5 replies to this topic

[thanhsvh5]

my name is thanh, a process Engineer. I only have 6 months to operate CCR unit. Could you help me some questions:
1. How to predict Hydrogen/hydroccbon ratio by your experiences (we have H2 recycle gas flow, h2 net gas flow, and feed flow).
2. How to predict the catalyst age.
thanks a lot

[Himanshu Sharma]

Hi !

I would like you to be more clear...do you want to know fundamentals or you are going to process a feed for which the unit is not designed and there's some tuning required for H2/HC ratio???

H2/HC ratio in CCR is tried to be as less as possible,the lower the better.

Typically i have seen H2/HC Molar ratio of 2~2.5 been employed though its not unusual to have a ratio of 4~6 or as high as 20(SR beds) .This ratio is an important control variable for Reforming and kept fixed for Design case of Crude.

H2/HC ratio is dependent on Conradson carbon content of feed and there's a ratio calculator (Programmable logic based software) on feed that analyses this ratio.Conradson carbon residue (CCR) is a standard petroleum industrial coking test for characterizing the coke forming tendency of petroleum liquids that now a days is measured by the Microcarbon method(ASTM D4530).Generally results shows that the CCR is a linear function of hydrogen content.The addition of hydrogen increases the coke induction period by lowering the solubility parameter and mesophase of coke formation.

I would advice that if you want to tweak out H2/HC ratio for some diff crude other than design crude get back to your licensor as there are chance of catalyst pining and other damage.

As far as catalyst aging is concerned you may notice it when you have to increase temperature of reactor to keep product on-spec...other wise you can take catalyst sample through sampling devices and check them in lab.

[Root]

my name is thanh, a process Engineer. I only have 6 months to operate CCR unit. Could you help me some questions:
1. How to predict Hydrogen/hydroccbon ratio by your experiences (we have H2 recycle gas flow, h2 net gas flow, and feed flow).
2. How to predict the catalyst age.
thanks a lot

Hi,
H2/Hc is 2.0 mol/mol but you need 2.9mol/mol, follow this procedure and you calculate what is your H2/Hc ratio,
assume 1m^3 of feed
Net H2 is 224nm^3/m^3 *0.9/22.4 nm^3/kgmol=9kgmole H2
feed is
1m^3*700kg/m^3/100=7kg mole feed
so net gas H2/Hcis 9/7=1.29 mol/mol
so tatal H2/Hc=2.0+.7*1.29=2.9
Further to Catalyst aging,
You need to know efficiency, surface area and retention of chloride, hope your using R134 for CCR operation.
Cheers

[Himanshu Sharma]

@Toor

Sir this calculation seems Wonderful but i have few doubts

1.If H2/HC molar ratio is always 2 irrespective of feed Processed in the unit???(specifically even if we are processing a portion of coker Naphtha)

2.C5+ cut processed in CCR has a range of Densities between 650 to 720(based on reforming units i have worked on..producing gasoline or Aromatic Feedstock ) and Mol. Wt also varies from some where 85~110. Kindly guide me the basis for a good assumption as you have made.

As per Axens H2/HC molar ratio is defined by this formula..

Ratio= ((Recycle flow rate kg/h /mol wt)*(Vol % of H2 in Recycle gas))/((Feed Kg/h)/Mol Wt)

Edited by Himanshu Sharma, 16 November 2009 - 11:02 AM.

[thanhsvh5]

in refinery, UOP licensor. We want calculate H2/HC ratio how much: feed:100 m^3, recycle gas: 45000m^3, net gas 30000m^3, density of feed 750. So how to calculate and how much mol of H2 and HC and how much h2/HC ratio(if we can predict and calcualte fast, not calculate follow the compostion of feed). I mean we can culate when we see only feed, recycle gas flow, net gas flow and density).
Thanks.

[Himanshu Sharma]

@thanhsv5

H2/HC ratio should be accurately determined because it pure money,Honey

More Hydrogen--more energy losses+compressor bottleneck
Less Hydrogen--Safety Concerns+Coking

Hmm ok, i can give you some idea about the typical range and then you may calculate a Good approximation for values of H2/HC ratio.

Hydrogen content in recycle gas it typical range of about 82-92 vol %(units i have seen)
Mol Wt of Feed--at least this should be known but range is between 80-98~100