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1 Ausgabe 60 • 2014

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TAKE YOUR TRAINING FURTHER NEW THALETECWORKSHOPS page 10

GLASS-LINED EQUIPMENT FROM THALETEC FOR THE PRODUCTION OF POLYALUMINUM CHLORIDE (PAC) page 2

DATESSEMINARS ON FURTHER TRAINING AND WORKSHOPS page 11

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2 Issue 78 • 2016

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Glass-lined equipment from THALETEC for the production of polyaluminum chloride (PAC)

Figure 1: Main use of PAC - water treatment (photo source: www.pixelio.de, Semalex)

The article gives comprehensive guidance on how glass-lined reactors should be desig-ned for the production of polyaluminum chloride.

PolyAluminum Chloride (PAC) is an effective combined flocculant and precipitant with which a series of dissolved substances can form insoluble matter and a great variety of suspended matter can be removed from watery solutions. Its general formula is Aln(OH)mCl3n-m

PAC is produced from the source materials, aluminum hydroxide and hydrochloric acid.

Polymers aluminum chloride have been used since the 1970s, inter alia, for the treat-

ment of service water, drinking water, waste water and swimming pools as flocculants and precipitants.

In Europe, PAC replaced aluminum sulpha-te, usual at the time, for the treatment of drinking water because of its technical and economic characteristics.

Its use has not spread much beyond Europe's borders, however.

Water treatment chemicals from the PAC

produced can be used for other, diverse applications.

The high concentration of the active subs-tances permits economic transportation.

The primary fields of application are:

• industrial and municipal waste water treatment

• drinking water treatment• sludge conditioning

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3 Issue 78 • 2016

Figure 2: Flow diagram for the production of PAC

THALETEC ABRISIST, the highly corrosion and wear resistant specialist glass lining, was developed for corrosive, abrasive pro-cesses, such as those for the production of PAC. ABRISIST is the standard glass lining for PAC processes.

It is available exclusively from THALETEC.

In addition to the improved resistance to acids, ABRISIST has finer bubbles than other glass. The fineness of the bubbles has a significant impact on the useful life

of equipment which is subject to corrosive and hydro-abrasive demands. As a conse-quence of the considerably more refined bubble structure of ABRISIST, compared with other glass linings on the market, the availability of the glass-lined equipment

• phosphate elimination• bulking sludge control• relief flocculation• service water treatment• demulsification• paper industry - sizing/retention/ impurities elimination

Application of ABRISIST to extend useful life

The PAC process is extremely corrosive and, as a consequence of the use of aluminum hydroxide, very abrasive:

Aluminum hydroxide and hydrochloric acid are mixed intensively in the agitated tank and with an increase in temperature and

pressure (up to 180°C and 8 bar pressure) with the introduction of water becomes PAC. By adding conditioning agents, the chemi-cal composition of the PAC end products can be adjusted and optimized for the respective application (Figure 2).

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4 Issue 78 • 2016

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The properties of the source materials as well as the chemical reaction in the production of PAC determine the use of glass-lined reactors.

These are generally designed for pressure not exceeding 8 bar in the glass-lined inner vessel and the double jacket.

In most cases reactors of the CE type in compliance with DIN 28136 are still used

BE reactors preferred

(Fig. 4). However, the use of BE type reactors in compliance with DIN 28136 are recommended:

Since BE reac-tors do not require the large mounting opening for the agitator, in practice problems occur far less often when sealing the flange and nozzles.

The usual dimension of PAC reactors is 16m3, whereby in a correspondingly sized

and designed plant about 20 metric tons PAC per year can be produced.

BE reactors require the use of a two-part agitator. The agitator shaft and agitating ele-ment are connected to each other here using a shrink-fit connection. THALETEC offers two similar operating principles, which each have specific advantages: In the Cryotec system there is a cylindrical, highly precisely machined working surface

subject to wear and corrosion can be signifi-cantly increased.

Since 2009 ABRISIST has been the standard technical glass for abrasive and chemically highly corrosive processes and therefo-re the optimum choice for PAC reactors. Furthermore, ABRISIST is also used in the digestion of ores or in the extraction of raw materials from sand. For the production of PAC, ABRISIST VC - Visual Control - is the preferred choice.

ABRISIST VC - "VC" stands for "Visual Control"- is a technical glass coating which is applied in several layers. On top of the obligatory ground coat which is applied as a "bonding agent" between the steel and the upper layers of technical glass, a layer of highly resistant ABRISIST/w (white) up to 0.5mm thick is applied. This layer is covered with blue ABRISIST/b until the final layer thickness reaches between 1.1 to approx. 2 mm (Fig. 3). If the blue glass layer becomes worn this can be easily recognized from a visual check without the need for any auxiliary aids. The white glass lying below the blue glass shows through in a loca-lized area. Despite this the chemical and abrasion resistance of the component is still present.

