汽油资源的整合与优化利用(含中英文word,可自行改为pdf)

1、Li Yajun, et al. Integration and Optimized Utilization of Naphtha ResourcesChina Petroleum Processing and Petrochemical TechnologyOptimization and Control2010，Vol. 12，No. 2，pp 51-56"丨丨丨Integration and Optimized Utilization of Naphtha ResourcesLiYajun; Zhang TingtingKey Laboratory of Enhanced He

2、at Transfer and Energy Conservation, Ministry of Education, School of Chemical and Chemical Engineering, South China University of Technology，Guangzhou 510640)Abstract: Naphtha is an important raw material for manufacture of clean fuels and ethylene products. However，China is experiencing a serious

3、imbalance between supply and demand of naphtha, due to its rapidly increasing car population and booming ethylene industry, the demand of which cannot be met by the domestic depleting crude oil resources. Focusing on alleviating the above-mentioned naphtha deficit, this paper puts forward an idea su

4、ggesting that Chinas limited naphtha resource should be used reasonably. Naphtha feedstocks with more potential aromatic content should be used in catalytic reforming process to produce clean fuel products, and those feedstocks with more paraffinic content should be used in ethylene production. Mean

5、while, industry tests show that the low-valued naphtha byproduct from ethylene plants and the products of secondary processing units at refineries can also be applied so as to extend the naphtha supply for manufacture of cleaner fuels and ethylene derivatives.71994-2015 China Academic Journal Electr

6、onic Publishing House. All rights reserved, Key words: cleaner gasoline; ethylene, naphtha; feedsto1 IntroductionCurrently in China, the oil refineries are facing a severe challenge arising from the shortage of oil resources, the sharp increase in the consumption of gasoline as well as the large dem

7、and for cleaner fuel with low sulfur and low olefin content. On one hand, the unreasonable gasoline composition results in an increasingly severe air pollution caused by exhaust emissions from motor vehicles. On the other hand， the existing refinery process units restrict the quality improvement of

8、liquid fuels, so it is necessary to optimize gasoline composition by readjusting refinery processes, i.e. increasing the production capacity of cleaner gasoline with less content of olefin and high octane number. In addition, the straight-run naphtha, as a common raw material needed by both the ethy

9、lene industry and the oil refining industry, particularly for the production of three major synthetic materials, plays an ever important role in oil refining and petrochemical sectors. However, with the expansion of both the ethylene production capacity and the share of naphtha in the ethylene feeds

10、tock supply, the violent competition on acquiring naphtha supply will be inevitable. As a result, the development of cleaner fuel and ethylene industry would be affected by the shortage of naphtha supply in China. So, in order to keep a sustainable development of the energy sector, the national econ

11、omy and the environment, this paper points out that the rational allocation and optimal utilization of naphtha materials between the cleaner fuel production and ethylene industry has become an important issue.2 Raw MaterialsThe Key Point for Development of Chinas Ethylene IndustryUsually, ethylene p

12、roduction capacity represents the scale and level of petrochemical industry in a country because of the importance of ethylene. With the rapid development of Chinas petrochemical industry and national economy，the ethylene demand increases at a prodigious rate. In 2007， Chinas ethylene production cap

13、acity had reached 9.96 Mt/a, 1.3 times that in 2000. However, the equivalent ethylene demand grew to 21.12 Mt/a, and the self-sufficiency rate was only 48.7%【12】. Moreover, the share of naphtha in steam cracking feedstock is growing year by year, from about 35% in 1992 up to around 58% in 2003 and 6

14、7% at present3_4. Much more pressure on steam cracker feedstock availability has been experienced due to the higher growth rate of ethylene, propylene and its derivatives. Predictions on ethylene supply and demand are illustrated in Table 1(5'71. A forecast study points out that Chinas ethylene

15、production capacity will reach 16.0 Mt/a in 2010. Furthermore, the naphtha demand is expected to reach about 37.5 Mt/a by 2010， accounting for about 75% of the steam cracking feedstock1' The conclusion is that naphtha materials are the key point for development of Chinas ethylene industry.3 Chal

