| Distillation residues were widely found in different industries such as coal chemical industry and petrochemical industry,which were large in volume and complex in composition,and were classified as hazardous waste of toxicity.If not properly handled,distillation residues will not only enter the ecosystem bringing serious environmental pollution,but also cause the waste of residues resources.The paper focused on the high value utilization of light fraction by deep-vacuum distillation of phenolic distillation residues,which were used in the preparation of resin for Mg O-C refractory by using thermochemical conversion and water washing extraction methods.In this paper,Yunnan Xianfeng medium and low temperature coal tar phenolic distillation residues were studied,the light mixtures of phenolic distillation residues(LPDR)were collected at 20 k Pa and 220°C.According to the variability of the phenolic condensation reaction rates of different phenol monomers in LPDR,the key components in LPDR were selected firstly as the model mixed phenols to react with formaldehyde.By adding phenol to phenol/total phenolic compounds of 0.80,the free phenol in the model phenolic resin MPF was reduced from 21.4% to 11.7%.By adding boiling water(boiling water/resin = 1:1)to extract the free phenols,the free phenols in MPF could be further reduced to 8.7%.The indicators of the finished MPF products obtained after vacuum dehydration and viscosity basically meet the industry standard YB/T 4131-2014 Phenolic Resin for Refractory Materials(hereinafter referred to as "industry standard").On this basis,LPDR was used to instead of model mixed phenols to synthesize residues phenolic resin RPF in the same way.After testing,the viscosity of RPF is 27-30 Pa-s,moisture ≤ 2.5%,solids content ≥ 77%,carbon residue ≥ 43% and free phenol ≤ 11.5%,which all meet the industry standard.The modified RPF was obtained by adding 9 wt% of ferrocene(Fc)modifier to the hexamethylenetetramine cured RPF.The graphitization level of the modified RPF was as high as 61.6% and the residual carbon rate was as high as 41.4% with a heating rate of 4 ℃/min and a pyrolysis temperature of 1100℃,and the thermal stability at high temperature is better than commercial resin Nv.The modified RPF was used as a binder,and mixed with magnesium sand and graphite to prepare the Mg O-C refractory MT-RPF.The basic properties of MT-RPF were not significantly different from those of MT-Nv.And the graphitic carbon and Fe-containing compounds generated after high-temperature firing of the modified RPF were beneficial to enhance the bonding strength of the grains in MT-RPF,thus enhancing the oxidation resistance of the material.In order to investigate the universality and scale-up applicability of this process route,light fraction by deep-vacuum distillation of Henan Hongye medium and low temperature coal tar phenolic distillation residues(LPDR-HN)were selected,and the resins HPF1 and HPF were synthesized in 250 m L and 2 L reaction vessels,respectively,according to the optimized conditions.Modified HPF(MHPF)was obtained by adding 5 wt% of Fc to the cured HPF,which increased the residual carbon rate of HPF from 32.3% to 38.2% and greatly reduced the thermal decomposition rate.Mg O-C refractories MT-HPF and MT-MHPF were prepared at Dinur(Yingkou)Refractory Materials CO.,LTD.using HPF and MHPF as binder,respectively.Physical and chemical performance results show that the two Mg O-C refractories are met the requirements of the national standard GB/T 22589-2017 Mg O-C refractory,belong to qualified products. |
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