Title of Invention

"A PROCESS FOR THE PRODUCTION OF MAGNESIUM SULPHATE HEPTA-HYDRATE FROM INDUSTRIAL WASTE"

Abstract A process for the production of magnesium sulphate hepta-hydrate from the industrial waste by grinding and screening the industrial waste dust, neutralizing the above said industrial waste dust with 60-90% H2SO4 of strength ranging between 1-35N and water at the temperature in the range of 60-100°C followed by solid-liquid filtration to obtain the sludge, recovering magnesium sulphate hepta-hydrate by counter current washing of the above said sludge with water followed by vacuum crystallization at a temperature in the range of 10-60°C and recovering the crystals of the magnesium sulphate hepta-hydrate by separating the mother liquor by known method.
Full Text The present invention relates to a process for the production of magnesium sulphate hepta-hydrate from the industrial wastes. These wastes are generated during the manufacturing of magnesite refractories by calcining magnesite in rotary/shaft kiln. The present invention will be useful for manufacturing of magnesium sulphate hepta-hydrate which is used for manufacturing of quality magnesite bricks, micro-nutrient to tea and cotton growing areas, fire proofing compositions and as tanning agents etc.
A recent survey reveals that production from existing units for the manufacturing of magnesium sulphate hepta-hydrate and its growing demand of large industries in steel, chemicals, Pharmaceuticals etc. leaves a big gap in supply. The tea gardens in India consume magnesium sulphate to the tune of 4000-5000 Mt per annum and refractory industries more than 2000 Mt per annum for making special quality refractories in India.
Conventionally magnesium salts are produced from magnesite bearing minerals such as natural kieserite, langbeinite, brucite, seawater concentrates, natural brines, magnesite and dolomite. In the conventional commercial process (Kirk Othmer, Encyclopaedia of Chemical Technology 2nd Ed.,Vol.l2,page711-715) of producing magnesite sulphate, magnesium minerals are decomposed by heating at 850°C -900°C to magnesium oxide, sulphur dioxide (802) is absorbed in the slurry of magnesium oxide to form magnesium
bi-sulphate solution which is followed by aerial oxidation at 50-60°C in presence of metallic catalyst. The process is not economic besides the extensive purification to recover magnesium sulphate in pure form, for supplying heat energies for decomposition of mineral. The decomposition of mineral is, however, both an energy intensive and sensitive process.
In an another conventional method the magnesium sulphate is produced by method of double decomposition of gypsum and magnesium carbonate. The major disadvantages of the process is the reaction for producing magnesium sulphate being reversible and thus difficult to carrying it out to its completion unless magnesium sulphate is constantly removed from the system.
Reference may be made to US Patent no.4264570 here in the magnesium sulphate is produced by interacting ferrous sulphate with compounds including magnesium carbonate,
oxides and hydroxides. The step of inter reacting the starting reagents is conducted in water medium in the presence of carbon dioxide and is effected in the temperature range of 80-100°C. The major disadvantage of the process is not economically viable due to the raw material being costly. Besides, the purification of the magnesium sulphate is also very difficult.
The above mentioned process are for the production of magnesium sulphate. Under some controlled condition and in the presence of water magnesium sulphate hepta-hydrate (MgSO4.7H2O) is formed.
In the present invention the widely used magnesium chemical magnesium sulphate hepta-hydrate (MgSO4.7H2O) is produced from the industrial wastes generated from most of the refractory sections of the integrated iron and steel plants, refractory and cement industries manufacturing magnesite refractories, which have installed rotary/shaft kiln for calcination of magnesite mineral. These dust and fines are produced during the process of calcination of magnesite in the rotary/shaft kiln, when off gases are passed through cyclone for dust collection. These dust and fines are used for environment friendly economic process for the manufacture of the important chemical magnesium sulphate hepta-hydrate.
The main object of the present invention is to provide a novel process for the production of magnesium sulphate hepta-hydrate from industrial waste, which obviates the drawbacks as detailed above.
Another object of the present invention is to utilise the industrial waste generated during the manufacturing of magnesite refractories and thereby reducing the industrial pollution.
Still another object of the present invention is to provide a eco-friendly and economic process for the production of magnesium sulphate hepta-hydrate.
Accordingly, the present invention provides a process for the production of magnesium sulphate hepta-hydrate from the industrial waste which comprises grinding and screening the industrial waste dust having the following composition [MgO : 40-50%, CaO : 2-3%, FeO : 3-4%, SiO2 : 8-10%] to 60-80 mesh size, neutralizing the above said industrial waste dust with 60-90% H2SO4 of strength ranging between 1-35N and water at the temperature in the range of 60-100°C followed by solid-liquid filtration to obtain the sludge, recovering magnesium sulphate hepta-hydrate by counter current washing of the above said sludge with water followed by vacuum crystallization at a temperature in the range of 10-60°C and recovering the crystals of the magnesium sulphate hepta-hydrate by separating the mother liquor by known method such as herein described.
In an embodiment of the present invention, the sulphuric acid used is of analytical grade having concentration preferably in the range of 20-33N.
In yet another embodiment the magnesium sulphate hepta-hydrate recovered is in the range of 67-98%.
In still another embodiment the temperature used in neutralizing the industrial waste is preferably in the range of 50-80°C.
The invention is illustrated by the following examples which should not be construed to limit the scope of the present invention.
EXAMPLE 1
The MgO obtained from the 41 g industrial waste dust containing 40% MgO, 2% CaO, 3% Fe2O3 10% SiO2 neutralised with 70g of 60 % sulphuric acid (22N) and 42g of water in a steam jacketed stirred tank reactor under the temperature conditions of 60°C. This is followed by solid liquid separation by filtration, recovery of mag-sulph, hepta-hydrate by counter current washing of the sludge and by vacuum crystallisation of MgSO4,7 H2O at 50°C. The crystals were recovered by separating the mother liquor in a centrifuge The process was effective in achieving the yield of MgSO4,7 H2O of 80% i.e of about 80g.
EXAMPLE 2
The MgO obtained from the 35 g industrial waste dust containing 50% MgO, 2% CaO, 3% Fe2O3 10% SiO2 neutralised with 70g of 60 % sulphuric acid (22N) and 42g of water in a steam jacketed stirred tank reactor under the temperature conditions of 60°C. This is followed by solid liquid separation by filtration, recovery of mag-sulph, hepta-hydrate by counter current washing of the sludge and vacuum crystallisation of the MgSO4, 7 H2O at 50°C. The crystals were recovered by separating the mother liquor in a centrifuge. The process was very effective in achieving the yield of MgSO4, 7 H2O of 85% i.e. of about 85g. However the only draw back was that the process involved enormous amount of liquid handling due to the use of dilute sulphuric acid. Besides, it required a lead/glass lined reactor for the acid being below 67% is highly corrosive.
EXAMPLE 3
The MgO obtained from the 35 g industrial waste dust containing 50% MgO, 2% CaO, 3% Fe203, 10% SiO2 neutralised with 60g of 70 % sulphuric acid (26N) and 42g of water in a steam jacketed stirred tank reactor under the temperature conditions of 60°C. This is followed by solid liquid separation by filtration, recovery of mag-sulph, hepta-hydrate by counter current washing of the sludge and vacuum crystallisation of the MgSO4,7 H2O at 50°C. The crystals were recovered by separating the mother liquor in a centrifuge The
process was more effective in achieving the yield of MgSO4,7 H2O of 90% i.e of about 90g. It, however, did require a lead/glass lined reactor which is rather an expensive material of construction for handing dilute sulphuric acid.
EXAMPLE 4
The MgO obtained from the 35 g industrial waste dust containing 50% MgO, 2% CaO, 3% Fe2O3, 10% SiO2 neutralised with 50g of 80 % sulphuric acid(29N) and 50g of water in a steam jacketed stirred tank reactor under the temperature conditions of 60°C . This is followed by solid liquid separation by filtration, recovery of mag-sulph, hepta-hydrate by counter current washing of the sludge and vacuum crystallisation of the MgSO4,7 H2O at 50°C. The crystals were recovered by separating the mother liquor in a centrifuge The process was most effective in achieving the yield of MgSO4,7 H2O of 96% i.e of about 96g and it did not require any special material of construction for the reactor. Mild steel sufficed the purpose.
EXAMPLE 5
The MgO obtained from the 35 g industrial waste dust containing 50% MgO, 2% CaO, 3% Fe2O3, 10% SiO2 neutralised with 45g of 90 % sulphuric acid(33N) and 50g of water in a steam jacketed stirred tank reactor under the temperature conditions of 60°C . This is followed by solid liquid separation by filtration, recovery of mag-sulph, hepta-hydrate by counter current washing of the sludge and vacuum crystallisation of the MgSO4,7 H2O at 50°C. The crystals were recovered by separating the mother liquor in a centrifuge The process was although effective in achieving the yield of MgSO4,7 H2O of 86% i.e of about 86g , which is rather less than that is achieved in the previous example 5.
The main advantages of the present invention are :
1. The present invention uses industrial wastes material as raw material and it thus minimises the waste generation.
2 The process helps produce a valuable chemical which can serve as the starting
material for other Magnesium chemicals.
3 The process is environmentally friendly and free of any waste generation.
4 The raw material being the waste from the Magnesite calcination kiln it completely
avoids the input of energy for production of MgO
5 There is no need of extensive purification to recover magnesium sulphate , hepta-
hydrate.