16、lenges Facing Chinas Oil Industry Compared with other countries, the process flow scheme isCorresponding author: Li Yajun, Telephone: +86-20-87112044; E-mail: Liyajun52Table 1 Prediction on ethylene supply & demand in ChinaItems201020152020Production capacity, Mt/a16.0020.1326.18Equivalent deman

17、d, Mt/a26.8436.9042.32Raw materials demand, Mt/a50.0067.85103.88Self-sufficiency rate, %545660simple at Chinese oil refineries. The atmospheric & vacuum distillation unit and fluid catalytic cracking (FCC) unit always undertake the most processing tasks. It is reported that the share of FCC unit

18、s in crude oil processing reaches 20.48%, higher than the world average level of 17.76%. On the contrary, other processes that can provide excellent gasoline components such as catalytic reforming, alkylation, isomerization and hydrotreating only occupy a less proportion. Compared to the American an

19、d the European gasoline components in which the blending ratio of FCC gasoline, reformate, alkylate and isomerization component account for 1/3 of the gasoline pool, respectively, but 75%_ 80% of Chinas gasoline blending components come from FCC unit and other blending components only account for 20

20、% approximately191. At the same time, as the FCC process uses a high blending ratio of residual oil in its feed and the deeper cracking operation is widely used to obtain more liquid products, the olefin content in FCC gasoline is as high as 45%55%, by 20%25% higher than the FCC naphtha ratio in the

21、 US. That is why the Chinese gasoline has higher sulfur and olefin contents and cannot satisfy the increasingly strict environmental regulations. To improve the quality of gasoline is a key problem for Chinese oil refineries.China has made considerable progress in its economic development in the pas

22、t decade. Benefited by the rapid development of the transportation sector and strong purchasing desire for private cars in China, the annual growth rate of automobile sales was more than 30% in the past several years. A forecast shows that the gasoline consumption will increase at an annual average

23、growth rate of 3.7% in 2010, and the annual gasoline consumption will reach 48.79 Mt/a in order to satisfy the demand of about 61 million vehicles ll0. With the rapid growth of domestic car population and hence the increasing gasoline consumption，the air pollution caused by exhaust emissions from au

24、tomobiles will be the consequential outcome. Therefore, Chinas oil refineries have to readjust their process equipment configuration and enlarge the clean fuel production capacity so as to narrow the gap between China and other advanced countries step by step.As one of the three excellent gasoline b

25、lending components, the reformate gasoline has been playing a very important role for manufacture of cleaner fuel because of its good stability characteristics, high octane number (100105 RON )， low olefin content (0.1 %1.0 %), and lower sulfur, nitrogen and oxygen contents. In 2008, the capacity of

26、 catalytic reforming units was 7.654 Mt/a in China and that in the US was 151.54 Mt/a, which accounted for 32.71% of the worlds total. In China the share of catalytic reforming capacity in the total amount of crude oil processed was only 2.37%, and, as a sharp contrast, that share in the US was 17.4

27、4%11"121. As the worlds largest producer of polyester, Chinas paraxylene (PX) self-sufficiency rate is only 40% owing to the increasing demand for PX used as the raw materials for manufacture of pure terephthalic acid (PTA) and polyethylene terepthalate (PET). It is a very different scenario co

28、mpared to the overseas situation that more than 70% of catalytic reforming units in China are dedicated to the production of aromatic hydrocarbons instead of gasoline. The unreasonable refinery process configuration has become the main obstacle for improving fuel quality. To solve the problems relat

29、ed with the rapidly increasing gasoline consumption and the strong demand for cleaner fuels, a due attention should be concentrated on the development of catalytic reforming process, in addition to increasing the capacity of alkylation and isomerization units. If the proportion of reformate gasoline

