The Study Of Mechanism Of Lignite Binderless Briquetting

The reserve of lignite is very abundant. Lignite is playing an increasing importantrole in supplying primary energy in developing countries such as China. The highmoisture content of lignite leads to high transportation cost and high carbon dioxideemissions. The value of lignite can be significantly increased through drying andbriquetting. Briquetting can also decrease the spontaneous combustion tendency oflignite. Therefore, drying and binderless briquetting of lignite is critical to theefficient utilization of lignite resources. This thesis studies the character of lignitebinderless briquetting and the mechanistic on binderless briquetting of lignite.Systematic investigation of the operating parameters on the binderless briquettingcharacteristics of HL lignite was studied, and compared with YN lignite. In this studythe effects of operating parameters such as briquetting pressure, coal moisture content,coal particle size, briquetting temperature, and coal chemical structure on compressivestrength of briquettes were studied. The results indicate that compressive strength ofbriquettes increased with increasing operating pressure. The compressive strength ofbriquettes made form YN lignite is higher than HL lignite. There existed an optimummoisture content range14-16%, at which the maximum compressive strength wasachieved. With fraction of the–125μm size increase the briquettes strength was alsoenhanced. Optimum strength was obtained at the briquetting temperature of150°C.The compressive strength of the briquette made from oxidized coal was higher thanraw coal. FTIR analysis showed that the oxygen functional groups such as hydroxyl(–OH), carboxyl (–COOH), and carbonyl (C=O) increased after oxidization, asignificant effect to the briquettes strength due to the ability to form hydrogen bonds.Analyze briquette interaction forces between particles from the perspective ofmicro-scale and meso-scale to study the mechanism of lignite binderless briquetting.In lignite binderless briquetting process, van der Waals forces, hydrogen bondingforce, long-range force, capillary force and liquid bridge force among the particles ofcoal play key role in binderless briquetting. Different types of force to the coalparticles have different levels of contribution on binderless briquetting. Therelationship of forces among coal particles along with the change of moisture contentis same with briquettes’ macroscopic strength with water content change rule, thereare the best moisture value range. Analysis the reasons of the destroy of briquettesfrom different dimensions. According to Griffith theory and Weibull theory,established the relationship of micro briquette strength and briquettes macroscopicstrength.