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P a t e n t s

Saving the planet: fixing carbon dioxide The problem of r i s ing a tmospher ic ca rbon dioxide content a n d i ts p robab le effect on average t empe ra tu r e s appea r s to be exercis ing the J a p a n e s e company Mitsubish i Heavy Indust r ies . It h a s a long t rack record in offering convent ional gas - t r ea tmen t p roceses in the chemical a n d power genera t ion indus t r ies , bu t a p p e a r s to be tu rn ing its a t t en t ion to pho tosyn thes i s as a gas t r ea tmen t process .

In i s sue 1993 /5 we repor ted on a b ioreactor employing paraUel opt ical fibres and hollow fibres: the former conduc t ing light a n d the Latter car ry ing a su spens ion of algae into which a tmospher ic ca rbon dioxide could diffuse. The p resen t invent ion employs wha t appea r s to be an algal m e m b r a n e on the exterior of a hollow tube or fibre. Nutr ien ts are c i rcu la ted over the m e m b r a n e by an air-l if t p u m p and sunl igh t sh ines on the whole a p p a r a t u s (Figure 4).

Patent number: JP 4370087 Date: 22 December 1992 Inventor: H. FuJita Applicant: Mitsubishi Heavy Indus t r ies Ltd

Helium recovery Natura l gas a n d c rude off are far from simple to process . They m a y conta in e lements such as s u l phu r a n d v a n a d i u m which m u s t be removed, and whose presence might not be expected in wha t is p re -eminent ly a mixture of hydrocarbons . Another advent i t ious e lement is hel ium, p resen t in na t u r a l gas in some a reas of the USA. Unlike the two previous elements , he l ium more t han repays the cost of i ts recovery, and m e m b r a n e separa t ion is an appropr ia te technology to use, given he l ium's permeabi l i ty th rough most membranes .

In Kobe Steel 's recovery process , impure gases conta in ing hel ium are pa s sed over an adso rben t bed: h igh-pur i ty hel ium is desorbed and con tac t s

hollow~re _ _ ~;:> sunlight 1 I I 1 ~me~gralane

culture liquid Figure 4: Fixing carbon dioxide

a m e m b r a n e to purify it further, u s ing the energy in the p ressu r i zed feed gas to provide power for the operat ion. The recovery p rocess incu r s no energy costs, unl ike a convent ional cryogenic recovery process .

Patent number: JP 4367506 Date: 18 December 1992 Inventor: K. Otsu Applicant: Kobe Steel Ltd

Hollow fibres manufacture Spinn ing fibres, solid or hollow, is a widespread technology and is a major source of symmetr ic and asymmet r i c membranes . Processes for mak ing highly a symmet r i c membranes , in which the pores a t one side differ greatly in size from those a t the other with good effect on their s epa ra t ion propel-ties, are much sought after. Union Carbide h a s several p a t e n t s in th is a rea of technology.

The signif icant p rocess improvement c la imed in th is invent ion is the sp inn ing of mol ten polymeric mater ia l , to form a fibre precursor , th rough a coaxial sp inne re t into a par t ia l vacuum. The sp inne re t is pos i t ioned up to 2 met res above the coagula t ion ba th , bu t typical ly 0 .5-30 cm above it. The r educed p r e s s u r e in the vacuum chamber is 10-35 cm Hg, or 0.15-0.45 atm. The coagulat ion b a t h t empera tu re is lower t han tha t of the fibre precursor .

The p rocess can be applied, with appropr ia t e select ion of the coagula t ion bath , to m a n y membrane - fo rming mater ia ls , and can also be used to m a n u f a c t u r e s u b s t r a t e fibres onto which a n active layer is coated.

Patent number: US 5181940 Date: 26 J a n u a r y 1993 Inventors: B.K. Bikson, J.T. Macheras , J.K. Nelson Applicant: Union Carbide Indus t r i a l Gases Technology Corp.

M e m b r a n e Techno logy No. 42 11