DESC:TECHNICAL FIELD
[001] The present invention relates to a system and a process for producing ethanol in batches. The present invention further discloses a digester for pre-treatment and digesting of a raw material in batches.
BACKGROUND
[002] Generally, it is known that the world's dependency on fossil fuels has caused unfavourable effects, including lessening of crude oil reserves, decreasing air quality, rising global temperatures, unpredictable weather changes, and so on. As the effort to promote sustainability and independency from fossil fuels, ethanol is now favoured as the blend of fossil petrol or diesel substitutes.
[003] However, first-generation ethanol production is severely restricted due to the use of edibleness of the raw material, which is primarily used for feeding purposes. Such an impractical gap in first-generation ethanol production is fulfilled by second-generation (2G) ethanol production, which employs non-edible feedstock sourced from agriculture residues and forestry wastes.
[004] Conventional systems and processes for manufacturing second-generation (2G) ethanol are continuous processes. However, conventional systems and processes have inherent limitations. Operational time in the conventional process employed by the conventional system is lengthy. It demands a larger reactor volume, which increases land occupation cost, land requirement and other associated manufacturing costs. Besides, such conventional processes require systems to be operated under very harsh operating parameters such as at very high temperatures and pressure. Further, the conventional systems are inefficient because steam supplied is inadequate for pre-treatment process and proper digestion of the raw material. Sufficient size reduction of biomass is therefore significantly difficult to achieve by the conventional systems and processes. Such known conventional systems and processes require additional units for physical/mechanical processing of raw materials, especially prior to enzyme treatment and predominantly require large supply of enzymes. Other shortcomings of the conventional systems and processes include dependency on enzyme suppliers, inefficient unloading of the pretreated biomass requiring very high pressure, excess consumption of water and unnecessary blockages of the biomass at the outlet line of a digester deployed in the conventional system. Further, such conventional system and process are ineffective in utilizing intermediaries and re-cycling residues of the raw material generated during the continuous operating processes of the system.
[005] Therefore, there is an unmet need for a system and process for producing ethanol and a digester that addresses one or more aforementioned problems.

