FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
A Process For The Manufacture Of Sulfur Dioxide, Sulfur Trioxide, Sulfuric Acid, And Sulfonated Compounds
Navdeep Enviro and Technical Services Pvt. Ltd.
Indian company registered under Companies Act, 1956
Behramji Mansion, 4th floor, Sir. P. M. Road, Fort Mumbai 400001, Maharashtra
State, India
The following specification particularly describes the invention and the manner in which it is to be performed:

Field of Invention:
The invention relates to the manufacture of Sulfur Dioxide, Sulfur Trioxide, Sulfuric Acid, and Sulfonated compounds like, and not limited to, Methane Sulfonic Acid (MSA), Para Toluene Sulfonic Acid (PTSA), Sulfamic Acid. The invention particularly relates to a process for the manufacture of SO3 using a 'Cold Process' utilising unique properties of liquid SO2 and liquid SO3, which leads to a higher quality and economic efficiency in the production of SO3 than conventional processes, which further leads to higher quality and efficiency in the manufacture of the aforementioned derivative compounds. The invention is directed to reduced capital investment and utility cost, less plant area/size, and zero emission of sulfur dioxide.
Background:
The production of Sulfur Dioxide (SO2) is a basic intermediate step in the manufacture of high-grade Sulfur Trioxide (SO3) and Sulfuric Acid (H2SO4). It is also an intermediate step in the manufacture of sulfonated compounds like, and not limited to, Methane Sulfonic Acid (MSA), Para Toluene Sulfonic Acid (PTSA), Sulfamic Acid.
The conventional method for the production of SO2 is based on burning Sulfur in a high-temperature furnace based on the reaction S + O2 -> SO2. This reaction is highly exothermic and must be performed in a furnace able to withstand very high

temperatures. A higher-temperature in the furnace due to a higher concentration of
S02 in the outlet-gas mix requires costly high-alumina brick lining and repeated
maintenance costs.
The SO2 produced in this manner is then fed to a Converter that converts SO2 to
S03 with the aid of a catalyst. The SO3 is further purified to obtain SO3 as an end-
product, or is used in the manufacture of H2SO4, or is used for sulfonation to
produce the aforementioned sulfonation compounds. Typically, the sulfur burning
furnace is operated at 1050-11000C. At this temperature, only 9.5-11%
concentration by volume of SO2 in the output-gas mixture is achieved. There are
multiple downsides to this:
1. The low concentration of SO2 leads to lower production of SO3.
2. The SO2 output from the furnace is at about 11000C and must be cooled to a temperature appropriate for the catalyst in the SO3 converter. Vanadium Pentoxide is a commonly used catalyst that requires cooling to about 410-4300C. The need to cool the gas mixture by almost 7000C requires an elaborate arrangement requiring additional capital expenditure and operating costs. Also, the high incoming temperature precludes the use of a Cesium-activated catalyst that is more effective than the conventional Vanadium Pentoxide catalyst, but requires a lower operating temperature of 360-3800C.
3. The high operating temperature of the furnace reduces the furnace’s lifetime causing faster depreciation in the furnace’s economic value and additional

capital expenditures to replace the furnace frequently. In fact, higher concentrations of SO2 using this process can only be obtained by allowing the furnace to operate at higher temperatures since the reaction of Sulfur and Oxygen is highly exothermic. Higher than 11000C temperatures in the furnace are practically impossible, which precludes being able to obtain higher SO2 concentrations using this process.
Objects of the invention:
Accordingly, the present invention has the following objectives:
- To provide a high concentration of SO2 leading to higher level of concentration in the production of SO3.
- To produce SO2 at lower temperatures than conventional processes.
- To provide a process of manufacture of SO2 that will increase a furnace's lifetime.
- To apply the SO3 produced at higher concentrations as above in the economically and environmentally efficient manufacture of H2SO4 and the aforementioned sulfonation compounds.
List of Figures:
Figure 1 shows a block diagram for a typical conventional plant for manufacture
of H2SO4 acid/oleum/SO3

