INTRODUCTION

Pig feeding constitutes an extremely serious problem according to Campabadal (2009), taking into account that the pig performs an impeccable competition with man because its traditional diet consists of cereals and other products for human consumption and since its requirements of proteins are 5 to 8 times higher than those in man (Iglesias & Soto, 1987; Martinez, 2011). Due to the increase in food needs in the population in terms of eggs, meat and milk, it is desired that the nutrition of farm animals not only depend on plant sources but also on animal by-products (BPFA-ICA, 2020; FAO e IFIF, 2016; Keene et al., 2005; Uribe et al., 2011). Poultry and pig industries are the main consumers of meat and bone meal (Hamilton and Kirstein, 1996). To obtain a quality food, it is necessary to observe a series of zootechnical requirements that must be taken into account when submitting a material to the grinding process, mainly in relation to the size of the particle (Buitrago et al., 2004; Careeta, 2013; Covenin 1882-83: 83, 1983; Parra & Portilla, 1987). A feasible method for obtaining these flours is through the use of mills (Martínez, 2007; 2009; Paneque, 1988; Paneque et al., 2018). For this reason, the present work aims to evaluate the working regimes of hammer mills and fingers and nose mills during the obtaining of cattle bone meal of zootechnical quality for feeding pigs, with rational use of electrical energy.

MATERIALS AND METHODS

Two types of bones, scapula and femur, were selected as raw materials, since they meet the geometric conditions to guarantee their dimensioning more reliably and the hammer mill and the finger and nose mill were used (Chirino, 1980; Castillo, 2011). The bones came from two small meat industries in the area (Bodegón el Destete and Bodegón Doña África), located in the city of El Tigre, Anzoátegui State, Venezuela.

The physical and mechanical properties of the bones to be considered in the evaluation of the working organs of the mills were:

1. a.) Physical properties: humidity, mass, length, diameter and density.

2. b.) Mechanical properties: energy absorbed on impact (force and effort).

The grinding procedure was carried out in the Workshop of Warehouse 4, belonging to the UPTJAA's National Mechanics Training Program (PNF-Mechanics), which has an area of 1,500 m², which is equipped with machines and equipment necessary for teaching.

In the tests carried out with scapula and femur bones, the experimental conditions were considered, taking different photographic images, with their respective dimensions in order to characterize:

1. a) Natural condition, in which the scapula bones are white, with solid shape and almost trapezoidal geometry and the femur bones are light white and with elongated hollow cylindrical shape and a soft moist mass inside.

2. b) Chopped condition (pieces of approximately between 10 and 12 cm).

3. c) Ground condition, to appreciate coloration and granulometry in bone meal (Ramos, 2010).

The DPM 4 hammer mill, manufactured in Brazil, is located in the Workshop of Warehouse 4, belonging to the UPTJAA National Mechanics Training Program. It is a stationary machine, used to grind mainly grains, activated by means of a three-phase electric motor that is turned on manually and has the following characteristics: power 8 kW, voltage 220 V, nominal current 15.7 A, nominal speed 3,300 rpm (rotation frequency), it has 24 hammers, drum diameter 0.293 m, drum length 0.095 m, hammer length 0.115 m, hammer width 0.042 m and hammer thickness 0.005 m. It should be noted that due to the lack of the original motor of this mill, it was worked with a 4 kW and 1 790 rpm motor.

The tool or working organ consists of a hammer (mobile) and blades (fixed), which act by impacting the raw material, successively cutting it into smaller pieces until the corresponding flour granulometry is obtained.

The CADELMA brand finger and nose mill, manufactured in Maracaibo, Venezuela, is located in the same place and is a stationary machine that is used to grind mainly grains. It is activated by means of a three-phase electric motor that is turned on manually by the operator and it has the following characteristics: power 4 kW, voltage 220 V, nominal current 15.7 A, nominal speed 1,790 rpm (rotation frequency), it presents 3 steel blades in the shape of hands 0.15 m high, 0.8 m wide and 0.01 m thick, drum diameter 0.34 m and drum length 0.14 m. The tool or working organ consists of paddles in the form of fingers and fixed blades that cut the material before crushing it.

Both mills work with a motor whose power is below the technical requirements established by the manufacturers (15 kW).

To obtain the flour from the selected raw material, the following steps were carried out:

• Reception of the raw material: The used bones were minced in sizes of different measures (random) to be able to be processed by the mills.

