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

A local thermal stress model of water-cooled-wall pulverized-coal gasifier was built, and ANSYS was used to simulate 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 therma I 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.

Performance assessment of water mist applied in gas burning suppression in underground coal mine

The main objective of the present study was introduced water mist suppressiontechnology to prevent and control gas burning which occurred during drilling at Wu20160working-face in No.10 coal mine of Pingdingshan Ltd..Based on the self-developed ex-periment platform,a series of fire suppression tests to evaluate the performance of a watermist system were conducted.The detailed measurements of the spray characteristics,i.e.,the Sauter Mean Diameter(SMD),the velocity and spray angle which are the main pa-rameters considered in the Study,were obtained by using LS-2000 Sizer.The amount ofwater consumed and the water flux density distribution over the cross section downstreamthe nozzle exit were measured by cup collector method.The operating pressure of thewater mist nozzle is set to 0.5 MPa,the droplet SMD of 104 pm,the water flux density dis-tribution from 0.71 to 8.47 L/(m^2.min),the average velocity of 2.14 m/s.The experimentalresults show that the averaged time required for extinguishment is 3.14 s,and the corre-sponding amount of water used during fire test is about 0.11 kg.The gas fire suppressionsystem reduces the temperature in combustion chamber of the experimental apparatusbelow the ignition point of the gas,which can effectively avoid the occurrence of the gasfire in coal mine.

Safety research in the gasification process of novel multi-thermal-source coal gasifier

In order to collect the gas safely produced in the gasification process of the novel multi-thermal-source coal gasifier,based on its gasification skill and the characteristics of the products,this paper analyzes the possible dangers in the gasification process,devises the gasifier eruption and explosion experiments,explores the conditions of gasifier eruption and gas explosion,studies their effects on the gasification process and establishes safe operation measures.Gasifier eruption hazard occurs easily in the gasification process of one-thermal-source coal gasifier when MSiO2 is far higher than that in the normal adjuvant.The gas permeability in the gasifier is not the same and the power supply is too large.However,similar conditions in the gasification of multi-thermal-source coal gasifier do not produce a gasifier eruption accident so easily.When it erupts,the gasifier should be stopped and then cooled down naturally or inert gas can be sprayed on the gasifier to cool it off,and thus gas explosion can be avoided.There is a possibility of direct gas explosion,but it can be avoided when the gas in the gas collecting space is replaced slowly by supplying a small amount of power or the inert gas fills the space in the previous gasification.The time a fire is lit is strictly controlled,the gas is drawn in by using the aspirator pump,and the gasifier pressure is kept in the state of micro-positive pressure in the middle and later gasification process.The conclusion is that the gasification process of the novel multi-thermalsource coal gasifier is safe according to normal operation rules.

Influence of Water Injection Fracturing on Crack Damage in Soft Coal and Application in Gas Extraction

In order to study the hypotonic and rheological particularity of “three soft” coal seam in west Henan, China, this paper explored the stress and damage characteristics of crack in coal under condition of water injection fracturing based on ABAQUS platform;The cohesive element in T-P damage evolution criterion was used to describe the approximately linear relationship between crack width and extending distance in soft coal. The simulation results show that stress evolution and crack damage in soft coal is a gradually developing process under condition of water injection fracturing. When the static pressure is 4 - 10 MPa, and the injection time is about 1 - 2 hours, the damage range of crack in soft coal can basically reach an ideal data of 80 - 100 m, and then greatly improve the hypotonic performance of “three soft” coal seam.

Three Stage Equilibrium Model for Coal Gasification in Entrained Flow Gasifiers Based on Aspen Plus

A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. The model is divided into three stages including pyrolysis and combustion stage, char gas reaction stage, and gas p.hase reaction stage. Part of the water produced in thepyrolysis and combust!on stag.e is assumed to be involved inthe second stage to react with the unburned carbon. Carbon conversion is then estimated in the second stage by steam participation ratio expressed as a function of temperature. And the gas product compositions are calculated from gas phase reactions in the third stage. The simulation results are consistent with published experimental data.

Hydraulic drill hole reaming technology with large flow and draining of coal mine gas

This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas,and the following conclusions were made.Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine,and can improve the efficiency of gas extraction to different degrees.The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal.When the coal seam basically becomes integrated,the critical water jet pressure increases,the discharge becomes relatively easy to achieve,the blocking effect on the gas extraction decreases,and the gas extraction significantly increases after the reaming process.When the coal seam is broken,the critical water jet pressure decreases,the discharge becomes difficult to achieve,the blocking effect on the gas extraction becomes obvious,and the gas extraction changes slightly after reaming.

Double Fire-Two Stage Method and Parameter Calculation of Underground Coal Gasification

The double fire two stage method of underground coal gasification was suggested. On the basis of material balance, the ideal gasification parameters were calculated, and the field test process was briefly introduced. In addition, the cause for a middle to a high heat value of water gas was described. And the reasonableness and feasiblity of the method was proved, showing that the double fire two stage gasification is an important technique for commercialized production.

