Application of the Technique For Order Preference By Similarity To Ideal Solution Method in Determining Contract Employees to Become Permanent Employees

Refratech Mandala Perkasa (RMP) is a refractory cement manufacturing company. The company also operates in the manufacture of refractory cement made for repair of hot coatings, boilers, rotary kilns, incinerators, ovens and chemicals for steel metals, as well as ferrous & non ferrous foundries. In this company there are contract employees and permanent employees, contract employees are employees or workers whose working period is limited by a certain time according to the agreement within the company. While permanent employees are workers whose working period is approximately until they receive certain benefits according to the work agreement. This research was conducted to assist companies in decision support using the Topsis method in determining the appointment of contract employees to permanent employees based on predetermined criteria, namely Knowledge and Skills at work, Quantity and Quality of Work, Job Responsibilities, Initiatives in Work, and Compliance. on rules or discipline. The results of this study indicate that the determination of the ranking of prospective permanent employees can be obtained from the calculation results of the TOPSIS method, where the results of prospective employees are based on predetermined administrative criteria. Prospective permanent employees who have the highest rank have the right to be selected first. The accuracy of the implementation of the TOPSIS method on the system plays a major role in the effectiveness and efficiency of the company's services to consumers compared to before the system was implemented. With the implementation of this DSS system, it can help companies to make it easier to make decisions to survey prospective permanent employees and optimize employee performance.

PROBLEMS OF DRIVE MECHANISMS OF TECHNOLOGICAL SECTION OF FIRING AND GRINDING DURING CEMENT PRODUCTION

The analysis of conditions of long operation of driving mechanisms of technological sites of firing and grinding at cement production is carried out in the work. Typical variants of mutual arrangement of crown pair elements in case of rectilinear axis of rotation of technological unit body and axial beating of gear ring, as well as variant of mutual arrangement of crown gear elements in case of curved axis of rotation of rotary unit body are considered. A technique for determining the total angle of skew of the teeth of the crown pair, taking into account the errors of manufacture and the relative position of the wheels of the open gear. On the basis of experimental data the dependences of the total skew angle of the teeth of the crown pair as a function of the rotation angle of the gear crown are constructed and the possible range of the total skew angle under different operating conditions of the considered large rotating units is determined. To assess the stress-strain state of the elements of the ring gear mounted on the furnace body, a solid model was created in the software environment Solid Works Simulation. As an example, the dependences of the change in the magnitude of the deformation of the teeth of the toothed crown in the plane of action of a uniformly distributed normal force are determined. Practical recommendations for improving the design of the crown gear pair are offered. Keywords: rotary kilns; mills; crown gear; toothed crown; the angle of skew of the teeth; finite element method

Alternative Clinker Technologies for Reducing Carbon Emissions in Cement Industry: A Critical Review

Currently, the production of one ton of ordinary Portland cement (OPC) releases considerable amounts of CO2 into the atmosphere. As the need and demand for this material grows exponentially, it has become a challenge to increase its production at a time when climate-related problems represent a major global concern. The two main CO2 contributors in this process are fossil fuel combustion to heat the rotary kiln and the chemical reaction associated with the calcination process, in the production of the clinker, the main component of OPC. The current paper presents a critical review of the existent alternative clinker technologies (ACTs) that are under an investigation trial phase or under restricted use for niche applications and that lead to reduced emissions of CO2. Also, the possibility of transition of clinker production from traditional rotary kilns based on fuel combustion processes to electrification is discussed, since this may lead to the partial or even complete elimination of the CO2 combustion-related emissions, arising from the heating of the clinker kiln.

PERICLASE-SPINEL REFRACTORY MODIFIED ТІО2

Over the past decades, the development and improvement of refractory materials for lining high-temperature zones of rotary kilns continues. The main requirements for refractory products for lining rotary kilns for cement clinker roasting are: high density and ultimate compressive strength, low porosity and gas permeability, increased abrasion resistance, low thermal conductivity, high corrosion resistance and the ability to form a protective layer.Today, the main goal of modern researchers is to create a heat-resistant refractory with a flexible structure that ensures its integrity at high temperatures and mechanical loads, which have the ability to form a protective coating layer. In this work, a technological approach has been tested for introducing a vibro-milled modifier (briquette based on a high-alumina component and a titanium-containing additive) into the composition of the raw charge for periclase-spinel refractory in the form of a pre-synthesized product containing crystalline phases of the Al2O3 – TiO2 – FeO system. The basis for the production of periclase-spinel refractories modified with TiO2 is the four-component system MgO – Al2O3 – FeO – TiO2, on the basis of thermodynamic calculations of which the content of individual components of the charge was selected and the operational characteristics were predicted. The interrelation of physical and mechanical properties with the content of individual components in the initial charge warehouses is shown, and the directions of solid-phase processes with their participation are noted. The features of the microstructure of the sample material are noted in relation to the formation of an optimal set of properties. It is shown that the nature of the organization of micropores is favorable for increasing the thermal stability of the material, which complements the phase adaptation mechanism also with the structural effect of damping mechanical stresses during thermal cycling.

