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Principle of Gas Processing

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Language: en

00:00:26.420
natural gas a clean efficient source of
00:00:29.870 00:00:29.880 fuel and heat for our homes and
00:00:31.910 00:00:31.920 industries but in order for natural gas
00:00:35.090 00:00:35.100 to be useful like this it must undergo
00:00:37.790 00:00:37.800 many changes on its trip from the well
00:00:39.799 00:00:39.809 to the end-user how natural gas is
00:00:43.250 00:00:43.260 transformed from its raw state to a
00:00:45.229 00:00:45.239 useful product is what this module is
00:00:47.869 00:00:47.879 all about
00:00:51.970 00:00:51.980 this is the first section of a two
00:00:54.620 00:00:54.630 section module on the principles of gas
00:00:57.230 00:00:57.240 processing in this section you will see
00:01:00.440 00:01:00.450 an overview of how gas is usually
00:01:02.540 00:01:02.550 processed as well as some methods for
00:01:05.090 00:01:05.100 removing contaminants from the gas
00:01:06.590 00:01:06.600 stream
00:01:10.740 00:01:10.750 the natural gas coming at it as well
00:01:13.270 00:01:13.280 often has too many contaminants to meet
00:01:15.910 00:01:15.920 the quality specifications of natural
00:01:17.860 00:01:17.870 gas buyers also the gas stream may
00:01:21.220 00:01:21.230 contain natural gas liquids or NGLs that
00:01:24.730 00:01:24.740 could have increased value if separated
00:01:26.680 00:01:26.690 from the gas stream so the gas is
00:01:29.830 00:01:29.840 processed to make it more usable and in
00:01:32.440 00:01:32.450 some cases to make it byproducts more
00:01:35.230 00:01:35.240 marketable let's take a look at how that
00:01:39.220 00:01:39.230 typically happens gas processing starts
00:01:42.550 00:01:42.560 here at the wellhead gas coming out of
00:01:45.400 00:01:45.410 the ground normally contains fluids such
00:01:47.800 00:01:47.810 as oil and water
00:01:49.770 00:01:49.780 now these liquids must be removed before
00:01:52.719 00:01:52.729 the producer can sell the gas this is
00:01:55.630 00:01:55.640 usually done at the wellhead using a
00:01:57.219 00:01:57.229 device known as a separator after
00:02:01.510 00:02:01.520 separation the gas is routed through a
00:02:04.060 00:02:04.070 meter station and onto a processing
00:02:06.340 00:02:06.350 facility by pipeline metering is a vital
00:02:10.330 00:02:10.340 link in the processing chain because in
00:02:12.370 00:02:12.380 order to maximize profits it is critical
00:02:15.070 00:02:15.080 to know how much gas is leaving the well
00:02:17.620 00:02:17.630 and how much is arriving at the
00:02:19.449 00:02:19.459 processing facility a significant
00:02:22.570 00:02:22.580 difference in those two amounts could
00:02:24.820 00:02:24.830 indicate a problem such as a leak in the
00:02:27.250 00:02:27.260 pipeline to get more information on
00:02:30.640 00:02:30.650 metering you may study the module in
00:02:32.920 00:02:32.930 this series entitled orifice meter
00:02:35.050 00:02:35.060 station fundamentals now in order to
00:02:39.009 00:02:39.019 process gas efficiently at a duty pipe
00:02:42.100 00:02:42.110 for many producing locations to a
00:02:44.410 00:02:44.420 central processing facility this is
00:02:48.280 00:02:48.290 called gas gathering and is much more
00:02:50.740 00:02:50.750 economical than setting up separate
00:02:52.840 00:02:52.850 processing facilities for each
00:02:54.520 00:02:54.530 production stream these gas gathering
00:02:57.850 00:02:57.860 systems can be anywhere from a mile to
00:03:00.340 00:03:00.350 thousands of miles in length and are
00:03:02.710 00:03:02.720 made up of pipelines and booster
00:03:04.540 00:03:04.550 stations that increase the gas pressure
00:03:06.850 00:03:06.860 as needed to move the gas to its
00:03:09.340 00:03:09.350 processing destination once the gas
00:03:13.150 00:03:13.160 reaches a central facility it has put
00:03:15.910 00:03:15.920 through several processes to meet sales
00:03:17.949 00:03:17.959 quality specifications
00:03:19.950 00:03:19.960 these processes can be broken down into
00:03:22.020 00:03:22.030 two main categories removal of
00:03:24.960 00:03:24.970 contaminants and the removal of natural
00:03:27.450 00:03:27.460 gas liquids contaminants must be removed
00:03:30.570 00:03:30.580 from natural gas in order to meet
00:03:32.460 00:03:32.470 pipeline quality specifications the most
00:03:35.880 00:03:35.890 common contaminants in a natural gas
00:03:37.920 00:03:37.930 stream are water hydrogen sulfide and
00:03:42.440 00:03:42.450 non combustible inert gases like carbon
00:03:45.690 00:03:45.700 dioxide and nitrogen now for the next
00:03:49.560 00:03:49.570 few minutes we'll discuss these
00:03:51.120 00:03:51.130 contaminants and the various common
00:03:53.160 00:03:53.170 methods for removing them from the gas
00:03:54.870 00:03:54.880 stream let's start with water even
00:03:59.280 00:03:59.290 though the separator removes most of the
00:04:01.020 00:04:01.030 water from the gas at the wellhead there
00:04:03.840 00:04:03.850 is still water vapor in the gas stream
00:04:06.080 00:04:06.090 this vapor can cause hydrates to form
00:04:10.130 00:04:10.140 hydrates are a combination of
00:04:12.120 00:04:12.130 hydrocarbon molecules and water that
00:04:14.670 00:04:14.680 form a solid and deposit themselves on
00:04:17.130 00:04:17.140 pipeline interiors restricting the flow
