Q & A > Energy Efficiency and Energy Management
Date  Replies
30/03/2021 Q: One of our fired heater gas burner's riser pipes is frequently plugged with coke-like formations on the internal periphery. Since it was identified that our fuel gas sulphur content was pretty high, my best guess for the cause of black material deposits was iron sulphide. But I read somewhere that fuel gas with high olefins can also coke up inside the riser pipes. Anyone else faced similar problems in their fired heater? If so, what was the mitigative measure taken to overcome this? (5)
24/10/2020 Q: 1.What is the expected heat loss ( drop in temperature) from the main fractionator bottom to the furnace inlet in coker unit with some recycle?
2.How does the Cp value of the bottom stream of MFC change when the recycle ratio changes?
19/10/2020 Q: Why aren't the draw off temperatures close to the IBP, FBP of the products? For example, the draw temperature of kerosene is 193degC where as the lab results suggest 140degC IBP and 240degC FBP. (1)
12/10/2020 Q: What are the approximate costs of utilities like HP steam, MP steam, fuel gas, DM water, plant air, and instrument air for calculating the operating cost of any plant? (2)
04/10/2020 Q: In an energy conservation programme I'm focusing on steam calculation starting from the reboiler and the distribution lines in the refinery. Could you please tell me the first step to do this calculation, whether anyone has a relevant book or article, and can I use Hysys software? (1)
04/10/2020 Q: What is the typical discount rate in an oil refinery feasibility study to get an optimum result for NPV? (3)
10/08/2020 Q: For a crude distillation unit, what should be the top temperature of the column, draw off temperatures for naphtha, kerosene and diesel, and the bottom temperature of the column? (2)
30/07/2020 Q: In our hydrogen generation unit, a waste heat boiler functions to recover reformer O/L heat to produce HP steam. Boiler is single pass shell and tube exchanger with fixed tube. Since last year the boiler is not able to recover heat upto expectation as indicated by the raised process gas O/L temperature. The process gas O/L temperature is now around 288oC instead of 265 oC earlier. In the last 2 shutdowns the tubes have been cleaned thoroughly from inside but no benefit observed. Now it is suspected that there is fouling (maybe of silica) on the shell side. There is no provision to open and clean the shell side assembly. Is there is any technology available for online removal of such fouling (maybe some kind of chemical cleaning)? (1)
25/07/2020 Q: Why is furnace oil for burners blended with diesel? (3)
22/07/2020 Q: As a DCS Operator, what parametric and/or qualitative changes suggest the following problems?

Flooding, dumping, jet flooding, entrainment, weeping and foaming.
09/07/2020 Q: Pumparound flows through a preheat exchanger and after that passes through a control valve and back into the column. While deciding how much pump should be used, what should we consider?
Condition #1: Reduce the control valve opening, provide the pumparound more residence time inside the exchanger which will cool it down more and then it will return at a lower temperature but with a lower flow rate.
Condition #2: Increase the control valve opening which will allow more flow to be fed back into the column but with a relatively higher temperature.
Which one should we choose?
27/05/2020 Q: Hi,
I am working in optimizing the fuel gas for our fired heater, so can anyone help me in providing the fired heater efficiency calculation in Excel format. Your support will be much appreciated.
Also, any calculation available to help us to assess the heater performance will be very helpful.
Your prompt response will be highly appreciated!
04/03/2020 Q: Could any one tell me what is the cost of refining a barrel of crude oil or how can i predict it for typical refineries ,as well as the forecast ,thank you in advance (4)
03/03/2020 Q: We have two boilers working in paralel. However, due to high steam generation from the waste heat boiler in CCR unit (about 25%) being higher than design, both boilers are maintained operating at about 50% capacity of design. Still steam generation is higher than our requirements. We are maintaining both boilers running due to reliability concerns as stopping one boiler will lead to a delay in startup in case of emergency?
So could you please share if you have similar experiences and is there any hot stand-by procedure for boilers or any procedure that can help us to immediately startup a boiler in case of a running boiler trip as now there are huge losses of energy due to unused steam venting and condensing.
18/02/2020 Q: A boiler to produce low pressure steam
• Boiler has a rudimentary design. • Total volume is 1 m3
. • Check valve, pressure and level indicators are present. The check valve opens when the required pressure is achieved. It
can also be manually operated. • Mode of operation of boiler is unchanged- Half of the boiler volume filled with water, then fired. Steam builds up to the
required pressure. When the required pressure is achieved, check valve opens letting out steam. Once steam generation
begins, level of the water in boiler is maintained and continuous operation is achieved. • A flow measuring device is installed upstream to measure steam flow rate. • The start-up requires 352 seconds. • Due to severe clogging, boiler is swapped with a temporary one. The new boiler is double the size of the previous one.