SUMMARY
[006] Accordingly, an aspect of the present invention discloses a system for producing ethanol comprising a system for producing ethanol in batches, comprising a digester for pre-treating and digesting a directly loaded raw material along with water, said digester having: an inlet for loading the raw material into the digester; a helical agitator having a plurality of blades mounted across a length of the horizontal rod for uniformly mixing the raw material; a plurality of steam injection ports spaced apart along the length of the digester for continuous supply of steam into the raw material for complete pre-treatment and digestion of the raw material; and an outlet for unloading the digested material without blockage; an enzymatic hydrolysis unit interconnected with the outlet of the digester for receiving and treating the digested material with an enzyme; and a fermentation unit interconnected with the enzymatic hydrolysis unit for receiving and fermenting output from the enzymatic hydrolysis unit to obtain ethanol.
[007] According to another aspect, the present invention discloses a digester for pre-treatment of a raw material in batches, comprising a helical agitator having a plurality of blades mounted across a length of a horizontal rod for uniformly mixing the raw material, the horizontal rod is a centrally mounted continuously rotating rod extending throughout a length of the digester; and a plurality of steam injection ports spaced apart along the length of the digester at a top and a bottom circumferential surface of the digester for continuously supplying steam into the raw material for complete pre-treatment and digestion of the raw material.
[008] According to still another aspect, the present invention discloses a process for producing ethanol in batches, comprising the steps of: a) digesting including pre-treating a raw material in a digester at a temperature in the range of 110°C-200°C and pressure in the range of 5 to 10 bar pressure to obtain a digested material; b) treating the digested material with an enzyme in a hydrolyser at a temperature in the range of 40°C to 55°C and pH in the range of 4-6 to obtain free sugars and a first residue ; and c) subjecting said sugars to fermentation in a fermenter at a temperature in the range of 30°C to 40°C, and pH in the range of 4-6 to produce ethanol.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[009] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
[010] Figure 1 illustrates a schematic block diagram of a system for producing ethanol, according to an aspect of the present invention;
[011] Figure 2 illustrates a schematic cross-sectional front view of a digestor, according to another aspect of the present invention; and
[012] Figure 3 illustrates a process for producing ethanol, according to still another aspect of the present invention.
[013] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to the other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that reference signs are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
[014] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiment illustrated. Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Embodiments are provided to convey the scope of the present disclosure thoroughly and fully to a person skilled in the art. Numerous details are set forth relating to specific components to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
[015] In general, the present invention discloses a system for producing ethanol. The present invention also discloses a process for producing ethanol. The system includes a digester, a steam generation and supply unit, a water supply unit, an enzymatic hydrolysis unit, a fermentation unit, and a distillation unit.
[016] In an exemplary implementation of the present invention, the present invention discloses a digester for pre-treatment of a raw material. The digester may include for example a helical agitator with a plurality of blades. The digester may be horizontally mounted. The helical agitator may be mounted on a horizontal rod located centrally within the digester. Each said plurality of blades may include but not limited to a length of 2600 mm, a diameter of 1700 mm. The blades may include a pitch that includes but not limited to 430 mm. The helical blades may include a helix angle that includes but not limited to 25° having a thickness that includes but not limited to 100 mm. In the digester of the present invention, the helical stirrer of the plurality of blades aids in maintaining proper turbulence in the digester, leading to efficient solid liquid mixing by counter flow, maintaining the uniformity in all the operating parameters.
[017] With the teachings of the system, the process for producing ethanol, when compared to a digester with a normal stirrer that has an operation time of 4 hrs to complete the digestion and still is left with uncooked fibres, the helical stirrer in the digester of the present invention, includes an operation of 1.5 to 2 hrs approximately to complete the pre-treatment process with properly cooked fibres and obtaining uniform digested biomass. With the teachings of the present invention, due to the reduction in the digestion time, there is a significant improvement in the combined severity factor, thereby leading to the improvement of enzymatic hydrolysis. When compared to the conventional systems, digester and process, with the teachings of the system, process and digester of the present invention, the efficiency of ethanol manufacturing has improved to 55 to 65% from 35 to 45%. With the reduction in time cycle and the digestion time within the digester, the operating cost of the system have been reduced by 30 to 35% when compared with conventional systems, processes and digesters. With the teachings of the present invention, there is significant improvement in hydrolysis efficiency, using the same or small amounts of enzyme, thereby the output of the product has improved. Furthermore, the cost of production of ethanol may be 20-30% less as compared to existing processes . When compared to the conventional process or system, in the present invention all the effluents which are generated during the process are utilized and recycled. Hence, the process is complete zero liquid discharge (ZLD) and the byproducts such as xylose and arabinose generated during the process are effectively utilized in terms of value addition to the feedstock. In the system and process of the present invention, all operating parameters are at mild conditions compared to thermochemical process, operational and accidental risks are less in safety point of view. Further, process efficiencies at each stage are higher compared to conventional technologies. In the present invention, the "Second generation (2G) ethanol" obtained is processed using inedible resources as raw materials. This process does not compete for food resources and leads to reduced CO2 emissions. The "2G-sugar" obtained an intermediate in the process of the present invention may be used as a material for bio-based chemicals. The obtained ethanol is widely used as a fuel additive and as an engine fuel. Some forms of gasoline are known to contain up to 15 - 25% ethanol.
[018] The terminology used in the present disclosure is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. As used in the present disclosure, the forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated elements, units and/or components, but do not forbid the presence or addition of one or more other elements, components, and/or groups thereof.
[019] The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Accordingly, it should be apparent to those skilled in the art that the following description of the system, the process for manufacturing/producing ethanol and the digester referred in the description for the purpose of the understanding and nowhere limit the invention. The skilled person will be able to devise various structures and shapes of the digester, connections both of piping and electrical sensors, temperature, pressure, pH detectors, and intelligent communications controlled by a controller, and their maintenance at desired ranges that, although not explicitly described herein, embody the principles of the present invention. All the terms and expressions in the description are only for the purpose of understanding and nowhere limit the invention. Terms like plurality, first, second, third, larger, and smaller, angle, inclination, horizontal, parallel, central are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. Thus, while structure of the system, digester with desired configuration, shape, lengths, diameters, angles, inclination, angles, degrees, dimensions, have been disclosed, nowhere limit the invention, and are provided for understanding of the invention. It will be appreciated those of ordinary skill in the art that various changes and modifications of the embodiments manufactured with other design parameters and configurations as well and are not limited to those described herein above may be as per operational requirements by making necessary changes without departing from the scope of the invention.
[020] Referring to Figures 1-3 discloses a system (100), a raw material (110), a water supply unit (115), a digester (120), an inlet (122), an outlet (124), intermediaries (125), a centrally mounted horizontal rod (126), a helical agitator (128), a steam generation and supply unit (130), a plurality of parallel steam injection ports (135), an enzymatic hydrolysis unit (140), a first residue (145), a fermentation unit (150), a distillation unit (160), a second residue (165) ethanol (170) and a process (200).
[021] The system (100), the process (200) for manufacturing/producing ethanol and the digester (120) shall now be described in detail herein. Referring Figure 1, according to a first exemplary aspect of the present invention, illustrates a system (100) for manufacturing/producing ethanol. The system (100) comprises a water supply unit (115) for supplying water to a raw material (110). The ethanol manufacturing system (100) of the present invention includes a pre-treatment unit. The pre-treatment unit for example may comprise a digester (120) for pre-treating and digesting a directly loaded raw material (110) along with water. The system (100) further may comprise a steam generation and supply unit (130) coupled to the plurality of steam injection ports (135) of the digester (120) for continuous supply of steam into the raw material (110) for complete pre-treatment and digestion. The system (100) also includes an enzymatic hydrolysis unit (140) interconnected with the outlet (124) of the digester (120) for receiving the pre-treated and digested material (110) for treatment with an enzyme and a fermentation unit (150) interconnected with the enzymatic hydrolysis unit (140) for receiving output from the enzymatic hydrolysis unit (140) and fermenting the output to obtain ethanol (170).
[022] Referring Figure 2, according to a second exemplary aspect, the present invention discloses a digester (120) for pre-treatment of a raw material (110). The digester (120) may comprise an inlet (122) for directly loaded raw material (110) along with water and an outlet (124) for unloading the pre-treated and digested material (110) without blockages in the outlet (124). The digester (120) for example according to an embodiment may include but is not limited to having a horizontal rod (126) extending throughout a length of the digester (120). The digester (120) may be mounted horizontally and includes a helical agitator (128). The horizontal rod (126) for example is a centrally mounted continuously rotating rod mounted within the digester (120). The digester (120) may further comprise the helical agitator (128) having a plurality of blades mounted across a length of the horizontal rod (126) for uniformly mixing the raw material (110) with water. Each of the plurality of blades have a surface area equal to width of the digester (120) for uniformly mixing the raw material (110) with the plurality of blades of the helical agitator (128) throughout the length of the digester (120). The digester (120) includes plurality of parallel steam injection ports (135) spaced apart along the length of the digester (120) at a top and a bottom circumferential surface of the digester (120) for continuous supply of steam into the raw material (110) for complete pre-treatment and digestion of the raw material (110). The inlet (122) and outlet (124) may be located parallel and opposite to each other at a top and bottom outer circumferential surface of the digester (120).
[023] In an exemplary embodiment, referring to Figures 1 and 2, the steam generation and supply unit (130) according to the exemplary embodiment is connected to the digester (120) at plurality of inlets (135) throughout length of the digester (120) for continuous supply of steam to the raw material (110). The water supply unit (115) supplies water to the raw material (110) loaded in the digester (120). In the present invention, the raw material (110) is processed in batches to produce ethanol. The raw material (110) is directly loaded in batches into the digester (120). The configuration and locations of steam inlets (135) on the digester (120) ensure that the raw material (110) is completely and efficiently pre-treated and digested for homogenous treatment with enzyme to enable efficient generation of ethanol as output of the system (100). The digester (120) of the pre-treatment unit of the system (100) of the present invention directly converts whole input raw material (110) and provides a complete hydrolysable digested material (110) as an output for efficient processing and generation of ethanol. Therefore, the present invention does not require and completely avoids the requirement of additional physical/mechanical processing for example size reduction or any physical/mechanical processing and de pithing of the raw material before loading into the digester (120) for pre-treatment. This configuration of the system in accordance with the present disclosure saves considerable energy and operating time of the system (100) and consequently reduces the operating costs. Also, in the pre-treatment unit of the system (100) of the present invention there is no requirement of any chemical addition and only steam (130) is supplied continuously for pre-treatment and digestion of the raw material (110).
[024] According to the exemplary embodiment, the helical agitator (128) of the digester (120) uniformly mixes water and raw material (110) such that the injected steam at desired locations (135) of the digester (120) penetrate continuously into the raw material and pre-treats, digests the raw material (110) impacting in breakage of bonds of the raw material (110) resulting into efficient pretreatment.
[025] According to the exemplary embodiment, the operating parameters of the digester (120) of the system (100) of the present invention have pressure in the range that includes but not limited to 6 to 9 bar pressure, and temperature in the range that includes but not limited to 150 to 190 ° C. The raw material (110) is pre-treated and digested in the digester (120) for a duration of 90 to 150 minutes.
[026] According to the exemplary embodiment, the operation of the system (100) includes passing of the pre-treated and digested material into the enzymatic hydrolysis unit (140) of the system (100) of present invention. Unlike conventional systems, in the present invention, since the raw material (110) is effectively pre-treated and digested, there is only a minimal loading of commercially available enzyme is required in the range that includes but not limited to for example 10 to 20 mg of enzyme per gm of pre-treated and digested material into the enzymatic hydrolysis unit (140) of the system (100). The enzymatic hydrolysis unit (140) of the system (100) is optimized and operated at very mild conditions such as the pressure is for example atmospheric, and temperature is for example in the range that includes but not limited to 45 to 55 ° C. In the enzymatic hydrolysis unit (140) of the system (100) of present invention pH is in the range that includes but not limited to 4.8 to 5.2. According to the exemplary embodiment, the hydrolysis time in the enzymatic hydrolysis unit (140) of the system (100) of present invention to obtain the maximum output from the pre-treated material is for example in the range that includes but not limited to 48 to 72 hrs. According to the exemplary embodiment, the output of the enzymatic hydrolysis unit (140) of the system (100) of present invention is for example in the range that includes but not limited to 60 to 75% converted pre-treated and digested material.
[027] According to the exemplary embodiment, the operation of the system includes passing the output from the enzymatic hydrolysis unit (140) of the system (100) of present invention into the fermentation unit (150) to obtain the ethanol (170) by using the commercially available yeast. The output from the fermentation unit (150) is passed into the distillation unit (160) (optional) to obtain the final distilled output of ethanol (170). The operating parameters of the fermentation unit (150) are for example atmospheric pressure in the range that includes but not limited to 32 to 35 ° C temperature and pH in the range that includes but not limited to 4.5 to 5.5.
[028] The system (100) for manufacturing/producing ethanol in accordance with the present disclosure provides ease in unloading of the pretreated and digested biomass without requiring very high pressure, or excess consumption of water and obviates unnecessary blockages of the biomass at the outlet line of the digester. According to the exemplary embodiment, the intermediaries (125) and the first and second residues (145, 165) that are obtained at the digester (120), enzymatic hydrolysis unit (140), fermentation unit (150) and/or distillation unit (160) are effectively utilized and re-cycled in the system (100) of present invention in the form of materials for other industrial products and also for example for co-generation as steam and power. According to the exemplary embodiment, the system (100) of the present invention reduces the CO2 emissions. The output second generation ethanol (170) obtained may be widely used as a fuel additive and as an engine fuel. The output ethanol (170) may also have application in the form of gasoline in the range that includes but not limited to 15 - 25% ethanol.
[029] Referring to Figure 3, in a still another exemplary aspect, the present invention discloses a process (200) for producing/manufacturing second generation ethanol in batches. The process (200) comprises the steps of: a) digesting including pre-treating a raw material (110) in a digester (120) at a temperature in the range of 110°C-200°C and pressure in the range of 5 to 10 bar pressure to obtain a digested material; b) treating the digested material with an enzyme in a hydrolyser (140) at a temperature in the range of 40°C to 55°C and pH in the range of 4-6 to obtain free sugars and a residue (145); and c) subjecting said sugars to fermentation in a fermenter (150) at a temperature in the range of 30°C to 40°C, and pH in the range of 4-6 to produce ethanol.
[030] According to an exemplary embodiment, the step of a) pre-treating the raw material (110) further comprises the steps of: (210): mixing water from a water supply unit (115) with a raw material (110) and directly loading the raw material (110) with water in batches into a digester (120) of a pre-treatment unit; (220): mixing slurry of the raw material (110) within the digester (120) uniformly and continuously with a helical agitator (128) having a plurality of blades for a predetermined time; (230): heating the slurry of the raw material (110) with a continuous supply of steam (130) obtained through a steam generation and supply unit (130) connected to plurality of steam injection ports (135) of the digester (120) for complete pre-treatment digestion of the raw material (110) throughout the length of digester (120). The slurry of the raw material (110) is heated with the steam at predetermined pressure and temperature for a predetermined time to obtain proper and uniform pre-treatment digestion of the raw material (110) throughout the length of digester (120). The process (200) further comprises the steps of (240): cooling the completely digested pre-treated raw material by circulating water from the water supply unit (115) into the digester (120) jacket. The process (200) after the step of (240), the process (200) includes the step (245) of loading the cooled digested material into an intermediate vessel for collecting intermediaries (125) (such as hydrolysed mixture of monomer sugars) obtained from the digester (120) The process (200) in step b) includes (250) loading the cooled digested pre-treated raw material (110) into an enzymatic hydrolysis unit (140) for treatment with an enzyme and treating at a pre-determined temperature and a pH value for a predetermined time. In an embodiment, the enzymatic hydrolysis unit (140), the pH of the cooled digested pre-treated raw material is adjusted to desired pre-determined pH value using known substances for example caustic lye, lime .In the enzymatic hydrolysis unit (140), the raw material can be treated with commercially available enzymes. In the enzymatic hydrolysis unit (140), after the temperature and pH reached to desired level the commercially available enzyme is added and treated for the predetermined time. After the step b), the process (200) may optionally include the step (255) of filtering the output from the enzymatic hydrolysis unit (140) for collecting a residue (145). The output from the enzymatic hydrolysis unit (140) in the form of slurry is filtered through filter press and first residue (145) is collected, treated, and utilized for other purposes. The process (200) in the step c) may further include the step of (260): loading the filtered output of the enzymatic hydrolysis unit (140) into a fermentation unit (150) to obtain ethanol (170). In the fermentation unit (150), a predetermined quantity of yeast is mixed, and the mixture is treated for a predetermined time at predetermined temperature. Analysis of the output of the fermented mixture from the fermentation unit (150) shows an efficiency of fermentation of 90%. The process after the step c) includes the step (265) of distilling (160) the output of the fermented mixture from the fermentation unit (150) to obtain distilled ethanol (170) and the step (270) of collecting a residue (165). The second residues (165) are collected, treated, and utilized for other purposes. The system may include requisite piping along with associated electrical connections to form interconnection between the units (110, 115, 115, 120, 130, 140, 150, 160, 170) of the system (100).
[031] According to the exemplary embodiment, the raw material may be a lignocellulosic biomass selected from sugarcane bagasse, rice straw, wood chips, wheat straw or any other lignocellulosic substance known to a person skilled in the art. Preferably, the lignocellulose can be sugarcane bagasse. The pretreatment in the digester (120) may be done by subjecting the raw material (110) to steam (130) for 30 to 120 minutes. The pretreatment and digestion of the raw material may be carried out at a temperature in the range of 110°C- 200°C or 120°C-200°C. The temperature may also be in the range of 150°C-190°C. The pressure may be in the range of 5 to 10 bar. The pressure may also be in the range of 6 to 9 bar. The raw material (110) may be pre-treated and digested in the digester (120) for a duration of 90 to 150 minutes. Pretreatment breaks the bond of the raw material and converts raw material to hydrolysable digested material very easily and is efficient at a very low cost.
[032] According to the exemplary embodiment, the enzyme hydrolysis may be carried out at atmospheric pressure. The temperature may be 40°C-55°C. Preferably the temperature may be 45°C-55°C. The pH may be 4-6. Preferably, the pH may be 4.8 to 5.2. The enzyme hydrolysis may be carried out for 48hrs to 96hrs. Preferably, the enzyme hydrolysis may be carried out for 48hrs to 72hrs. Enzyme hydrolysis helps in 60 to 75% conversion of hydrolysable material to free sugar. The free sugar may be fermented in fermenter (150) in presence of yeast for example the quantity of yeast required for can be in a range of 5% to 20%, preferably 10% inoculum of total fermenter volume. Fermentation may be carried out at atmospheric pressure. The temperature may be maintained at 30°C-40°C. Preferably, the temperature may be 32°C-35°C. The pH may be 4-6. Preferably, the pH may be 4.5 to 5.5. In the step c), the fermentation unit (150) is operated for a duration in the range of 36 hrs to 48 hrs to carry out fermentation of the output from the hydrolyser (140) to obtain ethanol. The process may further comprise the step of distilling (160) ethanol to obtain distilled ethanol. The alcohol content obtained by the process of the present invention may be 2.5% to 3%. The fermentation efficiency may be from 90-95%. The fermentation efficiency may be 90%. The first and second residues (145, 165) of the raw material left after manufacturing / producing of ethanol and/or spent wash can be used for generation of steam and power.
[033] In an embodiment of the invention, enzymes such as cellulase, hemicellulase or an enzyme complex containing multiple enzymes may be used. Commercially available enzymes such as Cellic® Ctec 3 may be used.
[034] In an embodiment, yeast may be Saccharomyces cerevisiae and/or Pichia stipitis
[035] Working examples in respect of the system (100), process (200) and the digester (120) of the invention are as follows:

Example 1 –
[036] 500 kg sugarcane bagasse with 90% dryness and 1500 liter of DM Water was taken in the digester. The slurry was mixed properly in the digester with the help of digester for 10 to 15 minutes. Heating with the direct steam injection was started at 8 bar (g) and 160? temperature. It took 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel. After digestion, the mixture was cooled by cooling water circulation in the digester jacket. After cooling, the mixture was unloaded in the intermediate vessel. At the end of the digester the total weight of the slurry was 2600 kg, as the 600 kg was contributed by live steam in the form of condensate, so the solid loading was about the 17.3%. The mixture contains 3.8% C5 sugar and left over cellulose, lignin, other organic acids and ashes. With this quantity the pretreatment efficiency of xylan to xylose was about 88%. Digested slurry was then sent for the enzymatic hydrolysis at hydrolyser where the temperature and pH was maintained at 50? and 5.2 respectively. pH was raised from 2.5 to 5.2 by using caustic lye. After the temperature and pH reached to desired level the commercially available enzyme Cellic® Ctec 3 was added in an amount of 20 mg per gm of cellulose and 5.5 mg of PEG4000 per gm of cellulose was added. Then the mixture was maintained at the same condition for 72 hrs. Upon checking, it was observed that C6 sugar has reached up to 5.8% of the total slurry. After enzymatic hydrolysis, the slurry was filtered through filter press and lignin residue with unreacted cellulose was separated and 2200 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from conversion of cellulose to glucose was 61%. Filtered broth was transferred to fermenter for fermentation, where yeast Saccharomyces cerevisiae and Pichia stipitis was used and the fermentation was done at 35? temperature and 4.5 pH for 30 hrs. After completion of fermentation the alcohol content was 2.66 % by weight which shows that the efficiency of fermentation was around 90%.

