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Theoretically you can can calculate either of the one parameter if you know the other 3 parameters but reactor inlet temperature at LHSV2 is adjusted according to the product quality requirement. The actual temperature might not be the same as theoretical. Normally, when feed rates to reactor are adjusted the reactor inlet temperature does no go below the minimum defined temperature by the designer and temperature can be increased at high LHSVs as required to meet the product quality.
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LHSV is the liquid hourly space velocity, which is the ratio of liquid volume flow per hour to catalyst volume. LHSV is inversely proportional to residence time. As the flow rate increases, the LHSV increases. In most systems with a fixed catalyst volume & activity, temperature is increased to offset the negative reaction consequences of increasing LHSV. In systems that can replace catalyst and/or regenerate it online, an increase in catalyst make up rate can also be used to offset an increase in LHSV.
It signifies the residence time of feed in the reactor. Higher the value lower the reaction rate. It is dependent on the reaction kinetics. -
Increasing hydrogen partial pressure in a hydrocracker will increase conversion for the same reactor temperatures.
1. Increasing hydrogen partial pressure at constant conversion requires lower reactor temperatures and thus increases the cycle length of the catalyst.
2. The higher partial pressure favors the desired reactions (cracking) and supresses the undesired reactions (coking).
3. Complete the hydrotreating reactions due to high conversion rates at the catalyst.
4. Ensure availability and physical contact of hydrogen for reactions at the catalyst bed.For how to improve the hydrogen partial pressure view, https://thepetrosolutions.com/improving-hydrogen-partial-pressure-in-hydrotreating-units/
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Causes of fouling in HP Amine Absorber of Hydrocracking unit are as follows;
suspended solids, plugged trays, antifoam performance, off-spec inlet gas, hydrocarbons content, corrosion and erosion of metal components, low filtration/separation efficiency.
The most prominent cause of foaming related to the Hydrocakcing unit is the over-cracking of hydrocarbon feed in the reactor. Due to these lighter hydrocarbons (C1~C4) content in the recycle gas is increased and in the end this would cause foaming in the amine absorber. -
I think it is not a good idea to process the cocker Naptha directly in the hydrotreating reactor bypassing the diolefins reactor. Because high olefin content will result in higher catalyst deactivation, higher hydrogen consumption, and a higher temperature rise across the catalyst bed. Further, silicon and high sulfur content will also cause catalyst poisoning and higher deactivation rates. The hydrotreating HDS/HDN reactor needs to run under severe operating conditions to meet product specifications.
The Fractionator column will have less flow of lighter naphtha range, but I think it will not be so much problematic. If the naphtha flow is too low, that fractionar can’t run properly, then the minimum flow of coker naphtha can be processed. Otherwise, it is better to not process the cooker naphtha without passing through the Diolefins reactor.Reegards,
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Further, once the WABT has been adjusted according 2 degree C for 1 % unit load, final adjustment can be done according to the product Sulfur results.
In addition, the the temperature rising rate can be different according to your unit conditions. Means, your rate can be 1~4 degree C according to your plant condition.
Unit, product sulfur online analyser will also help you to optimize the temperature rising rate. -
WABT of Diesel Hydrotreating is normally changed keeping in view the Diesel product Sulfur results. There is no fix method/rate of increase or decrease the WABT. Normally, we increase ~2 degree C WABT with 1 % unit load. Again, we can not fix the WABT rate with feed rate because the specifications of feeds and catalyst activity are not always the same. With fresh catalyst sometimes at low WABT you can achieve the desired desulfurization reactions.
After operation and WABT adjustment, practice you can tentatively fix the WABT rate with feed rate. We normally increase 2 degree C WABT with 1 % unit load increase and 2 degree decrease with 5 % unit load decrease.
But always keep in mind this practice for safety of Hydrotreating catalyst: First take the step of unit rate increase then go for WABT rise. In the same way, first decrease the WABT then go for unit rate decrease”. -
As per my point of view; the di-olefins reactor contains the active type of grading material. You don’t need to sulfide it like the main catalyst. It will require minor Sulfur, which it will pick from the diesel feed at the given operating conditions.
