Grinding kinetics and equilibrium states

The temporary and permanent equilibrium occurring during the initial stage of cement grinding does not indicate the end of comminution, but rather an increased energy consumption during grinding. The constant dynamic equilibrium occurs after a long grinding period indicating the end of comminution for a given particle size. Grinding equilibrium curves can be constructed to show the stages of comminution and agglomeration for certain particle sizes

Constitutive Model for Material Comminuting at High Shear Rate

The modeling of high velocity impact into brittle or quasibrittle solids is hampered by the unavailability of a constitutive model capturing the effects of material comminution into very fine particles. The present objective is to develop such a model, usable in finite element programs. The comminution at very high strain rates can dissipate a large portion of the kinetic energy of an impacting missile. The spatial derivative of the energy dissipated by comminution gives a force resisting the penetration, which is superposed on the nodal forces obtained from the static constitutive model in a finite element program. The present theory is inspired partly by Grady's model for comminution due to explosion inside a hollow sphere, and partly by analogy with turbulence. In high velocity turbulent flow, the energy dissipation rate is enhanced by the formation of micro-vortices (eddies) which dissipate energy by viscous shear stress. Similarly, here it is assumed that the energy dissipation at fast deformation of a confined solid gets enhanced by the release of kinetic energy of the motion associated with a high-rate shear strain of forming particles. For simplicity, the shape of these particles in the plane of maximum shear rate is considered to be regular hexagons. The rate of release of free energy density consisting of the sum of this energy and the fracture energy of the interface between the forming particle is minimized. The particle sizes are assumed to be distributed according to Schuhmann's power law. It is concluded that the minimum particle size is inversely proportional to the (2/3)-power of the shear strain rate, that the kinetic energy release is to proportional to the (2/3)-power, and that the dynamic comminution creates an apparent material viscosity inversely proportional to the (1/3)-power of the shear strain rate.Comment: 13 pages, 2 figure

Development of the New Method of the Melted Cheese Products Without Salt-melters Using Cryomechanolysis

The aim of the work is elaboration of the principally new method of deep processing of rennet cheeses to the melting using the complex action of freezing and cryomechanolysis on the raw material that gives a possibility to destruct the hardly soluble biopolymers and to transform them into soluble form.The principally new method of the deep processing of rennet cheeses for receiving the melt cheese products without salts-smelters was elaborated. It differs from the traditional ones by the complete exclusion of the salts-smelters. This method is based on the use of the influence of freezing and fine-dispersed comminution on the raw material. It allows open biological potential of the rennet cheeses more fully and to extract the hidden (bound) protein forms from nanocomplexes of lipids and mineral substances. It allows destruct the proteins of rennet cheeses to the separate polymers and dipeptides and tripeptides. The used technological methods gave a possibility to exclude the salts-smelters at the rennet cheeses manufacturing. They favor the transformation of lipid-proteins paracaseinate calcium phosphate complexes to the separate amino acids and peptides and allow receive homogenous plastic mass.It was established, that at the complex action of freezing and fine-dispersed comminution on the rennet cheese the destruction of hardly soluble lipid-protein nanocomplexes and release of protein from the bound state into free one – nanoform (by 33,5…35 % more) takes place. The mechanisms of this process, connected with cryomechanodestruction of connections between lipids and proteins and non-fermented catalysis of nanocomplexes were described.It was established, that cryomechanodestruction and non-fermented catalysis of protein to the separate monomers – α-amino acids (by 55…60 %) takes place at freezing and fine-dispersed comminution of rennet cheese before melting. The mechanism of freezing and non-fermented analysis, connected with cryomechanocracking of protein molecules at the expanse of peptide protein connections destruction to the separate α-amino acids and their transformation into the free form was described. It was also demonstrated, that the conformational changes of protein molecules take place synchronously.The offered and elaborated nanotechnology of melt cheese products on the base of rennet cheeses without salts-smelters includes complex action of freezing and fine-dispersed comminution. The mechanisms of processes, connected with cryomechanodestruction of connections between lipids and protein to the separate α-amino acids are described.The cheese fillings for “Pancake” confectionary and cheese snacks – falafels were manufactured on the base of cheese mass, received using the new method and enriching vegetable nanoadditives. They exceed the well-known analogs by chemical composition and are remarkable for the storage life, increased in 2 times. At the same time the significant part of substances (BAS and biopolymers) in cheese filings is in nanodimensional form (55…60 % of protein), especially, free α-amino acids, easily assimilated by the human organism. The recipes and technologies of sauces-dressings, sauces-deeps, cheese snacks and so on are also elaborated on the base of cheese mass, received by the new method

