Magnetic Material Element Composition Analyzer

Petroleum coke is a solid residue in the refining process and an important raw material for producing various carbon materials such as graphite electrodes, negative electrode materials, and carbon. The impurity elements in petroleum coke are mainly inherent in crude oilS. Fe, Ni, V, Ga and other elements are the main elements, and the deterioration of crude oil is becoming increasingly severe, leading to an increase in the content of impurity elements in petroleum coke. The control of trace element content in petroleum coke is an important link in producing high-quality petroleum coke and improving its market competitiveness.

Figure 1: Physical image of petroleum coke

The testing methods for trace elements in petroleum coke include atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectroscopy (ICP-OES), etc. Most of these detection methods require strict pretreatment and are complex to operate, relying heavily on the subjective experience of experimental personnel. In the revised petroleum coke product standard "NB/SH/T 0527-2019 for petroleum coke (raw coke)", XRF method has replaced the original ICP-OES method as the arbitration method for trace element determination in petroleum coke.

table1: Quality standards for ordinary petroleum coke (raw coke) and petroleum needle coke (raw coke)

Compared to wavelength dispersive XRF instruments, energy dispersive XRF instruments are more lightweight, suitable for various scenarios, and easier to maintain. The use of ED-XRF can increase daily monitoring of trace elements in petroleum coke, meet the rapid evaluation of raw materials in production sites, and have important guiding significance for adjusting and optimizing process parameters of the device.

1. Equipment and reagents

EDX 6000C Energy Dispersive X-ray Fluorescence Spectrometer

2. Sample collection, storage, and pre-processing

According to the sampling standard for petroleum coke, take 100g of petroleum coke sample and dry it in a drying oven at 105 ℃ for 2 hours. Use a grinder to grind the petroleum coke sample to 0.074mm or below. Weigh 3.0g of petroleum coke sample and 10.0g of boric acid powder, use boric acid powder as filler, and press them into tablets under a pressure of 15-20 T. Then, label the sample and place it in a sample bag for later use.

3. Establishment of working curve and sample analysis

Set appropriate measurement conditions and use an X-ray fluorescence spectrometer to scan a series of secondary standard samples of petroleum coke (raw coke) with known content (petroleum coke calibrated according to industry standards). Establish a first-order linear correction curve for the content and intensity of the elements of interest S, V, Fe, and Ni in petroleum coke. Then, measure the unknown petroleum coke (raw coke) sample.

image2: Linear relationship between S, V, Fe, Ni element content and strength

The above figure shows the measurement of secondary standard samples of petroleum coke with different contents using EDX 6000C energy dispersive fluorescence spectrometer, and the establishment of primary or secondary calibration curves for the content and intensity of S, V, Fe, and Ni elements. As shown in the figure, there is a very good linear relationship between the content of S, V, Fe, and Ni components and strength.

Figure 3: Fluorescence spectrum of petroleum coke sample

Figure 3 shows the test spectrum of an unknown sample (named petroleum coke 1 #) used in the test. The characteristic peaks of S, V, Fe, and Ni elements can be clearly observed in the spectrum, and trace amounts of Al, Si, Ca, and Zn elements are also present in this sample. After conducting repeatability tests on the sample, the repeatability of S, V, Fe, and Ni elements in the test results reached 0.28%, 3.33%, 1.10%, and 0.71%, respectively, indicating that the instrument has a good detection effect on petroleum coke samples.

Table 2: Repeatability test data of petroleum coke 1 # sample