The Importance of Lab & Pilot Testing

Our Testing Process

We at DrM believe that lab scale and pilot testing are indispensable tools for selection, sizing and validation of process equipment.

This is why we offer a unique fleet of testing and rental equipment ranging from a 0.001 m2 lab Nutsche, via our 0.012 m2 TSD pocket filter and mono-candle pilot units up to full scale production skids. Our skilled laboratory staff and process specialists are at your disposal to solve almost every filtration problem.

A new or unknown filtration task usually starts with Nutsche tests followed by lab scale trials on our TSD pocket filter. These tests are often performed at DrM’s in-house filtration laboratory using the original product mixtures at realistic condition whenever possible. Clients are invited to attend the testing, become an eye-witness and discuss the results as they are generated. Already at this stage important data on flow, pressure, filtrate quality, residual moisture, washing yield, filter aid demand and other parameters are determined. After significant lab scale testing it is possible to size the full-scale production equipment, provide budgetary quotes and preliminary layouts.

In a next step larger scale testing on mono-candle pilot units or semi-scale demonstration units follows under most realistic conditions. During such campaigns the lab results are refined and the processes are optimized. The goal now is to achieve a stable and continuous operation, gain experience and fine-tune the filtration system. The insight serves the process engineer and plant designer for sound planning and specification of the full-scale production equipment. After the execution of significant pilot tests the determination of a performance or process guarantee is normally possible.

Test Report

A consistent and precise testing procedure must be accompanied with an efficient and functional reporting system. For this DrM developed its own test reporting database which is running in the cloud and can be accessed by our whole team. This allows our service engineers and partners to get access from anywhere around the World. Data is entered in an organised fashion and reports including graphical views are produced within minutes. Pictures and videos taken during the testing can be added to document the trials. The system can be accessed on mobile devices, laptops or through any web browser.

June 11-15, 2018 Frankfurt, Germany

DrM at Achema 2018

Once again the chemical processing World is in the midst of its preparation for the biggest show in its field: Achema 2018 in Frankfurt. Also at DrM activities are being intensified to get ready for the event in June.

However, this year the stakes are especially high: Some time back we started with a number of development projects which are coming to a closing end and we will use the show to introduce those to the broader industry. We are proud to have no less than 5 new patents and patent applications which we will show off in form of working products, models or animations. As a teaser to this important event we want to let you have a sneak peek into our presentations. But please take the opportunity to come and see us at our booth and get a life demonstration of these innovations. Because there’s nothing better than the real thing!

FUNDABAC® Overfill Protection Device 

Damage of filter internals due to overloading with solids can be a major headache for operators who run filtration systems at certain conditions.  Various designs, devices and instruments to prevent such incidences have been developed in the past but often not with satisfactory results. We now have chosen an entirely different route which we will present to you. The patented device can be installed both in new and existing filter systems and will help protect your equipment. 

FUNDAMIX® S

The legendary vibratory mixer which has been on the market for the last few decades has its well established clientele in the pharma and biotech industry. It is a proven technology with thousands of units in operation. But now we are taking a big leap to an entirely new vibratory design. And it will be so silent you would not believe it is in operation.

FUNDABAC® SU Single Use Filter Technology

Single Use Filter

The biotech industry is jumping more and more onto Single Use technology. It promises a number of advantages to the traditional stainless steel equipment. But existing single use filtration technology seems to rely on old principles. At DrM we were hard at work to come up with an entirely new device which will significantly reduce operating cost. We have done it the typical DrM fashion and developed an entirely new process around a novel single use filter design to come up with a compact and cost efficient equipment. And it is not only for biotech. Also chemical companies have shown interest for cases where operators need to be protected from hazardous substances.

FUNDAMIX® SU Single Use Mixing Technology

FUNDAMIX SU

Vibratory devices are very well suited for single use equipment as rotating parts often create sealing issues. Lacklustre mixing devices for single use equipment on the market hardly have any punch. The FUNDAMIX® with its extremely effective high frequency mixing plate can create amazing mixing results at low shear forces. The complete system is patented and will be presented in conjunction with the FUNDABAC® SU.

Single Use Valve

This innovative valve was developed due to the need to find a single use ON/OFF valve which can operate at higher pressures required for filtration. Most of the items on the market can only pinch tubes at atmospheric pressure or require an expensive replacement head for every change. This single use pinch valve can securely operate at 4 bar pressure and does not require any replacement parts apart from the single use tubing.

