Preparation Of Briquetted Activated Carbon For Water Treatment From Datong Coal And Blended Coals

Datong is rich in coal resources,and the Jurassic,Permo Carboniferous low metamorphic bituminous coal in Datong has the characteristics of low ash,low sulfur,moderate volatile content and good chemical reactivity,which is the suitable raw material for the production of activated carbon.Since 1950's,Datong coal was used in the production of activated carbon.At present,water treatment,mainly the deep purification of drinking water,is the largest application area of coal based activated carbon at home and abroad.Briquetted activated carbon which has large production scale and low coat to production has properties of low floating rate and high strength and rough surface easy hang biological film very suitable for water treatment.Datong area is main bases of coal based activated carbon production in China.Tong-Mei group has constructed of the world's largest 100,000 tons/year of coal based activated carbon projects,of which 50,000 tons/year production capacity is the production of briquetted activated carbon;CRRC Datong Corporation Limited has also has constructed of 40,000 tons/year of coal based activated carbon projects,of which22,000 tons/year production capacity is the production of briquetted activated carbon.So far,the preparation of coal based activated carbon,especially the preparation of activated carbon from Datong coal,has carried out extensive,in-depth and meticulous research work,and achieved many practical application results.However,with Datong coal as raw material for production of high quality water treatment by briquetted activated carbon still exists the following problems:Briquetting is the initial link of the briquetted activated carbon production process,but briquetted for Datong coal especially under the condition of Datong coal blending have not grasp the main factors of briquetting and parameter optimization of briquetting process is not obtained;water treatment requires that activated carbon has more developed mesopore,and can adjust pore structure of activated carbon according to water quality characteristics,however,the study of pore structure adjustment method of briquetted activated carbon prepared by Datong coal is lack of systematicness,and the adjustment range of pore structure is not clear;activated carbon is widely used in the field of water treatment,the demand of high efficiency and economical recovery of activated carbon is put forward,magnetic separation is the effective method for recovering activated carbon from activated carbon,however,whether coal can be used as raw material,coal blending,magnetic mixing and pore adjusting method are used to prepare directional activated carbon for high quality water treatment under the condition of briquetted activated carbon preparation.Furthemore,the activated carbon for water treatment using iodine and methylene blue value as its water treatment performance,however these indexes correlation between the Natural Organic Matter?NOM?and Synthetic Organic Matter?SOM?in water sources is poor.The activated carbon for water treatment has not been prepared according to the pollutant characteristics of water sourcesIn this paper,a series of granular activated carbons were prepared by briquetting method from Datong bituminous coal as main raw material and blending metamorphic coal in the presence of Fe₃O₄ on the basis of optimized briquetting process.The activated carbon for water treatment from Datong coal blended with easy magnetic separation was studied by interpreting of pore structure and magnetic mechanism of activated carbon controlled by coal blending and additive Fe₃O₄.In the course of the research,besides determination of activated carbon iodine value and methylene blue adsorption value,caramel decolored ratio was used as index to water treatment capability of activated carbon samples.The pore structure and adsorption performance of activated carbon samples were obtained using Density Functional Theory?DFT?to calculating N₂ adsorption/desorption isotherm of nitrogen at 77 K and the magnetic properties of activated carbon were characterized by vibrating sample magnetometer.The main contents of this paper conclude:1)The effects of particle size of coal,adding amount of pitch,additional moisture and brequetting pressure on strength;2)Influence factors of coal quality on adsorption performance and pore structure development of activated carbon which prepared by Datong bituminous coal blending different metamorphic typical coal;3)The preparation of activated carbon by coal blending in the presence of Fe₃O₄ and the mechanism of catalyst pore making and magnetic assigning were studied;4)The high quality activated carbon for water treatment was prepared by orthogonal experiment optimizing process parameter,The influence of coal blending and technological parameters on the pore structure development was investigated.The