Because of the easily recognizable change in color of the glass lining, the operator is able to plan the replacement of the worn component and carry out precautionary

repairs without the availability of the plant suffering from a sudden failure. ABRISIST VC thus aids the preventive maintenance of the plant.

Since the introduction of the wear-resistant technical glass, ABRISIST, to date overall more than 1,000,000 l reactor volumes and innumerable parts such as agitator shafts, agitating elements, baffles and other at-tachments have been coated with it.

About 40% of these were for reglassing: the used and worn equipment comes to Thaletec, the worn glass layer is removed

Figure 3:Cross-section through a glass layer made of ABRISIST VC

and a new glass layer made of ABRISIST is applied. Thus there are cost savings and the availability of the plant is increased.

Reactors and components which were pre-viously produced by a third party manufac-turer can, of course, also be reglassed using ABRISIST.

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5 Issue 78 • 2016

The AMT turbine (Fig. 5) was developed and optimized specifically for processes which can lead to abrasive wear during stirring: i.e. processes such as the suspension of solid matter, crystallization or the precipitation of solids from solutions etc.

The THALETEC AMT turbine is a twin blade agitating element with a d/D ratio ≥ 0.5.

The agitator can thus be operated at this diameter ratio at low rotational speeds, i.e. reduced circumferential speeds, which is particularly beneficial. The special blade geometry permits the largest possible thickness of the glass layer at the places where there is the greatest hydro-abrasion which ensures a particularly large wear reserve.

The correct agitating element

The performance characteristics of the AMT permits an adequately high power input for agitating processes in which solids are processed. The arrangement of the blades creates a predominantly radial flow, at the

same time, however, also an axial flow com-ponent in order to keep sedimenting solids floating, which would otherwise settle on the floor of the reactor.

Figure 4: CE and BE reactors in compliance with DIN 28136. The large mounting opening and the gasket necessary for sealing are not required and the operation of the BE reactor is safer.

Figure 5: THALETEC AMT agitator for the production of PAC

on the agitator shaft and the inside of the agitator seam is also machined in a precise cylindrical shape.

By cooling the agitator shaft using liquid nitrogen, the diameter of the shaft decre-ases during the installation process so that the agitating element can be pulled over the working surface.

After the temperature has equalized between the shaft and seam the agitating element sits firmly on the agitating shaft.

The Multiflex system functions in a compa-rable way to the Cryotec system, however the machined working surface here has a tapered design. In the Multiflex system too, the agitating element is fitted onto the agitator shaft, which is cooled with nitrogen, and after the temperature equali-zation sits firmly on the agitator shaft.

In both cases, the agitator shaft as well as the agitating element are coated comple-tely with technical glass so that all surfaces are protected from corrosive attack.

The Multiflex system with a tapered wor-king surface is preferred for PAC processes because deposits of solid matter in the area of the joint between the shaft and the agitating element should not lead to problems when dismantling the agitating element.

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6 Issue 78 • 2016

Figure 6: Delta baffle

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Optimum stirring of media containing solids depends on the highest possible specific per-formance level.

The THALETEC Delta baffle is an innovative and highly effective design for the optimum interference effect in the glass-lined reactor.

The fundamental concept of the baffle is based on the fact that the flow cross-section takes the form of an equilateral, right-angled triangle (Fig. 6).

It has been shown that for hydro-abrasive, abrading and solids-loaded processes there is less wear than with conventional baffles if the flow is directed towards the tip of the triangle. Experience shows that technical glass wears firstly and predominantly on surfaces which the solids hit almost verti-

The best baffle

cally. The wear is also greatest where the flow hits narrow radii.

There are no such radii on the triangular profile of the Delta baffle.

Measurements have shown that the trian-gular flow profile in one of the two moun-ting positions has more than a 10% greater degree of effectiveness than the conventi-onal paddle baffle (based on power input with otherwise unchanged parameters).

The new Delta ARB baffle has a concave bottom end, in the center of which a tem-perature measuring tip, QuickTip, is used.

In order to protect the temperature measu-ring tip better against wear from the lateral flow of liquids which may contain solids, the

bottom end of the ARB baffle was designed to be concave (see Fig. 7).

The temperature measuring tip for flexsens probe is located in the center of the spheri-cal surface, protected from the direct flow.

A simulation of the flow around the bottom end of the baffle is available on YouTube.

