Preparation And Performance Of Coal Gasification Fine Slag/rubber Composite

Coal gasification fine slag（CFS）is the solid waste discharged from the coal gasification process,the annual emission of which is as high as 60 million tons.At present,the main treatment method of CFS is piling up and landfill,which occupies land resources and causes air and soil pollution as well as groundwater,which is a serious hazard to human health.Therefore,it is urgent to explore the way of resource utilization of CFS.Although carbon black（CB）,silica,and calcium carbonate as typical commercial rubber fillers can effectively strengthen rubber,its raw materials are extremely dependent on natural resources such as petroleum and minerals,and the production process has high energy consumption,high carbon emissions,and more serious pollution of the natural environment.CFS is composed of residual carbon and inorganic microbeads,and its main composition is similar to carbon black and silica,which has the potential to replace commercial fillers for reinforced rubber with fine particle size.In this paper,the physicochemical properties of CFS are studied,and the feasibility of replacing carbon black,silica,and calcium carbonate for rubber fillers is investigated.The CFS is composed of amorphous glass micro-beads and random lumpy unburned carbon,and most of the glass beads are embedded with unburned carbon.Inorganic glass microbeads are mainly composed of silica and various metal oxides such as aluminum oxide,calcium oxide,and iron oxide.when the volatile fraction in coal turns into gas and expands outward during the coal gasification process it breaks through the carbon skeleton,forming a rich pore structure and expanding the specific surface area.In this paper,the optimum replacement ratio of calcium carbonate and carbon black by CFS and the optimum number of parts of CFS for the filler of Natural Rubber（NR）and Ethylene Propylene Diene Monomer（EPDM）were investigated,and then mesoporous silica fillers（FS-Si O₂）with different p H were prepared with CFS as raw material to replace precipitated silica（P-silica）for Styrene butadiene rubber（SBR）filler.The construction-bearing rubber formulation of Hengshui Rubber Factory containing natural rubber,carbon black N330 and calcium carbonate was used for the study.The effects of the addition of CFS and the ratio of substituted calcium and carbon black on the properties of NR composites were studied.The results showed that the best tensile strength and elongation at break of the NR composites were obtained at a ratio of 3:1 for 15 phr of CFS substituted calcium and carbon black,and the peel strength was significantly increased compared with the original formulation rubber.The rubber molecular chain migration kinetics showed that the addition of CFS effectively restricted the movement of rubber molecular chains,improved the filler-rubber interaction and crosslink density,and increased the thermal stability of vulcanized rubber,which initially verified the feasibility of replacing part of carbon black N330and calcium carbonate filled NR with CFS.In order to investigate the universality of CFS for rubber filler,the basic formulation of automotive sealant of Hebei Xinhua Auto Parts Group Co.,Ltd.containing EPDM rubber,carbon black N550,and calcium carbonate was selected to study the best ratio and addition amount of CFS to replace calcium powder and carbon black N550.The results showed that the tensile strength,elongation at break,and permanent deformation in compression of EPDM composites were best when the ratio of 30 phr of CFS replacing light calcium and carbon black was 2:1,and Mooney viscosity of the first-stage rubber and blended rubber was slightly decreased,which was beneficial to improve the processing performance of the rubber.Solving the vulcanization delay of coal gasification fines became the focus of research.In order to investigate the mechanism of CFS affecting the rubber vulcanization reaction,an experimental formulation of SBR with fewer types of rubber agents was selected as the basis,and P-silica was used as a reference filler.The light-colored FS-Si O₂ was firstly prepared by acid leaching and calcination with 16 wt.%hydrochloric acid,and then the p H of the FS-Si O₂ slurry with a mass fraction of 10 wt.%was adjusted by using 0.025 mol/L dilute sodium hydroxide solution,and the FS-Si O₂ fillers with different p H were prepared to replace all the P-silica for the preparation of SBR composites and to study their properties.As the p H of the fillers increased,the specific surface area of FS-Si O₂ decreased,the pore volume increased,and the silicone hydroxyl content decreased.The optimistic vulcanization time T₉₀ of the rubber was reduced slightly with the increase of the filler’s p H.The best mechanical properties were obtained for the filler with mesoporous spherical silica which p H is 6.3（FS-6.3）.The experimental results of using FS-6.3 as a partial replacement of P-silica in the filler of SBR composites showed that the induction period ts₁ of the vulcanization of SBR composites was significantly reduced and the positive vulcanization time T₉₀ was shortened by 47%when the amount of FS-Si O₂ substitution was increased from 0 phr to 20 phr.The quantification of vulcanization reaction kinetics demonstrated that the vulcanization reaction rate increased significantly with the addition of FS-Si O₂.The lower surface silica hydroxyl content of FS-6.3 and its weakening of the filler network were the main reasons for the increased vulcanization reaction rate.In addition to this,the tensile strength,elongation at break,and tear strength of the vulcanized rubber were maintained at a high level when the filler content of FS-6.3 was not greater than 15 phr.In this study,we proposed the idea of using CFS to replace carbon black,calcium carbonate and P-silica for rubber filler,and verified its feasibility,which provides a new strategy for the resource utilization of coal gasification fine slag.