CN87101684A

CN87101684A - Method for maintaining stabilized coal-water slurry

Info

Publication number: CN87101684A
Application number: CN87101684.2A
Authority: CN
Inventors: 梶隆一; 村中廉; 菊池秀雄; 宫寺博; 齐藤一一
Original assignee: Babcock Hitachi KK; Hitachi Ltd
Current assignee: Hitachi Ltd; Mitsubishi Power Ltd
Priority date: 1986-03-05
Filing date: 1987-03-05
Publication date: 1988-03-02
Also published as: CN1017062B; CA1275020A

Abstract

The present invention relates to a method for keeping the viscosity of coal slurry low and stable without deteriorating its properties during long-term storage by adding alkali metal silicates and/or alkali metal silicates that can form insoluble water compounds with calcium ions or magnesium ions into the slurry or carbonates, the amount added should be sufficient to maintain the concentration of these ions at a predetermined level by converting them into water-insoluble compounds, and the amount added should also be dissolved in the slurry by continuous or intermittent detection. Calcium ions and magnesium ions in the supernatant liquid to control.

Description

The present invention relates to a kind of method that keeps stabilization coal water slurry, the viscosity of this coal water slurry is very low, also can pass through pipeline transmission without difficulty even preserved a very long time.

The technology of people from beginning one's study very early and transporting powder with the form of slurry, its reason is that the fluid that transports pressed powder is easy to be handled.Recently, people have carried out many investigation for a kind of production high concentration water coal of research, and the purpose of producing high-concentration coal-water slurry is to improve by pipeline transports the efficient of coal and don't the spontaneous ignition that produces flying dust with the form of slurry.High-concentration coal-water slurry is to produce like this: the size distribution of control coal dust makes void ratio reach minimum, then the coal dust in small, broken bits that obtains is mixed with water, obtains percentage of coal content in 60% to 70% weight percent or higher coal water slurry.This delivered in a lot of publications.

The viscosity of Zhi Bei emthod of high-concentration coal-water slurry is greatly between 1000 to 2000 centipoises like this, so its flowability is enough to carry out pipeline transportation.But comprise closelypacked a large amount of pulverized coal particle in such high-concentration coal-water slurry, each pulverized coal particle all runs foul of each other with other particles in transportation.Coal concentration in the coal water slurry is high like this, as long as the composition of slurry changes for a short time or sneaks into small amount of impurities, its mobile just energy noticeable change.When high-concentration coal-water slurry when flowability changes in the pipeline transportation process, the orthicon road will occur and stop up such problem.

Very big influence takes place to its viscosity in the pH value of highly dense coal water slurry as you know.In other words, the pH value is high more, and the viscosity of slurry is low more.Suppose that this is because the hydrogen ion concentration in the slurry changes the variation of function caused the variation of pulverized coal particle surface charge amount or to have caused the tensio-active agent of pulverized coal particle surface adsorption, interaction between the particle is even have only slightly variation so, the viscosity of high-concentration coal-water slurry will change greatly, this is that the distance between the particle has greatly been reduced because the pulverized coal particle in the high-concentration coal-water slurry is closelypacked.

Except hydrogen ion, metal ion (polyvalent metal ion that particularly has positive charge) also can make the viscosity of slurry increase.

Known in the present technique field, though the acidity on coal surface can change according to grade and storage condition, coal water slurry normally is tart.Contain coal ash in the coal, mainly comprise silicon oxide and aluminum oxide in the coal ash, also have the salt of alkaline-earth metal (as calcium and magnesium) and heavy metal (as chromium, vanadium and iron) in addition, they can be dissolved in the acid slurry, and the viscosity of slurry was increased in for some time.

In order to overcome this shortcoming, people have proposed such method, add alkali to improve the pH value of slurries when the preparation slurry.But the alkalescence slurry of the preparation that comes to this also can become acidity after long storage time.Therefore this method can not overcome above-mentioned shortcoming effectively.

The contriver also once proposed a kind of method of producing high-concentration coal-water slurry in the past, and this method is characterised in that mixes the levigated coal dust with one of the water that contains tensio-active agent and following two kinds of materials: a kind of material is an alkali metal salt (its negatively charged ion can generate indissoluble or dissolved salt not with polyvalent metal ion); Another kind of material is inorganic complexing agent (can generate high stability bath compound with polyvalent metal ion), (openly applying for No. 20691/1984 referring to Japanese Patent).But similar to the method for control pH value above-mentioned, additive follows the polyvalent metal ion that discharges in for some time to react, and the amount of additive is reduced, and to the end, the additive in present method has just lost activity.Like this, when slurries were stored, additive must be replenished.With eliminate in the slurry many hydroxyls positively charged ion for from done after a large amount of investigation, the contriver finds additive even without reacting with polyvalent metal ion, itself also can lose activity because of sex change in for some time.Therefore, this method also has shortcoming economically.Particularly the particle in the high-concentration coal-water slurry is ground quite carefully for increasing flowability, and the temperature that the result starches in levigate this step will rise.Temperature is high more, and the speed of additive sex change is fast more, and benefit is also just low more.