main conclusions of this paper are as following:1)In the range of pulverized coal particle size,the finer the particle size of Datong coal,the higher the compressive strength of briquette and carbonized material obtained by carbonization;influence of moisture on the molding material compressive strength is not significant;increase the mixing quantity of pitch binder will enhance the compressive strength of briquetted material;the increasing of brequetting pressure help enhance compressive strength,but the high pressure will cause the coal particles rebound or collapse,cracks decrease the compressive strength of briquetted material;2)Pitch has little effect on the pore size of activated carbon,but it is not conducive to the development of micropores.Therefore,the addition of pitch can reduce the specific surface area of activated carbon,resulting in the decline of adsorption performance of activated carbon.Compare the activated carbon sample preparation by pitch dosage of 10%with activated carbon of no pitch adding,the methylene blue value which reflects the degree of mesopores changes a little but iodine value of activated carbon pore developed a drop of 14.1%.3)The degree of metamorphism of the raw coal largely determines the graphitization degree of the carbonized material,and the graphitization degree of the carbonization material and the kinds and quantities of inorganic minerals affect the pore structure development of the activated carbon:The graphitization degree is low,the mineral composition of the"active content"of the higher,the more conducive to the activation;under the same activation conditions,the greater the burning off of the char,the wider the mean pore diameter and the more developed in the mesopore and macropore.4)The pore structure development of coal blending activated carbon is not a simple superposition of pore structure of activated carbon of each single coal under the condition of briquetted activated carbon preparation.At the same time,Datong coal blending Taixi anthracite and Shengli lignite separately in the preparation of activated carbon render different degrees of change of total pore,which adding anthracite will enhance the micropore volume and micropore rate,and mixing of lignite is decreased in the mesopore and mesopore rate.5)Presence of Fe₃O₄ in the preparation process of activated carbon promotes burning off and caramel decolored ratio.The activated carbon by 100%Datong bituminous in adding of additives increased caramel decolored ratio from 24%to 50%.Burn off ratio of activation significantly increased and beyond 60%in the presence of additives by coal blending render caramel decolored ratio from 0%increased to 43%and 56%by anthracite coal and lignite blending respectively.The presence of Fe₃O₄can be catalytic activity point promoting the formation of micropores and accelerating the ablation of carbon and water vapor around it thus enlargeing micropore to mesopore and cacropore.It is Fe₃O₄ act as catalyst promotes activator ablation and enlargement of pore which play the role of pore adjustment.6)Activated carbon magnetic susceptibility of 0.15⁶×10^-5m³/kg due to the reaction between carbon and high hot water vapor,the reduction atmosphere of CO and H₂ reduced Fe₃O₄ to FeO and Fe by addition of 6%Fe₃O₄,which is adequate for the magnetic separation in high intensity magnetic field.7)Under the condition of optimized briquetting,carbonization and activation,the burning off of activation was 50%and the caramel decolored ratio of activated carbon was 24%;the development of pore structure of activated carbon is affected by the pore enlarging of additive Fe₃O₄ and the coal quality of coal blending:in the presence of additive the Datong coal blending higher degree of metamorphism of Taixi anthracite prepared activated carbon with mesopore rate of 46.6%lower than the 55.5%mesopore rate of activated carbon preparation by Datong bituminous coal;with lower metamorphic rate;Datong coal blending lower degree of metamorphism of Shengli lignite can promoting mesopore rate of activated carbon to 71.1%.8)By adding 6%Fe₃O₄ into raw coal,optimizing the process parameters by orthogonal experiment,Datong coal or its coal blending can be used to prepare high quality activated carbon for water treatment:Datong coal only and 80:20 blending ratio of Datong coal and anthracite coal,the caramel decolored ratio of 79%and 70%respectively can be prepared.The parameters of affecting caramel decolored ratio through range and variance analysis in a desending order:activation temperature T>activation time t>ratio of blending coal.It is show that catalytic of Fe₃O₄ for ablating carbon matrix and enlarging pore play a dominant role in the activation.In this paper,recycled high quality activated carbon for water treatment can be directional preparation taking Datong coal as the main material,through blending coal,adding Fe₃O₄,optimization of process parameters,using prequetting process.