Underground coal gasification and its strategic significance to the development of natural gas industry in China

Based on the present situation and trend of underground coal gasification in China and overseas, this article puts forward the basic concept, mechanism and mode of underground coal gasification, and presents the challenges, development potential and development path now faced. In China, underground coal gasification which is in accord with the clean utilization of coal can produce "artificial gas", which provides a new strategic approach to supply methane and hydrogen with Chinese characteristics before new energy sources offer large-scale supply. Coal measure strata in oil-bearing basins are developed in China, with 3.77 trillion tons coal reserves for the buried depth of 1000-3 000 m. It is initially expected that the amount of natural gas resources from underground coal gasification to be 272-332 trillion cubic meters, which are about triple the sum of conventional natural gas, or equivalent to the total unconventional natural gas resources. According to the differences of coal reaction mechanism and product composition of underground coal gasification, the underground coal gasification can be divided into three development modes, hydrogen-rich in shallow, methane-rich in medium and deep,supercritical hydrogen-rich in deep. Beyond the scope of underground mining of coal enterprises, petroleum and petrochemical enterprises can take their own integration advantages of technologies, pipeline, market and so on, to develop underground coal gasification business based on their different needs and technical maturity, to effectively exploit a large amount of coal resources cleanly and to alleviate the tight supply of natural gas. It can also be combined with using the produced hydrogen in nearby area and the CO_2 flooding and storage in adjacent oil areas to create a demonstration zone for net zero emissions of petroleum and petrochemical recycling economy. It is significant for reserving resources and technologies for the coming "hydrogen economy" era, and opening up a new path for China's "clean, low carbon, safe and efficient" modern energy system construction.

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.

The R&D of a Novel Sulfur Tolerant CO Shift Catalyst and Its Application in the Integrated Low Water Gas Ratio Process

The QDB-5 sulfur tolerant CO shift catalyst, with anti-methanation property by supported compositing alkali promoters, has been proved to effectively reduce the outlet methane content in the condition of a low water gas ratio. Thus, a new technology based on a lower water/gas ratio than before has been developed with the new catalyst. The CO conversion at lower temperatures and catalyst stability were confirmed by long term industrial application. The high temperature catalyst performance also showed a better result than the conventional commercial catalyst, with higher CO conversion and well controlled methane outlet. Our research and the industrial application of catalyst have shown the importance of alkali metals as core promoters for such kind of catalysts.

Progress on the hydraulic measures for grid slotting and fracking to enhance coal seam permeability

A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.

A study on the flowability of gas displacing water in low-permeability coal reservoir based on NMR technology

Flowability of gas and water through low-permeability coal plays crucial roles in coalbed methane(CBM)recovery from coal reservoirs.To better understand this phenomenon,experiments examining the displacement of water by gas under different displacement pressures were systematically carried out based on nuclear magnetic resonance(NMR)technology using low-permeability coal samples of medium-high coal rank from Yunnan and Guizhou,China.The results reveal that both the residual water content(W_(r))and residual water saturation(S_(r))of coal gradually decrease as the displacement pressure(P)decreases.When P is 0-2 MPa,the decline rates of W_(r) and S_(r) are fastest,beyond which they slow down gradually.Coal samples with higher permeability exhibit higher water flowability and larger decreases in W_(r) and S_(r).Compared with medium-rank coal,high-rank coal shows weaker fluidity and a higher proportion of irreducible water.The relationship between P and the cumulative displaced water content(W_(c))can be described by a Langmuir-like equation,W_(c)=WLP/(PL+P),showing an increase in W_(c) in coal with an increase in P.In the low-pressure stage from 0 to 2 MPa,W_(c) increases most rapidly,while in the high-pressure stage(P>2 MPa),W_(c) tends to be stable.The minimum pore diameter(d′)at which water can be displaced under different displacement pressures was also calibrated.The d′value decreases as P increases in a power relationship;i.e.,d′the coal gradually decreases with the gradual increase in P.Furthermore,the d′values of most of the coal samples are close to 20 nm under a P of 10 MPa.

Continuous Method Development and Numerical Study of HHV Water Gas Production by Pulverized Coal

In energy industries, it is always of difficulty to produce high heat value（HHV） gas continuously using pulverized coal. In this paper, a new type furnace for partitioned alternative gasification using pulverized coal is developed, in which the oxidation and reduction reaction occur alternatively with the dropping of pulverized coal and finally HHV gas could be continuously obtained at the reduction zone exit and low heat value（LHV） gas at the oxidation zone exit. Furthermore, the gasification characteristics and their factors in furnace are numerically simulated under two dimensional model with a self-coded program, based on heat, mass and energy transfer as well as reaction principles. It is found that the producing rate of HHV gas is 1.10Nm3/kg with heat value of ll.72MJ/Nm3, how- ever, that of LHV gas is 2.58Nm3/kg with heat value of 5.30MJ/Nm3, and the coal gas efficiency is 81.16% under optimized conditions.