Figure 2 shows a flow diagram for part C of the process of invention as applied to
existing plants for manufacturing SO3 and H2SO4
Figure 3 shows a block diagram for parts A and B of the process of invention as
applied to existing plants for manufacturing SO3 and H2SO4
Figure 4 shows a block diagram for the process of invention as applied to new
plants for manufacturing SO3 and H2SO4
Summary of the invention:
The invention proposes a method or a process to produce SO2 by passing SO3 through liquid sulfur. The SO2 thus produced is then used as the sole source of SO2 for downstream processes. Alternatively, the SO2 thus produced is used to augment the SO2 produced using conventional processes of SO2 manufacture. The invention is applicable to a number of conventional processes for the manufacture of H2SO4 and liquid SO3 in particular as well as the aforementioned sulfonation compounds.
Description of the invention:
The invention discloses a process to manufacture SO3 and H2SO4using SO2,wherein the SO2 is manufactured in an innovative manner, as applied to existing plants for manufacturing SO3 and H2SO4 as well as new plants. Additional embodiments of the present invention disclose methods using SO2 that

is manufactured in an innovative manner to manufacture the aforementioned sulfonation compounds.
SO2,according to the present invention, is generated by passing SO3 through liquid Sulfur (S + 2SO3 -> 3SO2 - AH). This reaction is referred to as the “New Reaction” in the remainder of the present disclosure. The SO2 produced by means of the New Reaction is used as the sole source of SO2 or as an augmentation of the conventional steps of SO2 production outlined above. The new reaction is only mildly exothermic (in other words, generates less heat) compared to the burning of Sulfur. For the purpose of this disclosure, this component is called the “Cold SO2 Generator” or CSG. The SO2 so generated is used in the process of manufacturing SO3 or Sulfuric acid or the aforementioned sulfonation compounds. The New Reaction produces the SO2 at a lower temperature and at a higher concentration and pressure as described herein.
Augmentation of basic SO2 production and usage:
The liquid sulfur in the New Reaction is nominally maintained at 1400 C, which is also about the temperature at which SO2 is generated in the aforementioned CSG. In the augmented process (Figures 2 and 3), the generated SO2 is used in the following manner:
1. It is mixed with the SO2 from the furnace to increase the SO2 concentration that is input to the SO3 converter (the next stage). It is possible to increase

the concentration to 20-25%, which is ideal for the catalyst in the SO3 converter unit. 2. Since the SO2 generated in this manner is at about 1400C, its mixture with the SO2 from the furnace is used to cool the gas mixture. It is feasible to cool the gas mixture that is at a temperature in the range of about 950 oC to 1100 oC when coming out of the furnace to about 600-800 oC by mixing it with the SO2 from the aforementioned CSG. The lower SO2 mixture temperature is beneficial because it requires a less elaborate cooling system, and importantly, allows a Cesium-activated Vanadium Pentoxide catalyst to be used in the SO3 converter. As pointed out earlier, the Cesium-activated Vanadium Pentoxide catalyst lowers the operating temperature requirement to about 360-3800C as against the typical Potassium-activated Vanadium Pentoxide catalyst that requires a temperature of 410-4300C. The Cesium-activated Vanadium Pentoxide catalyst is desirable since it improves the efficiency of the SO3 converter. Using this process, higher steam generation is achieved than the existing Double Contact Double Absorption (DCDA) processes.
In effect, the combination of the higher SO2 concentration and the use of the Cesium activated catalyst enabled by the CSG unit enhances the overall efficiency of the Sulfur-to-SO3 subsystem.

