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HOW IT WORKS

The Aquatherm Technology

How it Works - Concept

Every Kilowatt of energy that is used in a laundry is eventually lost to the drain or to the atmosphere and must be replaced with ‘new energy’. A substantial proportion of the lost energy can be recovered and used again, reducing new energy consumed.

Water has become an expensive resource too, and with climate change and population growth, the pressure is on to reduce Industrial consumption to a minimum.

Aquatherm is a highly efficient heat recovery system that can extract 60% to 90% of the energy contained in laundry waste water (depending on temperatures and flows). The recovered energy is used to preheat incoming cold process water, reducing the need for steam in the washing process to a small fraction of the previous demand. As a by-product of this process, hot rinsing reduces the level of moisture retained after extraction. With a drier load heated all through, drying times are reduced, increasing output and saving energy at the same time.

In this site we describe the methods and systems that Aquatherm has developed over nearly 4 decades to reduce the use of gas, oil, coal, electricity, water, chemicals and time in laundries . By employing these methods correctly, a laundry business will run more efficiently, use less energy and have a smaller carbon footprint.

If you prevent energy and water from leaving the building, there is no need to replace it - it’s as simple as that.

Between 25 and 40% of the energy used by most laundries is used for heating water for washing. All of this energy goes to waste.

Aquatherm recovers 60% - 90% of this waste energy and recycles back into the process reducing the laundry’s total energy bill by an average of 25%.

80% of energy lost in washing is recoverable

How it Works - Technical

One of the most efficient ways of transferring heat from one liquid to another, without any contact between the two, is by using a ‘Shell and Tube’ heat exchanger. This type of heat exchanger consists of a shell (a large tube) with a series of small tubes inside it. Hot water flows through the tubes and cold water through the shell, transferring up to 90% of the energy from one to the other in minutes.

If it was that simple, of course most laundries would have installed such a system decades ago. However, laundry water consists of a cocktail of chemicals, dirt, lint and fibre that causes traditional heat exchangers to block very quickly, or need sophisticated filtration, or constant maintenance.

Up to 1200 metres (3/4 mile) of this tube carries the waste water through the exchanger, while the fresh water flows around the outside of every tube in perfect counter flow.

Simulator

When planning to reduce water and energy costs, there are many options to choose from to achieve the targeted result. As every laundry is different, finding the optimum solution for each one can be a complex and daunting task.

Aquatherm’s Simulator makes it possible to make a clear choice based on what makes the most financial sense out of the many options available.

The simulator examines 10 key areas:

  • Water Supply
  • Water Disposal
  • Energy for Washing
  • Energy for drying and finishing
  • Chemicals
  • Linen replacement
  • Productivity
  • kWh per kg consumption
  • CO2 emissions
  • Return on Investment

Having entered the data provided or measured , the results are calculated. This is just the start.

These results are then compared with management figures, and in the great majority of cases there is a difference between the 'bottom up' calculation and reality. Having identified any discrepancies, input data is adjusted to make sure that 'projected' and 'actual' figures match.

At this point the simulator data will be close to reality and a series of ‘What If?’ calculations can then be carried out to to determine the optimum solution.

This is a free service, and provides a clear and accurate analysis that can be trusted to reflect the results which will be experienced when the chosen solution is in operation.

At the heart of Aquatherm is a unique stainless steel tube, formed internally and externally into a double helix.
At the heart of Aquatherm is a unique stainless steel tube, formed internally and externally into a double helix

The waste water inside the tubes is kept in a state of high turbulence, which stops lint and dirt from sticking and increases heat transfer by 75% compared with plain tube. This combination ensures the extraordinary transfer of heat that is achieved in all Aquatherm systems, regardless of capacity.

Aquatherm’s unique design uses a combination of methods to achieve a very high rate of heat recovery throughout its long working life, without the need for cleaning or maintenance. In order to keep the system compact, the exchanger is constructed in sections, linked with continuous tubular headers, with specially formed stainless steel tubes carrying the waste water, creating a controlled velocity and high degree of turbulence . The system can deal with waste water from any number and type of washing machines.

