CN1152822C - Improved method for preparing low-concentration polyaluminosilicate microgels - Google Patents

Abstract

The present invention relates to an improved method and an improved device for preparing low-concentration polysilicate microgel by water-soluble silicate and strong acid. The silicate and the strong acid are mixed at the speed at which at least 400 reynold numbers are produced, and the mixture is aged and then diluted to the solution with the silicon oxide concentration of no more than 1.0 wt%. By the method, lower silicon oxide deposition is achieved in the preparation process of the microgel.

Description

The improved method for preparing low-concentration polyaluminosilicate microgels

Relevant U. S. application

The application is the part continuation application of the U. S. application 08/345890 of 28 propositions November in 1994, the latter is again the part continuation application of proposition on December 16th, 1993, resigned U. S. application 08/166679, back one application is again the part continuation application of US5312595, and the latter is dividing an application of US5279807.

Background of invention

The present invention relates to a kind of improved low-concentration polyaluminosilicate microgels that is used to prepare, the method that promptly has the aqueous solution of the active silica concentration that is usually less than about 1.0% weight, this aqueous solution is by with alkalimetal silicate or polysilicate, forms as sodium polysilicate (its most general form is that 1 part of Na2O is to 3 parts of SiO2 weight) part gelling.The microgel that is called " activity " silicon-dioxide (with respect to commercially available silicon oxide colloid) comprises that surface-area is at least the solution that about 1000 meters squared per gram, diameter are the silicon oxide particle that forms of interconnecting of 1-2 nanometer.These particles promptly interconnect in part gelatinization process in preparation process, form the group's material with three-dimensional net structure and chain.Then by will in this structure, importing aluminum oxide with the further modification of this polysilicate microgels.Can be categorized as poly-silico-aluminate microgel and can be by alumina modified polysilicate with this by the basic method of modifying of polysilicate microgels is made at an easy rate.A critical aspects of the present invention is can be in the rational time before microgel is standby, promptly be no more than in about 15 minutes time and make microgel, and solidified danger can not appear, also make the formation of undesirable silicon oxide settling in treatment facility reach minimum.In this respect, have been found that it is favourable importing aluminum oxide in polysilicate microgels, it can increase the formation speed of microgel.The polysilicate microgels that makes according to the present invention is specially adapted to water-soluble cationic polymers as drainage in the paper-making industry and retention aid.Be lower than under 5 the pH value, what these products were more suitable is to be called poly-silicic acid microgel.When the pH value raise, these products can contain the mixture of poly-silicic acid and polysilicate microgels, and both ratios are relevant with pH.For for simplicity, hereinafter these products are called polysilicate microgels.

Summary of the invention

The present invention is a kind of improved method and apparatus that is used for preparing continuously the lower concentration polysilicate microgels, it comprises that (a) will contain first materials flow of water-soluble silicate solutions simultaneously and contain second materials flow that pK is lower than 6 strong acid and imports in the mixing zone, in this mixing zone, these materials flows are with the angles that are not less than 30 degree and be enough to produce at least about the speed of 4000 Reynolds numbers and compile and formed silicate/acid mixture has the pH value of silica concentration and the 2-10.5 of about 1.0-6.0 weight %; (b) with aging for some time of this silicate/acid mixture, this time should be enough to the part gelling level (promptly forming microgel) that reaches required; Usually be at least for 10 seconds but be no more than about 15 minutes; And (c) will be no more than about 2.0 weight % to silica concentration, thereby make gel stabilityization through the aged mixture diluted.In order to make poly-silico-aluminate microgel, can at first in this acid materials flow, add water-soluble aluminium salt, then again it is mixed with the silicate materials flow.

In order to obtain optimum, when importing to two kinds of materials flows in the mixing zone, the silica concentration of water-soluble silicate starting soln is 2-10 weight %, and the concentration of strong acid (as sulfuric acid) is 1-20% weight.In the mixing zone preferred condition be Reynolds number greater than 6000, silica concentration is a 1.5-3.5% weight, pH is 7-10.Most preferred condition be Reynolds number greater than 6000, silica concentration is 2% weight, pH is 9.With the preparation process of alumina modified microgel preferably by soluble aluminium salt is carried out in about 0.1% weight to the mode that the amount that is up to this aluminium salt solubility boundary joins in the sour materials flow.The most useful poly-silico-aluminate microgel is to be 1: 1500～1: 25 with the Al2O3/SiO2 mol ratio, is preferably 1: 1250～those microgels of making at 1: 50.

