FORM 2
THE PATENT ACT 1970
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
METHOD FOR CONCENTRATION AND INCINERATION OF BIOMETHANATED SPENT WASH
2. APPLICANT
(a) NAME: PRAJ INDUSTRIES LIMITED
(b) NATIONALITY: Indian Company
(c) ADDRESS: PRAJ House, Bavdhan, Pune-411021, INDIA
3. PREAMBLE TO THE DESCRIPTION
The following specification describes the invention and the manner in which
it is to be performed.

4. DESCRIPTION
FIELD OF THE INVENTION
The invention relates to a method of simultaneous concentration and incineration of a biomethanated spent wash [BSW] produced in an alcohol distillery, more particularly to the incineration of concentrated BSW and using heat so generated to produce steam useful to perform work in said distillery plant.
BACKGROUND
Sugar industry is one of the largest agro based industry, which contributes substantially to the economic development of several communities worldwide. The sugar factories in India produce about 15 million tons of sugar by crushing about 150 million tons of sugarcane. The annual byproduct production is about 7 million tons of press mud and about 8 million tons of molasses. Molasses is utilized in distilleries for the production of ethanol. These distilleries producing alcohol generate billion litres of spent wash annually. The spent wash and press mud cause disposal and pollution problems. The raw spent wash contains very high values of BOD and COD, beside solids. Therefore, to alleviate the problem of spent wash disposal it is subjected to biomethanation process where significant reduction of BOD and COD occurs along with production of bio-gas as an energy source. The effluent discharged from biomethanation process is known as biomethanated spent wash [BSW]. Although BSW has significant fewer BOD and COD values and solids, it is still a biological hazard if left to open disposal sites as presently done, creating significant air, water and soil pollution. Recently, regulators have also tightened the requirements of BSW disposals and it is now imperative to sugar factories and distilleries to employ new methods of the treatment of BSW that are more effective, economical and eco-friendly.

BSW is made up of solid materials left unused in biomethanation process; these solids are mostly in the form of organic and inorganic complexes having very high BOD and COD demands for its degradation in natural environment creating pollution everywhere. A compositional analysis of a sample of BSW is provided in Table 1. Presently, BSW is left in open fields to compost and then remains' are used as fertilizer, etc. At some large factories it is evaporated to partially recover water that is disposed off in natural streams and the concentrated part is left for composting or drying.
TABLE 1: Typical composition of ordinary BSW feed stream:

Sr. No. PARAMETER UNIT VALUE
1 PH 7.0-8.0
2 COD ppm 30000 - 70000
3 BOD mg/L 10000-32000
4 Volatile Acids mg/L 700-1200
5 Alkalinity mg/L 12000-22000
6 Total Solids % by weight 1.5-8.0
7 Suspended Solids % by weight 0.2-1.0
In recent times due to increased need of preservation of water and its use for more important agricultural applications than alcohol production, there is significant pressure on sugar factories to reduce water consumption and recycle the process wastewater generated in plants more effectively. To this end, several technologies have been presented on the treatment of BSW and recovery / recycling of process wastewater. However, these technologies have achieved limited success due to composition of recycled water so obtained.

One current method of the BSW treatment is evaporation; herein BSW from biogas reactors is stored in open lagoons to get rid of volatile matters present in it as various gases. Then this BSW from lagoons is fed to a multiple effect evaporation process wherein it is concentrated up to 35 of total solids by weight. The process condensate water generated from this evaporation process is either disposed off or used for gardening or any other non-process applications due to high ammoniacal nitrogen content with other associated impurities of varying nature, rendering it not suitable for process and utility applications. Besides, the evaporation stage of BSW faces severe problem of clogging of heat exchanger surfaces due to fouling and scaling. This leads to significant expenditures on the cleaning of the evaporators and its working efficiencies.
However, evaporation of BSW in open fields is increasingly coming under restrictions, of regulators, hence new methods for treatment or destruction of BSW are needed that are economical and eco-friendly. The invention presented herein discloses a method of incineration of BSW having several advantages over known methods. Besides it provides additional steam generation by said incineration at the end of treatment that is directly usable in plant processes like evaporation of ethanol in distillation unit.
BRIEF DESCRIPTION OF THE DRAWINGS
Particular examples of a method in accordance with this invention will now be described with reference to accompanying drawing, in which:
FIGURE 1 is an exemplary plan of the invention showing several features that control the process of concentration of BSW feed stream and production of process reusable water from the aqueous part of BSW. The solids present in said BSW are concentrated up to 50% by weight and incinerated in a boiler leading to generation of steam. This scheme has . several elements that significantly contribute to the process of the invention.

