CN102079536A - Method for producing caustic soda and papermaking filler calcium carbonate by using natural alkali liquor - Google Patents

Abstract

The invention provides a method for producing caustic soda and papermaking filler calcium carbonate by using natural alkali liquor, comprising the following steps of: a, thermally decomposing the natural alkali liquor, simultaneously digesting and causticizing the thermally decomposed alkali liquor and quicklime; b, feeding the digested solution into a primary causticization reactor to be causticized continuously; c, feeding the causticized solution into a settling tank to be subjected to solid-liquid separation and evaporation concentration so as to obtain a caustic soda product, feeding a solid size into a secondary causticization reactor, adding the natural alkali liquor, and carrying out secondary causticization; d, feeding the solution subjected to the secondary causticization into three setting tanks to be subjected to solid-liquid separation so as to obtain a calcium carbonate size; e, carbonating by virtue of calcium carbonate; f, carrying out calcium carbonate particle balancing and refining on the produced size; and g, filtering the balanced calcium carbonate size, and drying and dehydrating to obtain a calcium carbonate product. By applying the method provided by the invention, water soluble component such as the caustic soda is recovered to the utmost extent, the quality of the calcium carbonate is improved, no waste water is discharged in the whole process, and a clean process for producing the caustic soda and the calcium carbonate by causticization is provided.

Description

A kind of natural alkali lye is produced the method for caustic soda and paper filler-calcium carbonate

Technical field

The present invention relates to the method that a kind of natural alkali lye is produced caustic soda and paper filler-calcium carbonate, belong to a kind of urao resources effective utilization, eco-friendly cleaning procedure.

Background technology

Ground such as China Henan, the Inner Mongol and Jilin are distributed with the urao resource, and it can make goods such as soda ash, caustic soda, sodium bicarbonate according to the difference of forming with suitable working method.It is a very sophisticated technological process that natural alkali causticization method is produced sodium hydroxide, and it utilizes the low advantage of natural alkali lye cost, the caustic soda that production prices are higher relatively.But causticizing process is produced caustic soda and is existed the comparison serious environmental problem at present, one ton of caustic soda of every production, the lime mud of by-product more than 2 tons can't be handled, because lime mud contains strong alkaline substances such as a large amount of caustic soda, soda ash and calcium hydroxide, the mode that can only take builds a dam stores up has caused huge threat to environment.

The technological process of causticizing process hydrogen manufacturing sodium oxide generally is used in the recovery of alkali in the black liquid.But after handling the black liquor problem, the processing of lime mud becomes the another severe problem that paper industry faces again.The treatment technology progress of causticization legal system caustic soda and lime mud mainly comprises three kinds of modes: first kind is the quality of strict control lime in the causticization process, the temperature of reaction of control causticization, the growth of regulation and control calcium carbonate crystal, to obtain qualified calcium carbonate product, present method requires the causticizing reaction temperature low, reaction efficiency is relatively low, simultaneously the calcium carbonate crystal particle is little, makes impurity such as its contained caustic soda be difficult to washes clean; The second way is that other technological process is constant, by the mode of wet-milling or dry grinding lime carbonate is carried out grain refine in the control lime quality, and outsourcing simultaneously or lime calcining reclaim carbonic acid gas and remove alkali.Present method is revised existing technology, existing at present the application, but cost is higher relatively.The third method promptly is that the lime carbonate of by-product is calcined, and the output calcium oxide recycles, but present method is higher to equipment requirements, and fuel cost is high simultaneously, is difficult to promote the use of.

Summary of the invention

The object of the invention has provided a kind of method of utilizing natural alkali lye causticizing process to produce caustic soda and paper filler-calcium carbonate.This method reclaims solvable compositions such as caustic soda to greatest extent, has improved the quality product of lime carbonate simultaneously, and whole process does not have discharge of wastewater, is the cleaning procedure that a causticizing process is produced caustic soda and lime carbonate.

In order to realize above-mentioned purpose, the present invention adopts following steps:

A. at first total alkali is carried out thermolysis at the natural alkali lye about 150～180g/L in the pyrolysis tower, 90～110 ℃ of decomposition temperatures, utilize alkali lye after the pyrolysis in limeslaker with contain calcium oxide content and reach that unslaked lime more than 90% digests, two reactions of causticization, causticizing efficiency reaches 75%;

B. step a is obtained postdigestive solution and enter in the one-level causticization reactor and continue causticization, 80～90 ℃ of causticization temperature, 2 hours causticization time, causticizing efficiency reaches more than 85%;

C. the causticization liquid that step b is obtained enters the first grade subsides groove, carry out solid-liquid separation, liquid enters smart filtering system and obtains the caustic soda refined liquid, and devaporation concentrates, and obtains required caustic soda product, solid slurry enters the secondary causticization reactor, add natural alkali lye, carry out the secondary causticization, 80～90 ℃ of causticization temperature, 2 hours causticization time, causticizing efficiency reaches more than 90%;

D. secondary causticization liquid among the step c is entered three subsiders, carry out three grades of solid-liquid separation, simultaneously three grades of subsiders are realized countercurrent washings, and wherein caustic soda is reclaimed, and obtain the calcium carbonate slurry of remaining caustic soda content below 0.1mol/L simultaneously;

E. the lime carbonate after settlement separate in the steps d is entered and carry out carbonation reaction in the continuous carbonization tower, pH is reduced to below 11, after flue gas after being purified, its carbon dioxide content is 10～15% from the dry device of follow-up lime carbonate or other fuel combustions for wherein required carbonic acid gas;

F. the slurries with step e output enter the process that reeling mill carries out calcium carbonate granule expansion and refinement, make the settling volume of lime carbonate bring up to more than the 2.2ml/g;

G. the calcium carbonate serosity behind the step f expansion is entered in the vacuum filter and filters, filter lime carbonate drying and dehydrating in solids dryer of back moisture 30%, after enter beater and break up, obtain the calcium carbonate product of polymolecularity.

