System and method for combusting high-moisture fuel to generate steam

Patent metadata

Field	Value
Publication number	US-12410914-B2
Application number	US-202016991633-A
Country	US
Kind code	B2
Filing date	Aug 12, 2020
Priority date	Aug 12, 2020
Publication date	Sep 9, 2025
Grant date	Sep 9, 2025

Abstract

A process for combusting a high-moisture fuel to generate steam in which the high-moisture solid fuel is first dried by contacting with an oxygen-depleted gas stream while being heated by indirect heat exchange with a recirculating thermal fluid. The dried fuel is then combusted with a combustion air stream to produce a combustion products stream whose heat first is used to generate steam, and then to preheat the combustion air stream by indirect heat exchange in which a portion of the combustion air stream and/or a portion of the combustion products stream bypasses the heat exchanger. The combustion products stream also provides heat to dry the solid fuel via the recirculating thermal fluid.

First claim

I claim:

1. A process for combusting a high-moisture biomass fuel to generate steam, the process comprising:
contacting a high-moisture solid biomass fuel with an oxygen-depleted gas stream while heating the high-moisture solid biomass fuel by indirect heat exchange with a recirculating thermal fluid to produce a dried solid fuel and a moist oxygen-depleted gas stream;
combusting the dried solid fuel on a grate with a combustion air stream to produce a combustion products stream having an amount of heat;
transferring a first portion of the amount of heat to generate steam by indirect heat exchange with the combustion products stream;
transferring a second portion of the amount of heat to preheat the combustion air by indirect heat exchange with the combustion products stream;
transferring a third portion of the amount of heat to the recirculating thermal fluid by indirect heat exchange with the combustion products stream;
bypassing a portion of the combustion air stream to form a combustion air bypass stream; and
transferring the combustion air bypass stream to a boiler;
wherein at least a portion of the combustion air stream travels through the grate to combust the dried solid fuel.

2. The process of claim 1 , wherein the high-moisture solid biomass fuel flows counter-current to the recirculating thermal fluid and co-current to the oxygen-depleted gas stream.

3. The process of claim 1 , further comprising adding an oxygen-enriched stream to the combustion air stream prior to combusting the dried solid fuel; and
controlling one or both of a flow rate of the oxygen-enriched stream and a location of adding the oxygen-enriched stream to control one or more of the following properties:
steam temperature, steam pressure, steam drum level, stoker grate temperature, temperature of the combustion products stream prior to transferring the first portion of the amount of heat to generate steam, temperature of the combustion products stream after transferring the first portion of the amount of heat to generate steam, temperature of the combustion products stream after transferring the second portion of the amount of heat the preheat the combustion air, temperature of the combustion products stream after transferring the third portion of the amount of heat to the recirculating thermal fluid, temperature of the moist oxygen-depleted gas stream, temperature of the dried solid fuel, moisture level of the high-moisture solid fuel, and moisture level of the dried solid fuel.

4. The process of claim 3 , wherein the oxygen-enriched stream and the oxygen-depleted stream are both produced by the same air separation unit.

5. The process of claim 1 ,
wherein when bypassing a portion of the combustion air stream, increasing or decreasing the amount of the portion of the combustion air stream bypassing indirect heat exchange with the combustion products stream to control one or more of the following properties: temperature of the combustion products stream prior to transferring the second portion of the amount of heat to the recirculating thermal fluid, temperature of the combustion products stream after transferring the second portion of the amount of heat to the recirculating thermal fluid, moisture content of the dried solid fuel, or moisture content of the oxygen-depleted gas stream after contacting with the high-moisture solid fuel.

Assignees

• Air Prod & Chem

Inventors

• D'Agostini Mark Daniel

Classifications

• F26B21/40

  using gases other than air · CPC title

• F23L7/007 Primary

  Supplying oxygen or oxygen-enriched air · CPC title

• F23K2201/20

  Drying · CPC title

• F23J15/006

  Layout of treatment plant · CPC title

• Y02E20/34

  Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery · CPC title