CN1208015A - Method for production of mono-calcium phosphate product - Google Patents
Method for production of mono-calcium phosphate product Download PDFInfo
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- CN1208015A CN1208015A CN 97116319 CN97116319A CN1208015A CN 1208015 A CN1208015 A CN 1208015A CN 97116319 CN97116319 CN 97116319 CN 97116319 A CN97116319 A CN 97116319A CN 1208015 A CN1208015 A CN 1208015A
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Abstract
Monocalcium phosphate producing process includes fast dispersing lime into water solution of phosphoric acid in mixing area to form reaction mixture and reacting lime with acid in the mixture to reach preset temperature. After reaching the preset temperature, the reacted mixture is fast transferred to reaction area, where the reaction is completed basically to produce monocalcium phosphate product and the product is separated out.
Description
The invention relates to a production method of a monocalcium phosphate product. The invention also relates to equipment for producing the monocalcium phosphate product.
According to one aspect of the present invention, there is provided a process for producing monocalcium phosphate, the process comprising the steps of:
rapidly dispersing quicklime in an aqueous phosphoric acid solution in a mixing zone to form a substantially uniform reaction mixture, and reacting the quicklime with an acid in the reaction mixture until the reaction mixture reaches a predetermined temperature;
when the reaction mixture has reached a predetermined temperature, rapidly transferring them to the reaction zone;
allowing the reaction to proceed to substantially completion inthe reaction zone to form a monocalcium phosphate product; and
separating the formed monocalcium phosphate product.
Thus, the reaction is carried out partly in the mixing zone and partly in the reaction zone.
The concentration of the phosphoric acid aqueous solution is about 45-48% (P)2O5Equivalent), the preferred concentration is about 47% (P)2O5Equivalent weight)。
Typically, the phosphoric acid is orthophosphoric acid.
The method comprises the step of mixing concentrated phosphoric acid with water in a mixing zone to form an aqueous phosphoric acid solution.
The term "concentrated phosphoric acid" means a concentration of 55-62% (P)2P5Equivalent) of phosphoric acid, i.e., about 75-84% H3PO4. Thus, the volume of water mixed with the concentrated phosphoric acid in the mixing zone should be such that the concentration of the aqueous phosphoric acid solution is from 45 to 48% (P) as described above2P5Equivalent weight). The reactivity of quicklime, which is available from different sources, may vary (as will be described in more detail below), and the concentration of phosphoric acid may be adjusted accordingly by routine experimentation based on the reactivity of the quicklime.
The order of mixing may be to add concentrated phosphoric acid to the water, or to add water to the concentrated phosphoric acid in reverse, or to add concentrated phosphoric acid and water to the mixing zone simultaneously. The concentrated phosphoric acid may contain about 0.04-0.10% fluorine, and typically contains about 0.07% fluorine.
The term "quicklime" means heated CaCO3And CaO produced. The reaction is represented by the formula Expressed, and the required temperature exceeded 960 deg.c.
The quicklime contains about 85-95% available CaO, preferably about 90% available CaO, i.e., about 64.3% calcium. The total calcium (calculated as CaO) may be from about 90 to 95%, typically about 92.5%. The particle size distribution of the lime is about 10% of the balance of the lime on a 2.35mm sieve.
Typically, the amount of quicklime and the amount of phosphoric acid used in the dispersion step are selected so that the monocalcium phosphate (MCP) product has a total phosphorus content of no less than about 21% (mass/mass), a total calcium content of no more than about 25% (mass/mass) (typically 21% P: 21% Ca), and a water content of about 1%. The product thus consists mainly of monocalcium phosphate. The monocalcium phosphate product of the present invention meets official registration requirements for monocalcium phosphate in south africa, and is registered according to the 36 th act of the republic of south africa of 1947.
The reaction between calcium oxide and phosphoric acid to produce monocalcium phosphate is shown by the following formula:
it must be noted that the above formula is only applicable to the production of MCP, where the exothermic heat of reaction removes all the water.
The amount of quicklime and the amount of phosphoric acid used in the dispersion step are selected so that the reaction mixture contains about 33-38% quicklime and about 46-50% P2O5And (3) equivalent weight. Generally, the amounts of quicklime and phosphoric acid are selected so that the reaction mixture contains about 35.6% lime and 48.8% P2O5And (3) equivalent weight.
