Dai Wencan * Zhu Yujin  Chen Qingbang   Liu Ruyi   Sun Shuiyu
Abstract: lime stone coal and the amount of additive, with an acid leach after calcination, the purity can be obtained more than 99 GB of vanadium pentoxide. Compared with the traditional sodium roasting, this method solves the problem of exhaust gas pollution in production, and can comprehensively utilize resources. It has the advantages of low cost, less pollution, and good economic, environmental and social benefits.
Key words: stone coal calcification roasting additive
The traditional stone coal extraction of vanadium is mostly sodium roasting. The process technology is mature and easy to operate. However, due to the use of salt as a sodiuming agent, a large amount of toxic gases such as C1 2 , HC1 and SO 2 are generated during roasting, causing serious damage to the surrounding environment. The destruction. With the strengthening of environmental protection requirements of the society, this method requires a large amount of funds to remediate the "three wastes" and compensate for the economic losses caused by the surrounding areas, which greatly increases the cost price of the products. In addition, the international vanadium price has fallen sharply in recent years. These companies have stopped production and closed down. Avoiding "three wastes" pollution, increasing the recovery rate of vanadium and reducing production costs are the key to the survival of stone coal. Many research institutes and factories have been studied a lot of new technology, such as an intermediate pickling salt method, low sodium salt method, a roasting method and the like, in particular roasting process, the exhaust gas free of HC1, Cl 2 and other harmful gases, The leaching residue after calcination does not contain sodium salt and is rich in calcium, which is beneficial to comprehensive utilization, such as in the building materials industry. However, the ordinary calcification roasting and vanadium extraction process has certain selectivity to the ore. Generally, the ore roasting has problems such as low conversion rate and high cost, and cannot be used in actual production. Our research on a mine in Guangxi shows that when a certain amount of additives is added during calcification roasting, the conversion rate is significantly improved, and the national standard 99 vanadium pentoxide product can be obtained. This process provides a new and effective method for the development and utilization of vanadium-bearing coal resources in China.
1 test procedure and method
1.1 test materials
Table 1 Analysis results of main chemical components of vanadium ore
ingredient | V 2 O 5 | Ca | Fe | Si | Volatile matter | Ash | radioactivity |
content | 1.47 | 10 | 10 | 0.5 | 2.5 | 97.5 | 23.5 |
1.2 Test reagents, equipment and analytical methods
The test reagents are calcium oxide, SM-1, lime, sulfuric acid, ammonia, N-263, sodium oxide, sodium hydroxide, ammonium chloride. The main test equipment is SMCQΦ180mm×200mm porcelain-lined ball mill , pelletizer (homemade), muffle furnace, constant temperature water bath agitator, SHB-B88 circulating water vacuum mercury , electric blast drying oven, pHS-25 type acidity meter.
Analysis of V 2 O 5 with a capacity of ammonium ferrous sulfate method.
1.3 Test ideas and processes
The low-valent vanadium in stone coal forms calcium metavanadate with calcium oxide during calcination roasting. Calcium metavanadate is insoluble in water but soluble in dilute acid. When acidity is extremely low, it can form hydrated vanadium pentoxide and further Polymerized into polyacid ions. During the acid leaching process, Fe 2+ , Fe 3+ , Ca 2+ , PO 4 3- , Si0 3 2- plasma enters the acidic solution, so it must be purified first; the leaching solution contains low vanadium and needs to be enriched to sink. Vanadium, extracted with N-263 as extractant, and then stripped, then vanadium, dried, and burned, can get the national standard 99 vanadium. The test flow is shown in Figure 1.
