Design of Flour Mill Ventilation

Contents

Introduction

1 Design Part

1.1 Identification of equipment to be aspirated

1.2 Calculation of air exchange multiplicity and justification of type selection

of the designed network

1.3 Aspiration Network Layout

1.4 Calculation and selection of dust collector

1.5 Determination of dust collector resistance

1.6 Pre-fitting the fan to the mains

1.7 Duct Route Design

1.8 Calculation of aspiration plant

1.8.1 Initial data, purposes and tasks of calculation

1.8.2 Design diagram of the network

1.8.3 Network Calculation

1.8.4 Determination of overall mains resistance and selection of fan

2 Aspiration network wiring diagram

3 Explosion safety of aspiration unit

Conclusion

List of sources used

Introduction

Modern technological processes are associated with the movement and mechanical treatment of bulk products, which are accompanied by a large release of dust into the environment. Therefore, the most important task of ventilation plants is to maintain air cleanliness and create comfortable working conditions in working rooms. The dust content of air in them according to sanitary standards should not exceed 2-6 mg/m3. This task can be accomplished by eliminating dust emissions into the air of working rooms by aspiration of equipment, that is, by suction of air from the equipment housings, sealing casings, where dust is formed.

Reducing dust emissions into the atmosphere through the use of high-efficiency dust collectors in aspiration plants not only protects the environment, but also saves valuable food and fodder products, of which dust consists.

Ventilation and aspiration plants are widely used in modern industrial enterprises of various industries. High technical level of these plants has been achieved.

The degree of perfection of aspiration plants depends greatly on the level of their design. This is a creative process based on the theoretical knowledge, experience, technical maturity and creative ability of a design engineer.

The purpose of this work will learn on a practical task to apply its knowledge of the theory of discipline: "Ventilation installations." The main task is to develop an aspiration network for the equipment of the peeling compartment of the cereal mill.

1.3 Aspiration Network Layout

Aspiration networks are arranged according to spatial, temperature principles, the principle of operational reliability and the principle of simultaneous operation.

According to the spatial principle, we combine closely located equipment into one network and prefer vertical ducts when combining equipment, since this makes the networks more economical and operational-reliable.

According to the principle of simultaneous operation, we combine equipment operating at the same time into one network.

According to the temperature principle, we do not allow combining equipment having different air temperatures into one network, since when mixing warm and cold air, condensation of water vapors and sticking of dust to the walls of the air duct are possible.

The temperature of our equipment is equal to the temperature of the room, that is, 2022 ° C.

According to the operational reliability of the machine with a controlled mode of air flow, as well as with its own fan, we design it into independent local installations. Draw a general view of the aspiration unit.

1.7 Duct Route Design

Before you design duct routes, the general drawings draw aspirated equipment with references to the main axes.

We begin the design of the route by drawing confusers (suction pipes) of aspirated equipment.

After that, in the drawings of the general view of the workshop, we draw the duct route in axes, then, choosing the optimal option, draw it at a scale of 1:50.

Ducts are conducted along the shortest path with the smallest number of taps, parallel and perpendicular to walls and beams, avoiding oblique long ducts that violate symmetry and worsen industrial aesthetics;

Horizontal air ducts are conducted above the windows under the ceiling at the same level so as not to obscure the premises and not worsen the industrial aesthetics.

We take standard diameters of air ducts; radius of taps is taken equal to, angles of tees are taken equal to 30 °, optimal angle of constriction of confusers of aspirated machines.

1.8 Calculation of aspiration plant

1.8.1 Initial data, purposes and tasks of calculation

The purpose of the calculation is to determine all the parameters of the aspiration plant for the final selection of the fan, which ensures its reliable and economical operation.

The calculation tasks consist in determining the diameters of the air ducts of all sections of the plant, pressure losses in each section and total plant pressure losses along the main main line; equalizing pressure losses in tees in parallel sections, as well as in final selection of fan in the network, finding power for fan drive and in selection of electric motor.

To calculate the aspiration plant, the following data are available: the location of the aspirated equipment, fan, dust collector and the location of the duct route, which are displayed on the project of the general view of the aspiration plant on a scale of 1:50. Air flow rate and pressure loss in aspirated equipment are given in Table 1. Straight section lengths and characteristics of shaped duct parts are given in Figure 1. Dust collector resistance.

2 Installation of aspiration network

The wiring diagram drawing is done at a scale of 1:20, with the exception of straight sections of ducts, which are drawn without observing the scale with breaks, based on uniform filling of the sheet. The installation diagrams are drawn flat .

The wiring diagram shows on a scale all parts of the ducts: straights, confusers, taps, tees, diffusers, etc. The diameters of the ducts are drawn based on the results of the network calculation. Fans and dust collectors on the wiring diagram are drawn without a detailed image, i.e. schematically. We draw flange joints and transverse folds with main lines, and do not draw longitudinal folds of air ducts.

2.1 Materials and types of duct connections

Air ducts are made of galvanized sheet steel with a sheet size of 1000 x 2000 mm or 1250 x 2500 mm. Sheet steel thickness is taken depending on duct diameter. For diameters up to 450 mm, we take thickness = 0.55 mm.

Longitudinal and transverse seams of air ducts are made non-detachable folding .

The width of the folds depends on the thickness of the steel sheet. With a thickness of 0.55 mm, the width is 8 mm.

Split connections of air duct links are made on flanges: for diameters up to 315 from strip steel with a diameter of 25 x 4 mm, for diameters from 355 to 560 mm from angular steel with a size of 25 x 25 x 3 mm. For attachment of flanges on ends of air duct links, edge flanges are made by 8 mm.

Flanges diameters up to 560 mm it is connected by M6 bolts h20 mm to application of laying from sheet rubber 3 mm thick. The number of bolts is assumed depending on the diameters of the round ducts in accordance with Table 38. [2, p. 160]

3 Explosion safety of aspiration unit

Ensuring explosion safety is to prevent the creation of an explosive situation in aspirated equipment, air ducts and other elements of the aspiration plant, as well as on the floors of the production room.

Dust in the air in the aerosol state forms explosive mixtures, which at certain concentrations and the presence of a heat source can explode.

During the operation of the equipment, a large amount of dust is formed inside it, which, when reaching dangerous concentrations, can cause a dust explosion. The hazardous concentration of dust in the air is 1520 g/m3. The aspiration plant provides dust removal from the equipment, which makes it possible to prevent the formation of explosive concentrations of dust in the equipment.

During the design of the aspiration network, the recommendations for the required amount of air discharged from the equipment were taken into account: for BKG machines - 720 m3/h, for 2DSHSA peeling machines - 700 m3/h.

Removal of the required amount of air from the machines prevents the occurrence of explosive concentrations in the workshop air and inside the equipment.

Conclusion

In this course project, aspiration of the cereal factory peeling machine was developed. During the calculations, the parameters of the aspiration plant were determined. Main characteristics of aspirated equipment (Table 1). The basic data obtained during the calculation is summarized in Table 2.

Multiplicity of air exchange on the third floor - i = 0.7 exchange/hour even - i = 2.7 exchange/hour network resistance along the main line, air flow rate.

A dust collector, cyclone 2 * 4UTs450, was selected, ensuring environmental protection, compliance with sanitary and hygienic conditions and ensuring the concentration of dust in the air emitted to the atmosphere less than 30% of MPC. VTsP5 fan with efficiency is selected.

Explosion safety of the plant is ensured, explosive dust concentration in equipment and air ducts is not allowed