DETAILED DESCRIPTION OF THE INVENTION
In one embodiment of present invention, as illustrated in Figure 1 BSW with at least 10% total solids by weight [1] is first received in a flash tank [31] and further directed to a venturi concentrator [30] where it is contacted with hot flue gas [6] coming from a boiler [36]. In said venturi concentrator [30] BSW is heated up due to said hot flue gas leading to evaporation of water in it. When repeated over a few cycles [2], BSW gets concentrated up to 50% of total solids by weight. This concentrated BSW [3] is subjected to incineration in said boiler [36] with auxiliary solid fuel like coal. The amount of coal fed to said boiler is so adjusted that all of said concentrated BSW is effectively burnt to generate energy, which is used to generate steam [14] useful to run other distillery processes. After this step of concentration in said venturi concentrator [32], separation of solids is achieved in a flash tank [31], vapours [8] from said flash tank [31] are further directed to a venturi scrubber [32] to remove impurities present in said vapours by scrubbing with process water [16]. Here vapours [8] are contacted with process water in said venturi scrubber [32] and when repeated over a few cycles [9] this step removes impurities present in said vapours [8] leading to formation of a clean gas [10] and waste water [20] streams. The clean gas [10] from gas liquid separator [33] is further directed through a blower [34] to a chimney [35] for release. Water used for cleaning [20] is recycled and reused.
In another embodiment, BSW [1] is contacted with hot flue gas [6] in a venturi concentrator heating said stream [1] to about 50 °C to 80 °C. Similarly vapours [8] from flash tank [31] are contacted with said process water [16] at a temperature of about 50 °C to 80 °C. The said concentrated BSW stream [3] contains about 30% to 50% total solids by weight before incineration. Further said clean gas stream [10] contains particulate matter below 150 mg/Nm3. Also the pressures in this whole system of simultaneous concentration and incineration of BSW are maintained below

atmospheric to prevent any leakages from the system of any vapours or gases.
In yet another embodiment, in an hour of operation a batch of about 6446 kg of BSW with about 18% of total solids by weight was subject to venture concentrator through a flash tank. In first step, hot flue gas of about 52106 kg was contacted with said BSW stream leading to formation of a concentrated stream with about 50% total solids by weight. This concentrated stream was incinerated in the boiler with equal amount of coal to generate steam. Next, the vapours of about 56306 kg generated by flash tank after said venturi concentrator were contacted with process water in a venturi scrubber to remove the suspended particles present in said vapours; and further this mixture was directed to a gas liquid separator to separate clean gas and waste water streams. Then clean gas of about 56300 kg so generated was released though a chimney by a blower. The scrubbing water with said suspended particles was subjected to purification to recover the process water.
Embodiments provided above give wider utility of the invention without any limitations as to the variations that may be appreciated by a person skilled in the art. A non-limiting summary of various embodiments is given above, which demonstrate the advantageous and novel aspects of the process disclosed herein.

5. CLAIMS
WE CLAIM:
1. A method for simultaneous concentration and incineration of
biomethanated spent wash comprising:
(a) providing a biomethanated spent wash;
(b) heating said biomethanated spent wash with a hot flue gas stream of a boiler to a desired temperature in a venturi concentrator leading to formation of a first stream;
(c) flashing said first stream in a flash tank at a desired vacuum leading to formation of a concentrated stream and a vapour stream;
(d) incinerating said concentrated stream in said boiler along with a solid fuel; and
(e) scrubbing said vapour stream in a venturi scrubber using water leading to formation of a clean gas stream; and
(f) generating steam using said boiler.

2. The method of claim 1, wherein said biomethanated spent wash is a waste product of distillery unit comprising at least 10% total solids by weight.
3. The method of claim 1, wherein said biomethanated spent wash is heated to about 50 °C to about 80 °C in said venturi concentrator.
4. The method of claim 1, wherein said venturi scrubber operates at a temperature of about 50 °C to about 80 °C.

5. The method of claim 1, wherein said concentrated stream comprises at least 30% total solids by weight before incineration.
6. The method of claim 1, wherein said concentrated stream preferably comprises about 50% total solids by weight before incineration.
7. The method of claim 1, wherein said clean gas stream contains suspended particulate matter below 150 mg/Nm3.
8. The method of claim 1, wherein process pressures are maintained below atmospheric pressure for effective operation of said method.