Effect of bubbles addition on teetered bed separation

To improve the separation efficiency of a conventional Teetered Bed Separator(TBS) in beneficiation of fine coal with a wide size range,an Aeration TBS(A-TBS) was proposed in this investigation.The bubbles were introduced to A-TBS by a self-priming micro-bubble generator.This study theoretically analyzed the effect of bubbles on the difference in hindered settling terminal velocity between different density particles,investigated the impact of superficial water velocity(V_(SW)) and superficial gas velocity(V_(Sg)) on bed fluidization,and compared the performance of the TBS and A-TBS in treating 1-0.25 mm size fraction particles.The results show that the expansion degree of fluidized bed which was formed by different size particles or has different initial height,is increased by the introduction of bubbles.Compared with the TBS,at the same level of clean coal ash content,the A-TBS shows an increase in the combustible recovery of clean coal,ash content of tailings,and practical separation density by 5.26%,6.56%,and 0.088 g/cm3 respectively,while it shows a decrease in the probable error(E_p) and V_(SW) by 0.031 and 3.51 mm/s,respectively.The addition of bubbles at a proper amount not only improves the separation performance of TBS,but also reduces the upward water velocity.

水煤浆气化炉协同处理过程中有机物排放特征——以多环芳烃和二噁英为例

采用工业化试验对水煤浆气化炉协同处理蒽醌染料、精馏残渣、废活性炭、废有机溶剂等多源有机废物过程中多环芳烃(PAHs)和二噁英(PCDD/Fs)的排放特征进行研究.结果表明,协同处理有机废物不会对水煤浆气化炉的气化压力、气化温度和小时产气量产生显著影响,但合成气中CO和CO_(2)的气体体积分数较空白工况有所变化,CO的气体体积分数由40.9%下降至31.5%,而CO_(2)气体体积分数则由23.4%增加至31.0%,主要原因可能是有机废物的引入使得气化炉燃烧更充分;协同工况下气态排放物中PAHs和PCDD/Fs分别以萘和低氯代同系物为主,其中PAHs和PCDD/Fs的总毒性当量分别在0.12–0.49ng-TEQ/m^(3)和1.22–3.82pg-TEQ/m^(3)之间,较空白工况下PAHs(0.06–0.11ng-TEQ/m^(3))和PCDD/Fs(1.34–2.97ng-TEQ/m^(3))的总毒性当量无明显增加,且仍远低于相关标准限值;协同工况下固态样品中PAHs和PCDD/Fs分别以低、中环和低氯代同系物为主,硫磺(0.49ng-TEQ/kg)和炭黑(0.37ng-TEQ/kg)的PAHs总毒性当量,以及碳酸氢铵(8.3pg-TEQ/kg)的PCDD/Fs总毒性当量分别高于其他固态样品的PAHs和PCDD/Fs总毒性当量.协同工况下固态样品中PAHs和PCDD/Fs的总毒性当量较空白工况均无明显增加,环境风险可控.

原料煤灰分含量对气流床煤气化的影响分析

分析原料煤灰分变化对气流床煤气化的影响对气化炉的设计选型、生产运行有重要意义。通过建立干煤粉气化炉和水煤浆气化炉的气化过程模型,研究了原料煤灰分发生变化时对有效气含量、产气量、氧耗等的影响。研究结果表明:在相同负荷及操作温度下,随着原料煤灰分含量的增大,两种气化炉的有效气产量降低,有效气含量未发生明显变化;干煤粉气化炉较水煤浆气化炉氧耗低,相较而言,干煤粉气化炉更能够适应高灰分煤种。

干煤粉气化炉黑水闪蒸系统工艺优化

针对GSP干煤粉气化工艺装置存在的闪蒸系统设备能力不足、闪蒸效果不佳、系统超负荷运行、管道设备磨损和堵塞、现场可燃气超标等影响长周期运行的问题,通过对合成气洗涤、旁闪、二级闪蒸等系统进行工艺优化,同时增加澄清槽和过滤机等技术改造,解决了闪蒸系统存在的问题,且1.0 MPa饱和蒸汽用量比改造前减少10.3 t/h,脱盐水用量比改造前减少110 t/h。

高效叶片式分离器在合成气洗涤塔的应用探索

某煤制油项目干煤粉气化炉运行后期出现洗涤塔易带水问题,无法满足高负荷运行需求。针对该问题进行了原因分析,并引入一种高效叶片式分离器,介绍了其结构、工作原理及性能指标、处理能力,通过CFD流体动力学模型和相关计算软件精确评估了其工作状况及可允许的最大气、液相处理能力,并对合成气洗涤塔进行了高效叶片式分离器改造试用。结果表明:改造试用实现了干煤粉气化炉长周期105%以上负荷运行。

气化炉长周期稳定运行探索分析

以生产企业实际运行数据为基础,着重就水煤浆气化及粉煤加压气化两种炉型从气化煤质、装置运行两个方面分析,找出影响其长周期稳定运行的因素,并给出各影响因素的控制指标。