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.

Comparison of Combustion Characteristics of Tars Produced with Tobacco Stem Biomass Gasification

In order to study the combustion characteristics of tar in biomass gasifier inner wall and gasification gas,“tobacco stem semi-tar inside furnace”,“tobacco stem tar inside furnace”and“tobacco stem tar out-of-furnace”were subjected to thermogravimetric experiments,and the combustion characteristics and kinetic characteristics were analyzed.The result shows that“tobacco stem semi-tar inside furnace”has the highest value and“tobacco stem tar out-of-furnace”is has the lowest value on ignition characteristics,combustion characteristics and combustible stability;“tobacco stem semi-tar inside furnace”has the lowest value and“tobacco stem tar outside furnace”has the highest value on burnout characteristics;“tobacco stem tar outside furnace”has the highest value and“tobacco stem tar inside furnace”has the lowest value on integrated combustion characteristics.

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.

Variation of toxic pollutants emission during a feeding cycle from an updraft fixed bed gasifier for disposing rural solid waste

The variation of toxic pollutants emission during a feeding cycle was examined by field monitoring from a batch feeding updraft fixed bed gasifier for disposing rural domestic solid waste. Results showed that the content of oxygen in flue gas gradually increased, while SO_2 and HCl in flue gas decreased with time after feeding in a whole feeding cycle. Although large amount of CO was produced during the gasifying, low CO content in flue gas could be obtained after the heat treatment with an electric heating device. The distribution characteristics of dioxin congeners in flue gas indicted the re-synthesis of dioxins after flue gas heating, and the increase of oxygen promoted the synthesis of dioxins. The emission content of dioxins could meet the standard(0.1 ng I-TEQ·m^(-3),GB18458-2014) of China when the oxygen content was controlled below 8.3%. Hence, for a batch feeding gasifier,low oxygen condition should be offered by reducing air intake at the later stage of feeding cycle in order to decrease the re-synthesis of dioxins after the flue gas heating.

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 EulerianLagrangian 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.

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.

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.

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.

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.

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.

Implementation of a Demoisturization and Devolatilization Model in Multi-Phase Simulation of a Hybrid Entrained-Flow and Fluidized Bed Mild Gasifier

A mild gasification process has been implemented to provide an alternative form of clean coal technology called the Integrated Mild Gasification Combined Cycle (IMGCC), which can be utilized to build a new, highly efficient, and compact power plant or to retrofit an existing coal-fired power plant in order to achieve lower emissions and significantly improved thermal efficiency. The core technology of the mild gasification power plant lies on the design of a compact and effective mild gasifier that can produce synthesis gases with high energy volatiles through a hybrid system: utilizing the features of both entrained-flow and fluidized bed gasifiers. To aid in the design of the mild gasifier, a computational model has been implemented to investigate the thermal-flow and gasification process inside this mild gasifier using the commercial CFD (Computational Fluid Dynamics) solver ANSYS/FLUENT. The Eulerian-Eulerian method is employed to model both the primary phase (air) and the secondary phase (coal particles). However, the Eulerian-Eulerian model used in the software does not facilitate any built-in devolatilization model. The objective of this study is therefore to implement a devolatilization model (along with demoisturization) and incorporate it into the existing code. The Navier-Stokes equations and seven species transport equations are solved with three heterogeneous (gas-solid) and two homogeneous (gas-gas) global gasification reactions. Implementation of the complete model starts from adding demoisturization first, then devolatilization, and then adding one chemical equation at a time until finally all reactions are included in the multiphase flow. The result shows that the demoisturization and devolatilization models are successfully incorporated and a large amount of volatiles are preserved as high-energy fuels in the syngas stream without being further cracked or reacted into lighter gases. The overall results are encouraging but require future experimental data for verification.

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.

Pre-Operational Analysis of a Prototype Downdraft Gasifier Fueled by Bamboo

Biomass gasification is a thermochemical conversion process that dates back to the 19th century. Nevertheless, designing and operating a gasifier system is not an easy task. Every biomass feedstock has different characteristics and the gasifier needs to be designed according to those qualities. Hence, many laboratory analyses on bamboo were carried out for this study. This study also concentrates on finding the best possible process variables for a bamboo fueled downdraft gasifier through a sensitivity analysis. A software program called Thermoflex was used for this purpose and the effect of gasifier temperature, air-fuel-ratio, moisture content of the fuel and temperature of pre-heated air on the syngas composition were simulated. The results show that bamboo is a decent gasification feedstock because of its low ash and sulfur content and satisfactory energy value. The simulations reveal that the best gas quality is obtained with the gasifier temperature between 700℃ and 800℃, A/F-ratio of 1.25 - 1.75 and dry basis moisture content between 10% and 15%.

Designing and Performance Evaluation of Biochar Production in a Top-Lit Updraft Up-scaled Gasifier

The Original Belonio Rice Husk Gasifier (OBRHG), initially of height of 0.6 m, diameter of 0.15 m and thickness of 0.025 m was tested for biochar production through air gasification of rice husk (RH) and the design was upscaled to height of 1.65 m, diameter of 0.85 m and thickness of 0.16 m. A total of 27 experiments were conducted to monitor the gasifier performance and the system can operate with the centrifugal blower operating at a power input of 155 W and a maximum flow rate of 1450 m3/hr regulated according to the air requirement. Building the UBRHG is simple and inexpensive to fabricate and with the fairly satisfactory performance and ease of construction along with the convenience of operation, the UBRHG with RH as feed would find abundant avenues of applications in a rural setting for biochar production alongside thermal, mechanical and electrical energy delivery.

Thermochemical Conversion of Coal and Coal-Biomass Blends in an Autothermal Moving Bed Gasifier: Experimental Investigation

A unique laboratory scale auto-thermal moving bed gasifier was designed for studying the thermochemical conversion of coal-biomass blends. For this purpose, two coals (lignite and sub-bituminous), two biomass materials (corn stover and switchgrass), and their respective blends were used. Gasification characteristics of the fuels were evaluated with an emphasis on improving the producer gas composition. The efficiency and product gas compositions reveal that utilizing the inner stainless-steel tubing better promotes heat transfer upwards in the axial direction when compared to utilizing quartz insulation. The H2/CO ratio at the same operating conditions is much higher due to the increase in bed temperature and heat transfer upwards in the axial direction. This improved the overall efficiency by at least 20%. Using pure oxygen and steam, efficiency greater than 50% was obtained for blends with corn stover at steam to oxygen ratio of 2:1. Also, using air as the gasifying agent greatly improved the H2/CO ratios and overall efficiency in blends with corn stover. In contrast, blends with switchgrass were not very effective with respect to the overall gasification characteristics. Blending switchgrass with coal may not be viable option from the viewpoint of generating high quality producer gas for downstream operations.

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.

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.