The minerals industry works with a wide range of ores and stones - from asphalt to cement, gypsum to lime. Each of these materials present unique environmental challenges when it comes to filter technology:
BWF Envirotec offers filter technology that focuses on productivity. Ensuring product quality and compliance with dust emission limits are central tasks for our industrial filters. Special requirements for filters include properties such as high abrasion resistance, dissipation of electrostatic charges and high chemical resistance.
BWF Envirotec filters offer technically sophisticated solutions for any filter technology process. We offer an extensive range of industrial filters and services for dedusting various production processes.
BWF Envirotec filters such as:
help our customers comply with legal requirements:
We help our customers meet their production goals. To this end, we carry out industrial filter and dust analyses for all filter technology applications in our laboratories, recommend solutions for optimising filter systems and provide training courses on filter media, industrial filters and operating know-how in our Training Academy .
|Filter medium||Location||Number of filter bags||Inlet load g/Nm3||Temperature Continuous/Peak °C|
|Cement industry - Clinker cooler||needlona® NO/NO 551 CS52||Iran||1,000||20||160/200|
|Cement industry - Chlorine bypass||needlona® PTFE/PTFE 704 MPS CS30||Germany||1,200||35||170-175/190|
|Lime, gypsum, clay industry - Shaft kiln||needlona® PTFE/PTFE 704 MPS CS30||France||572||10||184-205/230|
|Lime, gypsum, clay industry - Rotary kiln||PM-Tec® GL 750||South Africa||6,532||20||110-160|
|Cement industry - Rotary kiln||PM-Tec® GL 750||Brazil||7,800||80||
|Asphalt industry||needlona® NO/NO 401 CS17 AsphalTec||France||480||250||80/130|
Safeguarding product quality and complying with the dust emission limit values play a central role in dedusting in the cement industry. This equally applies to waste gases from cement kilns and exhaust air from silos, packing stations, mills and clinker coolers. Our high-performance filter bags ensure reliable, high plant availability and fulfil the highest demands in dedusting exhaust air and flue gas.
PM-Tec® and needlona® filter bags are custom-designed to suit the requirements of the dedusting process. This provides you the optimum technical solution for your filtration system. We supply filter bags for every type of filtration system and application together with the corresponding supporting cages.
Depending on the flue glass cleaning method, the high-efficiency filter media of the filter bag are enhanced with various surface, functional or protective finishes. These protect the filter medium even more effectively against harmful chemical and mechanical influences. Improved separation behaviour, effective cleaning, low residual dust emission and an extended service life of the filter bags are thus achieved.
Silo filter, packing station and conveyor systems are charged with dry dust, mostly under ambient conditions. Consequently, a low-cost needlona® needle felt made of polyester can be used. The additional Cementsurf® finish reduces the friction between dust and fibre, thereby not only increasing the degree of cleaning but also the service life of the filter bag.
High dust loads from the cement mill or the separator require a resistant filter medium. An oil and water repellent CS17® finish is recommended in countries with a high relative humidity and ensures that the agglomerating dust is not only separated, but is also effectively cleaned from the filter bag. Addition of grinding aids imposes very high demands on the filter medium, as they prevent agglomeration of the cement dust in order to increase mill efficiency. Limited agglomeration behavior hampers dust separation to a considerable extent and therefore maximum-efficiency MPS® or PM-Tec® filter bags are used in this case.
Since a drying process is involved in addition to milling, increase gas humidity is to be expected. This manifests itself in chemical attack on the polyester fibres due to hydrolysis, such that their resistance is weakened over the course of time. Consequently, BWF Envirotec combines the chemically more susceptible but mechanically stable polyester fibres with the chemically stable but mechanically weaker polyacrylnitrile fibres in order to achieve an optimum filter bag service life and high level of profitability with this compound medium. Owing to potential dust explosion, we recommend the antistatic ExCharge® filter medium for conducting static discharges, certified by DEKRA Testing and Certification GmbH.
The hot clinker dust emerging from the cement kiln is generally cooled with ambient air before further processing. Since they are applied in dry form and without harmful gasses, filter media for filter bags made of m-aramid can achieve long and economically efficient service lives. m-Aramide is characterized by greater sustained temperature resistance with low gas humidity, in addition to less mechanical wear through the effect of the abrasive clinker dust.
The currently increasing use of secondary fuels can for example increase the chlorine concentration in the exhaust gas and product to impermissible levels. By extracting a partial stream from the cyclone preheater followed by subsequent cooling, the harmful gases can be effectively separated in solid form by means of a filter bag. The high constant temperatures and corrosive gas and dust composition however require an extremely resistant filter medium. Filter media made of PTFE are perfect for efficient filtration.
The common method consists of a rotary kiln with an upstream cyclone preheater. Intensive material and heat exchange occurs here between the downwards flowing raw meal and the upwards flowing exhaust gas. In this manner, not only is the raw meal heated, but also binding of acid components contained in the exhaust gas occurs which might exert a chemical attack on the downstream filter bags. This absorption process is gaining in importance with increasing use of secondary fuels. Long service lives can be achieved with the very economically PPS filter bags at filter inlet temperatures of < 150°C. Filter bags made of polyacrylnitrile homopolymer are also suitable if owing to intensive heat recovery the filter inlet temperature can be reduced to constantly < 120°C and temperature peaks of > 140°C are avoided. A further reduction in costs can be achieved as a result. In case of higher tempratures, BWF Envirotec recommends use of high temperature fibre such as PFB, polyimide and fibreglass fabric.