So, if you make it to the Achema this year, take the opportunity to visit us at our booth: Hall 5.0 / Stand B16. We will have enough people present not to keep you waiting.

Introducing Patented FUNDABAC® Overfill Protection Device (OPD)

Filtration involves separation of two phases while one phase passes through a media and the other is retained. The retained phase accumulates in the filter and if not removed at certain intervals, it can lead to all sorts of complications, such as difficulties during removal, blocking or even disastrous damage of the filtering device. There were a number of attempts to control or monitor the loading of filters but results have been mediocre. This has to do with the fact that it is difficult to measure phase differences such as solid/liquid-phases inside the filtering device.

 

 

Solution:

DrM now developed and patented a new device which does not attempt to monitor the phase but rather the forces acting on the filtering device. When overfilling occurs the filtering elements are displaced and such displacement is detected and a signal indicates that filtration shall be terminated.

The design incorporates distance sensors which are mounted above certain sections of the filtering device. Displacements of a few mm are enough to activate a signal.

     

 

Flexible woven metal filter media with 3D-structure

Woven Filter Media

For liquid filtration at high temperatures the material of choice is often sintered metal powder (PM) type filter. Tubular elements are available in a range of alloys and with pore sizes below 1 micron. The operational life of the media can easily extend over years, and its low maintenance is a strong argument for adoption. At least, in theory…

In practice it is often another story. While there are cases where PM works as promised, there are instances where the results disappoint. To understand the reasons for this, we need to take a closer look at the design of such a sintered PM element:

The element wall is built of narrow sized stainless steel powder, which is sintered at high temperatures to form a rigid, but porous structure. Since the pore size is determined by the size of the sintered particles, the finer the particles, the smaller the resulting pore size.

In solid/liquid separation, typically a fraction of those particles finer than the pore size of the filtering media pass through, the largest particles are held back in the filter cake on top of the media and some get stuck within the PM structure. It is this last solids fraction, which normally cause trouble, because the rigid porous layer prevents any movement and back-flushing does not always remove those particles. Over time trapped solids accumulate and begin clogging the porous metal. Ultimately, the PM elements need to be either chemically treated to dissolve the entrapped solids, heated to a high temperature to burn off the impurities, or they have to be replaced altogether.

As an alternative to traditional sintered PM elements, and specifically to address operational deficiencies, DrM has recently developed a new type of filter media built on a 3D-woven structure made of stainless steel microfiber. This media has a significantly higher open area for flow than PM, but is still capable of retaining particles down to the 1 micron range. Another key feature is that the woven structure flexes outward during back-flushing. This expansion movement releases trapped particles, thus preventing solids build up and eventual clogging. In addition, the media is rated for temperatures well above 300ºC and both slurry and dry cake discharge is possible.

In short, the woven stainless steel microfiber elements significantly extend the application range of our filtration products without sacrificing any of the process options the well-established FUNDABAC filter provides.

Selecting this media makes sense for applications with high temperatures (above 200ºC) and where the feed solids have a tendency to clog. Target markets are in chemical syntheses where catalysts need to be removed at high temperatures, and in refineries for the removal of FCC catalyst fines from heavy cycle gas oil.

DrM Clampless Candles

DrM FUNDABAC® Clampless Candle

Ever since the introduction of the FUNDABAC® Filter various kinds of clamps have been applied to securely fix the filter flexible media to the FUNDABAC® filter element. The clamps come in various forms, such as plastic wedge rings, one way clamps in stainless steel and re-usable screw clamps in stainless steel, titanium and zirconium. Clearly, as with the materials of construction for the rest of the filtration system, the choice of clamping materials is dependent upon the properties of the materials being handled in the filter and the process conditions.

For applications like chlor-alkali, viscose and other processes where we employ our polypropylene (PP), polyvinylidenfluoride (PVDF) or polyphenylenesulfide (PPS) filter internals we have previously used polymeric PP, PVDF or PPS wedge rings or titanium or zirconium wire clamps. DrM is proud to announce the launch of a new clampless candle design, which will be offered in PP, PVDF and PPS.
With the introduction of the clampless design for our plastic filter elements, separate clamps become obsolete. Here, the filter media is fixed with a special screw mechanism that is part of the filter element.