A significant benefit of this scheme is that it can be retrofitted into an existing chemical plant for the manufacture of SO3 and H2SO4. The CSG unit is envisaged as an add-on into the existing system and the SO3 converter catalyst can be reloaded for the new parameters. In effect, the efficiency of an existing chemical plant can be improved at very low capital and operational cost.
When the SO3 converter is a part of an H2SO4 manufacturing chemical plant, the SO3 is nominally input into an Oleum Tower at 110-1300C. As a consequence of the lower converter temperature enabled by the aforementioned CSG unit, it becomes easier to achieve the required 110-1300C.
The process enhancement as described above can be utilized in various applications. Block diagrams for the various applications including the manufacture of H2SO4, and SO3 are shown in figures 2 and 3.
Process for H2SO4 Manufacture Using Liquid SO3
In a specific innovative application of the aforementioned process enhancement, the aforementioned CSG-based system for producing SO2 and SO3 is used to efficiently produce liquid SO3 with liquid SO2 as a solvent with further application in the manufacture of high-grade H2SO4. This process of manufacturing SO3 or H2SO4 according to the invention is divided into three parts:

Part A: Manufacturing liquid SO2 without compression or refrigeration Part B: Converting liquid SO2 into liquid SO3 using pure oxygen and
isothermal catalytic converter having cesium activated catalyst Part C: Conversion of SO3 to H2SO4 using demineralised water
Figure 3 shows a block diagram for application of the present invention for producing liquid SO3 (parts A and B described above) from an existing Sulfuric acid plant. The figure shows liquid SO3 and liquid sulfur plants that produce liquid SO2, which is then converted using a catalyst and dry air from the drying tower into SO3, which is passed through an Oleum tower after which it is dissolved into liquid phase producing H2SO4 and SO3 and H2S2O7.
The process of manufacturing SO3 according to the invention yields greater quantities of SO3 than existing plants. This is because in the process of the present invention, SO3 is first absorbed in H2SO4 and then condensed to yield gaseous SO3 at a higher yield.
Process for Manufacture of Sulfonation Compounds
In another innovative application of the aforementioned CSG-based process, the SO2 and SO3 produced therein is used in the augmentation of the manufacture of the aforementioned sulfonation compounds. A typical example of such process augmentation is to produce the sulfonation compound called Sulfamic Acid

(NH2SO2OH) by reaction of Ammonia (NH3) & SO3. The reaction carried out is NH3 + SO3 = NH2SO2OH, Δ H = -685.9 kJ/mol.
In some embodiments, the SO3 produced by the CSG and the SO3 converter is used with SO2 as a solvent for SO3. The heat of reaction is removed by evaporation of liquid SO2, which is injected in the reactor by a metering system after calculating the quantity based on the latent heat for the given temperature and pressure at which the reaction takes place. In order to transfer the product by overflow, additional liquid SO2 is provided to form a slurry, the amount of which will vary from case to case.
Isothermal converter:
This section describes the innovative application of the aforementioned CSG in the production of liquid (condensed) SO2, and pure liquid (condensed) SO3 with SO2 as a solvent. It has been described previously in the disclosure how the CSG can be used to augment SO2 production by injecting the CSG-produced SO2 into the SO2 stream generated by the Sulfur burning furnace. In a different pure-SO2 process, the SO2 produced by the CSG can be fed directly into the next stage (nominally the SO3 converter).
In an example of such a process, whereas the SO2 mixture in the earlier process is at about 1.1 Atmospheres, the pure-SO2 process would have SO2 at 6-8

Atmospheres (6-8 Kg/cm2) and 360 oC. Under such high pressure, it becomes possible to condense SO2 while leaving the residual SO2 in the gaseous state. As a result, the process enables the production of pure SO3 in liquid form. Note that this process is enabled by the production of pure SO2 at high pressure by the CSG unit. Given that this process produces pure SO3, its use in the manufacture of high-grade H2SO4 can lead to significant process simplifications. For example, it would become possible to avoid having to use an Oleum Tower altogether in such a process.
Detailed Plant Description
Figure 4 shows the process to manufacture SO3 and H2SO4 using a new plant. As shown in the figure it requires:
1. a metering system for liquid sulphur and pure oxygen, and
2. a metering system for gaseous SO2
3. a multipass catalytic converter and catalyst
4. a counter current heat exchanger
5. a thermic fluid system
6. a boiler at Pressure 10 kg/cm2with accessories and controls
7. an SO2 condenser
8. a dedicated cooling tower
9. a depressurising reactor (from 6-8 kgs to atmospheric pressure.)
10. a chilling plant
11. a condenser for sulphur dioxide using chilled brine
12. an alkali scrubber

