CN1272242C - Method for producing active carbon by using straw mixed raw material - Google Patents

Abstract

The invention discloses a method for producing active carbon by using mixed straw raw materials, which adopts crop straws, waste branches of fruit trees and tree sawdust as mixed raw materials, adopts a phosphoric acid method and a physical combination method to produce powdery or granular active carbon, or adopts a chemical physical combination method, adopts potassium hydroxide as an activating agent, and uses perchloric acid to pretreat the raw materials to produce powdery or granular active carbon. The product is not only used in industry, light industry and the like, but also has obvious ecological effect on the aspects of purifying air, water quality, environment, medical treatment and health and the like. Has no toxicity and public nuisance, and belongs to a product without residual toxicity and pollution. And a good foundation is laid for further comprehensive utilization of biological waste resources. The invention can be widely used in the fields of industry, agriculture, medical treatment, sanitation, epidemic prevention, environmental protection, production, life and the like.

Description

A kind of method of producing active carbon by using straw blend materials

Technical field

The present invention relates to the production technology of gac, particularly a kind of method with producing active carbon by using straw blend materials.

Background technology

Gac is a kind of black porousness solid, and its maximum characteristics are to have flourishing hole and very big specific surface area and adsorptive power.Below briefly introduce domestic and international existing gac pertinent data:

1. the physicochemical property of gac:

Gac is made of crystallite charcoal and amorphous carbon, contains the ash content that quantity does not wait, and is a kind of black porousness solid.Its maximum characteristics are to have flourishing hole and very big specific surface area and adsorptive power.As the specific surface area of charcoal, has only 100m ²/ g～400m ²/ g, the specific surface area of gac is then up to 1000m ²/ g～3000m ²/ g.Therefore, gac all has very strong adsorptive power to organic or inorganic material in gas, the solution and colloidal solid etc.

Gac has unique pore texture and surfactivity functional group as a kind of high-quality sorbent material, have enough chemical stabilities, physical strength and performance such as acidproof, alkaline-resisting, heat-resisting, water insoluble and organic solvent uses the back regeneration easily of losing efficacy, and therefore is widely used in each department.

2. external Activated Carbon Production, application scenario

2.1 the U.S. is first big country of present Activated Carbon Production in the world and application, its throughput was 17.24 ten thousand tons in 1994.Because the gac of the cheapness of a large amount of import South East Asia one band adds the continuous increase of domestic regenerated carbon output, so its change of production is little in recent years, does not reach full production, output maintains about 70% of throughput.

U.S.'s gac raw material mainly is timber, brown coal, Exocarpium cocois (Cocos nucifera L), charcoal, pitch coal.Produce used activation furnace multi-layer rake type stove, rotary kiln, fluid bed furnace etc. are arranged.Product has powdery carbon and particle charcoal.The U.S. attaches great importance to the regeneration of gac, and regenerated carbon is an important component part of U.S.'s Activated Carbon Production, and according to incompletely statistics, U.S.'s regenerated carbon output is greatly about more than 4.8 ten thousand tons.Low owing to the regenerated carbon productive expense, as to economize on resources, reduce environmental pollution, minimizing gac import, government extremely supports the development of regenerated carbon, estimates for some time from now on, the output of U.S.'s regenerated carbon can further increase.

2.2 nearest more than 20 years, Japanese Activated Carbon Production tempo was very fast, as 1975, Japanese gac output was 40,000 tons, and 1985 is 8.4 ten thousand tons; Reached 8.9 ten thousand tons in 1994,20 annual production have increased more than one times.

The development of Activated Carbon Production has also promoted the development of scientific research cause.The new achievement in research of gac has promoted again to produce to level development higher, that upgrade.Promoted the development of activated carbon technology, product innovation, novel process constantly occur.In recent years, develop, produced activated carbon fiber, ball shape active carbon, the contour product innovation of carbon molecular sieve.The grade of traditional product improves constantly, high benzene, high Cl ₄The disconnected mutually of gac, low grey gac come out, and the road of gac industry is just walked wideer and wideer, and output is increasing, and quality is become better and better.

2.3 the kind of gac

All kinds of and the title of gac is a lot, can be by classification such as raw materials for production, production method, mode of appearance, application.These kinds and title see Table 1.

The kind of table 1 gac

Classification foundation	Kind and title
		Raw material	Carbo lignius: comprise sawdust charcoal, fruit shell carbon (as the coconut husk charcoal), fruit stone charcoal, other raw material charcoals of ature of coal charcoal: as pitch, synthetic resins charcoal, activated carbon fiber
Production technique	Chemical activation method gac (chemical charcoal) (acid gac) physical activation method gac (physics charcoal) (alkaline gac)
		Mode of appearance	Powdery carbon particle charcoal: comprise amorphous carbon, cylindrical charcoal, spherical carbon, cellular charcoal isoreactivity charcoal fiber: comprise active carbon fiber fabrics, felt, paper etc.
Sorbency	Single type (selectivity) gac compound (diversity) gac
		Purposes	Gas phase absorption activated carbon: comprise liquid phase adsorption gacs such as protective carbon, purifying air charcoal, desulfurization charcoal: comprise water purification charcoal, carbon injection, sugar charcoal, monosodium glutamate, gold carbon, Medicinal Charcoal support of the catalyst gac carbon molecular sieve

Divide with the gac raw material, wood material gac, coal raw materials gac, pitch gac, synthetic resins gac etc. are arranged.The history of wood activated charcoal is the oldest, comprises various timber, wood chip, charcoal, shell, fruit stone etc.The raw material chemical constitution mainly is xylogen and Mierocrystalline cellulose, compares with coal raw materials, and its impurity is few, ash content is low, can be applied to the higher fields of specification of quality such as food, medicine.Carbo lignius is based on powdery carbon, refining as liquid glucose decolouring, monosodium glutamate, glucose in a large number, pharmacy etc.The coconut husk charcoal is top-quality a kind of in the carbo lignius, is amorphous granular, not only has and well depends on performance, has very high physical strength again.The fruit stone charcoal also has the characteristic of similar coconut husk charcoal, as peach-pit charcoal, almond charcoal result of use is preferably arranged also.Because wooden resource-constrained and cost are higher, the development of wood activated charcoal is restricted, thereby coal mass active carbon has had develop rapidly.The advantage of coal mass active carbon is that aboundresources, kind are many, price is low.Disadvantage is the ash content height, and impurity is many.

Divide with production technique, gac can be divided into chemical activation method and produce gac and physical activation method production gac two big classes.The chemical activation method pharmaceutical chemicals is an activator, and as zinc chloride commonly used etc., indivedual units use sulfuric acid, hydrochloric acid to be activator, are called for short chemical charcoal.The gac that makes with zinc chloride generally has more macropore and transitional pore, the acidic surface oxide compound is more, is commonly referred to as acid gac.Physical activation method is an activator with oxidizing gas such as water vapor, carbonic acid gas, claims the gas activation method again.This gac is called for short the physics charcoal.The physics charcoal generally has more microvoid structure, and it is more to generate the basic surface oxide compound during activation, therefore is called alkaline gac.This two big class gac is because of the manufacture method difference, and character is different, and its purposes is also inequality.Chemical method is used wood material more, and production technique and equipment are fairly simple.But maximum shortcoming is a contaminate environment, produces the exhaust emission atmosphere, produces the waste water that contains pharmaceutical chemicals in a large number during the product rinsing again.So on the gac developing history, the development of chemical charcoal is restricted, and the development of physics charcoal rapidly, and the output of physics charcoal has surpassed chemical charcoal at present.This trend also will continue.

