Page 356 - Pressure Swing Adsorption

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332 PRESSURE SWING ADSORPTION APPENDIX C 333

200c •r----'i-1ooc
18 29
related disclosures that were approved in 1964.' · Their first process was
Nz RICH
PRODUCT also used for upgrading reformer recycle gas, m the range of 50% hvctrogen.
112 412 with an ultimate purity of greater than 99% hydrbgen, u·sing activated ca_rbon
123 411 423
110 410 and activated alumma as the adsorbents. The ooeratmg conditions included a
ID7b pressure range of from 200 to 650 osig for ads0rot1on, and 8 to 12 0s1a for
407, 407b
desorPtIOn and ourgmg. The cycle mcluded a monthly thermal regeneration
407
at about 600°F, via an mert gas. The second patented process was apparently
the first that explicitly mentioned a cocurrent blowctown step that was used
directly partially to pressurize a parall"e! column. That idea, which is often
referred to as pressure eaualizatwn, has been claimed as a vnal nart of many
I
other patents, of which only a few are cited here as exampies:lfJ--i.i
J'1
C.2.9 Wilson
317 Another early patent application concernmg the actuai (versus hypothetical)
417
separat10n of oxygen and nitrogen from a1r m a single system was filed by
2.00CI IOOo 7
Wilson m 1959, although 1t was not approved until 1965. It contained several
novel ideas that recurred in later patents. For example, a three-step cycle was
used: pressunzatton (with orednect air), cocurrent blowdown (producing
ennchect oxygen, at 70 to 90%), and countercurrent blowdown (producmg
Figure· C.3 Flowsheet of a second PSA apparatus suggested by Skarstrom m I 958, enriched nitrogen, at subatmospheric pressure). He suggested an option of
which appeared in U.S. Patent No. 2,944,627 in 1960. This cqummcnt was apparently
designed for cxtrncting two nearly pure products from a smgle feed, such as splitting using heat to achieve a higher degree of desorption than by pressure aione.
nitrogen and oxygen from air. He also suggested usmg an oscillating ptston to dflve the pressure swmg, and
that idea has been borrowed, slightly modified, or remvented several
35 39
ttmes. - He suggested that the same ideas could be used to remove carbon
two or more adsorbents and couoling PSA systems) has been reinvented dioxide from a!f (e.g., m submarines) and to separate helium from natural
(with subtle twists) or borrowed several timcs. 16 24 gas.
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C.2.10 Stark
C.2. 7 Skarstrom
About 2 years after the flurry of patent applications for PSA hydrogen
Some early PSA patents concerned with hydrogen ourificatton, which fol-
lowed up on much earlier suggestions by Perley ID and Erdmann, were filed purification were filed by Skarstrom and his collbagues (see C.2. 7), another
14
by Skarstrom 10 1960 and awarded m 1963-64_ 25 27 The first oatent 25 patent that extended the seoaration capability was filed by the same company
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16
described upgrading reformer recycle gases from various types of processes, (Stark, filed m 1963 and awarded 10 1966 ). The application was also the
upgrading of reformer recycle gas, m the range of 80% hydrogen, to attain an
m the range of 50 to 80% hydrogen, with an ultimate purity of greater than
95% hydrogen, using activated carbon as· the adsorbent. The second de~ ultimate purity of 99.9% hydrogen at a recovery· of 75%. usmg silica gel as
scribed specific ooeratmg conditions, but did not specify the resulting perfor- the adSorbent. The ooerating conditions included a pressure range of from
500 psig for adsorption and 0 os1g for desorotton anct ourgmg.
mance. The third revealed more process details, and mentioned a potential
recovery of 70%, but did not state the corresponding punty.
C.2.11 Basmadjian and Pogorski
C.2.8 Hoke, Marsh, et al. An early PSA cycle that was apparently the first to use a rmse step (see
Section 4.4.5) was invented by Basmadjian and Pogorski. Their applicatmn
Within a year of filing of Skarstrom·s PSA oatents related to hydrogen was filed in 1963 and the oaten! issued m 1966. 411 This cycle was mtended to
I recover helium and possibly other light comoonents from nitrogen or natural
purification, his colleagues, Hoke, Marsh, Bernstem, Pramuk, and he filed