Calculation of aspiration and gas purification systems. Aspiration units: recommendations for selection and installation Calculate the hour of day of aspiration operation
To calculate the aspiration installation, it is necessary to know the location of the aspirated equipment, fans, dust collectors and the location of the air duct route.
From the drawings general view installation, we draw up an axonometric diagram of the network without scale and enter all the data for the calculation on this diagram. We divide the network into sections and determine the main highway and side parallel sections of the network.
The main highway consists of 7 sections: AB-BV-VG-GD-DE-EZH-ZZ; and has 4 lateral ones: aB, bV, vg, dg and gG.
The calculation results are summarized in table A.1 (Appendix 1).
Section AB
The section consists of a confusor, a straight vertical section 3800 mm long, 30° bend, straight horizontal section 2590 mm long.
The air speed in section AB is assumed to be 12 m/s.
Consumption - 240 m3/h.
We accept standard diameter D=80 mm. The cross-sectional area of the air duct of the selected diameter is 0.005 m2. We specify the speed using the formula:
where S is the cross-sectional area of the air duct, m2.
Pressure loss along the length of the air duct is determined by the formula:
where R is the pressure loss per meter of duct length, Pa/m.
Estimated length of the section, m.
Using the diameter D and speed v, using the nomogram, we find the pressure loss per meter of air duct length and dynamic pressure: R=31.4 Pa/m, Нд=107.8 Pa
We determine the dimensions of the confuser inlet opening based on the area of the inlet opening using the formula:
Where vin is the speed at the entrance to the confuser; for flour milling dust we will take 0.8 m/s.
The length of the confuser (suction pipe) is found using the formula:
where b is the largest size of the confuser on the suction machine,
d-duct diameter,
b - angle of narrowing of the confuser.
The resistance coefficient of the confuser is determined from table. 8 depending on lk/D>1 ib=30o-tk=0.11.
We find the radius of the outlet using the formula:
where n is the ratio of the bend radius to the diameter, we take 2;
D-diameter of the duct.
Ro=2·80=160 mm
The length of the bend is calculated using the formula:
Branch length at 30°:
Estimated length of section AB:
LAB=lk+l3o+Ulpr
LAB=690+3800+2590+84=7164 mm
We find the pressure loss in the AB section using formula 12:
RlАБ=31.4·7.164=225 Pa
Section aB
Section aB consists of a confuser, a straight vertical section 4700 mm long, a straight horizontal section 2190 mm long and a side section of the tee.
The air speed in section aB is assumed to be 12 m/s.
Consumption -360 m3/h.
We determine the required diameter using formula 8:
We accept standard diameter D=100 mm. The cross-sectional area of the duct of the selected diameter is 0.007854 m2. We clarify the speed using formula (10):
By diameter D and speed v, according to the nomogram, we find R = 23.2 Pa/m, Hd = 99.3 Pa.
Let's take one of the sides of the confuser b = 420 mm.
The resistance coefficient of the confuser is determined from table. 8 depending on lk/D>1 and b=30o-tk=0.11.
Ro=2·100=200 mm
We find the resistance coefficient of the 30° tap from Table 10.
Branch length at 30°
Estimated length of section aB:
LaB=lk+2·l9o+ Ulpr
LaB=600+4700+2190+105=7595 mm.
We find the pressure loss in section aB using formula 12:
RlaB=23.2·7.595=176 Pa
We find the resistance coefficients of the tee by specifying the diameter of the combined air duct D=125 mm, S=0.01227 m2.
The ratio of areas and costs is determined by the formula:
where Sp is the area of the passage duct, m2;
Sb - side air duct area, m2;
S-air duct area of combined flows, m2;
Lb - side air duct flow rate, m3/h;
L-air duct flow rate of combined flows, m3/h.
The ratio of areas and costs is determined by formulas (18):
The resistance coefficient of the tee is determined from Table 13: passage section zhpr = 0.0 and side section rbk = 0.2.
Hpt=Rl+UtHd
The pressure loss in the AB section is:
Npt.p=225+(0.069+0.11+0.0)107.7=244 Pa
The pressure loss in section aB is:
Npt.b=176+(0.069+0.11+0.2)99.3=214 Pa
UNpt.p=Npt.p+Nm.p.=244+50=294 Pa,
where Nm.p.=50.0 Pa - pressure loss in the hopper from the table. 1.
UNpt.b=Npt.b+Nm.b.=214+50.0=264 Pa,
where Nb.p. = 50.0 Pa - pressure loss in burat from the table. 1.
Pressure difference between sections AB and AB:
Ndiaf=294-264=30 Pa
Since the difference is 10%, there is no need to equalize losses in the tee.
BV section
The section consists of a straight horizontal section with a length of 2190 mm, a through section of the tee.
Consumption - 600m3/h.
The diameter of the air duct in the BV section is 125 mm.
Based on the diameter D and speed v according to the nomogram, we find R=20 Pa/m, Nd=113 Pa.
Estimated length of the waste water section:
RlБВ=20.0·2.190=44 Pa
Section bV
Section bV consists of a confuser, a straight vertical section 5600 mm long and a side section of a tee.
The air speed in section bV is assumed to be 12 m/s.
Consumption -1240 m3/h.
We determine the required diameter using formula 8:
We accept standard diameter D=180 mm. The cross-sectional area of the duct of the selected diameter is 0.02545 m2. We clarify the speed using formula (10):
Based on the diameter D and speed v, according to the nomogram, we find R = 12.2 Pa/m, Hd = 112.2 Pa.
We determine the dimensions of the confuser inlet hole based on the area of the inlet hole using formula 13:
Let's take one of the sides of the confuser b=300 mm.
We find the length of the confuser (suction pipe) using formula 15:
The resistance coefficient of the confuser is determined from table. 8 depending on lk/D>1 and b=30o-tk=0.11.
We find the radius of the outlet using formula 15
Ro=2·180=360 mm
We find the resistance coefficient of the 30° tap from Table 10.
We calculate the length of the bend using formula 16.