From mode of appearance, gac can be divided into powdered carbon and granulated active carbon two big classes again, and granulated active carbon has branch amorphous and the typing gac again.Amorphous carbon is called broken charcoal again.Directly be broken into the production of certain particle size post-treatment by raw material, also having behind the powder raw material briquetting again, fragmentation forms.Pressed active carbon has cylindrical gac because of the forming method difference, the gac of ball shape active carbon and other shapes.Powdered carbon can be processed into different fineness by service requirements.Powdered carbon is big because of fine size, outer surface area, so rate of adsorption is fast, is specially adapted to liquid phase adsorption.The current production rate maximum is cylindrical gac in the granular carbon, and it adopts the method for extruded moulding to be shaped to bar earlier, then these bars is cut into the particle of length-to-diameter ratio＜5, and bar fragments into required particle automatically in drying process sometimes.Owing in the process of extruded moulding, need to add the binding agent of some amount, as the coal tar wet goods, apply higher pressure during extrusion again, so the physical strength of this gac is higher.Ball shape active carbon is the granulated active carbon that latest developments are got up.Compare with cylindrical and amorphous gac, because it is ganoid spherical object, so fluid resistance is little, wear-resisting, be difficult for producing chip and powder in using.Granular carbon is used for adsorption column or adsorption tower operation more, can make adsorption operations become operate continuously after the multitower series connection.Another characteristics of granular carbon are convenient to regeneration exactly, after gac lost efficacy, can continue to use through manipulation of regeneration.Because the granularity of granular carbon is thicker, adsorption molecule is longer in the approach of gac internal divergence, and outer surface area is less, so its rate of adsorption is slower, loading capacity also is difficult to all performances.

Can be divided into the carbonaceous molecular sieve of gas phase gac, liquid phase gac, transformation absorption usefulness etc. again by the purposes gac.According to the difference of the pore texture of gac, dissimilar gacs has different purposes.During Gas Phase Adsorption, need a large amount of micropores; During liquid phase adsorption, except a large amount of micropores of needs have also required a certain amount of macropore and transitional pore.Because specific end use has specific specification of quality to gac, so the kind of many special-purpose activated charcoals occurred, as being used for the gold carbon that gold is produced, the sugar charcoal that is used for the liquid glucose decolouring, the monosodium glutamate charcoal that is used for refining gourmet powder, the Medicinal Charcoal of Shi Yonging pharmaceutically, the carrier active carbon that the catalyzer aspect is used is exclusively used in the desulphurized aetivated carbon of coal gas desulfurization etc.

2.4 raw material and tackiness agent

Produce the fine gac and need select the raw material that suits.After definite activated carbon variety, specification, at first to select raw material by test, and then definite technical process, equipment and operational condition.

Usually, many carbonaceous raw materials that contain can be used for producing gac.The raw material of producing gac at present mainly contains two big classes: plant class and mineral substance.Plant class raw material mainly contains timber, sawdust, shell, fruit stone etc.The mineral substance raw material mainly contains different classes of coal, as peat, brown coal, bituminous coal, hard coal; Different refinery cokes, petroleum pitch etc.Except above two big class raw materials, adopting sucrose, synthetic resins in order to make the very low gac of ash content is raw material, as thermosetting resin resol, furane resin, urea resin etc. are arranged, thermoplastic resin has polyvinyl chloride (PVC) RESINS, polyvinylidene dichloride resin, polycarbonate etc.The raw material of production activated carbon fiber is the fiber, asphalt base carbon fiber and the plastic waste that are spun into of polyacrylonitrile fibre, resol, waste rubber etc.

Should consider the following aspects when in industrial production, selecting raw material for use: 1. moulding, charing, activatory complexity; 2. whether the quality of activated carbon of Sheng Chaning meets service requirements; 3. whether raw material resources are abundant; 4. the height of price.

At present, the raw material of the graininess gac of industrial production is still based on shell, fruit stone, timber and coal; The raw material of producing powdered carbon is based on wood chip; The raw material of producd fibers shaped activated carbon is that organic fibre and pitch fibers are main.Up to the present, the applicant also not see and adopt crop material be the report of raw material production gac.

2.5 chemistry and physical activation method

Chemical activation method is made activator with pharmaceutical chemicals exactly carbon containing matter is activated the manufacturing process of active carbon.This method has a nearly one-hundred-year history.The early stage gac of China is mainly used this method production of zinc chloride.According to the investigation of agricultural department, the merchandise active carbon that zinc chloride process is produced accounts for about 66% of national ultimate production.Chemical method is used for the production of powdered carbon mostly, and the granulated active carbon intensity that this method is produced is relatively poor, not shock-resistant and wearing and tearing.The disadvantage of chemical activation method is the serious and environmental pollution of equipment corrosion.This has become very distinct issues current.It volatilizes many gases that are harmful to, are corrosive, pollutant atmosphere when charing, activation.When aftertreatment, in rinse cycle, produce a large amount of waste water.Therefore, this method immediate development is slower, and in China, the ratio of gac in the gac ultimate production that this method is produced drops to about 1/3.

The activating mechanism of chemical activation method and physical activation method is different, so the gac of producing has very big difference on pore texture and physico-chemical property.The gac that the physics method is produced, its pore texture is based on micropore, and macropore and transitional pore are less.And the gac that chemical method is produced, transitional pore is more, and in the oxide on surface of gac, acidic oxide is more, presents acidity, and oxide on surface has electronegativity.Physics method gac then based on basic oxide, be alkalescence, surperficial positively charged.Because transitional pore is more in the gac that chemical method is produced, and is suitable for adsorbing bigger molecule, so its caramel decoloring ability is stronger than physical activity charcoal.The chemically reactive charcoal relatively is suitable for liquid phase adsorption.Used activator mainly is a zinc chloride in the production process of chemical method, also has vitriolate of tartar, potassium sulphide etc. in addition.Activator used in the enterprise of China mainly adopts zinc chloride process.

Summary of the invention

The objective of the invention is to, a kind of method that adopts producing active carbon by using straw blend materials is provided, this method adopts physical chemistry to produce powdered carbon and granulated active carbon in conjunction with activation method.Utilize the mixed straw raw material to adopt potassium hydroxide activator and perchloric acid pretreating raw material simultaneously, develop better powdery of quality product and granular carbon.

To achieve these goals; the technical scheme that the present invention takes is; a kind of method of producing active carbon by using straw blend materials; it is characterized in that; it is mixing raw material that this method adopts crop material, the useless branch of fruit tree and trees sawdust; adopt phosphoric acid method and physical bond method to produce powdery or granulated active carbon, specifically comprise the following steps:

1) raw material is prepared

Above-mentioned raw materials is crushed to the granularity of 1-2mm with pulverizer, after the rolling shredder carries out fine grinding, crosses 120 mesh sieves, drying again;

2) preparation of phosphate impregnation liquid, batching

Prepare the concentration and the pH value of phosphate impregnation liquid according to the kind of gac; The prescription of craboraffin requires: 50～57 ° of Be '/60 ℃, pH value 3～3.5; The prescription of industrial activited carbon is: 45～47 ° of Be '/60 ℃, and pH value 1.0～1.5, manufacture is 0.75: 1 with the phosphoric acid and the stalk mixing wood chip ratio of Powdered Activated Carbon; When producing granulated active carbon, the phosphorus bits are than being 0.8～1.5; Sugar is more than 1.6: 1 with the phosphoric acid and the stalk mixing wood chip ratio of Powdered Activated Carbon;

3) dipping or wet mixing are pinched

Dipping is that dipping time can obtain impregnant greater than 8 hours with stalk mixing wood chip and the abundant mixing of phosphoric acid solution;

When adopting wet mixing to pinch, utilize mechanical stirring device to force stalk mixing wood chip and phosphoric acid are kneaded, the time of kneading is 10～15 minutes;

When producing granulated active carbon, dipping and wet mixing are pinched all a plasticizing process in the process, promptly under 130 ℃～150 ℃ heating condition, make the impregnant softness, rolls through kneading repeatedly again, and impregnant is mixed;

4) charing, activation

To carry out charing by the phosphorus bits material after pinching through dipping or wet mixing, the furnace temperature during charing is 500 ℃～700 ℃, and the material temperature is 300 ℃～400 ℃; The carbonization time of every batch of phosphorus bits material is 30 minutes～60 minutes;

Raw material after charing further activates, and the furnace temperature during activation is 700 ℃～800 ℃, and the material temperature is 500 ℃～600 ℃, and soak time is 2 hours～2.5 hours, every 15 minutes～20 minutes stirrings once;