How it Works - Installation

Installation
The Aquatherm Micro is a fully packaged water and energy system, complete with fresh and waste water buffer tanks, control panel and connections to level detection sensors, fresh and waste water flow valves, temperature sensors and waste water pumps, all pre-wired and tested. Floor space requirements are minimal and configurable - enabling even the smallest or most crowded of laundry buildings to take advantage of this technology.

When it comes to installation, the new Aquatherm Micro model is in a league of its own.

Installation is quick and inexpensive.

  • Connect fresh water
  • Install pump and waste pipe connections
  • Fix level sensor to pit
  • Plug in pump and level sensor
  • Connect electricity and compressed air
  • Ready to run!
Case Studies
October 1, 2022Aquatherm Case StudiesA well known landmark in Beijing, the Peking Union Medical College Hospital is a Class A tertiary comprehensive hospital committed to delivering state-of-the-art clinical care, innovative scientific research and rigorous medical education. It is designated by the National Health and Family Planning Commission as one of the national referral centers offering diagnostic and therapeutic care of complex and rare disorders, as well as one of the earliest Chinese hospitals offering medical care to senior leaders and foreign patients. PUMCH enjoys high reputation for its full range of disciplines, cutting-edge technologies and outstanding specialties. From 2009 to 2015, PUMCH has consecutively topped the “Best Hospital Ranking in China”, which was published by the Hospital Management Institute, Fudan University. In 2012 the decision was made to renew the on premise laundry, and an old wing of the hospital was rebuilt to suit. The movement to reduce industrial waste and pollution in China has been growing, and the decision was made at the start of the laundry project to reduce environmental impact to a minimum. Space and height limitations determined the selection of washing machinery and a total of 13 washer extractors were installed to meet the daily requirements of this large and busy hospital, typically between 10-15 tonnes of clean sterile linen per day, using 20,000 litres of water per hour. Aquatherm was consulted at an early stage, and worked with machine suppliers and engineers to find a solution within the limited space available. Underneath the main wash house there was a disused cellar with barely 1.5m headroom. Into this space two large buffer tanks were constructed, in between these tanks a specilly constructed low headroom Aquatherm was fitted, linked to a set of controls on the washroom floor above. All the hot waste water is collected in one of these tanks and pumped through the Aquatherm before going to drain at a temperature a few degrees above the incoming cold water. The incoming fresh cold water flows through the ‘clean side’ of the Aquatherm, reducing steam use for washing by 80% and making savings of gas 600 M3 per day, RMB 550,000 per year. The financial savings were sufficient to pay for the entire installation in well under 2 years, and reducing the all important carbon footprint of this site. The project was managed throughout by Leon Chen who has many years of experience in the Chinese Laundry market, and whose company A Kua Sen is actively engaged in the development and sale of water and energy systems. [...]
June 1, 2022Aquatherm Case StudiesThe biggest laundry group in South Africa comprises 3 businesses— [su_list] FGR itself, which provides facilities management, including garments, dustmats and mops. Boston Laundry - The leading supplier of hotel linen throughout the country Montana - which owns and operates numerous on premise laundries serving nursing homes, smaller hospital and similar institutions. [/su_list] Originally owned by the Fainman family, FGR recently became part of the successful Bidvest group and under the continued direction of Alan Fainman and a dedicated team of professional managers has continued to expand, despite the unique cocktail of economic pressures facing the South African economy. When Alan and his team came to the Frankfurt Laundry show in June 2008 it was with a sense of urgency to find ways of reducing the impact of rapidly rising costs. Giant sized statue of Nelson Mandela takes pride of place in Sandton Square, Johannesburg By the standards of the West, labour and energy costs were very low; however, the prices that customers are prepared to pay were also a fraction of those prevalent in the Industrial nations. Indigenous supplies of coal have provided the energy for power stations and steam boilers for years, but a crisis was looming; the growing demand for energy sources from India and China was driving the export price of coal to new heights, and within less than a year the price to the domestic