Effect of slag composition on corrosion resistance of high chromia refractory bricks for industrial entrained-flow gasifier

The slag composition corresponding to different coals varies significantly,which directly affects the operation of industrial entrained-flow gasifier and the service life of refractory bricks.In this study,the corrosion resistance of several typical coal slags for gasification on high chromia refractory bricks was comparatively investigated by static laboratory crucible tests and thermodynamic simulations.The results demonstrated that the corrosion degree of high chromia refractory bricks by different coal slags was high-Ca/Na slag>high-Fe slag>high-Si/Al slag.The surface structure of the refractory was relatively flat after corrosion by high-Si/Al slag,and the primary corrosion reaction was the partial dissolution of the matrix by the slag.High-Fe slag was prone to the precipitation of iron phases as well as the formation of(Mg,Fe)(Al,Cr)_(2)O_(4)composite spinel layer at the slag/refractory interface.The high-Ca/Na slag was susceptible to react with the refractory to yield a low melting point phase,which led to the destruction of the matrix structure of the refractory and an isolated distribution of particles.In addition,the monoclinic ZrO_(2) in the refractory reacted with CaO in the slag to formed calcium zirconate,which loosened its phase toughening effect,was the primary factor that aggravated the refractory corrosion.

CFD simulation on the gasification of asphalt water slurry in an entrained flow gasifier

Gasification technology is suggested to utilize asphalt particles, which are produced in the heavy oil deep separation process of using coupled low temperature separation of solvent and post extraction residue. In this work, the asphalt particles were first slurried with water and then gasified to produce synthesis gas. The gasification process of asphalt water slurry in an entrained flow gasifier was simulated using a three-dimensional computational fluid dynamics （CFD） model based on an Eulerian- Lagrangian method. The trajectories and residence time of asphalt particles, and the reaction rates, gas species distribution, temperature field and carbon conversion in the entrained flow gasifier were obtained. The predicted results indicated that the asphalt water slurry was a good feedstock for gasification. Moreover, the effects of particle size, oxygen equivalence ratio, and mass content of asphalt particles on the gasification performance of asphalt water slurry were investigated. These results are helpful for industrial application of asphalt water slurry gasification technology.

Assessment of coal gasification in a pressurized fixed bed gasifier using an ASPEN plus and Euler–Euler model

With the help of Aspen Plus,a two-dimensional unsteady CFD model is developed to simulate the coal gasification process in a fixed bed gasifier.A developed and validated two dimensional CFD model for coal gasification has been used to predict and assess the viability of the syngas generation from coal gasification employing the updraft fixed bed gasifier.The process rate model and the sub-model of gas generation are determined.The particle size variation and char burning during gasification are also taken into account.In order to verify the model and increase the understanding of gasification characteristics,a set of experiments and numerical comparisons have been carried out.The simulated results in the bed are used to predict the composition of syngas and the conversion of carbon.The model proposed in this paper is a promising tool for simulating the coal gasification process in a fixed bed gasifier.

Damage Mechanism of High Chrome Bricks for Opposed Multi Nozzle Gasifier and Their Improvement

To reveal the damage mechanism of high chrome bricks for opposed multi nozzle gasifier with expanded diameter,the chemical composition and the morphology of a used high chrome brick were researched using XRF,SEM and EDS,and the properties of the high chrome bricks were improved by adding ultra fine alumina,alumina-chrome-iron oxide synthetic material with spinel structure,and chromium metal.The results show that(1)the high chrome brick is seriously damaged by the chemical dissolution of chrome as well as the chemical reactions at the slag/brick interface,the slag penetration and the structural spalling;(2)FeO in the slag reacts with Cr_(2)O_(3)in the brick to form a FeCr_(2)O_(4)layer on the particle surface thus leading to spalling;CaO reacts with SiO_(2)and Al2O3 in the brick forming a metamorphic layer of low melting point materials;due to the different thermal expansion coefficients of the metamorphic layer and the original brick,cracks appear and continue to expand and deepen under multiple temperature and pressure fluctuations thus leading to spalling of brick layer;(3)the improved brick has decreased apparent porosity,increased bulk density and compressive strength,and better thermal shock resistance compared with the original brick;after one cycle of on-site application,the furnace lining surface is smooth and flat with little damage,indicating that the improved high chrome bricks basically meet the working condition requirements of the opposed multi nozzle gasifier with expanded diameter,however,the final effects need to be evaluated in detail after the whole furnace service.

