Modifying Sludge By Adding Shale And Fly Ash And Preparing Ceramisite

Shale is a type of rocks with relatively low moisture content and it is rich in nature reserves. To use shale producting building materials, such as bricks and ceramisite, has been commonly. Especially under the State's policy prohibiting clay bricks production and protecting arable land, shale products has become a very important building materials. As an industrial waste, fly ash is of great yield and need disposed effectively. The content of SiO2 and Al2O3 in fly ash is relatively high and it also contains ferric salt. Adding fly ash to sludge can not only improve molten composition but also enhance flocculation. Some research has been using mixtures of sludge and shale,fly ash to make ceramisite,bricks and other products, but most of the processes use of the drying sludge or sludge burning ash. Hence, it need to add water when blank forming or granulation which is waste of water in sludge. Previous study results show that the direct use of dehydrated sludge about 80% water content mixed with shale to fire ceramisite is an effective way to dispose the sludge, but the blend of the colloidal sludge and shale is difficult and the uniformity may impact the ceramisite properties. Therefore, based on the building materials utilization of sludge, the settling and dewatering properties of sludge added shale,fly ash has been studied in this paper. At the same time, using dewatered sludge to fire ceramisite to find a way that combine sludge dispose with materials utilization.Adding shale,fly ash in settling process with two kinds of method , uni doped and double doped. To measure the settling and dewatering properties by testing settling curve and specific resistance. At the same time, to investigate the effect in environmental properties of filtrate by testing pH value and COD. It indicates that the settling and dewatering performance of sludge added shale or fly ash has been improved; the specific resistance of thickened mixture decreased from 1013 magnitude to 1011 ; the moisture content of mixture after settlement and dewatering is low and it is beneficial to the subsequent processing. The volume of dewatered mixture increased, but the volume increment of dehydrated mixture is still be acceptable taking into account the utilization of it and other materials factors. Adding fly ash can improve the pH value and decrease COD. When adding both shale and fly ash with dosage of 5%, the settling and dewatering properties of sludge improved and the volume increment of dehydrated sludge is not obvious. There are two different kinds of fineness, gap gradation and continuous gradation, in this paper. Therefore, we can compare the effect of fineness gradation and different partical size. Under gap gradation, the addition of shale with particle size of 250～150μm and 150～80μm can improve the settling performance of sludge preferably. The specific resistance of sludge added shale with particle size of 425～250μm is the lowest. Under continuous gradation, the addition of shale with particle size <850μm and <425μm can improve the settling performance of sludge preferably. The specific resistance increased when the shale particle size <80μm. It illustrates that the whole gradation of shale is benefical to the settling and dewatering performance of sludge.The pH value should affect the settling and dewatering performance of sludge. Using NaoH with concentration of 1mol/L and H2SO4 with concentration of 0.5mol/L to adjust pH value to about 3,5,7,9,11 respectively. To investigate the effect by settling and dewatering experiments. Aimed at study the effect of shale in all different pH value, adding shale in the sludge which adjusted pH value and taking settling and dewatering experiments. It indicates that acid treatment is favorable to improve the settling and dewatering properties of sludge. The settlement ratio and specific resistance of sludge added shale decreased most significantly when the pH value is 11. Therefore, the shale can be used when dealing with the alkaline waste water and sludge.Using dewatered mixture added shale,fly ash or both of them to pruduct ceramisite through balling,drying,preheating,calcination process and testing the properties. The dewatered mixture added shale,fly ash or both of them can be fired ceramisite. The expansion property of ceramisite made by mixture added shale is better than fly ash. Under the same dosage, the particle strength of fly ash ceramisite is higher than shale ceramisite. The mixture added both shale and fly ash can be made ceramisite with excellent properties such as particle strength and 1h water absorption. When added both shale and fly ash with dosage of 5%, the particle strength and apparent density of ceramisite is 690N and 1107 kg/m3 respectively.