DESC:4. DESCRIPTION

Technical Field of the Invention

This invention relates to application of hydrodynamic cavitation phenomenon through multiple geometric unique stator -rotor configurations of the reactor for the purpose of sustainable biomass pre-treatment, delignification of cellulose pulp and valorization into different value-added products.

Background of the Invention

India is an agriculture based country and Indian economy is significantly dependent on agricultural growth. A vast majority of land is used for farming and a wide range of crops are cultivated in its different agro-ecological regions. On an average, there is a production of nearly 90-95 million tons (Mt) of wheat, 100-110 Mt of rice, 20-25 Mt of maize, 15-25 Mt of millets, 300-400 Mt of sugarcane, 5-10 Mt of fiber crops (Jute, Mesta, Cotton), 10-20 Mt of pulses and 30.0 Mt of oil seeds crops every year. As a natural consequence, a huge amount of crop residues (approximately 500-550 Mt) are also produced per year in the country both on-farm and off-farm.

Open field burning of surplus agro-residues by farmers (2.5 million farmer) in India is causing emissions of GHG and the productions of CH4 and N2O. As per a report, it is increased about 8.88% from 1997-98 to 2006-07. Although Govt. has taken several alternative initiatives those come with own share of problems such as, offering Happy Seeder - a machine mounted on a tractor, which removes the paddy straw while simultaneously sowing wheat for the next harvest. However, this machine along with a tractor costs nearly $15,000 which is certainly not affordable by most of the farmers. Another potential option is the use of bio-decomposer which turns crop residue into manure in 15 to 20 days. But mostly the farmers don't have so much time between crops. Alternatively, valorization of such bio-waste for the production of green fuels, chemicals and other commodity products is a very common practice owing to their massive potential to replace the presently dominated petrochemical based products. However, the processing of biomass to such products require several unit operations and treatment methodologies with higher economics and additionally with noticeable footprints on the environment that has curbed their appropriate commercialization. With this motivation, a new approach of biomass pre-treatment and conversion into various value-added products using hydrodynamic cavitation assisted Cavi-pulping reactor has been presented in this innovation.

Hydrodynamic cavitation (HC) is a versatile process technology tool with potential for application in different areas including delignification of biomasses, environmental, food processing, and biofuels production with substantial reduction in the treatment time, reduction in the chemical consumption and/or operating/reaction temperature from 150–180°C to ambient conditions. Moreover, it has the capability to substantially reducing the chemical consumption.

In order to utilize all these advantages of the cavitation phenomenon, the present invention relates to the design and development of a Cavi-pulping reactor based on hydrodynamic cavitation phenomenon for processing the crop residue to segregate the lignin and silica of the biomass (rice straw has rich silica content) from the cellulose pulp. Subsequently, the separated components would have separate commercial value for conversion into different value-added products. The proposed technology works at lower energy, enhanced mass transfer and chemical reaction rates as compared to the conventional chemical intensive, high yield of the product, less operating cost, easy to scale-up.

Brief Summary of the Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

It is an object of the invention to construct the Cavi pulping reactor for valorization of bio mass.

It is yet another object of the invention to pass the biomass in the form of slurry through cavitation zone where each particle fully experiences cavitational effect.

It is yet another object of the invention to extract valuable components of biomass effectively with high yield.

According to an aspect of the present invention, a hydrodynamic cavitation based cavi-pulping reactor system for biomass valorization is disclosed. The reactor system accepts biomass in the form of slurry through a cavitation zone continuously where each particle fully experiences the cavitational effect.

In accordance with the aspect of the present invention, the reactor system enables formation of gas vapour bubbles from the gas nuclei inherently present in the liquid medium due to rapid changes of pressure in the liquid medium leading to the formation of small vapour-filled cavities from the dissolved gas in the liquid, in places where the pressure is relatively low (less than the vapour pressure of the liquid).

In accordance with the aspect of the present invention, the liquid is allowed to pass through geometric flow constriction, a number of micro-bubbles (vapor cavities) are formed due to a sudden decrease in pressure below the vapor pressure of the liquid.

In accordance with the aspect of the present invention, the said micro-bubbles collapse due to slowed flow and pressure recovery. This bubble collapse is strong enough to generate localized ‘‘hot spots”.

