Design of a workshop for the production of artificial porous aggregates

Contents

Introduction

1. Nomenclature

2. Process Part

2.1. Raw materials and fuel

2.2. Composition of raw material mass

2.3. Selection of production method and process diagram

2.4. Description of the Production Flow Chart and Process

2.5. Physicochemical basis of production

2.6. Material balance of the workshop

2.7. Operating mode

2.8. Production program

2.9. Selection and calculation of main process and transport equipment

2.10. Calculation of Finished Goods Warehouse

2.11. Production control

3. Occupational safety

Bibliographic list

Introduction

Artificial porous inorganic aggregates used for the preparation of concretes for various purposes are called porous bulk gravel materials or crushed stone of the same shape, obtained, as a rule, in the heat treatment of natural silicate raw materials or corresponding industrial waste. The use of light porous aggregates allows to obtain efficient light concretes for heat insulation, wall panels, monolithic walls and various load-bearing structures. Replacing conventional heavy aggregates with porous ones allows you to significantly change the properties of concrete in the desired direction: reduce density, improve thermal insulation properties, etc. At the same time, the sufficient strength of a number of porous aggregates makes it possible to obtain high strength structural lightweight concretes based on them.

The main source of support for the construction and construction industry of our country with porous aggregates for light concrete is the specially created industry of artificial porous aggregates. This new industry is rapidly developing: if in 1960 there were 20 enterprises operating in the USSR with a total capacity of slightly more than 1 million m3, then in 1970 - about 200 enterprises and produced more than 13 million m3 of artificial porous aggregates, and in 1987 - more than 400 enterprises with a total capacity of about 50 million m3 per year. Plants for the production of artificial porous aggregates are established where they are needed, and they are usually based on local sources of raw materials. Artificial porous aggregates are characterized by higher quality and efficiency of use in concrete. Of the artificial porous aggregates, ceramic gravel and its varieties are the most common at present [1].

Ash and slag waste from thermal power plants is a widespread and inexhaustible source of raw materials for the production of artificial porous aggregates. The economic effect of the use of ash slags is achieved due to a decrease in the grade and specific capex in comparison with the current production of expanded clay. At the same time, the costs of organizing and maintaining dumps of ashes, slags and coal processing waste amount to about 400 million rubles annually, not counting the losses of arable land under dumps. The main consumer of TPP ashes and slags is the industry of wall materials, where they serve as an effective fuel-containing burnout and waste additive.

Roasted ash gravel is IPZ obtained by granulation in a plate granulator with subsequent swelling in short rotating direct-flow furnaces.

Ashes of thermal power plants, including from dumps after their hydraulic removal, serve as raw materials for the production of roasting ash gravel. The technology developed by VNIPI by the heat project involves drying and grinding ash, then rolling it into spherical granules with a diameter of about 15 mm. To facilitate granulation and ensure sufficient strength of the granules, the ash is wetted with an aqueous solution of LST (technical lignosulfonates) or clay is added. The granules are then dried and calcined in short, rotating direct-flow furnaces and fed directly into the high temperature (about 1200 C) furnace zone. Wood sawdust may be added to the ash to increase the porosity of the gravel.

The main purpose is structural heat insulation concretes.

When burning ash gravel, organic substances (coal, cmb) burn out and internal additional heat appears (about 10% of the total heat input), which ensures the intensification of pellet heating at a high heat use ratio. If wood sawdust is introduced into the granules, the role of the internal heat source increases [2].

The main characteristic of the porous aggregate is the bulk density in a dry state. For coarse porous aggregate grades of bulk density from 250 to 1200 kg/m3 are installed, and for porous sand - from 100 to 1400 kg/m3. Large porous aggregates are delivered separately in fractions 5... 10. 10... 20 and 20... 40 mm. Strength is determined by crushing a sample of coarse porous aggregate in a cylinder. The strength values for each type of aggregate are different. For ceramzite gravel, for example, it is 0.6... 2.5 MPa. Frost resistance of porous aggregates shall correspond to the grade not lower than F15. Thanks to the developed pore system, aggregates are able to absorb a significant amount of closure water, and the water absorption rate is especially high in the first 15... 20 min, i.e. at the time of preparation and laying of the light concrete mixture. Intensive absorption of water in the initial period is associated with the presence of large pores. In the future, thin pores and capillaries gradually saturate.

