Calculation of the inspiration pipe of the mixing drum ventilation. Calculation programs and design of natural, supply and exhaust ventilation systems. Mounting and maintenance features

When developing the technological part of the project, the issues of aspiration and dedusting technological equipment with the provision of relevant sanitary standards should be comprehensively.

When designing dust-pulling facilities for the purification of exhaust gases and aspiration air emitted into the atmosphere, the air or gas velocities in the devices must be taken into account; Physico-chemical properties and granulometric composition of dust, initial dusting of gas or air, type of fabric for hosted filters, temperature and moisture content of dust. The amount of exhaust gases and aspiration air from the technological settings is determined by the calculation by design.

Thus, for the aspiration system of the mill:

Q \u003d 3600 · s · v m \u003d 3600 · · v m, (5)

where q is the amount of air passing through the mill in 1 hour S - the cross-sectional area of \u200b\u200bthe mill; V M is the speed of air movement inside the mill, taking into account the subcometations in the system; D - Mill diameter.

The temperature of the incoming gases and aspiration air (at least) is 150ºС. V M \u003d 3.5 - 6.0 m / s. Then:

Dusting 1 m 3 of outgoing gases and aspiration air - 131. The permissible concentrations of dust in purified gases and air should not exceed 50 mg / m 3.

To clean the aspiration air, departing from the ball mill, we accept a two-step cleaning system:

1. Cyclone CN-15, purification degree 80-90%:

¾ 1 Battery: 262 - 262 · 0.8 \u003d 52.4 g / m 3;

¾ 2 Battery: 52.4 - 52.4 · 0.8 \u003d 10.48 g / m 3;

¾ 3 Battery: 10.48 - 10.48 · 0.8 \u003d 2.096 g / m 3;

¾ 4 Battery: 2,096 - 2,096 · 0.8 \u003d 0.419 g / m 3.

2. Electric stream C-7.5C, cleaning degree 85-99%:

0.419 - 0.419 · 0.99 \u003d 0.00419 g / m 3.

Dust-saving device. Cyclone CN-15

Cyclones are designed to clean the dusty air from suspended solid particles (dust) and operate at a temperature not higher than 400 ° C.

Figure 8 - A group of two cyclones CN-15

Choosing a dust career for supplying a product:

Q \u003d 3600 · · V m \u003d 3600 · · 5 \u003d 127170/4 \u003d 31792.5 m 3 / h.

Technological calculation can be produced by the formula:

M \u003d Q / Q \u003d 31792.5 / 20000 \u003d 1.59 (accept 2pcs.)

Then the actual coefficient of loading equipment in time: to B \u003d 1.59 / 2 \u003d 0.795.

Table 19 - Technical characteristics of a group of two cyclones CN-15

Electrchildren

The electric filter C-7.5C is intended for dusting gases, waste from drying drums, as well as for influencing air and gases sucking from mills.

To remove the dust on the electrodes, they are shaken in electrodes, they are shaken using the shaking mechanism. Dust separated from the electrodes falls into the bins teams and is removed through the sluice valves.

The electrostiliter reduces the concentration of dust in the air by 33.35%, while producing 1.75 grams into the atmosphere to the cube. meter.

Table 20 - Technical characteristics of the electric filter C-7.5C

Indicators	Dimensions and parameters
The degree of purification of air and gases from dust in%	95 – 98
Maximum speed of gases in m / s
Gas temperature at the entrance to the electrostatic stream in ° C	60-150
Gas temperature at the outlet of the electrostatic	No more than 25 ° C above their dew point
Electric stream resistance in mm waters. Art.	No more than 20.
Permissible pressure or vacuum in the electrostilifer in mm water. Art.
The initial dust of gas in g / m 3 is no more
The area of \u200b\u200bthe active cross section of the electrostatic stream in m 3	7,5
Number of electrodes in two fields:
precipitating
Corious
Shirt mechanism electric motor:
a type	AOL41-6
Power in kw
End of Table 20.
Indicators	Dimensions and parameters
The number of revolutions of 1 min
Gateway shutter motor:
a type	AO41-6
Power in kw	1,7
The number of revolutions of 1 min
Power of heating elements for 8 insulators in kW	3,36
Power supply of high voltage electrodes is made from the type of electrical unit	AFA-90-200
Rated power of the transformer in KVA
Nominal straightened current in ma
Nominal straightened voltage in kV
Overall dimensions in mm:
length
Width (without shaking mechanism
Height (without a gate shutter)
Weight in T.	22,7
Plant manufacturer	Pavshinsky Mechanical Plant of the Moscow Regional Council

Fan

Centrifugal high pressure type fans are designed to move air in the systems of supply and exhaust ventilation of industrial buildings with the total loss of full pressure to 500 seconds 2. Fans are manufactured both right and left rotation and are supplied complete with electric motors.

Production processes are often accompanied by the release of dust elements or gases that pollute the air indoors. The problem will be helped to solve aspiration systems designed and mounted in accordance with regulatory requirements.

We will figure out how they work and where such devices are used, which are the types of air purifying complexes. Denote the main work units, we describe the design standards and the installation rules for the installation of aspiration systems.

Air pollution is the inevitable part of many production processes. To comply with the installed air purity norms, use aspiration processes. With their help, it is possible to effectively remove dust, dirt, fibers and other similar impurities.

Aspiration is a suction that is carried out by creating in close proximity to the source of pollution areas of reduced pressure.

To create such systems, serious special knowledge and practical experience are needed. Although the work of aspiration funds are closely related to functioning, not any ventilation specialist will cope with the design and installation of equipment of this type.

