# US 2018/0038586 A1 · Bed material for bubbling fluidised bed combustion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0038586 A1 - Document ID: US20180038586A1 - Status: Published application - Kind: A1 - Application number: 15/537,233 - Filed: 2015-12-17 - Published: 2018-02-08 - Earliest claimed: 2014-12-22 - Applicants: Improbed AB - Inventors: Bengt-Ake Andersson; Fredrik Lind; Henrik Thunman - Web page: https://patentgrep.com/patent/US20180038586A1 ## CPC - F23C 10/20: Inlets for fluidisation air, e.g. grids; Bottoms - F23C 10/00: Fluidised bed combustion apparatus - F23C 10/12: the particles being circulated exclusively within the combustion zone - F23C 10/18: Details; Accessories - F23G 5/30: having a fluidised bed - F23G 2203/504: with essentially horizontal flow of bed material - F23C: METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN {A CARRIER GAS OR} AIR (burners F23D) - F23G: CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION ## Abstract The invention is in the technical field of bubbling fluidized bed combustion and relates to the use of ilmenite particles with an average particle size between 0.1 mm and 1.8 mm as bed material for a bubbling fluidized bed (BFB) boiler with an excess air ratio (λ) below 1.3 and to a method for operating a bubbling fluidized bed (BFB) boiler, comprising carrying out the combustion process with a bubbling fluidized bed comprising ilmenite particles as defined in any one of claims 1 and 4-5; and setting the excess air ratio (λ) to a value below 1.3. ## Claims ### Claim 1 Use of ilmenite particles with an average particle size between 0.1 mm and 1.8 mm as bed material for a bubbling fluidized bed (BFB) boiler with an excess air ratio (λ) below 1.3. ### Claim 2 (depends on 1) The use of claim 1, wherein λ is 1.25 or less, more preferably 1.2 or less, more preferably 1.1 or less, most preferably between 1.05 and 1.1. ### Claim 3 (depends on 1) The use of claim 1, wherein λ for the combustion of waste based fuel is 1.23 or less, preferably 1.1 or less, more preferably between 1.05 and 1.23, most preferably between 1.05 and 1.1; and/or wherein λ for the combustion of biomass fuel is 1.19 or less, preferably 1.1 or less, more preferably between 1.05 and 1.19, most preferably between 1.05 and 1.1. ### Claim 4 (depends on 1, 2, 3) The use of any one of claims 1-3, wherein i) the average particle size () of the ilmenite particles is at least 0.2 mm, preferably at least 0.3 mm, most preferably at least 0.4 mm; and not more than 1.8 mm, preferably not more than 1.0 mm, most preferably not more than 0.6 mm; and/or ii) the ilmenite particles have a particle size (dp) in the range from 0.1 mm to 1.8 mm, preferably in the range from 0.3 mm to 1.0 mm. ### Claim 5 (depends on 1, 2, 3, 4) The use according to any of claims 1-4, characterized in that the ilmenite is crushed rock ilmenite. ### Claim 6 (depends on 1, 4, 5) A method for operating a bubbling fluidized bed (BFB) boiler, comprising: a) carrying out the combustion process with a bubbling fluidized bed comprising ilmenite particles as defined in any one of claims 1 and 4-5; and b) setting the excess air ratio (λ) to a value below 1.3. ### Claim 7 (depends on 6) The method of claim 6, wherein λ is set to 1.25 or less, more preferably 1.2 or less, more preferably 1.1 or less, most preferably to a value between 1.05 and 1.1. ### Claim 8 (depends on 6) The method of claim 6, wherein λ for the combustion of waste based fuel is set to 1.23 or less, preferably 1.1 or less, more preferably to a value between 1.05 and 1.23, most preferably to a value between 1.05 and 1.1; and/or wherein λ for the combustion of biomass fuel is set to 1.19 or less, preferably 1.1 or less, more preferably to a value between 1.05 and 1.19, most preferably to a value between 1.05 and 1.1. ### Claim 9 (depends on 6, 7, 8) The method of any one of claims 6-8, wherein the bubbling fluidized bed further comprises silica sand particles, wherein preferably i) the silica sand particles have a particle size (dp) in the range from 0.25 mm to 2.0 mm, preferably in the range from 0.5 mm to 1.2 mm; and/or ii) the silica sand particles have an average particle size () between 0.6 mm and 0.8 mm. ### Claim 10 (depends on 6, 7, 8, 9) The method of any one of claims 6-9, wherein the amount of ilmenite particles as a proportion of the total bed mass is at least 10% by weight, preferably at least 20% by weight, more preferably at least 30% by weight, more preferably at least 40% by weight, more preferably at least 50% by weight, more preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight, more preferably at least 90% by weight, most preferably at least 95% by weight. ### Claim 11 (depends on 6, 7, 8, 9, 10) The method of any one of claims 6-10, characterized by setting the fluidizing gas velocity to at least 0.03 m/s, preferably at least 0.13 m/s, more preferably at least 0.19 m/s, more preferably at least 0.25 m/s, more preferably at least 0.28 m/s, more preferably to a value between 0.3 and 2.0 m/s, most preferably to a value between 0.3 and 1.5 m/s. ### Claim 12 (depends on 6, 7, 8, 9, 10, 11) The method according to any one of claims 6-11, characterized by providing at least 50%, preferably at least 70%, more preferably at least 80%, more preferably at least 90%, most preferably all of the combustion air as primary fluidizing air. ### Claim 13 (depends on 6, 7, 8, 9, 10, 11, 12) The method according to any one of claims 6-12, characterized by a sooting interval of at least 2 days, preferably at least 3 days, more preferably at least 5 days, more preferably at least one week, more preferably at least two weeks, most preferably at least three weeks. ### Claim 14 (depends on 6, 7, 8, 9, 10, 11, 12, 13) The method according to any one of claims 6-13, wherein fuel and/or the ilmenite particles are continuously supplied to the BFB boiler. ### Claim 15 (depends on 6, 7, 8, 9, 10, 11, 12, 13, 14) The method according to any one of claims 6-14, wherein the ilmenite particles are supplied to the BFB boiler at a rate of less than 3 kg/MWh thermal output, preferably at a rate of 1.5 kg/MWh thermal output or less, when biomass fuel is used; and at a rate of less than 6 kg/MWh thermal output, preferably at a rate of 3 kg/MWh thermal output, when waste based fuel is used.