The heat input rate and the check valve characteristics remain unchanged. • 400 seconds after firing the new boiler, it is observed that the pressure indicator is faulty. The level in the tank has shown
little deviation and the check valve has not opened. • What would be the most safe and efficient course of action? The boiler has emergency PRV, and is functioning at one
fourth of the pressure it is built to handle, and the maintenance of the clogged boiler will take 6 hours. If the issue with
the pressure indicator was diagnosed 1200 seconds after firing, with the check valve still being closed, would your
course of action have deviated from the previous one? If so, how?
05/01/2020 Q: The last time we opened the fired heaters of the Platformer units, we noticed lots of dust accumulating on the tubes. We are looking for ways to externally clean the coils online.

Is there a way to do it with our internal resources?

If not, what are the companies that offer this service?

23/08/2019 Q: What is permissible limit for bending of arbor/wicket coil in CCR box type fire heaters.
27/05/2019 Q: How do you calculate actual flow rate of Fuel Gas from the flow meter reading?
In our process plant we have Fuel Gas FTs which gives us reading in Nm3/hr and we want to calculate from this reading actual fuel gas flow taking into account temperature, pressure and density corrections.
Which is the most accurate formula for calculating flow rate? What are the best practices followed by other refineries in order to calculate the fuel gas flow, do they apply temperature and pressure correlations? Pressure or density which is better to take in account?
01/05/2019 Q: In our Delayed Coker Unit (DCU), we have a Feed Preheater which is a Balanced Draft Fired Heater. The Draft of heater is continuously hunting whenever the stack damper is fully closed so we are operating the same with stack damper 15% open.
Also the Excess Oxygen & Draft are on the higher side in this condition.
What can be possible cause for the same & possible solutions?
27/03/2019 Q: For a given gasoline car or bike (engine), does the efficiency increase by increasing the fuel RON? i.e., without changing the engine does the efficiency increase by just increasing the RON of fuel. (2)
11/10/2018 Q: How the Load on Furnace in Crude distillation unit on CIT of Furnace?
In our Furnace the design conditions of CIT/COT are 260/360 C and actual conditions are 250/350.
Is Furnace fired duty depends on Delta T only or is it depends on CIT of Crude?
02/08/2018 Q: What is the meaning "octane barrel"? (2)
28/07/2018 Q: We are using a fuel gas fired heater with 8 burners and an fd fan.
How do we increase the heat transfer of radiant zone?
it is currently 60% and we wish to take it to 75%.
23/07/2018 Q: What are the ways of cleaning fired fuel gas burners online?
The heater is fd fan type and fuel gas is used.
Also, what are the factors that could reduce its efficiency?
16/07/2018 Q: How do we improve the efficiency of a fired heater running on fuel gas and an fd fan? (8)
20/05/2018 Q: We are using born heaters for CRU unit where all heaters inlet lines are covered with ceramic fiber Jacket as air seal purpose but few outlets pipeline from radiation section are not covered. Currently bluish flame is observed coming out from gap/clearance between the outlet pipe and and heater shell casing pipe during night time. What could be the reason for that (from 3rd Heater which has no convection section but has common stack with 1st & 2nd heaters) ?
Another day in the same heater, red hot spot at the inlet of pilot line (pressurized ) was observed and became normal just after the pilot air line had been isolated/closed. But at the pilot inlet found little flame coming out from pilot fuel gas line and disappeared when pilot fuel was isolated. Although pilot should remain close just after the main burner lighted but in our case we keep the pilot in on position all the time. What could be the reason of this red hot spot?
We have VFD operated blower , some time blower noise becomes very high and try to reduce the noise by adjusting the VFD speed . So, what could be the reason for high sound ?
16/03/2018 Q: For a reboiler furnace in NHDT, is better:
to have reboiling liquid 34 m3/hr and furnace COT at 208 C or to have reboiling liquid flow at 40 m3/hr and furnace COT at 203 C?
Note: Reboiler furnace is the limitation for maintaining max throughput.
12/08/2017 Q: Decoking of the fired heater of VDU
During recent years , the skin temperature of one of the 4 coils developed a slightly higher skin temperature than the other 3 coils , the skin temperature is nearly 500 C , it is still in the safe range but we are now considering decoking to to remove any present coke during shutdown . Anyways , I am comparing SAD ( Steam Air Decoking ) to Pigging , There seem to be many hazards and incidents during SAD , i wonder if any of you witnessed any incidents with SAD ? ... Can anyone clarify the potential hazards and their severity ? do you recommend it or you recommend pigging ? ...... Thanks for your comments and replies in advance ....
24/07/2017 Q: We recently received a batch of jet fuel, which test within the refinery indicated was within specification (40 ° Celsius). However,when sent through a pipeline of 45 kilometres to the company's warehouse, and after being allowed an appropriate period of stability, we took homogeneous samples of the tank and found the flash point was was 37.8 Celsius. How has this change occurred? (7)
24/07/2017 Q: Is a microbiological assay for storage tanks necessary? (3)
10/05/2017 Q: We have platforming heaters tubes of alloy 2.25 Cr-1Mo (vertical tubes) .
The maximum design skin point temperature 595c while the limiting design metal temperature 650c as per API 530.
