BAVIERA STEAM SYSTEMS

Transcription

1 Steam Systems

2 BAVIERA STEAM SYSTEMS 1.- INTRODUCTION. Drawing BSS sh 08 The Baviera steam system for corrugators achieves, at the same time, energy efficiency and production flexibility. Condesates are recovered with high pressure and temperature, and pumped back directly to the boiler, achieving this way energy efficiency optimization (fuel savings). Pressures along the corrugator are controlled digitally and remotelly, achieving this way the necessary flexibility (production quality & waste reduction). This flexibility is especially important with light weight papers and recycled papers (difficulties in glue penetration suggests inverse pressure regulation of the Double Backer) Several controls guarantee adecuate condensate drainage under any circumstance, ensuring optimal heat transfer. Due to its conception and to the kind of components used (Spirals, Hybrid Traps, condensate pump, etc.), the Baviera Steam System is a long life maintenance free system. 2.- HEAT TRANSFER The system supplies direct steam to the whole corrugator. There is one individual Hybrid Trap or Spiral at each roll or steam chest, in order to optimize heat transfer - that is to say, to obtain the maximum corrugator heating Double backer. Spirals Spirals are robust steam traps with absolutelly no mobile parts and, therefore, a long life with no maintenance needs. Spirals give a continuous condensate drainage and, at the same time, a continuos and controlled blowthrough steam flow that ensures a perfect degasification. Please find a detailed explanation of spirals and their functionality further in the document Single facers and preheaters. Hybrid Traps Hybrid Traps are the combined result of Spirals and free ball steam traps evolution. Hybrid Traps are two way traps: First way: free ball steam trap

3 Second way: Baviera Spiral The combination of the free ball and the Baviera Spiral system results in a highly efficient steam trap with no maintenance, long life, high energy efficiency and optimal heat transfer. 3.- ENERGY PROFIT. FUEL SAVING Baviera Steam Systems are closed steam circuits were condensates are recovered at high pressure and temperature, achieving energy savings that round 20% of fuel consumption High pressure condensates recovery. CRU Baviera Steam Systems include a Condensate Recovery Unit (CRU) that recovers condensate with high pressure and temperature, and feeds it back directly to the boiler with no energy losses to the atmosphere. This equipment provides an aproximate 20% energy saving (fuel saving). The CRU is normally placed in the boiler room. A further description of the CRU equipment and its funcionality is included further in the document Double Backer condensates recovery. SPP & TSP In order to make compatible the free pressure regulation of the Double Backer (or the Single Facers) with pressurized, closed circuit, condensate recovery, Baviera Steam Systems include electro pneumatic steam pumps (SPP & TSP). These steam pumps use life steam to pump condensates from the Double Backer or Single Facer, up to the condensate recovery unit CRU. A further description of SPP and its funcionality is included further in the document. 4.- FLEXIBILITY Baviera Steam Systems give total flexibility to the corrugator, by enabling free pressure regulation with no energy losses to the atmosphere. This is particullary important in the Double Backer because of the glue s difficulties to penetrate the liner when dealing with light weight papers and recycled papers. This flexibility is some times important in Single Facers too, especially when dealing with light weight papers and small flutes.

4 CONDENSATE RECOVERY UNIT. CRU Energy efficiency optimization of steam systems on corrugators demands condensate recovery at pressure with direct reinjection of condensates to the boiler, maintaining their high temperature. Since condensates of all rolls and steam chests in a corrugator are purged with very high temperature and pressure, pressurized recovery of these condensates, avoiding their depressurization and its associated cooling down (with flash steam production), is the best way to avoid energy losses, maximizing energy efficiency and, therefore, reducing fuel consumption. Baviera condensate recovery system s design is the result of more than 25 years of experience within this field. It is a system that achieves energy profit optimization and, at the same time, heat transfer optimization, since several control systems make compatible both features. Moreover, because of the long experience with this kind of systems, all components that make up the condensate recovery unit are robust and practically exempt from any kind of maintenance. The Baviera condensate recovery unit is placed in the boiler house. It has a vertical tank, sealed at 18 bar, where condensates are recovered with pressure, around 8 bar, so that condensates are fed to the boiler at a temperature that rounds 175ºC. The KSB pump feeds the boiler from the lower side of the CRU. Although the pump works with high temperature condensates, its natural air cooled mechanical seal, placed far away from the hydraulic, works around 50ºC so that the working conditions of the mechanical seal are excellent resulting, in fact, a maintenance free pump with a long lifespan. The system has the following controls - Level control: 4-20 ma level control acting on the automatic M valve, that is placed in the pump impulsion. M valve is controlled by condensate level in the CRU and, eventually, also by the boiler level, when the signal is availiable. The KSB pump works continuously while the M valve regulates the boiler feeding flow. - Differential pressure control: There is an electronic and digital differential pressure control, where you can check and control the differential pressure of the installation (main steam supply pressure condensate recovery pressure). The differential pressure control acts on the automatic L valve, guaranteeing that, in any situation, the differential pressure of the installation is always higher than the set point, normally set at 4 bar. This is the condition that guarantees compatibility between optimal energy saving and optimal heat transfer.

