Method for estimating the vapor phase corrosion load
AssigneeKemira Oyj
InventorsMarko KOLARI, Iiris JOENSUU
Life of this patent
Estimating the term…
Abstract
The present invention relates to a method for estimating vapor phase corrosion load in a paper or board manufacturing system, method for controlling vapor phase corrosion load in a paper or board manufacturing system and an arrangement usable is those method. Said methods allow easy on-line follow up of the corrosion load and also adjusting biocide dosage.
Claims14
A method for estimating vapor phase corrosion load in a paper or board manufacturing system, comprising:
- i. determining in a defined location of an aqueous process flow a threshold rH value;
- and
- ii. determining rH values of said aqueous flow in said defined location over a defined time period in defined time points;
- and
- iii. calculating ΔrH in each time point as a difference between a determined rH value and the predetermined rH threshold value obtained in step i, wherein the calculated value ΔrH is at least zero;
- and
- iv. calculating ΣΔrH as a cumulative sum of ΔrH values obtained in step iii
- or alternatively
- v. calculating cumulative sum of each determined rH value obtained in step ii wherein the determined rH value is at least the predetermined rH threshold value;
- and
- vi. calculating ΣΔrH as a difference between the cumulative sum obtained in step v and the threshold value obtained in step i multiplied with the defined number of time points;
- and using the ΣΔrH obtained in step iv or vi to estimate the corrosion load
- wherein increase in ΣΔrH indicates an increase in corrosion load and decrease in ΣΔrH indicates a decrease in corrosion load.
A method for controlling vapor phase corrosion load in a paper or board manufacturing system comprising:
- i. determining in a defined location of an aqueous process flow a threshold rH value;
- and
- ii. determining rH values of said aqueous flow in said defined location over a defined time period in defined time points;
- and
- iii. calculating ΔrH in each time point as a difference between a determined rH value and the predetermined rH threshold value obtained in step i, wherein the calculated value ΔrH is at least zero;
- and
- iv. calculating ΣΔrH as a cumulative sum of ΔrH values obtained in step iii or alternatively
- v. calculating cumulative sum of each determined rH value obtained in step ii wherein the determined rH value is at least the predetermined rH threshold value;
- and
- vi. calculating ΣΔrH as a difference between the cumulative sum obtained in step v and the threshold value obtained in step i multiplied with the defined number of time points;
- wherein a cumulative ΔrH value for the predetermined time period is used to estimate the corrosion load;
- and
- vii. using the estimate to determine how to adjust the dosing of an oxidizing biocide in a paper or board making process;
- and
- viii. adjusting the amount of the oxidizing biocide based on the estimate obtained regarding vapor phase corrosion.
The method of any of the preceding claims, wherein the predetermined threshold rH value is selected as an rH-value determined at lowest effective oxidative biocide content for said system.
The method of any of the preceding claims, wherein rH values are determined using on-line system, said system including means for pH, redox and temperature measurements.
An arrangement for use in connection with paper or board manufacturing system, comprising:
- i. at least one computing device;
- and
- ii. a method application executable in the at least one computing device, the method application comprising:
- logic that obtains information regarding the estimated load of vapor phase corrosion over a time period;
- and
- logic that uses the information to determine how to adjust the dosing of an oxidizing biocide in a paper or board making process.
Dependencies are inferred from the claim text.