums, the convective beam, the front, side and rear screens that form the combustion chamber.
Boilers with steam capacity 4; 6.5 and 10 t/h are made with a single-stage evaporation scheme. In boilers with a capacity of 16 and 25 t/h, two-stage evaporation is used.
The boilers are supplied in two blocks, including upper and lower drums with internal drum devices, a pipe system of screens and a convection beam (if necessary, a superheater), a support frame and a piping frame.
Type E (DE) boilers are equipped with additional equipment (Table 49).
Steam gas and oil boiler type E-25-2.4GM. Designed to generate superheated steam with a working pressure of 2.4 MPa (24 kgf/cm2) and a temperature of 380°C, used for drive steam turbines and for the technological needs of the enterprise.
The E-25-2.4GM (DE-25-24-380GM) boiler is a two-drum vertical water-tube unit equipped with a fully shielded firebox.
The combustion chamber screens are made of pipes 0 51 X 2.5 mm. The boiler is equipped with a cast iron economizer made from VTI pipes type EP-1 from to
heating surface 808 m2, VGDN-19 smoke exhauster with 4A31556UZ electric motor and VDN-11.2 fan with 4A200M6 electric motor.
A GMP-16 burner with a two-stage fuel combustion chamber was used as a burner device. The burner device consists of a GM-7 gas-oil burner and a combustion chamber lined with refractory bricks with a ring air guide device in its middle part.
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Technical characteristics of the boiler E-25-2.4GM
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Steam boilers DKVR-2.5; DKVr-4; DKVR-6.5 and DKVR-10 with gas-oil furnaces. Designed to produce saturated or slightly superheated steam used for the technological needs of enterprises, heating, ventilation and hot water supply systems.
Currently, serial production of DKVR type boilers has been discontinued, however, a significant number of these boilers are used at canning enterprises (Tables 50, 51).
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Indicators |
DKVR - 6.5-14 GM |
DKVr - 10-14 GM |
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Steam capacity, |
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Steam pressure, MPa |
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(kgf/cm') |
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Saturation temperature/ |
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Superheated steam, C |
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Nutrient temperature |
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Heating surface area, m2 |
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Radiation |
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Convective |
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Superheater |
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Boiler volume, m’ |
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G.V. Maslovsky, manager-consultant,
CJSC "Energomash (Belgorod)", Belgorod
Today, some enterprises prefer to use steam boilers with a unit capacity of up to 25 t/h inclusive, where previously it was planned to place boilers with 35 or 50 t/h with the same total installed capacity. At the same time, as calculations show, installation costs are sharply reduced (almost 3 times) at practically the same or even lower total cost of boiler equipment, and the efficiency of managing the available power is also improved.
Description and features basic design boiler
In 1995, a fundamentally new basic model of the transportable boiler block of the gas-oil boiler BEM-25/1.4-225GM was created (Fig. 1, 2). The boiler was designed for use as a starting boiler for the North-Western Thermal Power Plant in St. Petersburg. This is a water-tube, natural circulation, two-drum boiler with horizontal flame development in a fully shielded firebox and a convective gas duct adjacent to the firebox, where boiler (evaporation) bundles and (if steam superheating is necessary) a steam superheater are located.
What is new in this design is, first of all, a closer approximation of the external outlines of the cross-section of the main boiler block (BBC) to the standard main transportable dimensions railway due to the cross-sectional configuration, which allows the center of the upper drum of the block to be placed during transportation (Fig. 3) in the area of the bisector of one of the upper obtuse angles of this dimension, and the lower drum - in the area of the opposite lower right angle.
Structurally, this leads to the fact that the vertical axis, which in working condition connects the upper and lower drums, acquires an inclined position during transportation at an angle of more than 15 ° to the vertical. As a result, sections of pipes that are horizontal during transportation, for example, the side screens of a furnace in working condition, are located in space at fairly steep angles, which ensures their reliable operation, because conditions for the stratification of the steam-water mixture during operation of these pipes as evaporation pipes are excluded.
Another important difference is that the combustion chamber is made with all walls enclosed from all-welded screens, which are closed not to drums, but to lower and upper collectors, in turn connected by short pipes to the corresponding drums. Such solutions have a number of advantages both from the point of view of manufacturing and operation. An autonomous (structural) firebox can be manufactured separately in a parallel section of the workshop, which expands the scope of work. The absence of drum sections heated by flue gases increases the reliability of the boiler. Complete gas tightness reduces suction, therefore, the efficiency of the boiler increases and the prerequisites are created for more stringent control over maintaining the optimal excess air ratio throughout the gas path of the boiler, which, in turn, affects both the efficiency and the formation of harmful emissions. It is also possible to operate the boiler under pressure.