The reaction between the lime and the aqueous phosphoric acid solution is exothermic and the temperature of the mixture of lime and aqueous phosphoric acid solution can rise rapidly to above 100 ℃. This has the following disadvantages: the reaction mixture boils above 100 ℃ and foaming occurs subsequently. At 100 ℃ and above 100 ℃, the viscosity in the reaction mixture also increases. This results in extended discharge times and thus extended batch reaction times. It also causes a layer of solidified product to be produced which remains in said mixing zone, thereby reducing the rate of heat exchange between the reaction mixture and the mixing vessel wall. The product remaining in the mixing zone will also react with the next batch of phosphoric acid added.
Moreover, if the rate of lime addition to the aqueous phosphoric acid solution is too slow, the reaction mixture will reach boiling point before all of the lime is added. In addition, if the reaction mixture is not sufficiently mixed to disperse lime in the aqueous phosphoric acid solution so that the reaction mixture quickly becomes homogeneous, local overheating, which is almost explosive, occurs.
It is therefore important that the lime is dispersed in the aqueous phosphoric acid solution in the mixing zone as quickly as possible to form a homogeneous mixture so that a highly efficient reaction between the lime and the aqueous phosphoric acid solution takes place without local overheating. In order to limit the extent to which the reaction takes place in the mixing zone and the accompanying temperature rise, it is also important to transfer the homogeneous reaction mixture from the mixing zone to the reaction zone as quickly as possible so that the reaction takes place predominantly in the reaction zone. Furthermore, in order to keep the cycle time of the batch reaction as short as possible, the mixing, dispersing and transferring steps should be carried out as quickly as possible.
The term "cycle time of a batch reaction" refers to a predetermined time between mixing concentrated phosphoric acid and water to produce an aqueous phosphoric acid solution and discharging the reaction mixture from the mixing zone. For a batch of known material, the time should be selected to ensure a predetermined yield.
Therefore, in order to prevent the main reaction from occurring in the mixing zone and the associated temperature increase and foaming before the reaction mixture is transferred to the reaction zone, the rate at which lime is dispersed into the aqueous phosphoric acid solution to form a substantially homogeneous reaction mixture should preferably be as high as possible, and the time during which the lime and phosphoric acid are reacted in the mixing zone should be sufficiently short to prevent the temperature of the reaction mixture from reaching above 90 ℃ before the reaction mixture is transferred to the reaction zone. The reaction zone is preferably provided with temperature monitoring means which initiates transfer of the reaction mixture from the mixing zone to the reaction zone when the temperature in the mixing zone reaches about 90 ℃.
Therefore, the predetermined temperature should be about 85-95 deg.C, and preferably about 90 deg.C.
Each batch may be 250 kg. The term "250 kg batch" refers to a batch containing sufficient lime and phosphoric acid to produce about 250kg monocalcium phosphate.
In order to meet the above requirements for 250kg batches, the lime should be added to the aqueous phosphoric acid solution in as short a time as possible, typically less than 8 seconds, preferably about 4 to 8 seconds.
The mixing of concentrated phosphoric acid and water is also an exothermic process. Therefore, in order to keep the batch reaction time as short as possible, themixing of concentrated phosphoric acid and water should also be carried out as quickly as possible. The mixing time should also be kept as short as possible so that the resulting mixture can be cooled as long as possible before mixing with lime.
To meet the above requirements, water may be added to the concentrated phosphoric acid to bring the concentrated phosphoric acid from about 55-62% (P) in about 4-8 seconds2O5Equivalent) is diluted to about 45-48% (P)2O5Equivalent weight). Therefore, to achieve a 250kg batch, the concentrated phosphoric acid can be diluted with about 30-60 liters of water over a period of about 4-8 seconds.
For a 250kg batch, about 94kg of lime is generally added to the aqueous phosphoric acid solution over a period of about 4 to 8 seconds, preferably 4 seconds. On this scale, the time for the lime and aqueous phosphoric acid solution in the reaction mixture to react will be about 7 to 10 seconds before the temperature of the reaction mixture reaches about 90 c and is transferred to the reaction zone. The transfer step should also be performed as quickly as possible, usually in about 5-8 seconds, and typically in about 7 seconds. This time is essentially unchanged if the increase or decrease per batch is about 20%.