00:04:19.530 00:04:19.540 of gas water can also contribute to
00:04:23.070 00:04:23.080 corrosion in pipelines the process of
00:04:27.210 00:04:27.220 removing water from a substance is
00:04:28.830 00:04:28.840 called dehydration the most common
00:04:32.130 00:04:32.140 method for dehydrating a natural gas
00:04:34.020 00:04:34.030 stream uses a liquid desiccant or a
00:04:36.540 00:04:36.550 drying agent called glycol during this
00:04:40.740 00:04:40.750 dehydration process glycol absorbs the
00:04:43.950 00:04:43.960 water from the gas stream drying the gas
00:04:46.550 00:04:46.560 the glycol in effect acts as a kind of
00:04:50.070 00:04:50.080 sponge soaking the water out of the gas
00:04:52.110 00:04:52.120 stream the most common glycol
00:04:54.870 00:04:54.880 dehydration methods use a triethylene
00:04:57.240 00:04:57.250 glycol contactor column or an ethylene
00:05:00.390 00:05:00.400 glycol injection system to learn more
00:05:03.990 00:05:04.000 about this process you may study the
00:05:06.270 00:05:06.280 modules in this series entitled
00:05:07.880 00:05:07.890 principles of glycol dehydration and
00:05:11.120 00:05:11.130 glycol dehydration unit operation
00:05:14.960 00:05:14.970 another gas dehydration method uses a
00:05:18.090 00:05:18.100 solid bed desiccant instead of a liquid
00:05:20.580 00:05:20.590 desiccant a common example of this is
00:05:23.610 00:05:23.620 the molecular sieve which is made up of
00:05:26.250 00:05:26.260 pellets that are electronically polar to
00:05:28.500 00:05:28.510 water when placed in line with the gas
00:05:31.770 00:05:31.780 00:05:32.700 00:05:32.710 the polarity of the pellets attracts the
00:05:34.830 00:05:34.840 water out of the gas into molecule sized
00:05:37.409 00:05:37.419 pores on the surface of the pellet the
00:05:39.950 00:05:39.960 water is held there until the pellets
00:05:42.390 00:05:42.400 are saturated the pellets themselves are
00:05:45.540 00:05:45.550 then dehydrated by a small volume of
00:05:47.730 00:05:47.740 heated gas so they can be used again a
00:05:51.050 00:05:51.060 third method for dehydrating gas streams
00:05:54.140 00:05:54.150 involves methanol injection methanol is
00:05:57.450 00:05:57.460 injected into the gas stream absorbing
00:05:59.730 00:05:59.740 water in the process the methanol and
00:06:02.400 00:06:02.410 water mixture is then disposed of in an
00:06:04.920 00:06:04.930 environmentally safe manner
00:06:06.439 00:06:06.449 now methanol injection is rarely used
00:06:09.779 00:06:09.789 for dehydration because it is toxic
00:06:12.170 00:06:12.180 expensive and disposal is complicated
00:06:16.400 00:06:16.410 those then are the three basic methods
00:06:18.810 00:06:18.820 for removing water from the gas stream
00:06:20.990 00:06:21.000 liquid desiccants solid bed desiccants
00:06:25.350 00:06:25.360 and methanol injection now let's move on
00:06:29.460 00:06:29.470 to the second major contaminate on the
00:06:31.140 00:06:31.150 list hydrogen sulfide which is also
00:06:34.050 00:06:34.060 known by its chemical symbol of h2s
00:06:36.689 00:06:36.699 hydrogen sulfide is an acid gas an acid
00:06:41.879 00:06:41.889 gas is a gas that forms an acid when
00:06:44.010 00:06:44.020 combined with water two examples of acid
00:06:47.310 00:06:47.320 gases are hydrogen sulfide and carbon
00:06:49.140 00:06:49.150 dioxide hydrogen sulfide is corrosive
00:06:53.129 00:06:53.139 and highly toxic it can be deadly
00:06:55.890 00:06:55.900 if proper safety procedures are not
00:06:57.719 00:06:57.729 followed when working in h2s areas for
00:07:01.800 00:07:01.810 detailed information on dealing safely
00:07:03.899 00:07:03.909 with h2s you can study the module
00:07:06.659 00:07:06.669 entitled hydrogen sulfide principles as
00:07:11.159 00:07:11.169 with water there are several different
00:07:13.439 00:07:13.449 methods for removing hydrogen sulfide
00:07:15.540 00:07:15.550 from a gas stream the most common
00:07:18.270 00:07:18.280 methods include chemical reactions
00:07:21.170 00:07:21.180 membrane separation
00:07:23.620 00:07:23.630 and batch processes during chemical
00:07:27.370 00:07:27.380 reaction processes a chemical is mixed
00:07:30.280 00:07:30.290 with the gas stream to neutralize h2s
00:07:33.090 00:07:33.100 this is referred to as gas sweetening
00:07:36.630 00:07:36.640 the most common of these chemical
00:07:39.070 00:07:39.080 reaction processes is called
00:07:40.840 00:07:40.850 amine sweetening during a mean
00:07:44.530 00:07:44.540 sweetening sour gas which is natural gas
00:07:47.170 00:07:47.180 containing acid gas is subjected to a
00:07:49.810 00:07:49.820 stream of a means the amines absorb the
00:07:53.470 00:07:53.480 acid gas leaving sweet gas behind the
00:07:57.880 00:07:57.890 immune solution containing the acid gas
00:07:59.950 00:07:59.960 then goes through a process of
00:08:01.930 00:08:01.940 distillation to remove the acid gas the
00:08:05.980 00:08:05.990 regenerated amine solution can now be
00:08:07.990 00:08:08.000 used again essentially what happens
00:08:10.960 00:08:10.970 during a mean sweetening is that the
00:08:12.760 00:08:12.770 alcohol amines which are weak bases
00:08:14.940 00:08:14.950 react chemically with acid gases like
00:08:17.920 00:08:17.930 hydrogen sulfide to form salt complexes
00:08:21.540 00:08:21.550 these salt complexes can then be broken
00:08:24.550 00:08:24.560 down so the amines are relieved of the
