面包制作工艺的探讨

简要介绍了面包制作的基本工艺,并就面包制作过程中的各个环节应注意的问题提出了自己的观点。     

难处理金矿石选冶工艺研究

本文介绍了四川省东北寨金矿石的选冶工艺研究。该矿中的金以次显微状分散在黄铁矿（砷黄铁矿等）硫化矿物和粘土矿物中,在电子显微镜和电子探针下都未见到金矿物,矿石中还富含有害杂质砷、硫和碳,属极难处理矿石。经多方案比较,提出的处理该类型矿石的选冶流程为：浮选－精矿焙烧－浸出（有氰和无氰）工艺,其中氰化浸出的选冶总回收率达８１．３４％,无氰强化浸出的选冶总回收率达８２．１５％。     

Confirmation that the Maillard reaction is the principle contributor to the antioxidant capacity of coffee brews

Chemical characteristics related to the antioxidant activity of roasted coffee (RC) were evaluated, using non-roasted coffee beans (NRC) and model Maillard reaction products (MRPs) as controls. The formation of MRPs and the degradation of phenolics in RC were characterized by employing a battery of fluorescence, UV-vis spectra and tri-stimulus color parameters measured on NRC, RC and the model MRPs. Total chlorogenic acid (CGA) and caffeine contents in NRC and RC extracts were also quantified using HPLC. Both RC and controls showed high antioxidant activity in three chemical based assays irrespective of caffeine content. Data from this study suggested that natural phenolics present in NRC had higher antioxidant activity compared to MRPs derived from coffee and model MR systems. However, MRPs were the prevailing antioxidants in RC as free CGA was lost (> 90%). The mechanisms of the antioxidant action associated with coffee MRPs involved hydrogen atom transfer and single electron transfer mechanisms.     

Real time monitoring of free radical processes during the roasting of coffee beans using electron paramagnetic resonance spectroscopy

Because of the roles of free radicals in the formation of Maillard reaction products and as markers of oxidation processes in foods, the dynamics of free radical generation during the roasting of coffee beans have been measured, and some exploratory investigations conducted on the extent to which these are influenced by the bean type, and the atmosphere (air vs. N₂), in which the beans were roasted and cooled.     

高铜金精矿焙烧浸出提取金铜

对通常氰化法难以处理的高铜金精矿（Ｃｕ１５％、Ａｕ４２ｇ／ｔ）采用焙烧浸出新工艺，可获得金９８．７４％、铜９３．０３％的冶炼回收率。建设５０ｔ／ｄ规模冶炼厂的投资利税率２３．４８％，利润率１５．９４％，内部收益率１８．１５％，效益显著。本工艺技术经济指标优于火法     

焙烧—氰化法从铜精矿中提取金银铜的试验研究

对某浮选铜精矿进行了焙烧一氰化法提取金、银和铜的工艺方法研究。研究表明,将浮选金精矿(0.074 mm所占比例>90%)于600℃条件下焙烧,产生的SO2用于制酸,焙砂采用5%H2SO4浸取回收铜,酸浸渣先用新型调整剂(NH4HCO3+NaOH)调浸出液pH值≈9.5,以氰化法进行浸出。其金、银和铜的浸出率分别达到98.18%、32.17%和93.6%,经济效益和社会效益显著,为铜精矿的湿法提取工艺提供了一个有效的工艺方法。     

Defluorination of bastnaesite by steam roasting process

The bastnaesite was defluorinated by steam roasting process, and fluorine was removed in the form of hydrogen fluoride to realize the separation from rare earth. The effects of particle size of raw material, roasting temperature and time on defluorination rate of bastnaesite were studied. The suitable conditions of steam roasting process are that the particle size of raw material is less than 74 μm, the roasting temperature is 1000 °C and the roasting time is 4 h. The defluorination rate of bastnaesite is close to 100% under above these conditions. When the temperature rises to 1000 °C, the voids on the surface of the particles increase obviously, and there is a developed network of voids, which indicates that the fluorine oxides in bastnaesite react fully with the saturated water vapor at this stage, and a large amount of fluorine escapes in the form of hydrogen fluoride from the surface and inside of the mineral. X-ray diffraction results show that there are only rare-earth oxides in the form of Ce_0.33La_0.33Ca_0.33O_1.5 and Ce₇O₁₂ in the slag. The results of energy spectra and chemical analysis show that the fluorine in the baking sand was basically completely removed.     

含砷金精矿的焙烧和氰化浸出试验及焙砂和浸渣的矿物学研究

采用两段焙烧——焙砂水淬(稀酸介质)——氰化工艺从某含砷难处理金精矿中提金,提取率可达92．2％,而采用常规的焙烧——氰化浸出工艺只能达到84．5％。对焙砂及氰化渣的矿物学研究表明,残留于渣中的大多数金均以超细的不可见金粒的形式为Fe_2O_3相包裹,因此,自该类型精矿中充分回收金的前提条件是尽可能破坏Fe_2O_3相。     

Decomposition of mixed rare earth concentrate by NaOH roasting and kinetics of hydrochloric acid leaching process

A new clean extraction technology for the decomposition of Bayan Obo mixed rare earth concentrate by NaOH roasting is proposed.The process mainly includes NaOH roasting to decompose rare earth concentrate and HCl leaching roasted ore.The effects of roasting temperature,roasting time,NaOH addition amount on the extraction of rare earth and factors such as HCl concentration,liquid-solid ratio,leaching temperature and leaching time on the dissolution kinetics of roasted ore were studied.The experimental results show that when the roasting temperature is 550℃ and the roasting time is 60 min,the mass ratio of NaOH:rare earth concentrate is 0.60:1,the concentration of HCl is 6.0 mol/L,the ratio of liquid to solid(L/S) 6.0:1.0,and the leaching temperature 90℃,leaching time 45 min,stirring speed 200 r/min,and the extraction of rare earth can reach 92.5%.The relevant experimental data show that the process of HCl leaching roasted ore conforms to the shrinking core model,but the control mechanism of the che mical reaction process is different when the leaching temperature is different.When the leaching temperature is between 40 and 70℃,the chemical reaction process is controlled by the diffusion of the product through the residual layer of the inert material.The average surface activation energy of the rare earth element is E_a=9.96 kJ/mol.When the leaching temperature is 75-90℃,the chemical reaction process is controlled by the interface transfer across the product layer(product layer interface mass transfer) and diffusion.The average surface activation energy of rare earth elements is E_a=41.65 kJ/mol.The results of this study have certain significance for the green extraction of mixed rare earth ore.     

PID技术在氧化铝焙烧炉上的应用

针对氧化铝焙烧温度采用人工手动控制存在精度低、温度波动范围大、稳定性差的缺点,利用经典闭环控制理论以及DCS自带的PID控制模块设计了温度闭环PID控制系统.该系统通过输入PID参数进行运算,由控制执行机构来精确控制燃料和炉内氧化铝量,从而实现氧化铝灼烧温度的稳定控制,保证了氧化铝的生产质量.