Fluid Catalytic Cracking Process Ε. V. MURPHREE
Downloaded by MICHIGAN STATE UNIV on February 18, 2015 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch004
Standard Oil Development Co., New York, Ν. Y.
Catalytic cracking is an outgrowth of the oil industry's quest for more efficient utilization of the heavier petroleum fractions present in crude oil. Fluid catalytic cracking is but one of the processes that have resulted from the extensive technical effort to develop efficient and improved means for carrying out this cracking reaction. The Fluid process, however, is of particular interest not only because of its leading position in refinery applications, but also because it represents the first widespread application of a new chemical engineering unit operation, the Fluid solids technique. This paper reviews the development of the process and describes its more pertinent process and engineering features.
C a t a l y t i c cracking is a n outgrowth of the oil industry's quest for more efficient utiliza tion of the heavier petroleum fractions present i n crude oil. F l u i d catalytic cracking is but one of the several processes that have resulted from the extensive technical effort to develop efficient and improved means for carrying out this cracking reaction. The F l u i d process, however, is of particular interest not only because of its leading position i n refinery applications, but also because i t represents the first widespread application of a new chemical engineering unit operation, the F l u i d solids technique. This paper reviews the development of the process and describes its more pertinent process and engineering features.
Development I n catalytic cracking, oil is passed over a catalyst to obtain the desired conversion. This is accompanied b y deposition of a cokelike deposit on the catalyst, which can be re moved b y burning with air. The first catalytic cracking plants used fixed catalyst beds, the shortcomings of which were evident from the first work done i n this field. The sub stantial deposits of coke formed during the reaction necessitated frequent regeneration and resulted i n a discontinuous process i n so far as the catalyst was concerned. F r o m a mechanical standpoint, this discontinuity meant more equipment and consequently greater cost. F r o m a process standpoint, flexibility i n operations was severely limited; i n addition, attainment of accurate and uniform temperature control during the cracking or regeneration cycles was difficult even with complicated and ingenious mechanical design of the reaction vessels. The large quantities of heat liberated during regeneration of the catalyst could not be transferred efficiently to the cracking section, where a substantial heat input was required to heat and to vaporize the oil and to satisfy the heat of reaction. Experimental work was accordingly begun on cracking systems using powdered catalyst fed continuously with the oil. The initial work, carried out i n small coil-type reactors, indicated promise. Investigations were therefore initiated to obtain knowledge on the physical phenomena involved i n the flow of this system of mixed-phase gas and 30
In PROGRESS IN PETROLEUM TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1951.
MURPHREE—FLUID CATALYTIC CRACKING PROCESS
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Downloaded by MICHIGAN STATE UNIV on February 18, 2015 | http://pubs.acs.org Publication Date: January 1, 1951 | doi: 10.1021/ba-1951-0005.ch004
powdered solids. This work resulted i n the fundamentally important discovery that the degree of slippage between a rising gas stream and fine solids suspended i n that gas was great enough, under certain conditions, to establish a dense phase of solids, and thus the concept of the F l u i d bed was established. The degree of slippage so obtained was con siderably greater than that expected, based on knowledge existing at that time. The high concentration of catalyst so obtained afforded a major economic advantage i n providing small reactor volume and low pressure drop through the catalyst flow system. T h e similarity i n appearance of the Fluid solid bed to a boiling liquid led to the idea of using an aerated standpipe for raising pressure on a powdered solid when transfer of the material was required. This standpipe represented a major development, i n that i t provided a simple means for circulating the catalyst, eliminating need for complicated mechanical devices such as pumps or lock hoppers. 1200
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