Ash gravel is produced by granulation of prepared ash-slag mixture or ash-fly of thermal power plant with subsequent sintering and swelling in rotary furnace at temperature 11501250 ° C. Fe2O3 content in the feedstock shall be not less than 7%, (CaO + Mg0) - not more than 8%. If the feed contains more than 3% of the fuel residues, the pellet swelling process deteriorates. Roasting ash gravel should be produced in accordance with the requirements of the current standard: from 5 to 10; 10 to 20; 20 to 40 mm. By agreement of the manufacturer with the consumer, it is allowed to manufacture gravel from 2.5 to 10 mm and a mixture of fractions from 5 to 20 mm and for heat insulation backfills from 5 to 40 mm.

The use of a direct flow pattern of material (ash pellets) and heat carrier (fuel combustion products), as well as the need to create a neutral or weakly reducing medium in the sintering zone, led to the fact that the air supply to the furnace during the operation of the nozzle was limited and the excess air coefficient was only 1.25. In this way, the cooling effect of the air sucked into the furnace was minimized, which ensured a high temperature in the initial zone (1240 ° C) at a relatively low fuel consumption (70-80 kg per 1 m3 of ash gravel). As with the calcination of expanded clay, the heat loss with the exhaust gases during sintering of the pellets in the rotary furnace is quite large and the heat consumption for drying the ash reduces these losses by only 10.8%. Calcined ash gravel is cooled slowly and gradually in refrigerators of various types. Otherwise, stress concentration centers may occur, resulting in pellet decay. After cooling, the ash gravel is sorted into commercial fractions and stored.

In addition, in some cases, production can be organized, for example, coal-free ash gravel, gravel based on clay-perlite mixtures, etc. In the presence of several raw materials or industrial wastes in the region, the issue of organizing the production of fillers should be preceded by a feasibility study [1].

In this work, the technology for the production of roasting ash gravel with a humidity of 22% is considered; 300 grade and capacity 150,000 m3/year. Ashes of thermal power plants, including from dumps after their hydraulic removal, serve as raw materials for the production of roasting ash gravel. The bulk density of ash gravel is 350-800 kg/m3. The compression strength in the cylinder approximately meets the requirements for expanded clay gravel of the same bulk density.

Product nomenclature

All aggregates by methods of formation are divided into natural, artificial and from industrial waste.

The natural fillers may be of inorganic and organic origin.

Inorganic natural fillers are materials obtained without changing their chemical and phase composition, and are characterized by the origin and petrographic name of the rocks from which they are formed. Such fillers include varieties obtained by crushing and sowing rocks (granite, diabase, diorite, limestone, volcanic tuff, pumice, quartzite, marble) or only sowing (gravel, quartz sand).

Organic aggregates are wood harvesting and processing wastes (sawdust, chips, wood fibres, etc.); waste of agricultural products processing (stems of reeds, cotton, louse seeds, fibre of linen and hemp crops, etc.); wastes and products of polymer materials industry (plastics, polymer fibres, rubber particles, etc.). Based on these aggregates, various types of building materials are produced, cement fibrolite (aggregate - wood wool), polymerbeton (aggregate - low molecular weight polyethylene).

Artificial fillers are a large class of materials obtained from natural raw materials and industrial waste by thermal or other treatment. These include ceramzite (roasting with swelling of clay raw materials), slag pumice (poration of slag melts), charcoal-free ash gravel (hydration hardening of granules from prepared mixture of ash and binder), aggloporite (roasting before sintering of fuel-containing sand-clay mixtures) [2].

Artificial porous fillers include ceramzite, agloporite, slag pumice, shungisite, azerite, thermolite, roasted ash gravel, charcoal-free ash gravel, expanded perlite, expanded vermiculite, etc.