What is the maximum temperature we can reach it above the maximum design and below the limiting design to avoid the oxidized of the metal?
21/04/2017 Q: What is the relationship between the top temperature of a vacuum tower in a vacuum distillation unit and the rate of corrosion in the overhead condensers?

20/04/2017 Q: What is the relation between the amount of overflash used in a vacuum distillation tower and the stripping steam injected at the bottom of this tower? (3)
20/04/2017 Q: For a cooling top pumparound for a vacuum tower, which is more useful: to use a larger flow rate (140 m3/h) at higher temperature (78C) or use smaller flow rate (100 m3/h) at lower temperature (70C) (2)
30/03/2017 Q: How can I determine the amount of stripping steam for a side stripper? (3)
22/02/2017 Q: Does anyone know about the economic feasibility of Organic Rankine Cycle in Crude Distillation Unit? We are having sub-cooled condenser duty of 20-24 GKcal/hr with overhead temperature in range of 120-130°C. (1)
19/01/2017 Q: We have a 50,000 bbl/d capacity crude unit designed for Iranian light crude oil. The main crude column needs to be replaced due to ageing. We would like to take this opportunity to revamp to unit capacity as well to about 70,000 bbl/d. Based on a previous study carried out, the unit capacity can be increased up to 70,000 bbl/d by installing a pre-flash drum before the charge heater. However, now we have to replace the main column. In another study carried out, it has been identified that the some modifications are required to be done to the charge heater such as re-tubing with different metallurgy and changing the passes from 1 to 2 etc. if the unit capacity is increased up to 70,000 bbl/d (without a pre flash drum).
I would like to know whether installation of straight 70,000 bbl/d capacity column or installation of same capacity 50,000 bbl/d along with a new flash drum (to avoid charge heater modifications) is more economical.
15/01/2017 Q: What is the best technique in terms of cost and time for online sealing of valve body leakage in which high pressure boiler feed water is streaming?  
28/06/2016 Q: What is the average energy efficiency of Steam turbine driven centrifugal compressor (Total Condensing)? (1)
17/05/2016 Q: In our CCR we are facing with the feed side plugging of the Packinox CFE heat exchanger. Could you tell me the reasons of this phenomenon? Have anybody experienced the same? What about the solutions? Till when is it worth cleaning? (7)
15/05/2016 Q: Crude heater is twin cabin type which is operated at 367degC for heating crude from preheat-2 to crude distillation column. There are total 8 passes, 4 passes in each cabin.Pass 1-4 in one cabin and rest 5-8 in another cabin.From past 8 months, To minimize the deviation in all passes coil outlet temperature,when flow is increased in pass 5 & 8,its coil outlet temperature increased rather than decreasing and pass 6 & 7 coil outlet temperature reduced when its flow reduced.Also, this effect is observed in skin temperature.
However, it is confirmed by checking temperature of radiation outlet with temperature gun and ensured the deviation.
When flow in passes 5-8 is made equal, deviation in its coil outlet temperature reduced for the same heater box temperature.
However no such issue is found in rest passes i.e. pass 1-4. What can be the possible reason?
14/04/2016 Q: In Some refineries ( not in all ) There is provision Secondary air supply to Burner in Fired Heater to keep flame pattern in shaped. but as Secondary air is not taking part in Combustion process will it not effect to Excess O2 % calculation ?? Is value shown by Digital Device ( Excess 02 %) will be reliable in thus case ????
10/03/2016 Q: Does anyone have any experience in using fuel oil for heaters/boilers firing?
What is the typical size of bucket filter (i.e. mesh size) at pump discharge that supplies acceptable particle size to the burners?
What would be the typical minimum filtration size, anything lower than < 10 micron with bucket filter?
16/11/2015 Q: We have recently observed a high production of off-gases from our Vacuum Distillation Column. We performed the distillation for the feed and observed that the initial and 5% boiling point had reduced significantly. Could this be the reason for the increase in the off-gases?
On the other hand, we suspect an air ingress into the system. Is there is any way to detect/prove that there is an air ingress into the system?

Added by questioner:
Thank you very much for your input. I gained a lot of insight from your answers.
After closely studying all your suggestions, we took into consideration a number of points and implemented them.
One of them was sampling the off-gases, from which we found a high % of Nitrogen which clearly indicated air ingress. As a result, we tightened the transfer line gasket and the off-gases flow reduced by 50%.
Thanks once again.