00:08:26.770 00:08:26.780 acid gas and can be recycled if you
00:08:30.760 00:08:30.770 would like more detailed information you
00:08:32.740 00:08:32.750 can refer to the module in this series
00:08:35.010 00:08:35.020 principles of amine sweetening a second
00:08:39.310 00:08:39.320 method for removing h2s uses membrane
00:08:41.770 00:08:41.780 separation membranes are thin polymeric
00:08:45.550 00:08:45.560 films wound in a spiral the gas stream
00:08:49.450 00:08:49.460 flows along the membranes allowing the
00:08:52.300 00:08:52.310 contaminants h2s carbon dioxide and
00:08:55.120 00:08:55.130 water to permeate to the core while the
00:08:58.390 00:08:58.400 rest of the gas continues unaffected by
00:09:00.550 00:09:00.560 the membranes this weakness and
00:09:03.460 00:09:03.470 dehydrates the gas simultaneously some
00:09:06.370 00:09:06.380 hydrocarbon losses to occur with this
00:09:08.290 00:09:08.300 process
00:09:09.040 00:09:09.050 but not a significant amount membranes
00:09:12.250 00:09:12.260 provide low maintenance and operating
00:09:14.560 00:09:14.570 costs when compared to other methods but
00:09:17.590 00:09:17.600 because they are not quite as efficient
00:09:19.600 00:09:19.610 as other processes the membrane system
00:09:22.509 00:09:22.519 is often used in conjunction with other
00:09:24.699 00:09:24.709 h2s and co2 removal methods the final
00:09:28.960 00:09:28.970 method we'll discuss regarding hydrogen
00:09:31.030 00:09:31.040 sulfide removal is the batch process
00:09:33.900 00:09:33.910 under this method a chemical reaction
00:09:36.940 00:09:36.950 and/or absorption is used to remove h2s
00:09:40.630 00:09:40.640 what distinguishes a batch process is
00:09:43.780 00:09:43.790 having to regenerate or change solutions
00:09:47.019 00:09:47.029 at the end of each sweetening cycle the
00:09:50.139 00:09:50.149 most common batch processes are iron
00:09:52.990 00:09:53.000 sponge zinc oxide molecular sieves and
00:09:57.690 00:09:57.700 the caustic wash the iron sponge
00:10:01.900 00:10:01.910 requires the use of wood chips soaked
00:10:03.850 00:10:03.860 with iron oxide when the gas stream
00:10:06.579 00:10:06.589 contacts the chips the iron oxide and
00:10:09.790 00:10:09.800 hydrogen sulfide combine to form ferrous
00:10:12.850 00:10:12.860 sulfide neutralizing the acid gas
00:10:16.949 00:10:16.959 however since ferrous sulfide will
00:10:20.230 00:10:20.240 spontaneously combust when exposed to
00:10:22.540 00:10:22.550 air it must be kept wet until it can be
00:10:26.019 00:10:26.029 buried in a safe and environmentally
00:10:27.970 00:10:27.980 sound manner a second type of batch
00:10:31.720 00:10:31.730 process employs a combination of zinc
00:10:34.329 00:10:34.339 oxide zinc acetate water and a
00:10:37.870 00:10:37.880 dispersant the gas is bubbled through
00:10:41.319 00:10:41.329 the solution and the turbulence created
00:10:44.440 00:10:44.450 by the flowing gas bubbles keeps the
00:10:46.900 00:10:46.910 sulfur suspended in the solution several
00:10:51.010 00:10:51.020 chemical reactions take place with zinc
00:10:54.040 00:10:54.050 oxide finally reacting with hydrogen
00:10:56.230 00:10:56.240 sulfide to form zinc sulfide and water
00:11:00.720 00:11:00.730 the resulting slurry must be disposed of
00:11:04.030 00:11:04.040 in a safe and environmentally sound
00:11:06.220 00:11:06.230 manner
00:11:10.819 00:11:10.829 molecular sieve beds can also be used
00:11:13.679 00:11:13.689 for batch processing because the SIB bed
00:11:16.410 00:11:16.420 committee signs of sweet'n while it is
00:11:18.660 00:11:18.670 dehydrated and finally caustic wash
00:11:22.859 00:11:22.869 systems are yet another batch process
00:11:25.019 00:11:25.029 for hydrogen sulfide removal this method
00:11:28.350 00:11:28.360 employs a highly basic or caustic
00:11:30.539 00:11:30.549 substance like potassium hydroxide to
00:11:33.449 00:11:33.459 neutralize the h2s the caustic substance
00:11:37.229 00:11:37.239 used in this process can be either
00:11:39.299 00:11:39.309 liquid or solid let's briefly review
00:11:44.489 00:11:44.499 what we've covered so far about
00:11:45.809 00:11:45.819 contaminant removal water hydrogen
00:11:49.199 00:11:49.209 sulfide and non combustible inert gases
00:11:51.629 00:11:51.639 are the main contaminants in a natural
00:11:53.879 00:11:53.889 gas stream the primary methods for
00:11:56.850 00:11:56.860 removing water are liquid desiccants
00:11:59.519 00:11:59.529 like glycol solid bed desiccants like
00:12:02.249 00:12:02.259 molecular sieves and methanol injection
00:12:05.629 00:12:05.639 to remove hydrogen sulfide safely the
00:12:09.179 00:12:09.189 most frequently used methods are
00:12:10.739 00:12:10.749 chemical reaction processes like a mean
00:12:13.199 00:12:13.209 sweetening the membrane separation
00:12:15.869 00:12:15.879 process and batch processes like iron
00:12:19.499 00:12:19.509 sponge which brings us to the third type
00:12:22.859 00:12:22.869 of contaminant the non combustible and
00:12:25.769 00:12:25.779 nert gases the most common of these
00:12:28.470 00:12:28.480 gases are carbon dioxide and nitrogen
00:12:31.489 00:12:31.499 these and any other non combustible
00:12:34.139 00:12:34.149 gases must be removed from the gas
00:12:36.119 00:12:36.129 stream because I cannot burn and have no
00:12:38.489 00:12:38.499 heating value methods vary depending