Equipment according to the present invention comprises: first reservoir that (a) is used to hold water-soluble silicate solutions; (b) be used to hold second reservoir that pKa is lower than 6 strong acid; (c) have first import that communicates with said first reservoir, with second import that becomes 30 degree angles to be provided with at least with said first import and communicate and the mixing devices of an outlet with said second reservoir; (d) first pumping installation between said first reservoir and said mixing device, be used for said silicate solutions materials flow is pumped to said import by said first reservoir, and first control device, be used for controlled oxidation silicon and pump said solution simultaneously, thereby make that the concentration of silicon oxide in the solution of discharging is 1～6 weight % from mixing device in the concentration of said silicate solutions; (e) second pumping installation between said second reservoir and said mixing device, be used for sour materials flow is pumped to said second import from said second reservoir, its speed will be enough to produce at least 4000 Reynolds numbers in materials flow crosses the district with respect to the speed of said first pumping installation in said mixing device, thereby said silicate and said acid are thoroughly mixed; (f) be arranged in said outlet and said acid flowed into the aitiogenic mixture control device of flow velocity of said mixing device, be used for the pH of silicate/acid mixture is controlled at 2-10.5; (g) receiving tank; (h) the elongated transmission loop that communicates with said mixing device and said receiving tank is used for said mixture is transmitted between them; (i) air mix facilities is used for silicate/acid mixture with receiving tank and is diluted to silica concentration and does not exceed 1.0 weight %; (j) be used to hold the 4th reservoir of water-soluble aluminium salt; (k) be used for aluminium salt is introduced the 4th pumping installation of sour materials flow; And (l) to aluminium salt flow respond and with the parallel control valve that links to each other of silicate control valve, this control valve is between the 4th pumping installation and aluminium salt import a little in this acid materials flow.

In another kind of scheme, equipment of the present invention comprises NaOH reservoir and be used for regularly washing the device of this manufacturing system with the hot NaOH that is heated to 40～60 ℃ of temperature, thereby can dissolved oxygen siliceous deposits thing and be removed.

In another embodiment of the present invention, a kind of air-flow such as airflow or nitrogen gas stream or other inert gas flow of stirring can be mixed the junction or near another import it imports to said mixing device by being arranged in.Gas stirring provides important industrial advantage, and it can adopt lower silicate flow velocity to keep required turbulent flow and Reynolds number simultaneously in the mixing zone.

In another embodiment of the present invention, the mixing of acid, aluminium salt and water-soluble silicate solutions can be finished in the tubulose mixing device.This device can be to stretch in the bigger pipe and enter this than the interior pipe in the bassoon.Should in tube drainage point usually but not necessarily be positioned at outer tube inside with one heart.Want a kind of in two kinds of fluids of blended and infeed interior pipe.Second kind of fluid infeeds outer tube and round the flows outside of interior pipe.Two kinds of fluidic mix occur in first kind of fluid leave in pipe and with second kind of fluid bonded place in bigger outer tube.Usually, this acid and aluminum salt solution are pre-mixed before in infeeding wherein a pipe.

In order to mix two kinds of liquid, water-soluble silicate solutions and acid can be infeeded outer tube or interior pipe, its speed make two kinds of materials flows in conjunction with the time in the mixing zone, produce Reynolds number greater than 4000.Randomly also can use the stirring air-flow, to help to mix these two kinds of materials flows.

As another embodiment of the present invention, mixing of sour and water-soluble silicate solutions can be finished to produce in the essential turbulent container being furnished with mechanism, finishes thereby make the mixing of two kinds of materials flows can be higher than under 4000 the Reynolds number.Randomly, this container can be furnished with baffle plate.Sour and water-soluble silicate solutions can but not necessarily leave no choice but send in the container simultaneously.

In order to produce poly-silico-aluminate microgel, with aluminium salt, as the strong solution of Tai-Ace S 150 by another reservoir pumping and the acid of dilution and silicate materials flow mix and the position that arrives before it is mixed in the sour materials flow of dilution.By aluminium salt being joined in this acid materials flow, the formation speed of microgel can improve and be formed on the poly-silico-aluminate microgel that imports aluminum portions in the whole microgel structure

Method and apparatus of the present invention can be no more than in time of about 15-16 minute short, but be generally 30-90 and prepare stable polysilicate and poly-silico-aluminate microgel in second, it causes less silicon oxide deposition, and does not have solidified danger and make undesirable silicon oxide settling of formation reach minimum in processing unit.Service temperature is generally 0～50 ℃.

Silicon oxide in producing apparatus deposition is undesirable, and this is because it can cover whole internal surfaces of this equipment and unfavorable to the function of important movable part and device.For instance, the silicon oxide settling can be deposited in the local and restriction materials flow that valve no longer works and flows through pipe.It also is inappropriate on the pH sensitive electrode that silicon oxide is deposited on, and this is that the pH value is the quality-controlling parameters of the key in the silicon oxide microgel preparation process because it is unfavorable for monitoring the pH value of this technology.