The activated material of coming out of the stove was stacked 8 hours～16 hours, utilized the wet continuation atomizing of material, adjust the aperture;

5) reclaim phosphoric acid

Phosphoric acid solution with lower concentration extracts activated material, and the recovery liquid that extraction for the first time obtains if reach the impregnation concentration requirement, can be got back in the Production Flow Chart and use; Repeatedly extract with the lower phosphoric acid solution of concentration later, use hot wash at last, phosphorus acid content is lower than till 1% in gac, about 1.5 hours～3 hours of the time of whole recovery process;

When recycling, in reclaiming liquid, need to add zinc sulfate and remove impurity for the phosphoric acid solution that contains impurity that reclaims;

6) rinsing

Rinsing comprises pickling and two steps of washing:

Pickling is to add an amount of phosphoric acid with finishing the gac that reclaims behind the phosphoric acid in rinsing tub, feeds steam and boils 2 hours, makes water-fast impurity become water soluble compounds, removes with water;

After the pickling, add the alkali neutralizing acid, generate phosphate anion, and remove various water-soluble impurities with the hot water repetitive scrubbing, the phosphate anion content that is washed in the filtrate is lower than till 0.16%;

7) dehydration and dry

Adopt centrifuge dewatering, the gac moisture content is dropped between 60～65%; Carry out drying then, make the gac moisture after the centrifuge dehydration further be reduced to below 10%;

8) grind

Use the continous way ball mill to grind dried gac, promptly obtain powdery or granulated active carbon.

Above-mentioned crop material is wheat stalk, maize straw and cotton stalk, and its ratio is 1: 1: 1.

Another technical solution used in the present invention is: a kind of method of producing active carbon by using straw blend materials, it is characterized in that, it is raw material that this method adopts wheat, corn, cotton stalk, the useless branch of fruit tree and trees sawdust, adopt the chemical physics combining method, with potassium hydroxide is activator, with perchloric acid raw material is carried out pre-treatment, produce powdery or granular carbon, specifically comprise the following steps:

1) raw material adopted crop material, the useless branch of fruit tree and trees sawdust, in 1: 1: 1 ratio.Earlier with raw material with crusher with the stalk coarse crushing after, with atomizer mill the particle stalk is carried out fine grinding again, the mixing raw material powder after the fine grinding is crossed 120 purposes sieve;

2) take by weighing mixing raw material powder 145g, adding concentration is 36.5% hydrochloric acid 10mL, and concentration is 73% hydrofluoric acid 10mL, and concentration is 37% perchloric acid 20mL, and water 50mL stirs, and soaks 24h under the room temperature;

3) adopt the suction filtration device that above-mentioned raw materials is washed, after being washed till pH value and being 6, place and dry moisture content in the electric drying oven with forced convection, take by weighing oven dry back mixed straw wood chip 10g, adding concentration and be 10% potassium hydroxide solution 10mL is activator, stirs into pasty state, puts into porcelain boat, place in the activation furnace, feeding flow is 1.0L/min nitrogen, rises to 800 ℃, insulation 45min with the heat-up rate of 8 ℃/min～10 ℃/min, after the cooling, obtain activation products;

4) activation products are soaked 20min with hydrochloric acid soln, wash with water then to the pH value be dewater after 6, drying, promptly obtaining the gac iodine number is 980mg/g, specific surface is 1180m ²The powdery of/g or granulated active carbon.

The gac series that adopts the inventive method to produce, its scale of investment little (about 2,000,000 yuan), cost is low, the income height, instant effect is convenient to operation, and 30～50 people just can organize production.Its product not only is used for industry, light industry etc., purify air, aspect such as water quality, environment and health care has significant Ecology Action.Nonpoisonous, non-environmental-pollution belongs to the pollution-free product of no residual hazard.Have laid a good foundation for further fully utilizing biological waste resource.The present invention can be widely used in fields such as industry, agricultural, medical treatment, health, epidemic prevention, environmental protection, production, life.

Description of drawings

Fig. 1 is that the present invention adopts the phosphoric acid continous way to produce the process flow diagram of powdered carbon;

Fig. 2 is a phosphoric acid method powdered carbon flow process (I);

Fig. 3 is a phosphoric acid method granulated active carbon flow process (II).

Below in conjunction with the specific embodiment that accompanying drawing and contriver provide the present invention is done further to describe in detail.

Embodiment

For a more clear understanding of the present invention, at first introduce the mechanism of action of physical chemistry in conjunction with activation method:

Physical chemistry is in conjunction with the mechanism of activation method

Though chemical activation method has very long history, also not fully aware of to its activating mechanism, the viewpoint that has is disunity also.Further understanding and research chemistry and physically activated mechanism have crucial realistic meaning to the gac that improves technology, improves the quality of products and develop the new nearly ability of higher absorption.Mainly introduce phosphoric acid method and physics method (water vapour method) bonded activating mechanism below.

1. swelling and peptization

The main chemical constitution of thing class raw materials such as stalk mixing wood chip is a carbohydrate, i.e. carbohydrate such as Mierocrystalline cellulose, hemicellulose and pectin substance.The cellulose comprises 60～70% of higher plant.In the phosphorus oxide solution impregnation with when kneading, swelling can take place in components such as Mierocrystalline cellulose, and hydrolysis reaction and oxidizing reaction take place simultaneously.It raises with temperature and aggravates.Under 150～200 ℃, Mierocrystalline cellulose can be dispersed into the peptization state, and macromolecular compound depolymerizes to than small molecules, and whole material has plasticity-and viscosity.When phosphoric acid legal system granulated active carbon, the phosphorus bits material that this process is fully kneaded has good plasticity, makes particulate state.

2. change organic substance pyrolysated course

Stalk mixing wood chip generates gases such as volatile organic compoundss such as various acids, alcohols, aldehydes, ketone, tar and carbonic acid gas in pyrolytic process.Overflow owing to contain the decomposition of charing compound in a large number, the mixing sawdust charcoal that finally stays only accounts for about 15% of over dry mixing wood chip.Behind stalk mixing wood chip impregnation of phosphoric acid or other pharmaceutical chemicalss, its thermolysis course changes.At first, show that heat decomposition temperature reduces.For example, the temperature when gas evolution speed is maximum under the normal condition is 250～350 ℃, and drops to 150～300 ℃ after the impregnation of phosphoric acid (1: 1).Secondly,, thereby suppressed the formation of carbon containing volatile matter, more carbon is retained in the solid product because the katalysis of phosphoric acid impels the carrying out of hydroxyl decomposition and dehydration reaction.So the suction rate of gac improves greatly, be generally about 40% of stalk mixing wood chip oven dry weight.If calculate with carbon content, the carbon utilisation rate of gac reaches about 80%.The 3rd, the pharmaceutical chemicals dipping, the generation of tar avoids pyrogenous origin pore to be stopped up by tar when suppressing the pyrolysis of stalk mixing wood chip, reduces the quantity of closed pore, increase effective air gap.

In the phosphate impregnation process, because peptization takes place, make the cell walls swelling of original plant, the whole plants tissue has generated the glucose, aldopentose, furfural etc. of small molecular weight by hydrolysis and oxidizing reaction.Thermolysis takes place in them under the temperature more than 300 ℃, thermal polycondensation Cheng Duohuan aromizing structure under higher temperature then finally forms the disorderly layer microlitic structure of hole prosperity.

3. skeleton function

Phosphoric acid is evenly distributed in the raw material after making stalk mixing wood chip peptization become mouldable gelatinoid.During the raw material charing, the organic decomposition, and phosphoric acid has become the sedimentary surface of pyrolytic carbon.When these phosphoric acid and water dissolution, come out in the surface of carbon, become the internal surface area of gac.Originally the shared space of phosphoric acid has become the pore texture of gac.So, under certain condition, the proportional relation of the consumption of the porosity of gac and specific surface area and phosphoric acid.

4. the special influence of different chemical medicine

The different chemical medicine makes a difference to the surface molecular structure of gac and the spatial disposition of carbon atom.

