A method for monitoring hydrophobic particles contained in a pulp suspension, includes obtaining a sample from a pulp suspension or a filtrate of the pulp suspension. A fluorescent dye is added to the sample to stain particles in the sample. The sample is fractionated to obtain at least a first fraction and a second fraction, wherein the second fraction is a fiber fraction. The method includes for the obtained fractions, fluorescence emitted by the particles in the fractions, calculating an integral of the fluorescence measured for the fractions excluding the fiber fraction, and correlating the calculated integral of the fluorescence to the amount of acetone soluble material in the pulp suspension, and optionally measuring light scattering signal of the particles in at least first and second fractions.

[Problem] To provide a contamination preventing agent composition capable of effectively preventing pitch contamination in a dry part. [Solution] The present invention relates to a contamination preventing agent composition for preventing pitch contamination in a dry part D of a papermaking process, the composition containing: a linear polysiloxane compound represented by formula (1); and a cyclic siloxane compound. [In formula (1), a substituent R.sup.1 represents, in the same molecule, a hydrogen atom, an alkyl group, a methylphenyl group, a polyether group, a higher fatty acid ester group, an amino-modified group, an epoxy-modified group, a carboxylic group, a phenol group, a mercapto group, a carbinol group, or a methacrylic group, and a repeating number n of a siloxane unit represents an integer of 20-1430.]

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Provided is a method for producing paper that enables to fix an increased amount of starch components contained in papermaking process water to a papermaking raw material (suspended solid: SS) contained in the papermaking process water, and enables (1) enhancement of the strength of paper, (2) reduction in the contamination of the papermaking process water by microorganisms, etc., (3) suppression of the foaming of the papermaking process water, (4) decrease in the load of the waste water treatment, etc. The method comprises a step of adding a polymer having a polyalkylene oxide moiety to papermaking process water containing SS containing a papermaking raw material and unfixed starch. At this time, the concentration of SS contained in the papermaking process water is 100 mg/L or more, the concentration of the unfixed starch is 10 mg/L or more, and the salt viscosity of the polymer is 3 mPa.Math.s or more.

A method is disclosed for predicting the microbial status of a paper or board making process and/or quality of the dry board or paper obtained from the process for controlling microbial status of a paper or board making process or quality of the dry board or paper obtained from the process. Surface level and duration of time in at least one storage tower or pulper are monitored and correlated with respective predetermined values for the tower or pulper in order to predict the risk of microbial activity.

A method is disclosed for predicting the microbial status of a paper or board making process and/or quality of the dry board or paper obtained from the process for controlling microbial status of a paper or board making process or quality of the dry board or paper obtained from the process. Surface level and duration of time in at least one storage tower or pulper are monitored and correlated with respective predetermined values for the tower or pulper in order to predict the risk of microbial activity.

There is provided an efficient pitch trouble prevention method in a papermaking step of paper production. The pitch trouble prevention method in a papermaking step of paper production includes: an aeration step of exposing at least one of white water and adjusted water to gas; and a pitch control agent addition step of adding a pitch control agent to at least one of the white water and the adjusted water.

There is provided an efficient pitch trouble prevention method in a papermaking step of paper production. The pitch trouble prevention method in a papermaking step of paper production includes: an aeration step of exposing at least one of white water and adjusted water to gas; and a pitch control agent addition step of adding a pitch control agent to at least one of the white water and the adjusted water.

A method of measuring hydrophobic contaminants in a pulp slurry or a papermaking system includes the steps of providing an aqueous paper mill sample, filtering the aqueous paper mill sample to produce a filtrate comprising particles, and collecting an image of the particles in a measured volume of the filtrate. The method also includes the steps of analyzing the image to determine a size and morphology of the particles in the measured volume of filtrate, identifying spherical particles having a size of from about 1 micron to about 20 microns in the measured volume of filtrate, and quantifying a number of the spherical particles having the size of from about 1 micron to about 20 microns in the measured volume of filtrate. This method is useful for papermakers for deposition diagnostics, prevention, and contaminant control treatment optimization.

A method of measuring hydrophobic contaminants in a pulp slurry or a papermaking system includes the steps of providing an aqueous paper mill sample, filtering the aqueous paper mill sample to produce a filtrate comprising particles, and collecting an image of the particles in a measured volume of the filtrate. The method also includes the steps of analyzing the image to determine a size and morphology of the particles in the measured volume of filtrate, identifying spherical particles having a size of from about 1 micron to about 20 microns in the measured volume of filtrate, and quantifying a number of the spherical particles having the size of from about 1 micron to about 20 microns in the measured volume of filtrate. This method is useful for papermakers for deposition diagnostics, prevention, and contaminant control treatment optimization.

A method is disclosed for predicting the microbial status of a paper or board making process and/or quality of the dry board or paper obtained from the process for controlling microbial status of a paper or board making process or quality of the dry board or paper obtained from the process. Surface level and duration of time in at least one storage tower or pulper are monitored and correlated with respective predetermined values for the tower or pulper in order to predict the risk of microbial activity.