WO2012077124A1

WO2012077124A1 - A method for co-processing of distillery effluent (spent wash)

Info

Publication number: WO2012077124A1
Application number: PCT/IN2011/000431
Authority: WO
Inventors: Prasad Gautam Sant
Original assignee: Central Pollution Control Board
Priority date: 2010-12-07
Filing date: 2011-06-29
Publication date: 2012-06-14

Abstract

This invention relates to a method for co-processing of distillery effluent comprising steps of: -neutralization of spent wash (optional), -concentration the spent wash, -co-processing of concentrated spent wash in a cement plant.

Description

A METHOD FOR CO-PROCESSING OF DISTILLERY EFFLUENT (SPENT WASH) FIELD OF INVENTION

This invention relates to a method for co-processing of distillery effluent (Spent Wash).

PRIOR ART

In recent years, industrial effluents have been regarded as common source of environmental pollution because of inadequate treatment and improper mode of disposal of effluents generated by industries. Under these circumstances, aquatic life suffers resulting in loss of productivity and deterioration of water quality to such an extent that the water becomes unusable. The alcohol industry is based on molasses as the principal raw material. Molasses contain 40 to 45% sugar in which around 6% is non-fermentable sugar and the remaining is utilized for conversion into alcohol during fermentation. The balance organic and inorganic chemicals in the molasses find their way into the effluent popularly known as spent wash which is acidic in nature. Spent wash, which is dark in colour has high Bio-chemical oxygen demand, Chemical Oxygen Demand Total Dissolved Solids content. The dark colour is mainly due to plant pigments, melanoidins, polyphenolic compounds and caramels that are produced by thermal degradation and condensation reactions of sugar, if this spent wash is not treated, it can create pollution on soil, surface water and ground water, odour, etc.

Distilleries producing ethyl alcohol from various raw materials especially molasses derived from cane sugar gives rise to large volume of highly polluting aqueous effluent, which pollutes the surrounding environment. Depending on type of technology used for fermentation and/or distillation, the quantity of effluent can vary from 9 to 15 liters per liter of ethyl alcohol produced. The spent wash has high content of Chemical Oxygen Demand Bio-chemical oxygen demand Total Dissolved Solids and Total Suspended Solids, as evaluated in terms of pollution control parameters practiced worldwide. Controlling of pollution arising from the distillery spent wash is carried out by various methods which are as below:

• Anaerobic treatment (Bio gas generation) followed by aerobic treatment (through Activated sludge process) • Anaerobic treatment followed by bio-composting to achieve zero discharge

• Anaerobic treatment followed by RO and bio-composting

• Anaerobic treatment followed by two stage aerobic treatment and ferti- irrigation with dilution

• Spent wash concentrated in multiple effect evaporator followed by incineration in boiler

Incineration being capital intensive is seldom practiced. Thus biogas and composting are methods of choice. However, biogas method does not remove the colour, even after aeration. Complete composting many times is difficult due to non-availability of filler material (press-mud) in right ratio.

These difficulties are solved by application of reverse osmosis technique to generate about 50% clean colour-less reusable water and the balance 50% concentrate can be easily composted. This method thus creates an opportunity to arrive at zero liquid discharge status. Secondly, evaporation is becoming increasingly popular as means of reducing the volume of the spent wash stream to reduce the quantity of filler material (press mud) and land requirements for composting. Multiple Effect Evaporators (MEE) is used to concentrate the spent wash stream released from distillery.

Now, reference may be made to the following known arts:

Application No 538/DEL/2000 relates to a process for treating dyes wastewater. The process comprises a primary step of chemical treatment followed by secondary and tertiary steps of biological treatment performed in bio-reactors.

US patent No. 6589427 is directed to a process for treating an effluent comprising a mixture of spent wash and black liquor. The said process comprises mixing the effluent with a flocculating agent consisting of a mixture of salts of Group III and transition metals, mixture of natural earth's along with an oxide of alkaline earth metal followed by a treatment with a combination of ion exchange resins.

Publication No. GB1018606 describes the treatment of distillery waste. Spent wash which has been pretreated, for example by evaporation, has a solid content of 15-70% wt, is mixed with draft in a mixing vessel into a substantially homogenous mixture, which is then automized and simultaneously dried by heated air, preferably at 300- 600°F., to form a granular fibrous material which is collected and may be used as an animal fodder.

