lightweight expanded clay aggregate (leca) production line | fote machinery
expanded clay aggregate or expanded clay aggregate (LECA or ECA), also called ceramic
pellet, is one of the most popular lightweight aggregate made by sintering clay
in a rotary kiln to about 1200C.
Current lightweight expanded clay aggregate
market data shows that the market of LECA has shifted its direction from
traditional construction engineering to craft products and horticultural
The production materials of traditional materials
such as clay and shale have been replaced by industrial waste residue and silt
and the development trend of machinery has evolved into a large scale and
In the following future, while focusing on
economic development, the LECA suppliers should pay attention to reduce
pollution and resource waste to ensure the rapid and stable development of
There are usually two types of LECA
manufacturing techniques: sintering and sintering-expanded. The difference
between them is in the process of sintering-expanded, the aggregate expands by
a larger volume.
Jaw crusher is the primary machine which is
used for coarse, medium and fine crushing of various ores and rocks with a
comprehensive strength between 147 and 245 MPa, and processes them into small
pieces of 10-350 mm.
Advantages: In recent years, FTM has
specially developed a powerful jaw crusher to meet the needs of crushing
high-strength and high-hardness micro-carbon ferrochrome in metallurgical,
mining, construction and other industrial sectors.
The ball mill is the key equipment for grinding
the material after crushing. Ball mill is widely used in the production of cement,
silicate products, new building materials, refractory materials, fertilizers,
black and non-ferrous metal dressings and glass ceramics, dry or wet grinding
of various ores and other grindable materials.
The granulation disc adopts an overall circular
arc structure, and the granulation rate can reach 93% or more. The granulation
tray has three discharge ports, which facilitate intermittent production
operations, greatly reducing labor intensity and improving labor efficiency.
The dryer is mainly used for drying certain
moisture or particle size materials of mineral processing, building materials,
metallurgy and chemical industry, and the equipment operation is simple and
Advantages: The equipment has an
application range and it also can be customized. It has low noise, high
efficiency and environmental protection, advanced lubrication system, long
service life, small installation inclination angle and good screening effect.
The single-cylinder cooler is one of the
important equipment in the rotary kiln system. The clinker from the rotary kiln
(1000-1200 C) is fully exchanged with the air through the cylinder rotating
belt to cool the material to below 200 C, at the same time improve clinker
quality and grindability.
Fote Mining Machinery (FTM) located in
Henan is one of the most famous mining machinery suppliers, which is committed
to manufacturing mining machines of green building materials, and provides
intelligent mining products and advanced solutions.
FTM is a professional supplier of
lightweight expanded clay aggregate machinery and equipment, and all the equipment
has high quality and significant advantages, and the prices are also very reasonable.
In a word, Fote Mining Machinery is a good
choice for LECA suppliers to choose lightweight expanded clay aggregate
machinery manufacturers. Welcome to consult us if you have any requirements
about the LECA production line.
As a leading mining machinery manufacturer and exporter in China, we are always here to provide you with high quality products and better services. Welcome to contact us through one of the following ways or visit our company and factories.
Based on the high quality and complete after-sales service, our products have been exported to more than 120 countries and regions. Fote Machinery has been the choice of more than 200,000 customers.
FEECO is a leading manufacturer of highly engineered, custom rotary kilns for processing solids. Our high temperature kilns have earned a reputation for their durability, efficiency, and longevity. We offer both direct- and indirect-fired units.
Rotary kilns work by processing material in a rotating drum at high temperatures for a specified retention time to cause a physical change or chemical reaction in the material being processed. The kiln is set at a slight slope to assist in moving material through the drum.
Direct-fired kilns utilize direct contact between the material and process gas to efficiently process the material. Combustion can occur in a combustion chamber to avoid direct flame radiation, or the flame can be directed down the length of the kiln.
