Cold-modeling study of a circulating fluidized bed reactor for flue gas desulfurization (FGD)

Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process performance is to employ fluidized bed reaction in replacement of entrained bed reaction on normally used in cool side desulfurizaiton. This paper describes cold modeling study of a circulating fluidized bed reactor. Several aspects of the problem are discussed: fluidization behavior of CaO, attrition of the sorbent and solids entrainment from the fluidized bed. Mechanisms and key controlling parameters are identified, and an integral model based on rate of attrition and mass balance is developed for predicting steady state mass flows and particle size distributions of the system. A process flow scheme is finally presented for conducting desulfurization tests in the second stage of the study.

Numerical Calculations and Cold Tests for Flow Fields of a 220t/h Retrofitted Oil-Boiler

In this paper, cold simulation experiments and numerical calculations are conducted to predict 3 D flow field aerodynamics for an oil furnace after being retrofitted due to its fuel variation. K ε model and SIMPLE program under body fit coordination (BFC) system, in which TTM non orthogonal method is used to control the irregular geometric boundary, are adopted to solve the control equations. Model tests are conducted to check the calculation results, showing that they are in agreement with each other. Three different alternatives with different side window locations are also calculated to optimize the designs. The field retrofitting results show that the combination of cold tests with numerical calculations has prosperous application in retrofitting or renewing medium and small boilers.

Cold Model Study and Commercial Test on Novel Vapor-Liquid Distributor of Hydroprocessing Reactor

A novel vapor-liquid distributor was developed on the basis of sufficient study on the existing distributors applied in hydroprocessing reactors. The cold model test data showed that the fluid distribution performance of the novel vapor-liquid distributor was evidently better than the traditional one. Com- mercial tests of the new distributor were carded out in the 300 kt/a gas oil hydrotreating reactor at SINOPEC Changling Branch Company, showing that the new vapor-liquid distributor could improve the fluid distribution, promote the hydrotreating efficiency and lead to better performance than the traditional one.

Model test study of frost heaving pressures in tunnels excavated in fractured rock mass in cold regions

Based on the similarity theory, taking the horseshoe, city-gate and round linings as examples, the value and distribution regularities of normal frost heaving pressures （hereinafter as frost heaving pressures） in tunnels excavated in fractured rock mass in cold regions under different constraints and freezing depths were studied by a test model. It was found that the larger the frozen depth, the larger the frost heaving pressure, and the stronger the top constraint, the larger the frost heaving pressure. For the horseshoe lining and city-gate lining, the top constraint has a greater effect on the frost heaving pressures on the arch and the inverted arch. For the round lining, the influences of the top constraint on the frost heaving pressure in all linings are almost the same. The frost heaving pressure is maximum on the city-gate lining and minimal on the round lining. The largest frost heaving pressure all occur near the foot of the inverted arch for the three kinds of lining. Thus, the test data basically coincide with the observed in situ data.

A Cold Model Aerodynamical Test of Air-Staged Combustion in a Tangential Firing Utility Boiler

The purpose of this paper is to present the flow field in the 300MW tangential firing utility boiler that used the Low NOx Concentric Firing System （LNCFS）. Using the method of cold isothermal simulation ensures the geometric and boundary condition similarity. At the same time the condition of self-modeling is met. The experimental results show that the mixture of primary air and secondary air becomes slower, the average turbulence magnitude the relative diameter of the tangential firing enlarges of the main combustion zone becomes less and when the secondary air deflection angle increases When the velocity pressure ratio of the secondary air to the primary air （p2/p1） enlarges, the mixture of the secondary air and the primary air becomes stronger, the average turbulence magnitude of the main combustion zone increases, and the relative diameter of the tangential firing becomes larger. Because the over fire air （OFA） laid out near the wall has a powerful penetration, the relative diameter of the tangential firing on the section of the OFA is very little, but the average turbulence magnitude is great. When the velocity pressure ratio of the OFA to the primary air POFA/p1 increases, the relative diameter of the tangential firing on the section of the OFA grows little, the average turbulence magnitude becomes larger and the penetration of the OFA becomes more powerful.