00:12:41.069 00:12:41.079 upon the type of gas being removed
00:12:43.460 00:12:43.470 plastic wash and amine processes are
00:12:46.769 00:12:46.779 usually used to remove carbon dioxide
00:12:48.499 00:12:48.509 the same way they do hydrogen sulfide
00:12:52.429 00:12:52.439 nitrogen can be removed by a nitrogen
00:12:55.439 00:12:55.449 rejection unit or n ru usually referred
00:12:59.939 00:12:59.949 to as cold boxes they kill the gas
00:13:02.999 00:13:03.009 stream to about minus 300 degrees
00:13:04.829 00:13:04.839 Fahrenheit liquefying all the
00:13:07.499 00:13:07.509 hydrocarbon gases and leaving the
00:13:09.840 00:13:09.850 nitrogen in a gaseous state water carbon
00:13:14.759 00:13:14.769 dioxide and hydrogen sulfide have all
00:13:17.189 00:13:17.199 been removed by other methods before
00:13:19.289 00:13:19.299 subjecting the gas stream to these
00:13:20.819 00:13:20.829 extreme
00:13:21.670 00:13:21.680 creatures the nitrogen is then vented or
00:13:25.329 00:13:25.339 in some cases injected back into the
00:13:28.360 00:13:28.370 ground and used as a kind of gaseous
00:13:31.060 00:13:31.070 broom to sweep crude oil toward a well
00:13:33.310 00:13:33.320 and that brings us the end of section 1
00:13:36.579 00:13:36.589 please stop the video tape and read over
00:13:39.130 00:13:39.140 the material in your student manual
00:13:40.389 00:13:40.399 filling in the blanks as you go when you
00:13:43.210 00:13:43.220 finished we'll return with a look at
00:13:45.430 00:13:45.440 methods for removing natural gas liquids
00:13:47.290 00:13:47.300 from the gas stream
00:14:04.580 00:14:04.590 00:14:06.840 00:14:06.850 stream is only half the story of gas
00:14:09.090 00:14:09.100 processing there are other components in
00:14:12.180 00:14:12.190 the gas stream that must be removed for
00:14:14.190 00:14:14.200 different reasons those components are
00:14:16.560 00:14:16.570 known as natural gas liquids
00:14:20.580 00:14:20.590 this is the second section of a two
00:14:22.830 00:14:22.840 00:14:25.170 00:14:25.180 00:14:28.470 00:14:28.480 various methods of removing natural gas
00:14:30.570 00:14:30.580 liquids from a gas stream and here a
00:14:33.480 00:14:33.490 brief discussion of fractionation
00:14:39.090 00:14:39.100 natural gas liquids or NGLs are simply
00:14:42.520 00:14:42.530 hydrocarbons in a liquid state there are
00:14:45.280 00:14:45.290 many potential reasons for removing NGLs
00:14:47.470 00:14:47.480 from the gas stream for example the
00:14:49.960 00:14:49.970 hydrocarbon components may be more
00:14:52.030 00:14:52.040 valuable in their liquid state either
00:14:53.950 00:14:53.960 mixed or separated into their different
00:14:56.530 00:14:56.540 individual elements secondly pipeline
00:15:00.430 00:15:00.440 gas quality specifications may restrict
00:15:03.190 00:15:03.200 the amount of NGLs allowed in the gas
00:15:05.110 00:15:05.120 stream also temperatures drop to a
00:15:08.560 00:15:08.570 certain point
00:15:09.490 00:15:09.500 heavier NGLs can separate from the gas
00:15:12.130 00:15:12.140 stream restricting flow in the pipeline
00:15:15.270 00:15:15.280 finally the separated NGLs may be used
00:15:18.430 00:15:18.440 for reinjection on enhanced oil recovery
00:15:20.520 00:15:20.530 projects much like nitrogen the most
00:15:24.250 00:15:24.260 common processes used for separating ngl
00:15:27.010 00:15:27.020 from the gas stream are cryogenics
00:15:30.270 00:15:30.280 refrigeration and lean oil absorption
00:15:34.410 00:15:34.420 let's take some time now to briefly go
00:15:37.300 00:15:37.310 over each one of these processes in the
00:15:40.450 00:15:40.460 cryogenic process a gas stream is
00:15:43.060 00:15:43.070 chilled to below minus 50 degrees
00:15:45.310 00:15:45.320 Fahrenheit this allows the ethane and
00:15:48.400 00:15:48.410 heavier gas components to liquefy easily
00:15:51.750 00:15:51.760 the ethane and heavier hydrocarbons are
00:15:55.090 00:15:55.100 then separated from the methane
00:15:58.200 00:15:58.210 cryogenic processing of a natural gas
00:16:01.120 00:16:01.130 stream involves three basic steps
00:16:04.140 00:16:04.150 dehydration chilling and fractionation
00:16:08.580 00:16:08.590 because of the extremely cold
00:16:10.660 00:16:10.670 temperatures used the gas stream must be
00:16:13.180 00:16:13.190 almost totally dehydrated to prevent the
00:16:15.790 00:16:15.800 formation of hydrates this is usually
00:16:18.370 00:16:18.380 done with either a liquid or solid
00:16:20.860 00:16:20.870 desiccant depending on the water content
00:16:23.080 00:16:23.090 of the inlet gas at your facility
00:16:26.490 00:16:26.500 chilling of the dehydrated gas stream
00:16:28.990 00:16:29.000 can then be done by heat exchange with
00:16:31.840 00:16:31.850 cold gas and by pressure reduction or
00:16:35.080 00:16:35.090 pressure reduction with energy removal
00:16:38.640 00:16:38.650 the pressure reduction method using the
00:16:41.860 00:16:41.870 JT or Joule Thomson valve provides cold
00:16:45.760 00:16:45.770 temperatures in the range of minus 50
00:16:47.800 00:16:47.810 degrees Fahrenheit to minus 100 degrees
00:16:50.440 00:16:50.450 Fahrenheit
00:16:51.540 00:16:51.550 to get the lowest temperatures needed -
00:16:54.639 00:16:54.649 100 degrees Fahrenheit - minus 200
00:16:57.670 00:16:57.680 degrees Fahrenheit an expander
00:17:00.100 00:17:00.110 compressor is used to achieve pressure
00:17:02.050 00:17:02.060 reduction with energy removal cryogenics
