RICE STRAW COMBUSTION IN STEAM BOILER
RICE STRAW “Not a Waste, Until Wasted”
- Rice Straw Fired Steam Power Plant Highlights
- Single Drum, Natural Circulation, Tall Furnace ,3 Pass with Radiant Platen SH in all Three Zone. Operation scheme with 8,000 h/y planned operation , 8 h manned and 16 hrs unmanned operation with remote surveillance Power up 30 MWe Hot water Based APH. Water Cooled Oscillating Grate.
Tail end DeNOx
- MAGO THERMAL & Experienced TEAM ( Ex IIT & BHEL/ HITACHI) developed Rice Straw technology and also studied the experience and technology used in Straw Combustion world wide.Available Foreign Technology is not suitable for Indian Biomass as it contains lot of earth and other compounds with it.
New ADOPTIVE Technologies are:
- Adaptation of the water cooled vibrations grate as part of the high pressure boiler system
- A fuel handling system based on rectangular straw bales and suitabilty of other Biomass.
- Hanging slagging austenitic superheaters capable of high Superheater temperatures.
Challenges To Burn Rice Straw / Non Conventional Biomass
- Rice Straw & Non Conventional Biomass Present additional Challenges for use as fuel in High-Efficiency Steam Boilers owning to presence of a significant Proportion of alkali, alkali earth metals & silica in their composition. These Give rise in form of ash that is prone to forming a corrosive and very abrasive slag where its comes in contact with the radiant superheater in the furnace.
- Operating experience gained from sevral Biomass plants and Lab test conducted by Our PROF P.D. Grover has guided Mago Team with respect to the reformation and adhesion of volatised components of combustion gases when they come to contact with the radiant Superheater surface, extensive efforts have been made to remove these deposits with various forms of soot blowing but only to result in further corrosion and blockage of super heater.
- In order to overcome the challenges presented by Biomass/ straw as fuel, The steam Boiler must operate with slag melting conditions in the upper furnace and specially at radiant superheater. The steam boiler should not Operate less than 70 % of MCR otherwise S.H. will have insufficient gas temperature to reach the slag tap temperature required to keep the superheater clean and as a result blockage will occur.
- Rice Straw / Non Conventional Biomass from arable crops is , at first sight , a very attractive Biomass fuel. It is usually fairly dry, at average 12-14 % moisture content ( wet Basis): and is very readily available during crop season.
- Rice Straw contains a high proportion of silica and alkali metals (Potassium ,K) and alkali earth metals( calcium , Ca) as well as signification amount of chlorine( CL), magnisium (Mg), Phosphorous(P) and sulphur( S ). These all give rise to an Ash that has a low melting point and is volatile –it evaporates in furnace: then condensates on cooler surface e.g. the superheater, to form a slag layer.
- ULTIMATE & PROXIMATE ANALYSIS OF RICE STRAW
|Sno.||Particulars||Unit||Worst fuel||Worse fuel||Performance/design fuel||Best fuel|
|1.0||Gross Calorific Value “HHV”||Kcal/kg||2387||3081||3472||4056|
|Gross Calorific Value “LHV”||Kcal/kg||2075||2810||3181||3737|
|2.0||Ultimate Analysis (As Received Basis)|