GB2043617A - Process for the manufacture of phosphate fertilizers - Google Patents
Process for the manufacture of phosphate fertilizers Download PDFInfo
- Publication number
- GB2043617A GB2043617A GB7943210A GB7943210A GB2043617A GB 2043617 A GB2043617 A GB 2043617A GB 7943210 A GB7943210 A GB 7943210A GB 7943210 A GB7943210 A GB 7943210A GB 2043617 A GB2043617 A GB 2043617A
- Authority
- GB
- United Kingdom
- Prior art keywords
- weight
- slag
- process according
- waste sludge
- mixed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 239000003337 fertilizer Substances 0.000 title description 17
- 229910019142 PO4 Inorganic materials 0.000 title description 8
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 title description 7
- 239000010452 phosphate Substances 0.000 title description 7
- 239000010802 sludge Substances 0.000 claims abstract description 50
- 239000002893 slag Substances 0.000 claims abstract description 39
- 239000002699 waste material Substances 0.000 claims abstract description 35
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000000203 mixture Substances 0.000 claims abstract description 19
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 238000000746 purification Methods 0.000 claims abstract description 8
- 239000002686 phosphate fertilizer Substances 0.000 claims abstract description 4
- 239000008187 granular material Substances 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 6
- 239000000470 constituent Substances 0.000 abstract description 3
- 239000000047 product Substances 0.000 description 10
- 238000001035 drying Methods 0.000 description 9
- 235000021317 phosphate Nutrition 0.000 description 7
- 238000000227 grinding Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 239000003673 groundwater Substances 0.000 description 3
- 239000013067 intermediate product Substances 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 239000002352 surface water Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000002367 phosphate rock Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- YYRMJZQKEFZXMX-UHFFFAOYSA-N calcium;phosphoric acid Chemical compound [Ca+2].OP(O)(O)=O.OP(O)(O)=O YYRMJZQKEFZXMX-UHFFFAOYSA-N 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000010410 dusting Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 235000013379 molasses Nutrition 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000005549 size reduction Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000003900 soil pollution Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- 239000002426 superphosphate Substances 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B5/00—Thomas phosphate; Other slag phosphates
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Fertilizers (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
Phosphate fertilizer is manufactured by mixing together waste sludge from the purification of phosphoric acid produced by the wet process and steelworks slag to produce a mixture having, a dry weight -P2O5 content of 3 - 9% by weight. The constituents are preferably mixed in the weight ratio 70-85 parts slag to 30-15 parts sludge having a 40-60% by weight moisture content, and the mixture is suitably granulated and dried to a moisture content of 2-5% by weight.
Description
SPECIFICATION
Process for the manufacture of phosphate fertilizers
This invention relates to a process for the manufacture of phosphate fertilizers.
The composition of the waste sludge obtained in the purification of phosphoric acid produced by the wet process is such that the sludge is virtually useless for all purposes, mainly by virtue of the fact that the sludge contains substances which must not be allowed to mix with surface water or ground water. Such a sludge cannot therefore be freely dumped in the open.A typical composition of such waste sludge is as follows:
Fe 9.0%byweight P205 21.0 % by weight
CaO 6.2 % by weight SiO2 12.5 % by weight
MgO 5.8 % by weight Al203 2.7 % by weight Cr203 0.7 % by weight
V205 0.6 % by weight Na2O 18.0% by weight K2O 0.3 % by weight
F 1.7 % by weight C 2.5 % by weight S 0.3 % by weight
Remainder* 18.7% by weight 100.0 % by weight *consisting mainly of water of hydration and carbonate which has not decomposed at 105"C.
The dumping of this sludge therefore presents considerable problems. For example, the readily water-soluble alkali-bound phosphates contained in it are washed out by rain and will ultimately result in
heavy eutrophication of the local surface water. At the same time, certain of the other constituents are also washed out. In a wet phosphoric acid purification plant with an annual throughput of approximately 100,000 tonnes H3P04, the quantity of sludge obtained per year will be about 50,000 tonnes. There is, at present, no
alternative but to dump this sludge, and the cost of such temporary dump is determined mainly by the area
of land required, the plastics film covering and/or lining for the dump and the inspection requirements to
ensure that the ground water is not polluted.
