Efficiency on a large scaleCFB Steam Boilers

The Circulating Fluidized Bed Steam Boiler is an offering from Bosch Thermotechnology – a member of the worldwide Bosch Group. Globally renowned as a leading manufacturer of standard and customised boiler systems with a diversified product range, Bosch Thermotechnology has provided

Circulating Fluidized Bed Steam Boiler

Circulating Fluidized Bed Combustion

CFBC technology has evolved from conventional AFBC combustion as a means to overcome some of the drawbacks associated with conventional AFBC combustion.

CFBC technology utilises the fluidized bed principle in which crushed fuel is injected into the furnace or combustor and the fine combusted particles are elutriated out of the furnace with flue gas. The balance particles are then collected by solid separators and circulated back into the furnace.

There are no steam generation tubes immersed in the bed avoiding any erosion of bed tubes and their replacement due to wear and tear resulting in boiler stoppages.

The particle circulation provides efficient heat transfer to the furnace walls and longer residence time for complete combustion of fuel. The time available for combustion is infinite for unburnt particles as they are recirculated in the furnace, making the quantity of unburnt losses as minimal as possible.

The tall furnace design of CFBC boilers offers better space sorbent residence time for efficient combustion and SO2 capture and easier application of staged combustion techniques for NOx control than AFBC generators.

CFBC boilers are generally acclaimed for being more economical than AFBC boilers for industrial applications.

innovative, energy-efficient, eco-friendly and high-quality solutions and services for residential, commercial and industrial applications for over 140 years. In addition to industrial applications, Bosch Boiler Systems are also used for Space Heating in various industrial applications.

Furnace

This is an arrangement in fin and tube construction, which provides the advantage of a gastight chamber. This allows any influx of air to be avoided which, in turn, results in efficiency. Height and footprint are two critical parameters that determine a furnace. Footprint of the furnace is governed by the type of fuel and selection of combustor, while height of the furnace depends on the freeboard required for complete combustion. The membrane wall of the furnace, which usually applies to boilers >25t/h and >2,5 MPa, also ensures that heat is extracted from the flue gases and their temperature is reduced enough to enter the convection zone and that no fouling takes place.

Special-Bent Tube Bypass Kitout Structure

Converging membrane water wall section is provided at the interface of bottom conical furnace / combustor and freeboard area of furnace.

Water-Cooled Air Distributor

The air distribution system is made-up of a membrane-type water wall construction. This construction ensures optimum temperature of the distribution plate. The Air nozzles are arranged such as to have uniform air distribution across the fluid bed. This uniform air distribution helps for proper fuel combustion and to avoid clinker formation.

Built-In Bell Jar Air Cap

The Air Cap is a precision casting with heat- and wear-resistant cast steel. Long service life, uniform air distribution, excellent regulation performance and stable operation are some of the salient features enabled by this element.

Separate design for air cap and connecting tubes is convenient for replacement of the Bell Jar.

Volute-Type High-Temperature Cyclone Separator (Hot Cyclone)

Volute-type structure effectively captures small particles in the flue gas and reaches a separation efficiency of more than 99.5% with good fuel adaptability and high combustion efficiency

Volute-type cyclone separator - Flue gas enters the separator tangentially, with optimum entrance velocity and optimum entrance angle to enhance separation efficiency

The tangential flue gas entry into the cyclone adjusts with the flue gas velocity, thus enhancing efficiency and reducing wear

Highly efficient separation system to improve the utilisation of limestone, which ensures clean and environmentally safe combustion

The cyclone is made of steel plate and is safe, reliable and convenient for maintenance

High wear-resistant bricks and a new type of high temperature- and wear-resistant cement is used as inner lining of the cyclone

Fly Ash Reinjection System

It is a non-mechanical, self-balancing U-type fly ash reinjection system

It optimizes air supply to control the temperature of reinjection material to avoid any clinker formation in reinjection through the feeding chute