Thus, the dispersion step can be carried out in a time of 4 to 10 seconds. The preceding step of mixing concentrated phosphoric acid with water in the mixing zone may also be carried out over a period of 4 to 8 seconds.
The transfer step may be performed in a period of 5 to 8 seconds.
The total cycle time for each batch will be about 13-26 seconds.
The volume of the mixing zone is preferably 8 to 16 times greater than the volume of the reaction zone to allow for volume expansion of the reaction mixture boiling and foaming at the very high temperature of the mixing zone to minimize potential losses.
Thus, the volume of the mixing zone may be 8-16 times greater than the volume of the reaction zone.
The process may also cool the mixing zone during the mixing and dispersing steps. The reaction mixture in the mixing zone may be rapidly stirred to rapidly dissipate heat through the reaction mixture and the cooling may be effected by providing a heat exchanger which removes heat from the mixing zone.
Whenever a monocalcium phosphate product is prepared by the method described above, the invention extends to this product.
Of course, lime with a lower available CaO content may also be used in the process. The reaction time and temperature will be correspondingly longer and lower, and routine experimentation may be carried out in order to determine the optimum time and temperature necessary to produce monocalcium phosphate.
According to another aspect of the present invention, there is provided an apparatus for producing a monocalcium phosphate product, the apparatus comprising:
a mixing zone and a separate reaction zone;
dispensing means for dispensing a predetermined amount of phosphoric acid and a predetermined amount of quicklime into said mixing zone to form a mixture;
a dispersing device for rapidly dispersing quicklime into the phosphoric acid aqueous solution in the mixing zone to form a substantially uniform reaction mixture; and
a transfer means for rapidly transferring the reaction mixture from the mixing zone to the reaction zone when said reaction mixture has reached a predetermined temperature.
Typically, the dispersion apparatus dispenses H in the proportions required to produce the monocalcium phosphate product3PO4And CaO, said monocalcium phosphate product having a total phosphorus content of not less than 21% (mass/mass) and a total calcium content of not more than about 25% (mass/mass), e.g., 21% P: 21% Ca. As noted above, to meet this requirement, the reaction formulation contains about 35.6% lime and sufficient phosphoric acid to provide about 48.8% P2O5。
In addition, the dispensing device is also used to dispense a predetermined amount of water into the mixing zone.
The mixing zone may be provided with cooling means. For example, the mixing zone may be a mixing vessel and cooling means, which may be in the form of a water jacket for cooling the reaction mixture. The cooling jacket is preferably configured and shaped to provide the greatest cooling area possible for effective heat removal.
The dispersing means may comprise a feed hopper from which, in use, the quicklime, phosphoric acid and water are dispensed into the mixing vessel. The dispersing means may be a stirrer for dispersing the quicklime into the phosphoric acid aqueous solution. The stirrer is preferably constructed and configured for rapid stirring to optimize heat dissipation and heat exchange.
The dispensing device may have a feed chamber for measuring the mass of quicklime, phosphoric acid and water in the dispensing device.
The reaction zone may have two or more reaction vessels, such as two or more fixed chambers.
The apparatus may be provided with storage means for storing quicklime and phosphoric acid.
The mixing zone may comprise a mixing vessel made of stainless steel having a wall thickness of about 1.5-2.5mm to ensure rapid heat transfer through the wall of the mixing vessel. The mixing vessel is preferably a cylinder having a relatively large cross-sectional area and a relatively wide base so that the ratio of the wall/base surface area of the cylinder to the volume of the reaction mixture is relatively large, which allows heat to pass efficiently through the walls of the vessel and allows the reaction mixture to expand if foaming occurs when the reactivity of the lime used is high.
The transfer means may comprise at least one feed tube with a valve for allowing the reaction mixture to transfer to the fixed chamber under gravity for a predetermined period of time.
The apparatus of the invention may be provided with automatic control means such as a process logic controller which functions to control all functions and open the valves when the temperature in the mixing zone has reached a predetermined value (e.g. 90 c).
The present invention extends to the monocalcium phosphate product whenever it is prepared using the apparatus described above.
The invention is described below by way of example with reference to the only figure herein, which is a sketch of a plant for producing monocalcium phosphate according to the invention and table 1.
