The dairy industry. steam and condensate systems

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1 The dairy industry steam and condensate systems

2 The well managed use of high quality steam is a major factor in the efficient production of high grade dairy products 2 What is steam used for? Raw milk is processed into a wide variety of dairy products which include: pasteurised milk, cheese, butter and yoghurt. In the modern dairy, steam is used in a variety of processes to promote chemical reactions and physical changes in raw milk and to help maintain clean, sterile conditions. The need for high quality steam is used because it is an efficient carrier of heat. It is produced in the boiler and carried to the dairy processing plant by a pipework distribution system. At each process steam transfers its heat and condenses back to condensate. A very important property of saturated steam is that its temperature is directly related to its pressure. Therefore, the temperature of many processes can be accurately controlled by controlling the pressure of the steam. To enable accurate control of temperatures, it is essential to deliver high quality, dry saturated steam to the process at the correct pressure. Any entrained moisture or incondensable gases in the steam can lower its heat content and impair the heat transfer rate. This will make accurate control difficult and in some cases it may not even be possible to achieve the desired process temperatures. Temperature C saturation curve Pressure bar g

3 Spirax Sarco in the dairy industry For most of the 20th century Spirax Sarco has been the leader in improving steam plant efficiency, providing knowledge and high quality products to all branches of industry, including the dairy industry. We understand that the dairy industry has its particular needs and problems and that each application within the industry should be looked at individually. We provide solutions to problems throughout the complete steam and condensate system in the dairy industry, anywhere in the world. distribution generation control and management management The complete system To produce high grade dairy products whilst maintaining low production costs, it is essential that dairy processes are operated as efficiently as possible, making effective use of the heat available in the steam. To achieve this, it is necessary to consider the design and operation of the complete steam and condensate system, taking into account the individual requirements of each process, the local environment and the variety of dairy products manufactured. Consideration should also be given to future expansion plans and plans to upgrade existing equipment. 3

4 Spirax Sarco and steam generation leaving the boiler house should contain as little moisture and incondensable gases as possible. This ensures that the maximum amount of heat is available and minimises the risk of pipeline and equipment damage from waterhammer. Spirax Sarco has the expertise to help you produce high quality steam from your boilers, at the most economical cost, with a wide range of products specifically designed for the boiler house, all manufactured to the highest standards. Technical and sales literature is available on the subject of boiler house applications and equipment upon request. An essential part of boiler house design and operation is to ensure that the boiler operates at the highest possible efficiency. Every effort should be made to recover and reuse the heat available from secondary sources such as boiler blowdown. Your local Spirax Sarco engineer will be able to help and offer advice on how this can be achieved. Cold water make-up controls Boiler feedtanks Feedtank controls Deaerator heads Air vents and vacuum breakers Feedtank recirculation systems Boiler blowdown heat recovery systems Vent heads injection systems Boiler blowdown systems Blowdown vessels Blowdown inlet manifolds Level controls and alarm systems TDS control systems TDS measurement Feedpump check valves Sample coolers Flash vessels Residual blowdown heat exchangers Cooling water systems main start-up systems contamination detection systems dump valves Supplied by Spirax Sarco steam flash steam condensate 4

5 distribution High pressure steam from boiler Air vent Separator Pressure reducing valve station Reduced pressure steam header Spirax Sarco pressure reducing valve station From the boiler house the steam is carried to processes within the dairy by the distribution system, where it should be available at the correct pressure, in sufficient quantity and in the best possible condition. Air vent flow It is important that the pipework carrying steam from the boiler house to the equipment is sized correctly. Cost effective steam distribution depends upon keeping pipe sizes to a minimum. velocity should be at a reasonable level and the pressure drop kept to a minimum. This means designing for the highest acceptable distribution pressure between the boiler house and the areas of steam usage, then dropping pressure at the working area to the levels required for maximum heat transfer, efficiency and safety. Spirax Sarco pressure reducing stations are designed specifically to match this task and to assist you in energy management. Spirax Sarco will be happy to advise on your distribution pipework sizing. To ensure that radiation losses are kept to a minimum the steam distribution system should be insulated. Even when insulated some radiation losses will occur, with some steam condensing and forming condensate in the pipework. It is important that this condensate is removed so that the steam arriving at the process equipment is as dry as possible. The removal of condensate from the distribution pipework is also necessary to prevent damage from waterhammer. This occurs when slugs of condensate are propelled along the pipeline at steam velocity. flow Spirax Sarco relay point out can be removed by means of a separator as shown in the illustration of a pressure reducing station, and in the case of long distribution runs, a relay drain point should be installed. Provision should also be made for removing air and incondensable gases from the steam distribution system through strategically placed thermostatic air vents. forms due to radiation losses from the pipe If it is not removed, a slug of condensate can develop and be carried along the pipe at steam velocity. The cause of waterhammer 5