00:17:06.010 00:17:06.020 has relatively moderate energy
00:17:07.600 00:17:07.610 requirements and is considered currently
00:17:10.689 00:17:10.699 to be the most efficient method for
00:17:12.370 00:17:12.380 removing NGLs from the gas stream to get
00:17:16.179 00:17:16.189 more detailed information about
00:17:17.559 00:17:17.569 cryogenics see the module entitled
00:17:20.309 00:17:20.319 cryogenic principles refrigeration is an
00:17:24.610 00:17:24.620 ngl separation process that has been
00:17:26.829 00:17:26.839 used for many years the principle is to
00:17:29.950 00:17:29.960 cool the natural gas stream by passing
00:17:32.200 00:17:32.210 it through a chiller killing causes the
00:17:34.870 00:17:34.880 heavier hydrocarbons to liquefy and they
00:17:37.510 00:17:37.520 are then easily separated from the gas
00:17:39.310 00:17:39.320 stream now the big difference between
00:17:41.909 00:17:41.919 refrigeration and cryogenics is the
00:17:44.350 00:17:44.360 degree of chilling that occurs
00:17:46.350 00:17:46.360 temperatures during refrigeration range
00:17:49.180 00:17:49.190 only from zero degrees to minus 20
00:17:51.400 00:17:51.410 degrees which is much warmer than the
00:17:53.500 00:17:53.510 cryogenic temperatures although the
00:17:56.740 00:17:56.750 volume of heavier hydrocarbons recovered
00:17:59.110 00:17:59.120 is less with this method than with lean
00:18:01.780 00:18:01.790 oil absorption the amount of equipment
00:18:04.270 00:18:04.280 and energy needed is much less making
00:18:07.799 00:18:07.809 refrigeration a more economical method
00:18:10.600 00:18:10.610 than lean oil absorption now for years
00:18:14.370 00:18:14.380 lean oil absorption was the main method
00:18:17.890 00:18:17.900 of mgl recovery in the oil and gas
00:18:19.840 00:18:19.850 industry although this process is still
00:18:23.230 00:18:23.240 in use it is gradually disappearing as
00:18:26.340 00:18:26.350 refrigeration or cryogenics takes its
00:18:28.960 00:18:28.970 place during lean oil absorption
00:18:32.470 00:18:32.480 Leyna oil has flowed through a natural
00:18:34.780 00:18:34.790 gas stream absorbing the heavier
00:18:36.730 00:18:36.740 hydrocarbons as a context then those n
00:18:40.210 00:18:40.220 GL's are then recovered by distilling
00:18:42.010 00:18:42.020 them out of the now rich oil once the in
00:18:46.030 00:18:46.040 jails are cooked out of the oil the
00:18:48.039 00:18:48.049 regenerated lean oil is circulated back
00:18:50.320 00:18:50.330 through the system this process is
00:18:54.250 00:18:54.260 relatively expensive to operate because
00:18:56.590 00:18:56.600 it requires a lot of energy compared to
00:18:58.480 00:18:58.490 refrigeration or cryogenics
00:19:01.760 00:19:01.770 those then are the three primary ways of
00:19:04.250 00:19:04.260 removing NGOs from the gas stream now
00:19:07.220 00:19:07.230 let's talk a bit about fractionation
00:19:09.790 00:19:09.800 fractionation is a downstream option for
00:19:12.740 00:19:12.750 NGLs that means it is something that can
00:19:15.860 00:19:15.870 happen to the natural gas liquids after
00:19:18.200 00:19:18.210 they're separated from the gas stream
00:19:20.980 00:19:20.990 fractionation is a distillation process
00:19:23.780 00:19:23.790 for separating two or more components in
00:19:25.910 00:19:25.920 a mixture of two or more components
00:19:28.810 00:19:28.820 let's look at an example a depropanizer
00:19:33.160 00:19:33.170 separates propane from a stream that
00:19:35.419 00:19:35.429 contains propane and one or more heavier
00:19:38.210 00:19:38.220 hydrocarbons the propane is cooked out
00:19:41.450 00:19:41.460 of the mixture and is the overhead
00:19:43.250 00:19:43.260 product from the tower as you can see by
00:19:46.160 00:19:46.170 this graphic different NGLs are
00:19:48.530 00:19:48.540 distilled out of different towers
00:19:50.919 00:19:50.929 usually there are only two ways of
00:19:53.299 00:19:53.309 controlling the purity of the top and
00:19:55.010 00:19:55.020 bottom streams of these towers you can
00:19:58.250 00:19:58.260 vary the temperature at the top of the
00:19:59.870 00:19:59.880 tower or vary the temperature at the
00:20:02.210 00:20:02.220 bottom of the tower
00:20:03.640 00:20:03.650 generally speaking you cannot change the
00:20:06.770 00:20:06.780 pressure or the feed rate because this
00:20:09.830 00:20:09.840 would alter operating conditions in the
00:20:11.900 00:20:11.910 rest of the plant the fundamental
00:20:14.660 00:20:14.670 question of whether to fractionate NGLs
00:20:16.790 00:20:16.800 is an economic one is there a profitable
00:20:20.780 00:20:20.790 market for the fractionated product
00:20:23.140 00:20:23.150 market conditions for the natural gas
00:20:25.490 00:20:25.500 liquids can change rapidly and often so
00:20:29.150 00:20:29.160 this question must be constantly
00:20:30.680 00:20:30.690 answered there may even be times when
00:20:34.370 00:20:34.380 the mixed ng ales will be more valuable
00:20:37.070 00:20:37.080 than their separate components and that
00:20:40.880 00:20:40.890 brings us to the end of this module stop
00:20:43.850 00:20:43.860 the videotape and read over section two
00:20:46.220 00:20:46.230 in your student manual filling in the
00:20:48.020 00:20:48.030 blanks as you go now please
00:20:50.630 00:20:50.640 be sure to ask questions if there's
00:20:52.250 00:20:52.260 anything you don't understand and refer