The loop seal is divided into two sections. The first section is the dip-leg and the second section is the riser-leg. Proper air distribution in these individual sections helps in maintaining the required transfer rate of reinjection material into the furnace

Various temperature- and pressure-measuring points are provided in the boiler system to monitor and control important parameters during boiler operation

It has metal bellow expansion joints on the ash reinjection chute to maintain good sealing performance and keep the site clean and tidy

Economiser

This is a heat recovery device for efficiency improvement and is placed after the boiler bank

This equipment uses the heat of the flue gases coming out from the boiler to preheat the water going into the steam drum

This reduces the flue gas temperature which improves boiler thermal efficiency

Air Preheater

The air preheater is a last heat recovery system

It is a crossflow gas heat exchanger which preheats the combustion air that enters the fluid bed combustor and furnace through the secondary air nozzle

Pollution Control Equipment

Super Heater (for superheated steam boiler only) The superheater is constructed in two halves

which are connected to each other by an attemperator in between

The attemperator ensures that the temperature of the boiler outlet steam is controlled within specified limits by spraying of boiler feed water

The attemperator can be of two types: spray type or surface type

Boiling Tubes (for saturated steam boiler only) The boiling tubes form the convection zone

located in the tail shaft of a boiler They are arranged in line - longitudinal with

the flue gas flow

Multicyclone Dust Collector Bag Filter Electrostatic Precipitator

Fuel Handling System

Comprises:

Grizzly hopper

Belt conveyor

Crusher

Vibrating screen

Product conveyor / Bucket elevator

Ash Handling System

Ash Handling System supplied is complete with Bed Ash Handling and Fly Ash Handling

Bed Ash Handling System Comprises:

• Rotaryashcoolertocoolthehotash coming out of the bed

• ConveyorandBucketelevatorto take ash to silo

• Storagesilotoholdtheash

Fly Ash Handling System Comprises:

• Isolatingvalve

• Ashpot

• Pneumaticconveyingpipes

• Timer-basedcontrolandstoragesilo

Boiler Ignition System

Comprises:

LFO (Light Fuel Oil)/HSD storage tank

Pressure automisation pump

Pressure jet burner

Sequence controller

Deaerator Module

The Deaerator Module supplies steam boilers with degassed and chemically conditioned feed water and disposes of the desalting and waste water. It ensures:

Discharge and storage of condensate and make-up water

Thermal full deaeration of the feed water

Chemical conditioning of the feed water

Control for chemical dosing

Dry running protection feed pump module

Overflow protection

Typical Control Schemes

Advanced Controls

Fully Automatic Boiler Control Technology with:

Programmable Logic Control (PLC) Technology

Centralised Control System

Boiler is provided with Control Loops such as:

Three element Boiler Water Level Control System

Combustion Control System

Automatic Feed Water Control System

Furnace Draft Control System

Automatic Monitoring and Control of:

Steam Pressure

Steam Temperature

Feed Water Flow

Flue Gas Oxygen

Breakdowns and Historical Records:

Automatic recording of the time and causes of breakdowns

Accumulative recording of ignition times and fan operating time, water pumps and burners

Automatic display of the parameter curves such as pressure and temperature

Automatic recording of hot water / steam consumption to provide database for energy management

Product Range Offerings

Other capacities and pressures can be supplied on demand.

t/h

MPa

1.25 1.6 2.5 3.82 5.3

ºC

250 350 400 450 450 485

6 ✓ ✓ ✓

10 ✓ ✓ ✓ ✓

15 ✓ ✓ ✓ ✓

20 ✓ ✓ ✓ ✓ ✓ ✓ ✓

25 ✓ ✓ ✓ ✓ ✓ ✓ ✓

35 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

40 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

45 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

55 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

65 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

75 ✓ ✓ ✓ ✓ ✓ ✓ ✓

130 ✓ ✓ ✓

220 ✓