Ceramsite - obtained mainly in the form of ceramsite gravel. Its grains have a rounded shape. The structure is porous, cellular. On its surface there is often a denser crust. The color of expanded clay gravel is usually dark, in fracture - almost black.

Agloporite - an intumescent clay raw material suitable for the production of expanded clay is not often found. More common are small-plastic, skinny, stuffed clay rocks, loam, which do not swell during firing. These rocks can be used to produce another artificial porous aggregate - aggloporite.

Slag pumice is obtained mainly from blast furnace slags, not from dump slags (such slags still need to be melted), but directly from slag melts drained from blast furnace furnaces in a fiery liquid state. At cost, slag pumice is the cheapest artificial porous aggregate. Naturally, slag pumice is produced and used in the metallurgical industry.

Shungisite is obtained by swelling at burning of graphite-containing shale rock -shungite. A large shungite deposit is being developed in the Karelian Autonomous Soviet Socialist Republic. Rock in the form of fractionated crumbs is supplied to many enterprises using it as a raw material for the production of shungisite gravel. Shungisite gravel is produced by dry method. In essence, shungisite is a type of expanded clay, characterized by a type of raw material.

Azerite is an artificial porous aggregate that can be considered one of the varieties of expanded clay, but it is logical to distinguish it in a special kind of aggregate, since the technology and properties of azerite differ significantly from those described above.

Thermolite is a material in the form of crushed stone or gravel obtained during the firing of siliceous opalic rocks (trepels, diatomites, opocas) without swelling.

Charcoal-free ash gravel: The basics of obtaining charcoal ash gravel (BZG) are:

1) granulation of a humidified mixture of ash and binder;

2) hydration hardening of binder and its interaction with active components of ash.

Portland cement, lime, gypsum, gypsum-cement-puzzolane binders (MCPV) can be used for the production of BZG and dry TPP ashes (from filters and cyclones), as well as dried ashes from their water removal dumps (ash and slag mixtures) can be used.

Expanded pearlite is a material obtained by swelling during firing of prepared grains from volcanic water-containing rocks (pearlite, obsidian, vitrophir, etc.).

Deposits of perlites, as well as obsidians and other similar volcanic glasses have been identified in Transcarpathia, Armenia, Azerbaijan, Georgia, Primorsky Territory, Buryat Autonomous Soviet Socialist Republic.

Pearlite contains about 1... 2% (sometimes more) of bound water. During firing (1000... 1250 ° C) pearlite softens and under the vapor pressure of the released water swells strongly. Expansion factor --up to 10... 12. The larger it is, the lower the raw material consumption per unit volume of production. Therefore, many enterprises producing light expanded pearlite operate on imported raw materials with a moderate cost of production. However, if the expansion ratio is lower, the unit cost of transporting raw materials increases and the cost of production increases.

Vermiculite is a type of mica, magnesium-iron hydroaluminosilicate with a content of bound water 8... 18%. This is a relatively soft rock of golden color with pearlescent shine. In areas where there is no natural gravel and rocks suitable for the production of crushed stone (and such areas make up almost 2/3 of the territory of the USSR), it may be advisable to produce ceramic aggregate from local clay rocks, which will be cheaper than imported aggregates [8].

Aggregates from industrial waste:

Along the way, mined products. During the development of mineral deposits, it is often necessary to simultaneously develop various rocks in order to open access to the mineral. The volume of overburden works during the open development of deposits is especially large.

Often the volume of mineral resources is 10... 15%, and the volume of overburden rock up to 90%, and often mined rocks, which are essentially also minerals, are exported to dumps.

In this course work, a roasting production technology is being developed:

Roasting ash gravel:

Ashes of thermal power plants, including from dumps after their hydraulic removal, serve as raw materials for the production of roasting ash gravel.

The technology developed by VNIPI by the heat project involves drying and grinding ash, then rolling it into spherical granules with a diameter of about 15 mm. To facilitate granulation and ensure sufficient strength of the granules, the ash is wetted with an aqueous solution of LST (technical lignosulfonates) or clay is added. The granules are then dried and calcined in short, rotating direct-flow furnaces and fed directly into the high temperature (about 1200 C) furnace zone. Wood sawdust may be added to the ash to increase the porosity of the gravel.

