加压溶气上浮技术净化煤泥水

本文概述了气浮法净水的基本原理。介绍了加压溶气上浮设备净化煤泥水的工艺流程,主要技术参数及工业性试验结果。探讨了煤泥水气浮净化的几个主要影响因素。最后,对气泡与絮粒的粘附机理也进行了研究。

Optimum conditions to treat high-concentration microparticle slime water with bioflocculants

We studied how bioflocculants,produced by white-rot fungi,affect flocculation in slime water.Based on a test in an orthogonal design,flocculation conditions were optimized.The results show that flocculation activity is at its highest when the following conditions are met:slime water concentration 27.42 g/L;coagulant aid(CaCl_2) mass concentration 5.0 g/L;two-segment stirrings:the first at a stirring speed of 60 r/min for 180 s and the second 180 r/min for 60 s;a pH of 11 and a flocculant concentration of 15 mL/L.The flocculation activity can be up to 98.71%of bioflocculants at the time.Further experiments indicate that most of the flocculation active material is found outside the mycelium cells.This is the extracellular secretion produced by mycelium cells during the fermentation process.This flocculant has strong thermal stability.Many kinds of cations have a flocculation function to assist bioflocculants.This aid-flocculation effect of the divalent cation Ca^(2+) is obvious in the bioflocculant produced by the white-rot fungus.Therefore,this is of great value when applied to control engineering in the battle against water pollution.

Influence of ultra-fine fly ash on hydration shrinkage of cement paste

Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.

Adsorption properties of CFBC ash-cement pastes as compared with PCC fly ash-cement pastes

Circulating fluidized bed combustion （CFBC） ash can be potentially used as supplementary cementitious materials for concrete production due to its desirable pozzolanic activity. The adsorption properties of CFBC ash-cement pastes were studied, and ordinary pulverized coal combustion （PCC） fly ash-cement pastes were used as control. The water-adsorption and superplasticizer （SP）-adsorption properties of the pastes were evaluated by water demand and UV-visible absorption spectroscopy respectively. The results show that CFBC ash-cement system has greater compressive strength as compared with PCC fly ash-cement system at a given curing age, although the water demand of the former is significantly higher than that of the latter. CFBC ash-cement pastes possess higher adsorption ability of aliphatic SP than PCC fly ash-cement pastes and the adsorption amount increases with an increase in ash replacement ratio. CFBC ash- cement pastes exhibit lower workability with higher slump loss. It is concluded that CFBC ash can be potentially used as supplementary cementitious material in concrete production, but the mix design of CFBC ash concrete needs to be appropriately adjusted. It is suggested that CFBC ash is used for the production of the concrete needing low flowability.

A comparative investigation of the properties of coal-water slurries prepared from Australia and Shenhua coals

Two coal samples of similar rank were chosen from Australia and China to investigate the differences in Coal-Water Slurry （CWS） made from them. The effect of ash content and particle size gradation on these properties was also studied. Different grinding times were used when grinding the two coals and particle size analysis of these ground coals was used to select samples with a ＂double-peak＂ particle size distri- bution. All the ＂double-peak＂ samples were used to prepare a CWS. The concentration, viscosity, fluidity, and stability of each CWS were measured. The results show that the properties ofa CWS prepared from a coal sample with a ＂double-peak＂ size distribution are better than those CWS prepared from samples with a mono-modal particle distribution. The ash content of Australian coal is 21.72g higher than the ash content of Shenhua coal. The highest coal concentration in slurry from the Australia coal is 11.01% higher than in CWS from the Shenhua coat. The fluidity and stability of the CWS prepared from the Australian coal are both better than the fluidity and stability of slurry prepared from Shenhua coal. High ash content in the Australian coal imnroves the nulning results of a CWS made from it.

Experimental study on slime water flocculation sediment based on the montmorillonite hydration expansion inhibition

Through the montmorillonite settlement experiment in the clear water and electrolyte solution, the influence of slime water settling character was studied in clear water and different electrolyte solution, the montmorillonite＇s hydration ex- pansion effectively restrained was verified, the process method to wash coal with the electrolyte was put forward, and the re- sults indicate that the solution of 10 g/L KC1 is optimal inhibitor on the montmorillonite in the tested three kinds of electrolyte solution. With the contrast test in clear water and electrolyte solution, two reagent adding way can be selected in KC1 solution： one way is to add PAM separately, the effectively sedimentation can be made with simply 0.1% anion; the other way is the co- ordination with polymeric aluminum and PAM, the anionic of PAM and polymeric aluminum are 0.02% and 0.5% respectively. However, in clear water, the polymeric aluminum must be joined together with the anionic PAM, and the amount of the PAM reaches 0.5%, which is 25 times as great as that in KCL solution. The field work with raw coal further verifies the above con- clusions further.

Properties prediction of fly ash blended concrete using hydration model

Fly ash is an industrial by-product from coal combustion and has been widely used as mineral admixture in normal and high strength concretes. Owing to the pozzolanic reaction between calcium hydroxide and fly ash, compared with Portland cement, the hydration of concrete containing fly ash is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing fly ash. Similar to the hydration reaction of cement, fly ash activity is divided into three processes: an initial dormant period, a phase-boundary reaction process and a diffusion process. The mutual interactions between the cement hydration and fly ash reaction are considered through the available calcium hydroxide amount and available capillary water amount in the system. The properties of hardening fly ash blended concrete, such as the reaction degree of fly ash, chemically bound water, calcium hydroxide, and compressive strength, are determined from the contributions of cement hydration and fly ash pozzolanic reaction. The evaluated results show good accordance with the experimental results.