All FEECO equipment and process systems can be outfitted with the latest in automation controls from Rockwell Automation. The unique combination of proprietary Rockwell Automation controls and software, combined with our extensive experience in process design and enhancements with hundreds of materials provides an unparalleled experience for customers seeking innovative process solutions and equipment.
Indirect-fired kilns are used for various processing applications, such as when processing must occur in an inert environment, when working with finely divided solids, or when the processing environment must be tightly controlled.
Calcination refers to the process of heating a material to a temperature that will cause chemical dissociation (chemical separation). This process is used frequently in the creation of inorganic materials, for example, the dissociation of calcium carbonate to create calcium oxide and carbon dioxide.
Thermal desorption is also a separation process. This process uses heat to drive off a volatile component, such as a pesticide, from an inorganic mineral, such as sand. The component is vaporized at the increased temperature, causing a separation without combustion. In some cases, an indirect rotary kiln would be best for this application, because the volatile chemicals may be combustible. The indirect kiln will supply the heat for desorption, without the material coming into direct contact with the flame.
Organic combustion refers to the treatment of organic wastes with the intent of reducing mass and volume. Organic waste is treated in the kiln, leaving behind an ash with considerably less mass and volume. This allows for more efficient and effective deposit of waste materials into landfills.
Sintering is the process of heating a raw material to the point just before melting. This increases the strength of the material, and is commonly used in the proppant industry, where sand or ceramic materials are made stronger.
Heat setting involves bonding a heat resistant core mineral with another, less heat resistant coating material. Unlike an unheated coating process, here, a rotary kiln heats the coating material to just below liquefaction point, allowing it to coat the heat resistant core more evenly and more securely. This process is commonly seen in the manufacture of roofing granules, where a mineral such as granite is coated with a colored pigment, producing a product that is both durable and aesthetically pleasing.
Reduction roasting is the removal of oxygen from a component of an ore usually by using carbon monoxide (CO). The CO is typically supplied by mixing a carbonaceous material such as coal or coke with the ore or by feeding it separately. Examples are the reduction roasting of a hematite containing material to produce magnetite that can be magnetically separated. In the Waelz process, zinc oxide in steel mill wastes is reduced to metallic zinc and volatilized for recovery in the off-gas system.
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The advantages to a FEECO rotary kiln are that it is built to the highest quality standards and is backed by over 60 years of process design experience. The FEECO Innovation Center offers batch and pilot scale kilns that can simulate conditions in continuous commercial rotary kilns, allowing our customers to test small samples of material under various process conditions, as well as part of a continuous process. With options in both co-current and counter-current flow, and direct or indirect configurations, the FEECO test kilns offer a variety of options to suit your thermal testing needs. We also offer support equipment such as a combustion chamber, afterburner, baghouse, and wet scrubber for testing.
STALITE's strong end-use products begin with the production processing of our raw material slate. Slate possesses the high strength and lasting durability necessary to create a superior lightweight aggregate. Unlike shale or clay deposits formed from mineral or organic sediments, the slate used in STALITE was formed from volcanic ash. This volcanic ejecta, free of impurities which were burned away at very high temperatures, was deposited in a wet environment and compressed under extreme pressures for millions of years.
The resulting material is an extraordinary slate deposit whose unique properties contribute to making STALITE the very finest high performance lightweight aggregate in the world. In the foothills of NC, east of Charlotte, NC is the only known source of slate that is being used as a raw material for rotary kiln expanded slate lightweight aggregate
Several types of raw material can be expanded in a rotary kiln to produce structural lightweight aggregates. These materials can be classified as clays, shales and slates. The primary difference in these three classifications of materials is their strength, density and absorption. Clays and shales are naturally softer, and less dense than slate. After processing in a rotary kiln, clays and shales have 24-hour absorptions ranging between 15% and 30% (compared to 6% for STALITE). During mixing or pumping concrete, clay and shale absorptions can be as high as 50% (compared to 9% for STALITE). Due to the higher material strength of STALITE slate aggregate, higher strength concretes can be achieved with lower cement contents allowing for more economical concrete mixes. BEGIN STRONGER = END STRONGER.
