Preparation of CaO granules using the granulation method

ABSTRACT

Improving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)₂ particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min^?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%.     

钢液二次精炼用CaO基熔剂的脱磷能力

根据CaO基熔渣和钢液之间在1853K脱磷平衡实验结果，利用CaO-Fe2O3-CaF2和CaO-BaO-Fe2O3-CaF2熔剂对钢液进行二次精炼脱磷试验，试验发现，采用优化组成的CaO基熔剂，可得到大于90%的脱磷率，能将钢液磷含量从0.05%降低到0.005%以下。     

Silica removal from Mokai, New Zealand, geothermal brine by treatment with lime and a cationic precipitant

Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively.     

以DRE系列ICP发射光谱仪测定液碱中的CaO及SiO2含量

介绍以DRE系列ICP发射光谱仪测定液碱中CaO及SiO2含量的方法及其产生过程，验证了该方法的灵敏度和准确性。     

Reaction process of monazite and bastnaesite mixed rare earth minerals calcined by CaO-NaCl-CaCl2

The decomposition reactions of monazite and bastnaesite mixed rare earth minerals calcined by CaO-NaCl-CaCl2 were studied by means of TG-DTA and XRD. The results show that the process of the minerals decomposed by CaO involves two steps. The first step occurs in the temperature range of 425-540 ℃, and the main reactions are bastnaesite decomposition, i.e. REOF reacts with CaO to produce RE2O3 and CaF2, and Ce2O3 is oxidized to CeO2. During this step, CaCO3 is formed at about 500 ℃. The second step takes place in the temperature range of 610-700 ℃, and the reactions are monazite decomposition into RE2O3, Ca5F（PO4）3 and Ca3（PO4）2 by CaO and CaF2. In this process, the decomposition ability is improved because CaO from CaCO3 decomposing has high chemical activity. In calcining process, the new formed Ca5F（PO4）3 restrains fluorine that can escape in form of gaseous compound. The decomposition ratio of the mixed rare earth minerals reaches 90.8% at 700 ℃.     

Efficient MgO-doped CaO sorbent pellets for high temperature CO2 capture

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na⁺ and MgO on the structure and CO₂ adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5-1.5 mm exhibited an excellent capacity for CO₂ adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm³∙mol⁻¹) to CaCO₃ (36.9 cm³∙mol⁻¹) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO₂ capture capacity (9.49 mmol∙g⁻¹), average adsorption rate (0.32 mmol∙g⁻¹∙min⁻¹) and conversion rate of CaO (74.83%) after 30 cycles.     

等速升温流态化下CaO/生物质焦的SO2/NO联合脱除特性

燃煤锅炉污染物超低排放标准对电厂脱硫和脱硝系统提出了更高的要求。CaO作为脱硫剂可以实现循环流化床锅炉烟气中SO₂的高效脱除,焦炭作为还原剂直接还原NO,同时CaO的存在对焦炭还原NO起催化作用,可以实现燃煤烟气中SO₂/NO的联合脱除。为了探究连续温度变化对CaO/生物质焦联合脱硫脱硝性能的影响,在钙循环捕集CO₂技术背景下,研究了等速升温流态化下CaO/生物质焦的SO₂/NO联合脱除特性。探究了烟气中O₂和CO₂对CaO/椰壳焦脱除SO₂/NO的影响。结果表明,O₂通过对椰壳焦表面碳原子的活化作用降低了异相还原NO温度,在300~950℃等速升温过程中CaO/椰壳焦的NO脱除效率逐渐增加,780℃以上能实现100%脱硝。O₂也提高了CaO/椰壳焦的脱硫效率。CO₂与CaO的碳酸化反应以及与椰壳焦的气化反应对同时脱除SO₂/NO有明显抑制作用。O₂和CO₂共同作用下,在500~800℃内CaO/椰壳焦的脱硝效率随温度升高而增加,脱硫效率先降低后升高。NO促进了CaO/椰壳焦脱除SO₂,而SO₂对脱硝有抑制作用。800℃时CaO/椰壳焦同时脱除SO₂和NO的效率分别为97.7%和93.9%。     

添加剂CaO对含金、银硫精矿氧化焙烧过程的影响

云南某含金、银硫精矿硫品位 44.24%,金、银品位分别为 3.07g/t、36.3g/t,金主要以裸露金的形式存在,银主要以硫化银和硫化物包裹银的形式存在。氧化焙烧预处理后,金、银浸出率分别为 79.66%、68.13%,高温下氧化铁会出现熔融状态,对金、银进行二次包裹。加入焙烧添加剂 CaO,金浸出率提高至86.56%,银浸出率提高至 68.43%。CaO 与 Fe2O3、SiO2 的亲和力大于 ZnO,焙烧过程加入 CaO 与 ZnO·SiO2、PbO·SiO2 与 FeO·SiO2 反应,形成 CaO·SiO2,阻碍致密 ZnO·SiO2、PbO·SiO2 和 FeO·SiO2 形成,减少其对金、银的包裹,焙砂硅酸盐包裹金由 0.52g/t 降低至 0.13g/t。     

残留CO2对石灰在转炉初渣中溶解的影响

 在转炉炼钢过程中,石灰快速溶解对转炉高效脱磷具有十分重要的意义,石灰溶解过程中熔渣/石灰界面处形成的2CaO·SiO₂产物层被认为是阻碍石灰溶解的关键因素。制备了具有两种不同CO₂含量的部分煅烧石灰石,采用浸泡法研究了部分煅烧石灰石在转炉初渣中的溶解行为,并与纯石灰、石灰石的溶解行为进行比较。结果表明,石灰石溶解时在液态熔渣中CaO的传质系数为石灰的2.1倍,残留CO₂质量分数为10%的部分煅烧石灰石的传质系数高达石灰石的6.7倍。在CO₂质量分数为0～43.5%时,石灰的溶解速率先增大后减小。石灰溶解过程中形成的2CaO·SiO₂层严重阻碍了FeO_x的扩散,从而减缓了石灰的溶解。与石灰不同,石灰石分解产生的CO₂能够破坏2CaO·SiO₂层并破坏自身结构,有利于熔渣的渗透,这也适用于残留CO₂的部分煅烧石灰石。制备纯石灰的过程中为了确保石灰芯部完全煅烧,因此极易导致石灰外表面发生过烧,而制备部分煅烧石灰石能在一定程度上解决表面过烧的问题。此外,与石灰石相比,部分煅烧石灰石由于表面是石灰外壳,溶解初期其表面附近的炉渣温降相对更低,能够避免溶解初期出现停滞阶段。在转炉富余热量有限的情况下,部分煅烧石灰石的石灰替换比高于石灰石,这取决于部分煅烧石灰石中的CO₂残留量。     

Li2O对CaO基钢包渣系脱磷能力影响的热力学研究

渣金平衡实验表明Li2 O替代CaO基钢包渣系中等量CaO使渣系磷酸盐容量Cp提高。在此基础上进行钢液脱磷的工艺性实验 ,研究了Li2 O含量、渣系碱度及氧化性对渣系脱磷能力的影响 ,并给出了控制转炉钢液在钢包中回磷及钢包渣脱磷的渣系。