Napier or King Grass (Pennisetum Purpureum)
- A Viable Energy Crop -
Napier Grass Plantation & Harvesting - few facts -
Napier is a fast growing, deeply rooted, perennial grass growing up to 4 m tall that can spread by underground stems to form thick ground cover.
It has low water and nutrient requirements, and therefore can make use of otherwise uncultivated lands.
Napier is easy to establish and persistent; drought tolerant; suitable for cutting and very good for silage making.
Fresh Grass with 70% moisture is harvested first at 13 feet tall (4m) after 195 days of plantation and subsequently for every 120 days.
Recommended to remain in same field for 3 to 5 years.
Challenges in Firing 100% Napier Grass
Maximum total moisture in Napier Grass (as fired) shall be 55%.
Recommended size of the Milled Napier Grass shall be < 25 mm
Napier Grass shall be free from clay, shale, rock, stones, nails etc
Chlorine content shall be maximum 0.17%
High alkali constituents in ash
Continuous availability of Napier Grass matching plant size selected
NEED TO REDUCE FUEL MOISTURE
Difficulties in Air Drying of Fuel
Milled Napier Grass
Typical Characteristics of Milled Napier Grass and its Ash
Proven Technical Solution for Napier Grass
Mitigation of Challenges for firing 100% Milled Napier Grass
Once milled and the moisture is brought less than 55%, Milled Napier Grass is easily fired in a proven Continuous ash discharge Travelling grate boiler like firing any other fodder type biomass like Bagasse.
The Travelling Grate boiler is designed to suit high moisture, high alkali Ash content and few critical salient features are explained in subsequent slides.
The fuel handling and feeding system is so designed to ensure trouble free operation of the plant.
Many such boilers are in operation successfully in many countries across the globe
These boilers comply to all environment norms as stipulated in current regulations in most of the countries and International Standards.
Typical Milled Napier Grass fired Boiler with provision for Bio-Gas firing
Key Salient Features of Travelling Grate Boiler for Napier Grass
Continuous ash discharge Travelling grate boiler with tall furnace ensures adequate residence time for fuel to burn
Ensures optimum flue gas temperature (lower than initial deformation temperature of ash) at inlet of super heater thereby avoiding ash deposits, fouling and agglomeration.
Conservative grate area loading to ensure efficient combustion of fuel.
Higher furnace cross section to reduce flue gas velocity in the furnace hence reduced fuel carry over and less suspension / localized combustion in the upper furnace.
Refractory band of suitable coverage in the lower furnace to sustain combustion of high moisture fuel (Napier grass). The refractory band acts as a “heat sink” and provides a re-radiating effect to sustain combustion of fuel having high inherent / total moisture. The refractory also prevents corrosion in the lower part of the furnace where reducing atmosphere is encountered.
Napier Grass Feeding System
Napier Grass from slat chain carrier will be collected in boiler storage silos.
Fuel feeding system consisting drag chain feeders with drive motors suitable for VFD operation to feed Napier Grass into the furnace.
Motor operated gates are provided at the inlet of fuel silos.
From the outlet of drag feeders the fuel is fed into the pneumatic distributors (spreaders) for distributing uniformly across the furnace.
The fuel from the outlet of drag feeders fall on to a specially designed plate which is adjustable so that the trajectory of the fuel across the furnace can be varied and to spread across the whole plan cross section of the combustion chamber.
Bio Gas Generation from Extracts from Milling Napier Grass
Napier Grass or King Grass – a Viable Energy Crop (Some Tentative Facts)
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Now I want to farming the nepeir grass, will you supplying 200 stems of said grass.
Very good information on napier grass potential ,please share details for napier grass bio gas plant for 12 ton capacity per day thanks