Q & A > Sulphur Removal and Recovery
Date  Replies
30/10/2017 Q: We are interested in reducing treatment load on spent caustic treatment unit. Then we are going to idle visbreacker gasoline treatment process by feeding it to other units. At present we use sweetening process (washing with caustic and converting with Merox) for visbreacker gasoline product. The problem regarding to produced spent caustic as byproduct is unreliable spent caustic treatment process to meet the environmental specs. The alternatives are suggested as follows:
1- introducing to heavy naphtha hydrotreater unit (unifiner)
2- introducing to Kerosene/diesel hydrotreater unit
3- introducing to hydrocracker unit
4- sending to crude storage and refine it again
Would you please explain pros and cons about the abovementioned alternatives? What is the best alternative?
24/10/2017 Q: Is stripped water useful for amine dilution and caustic dilution? (1)
22/10/2017 Q: In my unit, Main fractionator is running steady all parameters are normal, suddenly one day, CLO Flash point came very low compared to earlier it was high(75-89 C) and used to fluctuate by 10 C. Now flash is always coming below 60 C. We have increased HCO Stripper stripping steam and Main Column bottom stripping(Agitation) steam to maximum but still CLO flash is not improving. Checked for FLO to bottom circuit, all locations blinded. Main Column Flash zone temp & bottom temperature are 356 C and 349 C respectively. Kindly suggest best ways to improve CLO flash and how to find out the problem? (3)
14/06/2017 Q: In a SCOT unit, what can produce black solids accumulation in the quench water column? (1)
14/06/2017 Q: Are there ways to monitor pressure drop on-stream across reheat exchangers, condensers and catalytic reactors in a sulfur recovery unit? Manual pressure survey is being done using pressure gauges attached to Strahman piston valves are the only current way to do this in our plant. What is an effective way in forecasting high pressure being experienced in the system?  
29/05/2017 Q: How LHSV in a pilot plant reactor can be calculated with the following data: feed flow rate=30grams/hour,hydrogen to hydrocarbon ratio=400 Nm^3/m^3 and temperature and pressure conditions are 270 degree celsius and 20 bar respectively? (1)
14/03/2017 Q: Is there any nitrogen species that may be present in LVN but is not present in HVN? We are detecting high nitrogen content in LVN but not in HVN. Also, our sulfur content is low. Even though we may see nitrogen in HVN (poison to reactor), the endotherm of the reforming reactor is not affected. Are there nitrogen species that can be detected by NSX but is not readily available for breaking down/reaction? (3)
08/06/2016 Q: A trip is provided on high tail gas temperature of Sulfur Recovery Unit. It will bypass the amine system & tail gases will be directly routed to Incinerator. Why this trip is provided?
05/12/2015 Q: TLV and STEL of H2S is 10ppm and 15ppm, for SO2 it is 2ppm and 5ppm! But H2S is considered more toxic than SO2. Why? (1)
13/04/2014 Q: We have a Steam methane reformer having side fired self respiratory burners. To attain the correct O2 in flue gas of primary reformer, burner dampers are being adjusted. What is the correct sequence for throttling the burners? Should the bottom most burners should be throttled more than the top ones or vice versa?  
04/06/2013 Q: If the tail gas of SRU contains more SO2 , is there any chance of smoke formation in stack after incinerator. If H2S slip smoke formation happens and increasing air ratio to control the stack some free. But sometimes in low throughput smoke is coming. is it because of more SOx and NOx...?  
10/04/2012 Q: When you have a scenario of low sulfur diesel (50 ppm), what is the impact of Diesel viscosity at 40°C on vehicle emissions? (1)
17/11/2011 Q: How to calculate the SOx and NOx emission rate in a heater stack? (2)
11/11/2011 Q: We find the crude heater tubes started slightly bowing towards the burner inside the radiation zone. The investigation drives my mind over the below written questions...
1. What can be the maximum height of the Fired heater's radiation zone (or) the maximum tube height allowed inside the radiation zone (vertical coil type) as per standard?
2. What is the efficient ratio which can be achieved between the radiation:convectional zone heat transfer(in percentage)? Its a balanced type heater and we could heat the combustion air up to 275 C max?
3. We use P9 material tubes inside the furnace (cylindrical-twin zone). We are puzzled as to why the bowing is towards the burner side? Why not towards the side and backwards?
4. What is the maximum pressure drop across the burners allowed? As we go increasing the throughput in varying the Fuel oil and Fuel gas burning, the skin temperature response in all the section of the heater is not uniform. So the heat flux variance is also expected. I would like to know the methods available to find the heat flux variance inside the radiation zone.
5. The burners (Low NOx/SOx) used are stretching over the design sometimes due to the lower inlet temperatures. Flue gas recirculation is also included in the design. What can be the problem when a burner is running over the design limits? We have oxygen, CO, NOx/SOx analysers but they don't seem to be reliable most of the time.