In the figure, reference numeral 10 denotes an apparatus for producing a monocalcium phosphate product. The apparatus 10 comprises two 230m3Is rich inPhosphoric acid storage tank 12, 14, 230m3A quicklime storage silo 16, a quicklime servo silo (duty silo)20, quicklime, water and concentrated phosphoric acid feed hoppers 22, 26, 28, a mixing zone in the form of a container 30, two fixed cells 34, 36 and a water reservoir 38. The vessel 30 is a cylindrical mixing vessel with a diameter of 1.5-1.6m with a conical bottom with a depth of about 24 cm.
A feed line 42 leads from the feed pump 40 and delivers concentrated phosphoric acid from the feed pump 40 to the phosphoric acid storage tank 12, whilea connecting line 44 connects the tops of the tanks 12, 14. The phosphoric acid outlet line 48 includes a valve 50, the line 48 leading from the tank 12 and being connected to a second phosphoric acid outlet line 52, the line 52 leading from the tank 14 and including a valve 54. The output line 48 extends downwardly through a pump 58 downstream of the line 52 to the phosphoric acid feed hopper 28 with a pneumatically actuated valve 60. Line 62 connects the connecting line 44 between the tanks 12, 14 with the outlet line 48 downstream of the pump 58 and upstream of the valve 60.
The lime storage silo 16 is provided with a rotary valve feeder 66, which feeder 66 feeds lime to an auger 70, which auger 70 transfers said lime to a bucket elevator 72, by which elevator 72 the lime is fed via a feed line 74 to the lime service silo 20. The second rotary valve feeder 76 delivers lime to the lime feed hopper 22 through a slide valve 78 and feed line 80. The lime feed hopper 22 is arranged on the feeding chamber 23 in order to measure the mass of lime in the feed hopper 22. The lime feed hopper 22 is connected to the reactor 30 by a second auger 88 and feed line 90.
The reservoir 38 is connected to the feed hopper 26 by a feed line 84 via a pump 86. A line 92 leads from the feed hopper 26 and is connected to the mixing vessel 30 via a valve 94, a pump 96 and a pneumatic valve 98. The feed water hopper 26 is also located on the loading chamber (not shown) so that the quality of the water in the feed hopper 26 can be measured.
A feed line 102 extends from the phosphoric acid feeder 28 through a pneumatic valve 104 to the mixing vessel 30. The phosphoric acid feeder 28 is provided with a level detecting device 29 for monitoring the amount of phosphoric acid in the feeder 28. The feed hopper 28 may also optionally be positioned above the loading chamber (not shown) so that the mass of acid in the feed hopper can be measured.
A feed line 108 extends from the bottom of the mixing vessel 30 through a valve 110 to the fixed chambers 34, 36. The mixing vessel 30 is provided with a water cooling jacket 120, the cooling jacket 120 having a water inlet line 122 and a water outlet line 124, the water inlet line 122 leading from the line 84 downstream of the pump 86, the water outlet line 124 leading through a valve 126 to the reservoir 38. The mixing vessel 30 is provided with an exhaust outlet 130 and an agitator 132.
In use, the concentration will be about 55-62% (P) via the phosphoric acid output lines 48, 522O5Equivalent) of concentrated phosphoric acid is delivered from the storage tanks 12, 14 to a phosphoric acid feed hopper 28. Water is delivered from the reservoir 38 to the feed hopper 26 by line 84 and pump 86, while lime is delivered from the lime storage silo 16 to the lime service silo 20 by the augers 70, bucket elevators 72 and feed line 74. The lime is then fed through rotary valve feeder 76, slide valve 78 and feed line 80To a lime feed hopper 20. The mass balance of the formulation is calculated to allow for changes in the feedstock characteristics (as described in more detail below). Table 1 below shows H3PO4/H2And (4) a calculation table of O.
