准格尔煤制备水煤浆的成浆性研究

Slurryability of coal water slurry prepared with Jungar coal

为提高准格尔煤粉煤灰中氧化铝的浸出效率,提出将准格尔煤以水煤浆的形式应用于循环流化床(CFB)锅炉的方法,即借助水煤浆的低温燃烧特性,进一步降低CFB锅炉的炉内煅烧温度,进而提高粉煤灰的反应活性及后续工艺的浸出效率。以水煤浆的制备试验为主线,系统比较了NNO、MF、LC和LS等4种常见水煤浆分散剂对准格尔煤水煤浆的分散效果,探讨了粒度对煤浆性能的影响,并利用流变数据与Herschel-Bulkley模型共同分析了浆体的流变特性。结果表明:分散剂NNO具备最佳的分散效果,其在用量仅为干基煤粉质量0.4%的条件下,可将准格尔煤水煤浆的表观黏度和流动直径由未加分散剂时的966 mPa·s(煤浆质量分数60%)和9.1 cm改善至468 mPa·s和13.2 cm;粒度对准格尔煤水煤浆的稳定性存在显著影响,随着煤粉平均粒度D_(50)由47.2μm减小至20.5μm,浆体的稳定性得到提高,硬沉淀的出现时间延长,且当D_(50)≤35.0μm时,煤浆的硬沉淀出现时间>7 d,满足生产需求;准格尔煤在D_(50)=35.0μm时制备出的水煤浆浆体综合性能最好,在煤浆质量分数为60%的条件下,浆体表观黏度仅为639 mPa·s,且流动直径为11.9 cm,流动等级为B^(ˉ)级,硬沉淀出现时间>7 d,低位发热量为10.06 MJ/kg,属于高品质水煤浆;准格尔煤水煤浆呈现出剪切变稀的流变特性,为假塑性流体,且符合Herschel-Bulkley模型,流变特性指数n<1。

In order to improve the leaching efficiency of alumina in Jungar pulverized coal ash,the method of applying Jungar coal in the form of coal-water slurry to circulating fluidized bed(circulating fluidized bed,CFB)boiler is proposed,that is,by virtue of the low-temperature combustion characteristics of coal-water slurry,the calcination temperature in the furnace of CFB boiler is further reduced,so as to improve the reactivity of coal ash and the leaching efficiency of subsequent processes.In order to explore the slurry-forming performance and the best slurry-making process of Jungar coal,taking the preparation experiment of coal-water slurry as the main line,the dispersion effects of four common coal-water slurry dispersants,such as NNO,MF,LC and LS,on Jungar coal-water slurry were systematically compared,and the influence of particle size on Jungar coal-water slurry was discussed,and the rheological properties of slurry were analyzed by using rheological data and Herschel-Bulkley model.The results show that the dispersant NNO has the best dispersion effect,and can improve the apparent viscosity and flow diameter of Jungar coal-water slurry from 966 mPa·s(coal slurry concentration 60%)and 9.1cm without dispersant to 468 mPa·s and 13.2 cm under the condition that the dosage is only 0.4%of the dry basis pulverized coal mass;The particle size has a significant impact on the stability of Jungar coal-water slurry.As the average particle size of coal powder D_(50) decreases from 47.2μm to 20.5μm,the stability of slurry is improved,and the occurrence time of hard precipitation is prolonged.When D_(50)≤35.0μm,the occurrence time of hard precipitation of coal slurry is more than 7 days,meeting the production requirements;The comprehensive performance of coal-water slurry prepared from Jungar coal at D_(50)=35.0μm is the best.Under the condition of coal slurry concentration of 60%,the apparent viscosity of the slurry is only 639 mPa·s,and the flow diameter is 11.9 cm,and the flow grade is B^(ˉ)Grade,hard precipitation occurrence time<7 days,low calorific value 10.06 MJ/kg,belonging to high-quality coal water slurry;Jungar coal-water slurry shows shear-thinning rheological characteristics,is a pseudoplastic fluid,and conforms to Herschel-Bulkley model,with rheological property index n<1.