CA1065120A - Manufacture of ferric sulphate - Google Patents
Manufacture of ferric sulphateInfo
- Publication number
- CA1065120A CA1065120A CA223,444A CA223444A CA1065120A CA 1065120 A CA1065120 A CA 1065120A CA 223444 A CA223444 A CA 223444A CA 1065120 A CA1065120 A CA 1065120A
- Authority
- CA
- Canada
- Prior art keywords
- ferric
- sulphuric acid
- ferric sulphate
- slurry
- ferric oxide
- 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.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/14—Sulfates
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the manufacture of ferric sulphate solution wherein ferric oxide is reacted with a molar excess of sulphuric acid at a temperature of 105°C. to 139°C. to form a hot slurry of sulphuric acid, unreacted ferric oxide, solid ferric sulphate and ferric sulphate solution. The hot slurry is then diluted with water sufficient to dissolve all the solid ferric sulphate, the diluted slurry being maintained at a temperature of 20°C. to 60°C. The unreacted ferric oxide is then separated to provide a product solution of ferric sulphate in aqueous sulphuric acid. Unreacted ferric oxide is recycled for reaction with additional sulphuric acid. The process provides ferric sulphate solutions suitable for waste water treatment and can employ ferric oxide available as a by-product of the metal industry.
A process for the manufacture of ferric sulphate solution wherein ferric oxide is reacted with a molar excess of sulphuric acid at a temperature of 105°C. to 139°C. to form a hot slurry of sulphuric acid, unreacted ferric oxide, solid ferric sulphate and ferric sulphate solution. The hot slurry is then diluted with water sufficient to dissolve all the solid ferric sulphate, the diluted slurry being maintained at a temperature of 20°C. to 60°C. The unreacted ferric oxide is then separated to provide a product solution of ferric sulphate in aqueous sulphuric acid. Unreacted ferric oxide is recycled for reaction with additional sulphuric acid. The process provides ferric sulphate solutions suitable for waste water treatment and can employ ferric oxide available as a by-product of the metal industry.
Description
This invention relates to a process for the manufacture of ferric sulphate.
Ferric sulphate is employed in water treatment processes where it serves to precipitate phosphates present in waste water~ In view of the large volume of ferric 3ulphate required by municipal sewage systems it is of ~' economic advantage to manufacture this material from by-products of metal producing industries. For example, it is known to prepare ferric sulphate by the reaction of sulphuric acid and iron oxide dust recovered from copper roasting ovens.
The manufacture of ferric sulphate by the reaction of sulphuric acid on iron oxide is disclosed in several patents. In United States Patent No.2,045,625 there is disclosed a process for manufacturing ferric sulphate by the action of sulphuric acid on pyrite cinder containing sulphides. In United States Patent No.1,644,250 and German Patent Nos.537,509 and 555,308 describe processes for manufacturing ferric sulphate by reacting iron oxide with sulphuric acid and an oxidizing agent are disclosed. In ~0 United States Patent No. 2,165,189 a process is disclosed wherein anhydrous ferric sulphate i8 manufactured by reacting iron oxide and sulphuric acid in two stages and then calcining the product.
In the reaction between iron oxide and sulphuric acid it is difficult to bring about complete reaction of the iron oxide even in the presence of a substantial excess of sulphuric acid. Attempts to overcome this in the prior art have involved carrying out the reaction in two stages.
However, for water purification applications it is not essential to obtain a solid product. Aqueous solutions containing sulphuric acid are acceptable.
'~
~: . . -.
A novel process for preparing aqueous solutions of ferric sulphate has been devised whereby in a continuous procedure iron oxide is reacted with sulphuric acid, the unreacted iron oxide being separated from the product ferric sulphate solution and mixed with fresh sulphuric acid and iron oxide to produce additional ferric sulphate. The process operates satisfactorily with waste iron oxide dust such as is available as a by-product in the operation of an open hearth ~urnace. The process provides a product which is an aqueous solution of ferric sulphate, containing sulphuric acid. In this form the product is suitable for use as a reagent in water purification systems.