Publication No. GB869059 relates to solids, which may be used as an animal feeding stuff. They are recovered from distillery effluent discharged from a distillation process. The process involves mashing and distillation stages by a process in which the effluents are concentrated to high solids content by evaporation in a multiple effect evaporator.

Reference may be made to an article by Y. Satyawali, M. Balakrishnan, TERI University. The article discloses molasses-based distilleries are one of the most polluting industries generating large volume of high strength wastewater. Different processes covering anaerobic, aerobic as well as physico-chemical methods have been employed to treat this effluent.

Publication No. GB 190509572 discloses the evaporator for evaporating the liquid in brewers wash, spent wash or pot ale from distilleries, sewage, waste or spent dyes and the like, and concentrating the Solids in the same. The evaporator is also applicable as a smoke washer.

US patent no. 5328707 is pertinent to a process for recovering waste liquid from the distillation of fermented rice liquor. After filtration of the waste liquid, the residue can be recovered as dry feed, and the filtrate which contains about 4-5% crude protein, 1% starch and 92 wt. % water is first concentrated to lower the water content to a bout 70-80 wt. %. The filtrate is then dried with a spray dryer to produce nutritious dry feed while a suitable chelating agent such as magnesium hydroxide is used to prevent the clinging of the product on the wall of the dryer.

The above said methods used for disposal of distillery spent wash are one time controlled land application after bio-methanisation and bio-composting with press mud available from sugar industry and more recently, concentration in multiple effect evaporators and consequent spray drying/ incineration in boiler. The former two methods, even though provide nutrient value to the soil, lead to contamination of ground and surface water sources. Also both methods cannot be practiced during rainy season. Later method, i.e, concentration followed by spray drying is not found technically feasible in most of the cases due to operational difficulties. Further, capital and operational costs are also high.

Further, the conventional treatment method uses acidic effluent, which leads to corrosion problems, filtration problems due to colloidal particles and incomplete removal of organic as well as inorganic matter in the effluent and color due to organics mainly caramels and mellanoidins.

Thus, there exists a requirement for the treatment of the effluent generated from alcohol production process which reduces pollution and is eco friendly.

The present invention provides a process for co-processing of distillery effluent in furnace such as cement kiln, which eliminates the organic and inorganic pollution load on environment and also used as supplementary resources or energy recovery.

OBJECTS OF THE INVENTION

The principal object of the present invention is to provide a method for co-processing of distillery effluent in cement kiln.

The other objectives of the present invention to provide a method for co-processing of distillery effluent, are.

- to adapt Eco-friendly method.

- to reduce the pollution load. »

- to convert the waste into energy source and product

- to have cost effective technology

- to eliminate the spent wash discharge from the plant

- to save considerable quantity of water.

- to have an efficient method of disposal of the waste STATEMENT OF INVENTION

According to this invention, a method is provided for co-processing of distillery effluent comprising steps of: neutralization of spent wash (optional),

concentration of the spent wash,

co-processing of concentrated spent wash in cement plant. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Further objectives and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:

Figure 1 shows: block diagram of co-processing of distillery spent wash in the cement kiln

Figure 2 A shows: firing of concentrated spent wash in the main burner of the cement kiln, along with coal utilizing the diesel firing line used for the start up of the cement kiln

Figure 2 B shows: firing of concentrated spent wash in the hot zone of the cooler

DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

The present invention discloses a method for co-processing of distillery effluent. The co-processing is carried out in cement kiln or thermal power plant or sponge/ steel furnace. Reference may be made to Fig 1, which shows co-processing of distillery effluent in cement kiln. Co-incineration of distillery spent wash in cement plants requires the spent wash to be concentrated in multiple effect evaporators and subsequently incinerating the concentrated spent wash in the cement kiln. Concentration in multiple effect evaporators is carried out to concentrate the spent wash to minimum 50 brix (50% solids), which is transported to cement plants for incineration.

To achieve 50% solid concentration, the spent wash can be treated in two ways, which do not involve any disposal issue.