In accordance with the aspect of the present invention, the said hotspots are formed with transient temperatures of about 10,000K, and pressure of about 1,000 atm, which induces chemical and physical transformations.

In accordance with the aspect of the present invention, the said cavitational effect results in the effective extraction of valuable components of the biomass at ambient condition with high yield.

In accordance with the aspect of the present invention, the technology developed is applied for multiple purposes as:
• Delignification of biomass for separation of cellulose-hemicellulose pulp
• Production of nano-silica

Further objects, features, and advantages of the invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

The objectives as described above as well as the uniqueness of the proposed technology along with its advantages can be better appreciated by referring to the following illustrative and non-limiting detailed description of the present invention along with the following schematic diagrams, wherein:

Figure 1A, 1B and 1C illustrate the schematics of the cavitation generating rotating units with multiple geometric configurations according to the embodiment of the invention.

Figure 2 illustrates the block diagram of the stator-rotor assembly and the designed reactor for the intended processing of biomass, according to the embodiment of the invention.

Figure 3 illustrates the schematic diagram representing multi-barrier approach to convert waste biomass to value-added products using the Cavi-pulping reactor according to the embodiment of the invention.

Figure 4 illustrates the pathway for generating nano-sized precipitated silica from rice husk ash as the biomass source since it has a high silica content (>70%).

Detailed Description of the Invention

It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The use of “including”, “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. Further, the use of terms “first”, “second”, and “third”, and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.

According to an exemplary embodiment of the present invention, a hydrodynamic cavitation based cavi-pulping reactor system for biomass valorization is disclosed. The reactor system accepts biomass in the form of slurry through a cavitation zone continuously where each particle fully experiences the cavitational effect.

In accordance with an exemplary embodiment of the present invention, the cavitating reactor unit comprises a stator-rotor based assembly with different geometric configurations including cylindrical stator-rotor assembly with multiple indentations made on the rotor surface (Fig.1A), conical shaped rotating unit with multiple holes on the surface (Fig.1B) and vortex shaped flow assembly (1C).

In accordance with an exemplary embodiment of the present invention, the rotating motion and the indentation made on the surface causes the pressure of the liquid to suddenly drop and create cavitation bubbles which on collapse in the downstream side creates the treatment condition. The rotating cavitation reactor unit is placed inside a closed container where the biomass slurry, undergoes the treatment and leaves through an outlet pipe and proceed to further treatment step.

In accordance with an exemplary embodiment of the present invention, the tracking of temperature inside the chamber at ambient condition, a temperature sensor is there surrounding the cavitation chamber. The cavitation reactor set up made of a material of construction of stainless steel with flow geometries for generating the cavitation bubbles installed in a closed container, a shaft and motor for rotating the cavitator, a slurry pump for re-circulating the liquid, inlet and outlet pipes, temperature sensors and pressure gauges at the upstream and downstream sides of the cavitation unit and flow meters. After treatment, the discharge or outlet pipe is connected to collect the treated biomass slurry.

In accordance with an exemplary embodiment of the present invention, the Cavi-pulping has advantages that it is easy to scale up, compact and operate at ambient temperature. The treated liquid then goes for further processing to get the ultimate product based on the raw material and end product requirement. The technology has potential to be applicable for processing of various agro-based biomass with around 10-15% reduction in overall cost and can be easily scaled up.

Fig.1A illustrates the rotor with specified indentations with each indentation having a diameter of 10 mm and depth of 18 mm equidistantly located around the circumference. The maximum speed of the rotor was 3500 rpm which was coupled with a motor (gear assembly) that was controlled by a variable frequency drive (VFD: ABB: ACS 560-01-062A-4). The gap between the rotor and the stator was kept fixed at 1.5 cm. Additionally, the opposite ends of the rotor has been made serrated with a matching stator disc with equal number of teeth grooves arranged on the surfaces of rotor and stator keeping the axial distance between the top of the teeth as low as possible (~10 mm) with an intention to avoid the mechanical erosion and other probable damages caused by bubble disruption.

