Heat Up Your Heat Transfer

Know-How

Heat Transfer eHANDBOOK

®

TABLE OF CONTENTSFree Up More Tubular Exchanger Area 5

Consider options besides changing bundle pitch when debottlenecking

Take a Closer Look at Direct Steam Injection 9

Technology responds rapidly to changing process conditions

Modular Boiler Systems Offer Flexibility 11

Compact size and start-up speed help to meet changing requirements

Additional Resources 14

AD INDEXPick Heaters • pickheaters.com 2

Miura • miuraboiler.com 4

Xylem • xylem.com/standardxchange 8

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 3

www.ChemicalProcessing.com

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Design margins incorporated in

most plants and equipment often

offer a cost-effective way to

increase asset utilization. Over time, a

site can use design margins to raise plant

capacity or improve product quality. How-

ever, constraints posed by just one or two

items frequently hinder overall improve-

ments — and make debottlenecking that

equipment important.

One recent example was a plant that

wanted to raise product yields at its cur-

rent capacity. Key to that was heating the

feed to a higher temperature. The feed was

heated by a combination of heat integration

followed by a fired heater. The plant already

was using all the spare duty capacity of

the fired heater. So, the most straightfor-

ward approach to get the additional duty

required was to modify the heat integra-

tion system.

The heat integration exchangers were

installed in a multi-level structure. Code

limitations precluded adding significant

weight to that structure. In addition, the

site only had limited open area suitable for

new equipment.

Modifications targeted two elements.

First, pinch analysis showed that one

exchanger in the existing heat integration

was nearly completely ineffective. Remov-

ing that exchanger would open up both

space and weight capability for installing a

much-more-effective heat integration unit.

Second, minor changes — even as little

as 5–6% more duty in specific services —

would provide significant benefits. So, here,

Free Up More Tubular Exchanger AreaConsider options besides changing bundle pitch when debottleneckingBy Andrew Sloley, Contributing Editor

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 5

www.ChemicalProcessing.com

we’ll look at how the plant got this extra

duty from a heat exchanger.

Figure 1 illustrates the tube-sheet layout

of one exchanger in the plant. It is a par-

tial-condensing exchanger with hot fluid

(vapor) on the shell side and cold fluid

(liquid) on the tube side. The exchanger

is a TEMA E-type shell with eight passes

on the tube-side, and downward shell-

side condensing flow. The pinch analysis

showed that nearly all exchangers in the

plant, including this one, were surface area

limited. Adding surface area would increase

exchanger duty most effectively.

Perhaps the most obvious change would

have been to switch the bundle pitch from

rotated square to triangular. This would

have allowed more tubes, increasing sur-

face area. However, because the exchanger

was in a fouling service, the benefits of

easier cleaning of the rotated-square pitch

outweighed the additional surface area pos-

sible with a triangular pitch.

Immediately downstream of the exchang-

er’s inlet nozzle is an open area with no

tubes and an impingement plate. If tubes

are too close to the inlet nozzle, they block

a large fraction of the flow area, creating

pressure drop and high inlet velocities. The

open area between the inlet nozzle and

tube bundle allows the vapor to flow along

part of the shell length before entering the

tubes. Effectively, this increases the inlet

area for vapor flow into the bundle.

The impingement plate prevents high veloc-

ity vapor from jet-impinging onto the tubes.

The vapor contains some liquid droplets, so

high velocity impingement could cause ero-

sion or other mechanical damage.

Providing open area under the inlet nozzle

is a conventional approach in exchanger

design. Open area also is used next to the

outlet nozzle if high velocities are expected

there as well. In this case, the tube removal

reduces the area possible in that shell diam-

eter by approximately 6%. So, decreasing

the inlet velocity another way would allow

TUBE LAYOUTFigure 1. Open area under the inlet nozzle for velocity reduction robs area available for the exchanger bundle.

Flow In

Flow Out

Area open for flow entry

www.ChemicalProcessing.com

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 6

replacing the exchanger bundle with one

having 6% more area.

Two other methods of inlet velocity reduc-

tion are possible: a dome at the inlet; or a

vapor belt that circles, or partially circles,

the shell to allow vapor into the bundle

at multiple locations. Both increase the

inlet area open for flow and decrease

inlet velocity.

Here, the plant opted for a vapor belt

because it required fewer external piping

modifications. Both the vapor belt and the

extra tubes added weight to the exchanger.

Keeping the weight within the allowable

limit required making the tubes and tube

sheet of thinner material.

While the modifications may seem extreme

for just 6% more duty, the extra feed heat

was critical and allowed for more product

recovery.

ANDREW SLOLEY is a contributing editor for Chemical

Processing. Email him at ASloley@putman.net

Other methods of inlet velocity reduction are possible.

www.chemicalprocessing.com/podcast/process-safety-with-trish-and-traci

Trish Kerin, director of IChemE Safety Centre, and Chemical Processing’s Traci Purdum discuss

process-safety issues offering insight into mitigation options and next steps.