Branch length at 30°
Estimated length of section bV:
LaB=lk+l30o+ Ulpr
LbV=220+188+5600=6008 mm.
We find the pressure loss in section bB using formula 12:
RlБВ=12.2·6.008=73 Pa.
We find the resistance coefficients of the tee by specifying the diameter of the combined air duct D=225 mm, S=0.03976 m2.
The resistance coefficient of the tee is determined from Table 13: passage section zhpr = -0.2 and side section rbk = 0.2.
Pressure loss in the area is calculated using the formula:
Hpt=Rl+UtHd
The pressure loss in the BW section is:
Npt.p=43.8-0.2113=21.2 Pa
The pressure loss in section bB is:
Npt.b=73+(0.2+0.11+0.069)112.0=115 Pa
Total losses in the passage section of the BV:
UNpt.p=Npt.p+Nm.p.=21.2+294=360 Pa,
Total losses on the side section:
UNpt.b=Npt.b+Nm.b.=115+80.0=195 Pa,
where Nb.p. = 80.0 Pa - pressure loss in the aspiration column from Table 1.
Pressure difference between the BV and BV sections:
Since the difference is 46%, which exceeds the permissible 10%, it is necessary to equalize the pressure losses in the tee.
Let's perform the alignment using additional resistance in the form of a side diaphragm.
We find the diaphragm resistance coefficient using the formula:
Using the nomogram we determine the value 46. Where does the depth of the diaphragm come from a=0.46·0.180=0.0828 m.
VG section
The VG section consists of a straight horizontal section 800 mm long, a straight vertical section 9800 mm long, a 90° bend and a side section of the tee.
The air speed in the VG section is assumed to be 12 m/s.
Consumption - 1840 m3/h.
We accept standard diameter D=225 mm. The cross-sectional area of the duct of the selected diameter is 0.03976 m2. We clarify the speed using formula (10):
According to the diameter D and speed v, according to the nomogram, we find R = 8.0 Pa/m, Hd = 101.2 Pa.
We find the radius of the outlet using formula 15
Ro=2·225=450 mm
We find the resistance coefficient of the 90° tap from Table 10.
We calculate the length of the bend using formula 16.
90° bend length
Estimated length of the VG section:
LВГ=2·l9o +Улр
LВГ=800+9800+707=11307 mm.
RlВГ=8.0·11.307=90 Pa
Section VG
Section vg consists of a confuser, a 30° bend, a vertical section 880 mm long, a horizontal section 3360 mm and a tee through section.
Consumption - 480 m3/h.
We determine the dimensions of the confuser inlet hole based on the area of the inlet hole using formula 13:
The resistance coefficient of the confuser is determined from table. 8 depending on lk/D>1 and b=30o-tk=0.11.
Ro=2·110=220 mm
We find the resistance coefficient of the 30° tap from the table. 10 .
We calculate the length of the bend using formula 16.
Branch length at 30°
Estimated section length vg:
Lвг=lk+l30+ Улр
lвг=880+115+300+3360=4655 mm.
The pressure loss in the section vg is found using formula 12:
Rlgv=23·4.655=107 Pa
Section dg
The dg section consists of a confuser, a straight vertical section 880 mm long and a side section of the tee.
Consumption -480 m3/h.
We choose a speed of 12 m/s. We determine the required diameter using formula 8:
We accept standard diameter D=110 mm. The cross-sectional area of the duct of the selected diameter is 0.0095 m2. We specify the speed using formula 10:
According to the diameter D and speed v, according to the nomogram, we find R = 23.0 Pa/m, Hd = 120.6 Pa.
We determine the dimensions of the confuser inlet hole based on the area of the inlet hole using formula 13:
Let's take one of the sides of the confuser b=270 mm.
The length of the confuser (suction pipe) is found using formula 14:
The resistance coefficient of the confuser is determined from table. 8 depending on lk/D>1 and b=30o-tk=0.11.
Estimated section length vg:
Lвг=lk+l30+ Улр
lвг=880+300=1180 mm.
The pressure loss in the section vg is found using formula 12:
Then, pressure loss along the length of the air duct:
Rlgv=23·1.180=27.1 Pa
We find the resistance coefficients of the tee by specifying the diameter of the combined air duct D=160 mm, S=0.02011 m2.
The ratio of areas and costs is determined by formula 18:
The resistance coefficient of the tee is determined from Table 13: passage section zhpr = 0.0 and side section rbk = 0.5.
Pressure loss in the area is calculated using the formula:
Hpt=Rl+UtHd
The pressure loss in the section vg is:
Npt.p=107+(0.069+0.11+0.0)120.6=128 Pa
The pressure loss in the dg section is:
Npt.b=27+(0.11+0.5)120.6=100 Pa
Total losses in the passage and side sections:
UNpt.p=Npt.p+Nm.p.=128+250=378 Pa,
UNpt.b=Npt.b+Nm.b.=100+250=350 Pa,
where Nm.p. = 250.0 Pa - pressure loss in the trireme from the table. 1.
Pressure difference between sections vg and dg:
Ndiaf=378-350=16 Pa
Since the difference is 7%, which does not exceed the permissible 10%, there is no need to equalize pressure losses in the tee.
Section GG
The section consists of straight horizontal sections 2100 mm long, and a through section of the tee.
Consumption of the area GG equal to the sum expenses in the VG and DG sections.
Consumption -960 m3/h.
The diameter of the air duct in the section GG is 160 mm.
The cross-sectional area of the air duct of the selected diameter is 0.02011 m2.
We specify the speed using formula 10:
By diameter D and speed v, according to the nomogram, we find R = 14.1 Pa/m, Nd = 107.7 Pa
Estimated length of section GG:
LgG=2100 mm.
Pressure loss along the length is found using formula 12:
RlгГ=14.1·2.1=29.6 Pa
We find the resistance coefficients of the tee by specifying the diameter of the combined air duct D=250 mm, S=0.04909 m2.