Thus the primary object of the invention is to provide a means for the manufacture of ferric sulphate from readily available iron oxide. Additional objects will appear hereinafter.
The process of the invention comprises the steps of (1) reacting ferric oxide with 50% to 60% sulphuric acid in molar ratio of sulphuric acid to ferric oxide of 3:1.0 to 6:1.0 at 105C. to 139C. at atmospheric pressure for a period of 1 to 3 hours to form an aqueous slurry of sulphuric acid, unreacted ferric oxide, solid ferric sulphate and ferric sulphate solution,
Ferric sulphate is employed in water treatment processes where it serves to precipitate phosphates present in waste water~ In view of the large volume of ferric 3ulphate required by municipal sewage systems it is of ~' economic advantage to manufacture this material from by-products of metal producing industries. For example, it is known to prepare ferric sulphate by the reaction of sulphuric acid and iron oxide dust recovered from copper roasting ovens.
The manufacture of ferric sulphate by the reaction of sulphuric acid on iron oxide is disclosed in several patents. In United States Patent No.2,045,625 there is disclosed a process for manufacturing ferric sulphate by the action of sulphuric acid on pyrite cinder containing sulphides. In United States Patent No.1,644,250 and German Patent Nos.537,509 and 555,308 describe processes for manufacturing ferric sulphate by reacting iron oxide with sulphuric acid and an oxidizing agent are disclosed. In ~0 United States Patent No. 2,165,189 a process is disclosed wherein anhydrous ferric sulphate i8 manufactured by reacting iron oxide and sulphuric acid in two stages and then calcining the product.
In the reaction between iron oxide and sulphuric acid it is difficult to bring about complete reaction of the iron oxide even in the presence of a substantial excess of sulphuric acid. Attempts to overcome this in the prior art have involved carrying out the reaction in two stages.
However, for water purification applications it is not essential to obtain a solid product. Aqueous solutions containing sulphuric acid are acceptable.
'~
~: . . -.
A novel process for preparing aqueous solutions of ferric sulphate has been devised whereby in a continuous procedure iron oxide is reacted with sulphuric acid, the unreacted iron oxide being separated from the product ferric sulphate solution and mixed with fresh sulphuric acid and iron oxide to produce additional ferric sulphate. The process operates satisfactorily with waste iron oxide dust such as is available as a by-product in the operation of an open hearth ~urnace. The process provides a product which is an aqueous solution of ferric sulphate, containing sulphuric acid. In this form the product is suitable for use as a reagent in water purification systems.
Thus the primary object of the invention is to provide a means for the manufacture of ferric sulphate from readily available iron oxide. Additional objects will appear hereinafter.
The process of the invention comprises the steps of (1) reacting ferric oxide with 50% to 60% sulphuric acid in molar ratio of sulphuric acid to ferric oxide of 3:1.0 to 6:1.0 at 105C. to 139C. at atmospheric pressure for a period of 1 to 3 hours to form an aqueous slurry of sulphuric acid, unreacted ferric oxide, solid ferric sulphate and ferric sulphate solution,
(2) adding sufficient water to the slurry to dissolve all the solid ferric sulphate, while maintaining the slurry at ' 20C. to 60C.,
(3) separating the unreacted ferric oxide from the ferric sulphate solution and sulphuric acid, and
(4) mixing the unreacted ferric oxide wi~h additional ferric oxide and sulphuric acid in-continuation of step (1)~
A preferred embodiment o~ the invention is illustrated by a flow sheet shown in the accompanying drawing. , The reaction between iron oxide and sulphuric acid takes place in stirred reactor 1. To the reactor are added `
on a continuous basis iron oxide 2, virgin sulphuric acid 3, wa3te sulphuric acid 4 and water 5. The sulphuric acid inlet lines are fed by pumps 6, 7 and controlled by valves 8, 9.