market had doubled. Water prices increased by 50% in the same period, and electricity costs were heading in the same direction. Even if customers were to accept steep increases in costs there would always be a period of months when costs would outgrow revenues, if nothing else changed... A short period after the Frankfurt show, Aquatherm surveyed all but one of the FGR laundries and produced a list of recommendations that ranged from pipe insulation to installing waste water heat recovery throughout. Agreement was reached to supply 9 Aquatherm systems, starting with the flagship Spartan plant outside of Johannesburg. The main washing equipment at Spartan consists of 4 Milnor 12 compartment 50 or 60kg continuous batch washers, arranged in pairs, divided between hotel linen and garments. Technical Director Gavin Strydom and Montana Managing Director Brian Shirley made a short study tour to see Aquatherm installations in use in the UK, Germany and Norway, after which with minimal assistance organised the integration into the Spartan plant to an exceptionally high standard. The results were immediate and impressive. One month after the installation, FGR reported that their total coal consumption for the plant was down by 20% and that all drying times had been substantially reduced. Non contact flow meter in the fresh water supply line controls the rate of waste water flow to ensure maximum heat extraction at all times. [...]
June 1, 2022Aquatherm Case StudiesThe leading group in Norway, NorTekstil Services has laundries operating all over the country, from several hundred miles inside the Arctic Circle to the southern capital of Oslo. Just outside Oslo in the city of Drammen is their flagship laundry, which was originally built in the early 2000’s to a standard of design and equipment that set a new Benchmark in the Norwegian Textile Industry. The plant combines a 2 tunnel linen processing plant for commercial and hospital linen with facilties for industrial uniforms and dustmats, making it a true ‘all purpose’ plant. As with all laundries in Norway, incoming cold water temperatures are low – in winter between 2 – 4 degrees – which places additional pressure on the already high costs of energy. For this reason, the plant was designed from the outset to have waste water heat recovery. Plant Manager Per Frøge with the new Aquatherm V20 All waste water is collected and pumped to a Swedish built Aquatech drum filter unit. which filters down to between 40 – 80 microns. The filtered waste water is then stored in one of two large reinforced fibreglass storage vessels. When the plant was originally commissioned, the hot waste water was pumped through a commercial plate exchanger with the intention of preheating the incoming cold water. After a short period, the performance of this system dropped off dramatically and it was discovered that the plate exchanger was blocked. After stripping down and cleaning, the performance returned to normal, only for the same to recur a few hours later. The idea was of course right, the technology was not. Even fine particles of lint will accumulate in the sharp corners and edges of a plate exchanger and lead to a drop in performance followed by blocking. The leading chemical supplier to the laundry industry in Norway at the time, Lilleborg A/s advised NTS to make changes to their system which were to have dramatic results. The plate exchanger was changed for a new Aquatherm V20 and the pipework was altered to eliminate the recirculation of cold and preheated water, which reduces thermal efficiency even if the exchanger is working perfectly. Immediately after commissioning, NTS reported a saving of 500 litres of oil a day – every day – with fresh water being heated to over 50 degrees and waste water being cooled to below what is required by law for discharge to the public drains – a limit which has now been reduced to 20 Degrees Celsius. 8 years later, fully paid for from savings many times over, the unit continues to self clean without the daily intervention of the engineering department. Cooled effluent, with a high pH and residual washing chemicals is now used for mat washing, making further inroads into the cost of service to this successful plant. In mid 2010 an extension to the laundry with 2 additional CBWs took place, with 2 more Aquatherm units and Lilleborg’s own system of water recycling making this one of the most efficient laundries in the world in its use of water and energy. [...]