The ratio of areas and costs is determined by formula 18:
The resistance coefficient of the tee is determined from Table 13: passage section zhpr = 0.2 and side section rbk = 0.6.
Pressure loss in the area is calculated using the formula:
Hpt=Rl+UtHd
The pressure loss in the VG section is:
Npt.b=90+(0.15+0.2)101.2=125.4 Pa
The pressure loss in the GG section is:
Npt.p=29.6+0.6·107.7=94.2 Pa
Total losses in the passage and side sections:
UNpt.p=Npt.p+Nm.p..=125.4+360.4=486 Pa,
UNpt.b=Npt.b+Nm.b =94.2+378=472 Pa,
Pressure difference between the VG and GG sections:
Ndiaf=486-472=14 Pa
The difference is less than 10%.
GD section
The plot consists of a straight horizontal section with a length of 1860 mm.
Consumption of the gas turbine section - 2800 m3/h
The diameter of the air duct in the GD section is 250 mm, S = 0.04909 m2.
We specify the speed using formula 10:
According to the diameter D and speed v, according to the nomogram, we find R = 11.0 Pa/m, Hd = 153.8 Pa.
The area of the inlet to the cyclone is equal to the area of the inlet pipe S2=0.05 m2
Estimated length of the main section:
lGD=1860 mm.
We find the pressure loss in the main pressure section using formula 12:
Then, pressure loss along the length of the air duct:
RlGD=11.0·1.86=20.5Pa
The pressure losses in the gas pressure section are:
UNpt.p=20+486=506 Pa
Section DE
Cyclone 4BTsSh-300.
Air consumption taking into account air suction:
The pressure loss in the cyclone is equal to the resistance of the cyclone and amounts to Hc = 951.6 Pa.
Total losses in the DE section:
Section EZh
The section consists of a confuser, three 90° bends, straight horizontal sections 550 mm and 1200 mm, a straight vertical section 2670 mm long, a straight horizontal section 360 mm and a diffuser.
We will determine the flow rate in the EJ section taking into account the suction in the cyclone equal to 150 m3/h:
The air speed after the cyclone is 10...12 m/s, since after the cyclone the air is purified.
The air speed in the EZh section is assumed to be 11 m/s.
We determine the required diameter using formula 8:
We accept standard diameter D=315 mm, S=0.07793 m2.
We specify the speed using formula 10:
According to the diameter D and speed v, according to the nomogram, we find R = 3.8 Pa/m, Hd = 74.3 Pa.
The area of the inlet in the transition pipe is S1 = 0.07793 m2, and the area of the cyclone outlet is S2 = 0.090 m2, since S1 Let's take one of the sides of the confuser b=450 mm. We find the length of the confuser using formula 15: The resistance coefficient of the confuser is determined from table. 8 depending on lк/D=0.6 and b=30о - tk=0.13. It is necessary to determine whether the adapter pipe at the fan inlet is a confuser or a diffuser. Since the outlet pipe has a diameter of 315 mm, and the diameter at the fan inlet is 320 mm, the adapter pipe is a diffuser with an expansion ratio: We find the radius of the outlet using formula 15: We find the resistance coefficient of the 90° tap from the table. 10 . We calculate the length of the bend using formula 16: Estimated length of the EZh section: LEF=989.6*3+2670+360+1200+550=7749 mm. RlEZh=3.78·7.749=29 Pa. UNpt.p=1458+29+(0.13+0.1+0.15·3)74.3=1538 Pa. Section ZhZ The section consists of a diffuser, a straight vertical section 12700 mm long, a 90-degree outlet and a diffuser with a protective umbrella. The air flow in this area is equal to the flow at the entrance to the fan, i.e. 3090m3/h. Air speed is 11.0 m/s. The diameters of the air ducts in the sections are assumed to be equal to the diameter upstream of the fan, i.e. 315mm. By diameter D and speed v, according to the nomogram, we find R = 3.8 Pa/m, Nd = 68.874.3 Pa. Let's determine what the adapter pipe at the outlet of the fan serves. Fan opening area S1=0.305x0.185=0.056 m2, cross-sectional area of the air duct with a diameter of 315 mm S2=0.07793 m2. S2>S1, therefore there is a diffuser with an expansion ratio: Let's set the diffuser expansion angle b=30?. Then from the table. 4 diffuser resistance coefficient w=0.1. Estimated length of the EZh section: lEZh=12700 mm. Pressure loss along the length of the air duct is determined by formula 11: RlEZh=3.78·12.7=48.0 Pa. The pipe has a diffuser with a protective umbrella. The loss coefficient is found in table. 6 f = 0.6. The pressure loss in the EF section is: UNpt.b=48+(0.1+0.6)74.3=100 Pa. The total network resistance along the main line is: UNpt.p=100+1538=1638 Pa. Taking into account the safety factor of 1.1 and the possible vacuum in the workshop premises, the required pressure developed by the fan is 50 Pa. Currently, aspiration systems are quite common, as the development of industry is only increasing every day. Filter installations with - this general systems which are the most common. They are designed to filter air containing solid particles up to 5 microns in size. The degree of purification of such aspiration systems is 99.9%. It is also worth noting that the design of this filter unit, which has a storage hopper, allows it to be used for installation in traditional systems air purification systems, which have an extensive air duct system, as well as exhaust fan high power. The central storage device in such systems is used to store, dose and dispense crushed wood waste. The production of this bunker is carried out with a volume from 30 to 150 m 3. In addition, the aspiration system is equipped with such parts as sluice loaders or augers, an explosion and fire protection system, and a system that controls the filling level of the bunker. There is also modular system air aspiration, which is intended for the following purposes: In order to calculate the aspiration system, it is first necessary to combine it into a common network. Such networks include: It is also worth noting that the optimal number of suction points for one aspiration system is six. However, a larger number is possible. It is important to know that if you have equipment that operates with a constantly changing air flow, it is necessary to design a separate aspiration system for this device or add a small number of “passing” suction points (one or two with low flow rates) to the existing one. It's important to carry out accurate calculations. The first thing that is determined in such calculations is the air consumption for aspiration, as well as pressure loss. Such calculations are carried out for each machine, container or point. Data can most often be taken from the passport documentation for the object. However, it is permitted to use data from similar calculations with the same equipment, if any. Also, air flow can be determined by the diameter of the pipe that sucks it out or by the hole in the body of the aspiration machine. It is important to add that it is possible to eject air entering the product. This happens if, for example, air moves through a gravity pipe