00:00Hi friends, welcome to our channel. Today we are going to discuss about how to design a boot or a
00:07drop leg for the three-page separator.
00:09Subscribe to the channel for getting such interesting videos.
00:14Step to design the drop leg or a boot.
00:17So basically a boot is the cylindrical portion extending downwards from the bottom of a horizontal separator vessel
00:28typically located near the outlet. This is generally the outlet of the three-page separator.
00:34The primary rule of the boot is to provide a specialized zone for the liquid-liquid separation.
00:40Basically use of this boot is, it prevents the carrier of water into the, because the oil outlet will be
00:48somewhere here
00:49or sometimes it will be here. So it will prevent the overflowing of that water into the,
00:58oil section. And the boot must be size large enough. This boot should be size large enough to handle the
01:05expected water flow.
01:07How much water is going to come in this, it has to be designed for that.
01:11So first step is calculate the diameter based on the residence time. Residence time means how much water we are
01:16expecting to come into this boot.
01:19And the second is to calculate the diameter based on the phase separation. Phase separation means if some propose the
01:24hydrocarbon comes in this section.
01:27If it takes how much time to separate. So step one is to size the boot or for the residence
01:37time.
01:38So residence time if you seen our earlier lecture in that we have mentioned that in the residence time we
01:44have mentioned if the droplet is having the level control available like this.
01:50Then we can go for the 5 to 10 minutes and if the level control is not there and the
01:56manual training is there then we have to take the residence time as a 60 minutes.
01:59So in this example we are saying that we will have a liquid control. So we are taking the residence
02:07time as a 10 minutes.
02:08And then we have to just calculate the holdup volume and holdup volume is Q into time that is 10
02:16minutes.
02:17And this holdup volume if you want to find out the diameter you have to cylindrical diameter this is the
02:24simple formula.
02:26So in this you have to find out the length. So length I am considering the drop length as a
02:333.5 feet or which is this is the standard engineering practice that considering the length 3.5 feet I
02:39will tell why this is 3.5 feet only which is equal to 1.07 meter.
02:44So we are talking about this length of the boot. So we are talking about this length of the boot
02:49which is 1.07 centimeter we are assuming and then we are finding out the diameter of this boot for
02:56the water flow rate or residence time.
03:00So this is the problem we are done in our lecture 4 and 5 for the 3 phase separator. So
03:07same this is your water which is has to be separated in this boot.
03:14So D is equal to if you simplify this equation it will come as a Q CHL. Q CHL is
03:21your flow rate of water flow rate basically.
03:25So this has to be converted into this is in kg per hour you have to meter per second you
03:30have to convert this and then multiply by 10 seconds is which is equal to 10 minutes which is equal
03:36to 600 seconds into 4 pi by L. L is 3.5 feet or 1.07.
03:42So then when you calculate it will come as a 0.45 meter diameter. So this is one with the
03:52step one we can get the diameter of D is equal to 0.45 which can be rounded up to
03:580.5.
04:01The calculation done on the first step we have shown here. We found out the volumetric flow rate in meter
04:08per second here for the water section and then just listed out what we want and this is the formula
04:14which we used and we got the D as a if you solve it because most important is the units
04:21and then just put it into this formula you will get this.
04:24So D square is 0.2 and then D is equal to 0.4533. So if you want an excel
04:30sheet we can I can share that.
04:33Tip 2 is calculating the diameter based on the phase separation. So in this boot the phase separation happened between
04:41the lighter liquid and the continuous water phase and we use the formula as a for the terminal velocity which
04:49is a Stokes law we will use.
04:50Similarly what we used in the earlier calculations as well.
04:54So just the velocity to segregate we just mentioned the suffix we have changed like density of heavy liquid phase
05:03to low liquid phase viscosity of heavy liquid phase like that and the particle size of this is the lighter
05:08liquid particle size and G is your acceleration due to gravity.