To achieve maximum efficiency, ventilation and aspiration methods are combined. The ventilating system in the production room should be equipped to ensure the continuous flow of fresh air outside.

Aspiration is widely used in such areas of industry:

• crushing production;
• wood processing;
• production of consumer products;
• other processes that are accompanied by the release of a large amount of substances harmful to inhalation.

Ensure the security of employees with standard protection means is not always possible, and aspiration may become the only opportunity to establish a safe production process in the workshop.

Aspirational installations are designed for efficient and rapid removal from the air of various small contaminants, which are formed in the industrial production process.

Removing contaminants using systems of this type is performed using special air ducts that have a large angle of inclination. This position allows you to prevent the appearance of so-called storage areas.

Mobile ventilation and aspiration plants are easy to install and operate, they are well suited for small enterprises or even for a home workshop.

An indicator of the efficiency of such a system is considered the degree of non-liberation, i.e. The ratio of the number of contaminants that were removed to the mass of harmful substances that did not go to the system.

Distinguish two types of aspiration systems:

• modular systems - stationary device;
• monoblocks - Mobile installations.

In addition, aspiration systems are classified by level of pressure:

• low-profrans - less than 7.5 kPa;
• average - 7.5-30 kPa;
• high-pressure - Over 30 kPa.

The equipment of the aspiration system of the modular and monoblock type is different.

In the hot shops, heating the air entering the outside is not needed, it is enough to make the opening in the wall and close it with the damper.

Conclusions and useful video on the topic

Here is a review of the unpacking and installation of the Mobile Aspiration System Rikon DC3000 for the Woodworking Industry:

In this roller, a stationary aspiration system used in the manufacture of furniture is demonstrated:

Aspiration systems are a modern and reliable way of cleaning air in industrial premises from dangerous pollution. If the design is properly designed and mounted without errors, it will demonstrate high efficiency at minimal costs.

Have something to add, or have questions about aspiration systems? Please leave comments to publication. The form for communication is located in the bottom block.

In one aspiration network, equipment is combined:
-rupt simultaneously;
- Library located;
- with the same dust, or close in quality and properties;
-Sone or with a small difference in air temperature.
The optimal number of suction points is no more than six, but you can more.
If in any machine the air flow mode periodically changes, i.e., adjustable in accordance with the technological process, then it is designed separate ventilation unit for it; or with a very small number of additional, "associated" points of suction (one - two with a small consumption).

Examples of layouts of aspiration settings - on the page.

Determine the air flow rate on aspiration and pressure loss (resistance) for each aspiracted machine, capacitance, points. Data to take from the passport documentation of the equipment or on "standards for aspiration" in the reference book. You can use similar projects.
Air flow can be determined by the size of the suction nozzle or the aspiration hole in the machine body, if the nozzle and the hole are made by the manufacturer and (or) on the size of the project organization.
If the incoming product ejects into the equipment some additional amount of air (for example, moving at high speed on the sampling pipe), then this additional volume should be added to the normative, defining it, too, by norms, or calculation methods, applied to this particular nourishing device and Product.
If a certain amount of air is carried out with a discharge product from the equipment, it should also be determined, and deduct from the air flow rate to aspiration.

An excessive ejection or air deposit can be reduced if the elements for reducing the velocity of the material, the product; Increase the degree of filling the device (pipe).
Ejecting, air deposits are completely insignificant and even absent if:
-proof feeder, the removal is completely filled with the product;
-Proach comes from the constantly filled tank;
-The submissive, discharge design is set to a sealing device (a locking shutter, valve, etc.).
If any equipment is periodically filled from the other with large one-time portions in a short time, then between them it is necessary to establish the air duct of the free flow of the displaced air and the distribution of excess pressures that occur inside the housings and containers at the time of unloading-unloading. A streaming duct - large diameter, vertical or strong, without horizontal sections.

All expenses to be folded, and divided into the volume of the room - normal air exchange for various enterprises is different, but is usually within 1 - 3 exchange per hour. Higher air exchanges are used in the calculation of secregnate supply-exhaust ventilation to remove harmful discharges, impurities, smells of indoor air.
To reduce the increased vacuum in a closed room, the influx of outdoor air to aspiracted equipment or to this room should be provided.

Reliable air transportation speed for various types of dust and bulk materials is made on the recommendations of industry instructions. You can use the names of thematic literature, data of similar projects, the parameters of existing aspiration and pneumatic transportation settings of the enterprise.
Air speed in pneumatic transport materials:
V \u003d k (10.5 + 0.57 · V VIT) m / s, where V VIT is the speed of the product of the product particles, K is the reserve coefficient, takes into account the load fluctuations on the pneumatic transformer. The calculation of the pneumatic transportation is considered on the page. If we assume that the load in the duct of aspiration is constant, then the stock coefficient must be equal to 1. For some of the vitations and pneumatic transport materials, see the "Calculation of the Aspiration" catalog of the drawings, schemes, pictures of the site. "

Type of dust separator Choose taking into account the characteristics of dust, planned (desired) air purification efficiency, operational reliability, complexity of the design. The throughput performance of the dust separator to determine the costs of all aspirated points and adding 5%. If the network has dots temporarily disabled (blocked) valves, each add another 100 m³ / hour of the suction to the total consumption.
Pressure loss (resistance) in the dust separator to take from its technical characteristics.