14/11/2015 Q: What could be the causes of sudden drop in conductivity of Jet fuel in a storage tank?? (2)
05/11/2015 Q: we are suffering coke formation inside our VDU heater, considering high tube hardness we can't preform steam air decoking, the other alternatives are pigging and chemical cleaning. Any advice about the difference between these methods, concerning risks, operation, concerns, disadvantages? (3)
28/10/2015 Q: We have cook formation inside the coils of VDU heater and the metal of this coils are suffering from a hardness, Which method is the optimum for decoking, steam air or pigging to avoid metal damage? (3)
28/10/2015 Q: Is it feasible to reduce CDU heater HOT to reduce CDU column pressure ? (2)
29/07/2015 Q: In our VDU furnace there are 4 cells & 1 coil/cell. In last few days suddenly few coils in cell 1,2 & 4 from the bottom started lifting up from the support inside radiation zone. Even few coils are floating continuously. While RCO entering the furnace pass4 comes first then 3,2 &1. Coils are horizontal. What could be the reason? (1)
23/07/2015 Q: In our VDU furnace there are 4 cells & 1 coil/cell. In last few days suddenly few coils in cell 1,2 & 4 from the bottom started lifting up from the support inside radiation zone. Even few coils are floating continuously. While RCO entering the furnace pass4 comes first then 3,2 &1. What could be the reason? (2)
02/07/2015 Q: Currently we have issues in our naptha cracker plant where our production is limited due to cooling water temperature. Since it is monsoon season, the cooling tower is not able to cool the water effectively. What are the alternative solutions or modifications that can be done to increase efficiency of cooling tower? (1)
21/06/2015 Q: In vortex flowmeter flow corrections ( for std volumetric flow ), when one should use compressibility and for automated calculation in a dcs or excel, instead of compressibility, can density be used?  
03/06/2015 Q: Why is the pilot tube placed at a 45 degree angle during installation for provided reading in flowmeter of cooling water supply and return header? What is the reason for placing at this angle?  
21/05/2015 Q: Would like to get expert advice on crude preheat train. We are not able to get the design preheat temp. In the preheat train the last two exchangers are in series. As per design tube side outlet of last exch. should enter at 323 temp. in the shell side of upstream exchanger with both exchangers operating at MTD of approx. 23-25 degC. However as per current operating conditions there is max. heat recovery in last exchangers with very high MTD and the outlet temp. is reduced to very low 290 degC. Due to which the upstream exchanger is operating at very low MTD 8 degC.
Based on this finding will it be advisable to partially bypass the last exchanger to achieve the tube side outlet design operating temperature or there is some other issue?

Additional Information:
Thank you for the replies. I have gone through detailed preheat train analysis and found that in one of the analysis where we were getting the desired preheat temp. there was no cross pinch in the same exchanger as the inlet temp. had sufficiently increased. And this was possible since the flow was meeting the design data. Thus we might have to increase the outlet temp. (keeping in mind the flowrate) from last exchanger but that again has to be analysed since there is one more exchanger in the upstream of train which is in series to these exchangers.
13/03/2015 Q: We are going to carry out steam air decoking in VDU during shutdown in our refinery for the first time. Before that only spalling has been done. I am a fresh Chemical Engineer. So I would like to know what are the problems those are generally faced while air burning process and what are the possible solutions to avoid these problems? (1)
21/02/2015 Q: We are proposing the idea of installing Auto drain valves in our product tanks viz HSD/MS/SKO. Can you all share your experience if any regarding its performance? Will it lead to reduction of HC loss during tank draining/preparation for product despatch? (1)
08/01/2015 Q: Why is autoignition for lighter hydrocarbon higher than for heavier hydrocarbon? (2)
25/12/2014 Q: To increase the energy efficiency of Steam turbine, we take it in extraction mode from total condensing mode. When we tried to increase the extraction steam flow, the turbine exhaust temperature increased. Why does the turbine exhaust temperature increase at these conditions? (2)
22/12/2014 Q: I have a question about energy optimisation in Oil Refineries: how we could monitor the best technology in plant , included the HTR and HCR units , as we know that the mail suggested methods are related to Pre-heat train of crude?  
11/12/2014 Q: In order to decrease storage costs and to get rid of some imposed restrictions for intermediate products as feed for downstream units, is it possible to connect output of upstream unit (e.g. distillation unit) to downstream unit (e.g. Hydrocracker) directly? Because of sequential changes in crude feed characteristics, we have encountered some surge and instability in straight run products of distillation unit. (2)
21/11/2014 Q: What are the Pros and cons of Steam stripping and Reboiler? When designing a column, what are the factors that decide to go with each of this? (2)
21/11/2014 Q: We have different fired heaters with fuel oil and gas burners in our refinery. It is seen that the metal tube surface is coated with fine layer of powder (slight yellow colour) externally. This is loosely held to its surface (as seen through inspection door) and reduces the heat transfer leading to high skin, arch and stack temperature. My suspicion on the Fuel oil quality became stronger. So I found that Clarified oil from FCC is not going to the Fuel oil tank. Upon testing the IFO for ash content, it came out to be 0.075%. Is this okay? Any other testing is required?
What probably might be the reason for this powder coating and measures to solve the problem?
18/10/2014 Q: We are operating our NHT unit at 125% of its capacity. To maintain NHT reactor RIT, its heater firing is very high. As per our observation firing is very high due to heaters absorption heat duty is 55% only. we want to modify our furnace to increase its absorption heat duty, kindly suggest us what modification is required to increase the existing heaters efficiency? (5)
15/06/2014 Q: We use a hot oil system. We are facing frequent failure of gaskets in it. The operating temperature is 330 dec C and pressure around 15 bar. we are currently using metallic spiral wound gasket. These leaks are resulting into unit shutdown or online sealing.