TABLE 1
Product description 21.3% P (48.8% P)2O5)
For every 1Te MCP produced, H is required3PO4Calculating in batches:
48.8+ acid% P2O5×100
Column 1: with P2O5(%) represents H3PO4Concentration column 5: h in acid of given concentration2O, column 2: percentage of impurities (salts of Mg, Al, Si, Fe, Cu, etc.) column 6: for each 1Te MCP produced, diluted to 47% P2O5The amount of external water required is column 3: MCP, H for every 1Te produced3PO4Amount of impurities (kg) in column 7: the amount of added water required to produce MCP per 250kg batch is column 4: h required for each production of 1Te MCP3PO4H required for producing Te MCP3PO4Calculation of the amount (kg): p in 48.8+ acid2O5(％)×100÷4
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
| H3PO4Concentration of | Solids content (％) | Mass of solid (kg) | Required H3PO4 Amount of (kg) | Amount of water in acid (kg) | In addition to the need for Water of (2) | Need in each batch With the addition of water | Description of the invention | |
| *→ | 67％P2O5 | 7,0％ | 51 | 728 | 0 | 288 | 72 | 93％H3PO4(7% diluted pure phosphoric acid) |
| Concentration Phosphorus (P) Acid(s) | 62％ 61％ 60％ 59％ 58％ 57％ 56％ 55％ 54％ | 7,0％ 7,0％ 7,0％ 7,0％ 7,0％ 7,0％ 7,0％ 7,0％ 7,0％ | 55 56 57 58 59 60 61 62 63 | 787 800 813 827 841 856 871 887 903 | 55 67 79 92 105 119 133 148 163 | 233 221 209 196 183 169 155 140 125 | 58 55 52 49 46 42 39 35 31 | Further calculation: A. mass of solids: h3PO4(kg)×0.07 B. Amount of water in acid: (H3PO4(kg) -solid (kg) -difference (728-51) C. The amount of water additionally required: 288-water in acid D. The amount of external water required per batch ÷ 4 |
| *→ | 47％ | 7,0％ | 73 | 1038 | 288 | 0 | 0 | H3PO4Average ideal concentration of aqueous solution |
In a typical batch production, it is sufficient to provide 48.8% P in the formulation2O5Is fed into the mixing vessel 30 after dilution and rapidly adds water (+ -50 kg) to said mixing vessel 30 while vigorously stirring with the stirrer 132 in less than 8 seconds while cooling the water at a rate greater than 20m3The rate of/h is pumped through the cooling jacket 120. The resulting acidic aqueous solution has a temperature of about 46-65 deg.C and is allowed to cool to about 30-45 deg.C during stirring for 12-20 seconds. 94kg of lime is then transferred via the boost feeder 88 and the feed line 90 to the mixing vessel 30 while being vigorously stirred by the stirrer 132 to form a homogeneous slurry, and the resulting slurry is stirred for a further 7-9 seconds in less than 8 seconds. During which the temperature of the reaction mixture rose to about 90 ℃.
In other embodiments of the invention, less reactive lime is used and the slurry is discharged at a temperature below 90 ℃. The flow of water through the cooling jacket 120 can be reduced and shut off to raise the temperature.
When the temperature in the mixing vessel 30 rises to 90 c, the hot slurry is automatically caused to exit the mixing vessel via feed line 108 and valve 110 into the stationary chamber 34, 36 for a period of about 8 seconds, and it is left in the stationary chamber for further reaction. The temperature of the reaction slurry present in the fixed cells was raised to about 160 ℃ to 170 ℃ over a period of about 40 minutes, during which time a substantial portion of the water was removed as water vapor. The temperature is also high enough to allow the water of crystallization in the monocalcium phosphate to be drained. Then, after about 40 minutes, the product, which is predominantly monocalcium phosphate as described above, is discharged from the fixed cells 34, 36, moved to a storage site where it is allowed to mature for 2-10 days before being packaged.
The monocalcium phosphate product typically contains a total phosphorus content of not less than 21% (mass/mass), a fluorine content of not more than 0.13% (mass/mass), and a calcium content of not more than 25% (mass/mass).
In order to ensure a total phosphorus content of at least 21% (mass/mass), the relative amounts of lime and phosphoric acid are generally chosen so as to bring the phosphorus content to about 21.3% (mass/mass). The mass balance is based on the average analytical value to allow for differences in the characteristics of the raw materials. Moreover, a loss of about 7% is generally allowed. To calculate the mass balance for this process, the total average water content in the monocalcium phosphate product is assumed to be 1% (mass/mass).