00:20:54.110 00:20:54.120 to the other modules we've mentioned if
00:20:55.760 00:20:55.770 you need more information now
00:20:58.299 00:20:58.309 understanding the basic information in
00:21:00.620 00:21:00.630 this module will give you the foundation
00:21:02.540 00:21:02.550 for more detailed study later on so be
00:21:05.870 00:21:05.880 sure you are thoroughly familiar with
00:21:07.370 00:21:07.380 this material before moving on
00:21:09.630 00:21:09.640 we'll see you next time
00:21:28.610 00:21:28.620 you will see various methods of removing
00:21:31.440 00:21:31.450 natural gas liquids from a gas stream
00:21:33.660 00:21:33.670 and here a brief discussion of
00:21:35.970 00:21:35.980 fractionation
00:21:40.649 00:21:40.659 00:21:43.979 00:21:43.989 00:21:46.739 00:21:46.749 many potential reasons for removing an
00:21:48.570 00:21:48.580 GL's from the gas stream for example the
00:21:51.419 00:21:51.429 00:21:53.489 00:21:53.499 00:21:55.379 00:21:55.389 00:21:58.019 00:21:58.029 00:22:01.889 00:22:01.899 gas quality specifications may we strict
00:22:04.649 00:22:04.659 the amount of energy ales allowed in the
00:22:06.419 00:22:06.429 gas stream also temperatures drop to a
00:22:10.019 00:22:10.029 00:22:10.950 00:22:10.960 00:22:13.589 00:22:13.599 00:22:16.729 00:22:16.739 00:22:19.919 00:22:19.929 for re-inject Chinon enhanced oil
00:22:21.779 00:22:21.789 recovery projects much like nitrogen the
00:22:25.469 00:22:25.479 most common processes used for
00:22:27.450 00:22:27.460 separating ngl from the gas stream are
00:22:29.749 00:22:29.759 cryogenics refrigeration and lean oil
00:22:34.889 00:22:34.899 absorption let's take some time now to
00:22:37.769 00:22:37.779 briefly go over each one of these
00:22:39.599 00:22:39.609 processes in the cryogenic process a gas
00:22:44.129 00:22:44.139 stream is chilled to below minus 50
00:22:46.469 00:22:46.479 degrees Fahrenheit this allows the
00:22:49.259 00:22:49.269 ethane and heavier gas components to
00:22:51.779 00:22:51.789 liquefy easily the ethane and heavier
00:22:55.499 00:22:55.509 hydrocarbons are then separated from the
00:22:57.749 00:22:57.759 methane cryogenic processing of a
00:23:01.950 00:23:01.960 natural gas stream involves three basic
00:23:04.109 00:23:04.119 steps dehydration chilling and
00:23:07.940 00:23:07.950 fractionation because of the extremely
00:23:11.849 00:23:11.859 cold temperatures used the gas stream
00:23:14.159 00:23:14.169 must be almost totally dehydrated to
00:23:16.799 00:23:16.809 prevent the formation of hydrates this
00:23:19.499 00:23:19.509 is usually done with either a liquid or
00:23:21.869 00:23:21.879 solid desiccant depending on the water
00:23:24.180 00:23:24.190 content of the inlet gas at your
00:23:26.310 00:23:26.320 facility chilling of the dehydrated gas
00:23:30.089 00:23:30.099 stream can then be done by heat exchange
00:23:33.210 00:23:33.220 with cold gas and by pressure reduction
00:23:36.389 00:23:36.399 or pressure reduction with energy
00:23:38.669 00:23:38.679 removal the pressure reduction method
00:23:42.539 00:23:42.549 using the JT or Joule Thomson valve
00:23:45.930 00:23:45.940 provides cold temperatures in the range
00:23:48.299 00:23:48.309 of minus 50 degrees Fahrenheit to minus
00:23:51.029 00:23:51.039 100 degrees Fahrenheit
00:23:53.030 00:23:53.040 00:23:56.100 00:23:56.110 00:23:59.130 00:23:59.140 00:24:01.560 00:24:01.570 00:24:03.510 00:24:03.520 reduction with energy removal projects
00:24:07.470 00:24:07.480 00:24:09.060 00:24:09.070 00:24:12.150 00:24:12.160 00:24:13.830 00:24:13.840 00:24:17.610 00:24:17.620 00:24:19.020 00:24:19.030 00:24:21.770 00:24:21.780 00:24:26.070 00:24:26.080 ngl separation process that have been
00:24:28.290 00:24:28.300 00:24:31.410 00:24:31.420 00:24:33.660 00:24:33.670 00:24:36.330 00:24:36.340 00:24:39.000 00:24:39.010 00:24:40.770 00:24:40.780 00:24:43.370 00:24:43.380 00:24:45.810 00:24:45.820 00:24:47.840 00:24:47.850 00:24:50.640 00:24:50.650 00:24:52.860 00:24:52.870 00:24:54.960 00:24:54.970 00:24:58.230 00:24:58.240 00:25:00.570 00:25:00.580 is less with this method then what lean
00:25:03.240 00:25:03.250 oil absorption in the natural gas stream
00:25:05.820 00:25:05.830 are water hydrogen sulfide and non
00:25:10.890 00:25:10.900 combustible inert gases like carbon
00:25:13.140 00:25:13.150 00:25:17.100 00:25:17.110 00:25:18.540 00:25:18.550 00:25:20.610 00:25:20.620 00:25:22.320 00:25:22.330 00:25:25.880 00:25:25.890 00:25:28.470 00:25:28.480 00:25:31.290 00:25:31.300 00:25:33.590 00:25:33.600 00:25:37.610 00:25:37.620 00:25:39.570 00:25:39.580 00:25:42.090 00:25:42.100 00:25:44.580 00:25:44.590 00:25:46.980 00:25:46.990 00:25:50.400 00:25:50.410 00:25:54.660 00:25:54.670 00:25:56.280 00:25:56.290 called dehydration
00:25:58.480 00:25:58.490 the most common method for dehydrating a
00:26:00.940 00:26:00.950 natural gas stream uses a liquid
00:26:03.100 00:26:03.110 desiccant or a drying agent called
00:26:05.430 00:26:05.440 glycol during this dehydration process
00:26:09.750 00:26:09.760 glycol absorbs the water from the gas
00:26:12.160 00:26:12.170 stream drying the gas the glycol in
00:26:15.670 00:26:15.680 effect acts as a kind of sponge soaking
00:26:18.400 00:26:18.410 the water out of the gas stream
00:26:20.310 00:26:20.320 the most common glycol dehydration
00:26:22.450 00:26:22.460 methods use a triethylene glycol
00:26:25.150 00:26:25.160 contactor column or an ethylene glycol
