Mmicroscopic Measurement of Vitrinite (Coal)Reflectance

1. Principle

The intensity of the reflected light (λ = 546nm) perpendicular to the incident light on the polished surface of the vitrinite is measured by the photoelectric converter under the oil immersion objective of the microscope.Compared with the reflected light intensity of standard materials with known reflectivity under the same conditions.

Due to the slight difference of optical properties among vitrinite particles in single coal seam, the difference is greater in mixed coal, so it is necessary to obtain enough measurement values from different particles to ensure the representativeness of the results.

2. Main Technical Conditions of Microscope and Photometer:

The light source should be a light source with sufficient brightness and stable output, preferably a halogen quartz lamp with a power of 50W or 100W.

The polarizer can be sheet polarizer or prism polarizer.

Objective lens: it is suitable for polarizing and oil immersion lens with refractive index of 1.518. It has low diffuse reflectance and magnification of 20 ~ 60.

Ocular lens consists of two observation eyepieces, one of which should be equipped with a cross wire. The magnification of the observation eyepiece should be consistent with that of the test eyepiece, and the total magnification of eyepiece, objective lens and connecting tube should be between 250 and 750.

Resolution: the reading of instrument display should be able to distinguish 0.01% reflectivity.

3. Detection Error

During the detection process, the variation range of the measured value of any reference material within 30 minutes should not be greater than 2% of the standard value of the reference material.

It should be linear when the reflectivity is between 0.59% and 7.45%.To determine the reflectivity of a series of reflectivity reference materials, the difference between the measured value and the standard value of any reference material should not exceed ±0.02%.

4. Implementation Standard

Method of detrmining microscoplly the reflectance of vitrinite in coal

MT/T1053-2008 Technical conditio of microscope photometer for vitrinite reflectance determination

a. Vitrosomes, transverse section, large tracheids of subsquare or subequidiameter polygons. b. Vitrinite of koda wood structure, diameter section. Shows cross fields and tight squeeze holes. c. Homogeneous vitrinite; d. vitrinite, secondary xylem, striatum.