Azduwin, you've only gotten part of the information here. Perhaps this will help:

Ultimate Analysis - also known as elemental analysis - is to determine the weight percent of carbon present as an element - just "C." (Also H, N, sometimes S, and O usually by difference). It combusts the sample and uses (usually) spectroscopy to determine the elements present.

Proximate Analysis - this is determination of volatile matter, fixed carbon, and inorganic/"ash" content. To perform Proximate analysis, we use TGA, and the sample is heated to 110°C in N2 and held until dry baseline. Then it is heated to (for ASTM standards) 900°C and held until no mass loss, again in N2. The mass loss over this is the "volatile matter." This includes carbon, and also H, N, O - it is the component that devolatilizes (pyrolyses). Then the sample is heated to 950°C in air (or O2), the portion of mass lost during this time is attributed to "fixed carbon" - carbon that will not volatilize (e.g. carbon that is entrained in mineral matter) but will oxidize. So, both VM and FC contain elemental carbon, but the element is distributed across these phases. (The stuff remaining after oxidation at 950°C is non-oxidizable mineral matter, loosely termed "ash"). There are modified versions of this, such as heating only to 600°C in N2/625°C in air as some mineral matter will change forms above this (for example, water of crystallization of SiO2 is lost above 625°C, and this would give you a false mass loss).

These two difference techniques tell us about the total elemental carbon and how it is distributed among samples. That's why you usually see them presented together.

I think you will get significant difference in between both the values. The Fixed carbon determined by the TGA is purely on the basis of change in weight with respect to temperature and in correspondence with the amount of volatile matter, ash and moisture content. This method is dependent on the pyrolysis of the sample in an inert medium. However, the elemental analysis is carried out by combustion method in which the sample is burned in the presence of pure oxygen to form oxides like CO, CO2 and SO2 and then elemental composition is determined. So the carbon content by elemental analysis is totally dependent upon the gases formed during combustion and the content of other gases. I think this will clarify your doubt.

Regards

Sumit

Sumit is right,

fixed carbon is more a practical value measured by thermogravimetry and definition of evaluation of the curve, whereas carbon content measured by elememtal analysis represents in combination with O and H the "formula"

Azduwin, you've only gotten part of the information here. Perhaps this will help:

Ultimate Analysis - also known as elemental analysis - is to determine the weight percent of carbon present as an element - just "C." (Also H, N, sometimes S, and O usually by difference). It combusts the sample and uses (usually) spectroscopy to determine the elements present.

Proximate Analysis - this is determination of volatile matter, fixed carbon, and inorganic/"ash" content. To perform Proximate analysis, we use TGA, and the sample is heated to 110°C in N2 and held until dry baseline. Then it is heated to (for ASTM standards) 900°C and held until no mass loss, again in N2. The mass loss over this is the "volatile matter." This includes carbon, and also H, N, O - it is the component that devolatilizes (pyrolyses). Then the sample is heated to 950°C in air (or O2), the portion of mass lost during this time is attributed to "fixed carbon" - carbon that will not volatilize (e.g. carbon that is entrained in mineral matter) but will oxidize. So, both VM and FC contain elemental carbon, but the element is distributed across these phases. (The stuff remaining after oxidation at 950°C is non-oxidizable mineral matter, loosely termed "ash"). There are modified versions of this, such as heating only to 600°C in N2/625°C in air as some mineral matter will change forms above this (for example, water of crystallization of SiO2 is lost above 625°C, and this would give you a false mass loss).

These two difference techniques tell us about the total elemental carbon and how it is distributed among samples. That's why you usually see them presented together.

one more remark: due to my experience the measure of fixed carbon is alo related to the kind of preprocessing of raw material e.g. sugar beet pulp; as a method based on heat rate the measurement can be is kinetically dominated, e.g. the development of graphite or PAK as a function of preprocessing; in contrary results of elemental analysis are not based on kinetics

TQ so much for all answers..crystal clear now...=)

I agree with sumit and Rodion kopitzky , meanwhile i have few more added questions here. First of all my question is regarding hydrochar and biochar , firstly, when we measure fixed carbon and then elemental carbon which one would be on higher composition ? Secondly if we measure CNH and S and then O from ultimate analysis , their compositions could depend on what factor. specially for carbon. If their collective composition is 40% then what are rest of things . ash?

Thanks