The present invention seeks to provide a process for utilizing the waste sludge from wet phosphoric acid
purification, to improve the handling characteristics of the sludge the high moisture content of which would
otherwise make it difficult to handle and also to improve the properties of the end product without using any
additives which would render the process more expensive, especially solid or liquid binders.
According to the present invention, there is provided a process for the manufacture of a phosphate fertilizer which comprises mixing such a waste sludge with steel works slag in such an amount that the final
mixture has a dry-weight P205 content of from 3 to 9 % by weight.
Preferably, the waste sludge is added continuously to warm prepared slag at a uniform rate.
A product having improved handling characteristics may be obtained most preferably by separate
grinding of the steel works slag, the ground slag then being mixed and granulated together with the waste
sludge. The two constituents are preferably mixed in amounts of from 70 to 85, more preferably from 75 to 80, parts by weight of ground steelworks slag and from 30 to 15, more preferably from 25 to 20, parts by
weight of waste sludge containing from 50 to 60 % by weight of water; these amounts are mixed and the
mixture is granulated; the granulated mixture is subsequently dried to a residual moisture content of from 2
to 5 %, preferably from 3 to 4 % by weight.This procedure yields a fine-grained product, the preferred grain
size being from 0.3 to 2mm diameter, having a citrate-soluble P205 content of from 3.5 to 6 % by weight. The
above mixing ratio and water content of the sludge resuits in the granulate being considerably solidified
during drying to a residual moisture content of 3 to 4 %.
The advantage attained by the process of the present invention is primarily that the waste product from
the wet phosphoric acid purification plant, which contains a relatively high proportion of readily
water-soluble and citrate-soluble P205 as well as a relatively high proportion of compounds which would
result in an unacceptable level of enviromental pollution is converted by a simple and straightforward
procedure into a product which may be used as a fertilizer and which is ultimately deposited on and enters
the soil over a large area.The other waste sludge substances thus distributed do not produce unacceptable
soil pollution since they are present in this type of fertilizer in a much lower concentration than in
conventional high-percentage phosphate fertilizers, for example superphosphate and mixed fertilizers,
since, when manufacturing high-percentage phosphate fertilizers directly from phosphate rock or from
unpurified wet phosphoric acid, the natural impurities are simultaneously introduced into the product.
Apart from those advantages the process according to the present invention also permits the P205 content of the steelworks slag to be increased, because the content of citric acid-soluble P205 in the sludge is considerably higher than in the slag. Even when using steelworks slag from modern converters that use oxygen where the P205 content of the slag has dropped to about 1 %, enrichment to about 3 to 9 % P205 by mixing in waste sludge will only increase the content of residual substances to a level that is far below the permissible limits. The use of waste sludge from wet phosphoric acid purification plants represents a new raw material source while obviating the necessity of using expensive phosphate rock.
Regarding the handling characteristics of the fertilizer produced according to the present invention, the use of binders that are otherwise commonly used, for example waste sulphite liquor and molasses, is unnecessary. As a result of the strength of the granules, only a small degree of abrasion is produced when the granulated product is handled, and the formation of lumps is precluded.
The special advantage of the present invention is the fact that the product is an easily spreadable fine-grained lime fertilizer that is virtually non-dusting, is rich in phoshorus and enriched with citrate-soluble
P205 to the required extent, that is from 3.5 to 6%.
Tests have confirmed that the fertilizing effect of the lime fertilizer produced by the process of the present invention is comparable to that obtained with powdery fertilizers. Also, the process is especially economical due to the low cost of ground slag and waste sludge and since no otherfeedstock is required.
To perform the granulation, there can be used any type of granulating method that is capable of thoroughly mixing the clay-like waste sludge with the ground steelworks slag, if necessary with the aid of additional crushing or kneading elements. Mixers of this type are known as countercurrent intensive mixers with cutter-type rotors or double shaft granulators. The subsequent drying may be effected in a drying drum or in a fluidized bed drier. The advantage of using a drum-type drier is that the granulate is simultaneously stabilized and any adhering particles are separated.
According to a preferred process of the present invention, the waste sludge is mixed with only a part of the required amount of steelworks slag in ground form, the remainder being added in the form of lumps. In this way, the wet sludge is first converted to a semi-dry intermediate product that no longer tends to form lumps, and which is easier to convey and otherwise handle. The required size reduction and homogenization of the remaining slag and pre-dried sludge can be carried out subsequently by further grinding the mixture in a mill, in which the moisture still contained in the material is expelled to the required extent by heating the mill, a considerable portion of the thermal energy being produced by the grinding process itself. According to a further feature of this preferred process, part of the ready-ground mixture may be recycled and re-mixed with the waste sludge.