16/09/2011 Q: I have a question about DeSOx Unit of RFCC
Our plant has a DeSOx unit that removes SOx and spent Cat’ (=dust) in Regenerator flue gas to meet environment standard.
After removing SOx and spent Cat’ by Mg(OH)2 solution, the waste water that includes suspended solid like spent cat’ is removed through filter press.
Filter press is dual type. When one is working, the other is stand-by. (Running time :18~30hr)
Because operation time of the two filter presses is not fixed and unknown, the cleaning man has to stay on or near the filter press to clean it, when switching.
So I want to ask:
1. How do you treat resulting waste water to meet environment regulation?
2. If you use filter press, what is the best way of managing it?
26/07/2011 Q: I'm getting ahead of work on emission-reducing additives in diesel engines, I want to know experiences about the use of additives based on polyisobutylene, some information reports levels of NOx emissions reduction close to 25% and Reduction of particulate matter of 47%. Does someone have some information about this topic to help me?
11/05/2011 Q: What is the standard value of sox/nox in atmosphere if emitting from hydrogen generation unit reformer for fg/naphtha/off gas firing? (1)
21/01/2010 Q: In a sulfur recovery unit incinerator (where calus process in front end followed by CBA process), presently incinerator control temperature is 605 Deg C. Can I bring down to 550 DegC? What will be the consequences? What will be the ground level SO2 content? (1)
14/01/2010 Q: There are four SRU units in our refinery. During start up period, we face the SOx emission problem since bypass TGU (Tail Gas treating Unit) operation. We use MDEA as absorbent to H2S recovery in TGU, and bypass this unit during pre-sulfidation stage of start up. On the other hand, we face the SOx emission problem too because sulfur burning out before turn around. Please advise.  
01/12/2009 Q: For reducing SOx contents in exhaust of Gas Turbine (power plant operations), what could be suitable process?
I was thinking about scrubbers, but not sure if it is practical to handle a flow of 30MMSCFD flue gases for scrubbing?
04/06/2009 Q: In what situation is a pneumatic test at one kg/cm2 to be preferred to a hydro test at the design pressure of a vessel? (2)
10/04/2009 Q: If off gases contain nitrogen and they fired in fired heaters how will it affect NOx levels? (2)
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)
07/02/2009 Q: What is the standard value of SOX & NOX in furnace stack outlet? Are the Values different in case of fuel oil firing and fuel gas firing? (3)
25/04/2008 Q: I have read in analyzer vendor literature that NOx formation is the indication for best combustion in boilers (than Oxygen in flue gas). But we have to limit it. How far is it correct? can anybody give technical reference? (1)
28/02/2008 Q: While processing heavier and cracked feeds in Diesel Desulfurisation units the decativation could not take place due to metals poisoning or coke deposition. What are the views on predominant factor? If it is because of coke, is the only solution to make the feed lighter and process less of cracked stuff? However, if poisoning is due to metals, could a small bed of demet catalyst in the first bed prolong the life of the catalyst? (2)
12/02/2008 Q: Quite a large amount of Hydrogen is consumed in desulphurisation of fuels and hydrotreatments for product quality improvement which generate Hydrogen sulphide. A more economic process is required like catalytic decomposition of hydrogen sulphide into hydrogen and sulphur and the separation of the products of said decomposition to H2 and Elemental Sulphur. This would enable recovery of costly hydrogen and same can be re-utilised in the process of treatment. Are there any catalyst development taking place for such purposes? (1)
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.  
09/10/2007 Q: What are the various processes for Recovery of Sulfur from Acid Gas? (4)
19/09/2007 Q: Please advise on reduction of ammonia emissions from a fertiliser plant.
Our emissions from a urea plant stack is about 150 ppm, and we need to reduce them to 50 pp to comply with EPA regulations. I know some plants are provided with an acid washing system.
I would be grateful for advice from anyone with experience in this field.
07/09/2007 Q: What is the factor of amount of particulate in the flue gas from boiler? The fuel of boiler is fuel gas and fuel oil from the Olefins plant. (1)
28/07/2007 Q: What role does oxygen availability play in controlling FCC regenerator NOx emissions? What regeneraor design improvements are recommended for minimizing NOx emissions? (2)
28/07/2007 Q: What analytical techniques are recommended for predicting FCC regenerator NOx emissions and monitoring NOx additive performance? (2)
22/07/2007 Q: Can you comment on one or more unit-specific cases where additives reduced NOx emissions by up to 80%? In other cases, what conditions existed where "only" a 20% NOx reduction was observed --- and what (if anything) was done to further reduce NOx emissions? (3)
22/07/2007 Q: What role does oxygen availability play in controlling FCC regenerator NOx emissions? What regenerator design improvements are recommended for minimising NOx emissions? (3)
09/07/2007 Q: What are the most effective SOx reduction technology improvements the refining industry is investing in? What is some of the latest feedback on their performance, particularly with regard to their effect on FCCU maintenance and operations? (3)