The raw material mined by STALITE is an argillite slate located in a geological area known as the Tillery Formation. It is a thinly laminated, gray, fine-grained siltstone, composed of clastic (transported) rock fragments. The Tillery Formation is a complex system that must be selectively mined in order to separate the desirable product from the non-desirable to manufacture a high quality expanded slate aggregate.
The geologic history of the Tillery Formation began 550 million years ago in the Cambrian Period, approximately 330 million years before dinosaurs. Rock fragments of volcanic ash origin were deposited in a water environment (sedimentation) and later solidified into solid rock (lithification). Consequent burial and tectonic pressure then changed (metamorphosed) the rock into argillite slate. Along with the deposition of the volcanic ash was an occasional ash (debris) flow or gravitational mud-type flow into the same deposition basin. Additional layers, consisting of volcanic tuff with high calcite concentrations, formed within the system. Subsequent millions of years of geologic forces caused the alternating layers of material to fold and fault, causing disorder to the once ordered, layered system. Along with this disorder came diabase dike rock intrusions of Triassic-Jurassic age (about 180-220 million years ago), which caused additional rock structures of vertical emplacement that further complicated the system.
The calcareous tuff impedes the bloating process of lightweight aggregate production. At 2,000 degrees F (1,000 degrees C), the calcite simply calcines. At high temperatures of over 2,200 degrees F (1,200 degrees C),diabase rock (specific gravity of 3.0) melts to a glassy type of rock with no specific gravity change. Because this high specific gravity creates havoc on a desired lightweight specific gravity material, it should be avoided totally. The only way to avoid this material is through a process of selective mining. Extensive core drilling must be performed along with microscopic, chemical, and laboratory test bloating of the core in order to map the subsurface material and identify desirable versus non-desirable aggregate. Computer software must then be used to identify high-quality cross-sections of desirable versus non-desirable rock zones. Mining computer software can then be used to design the selective mining sequence. A modern fractionation plant with controllable radial stackers and feed systems then crushes the high-quality bloatable material to optimum size for processing and separates it to be conveyed to the raw feed storage silo.
STALITEuses a 3-D mapping process as a guide for selective mining of the slate that is best suited for the production of STALITE. The quarrys location allows the raw slate to be efficiently conveyed directly to the rotary kilns.STALITEhas confirmed reserves of raw material to supply our needs throughout the 21st century.
After blasting, pit loaders are used to load the blasted rocks into haul trucks. Haul trucks move the rocks from the pit to the primary crusher at the processing plant. The primary crusher breaks the large rocks from the pit into smaller pieces. The primary crusher can crush between 300 and 2,000 tons per hour. As the rocks pass through the crushers, they are moved around the processing plant on conveyor belts.
After crushing, rocks are broken down to smaller sizes and go through a screening process. By using various size screens, the crushed rock can be separated by size. Some screens are larger and they allow the bigger rocks to pass through. STALITEs process requires rocks be crushed and screened several times before they are put in a stockpile with other rocks the same size.
After being crushed to an optimum size for processing, the raw slate is fed into STALITE'spatented pre-heater. The pre-heater conditions the rock before entering the rotary kiln. The pre-heater slowly heats the rock as it comes down to the kiln. The kiln is fueled by coal that is pulverized and blown into the kiln. In the kiln, the slate is heated to approximately 2,200 degrees Fahrenheit. As the slate approaches this temperature it becomes almost molten, like lava. In this molten state, the rock is plastic enough to allow gases to evolve, forming small, unconnected voids uniformly throughout its mass. The expanded rock then falls to the cooler, where it is air-cooled. When the expanded slate is cooled, the cells remain allowing for its low unit weight.
Expanded slate aggregate is produced by the rotary kiln method. This discussion describes one specific lightweight aggregate manufacturing plant. Other rotary kiln process facilities are similar, but may have variations from the process described herein.
