The furnace, not the detector, decides which combustion analyser a works laboratory needs. How induction, resistance and impulse furnaces divide the job, and where the running cost actually sits.
A re-rolling mill, a cement plant and a foundry all say they need a carbon analyser. They need three different machines, and the reason has almost nothing to do with the detector. Every one of these instruments burns the sample and measures the gases that come off, and infrared absorption and thermal conductivity detection are common to all of them. What differs is the furnace, because the furnace decides what can be burned, how hot, in what container and with what interference.
Get the furnace right and the analyser will serve for a decade. Get it wrong and the laboratory spends that decade fighting blanks, contaminated cells and results that will not reconcile with the customer's.
There are three furnace types in routine use and they split the work cleanly.
Induction, for inorganic material. The ELEMENTRAC CS-i: Carbon / Sulphur Analyser burns steel, cast iron, ores and ceramics above 2,000 degrees Celsius in oxygen, and measures the resulting carbon dioxide and sulphur dioxide by solid state infrared absorption. The detail that matters on site is the handling of dust: these materials throw a lot of it, and the CS-i carries a heated dust trap and a platinum based catalyst reactor for exactly that reason. A steel or foundry laboratory in Bangladesh, running many samples a shift on the same alloy family, wants this machine.
Horizontal resistance, for organic material. The ELEMENTRAC CS-r: Carbon / Sulphur Analyser uses ceramic boats, which allow a high sample weight, and runs at a furnace temperature adjustable to 1550 degrees Celsius in one degree steps. Its infrared path is made of solid gold, which resists the halogen and acid combustion products that corrode aluminium cells. If the laboratory is analysing coal, coke, biomass, soil or anything containing chlorine, the gold path is not a refinement; it is what stops the cells being consumed.
Both, in one cabinet. The ELEMENTRAC CS-d: Carbon / Sulphur Analyser carries an induction furnace and a resistance furnace together, so organic and inorganic samples run on the same instrument without a configuration change, with up to four independent infrared cells covering different concentration ranges. For a contract laboratory or a group with mixed sample types, that avoids owning two machines and calibrating both.
Two further configurations exist for organic work in a vertical furnace. The CS-580A: Carbon / Sulphur Analyser covers simultaneous carbon and sulphur and also total organic and total inorganic carbon, and it requires an autoloader with 36 or 130 crucible positions for unattended running. Where hydrogen has to be reported as well, the ELEMENTRAC CHS-r: Carbon / Hydrogen / Sulphur Analyser measures all three simultaneously to DIN, EN and ISO methods in a horizontal resistance furnace, and the CHS-580A: Carbon / Hydrogen / Sulphur Analyser is the vertical equivalent. The high sample weight the ceramic boats allow matters more than it sounds for coal, coke and biomass, where a small aliquot of a heterogeneous material is simply not representative of the consignment.
Cement and gypsum are a separate case, because the question is not really carbon at all. The CW-800: Carbon Dioxide / Water Analyser determines carbon dioxide and water simultaneously in a quartz tube resistance furnace held at a fixed temperature up to 1000 degrees Celsius under nitrogen, measuring through a gold path so no halogen trap is needed. Where organic and inorganic carbon have to be separated, the CW-800M: Carbon / Water Analyser steps the furnace through up to five programmed temperatures in one run and separates them by release temperature rather than by acid treatment, which removes a wet chemistry step and the errors that go with it. Its maximum sample size is 32 by 145 mm in a quartz boat. And where the carbon of interest is a surface residue rather than bulk carbon, the SurfaceC-800: Surface Carbon Analyser varies both furnace temperature and carrier gas to a user defined programme so the surface fraction is driven off and measured separately from the matrix.