00:26:28.420 00:26:28.430 injection system to learn more about
00:26:31.570 00:26:31.580 this process you may study the modules
00:26:34.150 00:26:34.160 in this series entitled principles of
00:26:36.490 00:26:36.500 glycol dehydration and glycol
00:26:39.580 00:26:39.590 dehydration unit operation another gas
00:26:43.810 00:26:43.820 dehydration method uses a solid bed
00:26:46.300 00:26:46.310 desiccant instead of a liquid desiccant
00:26:48.670 00:26:48.680 a common example of this is the
00:26:51.520 00:26:51.530 molecular sieve which is made up of
00:26:53.710 00:26:53.720 00:26:55.960 00:26:55.970 00:26:59.230 00:26:59.240 stream the polarity of the pellets
00:27:01.570 00:27:01.580 attracts the water out of the gas into
00:27:03.580 00:27:03.590 molecule sized pores on the surface of
00:27:06.550 00:27:06.560 the pellet the water is held there until
00:27:09.400 00:27:09.410 the pellets are saturated the pellets
00:27:12.160 00:27:12.170 themselves are then dehydrated by a
00:27:14.200 00:27:14.210 small volume of heated gas so they can
00:27:16.690 00:27:16.700 be used again a third method for
00:27:20.140 00:27:20.150 dehydrating gas streams involves
00:27:22.600 00:27:22.610 methanol injection methanol is injected
00:27:25.570 00:27:25.580 into the gas stream absorbing water in
00:27:27.640 00:27:27.650 the process the methanol and water
00:27:29.920 00:27:29.930 mixture is then disposed of in an
00:27:32.350 00:27:32.360 00:27:33.900 00:27:33.910 00:27:37.210 00:27:37.220 00:27:39.600 00:27:39.610 00:27:43.859 00:27:43.869 00:27:46.269 00:27:46.279 00:27:48.450 00:27:48.460 liquid desiccant solid bed desiccants
00:27:52.810 00:27:52.820 00:27:56.889 00:27:56.899 to the second major contaminant on the
00:27:58.599 00:27:58.609 00:28:01.479 00:28:01.489 00:28:04.149 00:28:04.159 00:28:09.340 00:28:09.350 00:28:11.469 00:28:11.479 00:28:14.769 00:28:14.779 00:28:16.599 00:28:16.609 00:28:20.799 00:28:20.809 and highly toxic it can be deadly if
00:28:23.499 00:28:23.509 proper safety procedures are not
00:28:25.149 00:28:25.159 00:28:29.259 00:28:29.269 00:28:31.330 00:28:31.340 00:28:34.089 00:28:34.099 00:28:38.589 00:28:38.599 00:28:40.899 00:28:40.909 methods chemical reactions take place
00:28:43.139 00:28:43.149 with zinc oxide finally reacting with
00:28:46.180 00:28:46.190 hydrogen sulfide to form zinc sulfide
00:28:49.419 00:28:49.429 and water the resulting slurry must be
00:28:53.799 00:28:53.809 disposed of in a safe and
00:28:55.509 00:28:55.519 environmentally sound manner
00:29:01.269 00:29:01.279 molecular sieve bets can also be used
00:29:04.129 00:29:04.139 for batch processing because the sieve
00:29:06.649 00:29:06.659 bed can be designed to sweeten while it
00:29:08.990 00:29:09.000 is dehydrated and finally caustic wash
00:29:13.310 00:29:13.320 00:29:15.470 00:29:15.480 00:29:18.769 00:29:18.779 00:29:20.990 00:29:21.000 00:29:23.899 00:29:23.909 00:29:27.649 00:29:27.659 00:29:29.720 00:29:29.730 00:29:34.940 00:29:34.950 00:29:36.230 00:29:36.240 00:29:39.649 00:29:39.659 00:29:42.080 00:29:42.090 00:29:44.299 00:29:44.309 00:29:47.299 00:29:47.309 00:29:49.940 00:29:49.950 00:29:52.700 00:29:52.710 00:29:56.049 00:29:56.059 00:29:59.629 00:29:59.639 00:30:01.190 00:30:01.200 chemical reaction processes like amine
00:30:03.649 00:30:03.659 00:30:06.289 00:30:06.299 00:30:09.919 00:30:09.929 00:30:13.009 00:30:13.019 00:30:16.190 00:30:16.200 00:30:18.919 00:30:18.929 00:30:21.940 00:30:21.950 00:30:24.590 00:30:24.600 00:30:26.570 00:30:26.580 00:30:28.940 00:30:28.950 00:30:31.519 00:30:31.529 00:30:33.909 00:30:33.919 00:30:37.159 00:30:37.169 00:30:38.950 00:30:38.960 00:30:42.879 00:30:42.889 00:30:45.889 00:30:45.899 00:30:50.389 00:30:50.399 00:30:53.419 00:30:53.429 00:30:55.279 00:30:55.289 00:30:57.950 00:30:57.960 00:31:00.259 00:31:00.269 00:31:05.180 00:31:05.190 00:31:07.610 00:31:07.620 00:31:09.560 00:31:09.570 00:31:11.269 00:31:11.279 extreme temperatures
00:31:13.210 00:31:13.220 the nitrogen is then vented or in some
00:31:16.660 00:31:16.670 cases injected back into the ground and
00:31:19.390 00:31:19.400 used as a kind of gaseous broom to sweep
00:31:22.150 00:31:22.160 crude oil toward a well and that brings
00:31:25.930 00:31:25.940 us the end of section 1
00:31:27.220 00:31:27.230 please stop the videotape and read over
00:31:29.560 00:31:29.570 00:31:30.820 00:31:30.830 00:31:33.640 00:31:33.650 00:31:35.860 00:31:35.870 00:31:37.720 00:31:37.730 00:31:55.020 00:31:55.030 00:31:57.280 00:31:57.290 00:31:59.530 00:31:59.540 00:32:02.650 00:32:02.660 00:32:04.630 00:32:04.640 00:32:07.000 00:32:07.010 00:32:10.899 00:32:10.909 00:32:13.269 00:32:13.279 00:32:15.609 00:32:15.619 processing in this section for removing
00:32:19.029 00:32:19.039 hydrogen sulfide from a gas stream the
00:32:22.119 00:32:22.129 most common methods include chemical
00:32:24.669 00:32:24.679 reactions membrane separation and batch
00:32:28.810 00:32:28.820 processes during chemical reaction
00:32:32.379 00:32:32.389 processes a chemical is mixed with the
00:32:35.049 00:32:35.059 gas stream to neutralize h2s this is
00:32:38.710 00:32:38.720 referred to as gas sweetening the most
00:32:42.279 00:32:42.289 common of these chemical reaction
00:32:43.989 00:32:43.999 processes is called