May 1, 2022Aquatherm Case StudiesAltnagelvin Hospital is part of the NHS Western Health & Social Care trust of Northern Ireland and one of five designated cancer units with 481 beds. Currently undergoing a major redevelopment programme, an Aquatherm V10 was installed and commissioned in March 2012. Since the Aquatherm was dedicated to one machine—a Lavatec 12/50 there was no requirement for extra fresh water buffering and for the waste water a drain trench, used many years before when the laundry employed washer extractors, was re-furbished and re-commissioned as a waste water buffer—thus saving expensive excavation or over ground tanking. Four months later the Aquatherm was showing a thermal recovery of 85.26% with savings of over £28,600 expected by year end. This representing 24.4% of their total fuel bill. The Assistant Linen Services Manager, Trevor Lynch said... [su_quote]What pleases me most is that since the installation of the Aquatherm I don’t get any more temperature stops. Before Aquatherm I was getting 5 or 6 temperature stops a day—each one taking 2-3 minutes out of production time[/su_quote] [...]
March 1, 2022Aquatherm Case StudiesLocated just outside historic Budapest, Central Laundry’s specialist workwear and mat laundry has in less than decade earned an enviable reputation for quality and service, and the loyalty of its predominantly industrial customer base. As a result of this success, volume has grown and in early 2014 the decision was made to increase capacity. The laundry comprises two main areas separating the production of dust mats and garments. Total output is approximately 95 tonnes per week, with mats being processed over 3 shifts and garments over 2. The laundry already uses many ‘best practice’ principles:- 1. Recycling of water 2. Precise process controls using computer driven chemical dispensers and chemicals precisely prescribed to match the fabrics and soiling experienced 3. Filtration of all waste water to remove solids and fibre However, a survey of the plant by specialists from Aquatherm revealed that more than 6,000 litres per hour of waste water was leaving the building at a temperature of 49 Celsius. There was clearly an opportunity to reduce the kWh per kg figure from the already low 0.55 kWh by at least 20%. In common with many Central European locations, there are large seasonal variations in temperatures. Fresh incoming water can drop to 5 Celsius in winter and rise to over 25 C at the height of the summer. All rinses use cold water, which in the colder months can add significantly to the time needed for drying. In common with many laundries, drying had become a ‘bottleneck’ to production. The Project The site survey took place over 2 days, during which time data loggers were used to record the temperature of the waste water and all relevant cost and consumption data was obtained from actual laundry records. After discussing the options with all participants (Customer, Diversey, Aquatherm) the agreed solution shown in the diagram was adopted. Waste water from the two separate sources Lindström, Budapest (T1 and T2) is collected in a buffer tank (T3)from which it is pumped through the Aquatherm and then to waste. Incoming fresh water is pumped through the Aquatherm at a constant rate and collects around three quarters of the otherwise lost energy. The preheated fresh water is stored in a 2,000 litre tank (T4) and pumped to machines on demand. Instead of feeding the machines with cold water the supply temperature is now a more or less constant 38 C and the waste water is sent to drain a few degrees above the incoming cold water temperature. Recovery runs at an average of 76% and a reduction in CO2 of over 200 tonnes a year is projected. When Aquatherm visited in 2016 the General Manager reported:- The system has operated perfectly from the start Savings of 5-6,000 M3 of gas per month resulted in a return on investment of under 18 months With hot rinsing and better dryers, mats are dried in 15 minutes instead of 30 [...]
February 1, 2022Aquatherm Case StudiesThe Irish business of CWS-Boco was not always as successful as it is today. In recent years and under different ownership the business was under threat from high costs on one side, and low priced contracts on the other. With the takeover by CWS Boco the opportunity was seized to restructure the entire business, closing several smaller plants in the process and focussing the main linen production on a new plant located on the outskirts of Cork. CWS-Boco itself is a division of The Haniel Group, a family owned €27.3 billion turnover group of companies headquartered in Duisburg, Germany. The Textile Care division is active in 18 countries and turns over 748m a year employing 7900 people in Europe, and now with 2 ‘state of the art’ laundries in China Cork is the second city of the Republic of Ireland, Motto: Statio Bene Fida Carinis - "A safe harbour for ships" one of the two CBW’s and supplies process water to the other CBW and the washer extractors. At the time of the survey this structure was in place, but finally all waste water exited the building at around 44 Degrees Celsius - a loss of heat energy valued at around €100,000 per annum. The hope was that this heat could