Carbon and sulphur are measured by burning the sample in oxygen. Oxygen, nitrogen and hydrogen cannot be, for the obvious reason. They are measured by hot extraction: the sample is fused in a graphite crucible under an inert carrier, and the gases released are carried to the detectors. That means a different furnace, a different gas system and a different consumable.
| Analyser | Elements | Note |
|---|---|---|
| ELEMENTRAC ONH-ps | Oxygen, nitrogen and hydrogen | Electrode impulse furnace exceeding 3,000 degrees Celsius in a graphite crucible; oxygen and hydrogen by infrared, nitrogen by thermal conductivity. The closed gas system keeps consumption low and argon can replace helium as carrier |
| ELEMENTRAC ONH-p | Oxygen, nitrogen and hydrogen | Impulse furnace on the hot extraction principle for steel, non-ferrous metals and ceramics |
| ELEMENTRAC ON-p | Oxygen and nitrogen | Oxygen measured as carbon dioxide by infrared, nitrogen by thermal conductivity. For laboratories where hydrogen is not in the specification |
| ELEMENTRAC OH-p | Oxygen and hydrogen | Removing the nitrogen channel simplifies gas handling and shortens the analysis |
| ELEMENTRAC H-r | Hydrogen only | Hot extraction below the melting point, so diffusible hydrogen is released without fusing the matrix |
The carrier gas point on the ELEMENTRAC ONH-ps: Oxygen / Nitrogen / Hydrogen Analyser deserves attention in Bangladesh specifically. Helium supply is expensive and intermittent here, and an analyser that can run on argon instead removes a dependency that has left instruments idle in other laboratories. Ask the question at the quotation stage rather than after the first cylinder runs out.
The ELEMENTRAC H-r: Hydrogen Analyser is worth singling out for steel and iron producers. Hydrogen content governs susceptibility to cracking, and because it is measured below the melting point it is a genuinely different determination from the total hydrogen an impulse furnace reports. A mill investigating cracking needs the diffusible number.
Two instruments in the range sit outside the metals world. The ELEMENTRAC CN-r: Carbon / Nitrogen / Protein Analyser is a Dumas combustion analyser that calculates protein from the nitrogen result, and it is the alternative to Kjeldahl digestion for food, feed, soil and fertiliser laboratories, avoiding the concentrated acid and catalyst the wet method requires. For a Bangladeshi feed mill or soil testing laboratory, removing sulphuric acid from a routine method is a safety improvement as much as an analytical one. And the TGA THERMOSTEP: Thermogravimetric Analyser determines moisture, volatile matter, ash and loss on ignition in one programmed run by weighing continuously as the furnace steps through temperature stages, carrying up to 19 samples on a carousel. For coal, coke, biomass and mineral laboratories running proximate analysis, that single instrument replaces a morning of oven and muffle work.
Combustion analysis consumes something on every single run. Crucibles, ceramic and quartz boats, reagents, catalysts and furnace parts are all listed as Consumables for Elemental Analysers, and the reason they belong in the analytical method rather than in general stores is that the grade of crucible and reagent sets the blank value. A cheaper crucible with a higher carbon background raises the blank, and at low carbon levels the blank is a large fraction of the result.
Three practical consequences follow.
Sample preparation sits upstream of all of this and is the other place results are lost. A combustion analyser sees a small aliquot, so it can only be as representative as the grinding and dividing that produced it. For spectral and combustion work the sample generally needs to be at a fineness a vibratory disc mill will reach in seconds, and it needs to be split properly rather than scooped from the top of a bag.
Finally, the software layer. ELEMENTS: Elemental Analyser Software handles method setup, calibration, result filtering and report generation for the ELEMENTRAC generation, and it is the operating layer of the instrument rather than an optional extra. ELEMENTS Cloud: Remote Instrument Management allows an analyser to be monitored and managed remotely, which is aimed at organisations running several analysers across sites. For a group with plants in Dhaka, Chattogram and Gazipur, remote visibility of instrument status is a practical way to keep three laboratories reporting the same way, and it shortens the diagnostic conversation when one of them stops.