Self-heating of dried industrial tannery wastewater sludge induced by pyrophoric iron sulfides formation

Numerical Analysis of the Spontaneous Combustion Accidents of Oil Storage Tanks Containing Sulfur

In order to study various influencing factors of spontaneous combustion accidents of sulfur-containing oil storage tanks, this paper constructed a two-dimensional model of the storage tank wall by COMSOL Multiphysics software. The proposed model takes temperature change trend as an observation index to explore the heat transfer process of the tank wall. By fitting the function curve of heat release with oxidation reaction temperature of sulfur corrosion products and comparing with constant heat sources, it is found that heat source intensity will affect the temperature growth trend of tank spontaneous combustion. In addition, the air convection heat transfer coefficient represents the interference degree of external environment to the spontaneous combustion heating process, and the wall heating rate decreases with the increase of air convection heat transfer coefficient. The different heat release rates in varying oxidation stages will lead to distinct temperature growth trends. The larger the air convection heat transfer coefficient, the greater the temperature difference between the inner and outer walls of the tank, which is not conducive to the detection of the abnormal temperature of the heat source. The difference of thermal insulation and thermal conductivity of tank materials also affects the wall heat transfer, so the material properties should be considered comprehensively in actual production. The research results can provide a research basis and a theoretical basis for monitoring, prevention, and control of spontaneous combustion of sour oil storage tanks.

Characterization, classification and stabilization of industrial wastes for hazard property HP3: Flammable self-heating; assessment and evaluation of 50 industrial wastes

A pilot assessment procedure is introduced and used for the self-heating behavior of 50 industrial wastes based on UN N. 4 test and their subsequent classification as hazardous or non-hazardous, according to the Waste Framework Directive (WFD). When a waste contains self-heating substances it is classified as 'Hazardous Waste' by hazard property HP3: Flammable according to Regulation (EU) No 1357/2014. Self-heating is considered as a precursor stage to spontaneous ignition and fire under certain circumstances, with environmental effects and both human and property losses. The influence of the following parameters on the self-heating nature of the industrials wastes was assessed: temperature, granulometry and moisture. It was demonstrated that although some wastes are classified as absolute non-hazardous (ANH), they may still exhibit self-heating and thus must be classified as hazardous by HP3. It seems that there is a gap between the definition of hazardous waste according to WFD and the entry type of List of Wastes (LoW), regarding the ANH entries. This was found to be the case with two of the wastes examined. Finally, for a waste exhibiting self-heating, experiments were performed with addition of inert material, in order to secure safe management of the waste.

Effect of sewage sludge composition on the susceptibility to spontaneous combustion

The different technologies applied to the sewage sludge management have in common a first step devoted to the storage. In the case of dried sludges, this storage leads to important safety concerns because of the explosive character of the resulting dusts. In order to ensure safety in the storage step, it is necessary to evaluate the spontaneous combustion trends on terms of measurable chemical and physical properties of the dried sludges. In order to accomplish this scope, twelve samples from different wastewater treatment plants were characterized, correlating the susceptibility to spontaneous combustion with both the sludge composition and the heating value. Equations traditionally used for coals were used to determine the higher heating value from the chemical composition, finding as main source of error the high oxygen content of the sludge samples. Concerning the thermal susceptibility, different parameters were obtained (Maciejasz Index, induction temperature, maximum weight loss temperature, characteristic temperature and activation energy), being in all cases the spontaneous combustions favored by high H/C and low O/C ratios. Likewise, the presence of sulphur in the dried sludge was found to increase the thermal susceptibility of the material. This effect is tentatively explained with the formation of pyrophoric iron sulfides.

Combined heating and chemical treatment for oil recovery from aging crude oil

With increasing use of chemical oil displacement agents in tertiary recovery and the application of various demulsifiers for crude oil dehydration, a large amount of aging crude oil containing a high ratio of water is produced, and it is very difficult for processing and utilisation. In this article, we chose aging crude oil samples from a union station in an oilfield in China. Sample composition was analysed to demonstrate that the key of aging crude oil dehydration is the removal of solid impurities. Thus, an efficient method of combining heating and chemical treatments was developed to treat aging crude oil. It includes two steps: The first step is washing of aging crude oil with hot water with sodium dodecylbenzene sulfonate; the second step is chemical demulsification of the above mixture with hydrochloric acid and sodium chloride solution. The result showed that 2.9% of solid impurities and 29.2% of water were removed in the first step; 27.2% of oil, 24.3% of water, and 3.47% of solid impurities in the aging crude oil were recycled in the second step. A total 87.07% of aging crude oil could be solved with this method. The present two-step treatment method can ensure that the dehydration process runs normally and efficiently in the union station, making it a promising method in the recycling of aging crude oil.