6 Pneumatic valve with p Spirax Sarco and Pre-heating Pasteurisation Raw milk Pasteurisation / homogenisation Chiller Holding tank Pasteurisation / homogenisation Separator Past Pneumatic actuated valve with positioner Vacuum breaker Hot water circulation Unpasteurised mi Pasteurised milk Pasteuriser Spirax Sarco pasteuriser control equipment 6

7 the dairy industry UHT milk injector Expansion vessel Homogeniser Processing and ripening Cheese Cheese vat Yoghurt Bulk starter tank Incubator tank Pasteurised milk Milk powder Evaporator Spray dryer Skimmed milk Condensed milk eurisation / homogenisation Cream Butter Cream pasteurisation Butter maker Pre-heated milk lk Pressure reducing valve set UHT ring nozzle injector Clean steam filter Milk to homogeniser actuated ositioner Cooling water in Spirax Sarco hygienic steam trap Cooling water out Spirax Sarco direct UHT controls 7

8 is used in the dairy for indirect heating, direct heating and sterilization processes. It is essential that in all of these applications high quality steam is available at the correct temperature and pressure. These applications will include: Hot water heaters. Indirect plate heat exchangers. Clean in place (CIP) units. Sterilize in place (SIP) systems. jacketed vessels for processing butter oil. Where is steam used Direct UHT sterilisers used to pasteurise milk at higher temperatures. Air heater batteries which provide hot air for spray drying and can drying. Multi-effect evaporators used to produce condensed milk. Aseptic storage to provide a sterile barrier on product change over in pipework and tanks. Dairy effluent holding tanks (waste fat) are kept warm to prevent solidification prior to disposal. Measuring steam flow can provide vital information for the accurate costing and monitoring of production processes. Spirax Sarco Spiraflo meters are specifically designed for use on steam systems to give consistent, accurate flow measurement information about the flowrate, pressure and temperature of steam. Spirax Sarco can also provide other types of flowmeter suitable for many fluids and gases. Air vent Flow computer Various outputs Alarms R232C Interface Timers flow flow Separator Spiraflo meter Wafer check valve out Spirax Sarco steam metering station In a dairy, saturated steam is normally generated at between 11 bar and 17 bar. It should be distributed at the highest possible pressure to keep the distribution pipework as small as possible, and then reduced in pressure to meet individual process requirements. Different types of steam pressure reducing valves are available, from simple direct acting valves to the more pressure control flexible pneumatic actuator, valve and electro / pneumatic positioner combinations. The type of system required depends on the needs of the process. Spirax Sarco supplies many different types of steam pressure control systems and can advise on the best choice for a particular application. 8

9 Pneumatic actuated valve with positioner Vacuum breaker Controller flow Flash steam to preheater Preheater Air vent Heater Sensor Heated air to spray dryer Flash steam recovery vessel Spirax Sarco air heater control system with flash steam preheater Plate heat exchangers are used throughout the dairy in a variety of heating and cooling applications. For heating applications steam is frequently used as the primary medium. It is easily controlled and its excellent heat carrying properties allow pipe and exchanger sizes to be kept to a minimum. A temperature control valve constantly adjusts the primary steam flowrate and pressure to compensate for fluctuations in the secondary fluid's inlet flowrate and temperature. This will ensure the product flow from the exchanger is always at the correct temperature. When steam gives up its heat it condenses and this condensate must be drained immediately to allow steam to continue to enter the exchanger and carry on the process. If condensate is allowed to remain in Plate heat exchangers the exchanger, poor temperature control will result and there will be an increased possibility of damage from waterhammer. If the correct type of steam trap is selected, and provided the pressure in the steam space of an exchanger is higher than the pressure in the condensate return system, condensate will drain from the exchanger as soon as it has formed. However, pressure inside the steam space of a plate heat exchanger is never constant, and may fall into a vacuum condition under light loads. When the pressure within the condensate return system is greater than the pressure within the exchanger steam space, the exchanger is described as being in a 'stall' condition. In this condition condensate will not be able to drain from the exchanger. 9

