Armin K. Silaen

Investigation of Heat Transfer and Gasification of Two Different Fuel Injectors in an Entrained Flow Coal Gasifier

One of the problems frequently encountered in a coal gasifier operation is fuel injector failure. Operating in extreme high pressure and high temperature, the typical fuel injector life span is 6-12 months. Numerical simulations are performed to study the flow and temperature fields in the vicinity of the injector tip and the metal temperature of two different fuel injector designs-one with a conical-nozzle tip and the other with a blunt tip—in a dry-,fed, entrained-flow coal gasifier. The complete 3D Navier-Stokes equations are solved. The instantaneous gasification model is employed to simulate three global heterogeneous reactions and three homogeneous reactions, including volatile combustion. The results show that the two different injectors give very different temperature and species distributions inside the gasifier. In the gasifier with the conical injector tip, the highest temperature inside the gasifier occurs at the center of the gasifier, whereas in the gasifier with the blunt-tip injector, the highest temperature occurs near the wall. There is a potential of flash-back combustion in the nozzle at the tip of the conical injector due to its premixing feature of fuel and oxidant in the nozzle. The highest temperatures on both injectors are the same, which is around 1600 K. However, the highest temperature on the conical-tip injector is concentrated at one location with an extended region of 30 mm between 1600 K and 1100 K, whereas on the blunt-tip injector, hot spots are scattered and the hot region (1600-1100 K) only extends about 3 mm. Experimental results support the simulated results and has demonstrated a short life of the conical-tip fuel injector and much extended life for the blunt-tip fuel injector.

Top Fuel Injection Design in an Entrained-Flow Coal Gasifier Guided by Numerical Simulations

A computational fluid dynamics scheme is employed to simulate the effects of potential fuel injection techniques on gasification performance. The objective is to help design the top-loaded fuel injection arrangement for an entrained-flow gasifier using coal water slurry as the input feedstock. Two specific arrangements are investigated: (a) coaxial dual jet impingement with slurry coal in the center and oxygen in the outer jet and (b) four jet impingement with two single slurry coal jets and two single oxygen jets. When the heterogeneous finite-rate solid-gas reaction scheme is implemented, it is discovered that the particle collision model cannot be implemented with the heterogeneous gasification scheme in the present computational model. The instantaneous gasification model is later employed to examine the particle collision phenomenon by implementing the particle collision model, in which the coal (consisting of carbon and volatiles) is injected as gas, and the water is injected as droplets. The result of droplet tracks shows that the droplets are not bounced around, as speculated, at the intersection where the jets meet, and majority of the droplets pass through the jet impingement section and hit the wall as in the finite-rate case. This implies that the results of the finite rate are acceptable even though the particle collision model is not implemented. The finite-rate result actually presents a worst-case scenario for predicting wall erosion. The particle tracks for both the two concentric and four separate injection configurations show that the coal particles hit the wall and can accelerate the deterioration of the refractory bricks. The case employing two concentric injections provides better fuel-oxidant mixing and higher heat-I ing values than the case using four separate injections.

CFD Study of Gas-Liquid Phase Interaction Inside a Submerged Lance Smelting Furnace for Copper Smelting

Bath smelting technology, such as the submerged lance smelting furnace, is used in the modern copper making industry. The first submerged lance smelting furnace developed by Dongying Fangyuan Nonferrous Metals Co., Ltd has shown potential for high productivity and energy savings. In this study, computational fluid dynamics (CFD) was applied to investigate the current design of the furnace. A three-dimensional multiphase CFD model was developed to study the interaction between injected gas and the liquid bath. The multiphase Eulerian model was used for simulating gas/liquid two-phase flow. The flow pattern in the submerged lance smelting furnace indicated rapid flow development and strong turbulent interactions between the gas and liquid phases. The model was validated based on a water model experiment of the mixing process. Mixing times from the simulation results show good agreement with experimental data. Additionally, based on this model, the gas residence time and liquid copper matte splashing phenomena under varying gas flow rates were investigated.

CFD Modeling of Flow and Chemical Reactions in a Submerged Lance Copper Smelting Furnace

The submerged lance smelting furnace (SLS) for copper smelting has been developed and used by Dongying Fangyuan Nonferrous Metals Co., Ltd. The technology has shown advantages such as high oxygen enrichment, good feed adaptability, short processing time, high SO2 concentration for acid plant, and auto-thermal operation. In this study, computational fluid dynamics (CFD) was used to investigate the gas/matte two-phase flow characteristics and the chemical reactions in the SLS during typical operational conditions. The Eulerian-Eulerian approach was employed to model the phase interactions. The chemical reactions were modeled by calculating the mass transfer coefficients and using the eddy-dissipation model. The simulation was conducted using the commercial software ANSYS Fluent®. The developed CFD model is able to predict the flow, temperature, and species distributions inside the SLS under various operating conditions.