This offers a number of advantages over the previous design:

• Smooth design: No cake deposit on the clamp
• Metal free
• No difference in thermal expansion
• No corrosion attack
• Suitable for metallic and plastic registers
• Suitable for a wide range of filter media
• Filter elements can be supplied with the filter media already assembled

The clampless candle is now being offered as a standard option at DrM.

Tianqi Lithium

Kuala Lumpur, Malaysia. DrM, Dr Mueller AG has signed a contract for the supply of specialised filtration equipment for Tianqi Lithium Australia’s newest lithium hydroxide processing plant, which will be located in Kwinana, Western Australia.
Tianqi Lithium, which controls a majority stake in the Greenbushes mine, the world’s premier producer of lithium concentrate from spodumene, is building a downstream processing plant for lithium hydroxide in Kwinana, 40 km south of Perth. The plant will convert around 161,000 Te per year of spodumene concentrate into 24,000 Te of lithium hydroxide, for use in the growing global market for lithium ion batteries.

CONTIBAC® SM Filter

DrM has won a contract for supplying equipment that will support critical functions in the overall process. DrM’s CONTIBAC® candle filters will be used as main process filters on three key extraction stages and a number of DrM CONTIBAC® SM filters will be deployed in key areas as guard filters.
Whilst the commercial aspects of the project were handled from DrM’s SEA Sales and After-Sales Service Centre in Malaysia, the units will be manufactured at DrM’s Asian production plant located in Shanghai and be supplied as complete modular skid mounted filtration units. DrM has already supplied a number of process filters to Tianqi’s lithium processing plants in P R China and Tianqi now operate a range of DrM CONTIBAC® candle filters (slurry discharge) and FUNDABAC® candle filters (dry cake discharge) units
for lithium processing.
This latest contract has been awarded due to DrM supplying “the best available technology” and the long-term experience with the economy of operation, reliability and efficiency of the DrM systems.

Facts:
Scope: 5 x CONTIBAC® candle Process units, 6 CONTIBAC® SM Guard units
Customer: Tianqi Lithium, Australia
EPC: MSP, Perth
DrM

DrM Filter Testing Pilot Plants & Scale Up

In many chemical processes, the filtration step is considered a bottleneck. Therefore a properly designed filter that factors in its sizing is critical for successful plant operation.

In addition to DrM’s extensive filtration experience and know-how in hundreds of different processes which DrM has acquired as a result of its 3000 filter references, DrM is capable of supplying a wide array of pilot filters ranging from lab scale (0.012 m2 filtration area) to industrial production scale (50.7m2 filtration area).

Test Filters Systems

Many conclusions can be drawn as a result of observing the following 8 pilot testing aspects:

1. An accurate flux rate per m2, essential in order to properly size an industrial filter, can be determined

2. The best performing filter cloth can be selected as a result of observing  filtrate quality

3. The determination of filter cake thickness

and dehydration potential, as well as filter cake discharge behavior (the latter, in the case of the FUNDABAC® filter)

4. The performance of filter cake washing, if required for the process

5. The determination of optimal filter cake formation

6. Solids concentration or Total Suspended Solids (TSS), in the case of  CONTIBAC® slurry discharge

7. Determination of an optimal cloth cleaning procedure to ensure original flow rate repeatability, batch after batch to ensure a much longer cloth life time

8. Cake discharge procedure as a result of cake discharge observation

DrM has recently developed a new test software in which the most important parameters for filtration unit design are highlighted. The parameters include:

– Required flow rate to correctly size a filter

– Cake thickness and dryness to obtain an accurate estimate of waste associated costs or alternatively the design of post treatment driers

– Optimum total cycle time considering both filtration and down times (filter filling, draining, drying, washing and cake discharge)

Tests on Lab Scale Candle Filters

Once key parameters are known, industrial filter sizing for optimal operation can be determined accordingly.

The Role of Filtration in Water Conservation

Water has become a scarce product in many parts of the World. Once an abundantly available resource, supply is running low and demand both for private and industrial use has constantly increased over the years. While historically we have never given too much attention to conservation of this valuable product, we today find ourselves increasingly fighting for a larger share of what lies to our disposal. In certain regions of China for example, the maximum amount of water usage is specified inside licenses for new production plants. As the size of the plant is hence defined by its water usage, the process technology which uses the least amount of water will also allow for the largest plant to be built within the given license agreement.