Place the installation of the fan and air cleaner to choose, taking into account their dimensions and the size of the air ducts connected to them. Provide the possibility of removal of dust and waste, compactness of the network of air ducts, ease of maintenance and repair. Take into account the recommendations for their location on the network. For example, the suction filter is further installed from the machine with the greatest resistance to create a necessary vacuum for reverse fabric purge. Before entering the cyclone, especially the battery, there must be a direct portion of at least two diameters of the air duct. The location of the fan is preferable after the dust separator in the course of the network, i.e. On the purified air.
An outlared air duct track, preference to give up vertical or strong, if they do not violate industrial aesthetics. If possible, reduce the length of horizontal sites, the number of turns (taps). Avoid sections with dust air on the fan insertion, especially indoors.

Draw a calculated aspiration scheme. Split the network to the sections:
- Machines to the merger points including a tee;
- the merger point to the next tee inclusive;
-the point of the last merger to the dust separator (or fan);
-pastes between dust separator and fan;
-Wefigured area with exhaust.
In the diagram, indicate air costs and pressure loss in aspiracted equipment. Calculate and specify air costs on each site. Specify the length of each section of the air ducts, including the length of all its shaped parts. Specify the pressure loss (resistance) of the dust separator.

The diameters of the air ducts of each site to select at the accepted velocity V (m / s) and air consumption q (m³ / hour) in the "data table for calculating round steel air conductives", which is in the reference book on aspiration. One of the options is given in the section "Calculation of aspiration" catalog "drawings, schemes, pictures of the site." From the same "table" take Dynamic pressure ND (PA) and R - Pressure loss per 1 meter length (PA / M) for this site. These data are applied to the scheme or in a special calculated table. For selecting diameters and calculation of air ducts You can use special.

As a rule, technological and transport equipment is supplied complete with suction pipe. The equipment passport provides data on aspiration mode.
Sizes and configuration of sucking nozzles, recommended input speeds For various materials, see aspiration and pneumatic transport directories.
The cross-sectional area of \u200b\u200bthe inlet nozzle (confused, "transition") is calculated by division air flow on the input speed.
To reduce the injury of the product and dust, to prevent explosive concentrations in the air ducts, to reduce the dust load on the filter, the input speed is made minimally possible and depends on the type of dust and the properties of the main product. Open sources of dust shape aspirate upper or side suction. The optimal angle of narrowing the confusion 45 degrees.

On each site to determine The amount of coefficients his local resistances (shaped parts): suction nozzle (confusion), taps, expansion-narrowings, tee, etc. The coefficients of all types of resistance are known and easily located in regulatory tables.
Calculate pressure loss when air passes through local resistance: multiplying dynamic pressure on the The amount of coefficients Plot.
Calculate the loss of pressure on the friction of the air along the length of the site: multiplying loss of 1 meter for all length Plot.
Fold: pressure loss in an aspiracted machine + losses on local resistance + loss along the length of the site. The resulting amount of loss of each site is applied to the scheme and in the calculated table.
Pressure loss in areas between tees is considered from the merger point (not including a tee) to the next union including a tee.

Leveling pressures.
For the main highway to take a sequence of sites that create the greatest pressure loss along the path of air movement.
To the loss of pressure of each site of the main line, add losses of all previous sections of the main highway (only the main one) and indicate this amount at the point of association with side.

At every point of the association (tee) compare the pressure loss of the main line with losses in the joined side section. For the correct air distribution, these losses must be made the same. Permissible difference - 10%. With large discrepancies, the diameter of the site with less resistance should be reduced (usually lateral), it will increase the speed in it. (at the same expense!), dynamic pressure and all losses. Recalcute the new resistance of the side of the side and compare again with the trunk at the merger point. Reduce diameter less than 80 mm can not.

If this way is not possible to level the pressure, then take the option with the closest values, and in a plot with less pressure loss sets additional local resistance: the diaphragm between the two flanges, but better - the adjusting valve. - on the tables of local resistances or by calculation.

Selection of fan.
The performance of the fan is equal to the performance of the dust separator plus the air seats in the sealing device of the dust separator. Sumps in suction filters take 15% of the useful flow of the network, or by the standards. Sumps in cyclones are taken into account if they are installed on the suction side of the fan: for COL, 4BTSSH, single-row UC to take 150 m³ / h, for a two-rowed UC - 250 m³ / hour.
The pressure that the fan should develop is equal to the overall network resistance by the main line plus 10% of the stock.
The total resistance of the network is the sum of the loss of pressure of the plots only the main highway, Including: resistance of the first aspiracted machine, loss of pressure in the air ducts of each piece of ch. Mainstroils, dust separator resistance, pressure loss on the site between the dust separator and the fan, the pressure loss in the exhaust section and the resistance of the exhaust.

According to the pressure and consumption of all numbers and types of dust fans, it is selected by the aerodynamic characteristic of which the intersection of these parameters gives the point of the largest kp. You can choose by catalogs and recommendations of manufacturers and trading organizations of ventilation equipment and equipment.
The frequency of rotation of the impeller of the fan is determined by its aerodynamic characteristic. Power on the shaft of the fan (kW): NB. \u003d (QH) / 1000kpd where q is the performance of the fan in m³ / s, i.e. m³ / hour should be divided into 3600; H - fan pressure in pa; efficiency - the efficiency of the fan.
Power of the electric motor, kW: NE \u003d (k · nv) / n · p- Н \u003d 0.98 - Bearing efficiency; P - efficiency of the transmission: when planting the impeller of the fan on the shaft of the electric motor P \u003d 1, when transmitted through the coupling P \u003d 0.98, with the clinorem transmission n \u003d 0.95. Electric motor power supply coefficient K \u003d 1.15 for electric motors with a capacity of up to 5 kW; k \u003d 1.1 for electric motors with a capacity of more than 5 kW. The practical example of the fan selection to a specific aspiration network is given on the "Select and Fan Calculation" page.

