CN104947493A

CN104947493A - Method for separating lignin from alkaline pulping black liquor

Info

Publication number: CN104947493A
Application number: CN201510353175.5A
Authority: CN
Inventors: 汪传松
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-06-19
Filing date: 2015-06-19
Publication date: 2015-09-30

Abstract

The invention relates to a method for separating lignin from industrial waste water alkaline pulping black liquor. Chemicals are added to the black liquor, lignin sodium salt in the black liquor is quickly converted into insoluble lignin to be precipitated and solidified into coarse grains with good filterability through chemical reactions, the density of the black liquor is increased through the added chemicals, minute bubbles are generated and attached to the lignin grains, the lignin floats on the liquid level, and then the lignin can be removed and dewatered. Equipment needed in the technology is less, investment in the equipment is low, production startup is quick, the recovery rate of alkaline and the lignin is high, operation is easy and convenient, the influence of temperature is avoided, production efficiency is extremely high, no secondary pollution is generated, the requirements for enterprise scale, economic power and technical capacity are not high, the application range is wide, the method can be used for treating black liquor formed by various plants, especially, the separated lignin can be converted into high value-added commodities through deep processing, and then considerable economic benefits are acquired.

Description

The separation method of lignin in alkaline pulping black liquor

Technical field

The present invention relates to the process of industrial wastewater, particularly relate to the separation method of lignin in alkaline pulping black liquor.

Background technology

In prior art, the black liquor produced when producing string with highly basic boiling plant, by the lignin that the chemistry such as acid out, flocculation or physico-chemical process are separated, all be deposited in bottom liquid layer, and its particle is tiny, the combination between particle loosely, slightly disturbance just disperses to form dirty solution in a liquid again, inconvenience is filtered and is moved apart from black liquor, is not thus suitable for industrialized production, so that have to adopt alkali recovery furnace process black liquor.And equipment investment needed for alkali collection oven process is huge, the installation and debugging phase is longer, runs big energy-consuming, cost is high, disposal ability is by the restriction of alkali recovery furnace scale, and burning lignin produces a large amount of carbon dioxides, simultaneously, the value of lignin is very low, its serious waste of resources.

Summary of the invention

The object of the present invention is to provide a kind of black liquor treatment method, while making the lignin sodium salt in alkaline pulping black liquor be transformed into rapidly the precipitation of slightly solubility lignin, the lignin of precipitation is also made to form macrocrystalline comparatively closely fast, float to liquid level, separate with the liquid layer under it, so that it is moved apart from black liquor and dewaters further.

The present invention adds chemicals and realizes its object in black liquor.It is by the chemical reaction of lignin sodium salt in chemicals and black liquor, lignin lignin sodium salt being converted into rapidly be insoluble in water and separating out from black liquor, make the lignin of precipitation connect into rapidly structure by the effect of medicine tightr simultaneously, the macrocrystalline that filtrability is good, and form minute bubbles in black liquor by acting on of medicine and be attached on lignin crystal grain, lignin crystal grain is floated, the density of liquid is increased in addition by adding of chemicals, to strengthen the difference of lignin and fluid density, the floating of further promotion lignin crystal grain, it is made to float to liquid level rapidly.Because the lignin floating over liquid level is water insoluble, and particle is comparatively thick, and grain structure is comparatively tight, thus it can be moved apart from liquid level very easily, transfer to other places.Meanwhile, because lignin crystal grain is comparatively thick, grain structure is comparatively tight, thus it has good filtrability, has both been easy to pile up natural-dehydration, and be also easy to filtering means dehydration and oven dry, this makes the recovery of lignin become very convenient.