A this influence part may be change charing, activation temperature produces, may to be some non-carbon atoms be absorbed in certain zone on the surface of charcoal another part, so that have influence on that those preferentially are etched the position of the carbon atom of removing in the oxidising process.Simultaneously, this effect, also comprise and inorganic components between point of connection on oxygenizement.

Different non-carbon atoms are to the activation difference of carbon.Can be penetrated between the crystallite sexangle carbon net plane as potassium, influence pore texture thereby influence turbostratic carbon stratum reticulare spacing.Oxygen can form oxide on surface at carbon surface.Find according to the study.The combination of sulphur and carbon also is the Chemical bond that is similar to oxide on surface.Nitrogen is to combine with similar itrile group form with carbon.The non-carbon atom of mortise some on gac improves the adsorptive power of gac for gac provides some adsorption bonds.For example, some gac has special adsorptive power and katalysis, exactly because there are non-carbons such as oxygen, iron, nitrogen in activated carbon surface.

5. the physicochemical property of mixed stalk raw material gac

The mixed stalk raw material gac, its main chemical elements is a carbon.Carbon in the gac has two kinds of structures basically, and a kind of is the microlitic structure of graphite, and another kind is the crosslinking structure of irregular carbon.Preceding a kind of structure has hexagonal carbon net plane, carbon net plane also image-stone China ink equally exists parallel aspect to pile up, so, on the X diffractogram, can see the band identical with graphite, the proof gac has the structure of similar graphite, but its size has only tens A °, therefore, is called the graphite microcrystal structure.The parallel aspect of these crystallites is not to arrange along common vertical axis fully, and layer is mixed and disorderly to the angular travel of another layer.Exactly because each layer piles up brokenly mutually, so, the macroscopic crystallographic properties do not had, the random layer of the two dimension crystallite that just size is different.This structure and complete graphite-structure comparison have following characteristics:

5.1 layer plane is not perfect, has various defectives such as hole, dislocation, heteroatoms and other impurity.

5.2 piling up of layer plane is not complete ordering, all perpendicular to the C axle, but there are certain angle in the normal of layer plane and C axle, and preferred orientation is poor.

5.3 interlamellar spacing is big.Generally between 3.36～3.44A °, and interlayer exists carbon atom, hydrogen atom or other group.

5.4 microcrystal is smaller, generally is no more than 600A °.

The another kind of structure of mixed stalk raw material gac then is the crosslinking structure of fully unordered carbon.The carbon that has is sexangle carbon net plane, and what have causes carbon net plane distortion or form heterocycle structure because of other heteroatomic existence.The band of any sign crystal property does not appear in the crosslinking structure of this irregular carbon in the X diffraction, this structure is only real amorphous carbon.

The structure of gac is relevant with raw material and preparation process condition.In general, the gac that generates by the liquid phase charing owing in thermal decomposition process, there is intermediate phase, final generate mostly be mosaic.

The physico-chemical property contrast of table 1 physics method gac and active carbon by chemical method

	Project	The vapour method gac	Phosphoric acid method gac
				Pore texture	Main body micropore (%) transitional pore (%) macropore (%) specific surface area (m of hole 2/ g)	With the micropore is main about 80 7 20 1180	More transitional pore about 50 30 17 1000 is arranged
Oxide on surface		The carbon oxide compound is more, tool basic oxide positively charged	Acidic oxide is more, the electronegative property of tool acidic oxide
				Characterization of adsorption		Big to the iodine adsorptive power, little to the adsorptive power of caramel.Liquid phase adsorption speed is slow	Little to the only attached power of iodine, big to the adsorptive power of caramel.Liquid phase adsorption speed is fast
Particle charcoal intensity		Physical strength is good, is difficult for efflorescence	Physical strength is relatively poor, easily efflorescence

6. precaution

6.1 raw material

According to the mechanism of phosphoric acid activation method, raw material need have certain oxygen level and hydrogen richness, generates water and constitutes pore structure in order to charing, when activation.The general requirement oxygen level is greater than 25%, and hydrogen richness is greater than 5%.Except timber, peat and age, short brown coal (young brown coal) all were fit to this condition, but the practice in experimental study analysis and production is adopted crop material to make raw material and also had the high characteristics of cost poor benefit.

In addition, in steeping process, fully be penetrated into the inside of raw material mix, require raw material that enough initial holes are arranged in order to make phosphoric acid solution.Hard ware material almost lacks the hole of abundant prosperity, and the domestic raw material that is used for the phosphoric acid method mainly is timber bits, wood shavings, oil tea shell powder, bagasse etc., but does not have stalk to make the report of raw material.Abroad, the active carbon by chemical method amount that short brown coal (young brown coal) of peat and age are produced is quite a few, does not also have stalk to make the precedent of raw material.

The kind of raw material has bigger influence to the charcoal absorption performance.For example, when making craboraffin, cedar sawdust is better than pine sawdust, and pine sawdust hardness ratio weed tree sawdust is good, and mixed stalk raw material combines the advantage of various straws, and ratio is scientific and reasonable.Optimization production by processing condition goes out qualified craboraffin.Our novel process, novel method and product innovation are exactly the method for taking the mixed straw mixing raw material, quality product is improved constantly reach standard.

Stalk mixing wood chip levels can influence the absorbed dose and the seepage velocity of phosphoric acid solution.Stalk mixing wood chip moisture content height, the absorbent phosphoric acid quantity of institute is just few during dipping.For example; when producing granulated active carbon; must absorb the lower phosphoric acid solution of concentration of some amount; so require stalk mixing wood chip water content less than 5%; when producing craboraffin, require to absorb the high concentrations of phosphoric acid solution of sufficient amount, for example stalk mixing wood chip moisture content height; certainly will reduce phosphoric acid concentration, finally influence the pore size distribution of gac.

Stalk mixing wood chip moisture content can influence the infiltration speed of phosphoric acid, thereby influences dipping time, and general stalk mixing wood chip water content is when fiber-saturation point is above, and the seepage velocity of phosphoric acid solution is slower.Therefore, when stalk mixing wood chip water content surpassed 30%, dipping time required more than 8 hours.When using kneading machine to mix and stir stalk wood chip and phosphoric acid solution, because the time of kneading is short, stalk wood chip water content requires below 15%.

When producing powdered carbon, stalk mixing wood pellet is 6～40 orders.When producing granulated active carbon, stalk mixing wood chip granularity is influential to granulated active carbon intensity and proportion, considers to be worth doing when smaller when phosphorus especially.For example, phosphorus is considered to be worth doing than being 80% o'clock, and during stalk mixing wood chip granularity 0.25mm, intensity is 93%, and proportion is 0.707, and granularity is respectively 86% and 0.658 when being 1.6～2.0mm.

6.2 immersion condition

Various activated carbon varieties can be adjusted and prepare to immersion condition and phosphorus bits also than the quality that can determine made quality of activated carbon, by the adjustment to different material immersion condition and phosphorus bits ratio, can produce high grade activated carbon.

Phosphoric acid solution concentration height, the pH value is just low, the phosphoric acid solution of general 50% concentration, its pH value is about 3.2.The pH value of phosphoric acid solution is very big to the quality and variety relation of product.To rigid timber, stalk cutin, when flooding with phosphoric acid solution, the pH value is on the low side for well.

Dipping temperature and time, both are mutually related, and the low then dipping time of general phosphoric acid solution temperature must prolong, and not so the impregnant infiltration is complete inadequately, influences quality of activated carbon.On the contrary, steeping fluid temperature height, dipping time can shorten.But temperature can not be too high, as with 90 ℃ of phosphoric acid solutions dipping stalk mixings wood chips, and impregnant facile hydrolysis peptization pulp body, unnecessary phosphoric acid solution can't the precipitating separation.In material content 20%, phosphoric acid solution concentration is to flood more than 8 hours the unnecessary phosphoric acid solution of emanating under 50%, 30～50 ℃ of liquid temperature.The ratio of raw material and solution is within 1: 4.5～6.0 scopes.In order to reduce dipping time, make phosphoric acid solution can be penetrated into the inside of stalk wood chip better, to knead with kneading machine now, as long as the time is 10～15 minutes.

