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Energy Consumption in a Crude Oil Refinery Distillation Process

03/17/2015 10:02 AM

Hello all,

I am looking for advice in determining an analytical estimate for energy consumption in the distillation process of crude oil refining. My questions are as follows:

I believe that the highest fossil fuel usage will be in heating the crude oil from ambient temperature to its vaporization point. What devices are used in this process?

I believe that there is also a significant amount of energy consumed in producing steam for the distillation process. Where is the steam used in the greatest quantities and does anyone know of methods or resources to determine analytically the amount of steam that needs to be produced?

Thank you for your time and advice,

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#1

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/17/2015 11:57 AM

I bet james stewart could explain this.

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#2

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/17/2015 2:16 PM

That advice may be found in the design documentation and the commissioning records for the plant. No-one else here can see it.

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#3

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/17/2015 7:01 PM

Is this for a term paper?

Thesis?

Have you asked the API?

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#4

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/17/2015 11:56 PM

..." A direct-fired furnace heats the crude oil to 650-750°F (343-400°C) before it enters the flash zone of the atmospheric tower."...
..."Most units follow a heat balance design, where the heat produced during regeneration supplies the heat consumed during the endothermic cracking reactions. From a utility perspective, some units are net energy producers given the large quantities of hot flue gas produced in the regenerator that are used to generate steam and power. A catalytic cracker constantly adjusts itself to stay in thermal balance. The heat generated by the combustion of coke in the regenerator must balance the heat consumed in the other parts of the process, including the temperature increase of feed, recycle and steam streams, temperature increase of combustion air, heat of reaction, and other miscellaneous losses including surface radiation losses."...

http://energy.gov/sites/prod/files/2013/11/f4/bandwidth.pdf

http://en.wikipedia.org/wiki/Oil_refinery

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#5

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/18/2015 2:58 AM

Much depends on factors as yet unmentioned...such as throughput of the plant ie the capacity of various vessels and consequent heating requirements are dependent on this. Note that the whole process is a distillation, so vessel heat requires to be maintained in the face of process heat losses (ambient losses are largely contained by lagging/ cladding)

If we are to read your question as "how much energy is required per unit of oil (bbl or gallon)", it leaves me lost. There are phases in the distillation that do not require addtional energy, such as the taking off of light ends in a distillation tower etc...

There are smarter guys than myself here, but your question, to my mind, can only be answered after analysing a specific plant design. There is no generic value for the enrgy usage. Even on a known, running plant, mass balances on the process are calculated daily, which means there is uncertainty in the overall design, which is also not necessarily predictable.

Your best source for an answer would be from an operating refinery.

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#6
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/18/2015 10:12 AM

Your best source for an answer would be from an operating refinery.

Good luck with that these post 911 days. I got run down, cornered, and then run off from the public road beside a refinery last month for taking pictures, per instructions from NSA. I doubt any are going to discuss operations anymore.

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#7

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/18/2015 2:34 PM

http://www.ilo.org/iloenc/part-xii/oil-and-natural-gas/item/384-petroleum-refining-process

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#8

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/19/2015 4:25 AM

Sorry, I should have concentrated on steam, not heat.

The answer remains roughly the same. Any plant generating it's own steam, will use that steam for heat-tracing it's piping and vessels. There is also a requirement for super-heated steam.

Generally heat losses would arise from: Geometry of the plant (piping especially, owing to length of pipe runs; plant and vessel size; integrity of insulation; efficiency of steam turbines; boiler capacity/ throughput etc ....

Steam losses occur due to integrity of vessels and piping, valve packing, turbine efficiency etc etc...once you have a home grown supply, in-house engineers find it more and more attractive to power up modifications to plant and to power additional plant equipment. There are losses to both heat and steam during routine maintenance outages, and also breakdown in the steam supply equipment eg pressure let-down stations, pressure and temerature control valves, steam-cuts on fittings, failed gaskets etc...etc..ad nauseum.

