WO2020208648A1

WO2020208648A1 - Energy generation from distillery effluent streams.

Info

Publication number: WO2020208648A1
Application number: PCT/IN2020/050332
Authority: WO
Inventors: Ghanshaym Baburao DESHPANDE; Ajit Prabhakar Deshmukh; Bharat Ashok KADU
Original assignee: Praj Industries Limited
Priority date: 2019-04-11
Filing date: 2020-04-06
Publication date: 2020-10-15
Also published as: AR118473A1; CO2021013966A2; BR112021020559A2; PE20220303A1

Abstract

Energy generation from distillery effluent streams. The invention relates to a method for the generation of steam and electricity using effluent streams, like raw spent wash stream, produced in alcohol distilleries. More particularly it relates to the use of high-brix evaporation concentration system (HBCS) to produce a concentrated semi-solid stream having more calorific value, which is self-combustible and useful to produce steam and electricity to be used in distillery.

Description

TITLE: ENERGY GENERATION FROM DISTILLERY EFFLUENT STREAMS.

FIELD OF THE INVENTION The invention relates to a method for the generation of steam and electricity using effluent streams, like raw spent wash stream, produced in alcohol distilleries. More particularly it relates to the use of high-brix concentration system (HBCS) to produce a concentrated semi-solid stream having more calorific value, which is self-combustible and useful to produce steam and electricity to be used in distillery.

BACKGROUND

Sugar industry is one of the largest agriculture-based industry, which contributes substantially to the economic development of several communities worldwide. Molasses, sugar industry by-product, is utilized in distilleries to produce ethanol. These distilleries producing alcohol generate billion litres of raw spent wash annually. The spent wash is a waste of distillery processes. In recent years, due to expansion of distilleries in sugar cane growing countries, the disposal of spent wash has become an acute problem. The spent wash is produced is characterized by undesirable colour, foul odour, high biological oxygen demand and chemical oxygen demand, which has created an acute problem of spent wash disposal with the expansion of distilleries in the sugar cane growing countries.

The conventional method of disposal of spent wash is bio-methanation, composting, concentration and incineration. The effluent discharged from bio methanation has a biological hazardous creating significant air, water and soil pollutions, so, it requires secondary treatment. Composting procedure requires large land and because of more solids in the form of organic and inorganic complexes with very high BOD and COD creates pollution everywhere. Presently, spent wash or biomethanated spent wash 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 of in natural streams and the concentrated part is left for composting or drying. But recently regulators have also tightened the requirements of spent wash disposals and it is now imperative to sugar factories and distilleries to employ new methods of the treatment of spent wash that are more effective, economical and eco-friendly. 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. The methods of concentration and incineration also have limits as these effluents are hard to handle at high total solids content with frequent equipment malfunction and downtime during the process of concentration and again require auxiliary fuel for its burning in the boilers. The simple evaporation units normally concentrate the effluents streams up to 50-55% W/W TS. However, operating these units to achieve 60% or more W/W TS is not practical and continuously running it for longer periods is not possible due to choking caused by very viscous materials formed and they require periodic cleaning at the intervals of about 15 days or so.

The invention herein discloses a method using a high-brix evaporation system for the concentration of effluent streams, like distillery raw spent wash, to semi-solid self-combusting material that can be directly incinerated in the boiler to generate steam and electricity, having several advantages over known methods. High-brix evaporation means the input stream has higher solids content up to 50-55% W/W of TS and the output stream has solid content up to 65-80% W/W of TS.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:

FIGURE 1 depicts a process flow diagram for generation of energy from said effluent stream. The effluent stream is subjected to simple evaporation system to produce a first stream. Next, said first stream is fed to high-brix evaporator system to produce a second stream, which is semi-solid and directly used as a fuel for boiler for the generation of steam and electricity.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the present invention, as illustrated in FIGURE l the disclosed process includes following steps: a) effluent collection [stream (3)], b) simple evaporation (E), c) high-brix evaporation (RE), and d) incineration in boiler furnace(B) to generate steam and electricity. The molasses is major raw materials for ethanol production. It mainly contains up to 58% sugar by weight. In molasses-based distillery, molasses (1) gets fermented in fermentation unit(R) to produce fermented mash stream (2) and carbon dioxide (12). Said fermented mash is then send to distillation column (C) to recovered ethanol (6). The remaining stream (3) of distillation column is rich in non-sugar fractions of molasses and dead yeast cells and comes out as effluent generally called as vinasse, raw spent wash, distillery effluent, stillage, distillery slops, etc. This effluent stream (3) is rich in organic matters with good fuel value. This effluent stream (3) with from 10 % to 25 % W/W of total solids (TS) is partially concentrated in a multiple effect evaporator (E) to produce a first stream (4) and a first condensate stream (7). This is a conventional evaporation process which concentrates said effluent stream from about 10 % to 25 % to about 30 to condensate stream is recycled for process and utility application. Next, said first stream (4) is further fed to a high-brix rotary type evaporator (RE) where said first stream is heated to between 70°C and ioo°C to produce a second stream (5) having about 65% to 8o%W/W of TS with calorific value between 1900 and 2400 kcal/kg, which is semi-solid and self-combustible suitable for direct incineration. Said second stream (5) is flowable and pumped further to boiler (B) and incinerated to generate high pressure steam (9), which is expanded further in turbine (T) to produce low pressure steam (10) and electricity (11) to be used for the purposes of the distillery plant.

