Title: MAIZE WET COB DRYING WITH HEAT ENERGY OF PRODUCER GAS GENERATED FROM MAIZE DRY SHANKS.

Field of the invention: This invention relates to the maize wet cob drying and in particularly relates to the producer gas generated from maize dry shanks.

Background of the invention:

Till date the dry maize shanks have been used either for burning directly in a heat exchanger or the dry maize shanks are disposed off as scrap or as fuel to others. For the first time the dry maize shanks have been used for production of producer gas. The primary purpose of the invention is to use the dry maize shanks generated in the process of maize cob drying in a useful and purposeful way by producing the producer gas through a gasifier and burning it as a clean fuel for generating the heat required for maize cob drying.

We, for the first time in India Bio-Mass gas produced in the Gas Producer by using corn shanks bio-waste generated in the process of Ear Com Drying as the prime source of heat required for Ear Corn Drying and for Seeds Drying without affecting the quality parameters laid down by the Statutory Governmental and Non Governmental Institutions

A preliminary literature survey was carried out and the information available from the articles from universities and literature made available by reading equipment manufacturers particularly ear corn dryers and seed dryers and also the patent search though to a limited extent was the basis for our claim. The literatures search predominantly concluded that the fuel used is LPG or Natural Gas depending upon the availability which formed the backbone of the industry.

However, it should be noted that Bio-Mass gasification in a standard producer gas generator per say is not a novel equipment to the process industry. The earlier attempts made did not succeed primarily due to the quality if Gas which was responsible for passing on the dried product its odour and deposition of un burnt tarry matter.

Our gasification technique has successfully eliminated these draw backs as our design has done away with the air stream distribution grate which supports bio mass limiting the operating temperature. Our gas generator has done away with the metallic grade which permits us to reach much higher temperatures which help in cracking of Tarry material thus eliminating problems mentioned above.

Summary of the invention:

Production of Producer Gas using the shanks remaining after shelling the seed from com cobs, and using the gas thus produced for drying the corn cobs, is the unique phenomena tried for the first time for com cob drying in the seed industry. Producer Gas from the shanks is the non-conventional fuel used for the first time for corn cob drying. The gas produced from the corn cob shanks is cost effective and environment friendly, helps in better utilisation of the agricultural residue. The hot air generated by burning the producer gas is used in turn for drying the wet cobs. Thus the process established is helpful in recycling of the agricultural residue, i.e., corn cob shanks, for drying the com cobs. The technology area to which the invention relates to is the process of "gasification of com cob shanks for drying of wet corn cobs". The producer gas from com cob shanks is a cost effective noncoventional energy fuel for drying the com cobs. This producer gas is replacing the LPG, wood and other conventional fuels being used for drying the com cobs.

For production of quality hybrid maize seeds, maize cobs are harvested/picked up from the fields with moisture ranging from 25-35%. These wet cobs are mechanically dried by blowing hot air with temperature not exceeding 45 degrees C. Traditionally LPG gas and/or wood is used for producing hot air required for maize wet cob mechanical drying process. Chenai Seeds & Oils Ltd., (CSO) had set up the maize cobs drying plant at Kamavarapukota which is located at a distance of 36 Km., from Eluru on Eluru-Jangareddygudem Road in West Godavari District, Andhra Pradesh. The maize cob drying facility has been established by installation of heat exchangers, blowers and bins. Initially wood has been used in the heat exchanger for heating the air to 40-45 degrees C. After drying the maize cobs to 9%-l 1%, the maize seed is removed from the maize cobs through the process of shelling. The maize dry shanks were used for burning in the heat exchanger. This process has created large quantities of fine dust and is polluting the atmosphere. CSO had recognised the high calorific value in the maize dry shanks and searched for the best route to burn the shanks in controlled conditions through a gasifier. CSO had taken trials in September 2007 and found that maize shanks is suitable material for gasification. With the assistance of the Consulting Engineers, CSO had designed and installed the gasifier of 500 Kg. per hour of maize dry shanks at Kamavarapukota and generated the producer gas in March 2008. This producer gas is brunt through a burning chamber which is placed near the inlet of the blower.