at high speed. In this case, additional costs arise that must also be taken into account. In addition, in some aspiration systems it also happens that a certain amount of air leaves along with the discharged products after cleaning. This amount must also be added to the expenditure. After all the work has been done to determine the air flow and possible ejection, it is necessary to add up all the obtained numbers, and then divide the sum by the volume of the room. It is worth considering that the normal air exchange is different for each enterprise, but most often this figure ranges from 1 to 3 aspiration cycles per hour. Large quantity most often used to calculate the installation of systems in premises with general exchange This type air exchange is used in enterprises to remove harmful fumes from the premises, to remove impurities or unpleasant odors. When installing an aspiration system, an increased vacuum may be created due to the constant suction of air from the room. For this reason, it is necessary to provide for the installation of an influx of outside air into it. Currently, the aspiration fire system is considered the best way protection of the premises. In an effective way alert in this case is considered aspiration with ultrasensitive laser Ideal place applications of such systems are archives, museums, server rooms, switch rooms, control centers, hospital premises with high-tech equipment, “clean” industrial zones, etc. In other words, the aspiration system fire alarm This type is used in premises that are of particular value, in which material assets are stored, or in which it is installed a large number of expensive equipment. Its purpose is as follows: to carry out sanitation of the tracheobronchial tree under conditions artificial ventilation lungs and while maintaining asepsis. In other words, they are used by doctors to perform complex operations. This system includes the following: Currently, there is a fairly broad classification of types of filter systems. Some companies, such as Falter, manufacture almost any type of aspiration system. The first division of systems is carried out according to the nature of air circulation. Based on this feature, they can all be divided into two types: recirculation and direct-flow. The first class of systems has such a significant difference as the return of selected air from the room back after passing complete process cleaning. That is, it does not produce any emissions into the atmosphere. Another advantage follows from this - high savings on heating, since the heated air does not leave the room. If we talk about the second type of systems, then their operating principle is completely different. This filtering unit completely takes the air from the room, after which it is completely cleaned, in particular from substances such as dust and gas, after which all the taken air is released into the atmosphere. In order to begin the installation phase of the filtration system, design work is first carried out. This process is very important, and therefore it is given Special attention. It is important to say right away that an incorrectly carried out design and calculation stage will not be able to provide the necessary cleaning and air circulation, which will lead to bad consequences. For successful design and subsequent installation of the system, several points must be taken into account: Carrying out calculations and drawing up a project is not full list what needs to be done before starting the system installation process. In other words, we can say that installing filters is the simplest and last thing that professionals undertake. Air aspiration system removes industrial pollution inner space assembly paint and varnish and production workshops. Simply put: an aspiration system is one of the types of “industrial” filters, focused on the disposal of welding fumes, paint aerosols, oil suspensions and other industrial waste. And if you are guided by safety precautions or common sense, then it is simply impossible to be in a production room without aspiration. Any aspiration system consists of three main components: A special “Cyclone” type installation is used as a fan in aspiration systems, which generates both exhaust and centrifugal force. At the same time, air extraction is provided by the same force, and centrifugal force performs primary, “rough” cleaning, pressing “dirt” particles against the inner walls of the “Cyclone” body. Both external cassettes - roof filters - and internal bag filters are used as filtration units in such installations. Moreover, the hose elements are equipped with a pulse cleaning system, which ensures that the accumulated “dirt” “drains” into the bunkers. In addition, air ducts for aspiration systems of woodworking enterprises are also equipped with chip catchers - special filters that “collect” large industrial waste. After all, bag filters are used only for fine cleaning– they capture particles with a caliber of more than one micrometer. Such equipment, which involves equipping cyclones and air ducts with cassettes and primary cleaning systems and fine filters, guarantees the collection of about 99.9 percent of industrial emissions even at the most environmentally unfavorable enterprise. However, each production “generates” its own type of industrial waste, the particles of which have a certain density, mass and state of aggregation. Therefore, for successful operation of the installation in each specific case, it is necessary to individually design aspiration based on physical and chemical characteristics"waste". Despite the exceptionally individual performance characteristics, which literally all aspiration schemes have, structures of this kind can nevertheless be classified according to the type of layout. And this sorting method allows us to distinguish the following types of aspirators: In addition, all aspiration systems can also be classified according to the principle of removing the filtered flow. And according to this sorting principle, all installations are divided into: From a security point of view the best option The design is a direct-flow installation that removes waste outside the workshop. And from the point of view of energy efficiency, the most attractive design option is a recirculating aspirator - it returns filtered and warm air, helping to save on heating or air conditioning space. When drawing up a project for an aspiration installation, calculation work is carried out according to the following scheme: At the same time, during calculations it is necessary to take into account not only reference characteristics, but also individual parameters, such as temperature and humidity, shift duration, etc. As a result, the calculation work carried out taking into account the individual needs of the customer becomes almost an order of