Natural gypsum, natural anhydrite 


Мы поможем в написании ваших работ!



ЗНАЕТЕ ЛИ ВЫ?

Natural gypsum, natural anhydrite



A common ornamental stone is natural gypsum, featuring a wide variety of colors - from white to blue. The low hardness of gypsum makes it easy to produce from his complex sculptural products for the interiors of buildings, as well as use it as a facing material more economical than marble.

In the experiment 4, students compared the construction and gypsum. Building (hemihydrate), gypsum hardens quickly in the air. To slow setting plaster of paris applied a solution of hydrated lime and organic adhesives.

Gypsum binders produced from natural gypsum CaSO4 2H2O or from natural anhydrite - anhydrous calcium sulfate CaSO4 are several types of gypsum binders: plaster, molding plaster, cement gipsovoangidritny, Oestrich-gypsum.

Building plaster is obtained by calcining natural gypsum, followed by grinding to a fine powder. When mixed with the gypsum formed gypsum slurry water, which gradually thickens and becomes a stone-vpdnoe condition. When exposed to moisture set gypsum strength is significantly reduced, so it is used for internal plaster walls, partitions manufacturing, architectural details.

Gypsum binders are obtained by calcining natural gypsum or anhydrite. Deposits of them are available in many areas of the USSR.

Gipsyuvye binders obtained from natural gypsum CaSO4 - 2H2O or natural anhydrite - anhydrous calcium sulfate CaSO4 by firing them. Depending on the firing temperature, a variety of products: building or hemihydrate gypsum CaSO4 - 0 5H2O (calcining temperature 120 - 200 C), cement gipsovoangidritny - anhydrous calcium sulfate CaSO4 (calcining temperature 500 - 700 C) or other products.

Gypsum binders produced from natural gypsum CaSO4 - 2H2O or from natural anhydrite - anhydrous calcium sulfate CaSOi by their firing. Depending on the firing temperature, a variety of products: building or hemihydrate gypsum CaSO4 - 0 5H2O (calcining temperature 120 - 200 C), cement gipsovoangidritny - anhydrous calcium sulfate CaSOi (calcining temperature 500 - 700 C) or other products.

 

The natural anhydrite

The natural anhydrite - rock of sedimentary origin composed mainly of mineral-anhydrous calcium sulfate anhydrite deposits CaSCV typically underlie a layer of gypsum dihydrate. Under the influence of groundwater anhydrite slowly Hydra-tiruetsya and goes into gypsum dihydrate. Therefore anhydrite rarely in nature consists of one of anhydrous calcium sulfate and typically contains up to 5.10% or more dihydrate gypsum.

Anhydrite - rock is denser and stronger than gypsum dihydrate. His true density reaches 2,9- 3,1 g / cm3. Pure white anhydrite, and depending on the impurities it is, as gypsum, has various hues. In nature, anhydrite rarer than gypsum dihydrate. In the USSR, anhydrite deposits are in Bashkiria, in Central Asia and Ukraine.

As starting materials for the production of gypsum and anhydrite binders efficient use of by-products (waste) chemical industry - phosphogypsum, borogipsa, ftorogipsa and others.

This binder is obtained by calcining natural gypsum dihydrate or natural anhydrite at a temperature of 800, followed by grinding to a powder sintering product. It is often called estrihgipsom or hydraulic plaster. As a result of firing of the material obtained anhydrous calcium sulfate white, slightly yellowish or reddish.

Vysokoobzhigovy gypsum (Oestrich-gypsum) is obtained by firing gypsum dihydrate or natural anhydrite at a temperature of 800 - 1000 ° C in shaft or rotary kilns. It was then pulverized. Start setting it should occur no earlier than 2 hours, the end of the setting is not standardized. It is used for masonry and plaster solutions for floors, the manufacture of artificial marble.

The raw material for their production is a natural gypsum dihydrate CaSO4 2H2O, natural anhydrite CaSO4 and waste production of phosphoric acid - phosphogypsum.

Analysis of the solid phase: Chem. and micro, We used natural anhydrite containing 99 62% CaSCU and admixture of ammonium sulfate.

Vysokoobzhigovy plaster (gypsum-Oestrich) was obtained by calcining natural gypsum dihydrate or natural anhydrite at 800 - 1000 and then crushed. When this occurs not only dehydration dihydrate hydrate, but partial decomposition of CaS04 to form free lime. This lime plaster vysokoobzhigovom plays a catalytic role.

Vysokoobzhigovy gypsum, or Oestrich-gypsum is produced by burning natural gypsum or anhydrite in shaft or rotary kilns at 800 - 1000 C, followed by pulverizing the calcine.

Vysokoobzhigovy gypsum, EFI Oestrich-gypsum, produced by the burning of natural gypsum or anhydrite in shaft or rotary kilns at 800 - 1000 C, followed by pulverizing the calcine.

Gypsum binders produced from natural gypsum CaSO4 2H2O or from natural anhydrite - anhydrous calcium sulfate CaSO4 are several types of gypsum binders: plaster, molding plaster, cement gipsovoangidritny, Oestrich-gypsum.