Existing chemistry, the physical chemistry processing method of this method and black liquor are the same, have equipment needed thereby and a series of feature such as high, the comprehensive production cost of small investment, alkali and lignin recovery rate is low, non-secondary pollution.In addition, because the lignin particles adopting this method to be formed swims in liquid layer surface, and its particle is comparatively thick, and grain structure is comparatively tight, not easily again disperses in a liquid and forms dirty solution, from black liquor, thus moving apart lignin very convenient.Meanwhile, the lignin filtrability moving apart out from black liquor is good, both directly can pile up dehydration, is also easy to filter and dry.In addition, its chemical reaction velocity is exceedingly fast, under natural temperature condition, after chemicals contacts with black liquor, lignin sodium salt just can be made in one minute to be converted into lignin and to float to liquid level, and it react not temperature influence, thus can be continuously produced, its production efficiency is high.On the other hand, this method is easy to operation, goes into operation fast, requires not high to the scale of enterprise and economic strength, technical capability, and widely applicable, can be used for the black liquor process that all kinds of plant is formed.The more important thing is, the lignin reclaimed can carry out deep processing, to be converted into the commodity of high added value, thus the part offset needed for black liquor process drops into, thus the economic benefit of slurrying can be improved significantly, before making " for process " and the improvement black liquor that is forced to that processes changes enterprise into and initiatively utilizes black liquor to obtain the conscious action of economic interests.

Specific embodiments

Embodiment one: build a black liquor treatment pond, makes liquid by the special-purpose medicaments of process black liquor simultaneously.The special liquid of black liquor and process black liquor is injected treatment pond simultaneously or successively, makes the two mixing.After liquid mixes with black liquor, just there is chemical reaction immediately, the lignin on the one hand the lignin sodium salt in black liquor being converted into rapidly to be insoluble in water and separating out, and formed rapidly under the effect of medicine structure comparatively closely, the good comparatively coarse crystallization particle of filtrability.On the other hand, generate minute bubbles by the reaction of medicine and black liquor and be attached on the crystal grain of lignin, impel lignin crystal grain to float.Meanwhile, process makes the density of liquid increase adding of medicine, impels the floating of lignin crystal grain further, makes it rapidly floating to liquid level.After lignin crystal floats to liquid level, with scrapper conveyor, the lignin swimming in liquid level is scraped from liquid level, transfer to stack-up-yard and pile up dehydration.Remove the raffinate after lignin then for the flushing of paper pulp, through recycling several times, then mix with lime, react, change into strong base solution and white clay.Strong base solution is wherein got back to rotary spherical digester and is reused for plant boiling, and white clay is then sold as building materials or chemical goods.

Embodiment two: build a black liquor treatment trough, at the caudal end egress peripheral hardware band filter for the treatment of trough.The upper limbs strainer of band filter is lower than the outlet for the treatment of trough.First the special-purpose medicaments of process black liquor is made liquid, then by the while of black liquor and process liquid or in priority input processing groove, make the two mixing.Chemical reaction is there is immediately after medicine mixes with black liquor, lignin sodium salt in black liquor is transformed into rapidly be insoluble in the lignin of water to be separated out, and form the macrocrystalline that structure is comparatively tight, filtrability is good, in black liquor, form minute bubbles and be attached on lignin crystal grain simultaneously, impelling lignin crystal grain to float.In addition, adding of medicine makes the density of black liquor increase, thus promotes the floating of lignin crystal grain further.Like this, lignin crystal grain, in the process shifted to treatment trough afterbody with liquid, floats to liquid surface gradually, when it arrives the outlet for the treatment of trough afterbody, the upper limbs strainer being discharged to band filter with liquid filters, is transported to stack-up-yard after filtration and piles up dehydration.The filtrate obtained is then for the flushing of paper pulp, and through recycling several times, then mix with lime, react, change into strong base solution and white clay, the former gets back to rotary spherical digester and is reused for plant boiling, and latter is sold as building materials or chemical goods.

Claims

1. the separation method of lignin in alkaline pulping black liquor, add chemicals in black liquor, by the chemical reaction of medicine and black liquor, the lignin sodium salt in black liquor is made to change lignin into rapidly and separate out, it is characterized in that: the lignin of precipitation forms the good comparatively coarse crystallization of filtrability, and floats to liquid level.