The present invention includes following method:

1. be used for the method for the poly-silico-aluminate microgel of preparation continuously, this method has than low silica and deposits, wherein this microgel comprises that 1-2 nanometer diameter, surface-area are at least 1000 meters squared per gram and are interconnected to the solution of each chain with the silicon oxide particle of formation three-dimensional net structure, and this method comprises:

(a) will contain first materials flow of water-soluble silica solution and contain second materials flow that pKa is lower than 6 acid and aluminum salt solution and import in the mixing zone simultaneously, in this mixing zone, the speed that these materials flows produce at least 4000 Reynolds numbers with the angles and being enough to that are not less than 30 degree compiles and formed silicate/acid/salt mixture has the pH value of silica concentration and the 2-10.5 of 1-6 weight %.

(b) with aging for some time of this silicate/acid/salt mixture, this time should be enough to the part gelling level that reaches required, but is no more than 15 minutes; And

(c) will be no more than 2.0 weight % to silica concentration through the aged mixture diluted.

2. be used for the method for the poly-silico-aluminate microgel of preparation continuously, this method has than low silica and deposits, wherein this microgel comprises that 1-2 nanometer diameter, surface-area are at least 1000 meters squared per gram silicon oxide particles and are interconnected to each chain to form the initial silica content particulate solution of three-dimensional net structure, and this method comprises:

(a) will contain first materials flow of water-soluble silica solution and be lower than 6 acid and second materials flow of aluminum salt solution imports in the annular mixing device simultaneously by pKa, in this mixing device, these materials flows cross by being discharged into from the materials flow of pipe in the mixing device to form from effusive second materials flow of outer tube, and its speed is enough to produce at least 4000 Reynolds numbers in the mixing zone of this mixing device and formed silicate/acid/salt mixture has the pH value of silica concentration and the 2-10.5 of 1-6 weight %;

(b) with aging for some time of this silicate/acid/salt mixture, this time should be enough to make the initial oxidation silicon grain to interconnect and form said three-dimensional structure and keeps solution state simultaneously, but is no more than about 15 minutes; And

(c) will be no more than 2.0 weight % to silica concentration through the aged mixture diluted.

The present invention also comprises the equipment of the poly-silico-aluminate microgel that continuous production is stable, and it comprises:

(a) hold first reservoir of water soluble silicate solutions;

(b) hold pKa and be lower than 6 acid and second reservoir of aluminium salt;

(c) have first import that communicates with said first reservoir, with second import that becomes 30 degree angles to be provided with at least with said first import and communicate and the mixing devices of an outlet with said second reservoir;

(d) first pumping installation between said first reservoir and said mixing device, be used for said silicate solutions materials flow is pumped to said first import by said first reservoir, and first control device, being used for controlled oxidation silicon is that 1～6 weight % pumps said solution simultaneously in the concentration of formed silicate/acid/salt mixture;

(e) second pumping installation between said second reservoir and said mixing device, be used for the materials flow of acid and aluminium salt is pumped to said second import from said second reservoir, its speed will be enough to produce at least 4000 Reynolds numbers in materials flow crosses the district with respect to the speed of said first pumping installation in said mixing device, thereby said silicate and said acid and aluminium salt are thoroughly mixed;

(f) be arranged in said outlet and said acid flowed into the aitiogenic mixture control device of flow velocity of said mixing device, be used for the pH of silicate/acid/salt mixture is controlled at 2-10.5;

(g) receiving tank;

(h) the elongated transmission loop that communicates with the outlet and the said receiving tank of said mixing device is used for said mixture is transmitted between them; And

(i) air mix facilities is used for silicate/acid/salt mixture with receiving tank and is diluted to silica concentration and does not exceed 2.0 weight %.

The accompanying drawing summary

Fig. 1 is the synoptic diagram of this technology, and it comprises the NaOH reservoir and is used for the device of this manufacturing system of periodic flushing.

Fig. 2 is the synoptic diagram of two-wire polysilicate microgels manufacturing system, and it provides continual microgel production process.

Fig. 3 is the synoptic diagram that the present invention is used to prepare the method for gathering the silico-aluminate microgel, and it comprises aluminium salt reservoir and is used for said salt is imported the device of diluted acid materials flow.

Detailed Description Of The Invention

Active silica is the silicon oxide particle of the special shape that forms of the particle of 1-2 nanometer by very tiny diameter, and these particles interconnect in chain or network, form three-dimensional structure, i.e. known " microgel " of people. The active oxidation silicon particle, namely the surface area of microgel is at least about 1000 meters squared per gram. Conventional method for the preparation of polysilicate microgels is disclosed among the US4954220, and the content of the document is incorporated herein as a reference. Wherein in the said method, with a kind of inorganic acid or organic acid, the dilute aqueous solution that is lower than 6 strong acid acidizing alkali metal silicate such as pKa is a kind of method of particularly suitable of the present invention. The present invention can not form at the scene of required consumption, in process equipment under undesirable silica sedimentary condition and in very rational ageing time, be usually less than for 15 seconds, be preferably 10-90 reliable and continuous low concentration polysilicate and poly-alumino-silicate preparation method was provided in second.

