Rod homogenizer – calcium silicate brick production equipment
Calcium silicate brick is a brick consisting of quartz sand and lime. Calcium silicate brick is considered to be an environmentally sound construction material as it contains only natural raw material: sand, water and lime. Colouring pigments are used in brick production in modern construction industry.
Calcium silicate brick is applied in civil and industrial construction, but it can not be used for furnace or fireplace liming, building foundations and other structures which will be often exposed to high temperature and water. Calcium silicate brick advantages are frost resistance, high sound insulation characteristics (it can be used for construction of walls between flats and rooms). In terms of strength calcium silicate brick is comparable with natural stone.
Calcium silicate brick specifications
For the calcium silicate brick to be qualified as a quality product, it shall meet some specification. For example, calcium silicate brick ultimate compression strength shall be no less than 15 to 20 MPa. This parameter is marked with "M" letter with a number with a number (ultimate strength). For example: М110, М125. This characteristic is very important for construction. Another brick characteristic is its average density. It shall not be less than 1300 kg/m. There is also brick frost resistance characteristic. This value is the number of frosting and defrosting cycles which are reliably withstood by calcium silicate brick. The last characteristic is operating temperature: it shall not exceed 550 °C.
Preparation of mixture in a rod attritor homogenizer:
The production is based on autoclave synthesis: 9 portions of quartz sand, 1 portion of air-hardening lime and additives. Then the whole batch is pressed by dry method (thus brick is shaped) and autoclave-treated (exposure to water steam at 170–200 °C at 8–12 atm.). Different pigments can also be added to this mixture so that to obtain calcium silicate bricks of different colours.
The calcium silicate production process, just like any other production process, begins with preliminary processing of all raw components. Preparation of silicate mixture for brick production begins with batching of components which would be raw material composition components. The lime percentage in the batch is determined by calculation at each of enterprises, usually it is about 6 to 8%. If freshly burnt lime is delivered to a production facility, the required lime quantity is reduced, and if lime was stored or contains large quantity of admixtures, the required quantity is increased. Before adding lime to the batch its activity is checked, this process is carried out several times during the whole silicate mixture preparation process. The sand necessary for production is weighed on hopper scales.
Water is required for final mixture preparation: it completes the lime slaking reaction and aids in attaining silicate mixture which is plastic and is easy to shape finished products. In addition, it ensures proper chemical process flows in brick structure during autoclave curing.
Just like volumes of other mixture components, the water quantity in the mixture shall be specified clearly. The exact quantity of water is determined by index of humidity of sand fed to the production facility. It is measured in laboratory conditions. The whole volume of water fed into the mixture is distributed in it in accordance with the following proportion: 2.5% is consumed for lime slaking, 3.5% is consumed for evaporation during lime slaking, and about 7% is used for moistening of the produced stock.
Being fed to the mixer, lime and sand are thoroughly mixed and moistened. A rod attritor homogenizer will be the best type of batching equipment. It is designed for rubbing, homogenisation and additional moistening of the mixture in calcium silicate production. Material is fed into a charging funnel, then is passes through a hollow spigot and is charged into the drum. In the drum the material is homogenised and rubbed by rods, and then it passes through unloading outlets of the drum to the discharging chute and further as intended. The rod attritor homogenizer consists of a drum housing, charging cap, bottom, idler, discharging chute support, charging funnel and a drive. The drum housing interior is lined with rubber plates which protect the housing against wear. To protect against wear, the inner surface of the bottom is lined with high-manganese steel plates. The drum assembly is supported by an idler on the charging side.
Homogenisers are different in terms of their overall dimensions and, consequently, in terms of their capacity. The Samara Strommashina plant manufactures and sells rod homogenisers with capacity of 3 to 100 tons per hour. As distinct from mixer, homogeniser performs several functions simultaneously – it mixes, grinds, equalising the mixture particles in size and additionally moistens the mixture to the required consistency. Such a comprehensive solution allows significant saving of time and power during calcium silicate production.
The finished mixture is fed onto inclined belt conveyor, and via a belt gallery the material is distributed into reactor silos. Lime is slaked, and slaked fine lime is coated with sand particles, and silicate mixture is homogenised additionally in reactor silos. When lime is slaked, heat is released also. It is necessary for normal raw brick pressing mode.
Then the silicate mixture ready for mould pressing is fed by a belt conveyor to a receiving bin of the press from where the dosed quantity of silicate mixture is fed to the press by a conveyor belt. The raw bricks are pressed in the press.
The raw bricks pressed on press moulds are grabbed from the belt conveyor by a gripping mechanism of press placing machine and are placed onto autoclave bogies according to the specified placing mode.
Upon completion of the pressing process the raw bricks are fed into autoclave for steam treatment.
The process flow chart of calcium silicate production can be built using Strommashina brand equipment. The Samara Strommashina plant designs and supplies lime processing equipment (lime burning kilns, crushers and lime grinding mills), sand drying equipment (sand drying drums, rotary sand kilns), screening equipment, conveyors.