In another embodiment of the invention, said simple evaporation system uses one or more of rising film, falling film, forced falling film or forced circulation type evaporation unit.

In yet another embodiment of the invention, said self-cleaning high-brix concentration system (HBCS) uses by one or more rotary, agitated thin film, wiped film or pan type evaporator unit. These high-brix evaporators are self-cleaning meaning they do not accumulate the concentrated materials and due to its internal structures remove all the materials from its body. Therefore significantly reducing overall cleaning chemical requirement of said concentration / evaporation system. In yet another embodiment of the invention, the second stream having more than 80% W/W TS is maintained flowable by adding viscosity reducing agents / enzymes depending upon said stream behaviour at higher concentrations.

In yet another embodiment of the invention, auxiliary fuel is sometime required to meet the increased energy requirement of distillery plant depending on molasses sugar content. Coal, bagasse, wood, fuel oil, diesel, natural gas or biogas, rice husk, or any other biomass can be used as an auxiliary fuel.

The invention discloses a combine effect of simple evaporation system and rotary type self-cleaning high-brix evaporation system to generate a self combustible concentrated stream from effluent streams of distilleries. The process has several advantages over the known methods as listed below:

1) The rotary type evaporator has rotating scrappers either fixed type or hinged type which scraps the evaporator heating surface so that it is free from fouling and scaling while concentrating the effluent stream to up to 8o% W/W TS. This type is called a self-cleaning high-brix evaporator system.

2) Because of less fouling and scaling of the rotary evaporator the process plant can be continuously run up to 6o days or more compared with the conventional evaporator, which is ordinarily run to maximum 15 days and then cleaned for next run. Hence significant reduction in overall cleaning chemical reduction in concentration system is achieved.

3) The generated steam and electricity are adequate to run the distillery plant / complex that generates the effluent streams.

Examples provided below 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 experimental results is given in the examples, which demonstrate the advantageous and novel aspects of the method wherein high brix evaporation is performed to produce high energy stream from distillery effluent.

EXAMPLE

A batch of 396 metric ton (MT) of cane molasses (with about 43% w/w fermentable sugars and 80% w/w total solids) was used for ethanol production in a distillery plant. Said molasses was fed to fermentation unit to produce about 879 MT fermented mash and about 75 MT carbon dioxide gas. Said fermented mash was further treated in a distillation column to recover about 100 KLPD ethanol and said fermentation batch produced about 619 MT raw spent wash stream or effluent stream with about 25% w/w total solids (TS). Said effluent stream was the firstly treated by simple evaporation to partially concentrated first stream having about 50% w/w TS. Next, said first stream was further fed to high-brix evaporation system in a rotary evaporator to produce a second stream having about 72% w/w TS, with calorific value of about 2200 kcal/kg. This second stream being self-combustible and flowable, and was pumped further to boiler for incineration to generate steam and power. The above process produced about 215 MT second stream and which on incineration produced about 26.5 TPH gross steam and 2.6 MWh Power which was sufficient to run the distillery plant, requiring no additional external source of fuel or energy.

Claims

WE CLAIM:

l. A method for generation of energy comprising:

(a) providing an effluent stream with between 10 and 25 % solids by weight;

(b) concentrating said effluent stream by simple evaporation forming a first stream with between 30 and 50 % solids by weight and a first condensate stream;

(c) subjecting said first stream to a high-brix evaporation forming a second stream with between 65% and 80% W/W total solids and a vapour stream; and

(d) subjecting said second stream as such to incineration in a boiler to generate steam and electricity.

2. The method as claimed in claim 1, wherein said effluent stream is a waste product of distillery unit obtained after distillation of ethanol from fermented beer or spent wash or paper mill blackstrap liquor.

3. The method as claimed in claim 1, wherein said effluent stream is heated between 50 °C and 90 °C in said simple evaporation.

4. The method as claimed in claim 1, wherein said first stream is heated between 70 and 100 °C in said high-brix evaporation.

5. The method as claimed in claim 1, wherein said simple evaporation is performed by one or more of rising film, falling film, forced falling film or forced circulation evaporation unit.

6. The method as claimed in claim l, wherein said high-brix evaporation is performed by one or more of rotary, agitated thin film, wiped film or pan type evaporation unit.

7. The method as claimed in claim 1, wherein said high-brix evaporation is performed by a self-cleaning type evaporator unit.

8. The method as claimed in claim 1, wherein said second stream is as such used in said boiler for energy generation without addition of any other solid fuel to it.

9. The method as claimed in claim 1, wherein said second stream has energy content of between 1900 and 2400 Kcal/Kg.

10. The method as claimed in claim 1, wherein said second stream is self-combusting.

11. The method as claimed in claim 1, wherein said steam or electricity generated is utilised in production plant.

12. The method as claimed in claim 1, wherein said vapour stream is used as an energy source in process plant or in said simple evaporation.