The recent market has seen an increased growth of Cenospheres in terms of production and consumption. An Industrial survey conducted to evaluate the market value of Cenosphere concluded that the net worth of Censosphere has increased from 346.8 Million in 2016 to USD 689.2 Million by 2022. The increased demand for Cenopshere is due to its versatile use in the Construction Industry, Paint & Coatings, Oil & Gas, Plastics & Resin etc. Cenospheres are the by-product of coal combustion and are inert, hollow, and lightweight. They are free-flowing aluminosilicate microspheres with low density and high thermal insulation. The average compressive strength of the cenosphere is 3000+ psi and its size varies from 1 to 500 microns.
The utility and processing capacity of coal has never decreased. In fact, 53% of the total installed power plant in India is based on coal. India produces 160 million tons of fly ash every year out of which only 80 million ton is utilized inappropriately. Thus, there was a huge demand to set up processing plants for Cenospheres so that the product can be consumed up to its full strength. One of the biggest production units of Cenosphere in India is in Bhavnagar by PETRA BUILDCARE PRODUCTS. They have a huge plant and machinery with a capacity of 10,000 MT/Annum. They have a team of experienced research professionals to meet the demand of customers. Their cenospheres are processed and graded with the finest quality of crush strength, gravity, and particle size.
As Cenospheres are 35% - 75% lighter than resins and other used minerals thus their production is done on a vast scale in the global market. Cenospheres can enhance the lubricity during higher filling of the product. They have lower shrinkage properties and lower viscosity which makes them versatile. Since Cenospheres are used in various Industries, the manufacturer keeps in mind certain aspects to be considered during the production process. They are as follows:
- Cenospheres must have a particle size between 5 to 500 g/cm3 and a density between 0.45 – 0.55 gms/cc.
- Cenospheres have water absorption capacity thus their moisture content should be less than 0.5%
- Cenospheres should have melting points between 1350 to 1450 degrees Celsius and their shrinkage property must be less than 5%.
The conventional methods to bifurcate cenospheres from coal fly ash are through the sink float method and centrifuge method. However, in recent times Vertical Thermal Flame (VTF) process is used to separate Cenosphere through fly coal ash. In this process two particle sizes of fly ash 63 to 90 µm and 90 to 126 µm are selected to undergo Vertical Thermal Flame (VTF) process. Before going through the process, the particles undergo a pre-treated process that includes spray drying, ball milling, and sieving. A vertical flame is set up as a heat source at a constant height of 7cm to perform the VTF process. A quartz tube is vertically placed on the record stand in which the fly ash particles are treated. The treated particles are cooled down and then collected at the bottom of the funnel. This process is repeated twice to observe the morphological changes in the coal particle through the TM-1000 tabletop Scanning Election Microscope (SEM).
VTF process equipment set up (Image taken from research paper on Production of Cenospheres from Coal Fly Ash through Vertical Thermal Flame (VTF) Process
Then the finest quality of Cenospheres is extracted. Later, to determine the needed density of Cenospheres, special apparatus is used to measure it. All the particles of the Cenosphere are not similar in nature. Some have very fine quality and some are not processed to the finest extent. It also depends upon the quality of coal and the processing plant in which the fly ash has been processed. The cenospheres are extracted according to the need of the industrial purpose. The smooth spherical particles must have a density between the range of 0.2 - 0.8 g/cm3.
The Cenospheres have versatile properties thus they are used in acoustical panels, roofing material, gunite, and goal pieces of equipment. For automotive purposes, it is used in brake pads, composites, trim moldings, and soundproofing materials. In ceramics, Cenospheres are used in high-density polyethylene, extruding PVC flooring, insulation of wires, nylon, and polypropylene.