Fuel pellet

Abstract

Fuel pellets which include substantial amounts of agricultural biomass having a relatively low lignin content are provided. The fuel pellets have a low ash content, good pellet durability (e.g., as determined by their pellet durability index) and heating values comparable to conventional hardwood fuel pellets. The fuel pellet may be formed by pelleting a mixture comprising agricultural biomass which includes whole corn, corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp and/or sunflower hulls. Other suitable agricultural biomass materials which may be used to form the fuel pellets include co-products from corn milling processes (e.g. corn gluten feed, white fiber), oat hulls, rice hulls, rapeseed meal, rapeseed fractions, bagasse, ground barley, cottonseed hulls, whole cottonseed, ground milo, oatmeal, oat flour, rye, broken rice and empty palm fruit bundles.

1 . A fuel pellet comprising an agricultural biomass; wherein the pellet has a lignin content of no more than about 10 wt. % (dry basis), an ash content of no more than about 4 wt. %, a PDI of at least about 90, and a heating value of at least about 7,000 BTU/lb (dry basis). 
     
     
         2 . The fuel pellet of  claim 1 , wherein the fuel pellet has a moisture content of no more than about 15 wt. %. 
     
     
         3 . The fuel pellet of  claim 1 , wherein the fuel pellet has a triacylglyceride content of no more than about 5 wt. %. 
     
     
         4 . The fuel pellet of  claim 1 , wherein the mixture comprises about 40 to 80 wt. % cracked corn. 
     
     
         5 . The fuel pellet of  claim 1 , further comprising a pelleting aid. 
     
     
         6 . The fuel pellet of  claim 5 , wherein the pelleting aid comprises a sugar alcohol component. 
     
     
         7 . The fuel pellet of  claim 6 , wherein the sugar alcohol component comprises glycerol. 
     
     
         8 . The fuel pellet of  claim 1 , wherein the pellet comprises at least about 60 wt. % (dry basis) of the agricultural biomass. 
     
     
         9 . The fuel pellet of  claim 1 , further comprising a processing aid which includes paraffin wax, thermoplastic polymer, hydrogenated triacylglyceride, tallow, or a mixture thereof. 
     
     
         10 . The fuel pellet of  claim 1 , wherein the pellet further comprises about 0.1 to 30 wt. % glycerol. 
     
     
         11 . The fuel pellet of  claim 1 , wherein the agricultural biomass has a lignin content of no more than about 10 wt. % (dry basis). 
     
     
         12 . The fuel pellet of  claim 1 , wherein the pellet has a sulfur content of no more than about 0.4 wt. %. 
     
     
         13 . The fuel pellet of  claim 1 , wherein the pellet has a density of about 40-45 lbs/ft 3 . 
     
     
         14 . The fuel pellet of  claim 1 , wherein the pellet comprises at least about 60 wt. % (dry basis) of an agricultural biomass which includes whole corn, corn cobs, corn stover, wheat, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls, co-products from corn milling processes, co-products from wheat milling processes oat hulls, rapeseed meal, rapeseed fractions, bagasse, rice hulls, empty palm fruit bundles and mixtures thereof. 
     
     
         15 . The fuel pellet of  claim 1 , wherein the agricultural biomass is selected from the group consisting of cracked corn, whole corn, corn cobs, corn stover, wheat, wheat middlings, soy beans, soy bean hulls, soy cotyledon fiber, dried distillers grain, oats, sugar beet pulp, sunflower hulls and mixtures thereof. 
     
     
         16 . The fuel pellet of  claim 1  comprising about 40 to 90 wt. % corn. 
     
     
         17 . The fuel pellet of  claim 1 , wherein the fuel pellet has an ash content of no more than about 5 wt. %, and a heating value of at least about 7,500 BTU/lb (dry basis). 
     
     
         18 . A fuel pellet formed by pelleting a mixture comprising:
 about 40 to 90 wt. % corn; and   about 10 to 60 wt. % of an agricultural biomass which includes corn cobs, corn stover, wheat, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls, co-products from corn milling processes, co-products from wheat milling processes, almond hulls, walnut meal, oat hulls, rapeseed meal, rapeseed fractions, bagasse, rice hulls, empty palm fruit bundles or a mixture thereof;   wherein the fuel pellet has an ash content of no more than about 4 wt. %, a PDI of at least about 90, and a heating value of at least about 7,000 BTU/lb (dry basis).   
     
     
         19 . The fuel pellet of  claim 18 , wherein the mixture further comprises about 0.1 to 5 wt. % glycerol. 
     
     
         20 . The fuel pellet of  claim 18 , wherein the mixture includes about 10 to 60 wt. % whole corn, cracked corn, corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls or a mixture thereof. 
     
     
         21 . A fuel pellet comprising at least about 60 wt. % (dry basis) of an agricultural biomass selected from the group consisting of whole corn, cracked corn, corn cobs, corn stover, wheat, soy beans, soy bean hulls, soy cotyledon fiber, dried distillers grain, oats, sugar beet pulp, sunflower hulls, co-products from corn milling processes, co-products from wheat milling processes, oat hulls, rapeseed meal, rapeseed fractions, bagasse, rice hulls, empty palm fruit bundles, almond hulls, walnut meal and mixtures thereof;
 wherein the fuel pellet has an ash content of no more than about 4 wt. %, a PDI of at least about 90, and a heating value of at least about 7,000 BTU/lb (dry basis).   
     
     
         22 . A method of producing heat comprising burning a fuel pellet formed by pelleting a mixture comprising an agricultural biomass which includes whole corn, cracked corn, corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls, co-products from corn milling processes, oat hulls, rapeseed meal, rapeseed fractions, bagasse, rice hulls, empty palm fruit bundles, almond hulls, walnut meal and mixtures thereof;
 wherein the fuel pellet has a PDI of at least about 90, and a heating value of at least about 6,000 BTU/lb (dry basis).   
     
     
         23 . The method of  claim 22 , wherein the agricultural biomass is selected from the group consisting of cracked corn, whole corn, corn cobs, corn stover, wheat, wheat middlings, wheat straw, soy beans, soy bean hulls, soy cotyledon fiber, alfalfa, dried distillers grain, oats, oat straw, sugar beet pulp, sunflower hulls and mixtures thereof. 
     
     
         24 . The method of  claim 22 , wherein the mixture further comprises a pelleting aid. 
     
     
         25 . The method of  claim 22 , wherein the fuel pellet includes at least about 60 wt. % (dry basis) of the agricultural biomass; and the fuel pellet has a heating value of at least about 7,000 BTU/lb (dry basis) and an ash content of no more than about 15 wt. %.