Because the dispersion medium of high-concentration coal-water slurry is a water, so in case slurry forms, the surface of coal dust particle promptly contacts with water.Well-known water is a kind of polarization solvent, and some ionogen are high dissolution in water.And coal is the mixture of carbonaceous material and coal ash.Coal ash contains the salt of silica alumina and some other metal, and the part coal ash is exposed to particle surface when grinding.Therefore, the coal ash that contains in the high-concentration coal-water slurry also contacts with water always.Water is good solvent, and a part of grey participant is dissolved in the water, thereby resembles the viscosity that increases slurry foregoing.When the pH value reduces, the dissolving of coal ash generally will be accelerated.It is impossible wanting the total ban dissolving in any pH value scope.Even use thing such as sodium hydroxide to make high-concentration coal-water slurry be alkalescence in the preparation usually, the ash content in the coal also can be dissolved in for some time in the slurry, and viscosity is increased.Great changes have taken place with the character of contained ash content in the coal in the dissolving of coal ash.Some coals are difficult for making the high-concentration coal-water slurry with high fluidity, because there are a large amount of coal ash to be dissolved out in preparation process.

Do not worsen the character of coal slurry when purpose of the present invention just is to be provided at long-term storage, make the viscosity of coal slurry keep low and stable method.Above-mentioned purpose of the present invention can realize by add alkali-metal silicate and/or carbonate to coal slurry.These alkali-metal silicate or carbonate energy and calcium ion and/or magnesium ion generate the salt of water-fast compound.When beginning to prepare coal slurry, water and tensio-active agent are added in the levigated coal dust.The quantity of salt must enough can maintain ionic concn on the predetermined level by the approach that ion is converted to the insoluble compound of pointing out above.

Fig. 1 represents the viscosity of coal slurry and the relation between storage period by the comparison of two kinds of different coal slurries.

Fig. 2 represents to have a kind of viscosity of coal slurry of different sodium silicate silicates and the relation between storage period.

Fig. 3 represents the calcium ion concn in the supernatant liquid and deposits the relation of storage period.

SiO during Fig. 4 represents viscosity and starches ^2- ₃And Ca ²⁺Mol ratio between relation.

Fig. 5 represents Ca in viscosity and the coal slurry ²⁺Relation between the concentration.

Fig. 6 and Fig. 7 represent the relation between the pH of ionic concn and coal slurry.

Fig. 8 and Fig. 9 represent the relation between the coal concentration in viscosity and the coal slurry.

Figure 10 is the synoptic diagram of the storage facility of high-concentration coal-water slurry.

Figure 11 is the synoptic diagram of coal slurry preparation facilities.

Done after a large amount of investigation for overcoming shortcoming above-mentioned, the inventor thinks that in time increase increases owing to underlying cause for the viscosity of high concentration coal slurry;

Preparation during high-concentration coal-water slurry for reducing normally cationic surfactant of the used surfactant of its viscosity since the hydrophobicity of surfactant it adsorbed by the surface of pulverized coal particle, therefore coal dust is with negative electricity. Like this, anion surfactant has changed into hydrophilic surface to hydrophobicity coal dust surface. In other words, surfactant has changed into hydrophilic colloid to high-concentration coal-water slurry from hydrophobic colloid. According to two kinds of functions of surfactant above-mentioned, add the viscosity that anion surfactant just can reduce high-concentration coal-water slurry. More particularly, first: surfactant makes the coal dust particle surface be hydrophily, thereby forms a very thin water layer around each coal dust particle, and the caking of coal slurry particle just is prevented from because of steric hindrance. Second: coal dust particle all is with negative electricity, has produced electrostatic repulsion forces between them, thereby has prevented the caking of coal dust, thereby reduces the viscosity of slurry. Although what have first above-mentioned effect not only has an anion surfactant, also has nonionic surface active agent, but in high-concentration coal-water slurry, preferably use anion surfactant, this is because the concentration of coal dust particle is up to 70% percentage by weight or higher in coal slurry, wherein coal dust particle is mutually tightly packed, and the electrostatic repulsion forces between the particle cuts much ice aspect the caking preventing.