6.3 activation temperature

The top temperature of activated material when activation temperature refers to activate.It is another important factor that influences quality of activated carbon.

Activation temperature is as shown in table 2 to the influence of quality of activated carbon.

Table 2 activation temperature is to the influence of quality of activated carbon

The phosphorus bits are than (%)	Temperature (℃)	Benzene-absorbing rate (milligram/gram)		Intensity (%)	Proportion	Specific pore volume amasss (milliliter/gram)
										Specific pressure		The total pore space	Micropore	Filter pore	Macropore
		0.12	0.90

80	400 500 600 700 800	451 588 466 421 409	538 544 612 454 430	88 87 88 92 93	0.634 0.615 0.630 0.658 0.709	0.996 1.043 1.012 0.970 0.877	0.513 0.555 0.529 0.478 0.462	0.099 0.063 0.053 0.038 0.024	0.384 0.425 0.430 0.454 0.398
										200	400 500 600 700 800	476 596 592 562 533	825 956 910 820 756	88 76 80 85 87	0.499 0.405 0.427 0.451 0.501	1.490 1.886 1.791 1.670 1.441	0.542 0.676 0.674 0.638 0.606	0.390 0.410 0.361 0.294 0.254	0.430 0.789 0.756 0.738 0.586

As seen from Table 2, in each time test, 500 ℃ of prepared gacs have maximum specific pore volume and amass proportion and intensity minimum, the adsorption rate maximum of benzene.This is because 500 ℃ the time, the volume maximum that phosphoric acid occupies in the charcoal skeleton that forms, after, along with activation temperature raises, the amount of vaporization of phosphoric acid increases in the charcoal, and charcoal begins to shrink, so proportion and intensity increase thereupon.

6.4 soak time

Soak time is meant the time that is incubated under certain activation temperature.When activation temperature is below 600 ℃ the time, in 2 hours scope, prolong the intensity that soak time can improve gac.

Below be the embodiment that the contriver provides:

Embodiment 1: the mixed stalk raw material process for preparing activated carbon

Present embodiment mixes by a certain percentage with agricultural crop straw, the mixing raw material of crop material, the useless branch of fruit tree, trees sawdust, its ratio is 1: 1: 1, stalk is cotton stalk, wheat stalk and maize straw, produce powdered carbon, as craboraffin, injection-use activated carbon, pharmacy, monosodium glutamate active carbon for decolorization, medicinal carbon, agent of activity charcoal etc.Combine through practical studies phosphoric acid activation method and physics method and also can produce granulated active carbon.

1. the phosphoric acid method is produced powdered carbon

1.1 technical process

The technical process of producing powdered carbon generally comprises pre-treatment, charing and activation and aftertreatment three parts referring to accompanying drawing 1～3.Pre-treatment comprises the screening of stalk mixing wood chip, drying; The quality of the preparation of phosphate impregnation liquid and stalk mixing wood chip and dipping and or soak aloof from politics and material pursuits.Charing and activation are the groundworks of producing, and with high-temperature flue gas impregnant are handled.The aftertreatment main purpose is to reclaim phosphoric acid and make product reach the foreign matter content requirement through rinsing.Aftertreatment comprises that also the grinding of product, drying and the three wastes handle.The three wastes are handled and are comprised the treatment of waste gas system, mainly reclaim phosphoric acid and waste water treatment system in the waste gas.Flue gas is handled, earlier will be by multistage dedustings such as settling pockets, and naturally cooling equipment makes flue-gas temperature drop to 120 ℃, just can remove most of charcoal dirt, enters the droplet that steam phase segregator is removed phosphoric acid and water vapor formation again, and remaining charcoal dirt.At this moment flue-gas temperature descends below 100 ℃.And then enter condensation in the condenser, make flue-gas temperature drop to the condensation of at this moment most phosphoric acid water steam mist below 50 ℃.The flue gas that condenser comes out is pollution-free, no recovery value.Earlier through the effective water hydro-peening of Venturi, further remove acid mist through entrainment trap and absorption tower again before the emptying.The phosphoric acid waste water that generates when rinsing and flue gas are handled is handled with normal wadding method, further recycle again after the conformance with standard.

1.2 production operation step

1.2.1 raw material is prepared

The stalk wood chip is removed wooden unit and powder and foreign material such as straw phloem and pulp cavity with vibratory screening apparatus or trommel screen screening.As being raw material with trees sawdust, fruit tree branch, stalk, its ratio is 1: 1: 1, then needs with pulverizer the granularity of raw material pulverizing to suitable (1-2mm), again through rolling shredder fine powder 120 orders that sieve.

General stalk mixing wood chip water content about about 40%.When adopting kneading process, requiring mixing raw material moisture is 10～20%.When adopting dipping method, stalk mixing wood chip moisture can be higher, but should be lower than 30%, and at this moment the concentration of phosphate impregnation liquid should improve.

Stalk mixing wood chip drying means has two kinds, and a kind of is to use the pneumatic dryer drying, and another kind is to use the rotary kiln drying.The heating medium of pneumatic dryer has two kinds: a kind of is stack gas and the air mixed that burning generates, and directly contacts with mixing wood chip, carries out heat exchange; Another kind is the indirect heating mode, adds warm air by high-temperature flue gas, and warm air remakes heating medium the stalk wood chip is carried out heat exchange.The former thermo-efficiency height, the spontaneous combustion but the stalk wood chip catches fire easily.

When adopting rotary kiln dry, the high-temperature flue gas that process furnace produces infiltrates air, temperature is reduced to about 400 ℃, following current is directly touched with stalk mixing wood chip in rotary kiln, carry out heat exchange, be 20 minutes general time of drying, makes stalk mixing wood chip moisture content drop to 20～25%, flue-gas temperature drops to about 120 ℃, is discharged in the atmosphere.

1.2.2 the preparation of phosphate impregnation liquid

The concentration of phosphate impregnation liquid is relevant with the crop species of product category, stalk mixing wood chip with the pH value, also is decided by impregnation method and phosphorus bits ratio.Phosphoric acid concentration degree Beaume commonly used is represented.The prescription of general craboraffin requires: 50～57 ° of Be '/60 ℃, and pH value 3～3.5, the prescription of medicinal carbon is: 45～47 ° of Be '/60 ℃, pH value 1.0～1.5.

1.2.3 batching, mix and to pinch or flood

Phosphorus is considered to be worth doing than the pore texture that is related to gac, gained gac porosity height, and hole is big, the transitional pore prosperity.Manufacture with the phosphorus of gac bits than being 0.75: 1; The phosphorus of craboraffin bits are than being more than 1.6: 1.

Dipping and mixed quality purpose of pinching are in order to make the abundant mixing of stalk mixing wood chip and phosphoric acid solution, phosphoric acid to be penetrated into the inside of mixing wood pellet.It is longer to flood the used time, and generally greater than 8 hours, and wet mixing utilizes mechanical stirring device to force to knead, so as long as 10～15 minutes when pinching.

The periodical operation processing condition are as shown in table 3

Table 3 mixes pinches processing condition

Project	The industry charcoal	The sugar charcoal
			The pH value of phosphoric acid solution phosphorus concentration acid solution	45～47 1～1.5	50～57 3～3.5

Solid-liquid ratio mixes and pinches the time

1∶3 10～15

1∶4～5 10～15

1.2.4 charing, activation.

Charing and the activation be the critical process of phosphoric acid activation method, it be related to phosphoric acid consumption what, the height of gac yield, seriously polluted degree etc.

The principle of decision charing, activation temperature is to guarantee finishing of charing, reactivation process, guarantees quality product, requires again temperature is controlled at lower state.Its reason be the more important thing is the evaporation effusion that reduces phosphoric acid steam except energy-conservation, to reduce the phosphoric acid consumption, reduces environmental pollution and equipment corruption.Generally carbonization temperature is fixed on below 400 ℃.Activation temperature is controlled between 500～600 ℃.Because at this moment the vapor partial pressure of phosphoric acid is not high, overflow seldom.

The used rotary kiln of the structure of rotary kiln and physical activation method is similar.

1 meter of body of heater internal diameter, long 13 meters, 2 °～5 ° of obliquitys.Throughput is 1～2 ton of daily output gac.