Example 2:
[037] 450 kg sugarcane bagasse with 90% dryness and 1400 liter of DM Water was taken in the digester. The slurry was mixed properly in the digester with the help of digester for 10 to 15 minutes. Heating with the direct steam injection was started at 8.5 bar (g) and 165? temperature. It took 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel. After digestion, the mixture was cooled by cooling water circulation in the digester jacket. After cooling the mixture was unloaded in the intermediate vessel. At the end of the digester, the total weight of the slurry was 2350 kg, as the 500 kg was contributed by live steam in the form of condensate, so the solid loading was about the 17.2%. The mixture contained 3.7% C5 sugar and left over cellulose, lignin, other organic acids and ashes. With this quantity, the pretreatment efficiency of xylan to xylose was about 86%. Digested slurry then sent for the enzymatic hydrolysis at hydrolyser where the temperature and pH was maintained at 50? and 5.0 respectively. pH was raised from 2.8 to 5.0 by using caustic lye. After the temperature and pH have reached up to the desired levels, the commercially available enzyme Cellic® Ctec3 was added in an amount of 20 mg per gm of cellulose and 5.5 mg of PEG4000 per gm of cellulose. Then the mixture was maintained at the same condition for 70 hrs and upon checking, it was observed that the C6 sugar has reached up to 6.1% of the total slurry. After enzymatic hydrolysis the slurry was filtered through filter press and lignin residue with unreacted cellulose was separated and 2000 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from conversion of cellulose to glucose was 65%. Filtered broth was transferred to fermenter for fermentation where yeast Saccharomyces cerevisiae and Pichia stipitis was used, and the fermentation was done at 35? temperature and 4.5 pH for 36 hrs. After completion of fermentation, the alcohol content was 2.8 % by weight which shows that the efficiency of fermentation was around 90%.