Method of the present invention can import to mixed zone or mixing joint with aluminium salt simultaneously by the material of water-soluble silicate solutions stream and pKa being lower than 6 strong acid material stream, thereby make these material streams each other usually to be not less than the angle of intersection of 30 degree, its speed is enough to produce at least 4000 in the zones that two material streams intersect, and is preferably about 6000 or higher Reynolds number. Reynolds number is the dimensionless number that is used for describing liquid in pipe flox condition on the engineering. It is laminar flow (mixing relatively poor state) that numeral is lower than 2000 expressions, and numeral is 4000 or higher expression turbulent flow (good admixture). In principle, Reynolds number is larger, and it is better to mix. The Reynolds number (Re) that is used for flowing in the pipe is determined by following equation:

$\mathrm{Re}=\frac{Q\×d}{D\×u}$

In the formula: the Q=flow velocity, cubic feet/second (cubic centimetre/second)

D=proportion, pound/cubic feet (kilogram/cubic centimetre)

D=manages diameter, foot (centimetre)

U=viscosity, pound/feet per second (kg/cm second)

The Reynolds number that is used for the propeller agitation container is determined by following equation:

Re＝(D ²×N×p)/u

In the formula: the D=airscrew diameter, centimetre

The N=rotary speed, revolutions per second

The p=fluid density, g/cc

U=viscosity, Grams Per Second centimetre

Concentration to the silicate solutions that crosses and acid/aluminium salt material stream is controlled, thereby so that prepared silicate/acid blend has the pH value of silica concentration and the 2-10.5 of 1-6% weight. More preferably, the concentration of silica is 1.5-3.5% weight, and pH is 7-10. Most preferred operating condition be Reynolds number greater than 6000, silica concentration is 2 % by weight, pH is 9.

Aging normally by this silicate/acid blend is passed through elongated transmission loop until the finished product pans carried out for 10 seconds, the longest to 90 seconds, in these finished product pans, this mixture dilutes immediately, then keep the active oxidation silicon concentration to be no more than 2.0 % by weight, be preferably and be no more than 1.0 % by weight. In ageing process, reach the part gelling, the three-dimensional that produces high surface active oxidation silicon grain gather materials network and chain. Silicate/acid blend is diluted to low concentration so that gelation process stops and make microgel stable, to be used for consumption subsequently.

The below will contrast accompanying drawing and be described in detail to method of the present invention with for the equipment that carries out the method. In the accompanying drawings, Fig. 1 is the schematic diagram of the technique of the simplest preparation polysilicate microgels. Wherein said size, volume and speed can be mainly according to the quantity of required polysilicate microgels and required depletion rate and in wider scope, change. For the said size of accompanying drawing and volume relate to for the preparation of, namely usually be created in continuously in the paper industry polysilicate microgels that consumes as drainage and glidant, in paper industry, depletion rate is about 10-4000 pound microgel/hour (4.5-1800 kilogram microgel/hour).

As shown in fig. 1, dilution water reservoir 10, sour reservoir 12 and silicate reservoir 14. Reservoir, be that tank comparatively conveniently is to be made by polyethylene, reservoir of water has the volume of 500 gallons (1892.5 liters), and sour reservoir has the volume of 100 gallons (378.5 liters), and the silicate reservoir has the volume of 300 gallons (1135.5 liters). Other container that is shown among Fig. 1 is NaOH purge tank 16 and finished product pans 18. The NaOH purge tank is by incorrosive material, makes such as 316 stainless steels, and its volume is 20 gallons (75.7 liters) and with resistance drum heater (Cole-Palmer, 2000 watts, the 115 volts) heating of twining thereon. The volume of finished product pans is 1000 gallons (3875 liters) and made by polyethylene.

A critical component of this technique is to mix connecting portion 20, and it has determined a mixed zone, and wherein acid material stream and water-soluble silicate material stream are imported by separately path, they in the mixed zone usually to be not less than 30 angle of intersection of spending. Mixing " T " or " Y " connecting portion is applicable to implement the present invention and can relatively easily by 316 stainless steels " Swagelok " the pressurization connector formation of suitable size, be furnished with stainless steel tube on it. Usually preferably " T " connecting portion.

