偏钒酸钠氢还原制备钒氧化物清洁冶金新过程的应用基础研究

The proposed research focuses on high concentration ammonia nitrogen wastewater containing vanadium and chromium in the existing industrial vanadium precipitaiton process of vanadium metallurgy, the key problem which restricts the development of the vanadium industry. NaVO3 as raw material obtained before the industrial vanadium precipitation process, is reduced by low temperature hydrogen reduction new process, instead of traditional ammonia vanadate precipitaion process, avoiding the high concentration ammonia nitrogen wastewater.. With the new subject, key scientific problems- valence, strucuture and chemical composition changes of reduction products of NaVO3 reduction process and deep removal of Na and valence change of vanadium of the reduction products in the hydrolysis- are further researched, elucidating selective reduction of different valence states of sodium vanadates Na2V2O5 or NaVO2, revealing strengthening hydrolysis mechanism in the oxidation hydrolysis or mechanical activation-pressurized hydrolysis, and mechanism of vanadium crystallization - removing impurities by adding Ca in the vanadium - containing NaOH solution as byproduct, achieving V2O5 / V2O3 preparation and recycling of NaOH containing vanadium. . This proposal forms the NaVO3 low temperature selective hydrogen reduction - enhanced hydrolysis removing Na - alkali solution efficient circulation - vanadium oxide product engineering and vanadium - containing alkali solution circulation new process, benefits to realizing zero emission of the wastewater, provides theoretical basis for vanadium oxide clean metallurgy new process with economy - environment dual effect.

本项目面向现行钒冶金沉钒过程产生的含钒铬高浓度氨氮废水这一制约钒工业发展的关键问题，以沉钒过程前中间体NaVO3为原料，采用低温氢还原新工艺，取代了传统钒酸铵沉钒工艺，避免了沉钒废水的产生。针对这一研究新课题，深入开展NaVO3氢还原过程还原产物价态、化学成分、结构变化规律和氢还原产物强化水解脱Na、钒价态转变行为等关键科学问题的研究，阐明还原产物（不同价态钠钒氧酸盐Na2V2O5或NaVO2）的选择性还原行为，揭示氧化水解或机械活化-加压水解的强化水解机理和副产物含钒NaOH溶液的结晶沉钒-加钙除杂机制，实现V2O5/V2O3产品制备与含钒NaOH副产物循环利用。通过本项目的研究，形成NaVO3低温选择性氢还原-强化水解脱Na-碱液高效循环的钒氧化物产品工程与含钒碱液循环新方法、新过程，实现沉钒过程废水零排放，为建立具有经济-环境双重效应的钒氧化物清洁冶金新过程提供理论基础。

本项目针对沉钒过程含钒铬高浓度氨氮废水问题，以NaVO3为原料，创新性地采用氢还原新工艺制备钒氧化物，取代传统铵盐沉钒―偏钒酸铵热解工艺。主要取得了以下进展：采用氢气还原NaVO3―水解脱Na―选择性氧化方法制备钒氧化物。研究结果表明,低温下（<400℃），NaVO3未被还原，450~700℃时NaVO3逐步由V5+被还原成V4+，V3+；控制在700℃以上，还原时间为3h，料层厚度为1.5cm时，可获得单一的还原产物NaVO2，且还原率92%。NaVO2控制水解温度为200℃，水解时间为3h，液固比为13:1，Na的脱除率达到98%，所得中间产物主要由V2O5、V2O3和多钒酸组成；含NaOH溶液可以直接循环用于含钒原料焙渣的浸出。中间产物在空气气氛下、550℃煅烧3 h，可以得到层状、平均粒径小于0.1 μm的V2O5；在氢气气氛下、550℃煅烧3 h，可以得到片状、平均粒径70 μm的V2O3；在氮气气氛下、550℃草酸还原3 h，可以制备出球形、平均粒径10 μm的V2O3。本项目实现了V2O5和V2O3的制备和副产物NaOH的循环利用，避免了沉钒过程废水的形成，实现工艺废水零排放。可望从根本上解决目前含钒含铬高浓度氨氮沉钒废水问题，研究工作具有原创性。