TECHNICAL FIELD
Present disclosure relates to a process of juice extraction in a diffuser station of a sugar mill. More particularly, the present disclosure relates to a process which involves use of direct contact juice heaters utilizing low pressure vapour.

BACKGROUND OF THE DISCLOSURE AND PRIOR ARTS
In the present scenario of sugar sector, the survival of the business is very tough due to poor recovery and the poor prices of sugar in the open market. Therefore, to compete in the open market it is necessary to reduce the cost of sugar production.

Generally, in a diffuser station of sugar mill, live or exhaust steam is utilized for various stages of juice heating, such as scalding, press and stage juice heating. In a conventional set up vapour from first effect or exhaust steam from turbine is utilized for press juice, stage juice and scalding of juice.

Referring to FIG. 1, which illustrates a schematic diagram of a conventional diffuser station (100) for juice extraction. Operation of the diffuser is based on systematic extracted current washing of prepared / shredded sugarcane (108) by means of imbibition water (IW) and press water (PW) and recirculation of extracted juice. Conventionally, this is achieved by forming a bed of prepared cane on a conveyor (102) having a feed end and a discharge end. As shown in FIG.1, heated press juice (juice extracted from bagasse) and imbibition water (IW) is added at the discharge end of the conveyor (102) and percolates through the bed of prepared cane and perforated slats of the conveyor (102). The water dissolves sugar from the prepared cane and thin juice thus formed is collected in a hopper.

During the whole duration of its passage through the diffuser, the bed of prepared cane is submitted to intensive sprays of juice of progressively decreasing concentration. This juice is moved forward one stage by pumping and the process is repeated until the juice reaches maximum concentration at the feed end of the diffuser and the maximum concentrated juice, also known as draft juice (106), is pumped for further processing. There are multiple stages of collecting less concentrated juice and pumping the same to next stage called stage juice. The stage juice is heated intermittently to maintain the temperature of cane bed around 70 ºC to achieve maximum extraction.

Scalding juice is the juice near the cane entry of the diffuser which is withdrawn, heated to 95-98 ºC in a scalding juice heater (104), which is a tubular juice heater, and sprayed onto the prepared cane closest to the cane entry. The prepared cane is at ambient temperature. Part of the scalding juice percolated through the incoming cane bed is pumped for further processing and is called draft juice. This spray of heating juice not only increases the sugar loss in the residue but also reduce the chances of microbiological loss of the sugar in the travel time of prepared cane through the diffuser bed.

As shown in FIG.2, which illustrates a conventional multi-stage evaporator. The multi-stage evaporator includes five evaporator bodies (E1, E2, E3, E4 and E5), each giving respective effects of vapours (V1, V2, V3, V4 and V5). Live steam (A) and/or vapour (V1) is fed to the conventional diffuser station (100) for heating, as shown in FIG. 1 and FIG. 2. The live steam (A) is required for scalding juice heating by conventional tubular juice heater (104). Press and Stage juice heating also requires high pressure vapours (V1) as it needs to overcome hydrostatic pressure of shredded cane mixed with juice. Use of high pressure vapour (V1) increases the steam demand of the plant and hence increase the overall cost of sugar production. In addition, conventional diffuser station (100) uses the tubular juice heater (104) which achieves a 10 ºC approach temperature, i.e. the juice temperature can achieve 10 °C less than the temperature of applied vapour. The other disadvantage of using tubular juice heater (104) is that it requires high pressure and temperature vapour for juice heating. Also, the tubular juice heater requires frequent cleaning to remove scaling and requires high pressure pump as head loss is high. Additionally, the tubular juice heater (104) is not steam economic since it uses high temperature and pressure steam, thus increasing the total steam consumption of the sugar plant.

An article titled “Determination of optimum vapour bleeding arrangements for sugar juice evaporation process.” published by S. Chantasiriwan in the “Journal of Food Processing” discloses a sugar juice evaporation process that consist of juice heater, evaporator, and crystallizer. It discloses an optimization model for optimum allocation of a fixed surface among the four heat exchangers of the juice heater, which is used to increase juice temperature to the boiling point before entering the quintuple effect evaporator.