be recovered and recycled to reduce the ‘new energy’ needed to provide the process requirements. After receiving a detailed proposal from Aquatherm, the decision was made to install an XV20 to extract the energy from the entire effluent flow. In order to collect the waste water from the bank of washer extractors, which are physically separated from the main washing area, a filter pump supplied by Aquatherm was used. The waste water from the washer extractors is mixed with the effluent from the tunnel washers, before making an impact there too. Today CWS-Boco Ireland is one of the country’s leading provider of hotel and restaurant linen, washroom hygiene, workwear, dust control mats and sterile surgical supplies. As part of the ongoing efforts to improve the operating efficiency and reduce energy use, Aquatherm were asked to survey the Cork plant in Spring 2012. It was immediately apparent that there was an unusually good understanding of the methods and potential for energy and water saving amongst the CWS Boco Management team, and equally impressive was the range and detail of the management information relating to services and production. This was manifested by the way in which the services have been carefully arranged to maximise the benefit of future recovery systems. Two features were particularly notable for their effectiveness; all water supplied to the washing plant is preheated, which has a positive impact on process times and provides the well known benefits of hot rinsing. There is also a water reuse system in operation which takes waste water from all of the waste water is pumped through the Aquatherm XV20. All the pre-heated fresh water from the Aquatherm is piped to a 12m3 hot water buffer tank located in the boiler house from which all the machines draw their hot water supply. The original calculations were based on the plant operating a double shift (80 hours) and processing 216 tonnes a week. The system was estimated to recover 65% of the energy currently going to drain with the added benefit of a 481 tonnes saving in CO2 emissions. The estimated payback for the project is under 12 months and the all important energy consumption for production is now below 0.8 kWh per kg. Several months later, an email from Ciaran Kearney, the Maintenance Manager for the Cork plant summed things up nicely - [su_quote]if we were to buy a waste water recovery system again I believe it would be a one horse race...your product does not need selling if the right person with the right 'know how' sees it working in a plant[/su_quote] [...]
February 1, 2022Aquatherm Case StudiesEstablished in Lincoln in 1841 and with a history that has been traced back to Newark in 1791, Jacksons is one of the oldest family run dry cleaning companies in the UK. Over the years Jacksons has seen many nationally recognised firms come and go, but at the same time has managed to firmly establish itself as a household name in the Lincolnshire area. Today Jacksons specialise in laundry and dry cleaning services from two outlets in Lincoln, North Hykeham and Newport, as well as providing a collection and delivery service to many professional organisations in and around the City of Lincoln. In early 2010 under the direction of Chairman Alastair McKinder and guidance of Engineering Manager Steve Allen a program to reduce the energy use of the main laundry plant was initiated, starting with the major steam consumer in the plant — the wash house. Jacksons has always used ‘conventional’ washer extractors to achieve the high standards for which they are known. Now somewhat of a rarity, the high performance Broadbent JB 350 machines set a benchmark when they were introduced 30 years ago that has never been bettered. Meticulous maintenance has kept the 9 machines in perfect condition, and likely to remain so for years ahead. What has changed is the cost of water and energy, and Jacksons have once again read the signs and decided that action was needed. A visit to nearby Industry pioneer Fenland Laundry confirmed the choice of Aquatherm to provide the equipment and expertise needed to implement a comprehensive review of the plant engineering aimed at reducing energy losses – and costs – to the lowest level achievable. An existing pit used to buffer the waste water and allow to cool before going to the town drain was modified to provide a 30 minute capacity for all of the waste water. Initially this comprised a mixture of hot pre wash and wash water, with cold rinses. Inside the building, the heavy duty Aquatherm pump transfers the hot waste water from the pit to the main Aquatherm Heat Exchanger. With a footprint of only 0.5 M2 the Aquatherm unit was installed in an unused corner of the washouse and connected to the main incoming cold water supply. Preheated to 40 degrees by extracting the energy from the waste water, the fresh