In this way, you can calculate the ventilation unit for aspiration or pneumatic transport of dusty, fine materials in the low concentration of aerosmes in the storage and processing enterprises and the processing of grain, for cleaning from impurities and enrich cereals, on flourolous and feed production, in woodworking for removing sawdust and chips from machines, In the food, textile industry and others, where there are sources of dust. Low concentration is considered to be the content of dust or waste not more than 0.01 kg in 1 kg of air. Pressure loss in air ducts with greater dusting are calculated.

Separate pages are devoted to the aspiration of admission, storage and purification of grain: calculation of the aspirational installation of the grain-cleaning department, the tower or the paragraph of the bake-receiving enterprise, the system of aspiration of the floors of the working building and the elevator scene body.

Introduction

Local exhaust ventilation plays the most active role in the complex of engineering tools to normalize sanitary and hygienic working conditions in industrial premises. At enterprises related to the processing of bulk materials, this role is carried out by aspiration systems (AC), providing localization of dust in the places of its formation. Community ventilation to date played an auxiliary role - ensured air compensation that was removed by the AU. Studies of the Department of Mope Belgtasm showed that general ventilation is an integral part of a complex of systems of dedustivation (aspiration, system of combating secondary dust formation - hydraulic or dry vacuum dust removal, general ventilation).

Despite the long history of development, the aspiration received a fundamental scientific and technical basis in recent decades. This was facilitated by the development of fan buildings and improving air purification techniques from dust. The need for aspiration has grown from rapidly developing industries of the metallurgical construction industry. A number of scientific schools aimed at solving emerging environmental problems. In the field of aspiration, the Uralskaya became famous (Butikov S.E., Gervasyev AM, Glushkov L.A., Kamyshenko M.T., Olifer, V.D., etc.), Krivoy Rod (Afanasyev I.I., Boschnak E.N. ., Neakov OD, Logachev I.N., Minko V.A., Serenko A.S., Shelektin A.V. and American (Hemeon V., Pring R.) Schools that created the modern framework of design and techniques Calculation of localization of dust emission with aspiration. The technical solutions developed on their basis in the field of design of aspiration systems are fixed in a number of regulatory and scientific and methodological materials.

These Methodological Materials generalize the accumulated knowledge in the design of aspiration systems and systems of centralized vacuum dust collectors (CPU). The use of the latter expands especially in production, where the hydraulic is unacceptable for technological and construction considerations. Methodical materials intended for training engineers complement the course "Industrial ventilation" and provide for the development of practical skills in high school students on 17.05.09. These materials are aimed at ensuring that students are able to:

Determine the necessary productivity of local speckrs of the CPUs and nozzles of the CPU;

Choose rational and reliable pipelines with minimal energy loss;

Determine the required power of aspiration installation and select the appropriate instruments

And knew:

The physical basis for calculating the performance of local speckrs of the AC;

The fundamental difference between the hydraulic calculation of the CPU systems and the network of the AU ducts;

Constructive design of shelters of overload assemblies and caps of the CPU;

Principles of ensuring the reliability of the AC and CPU;

Principles of fan selection and features of its work on a specific system of pipelines.

Methodical instructions are focused on solving two practical tasks: "Calculation and selection of aspiration equipment (practical task No. 1)," Calculation and selection of equipment of a vacuum system of cleaning of dust and waking up (practical task №2) ".

The testing of these tasks was carried out in the autumn semester of 1994 in the practical training of groups of AG-41 and AG-42, whose students are appropriate to be appreciated for the inaccuracy and technical errors identified by them. Attentive studies of materials by students Titov V.A., Seroshthan G.N., Eremina G.V. They gave us the basis to make changes to the content and edition of the methodological instructions.

1. Calculation and selection of aspiration equipment

Objective: Determination of the necessary performance of aspirational installation, serving the system of aspiration shelters for loading belt conveyors, the choice of the system of air ducts, dust collector and fan.

The task includes:

A. Calculation of the performance of local suns (aspiration volumes).

B. Calculation of the dispersed composition and concentration of dust in the aspiroured air.

B. Choice of dust collector.

G. Hydraulic calculation of the aspiration system.

D. Choosing a fan and electric motor to it.

Initial data

(The numerical values \u200b\u200bof the initial values \u200b\u200bare determined by the number N number of N. in brackets are values \u200b\u200bfor the variant N \u003d 25).

1. Consumption of transported material

G M \u003d 143.5 - 4.3N, (G M \u003d 36 kg / s)

2. Density of bulk material particles

2700 + 40N, (\u003d 3700 kg / m 3).

3. Original material moisture

4.5 - 0.1 n, (%)

4. Geometric parameters of overload chute, (Figure 1):

h 1 \u003d 0.5 + 0.02N, ()

h 2 \u003d 1 + 0.02N,

h 3 \u003d 1-0.02n,

5. Types of shelters of the location of the belt conveyor:

0 - shelter with single walls (for even N),

D - shelter with double walls (for odd N),

Ribbon width conveyor B, mm;

1200 (for n \u003d 1 ... 5); 1000 (for n \u003d 6 ... 10); 800 (for n \u003d 11 ... 15),

650 (for n \u003d 16 ... 20); 500 (for n \u003d 21 ... 26).