10 Controller Pneumatic valve and actuator with positioner Secondary flow out flow supply to pump Secondary flow in Plate heat exchanger trap Pressure powered pump Spirax Sarco plate heat exchanger temperature control and condensate drainage A simple and effective solution to this common problem is to install a combination pump/steam trap unit. This will ensure that condensate is drained from the heat exchanger under both normal and 'stall' operating conditions. Spirax Sarco can advise on whether a 'stall' condition may occur on a heat exchange application and how to ensure its adverse effects are avoided. Many of the steam using processes in the dairy will require a temperature control system to ensure that the product is heated up to and maintained at the correct temperature. Spirax Sarco provide many different types of temperature control system and will be able to Temperature control recommend the most suitable for each of the many different processes. A simple, robust self-acting control system will often be the most suitable for a hot water tank, while a more sophisticated electro/pneumatic system will be required for pasteurisation or a UHT process. Pressure reducing valve station Self-acting temperature control Level control system Water Spirax Sarco hot water tank controls 10

11 Clean steam is widely used in the dairy industry to reduce the risk of product or process contamination, not only during UHT sterilisation but also during the CIP and SIP processes. Spirax Sarco provide a wide range of stainless steel products designed for use on clean steam systems, Clean steam including the filters necessary to provide culinary grade steam from process steam. The stainless steel construction of Spirax Sarco clean steam products ensures the risk of contamination is reduced and that sanitary conditions are maintained. Heat recovery Approximately 31 % of the heat used to generate saturated steam at 17 bar remains in the condensate when the steam condenses. In effective condensate management, consideration should be given to recovering and using as much of this heat as possible. Flash steam recovery Flash steam is released from condensate when its pressure falls. Typically this happens when it passes from the process, through a steam trap, to a low pressure condensate system. Low pressure condensate has a smaller sensible heat content than high pressure condensate and this sudden excess heat content will cause some of the condensate to 'flash off' into steam at the lower pressure. The recovery of this flash steam using flash vessels can be used to supplement the steam supply to applications that require low pressure steam. management return The final stage in condensate management is to return as much condensate to the boiler house as possible. in Vent Pressure powered pump Overflow out Low pressure flash steam Spirax Sarco pressure powered pump condensate return unit. from high pressure steam Flash vessel Even after flash steam has been recovered, the low pressure condensate still contains sensible heat - over 400 kj/kg at atmospheric pressure; and will require no further boiler feed treatment before it re-enters the boiler. Methods of returning condensate can include simple gravity return systems, electric pumping systems or systems incorporating the versatile pressure powered pump. Spirax Sarco flash steam recovery set out Spirax Sarco will be pleased to advise on the most cost effective means of achieving a highly efficient condensate return system. 11

12 Spirax Sarco provides knowledge, service and products worldwide for the control and efficient use of steam and other industrial fluids in the dairy industry. Our comprehensive product range includes: l Boiler controls l Worldwide support from a team of dedicated employees. l Local access to Spirax Sarco's expertise and products through 39 group companies in 32 countries. l Valuable information, advice and interchange of ideas from customer training courses held in any of our 31 training centres worldwide. l A comprehensive range of the highest quality products. Spirax Sarco worldwide service Europe Austria Vienna Belgium Zwijnaarde Czech Republic Prague Denmark Copenhagen Finland Helsinki France Trappes Germany Konstanz Hungary Budapest Ireland Dublin Italy Milan Netherlands Maarn Norway Oslo Poland Warsaw Portugal Lisbon Russia St. Petersburg Spain Barcelona Sweden Stockholm Switzerland Zürich - Zollikon United Kingdom Cheltenham Africa Kenya Nairobi Nigeria Lagos South Africa Johannesburg Americas Argentina Buenos Aires Brazil São Paulo Canada Toronto Mexico Monterrey USA Columbia, S.C. Asia & Middle East China Shanghai Hong Kong lndia Poona Indonesia Jakarta Japan Tokyo Korea Seoul Lebanon Beirut Malaysia Kuala Lumpur Pakistan Karachi Philippines Manila Singapore Taiwan Taipei Thailand Bangkok Australasia Australia Sydney New Zealand Auckland l Flowmeters l Pneumatically and electronically actuated control valves l Pressure reducing valves l Self-acting temperature control valves l Programmable electronic controllers l Pneumatic transmitter controllers l Safety valves l traps l trap monitoring systems l pumps l Flash vessels l Separators l Strainers l Stop valves l Check valves l Humidifiers A further 46 agencies operate throughout the world. If you have difficulty finding a local contact please contact us at the number shown below. DRY Spirax-Sarco Limited, Charlton House, Cheltenham, Gloucestershire, GL53 8ER UK. Tel: +44 (0) Fax: +44 (0) Enquiries@SpiraxSarco.com Internet: Copyright 2000 Spirax Sarco is a registered trademark of Spirax-Sarco Limited SB-GCM-10 CM Issue 2