Granulated Expanded Glass Manufacturing Method Using Electromagnetic Waves

The paper presents experimental results obtained in the process of experimental manufacture in a microwave oven of lightweight granulated glass aggregates. The process was conducted to obtain the highest dimensional class (between 18-23 mm), the almost spherical shape of the aggregates being facilitated by cold processing of raw spherical pellets (between 11-15 mm) containing the powder mixture formed by glass waste, borax. calcium carbonate, aqueous sodium silicate solution and water addition and then rotation of the high electromagnetic wave susceptible ceramic crucible containing raw pellets during the heat treatment at temperatures between 822-835 ºC. In terms of quality, the expanded glass aggregate granules are almost similar to those manufactured in conventional rotary kilns heated by burning fuel, having the following characteristics: bulk density of 0.17 g/cm3, compressive strength of 2.2 MPa, thermal conductivity of 0.047 W/m·K, water absorption of 1 vol. % and pore size between 0.3-0.6 mm. The experimental product has not yet been tested as a raw material in the manufacture of some light weight concretes, but the use of similar granulated glass aggregates manufactured in the world confirms the ability of this aggregate type to produce light weight and energy efficient concretes for building construction.

Granulated Expanded Glass Manufacturing Method Using Electromagnetic Waves

The paper presents experimental results obtained in the process of experimental manufacture in a microwave oven of lightweight granulated glass aggregates. The process was conducted to obtain the highest dimensional class (between 18-23 mm), the almost spherical shape of the aggregates being facilitated by cold processing of raw spherical pellets (between 11-15 mm) containing the powder mixture formed by glass waste, borax. calcium carbonate, aqueous sodium silicate solution and water addition and then rotation of the high electromagnetic wave susceptible ceramic crucible containing raw pellets during the heat treatment at temperatures between 822-835 ºC. In terms of quality, the expanded glass aggregate granules are almost similar to those manufactured in conventional rotary kilns heated by burning fuel, having the following characteristics: bulk density of 0.17 g/cm3, compressive strength of 2.2 MPa, thermal conductivity of 0.047 W/m·K, water absorption of 1 vol. % and pore size between 0.3-0.6 mm. The experimental product has not yet been tested as a raw material in the manufacture of some light weight concretes, but the use of similar granulated glass aggregates manufactured in the world confirms the ability of this aggregate type to produce light weight and energy efficient concretes for building construction.

Design of Magnesia–Spinel Bricks for Improved Coating Adherence in Cement Rotary Kilns

It is well known that doloma bricks present better coating adherence than magnesia–spinel bricks when applied in cement rotary kilns, which is related to the different coating formation mechanism. The coating has an essential role in prolonged operation by protecting the refractory lining; thus, it is important to improve its adherence on magnesia–spinel refractories. The objective of this investigation is to study different compositions of magnesia–spinel bricks, achieved by varying additives used (calcined alumina, limestone, hematite and zirconia) and firing temperature (1500 °C and 1700 °C), to enhance the coating adherence measured by the sandwich test. The results have pointed out that the use of higher firing temperature contributes positively to physical adherence due to well-sintered refractory structure and elevated permeability, attaining coating strength superior to 2 MPa. For the chemical adherence, the addition of 2 wt.% of limestone increased the coating strength to 3 MPa, but resulted in a drop in hot properties. In this context, the most suitable approach to improve adherence of clinker coating and maintain hot properties in suitable levels is to increase the firing temperature.

ROTARY FURNACE LINING TO REDUCE THERMAL STRESS

The aim of the study is to reduce the thermal stresses of the lining in the areas adjacent to the flare sintering zone of rotary kilns intended for the production of cement clinker. It is proposed to use a lining made of parallel rows of alternating chamotte and chromium-magnesite refractory products to reduce thermal stresses in the areas adjacent to the flare sintering zone by up to 20%, increase the service life of the lining by 1.1-1.2 times as a result of equalizing thermal stresses in the areas of the sintering zone. Optimization of the initial raw material mixture, in turn, made it possible to reduce the temperature of clinker formation and led to fuel savings.