Estimation of the wear rate associated with ball mill of Mahd Ad Dahab Gold Mine, Saudi Arabia (KSA)

Purpose. This study aims to estimate the wear of the middle chrome grinding balls in both dry and wet grinding media. The selected ball mill for this study is located at Mahd Ad Dahab Gold Mine, Saudi Arabia. Methods. The amount of wear is determined based on the decrease in the balls weight with respect to grinding time. Findings. The results show that, the loss in the balls weight is proportionally related to their diameters. Also, the amount of wear is reduced by almost 12% when using wet grinding than dry medium. Originality. This study provides a methodology to evaluate the performance efficiency of grinding operation as a function of the amount of wear results in the grinding medium. Practical implications. Grinding is an intrinsic step in almost all mineral processing. Such step is very expensive; but, it is essentially required to reduce the size of the run-of-mine (ROM) material, to liberate valuable minerals from the ore matrix and to increase the surface area for higher reactivity. Thus, this study sheds light on the cost of wear rate associated with ball mill at Mahd Ad Dahab Gold Mine, Saudi Arabia, and its significant impact on the efficiency of grinding operation.Мета. Оцінка ступеня зносу куль у сухого та вологому подрібнюючому середовищі в залежності від їх технологічних параметрів на прикладі кульового млина золоторудної шахти Мад Ад Дахаб (Саудівська Аравія). Методика. Для досліджень використовувалися зразки кварцу золоторудної шахти Мад Ад Дахаб. Лабораторна щокова дробарка використовувалася для зменшення розміру зразків гірських порід до –3.15 мм, щоб бути придатними для подальшого подрібнення у кульовому млині. Дроблені зразки просіювали для отримання необхідної для параметрів лабораторного млина фракції –3.15 + 2.5 мм. Лабораторний кульовий млин із внутрішнім діаметром барабана 300 мм і його довжиною також 300 мм використовувався для досягнення вихідної фракції (80% –0.074 мм). Варіювався час подрібнення – 4, 8, 16, 24, 48, 72 і 96 годин. Знос куль розраховувався шляхом віднімання ваги куль після кожного випробування з маси початкових куль при завантаженні. Результати. Дослідження показали, що втрата ваги куль знаходиться у прямо пропорційній залежності від їх діаметру. Експериментально доведено, що при вологому подрібненні ступінь зносу куль на 12% менше, ніж при сухому. Встановлено, що швидкість зносу куль значно зростає зі збільшенням часу подрібнення, а коефі-цієнт зносу пропорційний діаметру куль. Найбільш висока швидкість зношування куль (0.858%) досягається при самому тривалому часі подрібнення (96 годин), найбільшому діаметрі куль (30 мм) та у сухому подріб-нюючому середовищі. Визначено коефіцієнт зносу куль в технологічному циклі збагачення рудника Мад Ад Дахаб, який становить близько 1.2% в день. Наукова новизна. Виявлено взаємозв’язок ступеня зносу подрібнюючих куль в залежності від їх діаметра і швидкості зносу від часу подрібнення зразків кварцу для кульового млина шахти Мад Ад Дахаб. Розроблено методологію оцінки ефективності процесу подрібнення в залежності від величини зносу подрібнюючого середовища. Практична значимість. Отримані результати дозволяють оцінити загальні експлуатаційні витрати, пов’язані зі зносом кульового млина та його значним впливом на ефективність процесу подрібнення. Корегування режимів та параметрів подрібнення є основою для зниження цих витрат.Цель. Оценка степени износа мелющих шаров в сухой и влажной мелющей среде в зависимости от их технологических параметров на примере шаровой мельницы золоторудной шахты Мад Ад Дахаб (Саудовская Аравия). Методика. Для исследований использовались образцы кварца золоторудной шахты Мад Ад Дахаб. Лабораторная щековая дробилка использовалась для уменьшения размера образцов горных пород до –3.15 мм, чтобы быть пригодными для последующего измельчения в шаровой мельнице. Дробленные образцы просеивались для получения необходимой для параметров лабораторной мельницы фракции –3.15 + 2.5 мм. Лабораторная шаровая мельница с внутренним диаметром барабана 300 мм и его длиной также 300 мм использовалась для достижения выходной фракции (80% –0.074 мм). Варьировалось время измельчения – 4, 8, 16, 24, 48, 72 и 96 часов. Износ шаров рассчитывался путем вычитания веса шаров после каждого испытания из массы начальных шаров при загрузке. Результаты. Исследования показали, что потеря веса шаров находится в прямо пропорциональной зависимости от их диаметра. Экспериментально доказано, что при влажном размоле степень истирания шаров на 12% меньше, чем при сухом. Установлено, что скорость износа шаров значительно возрастает по мере увеличения времени измельчения, а коэффициент износа пропорционален диаметру шаров. Наиболее высокая скорость изнашивания шаров (0.858%) достигается при самом длительном времени измельчения (96 часов), наибольшем диаметре шаров (30 мм) и в сухой среде измельчения. Определен коэффициент износа шаров в технологическом цикле обогащения рудника Мад Ад Дахаб, который составляет порядка 1.2% в день. Научная новизна. Выявлена взаимосвязь степени износа мелящих шаров в зависимости от их диаметра и скорости износа от времени измельчения образцов кварца для шаровой мельницы шахты Мад Ад Дахаб. Разработана методология оценки эффективности процесса измельчения в зависимости от величины износа мелющей среды. Практическая значимость. Полученные результаты позволяют оценить общие эксплуатационные затраты, связанные с износом шаровой мельницы и его значительным влиянием на эффективность процесса измельчения. Корректирование режимов и параметров измельчения является основой для снижения этих затрат.The author acknowledges the support of Mahd Ad Dahab Gold Mine (Metallurgical section), Saudi Arabia (KSA) for getting technical data used in this study. The author is grateful for their endless support and sincere cooperation