Figuere 7: Concave baffle end for abrasive stirring processes

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7 Issue 78 • 2016

Of course, there is also highly dynamic tem-perature measuring technology available for the Delta baffle.

This comprises the new THALETEC flexsens 100 temperature sensor which can be easily inserted into the baffle and quickly remo-ved for calibration (Fig. 8).

Temperature measurement

Energy efficiency ensured with the PowerBaffle

A B

C D

Figure 8: FlexSens temperature measuring probe

Figure 9: PowerBaffle, fitted in a glass-lined reactor, instead of a conventional baffle

At the end of each batch process the con-tent of the reactor must be cooled down from the reaction temperature (approx. 160°C) to about 60°C.

With a 16m3 reactor, filled with PAC, about 1,500 KWh energy must be discharged res-pectively in the shortest possible time.

It makes sense to use this thermal energy.

It is effective to preheat the receiver hydro-chloric acid and thereby make the thermal energy stored in the PAC available for the fol-lowing batch process again.

The cooling-down process can be done quickly and efficiently by heat discharge via a PowerBaffle.

One of the two Delta baffles is thereby replaced by a PowerBaffle, which in addition to its baffle function, also acts as an internal

heat exchanger. The thermal energy is discharged through the cool water introdu-ced in the interior of the PowerBaffle and can then be used to heat the hydrochloric acid receiver.

In addition to the use of process heat and a massive energy saving, this procedure has the advantage that the time it takes to cool down the tank contents can be reduced by 35% (compared with cooling using a double jacket alone). If both Delta baffles were replaced by PowerBaffles the time taken to cool down the tank contents could be reduced by more than half!

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8 Issue 78 • 2016

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When media, whether liquid hydrochloric acid or solid aluminum hydroxide, are introduced, there is always the risk that the glass-lining of the reactor may be dama-ged.

To minimise this risk, experienced PAC pro-ducers adopt the use of PTFE feed pipes which prevent direct contact between the tank nozzles and the introduced medium. THALETEC suitably offers, for all nozzles of glass-lined apparatus, standardised and readily available PTFE feed pipes which can be used in the critical nozzles.

In practice, glass-lined bottom outlet valves from THALETEC have proved their worth in the production of PAC (Fig. 11).

Even at high temperatures the bottom outlet valves are absolutely tight.

A large, unobstructed cross-section facili-tates fast emptying of the reactor.

The valve spindle is hermetically sealed with PTFE corrugated bellows and protec-ted securely from wear and corrosion.

A temperature measuring probe fitted into the valve also enables redundancy of temperature measurement.

Longer useful life using PTFE feed pipes

Glass-lined bottom outlet valve

As well as virgin PTFE feed pipes, those made of electrically conductive PTFE which can safely divert electrostatic charges are available.

Fig. 10: Standardized PTFE feed pipe to protect feed nozzles

Figure 11: THALETEC bottom outlet valve for emptying PAC reactors

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9 Issue 78 • 2016

As a brief overview, please find below the technical specifications once again in a compact form

Reactor• Reactor 16,000l, type BE DIN 28136 with

double jacket• Temperature: -25/+200°C• Pressure of inner vessel:-1/+8 bar• Pressure of jacket: -1/+8 bar• Technical glass: ABRISIST VC, plug free

Agitator technologyMultiflex agitating system comprising• 1 stage agitating shaft• Agitating element: AMT turbine, diame-

ter 1500mm

The optimum PAC reactor exists; it can sim-ply be configured from a variety of existing and proven components from the supply program of THALETEC GmbH.

A BE type reactor agitated tank with 16 m3 nominal volume, glass-lined with the par-ticularly corrosion and abrasion resistant ABRISIST technical glass, is a good starting point.

A stirring system in-stalled in it with an AMT agitator ensures thorough mixing of the tank contents with minimal wear.

• http://www.wasser-wissen.de/abwasserlexikon/p/polyaluminiumchlorid.htm

• http://www.feralco.com/DE/DE/page452-polyaluminiumchlorid.php

• http://www.cac-chem.de/Portaldata/1/Resources/publikationen/polyaluminiumchlorid_d.pdf

• http://www.sbf-online.com/media/pdf/sbf_info_flockung.pdf

Specification of the optimum PAC reactor

Conclusions

Literature

Baffle• 1 Delta baffle, DN 300, with fitted

temperature measuring probe flexSens 100 with 2xPT100 in a 4 wire connec-tion, with a concave baffle end ARB and QuickTip temperature measuring tip

• 1 PowerBaffle DN 300 with 11m2 equiva-lent heat exchange surface

Drive unit• TRD, shaft diameter 125 mm, frequency

controlled, 18 - 88 rpm, 30 KW motor ca-pacity

One or two Delta ARB baffles with concave ends and a temperature measuring tip QuickTip, together with the easily installed temperature sensor flexsens 100, ensure a high degree of interference and a fast and accurate temperature reading.