magnitude more complex. Therefore, only the most experienced design bureaus undertake such work. At the same time, you shouldn’t trust beginners or non-professionals in this case - you can lose not only equipment, but also workers, after which the enterprise can be closed by a court decision, and the responsible persons who made the decision to put dubious equipment into operation will face even greater troubles. When developing the technological part of the project, the issues of aspiration and dust removal of technological equipment must be comprehensively addressed, ensuring appropriate sanitary standards. When designing dust collection installations for cleaning waste gases and aspiration air emitted into the atmosphere, it is necessary to take into account the speed of air or gas in the devices; physical and chemical properties and particle size distribution of dust, initial dust content of gas or air, type of fabric for bag filters, temperature and humidity of dust. The amount of exhaust gases and aspiration air from technological installations determined by calculation during design. Thus, for the mill aspiration system: Q = 3600·S·V m = 3600··V m, (5) where Q is the amount of air passing through the mill in 1 hour S is the cross-sectional area of the mill; V m is the speed of air movement inside the mill, taking into account suction in the system; D is the diameter of the mill. Temperature of exhaust gases and aspiration air (not less) - 150ºС. V m = 3.5 – 6.0 m/s. Then: Dust content of 1 m3 of exhaust gases and aspiration air is 131 g. Permissible dust concentrations in purified gases and air should not exceed 50 mg/m3. To purify the aspiration air leaving the ball mill, we take two-stage system cleaning: 1. Cyclone TsN-15, purification degree 80-90%: ¾ 1 battery: 262 - 262·0.8 = 52.4 g/m3; ¾ 2nd battery: 52.4 - 52.4·0.8 = 10.48 g/m3; ¾ 3rd battery: 10.48 - 10.48·0.8 = 2.096 g/m3; ¾ 4 battery: 2.096 - 2.096·0.8 = 0.419 g/m3. 2. Electric precipitator Ts-7.5SK, purification degree 85-99%: 0.419 - 0.419·0.99 = 0.00419 g/m3. Dust settling device. Cyclone TsN-15 Cyclones are designed to clean dusty air from suspended solid particles (dust) and operate at temperatures not exceeding 400°C. Figure 8 – Group of two cyclones TsN-15 Selecting a dust settling device for product supply: Q = 3600 · ·V m = 3600 · ·5 = 127170/4 = 31792.5 m 3 /h. Technological calculation can be made using the formula: M = Q/q = 31792.5/20000 = 1.59 (accept 2 pieces) Then the actual equipment load factor over time: K in = 1.59/2 = 0.795. Table 19 - Technical specifications groups of two cyclones TsN-15 Electrostatic precipitator The Ts-7.5SK electric precipitator is designed for dust removal of gases and waste from drying drums, as well as for removal of dust from air and gases sucked out of mills. To remove dust settled on the electrodes located in the electrostatic precipitator, they are shaken using a shaking mechanism. Dust separated from the electrodes enters collecting hoppers and is removed through sluice gates. The electrostatic precipitator reduces the concentration of dust in the air by 33.35%, while releasing 1.75 grams per cubic meter into the atmosphere. meter. Table 20 - Technical characteristics of the electrostatic precipitator Ts-7.5SK Fan Centrifugal fans high pressure VVD type are designed to move air in supply and exhaust ventilation systems industrial buildings with a total loss of total pressure of up to 500 sec/m2. Fans are manufactured in both right and left rotation and are supplied complete with electric motors. Introduction Local exhaust ventilation plays the most active role in the complex of engineering means for normalizing sanitary and hygienic working conditions in production premises. At enterprises associated with the processing of bulk materials, this role is played by aspiration systems (AS), ensuring the localization of dust in places of its formation. Until now, general ventilation has played an auxiliary role - it provided compensation for the air removed by the AS. Research by the Department of MOPE BelGTASM has shown that general ventilation is integral part a complex of dust removal systems (aspiration, systems to combat secondary dust formation - hydraulic flushing or dry vacuum dust collection, general ventilation). Despite long history development, aspiration received a fundamental scientific and technical basis only in recent decades. This was facilitated by the development of fan manufacturing and the improvement of air purification techniques from dust. The need for aspiration from the rapidly developing sectors of the metallurgical construction industry also grew. A number of scientific schools have emerged aimed at solving emerging environmental problems. In the field of aspiration, the Ural (Butikov S.E., Gervasyev A.M., Glushkov L.A., Kamyshenko M.T., Olifer V.D., etc.), Krivoy Rog (Afanasyev I.I., Boshnyakov E.N., etc.) became famous , Neykov O.D., Logachev I.N., Minko V.A., Sheleketin A.V. and American (Khemeon V., Pring R.) calculating the localization of dust emissions using aspiration. Technical solutions developed on their basis in the field of designing aspiration systems are enshrined in a number of regulatory and scientific-methodological materials. Real teaching materials summarize the accumulated knowledge in the field of designing aspiration systems and centralized vacuum dust collection systems (CVA). The use of the latter is expanding especially in production, where hydraulic flushing is unacceptable for technological and construction reasons. The methodological materials intended for the training of environmental engineers complement the course “Industrial Ventilation” and provide for the development of practical skills among senior students of the specialty 05/17/09. These materials are aimed at ensuring that students are able to: Determine the required performance of local suction pumps and CPU nozzles; Choose rational and reliable systems pipelines with minimal energy losses; Determine the required power of the aspiration unit and select the appropriate draft means And they knew: The physical basis for calculating the performance of local suction stations; The fundamental difference between the hydraulic calculation of central control systems and the AC air duct network; Structural design of shelters for reloading units and CPU nozzles; Principles for ensuring the reliability of AS and CPU operation; Principles for selecting a fan and features of its operation for a specific pipeline system. The guidelines are focused on solving two practical problems: “Calculation and selection of aspiration equipment (practical task No. 1), “Calculation and selection of equipment for a vacuum system for collecting dust and spills (practical task No. 2).” The testing of these tasks was carried out in the autumn semester of 1994 in practical classes of groups AG-41 and AG-42, to whose students the compilers express gratitude for the inaccuracies and technical errors they identified. Careful study of materials by students Titov V.A., Seroshtan G.N., Eremina G.V. gave us grounds to make changes to the content and edition of the guidelines. 