【摘要】：鎂還原渣是硅熱還原法煉鎂產(chǎn)生的工業(yè)廢渣，主要組成為SiO2、CaO及MgO。硅熱還原法煉鎂屬于高耗能、高污染行業(yè)，生產(chǎn)1t原鎂需消耗11t白云石、10t左右煤炭、1.2t硅鐵，同時(shí)排放35t CO2氣體和0.2t SO2氣體，產(chǎn)生7t左右鎂還原渣。2014年，我國(guó)原鎂產(chǎn)量87.38萬噸，產(chǎn)生600余萬噸鎂還原渣。 鎂還原渣易粉化，水化溶液顯堿性，嚴(yán)重污染環(huán)境。隨著鎂還原渣的大量排放堆積，不僅造成大量資源流失，而且占用了大量土地資源、破壞了地貌和植被。鎂還原渣隨著雨水的沖淋匯入江河湖泊對(duì)農(nóng)作物和周圍環(huán)境造成了極大的影響，嚴(yán)重危及到人類的身體健康及農(nóng)作物的生長(zhǎng)。同時(shí)，鎂還原渣含有豐富的土壤缺乏的營(yíng)養(yǎng)元素，但不能直接被農(nóng)作物吸收。 本文針對(duì)上述問題，首先對(duì)鎂還原渣制備硅鈣鎂復(fù)合肥的可行性進(jìn)行了研究，然后對(duì)提高鎂還原渣中有效硅的含量進(jìn)行了研究，并采用XRD、SEM、紫外光譜等對(duì)實(shí)驗(yàn)結(jié)果及機(jī)理進(jìn)行了分析，結(jié)果表明： （1）在查閱大量文獻(xiàn)的基礎(chǔ)上，結(jié)合鎂還原渣的理化特性，初步制定了鎂還原渣制備硅鈣鎂復(fù)合肥的工藝流程。 （2）鎂還原渣中含有農(nóng)作物所需的硅鈣鎂元素，其組分能夠滿足硅鈣鎂復(fù)合肥所需的基本元素及含量，，且重金屬元素含量極少，滿足制備硅鈣鎂復(fù)合肥的基本要求。 （3）鎂還原渣加入石英砂焙燒后發(fā)生相變，由反應(yīng)活性較低的Ca2SiO4轉(zhuǎn)化為反應(yīng)活性較高的CaSiO3，有利于用鹽酸溶解。焙燒時(shí)，添加13.53%石英砂，即鎂還原渣中SiO2的含量達(dá)43%時(shí)，焙燒所需的溫度最低，為1460℃。 （4）鎂還原渣酸浸采用的鹽酸濃度為4mol/L時(shí)，鹽酸可使鎂還原渣中的氧化鎂、氧化鈣、氧化鐵全部溶解進(jìn)入溶液。 （5）酸浸渣在溫度為140℃~400℃的焙燒過程中發(fā)生硅酸體系分解為二氧化硅的化學(xué)反應(yīng)過程以及部分無定形二氧化硅的晶格結(jié)構(gòu)被破壞，發(fā)生晶格重構(gòu)的過程。低于140℃時(shí)，酸浸渣僅脫去物理吸附水；高于400℃時(shí)，酸浸渣中無定形二氧化硅晶型轉(zhuǎn)變?yōu)榛瘜W(xué)性質(zhì)穩(wěn)定的二氧化硅晶體。提高酸浸渣有效硅含量的溫度宜控制在140℃~400℃。 （6）正交試驗(yàn)結(jié)果表明：提高有效硅含量的最佳工藝條件為在酸浸渣中加入助劑KOH于200℃溫度下焙燒6h，有效硅含量可達(dá)25.62%，比未處理的酸浸渣有效硅含量(3.62%)提高了6.1倍；比原始鎂還原渣的有效硅含量(4.35%)提高了4.9倍。 （7）利用氨水控制pH可分離濾液中的三價(jià)鐵元素，除鐵率約為76%。
[Abstract]:Magnesium reduction slag is an industrial waste produced by silicon thermal reduction process for magnesium smelting. The main components of magnesium reduction slag are SiO2,CaO and MgO.. Smelting magnesium by silicon thermal reduction method belongs to high energy consumption and high pollution industry. The production of 1t raw magnesium requires 11t dolomite, about 10t coal, 1.2t ferrosilicon, and at the same time releases 35t CO2 gas and 0.2t SO2 gas to produce about 7t mg reduction slag. In 2014, the production of 1t raw magnesium requires 11t dolomite, 10t coal and 1.2t ferrosilicon. The output of raw magnesium in China is eight hundred and seventy three thousand seven hundred and ninety nine tons, and more than 6 million tons of magnesium reduction slag is produced. Magnesium reduction slag is easy to be powdered, hydrated solution is alkaline, and the environment is seriously polluted. With the massive discharge and accumulation of magnesium reduction slag, not only a lot of resources are lost, but also a lot of land resources are taken up, and the landform and vegetation are destroyed. Magnesium reduction residue has caused great influence on crops and surrounding environment with Rain Water's flushing into rivers and lakes, which seriously endangers human health and the growth of crops. At the same time, mg reduction residue contains rich nutrient elements in soil, but can not be directly absorbed by crops. In order to solve the above problems, the feasibility of preparing silicon calcium magnesium compound fertilizer from magnesium reducing slag was studied firstly, and then the increase of available silicon content in magnesium reduction slag was studied, and XRD,SEM, was used to study the feasibility of preparing silicon calcium magnesium compound fertilizer from magnesium reducing slag. The experimental results and mechanism were analyzed by UV spectra. The results showed that: (1) on the basis of consulting a large number of literatures and combining with the physical and chemical properties of magnesium reducing slag, the process of preparing Si-Ca-mg compound fertilizer from mg-reducing slag was preliminarily worked out. (2) the reduced slag contains Si-Ca-mg elements required for crops, its components can meet the basic elements and contents of Si-Ca-mg compound fertilizer, and the content of heavy metal elements is very small, which can meet the basic requirements of preparation of Si-Ca-mg compound fertilizer. (3) after calcination of magnesium reducing slag with quartz sand, the phase transition occurs. The conversion from Ca2SiO4 with low reaction activity to CaSiO3, with higher reaction activity is propitious to dissolve with hydrochloric acid. When adding 13.53% quartz sand, that is, the content of SiO2 in magnesium reducing slag is up to 43%, the minimum calcination temperature is 1460 鈩

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