Example 3:
[038] 600 kg sugarcane bagasse with 90% dryness and 1800 liter of DM Water was taken in the digester. The slurry was mixed properly in the digester with the help of digester for 10 to 15 minutes. Heating with the direct steam injection was started at 8.0 bar (g) and 160? temperature. It took 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel. After digestion, the mixture was cooled by cooling water circulation in the digester jacket. After cooling, the mixture was unloaded in the intermediate vessel. At the end of the digester, the total weight of the slurry was 3100 kg, as the 700 kg was contributed by live steam in the form of condensate, so the solid loading was about the 17.42%. The mixture contains 3.78% C5 sugar and left over cellulose, lignin, other organic acids and ashes. With this quantity, the pretreatment efficiency of xylan to xylose was about 87%. Digested slurry was then sent for the enzymatic hydrolysis at hydrolyser where the temperature and pH was maintained at 50? and 5.1 respectively. pH was raised from 2.6 to 5.1 by using caustic lye. After the temperature and pH reached the desired level, the commercially available enzyme Cellic® Ctec3–- was added in an amount of 20 mg per gm of cellulose and then 5.5 mg of PEG4000 per gm of cellulose was added. Then the mixture was maintained at the same condition for 72 hrs and upon checking, it was observed that the C6 sugar has reached to 6.0% of the total slurry. After enzymatic hydrolysis, the slurry was filtered through filter press and lignin residue with unreacted cellulose was separated and 2500 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from the conversion of cellulose to glucose was 60%. Filtered broth was transferred to fermenter for fermentation where yeast Saccharomyces cerevisiae and Pichia stipitis –was used and the fermentation was done at 35? temperature and 4.8 pH for 36 hrs. After completion of fermentation, the alcohol content was 2.75 % by weight which showed that the efficiency of fermentation was around 90%.