1. Do others have the same issue of gasket leaks in hot oil system?
2. What kind of gasket will resolve above issue?
3. Any special make of gasket?
4. Might changes in operating condition help?
18/02/2014 Q: We have a kettle type ammonia vaporiser. Shell side is ammonia and tube side is steam to vaporise the ammonia. We have observed that tube side (steam side ) remains filled with condensate almost 80% due to its low load operation against the design. Is this operation is correct to run the vaporiser with filled tube condensate? (5)
12/11/2013 Q: In DHDT unit, RGC anti-surge control valve is opened at around 13-15 %, at this opening deviation from surge line is 0.14-0.20. The design molecular weight of Recycle gas considered is 2.94 whereas actual Recycle gas molecular weight is in the range of 2.25-2.4. Suction temp/ Pres:63 deg C /110 kg/cm2;Discharge temp/ Pres:90 deg C /131 kg/cm2
1.0 Can we fully close the anti-surge valve in order to increase energy efficiency of RGC ?
2.0 what other actions can be taken to minimize RGC anti-surge opening ?
3.0 By Incorporating the actual recycle gas molecular weight in anti surge controller block and compression suction flow transmitter, will there be any improvement in deviation from surge line ?
18/09/2013 Q: How can I calculate the optimal velocity in furnace tubing? At our gasoil/kero hydrotreater we operate usually at low throughput, but we keep the recycle gas at a higher value than needed for the reaction, to prevent the coking of furnace tubes. I guess that the optimal recycle gas amount could be calculated, but I don't know how to do it.

Some additional info: It's the unit manager's explanation that he doesn't want to decrease recycle gas to prevent heater coking. We are usually running on low throughput with 4-500 Nm3/m3 H2/CH ratio. In the last cycle we had pressure drop problems on our reactor, we found solid deposit on top of the bed. We performed a furnace coke burning process during the last turnaround, and found that there was some significant coking in the furnace. Our licensors suggestion is, that H2/CH ratio should be approx. 5 times the H2 consumption. Based on this, 100-200 Nm3/m3 would be enough, but we are running often at 400-500 ratio, which is way higher than suggested.
14/08/2013 Q: Can anyone share experience of putting Refinery Off Gas as Gas Turbine Feed? Advantages, Problems, Modifications required if any? (1)
27/04/2013 Q: How long can a Refinery Heater be operated above design duty in case skin temperatures are within range and heater tubes design life is completed. Can decoking of such a heater result in any tubes problem i.e bulging, sagging or rupture? (4)
19/04/2013 Q: Why do multistage reciprocating compressors have different compression ratio for each stage? (1)
15/03/2013 Q: What is the Nelson Complexity number for MEROX Process and for Deep Catalytic cracking process ?  
12/03/2013 Q: In one of our FCCUs we have problems closing heat balance due to the processing of a very hydrotreated feedstock. We have to use torch oil (LCO or fresh feed) to maintain regenerator at its minimum temperature.
We are evaluating the possibility of using other feedstock as torch oil. Has anyone experience in using fuel gas or natural gas as torch oil in the regenerator? What major modifications in hardware are required?
26/02/2013 Q: How do you improve fuel gas composition if Refinery Fuel Gas System is found to be 'Too Rich', and thereby improve refinery margin? What should be typical FG composition (minima/maxima) to be maintained for an integrated refinery (full conversion) with downstream petrochemicals (say, 400,000 barrels/day crude processing)? What kind of process adjustments, do you recommend to bring the FG composition acceptable in the above minima/maxima range, so that there is a 'value addition' to utilise Fuel Gas System to utilise 'optimal quantity/quality' in the Fired Heaters in the Complex? (1)
23/12/2012 Q: In our CDU column we draw off naphtha (overhead) , kerosene , light diesel , heavy diesel and AGO fractions and 4 pumparound circuits (on kero, light diesel , heavy diesel and AGO sections). The top of the column is cooled by reflux (overhead –air coolers-receiver – column) . From a simulation it appears that approximately 55 % of heat from the atmospheric column is wasted in overhead line (air coolers) and the rest 45% is recovered in pumparounds heat-exchangers. We would like to introduce the additional pumparound (TPA) and recover some of the heat in new heat exchanger(s) upstream the desalter - of course the exact location of the added heat exchanger will be analyzed with pinch study. What do you think about the solution of introducing the additional pumparound in order to recover some of the heat which is currently wasted in air coolers? Maybe some other recommendations about recovering this heat to the process. (7)
09/12/2012 Q: Is it a myth or reality that in a refinery fired heater for the same throughput, same coil outlet temperature and everything else being the same, a fuel oil fired furnace will give a lower skin temperature in the convection section than a natural gas fired one? (5)
07/08/2012 Q: Our Desalter transformer has got three transformers supplying to individual grids. This step up transformers are facilitated with three outlet tappings with higher ratings. We always run the desalters with same outlet tappings for all three transformers. Is it advisable to run it with different outlet tappings in all three transformers in a desalter?