From questioning if inherently safer design is really safer to lessons learned from significant

incidents, these podcasts have one goal:

To ensure workers return home safely after every shift.

PROCESS SAFETY

With Trish & Traci

www.ChemicalProcessing.com

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 7

For over 100 years, Standard Xchange heat exchangers have kept mission-critical systems up and running. Today we still set the standard – engineering and building the most reliable, innovative heat transfer technology in the USA. So whether you’re looking for a part or building a plant, you know you’ll get the optimal heat transfer solution.

Find out what we can do for you at xylem.com/standardxchange

Inline heating of liquids or slurries is a requirement in many chemical and pharmaceuti-

cal operations as numerous industrial applications need an unlimited and instantaneous

supply of hot water.

While choices for heating water, liquids and slurries abound, direct steam injection (DSI) heaters

(Figure 1) should be at the top of the list of options for these challenging applications.

WHY CHOOSE DSI? DSI has certain characteristics that are ben-

eficial or even necessary depending on

the process:

• It offers precise temperature control within

±1 °C.

• It is easy to install and can be used wherever

medium- to high-pressure steam is available.

• Precisely machined variable orifice injector

with spring-loaded piston eliminates damag-

ing vibration and steam hammer.

• Compared to alternatives such as tank steam

sparging or indirect heat exchangers, DSI

Take a Closer Look at Direct Steam InjectionTechnology responds rapidly to changing process conditions

By Paul Pickering, Pick Heaters Inc.

DIRECT STEAM INJECTION HEATERSFigure 1. These units are an ideal choice when a well-controlled, instantaneous supply of water is needed.

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 9

www.ChemicalProcessing.com

heaters can cut fuel costs by as much

as 28% because the liquid absorbs 100%

of the available energy (BTUs) from the

steam instantly.

• It features a low liquid-side pressure drop

— less than 2 psi.

• It is environmentally safe and nonflamma-

ble, unlike heat transfer fluids that require

special handling and constant monitoring.

EXAMPLES OF DSI IN INDUSTRIAL PROCESSESDSI is better than indirect exchangers for

heating water in industrial applications

because it provides a rapid response to

changing process conditions and enables

precise temperature control within a

single degree Celsius. As such, DSI heat-

ing is suitable for a variety of industrial

processes as illustrated in the follow-

ing examples:

• Many processes in the chemical industry

require water temperature to be con-

trolled precisely before adding it to a

batch process. A DSI system provides

instant temperature control, reducing the

cycle time and increasing productivity.

• DSI also is ideal for heating large-capacity,

closed-loop jacketed vessels, tanks and

blenders; mixing two condensate steams;

or even dispersing gas into a liquid.

• Applications such as plant sanitization,

clean-in-place (CIP) and washdown hose

stations require hot process water. Instan-

taneous and accurately controlled hot

water must be available to meet stringent

plant demands.

• In pharmaceutical processing, DSI tech-

nology is used in such applications as the

continuous-flow heat treatment of bio-

waste. The precise temperature control

enables wastewater with living cells to

be killed or inactivated and then cooled

before disposal. For example, one waste

steam inactivation system required the

waste from multiple reactors to be heated

to 140 °C, held for a period of time and

then cooled to 60 °C. Read more here.

PAUL PICKERING is a writer for Pick Heaters Inc. Pick

Heaters produces DSI heaters in 10 standard sizes for

liquid flow rates up to 5,000 gpm, and steam flow

rates from 150 lb/hr to 50,000 lb/hr. For more infor-

mation, visit www.pickheaters.com/Products.htm.

DSI provides a rapid response to changing process conditions and enables precise temperature control

within a single degree Celsius.

www.ChemicalProcessing.com

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 10

Chemical processors have been chal-

lenged to rethink certain operations,

and having options has become a

valuable asset.

Whether you are facing a crisis or need to

be able to adjust your steam requirements

quickly, you’ll want to consider a modular

boiler system that maximizes flexibility and

provides a range of advantages for stay-

ing competitive and meeting production

demands.

Modular steam systems comprise multiple

connected steam boilers configured to meet

demand at different stages to provide just

the right amount of steam only when steam

is required.

Typically, modular boilers feature a fast

start-up that can achieve full steam from

a cold start in less than five minutes and

shut down just as promptly (Figure 1). This

gives processors critical advantages, includ-

ing features that support environmentally

friendly initiatives, maximize in-service

efficiency, conserve resources, reduce emis-

sions and control fuel costs.

In 2020, we witnessed a radical shift in the

entire U.S. economy, making it essential for

companies that needed to increase steam

production quickly, as well as those who

needed to closely monitor their output, to

be able to do so rapidly while adjusting to a

climate of continued uncertainty.

Now, a little more than a year later, as we con-

tinue to make our way back, lessons learned

should never be forgotten, and being able to

react and respond quickly should be the basis

for investing in a steam boiler system.

