Research Highlight: Synthesis of High Quality Zeolites from Coal Fly Ash

- Perth, Australia

Dr. Kevin Li (Gang Li), participated in CAA2017 on behalf of the Centre for Energy, School of Mechanical & Chemical Engineering at the University of Western Australia in Perth, Australia. Dr. Li, a returning speaker to Coal Ash Asia, focused his presentation on synthesizing zeolites and necessary related conditions. The below abstract is an overview of the research presented at the conference. For more of Dr. Li’s publications and research, please click the link at the bottom of the abstract.

Abstract: Coal fly ash is a hazardous industrial waste generated from coal combustion and has been considered as an appropriate raw material for zeolite synthesis. In this study, synthesis of a high-quality type A zeolites (471m /g surface area) from fly ash at high conversion rate (98.2% aluminium and 96.5% silicon) has been achieved via a two-step alkali fusion and hydrothermal procedure. Furthermore, in preparation for production in commercials scale, up scaling of the developed synthesis process has been undertaken by using 150L reactor. More importantly, we tracked the migration of elements and quantified their distribution from fly ash to product zeolites and waste water throughout the synthesis process. Metalloid elements including arsenic and selenium, and those with strong amphoteric properties such as molybdenum were found highly mobile and mostly collected in the waste water. In comparison, less than 20% of heavy metal elements of weak amphoteric nature including copper, chromium and lead originated from the fly ash went to the waste water; the rest of these three heavy metals along with almost all of the cadmium, iron and nickel were fixed into the product zeolites. Despite the accumulation of hazardous elements in product zeolites, none of them was leachable under various harsh conditions, ensuring safe applications of such zeolites.

If you are interested in attending Coal Ash Asia 2018 in Shuozhou, please click the "CAA2018" link to register, and our event team will assist you in finding the participation that's right for you.

High Value-added Utilization of Coal-Related Solid Wastes

Dr. Li Hui Quan, a researcher at Chongqing University recently presented at the recent Coal Ash Asia conference in Beijing, China from July 21-24, 2017. The following is the fully translated abstract of their research. For more information, or to contact this researcher please contact the team at Asian Coal Ash Association.

Thermal power generation is an important component of Chinese energy. Shanxi and Inner Mongolia are regarded as the most important energy bases of China. Large amounts of coal gangue, fly ash, desulfurization gypsum and waste denitration catalyst emerge during the processes of coal mining and coal to electricity conversions. This causes terrible environmental problems due to the low waste utilization ratio. Many metal elements such as Al, Li and Ga, enrich coal-related solid wastes. Our team proposes a theoretical system of the mild separation of active components, the coordinated control of mineral structure and the step by step extraction of associated elements.

We found key technologies of the mild activation by proton acid and deep desilication of silicon, the extraction of alumina by sub-molten salt, the selective adsorption and separation of rare metals, and the directional conversion of silicon resources. The technical system of utilizing alumina & silicon, the step by step extraction of associated elements and the clean recycling & carrier generation of waste denitration catalyst are established. A 3000 tons / annual experimental production line of Al-Si composite from high-alumina fly ash by deep desilication process has been built. The Al-Si composite can replace 80 Bauxite sinter. The establishment of this technical system should be standard practice for the new recycling economy pattern of energy output; low emissions and material preparation, forming green, intelligent and cyclic factories with high resources and ecology amalgamation.

India, Institute for Solid Waste Management and Ecological Balance: Fly Ash used in higher performance and energy efficient road construction

Nellore, India - November 29, 2015
Springtime brings flooding to many parts of southern India. Roads made of tar or bitumen are commonly subjected to this flooding, especially near water causeways, as has happened recently between Nellore and Tada. In road construction, cement concrete is superior but is an expensive alternative and therefore cannot be implemented widely. Road construction companies are now experiencing an industry wide change to address this issue. Coal fly ash aggregates are being implemented to improve the quality of roads with increased maneuverability and cost efficiency.

The Institute for Solid Waste Management and Ecological Balance, among other institutes of it’s kind, widely advocate for the utilization of fly ash for road construction. Due to several of its physical and chemical properties, fly ash makes a choice material for road construction. During construction, it settles less than 1%. When properly compacted, fly ash does not exhibit any long-term settlement issues and can be compacted easily while utilizing sufficiently less water than its industry alternatives. With the use of regular construction equipment, it can be mixed with lime to spread along soil providing significant strength unmatched by its competitors.

Its hardening property is useful for road embankment/pavement construction necessary to reduce pressure on retaining walls. When used as filler, expansive properties of soil can be reduced considerably. It stabilizes well with lime and cement, facilitating its use as filler material. The high permeability factor of fly ash eases free drainage during rainfall and afterwards.

Fly ash provides a cost-effective solution, saving approximately 75% of costs. Its use in construction leads to numerous environmental benefits. Notably it helps with the disposal of fly ash, generally viewed as a waste material. And of course, it reduces fossil fuel burning that otherwise would have needed for producing more cement and other road construction materials.