scholarly journals Markov Chain Simulation of Coal Ash Melting Point and Stochastic Optimization of Operation Temperature for Entrained Flow Coal Gasification

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4245
Author(s):  
Zhang ◽  
Guan ◽  
Hou ◽  
Zhang ◽  
Li ◽  
...  
Keyword(s):  
Markov Chain ◽  
Melting Point ◽  
Stochastic Programming ◽  
Optimization Model ◽  
Coal Gasification ◽  
Coal Ash ◽  
Entrained Flow ◽  
Sample Data ◽  
Ash Melting ◽  
Mc Simulation

In the entrained flow coal gasification process, the gas production is critically affected by the operating temperature (OT) and coal ash melting point (AMP), and the AMP is one of key factors for the determinations of OT. Considering the fact that coal is a typical nonhomogeneous substance and the coal ash composition varies from batch to batch, this paper proposes the application of the Markov Chain (MC) method in simulation of the random AMP series and the stochastic optimization of OT based on MC simulation for entrained flow coal gasification. The purpose of this paper is to provide a more accurate optimal OT decision method for entrained flow coal gasification practice. In this paper, the AMP was regarded as a random variable, and the random process method, Markov Chain, was used to describe the random AMP series of feed coal. Firstly, the MC simulation model about AMP was founded according to an actual sample data, 200 sets of AMP data from an industrial gasification plant under three simulation schemes (the sample data were individually divided into 16, eight and four state groups,). The comparisons between the simulation results and the actual values show that the founded MC simulation model descries the AMP series very well. Then, a stochastic programming model based on MC simulation for OT optimization was developed. Finally, this stochastic programming optimization model was optimized by genetic algorithm (GA). Comparing with the conventional OT optimization method, the proposed stochastic OT optimization model integrated MC simulation can ascertain a more accurate OT for guiding the coal gasification practice.

Effect of High-Efficiency Flux on the Melting Characteristics of Coal Ash

2013 ◽  
Vol 295-298 ◽  
pp. 3094-3097 ◽  
Author(s):  
Han Xu Li ◽  
Zi Li Zhang ◽  
Yong Xin Tang
Keyword(s):  
Melting Temperature ◽  
Coal Gasification ◽  
High Efficiency ◽  
Coal Ash ◽  
Fusion Temperature ◽  
Gasification Process ◽  
Ash Fusion Temperature ◽  
Melting Characteristics ◽  
Temperature Detector ◽  
Ash Melting

High-efficiency flux was developed to lower the ash fusion temperature of coal LQ and reduce the addition content in coal gasification process. The effect of high-efficiency flux on the coal ash melting temperature and mineral transformation were studied by ash fusion temperature detector and XRD (X-ray diffractometer) respectively in reducing atmosphere. Compared with limestone flux, the high-efficiency flux can decrease the coal ash melting temperature effectively with half addition content. The ash flow temperature (FT) of coal LQ can be lowered to less than 1350°C with the addition of 3% high-efficiency flux ,while limestone flux need to add more than 8% to reach to this temperature. With the high-efficiency flux added, cordierite, anorthite and Mg-Fe-Al oxide were formed at high temperature, which is the main reason to sharply decrease the ash fusion temperature.

scholarly journals Study on the Influence of mixed burning Sludge on slagging characteristics of easily slagging Coal

2020 ◽  
Vol 204 ◽  
pp. 01006
Author(s):  
Zhang Limeng ◽  
Dong Xinguang ◽  
Hou Fanjun ◽  
Zhao Zhonghua ◽  
Liu Ke ◽  
...  
Keyword(s):  
Melting Point ◽  
Alkali Metals ◽  
Theoretical Calculations ◽  
Coal Ash ◽  
Calorific Value ◽  
Mixing Ratio ◽  
Ash Melting ◽  
Aluminum Compounds ◽  
Sludge Ash