Example 4:
[039] 500 kg Rice Straw with 90% dryness and 1600 litre of DM Water was taken into the digester. The slurry was mixed properly in the digester with the help of a helical agitator of the digester for 10 to 15 minutes. Next, the slurry was heated with the direct steam injection starting at 8 bar (g) and 160? temperature. It took 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel of the digester. After digestion, the mixture was cooled by cooling water circulation in the digester jacket. After cooling, the mixture was unloaded in the intermediate vessel. At the end of the digester, the total weight of the slurry was 2700 kg, as the 600 kg was contributed by live steam in the form of condensate, so the solid loading was about 18.5%. The mixture contained 3.8% C5 sugar, leftover cellulose, lignin, other organic acids and ashes. With this quantity, xylan to xylose pretreatment efficiency was about 88%. The digested slurry was then sent for enzymatic hydrolysis at hydrolyser, where the temperature and pH were maintained at 50? and 5.5, respectively. pH was raised from 2.5 to 5.2 by using caustic lye. After the temperature and pH reached the desired level, the commercially available enzyme Cellic® Ctec3- was added in an amount of 20 mg per gm of cellulose and 5.5 mg of PEG4000 per gm of cellulose was added. Then, the mixture was maintained at the same condition for 72 hrs, and upon checking it was observed that the C6 sugar was up to 5.5% of the total slurry. [After enzymatic hydrolysis, the slurry was filtered through a filter press and lignin residue with unreacted cellulose separated, and 2300 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from cellulose conversion to glucose was 61%. Filtered broth was transferred to a fermenter for fermentation, where yeast Saccharomyces cerevisiae and Pichia stipitis was used, and the fermentation was done at 35 °C temperature and 4.5 pH for 30 hrs. After fermentation, the alcohol content was 2.66 % by weight, which shows the fermentation efficiency was around 90%.

Example 5 –
[040] 550 kg Wood Chips with 90% dryness and 1500 litre of DM Water was taken into the digester. The slurry was mixed properly in the digester with the help of a helical agitator of the digester for 10 to 15 minutes. Next, the slurry was heated with the direct steam injection starting at 8.5 bar (g) and 165°C temperature. The exemplary data reflects taking 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel of the digester. After digestion the mixture was cooled by cooling water circulation in the digester jacket. After cooling the mixture was unloaded in the intermediate vessel. At the end of the digester, the total weight of the slurry was 2400 kg, as the 500 kg was contributed by live steam in the form of condensate, so the solid loading was about 17.2%. The mixture contains 3.6% C5 sugar and leftover cellulose, lignin, other organic acids and ashes. With this quantity, xylan to xylose pretreatment efficiency was about 86%. Now, the digested slurry was then sent for enzymatic hydrolysis at hydrolyser, where the temperature and pH were maintained at 50°C and 5.0, respectively. pH was raised from 2.8 to 5.0 by using caustic lye. After the temperature and pH reached to desired level, the commercially available enzyme was added 20 mg per gm of cellulose and 3 mg of PEG4000 per gm of cellulose. Then the mixture was maintained at the same condition for 70 hrs, and the C6 sugar reached to 6.1% of the total slurry. After enzymatic hydrolysis, the slurry was filtered through a filter press, and lignin residue with unreacted cellulose separated and 2000 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from cellulose conversion to glucose was 65%. Filtered broth was transferred to a fermentor for Fermentation, where yeast Saccharomyces cerevisiae and Pichia stipitis was used, and the fermentation was done at 35°C temperature and 4.5 pH for 36 hrs. After the completion of fermentation, the alcohol content was 2.8 % by weight, which shows the efficiency of fermentation was around 90%.

