【 Weak current College 】 fire and explosion of stealth with fire source analysis

1 Introduction
Combustion and explosion in human life and the production process with great creativity, however, once they lose control, would lead to disaster. According to data provided by the Ministry of public security office, 1997, a total of over 13 million fire (not including forest and grassland fires), direct property loss of approximately 14 billion. Where the fire occurs (a death of 10 or more, or direct property losses of $ 1 million or more or the affected more than 50 families) 86, death 453, wound 358, direct property losses of nearly $ 400 million. According to another report, 1997, world-wide occurrence of the accident, the death of 22, 620, and result in major economic loss. Repeated occurrence of these shocking accident resulted in numerous casualties and enormous economic losses, cannot fail to draw attention to fire and explosion of great concern and reflection. Therefore, the study cited cause of fire and explosion of stealth with fire is of great practical significance.

2 combustion and explosion of conditions and real

Combustion is a heat-emitting of oxidation. Combustion is conditional, it must be on combustible, antioxidants and a fire that three basic conditions with and interaction into a combustion system, combustion will produce. And of the explosion, apart from certain industries, factories and enterprises of the explosion are combustible gas, flammable liquid and vapour and combustible dust and air (or oxygen) in case of a mixture of fire and explosion. Combustible substances chemical explosion must also possess the following three conditions: the existence of flammable substances a), including flammable gas, vapour or dust; b) flammable substances and air (or oxygen) mixed and reach the explosion limits, forming an explosive mixture; explosive mixtures in c) fire effect.

Analysis and comparison of combustion and combustible chemical explosion criteria can be seen, both are required to have fuel oxidizer and fire the three basic factors. Thus, combustion and chemical explosion, its essence is the same, are combustible substances of oxidation reactions. The Elimination of fuel and oxygen as agent or to fire these three conditions in any section, or avoid the interaction of three conditions is to prevent fire and explosive flammable mixtures of basic measures. Because flammable substances, particularly flammable gases, flammable liquids and flammable substances ignited dust, and hundreds of dangerous goods is widely used in the production and life, or as an energy source, or as raw materials. And oxidants air and oxygen is widespread, that is to say, with fire and chemical explosion, three essential conditions of the two conditions. Therefore, eliminating the ignition source is the basic measures for fire and explosion-proof in the most basic measures. In order to eliminate the fire source, we must first understand what is the source of fire. Hidden and dangerous to open fire "," it is particularly important to understand which is invisible to the source of fire.

3 stealth with fire source analysis

The fire source refers to a certain temperature and thermal energy. Industrial production process, there are a variety of fire and explosion of an ignition source, such as chemical enterprises common fire with fire, chemical reaction heat, chemical raw materials of decomposition temperature of spontaneous combustion, thermal radiation, surface, friction and impact, adiabatic compression, electrical equipment and wiring of overheating, sparks, lightning and electrostatic discharge, sunlight, etc. Where a chemical reaction heat of decomposition, chemical raw materials, radiation, etc. are spontaneous combustion as eye invisible stealth with fire. Following the perspective from the energy of the fire source for analysis of invisible.

3.1 chemical energy into heat energy

3.1.1 decomposition heat

Some substances while itself does not have the nature of combustion, but in the decomposition will release a large amount of heat, and therefore there is a potential of a fire. Ignited substances have water decomposition, produce combustible gas and heat, fire or explosion hazard. If such substances, substances occurring severe reactions, releasing high-heat the reaction of combustible gas heated to self-ignition point without ignition will ignition, such as sodium, calcium carbide, etc. Calcium carbide chemical reaction with water as follows:

CaC2+2H2O=C2H2+Ca(OH)2+Q

Where Q is a chemical reaction heat, heat the reaction heat of product can cause explosive nature of acetylene.

2C2H2+5O2=4CO2+2H2O+Q

Belong to this class of substances is lively and metal (such as lithium, sodium, potassium, etc.) and the metal hydrides, sulphur compounds, boron and phosphorus compounds, etc.

3.1.2 to spontaneous combustion

Combustible substance heated sanitary warm without flame effect. You can own the phenomenon known as spontaneous combustion. Exothermic chemical reaction will release a large amount of heat that may result from the surrounding combustible heat spontaneous combustion, such as on the building site with water because of quicklime, combustible materials caused by the heat of fire incidents, etc.