From top result of study, the inventor believes that the electric charge on the coal dust particle is playing very important effect aspect the reduction viscosity. Under the condition that the quantity of electric charge reduces, the viscosity of slurry increases. The electric charge of taking to increase on the coal dust particle for the viscosity that reduces slurry is very effective with the method for the dispersion that increases particle. At United States Patent (USP) the 4th, 282, in No. 006, delivered and in slurry, mixed some additive with the electric charge on control coal dust surface. As everyone knows electronegative Great changes have taken place with concentration is different according to cationic kind in the solvent for the quantity of electric charge of colloidal particle, and this is because on every side or on the surface of electronegative particle can optionally be concentrated and/or be adsorbed on to cation, and the charging neutrality of electronegative particle is fallen. Cationic absorption is more strong, and the quantity of electric charge of coal dust is more little. This phenomenon of stability people that electronegative particle Liquidity limit affects hydrophilic colloid have studied for a long time. As everyone knows, in cation, on electronegative particle hydrogen ion adsorption the strongest secondly be polyvalent metal ion. The valency of polyvalent metal ion reduces, and its adsorptivity also reduces. This is true relevant with the charge density of anion. The charge density of ion is more high, and its adsorptivity is also more strong.

These facts can illustrate well that the viscosity of the high-concentration coal-water slurry that the front was said changes and this character of noticeable change with the pH value.

In the investigation that high-concentration coal-water slurry is done, the contriver has also found the phenomenon that can not explain with the variation of pH value separately.Here it is, and when high-concentration coal-water slurry was stored certain hour after preparation, its viscosity was incited somebody to action growth in time and increased.According to the discovery that the front inquiry agency gets, get the supernatant liquid of slurry and analyze, found that the concentration of concentration ratio during firm preparation of positively charged ion (as calcium ion or magnesium ion) shows a considerable increase.The contriver once proposed a kind of method of removing the polyvalent metal ion in the slurry in the past, this method adds in the slurry the negatively charged ion of energy and polyvalent metal ion generation difficulty soluble salt or the complexing agent that can generate stable metal complex shelters deleterious polyvalent metal ion, preventing that these metal ions from being adsorbed by coal dust, thereby reduced the viscosity of high-concentration coal-water slurry.Like this with regard to the stable slurry of availability matter.But the slurry that is exactly this method preparation is when long time stored, and the cation concn in its supernatant liquid also can increase, thereby increases the viscosity of slurry.The rate of increase that the contriver also finds viscosity changes with the kind of additive.Magnification is very high if these find explanation viscosity, then additive sex change itself.

And after having done a large amount of investigation for the cheap additives of the high-strength bonding force of seeking high stable with antitypy and polyvalent metal ion and the excellent properties of removing above-mentioned metal ion, the method that the contriver has found the viscosity that prevents to starch in storing the pipeline transportation to rise, the best implementation method that will describe below this comprises that interpolation water glass and/or yellow soda ash are as the polyvalent metal ion remover.

The following examples will further specify the present invention.

(preparation embodiment 1)

The sodium salt (as anion surfactant) of coal, water and sulfonated naphthalene formaldehyde condensation products sent into carry out wet-milling in the ball mill, the coal particle size that obtains is distributed as 60 orders or littler particle accounts for 99%, 100 orders or littler particle account for 93%, 200 orders or littler particle account for 80%, 400 order or littler particle accounts for 65%.The coal concentration of Zhi Bei high-concentration coal-water slurry is 69% weight percent like this, adds 0.5% weight percent (is benchmark with the dry coal) anion surfactant in slurry.In the process of preparation slurry, add the sodium hydroxide of 0.3%(weight percent (is benchmark with the dry coal) in the slurry, the pH value of starching is adjusted to be approximately 8.The viscosity of the slurry that obtains like this is 4200 centipoises.This slurry be called " former slip " later on though in the present embodiment the pH value adjust to 8, in fact the pH value in 6 to 11 all is fine among the present invention.

The negatively charged ion of dissolved salt is added in the slurry of gained as generating not with multivalent metal cation Sodium hexametaphosphate 99, and the viscosity of slurry is dropped to 1200 centipoises, and coal concentration is 69% weight percent.The quantity of the Sodium hexametaphosphate 99 that adds is 0.1% of dry coal weight in the slurry.Contain below the slurry of Sodium hexametaphosphate 99 and be called " slurry A ".

Water glass (water glass) with dry coal weight 0.1% in the slurry replaces Sodium hexametaphosphate 99 to be added in the former slip, and the viscosity of slurry becomes 1200 centipoises, and this equates with the viscosity of slurry A when coal concentration is 69% weight percent, is called " starching B " below containing the slurry of water glass.

Can find out that like this effect of Sodium hexametaphosphate 99 on the viscosity that reduces slurry is identical with water glass.Slurry A for preparing above and slurry B are stored under 65 ℃ the temperature, and in the given timed interval its viscosity are measured.