I would like to know electrical feasibility as well as process advantages?
10/05/2012 Q: Waste Heat Recovery from Low Pressure Saturated Steam
We use circulated hot cooling water to cooling our reactors that operate at high temperature, and we use the flash low pressure saturated steam from this system to heat exchangers in our plant.
Since the supply and demand is un-balanced, we use air finned condenser to condense the excess flash steam and recover the condensate.
During normal operation period, 19,600 kg/hr excess flash steam is condensed at saturated condition(2.86 kg/cm2g, 142 oC). 10.5 MMkcal/hr heat release to atmosphere.
We plan to recover this energy using the adsorption chiller technology or other technology.
1. Since the chilled stream we required (-20 oC / -40 oC and -70 oC three grades) may be not suitable from adsorption chiller, we want to know the electrical power recovery from adsorption chiller technology is suitable or not.
2. Is there standard package suitable for the service mentioned above?
28/01/2012 Q: In one of our FCC units (Kellog Orthoflow model), we are suffering severe problems of fouling (fines deposition) in the turboexpander. The scheme of the flue gas circuit is: two stage cyclones in the regenerator + Shell Third Stage Separator before turboexpander + 4th Stage Separator (cyclon) to recover flue gas from fines coming from TSS.
We have also observed high level of moisture in the fines from 4th Stage Separator (10-15%wt). So we suspect that the fouling of the expander is due a cold point in the flue gas circuit (where flue gas humidity is condensed) or an uncontrolled inlet of water / steam.
Has anyone experienced this kind of problems in an FCCU? What could be the potential causes of the severe fouling of the expander?
15/01/2012 Q: My question relaters to the maximum temperature that can be reached in the feed preheater furnace in FCC unit. We operate one of our FCC units in maximum distillates mode and we want to decrease cat/oil to minimum. Currently, we have the following design limits in the feed preheater furnace: 360C (680 F) in the process size and 419C (786F) in the skin points of the furnace tubes. According to a study by our engineering department, temperature in the skin points could be increased to 467C (873F). But our main concern is that an increase in temperature in furnace tubes could cause coking of the feed. Although the feed to the unit is Mild Hydrocracker residue, that has low tendency to coking.
Has anyone experience running FCC units at feed preheat temperatures higher that 360C (680F) in process / 419C (786F) in skin point?
25/12/2011 Q: Normally Overflash is 3-5 Vol% of CDU Feed. How Overflash may be calculated so that the formula may be incorporated in DCS for optimum Heater Operation resulting in energy saving. Please share some reference for information & study please. (2)
14/12/2011 Q: There has been a technology of corra coatings in Pumps impeller which reduce the friction and ultimately the power consumption is reduced. What are the proven practical benefits and who are the vendors? (1)
09/08/2011 Q: What are current views on twisted tube heat exchanger configurations in refineries, particularly in comparison with conventional shell and tube configurations? (7)
21/07/2011 Q: In our Vacuum Distillation Unit we have a vacuum system consisting of overhead water coolers, two ejectors with condensers and a liquid ring vacuum pump. During the summer time when the cooling water to overhead coolers and ejector’s condensers increase above 23C we observe increased pressure on the top of the vacuum column to approx 5-6 Kpa (from 3 Kpa) which is of course logical. In this situation when we want to increase the temp to the vacuum column in order to maximize yields , the pressure will increase too and the result is quite opposite. The significant fluctuation of temp of cooling water (sometimes during the day it is about 5C) makes it also impossible to optimize yields from the vacuum column. Please advise what to do in this situation in respect to our plant, how we can keep pressure steady and low , how to improve yields in this circumstances from the vacuum column. Maybe you have similar problems and please write how you deal with that. Some recommended literature/web sites on this subject would be very helpful too. (4)
22/06/2011 Q: Recently it was observed that the some of the radiation tubes of our atmospheric distillation heater were deformed. The tubes have been in operation for almost 30 years. Some of the tubes (specially at the middle section) deformed to the center of the furnace. Some deformed laterally to the adjacent tube. I want to know the possible reasons behind the phenomenon. Also please advise me what is the standard of replacement of the tubes in this mentioned condition.

30/05/2011 Q: Some steam Jet ejectors are designed with a nozzle extension. What is the role of this extension in the ejector performance? During the last shutdown of our VDU, we noticed that the first (and largest) ejector steam nozzle was mounted without such an extension.
How could this impact on the ejector performance?
29/05/2011 Q: We are facing frequent fouling in our falling film evaporators because of tar content in our feed. Currently we down our plant once in 3 months for cleaning these evaporators. Can anyone suggest the best method in reducing this fouling?? how about tube inserts ?? or do we have any advance technology in heat transfer for reducing fouling??
