Research And Development Of Pressurized Submerged Combustion Evaporator

Pressurized submerged combustion is a new technology developed fromconventional submerged combustion, which overcomes many disadvantages andbreaks the limits for application fields of the traditional technology. However, thistechnology has not attracted experts’ much attention yet. To study its principle andstructural design, theoretical analysis and hot experiment are presented in this paper.The main work is as follow.Based on the analysis of energy conservation and environmental protection, thetotal energy consumption of pressurized submerged combustion evaporator iscompared with steam boiler used in oil fields. Results show that, as producing steamunder the condition of same pressure ranged from0.5-21MPa, pressurized submergedcombustion evaporator makes a better performance than the steam boiler in therespect of energy-saving. It proves that this technology is really an energy-savinginstrument, which not only owns the inherent strongpoint, but also has much brighterapplication prospect and the possibility to be applied in wilder fields.Pressurized submerged combustion evaporator was constructed and systematicexperiments were carried out to investigate the effects of pressure and burner structureon the system performance. In the respect of observing the pressure factor, thepressurized submerged combustion evaporator can work stably under the condition of0.15MPa and0.22MPa, respectively. As the pressure is0.22MPa, the toptemperature of the liquid is108℃, and the flue gas temperature is120℃. As thepressure is0.15MPa, the liquid temperature and the flue gas temperature isrespectively97℃and107℃. It shows that pressurized submerged combustiontechnology really achieves the expected targets. On the other side, although thepremixed burner has lots of advantages on combustion characterization and pollutantemissions than the diffusion burner, its flame instability is the most serious problem asthe back-pressure changes.In order to study the effects of pressure on combustion characteristics and helpthe design for the high back-pressure burner, numerical simulation of2-Daxisymmetric coflow CH4-air flame at pressures between5-30atmospheres is carriedout. For ideal gases, pressure is proportional to density value, which causes densityincrease sharply at high-pressure environment. The simulation results show that thevelocity of gases reduces with the pressure increases. Combustion reaction rate andtop flue gas temperature, as well as pollutants concentration, increase with pressure.This proves that high pressure will help improve the combustion characteristics inpressurized submerged combustion technology.Based on the bubble dynamics, by establishing mathematical models of bubble formation size and penetration depth from top submerged bubbling tube, it is seen thatbuoyancy force is the uppermost factor that influences the course of the bubbleformation and motion in liquid resulted from the great density contrast between gasand liquid. It is known that bubble penetration depth is closely related to the hold-uptime of bubble in liquid and the heat transfer intensity between hot gas and liquid.Increasing the speed of the flue gas can improve the depth. However, it will inducethe pressure variation which makes the burner instability.According to the phenomena of burner instability and low speed of flue gas inthe pressurized submerged combustion evaporator, a new burner structure withconvergent nozzle which can speed up the flue to the choking flow is designed. Thenew burner is able to avoid the combustion chamber pressure influenced by the backpressure variation. Numerical simulation for this burner is done and the results showthat the design idea is reasonable.