DRAX Ultra-hot burners : a brief history

Background
DRAX ultra-hot burner technology began in London, England in 1995.  It is well-known that an ordinary propane gas flame cannot heat a work-piece above about 1000 C.  Operations involving metal working or brazing, requiring well over 1000 C are impossible without using special gases such as acetylene and oxygen. However, DRAX burner changes all this!  The initial concept was to simply preheat the air supply to a conventional propane burner in order to boost the flame temperature.  With a higher flame temperature,  heat would be transferred from work-piece much more efficiently, allowing metal working above 1000 C and also speeding up processes which did not need such a high temperature.

First Propane Burners to Melt Steel
Initially an auxiliary gas flame was used to preheat the air supply.  After some difficulties with heat transfer and flow channelling, DRAX developed efficient helical tube designs which could preheat air to 500-700 C.  These flames were hot enough to melt steel samples a few millimetres in diameter.  Instrumented test pieces 10mm in diameter were raised in temperature to 1400 or 1500 C.  In order to increase the temperature further other techniques were investigated, such as preheating of the fuel gas.  This gave rise to additional problems which required solution: with such a hot flame, the wrong design could lead to the burner overheating or even melting itself.   Once these design rules were established, DRAX made the first working demonstration of a hand-held portable burner - using only propane gas and a standard compressed air supply.

Collaborative work with Southampton University 
It was becoming clear that the 'flame intensity', the heat generated per unit volume in the flame, was an key parameter, necessitating more concentrated flames, using higher flow rates and a high degree of turbulence.  The Department of Aeronautics at Southampton University, England, were engaged By DRAX TORCHES to assist in the optimisation process at this point.  Dr. Graham Ball and Gavin Connibear were responsible for this work.  The new torches were made from better, although still inexpensive, materials, to maximise the lifetime of the burner.  Preheat of the propane gas was boosted further, allowing both a higher flame temperature and a greater intensity of combustion.  With this higher fuel preheat, sooting was encountered, and solutions involving inexpensive catalysts such as zeolites and involving air bleed were investigated, the latter being the solution adopted for later burners.  The burners could now melt or burn through substantial sheets of steel, the flames having much the same capability as an oxy / propane or air /acetylene flame.  Work-piece temperatures of 1800 C could be achieved, and pure platinum samples could be melted at 1770 C. Another working hand-held portable burner was constructed, demonstrating all the essential features of DRAX technology.

DRAX - Press Announcements
The invention was announced to the world, an article about the DRAX burner (Cutting edge A humble lab tool could burn holes in gas firms' profits) appeared in the New Scientist magazine, and short features on the burner was broadcast by the BBC.  The BBC reporter was impressed and surprised at the spectacular showers of 'sparks' produced when the burner melts iron, and was given a piece of melted steel as a souvenir.  As a result of this publicity, we received enquiries about DRAX worldwide.  Enquiries have come from wide geographical locations: Australia, India, South Africa and Nigeria, as well as Europe and the USA.  Many enquirers have been distributors seeking to supply mass-produced versions of the burners.

Recent work on Electric preheat burners
Recent development has focused on electric preheat (rather than gas), which promises a simple and inexpensive approach for smaller DRAX burners.  After significant development effort to prevent premature failure of the heaters, we now have a superb demonstration electric preheat torch. Made entirely of transparent fused quartz, the burner allows the glowing elements of the electric heaters to be seen during operation of the burner. The influence of the quality of the electric elements and the effect of gas flow and electric power can be clearly seen.