The rotary kiln is a long tube that rotates on large bearings. The kiln is lined with insulation and refractory materials. Raw slate is fed from the storage silos into patented pre-heaters that allow the rock to heat up at a moderate rate. It then enters the upper end of the kiln where it slowly revolves and moves toward the burn zone near the lower end of the kiln. The burn zone reaches temperatures in excess of 2,200 degrees F (1,200 degrees C).
STALITE uses high BTU, low sulfur coal and natural gas for its heat sources. Some lightweight aggregate production facilities use only natural gas, while others supplement these traditional energy sources by burning hazardous wastes. In the burn zone of the rotary kiln, the slate becomes sufficiently plastic to allow expanding gases to form masses of small, unconnected cells. As the expanded slate cools, these cells remain, giving the aggregate its low unit weight and low absorption. The expanded material, called clinker at this point, leaves the lower end of the kiln and enters a forced-air cooling system. This cooling process reduces the chance that the aggregate will crystallize as can happen in water-cooled systems where the very hot expanded material is dropped directly into a pit filled with cold water.
From the cooler, the clinker is conveyed to a classification area. Here the material is crushed and screened to various size fractions. These different size fractions are kept separate until, by means of an automatically controlled blending system, specified gradations are produced for various applications. After blending, actual moisture content is automatically adjusted to a predetermined level.
The expanded slate aggregate is then tested for proper gradation, moisture content, specific gravity and unit weight. After testing is completed, the expanded slate aggregate is stored or conveyed directly to trucks or railcars for shipment.
Prior to loading, trucks and railcars must be inspected for cleanliness and washed when needed. A particular procedure is carefully followed when loading material from either the storage silos or the stockpiles to ensure that material consistency is maintained. A rigid quality control and testing program confirms compliance with the customer's specified needs.
The cooled, expanded slate is conveyed to the classification area. There it is crushed and screened into different size fractions. After crushing, the different size fractions are stored in separate silos until they are blended into standard or custom gradation blends.
Environmentally Conscious STALITE uses high BTU, low sulfur coal for its heat source.Fly ash and STALITE pozzolan are collected in high efficiency bag houses supplied by the StaClean Corporation.STALITE uses lime slurry misting and caustic systems to constantly scrub CO2 and other gases out of our air streams.
These products are sold and recycled to concrete product companies as supplemental cementitious materials. STALITE uses state-of-the-art Controlled Emissions Monitors (CEM) and is continuously monitored by the North Carolina Department of Environmental Quality.
multitask kiln: several ideas to use your kiln during production downtime and also reduce costs - dynamis
As many applications of rotary kilns are similar in terms of temperatures, pressures and flows, it is possible that the same kiln can be used for the production of different materials. For this reason, there are several cases of cement kilns that have been modified to be used on a new mission, such as lime production, ores calcining or calcined clay production.
There are numerous examples
of modified cement kilns in the industry, but only a few with easily reversible modifications or that fit
to a wide range of processes. This leads us to some questions: Nowadays, why use
single product processing kilns? Why not produce different products according
to market demands? Why not use the periods when clinker silos are full for drying
cement mill additives such as slag, gypsum and clay?
We know that there are
several reasons why most clinker kilns produce only this material, such as operational
efficiency and modification costs, but we are convinced that it is possible to
reach the production flexibility that todays market requests with low costs
and high efficiency, through multitask kilns.
FLEXIBILITY: this is the biggest
advantage of a multitask kiln. By having several different applications with
few reversible changes in configurations or equipment, a multitask kiln can adapt
its production to a specific period of the year, or to a market opportunity. In
a scenario of low cement demand, such as the one we are experiencing, your
clinker kiln could be used, for example, to:
Obviously not all materials
can be dried, calcined or processed in a particular clinker kiln, as the
flexibility of a kiln is limited by minimum and maximum allowed values of air
and fuel flows and material temperatures and grain size, among other factors.