• Storage: The raw material was transported to Warehouse 4 belonging to the Department of Mechanical Engineering of the UPTJAA, where it was stored to later proceed to carry out the experiments.

• Weighing and bagging in masses: The chopped bone pieces were weighed in mass samples of 1, 2, 3, 4 and 5 kg (three portions or samples for each kg of weighed mass respectively), being subsequently bagged.

• Grinding: Once the distribution of the samples was completed (weighing and bagging), they were ground in both mills under the same weight and motor power conditions (4 kW) in the same weighing order.

• Drying process: The ground bone samples were subjected to free or natural convection drying for a period of sixty-seven (67) days.

• Sifting: After the drying process, the ground material was sifted through 4, 2 and 1 mm sieves.

RESULTS AND DISCUSSION

Analysis of the Physical-Mechanical Properties of Cattle Bones for their Crushing

Tables 1 and 2 show the measurements of mass, length, thickness and diameters of the bones of cattle scapulae and femur, with their respective averages; while Table 3 shows the function models: exponential, linear, logarithmic, polynomial order 2 and potential (Walpole et al., 1999; 2012).

TABLE 1

Scapula bone measurements

TABLE 2

Measurements of the femur bones

TABLE 3

Function Models, statistical requirement of correlation R²

According to the data obtained in Tables 1 and 2, it can be observed that, for the scapula bone, the thickness has better conditions regarding the position for the impact test on the Sharpy pendulum.

On the other hand, for the femur bone, the best position for the impact test is the diameter compared to the length in the Sharpy pendulum.

Analysis of the Operational Parameters Depending on the Quality of the Crushed

Table 4 shows the operational parameters of the finger, nose and hammer mills.

TABLE 4

Matrix of operational parameters of the finger and nose mill and hammer mill

Source. The authors

Figure 1 shows the measurements (length, thickness and diameter) against bone mass (scapula and femur). According to the data obtained in Figure 1, it can be observed that, for the scapula bone, the thickness has better conditions regarding the position for the impact test on the Sharpy pendulum. On the other hand, for the femur bone, the best position for the impact test is the diameter compared to the length in the Sharpy pendulum.

FIGURE 1
Measurements (length, thickness and diameter) against bone mass (scapula and femur).

Figure 2 shows the behavior of the initial mass as a function of time of the finger and nose mill to determine the mass after the grinding and drying process.

FIGURE 2
Mass as a function of time of the finger and nose mill.

Figure 3 shows the granulometric behavior of the femur and scapula bones, for the finger and nose mill after 67 days of free convection drying using 1, 2 and 4 mm sieves. It was observed that for the 1 mm and 2 mm sieves, the amount of mass was very low. However, using the 4 mm sieve, it was observed that for the scapula bone the amount of mass that passed through the sieve was greater than the amount of the femur bone mass that passed through it. Therefore, the scapula bone is better for sieving in this type of mill. Figure 3 shows the behavior of the initial mass as a function of the hammer mill time to determine the mass obtained after the grinding and drying process.

FIGURE 3
Initial mass as a function of hammer mill time (Table 4).

Figure 3 shows the granulometric behavior of the femur and scapula bone for the hammer mill after 67 days of free convection drying using 1, 2 and 4 mm sieves. It was observed that for the 1 and 2 mm sieves, the amount of mass obtained was very low.

However, using the 4 mm sieve it was observed that for the scapula bone the amount of mass that passed through the 4 mm sieve was greater than the amount of mass of femur bone that passed through it. Therefore, the hammer mill also has a better response in crushing the scapula bone as a greater amount of final mass is obtained during sieving.

Considering the operational parameters of the mills (finger and nose and hammer mills), where both worked with a 4 kW motor, and according to Figures 2 and 3, it was observed that the hammer mill carried out the crushing process of the bones in less time and with a greater quantity of flour passed through the 4 mm sieve, the scapula bone being better.

Analysis of Operational Parameters Based on Energy Consumption

Table 5 establishes the operational parameters of the finger and nose mill and the hammer mill for determining energy consumption.

TABLE 5

Matrix of energy consumption parameters of the finger and nose mill and hammer mill

Source. The authors

Figure 4 shows the variation in intensity as a function of the mass processed for the finger and nose mill.

FIGURE 4
Graph of the final mass and intensity of the finger and nose mill (Table 5).

