Title of Invention

A PROCESS AND A PLANT FOR PRODUCING BAGASSE WITH REDUCED MOISTURE CONTENT

Abstract

This invention relates to a process for producing bagasse of reduced moisture content from the bagasse obtained from cane milling. It consists of two stage heating of condensate water first with vapour condensate from pan and evaporators. This preheated condensate is further heated in heat exchangers by utilizing the heat of the steam from boiler cycles. Heated condensate is fed to boilers to generate steam and electricity. The condensate water from the first stage heat exchanger is used to preheat air in a water-air heat exchanger. Preheated air is fed to a steam-air heat exchanger to further heat it. This hot air is fed to a bagasse drying chamber to dry bagasse of 50% moisture content to a moisture content of 40% or below. This invention also includes a plant consisting of a first heat exchanger, a deaerator, a water-air heat exchanger and a steam air heat exchanger. A drying chamber is provided to dry bagasse with this hot air to reduce its moisture content.

Full Text

This invention relates to a process and a plant for producing bagasse with reduced moisture content. In conventional sugar manufacturing units, cane is milled to extract cane juice which is further processed to obtain sugar. One of the byproducts of sugar industry is bagasse which is the refuse containing crushed sugar cane fibres. Bagasse is conventionally used as fuel in the sugar factory itself for boilers producing steam to generate power. Generally, the system is self supporting, the power generated being sufficient to run the sugar processing unit. However, considerable energy is unutilized and wasted in the existing sugar plants. ES 2068776 discloses a system for drying bagasse and other moist by-products. With the present day energy crises, the trend is to conserve, save and utilize as much recycleable energy as possible. One of the objects of this invention is to harness the heat energy which has not been fully utilized to produce bagasse with reduced moisture content which obviously burns better and produces more heat energy than bagasse with high moisture contents. A recent development in utilization of energy from sugar processing industry is bagasse-cogeneration plant which uses bagasse waste to produce more electricity than the actual requirement of the sugar plant itself. Bagasse co-generation plants prevent heat energy loss to a certain extent but energy waste is not completely avoided. Optimum use of heat energy for maximum power generation is aimed at, by the improvement developed by the inventor (s). In the existing bagasse-cogenration paints, condensate water obtained from condensing turbines in the plant is fed to a deaerator which receives steam from the boiler cycles of the unit. This steam heats the condensate water from the turbine and is fed to the boilers. Evaporation and pan stations of sugar processing units generate hot water which is termed as vapour condensate in this industry. Heat energy confined in this, has not yet been harnessed and used. The plant developed by the inventors adequately taps and uses heat energy from pan and evaporator condensates. Hot water obtained from these two stations of the unit has a temperature of above 90°C. This hot water is used to heat condensate water from the condensing turbines of the cogeneration plants before it enters the deaerator. Condensate water entering a heat exchanger at 45°C is heated by vapour condensate at around 90°C and thus the water which enters the deaerator is preheated to about 80°G which is further heated by the steam in the deaerator to a temperature of 105°C before it enters the boiler. After partial heat exchange in a first heat exchanger, this vapour condensate is used to heat atmospheric air in an air water heat exchanger to heat it to a temperature of about 77°C. This preheated atmospheric air enters a second air heater which is termed as steam air heater as turbine exhaust steam is utilized to exchange its heat with the incoming air. Air thus heated to about 120°C is fed to a bagasse drier which has bagasse of at least 50% moisture content. The temperature of bagasse in this chamber is about 55°C. Hot air entering the chamber dries bagasse to approximately 40% moisture content which is used as fuel for boilers. This reduction of moisture content to the tune of 10% increases the calorific value of bagasse from 1800 Kcal/kg tol915 Kcal/kg. This in turn increases the steam production by approximately 10%. This steam is capable of generating approximatley 1262kw or more of power in a standard 2500 tmsk/day co-generation sugar plant. The following flow chart illustrates the sequence followed by the plant deviced by the inventors. This water obtained after heating air in the first water air heater segment may be pumped to overhead tanks for recycling and the water obtained from the steam air heater may be recycled to boiler feed water tank. This invention relates to a process for producing bagasse with reduced moisture content from the bagasse obtained after cane milling in sugar industry which comprises the steps of two stage heating of condensate water form condensing turbines, in heat exchangers, heat of vapour condensate derived from evaporators and pan stations of a sugar producing plant being exchanged at the first stage of heating to preheat said condensate water, feeding said preheated condensate to a deaerator to be further heated by boiler, recycled steam, and feeding the same to a boiler, preheating atmospheric air in a water-air heat exchanger with the vapour condensate flowing out from said first stage heat exchanger, further heating said preheated air in a steam-air heat exchanger utilizing heat from turbine exhaust