30、 could amount to more than 30% of gasoline pool in China, the liquid fuel quality at refineries would be improved directly and effectively.4 Competition on Raw Material Naphtha Between Clean Oil Production And Ethylene IndustryNaphtha is a main raw material for both the clean gasoline production thr

31、ough catalytic reforming and ethylene and aromatic hydrocarbon production in petrochemical industry. Because of the quick increase of domestic car population and ethylene capacity, the consumption of liquid fuel and the demand for petrochemical materials will grow at a high speed. In the near future

32、, the naphtha demand will rapidly grow, and the annual average growth rate of naphtha demand will be far higher than that of automotive fuel. In particular, the growth in demand of ethylene industry for naphtha will be much higher than the growth rate of crude China Petroleum Processing and Petroche

33、mical Technologyoil processing capacity. Even if all naphtha would be used as the feedstock for manufacture of ethylene in China, the needs could not still be satisfied. A competition on naphtha supply between the oil refining industry and the ethylene industry will be inevitable.Unfortunately, in C

34、hina, the yield of straight-run naphtha is lower (around 5%一8%) due to the heavier crude oil supply. Furthermore, the supply of domestic crude oil will dwindle with time. Chinese crude oil import dependency has been rising, reaching 46% in 2007, and is estimated to top 60% by 2020【丨3-14】. It is impo

35、ssible to solve the dramatic deficit of naphtha in short term and the development of cleaner fuel and ethylene production will be constrained directly. So it is necessary for China to coordinate correctly the interrelation of the raw material supply between oil refining industry and ethylene industr

36、y under the background of severe shortage of crude oil supply and heated competition for naphtha. Otherwise, the ethylene industry cannot possess enough feedstock, and the development of cleaner fuel will be hindered.5 Optimal Utilization of Naphtha ResourcesEvidently, the effective use of naphtha r

37、esources plays an important role in both the clean gasoline production and the development of ethylene industry. As the basis for naphthas rational and optimal utilization, the refinery/chemical integration is the developmental trend in Chinese petrochemical enterprises, and its advantage lies in th

38、e optimal use of resources and optimization of product slate and quality to achieve the efficiency of enterprises, especially the integrated utilization of by-products in oil refinery and petrochemical industry can enhance the feedstock flexibility and extend the scope of raw materials for productio

39、n of ethylene and reformate gasoline.5.1 The principle of distribution and optimization of naphthaGenerally, naphtha mostly comes from the atmospheric- vacuum distillation unit, the catalytic cracking unit, the hydrocracking process, the delayed coking unit, and the pyrolysis gasoline byproduct from

40、 ethylene plant. The amount of straight-run naphtha accounts for more than 80% of naphtha pool. Not all the naphtha streams produced from the crude oil are suitable for use as the ethylene or reforming feedstock, because the different nature of crude oil leads to different composition of naphtha. St

41、raight-run naphtha is characterized by its low olefin content, high content of al- kanes and cycloalkanes (with their mass fraction reaching up to 80%), and the various potential aromatic contents (about 25%一55%). However, a big discrepancy about composition and impurity content exists in the second

42、arily processed naphtha, and furthermore, different operating conditions can result in different naphtha compositions. Therefore, rational distribution and utilization of naphtha feedstock should be carried out according to the different components of naphtha that are suited for production of either

43、 clean fuel or ethylene. By virtue of the ethylene cracking feedstock law，the lighter the naphtha is, the higher al- kane content and better pyrolysis performance will be. However, the naphtha with a high potential aromatic content of more than 40% as well as a high naphthenic hydrocarbon content sh

44、ould be an excellent catalytic reforming feedstock. Thus, all in all, those naphtha feedstocks with more potential aromatic content should be used in catalytic reforming process to produce clean fuel products, and those with more alkane content should be used in the steam cracking process.52 The ind

45、ustrial application of optimized naphtha resource5.2.1 The industrial application of the pyroJysis aromatic raffinate oil as the catalytic reforming feedstockPyrolysis gasoline produced by ethylene plants accounts for about 70% of steam cracker byproduct output, from which the hydrogenated benzene-t

