A study of the polymerization of a monofunctional benzoxazine monomer based on phenol and aniline and its copolymerization with epoxy resins

In the work, the liquid monofunctional benzoxazine monomer based on phenol and aniline (P-a) was synthesized in melt and benzoxazine-epoxy compositions based on it were obtained. The processes of polymerization of a benzoxazine monomer and its copolymerization with epoxy resins of various structures and functionality in catalyzed and non-catalyzed systems have been investigated, and the rheological properties of the compositions have been evaluated. For the obtained polybenzoxazines and benzoxazine-epoxy copolymers, the thermal characteristics were determined, in particular, the glass transition temperature, the temperature of the onset of intense destruction and the coke residue. It has been established that the structure and functionality of epoxy resins have a different effect on the thermal characteristics of the copolymers.

Thermal Characteristics of the Waste Tire Pyrolysis Process

A significant annual growth in the number of spent car tires creates a serious environmental problem and calls for the need to continue searching for efficient resource-saving methods of their recycling. There is a growing number of efforts aimed at studying waste tire thermochemical conversion processes, including their pyrolysis to obtain valuable products, including a solid fraction (coke residue), liquid hydrocarbon fraction (pyrolysis oil), and noncondensable gaseous fraction (pyrolysis gas). Commercial and pilot pyrolysis plants and reactors are reviewed. A rotating drum reactor, shaft and screw reactors are the most promising solutions for implementing a continuous process. The development of new resource-saving solutions for the pyrolysis of waste tire requires knowledge of the thermal characteristics of this process, including information on the material and heat flows in the pyrolysis reactor. The composition and thermal properties of waste tire, as well as specific outputs, composition and fuel properties of pyrolysis product material flows, including pyrolysis gas, pyrolysis oil and coke residue, are presented. Information on the pyrolysis plant or reactor heat balance structure is either absent or incomplete. Based on the data available in the literature, the heat balance of a commercial pyrolysis plant equipped with screw reactors characterized by a specific thermal destruction heat of 0.640 MJ/(kg of tires) is drawn up and studied. The numerical analysis results correlate with the data published for the commercial-grade plant. Information on the pyrolysis chamber heat balance structure is correct enough for use in engineering practice. It has been found that the specific heat consumption for the pyrolysis process is 2.269 MJ/(kg of tires). This value can be used in numerically analyzing pyrolysis plants equipped with other designs of pyrolysis reactors.

Modification of the Recipe of Industrial PVC Plastic for Increasing its Fire Resistance

A directed modification of the formulation of industrial PVC plastic brands I40-13A was carried out using zinc borate, antimony oxide and chalk. It was found that the introduction of these additives into the compound can significantly increase the values of the oxygen index and the coke residue of the initial PVC plastic. It was found that a modification of the formulation of industrial PVC plastic leads not only to an increase in fire resistance, but also to a noticeable improvement in the basic physical and mechanical properties of the compound. It is shown that with a slight modification in the formulation of industrial PVC plastic compound it is possible to obtain materials that meet fire safety requirements

Modeling and Studying the Cooling of Waste Tire Solid Pyrolysis Products

Every year, 1.5 billion tires are produced around the world, and each of them eventually falls into the waste stream. The growing volume of waste tires and limited possibilities for their disposal generate the need to develop methods for recycling them. A review of papers addressing the waste tire recycling problem with the use of proposed mechanical and thermochemical processing methods is presented. It is shown that researchers take interest in pyrolysis as a technology for thermochemical conversion of waste tire to produce valuable products: a solid fraction represented by coke residue (carbon black), a liquid hydrocarbon fraction (pyrolysis oil), and non-condensing gaseous fraction (pyrolysis gas). In a number of published papers, focus is placed on improving the consumer properties of each fraction. Conditions under which the coke residue quality can be improved to the level of activated carbon are, and methods for implementing this are developed. The cooling of solid pyrolysis products can be a limiting factor for the pyrolysis plant operation. Unloading of the coke residue at increased temperatures with outdoor cooling can lead to its burning out. To develop an efficient coke residue cooling heat exchanger, it is necessary to know the physical properties of this substance. A method for determining the thermal conductivity of fine coke residue based on the use of physical and mathematical modeling of the cooling process has been developed and implemented. Experiments on studying the coke residue bed cooling process in air in the temperature range from 500 °C to the ambient temperature were carried out. The time dependences of temperature at several points of the bed layer are obtained. A measuring chamber mathematical model reproducing the experimental conditions is developed. By studying the model, it is possible to determine the coke residue thermal conductivity, which approximates the calculated cooling process temperature curves to those obtained in the experiment with satisfactory accuracy. Based on the analysis of experimental data, two temperature ranges are identified, and a linear dependence of the bed thermal conductivity on the temperature is found in each of them. The coefficients of these functions are determined by minimizing the response function using the Box--Wilson method. The obtained results are used for the development of industrial thermal power engineering facilities.