In this paper, combined with experiments and theoretical calculations, the effect of urban low-calorific value sludge on the slagging characteristics of easy-slagging coals is studied. The results show that when the melting point of sludge ash is lower than that of coal ash, the ash melting point of the mixture after the two blends will be lower than the melting point of raw coal ash. When SiO2 and Al2O3, which are relatively high in sludge, are used as single additives, the ash melting point of coal will first decrease and then increase. As the mixing ratio of sludge increases, coal ash slagging characteristics show a trend of gradual relief. For coals that are prone to slagging and rich in alkali metals, they can be appropriately mixed with sludge rich in silicon and aluminum compounds or additives to improve Slagging characteristics.

scholarly journals Investigation of the Coal Gasification Process Under Various Operating Conditions Inside a Two-Stage Entrained Flow Gasifier

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Armin Silaen ◽  
Ting Wang
Keyword(s):  
Coal Gasification ◽  
Operating Conditions ◽  
Coal Slurry ◽  
Two Stage ◽  
Heating Value ◽  
Fuel Distribution ◽  
Entrained Flow ◽  
One Stage ◽  
Gasification Process ◽  
Entrained Flow Gasifier

Numerical simulations of the coal gasification process inside a generic 2-stage entrained-flow gasifier fed with Indonesian coal at approximately 2000 metric ton/day are carried out. The 3D Navier–Stokes equations and eight species transport equations are solved with three heterogeneous global reactions, three homogeneous reactions, and two-step thermal cracking equation of volatiles. The chemical percolation devolatilization (CPD) model is used for the devolatilization process. This study is conducted to investigate the effects of different operation parameters on the gasification process including coal mixture (dry versus slurry), oxidant (oxygen-blown versus air-blown), and different coal distribution between two stages. In the two-stage coal-slurry feed operation, the dominant reactions are intense char combustion in the first stage and enhanced gasification reactions in the second stage. The gas temperature in the first stage for the dry-fed case is about 800 K higher than the slurry-fed case. This calls for attention of additional refractory maintenance in the dry-fed case. One-stage operation yields higher H2, CO and CH4 combined than if a two-stage operation is used, but with a lower syngas heating value. The higher heating value (HHV) of syngas for the one-stage operation is 7.68 MJ/kg, compared with 8.24 MJ/kg for two-stage operation with 75%–25% fuel distribution and 9.03 MJ/kg for two-stage operation with 50%–50% fuel distribution. Carbon conversion efficiency of the air-blown case is 77.3%, which is much lower than that of the oxygen-blown case (99.4%). The syngas heating value for the air-blown case is 4.40 MJ/kg, which is almost half of the heating value of the oxygen-blown case (8.24 MJ/kg).

scholarly journals Calcium‐Bearing Minerals Transformation during Underground Coal Gasification

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 708 ◽  
Author(s):  
Liu ◽  
Ma
Keyword(s):  
Coal Gasification ◽  
Ternary Phase Diagram ◽  
Energy Dispersive Spectrometer ◽  
Coal Ash ◽  
Scientific Basis ◽  
Experimental Results ◽  
Underground Coal Gasification ◽  
Morphological Transformation ◽  
Reaction Conditions ◽  
High Calcium