Measuring result is seen Fig. 1.For slurry A, viscosity rises after storing the test beginning immediately, and viscosity promptly reaches the value identical with former slip after 3 days; Slurry B then is different from slurry A, and the value that its viscosity equals just to have prepared was not seen any growth in 30 days even store yet.

The reason that the viscosity of slurry A increases is in for some time, and coal ash is dissolved out from coal, and the multivalent metal cation that produces from coal ash and the hexa metaphosphoric acid negatively charged ion water-fast phosphoric acid salt of generation that reacts causes the consumption of the hexa metaphosphoric acid that adds.In addition, being also noted that hexametaphosphate will be looked the pH value, temperature is different with other condition is converted into orthophosphoric acid salt or is converted into phosphoric acid salt by polycondensation.The hexametaphosphate that transforms no longer have with the dissolved polyvalent metal mutually ion generate the character of water-fast salt.Another reason that the superincumbent shelf test medium viscosity of slurry A significantly rises probably is the sex change of hexametaphosphate itself.

Though silicate can polycondensation as hexametaphosphate in the aqueous solution under certain conditions, can clearly be seen that from Fig. 1 the viscosity of slurry B does not continue in time and increases, be to keep stable.The contriver believes that this is that its polycondensation speed is quite low, also is negligible even polycondensation in this section period that takes place when being aqueous solution state because of silicate in slurry; Even or, generate water-fast salt because the polycondensate of silicate also can react with polyvalent metal ion.

Embodiment 1 can obviously find out from preparation: the water glass tool reduces initial viscosity, and reducing water slurry viscosity increases, and can keep the stable fabulous effect of flowing property of slurry in very long for some time.

(preparation embodiment 2)

Is various quantity 0.005,0.01,0.05, the water glass of 0.1% weight percent (is benchmark with the dry coal) respectively is added in the former slip that makes among the preparation embodiment 1, the every kind of slurry that makes like this, C(0.005% weight percent), E(0.05% weight percent D(0.01% weight percent)) and the F(0.1 weight percent) viscosity when coal concentration is 69% weight percent when just adding water glass is 1200 centipoises.These slurries are carried out and the test the same shelf test of preparation among the embodiment 1, and the viscosity to every kind of slurry is measured in the given time limit.Test result is seen Fig. 2.If as can be seen from Figure 2 the water glass amount that adds reduces, then viscosity increase in time will be quickened.This be not because silicate in time disappearance and sex change (inefficacy), lose the ability of picked-up polyvalent metal ion, but because coal ash growth in time is dissolved in the coal slurry water at leisure, the relative quantity of result's silicate for the amount of dissolved coal ash just becomes not much of that.To the calcium ion concn (Ca in the supernatant liquid of every kind of slurry ²⁺) also measured, what obtain the results are shown in Figure 3.Be appreciated that Ca in the supernatant liquid ²⁺Concentration increases, and the viscosity of slurry also increases.Water glass amount as adding is very little, and its absolute magnitude is just not much of that for dissolved coal ash amount.

(preparation embodiment 3)

The preparation of former slip is the same among the embodiment 1 with preparation, except selecting different coals for use.The contained coal ash content of the coal of selecting for use among this embodiment is lower, therefore can think little than among the preparation embodiment 1 of the meltage of coal ash.Calcium ion concn in the supernatant liquid is low reach 3.2 mmoles/liter.In slurry, add calcium chloride (CaCl ₂) with the dissolving of simulation coal ash.Add silicate again in the slurry that makes, the viscosity of measuring slurry is to confirm its effect.Measurement result is seen Fig. 4.Its coal concentration of slurry used in the present embodiment is 67% weight percent, the CaCl of adding ₂Amount be 0.071% weight percent (is benchmark with the dry coal).Dotted line B among Fig. 4 represents to add CaCl ₂The viscosity of preceding slurry, some A represents to add CaCl ₂The viscosity of back slurry.Measurement result from Fig. 4 can clearly be seen that, if every mole of Ca ²⁺2 moles of (SiO of middle adding ^2-) water glass, the viscosity of slurry determines to drop to adding CaCl ₂Value before.From this preparation embodiment, can know ability that obtains its picked-up polyvalent ion and the amount that reduces the necessary water glass of viscosity of slurry.

(preparation embodiment 4)

In various coal slurries, add CaCl ₂, then its viscosity variation is measured.Test result is seen Fig. 5.Wherein η ° of expression adds CaCl ₂The viscosity of preceding slurry, η represents to add CaCl ₂The viscosity of back slurry.Result from Fig. 5 can be clear that very much: if the Ca in the supernatant liquid ²⁺Concentration surpasses 600-700ppm, and then Jiang viscosity is for adding CaCl ₂Before 1.5 times of viscosity.If but the calcium ion concn in the supernatant liquid is lower than 600ppm, the viscosity of slurry is just very low, almost equals to add CaCl ₂Preceding viscosity.

