EUREKA DECEMBER 2002

Shocks blast way to new technologies

(Original full two page version of story edited down to single page in Eureka )

Cleaning old pipes or crunching concrete is a doddle in an environmentally friendly new process. Tim Neshitov reports

Controlled electric explosions – made by passing short pulses of very high current through water – produce massive shock waves capable of shattering unwanted material or killing bacteria.

The idea has been around for decades, but nobody until now has done much with it commercially, apart from the high voltage sparkers used as sound sources in undersea geophysical surveying.

The idea has been proven in mining applications in parts of the former Soviet Union, but new commercial applications are now being developed. These include the effective cleaning of sewage and heating pipes, rendering water drinkable, and breaking up unwanted concrete blocks.

Explosive techniques based on the electrohydraulic effect were discovered about half a century ago and have always been considered vaguely profitable. However, the lack of suitable materials and relative expense of electronic equipment previously blocked the way for any substantial experiments and research in this area. The Dutch company, GEO Resources currently uses a related method in its high-resolution multi-tip sparkers, which produce sound waves capable of penetrating layers of sediment on the bed of the sea. (more information at www.geo-resources.com) The technique is also said to be being used by the Canadian copper mining giant, Noranda.

Dr Anatoly Mnukhin, of the Ukrainian Academy for Engineering Sciences, explains that in his view, the method has great potential in agriculture, radioactive emergencies and even ‘social troubleshooting’.

During one of the in-water explosions, the electric field energy is swiftly converted into mechanical energy. In a 5,000 V circuit, instantaneous current goes up to 20,000-30,000 A. This heats the electric plasma charge immensely (up to 20 000o C), which, in turn, brings about a powerful, precisely localised explosion wave with pressures of up to 30,000 atmospheres.

Dr Mnukhin is the holder of 29 patents and authorising permits, and chairs the executive board of Electrohydraulics, an R&D company based at Makeevka in Donetsk, part of the Ukraine. The company has come up with a number of explosion machines each aimed at carrying out a specific kind of demolition or cleaning job. "We’ve worked out the production parameters and outlined the general modus operandi for a company wishing commercialise the electrohydraulic explosion technique", he says. "We calculate that with an annual investment of $ 200,000 to 250,000 an average company using electrohydraulics could achieve profits of 96 to146 %."

Characteristics of four types of system configuration are shown in the table:

Type of rig

Impulse 1

Impulse 3

Impulse 4

Impulse 5

Circuit voltage, (V)

380/660

380

380/660

380

Max. supply voltage, (kV)

5,0

5,0-6,3

4,8

5,0

Max. current (kA)

30

30

30

30

Capacitors, (F)

0,016

0,000002 – 0.006

0,016

0,0006

Source power, (kW)

400

40

400

1,5

Charging time (s)

15

0,1-10

15

10

Energy stored (kJ)

200

0,044-75

200

7,5

Length of cable (m)

500

200

1000

40

Diameter of cable, min (mm)

42

15

42

-

Staff required to operate

5

2-3

4

0

Approx. cost, US $

55,0

20,0

65,0

2,0

The technique has been tested and has been proved to be of great help in the mining sector. Specifically, several leading coal mines in the Ukraine have used in a major explosion-based pipe cleaning programme. In additions, a number of cement producing and metallurgic facilities have cleared their sewage, drainage and heating systems quite efficiently. What makes the electrohydraulic method even more attractive to industry giants is the fact that the production/processing process need not be brought to a halt or even interfered with during an explosion.


Electrohydraulic rig "Impulse-1"

Apart from the areas of application already mentioned, Electrohydraulics has been used to carry out a large-scale cleaning of underground mining equipment and railway cisterns, notorious for their hard-to-reach kinds of dirty surfaces.

 


Destruction of concrete bases in the Enakiyevski metallurgical factory

The Impulse-4 rig has managed to effectively annihilate some very strong (100 year old) concrete bases and supporting constructions in the Enakiyevski metallurgical factory without having to stop any of the running production lines. The electric explosion method has even been used to blow up iron-coated columns, which are pretty hard to tackle by means of traditional explosive techniques.


Shattering of concrete columns. The "Impulse-4" rig is in the bavkground

The explosive potential of an Impulse rig can be doubled by dint of optional liquids added into the machine and is said to go as far as to allow the equipment to extract diamonds from left-over rock species.

Surprisingly, one of the rigs, Impulse-5, has shown an outstanding ability to kill microbes in drinking water. After 5 explosions in 0,8 m3 of river water, which took 1 minute and used up 350-550 kJ of energy, the overall number of microbes was seen to fall to 186 against the initial 1,840 which almost meets the CIS drinking water standard. As soon as the test results were out, the company nailed a contract with Oktabrugol, a major coal mine, setting up a bathing facility for the miners.

Other Impulse applications that have proved successful but still need further research and on-the-spot adjustment include sewage cleaning, vessel rust cleaning (80-90 % efficiency), and nitrogen production. The last one is possible due to the fact that ordinary water, when electrohydraulised and simultaneously saturated with adequate amount of air, tends to become rich in nitrogen-containing compounds.


A sample of mine water drainage pipe (a) before cleaning (b) after cleaning

What makes Electrohydraulics managers most comfortable is the literal absence of any serious competition whatsoever. The Ukrainians have hit their pay dirt and they know it. Although the area of electrohydraulics is being incessantly investigated as one of the most promising, Russian researchers haven’t gone further than theoretical speculations, whereas their Canadian colleagues seem to stick with strictly metallurgical applications of this outstanding method. "And then, their electrodes aren’t quite reliable as ours, leave alone their far less durable hydrovalves", claims Dr Mnukhin.

What gives the Ukrainian entrepreneurs a competitive edge in the new field is the availability of low cost material and workforce resources alongside a huge research data base ready for R&D deployment in case of emergencies. Setting up a three part electrohydraulic production facility with all the necessary infrastructure costs $ 208,000, with each rig’s price ranging from $ 45,000 to $69,000 depending on it’s target functions. (more information: mnukhin@ua.fm or maknii@tr.dn.ua )

Note: Author Tim Neshitov is currently completing a degree course on international journalism at the State University of St Petersburg in Russia. The article was written in the course of international work experience at Findlay Publications

Design Pointers

Electric explosion allows for efficient demolition of ageing concrete and iron coated blocks on factory premises without paralysing the production lines

Electric explosions need not necessarily be used to blow things up. Ukrainian scientists have successfully directed the electrohydraulic impulse to cleaning out coal mine tunnels, sea vessels and underground metallurgic equipment, as well as killing off microbes in drinking water

For more technical developments see www.eurekamagazine.co.uk

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