Calcium‐bearing minerals are one of the main typical minerals in coal and coal ash. In the process of coal thermal conversion, calcium‐bearing minerals undergo different morphological transformation in which the reaction temperature, pressure, and atmosphere are important factors affecting their transformation. The reaction process of underground coal gasification (UCG) could be clearly divided into pyrolysis, reduction, and oxidation and the typical calcium‐bearing minerals are expected to indicate the actual reaction conditions of UCG. A high‐calcium coal, Zhundong coal, was used in this research. The products of UCG were prepared and the minerals were identified by X‐ray diffraction (XRD) and a scanning electron microscope coupled with an energy‐dispersive spectrometer (SEM‐EDS). The thermodynamic calculation was used to assist in understanding the transformation behaviors of calcium‐bearing minerals. The experimental results show that the calcium‐bearing mineral is gradually converted from gypsum (CaSO4·2H2O) in the raw coal into anhydrite (CaSO4) during the pyrolysis process. In the reduction stage, anhydrite reacts with the reducing gas (CO) to produce oldhamite (CaS), and the oldhamite is stably present in the reduction ash. During the oxidation process, oldhamite is first transformed into CaSO4, and then CaSO4 is converted into CaO. Finally, CaO reacts with Al2O3 and SiO2 to produce gehlenite (Ca2Al2SiO7) at 1100 °C. As the oxidation temperature rises to 1400 °C, gehlenite is transformed into the thermodynamically stable anorthite (CaAl2Si2O8). With the further progress of the reaction, anorthite will co‐melt with iron‐bearing minerals above 1500 °C. The ternary phase diagram of SiO2–Al2O3–CaO system proves that anorthite and gehlenite are the typical high‐temperature calcium‐bearing minerals when the mole fraction of SiO2 is higher than 0.6. Moreover, the gehlenite is converted to anorthite with the temperature rise, which is consistent with experimental results. This study provides a scientific basis for understanding the UCG reaction conditions.

scholarly journals Experimental Study on Coal Gasification in a Full-Scale Two-Stage Entrained-Flow Gasifier

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4937
Author(s):  
Guangyu Li ◽  
Luping Wang ◽  
Chaowei Wang ◽  
Chang’an Wang ◽  
Ping Wu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Coal Gasification ◽  
Full Scale ◽  
Input Rate ◽  
Two Stage ◽  
Entrained Flow ◽  
Operation Period ◽  
Entrained Flow Gasifier ◽  
Coal Resource ◽  
First Time

In this paper, coal gasification characteristics in the reductor were investigated in a full-scale two-stage pressurized entrained-flow gasifier, which has been seldom conducted previously. The present study aimed at elucidating the effects of gasifying agent concentration, coal input rate, and operation period under full reductor load on the performance of a utility two-stage pressurized entrained-flow gasifier for the first time. When the steam input in the combustor was raised from 3318 kg/h to 5722 kg/h, the total outputs of H2, CO, and CO2 were increased by 1765 Nm3/h and 2063 Nm3/h, respectively, while the CH4 output was decreased by 49 Nm3/h. The coal conversion rate was minimal at low steam input. In addition, more coal gasified in the reductor could increase the output of CH4, while CH4 could reach 1.24% with the coal input in the range of 8000–10,000 kg/h. The present work can offer a further understanding of the gasification performance in the reductor of the full-scale two-stage pressurized entrained-flow gasifier, and motivates the potential for clean utilization of coal resource.

A Stochastic Programming Optimization Model of Container Shipping of Sea-Carriage

2013 ◽  
Vol 411-414 ◽  
pp. 2715-2720
Author(s):  
Bin Wang ◽  
Tao Yang
Keyword(s):  
Integer Programming ◽  
Stochastic Programming ◽  
Optimization Model ◽  
Container Shipping ◽  
Empty Container ◽  
Shipping Company ◽  
Shipping Cost ◽  
Total Profit ◽  
Empty Containers ◽  
The Cost

The paper dose research about the optimization of container shipping of sea carriage for meeting the goods transport requirement by use of stochastic programming. Both laden and empty containers are combined into a system. In particular, the effect of special laden container shipping capacity on the shipping plan is investigated. In the model, the objective function is to maximize the total profit of container shipping. The profit caused by laden container shipping minus the cost caused by both laden and empty container shipping equal to the total profit. The constraints to the model include meeting the need of both laden and empty containers, shipping limit to both common and special laden containers, the number of empty container supported. The number of empty containers is stochastic and the model is transmitted to an integer programming. Lingo9.0 is used to solve the model and shipping methods in varied parameters are shown by simulation. The aim of the paper is to provide a reasonable plan of container shipping of sea-carriage, so the container shipping cost of a shipping company can be reduced and the its profit made by container shipping are maximized.

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