The main elder generation of technology of the present invention has carried out pre-treatment to natural alkali lye and has reduced the lime consumption, take the mode of countercurrent washing, reclaim solvable compositions such as caustic soda to greatest extent, improved the quality product of lime carbonate simultaneously, take the mode of flue gas continuous carbonization to reduce lime carbonate pH value, utilize reeling mill that the particle of lime carbonate is modified, improve the settling volume of lime carbonate, liquid is got back to settling separation system, enter caustic soda product preparation flow process, calcium carbonate content in the prepared calcium carbonate product that goes out is more than 93%, whiteness is more than 90, the pH value is below 11, more than the settling volume 2.2ml/g, other indexs reach the requirement of paper filler-calcium carbonate.Whole process does not have discharge of wastewater, is the cleaning procedure that a causticizing process is produced caustic soda and lime carbonate.

Description of drawings

Describe embodiments of the invention in detail below in conjunction with accompanying drawing.

Fig. 1 is that the natural alkali lye of the present invention is produced caustic soda and paper filler-calcium carbonate schema.

Embodiment

Embodiment

With natural alkali lye (total alkali 160g/L, sodium bicarbonate content 100g/L) 7m ³/ h carries out pyrolysis, and 100 ℃ of pyrolysis temperatures make NaHCO in the solution ₃50g/L mixes at digestive organ with 1400kg/h unslaked lime (CaO content is greater than 90%) then, and reaction conversion ratio reaches 76%, enters causticization reactor then, adds 2m ³The natural alkali lye of/h, reaction back liquid enters the first grade subsides groove, liquid-solid separation, solid enters the secondary causticization reactor, adds 1m ³The natural alkali lye of/h, reaction conversion ratio reaches 90%, enters three grades of subsiders then, and countercurrent washing finally obtains the sodium hydroxide solution 11m of 105g/L ³/ h is as product.Caustic soda content is at 0.1mol/L in the lime carbonate after the washing, enter the continuous carbonization tower then and carry out carbonization, carbonic acid gas is from the flue gas of pan dryer, gas concentration lwevel 13%, the pH value is reduced to about 10.8, enter expansion in the reeling mill, make settling volume greater than more than the 2.2ml/g, carry out vacuum filtration then, cake moisture enters pan dryer and carries out drying 30%, acquisition lime carbonate is 2250kg/h, break up then, obtain calcium carbonate product, wherein in the product calcium carbonate content greater than 93%, whiteness is greater than 90, settling volume is greater than 2.2ml/g, and other indexs meet national light calcium carbonate salable product standard, adapts to the needs of paper industry filler.

Claims (1)

1. method that natural alkali lye is produced caustic soda and paper filler-calcium carbonate is characterized in that: adopt following steps:

A. at first total alkali is carried out thermolysis at the natural alkali lye about 150～180g/L in the pyrolysis tower, 90～110 ℃ of decomposition temperatures, utilize alkali lye after the pyrolysis in limeslaker with contain calcium oxide content and reach that unslaked lime more than 90% digests, two reactions of causticization, causticizing efficiency reaches 75%;

B. step a is obtained postdigestive solution and enter in the one-level causticization reactor and continue causticization, 80～90 ℃ of causticization temperature, 2 hours causticization time, causticizing efficiency reaches more than 85%;

C. the causticization liquid that step b is obtained enters the first grade subsides groove, carry out solid-liquid separation, liquid enters smart filtering system and obtains the caustic soda refined liquid, and devaporation concentrates, and obtains required caustic soda product, solid slurry enters the secondary causticization reactor, add natural alkali lye, carry out the secondary causticization, 80～90 ℃ of causticization temperature, 2 hours causticization time, causticizing efficiency reaches more than 90%;

D. secondary causticization liquid among the step c is entered three subsiders, carry out three grades of solid-liquid separation, simultaneously three grades of subsiders are realized countercurrent washings, and wherein caustic soda is reclaimed, and obtain the calcium carbonate slurry of remaining caustic soda content below 0.1mol/L simultaneously;

E. the lime carbonate after settlement separate in the steps d is entered and carry out carbonation reaction in the continuous carbonization tower, pH is reduced to below 11, after flue gas after being purified, its carbon dioxide content is 10～15% from the dry device of follow-up lime carbonate or other fuel combustions for wherein required carbonic acid gas;

F. the slurries with step e output enter the process that reeling mill carries out calcium carbonate granule expansion and refinement, make the settling volume of lime carbonate bring up to more than the 2.2ml/g;

G. the calcium carbonate serosity behind the step f expansion is entered in the vacuum filter and filters, filter lime carbonate drying and dehydrating in solids dryer of back moisture 30%, after enter beater and break up, obtain the calcium carbonate product of polymolecularity.

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