Adca Training - Multiplex Eng. Ltd. · Adca Training Part 2 This ... Combustion chamber and main...

Adca Training Part 2

This presentation is only a guideline, that can only be completed by a trained personnel.

(This document’s total or partial use and/or reproduction is only allowed if the reference to the source is kept)

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Part 2

The Boiler

Equipment Used on Boilers

Water Treatment

Bottom Blow down

TDS Control

Energy Recovery

Deaerators

Part 3

Pipeline Sizing – Water Hammer

Steam Trapping – Condensate Removal

Part 4

Pressure Reduction

Safety Relief Valves and Other Steam Valves

Part 5

Control Valves

Components of Control Valves

Humidification


Condensate

Process

Feed

wate

r

Ste

am

Feedtank

Boiler


One can simply define heat generator as an equipment design to energy

production through fuel combustion.

Heat generators are mainly built of two distinct elements:

Combustion chamber where the fuel is burned, producing hot gases that

will act as fluid heater.

Metallic body or generator itself closes the fluid to be heated, that will be

the means of transportation for produced energy.

Combustion chamber and main generator’s project may vary according with

type of boiler and fuel.

In compliance with legislation in force generators are supplied with several

auxiliary equipments appropriate to monitoring and assure generator’s good

functioning, such as: temperature and pressure indicators, safety valves,

pressostats, thermostats, pumps, valves, instrumentation, etc.


By virtue of the huge variety of factors, heat generators classification is a very

complex task. Here follows some examples:

According to Possibilities

Fuel Solid, Liquid or Gas

Fluid Produced Hot or Superheated water, Steam, Diathermic

oil, Hot air, …

Number of passes of combustion gases 1 to 4

Heating chamber Furnace, Fire tubes, …

Burners Pressure jet, Rotary Cup, …

Pipes Fire tube or Water tube

Inversion chamber Wet, Dry back, …


Burner

Fuel

Ste

am

Feed

Wate

r


The hot gases from

fuel combustion cross

the main chamber (1st

pass) and the smoke

tubes (2nd pass),

transfer the heat to

the surrounding water.

As far as the water

reaches saturation

temperature, steam

start to be produced,

being accumulated in

the space above,

ready to be delivery to

the system.

Burner


The hot gases from fuel

combustion cross the

main chamber (1st

pass) and the smoke

tubes (2nd and 3rd

pass), transfer the heat

to the surrounding

water.

As far as the water

reaches saturation

temperature, steam

start to be produced,

being accumulated

In the space

above, ready

to be delivery

to the system.


Cocks and gauge glass for

water level monitoring.

The safety valve (s)

function is to protect the

boiler shell from

overpressure and

explosion.

Some typical control and safety equipment...


For efficient and safe operation a steam boiler has also level controls and level alarms.

Level control probes can be installed internally in the boiler shell or externally using appropriate

level control chambers connected to the boiler shell.

Alternatively, float control systems are still used by some manufacturers.


Water quality is extremely important on the exploration of a thermal power station. The use

of hard water or poorly treated water may cause accidents or irreparable damages on the

generator and piping, apart from decreased heat transmission.

Water quality control must be done periodically. An effective treatment must keep it within

the required parameters.

Generally, water for a heat generator must be less hard as possible (≤1ºfH), be free of

suspension solids, have alkaline Ph (8,5 minimum) and low in O2 (≤ 0,02mg/l) and CO2.


Most current process of reducing water hardness is through ion-exchange method:

The raw water is guided through heavy-duty resin which has been enable by exchanger-

active sets to exchange cations or anions. The calcium and magnesium ions are absorbed

during the softening procedure while adequate amounts of sodium ions capable of

exchange (Na+) are released into the water. The exchange resin has physically

conditioned a limited capacity and is exhausted after a certain number of water

throughputs. The regeneration of the water softening system is performed by means of a

salt solution.

Ph correction, which value is associated with CO2 content may be done through a

controlled injection of chemicals for which is necessary adequate dosing instruments.

O2 and CO2 can be eliminated by chemical or thermal process. The chemical process

uses sometimes some products non-recommended in food industry ,thus the thermal

process offers more advantages as:

O2 Elimination

CO2 elimination

And by consequence, Ph correction


The timing of regeneration can be selected

manually or automatically .

If the softener is electronically controlled by a

timer, the regeneration has to be selected

outside the operational use of steam boilers.

The volumetric systems work in dependence

on the flow volume. The duplex design is

specially suitable for continuous operation,

because the regeneration is performed

alternatively without interruption of the soft

water supply.


During the vaporisation process the

suspended solids in the boiler water

are collect in the bottom of the boiler in

the form of sludge.

Manual blowdown valves are specially

designed for application on steam

boilers removing the concentrations of

solids (sludges) avoiding boiler

damages, unstable water level control

and other typical problems.

