Separating Between Potatoes and Clods Using the Coefficient of Restitution

Potato is one of the most valuable foods, after wheat, rice and corn, it is the fourth major crop in the world. Potato harvesting is one of the expensive and sensitive steps. In Iran, due to the lack of harvesting machines suitable for the fields of the country (the presence of stones and lumps and lack of humidity control, shortage and high wages of workers) the area under potato cultivation is small. Separating stones and lumps from potatoes and damaging the tubers are two basic and unavoidable problems of most potato harvesting machines. More separation of stones and lumps often leads to more mechanical damage to potato tubers, and less separation increases labor costs. It is serious that in most of the harvesting machines, several workers are placed next to the potato carrying belt and separate the stone from the potato to minimize the damage. The purpose of this study is to investigate the separation of potato from the potato by using the difference in the coefficient of restitution, in potato and clods. In this research, the effect of different factors on the accuracy of separation of potato tubers from clods was investigated.
Introduction
More than 370 million tons of potatoes are produced in the world every year and it is considered the fourth strategic product of the world after wheat, rice, and corn. Potato is one of the most valuable foods, after wheat, rice, and corn, it is the fourth major crop in the world. In addition to food consumption, it is used to prepare more than 50 kinds of products, including starch, flour, bread, glue, alcohol, cosmetics, canned food, chips, glucose, etc. are used. Potato harvesting is one of the most expensive and sensitive steps. In Iran, the area under potato cultivation is small due to the lack of harvesting machines suitable for the country's fields (the presence of stones and lumps lack of humidity control, shortage, and high wages of workers). Separating stones and lumps from potatoes and damaging the tubers are two basic and unavoidable problems of most potato harvesting machines. More separation of stones and lumps often leads to more mechanical damage to potato tubers, and less separation increases labor costs. It is serious that in most of the harvesting machines, several workers are placed next to the potato carrying belt and separate the stone from the potato to minimize the damage. The purpose of this study is to investigate the separation of potato from the potato by using the difference in the coefficient of restitution, in potato and clods.
Materials and Methods
In this research, a digester with a diameter of 60 cm was used and the volume of the digester was 0.4 cubic meters. The standard volume of the maximum substrate that can be loaded is 0.325 cubic meters. Digester stirring is done by a mechanical stirrer connected to an electric motor in the central part of the top of the cap. The whole digester has a capacity of three layers of materials, each layer has its own sensors. Acidity and temperature sensors collect the relevant variable status and store and transfer it to virtual memory through the electronic control system. The anaerobic digester system in the bioenergy and recycling laboratory unit has been repaired, and a sample of cow manure was prepared from the animal husbandry unit around Tabriz and transferred to the laboratory as a substrate for conducting research. The experiment was done in three repetitions, and in each repetition, 150 kg of fresh animal waste was poured into the digester tank with 150 liters of water. Then, to add methanogenic microorganisms to the substrate, 10% of the total weight of the tank (substrate), i.e. 30 kg of animal rumen, was prepared and added. Each repetition of this process continued for 30 days, and the temperature inside the tank was kept at the same temperature as the outside environment (30 degrees Celsius) in the first repetition, and at 35 degrees Celsius in the second and third repetitions. Mixing was done automatically for 5 minutes only in the second and third repetitions and every 6 hours, and the mixing speed was set to 100 and 150 rpm, respectively. After the system started working, gas was discharged twice a day (every 12 hours) according to the production rate and pressure. The total amount of methane produced until that day was measured on the meter and the percentage of methane gas produced daily was measured by the methanometer. Also, in this research, using computational fluid dynamics (CFD), the prediction of the kinetic process of biogas production from animal waste and the provision of the appropriate stirring cycle during the anaerobic digestion process was investigated. In the initial stages of the work, data related to an anaerobic digester with an agitator, and mixing speeds of 0, 100, and 150 rpm were recorded for one month, and the measured characteristics were converted into the inputs of the ADM1 model. Then, the initial values that were reported during the start-up stage of the digester were estimated.
Results and Discussion
The results of investigating the effects of the factors show that the effect of all 5 investigated factors on the separation accuracy is significant at the five percent level. Also, the investigation of the mutual effects of the factors shows that the investigated factors have a 5-way interaction effect on the separation accuracy of the system, in this case, there is no need to investigate the double, triple, and quadruple interaction effects to analyze the results. The best separation percentage was obtained at a rotational speed of 36 rpm and a distance of 34 cm from the cylinder axis to the separator and the steel cylinder. Maintaining high-efficiency values ​​requires a coordinated increase in the linear speed of the conveyor belt with the rotational speed of the cylinder.
Conclusion
For better separation, the horizontal distance between the axis of the conveyor belt and the rotating cylinder should be adjusted, because it changes the angle of impact of the material on the cylinder, so it is useful in the amount of effective separation. This distance is determined experimentally. By comparing the average results, it can be seen that the rotational speed of the cylinder alone does not have a specific effect on the separation rate, and the tests conducted at all three levels of the desired rotational speed have led to optimal results. In other words, to achieve the desired result for separation, any rotational speed value can be used in combination with suitable values ​​for other factors. It seems that the type of cylinder does not have much effect on the separation accuracy of the system, because the change of the kind of cylinder changes the amount of the coefficient of separation, but what is important for the separation index is the difference of the coefficient of separation of potatoes and lumps. Also, the amount of mechanical damage to the glands is very important. Its goal is to obtain the highest percentage of separation with the least amount of mechanical damage. The results show that the best separation accuracy is achieved with a steel cylinder, but when materials made of rubber and unbreakable plastic were used as treatment, it was observed that there is no significant difference in the results obtained, only the advantage that these materials have over steel is that they reduce the amount of possible mechanical damage. The horizontal distance of the axis of the conveyor belt from the axis of the cylinder is one of the factors that affect the separation accuracy at the level of 1% and 5%. The comparison of the average values ​​of separation percentage shows that this factor has a significant effect on the separation percentage. Changing the horizontal distance of the cylinder axis from the axis of the conveyor belt causes a change in the material collision angle. Increasing the linear speed of the conveyor belt causes the materials to be thrown to a greater distance, and if the rotational speed of the cylinder and the distance of the cylinder from the conveyor belt are adjusted in appropriate values, the distance of the cylinder from the divider will be the determining factor in the efficiency.