Analysis and Design Innovation on Underground Gasifier for Medium-Deep Coal Seam

Over the past 80 years,dozens of underground coal gasification(UCG)mine field tests have been carried out around the world.However,in the early days,only a small number of shallow UCG projects in the former Soviet Union achieved commercialised production.In this century,a few pilot projects in Australia also achieved short-term small-scale commercialised production using modern UCG technology.However,the commercialisation of UCG,especially medium-deep UCG projects with good development prospects but difficult underground engineering conditions,has not progressed smoothly around the world.Considering investment economy,a single gasifier must realise a high daily output and accumulated output,as well as hold a long gasification tunnel to control a large number of coal resources.However,a long gasification tunnel can easily be affected by blockages and failure,for which the remedial solutions are difficult and expensive,which greatly restricts the investment economy.The design of the underground gasifier determines the success or failure of UCG projects,and it also requires the related petroleum engineering technology.Combining the advantages of the linear horizontal well(L-CRIP)and parallel horizontal well(P-CRIP),this paper proposes a new design scheme for an“inclined ladder”underground gasifier.That is to say,the combination of the main shaft of paired P-CRIP and multiple branch horizontal well gasification tunnels is adopted to realise the control of a large number of coal resources in a single gasifier.The completion of the main shaft by well cementation is beneficial for maintaining the integrity of the main shaft and the stability of the main structure.The branch horizontal well is used as the gasification tunnel,but the length and number of retracting injection points are limited,effectively reducing the probability of blockage or failure.The branch horizontal well spacing can be adjusted flexibly to avoid minor faults and large cracks,which is conducive to increasing the resource utilisation rate.In addition,for multi-layer thin coal seams or ultra-thick coal seams,a multi-layer gasifier sharing vertical well sections can be deployed,thereby saving investment on the vertical well sections.Through preliminary analysis,this gasifier design scheme can be realised in engineering,making it suitable for largescale deployment where it can increase the resource utilisation rate and ensure stable and controllable operations.The new gasifier has outstanding advantages in investment economy,and good prospects for application in the commercial UCG projects of medium-deep coal seams.

Syngas cleaning with nano-structured micro-porous ion exchange polymers in biomass gasification using a novel downdraft gasifier

Sulphonated nano-structured micro-porous ion exchange polymers, known as sulphonated PolyHIPE Polymers （s-PHPs） were used in syngas cleaning to investigate their impact on tar composition, concentration and dew point depression during the gasification of fuel cane bagasse as a model biomass. The results showed that the s-PHPs used as a secondary syngas treatment system, was highly effective at adsorbing and reducing the concentration of all class of tars in syngas by 95%-80% which resulted in tar dew point depression from 90 ~C to 73 ~C. It was shown that tars underwent chemical reactions within s-PHPs, indicating that tar diffusion from syngas was driven by chemical potential. It was also observed that s-PHPs also captured ash forming elements from syngas. The use of s-PHPs in gasification as well as in an integrated thermochemical biorefinery technology is discussed since the tar loaded s-PHPs can be used as natural herbicides in the form of soil additives to enhance the biomass growth and crop yield.

Two-dimensional CFD simulation and pilot-scale experimental verification of a downdraft gasifier: effect of reactor aspect ratios on temperature and syngas composition during gasification

This paper focuses on a two-dimensional CFD simulation of a downdraft gasifier and a pilot-scale experiment for verification using wood pellet fuel.The simulation work was carried out via the ANSYS-Fluent CFD software package with in-house coding via User Defined Function.Three gasification parameters were taken into account in the simulation and validation to achieve highly accurate results;namely,fuel consumption,temperature profile,and syngas composition.After verification of the developed model,the effects of aspect ratios on temperature and syngas composition were investigated.Results from simulation and experimental work indicated that the fuel consumption rate during the steady state gasification experiment was 1.750±0.048 g/s.The average steady state temperature of the experiment was 1240.32±14.20 K.In sum,the fuel consumption and temperature profile during gasification from modeling and experimentation show an error lower than 1.3%.Concentrations of CO,CO2,H2,and CH4 were 20.42 vol%,15.09 vol%,8.02 vol%,and 2.6 vol%,respectively,which are comparable to those of the experiment:20.00 vol%,15.48 vol%,8.00 vol%,and 2.65 vol%.A high concentration of syngas is observed in the outer radial part of the reactor because of the resistive flow of the air inlet and the synthesis gas produced.The average temperatures during the steady state of the gasifier with aspect ratios(H/D)of 1.00,1.38(experiment),and 1.82 were 978.77±11.60,1256.46±9.90,and 1368.94±9.20 K,respectively.The 1.82 aspect ratio reactor has the smallest diameter,therefore the radiative heat transferred from the reactor wall affects the temperature in the reactor.Syngas compositions are comparable.Inverse relationships between the aspect ratios and the syngas LHV,(4.29–4.49 MJ/N m3),cold gas efficiency(29.66%to 31.00%),and carbon conversion(79.59%to 80.87%)are observed.