After the desired residence time in the reactor the slurry of unreacted iron oxide, solid ferric sulphate, ferric sulphate solution and sulphuric acid is transferred by pum~ 10 to stirred dissolution tank 11 where additional water is added through line 12. The water added is sufficient to dissolve all the solid ferric sulphate. The slurry of unreacted iron oxide, ferric sulphate solution and sulphuric acid is trans-ferred by pump 13 through heat exchange 14 to stirred mixing tank 15. In tank 15 a coagulant ~uch as a polyacrylamide, run in through line 16, i9 mixed with the slurry. The slurry then is transferred by pump 17 to coagulation tank 18 where coagulation of the fine particles of solid takes place. The coagulated material is then transferred by pump 19 to settling tank 20. The supernatant liquid from 20 is the product ferric sulphate solution admixed with sulphuric acid. This i9 trans-ferred by line 21 to storage. The underflow from settling tank 20 is divided into two streams by means of pump 22 and valves 23 and 24. One stream is transferred by line 25 to '' reaction l, thus recycling part of the unreacted iron oxide.
The other stream passes to centrifuge 26 where residual ferric sulphate solution and sulphuric acid are separated and trans-ferred by line 27 to product storage. The solid residue is a sludge which is transferred by line 28 to storage.
. ~ .
~ ~ .
In a preferred embodiment of the invention iron oxide is reacted with 50% sulphuric acid in molar ratio of sulphuric acid to iron oxide of 4:1 at 115C, and atmospheric pressure.
The residence time in the reactor is 2 hours. The product solution contains typically 33% by weight of ferric sulphate and 11.0% HzSO4.
The process of this invention produces a ferric sulphate solution suitable for the treatment of waste water employing raw materials that are available as by-products of the metal industry.
EXAMPLE
To a stirred reactor was added on a continuous basis iron oxide (ferric oxide) at a rate of 9.6 kg. per hour, 93%
sulphuric acid at 38~ kg.per hour and water at 34.5 kg. per hour. The reactor temperature was maintained at 110C.
The re~idence time of the ingredients in the reactor was 2 hours. The resulting hot slurry overflowed from the reactor into a dissolution tank whére water was added at a rate of 11.4 kg. per hour. The contents of the dissolution tank were pumped through a heat exchanger and returned to the dissolution tank. The temperature of the contents of the dissolution tank was maintained at 25C. Residence time in the dissolution tank was 1 hour. The outflow from the dissolution tank, a slurry unreacted iron oxide, ferric sulphate solution and sulphuric acid, was transferred to a mixing tank where a polyacrylamide coagulent was added at a rate of 5 mg. per liter of slurry. About 9 minutes was taken for mixing the coagulant with the slurry. The slurry then overflowed to a coagulation tank where slow agitation was employed to facilitate the fcrmation of flocs 10651;20 of the unreacted iron oxide. Residence time in the coagulation tank was about 6 minutes. The coagulated slurry then over-flowed to a settler having an area of 0.2 square meters. The ferric sulphate product solution overflowed from the settler at a rate of 71 kg. per hour. The settler discharged slurry from the bottom at a rate of about 63 kg. per hour. The slurry from the bottom of the settler contained 15% suspended solids. The stream of slurry from the bottom of the settler was divided into two equal streams. One stream was recycled to the reactor, the other fed to a centrifuge. A ferric sulphate product solution was recovered from the centrifuge at a rate of 22 kg. per hour. Sludge from the centrifuge contained 49% solids and was discharged at a rate of 9.5 kg.
per hour.
A preferred embodiment o~ the invention is illustrated by a flow sheet shown in the accompanying drawing. , The reaction between iron oxide and sulphuric acid takes place in stirred reactor 1. To the reactor are added `
on a continuous basis iron oxide 2, virgin sulphuric acid 3, wa3te sulphuric acid 4 and water 5. The sulphuric acid inlet lines are fed by pumps 6, 7 and controlled by valves 8, 9.