Modular Boiler Systems Offer FlexibilityCompact size and start-up speed help to meet changing requirements Andrew Eklind, Miura

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 11

www.ChemicalProcessing.com

STEAM THAT MEETS YOUR NEEDSAchieving full steam in minutes and plac-

ing boilers in standby mode quickly based

on the current steam demands, rather than

continuing to have them in an idle state

to stay warm, no longer can be thought

of as an interesting concept. It is an abso-

lute necessity.

This also applies to having the capability

to add a boiler fast, whether it is required

to expand steam output quickly, replace a

failing unit that seems to require daily main-

tenance or get you back up on your feet in

the aftermath of a natural disaster.

In the past, this often meant relying on rental

boilers to increase steam capacity tempo-

rarily, but the price is high, and it requires

installing and uninstalling the boiler. These

additional steps can be expensive, especially

if you’ve ordered a new boiler and are wait-

ing weeks or months to receive it.

More cost-effective and efficient solu-

tions can have a new boiler delivered to

you in approximately 48 hours, ready for

a quick, one-time installation, an option

that saves money and provides tremen-

dous flexibility.

BIG ADVANTAGES TO COMPACT DESIGNBigger is not always better, especially when

you are trying to add additional boiler units

to an existing boiler room. Modular boil-

ers feature upright pressure vessels, which

take up less floor space and can usually

be added even if your current boiler room

space is limited.

This is advantageous where real estate and

construction prices continue to go up or

where more space simply is unavailable.

Choosing a compact, low-water-content

modular boiler makes installation, operation

and maintenance much easier while provid-

ing greater output in less space. Modular

systems are replacing traditional boiler sys-

tems to increase steam capacity without

having to construct a new boiler room.

Taking these and other features and

advantages into account, it also is

STEAM FLOWFigure 1. The “floating header” design produces steam in less than 5 minutes, allowing users to turn boilers on or off as needed.

www.ChemicalProcessing.com

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 12

important to consider a boiler that

provides “only the steam you need,

when you need it.”

For example, some modular steam

boilers in multiple installations (MI)

adjust automatically to fit your steam

demands, so when you only require

30% of the full system output, the

system is using only 30% of the boiler

system capacity. The other 70% of

the system remains in standby mode,

using only relatively small amounts

of electricity to keep the communica-

tion system online.

Known as load-following technology, this pro-

vides a tremendous cost and resource-saving

advantage, especially as traditional systems

continue to use 100% of the system just throt-

tled down to produce less steam.

Investing in modular boiler systems that pro-

vide greater flexibility and green features

means being able to optimize your system for

your unique steam load, rather than oversiz-

ing your boiler system, as that strategically

may prove to be a bad investment. Mod-

ular boiler systems often are custom-sized

to meet your current requirements and

can grow cost-effectively as the situa-

tion demands.

STEAM-AS-A-SERVICEAnother option for large steam generation

facilities introduced around the start of

2020 is Steam-as-a-Service (SaaS), an inno-

vation that requires no upfront costs and

delivers state-of-the-art, fully-controlled

steam for a monthly fee.

This service has been developed by Miura

and its alliance partners, Hartford Steam

Boiler and Armstrong Services, to provide

an all-in-one solution.

BENEFIT FROM FLEXIBLE STEAM Flexible options are essential to better

preparation. As such, steam users need to

take a closer look at proven technologies

that address a range of possible concerns

and allow them to take advantage of new

services and innovations that make it easier

to operate within an environment of change

to meet current and future challenges.

ANDREW EKLIND is marketing manager for Miura. Con-

tact him at andrew.eklind@miuraz.com.

MULTI-UNIT SETUPFigure 2. Load-following technology in multiple installations, automatically adjusts steam output to provide the right amount needed.

www.ChemicalProcessing.com

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 13

Heat Transfer eHANDBOOK: Heat Up Your Heat Transfer Know-How 14

ADDITIONAL RESOURCESEHANDBOOKSCheck out our vast library of past eHandbooks that offer a wealth of information on a single topic,

aimed at providing best practices, key trends, developments and successful applications to help make

your facilities as efficient, safe, environmentally friendly and economically competitive as possible.

UPCOMING AND ON DEMAND WEBINARSTap into expert knowledge. Chemical Processing editors and industry experts delve into

hot topics challenging the chemical processing industry today while providing insights and

practical guidance. Each of these free webinars feature a live Q&A session and lasts 60 minutes.

WHITE PAPERSCheck out our library of white papers covering myriad topics and offering valuable insight

into products and solutions important to chemical processing professionals. From automation

to fluid handling, separations technologies and utilities, this white paper library has it all.

PODCAST: PROCESS SAFETY WITH TRISH & TRACITrish Kerin, director of IChemE Safety Centre, and Chemical Processing’s Traci Purdum discuss

current process safety issues offering insight into mitigation options and next steps.

ASK THE EXPERTSHave a question on a technical issue that needs to be addressed? Visit our Ask the Experts

forum. Covering topics from combustion to steam systems, our roster of leading subject

matter experts, as well as other forum members, can help you tackle plant issues.

Visit the lighter side, featuring drawings by award-winning

cartoonist Jerry King. Click on an image to view

the winning caption and all submissions

for that particular cartoon.

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