05:15So we are saying that the particles of oil coming up what is the time required or separate the time
05:26required is terminal velocity we are finding out for that and similarly we have to find out the continuous phase
05:34velocity.
05:34The constant phase velocity means water coming into this drop leg means this layer of water coming down up to
05:42the here and coming out of this nozzle how much time is required or how much velocity it is having
05:49that velocity we can calculate by the flow rate by cross sectional area of this boot.
05:54So we have to calculate the cross sectional area how we will do we first we calculate the terminal velocity
06:01if the terminal velocity which is the lighter particles required to go up if we make it same as the
06:08velocity of your water to come down up to this bootleg high length then it will be we can calculate
06:17the D.
06:19D.
06:20D.
06:22D.
06:32D.
06:48D.
06:51D.
06:51D.
06:51D.
06:51D.
06:54D.
06:54D.
06:55D.
06:55D.
06:55D.
06:55D.
06:55D.
06:56D.
06:57D.
07:01D.
07:04D.
07:07meter so here we explain that how we got that d is equal to 0.23 or 0.3 meter
07:14so this is the
07:15listed out the velocity of the q of the water in the meter per second we are converted here
07:22then g we have g is the acceleration due to gravity particle size concentration is 125 micron
07:30and then velocity of lighter phase sorry viscosity of the lighter phase then the density of the
07:37heavier phase and the lighter phase and just when you put it in this formula if you solve it this
07:42is
07:42the numerator we solved and the denominator and then d square we got this much and you can get
07:47the d as a the result if you want this excel sheet we can share with you so conclusion we
07:55have to
07:55select the largest diameter between the step 1 and 2 so which is coming out to be 0.5 diameter
07:59which is for the residence time and if you remember we have solved this problem for the other cases like
08:07separating the diameter for the total residence time then diameter for the vapor phase separation
08:12and the diameter for the liquid phase separation from the vapor phase and then liquid liquid
08:16separation this is 1.3 so we find the for the coalescing blanket which is a 2.1 now what
08:23are
08:23the diameter we calculated for the drop leg if it is less than your diameter of your vessel so half
08:30of
08:30the your vessel so it is already half of the vessel from from like if we selected 2.1 as
08:36our diameter of
08:37your vessel this diameter of the vessel we have considered 2.1 and now our boot diameter comes out 0
08:45.5
08:46which is half which is half which is less than half of the this the half of this is 1
08:51.05 so this which
08:54is less than your your boot diameter is less than this 1.05 then we can go ahead with the
09:02the what are
09:03the length of 3.5 we have considered for the boot height which is the standard practice because here
09:11here we are not going for any l by d ratio 3.5 feet which is coming on to be
09:161.07 meter so that is the
09:19general guideline and if the drop leg or a boot diameter is greater than half of the vessel suppose
09:25this instead of 0.5 if it comes around 1.2 and our selected diameter is 2.1 so it
09:32is more than half in
09:34that case what we have to do we have to get the diameter as exactly half of this so in
09:40that case
09:41diameter has to be considered only 1.05 half of this selected diameter and then you have to calculate
09:48the length for that then and then we can increase some length because we got the diameter as d and
09:54then you put in that pi d square by l by 4 formula and then you can get the length
10:01of it then your boot
10:02length can be changed so length of droplet can be three point feet diameter if droplet is diameter
10:10of the droplet is less than the half of the vessel diameter so which is in our case if it
10:14is not then
10:15you have to recalculate the length so this point has to be remember so i think this way you are
10:20able
10:20to understand how to calculate the boot design a boot or a droplet for the three-phase separator
10:27thank you for watching the video
10:31thank you very much if you have any question you can write to us or comment on the comment box
10:37or
10:37you can also reach on to us at conceptengineering2025gmail.com link of the sessions all the sessions
10:45we completed till it is module 1 pressure relief valve model 2 heat exchangers and model 3 separators
10:51are going on so links for all this available in description box you can go through it thank you
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