(preparation embodiment 5)

The ion that is dissolved out from coal dust is analyzed, checked the kind of the polyvalent metal ion relevant with the viscosity rising of two kinds of slurries.The coal dust of 60 gram particles footpath at 37-105um mixed with 300 gram water, and the pH of mixture is controlled on each value with hydrochloric acid or sodium hydroxide.Top mixture deposited the polyvalent metal ion in its supernatant liquid is analyzed after about one month.Find during analysis that wherein the higher polyvalent metal ion of concentration is seen Fig. 6 and Fig. 7.Can clearly be seen that in low pH value that from analytical results to aluminum ion and a large amount of strippings of iron ion, when the pH value rose, these ionic amounts obviously reduced.The pH value did not in fact observe dissolving at about 6 to 8 o'clock, and pH is 6 to 8 to be very common for general high-concentration coal-water slurry.In contrast alkaline-earth metal ions (resembling calcium ion and magnesium ion) even the pH value during up to 6-8 also with quite high concentration dissolving.The result who obtains from present embodiment can infer: to passing the polyvalent metal ion that the coal slurry multiviscosisty is played a major role in time is calcium ion and magnesium ion.

(preparation embodiment 6)

Preparation embodiment 5 has illustrated: even when pH value is very high, the relevant polyvalent metal ion of multiviscosisty is calcium ion and the magnesium ion that is in the coal slurry supernatant liquid of highly concentrated solution state very with slurry passing in time.Result among this embodiment can confirm the effect of water glass aspect reduction viscosity.With preparing coal slurry, remove and select for use and the coal all inequality for preparing in

embodiment

1 and 3 with the method identical with the method for preparing embodiment 1.Used coal has higher coal ash content in the present embodiment, and therefore, can infer positively charged ion can a large amount of dissolvings.When the preparation coal slurry, adding sodium hydroxide is adjusted to the pH value and is approximately 6.Add a certain amount of sodium hydroxide again toward the part coal slurry, the pH value is adjusted into 8.5.Perhaps use another kind of method, the water glass of 0.1% weight percent (with dry coal benchmark in the slurry) is added in the slurry.Obtain two kinds of slurries like this.Fig. 8 shows the viscosity of every kind of slurry and the relation between the coal concentration.Among Fig. 8, curve G represents just to prepare the viscosity that the pH value is 6 slurry, and curve H represents with sodium hydroxide pH to be adjusted to the viscosity of 8.5 slurry, and curve I represents to contain the viscosity of the slurry of water glass.From Fig. 8, can clearly be seen that: the pH value is adjusted to 8.5 viscosity that can reduce to starch.The viscosity degradation rate of our slurry of the results suggest that obtains among the preparation embodiment 4 is low to be because the calcium ion that contains in the supernatant liquid of slurry and the cause of magnesium ion.Therefore, if we remove calcium ion and the magnesium ion stayed in the supernatant liquid fully with the method that adds water glass, then the following general who has surrendered of viscosity is faster.

(preparation embodiment 7)

Coal ash content is about 18% coal and water and send into together in the ball mill as the sodium salt of the sulfonated naphthaldehyde condensation compound of anion surfactant levigate, thereby obtain a kind of coal water slurry.Ratio of mixture at this step control coal and water makes that the concentration of coal is 65% weight percent.Adding sodium hydroxide in the slurry of gained makes pH be adjusted into 8.The concentration of coal is controlled by water in the slurry.Measure the viscosity of slurry, what obtain the results are shown in Figure in 9 shown in the curve 3.

With preparing coal slurry with top identical method, unique water glass that is not both adding 0.1% weight percent (making benchmark) in levigate this step with coal.With measuring the viscosity of slurry with top the same method, what obtain the results are shown in Figure curve K in 9.Even coal concentration is the same, the viscosity that contains the coal slurry of water glass also is significantly less than the viscosity of the coal slurry of no water glass.This fact has confirmed effect of the present invention.

In addition, the coal slurry that does not contain water glass has false yield value and false plasticity-, that is to say that its apparent viscosity can descend with shear rate.Coal dust particle in this statement of facts coal slurry has very strong force of cohesion.Therefore be understood that the lysigenous positively charged ion of coal ash and the electric charge of coal dust particle from discovery above-mentioned.Thereby weaken interparticle repulsive force.In contrast, the coal slurry that contains water glass almost is a Newtonian fuid, does not almost observe yield value above-mentioned.The dispersity of this statement of facts coal dust particle in slurry increased.The coal slurry that contains water glass that obtains above is kept at 80,70,50 or 20 ℃ respectively, and the viscosity of measuring them over time.One week of the coal slurry back viscosity that is kept at 80 ℃ is 3000 centipoises, has lost flowability after one month fully.The viscosity of sample after one week that is kept at 70,50 and 20 ℃ is respectively 1700,1300 and 1300 centipoises, is respectively 3000,1300 and 1300 centipoises after one month.The coal concentration of used coal slurry is 65% weight percent in these tests, and viscosity is 1250 centipoises when then preparing.Ca under each temperature in the filtrate of preservation coal slurry after month ²⁺Concentration is respectively 1900ppm(80 ℃), 800ppm(70 ℃) and approximately 100ppm(50 ℃ and 20 ℃).

