Hu Jianjun 1Remington 2Shen Shengqiang 3Guo Qianhui 1Liu Junwei 4Li Zifeng4
College of Mechanical and Electrical Engineering, Henan Agricultural University, Zhengzhou 450002, Henan, China; 2. Henan Academy of Sciences, Zhengzhou 450008, China; 3. School of Energy and Power Engineering, Dalian University of Technology, Dalian 116026, Liaoning, China; 4. Henan Key Laboratory of Biomass Energy, Zhengzhou 450008)
Abstract: In this paper, the cold compression process of five kinds of straw particles was carried out in open test. The compression molding process was divided into four stages of loosening, transition, compaction and transition, and the pressure equations of different stages were regressed. The Matlab software was used to calculate The specific energy consumption during the whole process of compression molding was established.With wheat straw as an example, the quadratic regression general rotation combination design was used to establish the mathematical model of compression speed, material moisture content and specific energy consumption. The results showed that the compression speed The effect is greater than the moisture content, and both are negative effects.
0 Introduction
At present, the molding technology of straw compression molding technology at home and abroad is mainly divided into four kinds of wet-compression molding, hot-press molding, carbonization molding and cold compression molding at room temperature. The molding methods are classified into two types: closed type compression and open type compression [1], [2], Common molding equipment, including screw extrusion molding machine, piston stamping machine and pressure roller pelletizing machine [3]Regardless of the compression molding technology, the specific energy consumption is one of the important performance indicators to examine whether the compression molding process design is reasonable.Rate energy consumption refers to the amount of energy consumed to produce the molding fuel per unit time and the amount of energy The ratio of the quality of the formed fuel The energy required for compression molding is mainly composed of two parts: the energy consumed to overcome the friction between the material and the inner wall of the molded part and the energy consumed by the deformation of the material[4], [5].
Pressure roller granulator with low energy consumption, high yield, strong adaptability of raw materials, etc., which became the current research and development of hot spots.But the market pressure roller granulator design is not reasonable, resulting in its ratio High energy consumption, greatly restricted the degree of its industrial application.Therefore, this study uses universal testing machine and self-made 'open' compression molding device, the five kinds of straw 'open' particles cold compression process than Energy consumption test, research compression speed, moisture content and other factors compared to the impact of energy consumption, select the best compression molding parameters, press roller particle molding machine for industrial design to provide a reference.
1 test materials and devices
1.1 test materials
The test raw materials for the five suburbs of Zhengzhou City, the common straw (wheat straw, corn cob, corn stalks, straw and cotton stalks.) First, the use of micro-mill smash the raw materials, remove impurities in the raw materials, and then the raw material into the muffle furnace , And dried at 105 ℃ for 8h, then classified and sealed.When the temperature of the raw material dropped to room temperature, water distribution test was conducted according to the test requirements, and the raw materials were respectively sealed in black plastic bags according to different water content.
1.2 test device
The instrument used in this experiment is WDW-50 computer-controlled electronic universal testing machine, the rated pressure of the test is 50kN, the moving speed of the beam is 2 ~ 200mm / min.According to the characteristics of the pressure roller granulator, 'Particle compression molding test device (Figure 1) [6], Of which the inner diameter of the sleeve is 15 mm, the inner diameter of the die is 10 mm, the aspect ratio of the die is 5.2, and the taper of the die is 450.
Before the test, the pretreated straw material is pretreated so that the raw material fills the sleeve, and the universal testing machine program is started to automatically generate the pressure and displacement curve of each test.
2 test results and analysis
2.1 compression molding curve
From the test results we can see that, although the compression molding conditions are different, but their compression molding curve has the same variation (Figure 2).
As can be seen from Fig. 2, the cold compaction process of straw particles is quite complicated. In order to calculate the specific energy consumption data, the compressive forming characteristic curve is defined as four stages, that is, loose phase (oa interval), transitional phase (ab interval) , The compression phase (bc interval) and the transition phase (cd interval). In the loose phase and the transitional phase, the material mainly deforms elastically, and the material mainly undergoes plastic deformation during the compacting phase.[7].
2.2 Than the energy consumption calculation
In this study, the area of the curve formed by pressure and displacement is calculated and the specific energy consumption is calculated. The work done by the compression rod in the process of material compression molding can be approximated by the following formula:
Specific calculation steps of specific energy consumption: The experimental data under different compression molding conditions are extracted, and the regression analysis is carried out according to different compression molding intervals to obtain the pressure regression equation of each interval, which is substituted into equation (1) and calculated by Matlab software Energy consumption values, and then through formula (2) can be obtained than the energy consumption. 5 kinds of straw raw materials in different compression molding conditions than the energy consumption data in Table 1.
As can be seen from Table 1, although the specific energy consumption of the same straw raw materials under different compression molding conditions are different, but there are the same changes, that is, when the moisture content of the material is constant, with the compression rate increases, the ratio The energy consumption decreases gradually.When the compression speed is constant, the specific energy consumption decreases with the increase of water content.The specific energy consumption of different straw raw materials varies greatly, of which the specific energy consumption range of straw is the largest, , The specific energy consumption of wheat straw, corn stalks and cotton stalks is relatively close and small, indicating that the adaptability of straw and corn cob when the cold compression molding process parameters (such as material moisture content and compression speed) changes in a certain range Poor sex, poor compression molding.
2.3 Ratio of energy consumption regression model
From the results of cold compaction molding of five kinds of straw particles, we can see that the compression rate and the moisture content of the material have a greater impact on energy consumption.In order to further study the impact of the compression rate and moisture content on energy consumption, using wheat straw as an example, Quadratic regression general rotation combination design, establishment of quadratic regression model of wheat straw specific energy consumption.
2.3.1 Test methods
Table 2 shows the levels of factors in the experimental design.
2.3.2 test results
Compression speed and moisture content of the material compared with the results of energy consumption in Table 3.
Table 3, z0, z1, z2 for the single factor level, z1z2, z12, z22 for the two-factor interaction level, yi for the response variable.
2.3.3 Regression coefficient calculation
2.3.4 regression equation test
Since all the factors in the design are dimensionless linear coding, and the regression coefficients bj, the reciprocal terms and the average term regression coefficients are uncorrelated, the absolute value of the regression coefficient can be directly Comparing the effect of various factors on energy consumption, the influence of compression speed in this experiment is greater than the moisture content, and both are negative effects.
3 Conclusion
The cold compaction process of straw particles can be divided into the loose phase, the transitional phase, the compaction phase and the transitional phase. During the loose phase and the transitional phase, the material mainly deforms elastically. During the compaction phase, the material mainly undergoes plastic deformation and the material during the transition phase mainly occurs Viscous deformation.
② When the moisture content of the same straw raw material (within the scope of this study) is constant, the specific energy decreases with the increase of the compression rate. When the compression rate is constant, the specific energy Also be reduced accordingly.
③ Among the five kinds of straw raw materials selected in this experiment, the specific energy consumption range of straw and corn cob is the largest, which shows that the two kinds of straw raw materials have poor adaptability to process parameters and poor compression molding.
⑤ Compression speed and moisture content have different effects on the specific energy consumption of the 'open' compression molding device. The effect of compression speed is greater than the moisture content, and both are negative effects.
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