To two material flow to into, the speed that namely is pumped in the mixed zone is selected, to produce at least 4000, be preferably and be up to 6000 or higher Reynolds number, in fact it caused the moment of acid and silicate and thoroughly mixed, thereby make formed mixture have the silica concentration of 1.5-3.5 % by weight and the pH of 7-10. Can adopt any easily commercially available water-soluble silicate source, for example by " PQ (N) " sodium metasilicate (41Baume, SiO2: Na2O=3.22: 1 weight, 28.7 % by weight SiO2) of PQ group sale. This commercially available silicate is kept in the reservoir 14 undilutedly, and concentration is 24-36% weight usually, and it is such that erect image manufacturer provides, until need the time spent. Utilize low flow velocity gear or micropump 24 (such as Micropump Corp., model 140, Peak Flow Rate 1.7gmp), be transported to by suitable pipeline 22 (316 stainless steels, 1/4 inch (0.635 centimetre) OD) and mix junction surface 20. Preferably adopt incorrosive construction material, such as 316 stainless steels, dangerous with the doping of avoiding corroding with subsequently. The silicate supply line also comprises flow control valve 26 (Whitey, 316 stainless steels, 1/4 inch (0.635 centimetre) pin hole), the mobile analyzer 28 (Fisher of magnetic, Porter, 316 stainless steels, 1/10 inch (0.25 centimetre) size) and detect valve 86 (Whitey, 316 stainless steels, 1/4 inch (0.635 centimetre) internal diameter), thus amount and the direction of control and monitoring silicate material stream. In operating process, certain that dilution water is being arranged in that silicate/acid mixes 20 upstreams, joint portion makes things convenient for the position to import to silicate supply line 22, thereby silica concentration is adjusted in the scope of 2-10 % by weight. Mix fully in order to ensure silicate and water, online static mixer 32 (Cole-Palmer are set, 316 stainless steels, 1/2 inch (1.27 centimetres) pipe, 15 parts), then be a detection valve 30 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres) diameter). Dilution water is by pipe 34 (1/2 inch (1.27 centimetres) OD, 316 stainless steels) by centrifugal pump 36 (Easterb Pump, 1HP, Peak Flow Rate 54gpm) and rotation analyzer 38 (Brooks, Brass Ball, the 306gpm maximum) provide. Can adopt control valve 40 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres) NE pin hole) and detect valve 42 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres) diameter) with coutroi velocity and direction.

Although described multiple acid material, with for the preparation of active silica, the simplest and acidifying measure most convenient is to adopt pKa to be lower than 6 strong acid such as the salt of mineral acid, organic acid, ackd salt and gas, ion exchange resin and strong acid and weak base. Preferred acid is sulfuric acid. Be suitable for by the technical grade of DuPont manufacturing and other acid. In operating process, in sour reservoir 12, the acid concentration of sour stock solution is 5-100% weight. This acid is by pipeline 46 (316 stainless steels, 1/4 inch (0.635 centimetre) OD) and detect valve 88 (Whitey, 316 stainless steels, 1/4 inch (0.635 centimetre)), utilize gear or similarly micropump 44 (such as Micropump, model 040,1/4HP, Peak Flow Rate 0.83gpm) pump in the connection blender 20. With single cycle controller 90 (Moorw, model 352E) with pH conveyer 48 (big lake instrument, model 6028PO) combines, thereby automatic valve 50 (the control research that responds by the pH to silicate/acid blend of connecting the mixer outlet place, K Trim, 1/4 inch (0.635 centimetre) OD, 316 stainless steels) sour the flowing to connection blender 20 of control. In this control system, can also adopt automatic three-way valve 52 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres) diameter), thereby underproof silicate/acid blend can be separated in the sewer. Dilution water from reservoir 10 feeds by pipeline 54 (316 stainless steels, 1/2 inch (1.27 centimetres) OD), is diluted to predetermined 1-20% weight range thereby will be positioned at the acid that connects blender 20 upstreams. In the downstream that dilution water is fed the position in the acid tube line, static mixer 56 (Cole-Palmer, 316 stainless steels, 1/2 inch (1.27 centimetres) diameter, 15 times) is set, mix fully and dilute to guarantee acid. Adopt rotation analyzer 58 (Brooks, Brass Bal1,1.09gpm, maximum), control valve 60 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres), pin hole) detection valve 62 (Whitey, 316 stainless steels, 1/2 inch (1.27 centimetres) diameter) controls flow velocity and the flow direction of dilution water.

Leave the SiO that silicate/acid blend of connecting mixture 20 preferably has 1.5-3.5% weight₂Concentration, and its pH is 7-10. Most preferably, the concentration of silica remains on 2% weight, and pH is 9. This mixture is through elongated transfer line 64 (1.5 inches (3.81 centimetres) engineering 40PVC pipes, 75 feet (2286 centimetres) are long), until finished product pans 18. select the length of transfer line to account at least for 10 seconds to guarantee this transmission, but preferably in about 30-90 seconds, during this period, " wearing out " or part gelling occur in this mixture. Can reach 15-16 minute and still can produce gratifying result in the lower delivery time of low-down flow velocity. Just before mixture enters into finished product pans 18 or in other any easily place, by pipeline 66 (316 stainless steels, 1/2 inch (1.27 centimetres) OD) by reservoir 10 dilution water is joined in this mixture, make the stable silica concentration of gelatinization be lower than 1.0% weight as long as this silicate/acid blend is diluted to. Dilution water is supplied with centrifugal pump 68 (Eastern, 316 stainless steels, 1HP, 54gpm maximum) and rotameter 72 (Brooks, SS Ball, 12.46gpm maximum). Finished product pans 18 are furnished with level-regulating system 74 (Sensa11, model 502), it and automatic three-way valve 76 (Whitey, 316 stainless steel S, 1/2 inch (1.27 centimetres) diameter) together operation is so that if too high the mobile of silicate/acid blend that make of finished product level is rerouted in the sewer.