It is observed in Figure 4 that for the finger and nose mill, the increase in intensity was reflected in line 1 and line 2, for the femur bone compared to the scapula bone. However, in line 3 the increase in intensity was present in the scapula bone compared to the femur bone, although this difference was not significant.

Figure 5 shows the variation of the intensity as a function of the mass processed for the hammer mill.

FIGURE 5
Mass as a function of intensity, hammer mill (Table 5)

It is observed in the graph of Figure 5 that for the hammer mill the increase in intensity for line 1 was present with the femur bone with respect to the scapula bone. However, for line 3, the increase in intensity was reflected in the femur bone, compared to the scapula bone.

The comparison of the electrical consumption was determined with the finger and nose mills and the hammer mill in work operations of grinding the bones of the femur and scapula, since the motor source consumed electrical energy in a triphasic way (three lines of current). The behavior of this parameter is shown in Figures 4 and 5, indicating consumption decrease or increase in the crushing process as a function of time. As a result, the finger and nose mill consumed more electrical energy according to the increase in intensity since the contact between the grinding organ and the material required more grinding time because it was slower, making the grinding process slower.

Results of the Determination of the Theoretical (qt) and Real (qr) Productivity and the Efficiency (e) of the Hammer Mill and the Finger and Nose Mill

Hammer mill: Having the characteristics of this mill and using the equation represented in Table 6, the theoretical productivity of the hammer mill was obtained.

TABLE 6

Theoretical productivity of the hammer mill

From the data and the equation qr = m/t (amount of mass processed during machine work/clean work time), the real productivity (qr) was obtained, resulting in 0.028 kg / s for hammer mill. Substituting in the equation e = qr/qt, the efficiency of the hammer mill was obtained, resulting in 0.30 (30%).

Finger and nose mill: Having the characteristics of this mill and using the equation in Table 6, the theoretical productivity of the finger and nose mill was obtained, represented in Table 7.

TABLE 7

Theoretical productivity of the finger and nose mill

Using the same equation, the real productivity (qr) was obtained, resulting in 0.0076 kg/s, for the finger and nose mill. In the same way, the efficiency (e), of the finger and nose mill, was obtained, resulting in 0.12 (12%).

Determination of the Most Rational Variant of Bone Crushing Based on the Quality of the Crushing and Energy Consumption

Considering the operational parameters studied for finger and nose mill and hammer mill, when comparing the quality of crushing and their energy consumption, it was determined that the hammer mill has greater efficiency than the finger and nose mill (30% for the hammer mill and 12% for the finger and nose mills), in addition, the speed developed by the hammer mill during the milling process is higher than that of the finger and nose mills, which allows obtaining particles with a granulometry of the flour that meets the zootechnical requirement of pig feed. In reference to energy consumption, the finger and nose mill had higher consumption according to the increase in the intensity of the current, since the contact between the grinding organ and the material to be processed required more time in the grinding work, because it makes the crushing process slower and less efficient, due to its slower crushing speed.

CONCLUSIONS

• In determining the physical-mechanical properties, it was observed that the scapula bone has greater hardness than that of the femur, so it requires greater effort during the grinding process, with the hammer mill behaving with better destructive capacity than the finger and nose mill.

• The highest energy consumption was observed with the finger and nose mill, caused by the contact between the crushing organ and the processed bones, requiring a longer time in the grinding process, being less efficient and slower than the hammer mill.

• The actual productivity of the hammer mill was higher than that of the finger and nose mill during the process of grinding of the scapula and femur bones, so to obtain bone meal the hammer mill was more efficient with a 30%.

• The quality of the flour obtained from the zootechnical requirement established for feeding pigs with concentrated feed, better results were obtained with the hammer mill.

REFERENCES

BPFA-ICA: Buenas prácticas en la fabricación de alimentos para animales en Colombia, Instituto Colombiano Agropecuario, Grupo de Regulación Y Control de Alimentos para Animales, Bogotá D.C., Colombia, 2020.

BUITRAGO, G.V.; LÓPEZ, A.P.; CORONADO, A.P.; OSORNO, F.L.: ¨Determination of physical characteristics and mechanical properties of potatoes cultivated in Columbia¨, Revista Brasileira de Engenharia Agrícola e Ambiental, ISSN-1415-4366, 8(1): 102-110, 2004.

CAMPABADAL, C.: Guía técnica para alimentación de cerdos, 46pp., San José, Costa Rica, 2009.

CAREETA, R.: ¨Novel method to analyze post-yield mechanical properties at trabecular bone tissue level¨, Journal of the Mechanical Behavior of Biomedical Materials, 20(13), 2013.