The valves are provided with a manual

handwheel.

Valve aperture cycles depends from

the boiler manufacturer specification or

water treatment specialists.

VPA26S

(Manual)


During the vaporisation process the

suspended solids in the boiler water are

collect in the bottom of the boiler in the form

of sludge.

Automatic blowdown valve are specially

designed for application on steam boilers

removing the concentrations of solids

(sludges) avoiding boiler damages, unstable

water level control and other typical

problems.

The valves are provided with a diaphragm

actuator suitable for compressed air motive

fluid.

The opening signal is supplied by an

automatic intermittent control unit but they

can also have alternative manual operation.

Valve aperture depends from the boiler

manufacturer specification or water

treatment specialists.

VPA26S

(Automatic)


Some impurities remains in the boiler water in the form of dissolved solids and so they cannot

be eliminated trough the bottom blowdown. The concentration of this dissolved solids naturally

increase with steam production. When this concentration is

high, and in order to restore

the right levels, some of the

boiler contents must be

purged. Lost water will be

replaced by lower TDS

concentration feedwater,

replacing the correct

parameters.

A typical problem of excess

TDS concentration is water

foaming which origins bad

boiler performance and wet

steam.


Blowdown controller

Adcatrol

Blowdown control valve

Conductivity

probe

To BEX for expansion and

drain or flash vessel for

energy recovery.

Sample Cooler

When the TDS concentration reaches the set point measured by the conductive probe,

a controller gives an open signal to the blowdown valve.

Boiler manufacturer and water treatment specialists

usually indicates the maximum permissible

concentration.


The blowdown and cooling units are used in the modern boiler houses to cool hot

waste water and steam boiler blowdown before to discharge into a pit or drain to

prevent thermal pollution and pipe system damages. The waste water is discharged

into the unit which is at atmospheric pressure and the cooling water enters via a

control valve controlled by a thermostat, mixing with the hot water .

If flash steam can not be recovered or discharged to atmosphere an additional

condensing water spray system (optional) can be supplied . This one is fitted in the

top of the unit and can be controlled directly

either by another thermostat or the

same command used for the

automatic blowdown

valve control .

EH

Exhaust Head

BEX

Blowdown

Expansion Vessel


Sample coolers prevent steam flashing-off from hot pressurised liquid samples, which

can be dangerous and will result in an incorrect water sample.

Basically they operate as a small heat exchanger.

Hot Sample IN

Cooling Water

OUT

Cooling Water

IN Cold Sample

OUT

Cooling Water

OUT

Cooling Water

IN

Hot Sample IN

Cold Sample

OUT

SC32 SC32/F


For high pressure boilers and continuous analysing, special execution is necessary.

Clean steam systems also require a specific design and finishing surfaces.

SC332

SC432

SC532

Ts= 550ºC

Ps=245 bar

SC32P

Clean Steam

Internal Finished

to 0,5 micronsRa


One of typical applications for the use of

flash vessel is precisely in recovering flash

steam from the boiler blowdown.

This energy recovery can be used for

feedtank preheating, saving fuel.

Flash steam produced can be condensate

inside the vessel by using injectors

submerged in the water or it can simply be

used on the deaerator head.

Flash steam

Blowdown from

boiler

Contaminated

water

Adca

RV.../A

Flash Vessel


Condensate Flash Steam

Make up Water

Hot Water

Cold Water

Heat Recover from

Residual Blowdown

Flash Vessel

ADG

Atmospheric Thermal Deaerator

with Dome Flash Steam Inlet


Since many years ago it is common to recover condensate from steam systems to the boiler feed tank, saving water and energy, reducing water treatment chemicals, costs and consequently reducing CO2 emissions.

In some systems, the amount of recovered condensate and correspondent temperature is so high that the water feed tank temperature rise to the boiling point. Thus, most of the recoverable energy is lost in the form of flash steam through the vessel vent pipe. Besides, boiler feed pumps can cavitate (see NPSH) and be damaged.

FRECO – Flash Steam Heat RECOvery, consider the energy recovery downstream of boiler feed pump. High pressure avoids the water boiling. (FRECO can be supplied as a skid mounting system for easy installation and commissioning).

A raised of 6ºC in feed water temperature, corresponds to a saving of approximately 1% fuel.


Steam

Hot Water

Cold Water

Condensate

Flash Steam


A thermal deaerator is actually a deaerating feed water heater, which combines water heating, storage and deaeration capabilities.

Water is stored in a under pressure vessel typically about 3 bar g in order to aloud it to be kept at a temperature above 100ºC.

Thermal deaeration takes place in equipments especially designed for the job. There are existing two main kinds:

Tray type deaerators

Spray nozzle type deaerators

Tray type is by far the most used doing to is simplicity, versatility and performance.

Atmospheric deaerators also called partial deaeration systems or semi-deaerators are most times the economic choice for boiler capacities up to approximately 2000 Kg/h.