Spontaneous combustion can be divided into spontaneous ignition and heat itself. Itself is a spontaneous characteristics of fire from combustible internal out charring, spread, and heated to spontaneous combustion is often spread from external to internal. Combustible substances in oxidation induced spontaneous combustion is one of the main causes of fire. For example, coal spontaneous ignition of the fire, straw fire. Occurrence of spontaneous combustion of coal from the physical effects of heat and oxidation reaction caused by the build-up of heat. Prevent the main measures of spontaneous combustion of coal is to limit the height and the coal heap compaction. Plants of spontaneous combustion mainly biological effects cited, but in this process, there are chemical and physical effects. And in the compresses grease pure oxygen non contact, it is because of the violent release of thermal oxidation reaction can cause spontaneous combustion of oil fire. Prevent the primary method of spontaneous combustion of oil is the oil products (e.g., oilcloth, oil, cotton yarn, etc.) to tweak the storage to maximize heat dissipation area, rather than piling up or fold after another, indoor should have good ventilation. Anyone who installs a container containing oxygen, equipment, gas cylinders and management are not glued grease.

3.1.3 oxidizing and reducing agents

The most widespread of antioxidants is oxygen (the oxygen in the air). In addition, common oxidationAgents also have permanganate (such as potassium permanganate), chlorate and sodium chlorate, sodium hypochlorite salts, nitrate and nitrite and hydrogen peroxide, etc. Common reducer with zinc powder, potassium hydrogen sulfide, aldehydes, sncl2. In fire prevention regulations, specifically provides antioxidants and reducing agent is not stored with the library.

3.2 mechanical energy into heat energy

3.2.1 frictional and impact

Frictional and impact are often combustible gases, vapours and dusts, explosives, and other source of ignition and explosion. For example, machine bearing friction heating, iron and mechanical impact, steel tools of mutual impact, friction wheel etc can cause a fire. Even metal split it can produce sparks, caused by the escape of ignition of flammable gas or vapour.

3.2.2 adiabatic compression

Oxygen adiabatic compression temperature changes caused by this formula:

T2=T1(P2/P1)(k-1)k

Including T1, T2, respectively, before and after the adiabatic compression absolute temperature, P1 as adiabatic compression before local space pressure P2 as high pressure oxygen cylinder pressure, k is adiabatic index. At room temperature 15 ° c of various gases in the K value is oxygen 1.41, hydrogen, argon 1.67 1.04, carbon dioxide 1.30.

According to the above formula to find the oxygen cylinders at room temperature 15 ° c, pressure regulator in oxygen when 10Mpa adiabatic compression after the temperature is 548 ℃, which is higher than the temperature of many substances in combustion of oxygen, it may become an adiabatic compression ignition source, this should not be overlooked.

Electrical energy into heat energy 3.3

Electric fire and explosion in fire and explosion in occupies a large scale. Electrical equipment or lines appear in danger and arc temperature, electric spark, you become the cause of combustible gases, vapours and dust fire, explosion, a key to fire. Danger of electrical equipment, since the temperature of the main reasons is to run the process equipment and lines of short circuit, overload, bad, bad core heat, thermal, leakage, etc. Production and life of electrostatic phenomena is a common phenomenon, charged electrostatic protection of universally, it's dangerous for recognized. To prevent static discharge sparks caused by combustion and explosion, according to the production of specific circumstances to take appropriate measures against static electricity, for example, will tend to accumulate charge of metal equipment, pipes or containers such as installation and reliable grounding device to daochu electrostatic is to prevent static damage one of the basic measures. Increase plant or equipment, the air temperature is also essential to prevent static.

3.4 high temperature surface

Due to various causes of high temperature surface is also one of the source of fire.

3.5 other energy

In addition to the above discussion of the fire source, like sunlight, heat radiation, acoustic, etc. can also be blasting of a fire.

4 closing

In the social production and life, fire and explosion of the fire is very much. Eliminate the source of fire is fire and explosion prevention of the most basic measures to control the fire on the prevention of fire and explosion of great significance. Therefore we should carefully study the production and life might exist in all the fire source, particularly in invisibility with fire, avoid "accident" of fire and explosion.