GB1142463A discloses sugar cane diffuser in which bagasse on an endless conveyor is sprayed with water and sugared solutions. The sugared solutions are collected underneath the conveyor and the underneath conveyor chain assembly is made up of a plurality of elongated, perforated rectangular slats. The processes in the above prior art does not use full heat potential of low pressure vapour, thereby, huge amount of heat is wasted which results in higher energy cost for production of sugar.

In light of the above and other limitations of the conventional juice heating in a diffuser station, it is objectively desired to provide a process of juice heating in a diffuser station which is cost effective. It is also desired to utilize low pressure and low temperature vapour and prevent the wastage of heat which ultimately reduces the overall cost of sugar production.

SUMMARY OF THE DISCLOSURE
The present disclosure provides a process for juice extraction in a diffuser station from a bed of shredded sugarcane on a perforated conveyer, the perforated conveyer comprising a feed end and a discharge end, the process comprising a press heating stage step, stage juice heating steps and scalding stage steps. The press heating step includes adding of imbibition water and press water at the discharge end of the conveyer for obtaining a low concentrated mixture of juice and water, wherein the press water is pre-heated in a press water heater and wherein the press water heater is adapted to utilize vapour from a fourth effect of evaporator. The stage juice heating steps include heating the low concentrated mixture in stage juice heaters using vapour from the fourth effect of evaporator to obtain a first juice mixture; recirculating and reheating the first juice mixture on the perforated conveyer for further increasing the concentration of the juice mixture in multiple juice heating stages for obtaining high concentrated juice mixture. The scalding stage steps include feeding the high concentrated juice mixture in a first scalding juice heater and a second scalding juice heater, wherein the first scalding juice heater and the second scalding juice heater utilizes vapour from second and third effects of evaporator; spraying the heated juice mixture on the shredded sugarcane at the feed end of the perforated conveyer for obtaining maximum concentration of juice mixture; and pumping the maximum concentrated juice mixture for sugar production using at least one daft juice pump.

In an embodiment, the stage juice heating steps comprise recirculating the low concentrated juice mixture to stage juice heaters by stage juice pumps.

In an embodiment, the press water heater, the stage juice heaters and the scalding juice heater are direct contact juice heaters.

In an embodiment, the concentration of juice mixture increases from the press heating stage to the stage juice heating.

In an embodiment, the concentration of juice mixture increases from the stage juice heating to the scalding stage.

In an embodiment, the vapour from second, third and fourth stage of the evaporator are low pressure and low temperature vapour.

In an embodiment, the shredded sugarcane is fed at the feed end of the conveyer and discharged at the discharge end of the conveyer.

In an embodiment, the juice is extracted from the shredded sugarcane as the cane passes from the feed end to the discharge end of the perforated conveyer.

In an embodiment, the juice achieves a temperature which is 2° C less than the vapour temperature during stage juice heating and scalding stage heating.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
FIG. 1 shows a schematic diagram of a diffuser station for a process of juice extraction, according to conventional diffuser station;

FIG. 2 shows a flow diagram of a multi-stage evaporator, according to conventional diffuser station;

FIG. 3 shows a schematic diagram of a diffuser station for a process of juice extraction, according to an embodiment of the present invention;

FIG. 4 shows a front view of a direct contact juice heater shown in FIG. 3, according to an embodiment of the present disclosure; and

FIG. 5 shows a flow diagram of multi-stage evaporator, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE WITH REFERENCE TO ACCOMPANYING DRAWINGS
Provided below is a non-limiting exemplary embodiment of the present invention and a reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein, are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claim.