00:32:45.279 00:32:45.289 00:32:48.969 00:32:48.979 00:32:51.609 00:32:51.619 00:32:54.279 00:32:54.289 00:32:57.909 00:32:57.919 00:33:02.320 00:33:02.330 00:33:04.389 00:33:04.399 00:33:06.369 00:33:06.379 00:33:10.450 00:33:10.460 00:33:12.430 00:33:12.440 00:33:15.399 00:33:15.409 00:33:17.200 00:33:17.210 00:33:19.379 00:33:19.389 00:33:22.359 00:33:22.369 00:33:25.979 00:33:25.989 00:33:28.989 00:33:28.999 00:33:31.239 00:33:31.249 00:33:35.200 00:33:35.210 00:33:37.479 00:33:37.489 00:33:39.450 00:33:39.460 00:33:43.749 00:33:43.759 method for removing h2s uses membranes
00:33:46.239 00:33:46.249 00:33:49.989 00:33:49.999 00:33:53.889 00:33:53.899 00:33:56.739 00:33:56.749 00:33:59.560 00:33:59.570 00:34:02.830 00:34:02.840 00:34:04.989 00:34:04.999 00:34:07.899 00:34:07.909 dehydrates the gas simultaneously
00:34:10.430 00:34:10.440 some hydrocarbon losses do occur with
00:34:12.559 00:34:12.569 this process but not a significant
00:34:14.659 00:34:14.669 amount membranes provide low maintenance
00:34:17.930 00:34:17.940 and operating costs when compared to
00:34:20.149 00:34:20.159 other methods but because they are not
00:34:22.909 00:34:22.919 quite as efficient as other processes
00:34:25.220 00:34:25.230 the membrane system is often used in
00:34:28.129 00:34:28.139 conjunction with other h2s and co2
00:34:30.919 00:34:30.929 removal methods the final method we'll
00:34:33.889 00:34:33.899 discuss regarding hydrogen sulfide
00:34:35.930 00:34:35.940 removal is the batch process under this
00:34:39.500 00:34:39.510 method a chemical reaction and/or
00:34:42.079 00:34:42.089 absorption is used to remove h2s what
00:34:46.069 00:34:46.079 distinguishes a batch process is having
00:34:48.950 00:34:48.960 to regenerate or change solutions at the
00:34:52.069 00:34:52.079 end of each sweetening cycle the most
00:34:54.799 00:34:54.809 common batch processes are iron sponge
00:34:58.120 00:34:58.130 zinc oxide molecular sieves and the
00:35:03.140 00:35:03.150 caustic wash the iron sponge requires
00:35:06.799 00:35:06.809 the use of wood chips soaked with iron
00:35:08.750 00:35:08.760 oxide when the gas stream contacts the
00:35:11.990 00:35:12.000 chips the iron oxide and hydrogen
00:35:14.240 00:35:14.250 sulfide combine to form ferrous sulfide
00:35:18.069 00:35:18.079 neutralizing the acid gas however since
00:35:23.269 00:35:23.279 ferrous sulfide will spontaneously
00:35:25.120 00:35:25.130 combust when exposed to air it must be
00:35:28.819 00:35:28.829 kept wet until it can be buried in a
00:35:31.069 00:35:31.079 safe and environmentally sound manner a
00:35:34.599 00:35:34.609 second type of batch process employs a
00:35:37.880 00:35:37.890 combination of zinc oxide zinc acetate
00:35:40.569 00:35:40.579 water and a dispersant the gas has
00:35:45.079 00:35:45.089 bubbled through the solution and the
00:35:47.750 00:35:47.760 turbulence created by the flowing gas
00:35:49.789 00:35:49.799 bubbles keeps the sulfur suspended in
00:35:52.880 00:35:52.890 the solution several
00:36:21.880 00:36:21.890 00:36:25.310 00:36:25.320 00:36:27.380 00:36:27.390 00:36:30.530 00:36:30.540 00:36:33.260 00:36:33.270 00:36:35.240 00:36:35.250 00:36:38.690 00:36:38.700 00:36:40.700 00:36:40.710 00:36:43.340 00:36:43.350 all about this is the first section of a
00:36:49.880 00:36:49.890 2 section module on the principles of
00:36:52.310 00:36:52.320 gas processing in this section you will
00:36:55.880 00:36:55.890 see an overview of how gas is usually
00:36:57.980 00:36:57.990 00:37:00.620 00:37:00.630 00:37:02.030 00:37:02.040 00:37:06.200 00:37:06.210 00:37:08.730 00:37:08.740 00:37:11.370 00:37:11.380 00:37:13.349 00:37:13.359 00:37:16.680 00:37:16.690 00:37:20.190 00:37:20.200 00:37:22.140 00:37:22.150 00:37:25.290 00:37:25.300 00:37:27.900 00:37:27.910 00:37:30.690 00:37:30.700 marketable money let's take a look at
00:37:34.320 00:37:34.330 how that typically happens gas
00:37:36.930 00:37:36.940 processing starts here at the wellhead
00:37:38.960 00:37:38.970 gas coming out of the ground normally
00:37:42.180 00:37:42.190 contains fluids such as oil and water
00:37:45.230 00:37:45.240 00:37:48.089 00:37:48.099 00:37:51.000 00:37:51.010 00:37:52.680 00:37:52.690 00:37:56.970 00:37:56.980 00:37:59.520 00:37:59.530 00:38:01.800 00:38:01.810 00:38:05.790 00:38:05.800 00:38:07.830 00:38:07.840 00:38:10.530 00:38:10.540 00:38:13.079 00:38:13.089 00:38:14.910 00:38:14.920 00:38:18.030 00:38:18.040 00:38:20.280 00:38:20.290 indicate a problem
00:38:21.300 00:38:21.310 such as a leak in the pipeline to get
00:38:25.170 00:38:25.180 more information on metering you may
00:38:27.450 00:38:27.460 study the module in this series entitled
00:38:29.240 00:38:29.250 orifice meter station fundamentals now
00:38:33.960 00:38:33.970 in order to process gas efficiently at a
00:38:37.020 00:38:37.030 duty pipe for many producing locations
00:38:39.210 00:38:39.220 to a central processing facility this is
00:38:43.620 00:38:43.630 00:38:46.050 00:38:46.060 00:38:48.300 00:38:48.310 00:38:49.980 00:38:49.990 00:38:53.310 00:38:53.320 00:38:55.800 00:38:55.810 00:38:58.170 00:38:58.180 00:39:00.000 00:39:00.010 00:39:02.310 00:39:02.320 00:39:04.800 00:39:04.810 00:39:08.609 00:39:08.619 reaches a central facility it is put
00:39:11.370 00:39:11.380 00:39:13.410 00:39:13.420 00:39:15.400 00:39:15.410 00:39:17.650 00:39:17.660 00:39:20.440 00:39:20.450 00:39:22.930 00:39:22.940 00:39:26.020 00:39:26.030 00:39:27.910 00:39:27.920 00:39:31.329 00:39:31.339 common contaminants

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