Any formulation used to produce the MCP products of the present invention will depend on two base stocks H3PO4And the physical properties of CaO. To H3PO4Is subject to the presence of salts in different formsThe degree of dilution of the phosphoric acid and the variation of the assay is considerable. The variation of the CaO concentration in the quicklime can also be considerable. The mass balance is calculated as follows:
A. suppose H3PO4Contains 7% of impurities. H3PO4Has a molecular weight of 98.
72.4×0.93＝67.3％P2O5(in anhydrous phosphoric acid)
The target formulation was 21.3% P (48.8% P)2O5)。
48.8/0.673/72.5 parts of anhydrous H3PO4. Assuming the target content is 1.0% free water in the product: 72.5+ 1.0-73.5.
The available calcium is 100-73.5 ═ 26.5 parts (including impurities in lime).
B. It is assumed that lime contains on average about 90% (± 10% impurities) of total CaO.
The molecular weight of CaO is 56. 
26.5 × 0.865 ═ 22.9% Ca (including impurities in lime). It should be noted that all of the oxygen in the CaO is lost in the process of the present invention. The standard formulation is as follows: a.72.5 × 0.673 ═ 488kg P2O5(Te) MCPB.22.9 ÷ 0.643 ═ 356kg lime/Te MCP
Loss tolerance (loss allowances) can be empirically calculated into the standard formulation described above, providing a standard for cost. It should be noted that although 488kg P2O5Will remain constant but the amount of lime is calculatedon the basis of the assumed impurity levels in the acid and lime.
When preparing the stoichiometric balance of MCP using the best locally available raw materials, the total phosphorus content of the MCP product of the present invention is determined by the amount of available raw materialsThe total amount of P obtained gives:stoichiometrically balanced MCP1. 2. The molecular weight of (2) is 270.
22.96% P doped with ± 7% impurities contained 21.35% P in the stoichiometrically balanced MCP (taking into account the amount of impurities contained in the feed).
Dilution H3PO4The volume of water used must be determined by the temperature of the final product mass in the fixed cells 34, 36 in order to control the amount of water-soluble P in the MCP product of the present invention. Without being bound by theory, the applicant believes that the following reaction processes occur simultaneously in the process of the invention:
1.
2.
3.
4.
5.
the progressive reaction process of 1-4 requires a gradual increase in temperature to support the reactions of each step. Thus, the progressive reaction from m.c.p. to d.c.p. (calcium hydrogen phosphate) to t.c.p. (tricalcium phosphate) depends on the reaction temperature reached in the reaction zone (fixed cell) and the amount of available calcium. Excess water in the formulation allows for a large amount of potential energy dissipation by releasing water vapor from the reactive species in the reaction zone. The use of more water will result in more energy being dissipated, thus preventing the development of excessive final product block temperatures. It is desirable to use the maximum amount of water in the formulation, which is limited by the factor that the free water content in the product excluding the fixed cell does not exceed 2.0%. The temperature of the final product pieces in the reaction zone is therefore dependent on the water content in the formulation. It can also be seen that at the lowest temperatures that can be achieved in the fixed cell, the optimum monocalcium phosphate (which is water-soluble) will be formed.
The advantage of the present invention is that the yield of the present invention is higher than the yield of the plant known to the applicant for the production of monocalcium phosphate. The apparatus of the invention is capable of producing a product having the specifications listed above per hourGravy monocalcium phosphate 20 Te. The applicant envisages that the yield can be increased to 30Te per hour or more if larger reaction zones and additional fixed cells are used. Another advantage of the present invention is that the process is relatively safe and poses substantially no risk to the health of workers. The process also has substantially no harm to environmental pollution. From CaCO3The conditions for producing monocalcium phosphate differ, and the instruments and materials used in the process are standard, requiring no intricate instrumentation, materials and special skills. The process also does not require, for example, CaCO3Energy of the process. Another advantage of the present invention is that the control of the process and maintenance of the equipment requires only a low level of skill and that problems in the process are often easily diagnosed and identified. Furthermore, because of the standard nature of the equipment, the cost of maintaining the equipment and the expense required to set up the equipment is correspondingly low. Yet another advantage of the present invention is that accurate raw material proportioning can be achieved despite the relatively standard instrumentation used.