STUDY ON THE VARIATION MECHANISM OF CARBON CONTENT OF LIQUID IRON IN MELTING GASIFIER

This paper studied the changing principles of carbon content in direct reduction iron (DRI) and liquid iron in the COREX melting gasifier. Under the normal working conditions of experimental equipment, liquid nitrogen was poured into the melting gasifier from its tuyere to cool down quickly. And then seven cross sections were made to study the carburization reaction and its characteristics of the solid iron and the liquid iron, and also the reaction of carbon between the slag and the metal. According to the results, the influences of the thickness of the semi-coke layer and the temperature on the carbon content of liquid iron in the COREX melting gasifier were confirmed.

Overview coking plant & Lurgi gasifier plant waste water treatment

The paper described the coking plant and Lurgi gasifier plant waste water types and characteristics , comparing the COD and ammonia-N level in different source of waste water in the plant.The currently maturity coking plant waste water treatment method was statement in the paper and analyzed the pros and cons of each method.The primary cost analysis of each type of waste water treatment was also completed in the paper.According to these analyses , recommendation was prepared for coking plant and Lurgi gasifier plant waste water treatment.

Refractories Utilizability for Slagging Gasifiers

Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining＇ s life of slagging gasifiers is one of the most critical factors for a cost - effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost -effectiveness of high chromia refractories and possibility of the alternatives.

Discussion on Wear Mechanism of High Chrome Brick Used in Coal Slurry Gasifier

The microstructure and phase composition of high chrome brick used in coal slurry gasifier has been analyzed by means of SEM and Energy Spectrum. The results indicate that the used brick can be divided into different zones as slag-adhered zone, reaction zone, penetration zone and unaltered zone. The phase composition and microstructure are different and cracks occurred in different degree at these zones. A dense ring belt was formed with complex spinel (Mg,Fe)(Cr,Al,Fe 2O 4) in the reaction zone near the hot face. The wear mechanism of the brick during its employment has been discussed. It is considered that the reaction and penetration of coal slag and strong reductant bring about the composition change of the brick and destroys its original network inlayed structure and consequently result in its structure spalling and weakening strength, which is the main wear mechanism of the brick and followed by temperature fluctuation and high mechanical impact of flowing fluid with high-speed.

Main Influencing Factors on Service Life of High Chrome Refractories for Coal Water Slurry Gasifiers

The main characteristics of high chrome refractories for coal water slurry gasifiers were introduced. The damage mechanism of the refractories was analyzed by observing the microstructure of the used high chrome refractories with the aid of SEM. The main influencing factors on the service life of the refractories were summarized.

Study on Microstructure and Slag Corrosion Mechanism of High Chrome Bricks for Gasifier

Research was focused on slag corrosion mechanism of high chrome bricks used for different types of gasifier by comparing the structure of high chrome bricks for petroleum coke gasifier and water-coal slurry gasifier with slag corroded testing brick and water coal slurry gasifier through Scanning Electron Microscope （SEM） examination and X-ray diffi＇action. Results show that for high chrome brick used for petroleum coke gasifier, corrosion is mainly caused by Cr2O3 in the brick and V2O5 in molten slag and liquid phase generation at low temperature; for high chrome brick used for water-coal slurry gasifier, corrosion is caused by dissolution of Cr2O3 in molten slag and corrosion of ZrO2. For LIRR-HK95 brick, it performs better petroleum coke corrosion resistance than the others due to the optimal composition and structure.

