Quantifying relationships between subsidence and longwall face advance using DInSAR

Surface subsidence that results from longwall mining can be large magnitude and can affect significant areas. Conventional methods for subsidence monitoring include leveling, global positioning system(GPS), and photogrammetric surveys. Remote sensing techniques including, aerial LiDAR, terrestrial laser scanning, and satellite-based Differential Interferometric Synthetic Aperture Radar(DInSAR), are also used to measure deformation associated with subsidence. DInSAR data are different than data from conventional subsidence surveys. Images capture data over large areas(hundreds of kilometers), and each pixel(data point) in an image quantifies the average displacement over an area of square meters.DInSAR data can have fairly high time resolution; imaging periods typically range from weeks to months.DInSAR data can be useful to monitor subsidence sequentially over short periods. Regularly monitoring subsidence may help define if caving is progressing normally and can establish relationships between surface deformation and longwall face advance, which has potential to help quantify possible risks to mine stability. In this study, subsidence at a longwall trona mine is monitored over short periods, typically 12 days, as the longwall face is advanced through a panel. C-band interferometric wide swath synthetic aperture radar(SAR) images from the sentinel satellites are used to quantify the subsidence. The onset of subsidence occurs close in time to the beginning of the longwall face advance, and overall,the development of subsidence closely follows the longwall face advance.     

天然碱代替纯碱的磷矿选矿试验

经过煅烧的天然碱可以在浮选作业中代替纯碱使用。王集磷矿一、三层混合矿和宁夏贺兰山磷矿使用这种煅烧天然碱,浮选指标均优于原使用纯碱的工艺。该药剂来源广,价格低,可以为企业带来较大的经济效益。     

天然碱生产高质量纯碱的技术条件

针对天然碱加工制纯碱的生产过程，本文研究了生产流程、原料成份、操作技术对产品质量的影响；探讨了生产高质量纯碱的技术条件，给出了部分操作控制指标。     

A study on the conversion of trona to sodium bicarbonate

The deactivation model was used to explain kinetics underlying the conversion reaction of trona to NaHCO₃ (sodium bicarbonate). The model showed good agreement with the experimental data obtained from the conversion reaction of trona to NaHCO₃. It gave the value of 0.94 as an average correlation coefficient with the experimental data. However, at lower temperature, the model was in poor agreement with the data. This would be related to the structural variation of trona particles at the lower temperature. A trona particle is initially nonporous and then it begins to crack. This structural variation creates more surface area for the reaction with CO₂ and water vapor. However, at the lower temperature, the fissures on the surface of the particles are not fully developed during the beginning of the reaction. As a consequence, the level of the conversion of trona at the lower temperature is low during the beginning of the reaction and the time to approach the complete conversion is shorter as temperature increases. However, since the deactivation model does not include the term articulating the degree of the structural variation during the reaction, it does not fit well to the experimental data at the lower temperature. The deactivation rate constant, k_d is strongly temperature dependent and the change of the slope suggests the reaction mechanism changes as the reaction temperature increases.     

Soda Ash Production from Trona in a Spray Dryer

Production of soda ash from Trona solution was achieved in a spray dryer reactor. Fractional conversion of NaHCO₃ reached to values close to unity in this unit within a residence time of less than a second. Results indicated that above 140°C, heat transfer limitations played a significant role on the calcination process taking place in the spray dryer. Equilibrium limitations may become important only at very low temperatures and at high CO₂ and H₂O partial pressures. Results obtained in the spray dryer and from the thermal gravimetric analysis of Trona crystals agreed well. It was also shown that the predictions of the unreacted core model are in good agreement with the kinetic data. © 1997 SCI.     

Biomass gasification in supercritical water: II. Effect of catalyst

In this study, the effect of the type of catalyst on hydrothermal gasification of three specifically chosen samples of natural biomass was investigated. Biomass feedstocks, including lignocellulosic materials (cotton stalk and corncob) and the tannery waste, were gasified in supercritical water by the addition of catalyst. The catalysts used were K₂CO₃, Trona (NaHCO₃·Na₂CO₃·2H₂O), red mud (Fe-oxide containing residue from Al-production) and Raney-Ni. The gasification experiments were performed in a batch autoclave at 500 °C. The amounts and compositions of the gases and the amounts of water soluble compounds from gasification were determined. The effect of catalysts on gasification varied with the type of biomass. The catalysts significantly increased the hydrogen yield by supporting the water–gas shift reaction and the methane reformation.     

MICROWAVE INDUCED CONVERSION OF HYDROGEN SULFIDE

Abstract

The reaction of hydrogen sulfide with trona and calcium oxide in the presence of char started as soon as microwave energy was applied. However, with conventional heating, the reaction started only when the bed temperature reached approximately 540^°c. char absorbing microwave energy is rapidly heated to very high temperatures, enhancing the H₂S reaction with oxides contained in char or oxides added to char in the reaction. A 100% conversion of trona was achieved but the maximum conversion of calcium oxide was only 79%. The minimum content of char required to induce the reaction of H₂S with trona using microwave energy was 20% of char-trona mixture. When the trona content in the mixture of char-trona mixture was greater than 50%, an additional conversion of H₂S occurred to produce some amount of elemental sulfur that was deposited in the bed. This clearly demonstrates that char combined with microwave induces H₂S reaction with mineral oxides.     

天然碱碳酸化法生产纯碱(小苏打)的相图分析与相图计算

给出了又一种天然碱碳酸化相图及相图分析。以某天然碱加工厂提供的原料碱液为例 ,进行了相图计算 ,并对两种相图计算结果进行了比较。最终认为该相图同样可用于天然碱碳酸化相图分析与相图计算。     

An investigation on the production of sodium metaborate dihydrate from ulexite by using trona and lime

In this study, it was investigated the optimum conditions (extraction temperature and extraction period) for the production of sodium metaborate dihydrate (NaBO₂.2H₂O) by the reaction of ulexite (NaCaB₅O₉·8H₂O) with trona (NaHCO₃-Na₂CO₃·2H₂O) and lime (CaO). The optimum extraction conditions were determined as 50 °C and higher temperature; 6 h and longer extraction time. The characterizations of the product (sodium metaborate dihydrate crystals) were performed by thermogravimetric (TG-DTG) and X-ray diffraction (XRD) analyses. In addition, the percent purity of the product was found to be 96% by using a conductometric method.     

可溶性矿床的综合开采及利用

锡林郭勒苏尼特碱业有限公司的天然碱矿床是可溶性矿床 ,过去采用单一的采掘机械开采 ,回采率仅为78%左右。为此 ,公司组织技术人员总结经验、分析造成损失的原因 ,在扩采的基础上采用了多种采掘机械联合开采和配套碱田工艺系统进行碱份回收的综合工艺 ,大幅度减少了损失和贫化 ,回采率提高到 95 %以上 ,使有限的碱资源得以充分利用。