Crude hydrogen pressurizing and recovering method for styrene device

Abstract

The invention relates to a crude hydrogen pressurizing and recovering method for a styrene device. In the method, crude hydrogen from the top of a dehydrogenating exhaust absorbing tower of the styrene device firstly enters a suction tank of a hydrogen compressor; crude hydrogen at the top of the tank is compressed through four sections of compression of the hydrogen compressor; condensate produced among the sections is discharged in discharging tanks of each section; crude hydrogen at the top of the discharging tanks is conveyed to a variable-pressure adsorption device; condensate at the bottom of the suction tank of the hydrogen compressor and condensate in the discharging tanks of each section are discharged into condensate collecting tanks among the sections of the hydrogen compressor; gas at the tops of the condensate collecting tanks is discharged into a low-pressure torch; and gas at bottoms of the condensate collecting tanks is pumped in a crude styrene sedimentation tank. When the method is adopted, the volume fraction of aromatic hydrocarbon in crude hydrogen can be reduced by 0.02 percentage points, so that the quality of the crude hydrogen can meet the feeding requirements of a PSA device; and moreover, as the condensate is not discharged into a sewage tank, potential safety hazard is eliminated, aromatic hydrocarbon substances in sewage are avoided, and cost for sewage treatment is reduced.

Description

technical field [0001] The invention belongs to the dehydrogenation tail gas treatment technology in the production process of ethylbenzene catalytic dehydrogenation to styrene in the field of chemical engineering, and relates to a method for pressurized recovery of crude hydrogen in a styrene plant. Background technique [0002] There are three main processes for producing styrene, namely ethylbenzene catalytic dehydrogenation method, styrene-propylene oxide co-production method and ethylbenzene oxidative dehydrogenation method. The catalytic dehydrogenation of ethylbenzene occupies an absolute dominant position in the styrene industry, accounting for more than 90% of styrene production. In this process, the ethylbenzene dehydrogenation reaction product is firstly cooled by ethylbenzene through the material heat exchanger in and out of the reactor, and at the same time is cooled by high-pressure steam generated by the boiler feed water, and then condensed by the cooling wat...

AI Technical Summary

Problems solved by technology

One is that the crude hydrogen enters the suction tank of the hydrogen compressor, and the condensate at the bottom of the tank is discharged into the sewage tank. The condensate contains aromatics such as benzene, ethylbenzene and styrene, and entrains hydrogen, which poses safety and environmental risks; The condensate at the bottom of the discharge tank at the outlet of the fourth section is directly discharged into the crude styrene settling tank through the pressure reducing valve. Generally, it is discharged every 3 to 5 hours by manual operation, and each discharge is 2 to 5 minutes, which affects the crude styrene. Operation of settling tanks and associated systems

Another crude hydrogen pressurized recovery method has improved this. The condensate at the bottom of the discharge tank at the outlet of the first to fourth stages of the hydrogen compressor is discharged into the suction tank of the hydrogen compressor through a pressure reducing valve, and the discharge is all automatically controlled. It saves manpower and avoids affecting the follow-up system operation, but aromatics such as benzene, ethylbenzene and styrene contained in the condensate will form a mist in the suction tank of the hydrogen compressor due to decompression flash evaporation, affecting the inlet of the first section of the hydrogen compressor The quality of crude hydrogen increases, so that the content of aromatics in the hydrogen at the outlet of the fourth stage of the hydrogen compressor increases, which affects the life of the adsorbent in the downstream PSA device; the condensate at the bottom of the suction tank of the hydrogen compressor is pumped into the crude styrene settling tank, although Eliminates safety and environmental hazards, but during the pumping process, a small part of the condensate at the pump outlet enters the suction tank through the minimum flow return line, which will also form mist and affect the quality of crude hydrogen

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