Combustion of petroleum waste in the marine boilers – Waste preparation technologies and exhaust emission. Part 1: Preparation technologies and their influence on waste morphology

Abstract

Petroleum waste occurring during operation of marine power systems in compliance with Marpol convention [1] needs to be collected on the ship, and the crew is obliged to run the record of their amount in so called oil record book. Collected waste is transported to the land or can be used as a fuel on the ships. Physico-chemical properties of petroleum waste containing different types of petroleum waste mixed in different proportions are difficult to define what makes it more difficult to choose a correct heating temperature in order to obtain required viscosity that would enable correct spraying and obtaining good combustion quality. Moreover, petroleum waste usually contains high amount of water, solid emissions and coagulants originating as a result of reactions between different types of petroleum products that are part of petroleum waste. Petroleum waste before and after homogenization have undergone laboratory tests by processing microscopic images of their samples with the use of specialized computer programme and spectral analysis in order to specify the morphology of the waste. The physico-chemical properties of the waste have also been determined. The results of the studies carried out showed a significant variety of physicochemical properties and composition of petroleum waste taken from the ships. Density in 15 °C changed in the range of 924.9–986.1 kg/m3, kinematic viscosity in 50 °C in the range 12.25–28.74 mm2/s, water content from 9.80 to 28.74 % mass, caloric value from 21.5 to 33.2 MJ/kg, resins in the range 12.1 – 38.2 % mass, and asphaltenes insoluble in n-hexane from 3.2 to 28.3 % mass. The size of asphaltene-resin particles and a number of water droplets of minimal and maximal measured diameter affecting the quality of spraying process and fuel combustion changed in the following range:Asphaltene-resin particlesWater droplets.Particle size: Diameter and number: 0.5 µm: 0.0 – 0.8 % volume 5–15 µm: (1.0 – 11) 103.100 µm: 0.0 – 6.8 % volume50–100 µm: (0.6 – 0.8) 103.This requires proper preparation process of waste before combustion. Taking into consid- eration the fact that the combustion quality control is facilitated, petroleum waste can be used as a fuel in the boilers. The article presents studies’ results of morphology of petroleum waste that undergoes cleaning process and process of preparation for combustion with different methods, their physicochemical properties as well as exhaust emissions in the marine boiler For this reason we designed and made the modernization of fuel system for the ship boiler on the specialized ship for collection and combustion of petroleum waste with use of static and dynamic homogenizer. We have carried out homogenization with use of each of homogenizers at their serial operation. After homogenization petroleum waste samples were subjected to laboratory studies with use of microscope pictures processed with use of computer programme and spectral analysis in order to determine their morphology. Physico-chemical properties of studied petroleum waste have been determined. It has been proventhat the best effects have been achieved when both static and dynamic homogenizer were working in series. The sizes of asphaltene-resin particles and number of water droplets of minimal and maximal measured diameter changed in the following range:Asphaltene-resin particlesWater droplets.Particle size: Diameter and number: 0.5 µm: 0.2 – 3.2 % volume 5–15 µm: (24 – 45) 103.100 µm: 0.0 – 0.1 % volume 50–100 µm: (0.0 – 0.0) 103.In order to obtain the correct spraying quality of petroleum waste and their combustion it is required that asphaltane-resin particles are of size in the range from 5 µm to 30 µm and water roplets of diameter up to 20 µm. The developed technology of preparing for petroleum waste combustion ensures achieving the required diameters. It needs to be highlighted that all particles of size between 50 and 100 µm underwent fragmentation and the number of particles fragmented to the diameter of 0.5 µm and size of 5–15 µm increased.The authors believe that the obtained research results are valuable and worth making available through publication for a wide audience. The research was carried out with the use of 6 types of specific marine petroleum waste collected from ships, which differ significantly in composition, water content and properties. The designed and constructed fuel installation enables to obtain the morphology of waste enabling good quality of its atomization and combustion in the boiler furnace chamber. The technology developed in this way and the wide scope of research carried out with the use of marine petroleum waste are not found in the literature.