steam, and feeding said further heated air to a bagasse drier containing bagasse of at least 50% moisture content to air dry the same to reduce its moisutre content. This invention also includes a plant for producing bagasse with reduced moisture content from the bagasse obtained after cane milling which comprises a first heat exchanger to preheat condensate water from a condensing turbine with vapour condensate form evaporators and pan stations of a sugar producing plant, a deaerator to further heat said preheated water, said deaerator having heat exchange means to derive heat from boiler recycled steam, said deaerator being connected to a boiler, a water-air heat exchanger to preheat atmospheric air with the hot vapour condensate flowing out from said first heat exchanger, said air water heat exchanger connected to a steam-air beat exchanger provided with means to circulate turbine exhauset steam, to heat the incoming preheated air, a bagasse direr connected thereto to receive hot air therefrom and to dry bagasse to reduce its moisture content. In a particular embodiment in a 2500 tonns cane/day sugar plant, 23 tons/hours of condensate water at a temperature 45°C is heated with vapour condensate of 90T/h. The temperature of the condensate is around 90°C. During the first stage, the temperature of condensate water is raised form 45°C to 80°C while the temperature of the vapour condensate drops from 90 to 81°C. The second stage heating of the condensate water with steam increases the temperature to 105°C which is fed to the boiler. The vapour condensate flowing out from the preheating stage is fed to heat 58000Kg/hr of air per hour at the rate from 25 to 77°C at the air water heater exchanger. This preheated air is ted to a steam-air heat exchanger where 2.5 kg/cm3 steam at 175°C obtained from turbine exhaust steam exchanges its heat with it to raise the air temperature to 120°C. This hot air is used to dry bagasse to a reduced moisture content. Water obtained from the heat exchangers is recycled to the unit. Enchancement of power production using dry bagasse is considerable when heat from the vapour condensate is adequeately recovered and utilized to this end. WE CLAIM: 1. A process for producing bagasse with reduced moisture content from the bagasse obtained after cane milling in sugar industry comprising the steps of two stage heating of condensate water from condensing turbine in heat exchangers, heat of vapour condensate derived from evaporators and pan stations of a sugar producing plant being exchanged at the first stage of heating to preheat said condensate water, feeding said preheated condensate water to a deaerator to be further heated by boiler recycled steam and feeding the same to a boiler, preheating atmospheric air in a water-air heat exchanger with the vapour condensate flowing out of said first stage heat exchanger, further heating said preheated air in a steam-air heat exchanger utilizing heat from turbine exhaust steam, and feeding said further heated air to a bagasse drier containing bagasse of at least 50% moisture content to air dry the same to reduce its moisture content. 2. The process as claimed in claim 1, wherein the bagasse in the bagasse drier is dried to 45% or below. 3. The process as claimed in claim 1, wherein the water after heat exchange in said water-air heat exchanger and steam condensate from said steam-air heat exchanger are optionally recycled. 4. The process as claimed in claim 1, wherein said condensate water has a temperature of about 45°C and said surplus vapour condensate has a temperature of about 90°C. 5. The process as claimed in claim 4, wherein the vapour condensate flowing out of said first step heating has a temperature of about 81° C and is fed to said water air heat exchanger to heat atmospheric air to about 77°C. 6. The process as claimed in claim 5, wherein the steam supplied to steam air heat exchanger has a temperature of about 175°C which exchanges heat with the preheated air supplied thereto, to enhance its temperature to about 120°C. 7. A plant for producing bagasse with reduced moisture content from the bagasse obtained after cane milling comprising a first heat exchanger to preheat condensate water from a condensing turbine with vapour condensate from evaporators and pan stations of a sugar producing unit, a deaerator to further heat said preheated water, said deaerator having heat exchange means to derive heat from boiler recycled steam, said deaerator being connected to a boiler, a water-air heat exchanger to preheat atmospheric air with the hot vapour condensate flowing out of said first heat exchanger, said water air heat exchanger connected to a steam-air heat exchanger provided with means to circulate turbine heat exhaust steam, to heat the incoming preheated air, a bagasse drier connected thereto to receive hot air therefrom, and to dry bagasse to reduce its moisture content. 8. The plant as claimed in claim 7, wherein means are provided for recycling the outgoing streams from said water-air heater and steam-air heater. 9. A process for producing bagasse with reduced moisture content from the bagasse obtained after cane milling in sugar industry substantially as herein described. 10.A plant for producing bagasse with reduced moisture content from the bagasse obtained after cane milling substantially as herein described.

Documents:

0667-mas-2000 abstract.pdf

0667-mas-2000 claims-duplicate.pdf

0667-mas-2000 claims.pdf

0667-mas-2000 correspondence-others.pdf

0667-mas-2000 correspondence-po.pdf

0667-mas-2000 description (complete)-duplicate.pdf

0667-mas-2000 description (complete).pdf

0667-mas-2000 form-1.pdf

0667-mas-2000 form-19.pdf

0667-mas-2000 form-26.pdf

0667-mas-2000 form-3.pdf

0667-mas-2000 form-4.pdf