Thus, it is necessary to
carry out an initial study to verify the characteristics of lines main
equipment, obtain current operating parameters and determine the future ones
and, finally, identify the main bottlenecks and limitations for using the
clinker kiln in another process. Usually, the main limitations for kiln
Dynamis, with its technical
team of multidisciplinary and highly experienced engineers in various industry
segments, can assist you from an initial technical-financial feasibility study
to the mechanical and electrical detailing of the solution, in addition to
supplying all necessary equipment for kiln flexibilization. All these activities
are carried out within deadlines that meet the fast market changes, always allowing
a quick return to clinker production when necessary.
rotary kilns in expanded clay aggregate production
Expanded clay aggregates, also called exclay, or lightweight expanded clay aggregates (LECA), are a beneficial material in a growing number of industries most notably construction and horticulture, with water treatment and filtration applications likely next in line.
The unique structure and physical properties of expanded clay, which lend use to a variety of applications, are produced as a result of carefully controlled thermal treatment (typically referred to as either calcination or sintering) carried out in a rotary kiln.
Clays are typically crushed, agglomerated and/or dried as a means of feedstock preparation, though this process can vary. Extrusion seems to be the preferred method of agglomeration in this setting, but other methods may also be explored.
While feedstock preparation is essential in producing expanded clay aggregates, the key process behind expanded clay aggregates is a thermal treatment. This thermal treatment is where the expanded clay aggregate name is derived from, as it is used to physically expand the clay particles.
There are various terms to describe such thermal treatment techniques. In this setting, the treatment is typically referred to as either calcination or sintering. While the two terms are often used interchangeably, its important to note that they technically refer to different techniques. Since sintering technically happens at much higher temperatures, for the purposes of this article, well refer to it as calcination, though in some cases expanded aggregates may be truly sintered.
In the case of expanded clay, calcination has an essential role in creating a product that can serve as an expanded clay aggregate. The temperature, typically between 1050 C and 1250 C, causes gases to be released as a result of various changes within the material, including the decomposition and reduction of ferric oxides, the combustion of organics, the blowing of entrapped water, and the decomposition of carbonates.
This release of gases causes a physical expansion, or bloating of the clay, leaving it with a lower density, higher porosity, and a much greater surface area within the material, along with a hardened surface all characteristics that make it ideal for use as a lightweight aggregate.
As with most materials, various factors must be optimized in the production process in order to achieve the best results. An extensive study conducted on three different clay sources found that while a number of factors are important, the process parameters of the expansion process that are perhaps most critical include:4
Processing temperature is the most influential factor in the expansion process. Expansion was found to increase along with temperature, to just below the specific clays melting point (the melting point varies depending on the type of clay).
Pellet or agglomerate size was also found to have an effect on expansion, with expansion increasing in tandem with pellet size. Consequently, a decrease in pellet size correlates with less expansion.
Rotary kilns are available in either a direct- or indirect-fired configuration and are often referred to as a calciner. The production of expanded clay aggregates is typically carried out in a direct-fired kiln, in which the clay and products of combustion are in direct contact with each other.
Construction is the most common application for LECA. Expanded clay can be found in all manner of concrete, filler, and structural components of the construction and building materials industry. Benefits it can offer in this setting include:
The use of LECA in horticulture is a comparatively new application but remains a growing field. Expanded clay aggregates can promote a variety of benefits under various growing conditions. This includes:
As with many thermal processing endeavors, testing is a critical element of a successful clay expansion operation. Research has shown that the ideal process parameters are unique to the type of clay being processed.
Testing clay samples at batch-scale to gather initial process data is the first step in a successful testing program. Data gathered during batch testing can then be used to scale up testing to continuous, pilot-scale runs. Testing can also be used to aid in finding a balance between ideal process parameters and what is economically feasible.
