Removing Silicate Scale On Disk Disperser With Phonochemistry Method

In recent years, the paper-making industry has been developing rapidly in our country. From 2008, production and consumption in China have overstepped those in America and ranked first in the world. But as a big paper-making country, our country's forest coverage are not adequate to meet the need of paper-making materials. So, recovery and utilization of waste paper has increasingly catched the attention of paper-marking industry and its recovery rate is increasing year by year. Now, in our country, waste paper has already accounted for more than 60% of all papermaking materials . In the process of making recycled pulp, hot disperser is used before later flotation to obtain good pulp quality. But sodium silicate added as stabilizing agent of hydrogen peroxide could result in silicate scale in disk disperser. This will seriously affect the productivity and increase energy consumption, and present cleaning methods of scale can not solve this problem.Phonochemistry method is tried out to remove silicate scale on disk disperser. Through comparing the dissolving scale rate of phonochemistry with that of chemical method and reaching corrosion by acid solution, the feasibility, optimized technical parameters are researched to remove phonochemistry silicate scale on disk disperser.The results are as follows:(1) When alkaline solution was used to remove silicate scale on disk disperser and the scale is about 2mm in size, the dissolving rate of silicate scale is only 24% after reacting time of 3h, but the dissolving rate of silicate scale by alkaline phonochemistry can reach 63.27% after reacting time of only 1h, far higher than that without ultrasonic. Other things being equal, the rate of dissolving silicate scale by alkaline phonochemistry is 4.01-9.45 times of only by alkaline method. When ultrasonic power is 600W, the dissolving rate of silicate scale by alkaline phonochemistry is 4.58-9.45 times of only by alkaline method,1.14-1.24 times of when ultrasonic power is 400W.(2) When the thickness of silicate scale is not more than 2mm, the optimized parameters for scale dissolving are the solution concentration of 10-15%, temperature of 70-90℃, ultrasonic power of 500-600W.(3) The own-prepared mixing corrosion inhibitor has better eroding-inhibitive efficiency compared with normal hexamethylenetetramine. In order to avoid corrosion, concentration and temperature of mixing acid solution should respectively be less than 12% and 60℃.(4) When alkaline solution was used to remove silicate scale on disk disperser without ultrasonic and silicate scale was about 3mm in size。The dissolving rate of silicate scale is 19.70～32.94% after reacting time of 1h in every concentration acid solution The dissolving rate of silicate scale by acid phonochemistry are all over 70% in different condition。The highest is 84.38%, where almost all the scale dissolved, and corrosion rate of acid phonochemistry is less than that without ultrasound.(5) When the thickness of silicate scale is about 3mm, the optimized scale dissolving parameters are the temperature of 40～50℃, solution consistency of 8～10% and ultrasound power of 200～300W.(6) When the cleaning solution is a mixed acid, if the material has good quality and strong resistance to corrosion, lower ultrasonic power, higher temperature and solution concentration can be adopted; if the corrosion-resistance of metal is poor or the silicate scale is solid, higher ultrasonic power, lower temperature and solution concentration can make a better cleaning effect.(7) When cleaning industrial silicate scale, the choice of acid or alkaline solution as cleaner should be based on the thickness of silicate scale. Generally speaking, when the thickness is less than or equal to 2mm, alkaline solution is better. When the thickness is more than 2mm, acid solution combined with the suitable corrosion inhibitor is better.(8) When acid or alkaline phonochemistry is used to remove silicate scale, the dissolving rate of silicate scale will rise with the increase of solution concentration, temperature and ultrasonic power. But when the thickness is more than 3.35mm, temperature, concentration and time should be limited so as to avoid corrosion. In this condition, ultrasonic power can be enlarged. When silicate scale on disk disperser is cleaned in production field, the optimized parameters of concentration, temperature, time and ultrasonic power should be chosen.