As a result water conservation is playing a more dominant role in today’s decision making process. International process licensors and engineering companies are finding themselves adapting their designs to the local water usage regulations. Obviously, solid/liquid separation equipment play an important role in these processes. These can generally be categorized into:

  • Feed water treatment
  • Conservation and reuse of water
  • Product recycling from waste water streams
  • Process water recovery

As production plants usually have life cycles of a few decades we often find ourselves confronted with older process technologies, despite the fact that many plants have gone through revamping stages to modernize their equipment. The following paragraphs describe a number of cases where filtration technology had a major impact in the above categories. For space reasons, only some among the presented examples are described in more detail.

Feed water treatment

Sea water pretreatment prior reverse osmosis desalination
In coastal areas where sea water is available freely but potable or even utility water is a precious resource (e.g. Middle East), desalination by means of RO is a very common approach.
RO membranes are very susceptible to even low concentrations of suspended solids, therefore a pre-treatment is required in order to protect the membranes from fouling or contamination and extend their lifetime, respectively reduce the maintenance shut-down time. A special mention is needed for algae removal, among the most challenging tasks in such an application: algae proliferate unpredictably depending on sea water temperature and their colloidal behavior represents in general a serious challenge for filtration systems.
Conventional pre-treatment systems may include flocculant dosing, multi media (gravel-sand-anthracite) filtration, cross-flow filtration, just to name a few. An equipment such as the FUNDABAC® filter can replace a complete treatment system capable of removing virtually all suspended matters down to sub-micron levels.
DrM filters operating with filter aid can successfully deal with algae and other suspended solids present in sea water by removing them on a quantitative basis and producing water ideally suited to be processed by RO plants.

Conservation and reuse of water

  • Pre- and Postleach operations in TiO2 production
  • Produced water filtration

In Produced Water handling filters are installed downstream of the slug catcher or flash drum. During normal operation the water coming from the flash drum is processed, while on an intermittent basis various other process streams are treated, such as wash water or pigging water. Metal sulphates, FeS, free mercury and sand are among the solids to be removed. The amount of solids generated by the system and their tendency to foul increases dramatically during intermittent operations like pipeline pigging. Due to the possibility of using filter aid when confronted with reduced filterability, DrM filters can flexibly adapt to a very wide range of operating conditions.

With its fully enclosed design, the FUNDABAC® easily fulfills HSE requirements when dealing with hazardous substances (Hg, H2S, NORMs) typically present in well formation water.

Product recycling from waste water streams

  • Recovery of ABS from a waste water stream in ABS production
  • Recovery of terephtalic acid in PTA plants

PTA crystals are large and fast filtering solids and concentration in the mother liquor after crystallization is relatively high. Recovery is done on centrifuges or rotary pressure filters.
However, while cooling the filtrate additional PTA is precipitated in considerable amounts and this would be lost in the waste stream if no treatment was to follow. Additionally, the organic load in the waste water stream would significantly contribute to the COD level downstream in the biological treatment system.
The FUNDABAC® filter contributes significantly in reducing organic waste and increasing yields by up to 2% in PTA plants globally.

Process water recovery

  • CaSO4 removal in Chlor Alkali processes
  • Absorption column wash water filtration

Absorption columns for gas treatment is widely applied as an effective means to remove contaminants. Typically, also solids are removed and accumulate in the wash water. Since many years the FUNDABAC® has played a major role in removing such solid contaminants from absorption liquids in coal fired power plants, waste incineration plants and refineries (H2S removal).

  • Treatment of flushing water of electrostatic filter

Electrostatic filters applied in flue gas treatment processes need to be flushed regularly for regeneration. Without an appropriate solid/liquid treatment system the used flush water would have to be rejected, producing significant amounts of waste. The FUNDABAC® was proven ideal for this application and allows for a closed loop design in unmanned operations, virtually eliminating liquid waste.

  • Waste water recycling in PVC production

Waste water in PVC plants cannot be recycled unless COD is reduced and solids removed completely. The FUNDABAC® filter offers an elegant solution to take care of this stream.