5 - Condensate temperature control: Condensate temperature control acts on automatic valve L. It is important during machine start ups and shut downs. By opening the automatic L valve, during start ups, quick degasification and cold condensate removal occurs through the Hot Well, enabling a quicker heating up of the corrugator. During shut downs, condensate temperature control enables quick depressurization, allowing a quicker drying of the system. - Low pressure steam recycling: If there are low pressure steam services (showers, air heating, etc.), the T automatic valve of the CRU supplies steam coming from the upper side of the CRU for these services.

6 BAVIERA SPIRAL Spirals are robust steam traps with absolutelly no mobile parts and, therefore, a long life with no maintenance needs. In Baviera Steam Systems, each steam chest is provided with an individual Baviera spiral (or with a Hybrid Trap per Hot Plate Section). Spirals are specially designed to control a continuous drainage of produced condensate, together with a controlled blow through steam flow (about 1-2%). This combined flow (condensate and blowthrough steam) guarantees optimal degasification and, therefore, the highest temperature from heat transfer. The mechanism by which Baviera Spirals are able to drain condensate and blowthrough steam in a controlled way, has to do with the length and small diameter of the spiral through which condensate has to flow: condensates flows due to differential pressure in the installation (main steam pressure condensate back pressure). The length and small diameter of the spiral acts as a brake or resistance, being this the sole slowing down mechanism of the spiral. Although all spirals have the same external dimensions, there are spirals with different lengths and diameters, corresponding to different steam consumptions (spiral sizes). In our drawings or layouts, all spiral numbers or sizes are specified for each particular point in the corrugator.

7 HYBRID TRAP A Hybrid Trap is a combination of one free ball trap and one Baviera spiral. Hybrid Traps are two way traps: the free ball allows condensate to come out continuously and the Baviera spiral regulates the desired blow through steam. Rolls in single facers turn at machine speed, so contained condensate is liable to centrifugation. In spite of having the siphon or internal pipe for condensate collection correctly positioned, it is, in any case, liable to experience small vibratory movements that often will take it away from its right position. This vibrations make the siphon to be continuously taking in, together, condensate and steam. Under this circumstances, a conventional drainage (designed for condensate removal and cold air removal, not steam) would experience a steam blocking, what would increase the inner condensate ring thickness. The integrated spiral of the Hybrid Trap provides a blowthrough steam (around 5% of its roll steam consumption) that removes this steam parcels, avoiding steam blockings and the corresponding decrease in heat transfer, that is to say: Hybrid Traps allow faster heating of the rolls, quicker changes in their regulated pressure and bigger flexibility upon different production conditions leading, therefore, to higher heat transfer and higher energy efficiency. (DUCTILE CAST IRON FLANGED)

8 (STAINLESS STEEL SCREWED)

9 (STAINLESS STEEL FLANGED)

10 DOUBLE BACKER CONDENSATE RECOVERY. SPP The use of steam pumps for condensate recovery in the hot plates sections makes compatible condensate recovery in closed circuit with totally free pressure regulation in each Hot Plates Section. The operation of an electro-pneumatic steam pump is very easy: When the level controller detects condensate has reached the maximum level of the tank, the injection valve (VI) opens and pushes, with life steam, condensate through a check valve to the high pressure condensate recovery unit. This injection cycle lasts around 5-10 seconds and the filling cycle around 3-7 minutes (depending on the Hot Plates Section and on the regulated pressure, production speed and other parameters). Just after the injection cycle (that lasts 10 seconds), the recipient or tank is totally emptied and the decompression valve (VD) opens during 5 seconds in order to decompress the tank and start again a new filling cycle, filling the tank with condensates coming from the corresponding hot plates sections. Furthermore, there is a degasification spiral (spiral nº 25) that continuously allows the incondensable gases deareation. Therefore, the condensate recovery system with electro-pneumatic steam pump works as per the following cycles (these times may change from plant to plant): - Cycle nº 1: Filling of the recipient, lasting for 3 to 7 minutes. - Cycle nº 2: Pumping with life steam, lasting for 5 to 10 seconds. - Cycle nº 3: Decompression, lasting for 5 seconds. - The complete cycle starts again. The system has a VE valve whose only aim is to deviate the condensates from the hot plates sections up to the atmospheric condensate recovery at night when the steam supply to the corrugator is closed, or in the morning, during start ups, when a minimum pressure has not been reached yet. The whole process is electrically and digitally controlled by a PLC. The materials used (check valves, VI, VD, spirals) are of good quality and with no need of maintenance, so that a system which is apparently complex - as it consists of several condensate recovery units -, is indeed a system free of maintenance and without erosion because of time. You can find further information on Baviera SPP, in the following explanation video:

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12 STEAM PUMPS FOR SINGLE FACERS. SPPSF When dealing with light weight papers and especially with small flutes, it is convenient (it can even be indispensable) to regulate pressure in the Single Facers. The use of electro pneumatic steam pumps for condensate recovery in Single Facers makes compatible closed circuit condensate recovery at pressure with totally free pressure regulation in Single Facers. The operation of an electro-pneumatic steam pump is very easy: When the level controller detects that condensate in the injection tank has reached its maximum level, injection valve (VI) automatically opens and pushes condensate, with life steam, to the Condensate Recovery Unit (boiler house) through the high pressure condensate recovery. While life steam injection is taking place, the aspiration tank buffers coming condensate. If, after having ended the injection cycle, condensate in the aspiration tank reaches its maximum level, the decompression valve (VD) opens during 5 seconds in order to decompress the condensate tank and enable condensate flow from the aspiration tank to the condensate tank. Furthermore, there is a degasification spiral in each tank that continuously allows the air and rest of incondensable gases deareation. Therefore, the condensate recovery system with electro-pneumatic steam pump works as per the following cycles (these times may change from plant to plant): - Filling cycle: 2 to 7 minutes. - Injection cycle: 5 to 10 seconds. - Decompression cycle: 3 to 5 seconds. - The filling cycle starts again. This equipment has a VE valve whose only aim is to deviate the condensates from the single facer up to the atmospheric condensate recovery at night when the steam supply to the corrugator is closed, or in the morning during start ups when a minimum pressure in the steam supply has not been reached yet. The steam pump for single facer has an active control of the differential pressure between the single facer and the aspiration tank. The differential pressure control eventually acts over the VD valve, in case it falls below the set point. The whole process is electrically and digitally controlled by a PLC. The materials used (check valves, VI, VD, pressure differential transmitter, spirals, etc.) are of good quality and with no need of maintenance.

13 STEAM PUMP FOR SINGLE FACER

14 THE ZERO SECTION Recently, very good quality papers have appeared: low weight and high density papers. These papers are very good heat transmitters and, therefore, are very sensitive to warm-ups. Heat transfer to the glue is so efficient that crystallization occurs at the very beginning of the double backer, before there is time for the glue to penetrate the liner. Zero section: The zero section is formed by combining the double backer preheater and the first two steam chests of the first Hot Plates Section. The zero section is made independent, becoming a small fourth section of the Double Backer. The zero section is named that way after its location. The greatest advantage of the zero section is that, by regulating very low its pressure (around 1 bar, in any case, below 2 bar), the problem of the glue precrystallization is easily avoided. Also, the zero section is a great aid for lowering corrugating temperatures in the direction of cool corrugating conditions, permitting important glue and steam consumption reductions. Since only two steam chests of the first Hot Plate Section are sacrificed, the Double Backer remains with enough heat transfer capacity for the heaviest qualities. The following sketch shows the creation of a zero section starting from a conventional three sections Double Backer.

15 HEAT TRANSFER PROCESS CONTROL Work with recycled and light papers, very sensitive to heat, makes almost necessary a close control of temperatures in the corrugating process in order to achieve optimization of all production qualities. Moreover, paper overheating must be avoided, for economy and quality reasons. This is possible through an active temperature control system, such as the following described: A central processing unit monitorizes and controls the main temperatures of the corrugating process, measured through infrared transmitters, and shows them through local and remote screens. The systems keeps critical temperatures along the corrugating process in their set point, acting on the rolls wraps and regulating pressures (when wrap control isn t possible or enough). Recipes can be stored in the system in order to automatically reproduce certain production conditions, by simply loading a production program from the system. Historical graphs are stored in order to keep close control of production temperature parameters. All the system is controlled from the control cabin and from the local screens. The system is prepared to allow remote upgrades of the system s software through remote connections. Please find below an orientation list showing some papers best production temperatures, and a second screen showing the points of the corrugating pressure where temperatures are measured and controlled. For further information, please contact us on baviera@rbaviera.com or

16 (Temperatures measurement, pressure controls & wrap controls along the corrugator) (Temperature measurements, pressure controls & wraps controls in Single Facer) (Some orientative paper temperatures)

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