water is stored in a 5 000 litre insulated tank, sized to deal with the fluctuations in demand from 9 washer extractors with 4-5 stage processes. Every part of the process – prewash, main wash and all rinses – is supplied to the machines with a high capacity pump. Filling machines quickly, with preheated water reduces process time and boosts output. Riinsing at 40 degrees C (instead of 10 – 15) is more effective, and reduces moisture retention after extraction, cutting drying and tunnel finishing time. The entire project, including installation, was financed through an interest free Carbon Trust Loan, organised by Aquatherm Completed in July 2010, the new system saves 73% of the energy that would otherwise be lost. Wash processes are shorter, and the tunnel finisher speed has been increased. Waste water now goes to the town drain 6 degrees above the incoming cold water. The built in Aquatherm control monitors flows and temperatures every second to optimise recovery rates, and keeps a running record of kWh saved that can be used to calculate the financial savings that are expected to repay the investment in less than a year. [...]
January 1, 2022Aquatherm Case Studies33 years after the construction of the famous Blackpool Tower in 1894, Express Laundry opened its doors for business. Starting as a domestic laundry in 1927 the business has grown into one of the best recognised names in the UK laundry Industry. Today, both Tower and Laundry are thriving - one still attracting tourists from all over the UK, the other providing a top quality linen rental service to the hundreds of hotels and guest houses that service the town's many visitors. Over a partnership of 25 years, current owner, Eddie Bruce, and Chief Engineer, Gordon Edwards, have kept abreast of the latest developments in machinery and processes - often creating ideas that have kept their suppliers on their toes to deliver. In the 1980s, Express was one of the early customers of Aquatherm's original design, and reported steam use of 0.16 kg per kg processed - unheard of at a time when 0.4 - 0.5 was the norm for the newest tunnel washer laundries. 30 years later, with all of the original machinery upgraded—some more than once—to ’state of the art’ the decision was made to install water recovery as a means of saving both energy and water. This did not prove successful and a couple of years later Aquatherm was brought in to install a system to recover and reuse the significant volume of energy that was being lost to drain. A year after the installation total reduction in energy used for washing was nudging 1m kwh -sufficient to recover the entire cost of the equipment and. installation. [su_quote]We have not touched the unit since it was commissioned, said Gordon Edwards. It does exactly what it says on the box. We reckon that savings at our Vale Plant (another V10 installed at Express’s plant in North Wales) are over £50,000. It's been an excellent investment all round.[/su_quote] The Aquatherm deals with two Lavatec tunnels processing a mixture of hospitality and NHS linen. Clever use of chemicals and flows enables the laundry to achieve rinsing temperatures of over 50 C which results in faster and cheaper drying and finishing - a saving not included in the figures reported by the Aquatherm’s data records. The unit was installed and commissioned entirely by the engineering team at Express, and was running within days of being delivered to site. A visit to site a year later revealed that an average of 10,760 litres per hour was being heated from 8.1 C to 35.2 C using the waste water as a source. In turn the waste water was being cooled from 56.4 degrees to 24, resulting in a total recovery of 68% of the available energy. [...]
January 1, 2022Aquatherm Case StudiesIn common with most European and Scandinavian countries, many hospitals and public institutions in Danmark have turned to the private sector for the provision of linen services. One of the few remaining that have decided to retain their own processing facility is Vejle Sygehus (Sudenske Vaskeriet) located in the historic town of 55,000 inhabitants in Jylland (Jutland). The laundry was established in 1980 and re-equipped with modern equipment in the early 2000's. Processing 6-7 tonnes per day, the main washing plant comprises 2 x Senking, 12 compartment P18 tunnel washers with SEP 50 type presses, and a total of 5 x Senking and 2 older Passal dryers – all equipped with cross-flow plate exchangers to reduce energy use. Although the benefits of having an ‘on site’ service are many, the public sector is nevertheless duty-bound to obtain best value for money, and to keep processing costs to a minimum. For thirty years, the processing methods and chemicals have been supplied by Novadan, which in 2010 served more than 50% of Danish laundries. Early in 2011, René Larsen , the chemist who