After continued operation a period of time (this depends on the amount of the active silica that produces), active silica and water be can stop to produce and the down-stream system part of mixing bonding pad 20 and contacting with silicate/acid blend, i.e. pump, valve, dispatch tube etc. washed with hot NaOH. Wash this system and can remove any unwanted silica deposit, these deposits when since design restriction and can collecting in the partial devices can not keep required turbulent-flow conditions the time for example measure in the district at pH. Flushing process helps to keep this system not have the silica deposition and at first begins by closing dilution pumps 68, sour pump 44 and silicic acid salt pump 24. Come the downstream part that the dilution water of self-pumping 36 then circulates through this system to reach about 5 minutes, then close pump 36 and isolate the dilution water reservoir by shut off valve 40,60 and 70. Then start three road automatic valves 52 and 76 and hand-operated valve 78,80 and 82 (all be Whitey, 316S, 1/2 inch (1.27 centimetres) OD) starts simultaneously centrifugal circulating pump 84 (Eastern, 316 stainless steels, 1.5HP, the 15gpm maximum), so that concentration remains on 20% weight, temperature is the part of this system downstream of NaOH circulation process of 40-60 ℃, the time is no more than about 20-30 minute usually. NaOH circulating pump 84 and can,douche 16 break away from this system by again starting three-way valve 80-82, and again wash through down-stream system and be discharged in the downcomer with dilution water. Finish after cleaning/flushing process the production of activity recovery silica.

Referring now to Fig. 2,, the schematic diagram of two-wire production system of its expression active silica, thereby a line can operate always, and another line washes or keep wait state. Each part is numbered according to Fig. 1. Industrial system according to Fig. 1 or 2 can be made by stainless steel or polyvinyl chloride pipeline usually, and it typically has a diameter from 1 inch (2.54 centimetres) or less, and this depends on the needs of active silica. When adopting stainless steel tube, the connection of various devices, assembling, valve and each several part can be finished with " Swagelok " pressurized connector.

The schematic diagram of the improvement project of Fig. 3 presentation graphs 1 basic equipment, it is applicable to make poly-alumino-silicate microgel. The concentrated solution of aluminium salt, aluminum sulfate preferably, can pass through film measuring pump 102 (Pulsatron , model LPR2-MAPTCI, polypropylene with glass-filled, Teflon  film, Peak Flow Rate 12.5 ml/min) pump is taken out through pipeline (1/4 inch (0.635 centimetre) diameter, 316 stainless steels). Measuring pump 102 can be electrically connected on the controller 90 and can be with the silicate operating position parallel. Through after detecting valve 104 (Whitey, 316 stainless steels, 1/4 inch (0.635 centimetre) diameter), can locate aluminum salt solution is imported in the diluted acid pipeline at 106 by 316 stainless steels " T " connector. Be connected 20 places (thereby produce poly-alumino-silicate microgel) and before, can aluminium salt be thoroughly mixed with diluted acid by on-line mixing device 56 occurring in " T " with the reaction of silicate. The preferred aluminum salt solution that is used for the method is the commercial sulfuric acid aluminum solutions, such as liquid A l₂(SO ₄) ₃·14H ₂The O aluminum salt solution, it contains 8.3% weight Al₂O ₃, this American Cyanamid Company provides.

As above said, must be termly by the poly-alumino-silicate device of hot caustic soda solution flushing, so that it does not have the silica deposit.

Should be understood that by suitable variation two-wire equipment as shown in Figure 2, can form the another kind of two-wire equipment that is used for producing continuously poly-alumino-silicate microgel.

Embodiment 1-confirms the effect of turbulent flow in reducing the silicon oxide deposition

According to build up the laboratory generation device that is used to produce the silicate microgel as said principle among Fig. 1.Before dilution and mixing, silicate and sulfuric acid raw material contain 15% (weight) silicon oxide and 20% (weight) acid respectively.Crucial connection mixing tank is with 1/4 inch (0.635 centimetre), and 316 stainless steels " Swagelok " T-press fittings is made, and is furnished with 1/4 inch (0.635 centimetre) OD316 stainless steel tube arm that 6 inches (15.24 centimetres) are grown on it.The internal diameter of this accessory is 0.409 centimetre.For gas being imported to the test that mixes in the web member, can adopt similarly " Swagelok " X-pressurization web member, it has four X type arms as gas feed.Be about 12 inches away from acid/silicate junction (30.48 centimetres) to locate to place by diameter be that the blank pipe formed of the 60 order stainless steel meshs of 1 inch (2.54 centimetres) is with the seizure silicon oxide particle.When on-test each time, sieve weighed and when first time off-test flushing and dry after weigh once more, to determine the sedimental weight of silicon oxide.Carrying out Total Test, thereby at silicate acidifying point place condition is remained under 2% weight silicon oxide and the pH9 and test run time enough each time, is 1590 gram polysilicate microgels to produce total amount.The results are shown in the following table 1 of this test.The liquid stream that the expression of liquid stream is total, i.e. total materials flow of outlet pipe mesosilicic acid salt/acid mixture.In gas being imported with liquid stream and turbulent test, Reynolds calculates according to the flow velocity that liquid portion increases separately, supposes that liquid specific gravity and viscosity do not change.Take the reason of this method of calculation to be not have ready-made equation to calculate the Reynolds number of liquid/gas mixture.