Numerical Simulation of Thermal Stress Field of Water-cooled-wall Pulverized-coal Gasifiers

the stress field in the gasifier operation to research the damage of refractories and slag layer caused by the thermal stress.The results reveal that:(1)the maximum stress of water-cooled-wall gasifier appears at the interface between anchor nails and refractories as well as the interface between refractories and the slag layer,and the maximum stress of slag layer appears on the surface of the slag layer;(2)the increase of slag layer thickness can significantly reduce the thermal stress at the interface between anchor nails and refractories,but increase the thermal stress between slag layer and refractories;(3)when the thermal conductivity is 2-6 W•m^-1•K^-1,the thermal stress increases rapidly with the increase of the thermal conductivity,but when the thermal conductivity is 6-10 W•m^-1•K^-1,the thermal stress is basically stable;(4)the higher the cooling rate,the faster the decreasing speed of the temperature and thermal stress.

Investigation into characteristics of the char bed in the melter gasifier through tuyere probing

Tuyere coke probing was conducted at the Baosteel Corex Plant in order to gain a better understanding of the structure of the char bed in the melter gasifier （ MG ）. After screening, the specimens were observed by an optical microscope to determine the mechanism of the char bed formation. X-ray diffraction （XRD） was used to clarify the degree of graphitization and infer thermal history of coke. The results show that the amount of powder coming from lump coal in the burden is much more than that from coke. Based on this, measures for improving the char bed＇ s permeability are proposed.

Analysis of Spent High Chrome Brick in Slagging Gasifier

Wear of the spent high chrome brick in slagging gasifier was studied. The result shows that erosion and spalling are the m, ain wear mechanism of high chrome brick and the CaO content of coal slag is crucial to wear of high chrome brick.

Relations among Main Operating Parameters of Gasifier in IGCC

Gasification unit is one of the key subsystems in the IGCC power system;the operating parameters of gasifier directly affect syngas quality and performance of whole IGCC system. The system model of gasification unit with coal water slurry gasifier was simulated and calculated using THERMOFLEX software, and the relations of oxygen coal ratio (Roc), water coal ratio (Rsc), gasification pressure, gasification temperature and cold gas efficiency were mostly researched. The results show that Roc and Rsc have effect of mutual restriction on gasification temperature, cold gas efficiency and syngas composition. Gasification pressure mainly determines the capacity of the gasifier, little effects on syngas composition.

Design and implementation of gasifier flame detection system based on SCNN

Flame detection is a research hotspot in industrial production,and it has been widely used in various fields.Based on the ignition and combustion video sequence,this paper aims to improve the accuracy and unintuitive detection results of the current flame detection methods of gasifier and industrial boiler.A furnace flame detection model based on support vector machine convolutional neural network(SCNN)is proposed.This algorithm uses the advantages of neural networks in the field of image classification to process flame burning video sequences which needs detailed analysis.Firstly,the support vector machine(SVM)with better small sample classification effect is used to replace the Softmax classification layer of the convolutional neural network(CNN)network.Secondly,a Dropout layer is introduced to improve the generalization ability of the network.Subsequently,the area,frequency and other important parameters of the flame image are analyzed and processed.Eventually,the experimental results show that the flame detection model designed in this paper is more accurate than the CNN model,and the accuracy of the judgment on the flame data set collected in the gasifier furnace reaches 99.53%.After several ignition tests,the furnace flame of the gasifier can be detected in real time.

Environmental Impacts (ER CO₂) of an Improved Multi-Fuel Gasifier Forced Air Cookstove in the City of Kinshasa

Sub-Saharan African countries depend 80% on the biomass-wood to meet their daily needs in terms of cooking foods. Traditional cookstoves are much more used to this effect. Many change programmes for replacing cookstove model have been planned. Yet many of these programmes have not been preceded by environmental impact studies. This work offers high-performance cookstove models and determines their impact on the reduction of CO2 emissions, a very harmful greenhouse gas causing the planet warming and climate change. Replacing the traditional cookstove by an improved stove may lead to an economy in terms of fuel ranging from 33.2% to 75.4% according to the model of cookstoves. Yet the Gasifier using pellets as fuel remains the most beneficial stove in terms of fuel saving (75.4%) and in terms of ER CO2, i.e. 2748 t CO2/Year. An improved gasifier cookstove is multi-fuel. He can use charcoal, pellets and wood. This is an indispensable cooking tool with alternative fuels. In this work, the ER CO2 was evaluated using two methods. The KPT, which is a field method and the CCT which is a laboratory method. By the KPT method a gasifier ICS/GAS/P records up to an ERCO2 of 2748 t CO2/Year, while with the same gasifier, an ERCO2 of 2619 t CO2/year is found by the CCT method. The comparison between the two methods shows the same trend but with very high values of ERCO2 for the KPT method results. The variation between the two methods ranges between 1% approximately to 6.9 percent.