Process and plant for biomass treatment

A process for biomass treatment which includes:

• a step A, of thermochemical treatment of transformation of a biomass comprising sewage sludge into a carbonaceous solid, wherein said transformation provides treating said biomass at a treatment temperature between 150° C. and 300° C. and at a treatment pressure between 10 atm and 50 atm for a time, between 30 minutes and 8 hours, in the presence of water, with accessory production of a treatment gas including steam, carbon dioxide, nitrogen and sulfur compounds and traces of carbon monoxide and light aromatic hydrocarbons and polluting and odorous components;
• a step B, mixing of said treatment gas with an auxiliary gas containing oxygen compounds to obtain operating gas;
• a step C of thermochemical decomposition of a carbonaceous solid in an atmosphere consisting of said operating gas, wherein said thermochemical decomposition is apt to obtain a combustible synthesis gas which comprises carbon monoxide, molecular hydrogen, methane and carbon dioxide;
• wherein said operative gas determines an oxygen supply in said thermochemical decomposition which is determined by means of a first adjustment operation, which provides regulating a relative quantity of said treatment gas and of said auxiliary gas in said operating gas, and/or by a second operation of regulating a flow rate of said operating gas in said thermochemical decomposition;
• wherein said polluting and odorous components are decomposed in said step C.