Table 1

Silicon oxide deposition as the function of Reynolds number

Test number	Reynolds number	Working time minute	The flow rate of liquid ml/min	The gas flow rate ml/min	Sedimentary silicon oxide gram
						1	1036	330	250	Do not have	0.339
2	2072	165	499	Do not have	0.135
						3	4144	83	999	Do not have	0.009
4	6217	55	1498	Do not have	0.007
						5	10362	33	2497	Do not have	0.002
6	12433	27	2996	Do not have	0.008
						7	12260	120	694	Air, 2260	0.008
8	9064	120	694	Air, 1490	0.005
						9	5375	120	694	Air, 601	0.004
10	5375	120	694	N2，601	0.014

Test 1 is compared with the result of test 3-10 with 2, can clearly be proved the useful effect of turbulent flows (Reynolds number is greater than 4000) aspect reduction silicon oxide deposition.Under turbulent-flow conditions of the present invention, average oxidation siliceous deposits amount is 0.007 gram, and it only is 0.0004% of a handled silicon oxide total amount.When Reynolds number was lower than minimum value 4000 required for the present invention, unaccommodated silicon oxide was deposited into to reduce and adds about 15 times.In case reach the required minimum Reynolds number of method of the present invention, increase Reynolds and count to more than 4000, for example be increased to 6217 from 4144, be increased to 10362 or the like again, just can not reduce the deposition of silicon oxide more further.

Embodiment 2-equipment

According to as shown in Figure 1 synoptic diagram assembly industry scale be used for making the equipment of active silica microgel and being installed in industrial paper grind.Except the raw material supply reservoir, this equipment rigidity is installed on the steelframe, this steelframe is positioned on two sliding platforms, and each platform size is approximately 6 * 8 feet (182.88 * 243.84 centimetres).On a platform, installed and be used to be connected to the import of water glass and sulfuric acid industry source of supply and be connected to import on the town water that is used for diluting.Installed on platform 1 that dilution and flow control apparatus, silicate/acid mixes web member, pH measures and pH controller, sodium hydroxide flushing reservoir, required pump and valve and electric controller.Aging loop, storage of finished products device, horizontal controller and required pump and valve have been installed on platform 2.The total height of each platform is about 7 feet (213.36 centimetres).Adopt container that manufacturers provides to be directly connected to import suitable on the platform 1 as silicate and sulfuric acid reservoir and with them.

Continuous operation equipment reaches 6 days, produces 0.5% weight active silica during this period, and its production rate changes between 3-4.8 gallon per minute (11.36-18.17 liter/minute).Under the production rate of 3 gallon per minute (11.36 liters/minute), the Reynolds number that calculates for employed mixing zone is 4250.In connecting mixing tank 20, do not find the silicon oxide deposition, although after 12 hours, near the pH probe that connects the tight downstream of mixing tank, find some silicon oxide depositions in operate continuously.In order to eliminate this situation, carry out water/sodium hydroxide/water flush sequence, this process needs then to forward this system to the ordinary production state below 30 minutes.In whole 6 days production cycles, the fine active silica is produced in this equipment trouble-free operation, and it is used to produce the paper with Different Weight by shredder.

The poly-silico-aluminate microgel of embodiment 3-preparation

The commercial size unit that is used to prepare poly-silico-aluminate microgel according to principle assembling as shown in Figure 3.Except the raw material supply reservoir, this equipment rigidity is installed on the steelframe, this steelframe is positioned on two sliding platforms, and each platform size is approximately 8 * 8 feet (243.84 * 243.84 centimetres).On a platform, the import that is used to be connected to water glass, sulfuric acid, sodium hydroxide and paper grade (stock) alum industry source of supply has been installed and has been connected to import on the town water that is used for diluting.The reservoir of the required pump of each chemical reagent also being installed on platform 1 and being used to hold the poly-silico-aluminate microgel solution of finished product.Flow control valve, silicate/acid that water glass, acid and dilution water have been installed on platform 2 mix web member, pH determinator and pH controller, aging loop and sodium hydroxide flushing reservoir.The surge pump control that the speed that flows through of paper grade (stock) alum is directly proportional with the silicate flow velocity.Paper grade (stock) alum can import in the sour materials flow of dilution before silicate/acid mixes web member.Obtained poly-silico-aluminate microgel solution have about 1/1250 AL ₂O ₃/ SiO ₂Mol ratio.

