The Extraction Of Lignin, Modification And Its Comprehensive Utilization

Lignin is a kind of natural aromatic compound with much hydroxyl, whichenhances mechanical strength of the plant as cellulose and hemicellulose bondingmaterial in plant body. The source of lignin is a very wide range, which can beextracted directly from the core material of all kinds of plants and also can be recycledfrom waste pulp of paper making. Waste pulp of paper making brings a big load to theenvironment, in which the main pollution composition is the abandoned lignin.Therefore, extracting the lignin in waste pulp and synthesising it to the products ofindustrial application value by the chemical modification not only have theenvironmental protection sense and more economic significance.This thesis chooses the black liquor as raw materials which is difficult to betreated and carries out a system of experiments about the extraction and modificationof lignin and the application of lignin’s modified products in oilfield drilling.The first chapter of this paper includes the summarisation of this kind of naturalaggregate lignin, in which introducing the existence and distribution of lignin innature and lignin’s basic molecular structure as well as the physical and chemicalproperties of lignin. At the same time, the first chapter also introduces the lignin’spurification methods existed and summarizes present situation of application andfuture development trend about the thinnervisbreaker and filtrate reducer for drillingfluid .The second chapter of this paper introduces the purification of lignin from theblack liquor. The main chemical composition of the black liquor has be determinedroughly through the experiment. Two kind of purification methods which is physicaland chemical methods are used to purify the lignin. The purity of lignin with the twomethods are compared. Physical method is that the black liquor is acidified and thentreated through the plate frame type filter press, which can get filter cake of crudeproducts lignin. But large amount of acid is consumed by this method and the filtratestill exists great harm on the environment because of high acidity. The chemicalmethod used in this article is that using synergy of subordinate structure salt resisting surfactant DM-5522 and organic flocculants CPAM to get lignin of high purity. Thebest pH value about using DM-5522 is determined. The amountofusage of DM-5522and CPAM on the influence of lignin’s extraction efficiency is studied and and therelevant mechanism is discussed in this paper. The adbantages of the chemical methodused to purify lignin in this paper are: (1) consumption of acid is little, the processingcost is greatly reduced and it can’t produce secondary sewage; (2) it can’t cause theproblem of sludge difficult to deal with because of the introduction of metal ions; (3)lignin has high purity and high desalination rate after the process.In the third chapter of this paper, lignin purified by above chemical method asraw materials is synthesized to two kind of drilling fluid additive by chemicalmodification. They are thinnervisbreaker—chromium iron lignin sulfonic acid sodium(FCLS) and filtrate reducer for drilling fluid—sulfited lignin sulfomethylatedphenolaldehyde resin (SLSP). It makes an analysis for main characteristic peaks of thetwo modified products in infrared spectrum, and discusses the main influence factorsin the modifing progeess. In the fourth chapter of this paper, it makes the indoorperformance evaluation of the modified lignin product and discusses the best usage ofSLSP and FCLS respectively, and investigates their performance of temperatureendurance, salt resistance and calcium resistance. The results of experiments showthat the modified lignin products prepared in this paper have good performance andcan meet the need of oilfield drilling, and can solve the problem of large usage ofoilfield chemicals because the wide sources of the raw materials and low price.