I know twisted tubes can reduce fouling but can we use for falling film evaporator??
05/03/2011 Q: How can I access daily energy and utility product costs e.g. steam, cooling water, deminaralized water, desalinated water and so on?  
06/12/2010 Q: We have a methanol-Water stripping column, which uses direct injection of LP steam for stripping.
I want to know if it is better to use reboiler instead of steam injection.
Is there is any advantage in using direct injection of steam in methanol-Water stripping column?
30/11/2010 Q: In one of our furnaces we are facing problems with fuel oil dripping from burner blocks.
Atomising steam vs fuel oil dp is 2.5 kg/cm2 and fuel oil temperature is 170 deg C. Is the problem mainly due to improper atomisation or some problem in burners assembly adjustments, or insufficiency in air?
18/11/2010 Q: There is continuous increase and decrease in our column delta pressure in water methanol column. At the same time we noted that our temperature profile of the bottom and middle bed is also fluctuating.
I feel that our column is having vapor cross channeling.
There is some variation in feed flow and steam flow, but column is somewhat running at 100 % load.
If anybody experienced such problem in your plant, please throw some light to understand what causes this fluctuation in delta pressure and temperature profile in the bed and what action to be taken.
Additional information:
Steam direct injection for stripping
There are three bed made of PP intolox saddels
Steam flow is controlled by mid bed temp
Reflux is controlled by feed flow

More information:
This is a packed distillation column to strip methanol from water. We are using steam stripping in our case because there are some traces of Acetic acid in the bottom. To prevent corrosion we have to strip at low temperature, so we are using steam stripping. There is huge variation in temperature profile of the middle bed, at 100 % load First indication of channeling is the change in delta pressure and disturbance in temperature profile. Disturbance in temperature profile is caused by improper distribution of vapor flow in the bed. So thinking this is because of vapor cross channeling.
If it is channeling or flooding how can we deal with it?

More information:
Thanks a lot for all your suggestions, we have opened our tower found that steam deflector plate was installed wrongly, so steam was injecting directly into the packing, which caused packing to expand and that caused channeling in our tower. After rectifying this, now we don't face this problem.
04/10/2010 Q: Is there any simple tool for detecting passing among a valve (PSV,PCV,...)? I heard something about some pen type simple detectors for operators. Has anybody more information about this kind of tools? (3)
07/08/2010 Q: In a boiler with sootblowers, among all the variables that control the efficiency how we can find out the role of soot blowers in efficiency as percentage? (The steam consumption by sootblowers is unknown) (2)
25/07/2010 Q: Are variable speed drivers ever used in pumps?
If not, why not?
09/07/2010 Q: Could anyone please tell me how to calculate dew point of instrument air with a pressure of 10 bar? (2)
06/07/2010 Q: What is the best way of judging the efficiency of a desalter? (6)
21/05/2010 Q: What are the likely effects of water carry over from desalter on Crude heater and distillation column? What steps should be taken if this happens? (11)
21/05/2010 Q: We are planning to procure a new airpreheater for furnace with two cells K1 and K2 cell one for prefractionator reboiler and the other crude heater for fractionator.
I am just filling the process data sheet. On what basis should I fix the pressure drop across the air side and flue gas side?
16/04/2010 Q: We want to recover the energy from high temperature flue gas from our four process heaters. The heaters main design condition is shown below. Please advise.
The design information of these heaters
Heater-1, Vertical Cylindrical
Design Duty 4.48 Gcal/hr
Fuel type – Fuel Gas only
Flue gas from convection section 359 oC, mass velocity 1.959 kg/sec m2
Stack OD 1.2m
Heater-2/3, Vertical Cylindrical
Design Duty 6.91 Gcal/hr, each
Fuel type – Fuel Gas only
Flue gas from convection section 389 oC, mass velocity 2.315 kg/sec m2
Stack OD 1.378m
Heater-4, Vertical Cylindrical
Design Duty 6.57 Gcal/hr
Fuel type – Fuel Gas only
Flue gas from convection section 348 oC, mass velocity 2.482 kg/sec m2
Stack OD 1.4m
11/02/2010 Q: Crude circuit from wharf to Tank and Tank to Units is not insulated. I found seasonal feed temperature change affects on charge heater inlet temperature especially preheat train has been fouled after turnaround. its cost seems a lot.
Is the crude line insulation usual practice? Or do you think we'd better add one more exchanger with pinch study?
