According to the actual application, it fully meets the requirements of use and achieves better economic benefits. 1 Introduction Chlorination of pulp is the first stage of conventional multi-stage bleaching, the purpose of which is to remove most of the residual lignin in the unbleached pulp. In the chlorination process, chlorine gas is introduced into the slurry to mix the chlorine gas with the slurry, and the residual lignin in the slurry reacts with chlorine to form chloride, which causes the lignin to be degraded and dissolved. Factory practice shows that good mixing is the key to improving the chlorination effect. Using the pulp chlorine mixer can quickly and evenly mix the slurry and chlorine, improve the mixing effect and improve the quality of chlorination, reduce the amount of bleach used, and reduce the cost of bleaching. . In the past, our factory has done a variety of technical reforms and research, and the results are not satisfactory. For example, the SV type static slurry chlorine mixer produced by a factory has been used, and the mixing elements are heat-dissipating. Due to the dense distribution of the blades, and the pressure drop of such mixers is large, the slurry is often blocked and the production is affected. The slurry chlorine mixer is then no longer used to restore direct chlorine in the slurry as shown. This results in uneven mixing, poor chlorination, and a phenomenon of flowering in production, which consumes a large amount of chemicals. To this end, we have researched and improved the slurry chlorine mixer to solve the above problems to improve the chlorination effect. 2 Mixing Mechanism Analysis The pipe mixer is an efficient mixing device without mechanically moving parts. A plurality of mixing elements are arranged in a section of the pipe, and the pipe mixture is composed of a pipe casing, a mixing element and a connecting flange. Pulp and chlorine mixing is a solid-liquid-gas mixing process with a non-homogeneous phase. Because the concentration of the slurry (about 3%) is low, the effect of solid-phase mixing is neglected, and the mixture of pulp and chlorine is considered to be a non-homogeneous phase. A gas mixing process, and the reaction of chlorine gas with the slurry is very rapid, staggered, the two sides of the two elements connected to each other at 90 °, as recommended. 3.4 Pressure drop The pressure drop AP of the AP pipe mixer is small, can be ignored when the system pressure is high, and must be considered when the system pressure is low. The pressure drop AP is determined by the following formula 4 2063.5 parameters to determine the viscosity n = (to produce 60,000 tons of dry pulp per year, 330 days a year, 20 hours per day). Take the inner diameter Dn of the empty tube of the mixer as the inner diameter D of the pipe connected to it, that is, DN=D,=250mm, the comprehensive formula (1), (2): fluid velocity u=1.74m/s, in the data control range 1.2~ Within 14m/s; Reynolds number Re=5818>Rej fluid flow pattern is turbulent flow. Considering the chlorination process, manufacturing process, installation location and other factors, the working length of the mixer is L=2400mm. The pressure drop of the substituting type (4) is Ap=4.08X104Pa, which is equivalent to the fluid passing through the mixer and the flow cross section. 4 times the ratio of solid contact perimeter S, ie Dk=4A/S; *fluid flow rate (m/s); P* fluid density (g/m3)n*fluid viscosity (physical parameters p,n of Pa fluid can be Through the foundation, this combined structure, with a single mixing element in the middle, is convenient to make; the outer layer is a metal shell and a connecting flange, which can increase the mechanical degree of the mixer and facilitate the connection. 5 Application effect analysis The improved pipeline mixer was used as a pulp chlorine mixer in the bleaching workshop. It was put into use in early 1999. The actual use of more than two years indicates that it fully meets the requirements for use and achieves the design goal. 5.1 Improve the chlorination effect and improve the quality of the pulp. Previously, chlorine was directly passed through the pipeline without using a slurry mixer (see), resulting in partial chlorination of the slurry at the center of the tube. Cellulose and hemicellulose were more seriously degraded, resulting in decreased fiber strength and increased bleaching pulp. The yellowing of the tube; while the edge of the tube is not enough chlorine, the amount of bleaching agent needs to be increased, thereby increasing the destructive effect of the bleaching agent on the fiber and reducing the strength of the pulp. 51. Because of the simultaneous presence of the two kinds of pulp, the appearance of the bleached pulp exists. Color difference, that is, flower paste. After the pipe mixer is put into use, the chlorine pass mode is changed as shown. The quality of the chlorination is improved by the improvement of the mixing effect, so that the aforementioned problems are solved, and the quality of the pulp is improved and stabilized. 5.2 Improve the mixing effect and reduce the cost of bleaching. After the pipeline mixer is put into use, the reactants of the non-homogeneous chlorination system formed by the chlorine-water-slurry slurry are thoroughly mixed, the residual chlorine in the slurry is reduced, the amount of liquid chlorine is reduced, and the chlorine is improved due to the improvement of the mixing effect. Quality, reduce the amount of bleach, thereby reducing the cost of bleaching and increasing economic efficiency. 5.3 Maintenance costs are low. The pipeline mixer is compact in structure, simple in installation, low in equipment cost, convenient in management and maintenance; the mixer has no mechanical running parts, and is stirred and mixed by the fluid flow itself, and does not require additional power to save energy. It has been working normally for more than two years without any failure. 6 Conclusion Pipe mixer is used as a pulp chlorine mixer in the bleaching workshop. After more than two years of practical use, the pipeline mixer fully meets the non-uniform phase of the chlorination treatment of the low-concentration slurry. The effect is remarkable, achieving the purpose of chlorination and improving the quality of the pulp. The production cost report shows that the use of liquid chlorine is reduced by about 5% compared with the original, while reducing the use of other chemicals, reducing the cost of bleaching, and achieving good economic benefits. 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According to the actual application, it fully meets the requirements of use and achieves better economic benefits. 1 Introduction Chlorination of pulp is the first stage of conventional multi-stage bleaching, the purpose of which is to remove most of the residual lignin in the unbleached pulp. In the chlorination process, chlorine gas is introduced into the slurry to mix the chlorine gas with the slurry to make the residue in the slurry.