As shown in Figure 4, the liquefied SO2 produced using the process of the present invention and pure oxygen are supplied to a condensation reaction chamber containing a catalytic converter which is kept at a pressure of 6-8 kg/cm2. This produces liquefied SO3 by condensation, which is later depressurised to yield liquid SO3. The remnants of the mixture of SO2 and O2 with traces of SO3 are recycled into the reaction chamber carrying catalyst. The catalyst is preferably Cesium-activated vanadium pentoxide.
It is evident that the invention has at least the following embodiments:
1. A process for the manufacture of SO2 in higher concentrations in chemical plants producing SO3, H2SO4, or sulfonation compounds, said process comprising the step of passing gaseous SO3 through liquid sulfur.
2. A process for the manufacture of SO2 as disclosed in embodiment 1, wherein said liquid sulfur is nominally maintained at 140 0C.
3. A process for the manufacture of SO2 as disclosed in embodiments 1 and 2, wherein said SO2 generated is augmented with SO2 generated by any other processes such as sulfur burning furnaces to generate an augmented mixture of SO2, said SO2 generated from the furnaces being at a temperature in the range of 950 oC to 1100 oC.
4. A process for the manufacture of SO2 as disclosed in embodiment 3 wherein the concentration of said augmented mixture of SO2 is further supplied to downstream converter units to convert gaseous SO2 into gaseous SO3, said

converter units being maintained at a temperature between 360 oC to 380 oC using thermic fluid for removal of exothermic heat.
5. A process for the manufacture of SO2 as disclosed in embodiment 4 wherein the augmented mixture of SO2 is at a temperature of 600-800 oC.
6. A process for the manufacture of concentrated SO3 based on the manufacture of concentrated SO2 as disclosed in embodiments 1 through 5 wherein said SO2 is reacted with O2 in an isothermal catalytic converter in the presence of a catalyst to produce said concentrated SO3.
7. A process for the manufacture of concentrated SO3 as disclosed in embodiment 6 wherein a Vanadium Pentoxide-activated catalyst is used.
8. A process for the manufacture of concentrated SO3 as disclosed in embodiment 6 wherein a Cesium-activated catalyst is used.
9. A process for the manufacture of H2SO4 wherein the SO3 generated from said isothermal catalytic converter as disclosed in embodiments 7 or 8 is introduced into an oleum tower to produce liquid SO3 as an intermediate step.
10. A process for the manufacture of H2SO4 as disclosed in embodiment 9 wherein said liquid SO3 is introduced to a glass-lined reactor where it is reacted with demineralized water to produce liquid H2SO4.
11. A process for the manufacture of H2SO4 as disclosed in embodiment 10 wherein thermic fluid is used as a coolant for said glass lined reactor.
12. A process for the manufacture of liquefied SO2 using the gaseous SO2 manufactured in processes of embodiments 1 to 5, wherein said SO2 is liquefied