Phosphorus bits material after kneading is sent into the stove tail by hopper with helical screw feeder.Material moves to burner lentamente by the rotation and the obliquity of cylindrical shell.Burner does not have the combustion chamber, is fuel with coal gas or crude oil, and burning produces high-temperature flue gas and directly enters in the stove, and is moving to the stove wake flow by burner, directly contacts with the material adverse current.In order to prevent to stop up, the scraper of showing one's color with the chain polyphone is housed in stove, allow it along with the rotation of body of heater, ceaselessly clash into the furnace wall, the caking materials that is bonded at the furnace wall is scraped chipped away.

Rotary kiln charcoal activating process condition is listed in table 4.

Table 4 rotary kiln charcoal activating process condition

Project	Processing condition	Remarks
			The region of activation temperature of charge (℃) the charcoal soak time (minute) interior material fill factor (%) drum speed of stove (rev/min) furnace pressure (mmH 2The O post) end flue temperature (℃) stove tail temperature (℃) the discharge room interval (branch)	15～20 1～3 negative pressure 700～800 200～300 20 slightly about 500～600 40	Estimate that according to black furnace material accounts for furnace wall thorax volume from the discharge chamber discharging

During charing, requiring furnace temperature is 500 ℃～700 ℃, and the material temperature is 300 ℃～400 ℃.The requirement stove fire is even, and regularly stirring prevents caking.The carbonization time of every batch of material is 30 minutes～60 minutes.

During activation, furnace temperature is 700 ℃～800 ℃, and the material temperature is 500 ℃～600 ℃, and soak time is 2 hours～2.5 hours.Every 15 minutes～20 minutes stirrings once.The activated material of coming out of the stove was stacked 8 hours～16 hours, utilized the wet continuation atomizing of material.Adjust the aperture, to improve the quality of product.

So, in charing, activation act, must pay close attention to the recovery and the off gas treatment of phosphoric acid in the stack gases.

1.2.5 recovery phosphoric acid

Reclaiming in the activated material is to reduce the phosphoric acid consumption, reduces production costs and the critical process of environmental pollution.Usually the phosphoric acid solution with lower concentration extracts activated material.The recovery liquid that extraction for the first time obtains, concentration is higher, if reach the impregnation concentration requirement, can get back in the Production Flow Chart and use.Repeatedly extract with the lower phosphoric acid solution of concentration later.Use hot wash at last, phosphorus acid content is lower than till 1% in gac.About 1.5～4 hours of the time of whole recovery process.Because the charcoal of gac divides some metal oxide and phosphatase reaction in the neutralizing device, has generated the dissolubility salt, make the impurity in the phosphoric acid solution more and more, influence the quality that solution circulated is used the back product.At this moment, reclaim liquid and need add zinc sulfate.

1.2.6 rinsing

The purpose of rinsing is the various foreign material of removing from raw material and the production process, makes every foreign matter content of gac reach the requirement of quality index, as ash content, acid-soluble material content, iron level, cl content, sulphate content, cyanide content, sulfide content, heavy metal content etc. and pH value.Rinsing comprises pickling and two steps of washing.The gac of finishing reclaimer operation is added an amount of phosphoric acid in rinsing tub, feed steam and boiled 2 hours, at this moment water-fast impurity becomes water soluble compounds, removes with water.After the pickling, add the alkali neutralizing acid, generate phosphate anion, and use the hot water repetitive scrubbing.The main purpose of washing is to remove various water-soluble impurities.The phosphate anion content that generally is washed in the filtrate is lower than till 0.16%.About about 5 hours of total washing time.

1.2.7 dehydration and dry

The purpose of dehydration is to reduce gac moisture, reduces drying load and heat energy consumption.The general centrifuge dewatering that adopts drops to the gac moisture content about 60～65%.The exsiccant purpose is that the gac moisture after the centrifuge dehydration further is reduced to below 10%.Drying plant commonly used is the external-heating revolving drying oven, and the cylindrical shell specification is φ 1000 * 7000.The external-heat advantage is to avoid stack gas directly to contact with gac, reduces the contaminated possibility of product, but because gac contacts with the irony furnace wall, phase mutual friction meeting increases the iron level of gac.Temperature of charge in the rotary drying stove requires in 120 ℃～130 ℃.In order to prevent that dry charcoal from catching fire, strict control furnace temperature and feeding quantity.Oven-fresh gac because temperature is higher, preferably is placed on airtight container internal cooling.

1.2.8 grind

The particle of dried gac is inhomogeneous.Grind the epigranular that makes product of purpose and reach the requirement of quality index.General requirement is ground into below 120 orders.

Usually use the continous way ball mill to grind, for avoiding in mechanical milling process, increasing iron level, generally at ball mill liner one deck hardwood plate, and with porcelain ball replacement iron ball.Meticulous for fear of granularity of activated carbon, the filtration velocity when influence is used can adopt and strengthen drying and crushing machine or thunder illiteracy pulverizer.

1.2.9 the three wastes are handled

During smoke treatment, make flue-gas temperature drop to 120 ℃ by multistage dedustings such as settling pocket, naturally cooling equipment earlier, remove most of charcoal dirt.Enter vapour liquid separator again and remove the droplet and the remaining charcoal dirt of part phosphoric acid and water vapor formation.At this moment flue-gas temperature is reduced to 100 ℃.Enter condensation in the condenser then, flue-gas temperature is further dropped to below 50 ℃, at this moment most water vapors and phosphoric acid mist are condensed.The flue gas that condenser comes out only contains small amounts of phosphoric acid mist gas, has not had recovery value.Earlier through the effective water hydro-peening of Venturi, further remove acid mist through entrainment trap and absorption tower again before the emptying.The phosphoric acid waste water that generates when rinsing and flue gas are handled selects flocculence commonly used to handle, after the allow compliance with emission standards, and further recycle again.Temporary transient sharp exhaustless treating water is put into salt of wormwood (K ₂CO ₃) further neutralization is stand-by for three grades of settling tanks.

2 phosphoric acid methods are produced granulated active carbon

When producing granulated active carbon with the phosphoric acid method with raw materials such as straws, general adding additives not.In order to improve intensity, to improve absorption property or during for raw material, need use binding agent, as polyvinyl alcohol, coal tar, coal-tar pitch etc. with bituminous coal etc.

2.1 technical process.It is different because of raw material that the phosphoric acid method is produced the technical process of powdery and granulated active carbon.With stalk mixing wood chip be raw material technical process respectively as shown in Figure 2.

2.2 production operation

2.2.1 raw material screening and drying.In order to guarantee the physical strength of granulated active carbon, it is thin that the production powdered carbon of raw materials used stalk mixing wood chip is wanted, and is generally less than 0.8 millimeter.Too thick stalk mixing wood chip will be in advance through pulverizing and grinding.

The moisture requirement of stalk mixing wood chip is 5%.Drying plant is rotary kiln and pneumatic dryer.

2.2.2 the preparation of phosphoric acid solution.It is higher to produce the used phosphoric acid solution concentration of granulated active carbon, and generally more than 50%, and the acidity of solution is higher, in order to the hydrolysis and the saccharification of stalk mixing wood chip.

2.2.3 batching, the mixed moulding of kneading.Condition effect that the intensity of granulated active carbon and other physico-chemical properties are compared by the phosphorus bits all and dipping is kneaded.Under the same terms, phosphoric acid is than big, and then particulate intensity is lower, transitional pore is flourishing, absorption property is good, unit weight is little.On the contrary, the phosphorus bits are littler than little then pore volume, unit weight is big, intensity is high but adsorptivity is low.Industrial used phosphorus bits are adjusted because of the gac kind is different than being 0.8～1.5.

Powdered carbon is different with making, in phosphoric acid solution dipping and the kneading process plasticizing process is arranged, mix the saccharification of wood chip impregnant heating hydrolysis exactly, produce the hydrolysis alditol solution of pulpous state, under the heating condition about 150 ℃, make the impregnant softness, roll through kneading repeatedly again, impregnant is mixed, have cohesiveness and plasticity-.During stalk mixing wood chip phosphoric acid legal system granulated active carbon owing to do not add other binding agents, so the plasticizing quality is very important.The plastifying key is plasticization temperature and time.Generally heating can reach plasticizing half an hour between 130 ℃～150 ℃, between its water ratio about 12～15%.