Investigation of Combustion and Heat Transfer in an Industrial Reheating Furnace Using CFD

The reheating furnace is used to reheat steel slabs to a target rolling temperature in the steelmaking process. The flue gas temperature distribution inside the reheating furnace is one of the main determining factors of the furnace performance. In this study, a three-dimensional steady-state computational fluid dynamics (CFD) model was developed to investigate the flow field in an industrial reheating furnace. The commercial software ANSYS Fluent® was employed to solve the transport equations to calculate gas flow, combustion and heat transfer. The simulation was carried out based on real operating conditions and data collected from industrial manufacturers. Validation of the CFD model was conducted by comparing the temperature prediction by the model with the real thermocouple measurements. The simulation results indicate that the combustion gas flow characteristics inside the reheating furnace have a significant effect on the temperature distribution. The effect of fuel/oxidant input flow rate on the temperature distribution was also investigated.

Numerical Investigation of Thermoelectric Topping Cycle in Coal Fired Power Plant Boiler

Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ∼2250 K (adiabatic) and the high pressure steam temperature up to 900 K. This paper investigates the potential of harvesting this energy to produce additional electrical power using solid-state thermoelectric (TE) power generators placed into the gap between the flame temperature and the steam temperature. Three dimensional (3D) numerical model of a simplified TE module is developed. Different dimensions of fin added to the TE module were investigated to maximize the additional electrical power generation without sacrificing the boiler efficiency.Copyright

CFD Analysis of Blast Furnace Operating Condition Impacts on Operational Efficiency

Blast furnaces are counter-current chemical reactors used to reduce iron ore into liquid iron. Hot reduction gases are blasted through a burden consisting of iron ore pellets, slag, flux, and coke. The chemical reactions that occur through the furnace reduce the iron ore pellets into liquid iron as they descend through the furnace. Experimental studies and live operation measurements can be extremely difficult to perform on a blast furnace due to the extremely harsh environment generated by the operational process. Computational Fluid Dynamics (CFD) modeling has been developed and applied to simulate the complex multiphase reacting flow inside a blast furnace shaft. The model is able to predict the burden distribution pattern, Cohesive Zone (CZ) shape, gas reduction utilization, coke rate, and other operational conditions. This paper details the application of this model to investigate the effects of coke size and porosity, iron ore pellet size, and burden descent speed on blast furnace efficiency.

Numerical Model of FGD Unit in Power Plant

Numerical model technique was employed to model the reactive multiphase flow inside a flue gas desulfurization (FGD) unit. The model was divided into two parts: (a) the absorption tower model and (b) the reaction tank model. Eulerian-Lagrangian approach was employed in the absorption tower model. Discrete phase model was used to model the limestone slurry droplets and the SO2 absorption by the limestone slurry was included in the model. Eulerian-Eulerian approach was employed in the reaction tank model where the oxidation of the slurry to form gypsum was modeled. The absorption tower model and the reaction tank model are coupled. Parametric studies were performed to investigate the SO2 removal efficiency of the unit.Copyright

Numerical Simulation of an Industrial Fluid Catalytic Cracking Riser

A three-dimensional multi-phase, multi-species, turbulent reacting flow computational fluid dynamics (CFD) model was established to simulate fluid catalytic cracking (FCC) process inside an industrial FCC riser. FCC catalyst, oil, and air were used as the solid, liquid, and gas phases, respectively. A hybrid technique for coupling chemical kinetics and hydrodynamics computations was employed, where the simulation was divided into (a) reacting flow hydrodynamic simulation with a small but sufficient number of lumped reactions to compute flow filed properties and (b) and reacting flow hydrodynamics with many subspecies where complex chemical reactions occur. A four-lump kinetic model was used for the major species and a fourteen-lump kinetic model was used for the subspecies model. The results were validated against measurements from the actual riser.Copyright

Numerical Model of Thermoelectric Topping Cycle of Coal Fired Power Plant

Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ∼2250 K (adiabatic) and the high pressure steam temperature up to 900 K. However, some of this energy can be harvested using solid-state thermoelectric (TE) power generators which are placed into the gap between the flame temperature and the steam temperature that produce additional electrical power. This study investigates the potential placement of TE on water tube wall inside a boiler at a coal fired power plant. Three dimensional (3D) numerical model of a simplified TE module is developed and hot gas temperature and steam temperature from the boiler are used as boundary conditions at the hot side and cold side of the TE. The numerical results are compared with analytical calculations. The 3D effects of the thermal spreading in the TE module are investigated. Parameters such as TE leg cross-section area and TE fill factor are examined in order to maximize the electrical power production of the TE without sacrificing the boiler efficiency (i.e., reducing the steam temperature). The study also looks into the various locations inside the boiler that have good potential for TE installation.Copyright