Molecular Dynamics of Comminution in Ball Mills

We investigate autogenous fragmentation of dry granular material in rotating cylinders using two-dimensional molecular dynamics. By evaluation of spatial force distributions achieved numerically for various rotation velocities we argue that comminution occurs mainly due to the existence of force chains. A statistical analysis of theses force chains explains the spatial distribution of comminution efficiency in ball mills as measured experimentally by Rothkegel and Rolf. For animated sequences of our simulations see http://summa.physik.hu-berlin.de/~kies/Research/RotatingCylinder/rotatingcylind er.htmlComment: 15 pages, 13 figure

Development of a New Method of Storage and Maximum Separation of Chlorophils From Chlorophylcontaining Vegetables at Reception of Healthfull Nanoproducts

The aim of the work is the development of a new way of deep processing of chlorophyll-containing vegetables that gives a possibility not only to preserve chlorophylls a and b and other biologically active substances (BAS) of raw materials, but also to transform hidden bound (inactive) forms of chlorophyll in the free easy-digestible form at getting steam-thermally processed semi-products and healthy food products in the nanoform.For achieving the aim, the complex effect of steam-thermal processing and mechanolysis at fine-dyspersed comminution using the new equipment was applied as an innovation for thermal processing and comminution.There was developed the new method of getting healthy products of chlorophyll-containing vegetables (broccoli, spinach, Brussels cabbage, green leguminous haricot bean), steam-thermally processed (by hot steam) in the steam-convectional stove and fine-dyspersed with high contents of chlorophylls and other BAS and prebiotics. The method is based on the complex effect of processes of thermodestruction, mechanodestruction and non-enzymatic catalysis on raw materials at fine-dyspersed comminution. It was demonstrated, that at steam thermal processing of chlorophyll-containing vegetables (CCV) in the steam-convectomat during 5 minutes, there takes place not only preservation of chlorophylls a and b, but more full separation (in 1,33…1,4 times) from the hidden (bound) form, comparing with fresh vegetables. There was elucidated the mechanism of this process. The more full extraction of hidden forms of β-carotene (2 times more than in fresh CCV) takes place in parallel.The essentially more effect of transforming hidden forms was revealed at fine-dyspersed comminution of steam-thermally processed CCV. It was demonstrated, that thermally processed nanoproducts of CCV contain 2…2,1 more chlorophylls a and b, 2,0…3,3 times more carotenoids in the bound form than fresh vegetables.The quality of obtained new types of fine-dyspersated steam-thermally processed green products as puree and soups-purees of CCV exceeds one of known analogues by contents of chlorophylls a and b, β-carotene and other BAS, which are in nanosize easy-digestible form.Using new types of fine-dyspersated purees of CCV, there was developed the new green line of healthy nanoproducts: soups-purees, nanodrinks, nanosorbets, sauces-dressings, sauces-deeps, ice-cream, snacks and so on. It was demonstrated, that new products exceed existing analogues by BAS content (chlorophylls, β-carotene, L-ascorbic acid, phenol compounds)