After the desired residence time in the reactor the slurry of unreacted iron oxide, solid ferric sulphate, ferric sulphate solution and sulphuric acid is transferred by pum~ 10 to stirred dissolution tank 11 where additional water is added through line 12. The water added is sufficient to dissolve all the solid ferric sulphate. The slurry of unreacted iron oxide, ferric sulphate solution and sulphuric acid is trans-ferred by pump 13 through heat exchange 14 to stirred mixing tank 15. In tank 15 a coagulant ~uch as a polyacrylamide, run in through line 16, i9 mixed with the slurry. The slurry then is transferred by pump 17 to coagulation tank 18 where coagulation of the fine particles of solid takes place. The coagulated material is then transferred by pump 19 to settling tank 20. The supernatant liquid from 20 is the product ferric sulphate solution admixed with sulphuric acid. This i9 trans-ferred by line 21 to storage. The underflow from settling tank 20 is divided into two streams by means of pump 22 and valves 23 and 24. One stream is transferred by line 25 to '' reaction l, thus recycling part of the unreacted iron oxide.
The other stream passes to centrifuge 26 where residual ferric sulphate solution and sulphuric acid are separated and trans-ferred by line 27 to product storage. The solid residue is a sludge which is transferred by line 28 to storage.
. ~ .
~ ~ .
In a preferred embodiment of the invention iron oxide is reacted with 50% sulphuric acid in molar ratio of sulphuric acid to iron oxide of 4:1 at 115C, and atmospheric pressure.
The residence time in the reactor is 2 hours. The product solution contains typically 33% by weight of ferric sulphate and 11.0% HzSO4.
The process of this invention produces a ferric sulphate solution suitable for the treatment of waste water employing raw materials that are available as by-products of the metal industry.
EXAMPLE
To a stirred reactor was added on a continuous basis iron oxide (ferric oxide) at a rate of 9.6 kg. per hour, 93%
sulphuric acid at 38~ kg.per hour and water at 34.5 kg. per hour. The reactor temperature was maintained at 110C.
The re~idence time of the ingredients in the reactor was 2 hours. The resulting hot slurry overflowed from the reactor into a dissolution tank whére water was added at a rate of 11.4 kg. per hour. The contents of the dissolution tank were pumped through a heat exchanger and returned to the dissolution tank. The temperature of the contents of the dissolution tank was maintained at 25C. Residence time in the dissolution tank was 1 hour. The outflow from the dissolution tank, a slurry unreacted iron oxide, ferric sulphate solution and sulphuric acid, was transferred to a mixing tank where a polyacrylamide coagulent was added at a rate of 5 mg. per liter of slurry. About 9 minutes was taken for mixing the coagulant with the slurry. The slurry then overflowed to a coagulation tank where slow agitation was employed to facilitate the fcrmation of flocs 10651;20 of the unreacted iron oxide. Residence time in the coagulation tank was about 6 minutes. The coagulated slurry then over-flowed to a settler having an area of 0.2 square meters. The ferric sulphate product solution overflowed from the settler at a rate of 71 kg. per hour. The settler discharged slurry from the bottom at a rate of about 63 kg. per hour. The slurry from the bottom of the settler contained 15% suspended solids. The stream of slurry from the bottom of the settler was divided into two equal streams. One stream was recycled to the reactor, the other fed to a centrifuge. A ferric sulphate product solution was recovered from the centrifuge at a rate of 22 kg. per hour. Sludge from the centrifuge contained 49% solids and was discharged at a rate of 9.5 kg.
per hour.