Fig.1B illustrates the unit has a conical shaped stator-rotor unit where multiple holes are grooved on the rotor surface for creating pressure drop with keeping the gap between stator-rotor fixed at 1.5 cm. Fig.1C illustrates the unit has a vortex based stator-rotor flow assembly.

Fig.2 illustrates the entire stator-rotor configuration-based reactor for the intended processing of biomass. It carries a rotor with indentations made on the surface (1) placed inside a closed chamber (stator) (2) and the assembly is kept in horizontal position. The biomass in the form of slurry enters to the cavitation reactor through an inlet pipe (3). A flow meter (4) and a pressure gauge (5) are fixed at the inlet point to know the flow rate and pressure of the liquid at upstream side. A rotating shaft (6) is attached with the rotor. The entire stator-rotor assembly is placed inside one cooling jacket (7) with temperature sensor (8) attached to it to maintain the temperature at ambient. Post treatment, the processed biomass flows out of the chamber through an outlet pipe (9) where another set of pressure gauge (10) and flow meter (11) have been provided for the downstream side. The biomass then goes directly for final processing step depending on the end product requirement. The same reactor can be used for multiple biomass processing and easy to scale-up.

Fig.3 illustrates the scheme of multi-barrier approach to convert waste biomass in to value-added products. Different waste crop residues can be processed in the designed reactor using hydrodynamic cavitation to separate the cellulose-hemicellulose from the lignin, silica etc. While, biomass straws and stovers are easily available and low-cost sources of fodder for feeding ruminant animals meant for milk or meat production, the presence of silica in some of the crops make the them indigestible for the animals. Also, the presence of lignin at the outer layer of cellulose-pulp is another barrier for better digestion and providing good nutrition to the animals, hence need a pre-treatment. The de-lignified biomass can be used for producing high quality compound animal fodder through addition of necessary supplementary nutrients. Also, the cellulose-pulp can be used for making other commodity products such as papers, table ware having high demand as well as for other purposes. From the separated lignin, various value-added products such as concrete additive, adhesive can be prepared. Since, various crop residue such as rice husk, wheat-based biomass are rich sources of silica (lignocellulose (72-85 wt %) and silica (15-28 wt %)), silica can also be precipitated from the separated lignin to synthesize silica nanoparticles using hydrodynamic cavitation process.

Fig. 4 illustrates the pathway for synthesizing silica nanoparticles from rice husk ash as the biomass source. The silica was extracted from the rice husk ash in the form of sodium silicate (Na2SO3) through NaOH digestion in the designed hydrodynamic cavitation reactor at ambient condition. The extracted silica was then separated from the solid residue using a vacuum filter where the solid residue can be dried and used as the biochar. The precipitation of silica from the sodium silicate was carried out by purging CO2 gas into the second cavitation reactor which simultaneously creates the mechanical attrition or shear force to form nano sized precipitated silica.
Examples:
Study 1: Delignification of biomass
The proof of concept experiments were carried out in the proposed small-scale unit of 5 L tank capacity hydrodynamic cavitator using set quantity of chemicals (8-12% dry biomass) & water to biomass ratio (10- 14%).

The following observations were made:
• The reaction times substantially reduced from 3-4 h to 30-60 min
• The chemical consumption could be reduced by 15%.
• All the reactions were conducted at ambient temperature.
• Lignin analysis showed excellent delignification of 85-90%.
• Another significant factor was reduction in water consumption by almost 20%.
Compositional analysis of the processed biomass with and without alkali addition is shown in Table 1.
Exp No Biomass to Water ratio (solid loading) % alkali addition on dry biomass basis %Lignin in
Pre-treated straw Cellulose Hemi-cellulose
Geometry 1 (FIG 1A)
1 1:8 0 13.47 36.17 22.40
2 1:8 7 7.13 43.42 21.52
3 1:8 8 6.88 46.75 19.22
Geometry 2 (FIG 1B)
1 1:8 0 11.85 37.21 24.2
2 1:8 7 6.23 46.36 19.5
3 1:8 8 5.52 45.7 17.35
Geometry 3 (FIG 1C)
1 1:8 0 14.45 35.64 24.83
2 1:8 7 7.3 42.72 17.68
3 1:8 8 4.81 44.32 18.4
Study 2: Production of nano-silica from biomass
Many lignocellulosic biomasses are rich sources of silica and among them, rice husk is one of the most well-known for its high silica contents (lignocellulose (72-85 wt %) and silica (15-28 wt %)). The objective was to obtain high grade nanosilica as a sustainable source of production from the rice husk in bulk volume. The invented technology here utilizes CO2 gas for the precipitation step in the process replacing the use of mineral acids for precipitating silica, which also generates wastewater streams during precipitation.