Silicon removal from grinding and shaping operations in chip manufacturing

…and many others

DrM, Dr. Mueller AG is a world-leading supplier of solid-liquid separation systems established in Switzerland since 1982. Over 3’000 filtration units are installed worldwide to date, successfully operating on hundreds of industrial applications. What is presented above is therefore just a small selection of cases where DrM candle filters have been successfully deployed.Screenshot 2016-09-19 10.11.00

DrM’s core products are FUNDABAC® and CONTIBAC® candle filters, sophisticated systems capable of removing suspended solids down to 1 µm or less from liquid streams. As shown in the pictures below, vertical filtration elements (candles) are installed inside a pressure vessel and a textile filter cloth is fit around each candle by means of a simple, circular fixation clamp which dramatically minimizes potential for leakage with respect to competitive designs.

DrM filters work fully automatic and do not need operator intervention. Additionally, due to the absence of rotating or otherwise moving parts, maintenance is simple and limited to a few inexpensive items: routine maintenance only consists in the periodic (yearly) replacement of filter cloths. These can be selected among over 50 different types in order to finely adapt to the very specific requirements of each and every application.
The special proprietary design of DrM candles provides FUNDABAC® filters with the unique capability of discharging filtered solids as a 50-80% dry cake, thus minimizing the amount of waste to be disposed of.

Selection of equipment for solids removal in natural gas extraction operations – CAPEX vs. OPEX considerations

The extraction of natural gas requires the removal of suspended solids from the feed stream. Generally, these streams can be grouped as follows:

Produced Water (PW) and dirty liquid streams resulting from pipeline pigging operations

Rich monoethylene glycol (MEG) recycle streams which contain various salts from the produced water. The injection of MEG at the well head is the most common method to prevent formation of hydrates and avoid pipeline blockage. Hydrate inhibition is specifically requested when low temperatures are involved. Increased activities in offshore and deep sea drilling, where lower temperatures and longer pipelines to shore result in a significantly increased risk of hydrate formation, also triggered demand for MEG injection systems.

Hydrocarbon condensate which carry over solids from the slug catcher may also require further treatment.

The conventional FUNDABAC® filter is a sophisticated system capable of removing suspended solids down to 1 µm and smaller, is fully automatic and requires minimal operator intervention and maintenance expenditures.

The dry discharge capability of the FUNDABAC® filter allows for the disposal of a 50-70% dry cake and minimizes disposal requirements. Dangerous substances such as Hg, H2S and NORMs can be safely handled as a result of the fully enclosed design.

Filter aid can be used in situations where the process medium is difficult to filter, thus making FUNDABAC® filters suitable both for normal operation routines and for periodic, intermittent operations when solids generated by the system and their tendency to foul increase dramatically (e.g. pigging).
In some cases an automatic filter such as the FUNDABAC® may not be economically cost justifiable. Below a specific solid load, the OPEX of filter systems using disposable media (e.g. manual cartridge filters) may be desirable. This factor, coupled with a relative lower CAPEX, makes these systems more cost attractive.

In addition to being able to supply technically sophisticated FUNDABAC® filters, DrM also  offers its customers cartridge type filters. DrM’s extensive know-how in solid-liquid separation processes puts DrM in the unique position to propose the most cost-effective filtration solution for a given set of application operating parameters. DrM’s recommendations always take both CAPEX and OPEX into account.

DrM is committed to the continuous development of its cartridge filter design and aims to minimize operator exposure to harmful substances, often an issue when disposable elements need to be replaced. Information about DrM’s cartridge elements and unique housing design can be found below or by contacting DrM.

DrM technical sales representatives are often asked to provide a rough cost impact study that compares its cartridge filters to its fully automatic FUNDABAC® filters. It is clear that due to design specifications and materials there is a broad range of variables impacting CAPEX. By creating sets of assumptions however, we can project figures that can give a general indication of CAPEX and OPEX, as per example on the next page.

Input figures and life time cost calculations for some cases

Please note that above figures do not take into consideration the disposal cost of either the solids cake discharged from a FUNDABAC® Filter or alternatively filter cartridges.

Operating costs are also not considered in the above comparative analysis. It should be assumed that both of those cost drivers will favour of the FUNDABAC® Filter due to its automation and lower solid waste production. Geographical location can influence these values significantly. Business operators will likely want to include those numbers in their own calculations.

As expected, the lifetime cost of a cartridge filter system is lower than that of a FUNDABAC® Filter in low solid loading applications (say, below 5’000 kgs/year) since the number of replacement cartridges is fairly proportional to the solid load.