1. Calculation and selection of aspiration equipment Purpose of the work: determination of the required performance of the aspiration installation servicing the system of aspiration shelters for loading areas of belt conveyors, selection of an air duct system, dust collector and fan. The task includes: A. Calculation of the productivity of local suction (aspiration volumes). B. Calculation of the dispersed composition and concentration of dust in the aspirated air. B. Selecting a dust collector. D. Hydraulic calculation of the aspiration system. D. Selection of a fan and an electric motor for it. Initial data (The numerical values of the initial values are determined by the number of option N. The values for option N = 25 are indicated in parentheses). 1. Consumption of transported material G m =143.5 – 4.3N, (G m =36 kg/s) 2. Particle density of bulk material 2700 + 40N, (=3700 kg/m 3). 3. Initial moisture content of the material 4.5 – 0.1 N, (%) 4. Geometric parameters transfer chute, (Figure 1): h 1 =0.5+0.02N, () h 2 =1+0.02N, h 3 =1–0.02N, 5. Types of shelters for the loading area of the conveyor belt: 0 – shelters with single walls (for even N), D – shelters with double walls (for odd N), Conveyor belt width B, mm; 1200 (for N=1…5); 1000 (for N= 6…10); 800 (for N= 11…15), 650 (for N = 16…20); 500 (for N= 21…26). Sf – cross-sectional area of the gutter. Rice. 1. Aspiration of the transfer unit: 1 – upper conveyor; 2 – upper cover; 3 – transfer chute; 4 – lower shelter; 5 – aspiration funnel; 6 – side outer walls; 7 – side internal walls; 8 – hard internal partition; 9 – conveyor belt; 10 – end outer walls; 11 – end inner wall; 12 – lower conveyor Table 1. Geometric dimensions lower shelter, m
Conveyor belt width B, m Table 2. Particle size distribution of the transported material
Faction number j, Size of openings of adjacent sieves, mm Average fraction diameter d j, mm * z =100(1 – 0.15). At N =25 Table 3. Length of sections of the aspiration network
Length of aspiration network sections for odd N for even N Rice. 2. Axonometric diagrams of the aspiration system of transfer units: 1 – transfer unit; 2 – aspiration pipes (local suction); 3 – dust collector (cyclone); 4 – fan 2. Calculation of the productivity of local suction The basis for calculating the required volume of air removed from the shelter is the air balance equation: The air flow rate entering the shelter through the leaks (Q n; m 3 / s) depends on the area of the leaks (F n, m 2) and the optimal vacuum value in the shelter (P y, Pa): where is the density of the surrounding air (at t 0 =20 °C; =1.213 kg/m3). To cover the loading area of the conveyor, leaks are concentrated in the area of contact of the outer walls with the moving conveyor belt (see Fig. 1): where: P – perimeter of the shelter in plan, m; L 0 – shelter length, m; b – shelter width, m; – height of the conventional gap in the contact zone, m. Table 4. The magnitude of the vacuum in the shelter (P y) and the width of the gap ()
Type of transported material Median diameter, mm Shelter type "0" Shelter type "D" Lumpy Grainy Powdery Air flow entering the shelter through the chute, m 3 /s where S is the cross-sectional area of the gutter, m2; – the flow rate of the reloaded material at the exit from the chute (the final speed of falling particles) is determined sequentially by calculation: a) speed at the beginning of the chute, m/s (at the end of the first section, see Fig. 1) G=9.81 m/s 2 (5) b) speed at the end of the second section, m/s c) speed at the end of the third section, m/s – coefficient of sliding of components (“ejection coefficient”) u – air speed in the chute, m/s. The slip coefficient of components depends on the Butakov–Neikov number* and Euler's criterion where d is the average particle diameter of the material being handled, mm, (10)
(if it turns out that, should be taken as the calculated average diameter; - the sum of the local resistance coefficients (k.m.c.) of the gutter and shelters ζ in – k.m.s, air entry into the upper shelter, related to the dynamic air pressure at the end of the chute. F in – area of leaks in the upper cover, m 2 ; * Butakov–Neykov and Euler numbers are the essence of the parameters M and N widely used in normative and educational materials. – Ph.D. gutters (=1.5 for vertical gutters, = 90°; =2.5 if there is an inclined section, i.e. 90°); –k.m.s. rigid partition (for shelter type “D”; in shelter type “0” there is no rigid partition, in this case lane = 0); Table 5. Values for type “D” shelter
Ψ – particle drag coefficient β – volumetric concentration of particles in the gutter, m 3 / m 3 – the ratio of the particle flow velocity at the beginning of the chute to the final flow velocity. With the found numbers B u and E u, the slip coefficient of the components is determined for a uniformly accelerated particle flow according to the formula: The solution to equation (15)* can be found by the method of successive approximations, assuming as a first approximation (16)
If it turns out that φ 1 Let's look at the calculation procedure using an example. 1. Based on the given particle size distribution, we construct an integral graph of particle size distribution (using the previously found integral sum m i) and find the median diameter (Fig. 3) d m = 3.4 mm > 3 mm, i.e. we have the case of overloading lumpy material and, therefore, =0.03 m; P y =7 Pa (Table 4). In accordance with formula (10), the average particle diameter. 2. Using formula (3), we determine the area of the leaks of the lower shelter (bearing in mind that L 0 = 1.5 m; b = 0.6 m, at B = 0.5 m (see Table 1) F n =2 (1.5 + 0.6) 0.03 = 0.126 m 2 3. Using formula (2), we determine the flow of air entering through the leaks of the shelter There are other formulas for determining the coefficient, including: for a flow of small particles, the speed of which is affected by air resistance. Rice. 3. Integral graph of particle size distribution 4. Using formulas (5)… (7) we find the particle flow rates in the chute: hence n = 4.43 / 5.87 = 0.754. 