[next] 2 test results and analysis
2.1 Effect of calcination conditions on conversion rate
High-temperature heating and calcination of lime in stone coal, low-cost vanadium is converted into high-valent vanadium, and high-valent vanadium is reacted with calcium oxide to form calcium polyvanadate. The calcification roasting reaction is as follows:
V 2 O 5 +O 2 =V 2 O 5 (1)
2V 2 O 4 +O 2 =2V 2 O 5 (2)
V 2 O 5 +V 2 O 3 +4CaO+O 2 =2Ca 2 V 2 O 7 (3)
V 2 O 5 +V 2 O 3 +6CaO+O 2 =2Ca 3 (VO 4 ) 2 (4)
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2.1.1 Effect of lime addition on conversion rate
From the analysis of a mine in Guangxi, it was found that the conversion of lime to the conversion rate and leaching rate of stone coal is a key factor. Because of the strong affinity between lime and feldspar in clay during calcination, it is easy to form vanadium metavanadate. [1] , therefore, if too much calcium salt is added, polymorphic polyvanadate ions easily form insoluble salts with calcium ions during leaching, which reduces the leaching rate, while too little lime is not enough to destroy feldspar. The binding force shows that the conversion rate is the highest when the ratio of ore to lime is about 100:16, and the relationship between the amount of lime added and the conversion rate is shown in Fig. 2.
2.1.2 Effect of the addition amount of SM-1 on the conversion rate
When no additives are added, the conversion rate is only 60%. After testing, we found that when the additive SM-1 was added thereto, the conversion rate was significantly improved, and it could reach 87.62% or more. The test results show that the effect of SM-1 is about 1.3% of the original ore. The relationship between the amount of SM-1 added and the conversion rate is shown in Fig. 3.
2.1.3 Effect of calcination temperature on conversion rate
The calcination calcination temperature is higher than that of the sodium roasting. The temperature is too low to destroy the structure of the ore. However, if the temperature is too high, the calcination is easy to agglomerate, and the vanadium vanadium volatilization loss is caused, and the leachate is difficult to be filtered. Tests have shown that the calcination temperature is highest at around 950 °C. The relationship between conversion and calcination temperature is shown in Figure 4.
[next] 2 . 1 . 4The effect of baking time on conversion rate
The calcination time also has a great influence on the conversion rate. If the time is too short, the conversion is incomplete. If it is too long, it will be agglomerated. The volatilization loss of pentavalent vanadium will increase, and the leachate is difficult to be filtered. It is found that the roasting time is about 3 h. The relationship between conversion and calcination time is shown in Figure 5.
2.2 Effect of acid diffusion conditions on leaching rate
The acid leaching reaction is as follows:
Ca 2 V 2 O 7 +3H 2 SO 4 =2CaSO 4 +(VO 2 ) 2 SO 4 +3H 2 O (1)
Ca 3 (VO 4 ) 2 +4H 2 SO 4 =3CaSO 4 +(VO 2 ) 2 SO 4 +4H 2 O (2)
2VO 2 + +2H 2 O=V 2 O 5 H 2 O+2H + (3)
5 V 2 O 5 H 2 O=H 2 V 10 O 28 4- +4H + +2H 2 O (4)
H 2 V 10 O 28 4- = H V 10 O 28 5- +H + (5)
H V 10 O 28 5- =V 10 O 28 6- +H + (6)
2.2.1 Effect of acidity on leaching rate
If the acidity is too low during acid leaching, it is not conducive to (1), (2) reaction, so that pentavalent vanadium can not be leached; and too high acidity is not conducive to (3), (4), (5) reaction, making pentavalent vanadium It cannot be converted to soluble polyvanadate and cannot be transferred to the filtrate, and there are too many impurities. The experiment found that when the acidity is about 4%, the leaching effect is the best.
2.2.2 Effect of liquid-solid ratio on leaching rate
The liquid-solid ratio plays an important role in the leaching rate of acid leaching. When the liquid-solid ratio is too low, the leaching solution is easily saturated, and it is difficult to filter, and the optimal leaching effect cannot be achieved. If the concentration is too high, the concentration of the leaching solution is too low, so that the enrichment process It is more difficult and wastes acid. The test results show that the leaching effect is best when the liquid-solid ratio is 3-4:1.
