SU815099A1 - Method of pbtaining fibrous mass - Google Patents

Description

The invention relates to methods for producing pulp using pressure relief and can be used in the pulp and paper and forest industries in the manufacture of paper, cardboard and wood-fiber boards.

A known method of producing pulp is when lignocellulosic material with a moisture content of 50-90% in the form of chips is treated with microwaves (microwave energy) with a frequency of 10-300 thousand MHz for a short period of time. The water contained in the chips evaporates explosively, breaking the chips into individual fibers fl].

However, the efficiency of microwave energy is determined by the coefficient of dielectric loss of water, which decreases with increasing temperature. Since the implementation of the method provides for the heating of wood chips, then, therefore, the amount of energy going directly to the process of destruction of wood is only a few percent of the spent. In addition, the use of microwave energy for the separation of chips into fibers requires special protection from radio personnel and radio communications, which complicates the design of the device for implementing this method.

There is also known a method for producing pulp, which consists in loading wood chips into a digester, impregnating them with gas, for example, θ sulfur dioxide, heating them, thereby creating higher atmospheric pressure in the boiler and in the wood pores, then instantly depressurize using opening 15 valve. In this case, the impregnated wood chips are thrown out and split into fibers f2].

The disadvantages of the method are the frequency of the process, the complexity and the explosive risk of implementing structures of this method, which leads to the complexity of the technology and does not allow to intensify the process.

The purpose of the invention is the improvement of the process.

This goal is achieved in that the wood chips are heated to 40-95 ° C by electric current, and explosive separation into fibers is carried out by applying • a high-voltage electric pulse of 3-10 kV / cm for

1-100 ms.

The permeability of wood along the fibers for gases is 30-60 times higher than for liquids. Therefore, for processing wood chips with a moisture content of 35-50%, use sulfur dioxide in a gaseous form. The gas in the capillaries of the wood interacts with water to form an electrolyte. Wood thus prepared is heated by briefly passing an electric current of low density. Due to the fact that the heat capacity of wood is 2.5 p. Lower than the heat capacity of moisture, it is advisable to pass current periodically for uniform heating of the chips. This increases the conductivity of the current-carrying channels. ·

Having increased the electrical conductivity of wood, a high-voltage electric pulse is applied to it, creating a jump in the density of electric current in the capillaries of wood. This leads to instant boiling of fluid in the cells and a significant increase in pressure in them, as a result of which there is a rupture of the transverse bonds between the fibers and the chips turn into a fibrous mass. This method allows you to save the natural fiber length and at the same time intensify the process.

Example. Spruce wood chips with a humidity of 50% are placed in an autoclave, where sulfur dioxide is fed in the amount of 2.3% of the weight of absolutely dry wood under a pressure of more than 400 mm Hg. Then, an electric current of 220 V is passed through the wood for a short time within 2-4 s, bringing the chip temperature to dr 40-90 ° С, after which a high-voltage electric pulse of 3-10 kV / cm is supplied for 0.01-0.02 from. The liquid in the capillaries boils, high pressure is created and the chips are divided into fibers. The yield of the target product is 85-96%. Castings are produced from pulp with a degree of lying 40-60 ° SHR, _ breaking length of which is 2500-3000 m. ^{3 The} process of wood destruction is intensified by preliminary heating and creating excessive pressure in the pores of the wood by transmitting an electrical pulse in a short period of time (during

1-100 ms depending on the breed and the size of the raw material), which increases the productivity of the process of preparing 15 pulp in 3-5 p, with an energy consumption of 1 t of the target product 150-240 kW h

The process control is reduced to controlling the degree of chopping 20 of the wood by changing the voltage of the electric pulse, its shape, duration and power, as well as by changing the feed rate relative to the electrodes.

