High temperature combustion method, sulfur determination

Ultimate analysis of coal and coke, determination of total sulfur content, Eschka method Ultimate analysis of coal and coke, determination of total sulfur content, high temperature combustion method... 

The three most widely used test methods for sulfur determination are (1) the Eschka method, (2) the bomb washing method, and (3) the high-temperature combustion method, and all are based on the combustion of the sulfur-containing material to produce sulfate, which can be measured either gravimetrically or vol-umetrically. The Eschka method has distinct advantages in that the equipment... 

ISO 351. Determination of Total Sulfur High Temperature Combustion Method. 

Various standard procedures are available for the determination of the sulfur content of distillate fuels. In the lamp method (ASTM D-126, IP 107), which is widely used, the product is burned completely in a small wick-fed lamp, the gases formed by combustion are absorbed in hydrogen peroxide solution, and the sulfur is subsequently determined as sulfate. Several rapid methods, including X-ray absorption and high-temperature combustion, for the determination of sulfur are also available. 

A high-temperature combustion method for the determination of sulfur in solid fuels has also been adopted in many laboratories and is advantageous insofar as chlorine can be determined simultaneously. The method requires that the coal sample be heated to 1250°C-1350°C (2280 F-2460°F) in the presence of excess kaolin, ferric phosphate, or aluminum oxide to enhance the ranoval of the sulfur (as sulfate) from the ash. Oxygen is also included to produce oxides of sulfur which are absorbed in hydrogen peroxide (whereby sulfur dioxide is converted to sulfur trioxide). The solution is then titrated with standard alkali solution which gives the total acidity (due to the hydrochloric and sulfuric acids that are formed). 

Catalyst Characterization. Carbon contents were determined by the Carlo Erba method and sulfur content by high temperature combustion In O2 (ASTM-D1552-64). Surface area and pore volume distribution were measured via N2 adsorption desorption Isotherms (4). ESR measurements were carried out with a modified Varian Radical Assay Spectrometer at both 77 K and room temperature (3). 

Several methods of sulfur determination are used for carbon black. They include oxygen bomb calorimetry, high-temperature combustion with an iodometric detection procedure and an infrared detection procedure. The results are given as percentage of sulfur. 

For the determination of sulfur contents of residual fuels a variety of procedures are available. The bomb (ASTM D-129, IP 61) and quartz tube (ASTM D-155, IP 63) combustion methods have long been established. Other, more rapid techniques are becoming increasingly available, including high-temperature combustion (ASTM D-1552), X-ray absorption and fluorescence methods, and the Schoniger oxygen flask procedure. 

Spectrochemical methods such as IR detection of SO2 formed after high-temperature combustion require large amounts of sample material and also standards for accurate sulfur determination. A detection limit of 0.2 pg per g has been reported for sulfur in high-purity iron by this technique. 

Infrared absorption is one of three standard test methods for sulfur in the analysis sample of coal and coke using high-temperature tube furnace combustion methods (ASTM D-4239). Determination of sulfur is, by definition, part of the ultimate analysis of coal (Chapter 4), but sulfur analysis by the infrared method is also used to serve a number of interests evaluation of coal preparation, evaluation of potential sulfur emissions from coal combustion or conversion processes, and evaluation of the coal quality in relation to contract specifications, as well as other scientific purposes. Infrared analysis provides a reliable, rapid method for determining the concentration of sulfur in coal and is especially applicable when results must be obtained rapidly for the successful completion of industrial, beneficiation, trade, or other evaluations. 

Other procedures include high-temperature tube furnace combustion methods for rapid determination of sulfur in coal and coke, using automated equipment. The instrumental analysis provides a reliable and rapid method for determining sulfur contents of coal or coke. By this method, total sulfur as sulfur dioxide is determined on a continuous basis. 

The total sulfur content may be determined by one of several methods that convert it to sulfate by wet chemical analysis. One of these, the Eschka method, involves combustion of coal at 800°C in the presence of alkaline/oxidant medium (e.g., two parts of calcined MgO and one part anhydrous sodium carbonate) all sulfur is converted to sulfate that by the addition of barium chloride precipitates as barium sulfate, which is calcined to BaO and measured gravimetrically (see ASTM D3177). This is a standard method in many countries. Another is the high-temperature method where the coal is burned in oxygen at 1350°C, converting all sulfur present into SO2. The SO2 is then converted to sulfuric acid for titrimetric determination. 

---