This paper presents an analysis of the literature that studies the possibility of sewage sludge being used in the cement industry to reduce carbon dioxide emissions from cement production and thus solve the problem of disposing of sewage sludge so that it is no longer stored, avoiding soil pollution with heavy metals, and reducing pressure on the environment. The ash of sewage sludge is a good pozzolanic material, because when it is finely ground, it can be used as a partial substitute for Portland cement. This reduces waste storage costs. Sewage sludge ash was mixed with cement, and it was analyzed to determine whether the paste obtained could be used as a raw material in the cement industry. The presented results are on the hydration characteristics of the sewage sludge ash, the compressive strength of the cement determined after different days, the workability of the cement, and the porosity of the cement paste and the ash.

The widespread use of thermoplastic polymeric materials in various industrial fields has shown considerable interest in understanding the frictional and wear behavior. Among these polymers, polytetrafluoroethylene, also called PTFE, is a high-performance plastic that offers high chemical and thermal resistance and low friction. Additives such as fiberglass, carbon and graphite fillers are added to PTFE to significantly increase thermal conductivity, stiffness and self-lubricating properties. The materials subjected to the experimental analysis were pure PTFE, PTFE + 15% fiberglass, PTFE + carbon-graphite which slipped, under conditions of dry friction, on a sample of non-alloy steel construction SR EN 10025 from 1994. The tests were performed on a pin-on-disc tribometer. The effect of loading and sliding speed on the tribological properties of the polymer / steel combination under dry slip conditions was investigated and the specific wear rate for the experimental conditions was evaluated. The tests were performed at loads of the pin of Fn1=1N, Fn2=3N, Fn3=5N and Fn4=10N and sliding speeds of 1=1m/s, 2=3m/s. The results obtained indicated that the coefficient of friction decreases with increasing load. The wear rate for the analyzed materials was between 10-13...10-15 m2/N, the fiberglass reinforced PTFE material having the lowest wear rate. The present paper, through a comparative analysis of the friction and wear behavior, highlights the effects that the ingredients introduced in the basic material have, under the action of the exploitation factors (loading, sliding speed).

This article presents different solutions to reduce natural gas consumptions of the aluminum melting furnaces, through recovery of the heat from flue gases. In order to be able to analyze the recovery solutions, a mathematical model for energy balance of these furnaces was adapted. This mathematical model allows drawing up energy balances together with the main working technique and economical parameters of these types of furnaces, in actual conditions, and the same, under optimizing conditions, by applying recovery solutions. The mathematical model which can elaborate energy balances for aluminum melting furnaces, was transposed in M. Excel based software, where the quantification of different solutions for natural gas consumption saving is possible. One of the applications of this computer software for an aluminum melting furnace, either for actual working conditions or per upgraded furnace by use an air pre-heater, materials pre-heater, or a regenerative burner system, is presented in this article.

Due to the good properties related to wear resistance and vibration absorption capacity, the polymeric materials successfully replace the metallic materials. These are used in the production of sliding motion couples. Rubbing couples whose materials are polymer / steel based are of particular interest for technical use. In order to operate any mechanical system with sliding motion at optimum parameters, the indication of tribological characteristics for the materials of the frictional coupling is a convenient means of characterizing faster the tribological behavior, when the working conditions are modified. In this paper it is analyzed by the help of an experimental study, the factors affecting the wear of a coupling of polymer material/steel. Materials subjected to tribological analysis are polymeric materials, such as polyamide (PA) and polytetrafluoroethylene (PTFE) in contact with a metallic material (steel). The connection between the friction coefficient and the operating parameters (load, speed) and the rate of wear of these materials under experimental conditions will be established. Testing of the two materials was made on a pine stand on disc. The tribological tests were performed varying load and speed for a given length of friction, traveled pine. The wear of the two materials tested for the experimental conditions was measured. The experimental researches were carried out in dry friction conditions.

Knowing how to deform the Turcite thermoplastic material under the action of conical penetrators is a means of obtaining information on the processing of the counterpart (made from a metal material with higher hardness) with which it comes into contact.The paper aims to theoretically determine the depth of penetration of the thermoplastic material under the action of some conical penetrators and to establish the coefficient of static and kinetic friction under the action of these penetrators. The proposed model will be validated experimentally on a tribological stand made for this purpose.