S w - Cross-section area of \u200b\u200ba gutter.

Fig. 1. Aspiration of the transshipment unit: 1 - upper conveyor; 2 - upper shelter; 3 - Overloading chute; 4 - lower shelter; 5 - aspiration funnel; 6 - side outer walls; 7 - lateral inner walls; 8 - a rigid inner partition; 9 - conveyor tape; 10 - end outer walls; 11 - end inner wall; 12 - Lower Conveyor

Table 1. Geometric dimensions of lower shelter, m

Conveyor belt width in, m

Table 2. Granulometric composition of the transported material

Number j fraction,
The size of the openings of adjacent sieves, mm
The average diameter of the fraction D j, mm

* z \u003d 100 (1 - 0.15).

For n \u003d 25

Table 3. Length of the aspiration network

Length of the plots of aspiration network
	for odd n		for even N.

Fig. 2. Axonometric schemes of the aspiration system of overload nodes: 1 - overload assembly; 2 - aspiration nozzles (local suction); 3 - dust collector (cyclone); 4 - fan

2. Calculation of the performance of local suns

The basis for calculating the required amount of air removed from the shelter, the air balance equation is found:

The air flow coming into the shelter through the looseness (Q H; m 3 / s) depends on the area of \u200b\u200bstrokes (F H, M 2) and the optimal amount of picing in the shelter (P y, PA):

where - the density of the surrounding air (at T 0 \u003d 20 ° C; \u003d 1.213 kg / m 3).

To cover the location of the loop of the conveyor, the looseness is concentrated in the contact zone of the exterior walls with a moving ribbon of the conveyor (see Fig. 1):

where: P is the perimeter of the shelter in the plan, m; L 0 - shelter length, m; b - the width of the shelter, m; - Height of the conditioned slit in the contact zone, m.

Table 4. The size of the loss in the shelter (R y) and the width of the slit ()

View of the transported material	Mixed diameter, mm	Shelter type "0"		Shelter type "D"
Lumpy
Grainy
Powdery

Air consumption entering the shelter by the groove, m 3 / s

where S is the cross-sectional area of \u200b\u200bthe gutter, m 2; - The flow rate of the overloaded material when the gutter exits (the final speed of the particle fall) is determined by consistently with the calculation:

a) speed at the beginning of the gutter, m / s (at the end of the first plot, see Fig. 1)

G \u003d 9.81 m / s 2 (5)

b) speed at the end of the second plot, m / s

c) speed at the end of the third plot, m / s

- The sliding coefficient of components ("Ejection coefficient") U is the air velocity in the groove, m / s.

The sliding coefficient of components depends on the number of Buttakov-Neikov *

and criterion Euler

where d is the average diameter of the particles of the overloaded material, mm,

(10)

(if it turns out that, it should be taken as the calculated average diameter; - the sum of the coefficients of local resistances (k.m.c.) of chute and shelters

ζ Х - k.m.s, air input to the upper shelter, assigned to dynamic air intake at the end of the gutter.

F B is the surface area of \u200b\u200bthe upper shelter, m 2;

* The number of Buttakov-Neikov and Euler are the essence of the parameters M and N widely used in regulatory and teaching materials.

- K.M.S. gutter (\u003d 1.5 for vertical gutters, \u003d 90 °; \u003d 2.5 in the presence of an inclined site, i.e. 90 °); -K.M.S. a hard partition (to cover the type "D"; in the shelter of the type "0" the rigid partition is absent, in this case per \u003d 0);

Table 5. Values \u200b\u200bfor shelter type "D"

Ψ - particle frontal resistance coefficient

β - volume concentration of particles in the groove, m 3 / m 3

- The ratio of the flow rate of particles at the beginning of the gutter to the end flow rate.

For the found numbers B U and E U, the sliding coefficient of components is determined for a uniformly accelerated flow of particles by the formula:

The solution of equation (15) * can be found by consecutive approximations, believing as the first approximation.

(16)

If it turns out that φ 1

Calculation procedure Consider on the example.

1. On the basis of a given granulometric composition, we build an integrated graph of particle particle distribution (using the pre-found integral sum M i) and find the median diameter (Fig. 3) d m \u003d 3.4 mm\u003e 3 mm, i.e. We have an overload case of a lump material and, therefore, \u003d 0.03 m; P y \u003d 7 Pa (Table 4). In accordance with formula (10), the average particle diameter.

2. According to formula (3), we determine the area of \u200b\u200blow shelter looser (having in mind that L 0 \u003d 1.5 m; b \u003d 0.6 m, at B \u003d 0.5 m (see Table 1)

F H \u003d 2 (1.5 + 0.6) 0.03 \u003d 0.126 m 2

3. By formula (2), we determine the flow of air entering through the looseness of the shelter

There are other formulas to determine the coefficient incl. For the flux of small particles, at the speed of the movement of the air resistance.

Fig. 3. Integral Particle Distribution Schedule

4. According to formulas (5) ... (7) we find the flow rate of particles in the groove:

hence

n \u003d 4.43 / 5.87 \u003d 0.754.