VOLUMETRIC MASS TRANSFER COEFFICIENT BETWEEN SLAG AND METAL IN COMBINED BLOWING CONVERTER

The effects of operation parameters of combined blowing converter on the volumetric mass transfer coefficient between slag and steel are studied with a cold model with water simulating steel, oil simulating slag and benzoic acid as the transferred substance between water and oil. The results show that, with lance level of 2.1m and the top blowing rate of 25000Nm3/h, the volumetric mass transfer coefficient changes most significantly when the bottom blowing rate ranges from 384 to 540Nm3/h. The volumetric mass transfer coefficient reaches its maximum when the lance level is 2.1m, the top blowing rates is 30000Nm3/h, and the bottom blowing rate is 384Nm3/h with tuyeres located symmetrically at 0.66D of the converter bottom.

Study of a ceramic burner for shaftless stoves

A multi-burner-port annular flameless ceramic burner （MAFCB） of the shaftless stove for blast furnaces was designed. The characteristics of pressure drop, homogeneousness of the flows at burner ports, and distribution of the flows in the chambers and joint were studied by cold model experiments. This type of ceramic burner was successfully applied in 6# blast furnace at Liuzhou Iron ＆ Steel Co. Ltd. （LISC） and this practice proved that it could be used in the hot blast stove and other stoves with a higher efficiency and a higher steadiness of hot blast temperature at 1200℃. With the combustion of blast furnace gas alone, the thermal efficiency was up to 78.95%, saving energy remarkably.

Flow zone distribution and mixing time in a Peirce-Smith copper converter

Peirce-Smith copper converting involves complex multiphase flow and mixing.In this work,the flow zone distribution and mixing time in a Peirce-Smith copper converter were investigated in a 1:5 scaled cold model.Flow field distribution,including dead,splashing,and strong-loop zones,were measured,and a dimensionless equation was established to determine the correlation of the effects of stirring and mixing energy with an error of<5%.Four positions in the bath,namely,injection,splashing,strong-loop,and dead zones,were selected to add a hollow salt powder tracer and measure the mixing time.Injecting a quartz flux through tuyeres or into the backflow point of the splashing wave through a chute was recommended instead of adding it through a crane hopper from the top of the furnace to improve the slag-making reaction.

Single Parameter Model for Cosmic Scale Photon Redshift in a Closed Universe

A successful single parameter model has been formulated to match the observations of photons from type 1a supernovae which were previously used to corroborate the standard 𝛬 cold dark matter model. The new single parameter model extrapolates all the way back to the cosmic background radiation (CMB) without requiring a separate model to describe inflation of the space dimensions after the Big Bang. This single parameter model assumes that spacetime forms a finite symmetrical manifold with positive curvature. For the spacetime manifold to be finite, the time dimension must also have positive curvature. This model was formulated to consider whether the curvature of the time dimension may be related to the curvature of the space dimensions. This possibility is not considered in the more complex models previously used to fit the available redshift data. The geometry for the finite spacetime manifold was selected to be compatible with the Friedmann equation with positive curvature. The manifold shape was motivated by an assumption that there exists a matter hemisphere (when considering time together with a single space dimension) and an antimatter hemisphere to give a symmetrical and spherical overall spacetime manifold. Hence, the space dimension expands from a pole to the equator, at a maximum value for the time dimension. This is analogous to the expansion of a circle of latitude on a globe from a pole to the equator. The three space dimensions are identical so that any arbitrary single space direction may be selected. The initial intention was to modify the assumed geometry for the spacetime manifold to account for the presence of matter. It was surprisingly found that, within the error of the reported measurements, no further modification was necessary to fit the data. The Friedmann equation reduces to the Schwarzschild equation at the equator so this can be used to predict the total amount of mass in the Universe. The resulting prediction is of the order of 1051 kg. The corresponding density of matter at the current time is approximately 1.6 × 10-28 kg·m-3.