You will continue your sulfiding of the main reactor as per guidelines given by your vendor, the guard reactor will also be sulfided.
Please contact your vendor procedures for clarity. -
Normally, differential pressure of feed filters is considered. At high differential pressure > 1.0 Kg/cm2, the feed filters are switched to clean one (Manual) or back washing sequence starts in case of Auto back wash system.
High differential pressure or low pressure at downstream of filters will cause flow restriction, passing of particles through feed filters. In extreme case, feed filter cartridge may be damaged at > 2.5 Kg/cm2 differential pressure and passing through of particles to hydrotreating reactor.Therefore, it is critical to monitor and control the differential pressure of feed filters for reliable operation of the reactor.
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Operating conditions during sulfiding of hydrotreating catalyst depend upon the catalyst provider guidelines. Each catalyst vendor has its own procedure of sulfiding to ensure maximum performance after sulfiding. There are two reasons to control the pressure below the normal operating pressure.
1. The reactor pressure should never be increased above the temperature embrittlement limit, the reactor skin temperature needs to be increased above the Minimum pressurization temperature (MPT).2. If the hydrogen partial pressure is high and the temperature is also above the defined limit then catalyst metal oxide will be reduced to metal and which is useless and non-catalytic.
Further, in our UOP licensed Hydrotreating plant catalyst provided by Albemarle, we maintain the same operating pressure during both stages of sulfiding. Pressure remains low when we are below the MPT skin temperature of the reactor. After crossing the skin temperature safe limit we increase the system pressure up to operating pressure then we go for pre-wetting and sulfiding steps.
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There are two loops in the typical hydrotreating units;
1. The short loop is from the downstream of the HP separator Hydrocarbon line towards the product stripper. Then the line up of stripper downstream to diesel product header or slop tank. This can also be sent to the feed storage tank. For flushing, straight-run cold diesel is used.
The purpose of short loop circulation during commissioning is to clean, remove debris, checking leakages, etc and make ready the unit before commissioning. This can also be applied after turnaround or after any major overhauling of the stripper section.
Secondly, circulation with cold diesel is applied for cool down and hand over stripper feed exchangers or any hot equipment for a maintenance job.
2. Long loop circulation is through the complete unit. It is carried out after catalyst loading or Turnaround. Its purpose is to perform Pre-wetting the catalyst and remove catalyst dust and any other debris or loose materials from the reactor circuit and then passed through the fractionation section which has already been flushed.
For ~4-6 hours, the circulation is once through then internal circulation is started. After that sulfiding of the hydrotreating catalyst is carried out.Sulfiding of Hydrotreating Catalysts and its Troubleshooting
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Dear Zayed, Generally, the temperature controller is cascaded with fuel gas pressure to control the reactor inlet temperature. This setting is better with fine control of both temperature and fuel gas pressure.
For further discussion, please upload the file with a size less than 1MB=1000KB by compressing the file or selecting the file of a smaller size.
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Refractory dry out is the process to remove moisture from the refractory by applying controlled heat. The dry-out procedure and maximum temperature limit are provided by the vendor. But general
NOTE:
Heating rate, heating steps, and maximum heating temperature are provided by the relevant vendor. So follow his instructions for the safe and successfully dry out.
1. Temperature is usually monitored at the exit of the radiation section (heater arch). Initially pilot burners are light up and further burners are light up as per heating rate.
2. Normal heating rate is 20~25 C/hr ( as per vendor guidelines).
3. Heating is carried out in steps, Step1: Heat up to ~125 C and hold for 24 hours, Step2: heat up to 290~325 C and then hold for 24 hours. Step3: Further heat up to ~550 C and hold for 24 hours.
4.After completion of heating steps, the refractory is cooled down at the rate of ~40~55 C/hr.A typical refractor dries out trend is attached.
Media Inside the tubes
For hydrotreating or hydrocracking units, normally Nitrogen is being used because reactor dry out is also completed.
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