Study On The Preparation Of Oily Sludge-based Adsorbent Material By Pyrolysis

Oily sludge is inevitable by-products of oily field production, which would cause many serious environmental pollution problems if they are treated improperly. Therefore, the disposal and application of oily sludge have been not only one of the most important and urgent problems to solve for environmental protection in petrochemical industry at domestic and abroad, but also a great challenge for the continuous improvement of environmental quality and the sustainable development of economy. Nowadays, treating oily sludge by pyrolysis has many advantages including complete disposal,effectively reducing the quantity and volume, less secondary pollution and higher recovery of resources, which has aroused great concerns from researchers.In this paper, oily sludge is used to prepare pyrolysis residue-based adsorbents material through pyrolysis technology. In this process, activation of pyrolysis residue, physicochemical properties of pyrolysis residue, desulfurization and oil removal of modified pyrolysis residue have been mainly investigated, and the pyrolysis process,product and mechanism have also been preliminarily discussed.The oily sludge used in this study was obtained from the Sixth Joint Station in the Gudao Oil Production Plant at Shengli Oil Field.The water content, oil content and solid content of dry oily sludge are 13.57%,22.48% and 63.95%,respectively. Analysis curves from TG and DTA showed that there were three stages in pyrolysis process:50℃-175℃is the stage of water evaporation and emission of light hydrocarbon adsorbed on the surface; 175-600℃is the stage of volatile evaporation and heavy components pyrolysis, including the decomposition of light oil of mineral oil in oily sludge (180℃-370℃) and decomposition of oil of heavy mineral oil in oily sludge (370℃-600℃);after 600℃is the carbonization stage, in which oily slugde continued to react through dehydrogenation, polycondensation and rearrangement by pyrolysis.The results of L16(34) orthogonal experiment showed that the most important influence factor was pyrolysis temperature, secondly pyrolysis time and finally heating rate.The maximum benzene adsorbability of adsorbent material was 29.26mg/g.The optimum pyrolysis conditions of oily sludge in nitrogen atmosphere were 550℃,4h,10℃/min for the pyrolysis temperature, pyrolysis time and heating rate, respectively.According to activation methods of semicoke and activated carbon, high-pressure hydrothermal,HNO3,NaOH and KOH activation methods were adopted for activation of pyrolysis residue. The benzene adsorbability of activatied pyrolysis residue had several significant changes, and the content of ash reduced significantly. The results showed that HNO3 and NaOH were the best activation agent for pyrolysis residue, compared to other activation methods.The optimum conditions of activation were as follows:in HNO3 activation, volume ration of HNO3/residue was 4.5:1,activation time was 2.Oh under 80℃,calcination time were 1.4h under 700℃,the benzene adsorbability of activated pyrolysis residue was 51.35 mg/g and the content of ash discreased to 45.66%;in NaOH activation, volume ration of NaOH /residue was 2.0:1,activation time was 3.Oh under 150℃,the benzene adsorbability of activated pyrolysis residue was 59.58mg/g and the content of ash discreased to 13.20%.The characterization and analysis of pyrolysis product were performed by various detection methods and instruments.The results demonstrated that the light component and category of raw oil increased obviously,and the combustible gas had a larger proportion of non-condensable gas, which both illustrated that there was a significant effect of cracking after pyrolysis of oily sludge. The C content of pyrolysis residue was about 12%,and the metal element content was about 15%,which could be appropriate for preparation of flue gas desulfurization. Pore size of activated pyrolysis residue had a relatively centralized distribution and average pore diameter was about 3.4nm (mesoporous level),which could meet the requirement of oily wastewater treatment. Surface morphology of pyrolysis residue changed greatly after activation, which showed obvious,abundance surface pore structure and uneven pore distribution.In the simulated flue gas atmosphere, the desulfurization of pyrolysis residue and activated pyrolysis residue was studied via a flue gas desulfurization test with fixed-bed reactor. The results demonstrated that in SO2-N2 system,the sulfur capacity of unactivated pyrolysis residue was about 0.37% and breakthrough time was 39 min while the sulfur capacity of activated pyrolysis residue by NaOH was up to 1.96% and breakthrough time was 101 min. Furthermore, in SO2-N2-H2O system,due to the existence of steam, the sulfur capacity and breakthrough time of unactivated pyrolysis residue and activated pyrolysis residue by NaOH were 0.46% and 2.35%, 43min and 131min, respectively. Static adsorption method was used for the evaluation of oil removal by pyrolysis residue and activated pyrolysis residue.The results illustrated that oil removal rate of unactivated pyrolysis residue was 37.82%,however, the oil removal rate of activatied pyrolysis residue by HNO3 increased to 51.56%.