Referring to FIG. 3, which illustrates a schematic of a diffuser station (200) for juice extraction, according to an embodiment of the present disclosure. The juice is extracted from sugarcane by forming a bed of shredded sugarcane (201) on a perforated conveyer (202). The perforated conveyer (202) includes a feed end (204) and a discharge end (206). The shredded sugarcane (201) is fed on the feed end (204) of the perforated conveyer (202) and after juice extraction the bagasse is discharged at the discharge end (206) of the perforated conveyer (202). The term “bagasse” is defined as fibrous residue of sugarcane after extraction of juice. The shredded cane passes from the feed end (204) to the discharge end (206) and the juice is extracted by spraying a heated juice on the shredded cane. The process of extraction comprising a press heating stage (S1).

The press heating stage (S1) includes adding of process / imbibition water (IW) and press water (PW) at the discharge end (206) of the conveyer (202) for obtaining a low concentrated mixture of juice and water. The press water (PW) is obtained from drying mill (not shown), i.e. the water obtained after drying of sugar in the drying mill. As shown in FIG. 3, the press water (PW) is pre-heated in a press water heater (208). The press water heater (208) is connected to vapour (V4) from a fourth effect of a multi-stage evaporator (as shown in FIG. 5). The press water heater (208) is a direct contact heater (as shown in FIG. 4), where the press water (PW) is heated by direct contact with the vapour (V4). The vapour (V4) from the fourth effect of evaporator is a low pressure and low temperature vapour.

The pre-heated press water (PW) and the process / imbibition water (IW) is sprayed on the discharge end (206) of the perforated conveyer (202), where the shredded cane is heated and a low concentrated mixture of juice and water is obtained. The low concentrated juice and water mixture is collected in a hopper (210) positioned at bottom of the perforated conveyer (202). The low concentrated mixture is then pumped to stage juice heating steps (S2).

The process further includes stage juice heating steps (S2). The stage juice heating steps (S2) include heating the low concentrated mixture in stage juice heaters (212) using vapour (V4) from the fourth effect of the multi-stage evaporator to obtain a first juice mixture, which is a mixture of previous juice and the vapour (V4). The first juice mixture is then sprayed on the shredded cane on the perforated conveyer (202) for extracting juice from the shredded cane to obtain a high concentrated juice mixture. Thus, the concentration of juice mixture increases as the juice mixture passes from press heating stage step (S1) to stage heating steps (S2). The juice mixture is then recirculated to the stage juice heaters (212) using stage juice pumps (214). In the illustrated embodiment, the stage juice heating steps (S2) involves three stage heating and recirculating the juice mixture using three stage juice heaters (212) and stage juice pumps (214). The three stage juice heaters is connected to vapour (V4) from the fourth effect of the multi-stage evaporator (shown in FIG. 5).

The stage juice heaters (212) are direct contact juice heaters (300), where vapour (V4) is mixed with the recirculated juice from the stage juice pump (214). After multiple stage juice heating steps (S2), the high concentrated juice mixture enters the scalding stage steps (S3).

The scalding stage steps (S3) includes feeding high concentrated juice mixture in a first scalding juice heater (216) and a second scalding juice heater (218) using scalding juice pumps (220). The first scalding juice heater (216) utilizes vapour (V4) from fourth effect of the multi-stage evaporator for heating the high concentrated juice. The high concentrated juice is then passed to the second scalding juice (218) heater for further heating. The second scalding juice heater (218) utilizes vapour (V3) from third effect of multi-stage evaporator. The scalding stage (S3) further includes spraying the heated juice mixture on the shredded sugarcane at the feed end (204) of the perforated conveyer (202) for obtaining maximum concentration of juice mixture. The juice mixture having maximum concentration, also known as draft juice (224) is then pumped for sugar production using draft juice pumps (222). The first scalding juice heater (216) and the second scalding juice heater (218) are direct contact juice heaters (300).

