Integrated process and related system for obtaining energy from waste with low investments and high thermoelectric yields

Abstract

A process is described for obtaining energy from waste, comprising the following phases: a) bio-drying of municipal solid waste (MSW) to transform it into refuse-derived fuel (RDF), a dry, homogeneous material with piece size of around 20-30 cm, known by the name of RDF; h) compacting of the material obtained from phase a) into bales or BIOCUBr and storage of the BIOCUBI® in bioreactors; c) activation by wetting with water of the bioreactors to produce biogas by anaerobic digestion; d) combustion at the start of the material obtained from phase a) (RDF) and subsequently of the residue already digested in the bioreactors, and therefore not biodegradable, in a waste combustor provided with a system of purification of combustion gasses and production of superheated steam at approximately 400° C. and pressure of around 70 bar; e) combustion of the purified biogas in a conventional boiler provided with re-superheaters for raising the temperature of the steam produced by the waste combustor by approximately 100° C.; f) use of the steam produced in this way in a turbine coupled with an alternator for the production of electrical energy. The invention also relates to a system for the implementation of this method.

1 . Process for obtaining electrical energy from waste, comprising the following steps:
 a) bio-drying municipal solid waste (MSW) into refuse-derived fuel (RDF), said RDF comprising a dry, homogeneous material with piece size of around 20-30 cm;   b) compacting the RDF obtained from step a) into bales and storing the bales in bioreactors;   c) activating the bioreactors by wetting the bales with water to produce biogas and a non-biodegradable residue through anaerobic digestion;   d) combusting the non-biodegradable residue of step c) in a waste combustor provided with a system for combustion gasses purification to produce superheated steam at approximately 400° C. and pressure of around 70 bar;   e) combusting the biogas in a conventional boiler equipped with re-superheaters for raising the temperature of the steam produced by the waste combustor by around 100° C.; and   f) directing the steam produced in steps d) and/or e) in a turbine coupled with an alternator for production of electrical energy.   
     
     
         2 . (canceled) 
     
     
         3 . Process according to  claim 1 , wherein said bio-drying of step a) further comprises
 feeding the MSW in a closed space,   grinding the MSW roughly and   placing the ground MSW in heaps on a floor with holes, the MSW being divided into sectors through which a current of air is passed, wherein aerobic digestion of putrescible part develops heat, said heat causing evaporation of water which is removed by the current of air.   
     
     
         4 . Process according to  claim 1 , wherein said bales have a size of around 1×1×2 m and density of around 700 kg/m 3 . 
     
     
         5 . Process according to  claim 1 , wherein said bales are produced on site or transported from production stations distributed in the territory. 
     
     
         6 . Process according to  claim 1 , wherein said bioreactors used in step c) are divided into sectors forming large storage tanks, wherein said sectors are activated by injecting water into each of them, so as to provide a continuous production of biogas and provide, at the end of the life of each of said sectors, continuous availability of non-biodegradable exhausted material, wherein said non-biodegradable exhausted material is made up of inert and plastic. 
     
     
         7 . Process according to  claim 6 , further comprising blowing or aspirating air at the end of the life of each of said sectors so as to eliminate part of the residual water and obtain a low content of humidity, between 20 and 25%. 
     
     
         8 . Process according to  claim 7 , further comprising using hot air or mixtures of air/gasses from the combustion to accelerate evaporation of the water and/or obtain low residual humidity of the waste. 
     
     
         9 . Process according to  claim 1 , wherein the biogas produced in step c) is purified of possible residual traces of chlorinated products by passage on active carbon beds. 
     
     
         10 . Process according to  claim 1 , wherein said combustion gasses purification system comprises
 a series of cyclones for abating the substantial part of he solids conveyed,   a cooling tower for controlling the temperature,   a reactor fed with lime and active, carbons for neutralising the residual acidity and adsorption of the micropollutants and   a bag filter for retaining the fine dust before emission at the stack.   
     
     
         11 . Process according to  claim 1 , wherein the steam, expanded in the turbine, allows a yield of the thermal cycle of around 32%. 
     
     
         12 . System according to  claim 1  further comprising:
 a bio-dryer for drying and stabilizing the MSW for producing RDF, said RDF being reactive and activatable for anaerobic digestion in bioreactors; 
 means for the compacting of said RDF into bales; 
 at least one bioreactor fed with said bales for producing biogas; 
 a waste combustor provided with a combustion gasses purification system and production of superheated steam; 
 a boiler for combustion of purified biogas provided with re-superheaters for raising the temperature of the steam produced by the waste combustor; 
 a turbine coupled with an alternator for the production of electrical energy. 
 
     
     
         13 . Process according to  claim 1 , wherein contaminated air is produced at end of step a) 
     
     
         14 . Process according to  claim 13  wherein said contaminated air is used for the combusting in step d). 
     
     
         15 . Process according to  claim 1 , wherein the RDF of step a) is combusted in step e).