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Fire and Explosive Safety

#0355


Experimental and Theoretical Investigation of Filtration Ignition and Development of a Set of Criteria of Fire and Explosion Safety at Some Industrial and Agricultural Enterprises.

Tech Area / Field

  • MAT-EXP/Explosives/Materials

Status
8 Project completed

Registration date
12.01.1995

Completion date
09.07.2001

Senior Project Manager
Tocheny L V

Leading Institute
Institute of Structural Macrokinetics and Material Science, Russia, Moscow reg., Chernogolovka

Supporting institutes

  • Institute of Problems of Chemical Physics, Russia, Moscow reg., Chernogolovka

Collaborators

  • University of California / Department of Mechanical Engineering, USA, CA, Berkeley

Project summary

The Present proposal is aimed at the development of scientific fundamentals of accidents caused by filtration ignition. The term "filtration ignition" stands for a chemical interaction of porous materials with gaseous oxidant which causes combustion or self ignition of the materials ending in fires at the industrial facilities.

General theory of thermal explosion and ignition of a condensed matter was developed for homogeneous systems. In some cases, it was successfully applied to heterogeneous systems. The existing approach does not cover, however, a lot of phenomena in conventional processes which are essential for the environmental safety and ecology (e.g., at coal and peat storage, at storage and drying of products of wood-and-pulp industry; grain and products of its processing at drying and storage, a number of processes in powder metallurgy, thermal explosion synthesis, combustion synthesis etc.).

Methods of physical and mathematical simulation will be developed on the basis of the proposed theory. They are expected to allow reliable correlation between the experimental results obtained and actual scale of industrial technological conditions. Processes of heterogeneous oxidation and intrinsic thermal conversions of coal, peat and grain, and processes of high-temperature interaction of metals and solid and gaseous oxidants have been chosen for verification of the theory and methods developed within the present proposal.

The kinetics and mechanism of heterogeneous oxidation of metals, coal, peat, grain and products of its processing will be studied. The principal kinetic regularities determining the reaction rates will be derived. The values of heat release rates and exothermicity of oxidation processes will be determined esperimentally as well as the dependences of their rates on the major parameters of the system. Critical conditions and dynamic characteristics favorable for the development of thermal self-ignition of a large stock of coal and peat at their storage and grain drying and storage in the elevators or high-temperature synthesis of inorganic materials in various regimes will be determined on the base of the data obtained in the experimental research.

The Project realizationwill result in the development of the method of "a priori" evaluation of characteristics of filtration ignition and combustion of heterogeneous systems. It will include a computer based system wich will make possible calculations of parameters of interest by the user.Expected results:

Upon the completion of the project the following results are expected:

(1) A set of mathematical models describing the phenomena of heterogeneous system ignition accounting for the most universal and essential physicochemical processes (diffusion and filtration penetration of the oxidant, conductive and convective heat transfer, peculiar aspects of the heat release law); for practical applications some of the models will be implemented as computer programs;

(2) classification of thermal regimes, the area of their existence depending on thermophyslcal and kinetic characteristics, criteria of evaluation of the regimes, which are most hazardous in respect to the thermal selfignition under actual conditions within the given heterogeneous system;

(3) equations of heat release and kinetic parameters of high-temperature interaction of a porous or granular substances, illustrated by examples of oxidation of grain, coal, peat, metal powders, etc.;

(4) kinetic and activation parameters of each stage of hydration and dehydration of heterogeneous systems (grain, coal, peat) and its dependences on existing ambient conditions;

(5) experimental dependences of filtration ignition and critical conditions for combustion of a wide range of heterogeneous systems;

(6) criteria determining the origin of various thermal regimes of intensive reaction of grain and a guide to a proper choice of an aeration regime preventing or suppressing self-heating of grain;

(7) criteria determining the possibility of the material self-ignition at its drying by a hot gas flow and providing the choice of a the safe regime of the procedure;

(8) experimental methods of investigation of kinetic regularities of oxidation, characteristics of ignition and humidity of heterogeneous systems.

Finally, the results of the study will be used to develop criteria determining the onset of ignition, and the transition into flaming or explosions.These criteria could be applied to reduce the risk of fires and explosions in industrial, agricultural and urban environments.

The Role of Foreign Partner: Discussion of results of investigations. Other proposals on joint activities from the partners will be carefully considered.


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