Solidfication and reuse of coal fly ash by heating-compressive method

在第一年的研究中，在反应温度100-250℃，抗压强度0-10 Mpa的条件下，用热压方法固化了掺有某些添加剂的粉煤灰。将灰分、硅灰或矿渣粉(质量分数为5~20wt%)与15%的氢氧化钠溶液充分捏合，制得原料。将混合后的粉末放入内径为20 mm的圆柱形高压罐中，由于高压罐填料的收缩，在5 Mpa的压力下进行压缩。然后用油泵在一定的压力下用油缸连续压缩，加热到计划温度。用抗压强度和抗拉强度来评价固化体。根据60℃干燥后的质量和表观体积来测量固化体的密度。并对原料的主要元素进行了静态浸出试验。得出了以下结果：对于S…随着掺量的增加，材料的抗压强度也随之提高。当原材料在140℃、4 Mpa、掺量为10%的条件下固化时，其抗压强度明显高于普通混凝土，而密度明显低于普通混凝土。浸出试验结果表明，固化体主要元素的浸出量对固化体的抗压强度有影响，矿渣作外加剂，在230℃、10 Mpa固结条件下，掺入较小颗粒的矿渣粉(8000cm2/g)，固化体的抗压强度可达64.3 Mpa，且固化体的二次抗压强度较高，抗拉强度与普通混凝土相当，密度较低。第二年的研究中，采用比第一年更大的设备生产了大直径(50 Mm)的固化体。对于较小固体的结果考虑了固体的条件。特别是处理问题较多的非JIS飞灰，本研究采用的是非JIS飞灰。采用特氟隆高压灭菌器进行了100-200℃高温条件下对飞灰的改性试验，以确定其长期工作。根据去年的研究结果，采用比表面积为8000cm2/1g重量的矿渣，在150~250℃的温度下进行固化，在10 Mpa的压力下进行固化，得到了如下结果：(1)在250℃的反应温度下，得到了抗压强度高达50 Mpa、轻密度为1.80的固化体；(2)随着矿渣粉含量的增加，固化体的抗压强度提高。当掺量达到10%时，抗压强度得到极大提高。从经济和实力的角度来看。矿渣微粉的最佳掺量为20%。(3)在225℃下，随着反应温度的升高，混凝土的抗拉强度提高了2.9 Mpa左右，抗拉强度/抗压强度比为1/20，远小于普通混凝土砌块的抗拉强度/抗压强度。(4)在150℃的反应温度下，反应时间为30min时，粉煤灰在碱性(NaOH)溶液中的反应生成了合成沸石。较少

In this study of the first year, coal fly ash with some additives was solidified by a heat-compressive method at reaction temperatures of 100 - 250 degree C and at compressive strengths of 0 - 10 MPa. The ash and silica fume or the slag powder 5 -20 wt%) was kneaded well with NaOH solution (15% of powder weight) to prepare the starting material. The mixed powder was put into the autoclave, which has a cylindrical shape with a 20 mm of inner diameter, and compressed at 5 MPa because of the constriction of the packing of the autoclave. Then it was continuously compressed at the certain pressure with an oil cylinder by oil pump and was heated to a planned temperature.The solidified bodies were evaluated by the compressive strength and the tensile strength.Density of the solidified body was measured from its weight and apparent volume after drying at 60 dgree C.And static leach tests for main elements of starting material were performed.The following results were obtained ;In the case of s … More ilica fume as additive, the compressive strength was increased with the content. When the starting materials was solidified at 140 degree C, at 4 MPa, and the content of 10%, the compressive strength was much higher and the density was lower than that ordinary fly ash concrete. The results of leaching tests suggested that the leached amount of main elements for solid body affects the compressive strength.In the case of the slag as additive, the compressive strength of the solid body reached 64.3 MPa, when solid conditions were at 230 degree C at 10 MPa, and addition of the slag powder with smaller particle (8000cm2/g), And the solid body by above conditions has higher of twice compressive strength, same level of the tensile strength, and lower density than that of ordinary fly ash concrete.In the study of second year, the solid bodies with large diameter (50 mm) were produced with larger equipment than the first year. The conditions for solid were considered by results for smaller solid bodies. Especially non- JIS fly ash, which is more problem about the disposal, was used in this study. An alteration test under the elevated temperature at 100 - 200 degree C for the fly ash was performed with an Teflon autoclave in order to confirm the long period working. From results of last year, the starting material was solidified the tenperature at 150 - 250 degree C, the compression at 10 MPa, and using the slag with the surface area of 8000cm2 per 1g weight.The following results were obtained ;(1)The solid body with a high compressive strength of 50 MPa and a light density of 1.80 was obtained under the reaction temperature of 250 degree C.(2)The compressive strength of solid body was increased with the content of slag powder. When the content of 10% reached, the compressive strength was extremely increased. From economical and the strength view points. it suggested that the optimum content of slag powder is 20%.(3)The tensile strength was increased about 2.9 MPa with the increasing of reaction temperature up to 225 degree C.And the ratio of tensile strength / compressive strength showed 1/20. The value is much smaller than that of normal concrete block.(4)The alteration of the coal fly ash in alkaline (NaOH) solution produced some synthesis zeolites under conditions at the reaction temperature of 150 degree C and for the reaction time of 30 minutes. Less