Example 6
[041] 600 kg Wheat Straw with 90% dryness and 1900 litre of DM Water was taken in the digester. The slurry was mixed properly in the digester with the help of a digester for 10 to 15 minutes. Next, the slurry was heated with the direct steam injection starting at 8.0 bar (g) and 160°C temperature. The exemplary data reflects taking 60 minutes to reach the desired temperature and pressure. Heating time was maintained continuously for 120 minutes to have proper and uniform digestion throughout the vessel of the digester. After digestion the mixture was cooled by cooling water circulation in the digester jacket. After cooling the mixture was unloaded in the intermediate vessel. At the end of the digester, the total weight of the slurry was 3100 kg, as the 800 kg was contributed by live steam in the form of condensate, so the solid loading was about 18.18 %. The mixture contains 3.8% C5 sugar and leftover cellulose, lignin, other organic acids and ashes. With this quantity, xylan to xylose pretreatment efficiency was about 87%. Now, the digested slurry was then sent for enzymatic hydrolysis at hydrolyser, where the temperature and pH were maintained at 50°C and 5.1, respectively. pH was raised from 2.6 to 5.1 by using caustic lye. After the temperature and pH reached to desired level, the commercially available enzyme was added 20 mg per gm of cellulose and 7.5 mg of PEG4000 per gm of cellulose. Then, the mixture was maintained at the same condition for 72 hrs, and upon checking it was observed that the C6 sugar was upto 6.0% of the total slurry. After enzymatic hydrolysis, the slurry was filtered through a filter press, lignin residue with unreacted cellulose separated, and 2600 kg filtered mother liquor was collected. With these quantities, the enzymatic hydrolysis efficiency from cellulose conversion to glucose was 60%. Filtered broth was transferred to a fermentor for Fermentation, where yeast Saccharomyces cerevisiae and Pichia stipitis was used, and the fermentation was done at 35° C temperature and 4.8 pH for 36 hrs. After the completion of fermentation, the alcohol content was 2.65 % by weight, which shows the efficiency of fermentation was around 90%.
[042] There have been described and illustrated herein several aspects, embodiments of exemplary indicative implementation of the system (100), process (200) for manufacturing/producing ethanol and a digester (120). It will also be apparent to a skilled person that the embodiments described above are specific examples of a single broader invention, which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the description without departing from the scope of the invention. While embodiments of the invention have been described, it is not intended that the invention be limited to said configuration disclosed thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise not restrictive to the terminology described herein above. Any discussion of embodiments included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. The present invention is simple in construction and design, integrated, cost effective and easy to manufacture. While particular embodiments of the invention have been described, it is not intended that the invention be limited said configuration disclosed thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular structure specific type of pre-treatment unit, digester, steam generation and supply unit, water supply unit, enzymatic hydrolysis unit, fermentation unit and distillation unit, materials, elements, type of configurations, numbers, the electrical connections between the components, piping connections with valves, sizes, parameters have been disclosed, it will be appreciated that the embodiments may be manufactured with other design parameters and configurations as well as per operational requirements falling within the scope of the invention.

,CLAIMS:
1. A system (100) for producing ethanol in batches, said system (100) comprising:
a digester (120) for pre-treating and digesting a directly loaded raw material (110) along with water, said digester (120) having:
an inlet (122) for loading the raw material (110) into the digester (120);
a helical agitator (128) having a plurality of blades mounted across a length of the horizontal rod (126) for uniformly mixing the raw material (110);
a plurality of steam injection ports (135) spaced apart along the length of the digester (120) for continuous supply of steam into the raw material (110) for complete pre-treatment and digestion of the raw material (110); and
an outlet (124) for unloading the digested material without blockage;
an enzymatic hydrolysis unit (140) interconnected with the outlet (124) of the digester (120) for receiving and treating the digested material with an enzyme; and
a fermentation unit (150) interconnected with the enzymatic hydrolysis unit (140) for receiving and fermenting output from the enzymatic hydrolysis unit (140) to obtain ethanol (170).

2. The system (100) as claimed in claim 1, wherein the digester (120) of a pre-treatment unit is horizontally mounted and includes a continuously rotating horizontal rod (126) centrally mounted and extending throughout a length of the digester (120);

3. The system (100) as claimed in claim 1 or 2, wherein each of the plurality of blades have a surface area equal to width of the digester (120) for uniformly mixing the raw material (110) with the plurality of blades of the helical agitator (128).