5. By formula (11) we determine the amount of KM. Gutter taking into account the resistance of shelters. At f B \u003d 0.2 m 2 by formula (12) we have

At h / h \u003d 0.12 / 0.4 \u003d 0.3,

table. 5 we find ζ n ep \u003d 6.5;

6. According to formula (14) we find the volume concentration of particles in the groove

7. According to formula (13), we determine the windshield coefficient
Particles in Gheloba

8. According to formulas (8) and (9), we find respectively the number of Buttakov-Neikov and the number of Euler:

9. Determine the "Ejection" coefficient in accordance with formula (16):

And, therefore, you can use the formula (17) taking into account (18) ... (20):

10. According to formula (4), we determine the flow of air entering the lower shelter of the first transshipment unit:

In order to reduce the calculations, we put for the second, third and fourth overload nodes.

to 2 \u003d 0.9; K 3 \u003d 0.8; K 4 \u003d 0.7

The results of the calculations are in the first line of the table. 7, believing that all overload nodes are equipped with the same shelter, air flow inclusive by looseness of the i-th ottar, Q n i \u003d Q H \u003d 0.278 m 3 / s. Result We enter the second line tab. 7, and the sum of expenses Q g I + Q N I - to the third. The amount of expenses is the overall performance of the aspirational installation (air consumption entering the dust collector - Q n) and is entered in the eighth column of this line.

Calculation of the dispersed composition and concentration of dust in the aspiriable air

Dust density

Air flow inclusive in the wrestling of the chute - Q GI (through looseness to cover the type "O" - Q Hi \u003d Q H), removed from the shelter - Q AI (see Table 7).

Geometric shelter parameters (see Fig. 1), m:

length - L 0; width - b; Height - N.

Cross section area, m:

a) aspiration nozzle F wk \u003d bc.;

b) shelter between outer walls (for loss of type "O")

c) shelter between the inner walls (for shelting like "D")

F 1 \u003d B 1 H;

where b is the distance between the outer walls, m; B 1 - distance between the inner walls, m; H is the height of the shelter, m; C is the length of the input section of the aspiration nozzle, m.

In our case, at B \u003d 500 mm, for the shelter with double walls (the shelter of the type "d") b \u003d 0.6 m; b 1 \u003d 0.4 m; C \u003d 0.25 m; H \u003d 0.4 m;

F BX \u003d 0.25 0.6 \u003d 0.15 m 2; F 1 \u003d 0.4 0.4 \u003d 0.16 m 2.

Removal of aspiration funnel from a gutter: a) to cover the type "0" L y \u003d L; b) To cover the type "D" L y \u003d L -0.2. In our case, L y \u003d 0.6 - 0.2 \u003d 0.4 m.

The average speed of air inside the shelter, m / s:

a) for shelting like "D"

b) for shelter type "0"

\u003d (Q g + 0.5Q H) / F 2. (22)

Air input rate into aspiration funnel, m / s:

Q a / f in (23)

The diameter of the largest particle in the aspiroured air, microns:

By formula (21) or by formula (22), we determine the air speed in the shelter and the result is in line 4 tab. 7.

By formula (23), we determine the speed of air input into the aspiration funnel and the result is in line 5 tab. 7.

By formula (24), we determine the result in the string 6 Table. 7.

Table 6. Mass content of dust particles, depending on

J. fraction number	Fraction size, μm	Mass fraction of the particles of the j-th fraction (,%) at, μm

The values \u200b\u200bcorresponding to the calculated value (or the nearest value) are discharged from the column of Table 6 and the results (in fractions) in line 11 ... 16 columns 4 ... 7 Table. 7. You can also use a linear interpolation of the table values, but it should be borne in mind that as a result we will, 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).

The initial humidity of the material is,% (2).

Percentage in the overloaded particle material smaller -,% (at \u003d 149 ... 137 μm, \u003d 2 + 1.5 \u003d 3.5%. The consumption of dust, overloaded with the material -, g / s (103,536 \u003d 1260).

Aspiration volumes -, m 3 / s (). The speed of entry into aspiration funnel -, m / s ().

The maximum concentration of dust in the air, removed by the local suction of the I-th shelter (, g / m 3),

Actual dust concentration in air aspiracted

, (26)

where - correction coefficient determined by the formula

wherein

for shelters like "D", for the shelters of the type "O"; In our case (with kg / m 3)

Or when w \u003d w 0 \u003d 2%

1. In accordance with formula (25), calculate. And we entered the results in the 7 string of the summary tab. 7 (the specified dust consumption is divided into the corresponding numeric value of the string 3, and the results we enter into 7 string; for convenience in the note, i.e. in column 8, put the value).

2. In accordance with formulas (27 ... 29), with a mounted humidity, we carry out the calculated ratio of type (30) to determine the correction coefficient whose values \u200b\u200bin the line 8 are consolidated table. 7.

Example. By formula (27), we find the correction coefficient of Psi and M / s:

If the dustiness of the air turns out to be significant (\u003e 6 g / m 3), it is necessary to provide engineering methods to reduce the concentration of dust, for example: hydroature of the overloaded material, reducing the air input rate into an aspiration funnel, a device of precipitating elements in shelter or the use of local suits - separators. If the hydroature is possible to increase the humidity up to 6%, then we will have:

At \u003d 3.007, \u003d 2.931 / m 3 and as a calculated ratio for use the relation (31).

3. According to formula (26), we determine the actual concentration of dust in the i-M suction and the result is in line 9 tab. 7 (Values \u200b\u200bof the string 7 are multiplied by the corresponding I-MU suction - the values \u200b\u200bof the string 8).

Determination of the concentration and dispersed composition of dust before the dust collector

To select the dust setting of the aspiration system serving all local suction, it is necessary to find the averaged air parameters before the dust collector. For their determination, apparent balance sheet relationships of the laws of mass conservation transported through dust air ducts (believing 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 ratio:

Bearing in mind that the consumption of dust j-and fractions in the I - M local suction

It's obvious that

1. Multipling according to formula (32), the values \u200b\u200bof the string 9 and the string 3 Table. 7, we find the consumption of dust in the I - M of suction, and its values \u200b\u200bare in line 10. The sum of these expenses is simple in column 8.