Naturally, the boilers (aka 'steam generators') must be shut down for periodic inspection and maintenance (refer to ASME/ similar) and those losses (I call them losses, but other might not) must also be reckoned in....list just goes on and on..and that's why it becomes very difficult to predict. Of course , one can do estimates/worst case/ best case, but aside from an academic practice, there is no real value in those results.

OK i'm done now...feel a lot better for the mini-rant, thanks!

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#9
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/19/2015 3:08 PM

You really can't isolate steam from all the other energy intensive streams that go into a modern refinery. Every chemical engineer has to take a series of courses known as "Unit Operations"where every factor of process design is discussed, so the data is hardly a secret.

What is proprietary are the trade secrets that make one refinery more efficient than another; however mass, steam, energy, and material balances tend to contain the information you're looking for. As others have said, there is no universal guideline since each plant is different, and even in the same plant the differences in the raw feedstock require fine tuning of the processes so what's true today will be different tomorrow.

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#10
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/20/2015 3:09 AM

I agree, (as per my first response).

However, from the OP's post not directly addressed "Where is the steam used in the greatest quantities and does anyone know of methods or resources to determine analytically the amount of steam that needs to be produced?"

Calculating the amount of steam required, means having to know exactly what the total heat tranfser rate to the feedstock is, continuously and with certainty.

Nothing is impossible I guess (and I have worked with pretty smart Chem engineers in my time), but accurate calcs under the specified conditions were always above my pay grade in any case. I have no doubt that there exists a software simulation somewhere,that can do this, version number $$$$$!!!. Next best option is to call around the universities...maybe someone has done and published such a study.

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#11
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/20/2015 4:58 PM

Yes, there are simulators out there, as well as academic papers, these are the ones at the top of a Google search.

"...one can do estimates/worst case/ best case, but aside from an academic practice, there is no real value in those results..." I disagree, the real value is that they set the Bogey (target range) for the plant. Plant management is held accountable for any variations outside of these ranges. Without them how would you even know whether you are operating the plant properly and/or how efficient your operation is?

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#12
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/23/2015 7:15 AM

Ram,

You have provided good, considered responses, thanks. I have not ever had the joy of software package calcs on a new plant..what you read of mine previously are the opinions of the grunt tasked to do manual calcs on old (ish) plant with plenty of steam already escaping.

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#13
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/23/2015 9:26 AM

Hilton, Neither have I, but I do remember walking around a 660MW supercritical boiler when the windchill was -20ºF and feeling warm 5 ft from the walls. When I asked the chief engineer how much heat was being blown away he said, "...it's built into the design specifications..."

When you're burning 320+/- tons of coal per hour, a few pounds here and there are just part of the overall losses in power production. I did notice that the more modern plants had thicker insulation and tighter cladding as the escalating price of fuel started figuring into the calculations.

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#14
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Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/23/2015 10:02 AM

"...it's built into the design specifications..."

Yes...heard that one many times (in respect of other things as well), but never seen it in writing..

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#15

Re: Energy Consumption in a Crude Oil Refinery Distillation Process

03/24/2015 2:05 PM

In spite of Kulas "belief" in me, I must preface my post by stating I have absolutely no idea of the actual steam or heat requirements for any refinery in operation.

What I can say is that the burn off is in the furnace that pre-heats the oil upstream of the distillation unit.

The utilization of steam varies also, but I suspect that much steam is required for any plant that has to heavy hydrotreat to upgrade stocks from naphthenic to more of a paraffinic character, or adjust ratios between paraffinics and aromatics. Steam is also injected into the distillation unit side-strippers, but this steam is usually of a lower BTU value (temperature, pressure), and as such might not constitute the majority of steam demand. Some steam is usually available to drive rotating equipment as pumps, generators, gas compressors, etc., although in recent years the trend is to utilize gas turbine equipment to handle the job of prime mover.

Bottom line: As others have stated, this is a case-by-case basis, and deals with very sensitive proprietary information each company will guard closely.

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