As noted above, all sections of pipes shielding the firebox are located in space at an angle of at least 15 O, therefore there is no massive brickwork on the firebox floor, which is typical for other boilers of this type. This not only saves fireclay bricks, but also creates conditions for more intensive cooling of the torch, because 20% of the heating surface of the firebox is not excluded from heat exchange. In turn, in the new block, the structural surface of the beam-receiving walls of the firebox is more than 30% higher than that of similar boilers, also due to the fact that the drums are completely removed from the firebox, which also has a beneficial effect on the combustion process and heat perception in the firebox. Thanks to the wider firebox, the likelihood of fuel oil particles depositing on its side walls has been reduced.
The main design solutions of the basic boiler model are protected by patents of the Russian Federation (“Boiler” RU 2096680, “Space stand” RU 2132511).
Boilers of this type do not provide for the installation of an air heater in order to avoid excessive formation of NO x when burning natural gas, therefore, when burning fuel oil, it is recommended to equip the boiler with a small air heater, which would ensure heating of the air to 60^100 O C.
It is assumed that there are specific designs of standard sizes depending on the steam parameters, combustion of one or two types of fuel, open or closed boiler layout, the selected type of economizer and its geographical location in relation to the main boiler block.
The horizontal convective flue has a common (separating) side inner wall with the firebox - an all-welded tubular evaporation screen. This gas duct contains evaporative boiler bundles closed to drums and (if necessary) a steam superheater. In the case when the nominal heating of steam is about 30 ° C, the outer side wall is used as a superheater - a tubular all-welded screen, which in this case is made in such a way as to ensure a minimum temperature spread in the pipes of this screen along the depth of the gas duct. If higher steam superheating is required (up to 440 °C), the superheater is made in the form of a convective surface of one or two packages. The coils are located in horizontal planes to ensure complete drainage of the superheater. The outer side wall serves as an evaporative heating surface. The same solution regarding the side wall applies to boilers designed to produce saturated steam only.
At intermediate values of the required steam superheat (up to 310 ° C), the superheater is made in the form of drained convective screens.
The steam temperature is controlled by bypassing part of the gas flow above or below the superheater package through a special channel, at the outlet of which a special rotary gate is located. The gate and dividing partition between this channel and the superheater are made of high-alloy steel. The collectors located in the gas duct are protected from the direct thermal effects of the gas flow by insulation, closed from the outside by a dense metal casing, also made of high-alloy steel. One gas-oil burner of appropriate thermal power is installed at the front of the boiler in the center of the end screen.
Combustion products, due to the absence of massive lining in the firebox, due to moderate thermal stresses in the cross-section and volume of the firebox, which has a sufficient length for the horizontal development of the flame, approach the festoon cooled to a temperature of about 1000-1100 ° C, unfold in the festoon, which ends the dividing wall, and enter into the convective flue. The festoon is given a special aerodynamic shape, characteristic of the guide vane apparatus, and the pipes in the first boiler bundle are arranged in such a way that the velocity and temperature fields in the cross section of the gas duct in front of the superheater are brought to the most uniform state. This should minimize the presence of temperature sweeps in the superheater outlet package, increasing its service life.
The service life of the superheater also largely depends on the quality of the steam. Structurally, in the boilers under consideration, the tension of the evaporation mirror in the upper drum is low, however, a special intra-drum device is installed there. Depending on the pressure in the boiler, this device is made differently, but the common thing is that everywhere there are two stages of evaporation, and the rear part of the furnace, the festoon and the initial section of the convective flue adjacent to the rarefied convective beam are allocated to the salt compartment. Steam from the salt compartment enters the clean compartment of the upper drum; after mixing with the steam of the clean compartment, it enters the horizontal saturated steam collector. Next, the steam is directed, depending on the specific modification, to the superheater or directly to the outlet manifold.
With a wall-mounted superheater, steam enters the upper inlet manifold of the superheater. From this collector, steam flows through parallel pipes into the lower outlet collector of the superheater. The total flow area of the pipes of the wall-mounted superheater, located in the hotter gas zone, is significantly higher compared to the rest. This achieves a more uniform steam superheat temperature throughout the entire side wall of the convective flue. From the end of the lower collector, steam enters the superheated steam collector, which is installed by the operating organization in a place convenient for maintenance.
In the presence of a convective superheater, from a horizontal saturated steam collector (SSC), steam initially enters the superheater inlet manifold, located in a plane perpendicular to the SSC axis. After passing through the coils, the steam ultimately enters the outlet manifold, from which it is directed to the superheated steam manifold located outside the boiler.
Behind the superheater there are boiler bundles (one or more), where the gases at rated load are cooled to a temperature of 300^400 °C (depending on modification).
Gases after the OBC are sent to a separate, non-switchable economizer, installed in a place convenient for maintenance. The economizer can be made of steel finned pipes or cast iron, also finned, of the VTI design. For boilers with a capacity of 16 t/h or less, designed to operate
only on gas fuel, there is a boiler version with an economizer located within a transportable OBK.