The following Examples illustrate the invention.
Example 1
Approximately 250 tonnes ot waste sludge from a purification plant for phosphoric acid produced by the wet process are spread over an uncooled slag bed having an area of about 300 m2 and containing about 1000 tonnes of LD steelworks slag (LD = Linz-Donawitz process). The LD slag contains 1.2 % by weight soluble P2O5, while the sludge contains 21 % by weight soluble P205 (dry weight) and 50 % by weight mixture, As a result of bed drying and subsequent turning of the mixture, 10% of the moisture are expelled. The mixture is ground in a heater mill to produced a dry end product having a grain diameter of less than 0.315 mm and containing 3.4 % by weight soluble P205.
Example 2
Approximately 1400 tonnes of LD slag and 600 tonnes of waste sludge are mixed in a mixing bed prior to grinding. The LD slag had previously been enriched to 3.5 % by weight soluble P205 by mixing with P205bearing slag. The waste sludge contains 25 % by weight P205 (dry weight) and its moisture content had been reduced to 35 % in a pre-drying step. After processing the mixture in a combined grinding and drying unit, the product obtained is a lime-based fertilizer containing 8.2 % by weight soluble P205.
From Examples 1 and 2, it can be seen that while the P205 - content of the steelworks slag is increased, the other substances contained in the sludge are diluted. Whereas the dumping of about 50,000 tonnes per annum of sludge requires an area of 5000 m2, i.e. the amount of sludge per m2 is 10 tons or 10,000 kg, which results in an unacceptably high degree of pollution per m2 surface and ground water over a limited area, the spreading of 25 kg/100 m2 or 0.25 kg/m2 of fertilizer will result in an extremely low level of water pollution.
This means that, if the volume of the waste sludge is increased three-fold by adding steelworks slag, the annual output of about 50,000 tonnes of waste sludge can be distributed over an area of about 600 km2.
Example 3
Steelworks slag containing 1.3 % by weight citric acid-soluble P205 is ground so that 80 % of the particles have a diameter of less than 0.16 mm. The ground slag is temporarily stored in a bin. Phosphate waste sludge with a soluble P205 content of 25 % (dry weight) and a moisture content of 55 % by weight is stored in a second bin. The two components are continuously withdrawn from the respective bins, the slag by a belt-type production weigher and the phosphate waste sludge by screw conveyers, in a weight ratio of 5 parts of slag to 1 part of sludge and fed into a countercurrent intensive mixer with additional cutters.The material passes through the mixer in a total residence time of 4 minutes and leaves the mixer in the form of a fine-grained granulate, 83% of which have a particle diameter of 0.3 to 2 mm and the moisture content of which is 11 % by weight. In a drying drum downstream of the mixer, the granulate is further dried to a residual moisture content of 3 % by weight. After drying, 78% of the product have a particle diameter of 0.3 to 2 mm. The fines, i.e. the particles smaller than 0.3 mm diameter, are screened off and recycled into the process to be mixed with the waste sludge and ground slag. The product fertilizer granulate contains about 4.1 % by weight citric acid-soluble phosphoric acid, has a good abrasion resistance and can be spread without any dust formation.
Example 4
In a countercurrent intensive mixer, 4700 kg/h waste sludge containing 25 % by weight P205 (dry weight) and 55 % by weight moisture and 3200 kg/h recycled fertilizer fines are processed together, thus yielding a crumbly intermediate product with a moisture content of about 32 % by weight. This intermediate product is fed together with 14,800 kg/h lumpy LD steelworks slag ata uniform rate into a grinding/drying unit. The LD steelworks slag contains 1.2 % by weight soluble P205. The final product is a fertilizer containing 4.1 % by weight soluble P205. The quantity produced is about 20 t/h, of which 3200 kg are recycled, i.e. this quantity is re-mixed with unprocessed waste sludge.
Claims (13)
1. A process for the manufacture of a phosphate fertilizer, which comprises mixing the waste sludge obtained in the purification of phosphoric acid produced by the wet process with steelworks slag in such an amount that the resulting mixture has a dry weight P205 content of from 3 to 9 %, by weight.
