M0027-Final Report Zhongxing March 2010-YHM100330.pdf
原文：
5 Metallurgical evaluation.
HYL has developed a set of metallurgical tests, at laboratory scale, to evaluate the quality of iron ore feedstock for Direct Reduction. Test description is shown below.
5.1 Metallurgical test description.
Laboratory metallurgical tests that HYL currently carries out for pellet feedstock are:
Reducibility test.
Swelling test.
Low temperature disintegration test.
Sticking test.
Each test is carried out at constant conditions of temperature, gas flow and gas composition. The tests are carried out using samples with particle size between 9.5 and 15.9 mm (50% + 9.5 - 12.7 mm and 50% +12.7 - 15.9 mm). As it was stated before, for this sample all the tests were made with 100%pellets of particle size between 9.5 and 12.7 mm.
All tests are carried out at least three times, and the experimental results are averaged. Reducibility tests are performed at two temperature levels 800 and 950°C. The degree of reduction attained is 95 percent and the evaluation of reducibility of different ores is made by comparing the degree of reduction through the time. Comparison is made by two ways:
By comparing the plots of degree of reduction versus time for the tested ore and the reference ore. Reducibility is better when shorter reduction times are achieved.
By comparing the slope of the lines obtained by plotting the function versus time. Reducibility is better when higher values of the slope are obtained.
Swelling values are obtained by the direct measurement of the volume of the sample before and after the reduction. This is carried out using a mercury volume meter.
Low temperature disintegration test is carried out at 500°C. During reduction the reactor is rotated to promote disintegration. Particle size distribution of the reduced sample gives the required information on disintegration and fines generation.
A detail description of the tests is given in Appendix A.
5.2 Metallurgical test results.
The metallurgical results are given in Table 3 below.
Table 3. Metallurgical properties of IMDM
iron ore pellets
IMDM
2010 HYL
Recommendation
1. Reducibility
k at 800°C
k at 950°C 2.7
5.5 3.0 Min.
4.0 Min.
2. Swelling
at 800°C
at 950°C 1.6
9.0 15 Max.
15 Max.
3. Sticking
at 950°C
(uncoated)
(coated using a susp. 15% cement)
98.1
19.3
4. Low temperature disintegration
% + 6.3 mm
% - 3.2 mm
% Unbroken pellets 96.0
3.6
95.7 80 Min.
10 Max.
60 Min.
The reducibility plot is shown in Figure 2. In the plot the percentage of reduction versus time at 800°C is given. The required time to reach 95 percent of reduction was 108 minutes.
Figure 2. % of reduction vs. time of IMDM pellets at 800°C
Time (min)
% of reduction
Figure 3 shows the percentage of reduction versus time for the sample at 950°C. Inner Mongolia Dazhong Mining pellets reached 95 percent of reduction in 52 minutes. The reducibility of Inner Mongolia Dazhong Mining pellets is very good for the case of 950°C. No problems are foreseen regarding reducibility of the pellets in the HYL DR Process.
Figure 3. % of reduction vs. time for IMDM pellets at 950°C
Time (min)
The swelling during reduction at both temperatures is below the maximum value HYL recommends for a pellet. The swelling values are 1.6% and 9.0% at 800 and 950°C; HYL recommends a maximum of 15%.
Low temperature disintegration tests show that in the fraction above 6.3 m, Inner Mongolia Dazhong Mining pellets obtained 96.0 percent versus 80 that HYL recommends as a minimum. In the fraction below 3.2 mm, Inner Mongolia Dazhong Mining pellets obtained 3.6 percent versus 10 that HYL recommends as a maximum. Inner Mongolia Dazhong Mining pellets obtained 95.7 percent for the index of unbroken pellets versus 60 that HYL recommends as a minimum.
Figure 4 below shows graphically the LTD Test results.
Figure 4. Low Temperature Disintegration Test Result
IMDM 2010
80 minimum
% unbroken
Photograph 2 shows the material discharged after the LTD test for Inner Mongolia Dazhong Mining pellets. The results of this test confirm that this material has a low potential to generate fines the reduction process, which is a good property.
Photograph # 2. IMDM pellets after LTD test.
The tendency to form agglomerates showed by this pellet is high according to the average value of the sticking index of 98.1 with no coating agent. However, by adding 15% weight suspension of cement, the sticking index was decrease to 19.3% which a good value. The results were favourable and showed that the pellets can be used in a DR plant with an adequate coating to diminish the high sticking tendency of these pellets.
6 Conclusions.
All the results given in this report were obtained by testing the sample of iron ore pellets provided by Inner Mongolia Dazhong Mining.
Any further interpretation and/or extrapolation of these results will depend of how representative is the evaluated sample.
• The total iron content is 63.1 percent. The sample has an acid basicity and CaO must be added to the furnace in the meltshop to adjust the binary basicity of the slag.
• The main component of the gangue is silica.
• The porosity and bulk density are good.
• The results of the tumbler and show that Inner Mongolia Dazhong Mining pellets are mechanically strong. They can be handled without generation of fines before the charge to the reactor.
• The reducibility and swelling of Inner Mongolia Dazhong Mining pellets is good.
• Inner Mongolia Dazhong Mining pellet is mechanically strong during reduction; the LTD test shows that MSI pellets will not generate a large amount of fines.
• The sticking tendency of these pellets is high but they can be processed in a HYL reactor with the proper amount of coating to decrease their tendency to agglomerate.
In conclusion, from the Direct reduction process standpoint, these pellets can be processed 100% in an HYL reactor if and when they are properly coated with a coating agent that decreases its sticking tendency.