4. The system (100) as claimed in anyone of the preceding claims 1-3, wherein the inlet (122) and the outlet (124) are located parallel and opposite to each other at a top and bottom outer circumferential surface of the digester (120).

5. The system (100) as claimed in anyone of the preceding claims 1-4, wherein the system (100) includes a distillation unit (160) to further distillate the obtained ethanol (170).

6. A digester (120) for pre-treatment and digesting of a raw material (110) in batches, said digester (120) comprising:
a helical agitator (128) having a plurality of blades mounted across a length of a horizontal rod (126) for uniformly mixing the raw material (110), the horizontal rod (126) is a centrally mounted continuously rotating rod extending throughout a length of the digester (120); and
a plurality of steam injection ports (135) spaced apart along the length of the digester (120) at a top and a bottom circumferential surface of the digester (120) for continuously supplying steam into the raw material (110) for complete pre-treatment and digestion of the raw material (110).

7. A process (200) for producing ethanol in batches, the process (200) comprising the step of:
a) digesting including pre-treating a raw material (110) in a digester (120) at a temperature in the range of 110°C-200°C and pressure in the range of 5 to 10 bar pressure to obtain a digested material;
b) treating the digested material with an enzyme in a hydrolyser (140) at a temperature in the range of 40°C to 55°C and pH in the range of 4-6 to obtain free sugars and a first residue (145); and
c) subjecting said sugars to fermentation in a fermenter (150) by a microorganism at a temperature in the range of 30°C to 40°C, and pH in the range of 4-6 to produce ethanol.

8. The process (200) as claimed in claim 7, wherein the step of a) pre-treating the raw material (110) further comprises the steps of:
(210): mixing the raw material (110) with water supplied from a water supply unit (115) and directly loading the raw material (110) into the digester (120);
(220): mixing slurry of the raw material (110) within the digester (120) uniformly and continuously with a helical agitator (128) having a plurality of blades;
(230): heating the slurry of the raw material (110) with a continuous supply of steam obtained through a steam generation and supply unit (130) connected to plurality of steam injection ports (135) of the digester (120) for complete pre-treatment digestion of the raw material (110) throughout the length of digester (120);
(240): cooling the completely digested pre-treated raw material by circulating water from the water supply unit (115) into the digester (120).

9. The process as claimed in claim 7 or 8, wherein the raw material (110) is pre-treated and digested in the digester (120) for a duration of duration of 90 to 150 minutes.

10. The process (200) as claimed in anyone of the preceding claims 7-9, wherein the raw material (110) is pre-treated and digested in the digester (120) at a temperature in the range of 120°C-200°C, preferably in the range of 150°C-190°C.

11. The process (200) as claimed in anyone of the preceding claims 7-10, wherein the raw material (110) is pre-treated and digested in the digester (120) at a pressure in the range of 6 to 9 bar pressure.

12. The process (200) as claimed in anyone of the preceding claims 7-11, wherein the raw material is a lignocellulosic biomass selected from sugarcane bagasse, rice straw, wood chips or wheat straw.

13. The process (200) as claimed in claim 8, wherein after the step of (240), the process (200) includes the step (245) of loading the cooled digested material into an intermediate vessel for collecting intermediaries (125) obtained from the digester (120).

14. The process (200) as claimed in anyone of the preceding claims 7-13, wherein the step b), the digested material in the hydrolyser (140) is treated with enzyme at a temperature in the range of 40°C to 55°C.

15. The process (200) as claimed in anyone of the preceding claims 7-14, wherein the step b), the digested material in the hydrolyser (140) is treated with enzyme at a pH in the range of 4.8-5.2.

16. The process (200) as claimed in anyone of the preceding claims 7-15, wherein the step b), the digested material in the hydrolyser (140) is treated with enzyme for a duration in the range of 48 hrs to 96 hrs.

17. The process (200) as claimed in anyone of the preceding claims 7-16, wherein after the step b), the process (200) includes the step (255) of filtering the output from the enzymatic hydrolysis unit (140) for collecting the first residue (145).

18. The process (200) as claimed in anyone of the preceding claims 7-17, wherein the step c), the fermentation unit (150) is maintained at a temperature in the range of 32°C to 35°C.

19. The process (200) as claimed in anyone of the preceding claims 7-18, wherein the step c), the fermentation unit (150) is maintained at a pH in the range of 4.5 to 5.5.

20. The process (200) as claimed in anyone of the preceding claims 7-19, wherein the step c), the fermentation unit (150) is operated for a duration in the range of 36 hrs to 48 hrs to carry our fermentation of the output from the hydrolyser (140) to obtain ethanol.

21. The process (200) as claimed in anyone of the preceding claims 7-21, wherein the fermentation is carried out using commercially available yeast.

22. The process (200) as claimed in anyone of the preceding claims 7-20, wherein after the step c), the process (200) includes the step (265) of distilling (160) the output of the fermented mixture from the fermentation unit (150) to obtain distilled ethanol (170) and the step (270) of collecting a second residue (165).

23. The process (200) as claimed in anyone of the preceding claims 7-21, wherein the microorganism is a yeast selected from Saccharomyces cerevisiae and/or Pichia stipitis