using condensation reaction carried out at room temperature and at a pressure of 6-8 atmospheres, and without further compression or refrigeration.
13. A process for the manufacture of liquefied SO3 using the liquid SO2 as produced in the process of embodiment 12, wherein said liquid SO2 is converted into pure liquid SO3 using pure O2 in the aforementioned isothermal catalytic converter.
14. A process for the manufacture H2SO4 wherein the liquid SO3 as obtained in the process of embodiment 13 is converted into H2SO4 using demineralised water.
15. A process for the manufacture of a sulfonation compound wherein the intermediates SO2 and SO3 used in the sulfonation process are manufactured using the processes as disclosed in embodiments 1 through 13.
16. A process for the manufacture of a sulfonation compound as claimed in claim 15, wherein liquid SO3 of process of embodiment 13 is added in a quantity of 0.1% to 5% (by weight) to liquid SO2 of claim 12.
17. A process specifically for the manufacture of Sulfamic Acid wherein the SO3 produced using the processes as disclosed in embodiments 1 through 13 is reacted with NH3.
While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above

without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. A process for the manufacture of SO2 in higher concentrations in chemical plants producing SO3, H2SO4, or sulfonation compounds, said process comprising the step of passing gaseous SO3 through liquid sulfur.
2. A process for the manufacture of SO2 as claimed in claim 1, wherein said liquid sulfur is nominally maintained at 140 0C.
3. A process for the manufacture of SO2 as claimed in claims 1 and 2, wherein said SO2 generated is augmented with SO2 generated by any other processes such as sulfur burning furnaces to generate an augmented mixture of SO2, said SO2 generated from the furnaces being at a temperature in the range of 950 oC to 1100 oC.
4. A process for the manufacture of SO2 as claimed in claim 3 wherein the concentration of said augmented mixture of SO2 is further supplied to downstream converter units to convert gaseous SO2 into gaseous SO3, said converter units being maintained at a temperature between 360 oC to 380 oC using thermic fluid for removal of exothermic heat.
5. A process for the manufacture of SO2 as claimed in claim 4 wherein the augmented mixture of SO2 is at a temperature of 600-800 oC.
6. A process for the manufacture of concentrated SO3 based on the manufacture of concentrated SO2 as claimed in claims 1 through 5 wherein said SO2 is reacted with O2 in an isothermal catalytic converted in the presence of a catalyst to produce said concentrated SO3.

7. A process for the manufacture of concentrated SO3 as claimed in claim 6 wherein a Vanadium Pentoxide-activated catalyst is used.
8. A process for the manufacture of concentrated SO3 as claimed in claim 6 wherein a Cesium-activated catalyst is used.
9. A process for the manufacture of H2SO4 wherein the SO3 generated from said isothermal catalytic converter as claimed in claims 7 or 8 is introduced into an oleum tower to produce liquid SO3 as an intermediate step.
10. A process for the manufacture of H2SO4 as claimed in claim 9 wherein said liquid SO3 is introduced to a glass-lined reactor where it is reacted with demineralized water to produce liquid H2SO4.
11. A process for the manufacture of H2SO4 as claimed in claim 10 wherein thermic fluid is used as a coolant for said glass lined reactor.
12. A process for the manufacture of liquefied SO2 using the gaseous SO2 manufactured in processes of claims 1 to 5, wherein said SO2 is liquefied using condensation reaction carried out at room temperature and at a pressure of 6-8 atmospheres, and without further compression or refrigeration.
13. A process for the manufacture of liquefied SO3 using the liquid SO2 as produced in the process of claim 12, wherein said liquid SO2 is converted into pure liquid SO3 using pure O2 in the aforementioned isothermal catalytic converter.
14. A process for the manufacture H2SO4 wherein the liquid SO3 as obtained in the process of claim 13 is converted into H2SO4 using demineralised water.

15. A process for the manufacture of a sulfonation compound wherein the intermediates SO2 and SO3 used in the sulfonation process are manufactured using the processes as claimed in claims 1 through 13.
16. A process for the manufacture of a sulfonation compound as claimed in claim 15, wherein liquid SO3 of process of claim 13 is added in a quantity of 0.1% to 5% (by weight) to liquid SO2 of claim 12.
17. A process specifically for the manufacture of Sulfamic Acid wherein the SO3 produced using the processes as claimed in claims 1 through 13 is reacted with NH3.