The dissolving meeting that can clearly be seen that coal ash from top result is quickened with the temperature rising.Keep a long period to effect of the present invention, be good to be equal to or less than 70 ℃ temperature, is preferably 50 ℃ or be lower than 50 ℃ temperature.

(preparation embodiment 8)

The Sodium Tetraborate that with dry coal in the slurry is 0.1% weight percent of benchmark is added in the former slip of preparation among the preparation embodiment 1, and measures its viscosity.It was 1500 centipoises when coal concentration was 65% weight percent.This coal slurry is carried out the storage test identical with preparation embodiment 1.Its viscosity rises to 2500 centipoises after 30 days.

(preparation embodiment 9)

Repeat the step identical, except replacing Sodium Tetraborate with yellow soda ash with preparing embodiment 8.The viscosity of gained coal slurry is 2100 centipoises, stores 30 days viscosity and rise to 2500 centipoises under the condition identical with preparation embodiment 8.

(preparation embodiment 10)

Repeat the step identical, fallen with sodium sulfate and replace Sodium Tetraborate with preparing embodiment 8.The viscosity of gained coal slurry is 2800 centipoises, stores 30 days viscosity and rise to 3600 centipoises under the condition identical with preparation embodiment 8.

(preparation embodiment 11)

Repeat the step identical, except usefulness S-WAT substituted boracic acid sodium with preparation embodiment 8.The viscosity of gained coal slurry is 1900 centipoises, stores 30 days under the condition identical with preparation embodiment 8, and viscosity rises to 3000 centipoises.

(preparation embodiment 12)

Repeat the step identical, except usefulness Sodium Fluoride substituted boracic acid sodium with preparation embodiment 8.The viscosity of gained coal slurry is 1400 centipoises, and after storing 30 days under the condition identical with preparation embodiment 8, viscosity rises to 1500 centipoises.

(embodiment 1)

Grind coal, water with as the sodium salt of the sulfonated naphthalene formaldehyde condensation products of the anion surfactant ball mill of packing into, the coal particle size that obtains distributes as follows: comprising and being less than or equal to 60 purpose particles (weight) is 97%, be less than or equal to 100 purpose particles 89%, be less than or equal to 200 purpose particles 80%, be less than or equal to 200 purpose particles 80%, be less than or equal to 400 purpose particles 55%.Zhi Bei high density and the coal concentration in the coal slurry are the 62%(weight percent like this).Adding the 0.5%(weight percent in slurry, is benchmark with the dry coal) anion surfactant.

The slurry that obtains is kept at 20 ℃ respectively, and 50 ℃, under 70 ℃, after 30 days, the viscosity of these slurries will increase.

The coal concentration of used slurry is the 62%(weight percent in these tests), viscosity is 700 centipoises when just preparing.Respectively at 20 ℃, 50 ℃ or 70 ℃ preserved 30 days down after, viscosity is about 720,950 and 1500 centipoises respectively.

Ca in the supernatant liquid ²⁺And Mg ²⁺Concentration increases with temperature, and table 1 shows test result.

The increase degree of lay up period viscosity and the ionic lyolysis of top theory are all relevant with the kind of coal in the slurry.This trend all is identical for every kind of coal.

The pH value is held constant at 7.9 by the method that adds sodium hydroxide from start to finish when testing.

The negatively charged ion that silicate in the water glass generates can generate the salt that be insoluble in water with polyvalent metal ion, being slurry benchmark with the dry coal to wherein adding the 0.5%(weight percent after 70 ℃ are stored 30 days, to every mole of Ca ²⁺Add 2 moles of (SiO ^2-) silicate.When coal concentration was 62% weight percent (this is the value when just having prepared), viscosity was 700 centipoises.

Next use identical method, be added in 70 ℃ with yellow soda ash in 0.45% weight percent (with dry coal) without water glass and store down in 30 days the slurry.When coal concentration was 62% weight percent, viscosity was 700 centipoises.This result and coming to the same thing during with water glass.

