Study on the Recycling of Stone Processing Slurry for Environment Friendly Fertilizer

摘要

The quarry resources on earth are form billions ago, due to colorful grain, gloss and shinning, hard abrasion resistance and fire proof, there are mined massively and being used in building and coverage material. The stone used for construction have the final usage ratio of the building material is lesser than 25% because of mining, cutting, and processing procedure, with the wastage of 75% of natural resource. Being the primary stone processing region, the derivation of serpentine scrape, waste edge material and water content sludge is about 150,000 tons every in Taiwan. Excepted portion of serpentine scrape are crushed into particle of 5mm in diameter, serving as slag forming agent in steel refinery, the sludge generated from cutting and grinding are unable to be recycle resource. In order to precious the everlasting operation of earth mine reservation, this study adopts the sludge derivate from serpentine to recycle into silicone magnesium fertilizer.Serpentine formed by supper alkaline stone via metamorphism, the chemical composition is Mg_3SiO_5(OH)_4, containing ferric, boron, manganese, zinc, copper, molybdenum, cobalt and several dozen trace element which are essential for growth of plants. Among them the percentage of MgO and SiO_2 are 36-39% and 39～42% in weight. The rich magnesium element is the trace element required for formation of chlorophyll essential for growth of plants. But the plant is unable to absorb it in the form of natural stone. This study uses hydrogen hydrofluoric to destroy the crystalline structure of the SiO_2, and then gone through pelletization and firing in electrical open hearth. Precisely control firing temperature, resource recycle the serpentine sludge, transforming the MgO structure in the serpentine into alkaline fertilizer with Solubility in Citric acid. This study fond that the Solubility in Citric acid of MgO in serpentine is temperature sensitive. Dehydrate at 450 □, the dissolvability increase accompanying temperature rise; and dissolvability decrease rapidly accompanying temperature rise after reaching 850□, and absolute no dissolvability while exceeding 1000□. This study used conditions of sludge fineness at mesh #200 and more, temperature 800□±2□, with firing period of 90min, the maximum transformation of MgO to the form of MgO Soluble in Citric acid which absorbable by the plants reached 14.1%; under the same firing condition, the more fineness the MgO, the higher the dissolvability; and the palletize diameter is between 2mm to 8mm, there is no significant difference in dissolvability. The dissolvability is reduce to 35% at a firing time of lesser than 60min. There is no significant increased dissolvability for prolong firing time while firing time exceeded 90min. The Ph value of the fertilizer product obtained form resource study is lay between 9～10, meet the ROC CNS 4-01 fertilize requirement standard in term of agricultural crop soil improvement and plant fertilizer utility rate. And these resource fertilizers belong to non-water soluble fertilizer product, which dissolve and dissolve in case of citric acid release by the root of the plant. Thus it will not dissolve in rain water while applied in the soil, cause no pollution and consequent hyper-nutrition, is a long effect fertilizer which cope with the meaning of environment protection.