Safe, energy-saving and efficient high-temperature chlorine dioxide paper pulp bleaching method and bleaching device

Abstract

The invention discloses a safe, energy-saving and efficient high-temperature chlorine dioxide paper pulp bleaching method and a bleaching device. The bleaching device is composed of a pre-bleaching pulp washing machine, a medium concentration standpipe, an acidification steam heater, an acidification mixer, a n-type acidifier, a bleaching steam heater, a bleaching mixer, a high-temperature bleaching tower, a high-temperature leaching stage washer and the like. The bleaching method includes the following steps: firstly, acidifying paper pump in advance by using a high-temperature acidification pretreatment process to acidify and degrade HexA in the paper pulp and neutralize residual alkalis carried by the pulp before bleaching so as to prevent the residual alkalis from reacting with chloric acid produced by hydrolysis of chlorine dioxide; and secondly, mixing the pulp after the high-temperature acidification pretreatment with the chlorine dioxide, and then carrying out high-temperature chlorine dioxide bleaching. The safe, energy-saving and efficient high-temperature chlorine dioxide paper pulp bleaching method and the bleaching device can shorten the reaction time of conventional high-temperature chlorine dioxide bleaching, save the manufacturing cost of the high-temperature bleaching tower and reduce the steam consumption of the bleaching. Moreover, after concentrated sulfuric acid and an acidic mirabilite solution for acidification are mixed and diluted, pulp pipes are added, and so the corrosion is not strong and the production operation safe coefficient is high.

Description

technical field [0001] The invention belongs to the technical field of chlorine dioxide pulp bleaching, in particular to a safe, energy-saving and high-efficiency high-temperature chlorine dioxide pulp bleaching method and a bleaching device. Background technique [0002] As a bleaching agent with high bleaching efficiency, strong selectivity and low pollution load of bleaching wastewater, chlorine dioxide is currently widely used in the pulp and paper industry. But because of its high production cost (especially the production mode of raw materials such as purchasing sodium chlorate, the production cost per ton of chlorine dioxide is about 10,000 yuan), it greatly increases the production cost of pulp bleaching. [0003] In the traditional chlorine dioxide bleaching process, the conventional D 0 -Ep-D 1 Elemental chlorine-free bleaching process, bleaching finished pulp to 85% (ISO) brightness, bagasse pulp per ton of pulp consumes total chlorine dioxide (D 0 +D 1 ) is g...

AI Technical Summary

Problems solved by technology

[0004] High temperature chlorine dioxide bleaching process (D ht ) is exactly an optimized chlorine dioxide bleaching process, which replaces the traditional D 0 In the bleaching section, in the first chlorine dioxide bleaching process, concentrated sulfuric acid is added and the pulp is heated with steam, so that the pulp is subjected to high-temperature acidification while the chlorine dioxide reaction is carried out, so that the HexA in the pulp is degraded, so as to reduce the whole bleaching process. The purpose of chlorine dioxide consumption in the workshop section, but this process has the following disadvantages: 1) the concentrated sulfuric acid used for acidification is added in the slurry pipe, and it will be diluted and exothermic after mixing with the slurry (containing about 90% moisture), which is easy to cause Slurry pipelines are corroded and perforated, leading to high safety risks; 2) The high-temperature bleaching reaction temperature is as high as about 90°C, which requires a large amount of steam consumption. Although it can reduce the amount of chlorine dioxide, there is no significant advantage in overall production costs when the unit cost of steam is high; 3) The high-temperature bleaching reaction time is as long as 2 hours (conventional bleaching is 1 hour), so the chlorine dioxide bleaching tower required is large in volume (lined with anti-corrosion resin and pasted with acid-resistant tiles), high in cost, and large in project construction investment

[0005] In view of the above reasons, high temperature chlorine dioxide bleaching cannot be widely promoted

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