1. Concentration through Reverse Osmosis followed by Multiple Effect Evaporator (MEE)

The raw spent wash with or without neutralization is treated through Reverse Osmosis ( RO) Plant, the permeate generated from RO is recycled in process and the RO reject is subjected to Multiple Effect Evaporator for concentrating and to achieve more than 50% solid concentration. The condensate generated from MEE is recycled in the process.

(OR)

_^ 2. Concentration through Multiple Effect Evaporator (MEE) only.

The raw spent wash with or without neutralization is treated directly through Multiple Effect Evaporator for concentrating and to achieve solid concentration more than 50% and the condensate generated from MEE is recycled in the process.

The co processing of spent wash is carried out by firing it in the main burner or in the clinker cooling section. The concentrated spent wash is fired in two different locations as shown in Figure 2A which is in the main burner of the cement kiln, along with coal utilizing the diesel firing line used for the start up of the cement kiln and in Figure 2B which is the hot zone of the cooler where the clinker falls in the cooler from the kiln.

The concentrated (50% solid) spent wash had moisture content and the net calorific value ranging from lOOOKcal/Kg to 2000 Kcal/Kg depending upon the moisture content. The feed of the spent wash was carried out at different feed rate ranging from 100 - 1500 LPH.

In an example, initially the co-processing of spent wash was carried out in 3000 TPD cement kiln and the spent wash feeding rate started at 200 LPH and then raised to 1000 LPH. On second time, the co-processing of spent wash was carried out in 1200 TPD cement kiln and spent wash feeding rate was increased from 120 LPH to 1050 LPH in two phases. At this feed rate the Thermal Substitution Rate value ranged from 0.5% to 3% and the clinker quality remains unchanged. The chloride levels in hot meal values ranged upto 0.63% at maximum rate. At 1200 LPH, the burning zone temperature was dropped. There is no behavioral changes in the performance of kiln and no major coating / built up is observed.

Spent wash tends to contain Chloride levels in the range of 1.5- 5 % and Sulfur levels in the range of 1.0- 5.0 %. It also contains Alkalies (Potassium and Sodium) up to a level of about 2%. Alkalies, Sulfates and Chlorides are known to create problems in process in terms of coating due to their evaporation and condensation in the pre-heater section of the kiln. Hence, there is possibility of coating problems and refractory expansion in the kiln if the spent wash is co processed in the kiln section. Therefore, co-processing of this material is carried out in the cooler section by firing the same on the falling clinker having temperature far in excess of 1000- 1 100 °C. When the spent wash is sprayed on the falling clinker at the cooler section, i.e, immediately after the kiln, the temperature ranges from 1000°C to 1 100°C whereas when the firing of spent wash is done at main burner along with coal, the temperature ranges from 1200 °C to 1450°C. The evaporation of the alkalies and their carry over in the kiln section gets minimized due to absorption of these volatiles in the clinker. The enthalpy present in the spent wash gets absorbed by the secondary and tertiary air wherein the same travels in to the kiln section.

It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

Claims

WE CLAIM:

1. A method for co-processing of distillery effluent comprising steps of: neutralization of spent wash (optional),

concentration of the spent wash,

co-processing of concentrated spent wash in a furnace.

2. A method as claimed in claim 1, wherein the neutralization is carried out by means of alkali (optional)

3. A method as claimed in claim 1 or 2, wherein said concentration of the neutralized spent wash takes place in a multiple effect evaporator.

4. A method as claimed in any of the preceding claims, wherein condensate from the evaporator is recycled in process.

5. A method as claimed in any of the preceding claims, wherein the furnace may be cement kiln or thermal power plant or sponge/steel furnace in which the concentrate is mixed with coal/clinker.

6. A method as claimed in any of the preceding claims, wherein said spent wash contains 1.5-5.0 % by wt. of chloride, 1.0-5.0 % by wt. of sulfur and about 2.% by wt. of Alkali.

7. A method as claimed in any of the preceding claims, wherein said coprocessing is carried out either in the cooler section of the cement kiln by firing the concentrated spent wash on the falling clinker with a temperature in excess of 1000-1100°C or by firing at the main burner along with coal at 1200°C-1450°C.