Referring to FIG. 4, which illustrates the direct contact juice heater (300) according to an embodiment of the present disclosure. The direct contact juice heater (300) includes a cylindrical chamber (302) having a juice inlet (304), a juice outlet (306), a vapour inlet (308) and a vapour outlet (310). The juice flows inside the direct contact juice heater (300) from top to bottom of the heater (300). On the other hand, the vapour flows from the bottom to top of the heater (300) such that the juice and the vapour are directly mixed with each other during passage through the heater (300). Latent heat from the vapour is transferred to the juice, thus increasing the temperature of the juice. The direct contact juice heater (300) works on 2º C approach i.e. juice temperature can achieve 2° C less than the temperature of the vapour. Thus the lower approach temperature of direct contact heater makes it suitable to use low pressure vapour.

FIG. 5 illustrates a multi-stage evaporator, particularly a 5-stage evaporator, also known as quintuple. The quintuple has five evaporator bodies (E1, E2, E3, E4 and E5), each giving respective effects of vapours (V1, V2, V3, V4 and V5). The vapour from third (V3) and fourth effects (V4) are utilized in the diffuser station (200).

Experimental results:
The vapour consumption of a sugar plant generally depends on bleeding scheme. Generally, the effect of bleeding in steam consumption can be understood by the following equation:

Impact of bleeding on total steam consumption = B x (N-n) / N
Where:
“B” = Bled vapour in ton /hr
“N” is Number of effects in multi effect evaporator
“n” is Effect from which bled vapour is withdrawn

Assuming 7.5 Ton of bled vapour requirement for diffuser heating for a 100 TCD (Tons of cane per day) plant.

Case 1 (Conventional system)
Heating by high pressure vapour V1 i.e., Vapour from 1st effect of a quintuple (5-stage evaporator).

Impact of bleeding on total steam consumption = 7.5 x (5-1)/5 = 6 ton /hr addition in steam consumption.

Case 2 (Present invention)
Heating by low pressure vapour V4

Impact of bleeding on total steam consumption = 7.5 x (5-4)/5 = 1.5 ton /hr addition in steam consumption.

Thus, by using the process disclosed in the present invention there is a saving of 4.5 ton /hr of steam if V4 is utilized in place of V1. The steam saving varies depending on the vapour utilized.

In the present invention, vapour (V4) is utilized for press juice heating, stage juice heating. In the prior art, vapour (V2) is utilized for press juice heating, stage juice heating and scalding of juice. A two stage heating is done in the present invention for scalding of juice and vapour (V3) and vapour (V4) are utilized for heating scalding juice. Estimated steam saving as per flow diagram drawn is around 1.82 %. Actual steam % cane of the plant when vapour (V2) was utilized in diffuser station was 37.40 % and with alteration of steam bleeding with vapour (V4) and vapour (V3) the estimated steam consumption of the plant was 35.52 %.

Net saving in steam for 2500 TCD = 1.82 %

Net saving in tonnes per day = 2500*1.82/100
= 45.5 T/Day

Net saving in bag per day = 20.68 T/Day
(Taking steam fuel ratio 2.2)

Saving in 150 days (one season) = 20.68*150
=3102 T

Cost of bag / Ton = Rs 1000

Net saving in one season = 3102*1000
= Rs 31,02,000

Advantages
The process of extracting juice utilizing low pressure and low temperature vapours from fourth and third effects of the multi-stage evaporator, there is a definite reduction in vapour consumption of the sugar plant. The reduction in the vapour consumption is calculated to be 1.82 %. This provides reduction in the cost of production by reduction of vapour consumption

In an embodiment, the process involves using direct contact juice heaters. The advantage of using direct contact juice heaters is that the approach temperature is minimum in direct contact heating.

Industrial Applicability
The disclosed process finds its potential application in sugar industries for production of sugar from sugarcane. The process can be used for extracting sugarcane juice from sugarcane. The process may also be used extracting juice from other food items, such as fruits and vegetables.

While aspects of the present invention have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by modification of the disclosed device without departing from the scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present invention as determined based upon claims and any equivalents thereof.

