The Research On Petroleum Coke Slurryability And The Influence Of Different Additives On Petroleum Coke Gasification Reactivity

Petroleum coke is the final solid residue of crude oil distillation. It accumulates most of the polluting ingredients. Therefore, certain disadvantageous properties of the material varying from high sulfur contents, to high heavy acromatic-to-aliphatic ratios are notable. Petroleum cokes should be treated with care for their polluting potential.This study focuses on the feasibility of petroleum coke feed to coal gasification plant. In-depth investigations into the slurry of petroleum coke and gasification process characteristics were processed. Great efforts were made to improve the slurryability and gasification reactivity of petroleum coke. Black liquor, coarse slag, fine ash and black water were used to improve the reactivity. The investigation included reaction characteristics of petroleum coke under high temperature, the co-gasification kinetic of lignite and petroleum coke and the blending methods on the co-gasification reactivity. The mechanism of the dispersant, stabilizer and catalyst was investigated in detail.(1) Black liquor was used as dispersant to prepare petroleum coke water slurry.The optimum dosage, the highest petroleum coke mass fraction, the stability and the rheological properties of petroleum coke water slurries were investigated. The experiments proved that the rheological behavior and static stability of the slurry were remarkably improved by using black liquor as additive at appropriate dosage. In order to clarify the mechanism, the influence of the dosages of black liquor on the contact angle and zeta potential was also measured. The slurry viscosity decreases with black liquor dosage increasing until reaching a minimum when black liquor dosage is 1 wt% of petroleum coke, then increases with black liquor dosage increasing. So the optimum dosage of black liquor was 1 wt% of petroleum coke. The highest petroleum coke concentration is 70 wt% in coke-water system. The stability is enhanced by adding black liquor compared with the slurry without black liquor, and the static stability increased with the increase of black liquor dosage.(2) Solid residues (fine slag) and black water of entrained bed coal gasification was used as stabilizers for petroleum coke slurry preparation. The results showed that, fine slag and black water could obviously improve the stability of the slurry, the stability time increases upon an increase of the dosage of fine slag dosage. The maximum solids concentration of the slurries could be higher than 70 wt% with the superior apparent viscosity, fluidity and stability available for practical utilization. All the slurries exhibit pseudo-plastic behavior, which is shear-thinning. The variations of rheological properties, contact angle, fluidity, stability and zeta potential of the coke-water slurry were investigated. And the stable mechanism of fine ash was analyzed.The inorganic matters in fine ash and black water are hydrophilic. They could make the contact angle decreased and improve the hydrophilicity of petroleum coke. The solid concentration lignite increased when the inorganic matters decreased. The large surface area of fine ash could provide more contact positions for particles, so it could show interruptive effect when the particles deposited. The polyacrylamide in fine ash could bridge partiles and prevent sendiment.(3) The gasification reactivity of petroleum coke was improved greatly by black liquor and black water. Fine slag and coarse slag exert lower catalytic effect because of their cation form. The gasification reactivity was affected by different loading methods in the order:wet grinding> dry grinding> physical impregnation> dry mix. The carbon in petroleum coke didn't attend reaction when the temperature was lower than 1000℃. Alkali metals could make the carbon in petroleum coke attend reaction at a lower temperature. The catalyst can exert catalytic effect from 780℃to 1300℃. When the temperature is higher than 780℃, the alkali metals was melted and flow like liquid, they can exert catalytic effect efficiently because of the fast diffusion rate. By attaching an alkali atom to the carbon edge, the net charge of carbon atoms is substantially increased because of conjugate effect. Since H2O and CO2 prefer to chemisorb on the atoms with larger densities. When the temperature is too high, the volatile of alkali metal became dramatic, the volatile of the alkali increased with the temperature. The variations of different catalysts, the dispersion of the catalyst, the BET surface area were analyzed. The catalytic mechanism of alkali metals was discussed in detail.(4)The factors which influence the co-gasification of petroleum coke and lignite were researched. The reactivity was significantly influenced by blending methods. Wet grinding is much effective than dry grinding. In wet grinding, the newly generated interface will be wrapped by solution instantaneously, and the AAEM species of lignite will be dissolved in water and loaded on petroleum coke. So the more association chances between petroleum coke and AAEM species make petroleum coke be catalyzed effectively.For wet grinding and dry grinding, long grinding time makes higher reactivity. And the sample in long grinding time has more association chances between petroleum coke and AAEM species. A mixed model which combines both random pore model and normal distribution function model is the most appropriate model for fitting the co-gasification data.