Regeneration method of foundry waste sand thermal plasma

Abstract

The invention discloses a reclaiming method for cast waste sand hot plasmas. The reclaiming method includes the technical processes of waste sand pretreatment, hot plasma roasting, cooling and screening. According to plasma roasting, a resin film, an inorganic film and harmful impurities of metallic oxides such as sodium and potassium on the surface of waste sand are removed under the action of the high temperature, thermal shocks and surface melting of a hot plasma torch, and therefore high-performance cast reclaimed sand is obtained. The average temperature of the hot plasma torch is 2000-4500 DEG C, the surface temperature of the waste sand is 1000-3000 DEG C, and the heating time of the waste sand is 5-60 minutes. The reclaiming recycling rate of the reclaiming method is larger than or equal to 85%, the performance index of the reclaimed sand is superior than that of isogenesis new sand and reclaimed sand obtained through other reclaiming methods, the reclaimed sand can be completely recycled and reused through a casting plant, the tail gas exhaust index is far lower than the exhaust standard of China, Europe and America, the amount of generated fine powder is greatly reduced, and due to the high temperature and ionization action, the reclaimed sand is free of pollution and safe to the environment and can be directly used as the recycled building material.

Description

technical field [0001] The invention relates to a recycling method for foundry waste sand. Background technique [0002] With the development of my country's foundry industry, the average annual output of castings in my country has exceeded 45 million tons from 2012 to 2014, accounting for more than 40% of the global casting output. The proportion of sand regeneration and recycling is less than 10%, and a large amount of foundry waste sand is mainly disposed of in landfill or casual disposal, which on the one hand is a serious waste of natural resources. Potassium and other metal oxides and other harmful substances will cause great hidden dangers to the environment if they are disposed of in landfill or casually discarded, so it is imperative to recycle waste foundry sand. [0003] In recent years, my country's foundry enterprises and scientific research units have carried out a large number of waste sand regeneration work, and the regeneration of waste sand has achieved cert...

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Problems solved by technology

[0002] With the development of my country's foundry industry, the average annual output of castings in my country has exceeded 45 million tons from 2012 to 2014, accounting for more than 40% of the global casting output. The proportion of sand regeneration and recycling is less than 10%, and a large amount of foundry waste sand is mainly disposed of in landfill or casual disposal, which on the one hand is a serious waste of natural resources. Potassium and other metal oxides and other harmful substances will cause great hidden dangers to the environment if they are disposed of in landfill or casually discarded, so it is imperative to recycle waste foundry sand

[0004] Although natural gas (LNG) roasting at 600-900 °C combined with dry mechanical regeneration method can obtain reclaimed sand close to the quality level of original sand, but due to the low roasting temperature, it cannot destroy the dioxin precursors contained in the waste foundry sand. The most stringent tail gas emission standards under my country's new environmental protection regulations must add cumbersome tail gas treatment systems such as RTO, RCO, DBD, etc., which not only increases regeneration investment and operating costs, but also organic gas VOCs (phenols, aldehydes, esters, etc.) , cyanides, high-boiling hydrocarbons, alcohols, hydrocarbons, etc.) emission indicators are also difficult to meet the most stringent domestic standard of 20mg / m³

In addition, in order to ensure the quality of regenerated sand, it is necessary to add dry mechanical regeneration processes such as centrifugation and grinding in the follow-up, resulting in a regeneration recovery rate of less than 70% (accounting for the total amount of waste sand, 85% can be achieved by simple LNG thermal regeneration), and 25% A large amount of fine powder above needs to be landfilled or ceramicized for reuse, which is unfavorable to the cost and reuse of foundry waste sand regeneration

[0005] Guangxi Yulin Yuchai Industrial Chemical Co., Ltd. applied for the invention patent of "Method and Equipment for Recycling Waste Sand Foundry" in 2013, application number: 201310281323.8, and proposed a method for recycling waste sand foundry, including the following steps: waste sand Pre-treatment: the original waste sand is removed by a closed grid unloader to remove waste and old garbage, then through a suspended magnetic separator to remove scrap iron, then through a linear vibrating screen to remove large-grained waste sand, and finally through a through-type magnetic separator to remove waste Iron filings are stored in the waste sand storage tank; this method is a wet scrubbing combined with heat method, and the regenerated sand product obtained by drying and regeneration reaches or is better than the original sand quality level, although the regeneration recovery rate reaches 80%, there is no tail gas Emission problem, but wet regeneration requires more complicated water circulation treatment system and advanced sludge treatment and reuse process. Less than 1 / 3 of the sludge is reused by the foundry, and the remaining 2 / 3 can only be used by brick factories and other low-value uses Or ceramic treatment, which increases the regeneration process and cost burden

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