2. A process according to claim 1, wherein the waste sludge is mixed with warm pretreated slag continuously at a uniform rate.
3. A process according to claims 1 to claim 2, wherein the slag is ground and the ground slag is then mixed with the waste sludge.
4. A process according to claim 3, wherein the waste sludge is mixed with a part of the required quantity of slag in ground form, and the mixture obtained is subsequently mixed with the remaining slag in the form of lumps.
5. A process according to claim 4, wherein the mixture is further ground and simultaneously dried.
6. A process according to any one of claims 1 to 5, wherein a total of from 70 to 85 parts by weight of slag are mixed with from 15 to 30 parts by weight of waste sludge having a moisture content of from 40 to 60 % by weight.
7. A process according to claim 6, wherein a total of from 75 to 80 parts by weight of slag are mixed with from 20 to 25 parts by weight of waste sludge.
8. A process according to any one of claims 1 to 7, wherein the slag and the waste sludge are granulated during mixing to produce a granulate having a particle diameter of substantially 0.3 to 2 mm.
9. A process according to any one of claims 1 to 8, wherein the granulated mixture is dried to a residual moisture content of from 2 to 5 % by weight.
10. A process according to claim 9, wherein the granulated mixture is dried to a residual moisture content of from 3 to 4 % by weight.
11. A process according to any one of claims 1 to 10, wherein part of the ground mixture is recycled and mixed with the waste sludge.
12. A process according to claim 1 carried out substantially as described in any one of Examples 1 to 4 herein.
13. A phosphate fertilizer manufactured by a process according to any one of claims 1 to 12.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2854433A DE2854433C2 (en) | 1978-12-16 | 1978-12-16 | Process for the preparation of a P? 2? O? 5? -Containing fertilizer |
| DE19792926588 DE2926588A1 (en) | 1979-06-30 | 1979-06-30 | Phosphorus fertiliser prodn. from steel-making slag - by mixing with sludge from wet-process phosphoric acid mfr. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2043617A true GB2043617A (en) | 1980-10-08 |
| GB2043617B GB2043617B (en) | 1983-05-05 |
Family
ID=25776896
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7943210A Expired GB2043617B (en) | 1978-12-16 | 1979-12-14 | Process for the manufacture of phosphate fertilizers |
Country Status (4)
| Country | Link |
|---|---|
| FR (1) | FR2444014A1 (en) |
| GB (1) | GB2043617B (en) |
| IT (1) | IT1126553B (en) |
| NL (1) | NL7908791A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0680936A1 (en) * | 1994-05-02 | 1995-11-08 | Hochwald-Ton-GmbH | Method for processing sewage sludge |
| FR2757849B1 (en) * | 1996-12-31 | 1999-01-22 | Lorraine Laminage | PROCESS FOR THE PREPARATION OF A CALCIUM PHOSPHATE AMENDMENT |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE372565C (en) * | 1919-11-06 | 1923-03-29 | Plauson S Forschungsinstitut G | Process for improving fertilizers from insoluble phosphates |
| DE583577C (en) * | 1932-02-03 | 1934-03-24 | Hubert Kappen Dr | Process for the production of phosphoric acid fertilizers from blast furnace slag or similarly composed silicate slags |
| DE594902C (en) * | 1932-06-22 | 1934-03-24 | Hubert Kappen Dr | Process for the production of slag phosphates by the wet route |
| DE1033683B (en) * | 1957-02-16 | 1958-07-10 | Albert Ag Chem Werke | Process for the production of granulated phosphate fertilizers |
| BE674276A (en) * | 1965-01-07 | 1966-04-15 | ||
| GB1478749A (en) * | 1976-03-15 | 1977-07-06 | Fisons Ltd | Fertilizer composition containing slag and phosphate rock |
-
1979
- 1979-12-05 NL NL7908791A patent/NL7908791A/en not_active Application Discontinuation
- 1979-12-07 IT IT27976/79A patent/IT1126553B/en active
- 1979-12-14 GB GB7943210A patent/GB2043617B/en not_active Expired
- 1979-12-17 FR FR7930831A patent/FR2444014A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| NL7908791A (en) | 1980-06-18 |
| IT7927976A0 (en) | 1979-12-07 |
| GB2043617B (en) | 1983-05-05 |
| FR2444014A1 (en) | 1980-07-11 |
| IT1126553B (en) | 1986-05-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |