기계공학 취준일기 #16 HSR(HEAVY STRAIGHT RUN NAPHTHA), NHT

이전에 LSR처리 공정을 알아 보았으니 HSR처리 공정에 대해 알아보자.

 

Naphtha Hydrotreating Unit(NHT)에 대해 알아보자.

 

출처 구글

 NHT는 CDU에서 나온 HSR에 고온고압의 조건에서 HYDRO를 첨가하고 촉매(코발트와 몰리브덴)을 활용하여

 

황, 산소, 금속, 질소 등을 제거하고 올레핀을 포화시킨다. 그 이유는 이후 Reforming공정에서

 

중질 납사를 개질하는데 촉매에 독이되고, 효율을 떨어뜨림은 물론, 환경오염을 야기하기 때문이다. 

 

아래는 EGGCYCLOPEDIA에서 첨부한 파일이다. 어려운 내용 아니니 해석은 하지 않겠다.

Heavy Naphtha cut from the atmospheric crude oil distillation column in a refinery is sent to a ‘Naphtha Hydrotreating Unit’. After the naphtha hydrotreating unit, naphtha is sent to an isomerisation unit or a catalytic reformer unit, which often use reforming catalysts. Most reforming catalysts contain platinum as the active material. Sulfur and nitrogen compounds present in naphtha cut from atmospheric distillation column can deactivate the catalyst and must be removed prior to catalytic reforming.

Purpose of the naphtha hydrotreating unit is to remove sulphur and nitrogen compounds. The naphtha hydrotreating unit uses a cobalt-molybdenum catalyst to remove sulfur by converting it to hydrogen sulfide that is removed along with unreacted hydrogen. Some of the hydrogen sulphide-hydrogen mixture is recycled back to the reactor to utilize the unreacted hydrogen, using a compressor.

Reactor conditions for naphtha hydrotreating unit are around 400-500˚F (205-260˚C) and pressure of 350-650 psi (25-45 bar). As coke deposits on the catalyst, reactor temperature must be raised. Once the reactor temperature reaches ~750˚F (400˚C), the unit is scheduled for shutdown and catalyst replacement.

 

Figure 2 - Stripped in the naphtha hydrotreater unit

If required, the boiling range of the catalytic reforming charge stock can be changed by redistilling in the naphtha hydrotreater in a stripper as shown in Figure-2. Often light naphtha containing pentanes, hexanes and light naphtha are stripped off and sent directly to gasoline blending or pretreated in an isomerization unit prior to gasoline blending. The heavy naphtha from the bottom of the stripper column goes back to the catalytic reformer unit before blending with gasoline.