Finally, the THALETEC bottom outlet valves are the optimum choice for emptying PAC reactors.

Our specialists will be delighted to ad-vise you in preparing an enquiry about which PAC reactor would be the best for your application. Just contact us!

Bottom outlet valve• Glass-lined, DN 150/100 with lateral

connection nozzle, pneumatic drive, non-pressurised spring closing

Miscellaneous• Feed nozzle of reactor with feed pipes

made of virgin PTFE

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10 Issue 78 • 2016

Take your training further -New THALETEC workshopsGlass-lined process equipment is often the heart of a plant. The proper handling of these systems is therefore essential for the availability of the plant and its productivity. In addi-tion, there are a number of ways to optimise glass-lined process equipment - to get more out of the plant, save energy or increase production. We would like to draw attention again to two new workshops here:

Electrostatic charges can damage the glass-lining of your conventionally glass-lined process equipment.

In the course of this new Workshop, you will learn what tools and procedures to use to effectively prevent this, thereby ensuring the long-term availability of your plant.

The Workshop is aimed at process en-gineers and plant and process planners tasked with correctly designing, imple-

To make you even fitter for the selection and specification of process glass-lined equipment,THALETEC offers a Workshop on Engineering Technology.

The Workshop provides a series of basics relevant to practical conditions:

• The material glass-lining• Specification of glass-lined tanks• Dealing with glass-lined equipment• Agitation technique in glass-lined reac-

tors• Hydroabrasion in glass-lined equipment• Heat transfer in glass-lined equipment• Electrostatics in glass-lined equipment

THALETEC Workshop

Elektrostatik in emaillierten Apparaten

Electrostatic effects in glass-lined process equipment

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THALETEC Workshop

Workshop Ingenieurtechnik

Workshop Engineering

menting or optimising chemical processes which are inclined to form electrostatic charges.

The Workshop is likewise aimed at opera-ting engineers and operations managers who need to ensure and maximise the efficiency of process plants.

• Gassing processes in glass-lined equip-ment

• Developing LabTec processes in the labo-ratory

• Maintenance of glass-lined tanks

You will find more details on this Workshop, both the time and scope of which we are also happy to adapt to your individual needs and questions, in Flyer K102.

Workshop on Electrostatic Charges in glass-lined process equipment

THALETEC Workshop on Engineering Technology

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11 Issue 78 • 2016

Thema/Inhalt Topic

Sprache Language

Ort Location

Datum Date

Hinweise Remarks

Elektrostatik in emaillierten Apparaten Deutsch Thale 7.6.2016 Flyer K101

Electrostatic effects in glass lined equipment English Thale 21.6.2016 Flyer K101

Engineering glass lined equipment, part 1 English Thale 22.6.2016 Flyer K102

Engineering glass lined equipment, part 2 English Thale 23.6.2016 Flyer K102

Ingenieurtechnik Teil 1AUSGEBUCHT/ NOT AVAILABLE

Deutsch Thale 8.6.2016 Flyer K102

Ingenieurtechnik Teil 2AUSGEBUCHT/ NOT AVAILABLE

Deutsch Thale 9.6.2016 Flyer K102

Thema/Inhalt Topic

Sprache Language

Ort Location

Datum Date

Hinweise Remarks

Elektrostatik in emaillierten Apparaten Deutsch Thale 6.9.2016 Flyer K101

Ingenieurtechnik Teil 1 Deutsch Thale 7.9.2016 Flyer K102

Ingenieurtechnik Teil 2 Deutsch Thale 8.9.2016 Flyer K102

Electrostatic effects in glass lined equipment English Thale 13.9.2016 Flyer K101

Engineering glass lined equipment, part 1 English Thale 14.9.2016 Flyer K102

Engineering glass lined equipment, part 2 English Thale 15.9.2016 Flyer K102

EmRepEmailprüfung und Reparatur Deutsch Thale 20.-21.9.2016 Flyer K093

Wartung und Instandhaltung emaillierter Apparate

Deutsch Thale 27.-28.9.2016 Flyer K038

1. Halbjahr 2016 / 1st half year 2016

2. Halbjahr 2016 / 2nd half year 2016

Dates for training seminars and workshopsIn this overview you will find all previously scheduled dates for workshops and seminars for your training. For more details, simply download the relevant flyer below. You can easily register by emailing service@thaletec.com.