(embodiment 2)

The former slip for preparing among the embodiment 1 is stored test.This slurry is kept in the hold tank 1 among Figure 10.In order to prevent the coal dust precipitation in the coal slurry, make the slurry circulation with pump 2 by pipeline 3, and stir coal slurries with the stirring sheet in the jar 4.Ca in the slurry ²⁺Concentration is measured by detector 6 by the calcium ion electrode 5 that is inserted in the jar 1.When calcium ion concn during, just the sodium silicate solution in jars 9 of being stored in of predetermined amount is added in jar 1 greater than 100ppm.When detector 6 by electrode when recording calcium ion concn less than 50ppm, just stop in jar 1, supplying water glass by the pump 8 of pump controller 7 controls.

Viscosity to the coal slurry of the high viscosity in the present embodiment 30 days and 60 days is measured, found that 30 days with 60 days after the viscosity of coal slurry the same when just preparing.At duration of test, similar per 20 days of water glass is to jar 1 supply.The solution amount that adds is about 1.6 liters in slurry per ton.The concentration of jar 9 mesosilicic acid sodium is the 20%(weight percent).

Can clearly be seen that from top embodiment slurry is stored a very long time and do not made its viscosity that any increase is arranged, and not changing the character of slurry and keep its low viscosity at lay up period is fully possible according to the present invention.

(embodiment 3)

The coal that uses among the preparation embodiment 6 is starched the preparation test.That is to say, coal ash content being about 18% coal sends in the ball mill 111 among Figure 11 with 10 kilograms/hour flow rate, grind together with the sodium salt and the sodium hydroxide of water as the sulfonated naphthalene formaldehyde condensation products of anion surfactant, the coal concentration that obtains is 65% weight percent, the pH value is 8, and tensio-active agent is 0.5% weight percent (in a dry coal).The interior diameter of ball mill is 0.5 meter, about 1 meter of axial length, and many steel balls are equipped with in inside.For the pH value is adjusted to 8, measure the aequum of sodium hydroxide, should measure in advance.10% sodium hydroxide solution is added in the ball mill 111 by pump 113 from jar 112.40% anionic surfactant solution is added to the ball mill 111 by pump 115 from jar 114.For being adjusted into 65% weight percent water, coal concentration in the slurry is added to the ball mill 111 by pump 117 from jar 116.Also should take in the moisture in raw coal, sodium hydroxide solution and the surfactant soln when measuring the quantity of water.When the preparation coal slurry, at first the water glass of 0.1% weight percent (in dry coal) is added to the ball mill 111 by pump 119 from jar 118.Measure the calcium ion concn in the coal slurry supernatant liquid in the hold tank 120, and make calcium ion concn remain on 50-100ppm by controller 122 control pumps 119.The viscosity of coal slurry that obtains like this is 1250 centipoises, and coal concentration is 65% weight percent.But the coal slurry viscosity when coal concentration is 65% weight percent for preparing without water glass is 3100 centipoises.

As for the concentration of coal, consider the economy of fuel system, the coal concentration in the water slurry should reach 60% weight percent at least.This is mostly not to be 1.2% coal heat length because of the thermal energy differential of water consumption in slurry to per 10%.Therefore, coal concentration is high more good more, and to surpass 80% coal water slurry seemingly very difficult but prepare concentration with prior art.But the present invention is not confined to be lower than on 80% the coal concentration.

Coal particle size is distributed, the present invention is not limited on the examples of implementation that provide, but be suitable for its coal dust composed as follows at least: be less than or equal to 60 purpose particle weights and be at least 97%, be less than or equal to 100 purpose particle weights 85% to 90%, being less than or equal to 200 purpose particle weights is 75% to 80%, is less than or equal to 400 purpose particle weights 50% to 55%.

As above-mentioned, sodium carbonate has and the similar identical effect of sodium metasilicate. The inventor confirms to add the effect of the sodium carbonate additive in the slurry by experiment. These experiments no longer repeat here, because they almost are the reprints of given example here. Can generate slightly soluble or not other anion of dissolved salt also have oxalates, fluoride, sulfide, sulphite etc. The inventor has also studied the effect of these anion. But from the eye of economy, find that it is the most effective utilizing sodium metasilicate and/or sodium carbonate, in addition, contains the coal slurry of other top anion When burning, noxious material can be generated, thereby serious problem of environmental pollution can be caused.

Claims

1, a kind of method that keeps stabilization coal water slurry comprises the steps:

(1) a kind of at least 60% (by weight) coal dust that contains of preparation, the coal water slurry of 0.1% to 2% (weight percent is in dry coal weight) anion surfactant and remainder (in fact being water), the pH value of above-mentioned slurry is between 6 to 11, and viscosity is no more than 3000 centipoises;

(2) adding in the above-mentioned slurry with alkalimetal silicate and/or the carbonate that calcium ion and/or magnesium ion generate water-fast alkali metal compound, the amount of adding can change into above-mentioned water-fast compound to all above-mentioned ions basically;

(3) survey calcium or the magnesium ion that is dissolved in the above-mentioned slurry continuously or intermittently;

(4) add above-mentioned silicate and/or carbonate in above-mentioned slurry, the amount of adding can change into above-mentioned water insoluble compound to all above-mentioned ions that detect basically.