The chemical gypsum

The chemical composition of gypsum. Chemically pure gypsum (CaS04 • 2H20) contains:

Ca - 32.56 <7o; S03 - 46,51%; H20 - 20.93%.

Natural gypsum is usually contaminated with various impurities (sand, limestone, clay, pyrite, etc.). GIPS (from the Greek. Gypsos-chalk, lime) CaSO4 * 2H2O, the mineral water subclass sulfates. It crystallizes in the monoclinic system. Characteristically education plentiful. aggregates of crystals (drusen). It occurs often in the form of solid masses: granular (alabaster) and parallel-columnar or fibrous (selenite). Pure gypsum is colorless and transparent. color changes associated with the presence of fur. impurities and defects in the structure. Hardness of 1.5-2; tight. 2300 kg / m3; p-rimost in water 2.05 g / l at 20 ° C. At ~ 170 ° C passes into hemihydrate CaSO4 * 0,5H2O, further heating - anhydrite CaSO4. Gypsum is precipitated from aqueous p-ditch, rich sulfate salts (for desiccation of sea lagoons and salt lakes). In the zones of sulfide deposits changes released during the interaction. sulfuric acid p-ing with limestone. Deposits of gypsum formed as a result of hydrothermal processes, with anhydrite hydration. Gypsum is also formed in vulkanich. exhalation and soils.

Gypsum is calcium sulfate water. Colouring the mineral is white, pinkish, yellowish-cream. Physical properties: a) a thick crystals and tonkotablitchatye, sometimes very large; characterized by twins - Dovetail, b) dense aggregates, granular, foliated, fibrous (selenite), c) color white, often transparent, and gray and pink from impurities. Dash white, g) Gloss Glass, have differences of silk fiber, etc.) Cleavage very perfect on (010). By cleavage can be removed thin sheets, e) The hardness of 2 on a scale of IPRA, damn nail, g) Density 2.3. Applications. Gypsum is used in the form of cheese and baked. When heated to 120-140 degrees becomes hemihydrate CaSO4 * 0,5H2O (poluobozhzhenny gypsum or plaster) obtained calcined gypsum (stucco) at higher temperatures.

The calcined gypsum is used for plastering, architectural, plaster, in medicine, cement and paper industries. The crude gypsum is used in the manufacture of Portland cement, for sculpturing statues and as a fertilizer. The fibrous gypsum-selenite (especially from the region of the Urals Kungur) - is widely used for handicrafts.

UDDG- gypsum

Gypsum from flue gases is obtained by washing the exhaust gas installation for flue gas desulfitizatsii (UUSDG) and therefore is also called UUSDG-plaster It is formed from the wet, consisting of fine particles of the powder at desulfitizatsii gases (smoke) after combustion of fossil fuels (coal, lignite coal, oil) in large combustion plants, such as plants. Desulfitizatsiya carried out by washing the flue gases by means of lime or limestone slurry. Thus the flue gases contained sulfur dioxide, initially bound to calcium sulfite is converted to calcium sulfite hydrogenic easily soluble and thereafter by atmospheric oxygen is easily oxidized into gypsum. Ca (OH) 2 + SO2 → CaSO3 + H2O CaSO3 + ½ O2 + 2 H2O → CaSO4 · 2H2O

Owing to the flue gas cleaning with SO2 content of 800-1200 mg / m3 is reduced to about 100 mg / m3 in the exhaust gas. In this method, the introduction of large orders combustion plants (Keturah) By only vacuum dewatered gypsum filtration residue moisture of about 10% and, at the same time, freed of unwanted impurities, primarily chlorides. Suitable for the production of gypsum plaster particle structure can be achieved by pressing. From one ton of sulfur in the fuel of 5.4 m obtained gypsum. This method of producing gypsum from flue gas gypsum and cement industries technically possible and is of great economic calcium znachenie.Sulfat other origin produced, for example, in the manufacture of inorganic and organic acids (tartaric, citric, oxalic, boric acid), or during processing sulfate-containing waste water, because of the large content of undesirable impurities and high moisture content is not received still technical value. The ground shards of plaster molds of the ceramic industry are in part used as a setting regulator in cement production.

The main products in Central Europe are:

· Gypsum plaster for machine

· Plasterboard

· For spreading gypsum plaster.

For technical calcium sulfate used and various manufacturing agregaty- · · rotary furnace grate (cloth) · · autoclave digester. These plants can be processed like natural gypsum and gypsum-UUSDG.

UUSDG-gypsum is obtained as a wet fine product with a water content up to 10%. In a rotary kiln or autoclave it can be used without pretreatment, and the grate for gypsum-UUSDG web must first be dried and homogenized. In the future, they will be briefly explained the most important modes of production.



Поделиться:


Последнее изменение этой страницы: 2017-02-05; просмотров: 392; Нарушение авторского права страницы; Мы поможем в написании вашей работы!

infopedia.su Все материалы представленные на сайте исключительно с целью ознакомления читателями и не преследуют коммерческих целей или нарушение авторских прав. Обратная связь - 35.172.231.232 (0.009 с.)