Adopt this equipment to produce the poly-silico-aluminate microgel solution of 6000 gallons of (22710 liters) 0.5 weight % with the speed of 20 gallon per minute (75.7 liters/minute).The Reynolds number calculation result of mixing zone is 22700.After 5 hours, the place only finds the small amounts siliceous deposits at the pH electrode probe in operate continuously.In order to eliminate the silicon oxide deposition, carry out the sodium hydroxide flushing, this process needs then to forward this system to the ordinary production state below 30 minutes.Should be used to produce the liquid packaging cardboard by the paper mill by poly-silico-aluminate microgel solution, its result is very good.

Claims (7)

1. be used for the method for the poly-silico-aluminate microgel of preparation continuously, this method has than low silica and deposits, wherein this microgel comprises that 1-2 nanometer diameter, surface-area are at least 1000 meters squared per gram and are interconnected to the solution of each chain with the silicon oxide particle of formation three-dimensional net structure, and this method comprises:

(a) will contain first materials flow of water-soluble silica solution and contain second materials flow that pKa is lower than 6 acid and aluminum salt solution and import in the mixing zone simultaneously, in this mixing zone, the speed that these materials flows produce at least 4000 Reynolds numbers with the angles and being enough to that are not less than 30 degree compiles and formed silicate/acid/salt mixture has the pH value of silica concentration and the 2-10.5 of 1-6 weight %.

(b) with aging for some time of this silicate/acid/salt mixture, this time should be enough to the part gelling level that reaches required, but is no more than 15 minutes; And

(c) will be no more than 2.0 weight % to silica concentration through the aged mixture diluted.

2. be used for the method for the poly-silico-aluminate microgel of preparation continuously, this method has than low silica and deposits, wherein this microgel comprises that 1-2 nanometer diameter, surface-area are at least 1000 meters squared per gram silicon oxide particles and are interconnected to each chain to form the initial silica content particulate solution of three-dimensional net structure, and this method comprises:

(a) will contain first materials flow of water-soluble silica solution and be lower than 6 acid and second materials flow of aluminum salt solution imports in the annular mixing device simultaneously by pKa, in this mixing device, these materials flows cross by being discharged into from the materials flow of pipe in the mixing device to form from effusive second materials flow of outer tube, and its speed is enough to produce at least 4000 Reynolds numbers in the mixing zone of this mixing device and formed silicate/acid/salt mixture has the pH value of silica concentration and the 2-10.5 of 1-6 weight %;

(b) with aging for some time of this silicate/acid/salt mixture, this time should be enough to make the initial oxidation silicon grain to interconnect and form said three-dimensional structure and keeps solution state simultaneously, but is no more than about 15 minutes; And

(c) will be no more than 2.0 weight % to silica concentration through the aged mixture diluted.

3. claim 1 or 2 method, wherein silica concentration is that 1.5-3.5 weight % and pH are 7-10 in the mixture of resulting silicate/acid/salt.

4. claim 1 or 2 method, wherein pH is 2-7.

5. the process of claim 1 wherein that said silica concentration is not more than 1.0 weight %.

6. the equipment of the stable poly-silico-aluminate microgel of continuous production, it comprises:

(a) hold first reservoir of water soluble silicate solutions;

(b) hold pKa and be lower than 6 acid and second reservoir of aluminium salt;

(c) have first import that communicates with said first reservoir, with second import that becomes 30 degree angles to be provided with at least with said first import and communicate and the mixing devices of an outlet with said second reservoir;

(d) first pumping installation between said first reservoir and said mixing device, be used for said silicate solutions materials flow is pumped to said first import by said first reservoir, and first control device, being used for controlled oxidation silicon is that 1～6 weight % pumps said solution simultaneously in the concentration of formed silicate/acid/salt mixture;

(e) second pumping installation between said second reservoir and said mixing device, be used for the materials flow of acid and aluminium salt is pumped to said second import from said second reservoir, its speed will be enough to produce at least 4000 Reynolds numbers in materials flow crosses the district with respect to the speed of said first pumping installation in said mixing device, thereby said silicate and said acid and aluminium salt are thoroughly mixed;

(f) be arranged in said outlet and said acid flowed into the aitiogenic mixture control device of flow velocity of said mixing device, be used for the pH of silicate/acid/salt mixture is controlled at 2-10.5;

(g) receiving tank;

(h) the elongated transmission loop that communicates with the outlet and the said receiving tank of said mixing device is used for said mixture is transmitted between them; And

(i) air mix facilities is used for silicate/acid/salt mixture with receiving tank and is diluted to silica concentration and does not exceed 2.0 weight %.

7. the equipment of claim 6, wherein said first import and said second import are to be in the angle settings of 90 degree, and said acid is sulfuric acid, and said aluminium salt is Tai-Ace S 150.

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