Claims (3)
1. A process for the preparation of aqueous solu-tions of ferric sulphate comprising the steps of 1) reacting ferric oxide with 50% to 60% sulphuric acid in molar ratio of H2SO4 to ferric oxide of 3:1 to 6:1 at 105°C to 139°C and at atmospheric pressure for a period of 1 to 3 hours to form an aqueous slurry of sulphuric acid, un-reacted ferric oxide, solid ferric sulphate and ferric sul-phate solution, 2) adding sufficient water to the slurry to dis-solve all the solid ferric sulphate, while maintaining the slurry at 20°C to 60°C, 3) adding a coagulant to the slurry to coagulate the unreacted ferric oxide, 4) separating the product ferric sulphate solution admixed with sulphuric acid from the coagulant ferric oxide, 5) dividing the coagulant ferric oxide into two streams, 6) recycling one stream for mixing with additional ferric oxide and sulphuric acid in continuation of step (1), and 7) centrifuging the other portion to recover any further ferric sulphate solution and sulphuric acid as product, the residual solid sludge being recovered.
2. A process as claimed in Claim 1 wherein part of the sulphuric acid employed is waste sulphuric acid.
3. A process as claimed in Claim 1 wherein the coagulant is a polyacrylamide.
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA223,444A CA1065120A (en) | 1975-04-01 | 1975-04-01 | Manufacture of ferric sulphate |
| SE7602259A SE7602259L (en) | 1975-04-01 | 1976-02-24 | PREPARATION OF FERRY SULPHATE |
| FR7605776A FR2306169A1 (en) | 1975-04-01 | 1976-03-01 | PROCESS FOR PREPARING AQUEOUS SOLUTIONS OF FERRIC SULPHATE |
| NL7602720A NL7602720A (en) | 1975-04-01 | 1976-03-16 | PREPARATION OF FERRISULPHATE. |
| DE19762611313 DE2611313A1 (en) | 1975-04-01 | 1976-03-17 | PROCESS FOR THE PRODUCTION OF IRON (III) SULPHATE |
| GB12884/76A GB1527265A (en) | 1975-04-01 | 1976-03-31 | Manufacture of ferric sulphate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA223,444A CA1065120A (en) | 1975-04-01 | 1975-04-01 | Manufacture of ferric sulphate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1065120A true CA1065120A (en) | 1979-10-30 |
Family
ID=4102689
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA223,444A Expired CA1065120A (en) | 1975-04-01 | 1975-04-01 | Manufacture of ferric sulphate |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1065120A (en) |
| DE (1) | DE2611313A1 (en) |
| FR (1) | FR2306169A1 (en) |
| GB (1) | GB1527265A (en) |
| NL (1) | NL7602720A (en) |
| SE (1) | SE7602259L (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2173144A (en) * | 1936-03-31 | 1939-09-19 | Monsanto Chemicals | Method of preparing normal ferric sulphate |
| US2252332A (en) * | 1939-11-29 | 1941-08-12 | Tennessee Corp | Process of making ferric sulphate |
| DE2308467A1 (en) * | 1973-02-21 | 1974-09-05 | Metallgesellschaft Ag | Ferric sulphate prodn. from oxide and sulphuric acid - in fluidised suspension using oleum as reaction initiator, for economical flocculants |
-
1975
- 1975-04-01 CA CA223,444A patent/CA1065120A/en not_active Expired
-
1976
- 1976-02-24 SE SE7602259A patent/SE7602259L/en unknown
- 1976-03-01 FR FR7605776A patent/FR2306169A1/en active Granted
- 1976-03-16 NL NL7602720A patent/NL7602720A/en not_active Application Discontinuation
- 1976-03-17 DE DE19762611313 patent/DE2611313A1/en active Pending
- 1976-03-31 GB GB12884/76A patent/GB1527265A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2611313A1 (en) | 1976-10-21 |
| NL7602720A (en) | 1976-10-05 |
| GB1527265A (en) | 1978-10-04 |
| SE7602259L (en) | 1976-10-02 |
| FR2306169A1 (en) | 1976-10-29 |
| FR2306169B1 (en) | 1980-05-09 |
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