Title of Invention

A DEVOLATILISER AND A PROCESS FOR DEVOLATILISATION OF LIGNITE

Abstract

A process for the devolatilisation of lignite and an equipment therefore : The present invention provides a process for devolatilisation of lignite. The present invention also provides an equipment for production of devolatilised lignite. The said process comprises the step of charging lignite into a pre-heated chamber of the equipment having temperature in the range of 800 to 900 degree Celsius, allowing the charged lignite to be devolatilised in the presence of preheated air, removing the devolatilised lignite char from the said chamber followed by water quenching the hot mass

Full Text

A devolatiliser and a process for devolatilisation of lignite. The present invention relates to a process for devolatilisation of lignite, and an equipment therefore. The devolatilised lignite finds its use in vertical shaft kilns for cement production and to produce formed coke or briquetted fuel for industrial and domestic uses. Lignite contains high moisture and volatile matter and found unsuitable for industrial use as such. By devolatilisation, the moisture and volatile matter content can be brought down to the desired level. Due to high moisture content lignite gets crumbled into pieces and later on into the dust form as soon as it is heated. As a result, lignite drying and devolatilisation becomes very difficult in conventional devolatiliser / carboniser. Prior art search for devolatilisation of lignite was made based on literature survey and patent databases, which did not yield any relevant references. At present there is no equipment / device to devolatilise lignite. The main objective of the present invention is to provide a process for devolatilisation of lignite. Another objective of the present invention is to provide an equipment for production of devolatilised lignite. Yet another objective of the present invention is to provide energy efficient devolatiliser for faster devolatilisation. The invention provide a process and an equipment for the devolatilisation of lignite which comprises charging lignite into a pre-heated chamber having temperature in the range of 800 to 900 degree Celcius, allowing the charged lignite to be devolatilised in the presence of air preheated to a temperature in the range of 400 to 450 degree Celsius, removing the devoiatilised lignite char from the said chamber followed by water quenching the hot mass, in the present invention a new concept has been introduced and accordingly construction of devolatiliser has been done which has made the devolatiliser energy efficient, environment friendly and cost effective. Emission of pollutants take place around 600°C but the combustion of the pollutants take place at higher temperature which is not possible from the same bed itself. Secondary combustion system thus provided for removing these pollutants. Secondary combustion is done in sole flue by injecting hot air where a part of the pollutants are combusted. For combustion of the rest of the pollutants consisting mainly higher hydrocarbons, carbon dioxide, poly-aromatic hydrocarbons and suspended particulate matters, provision has been made to bring the entire flue gas, after getting combusted in the sole flue to trie red_hot bed of the adjacent chamber where the temperature is around 850 ± 50°C. During combustion of the pollutants the system becomes highly energy efficient resulting increase in the rate of devolatilisation. The npvelty of the present invention resides in devolatilisation of lignite to make it industrially usable. This is achieved by the inventive steps of getting the pollutants combusted completely in the system and in addition to this the in-built system is provided for producing hot primary and secondary air in-situ, which is re-circulated and significantly contribute in making the devolatiliser energy efficient. In Figure 1 of the drawing accompanying the specification, a schematic embodiment of the equipment of the present invention is shown. In figure 1, the various parts are: 1 Devolatilisation chambers 2 Removable Fixed doors 3 Covered opening 4 Sole Heating System 5 Ducts 6 Water Scrubber 7 Common Chimney 8 Common Duct Accordingly the present invention provides a process for the devolatilisation of lignite carried out with a devolatiliser , which comprises charging lignite into a pre-heated chamber (1) of the said devolatiliser having temperature in the range of 800 to 900 degree Celsius, allowing the charged lignite to be devolatilised in the presence of air preheated to a temperature in the range of 400 - 450 degree Celsius, removing the devolatilised lignite char from the said chamber and water quenching the hot mass by hot water. Accordingly the present invention provides a devolatiliser for the devolatilisation of lignite by the process as described above which comprises a plurality of devolatilisation chambers (1) having removably fixed doors (2), each of the said chambers being provided with top charging covered openings (3), the floor of the chambers having elevation of the order of 30 degrees and provided with sole heating system (4), the walls of each of the chambers being provided with ducts (5) capable of circulating pre-heated air to the chamber as well as to the sole, the said devolatilisation chambers being also connected to a water scrubber (6), and to a common chimney (7) through a common duct (8). In an embodiment of the present invention the chambers may be provided with metallic grate above the floor of the chamber for efficient devolatilisation of lignite. In an embodiment of the present invention the passage of the gas towards the chimney is controlled through dampers. In the process of the said invention, the chambers of the devolatiliser are made of standard refractory bricks and consist of rectangular chamber surrounded by an arched roof and closed at the back. The floor of the chamber has a gradient of the order of 30°. The said chamber is provided with a removable door on the front side. The chambers are connected with a common chimney through a water scrubber and are built in double rows arranged back to back. In a pre-heated empty chamber a grate is placed and lignite is charged from the centrally located charging hole on the arched roof. After the charging is over the door is closed. The volatiles coming out of the lignite is partly burnt and the heat generated during combustion of the volatiles help to maintain the temperature in the ovens. The partly combusted gas from the devolatilising chamber is passed through off-take pore(s) located at the back wall of the chamber which is/are in turn connected to the down corners of the sole flues by closing the dampers