46、oluene-xylene mixture (BTX) is manufactured after aromatics extraction. Unfortunately, some ethylene plants treat the raffinate from extraction unit, which is called the pyrolysis aromatic raffinate，as a low-grade fuel and is burned as a furnace fuel. The comparison on the data of reformate originat

47、ed from Chinas major refineries and aromatic raffinate oil is presented in Table 2. It can be seen from Table 2 that the pyrolysis aromatic raffinate oil has an extremely high naphthenic hydrocarbon content of about 75% and its potential aromatic content is as high as 62%. In addition, the pyrolysis

48、 aromatic raffinate oil has an index of aromatics yield equating to more than 70%.An industrial test on reforming feedstock has been conducted. The original reforming feedstock is blended with 5% to 20% pyrolysis aromatic raffinate oil and then is used as the new reforming feedstock at a Chinese pet

49、rochemical plant. The evaluation of the feedstock with 20% blended71994-2015 China Academic Journal Electronic Publishing House. All rights reserved, 53Table 2 Characteristics of catalytic reforming feedstock at different refineries of ChinaItemsDaqingDagangShengliLiaoheNorth ChinaXinjiangAromatic r

50、affinate oilDistillation range, °C79141751798717164175821578116270160Component, m%Alkanes58.643.349.146.457.753.123.51Cycloalkanes: including38.743.443.541.536.741.175.58c51.31.00.30.17.76c610.94.88.17.48.15.635.07Cr15.38.213.416.615.39.919.14c89.89.513.214.59.213.611.54c92.710.28.62.03.811.52.

51、07Cto9.40.20.4Aromatics2.713.37.412.15.65.80.91Potential aromatic content36.2631.0538.4947.2835.7932.8761.96Index of aromatics yield (N+2A)44.1070.0058.3065.7047.9052.7077.40pyrolysis raffinate is presented in Table 3. And Table 4 ex-As the test result showed, there is a high potential aromatichibit

52、s the comparison on data of aromatic hydrocarbon con-hydrocarbon content in the pyrolysis aromatic raffinate, andtent in the reformer gasoline.the distribution of aromatic hydrocarbons is concentratedTable 3 Result of commercial testsRaw materialReformateMixed with 20% pyrolysis aromatic raffinateRe

53、action conditionReactor inlet temperature, °C500500WABT, °C479.6480.5Reactor pressure, MPa0.350.35Volume space velocity, h'11.51.5Hydrogen to oil volume ratio800800High-value oil yield, m%86.5486.10Aromatic content of high-value oil, m%80.3880.80Aromatic content yield, m%69.5669.57Refo

54、rming conversion rate, m%155.5155.6Octane number of high-value oil, RONC102.2102.5Octane number yield, %88.488.3Hydrogen purity, %88.889.2G«is production, gas mL/mL of oil387.1401.8Table 4 Comparison of aromatic hydrocarbon content of reformergasolinem,%AromaticsReformateMixed with 20% pyrolysi

55、s aromatics raffinateBenzene6.3510.97Toluene17.4818.63Mixed xylenes23.9822.65C9f Aromatics32.5728.55Total aromatics80.3880.8054mostly in light aromatics. Therefore, compared with the intermediate-base feedstock (with a moderate potential aromatic hydrocarbon content), the industrial tests of the fee

56、dstock blended with 20% pyrolysis aromatic raffinate gave an indication that the bed temperature, gas production, hydrogen purity and light aromatic content had been enhanced albeit with small variations. That is to say, there are no significant changes on the overall reforming reaction and operatin

57、g status upon using the feedstock blended with an appropriate proportion (below 20%) of pyrolysis aromatic raffinate which can be used as an ideal reforming feedstock. Considering the heated competition in pursuit of clean fuel and ethylene industry feedstock, the utilization of low-vaiue byproduct naphtha formed during ethylene production must be imperative.5.2.2 The industrial application of reforming raffinate as steam cracking feedstockGenera