AU2017101027A4

AU2017101027A4 - Fluidised Bed Boiler Superheater and Efficiency Improvements

Info

Publication number: AU2017101027A4
Application number: AU2017101027A
Authority: AU
Inventors: John Raymond Smeed; Roger Charles Wilkinson
Original assignee: Smeed John Raymond Mr
Current assignee: Smeed John Raymond Mr
Priority date: 2017-07-31
Filing date: 2017-07-31
Publication date: 2017-08-24
Anticipated expiration: 2025-07-31

Abstract

Abstract A method of avoiding fouling of steam piping in fluidised-bed water-tube boilers (fluidised bed combustion boiler) especially, but not limited to boilers which are fired with contaminated fuels (e.g. municipal solid wastes, low-grade coals or biomass). This system utilises a fines arrestor system to collect fines, char and dusts from the hot products of combustion of the main combustion fluidised bed and discharges the collected materials into an adjacent air-fluidised bed which houses in-bed steam or super-heater steam piping. The fines arrestor may be cyclonic or impactural, both constructed from water-wall steam piping. The combustion bed and the super-heater bed are inter-connected with an air-lift system which controls the flow of the bed materials from or to each of the beds, to control the steam or super-heated steam temperature.

Description

2017101027 31 Μ 2017

Fluidised Bed Boiler

Superheater and Efficiency Improvements

Inventors :- Roger Charles Wilkinson and John Raymond Smeed

Description

The innovations described in this application relate to the improvements to the prior arts of Fluidised Bed, Spouted Bed, Multi-Spouted Bed, Multiple-Spouted Differentially-Fluidised Bed and Circulating Fluidised Bed boilers.

The innovations are usually applied to water-tube boilers which are required to produce super-heated steam when fired by either conventional fuels or 'contaminated' fuels such as Municipal Solid Wastes, low-grade coals, biomass, waste sludges, waste liquids, etc.

The innovations include methods of extracting hot fine grits, chars and dust and using those components which are elutriated from the main combustion process (which is usually conducted in a differentially-fluidised bed) within an adjacent fluidised bed which is fitted with in-bed tubes containing some of the steam or super-heated steam piping required.

The methods of extracting the fine grits, chars and dusts include cyclonic and/or impact arrestors, both of which are constructed from typical and conventional water-wall steam piping, and 'dump' the collected materials into an adjacent fluidised bed area which contains in-bed steam or super-heating steam piping.

The combustion bed and the super-heater bed are inter-connected by an air-lift system which allows bed material to flow, not-flow or reverse-flow from one bed to the other. This enables control of super-heated steam temperature.

The use of air to fluidise the super-heater bed avoids the impact of hot gaseous products of combustion onto the super-heater pipes and the subsequent 'slagging' and fouling which frequently occurs on those tubes when exposed to the hot products of combustion in boilers when consuming contaminated, sulphurous and/or halogenated fuels.

As the majority of bed material in the super-heater bed is fine and light-weight, that bed can usually be much deeper than the combustion bed and can therefore accommodate the necessary in-bed tube bundle.

An additional factor included in this innovation is the use of refractory panels within the water-walls of the main combustion chamber so as to complete the combustion of the volatiles and the small elutriated particles prior to their collection in the fines and dust collection system. This assists the de-contamination of the fines, char and dust materials in the super-heater bed and assures the gentle 'scuffing' of the in-bed tubes by relatively-uncontaminated fine and lightweight particles and the fluidising air.

Claims

Claims Claim 1. Separate Beds for Combustion and in-bed Superheater The primary Claim relates to a method of avoiding fouling of steam or super-heater piping in Fluidised-bed water-tube boilers especially, but not limited to boilers which are fired with contaminated fuels. This system utilises a fines-arrestor system at the discharge of the main combustion fluidised bed and the discharge of the collected materials in to an adjacent air-fluidised bed containing the collected fines, char and dusts extracted from the hot products of combustion (from the main combustion bed) and which houses in-bed steam or super-heater steam piping. The fines arrestor may be cyclonic or impactural, both constructed from water-wall steam piping. A preferred impact arrestor is formed from four rows of 'U' sections each constructed with two water-wall pipes across the gas steam and 'winged' with one water-wall pipe each side and facing in to the gas stream. The 'U' sections are placed approx. 100mm apart, with approx. 100mm between rows, with rows off-set to each other.
Claim 2. Pneumatic Control of Superheater Bed conditions The combustion bed and the super-heater bed are inter-connected with an air-lift system which controls the flow, non-flow or reverse-flow of the bed materials from or to each of the beds. Variations of the inter-bed material flow and the super-heater bed fluidising airflow are used to control the steam or super-heated steam temperature.
Claim 3. Avoidance of Superheater Pipe Fouling This feature avoids contact of the hot gaseous products of combustion with the super-heater piping and thereby eliminates the fouling of that piping at higher super-heat temperatures, as often experienced on such piping which is exposed to hot gaseous products of combustion from 'contaminated' fuels such as those containing sulphurous or halogenated components.
Claim 4. Decrease of Convective Steam Pipe Fouling The installation of fines, char and dust arrestors to capture such materials elutriated from the combustion bed reduces the entry of those materials in to the convection portion of the water-tube boiler thereby reducing the dust-fouling of piping within and beyond that component.
Claim 5. Increased Freeboard Combustion Efficiency This innovation includes a method of part-lining the main combustion chamber freeboard areas with refractory material, in the form of castable refractory or pre-fired blocks, placed inside (and in contact with) the water-wall piping 'jacket of the main combustion chamber and restrained by additional water-wall pipes with their side flanges restraining the refractory material from falling away from the main combustion chamber lining. In this way, approximately 60-80% of the combustion chamber walls and roof can have a refractory facing which can endure the rigorous conditions which exist in that chamber. Such refractory facing enhances the combustion of freeboard materials and further increases the combustion efficiency of the process.