Silicate material production equipment
What is "silicate materials"?
In 1880 a German scientist W. Michaelis invented a method which was used for production of calcium silicate (lime-and-sand) bricks. By the beginning of the twentieth century there have been five plants producing calcium silicate bricks.
Till 1950s the only type of steam-and-pressure cured silicate materials was calcium silicate bricks and small-size cellular calcium silicate concrete stones. However, thanks to works by Russian scientists, production of large-size calcium silicate concrete products for prefabricated construction. Currently almost all elements of buildings and structures (panels, floor slabs, stair units, etc.) can be made of reinforced calcium silicate concrete which is almost as high-performance as reinforced concrete, and thanks to use of local raw materials and industrial waste it is 15 to 20% cheaper than similar reinforced concrete elements based on portland cement.
Equipment for preparation of raw materials for silicate materials and products
Lime is one of the main components of raw mixture used for pressing products. Different types of crushing and screening equipment are used for primary lime processing. After that lime is fed into rotary burning kilns. Lime is highly reactive to earth silicon during steam treatment. This is why the second main component of raw material mixture is quartz sand or other mineral substances containing earth silicon, for example, slugs, ashes, etc. For the chemical reaction to be intensive enough, the earth silicon component is subjected to fine grinding in ball tubular double-chamber mills. The finer is sand grinding, the higher should be lime percentage in the mixture. Such fillers as non-ground quartz sand, slug, LECA, expanded pearlite, etc.
A raw material mixture containing 90 to 95% of sand, 5 to 10% of ground non-slaked lime and some water is used for modern calcium silicate brick production.
Silicate material production process
The silicate material production process includes the following stages:
1. Raw mixture preparation.
3. Product autoclave treatment.
4. Hold of finished products.
Production of silicate construction materials is based on hydrothermal synthesis of hydrated calcium silicates which is performed in autoclave reactor in saturated water steam medium at 0.8 to 1.3 MPa and 175 to 200°С. Hydrothermal synthesis can alternatively be performed with other autoclaving parameters, use not only steam treatment, but also steam-air mixture or steam-gas mixture or water treatment.
A major scope of works is the process of producing lime for raw mixture in this production. The lime production process includes the following operations: production of lime stone in quarries, its crushing and sizing, burning in rotary kilns, crushing or grinding of lump lime (slaked lime production).
Raw mixture is produced by two methods: drum and silo-based, which are different from each other in terms of lime-and-sand mixture.
An autoclave is a horizontal steel cylinder with covers which are tightly closed at cylinder ends. Bricks are hardened for 8 to 14 h in autoclave in saturated steam atmosphere at 0.8 to 1.3 MPa and 175 to 200°С.
Strength of autoclaved materials is attained as a result of two interacting processes: structure formation caused by synthesis of hydrated calcium silicates, and destruction caused by internal stresses.
To decrease internal stresses, autoclaving is performed using a definite mode including gradual steam pressure growth for 1.5 to 2 h, isothermal holding of products in the autoclave at 175–200°С and 0.8–1.3 MPa for 4–8 h and steam pressure decrease for 2–4 h. After autoclaving for 8–14 h silicate products are produced.
Almost finished products are discharged from autoclave and held for 10 to 15 days for carbonisation of unreacted lime with air carbon dioxide which results in increase of water resistance and strength of the products.
Processing temperature and total power consumption in calcium silicate brick production is significantly lower than in ceramic brick production, so calcium silicate bricks are more cost efficient.
The Samara Strommashina plant manufactures a wide range of equipment used in calcium silicate material production. The Strommashina designs and sells lime production plants, sand mills, sand drying drums, rotary lime kilns, screening and transporting equipment. Our plant's specialists are ready to perform calculations and designing of a production line, and select individual equipment. All equipment complies with high quality standards and is maintained by technical support by the manufacturer plant since design stage till installation and commissioning.