2, a kind of method that keeps stabilization coal water slurry comprises the steps:

(1) preparation is a kind of contains 60%(at least by weight) coal dust, 0.1% to 2%(by weight, calculate according to dry coal weight) cats product and the coal water slurry of remainder (in fact being water), the pH value of above-mentioned slurry is between 6 to 11, viscosity is no more than 3000 centipoises;

(2) add the alkalimetal silicate and/or the carbonate that can generate water-fast compound with calcium ion and/or magnesium ion in above-mentioned slurry, the amount of adding can be enough to above-mentioned ionic concentration is maintained on the predetermined level by the method that they is changed into above-claimed cpd;

(3) detect calcium ion and/or the magnesium ion that is dissolved in the above-mentioned slurry continuously or intermittently;

(4) add above-mentioned alkali-metal silicate and/or carbonate in above-mentioned slurry, the amount of adding can be enough to above-mentioned ionic concentration is maintained on the predetermined level by the method that they is changed into above-claimed cpd.

3, a kind of method that keeps stabilization coal water slurry comprises the following steps:

(1) preparation is a kind of contains 60%(at least by weight) coal dust, 0.1% to 2%(by weight, calculate according to dry coal weight) anion surfactant and the coal water slurry of remainder (in fact being water), the pH value of above-mentioned slurry is between 6 to 11, viscosity is for being no more than 3000 centipoises;

(3) add above-mentioned salt continuously or intermittently in above-mentioned slurry, the amount of adding can be enough to above-mentioned ionic concentration is maintained on the predetermined level by the method that they is changed into above-claimed cpd.

4, a kind of method that keeps stabilization coal water slurry comprises the steps:

(1) preparation is a kind of contains 60%(at least by weight) coal dust.0.1% to 2%(weight percent, the coal water slurry of the anion surfactant weight in dry coal) and remainder (in fact being water), above-mentioned coal dust composed as follows: be less than or equal to 60 purpose particle weights and be at least 97%, be less than or equal to 100 purpose particle weights between 85% to 90%, be less than or equal to 200 purpose particle weights between 75% to 80%, be less than or equal to 400 purpose particle weights between 50% to 55%, the pH value of above-mentioned slurry is between 6 to 11, and viscosity is no more than 3000 centipoises;

(2) add the alkalimetal silicate and/or the carbonate that can generate water-fast compound with calcium ion and/or magnesium ion in above-mentioned slurry, the amount of adding is enough to and can maintains above-mentioned ionic concentration on the predetermined level by the method that they is changed into above-claimed cpd;

(4) add above-mentioned salt to above-mentioned slurry, the amount of adding can be enough to above-mentioned ionic concentration is maintained on the predetermined level by the method that they is changed into above-claimed cpd.

5, a kind of method that keeps stabilization coal water slurry comprises the following steps:

(1) in one jar, add a kind ofly contain 60%(at least by weight) coal dust, 0.1% to 2%(weight percent, the coal water slurry of the anion surfactant weight in dry coal) and remainder (in fact being water), the pH value of above-mentioned coal slurry is between 6 to 11, and viscosity is no more than 3000 centipoises;

(4) add above-mentioned alkalimetal silicate and/or carbonate in above-mentioned slurry, the amount of adding is enough to and can maintains above-mentioned ionic concentration on certain level by the method that above-mentioned ion is changed into above-mentioned each thing.

6, a kind of method that keeps stabilization coal water slurry comprises the steps:

(1) in one jar, add a kind ofly contain 60%(at least by weight) coal dust.0.1% to 2%(weight percent is in the dry weight of coal) a kind of anion surfactant and the coal water slurry of remainder (in fact being water), the pH value of above-mentioned slurry is between 6 to 11, viscosity is 3000 centipoises;

(2) add the alkalimetal silicate and/or the carbonate that can generate the water-fast compound of above-mentioned salt with calcium ion and/or magnesium ion in above-mentioned slurry, the amount of adding is enough to and can maintains above-mentioned ionic concentration on the predetermined level by the method that above-mentioned ion is changed into above-claimed cpd;

(3) detect continuously or intermittently calcium ion and/or magnesium ion in the supernatant liquid that is dissolved in above-mentioned slurry;

(4) add above-mentioned alkalimetal silicate and/or carbonate in above-mentioned slurry, the amount of adding is enough to and can maintains above-mentioned ionic concentration on one level of being scheduled to by the method that above-mentioned ion is changed into above-claimed cpd.