低温硫铁化合物氧化诱导期试验研究

以设备腐蚀样品和均相沉淀样品为研究对象,运用差示扫描量热法测定硫铁化合物的氧化诱导期,并考察了粒径、升温速率和空气流量对硫铁化合物氧化诱导期的影响。结果表明,两种样品在125~200℃范围内均处于活跃的自热阶段,热稳定性较差,样品粒径在44~74μm范围内,升温速率越小,空气流量越大,样品自燃倾向性越高。

Experimental study on the oxidation induction time of ferrous sulfide under low temperatures

The present paper is aimed to identify and determine the oxidation induction time of iron sulfides.As is known,spontaneous combustion of iron sulfides should account for the principal cause leading to fire accidents for oil tanks with sulfur.Seeing the actual need,we have managed to apply the method of differential scanning calorimeters for simulating the oxidized pyrolysis process and the homogeneous precipitation samples to solve the problem by analyzing and controlling the tank or device corrosion by regulating the temperature concerned.In so doing,we have first of all worked out the oxidation induction time of iron sulfides by using the external tangent method.At the same time,we have also investigated the influential factors,such as the particle size,the heating rate and the air flow rate on the oxidation induction time of the iron sulfides.The results of our simulation show that the oxidation reaction proves highly intensive with the oxidation induction time-length being very brief at the extremely high oxidation induction temperature.Therefore,the corrosion and homogeneous precipitation may lead to active self-heating and poor thermal stability in a temperature range of 125 ℃ to 200 ℃,whereas the linear fit tends to be arranged just at lg(OIT) and 1/T in terms of the Dolye's induction period equation of the oxidation reaction.But according to the fitting curve,the equation of the corrosion rate of the sample container tends to be:f(T) =188.02T + 0.1109,whereas that of the homogeneous precipitation sample should be equal to f(T) =148.14T + 0.4419 in terms of the ultrafine particle size and the largest particles may go against the oxidation reaction of iron sulfur compounds.But when the sample size is in a range of 44-74μ m,the iron sulfides may incline to have a high spontaneous combustion tendency.In such a sifuation,the oxidation induction time of the testing sample and the heating rate may turn to be positively correlated between the combined effect of the heat-absorption and the self oxidation of the heat release.Since the air flow is beneficial for the diffusion of the oxygen molecules and prone to promote the oxidation process,the two samples,when staying in the self-heating stage or the stage of active self-combustion with the particle sizes being in a range of 44-74 μm,the slower the rate of the temperature rising and the greater the volume of the air movement are,the more intensive the self combustion of the sample would be.According to the fitting curve,the equation of the equipment corrosion sample is f(T) =188.02T +0.1109 and the equation of the homogeneous precipitation sample is f(T) =148.14T + 0.4419.samples at ultrafine particle size and sample the large particles go against the oxidation reaction of iron sulfur compounds.But when sample size is at the range of 44-74 μm,iron sulfides may have higher spontaneous combustion tendency.The correlation between the oxidation induction time of sample and the heating rate is positive under the combined effect of absorbing system heat and the self oxidation heat release.The flow of air is beneficial to the diffusion of oxygen molecules,promoting the process of oxidation.Therefore,it was found that the tends of induction period for oxidation reaction on equipment corrosion sample.But,when the sample sizes are limited to the range of 44-74 μm,the iron sulfides may tend to have higher spontaneous combustion tendency.The correlation between the oxidation induction time of the sample and its heating rate chosen tend to be positive under the combined effects of the heat release of the absorption system and its own self oxidation.It implies that,in the above said process,the air flow is beneficial for the diffusion of the oxygen molecules,that is to say,it helps to promote the process of oxidation.Therefore,it can also be inferred that the induction period for the oxidation reaction is endowed with somewhat effect on the corrosion of the sampling device.