LaplaceIt
Chemical
- Apr 17, 2007
- 3
The dust extraction system in question is in place in a large-scale continuous-operation OSB production facility. The problem section is the extraction from the OSB blenders & formers.
In the blenders wood strands are blended with resin binders (MDI & LPF) and a small amount of wax. In the formers strands go through the forming line where cross-directional layers are formed. Following these stages the layers of cross-directional strands are pressed under intense heat and pressure to form a rigid, dense structural panel of oriented strand board (OSB). Due to these processes, there is present at both stages an amount of dust, resin vapour and resinated dust.
The aim is simply to keep the formers under negative pressure, to prevent release of dust / vapour to the rest of the plant.
The air extracted from the blenders / formers is conveyed through the dust extraction piping (welded/flanged steel pipework)- where it mixes with unresinated dust from other areas of the plant- to the baghouse filter. At the baghouse, the dust is filtered out and the clean air is released to the atmosphere.
There are problems with the current realisation of this system.
Initially it was found that not all the resin vapour and resinated dust from the formers was not conveying through the pipework with the rest of the dust. Instead, this material was sticking to the inside of the pipework. The material continued to stick, with the effect of continuously reducing the inner diameter of the effected pipework, eventually blocking it entirely. Apart from the obvious lack of suction at the formers, this also meant that the rest of the system became unbalanced and did not function as designed. Furthermore, this build-up necessitated shutting down the process and clearing the pipes, with associated costs of downtime and maintenance.
To solve this problem, various different types of pre-filter have been installed in the extraction hoods (as shown in the diagram). Some of the filters work to keep all resin and dust out of the lines, while allowing enough extraction to keep the formers under negative pressure; this is what was hoped for. However, the problem with these filters is that they quickly become clogged with dust and resin, and need to be replaced. This again leads to downtime and maintenance.
A good solution to this problem is required, to eliminate the issue of resin sticking to the inside of the dust extraction pipework. Looking at possible solutions, the following questions arise:
- Is there a key conveying velocity to prevent build-up of resin in the pipework?
- Do suitable pre-filters exist that will prevent resin from entering the pipework?
- Can the filters be installed on the formers so that they will not become clogged during normal operation? Does a pre-filter system exist that allows continual regeneration of the filter? Automatic indexing roll filters would appear to be an option, however we have no experience with such a system.
In the blenders wood strands are blended with resin binders (MDI & LPF) and a small amount of wax. In the formers strands go through the forming line where cross-directional layers are formed. Following these stages the layers of cross-directional strands are pressed under intense heat and pressure to form a rigid, dense structural panel of oriented strand board (OSB). Due to these processes, there is present at both stages an amount of dust, resin vapour and resinated dust.
The aim is simply to keep the formers under negative pressure, to prevent release of dust / vapour to the rest of the plant.
The air extracted from the blenders / formers is conveyed through the dust extraction piping (welded/flanged steel pipework)- where it mixes with unresinated dust from other areas of the plant- to the baghouse filter. At the baghouse, the dust is filtered out and the clean air is released to the atmosphere.
There are problems with the current realisation of this system.
Initially it was found that not all the resin vapour and resinated dust from the formers was not conveying through the pipework with the rest of the dust. Instead, this material was sticking to the inside of the pipework. The material continued to stick, with the effect of continuously reducing the inner diameter of the effected pipework, eventually blocking it entirely. Apart from the obvious lack of suction at the formers, this also meant that the rest of the system became unbalanced and did not function as designed. Furthermore, this build-up necessitated shutting down the process and clearing the pipes, with associated costs of downtime and maintenance.
To solve this problem, various different types of pre-filter have been installed in the extraction hoods (as shown in the diagram). Some of the filters work to keep all resin and dust out of the lines, while allowing enough extraction to keep the formers under negative pressure; this is what was hoped for. However, the problem with these filters is that they quickly become clogged with dust and resin, and need to be replaced. This again leads to downtime and maintenance.
A good solution to this problem is required, to eliminate the issue of resin sticking to the inside of the dust extraction pipework. Looking at possible solutions, the following questions arise:
- Is there a key conveying velocity to prevent build-up of resin in the pipework?
- Do suitable pre-filters exist that will prevent resin from entering the pipework?
- Can the filters be installed on the formers so that they will not become clogged during normal operation? Does a pre-filter system exist that allows continual regeneration of the filter? Automatic indexing roll filters would appear to be an option, however we have no experience with such a system.
