Conradson carbon coke, determination

Conradson Carbon Number ASTM D-189 Determination of the weight of nonvolatile residue formed after evaporation and atmospheric pyrolysis of fuel or oil. This test method provides some information about the relative coke-forming or deposit-forming tendency of a fuel or oil. Products having a high ash value will have an erroneously high carbon residue value. 

Data reporting (i.e., the statement of the results of the proximate analysis test methods) usually includes (in some countries but not in all countries) descriptions of the color of the ash and of the coke button. As an interesting comparison, the test for determining the carbon residue (Conradson), the coke-forming propensity of petroleum fractions and petroleum products (ASTM D-189 ASTM D-2416), advocates the use of more than one crucible. A porcelain crucible is used to contain the sample, and this is contained within two outer iron crucibles. This corresponds to the thermal decomposition of the sample in a limited supply of air (oxygen) and the measurement of the carbonaceous residue left at the termination of the test. 

Figure 7 summarizes the main relations, which determine the effect of coke on deactivation. Note that a poor coke selectivity (or low cat-to-oil ratio) will aggravate the poisoning effect of the fraction of the Conradson Carbon Residue which is converted to coke. 

If biomass is subjected to the ASTM D 3172 procedure for determination of fixed carbon, chemical transformation of a portion of the organic carbon in biomass into carbonaceous material occurs as described here. All of the fixed carbon determined by the ASTM procedure is therefore generated by the analytical method. Furthermore, the amount of fixed carbon generated depends on the heating rate used to reach biomass pyrolysis temperatures and the time the sample is subjected to these temperatures. Nevertheless, such analyses are valuable for the development of thermal conversion processes for biomass feedstocks. But application of the ASTM procedures to biomass might more properly be called a method for determination of pyrolytic carbon or coking yields. In the petroleum industry, the Conradson carbon (ASTM D 189, differ-... 

Other test methods that are used for determining the coking value of tar and pitch (ASTM D-2416, ASTM D-4715), which indicates the relative coke-forming properties of tars and pitches, might also be applied to asphalt. Both test methods are applicable to tar and pitch with an ash content <0.5% (ASTM D-2415). The former test method (ASTM D-2416) gives results close to those obtained by the Conradson carbon residue test (ASTM D-189, IP 13). However, in the latter test method (ASTM D-4715), a sample is heated for a specified time at 550 10°C (1022 18°F) in an electric furnace. The percentage of residue is reported as the coking value. 

Carbon Residue—amount left after evaporation and pyrolysis to provide some indication of relative coke-forming propensity (ASTM Test Method D189, Conradson Carbon Residue of Petroleum Products, ASTM Test Method D524, Ramsbottom Carbon Residue of Petroleum Products, or ASTM Test Method D4530, Determination of Carbon Residue (Micro Method)), ASTM Method D4530 having gained wide acceptance. 

The Conradson carbon residue (CCR) results from ASTM test D189. It measures the coke-forming tendencies of oil. It is determined by destructive distillation of a sample to elemental carbon (coke residue), in the absence of air, expressed as the weight percentage of the original sample. A related measure of the carbon residue is called Ramsbottom carbon residue. A crude oil with a high CCR has a low value as a refinery feedstock. 

There are two older well-used methods for determining the carbon residue the Conradson method (ASTM D-189) and the Ramsbottom method (ASTM D-524). Both are equally applicable to the high-boiling fractions of crude oils that decompose to volatile material and coke when distilled at a pressure of 1 atm. Heavy oils and residua which contain metallic constituents (and distillation... 

Another approach was made for estimating the yield of coke, which is one of the key factors which determine the heat balance of the process. The coke yield is considered to be in close correlation with Conradson residual carbon content of the crude oil. This is experimentally confirmed as is shown in Figure 5, which gives the following equation. 

---