| 摘要 |
The catalyst circulation rate in a fluid catalytic cracking process is regulated by using a low pressure drop valve means in the spent catalyst circuit of said process in conjunction with a control riser in said circuit. More particularly, a reduced catalyst circulation rate may be obtained in a fluid catalytic cracking process, the spent catalyst circulation rate in said process being controlled by the injection of variable amounts of a control gas into the control riser so as to cause density variations therein, by employing a low pressure drop valve means in the spent catalyst circuit of said process such that the pressure drop across said valve means reduces the pressure drop across the riser and consequently the density within said riser. The reduction in density within the riser results in a lowering of the catalyst circulation rate. Use of the present invention enables stable operation of the catalyst circuit at circulation rates equivalent to lower mass velocities in the riser than possible without the low pressure drop valve means while maintaining the pressure differential between the regeneration zone and the cracking zone substantially constant.
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