Pulping method of non-wood fibers with no black liquor drained off as well as its boiler

Abstract

A process for preparing the pulp of non-woven fibres without black liquid drainage includes such steps as adding raw fibres and acetic acid into the enclosed digester, heating, holding the temp for acertain time, filtering to obtain waste acidic liquid, pumping it to waste acid tank, adding the washing alcohol solution, heating, holding the temp for a certain time, filtering the waste acid-alcohol solution, pumping it to waste acid-alcohol tank, washing fibres with clean alcohol, draining the washing liquid to waste liquid tank, stripping alcohol from fibres by low-pressure steam, adding hotwater to digester, and discharging raw pulp. Said digester has a jacket with steam inlet and condensed water outlet and a filter net at the discharge port.

Description

1. Technical field [0001] The invention relates to a papermaking pulping method and equipment thereof, in particular to joint cooking of non-wood fiber raw materials with acetic acid and ethanol, so that lignin and part of hemicellulose are dissolved in cooking liquid and separated from cellulose. Utilizing the characteristics that these solvents in the black liquor are easy to volatilize, they can be recovered by distillation and recycled. The lignin and hemicellulose are collected in the form of solids, thus realizing the emission of no black liquor and odorous gases such as hydrogen sulfide and mercaptan. Clean the pulping process and the corresponding digesters. 2. Background technology [0002] The two existing chemical pulping methods: kraft method and sulfite method have not changed much since they were developed more than one hundred years ago. As far as the representative kraft method of chemical pulping is concerned, the general process is: add fiber raw materials...

AI Technical Summary

Problems solved by technology

Such pulping method has the following problems: due to the use of sodium sulfide agent, malodorous gases such as hydrogen sulfide, mercaptan, and sulfur dioxide will be produced during cooking, which will have a serious impact on the atmospheric environment; due to the use of high-temperature and high-pressure cooking, lignin will deteriorate. As a result, bleaching is difficult. In order to obtain pulp with high brightness, multi-stage bleaching with chlorine bleaching agent is required. In this process, harmful substances such as organic chlorides will be generated, which will seriously affect the water environment; a large amount of alkali and other agents are used for cooking. , needs to be recovered from the black liquor. For this reason, the black liquor needs to be concentrated, burned, causticized, etc., which requires the use of complex and huge equipment, resulting in increased equipment investment costs; at the same time, the concentration of black liquor needs to evaporate a large amount of water. , the energy consumption is very high; precious resources such as lignin in the black liquor are only used in the form of heat energy in this process, and the added value is not high

The disadvantage of this method is that a large amount of acetone solution is used in the washing of pulp, which is troublesome to recycle and consumes more energy. After the cooking waste liquid is concentrated to a certain concentration, it is injected into 20 times of water to precipitate and separate lignin, resulting in a large amount of lignin. Acrylic acid

The recovery energy consumption of this part of propylene glycol is high

Therefore, the cost of chemical recovery is relatively high; the use of hydrochloric acid as a catalyst increases the corrosion of equipment and the content of organic chlorides in washing wastewater, causing adverse effects on the environment

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