What are the benefits of adding process steam in pre reformer inlet and reformer inlet separately? In some hydrogen plant it is mixed only in reformer inlet. What is the advantage of that?
Answers
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13/07/2010
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A:
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Balasubramanian Iyer, Nexen CNOOC Limited, balasubramanian.n@aol.in
1. Advantage of the introducing process steam Separately in both the reactors is the heat load on the Pre-Reformer Heating Coil is reduced as the Steam introduced is as per the Requirement in the Pre-Reformer. But the Load on Reformer Feed Heating Coil is same regardless of the Steam introduction in Pre-Reformer or in the Reformer Inlet.
2. Secondly one should be careful while starting-up of the plant as even a small amount of steam condensate carry over in the reformer inlet can cause detrimental effects to the tubes as steam reformer tube failure incidents have been witnessed from such mistaken action. One should ensure steam is completely dry before introduction in such cases.
3. If it is separately introduced one should be careful in letting in the process steam in Pre-Reformer in case of feed changes as the C/H ratio changes then the steam consumption will change and one should be careful and keep update with the feed composition changes. If not the pre-reformer catalyst will be deactivated, this is not the case if the entire Process steam is introduced in the Pre-reformer.
4. Any process upsets due to which the pre reformer inlet temperature drops due to which the bed temperature also drops. If the total process steam is introduced in the inlet of the Pre Reformer one should be careful with the lowest thermocouple in the pre reformer as it should not go less than the design low temperature of the catalyst. But in Case of the separate introduction much effect is not witnessed as the steam quantity is not such high that it will not lead to catalyst deactivation. We can have some cushion in that region during upsets.
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05/07/2010
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Nitin Mittal, HPCL Mittal Energy Limited, mitnit73@yahoo.co.in
The main purpose of the Prereformer is to reform all higher hydrocarbons completely simultaneously with methane reforming. In addition, incorporation of the prereformer has
following advantages
1.Considerable energy savings are obtained because heat recovered in the convection
section of the tubular reformer can be utilised for additional preheating of feed to the tubular reformer radiant section. Alternatively, this heat would be used
for steam production.
2. Operation with a lower steam/carbon ratio becomes possible hereby reducing the
mass flow through the plant. Also greater flexibility to variations in the steam to
carbon ratio and feedstock composition is allowed.
3. Prolonging life of tubular reformer catalyst due to prereformer catalyst will act also as guard.
I want to make clear that in Pre Reformer Steam is consumed as per stoichometric ratio only so the extra steam added in pre-reformer inlet will be utilize in Reformer inlet.
(but one thing is not clear to me how you can operate Pre reformer with out steam addition?)
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