Cast iron economizers are used when burning fuel oil in a boiler and when the steam pressure at the boiler outlet does not exceed 24 kgf/cm2. In other cases, a steel economizer is used, but when burning fuel oil, the step between the fins is 1.5 times greater than when the boiler operates exclusively on gas. The economizer can also be made from smooth pipes with their corridor arrangement in the lower gas duct.
The boiler, in which fuel oil is burned, is equipped with a stationary gas-pulse cleaning system, which includes compact combustion chambers, a connecting fuel line, fittings and automation. For cleaning heating surfaces as alternative option a shock wave generator can also be used.
In order to confirm the above, we present excerpts from reviews of the operating experience of BEM series boilers by several organizations.
A.V. Batselev, Chief Engineer, JSC "Mozyr Oil Refinery", Mozyr, Gomel region, Republic of Belarus.
At Mozyr Refinery OJSC, the BEM-25/4.0-380GM boiler has been in commercial operation since the beginning of 1999. The boiler operates on fuel gas (at many refineries this gas is burned on a candle, which leads not only to economic losses, but and causes irreparable environmental damage - author's note). Regulating the temperature of superheated steam with a gas valve, by bypassing part of the gases through a parallel gas duct, is usually used when lighting the boiler. Using a damper allows you to regulate the steam temperature within 7-9% (30-35 O C). We note the ease of maintenance of the boiler, a wide range of load control, reliability and environmental performance within acceptable standards. Specifications for this type of fuel are confirmed.
S.L. Kryachek, chief engineer of the plant, Angarsk Petrochemical Company OJSC, Angarsk, Irkutsk region.
At the Angarsk Petrochemical Company OJSC, the BEM-25/1.6-270GM steam boiler has been operating since 2002. The fuel used is gas of variable composition, produced at the plant’s installations with a calorific value of 5000-11000 kcal/m 3 (hydrogen content in the fuel gas is up to 70 %).
During the period of operation, this boiler has proven itself positively. Despite significant fluctuations in the composition of the fuel gas, the boiler stably provides the design productivity of 25 t/h (the maximum boiler productivity reached 27 t/h) and the temperature of superheated steam. No repair work was carried out on the evaporating surfaces during the period of operation.
P.T. Zayats, chief power engineer, VOJSC "Khimprom", Volgograd.
VOAO Khimprom operates two BEM-25/4.0-380GM steam boilers (one since August 1, 2001; the second since August 9, 2002) using natural gas.
During operation, they showed high economic efficiency and payback (on average about a year). The steam production process is easily controlled due to the use of a special program embedded in the automatic control system, which reliably and safely starts and regulates technological process steam production, selects the most economical mode for steam production and natural gas consumption.
Boilers of this type are dynamic in operation, maintain stable parameters, and are not susceptible to random technological disturbances. Maintenance boiler is easily accessible.
A.I.Sinyakov, chief power engineer, Berezniki Soda Plant OJSC, Berezniki, Perm region.
Three BEM 25/1.6-310G boilers, in operation since September 2003, have proven themselves with best side. The actual thermal performance and efficiency of the boilers are higher than the rated ones, low specific fuel consumption for the supplied thermal energy.
The only circumstance that prevented the commissioning of boilers was elevated temperature superheated steam (up to 400 ° C), which could not be reduced during the process of adjustment and adjustment work without reducing the steam output of the boilers. We purchased and installed steam coolers, which allowed us to regulate the steam temperature in the required range.
V.G. Ivanova, chief engineer, N.G. Borovskoy, Head of Thermal Power Plant, Rzhevsky Sugar Plant OJSC, p. Rzhevka, Shebekinsky district, Belgorod region.
At the thermal power plant of OJSC Rzhevsky Sakharnik, the BEM-25/2.4-380GM boiler has been operating for more than 7 years. After spending comparative analysis steam boilers DE-25/2.4-380GM and BEM-25/2.4-380GM, received the following data.
1. Boiler DE-25/2.4-380GM:
■ when maximum load does not produce the calculated amount of steam - instead of 25 t/h, the steam output is 17-18 t/h;
■ does not have an emergency discharge of water from the upper drum when the level rises;
■ less gas-tight boiler and water economizer;
■ the boiler furnace does not have safety explosion valves for safer operation of the boiler and operating personnel.
2. Boiler BEM-25/2.4-380GM:
■ has a smaller water economizer;
■ easier adjustment of the temperature of superheated steam using a gate on the bypass gas duct;
■ has two explosion valves in the boiler furnace;
■ has a gas-tight boiler and water economizer; during operation, the amount of combustion air supplied is significantly reduced, and therefore energy is saved on the fan and smoke exhauster;
■ at maximum load it can produce up to 30 t/h (steam).