Aggregate based on ash of thermal power plants in mixture with clays is also obtained in counter-current rotary furnaces according to the technology adopted in the production of expanded clay and ash gravel [1].

Process Part

Raw materials and fuel

To produce ash gravel, the following is used:

-dump ash slag,

-pyrite balls

-SDB,

-water.

As the main component of the charge, it is supposed to use waste ash.

Supplements.

Additives are used to improve the properties of ash gravel and intensify the physical and chemical processes of formation of this material, increase quality and increase productivity. By physical condition, additives are divided into solid and liquid.

As a binder, it is supposed to use sulphite-yeast vinasse, which meets the requirements of GOST 817974. SDB is a waste of the pulp and paper industry and is a mixture of calcium, sodium and ammonium salts with an admixture of reducing substances. In the production of ash gravel, SDB is used as a binder and plasticizing substance. In this production, KBZH5 SDB (liquid bard concentrate) is used.

SDB shall correspond to the following physical and chemical parameters:

- external appearance: uniform, thick, dark brown liquid;

- dry substances content in solution must be not less than 50%;

- content of insoluble substances shall not exceed 1.3%;

Typically, the RBD is supplied with a density of 1.21.25 g/cm3.

It has been experimentally established that the optimal density of RBD for the manufacture of ash gravel should be 1.06 g/cm3.

With lower density, the SDS properties are significantly weakened, and the use of SDS of higher density contributes to the development of the effect of gluing granules, which increases the cost of producing ash gravel. Therefore, the SDB concentrate is diluted with water.

Water used for production of ash gravel shall comply with the requirements of GOST 237322011, Technical water.

In the production of artificial aggregates, solid, liquid and gaseous fuel is used. Fuel consists of combustible part, moisture and mineral mass. One of the most important characteristics of the fuel is the heat of combustion. The highest and lowest heat of combustion differs.

Characteristics of solid fuels.

In accordance with standards, coals are divided into brown, stone and anthracites.

Brown coals (grade B) have the combustion heat of the mass of moist ash-free coal Qs < 23830 kJ/kg. Depending on humidity, they are divided into B1 (humidity by working mass Wt > 40%); B2 (Wt = 3040%); B3 (Wt < 30%).

The coals have Qs > 23830 kJ/kg and V > 9%. They are divided into the following brands: long-flame, gas, fatty, fatty, coke, coke, sintered, skinny, slightly sintered.

Anthracites are characterized by V < 9% and are subdivided depending on the volume yield of volatile constituents into semianthracites (PA V = 220330/g) and anthracites proper (A V < 220/g). Semianthracites have a slightly higher combustion heat (Qi > 35200 kJ/kg).

Characteristics of liquid and gaseous fuels.

Types of liquid fuel: fuel oil, gas condensate, diesel fuel, gasoline, kerosene, etc.

To estimate the combustion heat of liquid fuel, the ratio Qi = Ki • 29260 kJ/kg can be used, where Ki = 1.4 (fuel oil), 1.43 (diesel fuel), 1.47 (kerosene), 1.5 (gasoline).

Gas fuel mixture of various combustible and non-combustible gases, as well as dust particles. Natural, oilfield, refinery, coke, semi-coke, water, generator, blast furnace gases, as well as mine (methane, hydrogen, gases of fermentation processes) can be used as gaseous fuel.

In the production of artificial porous aggregates, as a rule, fuel oil is used.

Fuel oil is a thick liquid of dark brown color, the residue after distillation from gasoline, kerosene and diesel fuel fractions (density 0.891.00 g/cm3, combustion heat 39.440.7 MJ/kg)

For the production of roasting ash gravel, it is best to use fuel oil, since it is the cheapest and most affordable type of liquid fuel.