Atmospheric semi-deaerators are designed to

heat boiler feed water and to reduce oxygen and

carbon dioxide (oxygen values in the feed water of

less than 1,6 mg/l , can be achieved). Remaining

oxygen can be completely removed using oxygen

scavenging chemicals.

Basically the complete system consists of a

storage vessel, a deaeration head section and a

vent.

Hot return condensate is injected in the bottom of

the storage vessel using an adequate sparger pipe

and softened make-up water is introduced in the

deaerator head to be heated by a contact cascade

flash steam heating system (counter-current flow)

coming from the vessel. Part of dissolved gases are

liberated from the water at this point and they are

liberated to atmosphere trough the flash steam vent

line .

The semi-deaerated water then falls to the

storage vessel below, where a steam injection

system will provide an additional deaeration.

Make up

Water

Flash

steam

Condensate

Recirculation

Condensate

Vent

ADG

Atmospheric

Semi-Deaerator

Dome


Complete unit supplied including

all the necessary instrumentation

for temperature and level control.

Make up

Water

ADG/V

Complete unit


Thermal deaerators are designed to heat boiler

feed water and to reduce oxygen and carbon

dioxide (oxygen values in the feed water of less

than 0,02 mg/l - 0,02 ppm, can be achieved).

Remaining oxygen can be completely removed

using oxygen scavenging chemicals.

Basically the complete system consists of a

storage vessel, a deaeration section and a vent.

Return condensate and softened make-up water

are introduced in the deaerator dome to be heated

by a contact cascade steam heating system

(counter-current flow). The majority of dissolved

gases are liberated from the water at this point and

they are liberated to atmosphere trough the flash

steam vent line.

The deaerated water then falls to the storage

vessel below, where a steam blanket ensure that

no gases are reabsorbed.

A sparger pipe is installed inside the tank at the

bottom level providing the necessary heating

energy. A second low pressure steam supply can

also be necessary (double stage).

TDG

Thermal Deaerator

Dome

Double Stage

Make up Water Condensate

Steam


Complete unit

supplied including

all the necessary

instrumentation for

temperature,

pressure and level

control.

TDG/V

Complete unit

Make up Water

Condensate


Find the energy required to heat up the tank

content, from 5ºC to 65ºC in 1,5 hours – 90’.

V = 18000Kg of Water

T1=5ºC

T2=65ºC

Cp of Water=1 Kcal/Kg ºC

ΔT = 65º-5º=60ºC

Steam = 3bar g

Kcal/h 000 720 Q

90'

60' x 60º x Cº 1Kcal/Kg x Kg 18000 Q

90'

60' x T x Cp x m Q

How much Steam?

Steam is supplied at 3 bar. From steam tables we can see that at this pressure the total enthalpy of

steam (hg) at this pressure is 654,6 Kcal/Kg.

1221,2Kg/hM C)º Kcal/Kg 1 x C(65º654,6

000 720M

Cp) x (T2hg

QM

Kg/hKg/h

Kg/h

SI-125

SI-115


Using the same formulas it is possible to find the steam flow rate necessary to heat the tank material

and depending from insulation, ambient temperature, vessel design, etc, it is also possible to determine

the steam flow rate necessary to make up for the heat losses from radiation and water surface. Practical

calculation may accept an allowance based in a percentage of around 10%.

So, for our example we will consider 1221,2 Kg x 1,1 = 1343,4 Kg/h of steam.

NOTE: The tank must have enough free volume for the mass of steam added during the heating

process, 1343,4 Kg x 1,5 hr = 2015,10Kg.

The final water volume will be than 18000Kg + 2015,10Kg = 20015,10Kg.

At 3 bar the SI 140 has a capacity of 800 Kg/h, so, for the application we need

Steam Injectors SI 140 or Steam Injectors SI 125 268,1800

4,1343 598,4

270

4,1343

The vessel design, dimensions and the particular application may recommend the use of one

single big injector or more small units, with the equivalent total capacity.


Hot water (or other fluids) storage vessels for

industrial purposes can be divided in two types:

Accumulators

Semi-instantaneous

Any of these can be equipped with internal coils

or external heat exchanger.

In the first case there’s a pre determined lack of

time for heating a quantity of fluid that is ready to

be used. In this case, coil or heat exchanger’s

regeneration capacity during consumption

process is not particularly relevant.

On the second case there’s a combination

between accumulated volume and capacity of

instantaneous heating. These two parameters

combined must assure the maximum

consumption calculated.

ADCATHERM WAVE

with external STSV

Heat Exchanger


Heavy fuel oils and other viscous fluids are

stored in tanks heated by pipe coils or other

alternative systems. This is necessary to provide

the necessary temperature (viscosity) for

pumping. Too high temperature can represent

less viscosity and pump cavitation problems. So,

temperature control and correct condensate

drainage can be crucial.