Initial proof of concept study was carried out for the preparation of nano-silica using the invented technique with geometric configuration 1 (FIG 1A) of the stator-rotor assembly at 4 kg scale of rice husk ash and around 89% yield was obtained.

Rice husk ash properties used
? Silica content :76.50%
? Metal impurity content: 3.1%
? Tapped density: 0.48 g/ml
? Carbon content: 20.4%
? XRD: Amorphous

Silica properties obtained
? Process yield:89%
? Surface area: 150 m2/g
? Purity: = 98%
? Particle size: 76 nm
? Average pore diameter: 8 nm
? Density: 0.24 g/ml
? XRD: Amorphous

It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.

One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.
,CLAIMS:
5. CLAIMS
I/We claim
1. A hydrodynamic cavitation reactor system with stator-rotor geometric configuration for biomass valorization, comprises of:
a rotor (1), a motor, a shaft (6), a closed container (2), a temperature sensor (8), a cooling jacket (7), a slurry pump, a set of pressure gauges (5, 10), a set of control valves, flow meters (4, 11), inlet (3) and outlet (9) pipes;
the said motor is used to induce rotating motion to the reactor;
the shaft (6) is attached to the said motor for engaging the rotor (1) assembly to rotate with a maximum speed of 3500 rpm;
the entire rotating unit is placed inside a closed container for treating biomass slurry;
the said temperature sensor (8) inside the cavitation chamber used to track temperature in ambient conditions;
the said cooling jacket (7) is used to surround the reactor unit for temperature control;
the set of pressure gauges (5,10), flow meters (4,11) and control valves are used to track the pressure and flow created inside the reactor unit;
the slurry pump is used to recirculate the slurry liquid in the cavitation chamber;
the inlet pipe (3) is used for biomass entry and outlet pipe (9) is used for discharge;
Characterized in that
the said rotor (1) surface is made of different indentations with solid geometry;
the rotating motion of the said rotor (1) and indentations present on the rotor (1) surface creates sudden pressure drop leading to create cavitation bubbles;
the indentations on the surface of rotor (1) are of diameter 10 mm and depth of 18 mm equidistantly located around the circumference.

2. The system as claimed in claim 1, wherein the system provides multiple ways of biomass valorization at ambient condition in a sustainable way.

3. The system as claimed in claim 1, wherein the system provides a fast, sustainable way for delignification of biomass and separating the cellulose pulp.

4. The system as claimed in claim 1, wherein the system provides a sustainable way of producing Nano silica using the biomass.

5. The system as claimed in claim 1, wherein the system provides a sustainable way of agro-residue valorization alternative to stubble burning.

6. The system as claimed in claim 1, wherein the system is capable of reducing the average biomass processing time from 3-4 hours to 30-60 min.

7. The system as claimed in claim 1, wherein the system reduces the chemical consumption during process substantially.

8. The system as claimed in claim 1, wherein the system reduces amount of water consumption significantly.

9. The system as claimed in claim 1, wherein the system is adapted to be scaled up to bigger capacities.

10. A method of biomass valorization using the hydrodynamic cavitation reactor system having a stator-rotor geometric configuration, comprises steps of:
passing biomass in form of slurry through a cavitation zone;
creating a rapid change in pressure in liquid medium;
leading to formation of small vapour filled cavities from dissolved gases;
passing the liquid through geometric flow construction leading to creation of number of micro bubbles and collapse due to slow flow and pressure recovery;
collapsing create hotspots with temperatures of 10000 K, pressure of 1000 atm; and
extracting of valuable components of biomass at ambient condition with high yield.

6. DATE AND SIGNATURE

Dated this 21st July, 2022
Signature

(Mr. Srinivas Maddipati)
IN/PA 3124
Agent for applicant