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Zawartość zarchiwizowana w dniu 2022-12-27

ELECTRICAL ENERGY SAVING IN MEDIUM DENSITY FIBER BOARD INDUSTRY

Cel

A high pressure steam generator with superheater has been installed in a (Medium Density Fiber (MDF) board plant to produce 22 T/H of steam which will be supplied directly to a back pressure turbine driving a 4088KVA medium voltage three phase generator. This reduces electrical energy currently supplied by the grid by 2935 KWH (50 %). Heat from low and medium pressure steam and combustion gases are used for process drying and factory heating. The steam generator was installed instead of a conventional wood burning hot gas generator which is the traditional technology. The specific power consumption has been reduced from about 400 to 200 kWhe/m3 of finished product. The utilisation of a chp in the MDF industry is innovatory.L%
The project has been successfully carried out and the final implementation results exceed the design values by significant varying the rated power was increased from 3270 kWe to 5400 kWe while the energy savings were increased from 42 to 50%. The plant has achieved a specific power consumption of about 300 kWe/m3 MDF in while in the traditional technology the specific power consumption is about 400 kWe/m3 MDF which the available technology the plant autoproduces 150 kWe/m3 MDF resulting in significant energy savings.
The steam generator is fed with wood wastes which are burned over on a cooled vibrating grate, located at the furnace bottom. The dust from the production process is burned in suspension firing, above the grente.
The heat from the combustion gases is successively transfered to the furnace tubes, superheaters and convection tubes. After the steam generator outlet, the flue gas goes through the multicyclone to the boiler feedwater heaters and finally into the process dryer or to the atmosphere if the dryer is not operating. There are automatic control systems for combustion and boiler pressure. The water for steam production is demineralised by resin ion exchangers and thermally dearated in order to fulfil the minimum quality required by the system boiler/turbo generator. An external chemical conditioning for pH correction, residual oxygen removal and steam generator protection has been installed.
The boiler feed water, pumped from the deaerator/boiler feed water tank, is heated byflue gases up to about 200 deg. C which is lower than the vaporization. The water enters in the steam drum is distributed through the radiation and convection tubes. The level control is of the three elements type. On the drum the water/steam separation occurs. The steam passes through the superheater before utlization. The steam temperature control is made by a deaerated water injection into the superheater headers.
The superheated steam feeds the turbine. The turbine extraction will supply all the process medium pressure steam (defibrator and dryer) and the steam for combustion air heating. The turbine exhaust will provide all the low pressure steam for the process (defibrator and dryer), for combustion air heating and for water deaeration. A balance condenser allows to keep the power plant running in case of process shut down.
Reducing pressure and desuperheating stations enable the expansion of the high pressure steam to medium and low pressure, if the turbine is unavailable.For the desuperheating, deaerated water has to be used.
All the condensates from steam are recovered and reused as boiler feed water. The turbo generator has to be able for isolated or parallel operation with public network. The power produced supplies at low voltage the auxiliaries and the remainder goes to the process plant or for selling to the public grid. A chips washing system with hot water improves the energy balance and contributes to reduce the power consumption in the defibrator motor. The installation has considerable flexibility with the heat exchangers for low and medium pressure steam and the staggering of flue gases utilization in order to allow the adjustments to the process requirements with the maximum electrical output in all operating conditions.

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SOCIEDAD DE INICIATIVA E APROVEITAMENTOS FLOREST
Wkład UE
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Adres
APARTADO 76 TISCHBEINSTRASSE 6
3531 Mangualde Codex
Portugalia

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