For higher flow and solids concentrations, the FUNDABAC® filter is more cost economical than cartridge filter systems. It should be noted that this analysis only takes CAPEX and OPEX into account. Other factors such as operator and environmental safety, proximity of disposal sites as well as physical space requirements may impact investment decisions.

Looking at past experiences in natural gas extraction plants, we can deduce that for removal of divalent salts from MEG that a FUNDABAC® Filter should be the best filter choice due to the higher solids load, despite the fact that liquid flows are not so high.

For produced water we need to view things differently. When considering both pigging and normal water treatment, a FUNDABAC® filter should be the equipment of choice. It can cope with fluctuating input solid loads and as well, higher concentrations are easily managed. For normal operation however, a cartridge filter system may be good choice.

For hydrocarbon condensate we normally deal with a low solid load and high liquid flows. The final consideration will therefore depend on the detail input data. Here the tendency is towards cartridge filters. However, the operator may also want to consider operator exposure to toxic chemicals and their disposal cost.

Conclusion

As can be seen in the above analysis, filter type selection is not as clear cut as it may first seem. To get a better understanding, input values can be applied to run a cost simulation model which will help in the decision making process. In this regard, DrM can provide valuable input.

Safe Handling of Hazardous Chemicals

In the aftermath of the explosions at the port of Tianjin China and at a chemical plant in Shandong, we are once again reminded of the reality of the dangers involved in handling combustible and toxic chemicals. When running an automated production facility with a team of experienced operators, risks of incidents can be minimized. This having been said, accidents can still happen. Throughout DrM’s long involvement in the design and installation of filtration systems of hazardous products, it has encountered a number of incidents that merit mentioning.  Exposure to and knowledge of these incidents have allowed DrM to develop safe designs.

Material Handling Risk

The risk of industrial accidents involving liquid handling is generally very low as liquids can easily be conveyed in pipes and processed in closed equipment. Explosion-proof components such as pumps, agitators, valves and instruments are generally considered to be reliable and safe.

On the other hand, solids handling is another matter. Material blocking, accumulation, sticking and dust creation are just a few solids handling issues that can pose safety problems. Furthermore, the behaviour of a solid/liquid mix can significantly change as a result of varying concentrations. This can create unexpected and undesirable results.

Filter systems for solid/liquid separation are at intersection of liquid and solid handling.  Since the FUNDABAC® filter is often used to generate dry solids from a liquid stream, appropriate designs are required to handle those powdered solids. As long as the solids are contained in the enclosed filter, safety can be guaranteed. Once the solids are discharged, containment becomes significantly more challenging. Here are some typical issues that DrM has encountered.

Inert gas for cake drying
Unfortunately it still happens that inert gas gets contaminated with air. Depending on temperature, solids and liquid composition as well as dryness of the product the consequences are manifold.  In most of the cases we experienced, the pyrophoric cake, such as catalyst starts to glow and slowly burns. Luckily, oxygen levels are often low which may only cause some material damage. However, the consequences can be significantly more devastating and it is recommended to constantly monitor the inert gas quality.

Steam For Cake Drying
Some DrM clients prefer to use steam to dry the cake of solids. To prevent moist discharge, superheated steam can be used (please contact DrM for further information).

The use of superheated steam results in a hot cake of solids that could create issues during discharge that are not normally encountered with cake drying using inert gas. For example, while a cake may be handled safely at ambient conditions, it may become significantly more pyrophoric at elevated temperatures. To prevent any incidents, it is recommended to cool the cake by inert gas purging prior to discharge. As an alternative, saturated steam or water spray can be applied to keep the cake humid.

Solids Containment and Handling

Operators may decide that complete containment of the cake is required. This is easier said than done. If the solids are processed indoors, closed equipment can be installed on the discharge side of the filter.

Containers may be closed with a manual valve and transported to the next operation unit. Alternatively, the cake can be transformed into pulp for easier handling.fig5
When solids need to be shipped to another facility or disposed of, one way containers or barrels are preferred. These need to be positioned onto the discharge chute of the filter. If the discharge operation needs to be contained, an endless bag may be an option.

When solids are hot,  polyethylene bags may not be an option. An alternative would be to let the cake cool off in the filter by way of inert gas purging and discharged when the temperature falls below 60ºC. A flexible bellow, designed for manual or pneumatic operation, can be pressed onto a steel barrel.