The combined tar slurry and fixed bed hydrogenation technology is developed by Ningbo Institute of Industrial Technology (CNITECH), Chinese Academy of Sciences (CAS) and us. It is the advanced coal tar hydrogenation and kerosene co-refining technology which can achieve the maximum liquid yield.
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The research and development team of the tar slurry and fixed bed hydrogenation technology has overcome a number of technical problems over the years. At present, the technology has been commercialized and has been used for five years.
SBC is the abbreviation of slurry bubble column ,which indicates the fluid form of the coal tar hydrogenation:
1. The slurry shows that the reaction system contains solid, it is a liquid (oil) -solid mixture;
2. The bubbling shows that there is gas through the liquid - solid slurry, which plays a role of stirring, this makes the gas-liquid-solid three-phase mix back fully and uniformly and then contact completely;
3. The column indicates the reactor configuration, it is an empty barrel-shaped container with no inner components.
In SBC, the solid is a nanocatalyst or an inert solid, different solids can be used depending on the specific nature of the raw material.
The fixed bed hydrocracking technology can only be used to process the distillate oil with less impurities , such as light and heavy wax oil and so on.
The full range FCC gasoline of middle and low temperature coal tar are with the characteristics of large molecular weight, many heteroatoms, complex structure, high density, high residual carbon, high metal content and high asphaltene content.
The suspended bed hydrocracking technology can not only process the whole fraction of coal tar, but also process the coal and oil mixing, and the conversion rate is high, with a strong adaptability of raw materials and economy.
1, The first section of the suspension bed hydrocracking are combined with the second one of fixed bed hydrocracking which not only ensures the life of the catalyst in hydrogenation but also ensures the stable high-quality products are produced.
2, its unique powder additives ensure that the unconverted, high metal content of heavy oil can be captured and removed sufficiently, which can make sure the reaction goes on smoothly and effectively and prevent the equipment coking, extending the processing cycle of the device.
The comparison are made in terms of the raw material adaptability, the process flow, the catalyst life, the raw material properties, the product quality, the hydrogen consumption and others..
a) Raw material adaptability
The fixed bed can only process the distillate less than 500 ℃, which is 67% of the total raw coal tar, and the remaining 33% can only be sold as low valuable tar asphalt with poor economic returns.
The suspended bed can process the whole fraction coal tar, with reach 95% conversion rate of the fraction and> 525 ℃, the product yield is high with good economic returns.
b, Processing
The fixed bed should be equipped with a complicated three-stage distillation scheme for the separation of feeds which is suitable for the fixed bed hydrogenation unit. The process is complex, the operation cost is high and the energy consumption is large.
The suspended bed does not need complicated preprocessing, the investment and operating cost are low.
C, The contrast of the catalyst life
The catalyst in the bed of the fixed-bed reactor is in a quiescent state, it is not easy to wear. When the catalyst is not deactivated, the catalyst can be used for a long period. However, the coal tar contains a lot of impurities in raw materials, the rapid inactivation was caused seriously by the olefin polymerization ,the metal, the asphaltene and others. The catalyst life is not more than 3 months and the device processing cycle is short.
The catalyst is not required in the suspended bed ,only some powder additives are added, on which the impurities in the coal tar which will affect the catalyst life accumulate, ensuring the raw material into the fixed-bed reactor are with good quality, so the processing cycle of the device can be more than 2 years.
d, the raw materials properties
1) olefins
In the fixed bed the diene in the raw materials needs to be removed at a low temperature, which may affect the operation cycle of the unit.
By SBC technology, the raw materials was mixed with the additives before they are heated to the reaction temperature, and then with hydrogen, a high hydrogen partial pressure can inhibit the polymerization reaction. At the same time as the polymerization occurs on the surface of the additive, it will not affect the equipment and the pipeline, which guarantees the long-term operation of the device.
2) oxygen
The presence of oxygen in the fixed bed accelerates the polymerization of olefins, which results in serious fouling of the fixed bed protection reactor and the catalyst, so the apparatus can not run for a long period;
By SBC technology most of the oxygen in the suspended bed reactor are converted into water, which reduces the oxygen content of the feed to the fixed bed reactor and avoids the rapid polymerization of olefins.
e、Product quality
The density of the fixed bed product is high and the cetane value of the heavy oil is low, this is because the heavy oil fraction contains a large amount of aromatic hydrocarbons and the hydrogenation pre-saturation can not improve the properties of the feed effectively.
The quality of the SBC product is better than that of the fixed-bed technology, which can be used to produce the diesel blending components up to the emission standard of Europe Ⅳ and Euro Ⅴ
f、Hydrogen consumption
The hydrogen consumption of the fixed bed is about 6%, but the product yield is low and the property is poor.
The hydrogen consumption of the suspension bed is 6% of the raw material feed (medium and low temperature coal tar), but the yield is high and the property is good.
(1) The current market price of coal tar is about 1600 yuan / MT.
(2) The price of hydrogen. It can be made from coke oven gas , this technology is mature, so the price of hydrogen can be 11120 yuan / t (to 1.0 yuan / M3).
(3) the consumption conversion of the hydrogen is about 6.4% ,so for each Mt coal tar the consumption of hydrogen is 11120 yuan × 6.4% = 712 yuan, so the cost of raw materials is about 2312 yuan / MT.
(4) For the products, after the hydrogenation the clean fuel oil is made, the price is about 3,500 yuan / MT, if we calculate the light fuel yield as 95%, that is 3500 yuan / mt × 95% = 3325 yuan / MT.
(5) From the above data we know: Between the raw material costs and product prices there are about 1013 yuan gap, that is 3325 yuan /MT -2312 yuan / MT = 1013 yuan / MT.
(6) the processing cost for each metric ton of coal tar is 800 yuan, according to the current price there is only 200 yuan profit; The price of crude oil is very possible to rise in the long term, then it will be very economic.
In summary, it is a very economic project to make the clean fuel oil by the coal tar hydrogenation