placed at the common tunnel. The flues going to the sole also help in releasing the heat to the sole and increase the temperature of the sole . Moreover the combustible remained in the flue is burnt to the maximum extent possible. The outlet of the sole flue in turn is connected to the waste gas tunnel leading to the chimney via the water scrubber. The passage of flues towards the chimney can be controlled through dampers. The circulation of the flue gas generated during devolatisation not only enhance the temperature of the sole which reduces the devolatilisation time and increase productivity/chamber/day, but also allows the tarry matter coming out during devolatilisation to be completely burnt with the help of secondary air injected through the holes selectively placed inside the chamber. Entry of secondary air can be regulated through the side holes as well as dampers and if required can be utilised to dilute the emitted gas going through the chimney, thus resulting in reduced pollution. The novelty of the present invention resides in: 1. Devolatilising the lignite in static condition in comparison to available methods wherein on heating, the lignite gets crumbles into pieces and later on into the dust form resulting non-dispersement of heat required for complete devolatilisation. To overcome this problem, fluidization technique is adopted for the thorough penetration of heat. But in the present invention due to adoption of sole heating system and the metallic grate in the chamber, fluidization of the lignite mass is not required. 2. Pollutants are combusted completely in the system. During combustion of the pollutants, the system becomes highly energy efficient resulting in increasing the rate of devolatilisation. The inventive steps resides in getting the pollutants combusted and using hot primary and secondary air in-situ which is re-circulated and significantly contribute in making the Devolatiliser energy efficient and environment friendly. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention. Example-1 200 kg of lignite was charged in a previously heated chamber. The size of the lignite charged was from 0 to -150 mm and the chamber temperature was 800°C at the time of charging. The grate having screen of 12.5 mm size was placed on the floor of the chamber, +12.5 mm size lignite after being heated started crumbling and the undersize lignite fell on the floor of the chamber. By virtue of the sole heating system the under size lignite also got devolatilised. The hot material was taken out and quenched with water. (As received basis) Raw Lignite Devolatilised Lignite Moisture % 10.0 4.1 Ash% 17.7 23.2 Volatile Matter% 35.2 13.4 Fixed Carbon % 37.1 59.3 Example -2 200 kg of lignite was charged in a previously heated chamber. The size of the lignite charged was from 0 to -150 mm and the chamber temperature was 850°C at the time of charging. The grate having screen of 12.5 mm size was placed on the floor of the chamber, +12.5 mm size lignite after being heated started crumbling and the undersize lignite fell on the floor of the chamber. By virtue of the sole heating system the under size lignite also got devolatilised. The hot material was taken out and quenched with water. (As received basis) Raw Lignite Devolatised Lignite Moisture % 11.2 4.6 Ash% 14.9 19.7 Volatile Matter% 36.8 13.6 Fixed Carbon % 37.1 62.1 Example- 3 200 kg of lignite was charged in a previously heated chamber. The size of the lignite charged was from 0 to -150 mm and the chamber temperature was 900°C at the time of charging. The grate having screen of 12.5 mm size was placed on the floor of the chamber, +12.5 mm size lignite after being heated started crumbling and the undersize lignite fell on the floor of the chamber. By virtue of the sole heating system the under size lignite also got devolatilised. The hot material was taken out and quenched with water. (As received basis) Raw Lignite Devolatised Lignite Moisture % 12.3 5.2 Ash% 16.2 22.4 Volatile Matter% 34.3 12.6 Fixed Carbon % 37.2 59.8 The main advantages of the present invention are: 1. Economic, direct heating chamber for production of lignite char by devolatilisation of lignite, with the emissions well maintained within the permissible range with respect to suspended particulate matter, gaseous pollutants and heat besides being energy efficient. 2. The device of the present invention has arrangements of burning the volatile matters, suspended particulate matter and combustibles of the flue gases in different stages till it burns out almost completely. 3. Lignite as such was not useful. This is made useful by the present invention. 4. Common refractory materials have been used in most of the parts of the chimney. We Claim: 1. A devolatiliser for the devolatilisation of lignite characterized in that it comprises a plurality of devolatilisation chambers (1) having removably fixed doors (2), each of the said chambers being provided with top charging covered openings (3), the floor of the chamber having elevation of the order of 30 degrees and provided with sole heating system (4), the walls of each of the chambers being provided with ducts (5) capable of circulating pre-heated air to the chamber as well as to the sole, the said devolatilisation chambers being connected to a water scrubber (6), and to a common chimney (7) through a common duct (8). 2. A devolatiliser as claimed in claim 1 , wherein the chambers are provided with metallic grate above the floor of the chamber. 3. A devolatiliser as claimed in claim 1-2, wherein the passage of the flue gas towards the chimney is controlled through dampers. 4. A process for the devolatilisation of lignite carried out with a devolatiliser as claimed in claim 1-3 , which comprises charging lignite into a pre-heated chamber (1) of the said devolatiliser having temperature in the range of 800 to 900 degree Celsius, allowing the charged lignite to be devolatilised in the presence of air preheated to a temperature in the range of 400 - 450 degree Celsius, removing the devolatilised lignite char from the said chamber and water quenching the hot mass by hot water. 5. A process as claimed in claim 1 , wherein lignite used is of any quality . 6. A process for the devolatilisation of lignite substantially as herein described with reference to the examples. 7. A devolatiliser of lignite substantially as herein described with reference to specification and drawing accompanying this specification.

Documents:

63-del-2002-abstract.pdf

63-del-2002-claims.pdf

63-del-2002-correspondence-others.pdf

63-del-2002-correspondence-po.pdf

63-del-2002-description (complete).pdf

63-del-2002-form-1.pdf

63-del-2002-form-18.pdf

63-del-2002-form-2.pdf

63-del-2002-form-3.pdf