2.2.3 Effect of leaching temperature on leaching rate
The leaching temperature has a certain influence on the leaching effect. The leaching rate increases with the increase of temperature between 20 °C and 80 °C, but the heating requires certain equipment and energy consumption. The test found that under normal temperature conditions, the leaching for 12 h at room temperature. The leaching rate can be as high as 85% or more. Therefore, the test is carried out at room temperature and left for 12 hours.
2.3 Extraction and back extraction
The leachate cannot be used directly for vanadium precipitation and needs to be enriched first. We use N-263 as the extractant, octanol as the synergist, and sulfonated kerosene as the extraction solvent [2] . The extraction conditions are 15% N-263+3% octanol +82% sulfonated kerosene, compared with 1:2~3, four-stage countercurrent, organic saturated phase concentration up to 30g/L, pH value is 2~9 The extraction efficiency is good at 5 ° C to 45 ° C, the extraction rate can reach above 99.55%, the concentration of raffinate water is less than 0.0114 g / L; N-235 can also be extracted at pH value of about 2.5, the extraction rate can reach 99.62%, However, the application range of Sichuan is narrow. The saturated organic phase was treated with 1MNH 4 0H+4MNaCl as a stripping agent, and the counter-extraction was carried out by countercurrent extraction. The polyvanadate sodium salt was obtained from the aqueous solution at a concentration of 30 g/L or more, and the stripping rate was over 99.8%.
2.4 vanadium and deamination
The ammonium metavanadate precipitate can be obtained by adding ammonium chloride to the enriched solution: VO 3 - +NH 4 + =NH 4 VO 3 When the NH 4 Cl in the solution reaches saturation, the solubility of NH 4 VO 3 drops sharply. To precipitate ammonium metavanadate. In order to reduce the amount of NH 4 Cl, the addition of a small amount of NaCl during vanadium precipitation can drastically reduce the solubility of NH 4 Cl, achieving the same effect.
The vanadium is carried out at room temperature. In order to facilitate the crystallization of NH 4 VO 3 , the vanadium is stirred for 2~3 hours, then allowed to stand for more than 12h, vacuum dehydrated, dried, and then deaerated at 520 ° C to 550 ° C to obtain V 2 O 5 finished product.
2NH 4 VO 3=2NH 3 ↑+H 2 O↑+V 2 O 5
3 Conclusion
In this experiment, a certain amount of SM-1 was added as an additive, the calcination temperature was 950 ° C, the calcination time was 3 h, and the conversion rate was over 86%. The 4% H 2 SO 4 with liquid-solid ratio of 4:1 was leached at room temperature for 12 h. The leaching rate is above 85%; with N-263 as the extractant, 1MNH 4 OH+4MNaCl as the stripping solution, the extraction rate and stripping rate are both above 99.5%; after the vanadium precipitation, burning can get the national standard 99 V 2 O 5 , the total recovery rate is over 65%.
Resolving pollution in production without end-of-pipe treatment is a new direction and development trend in environmental protection. This experiment focuses on the comprehensive utilization of mineral resources, effectively controlling the “three wastes†in production, rather than managing it after production, overcoming In the past, the calcification roasting conversion rate is low, the economic benefit is poor, etc., which solves the most serious exhaust gas problem in vanadium mine production, and recycles the raffinate water after use, and the waste residue is used in the construction industry, thereby avoiding the environment to the utmost extent. Pollution, the integration of environmental protection and comprehensive utilization of resources, economic benefits and social benefits.
references
1. Jiang Yuhua. Calcification roasting method extracts vanadium pentoxide from stone coal. Hubei Chemical Industry, 1992(1): 20--22
2. Feng Guangxi. N-263 extraction of vanadium. Rare metal,
2. Feng Guangxi. N-263 extraction of vanadium. Rare metal,
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