Method and device for measurement of the retention profile and for control of the retention in a paper/board machine

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width from different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the headbox, the plurality of liquid flow lines introducing a flow of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile, wherein each of the plurality of first valves is a two-way valve in which a mixing ratio of two inlet flows is regulated, one of said inlet flows including the retention agent, wherein the mixing ratio is regulated so that, when one inlet flow is increased, tire other inlet flow is reduced by a corresponding amount, and the other way round, and that the combined flow is passed into the liquid flow line after the valve.

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width front different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the headbox, the plurality of liquid flow lines introducing a flow of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile;
• and
• a second valve positioned in each liquid flow line after the first valve, the second valves being Adjustable to regulate the flow quantity in each line.

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width from different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the headbox, the plurality of liquid flow lines introducing a Low of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile;
• and
• wherein the means for measuring the retention profile across the web width comprises:
• an analyzer,
• a sample collecting device positioned beneath the wire, the sample collecting device positioned to take a sample from the water that has departed from the wire;
• a carrier for the sample collecting device;
• and
• a sample transfer duct through which each sample is transferred to the analyzer for determining the retention profile.

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width from different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the headbox, the plurality of liquid flow lines introducing a flow of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile;
• and further comprising:
• a wire pit positioned beneath the wire to collect white water;
• a dilution header communicating with the plurality of liquid flow lines;
• and
• a flow connection for passing of dilution water from the wire pit to the dilution header, the dilution header being positioned upstream of the first valves.

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width from different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the beadbox, the plurality of liquid flow lines introducing a flow of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile;
• and
• further comprising:
• a wire pit positioned beneath the wire to collect white water;
• a retention agent header communicating with the plurality of liquid flow lines;
• a flow connection for passing of dilution water from the wire pit to the retention agent header, the retention agent header being positioned upstream of the first valves;
• a retention agent supply unit;
• and
• a flow connection for passing of retention agent from the retention agent supply unit to the retention agent header.

A device for measurement and regulation of a retention profile of a web in a paper/board machine, the device comprising:

• means for measuring the retention profile across the web width from different points of width of the web out of the white water drained from a wire part of the paper/board machine;
• a headbox;
• a plurality of liquid flow lines which communicate with points in the headbox which are spaced in a cross machine direction from one another,
• a flow of stock into the headbox, the plurality of liquid flow lines introducing a flow of liquid containing retention agent into the flow of stock to regulate the retention profile across the web width, and
• a first valve in each liquid flow line, each valve being adjustable to regulate the amount of retention agent being carried by each flow line, the valves being regulated on the basis of the measurement data obtained from measurement of the retention profile;
• and
• wherein a second valve is positioned in each of said flow lines, said second valves being positioned to permit regulation of a flow of a quantity of dilution water through said flow lines.

A method for forming a web in a papermaking machine having a headbox which discharges stock onto a moving wire, the method comprising the steps of:

• discharging stock on to the wire from the headbox, wherein liquid which is not retained on the wire and passes through the wire comprises white water;
• taking samples of the white water that passes through the wire at a plurality of web locations which are spaced from each other in a cross machine direction;
• measuring each sample to measure the properties of the white water at each of said web locations;
• introducing a flow of stock into the headbox;
• and
• introducing a plurality of second flows into the headbox, the second flows discharging into the beadbox at a plurality of positions spaced from each other in the cross machine direction, each second flow being controlled to adjust the amounts of dilution water and retention agent in each second flow, the proportions of dilution water and retention agent being controlled in response to the measured properties of the white water samples;
• wherein the step of taking samples of the white water further comprises the steps of:
• positioning a sample head at a first one of said plurality of web locations in the cross machine direction, and retaining the sample head stationary during the time of collecting a first sample;
• advancing the sample head in the cross machine direction a predetermined distance to bring the sample head to a second one of said plurality of web locations in the cross machine direciton, and retaining the sample head stationary during the time of collecting a second sample;
• and
• continuing to advance the sample head and hold the sample head stationary until each of
• said plurality of web locations has been sampled;
• and repeating the above steps.

A papermaking machine comprising:

• a headbox;
• a wire extending downstream from the headbox, wherein stock is discharged from the headbox onto the wire, and wherein a web is formed on the wire, and stock which is not retained on the wire passes through the wire as white water;
• a sampling device positioned beneath a plurality of locations which are spaced in the cross machine direction along the wire, the sampling device positioned to collect white water samples at each of the plurality of locations;
• a transfer pipe which communicates each white water sample to a white water analyzer which determines the white water in each sample;
• a paper machine control unit which receives data from the analyzer concerning each sample;
• a plurality of headbox supply lines which discharge into the headbox, the headbox supply lines discharging into the headbox at headbox locations which are spaced from one another in a cross machine direction;
• a supply of dilution liquid;
• a retention agent feed unit;
• and
• wherein the supply of dilution liquid and the retention agent feed unit are connected to communicate dilution liquid and retention agent to each of the headbox supply lines, the quantity of dilution liquid and retention feed so communicated being controlled by the paper machine control unit in response to the white water properties measured in the samples.