Fig. 4. Distribution of dust particles for size in front of the entrance to the dust collector

Table 7. The results of calculations of the volume of aspiracted air, the dispersed composition and the concentration of dust in local suction and before the dust collector

	Legend	Dimension	For the i-th suction				Note
							g / s with w \u003d 6%

2. Multiplying the values \u200b\u200bof the row 10 to the corresponding values \u200b\u200bof the strings 11 ... 16, we obtain in accordance with the formula (34) the value of the dust flow of the Jth fraction in the I-M suction. The values \u200b\u200bof these values \u200b\u200bwe enter on lines 17 ... 22. The next amount of these values \u200b\u200baffixed in column 8 represents the consumption of the Jth fraction before the dust collector, and the ratio of these sums to the total dust flow rate in accordance with the formula (35) is a mass fraction of the Jth fraction of dust coming into the dust collector. Values \u200b\u200bare affixed in column 8 tab. 7.

3. Based on the size of the dust particles calculated as a result of the construction (Fig. 4), we find the size of dust particles, the smallest of which in the initial dust contains 15.9% of the total mass of the particles (MKM), the median diameter (ICM) and dispersion Distribution of particles for size :.

The most widespread during the purification of aspiration emissions from dust received inertial dry dust collectors - cyclones of the TSN type; inertial wet dust collectors - cyclones - Syota tricks, coagulative wet dust collectors CMP and KCMP, Rotoklona; Contact filters - sleeves and grainy.

For overloading of unheated dry bulk materials, cyclones are usually used at a concentration of dust up to 3 g / m 3 and an IMM or sleeve filters at high dust concentrations and lower its size. In enterprises with closed water supply cycles use inertial wet dust collectors.

Consumption of air purified -, m 3 / s (1.7),

The concentration of dust in the air before the dust collector -, g / m 3 (2.68).

Dispersion composition of dust in the air before the dust collector - (see Table 7).

Medicated diameter of dust particles -, μm (35.0).

Dispersion of particle size distribution - (0.64),

When choosing, the following parameters are used as a dust collector of cyclones (Table 8).

aspiration conveyor hydraulic air duct

Table 8. Hydraulic resistance and efficiency of cyclones

Parameter
Μm - diameter of particles covered by 50% in cyclone with a diameter of m at air velocity, dynamic viscosity of air Pa C and density of particles kg / m 3
M / C - the optimal air velocity in the cross section of the cyclone
Dispersion of partial cleaning coefficients -
The coefficient of local cyclone resistances, referred to dynamic air 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, throwing into the atmosphere, g / m 3

at m 3 / c (37)

at m 3 / c (38)

Where the coefficient that takes into account the fibrogenic activity of dust is determined depending on the value of the maximum permissible concentration (MPC) of dust in the air of the working area:

PDC mg / m 3

Required degree of air purification from dust,%

Estimated degree of air purification from dust,%

(40)

where - the degree of air purification from the dust of the Jth fraction,% (perfection efficiency - is made on reference data).

Dispersed composition of many industrial dust (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 - the diameter of the particles covered by 50% in the cyclone with a diameter of D C with the average air velocity in its cross section,

- Dynamic air viscosity coefficient (at T \u003d 20 ° C, \u003d 18.09-10-6 PA-C).

The integral (41) is not permitted in quadratures, and its values \u200b\u200bare determined by numerical methods. In tab. 9 shows the values \u200b\u200bof the function found by these methods and borrowed from the monograph.

It is easy to establish that

this is the integral of probability, the tables of which are given in many mathematical reference books (see, for example,).

Calculation procedure Consider on a concrete makeup.

1. The permissible concentration of dust in the air after its purification in accordance with the formula (37) at the MPC in the working area of \u200b\u200b10 mg / m 3 ()

2. The required degree of air purification from dust according to formula (39) is

Such a cleaning efficiency for our conditions (MKM and CG / M 3) can be provided by a group of 4 cyclones CN-11

3. We define the necessary cross-sectional area of \u200b\u200bone cyclone:

4. Determine the calculated diameter of the cyclone:

We choose the nearest of the normalized series of diameters of cyclones (300, 400, 500, 600, 800, 900, 1000 mm), namely m.

5. Determine the air speed in the cyclone:

6. According to formula (43), we determine the diameter of the particles captured in this cyclone by 50%:

7. According to formula (42), we determine the parameter X:

The resulting result based on the method of niogas involves the logarithmically normal law of the distribution of dust particles on the size. In fact, the dispersed composition of dust, in the region of large particles (\u003e 60 μm), in the aspired air for the shelters of the pipelines of conveyors differs from the normal logarithmic law. Therefore, the calculated degree of purification is recommended to compare with the calculations according to formula (40) or with the methodology of the MOPE department (for cyclones), based on a discrete approach to a fairly fully illuminated in the course of "aerosol mechanics".

The alternative way to determine the reliable magnitude of the overall degree of air purification in dust collectors is to formulate special experimental studies and comparing them with calculated, which we recommend for an in-depth study of the process of cleaning air from solid particles.

9. The concentration of dust in the air after cleaning is

those. less permissible.

Currently, aspiration systems are quite common, since every day the development of the industry is only enhanced.