Heating Coils can also be used to heat water

in closed or open vessels.

Mainly on fuel oil systems and semi-

instantaneous heaters the coil is frequently

supplied with a sleeve, heating the oil locally as

it is pumped out of the tank.

The use of extruded low fin tube , has the

advantage that it can improve the external

surface and thermal performance (Adcatherm R-

Coils).

BM20


Heat exchangers are equipments designed to

transfer primary heat from one fluid to another.

Shell and tube heat exchangers are very popular for

steam to water heating since they can be designed

for any temperature and has relatively low cost

maintenance.

Plate heat exchangers can also be used on steam

applications under certain conditions, however,

maintenance is more expensive doing to the high

cost of gaskets.

Ready to install packaged units including heat

exchanger, control valve, steam trapping system and

all the necessary accessories, are recommended

since as a rule they save time installation, while

guaranty the correct assembly of all critical

components.


TUBE SIDE SHELL SIDE

FLUID SATURATED STEAM WATER

OPERATING PRESSURE bar bar

INLET TEMPERATURE º C * º C

OUTLET TEMPERATURE º C * º C

FLOW RATE Kg/h * Kg/h or m3/h

HEAT EXCHANGED (Option) KW or Kcal/h

MODEL REQUIRED (Please select) STH (Horizontal) STV(Vertical)

Remarks :

* Not necessary in case of saturated steam.

STH – Horizontal installation ; STV – Vertical

installation.

TUBE SIDE VESSEL SIDE

FLUID SATURATED STEAM WATER

OPERATING PRESSURE bar bar

INITIAL TEMPERATURE -------------- º C

FINAL TEMPERATURE -------------- º C

VESSEL CAPACITY -------------- Kg or m3

INITIAL HEATING TIME (In minutes) ‘

RECOVERY PERIOD (In minutes)

HEAT EXCHANGED (Option) KW or Kcal/h

VESSEL TYPE (Please select) HORIZONTAL VERTICAL

AVAILABLE DIMENSIONS (Send a sketch) Straight length mm Diameter mm

HOT WATER CONSUMPTION m3

INCOMING COLD WATER TEMPERATURE º C

DESIRED HOT WATER TEMPERATURE º C

LENGTH OF TIME (IN MINUTES) ‘

If the vessel is also operating as semi-instantaneous hot water heater,

please confirm :

Remarks : A coil in a cylindrical vertical vessel should be as close to

but not exceeding the diameter of the vessel as possible. A coil in a

horizontal vessel is typically approximately 2/3 the length of the vessel Before installing an instantaneous heat

exchanger, one must certify that there’s a sufficient

steam flow or primary energy available for the

effect.

Storage vessels and semi-instantaneous

systems can be inconvenient since they need

more installation space. However, by balancing

with initial heating time and the accumulation

capacity it’s possible to avoid undesired highs of

energetic consumption .

Heat Exchanger Storage Hot Water Vessels – Closed Type

Semi – Instantaneous Hot Water Heater


The steam/water Adcamix mixers provide cheap, instant

source of low pressure hot water by utilising existing steam

and cold water supplies.

The mixer incorporates a safety device to ensure that live

steam cannot accidentally be ejected, even if for some

reason the cold water supply fail.

The temperature of water at the outlet of the Adcamix is

easily controlled by using water and steam valves fitted to

the inlets.


Air heating of large industrial spaces

can be made through multiples

systems available nowadays (gas,

electricity, hot water, steam, etc).

A steam to air unit heater is

composed by a coil and a fan, which

forces air passage through the coil in

order to heat it.

Steam air heating batteries can also

be used in central air conditioning

units combined with filtration

modules, direct steam humidification,

etc.

Co

nd

en

sate

High pressure

Live steam

Steam to Air

Unit Heater


From higher pressure plants where the condensate enters into the vessel, the

flash steam is separated from the condensate. Through the top main connection of

the flash vessel the flash steam is then supplied to the lower pressure steam

network. The remaining condensate is discharged by an automatic float steam trap.

(See Adca Training I).

Installation of a flash vessel is

particularly convenient when both high

and low pressure steam equipments

are present in the same plant since

high pressure condensate can

generate low pressure steam.

To maximize the use of flash

vessels, it is convenient to design

them for the lowest possible pressure.

Model RV.../A

Blowdown

from boiler

Remaining

condensate

Flash Steam

ADCA

Flash Vessel

Model RV.../L


High pressure

Live steam Low pressure

Steam application

Fla

sh

ste

am

Condensate

Flash vessel

RV…/L


Adca Training - Multiplex Eng. Ltd. · Adca Training Part 2 This ... Combustion chamber and main...

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Transcript of Adca Training - Multiplex Eng. Ltd. · Adca Training Part 2 This ... Combustion chamber and main...