The method of moulding is a lot, and the setting charcoal of living has cylindrical, the sphere of rolling disk moulding of extrusion molding, the sheet of impacting moulding.Amorphous gac is made: will plastify material earlier and be pressed into bulk, and be broken into irregular small-particle then after charing.The maximum of domestic usefulness are extrusion process.Because the physical strength of granulated active carbon is decided by forming pressure to a great extent, so no matter adopt which kind of forming method, all require the forming pressure that reaches certain.In addition, moisture content also has a significant impact moulding during moulding.Requiring moisture content during extrusion molding is 12%～18%.

The later particle of moulding will carry out drying before carrying out charing.Processing requirement low temperature is dry for a long time, can guarantee particulate intensity like this.If rapid drying, moisture evaporation is too fast, and particle surface can crack, and has a strong impact on the intensity of gac.So drying temperature generally is no more than 180 ℃.

Target level of product quality

Processing parameter:

Moisture 6.8%

Ash content 2.1%

Volatilization 9.5%

Fixed carbon 81.6%

Size range 0.3～7.0mm, average particle size 2.35mm

Powdery 200 orders

Bulk density 506kg/m ³

Its processing parameter:

Charging 35kg/h

1050 ℃ of chamber temperatures

850 ℃ of activation furnace temperature

Air capacity 150m ³/ h

Saturated steam amount 70kg/h, (gauge pressure 50GPa)

Bed pressure reduction 700 ± 50Pa

Activation carbon yield 12.5kg/h

Embodiment 2: stalk environmental protecting physical Chemical bond legal system is made gac

Present embodiment is a raw material with agricultural crop straw (mixing), makes activator with potassium hydroxide, by the mode of sour pre-treatment and steam activation, develops the more excellent activated carbon sample of performance.Experiment shows, active optimum temps is at 750 ℃～800 ℃, and optimum temperature rise speed is 5 ℃/min～10 ℃/min, and activator level was with 1: 1 more excellent (raw material and activator mass ratio).The activated carbon sample iodine sorption value is 980mg/g, and specific surface area is 1180m ²/ g.Simultaneously the KOH activating mechanism is inquired into.The widespread use of gac makes the gac development have certain meaning.One of main direction of studying of straw-stem active charcoal.

Different types of crop material, its organic basic structural unit is discrepant.Contain less nuclear and more side chain and functional group in its basic structural unit of cutin stalk of low degree of lignification.The containing the oxygen lawsuit and can roll into a ball fewly of medium stalk, alkyl group side chain is few, and aromatic proton increases, and the bridged bond between the structural unit reduces.Stalk cutin, the aromatic proton that degree of lignification is high significantly increase, and are the desirable feedstock of making gac.So wooden gac development that all is used to carry out below not of the same race, the stalk of low degree of lignification is because loosely organized, degree of graphitization is low during charing, often just can prepare comparatively ideal gac by more weak activation environment (physically activated), but yield is low, the mixed straw raw material is because structure trends towards latticeization, easy greying during charing, so crystallite ordered arrangement, porosity is low during activation, influence activation effect, by using CO after the perchloric acid pre-treatment ₂The activatory method is prepared specific surface and is reached 1600m ²The gac of/g (yield is 30%).

The physically activated time is long, the activation temperature height.Agricultural crop straw output is abundant, wherein some stalk such as fixed carbon content height such as cotton stalk, fruit tree branch, and ash low (minimum reach 5.18%) is suitably the raw material of making gac.We by sour pre-treatment, have carried out gac development work with chemistry and physical bond activatory mode as raw material, and under certain activation condition, developing specific surface is 1180m ²The activated carbon product of/g (yield is 50%).

1 experimental section

1.1 instrument

The self-control activation furnace, QM-4H shredder, electric drying oven with forced convection, PE-60X100 jaw crusher.

1.2 method

With crusher with the stalk coarse crushing after, with atomizer mill the particle stalk is carried out fine grinding again, after stalk mixing wood dust crossed 120 purpose sieves, take by weighing stalk mixing wood dust 145g, add hydrochloric acid (36.5%) 10mL, hydrofluoric acid (73%) 10mL, 10 perchloric acid (37%) 20mL, water 50mL stirs, and soaks 24h under the room temperature.

With the suction filtration device above-mentioned raw materials is washed, after being washed till the pH value and being 6, place oven dry moisture content in the electric drying oven with forced convection.Take by weighing oven dry back mixed straw wood chip 10g, add potassium hydroxide solution (10%) 10mL, stir into pasty state, put into porcelain boat, place in the activation furnace, feeding nitrogen (flow is 1.0L/min) rises to 800 ℃ with the heat-up rate of 8 ℃/min, insulation 45min, after the cooling, product is soaked 20min with hydrochloric acid soln, wash with water then to pH value 6, drying, can obtain the gac iodine number is 980mg/g, and specific surface is 1180m ²The activated carbon product of/g.

2 results and discussion

2.1 raw material

Raw material adopts its technical analysis of mixed straw to the results are shown in Table 1

Table 1 mixed straw technical analysis result

Project	Ash analysis (%)			Ash fusion point (℃)
							SiO 2	Al 2O 3	Fe 2O 3	DT	ST	FT

Index

61.54

27.36

2.67

1000

1060

1260

As shown in Table 1, main component is SiO in the ash content ₂, owing to raw material ash content in the making gac process can stop the formation of micropore, product performance there is disadvantageous effect, therefore adopt hydrofluoric acid ash disposal mode.Ash content drops to 1.2% after acid treatment.

By with the processing of perchloric acid to mixed stalk raw material, obtain conclusion: perchloric acid is handled the back has material impact to the physically activated process of back: the one, can improve activation effect; The 2nd, increased the surfactivity of raw material after the preoxidation by raw material.Our hot analytical results by KOH and raw material straw powder mixture as can be seen, in the time of 210 ℃, DTG reaches extreme value (1.7%/min), may be that the carbon reaction generates carbonic acid gas in perchloric acid and the mixed straw this moment, these gas molecules penetrate feed particles inside, form the passage that many diameters are 1～10nm, help the chemical activation under the high temperature, thereby improve activation effect.

2.2 the influence of activation condition

In order to find the ideal chemical activating agent, use K respectively ₂CO ₃, Na ₃PO ₄, H ₅PO ₄, KOH, ZnCl ₂And H ₂SO ₄The mixed type crop material is activated, and activation condition and activation effect see Table 2.

The different activator activation effect of table 2 table

Activator	Activation temperature (℃)	Soak time (h)	Iodine number (mg/g)
				K 2CO 3	800	1	640
Na 3PO 4	800	1	240
				H 5PO 4	800	1	740
KOH	800	1	710
				ZnCl 2	800	1	650
H 2SO 4	800	1	380

According to table 2 data, selection KOH is an activator.Activation conditions such as activation temperature, soak time, heat-up rate and activator level have bigger influence to the activation product.We are that heat-up rate is 10 ℃/min, has carried out activating at 600 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃ respectively (soak time is 30min) under 1: 1 the situation in KOH and proportioning raw materials.

Temperature one timing, soak time is also influential to activation effect.Under the situation when activation temperature is 800 ℃, KOH and proportioning raw materials are 1: 1, and heat-up rate is 10 ℃/min, activates the different time respectively, and activation effect sees Table 2.

For inquiring into the influence of activator level to activation effect, 800 ℃ of activation, change 10 ℃/min of heat-up rate, soak time 45min activates with the amount of the different proportionings of raw material with KOH respectively.

In activation temperature is 800 ℃, and heat-up rate is 10 ℃/min, and soak time is 45min, and KOH and proportioning raw materials are under 1: 1 the situation, to activate with different heat-up rates, and iodine number descends during temperature to 850 ℃.