5. Using formula (11), we determine the amount of k.m.s. gutters taking into account the resistance of shelters. When F in =0.2 m 2, according to formula (12) we have With h/H = 0.12/0.4 = 0.3, according to table 5 we find ζ n ep =6.5; 6. Using formula (14) we find the volumetric concentration of particles in the gutter 7. Using formula (13), we determine the drag coefficient 8. Using formulas (8) and (9), we find the Butakov–Neikov number and the Euler number, respectively: 9. We determine the “ejection” coefficient in accordance with formula (16): And, therefore, you can use formula (17) taking into account (18)… (20): 10. Using formula (4), we determine the air flow entering the lower shelter of the first transfer unit: In order to reduce calculations, let us set the flow rate for the second, third and fourth reloading nodes k 2 =0.9; k 3 =0.8; to 4 =0.7 We enter the calculation results in the first row of the table. 7, assuming that all reloading nodes are equipped with the same shelter, the air flow rate entering through the leaks of the i -th reloading node is Q n i = Q n = 0.278 m 3 /s. We enter the result in the second row of the table. 7, and the amount of expenses Q f i + Q n i – in the third. The amount of expenses represents the total productivity of the aspiration unit (air flow entering the dust collector - Q n) and is entered in the eighth column of this line. Calculation of dispersed composition and dust concentration in aspirated air Dust Density The flow rate of air entering the exit through the chute is Q liquid (through leaks for the “O” type shelter – Q Нi = Q H), removed from the shelter – Q ai (see Table 7). Geometric parameters of the shelter (see Fig. 1), m: length – L 0 ; width – b; height – N. Cross-sectional area, m: a) aspiration pipe F in = bc.; b) shelters between the outer walls (for departure type “O”) c) shelters between the inner walls (for shelter type “D”) F 1 =b 1 H; where b is the distance between the outer walls, m; b 1 – distance between the internal walls, m; H – shelter height, m; с – length of the inlet section of the aspiration pipe, m. In our case, with B = 500 mm, for a shelter with double walls (shelter type “D”) b = 0.6 m; b 1 =0.4 m; C =0.25 m; H =0.4 m; F inx =0.25 0.6 =0.15 m2; F 1 =0.4 0.4 =0.16 m2. Removing the aspiration funnel from the gutter: a) for shelter type “0” L y = L; b) for “D” type shelter L y = L –0.2. In our case, L y =0.6 – 0.2 =0.4 m. Average air speed inside the shelter, m/s: a) for type “D” shelter b) for shelter type “0” =(Q f +0.5Q H)/F 2 . (22) Air entry speed into the aspiration funnel, m/s: Q a /F in (23) Diameter of the largest particle in the aspirated air, microns: Using formula (21) or formula (22), we determine the air speed in the shelter and enter the result in line 4 of the table. 7. Using formula (23), we determine the speed of air entry into the aspiration funnel and enter the result in line 5 of the table. 7. Using formula (24), we determine and enter the result in line 6 of the table. 7. Table 6. Mass content of dust particles, depending on
Fraction number j Fraction size, microns Mass fraction of particles of the jth fraction (, %) at, µm The values corresponding to the calculated value (or the nearest value) are written out from column 6 of table and the results (in shares) are entered in rows 11...16 of columns 4...7 of table. 7. You can also use linear interpolation of the table values, but you should keep in mind that the result will be obtained, as a rule, and therefore you need to adjust the maximum value (to ensure). Determination of dust concentration Material consumption – , kg/s (36), Density of material particles – , kg/m 3 (3700). Initial moisture content of the material –, % (2). The percentage of finer particles in the reloaded material is , % (at =149...137 microns, =2 + 1.5=3.5%. Consumption of dust reloaded with the material is , g/s (103.536=1260). Aspiration volumes – , m 3 /s (). The speed of entry into the aspiration funnel is , m/s (). Maximum concentration of dust in the air removed by local suction from the i-th shelter (, g/m 3), Actual dust concentration in the aspirated air , (26)
where is the correction factor determined by the formula wherein for shelters of type “D”, for shelters of type “O”; in our case (at kg/m3) Or with W=W 0 =2% 1. In accordance with formula (25), we calculate and enter the results in the 7th line of the summary table. 7 (specified dust consumption is divided by the corresponding numeric value lines 3, and the results are entered in line 7; for convenience in the note, i.e. in column 8, enter the value). 2. In accordance with formulas (27...29), at the established humidity, we construct a calculated relationship of type (30) to determine the correction factor, the values of which are entered in line 8 of the summary table. 7. Example. Using formula (27), we find the correction factor psi and m/s: If the dust content of the air turns out to be significant (> 6 g/m3), it is necessary to provide engineering methods to reduce the dust concentration, for example: hydro-irrigation of the material being reloaded, reducing the speed of air entry into the aspiration funnel, installing settling elements in the shelter or using local suction separators. If by means of hydroirrigation it is possible to increase the humidity to 6%, then we will have: At =3.007, =2.931 g/m3 and we use relation (31) as the calculated ratio for. 3. Using formula (26), we determine the actual concentration of dust in the first local suction and enter the result in line 9 of the table. 7 (the values of line 7 are multiplied by the corresponding i-th suction - the values of line 8). Determination of the concentration and dispersed composition of dust in front of the dust collector To select a dust collection installation for an aspiration system that serves all local exhausts, it is necessary to find the average parameters of the air in front of the dust collector. To determine them, the obvious balance relations of the laws of conservation of the mass transported through the air ducts of dust are used (assuming that the deposition of dust on the walls of the air ducts is negligible): For the concentration of dust in the air entering the dust collector, we have an obvious relationship: Keeping in mind that the expense dust j-i fractions in the i –th local suction It's obvious that 1. Multiplying in accordance with formula (32) the values of line 9 and line 3 of the table. 7, we find the dust consumption in the i –th suction, and enter its values in line 10. We enter the sum of these expenses in column 8. Rice. 4. Distribution of dust particles by size before entering the dust collector Table 7. Results of calculations of the volumes of aspirated air, dispersed composition and dust concentration in local suction and in front of the dust collector