The invention can be applied even to the maize shanks generated by shelling of the commercial maize. Large quantities of maize are produced in the country and after removing the maize cereal, the maize shanks are generally left in the field or used as fuel. These maize shanks can be used for generating the producer gas in various locations where the maize production is high. This producer gas can be used even for generating the power required for the farms through a process of consolidation by forming Self Help Groups (SHGs).

Description of the invention:

The present process predominantly uses LPG as fuel for drying of ear cobs in the ear cobs dryer. The process consists of the following

• Storage facility mostly in the form of large bullets.

• The bullets require as per statutory norms large space, huge quantities of water as per the requirements of statutory authorities.

• The use of water requires spray nozzles, pressure piping, dedicated water storage and pump. Instrumentation for flow measurement and temperature measurement etc.

• LPG facilities also is used in the form of cluster cylinders as many as 150 to 200 cylinders connected to a single header for its use as fuel.

• The expenditure in both the types of storage is quite high with associated expenditure towards safety.

• The fuel is burnt in a furnace and the hot gas mixed with atmospheric air is pumped into the dryer by a blower.

• The present system of LPG as fuel being burnt in the furnace attached to ear com dryer is not capable of complete utilisation of its heat content.

The System of Producer Gas and the Ear-Corn Dryer as conceived, planned and implemented partially (the producer gas part is completed and operated successfully whereas the furnace with mixing chamber along with recycle of hot gases with appropriate instrumentation and instrument controlled gas recirculation system is under progress)

The advantages of the proposed system as detailed above are listed below:

• The gas generator, the furnace, and the mixing chamber along with hot air circulating blower are placed in a manner that no storage of fuel gas is required thus eliminating the hazards normally associated with gaseous fuel storage.

• Producer gas is a low caloric value fuel and hence does not require the stringent safety measures normally associated with high calorific value gasses like LPG.

• As the gas is not required to be piped to a number of consumers the associated piping and instrumentation cost is also eliminated.

• As the raw material for gasification is the waste generated in the companies dryers, its use as fuel works out to be highly economical

• And hence the cost of gaseous fuel is also very competitive with respect to LPG.
Modifications to Ear-Corn Dryer in combination with furnace, mixing chamber and the circulation blower.

• It is planned to provide the total system with instrumentations to record temperature and pressure and also relative humidity to help decide on the quantity of heat pumped into the system.

• The monitoring of above parameters in combination with monitoring the pressure drop across the individual bins to ensure that volumetric flow rates are just adequate.

• Such a facility would greatly help us to ensure that neither excess heat is liberated nor there is a shortage of heat for the process.

• It is also intended to explore the possibility of manipulating the hot gas circulation by controlling system of doors and dampers based on the data made available to the operator generated by the proposed
instrumentation.

It is disclosed that the total system consisting of

1. Low cost fuel

2. Producer Gas Generator

3. Furnace

4. Mixing Chamber

5. Blower

6. Ear-Corn Dryer appropriately instrumented and modified

7. Modifications which include newly designed discharge doors ensuring no leakages and hence no wastage of hot gas and hence no wastage of fuel.

8. The new doors are very user friendly and can be controlled by one motion of the lever.

9. The instrumentation will help greatly to isolate the bins which are not in operation. This facility will be a great help in reducing the wastage of hot gases.

Step by Step Description of Process Flow sheet:

1. The gasification flow sheet at Annexure 1 consists of following items:

a) Ground level hopper for shanks

b) Vibratory discharger

c) Bucket Elevator for transporting shanks to the feed hopper.

d) Feed Hopper with discharge control mechanism.

e) Gas Generator

f) Dust catcher

g) Flare and Flare Pipe with Flare lighting arrangement

h) Scrubber

i) Ground Level Sump for Scrubber

j) Water recirculation pump

k) ID Fan

1) FDFan

m) Furnace with gas burner, refractory partition walls for achieving through mixing of all the
streams

n) Air Blower for the Burner

Gas Producer Operation:

Constructional Details:

The producer gas generator is constructed from boiler quality steel plates (IS2002). The plate thickness is normally 12mm thick. The special feature of the Gasifier is it is vertical conical shaped vessel and lined inside with refractory bricks. In a normal Gasifier the shell is cylindrical, vertical shaped with a refractory lining inside. This type of Gasifier requires a metallic grade (steam air blast distributer). The life of the metallic distributer is not more than a couple of years. Our design has done away with metallic blast distributer and instead the conical bottom of the shell supports the fuel bed and also distributes the air blast when operated updraft mode. This in itself is a achievement worth noting. The producer shell has 5 temperature zones. The bottom most portion which has water seal contains klinker and ash. This supports the bed of shanks starting from top portion. Starting from feed end going up to water seal bottom the five temperature zones are as follows

• Zone Nol is the drying zone where surface moisture is removed. The temperature here is in the range of 200 to 300 degrees centigrade.

• Zone No2 - De-volatization and Distillation zone: The temperature in this zone will be 350 to 550 degrees centigrade.

• Zone No3 - Reduction Zone: The temperature in this zone is between 550 and 1000 degrees centigrade.

• Zone No4 - Combustion Zone: Here the temperature ranges between 1000 to 1200 degrees centigrade.

• Zone No5 - Ash and Klinker cooling zone: Due to water seal through which ash and klinker is removed and also ambient air blast gets pre-heated during the passage through this zone the temperature here is nearer to ambient temperature.

The following description explains Zone wise reactions that take place:

• Zone Nol: The superfluous moisture and bound moisture in removed.

• Zone No2: The volatile matter present in the shanks driven off. The volatile matter thus removed passes through the burning zone where most of it is cracked ensuring that no further condensation of this matter is possible thus eliminating the disposal of condensed volatile matter.

• Zone No3: In the reduction zone the main reaction between carbon and oxygen takes place to generate carbon monoxide (CO), hence the gas main fuel component is CO. If the air blast contains water vapour, it will react with carbon to produce hydrogen (H2). The likely chemical reactions that occur are H20 + C = CO + H2 and CO + C = 2C0

• Zone No4: In the combustion zone the temperature of shanks is raised to a level of about 1000 degrees centigrade, so that the temperature of carbon is adequate for gasification reaction to be completed.

• Zone No 5: In the Ash Zone the burnt carbon leaves behind ash and also few percent of un-burnt carbon which is manually drawn through the water seal below.

The Producer Gas Generator has facility for operating under updraft condition during initial start-up and will be switched over to downdraft mode after attaining optimum temperature profile.
Putting Producer Gas Generator into Operation:

1. Water seal has to be filled with water.

2. To start with klinker and ash are fed from the top feed hopper. The quantity will be sufficient to reach the level of bottom gas distributer.

3. Burning shanks, wood pieces are dropped from the feed hopper which will now rest on the ash bed below.

4. Start the Forced Draft fan and introduce the air through the bottom lowers to provide combustion air.

5. Start feeding the raw material to ensure that the fire is not put off.

6. Keep on feeding the material, ie Shanks and simultaneously record the temperatures to ensure that the temperature zones described above are attained.

7. While this process is continuing the gas outlet damper after the dust separator is closed while the damper on the flare line is open.

8. The feed hopper is closed to ensure that the products of combustion do not escape through the open hopper.

9. The process of feeding shanks will continue till such time the gasses leaving the flare are rich enough to burn.

10. Once the flare is burning the generator is put on down draft mode.

11. Simultaneously the flare stack is closed and the gas is led to furnace for further operation.

12. As the fuel is completely burnt and converted into ash and klinker, periodically this ash is removed from the water seal manually.

13. The process and frequency of ash removal and simultaneously feeding the fresh fuel are the aspects that need to be optimised during the initial period of 72 Hours of operation.

14. The Induced Draft fan which is responsible for maintaining desired pressure at different locations in the gas supplied train is now comes into operation and depending upon the pressure balance the forced draft fan is shut off.

15. The gas leaving the generator and the dust separator is in the range of 180 to 350 degrees centigrade.

16. The ID fan supplies this gas to furnace for onward supply of hot air to the dryer.

I claim:

1. Maize wet cob drying with Bio-Mass gas produced in the Gas Producer by using corn shanks wherein bio-waste generated in the process of Ear Corn Drying is the prime source of heat required for Ear Com Drying and for Seeds Drying while not affecting the quality parameters.