ENVIROCELL Home | Consultancy | Training | Publications | CD-roms | Site map | Contact CONSULTANCY ACTIVITIES PAPERMAKING CHEMISTRY Paper chemistry is mainly concerned with the chemistry that takes place within the papermaking process, but also includes the upstream chemistry connected with making the raw materials and any downstream chemistry that may affect recyclability of the used paper. Papermaking chemistry is mainly about the wet end chemistry that takes place up to The point of sheet formation, but also includes chemical interactions that may take place during drying and storage. The chemical environment within the papermaking system is complex and variable with its precise composition depending on the outcome of the numerous interactions possible between furnish components (summarised in the diagram below). A central objective of wet end chemistry is to optimise the state of association of the whole papermaking furnish, which means maximising the efficient retention of raw materials consistent with maintaining other key variables such as paper quality (formation, strength, etc) and process efficiency (eg drainage, runnability, etc). In the context of papermaking chemistry, consultancy services can be provided in the following areas: Wet end chemistry optimisation This cannot be achieved without some basic knowledge of the chemical status at locations such as thick stock, thin stock, whitewater, fresh water, etc. Valuable chemical measurements include pH, temperature, conductivity, soluble calcium, dissolved organics (COD), particulate charge, soluble charge demand, fines content and consistency. Other measurements may be useful if there is some particular problem to be resolved, eg in the case of deposition, the composition of the deposit and the wet end distribution of its main components. Other essential information required to put the chemical measurements in perspective are the machine's fresh water consumption, the mass flows of materials and product quality data. Armed with this array of information, the experienced wet end chemist should be able to assess the system's closeness to optimal conditions and to pinpoint any potential problem areas. Audits of chemical use and system efficiency Chemical suppliers play an important role at many paper mills not only in supplying chemicals, but also in providing information on general wet end chemistry. The range of functional chemicals available from each supplier is also increasing in order to provide a "one-stop shop" for any customer mill. Working against this trend is the policy of many mills not to put all their eggs in one basket and the competitiveness amongst suppliers. Nevertheless, there is a tendency for mills to place an over-reliance on information generated by and interpreted by suppliers rather than by themselves, often due to inadequate experience and resources at the mill. This can be overcome by the use of an external independent expert to audit the system against "best practice" standards. Predicting the impact of system changes on process chemistry It is debatable whether any paper machine system achieves true equilibrium or steady-state conditions even under seemingly-constant conditions. Managed changes introduce systematic variability that can be predicted using simple spreadsheet models of the papermaking system. Examples of changes which are useful to model in this way are water closure (in terms of dissolved/colloidal solids and temperatures) and the extremes of pulp furnish (in relation to the contents of fines and solubles). Environmental selection criteria for raw materials In order to minimise the overall impacts from papermaking, the environmental characteristics of raw materials must be included in any realistic life cycle assessment. This includes impacts upstream and downstream of the paper mill (eg on product recyclability and disposability) as well as those directly from paper manufacture. This work requires expertis on environmental issues as well as on papermaking chemistry.
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CONSULTANCY ACTIVITIES
PAPERMAKING CHEMISTRY
Paper chemistry is mainly concerned with the chemistry that takes place within the papermaking process, but also includes the upstream chemistry connected with making the raw materials and any downstream chemistry that may affect recyclability of the used paper.
Papermaking chemistry is mainly about the wet end chemistry that takes place up to The point of sheet formation, but also includes chemical interactions that may take place during drying and storage. The chemical environment within the papermaking system is complex and variable with its precise composition depending on the outcome of the numerous interactions possible between furnish components (summarised in the diagram below).
A central objective of wet end chemistry is to optimise the state of association of the whole papermaking furnish, which means maximising the efficient retention of raw materials consistent with maintaining other key variables such as paper quality (formation, strength, etc) and process efficiency (eg drainage, runnability, etc). In the context of papermaking chemistry, consultancy services can be provided in the following areas:
Wet end chemistry optimisation This cannot be achieved without some basic knowledge of the chemical status at locations such as thick stock, thin stock, whitewater, fresh water, etc. Valuable chemical measurements include pH, temperature, conductivity, soluble calcium, dissolved organics (COD), particulate charge, soluble charge demand, fines content and consistency. Other measurements may be useful if there is some particular problem to be resolved, eg in the case of deposition, the composition of the deposit and the wet end distribution of its main components. Other essential information required to put the chemical measurements in perspective are the machine's fresh water consumption, the mass flows of materials and product quality data. Armed with this array of information, the experienced wet end chemist should be able to assess the system's closeness to optimal conditions and to pinpoint any potential problem areas.
Audits of chemical use and system efficiency Chemical suppliers play an important role at many paper mills not only in supplying chemicals, but also in providing information on general wet end chemistry. The range of functional chemicals available from each supplier is also increasing in order to provide a "one-stop shop" for any customer mill. Working against this trend is the policy of many mills not to put all their eggs in one basket and the competitiveness amongst suppliers. Nevertheless, there is a tendency for mills to place an over-reliance on information generated by and interpreted by suppliers rather than by themselves, often due to inadequate experience and resources at the mill. This can be overcome by the use of an external independent expert to audit the system against "best practice" standards.
Predicting the impact of system changes on process chemistry It is debatable whether any paper machine system achieves true equilibrium or steady-state conditions even under seemingly-constant conditions. Managed changes introduce systematic variability that can be predicted using simple spreadsheet models of the papermaking system. Examples of changes which are useful to model in this way are water closure (in terms of dissolved/colloidal solids and temperatures) and the extremes of pulp furnish (in relation to the contents of fines and solubles).
Environmental selection criteria for raw materials In order to minimise the overall impacts from papermaking, the environmental characteristics of raw materials must be included in any realistic life cycle assessment. This includes impacts upstream and downstream of the paper mill (eg on product recyclability and disposability) as well as those directly from paper manufacture. This work requires expertis on environmental issues as well as on papermaking chemistry.