The FEECO Innovation Center offers a variety of test kilns for conducting both batch and pilot testing. Kilns can be configured with various support equipment to simulate different conditions of commercial operation.
The Innovation Centers automation control system collects a broad range of data, which can be trended and analyzed in real time for unmatched process transparency. This includes data points such as feed and product rates, relevant temperature readings, system pressures, gas sampling and analysis, and more.
Expanded clay aggregates are a beneficial material in the construction industry, with applications in horticulture and water treatment growing. Rotary kilns are the device of choice for processing clay agglomerates into expanded clay aggregates.
The ability to optimize process parameters to produce a superior expanded clay product is critical to the success of an operation. FEECO offers extensive testing capabilities for those in the process and product development stages. We then use the data gathered during testing to engineer and manufacture custom, commercial-scale rotary kilns of the highest quality. For more information on our capabilities around expanded clay aggregates, contact us today!
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d-pozzolan calcined clay technology: the only one approved in the worlds largest calcined clay production plant - dynamis
IIn April 2019, the Cementos Argos new calcined clay production plant started its operation. Located at the Rioclaro site, in Colombia, this line was designed following the D-Pozzolan technology, which involves several patents of Dynamis. Other than the pyroprocessing, the most visible part of the plant, Dynamis took part of the entire project development activities, in close partnership with Argos. These activities started with initial laboratory tests, that developed into an engineering project and culminated in equipment supply and technical assistance during erection and start-up.
The most impressive point to stand out from this plant is the color changing technology. It is very interesting to see the reddish clay being fed to the dryer, changing its color inside the rotary kiln and finally leaving the cooler as grey calcined clay. This color-change technology is part of the D-Pozzolan Technology, a complete solution carefully designed by Dynamis to meet the specific needs of the clay calcination process. The grey color of the calcined clay allows high substitution rates and important reductions in the clinker to cement ratio, in the cost and also in the CO2 footprint of the cement produced.
The quarry is connected to the industrial plant by
trucks. The raw clay received at the plant is processed by deagglomerators
which are responsible for obtaining the ideal clay grainsizes for the D-FDryer
(the Dynamis flash drying system). Inside the dryer, the solid particles are
dragged by the cocurrent hot gas stream, making it possible to obtain high heat
and mass transfer coefficients in a relatively small equipment and with small
footprint. The preheated and dried material dragged by the gas stream is
separated from the flue gases by a set of cyclones.
The hot gas for material drying comes from the kiln
and is complemented by the D-HotGas, the Dynamis hot gas generator designed
for 100% coal or petcoke. It is important to have the correct gas flow at the
drying system to enable clay particles dragging. Furthermore, the hot gas
generator complements the thermal load for material drying.
Dynamis D-Pozzolan technology, with the application
of a D-Gasifier that operates with solid fuel (coal or petcoke), provides the
very tight control of temperature and oxygen content throughout the kiln, which
are fundamental points for obtaining thermally activated clay, for assuring its
color change and for achieving the desired quality. The
D-Gasifer is patented by Dynamis.
The product from the kiln is forwarded to a rotary cooler. As for the kiln and the dryer, it is important that material cooling is carried out in a controlled atmosphere so that the gray color obtained at previous stages does not reverse. Thus, the airflow for cooling is minimized. Lifters installed inside the cooler maximize the heat exchange coefficients between air and material. But the cooling process must be complemented by water. Dynamis installed water channels over the cooler promoting the formation of a water film on the shell. Thus, the low temperature of the calcined clay at cooler outlet is obtained by both the airflow inside the rotary drum and the flow of water outside the cooler shell. Finally, if any unexpected condition occurs and the calcined clay temperature exceeds the maximum set value, emergency lances spray water inside the cooler.
All these innovations applied in the largest calcined clay production plant in the world constitute Dynamis D-Pozzolan Technology, which is the result of intense search for innovation, partnerships with renowned players, intense investments, solid studies and large efforts of high-skilled engineers, prepared to solve problems and deliver results.