To correct the chemical composition of the ash and slag mixture, pyrite balls are used. Pyrite burns are wastes formed during the processing of iron colchedane (FeS2, pyrite) into sulfuric acid. When the enriched pyrite concentrate is fired, sulfur dioxide is obtained, which is further processed into sulfuric acid, and pyrite carbon is formed as a solid waste. Pyrite burns consist mainly of iron and have the following chemical composition: Fe2O3 5677%, SiO2 922%, Al2O3 118%, CaO 0.85%, MgO 0.10.2%. Pyrite balls shall comply with Specification 1130840878 and meet the following requirements for physicochemical properties:

- external appearance: small crumpled brown powder;

- moisture content: not more than 28%;

- iron content in terms of Fe2O3 not less than 62%;

The dusting powder is used to increase the temperature interval of the raw material swelling and reduce bulk density, reduce excess air and reduce the fuel consumption for firing.

The use of additives, especially complex ones, makes it possible to increase the charge expansion coefficient by two to three times, accordingly reduce the bulk density of ash gravel, significantly reduce its cost and increase the productivity of furnaces [3].

Composition of raw material mixture

Composition for production of roasting ash gravel, which includes ash of heat power engineering, Portland cement, ground blast furnace granulated slag, additive accelerating hardening of crude granules - sodium sulfate, additionally contains main ground rock - gornblendite , at

the following ratio of components, wt%: Portland cement - 15-20, ground blast furnace granulated slag - 0-25, sodium sulfate - 2; gornblendite - 10-25, ash.

invention relates to methods of producing roasting ash gravel based on ash and additives with or without subsequent heat treatment, which accelerates hardening of the product.

A mixture is known for the production of OZH, consisting of quicklime, 1020%, gypsum stone, 5%, calcium chloride, a binder hardening accelerator, 3%, and ash. A disadvantage of this composition is the delayed hardening of the product as granules.

Sodium sulfate is used as additive accelerating hardening of crude granules. In comparison with the calcium chloride used earlier, this salt does not cause corrosion of reinforcement in concrete at the OPG and is more convenient to use, since it is not hygroscopic.

The effectiveness of the claimed composition for producing OPG was checked on materials: Portland cement M300, i.e., the so-called "additional Portland cement, blast furnace granulated slag of the Nizhny Tagil Metallurgical Plant, technical sodium sulfate and sour (SiO2 > 65%) and main (SiO2 > 52%) rock - gornblendite. These materials were ground, thoroughly mixed in a predetermined proportion and granulated on a plate granulator. Then the granules were subjected to thermal moisture treatment in a steaming chamber at a temperature of 85 ° C for a duration of 6 hours, and then tested according to the standard (GOST 975790 Gravel, crushed stone and porous sand) [1].

Production control

Technological design issues also include the organization of technological control and quality of raw materials.

Technical quality control means a set of operations to ensure production of high quality products with optimal technical and economic indicators of its production, which is achieved, first, by maintaining the manufacturing process at a predetermined level and; secondly, improving the production process by collecting and analysing data on the quality of raw materials and products, technological parameters, establishing a connection between them, compiling new principles for conducting the process on the basis of revealed laws.

Depending on the place of organization, technological control is divided into:

- output control - control of ash slag, additives, process fuel, refractories and other materials coming to production;

- operational control - quality control of materials and process parameters during production;

- acceptance control - product quality control after completion of all technological operations for its manufacture;

Operational control, in turn, is divided into:

- operational, carried out by maintenance personnel;

- technological, carried out by the OTC service and the factory laboratory.

Operational control is carried out on separate, alterations and includes visual inspection of materials quality, control of instruments of the main process equipment. On-line monitoring information ensures maintenance of the process at the specified level, it allows maintenance personnel to control the units in accordance with the requirements of Job Instructions [3].

The process control is carried out mainly in order to constantly collect information and production modes, on the quality of the processed material and finished products. The information obtained is used to develop recommendations for improving the process.

To improve the reliability of the decision on the need to regulate the firing process, operational control can be carried out using control cards that are carriers of statistical information about the state of the process.

OTC and factory laboratory:

- prescribe and carry out random quality checks of finished products by a non-prudent process;

- they draw up documents certifying compliance of the accepted finished products with the established requirements;

- present the finished products to the customer's representative;

- record claims for non-conformity of delivered products by the enterprise [5].

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