We claim :
1. A process for the production of magnesium sulphate hepta-hydrate
from the industrial waste which comprises grinding and screening the
industrial waste dust having the following composition [MgO : 40-50%,
CaO : 2-3%, FeO : 3-4%, SiO2 : 8-10%] to 60-80 mesh size,
neutralizing the above said industrial waste dust with 60-90% H2SO4 of
strength ranging between 1-35N and water at the temperature in the
range of 60-100°C followed by solid-liquid filtration to obtain the
sludge, recovering magnesium sulphate hepta-hydrate by counter
current washing of the above said sludge with water followed by
vacuum crystallization at a temperature in the range of 10-60°C and
recovering the crystals of the magnesium sulphate hepta-hydrate by
separating the mother liquor by known method such as herein
described.
2. A process as claimed in claims 1-2 wherein the sulphuric acid used is
of analytical grade having concentration preferably in the range of
20-33N.
3. A process as claimed in claims 1-2 wherein the temperature used in
neutralizing the industrial waste is preferably in the range of 50-80°C.
4. A process for the production of magnesium sulphate hepta-hydrate
from the industrial waste substantially as herein described with
reference to the examples and drawing accompanying this
specification.

Documents:

1002-del-2002-abstract.pdf

1002-del-2002-claims.pdf

1002-del-2002-correspondence-others.pdf

1002-del-2002-correspondence-po.pdf

1002-del-2002-description (complete).pdf

1002-del-2002-drawings.pdf

1002-del-2002-form-1.pdf

1002-del-2002-form-2.pdf

1002-del-2002-form-3.pdf

1002-del-2002-form-4.pdf


Patent Number 195823
Indian Patent Application Number 1002/DEL/2002
PG Journal Number 41/2007
Publication Date 12-Oct-2007
Grant Date 08-Oct-2007
Date of Filing 30-Sep-2002
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 SWATANTRA PRAKASH NATIONAL METALLURGICAL LABORATORY, JAMSHEDPUR, JHARKHAND, INDIA.
PCT International Classification Number C01F 5/40
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA