The Project “Development and Commercial Application of Continuous Liquid-Phase Diesel Hydrotreating Technology”Passed SINOPEC’s Technical Appraisal

On December 12, 2013 the project “Development and commercial application of continuous liquid-phase diesel hydrotreating (SLHT) technology” jointly undertaken by RIPP, SEI, the Shijiazhuang Refining and Chemical Co. (SRCC) and the Anqing Petrochemical Co. has passed the technical appraisal organized by the Science and Technology Division of SINOPEC in Beijing.

Technical personnel engaging in this project upon delving into the principles of continuous liquid-phase hydrotreating of diesel first of all investigated the process regulations of upflow reactor, developed the method for automatic control over the continuous phase in the upflow reactor, finalized the technical route for realization of SLHT, and worked out the SLHT process scheme featuring a simple and intrinsically safe operation.

In pursuit of the Chinese content, the technical team for the first time designed an upflow reactor, developed the high-efficiency reactor internals in order to make the liquid phase inside the reactor function as the continuous phase with the gas phase serving as the dispersed phase. The space utilization rate is increased so that the internals can be easily fabricated and installed. A flow of excess hydrogen can be properly replenished at the reactor inlet and between catalyst beds to enhance the reaction rate, reduce the recycle ratio, and cut the equipment investment cost and operating cost. It is the first attempt to design the mass-transfer internals inside the high-pressure separator and reduce H2S concentration in the recycle oil by means of introducing a small amount of stripping hydrogen to promote the deep desulfurization reaction. A brand new process scheme for start-up and shut-down of equipment has been formulated in order to reduce the startup and shutdown time, while a new safety interlock and control theory and an emergency response program have been proposed. The interim commercial calibration tests of the SLHT process at SRCC have revealed that it is possible to manufacture a diesel fuel product meeting the national quality standard IV for diesel fuel by using a straight-run gasoil blended with 8% of coker diesel fraction. When the mixed feedstock containing 3 900 μg/g of sulfur and 217 μg/g of nitrogen was hydrotreated at a reactor inlet pressure of 9.0 MPa, an average reaction temperature of 365.3 ℃, a space velocity of 1.55 h-1, and a recycle ratio of 2.0, the diesel fuel product meeting the national quality standard IV was obtained. When the reaction temperature was raised to 376.3 ℃, the sulfur content in diesel could be reduced to less than 10 μg/g. The energy consumption for manufacture of diesel fuel meeting the national quality standard IV is equal to 6.24 kg of SOE/ton (for cold feedstock), or is tantamount to 4.81 kg of SOE/ ton of feedstock after being converted to heated feed oil at the design point, which is much less than the energy consumption achieved at the traditional trickle bed for hydrotreating of diesel. The outcome of an accumulated 10 months of operation has indicated that the continuous liquid-phase diesel hydrotreating (SLHT) technology is characteristic of simple and smooth operation coupled with good catalyst stability that can meet the commercial production needs. The test results have once more verified the pilot plant testing outcome.