Claims (2)

The invention relates to methods for producing pulp using pressure relief and can be used in the pulp and paper industry in the manufacture of paper, cardboard and fibreboard. There is a known method for producing pulp when the lignocellulosic material with a moisture content of 50-90% in the form of a process is treated with microwaves (microwave energy) with a frequency of 10-300 thousand mHz for a short time interval. The water contained in the chips evaporates explosively, breaking the chips into individual iQ fibers. However, the efficiency of the use of microwave energy is determined by the dielectric loss factor of water, which decreases with increasing temperature. Since the implementation of the method provides for heating wood chips, therefore, the amount of energy that goes directly to the implementation of the process of destruction of wood is only a few percent of the expended energy. In addition, the use of microwave energy for dividing chips into fibers requires special protection from radio emission from staff and radio, which complicates the design of the device for implementing this method. There is also known a method for producing pulp, in which chips are loaded into a digester, impregnated with gas, such as sulfur dioxide, heated, thereby creating atmospheric pressure in the boiler and in the pores of the wood, then instantaneous release of pressure by opening valve. In this way, the impregnated chips are thrown away and split into fibers. The disadvantages of the method are the periodicity of the process, the complexity and the explosiveness of the structures implementing this method, which leads to the complexity of the process and does not allow for the intensification of the process. The purpose of the invention is to in- process enhancement. The goal is achieved by heating the wood chips to 40-95 ° C with an electric current, and the explosive separation into fibers is carried out by applying a high-voltage electrical pulse with a voltage of 3-10 kV / cm for 1-100 MO. The permeability of wood along fibers for gases is 30–60 p-higher than for liquids. Therefore, for treating wood chips with a humidity of 35-50%, use sulfur dioxide in gas form. The gas in the capillaries of the wood interacts with water to form an electrolyte. The wood thus prepared is heated by briefly passing an electric current of low density. In connection with the fact that the heat capacity of wood is 2.5 times lower than the heat capacity of moisture, it is advisable to pass the current periodically for a uniform heating of the chips. This increases the conductivity of the current path of the channels. Having increased the electrical conductivity of wood, a high-voltage electric pulse is applied to it, creating a jump in the density of the electric current in the capillaries of the wood. This leads to an instantaneous boiling up of the fluid in the cells and a significant increase in pressure in them, as a result of which the cross-links between the fibers break and the chips turn into a fibrous mass. This method allows to preserve the natural length of the fiber and at the same time intensify the process. Example. Wood chips from 50% moisture content are placed in an autoclave, which supplies sulfuric anhydride in an amount of 2.3% by weight of absolutely dry wood under a pressure of more than 400 mmHg. Then, a short-term electric current of 220 V is passed through the wood for 2-4 seconds, the chip temperature is brought to 40-90 0, then a high-voltage electrical pulse is applied, with a voltage of 3-10 kV / cm for 0.01-0 , 02 s. The liquid in the capillaries boils creating high pressure and the chips split into fibers. The yield of the target product 85-96%. Castings with a breaking length of 2500-3000 m are made from pulp with a Poole 4D-60 PF. Intensification of the wood destruction process is carried out by means of preliminary electrically heating and creating an overpressure in the pores of the wood due to transmission of an electrical impulse in a short period of time -100 MO, depending on the breed and size of the sun), which increases the productivity of the pulp preparation process in 3-5 p, with the expenditure of energy per 1 ton of the target product 150-240 KWh. Control Processes svodits. to regulate the degree of crushing of wood by changing the voltage of an electrical impulse, its shape, duration and power, as well as by changing the feed rate of the raw material relative to the electrodes. The invention The method of obtaining pulp, including the processing of chips with sulfur dioxide gas under pressure, heating and explosive separation into fibers, characterized in that, in order to intensify the process, heating is carried out to a temperature of 40-95 with electric current, and explosive separation into fibers by applying a high voltage electric pulse with a voltage of 3-10 kV / cm for 1-100 ms. Sources of information taken into account in the examination 1. Swedish Patent 385027, cl. D 21 1/30, 1975. 2. Appita, 1976, 5, p. 356362 (prototype).