In response to the insufficient heat ex-change capacity of the fractionation top circulation system of the fractionation column in the 2.2 Mt/a catalytic cracking(DCC-plus)unit of Daxie Petro-chemical Co Ltd,CNOOC,even if the cold reflux pump ran at full load,there were still problems such as the high thermal load on the top of the fractiona-tion column,the excessive pressure drop at the top of the fractionation column,and even frequent exceed-ing of the dry point of crude gasoline.So the thermal joint utilization technical transformation was carried out on the DCC-plus unit and the gas separation unit.The results showed that after the transformation and operation optimization,the fractionation column ba-sically reached the optimal operating state.Not only did the dry point of crude gasoline meet the stan-dard,but also significantly decreased,and its opera-tion was stable and controlled at 177-185℃.More-over,the top circulation return temperature of the fractionation column was controlled at 105.2℃,which effectively slowed down the corrosion environ-ment of HCl-H2S-H2O and dew point corrosion of the top circulation heat exchanger.Comparing with that before the technical transformation,the cold return flow rate at the top of the fractionation column de-creased by 36.7%,and the number of overhead air coolers and cold reflux pumps in operation decreased by 6 and 1 units,respectively,which effectively avoided the potential system safety hazards when they ever all had to be running at full load in each high temperature summer season before.Moreover,the total consumption of low-temperature hot water in the gas separation unit reduced by 84.8 t/h.
The evaluation experiment was con-ducted on the catalytic cracking of different compos-ite light hydrocarbon raw materials to produce low-carbon olefins under the catalysis of A type dedicated catalyst on the 40 L fixed fluidized bed reactor to in-vestigate the effects of process conditions on raw ma-terial conversion rate,ethylene&propylene selectiv-ity and yield,molar ratio of propylene to ethylene,and the by-product yield of mixed C4 hydrocarbons,hydrogen and methane.The results showed that with the total yield of diolefins as the indicator,the catalytic cracking performance of light hydrocarbon raw materials to produce low-carbon olefins was ranked from high to low as follows:n-alkanes,isoalkanes,cycloalkanes and aromatic hydrocarbons.Adding isooctane to the light hydrocarbon raw mate-rial R could significantly improve the conversion rate of light hydrocarbon raw materials and the molar ratio of propylene to ethylene in the product during catalytic cracking,but the yield of ethylene&propy-lene and the total yield of diolefins in the product were slightly reduced.The optimal reaction condi-tions for catalytic cracking of light hydrocarbon raw material R with the addition of 10%(mass fraction)isooctane to produce low-carbon olefins with A type dedicated catalyst were as follows:the liquid space velocity at 0.64 h-1,the flow rate of nitrogen and the stripping water at 0.50,1 L/min respectively,the re-action temperature at 665℃,and the reaction pres-sure at 40 kPa.Under the above optimal conditions,the conversion rate of the composite light hydrocar-bon raw material was 80.11%,the total yield of di-olefins and the ethylene&propylene yield in the tar-get product were 50.03%and 43.50%,respectively,and the molar ratio of propylene to ethylene was 0.73.
The comprehensive analysis was con-ducted on the technological progress,industrial de-velopment status,production costs,and economy of coal to natural gas at home and abroad.The main problems in the development of China's coal to natu-ral gas industry were analyzed and considered,and the relevant suggestions were proposed.The conclu-sion was that China had basically mastered the key core technologies of the entire coal to natural gas in-dustry chain,and had made the significant progress in industrial development.However,there were also some problems that could not be ignored,mainly in-cluding:the excessive project planning,limited pro-duction,and risks and challenges in technology,en-vironmental protection and safety,so it was necessary to continue to promote the demonstration operation of industrial devices and technological progress.The e-conomy of projects'operation was not strong and the production costs was high,so it was necessary to fur-ther reduce costs and improve their market competi-tiveness.Their resource allocation,pipeline network access,and market access acceptance were low,and it was necessary to make efforts to promote the coor-dinated development with traditional natural gas.Due to the large CO2 emissions in their production process,so it was necessary to strengthen the appli-cation of CCUS(CO2 capture,utilization and storage)technology and the introduction of green hydrogen,promote carbon cycle and"zero carbon"emissions,and boost the large-scale development of coal to nat-ural gas industry.
In response to the situation of the short-age of raw materials supply for reforming units,as well as the surplus catalytic gasoline and the sluggish sales market,the technological transformation of catalytic hydrogenation gasoline cutting into mid-range fractions(75-165℃)and prehydrogenation refining process were carried out in the 600 kt/a aromatization unit of Zhongjie Petrochemical Co Ltd,CNOOC,then the blending was supplemented to re-forming raw materials to ensure the aromatic hydro-carbon production with greater economic benefits.The operation and calibration results showed that the content of sulfur,nitrogen,olefins and arsenic in the catalytic gasoline produced by the maximizing iso-paraffins(MIP)process was significantly higher than that of straight run naphtha,so it could not be direct-ly blended as the continuous reforming feedstock.After the technological transformation,the distilla-tion rate of the mid-range catalytic gasoline cut frac-tion in the new cutting tower was 75.1%,and the blending proportion to the mixture of continuous re-forming feed in the new prehydrogenation reactor was 25.4%,and its potential aromatic mass fraction was 3.6 percentage points lower than that of full straight run naphtha.Under 74%load of the mixed feed of reforming unit,the potential aromatic mass fraction of hydrotreated naphtha product was 41.0%.Com-pared with the relevant design indicators of main products,the mixed xylene yield increased by 1.64 percentage points,yet the yield of benzene,toluene,the mixed C≥9 heavy aromatouldics and the total aro-matics decreased by 0.84,0.34,2.50,2.04 percent-age points,respectively.Not only could the high load operation of the continuous reforming unit and the production of well-selling aromatics be solved expe-diently in the case of under the situation of insuffi-cient supply of straight run naphtha feedstock,but also helped to maximize the unit economic benefits under the situation of depressed sales market of catalytic gasoline products.
The research progress on selective catalytic reduction(SCR)denitrification catalysts deriving from Cu,Mn and other based hydrotalcite-like composite oxides(LDO)was reviewed.And the effects of preparation methods,metal modifications,and carrier types on the denitrification efficiency,ac-tivation temperature and water and sulfur resistance of such catalysts were emphatically analyzed.Final-ly,it was pointed out that the future research&de-velopment directions of such LDO catalysts were:to improve the water and sulfur resistance of the cata-lysts by cladding,doping,and other methods;to pre-pare the molding catalysts suitable for large handling capacity via using the methods such as coating and integrated extrusion.