List of referral numerals:
100: Conventional diffuser station
102: Conveyer of conventional diffuser station
104: scalding juice heater of conventional diffuser station
106: Draft juice from conventional diffuser station
108: Shredded sugarcane fed in the conventional diffuser station
PW: Press water from drying mill
IW: Imbibition or process water
200: Diffuser station according to present invention
201: Shredded sugarcane used in the diffuser station of the present invention
202: Perforated conveyer
204: Feed end of the perforated conveyer
206: Discharge end of the perforated conveyer
208: Press juice heater
210: Hopper
212: Stage juice heaters
214: Stage juice pumps
216: First scalding juice heater
218: Second scalding juice heater
220: Scalding juice pumps
222: Draft juice pumps
224: Draft juice
300: Direct contact juice heater
302: Body of direct contact juice heaters
304: Juice inlet
306: Juice outlet
308: Steam inlet
310: Steam outlet
A: Live steam
E1: First body of multi-stage evaporator
E2: Second body of multi-stage evaporator
E3: Third body of multi-stage evaporator
E4: Fourth body of multi-stage evaporator
E5: Fifth body of multi-stage evaporator
V1: Vapour from first effect of evaporator
V2: Vapour from second effect of evaporator
V3: Vapour from third effect of evaporator
V4: Vapour from fourth effect of evaporator

WE CLAIM:
1. A process for juice extraction in a diffuser station (200) from a bed of shredded sugarcane (201) on a perforated conveyer (202), the perforated conveyer (202) comprising a feed end (204) and a discharge end (206), the process comprising:
- a press heating stage step (S1) including:
adding of imbibition water (IW) and press water (PW) at the discharge end (204) of the conveyer (202) for obtaining a low concentrated mixture of juice and water, wherein the press water (PW) is pre-heated in a press water heater (208) and wherein the press water heater (208) is adapted to utilize vapour (V4) from a fourth effect of evaporator;
- stage juice heating steps (S2) including:
heating the low concentrated mixture in stage juice heaters (212) using vapour (V4) from the fourth effect of evaporator to obtain a first juice mixture;
recirculating and reheating the first juice mixture on the perforated conveyer (202) for further increasing the concentration of the juice mixture in multiple juice heating stages for obtaining high concentrated juice mixture; and
- scalding stage steps (S3) including:
feeding the high concentrated juice mixture in a first scalding juice heater (216) and a second scalding juice heater (218), wherein the first scalding juice heater (216) and the second scalding juice heater (218) utilizes vapour (V4, V3) from fourth and third effects of evaporator;
spraying the heated juice mixture on the shredded sugarcane at the feed end (204) of the perforated conveyer (202) for obtaining maximum concentration of juice mixture; and
pumping the maximum concentrated juice mixture for sugar production using draft juice pumps (222).

2. The process as claimed in claim 1, wherein the stage juice heating steps (S2) comprise recirculating the low concentrated juice mixture to stage juice heaters (212) by stage juice pumps (214).
3. The process as claimed in claim 1, wherein the press water heater (208), the stage juice heaters (212) and the scalding juice heaters (216, 218) are direct contact juice heaters (300).

4. The process as claimed in claim 1, wherein the concentration of juice mixture increases from the press heating stage (S1) to the stage juice heating (S2).

5. The process as claimed in claim 1, wherein the concentration of juice mixture increases from the stage juice heating (S2) to the scalding stage (S3).

6. The process as claimed in claim 1, wherein the vapours (V3, V4) from third and fourth effect of the evaporator are low pressure and low temperature vapours.

7. The process as claimed in claim 1, wherein the shredded sugarcane (201) is fed at the feed end (204) of the conveyer (202) and discharged at the discharge end (206) of the conveyer (202).

8. The process as claimed in claim 1, wherein the juice is extracted from the shredded sugarcane as the cane passes from the feed end (204) to the discharge end (206) of the perforated conveyer (202).

9. The process as claimed in claim 1, wherein the juice achieves a temperature which is 2° C lesser than the vapour temperature during stage juice heating (S2) and scalding stage heating (S3).