Lighting up metal pollutants in water

Fitter to promote clean coal power

In the near future the scientists hope to carry out the

A thin metal filter material

sintering process on a com-

developed at the US Depart-

mercial scale, and to test the

ment of Energy’s (DOE’s)

filter in a DOE demonstration

Ames Laboratory

power plant run by the

may hold the

key to allowing power plants

University

to burn high sulphur coal

Lighting up metal pollutants in water

cleanly. The technology

of North Dakota.

to burn this

type of coal has existed for

A team of US BrighamYoung

some time, and demonstration

University

plants have shown that

synthesized molecules

pressurzed-fluidized

glow in the presence

com-

bustion and integrated cation combined

gasifi-

scientists

has that of

specific metal pollutants. High levels of metals in the

cycles provide

high efficiency, low emission

environment

power generation.

activities

However,

often result from

such as mining, fossil

the resulting flue gases contain

fuel combustion

fly ash, which is high in

industrial

sulphides, chlorides and

sure to high levels of metals

sodium compounds. This not

and other

applications.

such as mercury,

Expo-

cadmium and

screening then spread out as a

zinc can pose serious health

thin layer (0.5 mm) and heated

risks. Methods of tracking

only poses a threat to air

made from superalloys

quality, but can also damage the

the aerospace

turbines that drive plants’

chose a nickel-chromium-

in a vacuum furnace

generators.

aluminium-iron

sintering process bonds the

but they tend to be labour

particles

intensive

To prevent the

used in

industry. They alloy because

together,

metal in water currently

forming

particles from reaching the

it maintained

turbines and the atmosphere,

high temperatures

the hot gas is normally passed

and was resistant to thermal

between the spheres, but at the

synthetic compounds

through banks of cylindrical

shock.

same time leaving air spaces.

out and bind metal ions.

ceramic candle filters. The

its strength at

. The

(850 “C)

The thin, permeable

sheets

Tests have shown that the material undergoes

maintained by regular cleaning,

cess called tap-densified

moderate

using an internal blast of

powder sintering.

compressed

is

loose

slow.

The latest technology

strong and smooth joints

of metal are formed by a pro-

filters’ operating efficiency

and relatively

exist,

only a

drop in yield

uses

that seek

Smaller synthetic molecules then bind to the metal-binding compounds

and act as fluo-

strength when going from

rescent ‘reporters’,

molten superalloy is converted

room temperature

glow brightly under UV light.

ceramic materials are

into a fine powder using a

operating

susceptible

high-pressure

series of bend radius tests the

compounds

air. Unfortunately, to thermal shock,

High purity

atomization

to high

temperatures.

In a

i.e. they

If no metal ion is bound, the remain dark.

so the abrupt change in tempe-

system. As the hot metal passes

material was also sufficiently

According

to reseachers,

rature caused by the com-

through a nozzle, a high-

ductile to be formed into cor-

technology

is paving the way

pressed air can often crack the

pressure jet of nitrogen gas

rugated tubes; an important

for the development

ceramic material.

breaks the liquid into millions

feature for strength,

early warning system for metal

of tiny metal spheres. The

for increasing the filter surface

contamination

resulting powder is sorted by

area.

water and waste streams.

Researchers

began looking

at developing metal filters

Filtration+Separation

as well as

the

of an

of drinking

October2OOl23