General

Filter installations C are common systems that are most common. They are intended to filter the air, in which solid particles are contained, the size of which reaches 5 μm. The degree of cleaning in such aspiration systems is 99.9%. It should also be noted that the design of this filter installation that has a storage bunker allows it to be used for installation in traditional air purification systems that have an extensive air duct system, as well as high-power exhaust fan.

The central drive in such systems is used to store, as well as dispense and produce crushed woodworking waste. 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 details such as gateway overloaders or augers, an explosion-fire protection system, a system that controls the bunker filling level.

Modular systems

There is also a modular air aspiration system, which is intended for the following purposes:

• Provide full and reliable dedustation of air in a production room at the level of levels that are prescribed by regulatory provisions.
• The most important task is to protect the atmospheric air from its pollution from the enterprise.
• Also, this system is intended to remove woodworking waste from the technological equipment in the form of a mixture of air and dust, as well as the subsequent supply of this mixture into dust collecting devices.
• The modular system is also intended to organize emissions from the air purification site to the place of its disposal. It can function in fully automatic mode.
• The last feature that this system performs is a dosage supply of sawdust to the fuel bunker. This operation can also function in fully automatic mode, but manual is also present.

Equipment for calculation

In order to carry out the calculation of the aspiration system, you must first combine it into the general network. In such networks include:

1. Equipment that functions simultaneously.
2. The equipment that is located close to each other.
3. Equipment with the same dust or close in quality, as well as properties.
4. The last thing you need to consider is equipment with a close or the same air temperature.

It is also worth noting that the optimal number of suction points for one aspiration system is six. However, more possibly is possible. It is important to know that in the presence of equipment that works with a constantly changing stream of air, it is necessary to design a separate system of aspiration for this device or add a small number of "associated" suction points (one or two with low consumption).

Calculation of air

For it is important to carry out accurate calculations. The first thing that is determined in such calculations is air flow consumption, as well as pressure loss. Such calculations are carried out for each machine, tank or point. The data most often can be taken from the passport documentation for the object. However, it is allowed to use AI and from similar calculations with the same equipment, if any. Also, air flow is completely possible to determine the diameter of the nozzle, which sucks it or on the hole in the case of the aspiration machine.

It is important to add that it is possible to ejection by air entering the product. It happens if, for example, the air moves along a self-e-pipe at high speed. In this case, additional costs arise, which must also be taken into account. In addition, in some aspiration systems, it also happens that a certain amount of air goes together with the discharged products after cleaning. This amount should also be added to the consumable.

Calculation of expense

After carrying out all the work on the determination of air flow and possible ejection, it is necessary to add all the numbers obtained, and then divide the amount on the size of the room. It is worth considering that the normal exchange of air for each enterprise is its own, but most often this indicator is ranging from 1 to 3 aspiration cycles per hour. More often, it is used to calculate the installation of systems in premises with a general branch. This type of air exchange is used in enterprises to remove harmful evaporation from the room, to remove impurities or unpleasant odors.

When installing an aspiration system, an increased vacuum can be created due to a constant air suction from the room. For this reason, it is necessary to provide an installation of an outdoor air intake.

Fire aspiration

Currently, the aspiration fire system is considered the best facility to protect the room. An effective way of alert in this case is considered aspiration with ultra-sensitive laser. The ideal place of application of such systems is the archives, museums, server, switching rooms, control centers, hospital rooms with high-tech equipment, "clean" industrial zones, etc.

In other words, the aspiration system of fire alarm system of this type is used in the premises, which are of particular value in which material values \u200b\u200bare stored or, within which a large number of expensive equipment has been established.

Closed aspiration system

Its purpose is as follows: conducting the rehabilitation of the tracheobronchial tree under conditions of artificial ventilation of the lungs and while maintaining aseptic. In other words, they are applied by doctors for complicated operations. This system includes the following:

• The design of the device is made entirely of polyethylene, polyvinyl chloride, polypropylene. The latex content in it is zero.
• The device contains a swivel angular connector, the size of which is fully standardized, and also has a movable inner ring. The presence of this part provides a reliable connection to the connector.
• The system is supplied with a protective cover for a sanitation catheter, which is designed to keep this part in hermetic conditions.
• The size of the catheter is encoded using color marking.

Types of Systems

Currently, there is a fairly wide classification of filtering systems. Some companies, such as Folter, are engaged in the production of aspiration systems of almost any kind.

The first separation of systems is carried out by the nature of air circulation. Under this feature of all, they can be divided into two types: recycling and direct-flow. The first class of systems has such an essential difference as the return of selected air from the room back, after passing the full purification process. That is, no emissions in the atmosphere does not produce. From this advantage it follows another - high savings on heating, as the heated air does not leave the room.

If we talk about the second type of systems, their principle is completely different. This filter unit completely takes the air out of the room, after which it performs its complete cleaning, in particular from such substances as dust and gas, after which the entire rougher air is thrown into the atmosphere.

Installation of aspiration systems

In order to start the stage of installation of the filtering system, first carry out design work. This process is very important, and therefore it pays special attention. It is immediately important to say that the incorrectly conducted stage of design and calculation will not be able to ensure the necessary cleaning and circulation of air, which will lead to poor consequences. To successfully draw up a project and subsequent installation of the system, you must consider several points:

1. It is important to determine the amount of air consumed by one aspiration cycle, as well as pressure loss in each place of its fence.
2. It is important to correctly define the type of dust collector. To do this, it is necessary to choose it in its own parameters.

Calculation and project preparation is not a complete list of what needs to be done before starting the installation process of the system. In other words, it can be said that the installation of filters is the simplest and most recent thing for which professionals are taken.