Claims (22)
1. A method for producing a monocalcium phosphate product, characterized in that it comprises the following steps:
rapidly dispersing quicklime in an aqueous phosphoric acid solution in a mixing zone to form a substantially homogeneous reaction mixture, and reacting the quicklime with an acid in the reaction mixture until the reaction mixture reaches a predetermined temperature;
rapidly transferring the reaction mixture to the reaction zone when the reaction mixture reaches a predetermined temperature;
allowing the reaction to proceed to substantially completion in the reaction zone to form a monocalcium phosphate product; and
separating the formed monocalcium phosphate product.
2. The method of claim 1, wherein the concentration of said aqueous phosphoric acid solution is 45-48% (P)2O5Equivalent weight).
3. A process according to claim 1 or 2, characterized in that the phosphoric acid is orthophosphoric acid.
4. The process according to claim 1, characterized in that it comprises the preceding step of mixing concentrated phosphoric acid with water in a mixing zone to produce an aqueous phosphoric acid solution.
5. A method according to claim 1, characterized in that the quicklime contains 85-95% available CaO.
6. A method according to claim 1 or 5, characterized in that the particle size distribution of the quicklime is 10% of the remainder of the quicklime on a 2.35mm sieve.
7. A method according to claim 1 or 2, characterized in that the amount of quicklime and the amount of phosphoric acid used in the dispersing step are selected so that the monocalcium phosphate product has a total phosphorus content of not less than 21% (mass/mass), a total calcium content of not more than 25% (mass/mass) and a water content of 1%.
8. A method according to claim 1 or 2, characterized in that the amount of quicklime and the amount of phosphoric acid in the aqueous solution used in the dispersing step are selected so that the reaction mixture contains 33-38% lime and 46-50% P2O5And (3) equivalent weight.
9. A method according to claim 1 or 2, characterized in that said predetermined temperature is 85-95 ℃.
10. A method according to claim 1 or 2, characterized in that said dispersing step is carried out in a time of 4-10 seconds.
11. The method of claim 4, wherein the prior step of mixing the concentrated phosphoric acid with water in the mixing zone is performed in a time period of 4 to 8 seconds.
12. A method according to claim 1 or 2, characterized in that said transferring step is carried out in a period of 5-8 seconds.
13. The process of claim 1 or 2, wherein the volume of said mixing zone is 8 to 16 times greater than the volume of said reaction zone.
14. A process according to claim 1 or 2, characterised in that the process comprises cooling said mixing zone.
15. An apparatus for producing a monocalcium phosphate product, characterized in that the apparatus comprises:
a mixing zone and a separate reaction zone;
a dispensing device arranged to dispense a predetermined amount of phosphoric acid and a predetermined amount of quicklime into said mixing zone to form a mixture;
a dispersing device in the mixing zone for rapidly dispersing the quicklime into the phosphoric acid to form a substantially homogeneous reaction mixture; and
transfer means for rapidly transferring the reaction mixture fromthe mixing zone to the reaction zone when said reaction mixture has reached a predetermined temperature.
16. The apparatus of claim 15 wherein said dispensing means is additionally adapted to dispense a predetermined amount of water into said mixing zone.
17. The apparatus of claim 15 or 16, wherein the mixing zone is provided with cooling means.
18. The apparatus of claim 16, wherein the dispensing means has a loading chamber for measuring the mass of the quicklime, phosphoric acid and water in the dispensing means.
19. The apparatus of claim 15 or 16, wherein said reaction zone is two or more fixed chambers.
20. The apparatus of claim 15 or 16, wherein said mixing zone comprises a mixing vessel made of steel having a wall thickness of 1.5-2.5 mm.
21. A novel process for the production of a monocalcium phosphate product, substantially as herein described.
22. A novel apparatus for producing a monocalcium phosphate product, substantially as herein described.
Priority Applications (1)
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|---|---|---|---|
| CN 97116319 CN1208015A (en) | 1997-08-08 | 1997-08-08 | Method for production of mono-calcium phosphate product |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97116319 CN1208015A (en) | 1997-08-08 | 1997-08-08 | Method for production of mono-calcium phosphate product |
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| Publication Number | Publication Date |
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| CN1208015A true CN1208015A (en) | 1999-02-17 |
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| CN 97116319 Pending CN1208015A (en) | 1997-08-08 | 1997-08-08 | Method for production of mono-calcium phosphate product |
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1997
- 1997-08-08 CN CN 97116319 patent/CN1208015A/en active Pending
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