Influence of drag laws on pressure and bed material recirculation rate in a cold flow model of an 8 MW dual fluidized bed system by means of CPFD

A cold flow model of an 8 MW dual fluidized bed （DFB） system is simulated using the commercial compu- tational particle fluid dynamics （CPFD） software package Barracuda. The DFB system comprises a bubbling bed connected to a fast fluidized bed with the bed material circulating between them. As the hydrodynam- ics in hot DFB plants are complex because of high temperatures and many chemical reaction processes, cold flow models are used. Performing numerical simulations of cold flows enables a focus on the hydro- dynamics as the chemistry and heat and mass transfer processes can be put aside. The drag law has a major influence on the hydrodynamics, and therefore its influence on pressure, particle distribution, and bed material recirculation rate is calculated using Barracuda and its results are compared with experimental results. The drag laws used were energy-minimization multiscale （EMMS）, Ganser, Turton-Levenspiel, and a combination of Wen-Yu]Ergun. Eleven operating points were chosen for that study and each was calculated with the aforementioned drag laws. The EMMS drag law best predicted the pressure and dis- tribution of the bed material in the different parts of the DFB system. For predicting the bed material recirculation rate, the Ganser drag law showed the best results. However, the drag laws often were not able to predict the experimentally found trends of the bed material recirculation rate. Indeed, the drag law significantly influences the hydrodynamic outcomes in a DFB system and must be chosen carefully to obtain meaningful simulation results. More research may enable recommendations as to which drag law is useful in simulations ofa DFB system with CPFD.

Effect of fluidizing velocity on gas bypass and solid fraction in a dual fluidized bed gasifier and a cold model

Dual fluidized bed gasifiers （DFBG） are effective in producing nitrogen-free syngas from biomass. How- ever, to improve the gasifier performance, pressure drops and solid fractions within the DFBG system need to be controlled. In this study, the effects of varying the fluidizing velocity in the fast fluidized bed （FFB） on the pressure drops and the solid fractions in the system were investigated in a 100 kW DFBG and in a dual fluidized bed cold model （DFCM）. Based on the experimental results, empirical correlations were developed to predict the height-averaged solid fraction in the bottom section of the FFB. Accuracy and advantages of the correlations were analyzed. The correlation is useful for design and modeling of the DFBG systems where the height-averaged solid fraction is required to be determined.

Improvement of Impeller Blade Structure for Gas Injection Refining under Mechanical Stirring

Abstract： The impeller blade structure for gas injection refining under mechanical stirring has been explored by water model experiments. A sloped swept-back blade impeller is＇proposed for the purpose. The central part of the impeller is disk- or plate-shaped, and the blades are fitted to the side of the disk or plate. In addition, a disk is put on the top side of the impeller blades. The impeller can strengthen the radial and downward flow between the blades and weaken the swirl flow in the zone above the impeller. These effects on flow phenomena are favorable for disintegration and wide dispersion of bubbles which are injected from a nozzle attached to the center of the underside of the impeller. In addition, the sloped swept-back impeller requires less power consumption. The impeller shaft should be placed away from the vessel center so as to disperse the injected bubbles widely in the bath under mechanical stirring even with unidi- rectional impeller rotation and without installing baffles. The number of gas holes in the nozzle and the direction of gas injection have a little effect on the bubble disintegration and dispersion in the bath. Highly efficient gas injection refining can be established under the conditions of proper impeller size, larger nozzle immersion depth, larger eccen- tricity and rotation speed of the impeller. The sloped swept back blade impeller can decrease the power consumption and vet improve the bubble disintegration and wide dist^ersion in the bath.

Size analysis of slag eye formed by gas blowing in ladle refining

The formation of slag eye in a gas stirred ladle was studied through cold models and industrial trials. In the cold model,water and sodium tungstate solution were employed to simulate liquid steel,and silicon oil was employed to simulate slag. The simulation results revealed that the gas flow rate and bath height had strong effects on the slag eye size. In particular,the thickness of slag layer played a strong role in the slag eye size. In addition,the slag eye could not be formed when the thickness of the top layer was more than 4 cm in water-silicone oil model.Besides,the section area of vessel had a great impact on the slag eye size. Industrial trials results showed a similar trend that the gas flow rate was very significant on the slag eye size. The predictions of the existing models showed larger predictions deviations compared with the experimental data. Moreover,a new model without fitting parameters was developed based on force balance and mathematical derivation,and verified by the experimental data. The new model provides the prediction with small deviations by comparing with the data acquired from cold models and industrial trials.