09/02/2010 Q: We want to by-pass our de-salters in order to check the consequences with and without desalters on CDU. Moreover we have stopped de-emusifier dosing prior to desalters. What impacts are anticipated in your opinion and what parameters to be monitored in case when there is no desalter in crude preheat trains? (9)
06/02/2010 Q: Recently we are facing topping unit furnace inlet becomes lower than expected. The normal temperature is 215-220 degree centigrade. But now we are getting only 200-205 degree centigrade. What are the probable reasons behind this? And what measures should be taken to overcome the problem? (6)
08/01/2010 Q: In our refinery we are going to replace our Vacuum Distillation Column. Please suggest some designer/manufacturers' names who work in this field. (1)
22/12/2009 Q: Is there any simple equation for estimating furnace efficiency only by excess air (oxygen) and flue gas temperature? (1)
20/12/2009 Q: I'm new to the refining field. We have eletrostatic desalter with three transformers (each of 22KV). and I have questions about this:
1. Why is a single heavier transformer is not used instead of three?
2. We have 2 PSVs on desalter. What is the reason for two PSVs?
3. Why the water injection before desalter is maintained 4.5% of crude charging?
4. What is the function of grills (grids) inside the desalter?
29/11/2009 Q: What is the difference between the Eductor and Ejectors? (3)
31/10/2009 Q: Is there a heat transfer fluid that can withstand a temperature of up to 600 deg C plus? (2)
20/10/2009 Q: VDU off-gases are being routed to LP flare header through a water seal drum (VDU ISBL). It has H2S content around 2 mol%. Is it possible to burn it in VDU furnace? Constraint is higher H2S content. Can we use water seal as amine seal to absorbe H2S?
Any other destination of these gases?
07/07/2009 Q: My company generates regular truckloads of quite pure benzene with under one percent of acetaldehyde and under one percent of a low molecular weight unsaturated ether. We are currently burning it but it should be useful to someone for production of benzene derivatives, such as nitrobenzene or a chlorobenzene. Does anyone know of another company in the southeast US that could make use of it? (1)
17/03/2009 Q: How will impending changes in marine diesel specifications affect bunker and residual fuels? Is there a long-term shift away from bunkers and residuals? Will this result in some niche opportunities for refiners? (1)
12/02/2009 Q: A coalescer is required to be installed in straight run kero line of the CDU. What are the requirements under OISD (Oil Industry Safety Directive ) for this? Are there any other safety directive norms that need to be considered? (1)
31/01/2009 Q: We have calculated EII for a long period and we have observed it was very clear that capacity and EII directly related to each other.
If you go on details to decrease bad effect of low on EII the best way to use VSD for every system. (One pump or fan for each system.)
But at this point we have two main doubts:
1. Reliability of the VSDs
2. VSD effect on control system.
Are we correct to have these concerns?
24/01/2009 Q: Are there any methods/systems that can utilize/recover for re-usage gases released into refinery flare system during non emergency periods? (2)
18/12/2008 Q: What is the best distributor for water feed to a atmospheric condensate drum to avoid steam losses to ambient?  
23/09/2008 Q: I am working a project where I am trying detect phase changes. The project consist of detecting phase changes from water to butane by using flow meter density detectors. This idea is only for ideal case, but the reality is that, caustic may be present. Here is where the issue comes.
The question that I have is this: what method should I use to detect different phases. For example, mixed water and caustic? mixed Butane and Caustic? Again, the point is to detect phase density changes from water to butane.
07/08/2008 Q: In addressing refinery CO2 management, can you comment on CO2 curtailment from on-purpose hydrogen plants through "minimised" involuntary'steam, internal heat recycle and captive integration?
07/07/2008 Q: In general, where has the influence of good fractionation allowed for significant improvements in meeting stringent petrochemical product specifications (e.g., propylene, styrene, etc.) at higher charge rates? Besides the recent improvements to fractionation column internals, what is the extent to which automation & control systems can be leveraged to deliver higher efficiency, run-lengths and resistance to corrosion in product recovery trains?  
05/06/2008 Q: What is the amount to which oxygen enrichment in a fired furnace helps to improve capacity and efficiency of a plant?  
06/04/2008 Q: Certain refiners are feeding vacuum residue and FCC slurry oil to the coker unit as part of their strategy for reducing (or eliminating) fuel oil production. To this end, what operational and hardware changes should be made to the vacuum tower and FCC main fractionator? (2)
07/02/2008 Q: Have hydraulic power recovery turbines (HPRTs) been included in any of the most recently completed or planned projects where core hydrocracking and amine regeneration is required? Besides energy savings incurred with the installation of an HPRT, how significant a role with HPRTs play in reducing CO2 emissions?  
05/02/2008 Q: In a Refinery, huge quantum of low level energy is wasted in cooling water. Other than exchanging heat of Crude overhead column vapour with cold crude oil feed, what are the technological developments to minimise such energy loss? (3)
22/01/2008 Q: Can anyone tell me the average time it takes to clean a flare line please? (4)
22/01/2008 Q: How much does it cost a refinery and/or petrochemical plant to produce 1 (one) tonne of CO2? I have worked out how much CO2 is produced per barrel of oil, for example, but now want to put a monetary value (or indeed an energy value) on to that tonnage of CO2. Thanks.  
26/11/2007 Q: I am still amazed at how few companies are using Inverter Technology on Fans and Pump applications.
Is there much demand for European manufactured Inverters within Petrochemical industry?
26/11/2007 Q: Is there any refiner using variable speed drivers in electrical motors of process units? (4)