Effect of Solid Waste-Petroleum Coke Residue on the Hydration Reaction and Property of Concrete

Taking advantage of the desulfurization petroleum coke residue obtained from circulating fluidized bed boiler technology to replace a part of cement clinker and prepare the concrete can not only reduce the production of cement clinker and related CO2 emissions, but can also improve the utilization rate and utilization level of petroleum coke waste, which has good environmental and economic benefits. In this study, through the comprehensive analysis of a compressive strength test, X-ray diffraction test, and Cl− penetration resistance test, the hydration mechanism of desulfurized petroleum coke residue in concrete is revealed, and the optimum replacement ratios of single-added petroleum coke residue, multi-added petroleum coke residue, and mineral admixtures in concrete are evaluated and proposed. The results showed that mixing the 10% petroleum coke residue and 40% blast furnace slag would be most appropriate to replace the cement in concrete, thus the effective utilization of mineral admixtures and coke residue in concrete without strength loss could be realized.

Factors influencing the fire-resistance of epoxy compositions modified with epoxy-containing phosphazenes

The fire-resistance (State Standard GOST 28157-89, analogue of UL-94 test) of epoxy compositions based on D.E.R.-330 resin, isomethyltetrahydrophthalic anhydride and new epoxy-containing aryloxycyclotriphosphazenes was studied. Thermogravimetric analysis and microstructural studies of the coke residue formed during combustion were carried out. It has been determined that resistance to combustion of the cured compositions increases significantly as grows phosphazenes content in them. This is due both to the increase in the amount of porous coke residue formed during combustion (which acts as a barrier to flame propagation and heat transfer from the flame to the sample), and to the increase in the size of the pores formed therein. The obtained data can be used to create tough and flame-resistant composites for microelectronics, aviation and other industries.

TECHNICAL SOLUTIONS FOR DECREASING NOX EMISSIONS AT COAL THERMAL ELECTRIC POWER STATIONS

Most power-generating units at the Ukrainian thermal electric power stations were designed to burn hard coal mined in Ukraine, but today due to physical depreciation of the stations, those units are in non-project manoeuvring peaking operation what leads to the increase in both the specific fuel equivalent consumption and in harmful environmental emissions. The purpose of the research is to develop recommendations on the selection of optimal technical solutions aimed at reducing NOx emissions of oxides at the operating boilers of Burshtyn thermal electric power stations (TEPS) under the conditions of regime-technological measures. The article analyzes the main approaches to developing and selecting technological methods aimed at reducing emissions of coal thermal power stations and identifies prospects for their work in accordance with modern environmental requirements. The mechanisms of the transformations the organic fuel bound nitrogen undergoes when heated are determined. To reduce the amount of NOx emissions in combustion products, it is offered to apply the regime-technological mode of the preliminary heating the pulverized coal mixture. The results of thermo chemical studies of coal samples used at Burshtyn TEPS are presented. The temperature ranges are determined at which the maximum emissions of volatile combustible compounds takes place before to the upper flammability limit of the pulverized coal mixture is reached. It was determined that under the conditions of actual burning process, there is a clear sequence: a release of volatile components and burning of the coke residue; heating of the pulverized coal mixture; emission of volatile combustible compounds; their burning; heating of the coke residue up to initiation of its combustion; the coke residue burning-out. A pulverized coal stream is brought into the furnace without being preliminary mixed up with air. While burning the pulverized coal stream, fuel particles are heated and degassed in the zone immediately adjacent to the burner section where there is a shortage of oxygen, whereas the oxygen concentration in the flow is a gradually increasing. The regime-technological measures that are aimed at inhibiting NOx oxides formation by preliminary heat treatment of the pulverized coal mixture; they make it possible to obtain the maximum emissions of volatile combustible compounds before the upper flammability limit of the pulverized coal mixture is reached. It was found out that heat treatment should be carried out at temperature from 540-580° C. This is the temperatures range when the maximum emission of volatile combustible compounds takes place. After this combustion occur in an environment that is practically devoid of oxygen, where competing reactions of formation of volatile components and molecular nitrogen occur simultaneously. Thereafter, combustion can proceed in the practically oxygen-free environment with competing parallel reactions the forming volatile components and molecular nitrogen. This method allows to almost halving the concentration of nitrogen oxides in flue gases.

Thermal decomposition and oxidation of coal processing waste

To expand the database of kinetic parameters used for modeling the ignition of coals and their processing waste, promising coal-water slurry and coal-water slurry containing petrochemicals, studies have been performed on an experimental set-up using thermal gravimetric analysis. The research into coals of various ranks (flame, gas, coking, low-caking, and non-baking) and their processing waste (filter cakes) has yielded the decomposition parameters of the organic matter of coal and the formation of volatile substances as well as the oxidation parameters of the coke residue of all the coals and filter cakes under study. The studies cover the temperature range of the burning processes: 450-1300 K (for low-, medium-, and high-temperature burning modes). We have ascertained the dependence of kinetic parameters (pre-exponential factor and activation energy) describing the thermal decomposition of the organic matter of coal on the rank of coals and filter cakes. The findings show that the kinetic parameters describing the thermal decomposition of the organic matter of coal and its processing waste are practically the same. The thermokinetic parameters of coke residue oxidation are close for all the coals under study but they differ significantly for coke residue of filter cakes. The values of thermokinetic parameters obtained in the research are necessary to devise adequate physical and mathematical models and perform numerical studies (for mathematical modeling) of fuel slurry combustion processes in the combustion chambers of power plants.