Dimension For the i-th suction Note g/s at W=6% 2. Multiplying the values of line 10 by the corresponding values of lines 11...16, we obtain, in accordance with formula (34), the amount of dust consumption of the j-th fraction in the i-th local suction. The values of these quantities are entered on lines 17...22. The row-by-line sum of these values, entered in column 8, represents the consumption of the j-th fraction in front of the dust collector, and the ratio of these sums to the total dust consumption in accordance with formula (35) is the mass fraction of the j-th dust fraction entering the dust collector. The values are entered in column 8 of the table. 7. 3. Based on the distribution of dust particles by size calculated as a result of constructing an integral graph (Fig. 4), we find the size of dust particles, smaller than which the original dust contains 15.9% of total mass particles (µm), median diameter (µm) and dispersion of particle size distribution: . The most widely used for cleaning aspiration emissions from dust are inertial dry dust collectors - cyclones of the TsN type; inertial wet dust collectors - cyclones - SIOT workers, coagulation wet dust collectors KMP and KTSMP, rotoclones; contact filters – bag and granular. For handling unheated dry bulk materials, as a rule, NIOGAZ cyclones are used with dust concentrations of up to 3 g/m 3 and microns, or bag filters with higher dust concentrations and smaller dust sizes. At enterprises with closed water supply cycles, inertial wet dust collectors are used. Purified air flow – , m 3 /s (1.7), Dust concentration in the air in front of the dust collector – g/m3 (2.68). The dispersed composition of dust in the air in front of the dust collector is (see Table 7). The median diameter of dust particles is , µm (35.0). Dispersion of particle size distribution – (0.64), When choosing CN type cyclones as a dust collector, the following parameters are used (Table 8). aspiration conveyor hydraulic duct Table 8. Hydraulic resistance and efficiency of cyclones
Parameter µm – diameter of particles captured by 50% in a cyclone with a diameter of m at air speed, dynamic air viscosity Pa s and particle density kg/m 3 M/s – optimal air speed in the cross section of the cyclone Dispersion of partial purification coefficients – The coefficient of local resistance of the cyclone, related to the dynamic air pressure in the cross section of the cyclone, ζ c: for one cyclone for a group of 2 cyclones for a group of 4 cyclones Permissible concentration of dust in the air, emitted into the atmosphere, g/m 3 at m 3 /s (37) at m 3 /s (38) Where the coefficient taking into account the fibrogenic activity of dust is determined depending on the value of the maximum permissible concentration (MAC) of dust in the air working area:
MPC mg/m 3 Required degree of air purification from dust, % Estimated degree of air purification from dust, % (40)
where is the degree of air purification from dust j-th fractions, % (fractional efficiency - taken according to reference data). Disperse composition of many industrial dusts (at 1< <60
мкм) как и пофракционная степень их очистки и инерционных пылеуловителю
подчиняется логарифмически нормальному закону распределения, и общая степень
очистки определяется по формуле :
wherein where is the diameter of particles captured by 50% in a cyclone with a diameter of Dc at an average air speed in its cross section, – dynamic coefficient of air viscosity (at t=20 °C, =18.09–10–6 Pa–s). Integral (41) is not resolved in quadratures, and its values are determined by numerical methods. In table Figure 9 shows the function values found by these methods and borrowed from the monograph. It is not difficult to establish that this is a probability integral, the tabulated values of which are given in many mathematical reference books (see, for example,). We will consider the calculation procedure using a specific make-up artist. 1. Permissible concentration of dust in the air after cleaning it in accordance with formula (37) with a maximum permissible concentration in the working area of 10 mg/m 3 () 2. The required degree of air purification from dust according to formula (39) is Such cleaning efficiency for our conditions (µm and kg/m 3) can be ensured by a group of 4 cyclones TsN-11 3. Let us determine the required cross-sectional area of one cyclone: 4. Determine the estimated diameter of the cyclone: We select the closest of the normalized series of cyclone diameters (300, 400, 500, 600, 800, 900, 1000 mm), namely m. 5. Determine the air speed in the cyclone: 6. Using formula (43), we determine the diameter of particles captured in this cyclone by 50%: 7. Using formula (42), we determine the parameter X: The obtained result, based on the NIOGAZ method, assumes a logarithmically normal distribution of dust particles by size. In fact, the dispersed composition of dust, in the region of large particles (> 60 microns), in the aspirated air for sheltering conveyor loading areas differs from the normal-logarithmic law. Therefore, it is recommended to compare the calculated degree of purification with calculations using formula (40) or with the methodology of the MOPE department (for cyclones), based on a discrete approach to what is fairly fully covered in the course “Mechanics of Aerosols”. An alternative way to determine the reliable value of the overall degree of air purification in dust collectors is to carry out special experimental studies and compare them with calculated ones, which we recommend for an in-depth study of the process of air purification from solid particles. 9. The concentration of dust in the air after cleaning is those. less than acceptable. 
General information
Modular systems
Calculation equipment
Air calculation
Flow calculation
Fire aspiration
Closed suction system
Types of systems
Installation of aspiration systems
Air aspiration system design
Typical air aspiration systems
Calculation of aspiration systems
Indicators Dimensions and parameters
Degree of air and gas purification from dust in % 95 – 98
Maximum gas velocity in m/sec
Temperature of gases at the inlet to the electrostatic precipitator in °C 60-150
Gas temperature at the outlet of the electrostatic precipitator No more than 25 °C above their dew point
Resistance of the electrostatic precipitator in mm water. Art. No more than 20
Allowable pressure or vacuum in the electrostatic precipitator in mm of water. Art.
Initial dust content of gas in g/m 3 no more
Active cross-sectional area of the electrostatic precipitator in m3 7,5
Number of electrodes in two fields:
precipitative
crowning
Shaking motor:
type AOL41-6
power in kW
End of table 20
Indicators Dimensions and parameters
number of revolutions per minute
Sluice gate motor:
type AO41-6
power in kW 1,7
number of revolutions per minute
Power of heating elements for 8 insulators in kW 3,36
The electrodes are powered with high voltage current from an electrical unit of the type AFA-90-200
Rated power of the transformer in kVA
Rated rectified current in ma
Rated rectified voltage in kV
Overall dimensions in mm:
length
width (without shaking mechanism drive)
height (without sluice gate)
Weight in t 22,7
Manufacturing plant Pavshinsky Mechanical Plant of the Moscow Regional Economic Council
particles in the chute