CASTILLO, D.L.J.: Proyecto de factibilidad de la instalación de una planta procesadora de grasa animal y harina de carne y hueso para grupo El Tunal, Universidad Centro Occidental, Barquisimeto, Venezuela, 2011.

CHIRINO, L.: Proyecto de complejo mecanizado para la ceba de 45 mil cerdos en base a residuos alimenticios y diseño de una trituradora de martillos, Tesis (en opción al título de Ingeniero), Instituto Superior de Ciencias Agropecuarias de La Habana (ISCAH), San José de las Lajas, Habana, Cuba, 1980.

COVENIN 1882-83: 83: Alimento Complemento para Cerdos, Normas venezolanas, Caracas, Venezuela, 1983.

FAO E IFIF: Buenas prácticas para la industria de piensos-Implementación del Código de Prácticas Sobre Buena Alimentación Animal, Ed. FAO, Roma. Italia, 2016.

HAMILTON, R.; KIRSTEIN, D.: Harina de carne y hueso. Una fuente valiosa de nutrientes en las dietas de animales y aves de corral, Compañía de Litografia Kirbi, USA, 1996.

IGLESIAS, C.C.E.; SOTO, W.: Mecanización de los Procesos Pecuarios, Ed. Departamento de Ediciones del ISCAH, ENPES, San José de las Lajas, Habana, Cuba, 1987.

KEENE, B.; KNOWLTON, K.; WILSON, J.; MCGILLIARD, M.; HOLTAWAY, C.: ¨Bone breaking strength in mature dairy cows¨, Transactions of the ASAE, ISSN-2151-0032, e-ISSN: 2151-0040, 48(4): 1637-1643, 2005.

MARTÍNEZ, C.: Datos del molino de martillo para el análisis experimental, Universidad Central de las Villas (UCLV), Santa Clara, Villa Clara, Cuba, 2007.

MARTÍNEZ, C.: Libro de Instalaciones Agropecuarias, Ed. UCLV, Santa Clara, Villa Clara, Cuba, 2011.

MARTÍNEZ, J.: Diseño y Construcción de un prototipo de trituradora de desperdicios domésticos orgánicos, Tesis (en opción al título de Máster en Ciencias), Instituto Politécnico Nacional, México, 2009.

PANEQUE, R.P.: Transportadores en la Agricultura, Ed. Departamento de Ediciones del ISCAH, ENPES, primera ed. , pp. 276, San José de las Lajas, Habana, Cuba, 1988.

PANEQUE, R.P.; LÓPEZ, G.; MAYANS, P.; MUÑOZ, F.; GAYTÁN, J.G.; ROMANTCHIK, E.: Fundamentos Teóricos y Análisis de Máquinas Agrícolas, Ed. Universidad Autónoma Chapingo, primera edición ed. , vol. 1, pp. 456, ISBN-978-607-12-0532-2, Chapingo, Texcoco, México, 2018.

PARRA, M.; PORTILLA, D.: Estudio de las Propiedades mecánicas del sistema Óseo, Tesis (en opción al título de Ingeniero), Universidad Nacional de Colombia, Facultad de Ingeniería, Bogotá, Colombia, 1987.

RAMOS, C.N.F.: Aprovechamiento del desecho de huesos de res para la obtención de harina de hueso en la fábrica Federer, Tesis (en opción al título de Ingeniero), Escuela Politécnica Nacional, Quito, Ecuador, 2010.

URIBE, F.; ZULUAGA, A.F.; RODONI, L.M.; ANDERSON, E.; OCHOA, L.M.: Buenas prácticas ganaderas, Ed. Gef, Banco MundiaL, Fedegán, Cipav, Fondo Accion, TNC, ISBN-958-8498-36-8, 2011.

WALPOLE, R.E.; MYERS, R.H.; MYERS, S.L.: Probabilidad y estadística para ingenieros, Ed. Pearson educación, ISBN-970-17-0264-6, México D.F., 1999.

WALPOLE, R.E.; TEVES DE ALMEIDA, R.H.; MYERS, S.L.; YE, K.: Probabilidad y estadística para ingeniería y ciencias, Ed. Pearson educación, vol. 162, México D.F., 2012.

Notes

Author notes

*Author for correspondence: Irania Quevedo Herrero, e-mail: iraniaq@unah.edu.cu

Conflict of interest declaration