2.3 properties of sample

Iodine number is one of main performance index of gac.Respectively raw material has not been carried out iodine sorption value mensuration with the activated carbon product of sour pre-treatment mixed straw making and the activated carbon sample of making of sour pretreated mixed straw by standard, not crossing the mixing wood dust with acid treatment, to make the gac iodine number be 707mg/g, it is 980mg/g that the pretreated mixing wood dust of acid makes active iodine number, as seen after using sour pre-treatment, the sample absorption property is significantly improved.

By the characterization of adsorption of gac in methylene blue solution, utilize Langmuir absorption agenda formula to measure iodine number and be 1180m for its specific surface area of activated carbon sample of 980mg/g ²/ g.

By Infrared spectroscopy (infrared spectrum slightly), the result shows: the gac that not additivated mixing wood dust makes is 1628cm in wave number ^-1And 1442cm ^-1Producing strong absorption peak, may be through judging for adjacent two carbonyls resonance get, so its surface group is the quinoid structure, its characterization of adsorption remains further to be studied.

The potassium hydroxide activation method is a kind of new activation method, once be used for intermediate phase charcoal microballon, pitch, polyacrylonitrile based preoxidation fabric, coal slime, bituminous coal etc., from the Properties of Activated Carbon that makes, the KOH activation effect is good, but because the corrodibility of KOH, to the equipment requirements height, also do not form suitability for industrialized production in China, adaptability and the activating mechanism of therefore studying its raw material mixed straw have certain realistic meaning.

From the hot analytical results of KOH and raw mix as can be seen, between 150～300 ℃, raw material weightlessness reaches 13.5%, and weightless part is mainly contained humidity and small-molecule substance in the raw material.In reactivation process, when being warming up to 280 ℃, by getting liquid phase sample, with gas chromatographic analysis (carrier gas: hydrogen; Separator column; Detector; Thermobattery).From color atlas as can be seen, retention time is that the component of 0.57min is a water, and retention time is that 1.42min and 3.38min etc. are small molecular alcohol or ester class in the raw material.When the heat analysis was warming up between 350～550 ℃, sample quality remained unchanged substantially, and activator potassium hydroxide this moment (fusing point: 360 ℃) has been molten, and KOH begins to decompose:

When above-mentioned reaction takes place, generation-the OK group replaces coal-tar middle oil some the H atom of raw material, raw material begins dehydrogenation, be released into out with the form of hydrogen, therefore, along with temperature continue to rise to 600 ℃ the time, alkali metal compound is (as K ₂O, K ₂CO ₃) begin to react with carbon, make carbon be released into out with oxide form, the formation of basic metal potassium is arranged simultaneously, and potassium walking between the graphite microcrystal plane, do not having to produce etching on the surface that exposes, thereby increase microvoid structure and change fragrant two dimensional structure and electron distributions situation thereof in the microcrystal, improve the performance of gac.

By thermal analysis experiment, obtain the weightlessness of activator, raw material and activator and raw mix and the relation between the temperature respectively.Reactivation process, when temperature rose to more than 200 ℃, the perchloric acid etch was fallen part carbon and is made it weightless.

The actual burning mistake rate of activator and raw material powder mixture and Theoretical Calculation gained curve (supposing no effect between KOH and the raw material powder) have bigger difference: after 600 ℃, because K ₂O and K ₂CO ₃And chemical reaction takes place between the carbon cause the actual mass rate of loss more much bigger than calculating, its reason is that alkali metal compound is (as K ₂O, K ₂CO ₃) begin to react with carbon, make carbon discharge with oxide form, when temperature during greater than 800 ℃, can cause burning the mistake rate on the one hand increases, the product yield is low, carbon that may be too much causes microvoid structure to cave in after burning and losing on the other hand, makes that the gac pore size distribution is undesirable, so suitable activation temperature is between 750～800 ℃.

3 conclusions

3.1 with the mixed straw wood chip is raw material, when KOH made activator, the pre-treatment of mixing acid had tangible benefit, can reduce ash content and the carrying out that helps priming reaction.

3.2 the mixed straw wood dust is a raw material, KOH is an activator when making gac, and suitable activation temperature is that 800 ℃, soak time are that 60min, activator and proportioning raw materials are 1: 1, and making the gac iodine number is 980mg/g, and specific surface is 1180m ²/ g.

Claims (2)

1. the method for a producing active carbon by using straw blend materials is characterized in that, it is mixing raw material that this method adopts crop material, the useless branch of fruit tree and trees sawdust, adopts phosphoric acid method and physical bond method to produce powdery or granulated active carbon, specifically comprises the following steps:

1) raw material is prepared

Above-mentioned raw materials is crushed to the granularity of 1-2mm with pulverizer, after the rolling shredder carries out fine grinding, crosses 120 mesh sieves, drying again;

2) preparation of phosphate impregnation liquid, batching

Prepare the concentration and the pH value of phosphate impregnation liquid according to the kind of gac; The prescription of craboraffin requires: 50～57 ° of Be '/60 ℃, pH value 3～3.5; The prescription of industrial activited carbon is: 45～47 ° of Be '/60 ℃, and pH value 1.0～1.5, manufacture is 0.75: 1 with the phosphoric acid and the stalk mixing wood chip ratio of Powdered Activated Carbon; When producing granulated active carbon, the phosphorus bits are than being 0.8～1.5; Sugar is more than 1.6: 1 with the phosphoric acid and the stalk mixing wood chip ratio of Powdered Activated Carbon;

3) dipping or wet mixing are pinched

Dipping is that dipping time can obtain impregnant greater than 8 hours with stalk mixing wood chip and the abundant mixing of phosphoric acid solution;

When adopting wet mixing to pinch, utilize mechanical stirring device to force stalk mixing wood chip and phosphoric acid are kneaded, the time of kneading is 10～15 minutes;

When producing granulated active carbon, dipping and wet mixing are pinched all a plasticizing process in the process, promptly under 130 ℃～150 ℃ heating condition, make the impregnant softness, rolls through kneading repeatedly again, and impregnant is mixed;

4) charing, activation

To carry out charing by the phosphorus bits material after pinching through dipping or wet mixing, the furnace temperature during charing is 500 ℃～700 ℃, and the material temperature is 300 ℃～400 ℃; The carbonization time of every batch of phosphorus bits material is 30 minutes～60 minutes;

Raw material after charing further activates, and the furnace temperature during activation is 700 ℃～800 ℃, and the material temperature is 500 ℃～600 ℃, and soak time is 2 hours～2.5 hours, every 15 minutes～20 minutes stirrings once;

The activated material of coming out of the stove was stacked 8 hours～16 hours, utilized the wet continuation atomizing of material, adjust the aperture;

5) reclaim phosphoric acid

Phosphoric acid solution with lower concentration extracts activated material, and the recovery liquid that extraction for the first time obtains if reach the impregnation concentration requirement, is promptly got back in the Production Flow Chart and used; Repeatedly extract with the lower phosphoric acid solution of concentration later, use hot wash at last, phosphorus acid content is lower than till 1% in gac, and the time of whole recovery process is 1.5 hours～4 hours;

When recycling, in reclaiming liquid, need to add zinc sulfate and remove impurity for the phosphoric acid solution that contains impurity that reclaims;

6) rinsing

Rinsing comprises pickling and two steps of washing:

Pickling is to add an amount of phosphoric acid with finishing the gac that reclaims behind the phosphoric acid in rinsing tub, feeds steam and boils 2 hours, makes water-fast impurity become water soluble compounds, removes with water;

After the pickling, add the alkali neutralizing acid, generate phosphate anion, and remove various water-soluble impurities with the hot water repetitive scrubbing, the phosphate anion content that is washed in the filtrate is lower than till 0.16%;

7) dehydration and dry

Adopt centrifuge dewatering, the gac moisture content is dropped between 60～65%; Carry out drying then, make the gac moisture after the centrifuge dehydration further be reduced to below 10%;

8) grind

Use the continous way ball mill to grind dried gac, promptly obtain powdery or granulated active carbon.

2. the method for claim 1 is characterized in that, described crop material is wheat stalk, maize straw and cotton stalk, and its ratio is 1: 1: 1.

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