had already achieved major savings in water and energy, proposed that the laundry invest in an Aquatherm Waste Water Heat Recovery System. A study was made of the flows and temperatures, and it was conservatively estimated that the total cost, including installation, would be recovered from energy savings in less than a year. All of the waste water from both tunnels, including press extract water, was individually piped to a two cubic metre insulated tank adjacent to the machines, the mixed contents averaging 47°C. An Aquatherm V20 automatically extracts the energy from the waste water, the resultant flow going to the outside drain at 5-6°C above the incoming cold fresh water – a recovery of 84%. A second collection tank is used to store some of the cooled effluent, which is used to supply the washer extractors with water for the pre-wash and main wash. The rinses use fresh water. Re-used water contains the 16-20% of energy not recovered by Aquatherm, and assuming 30% re-use, this boosts the recovery of energy used for washing to nearly 90% - without any need for cleaning or maintenance. Apart from the direct energy saving, the extractor now operates with the linen at over 40°C, which reduces the moisture content and results in lower energy consumption for drying and finishing. Using a clear 10” colour touch screen, the Danish staff can monitor flows and temperatures at all times, and all data is written to a data chip every second to provide a detailed record of performance whenever the plant is running. [...]
December 1, 2021Aquatherm Case StudiesIn 2008 the Victoria NHS Laundry was struggling to deal with the workload being processed through the 2 Senking tunnels they had installed some years earlier. George Ronald, the Estates Officer responsible for the engineering and building aspects of the plant had picked up on a reference to ‘side effects’ mentioned in the Aquatherm brochure that he had received – in particular the claim that waste water heat recovery reduced drying time of tumbler driers. With the increased load that the laundry was being asked to process, drying had become a major bottleneck to production, and the concept of being able to reduce drying times by 20% and save energy at the same time was attractive. After Aquatherm made a detailed survey it became clear that although a full waste water heat recovery system was viable on paper, the site conditions were far from ideal. The main water storage tanks and drainage system used by the laundry are located in a sub basement under the production floor, access to which is by a narrow flight of stairs. Once inside the basement the picture did not improve… A mixture of cast iron drains feeds waste effluent into a brick built buffer tank from which there is an outlet to the exterior drain. With around 13 cubic metres of waste water at a temperature of over 40 degrees, 60 hours per week the loss of energy was equivalent to £57,000 – a situation that could not be allowed to continue. Despite regular attention the pit would also become clogged with lint, plastic bags and small articles on linen. As Aquatherm prepared for the installation specialist contractors were working in the basement to remove the asbestos insulation used in earlier days to save energy…. The solution was as elegant as it was effective. First of all a stainless steel collection tank was installed to intercept the waste water drains from the wash house. The water collected was channelled through a tailor made rotary screen to remove the various detritus and then buffered in the original brick tank. From the tank, waste water is pumped through the Aquatherm to drain at a controlled flow matching the demand of fresh water called for by the washing machinery. Starting at around 42 degrees the waste water temperature rose to over 50 degrees—the so called ‘flywheel effect’ before being cooled by the incoming cold water to between 15 and 20 degrees, depending on the ambient temperature at the time of year. Estates Manager Dale Stewart (who had taken over the project) initially anticipated that the system would pay for itself in a year in direct fuel savings. In fact the system was operating so efficiently, feed temperatures were at times a little high for the process and some stain setting occurred. The ‘not to exceed’ temperature control in Aquatherm was set to 40 degrees, which dealt with the situation although prolonged the full payback by a few weeks. Linen Service manager Andrew Greer was delighted with the improvement in drying – times cut by a quarter – and the increase in productivity that resulted. And just how did our installation engineer get 750kg of Aquatherm down two flights of stairs without a scratch? When questioned, he smiled and said as he walked away – ’very quietly – you don’t want to know’ [...]
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