Grant; The main research direction: Pulp and papermaking in a given space, below a large paper equipment and its control. Gas pressure in the gas state. The vacuum state satisfies the special requirements of certain processes in industrial production, so vacuum technology is widely used in electric power, metallurgy, building materials, food, tobacco, leather, ceramics and other industries.
With the development of economy, the pulp and paper industry has further developed in the direction of high yield, low energy consumption and light pollution. In recent years, research on pressure impregnation technology at home and abroad has been very active, and the pressure pre-impregnation process has been applied in cooking processes and equipment, and economic and social benefits have been achieved.
In this paper, the vacuum low-pressure characteristics of the traditional sulfate cooking process and its equipment were explored to improve, focusing on the VPI cooking mechanism, process and vertical steamer analysis and research.
1 cooking mechanism analysis VPI's process method is: first under vacuum conditions, the use of negative pressure effect to maximize the exclusion of moisture and gas in the impregnated material to make the organization become loose, and then add the purified high concentration impregnating solution In the impregnation vessel, the use of a large pressure difference and the effect of a positive pressure accelerate the uniform penetration and diffusion of the impregnation liquid into the impregnated material.
The vacuum-pressure mechanism provides the following favorable dynamic conditions for the impregnation process: First, under vacuum conditions, negative pressure effects are used to maximize the elimination of moisture and gases in the raw materials to make the structure loose, and some weak cell membranes will rupture. Then, the preheated cooking liquor is added to the cooking vessel. The pressure difference exists in the contact and adsorption of the cooking liquor and the wood chips, and accelerates the vacancy left by the gas escaped from the cooking liquid into the wood tissue. . The vacuum negative pressure also promotes the timely release of the reaction-produced gas and other non-condensable gases, so that the reaction equilibrium and reaction kinetic conditions are changed in favor of impregnation and cooking. In short, the use of large pressure differentials and positive pressure effects can accelerate the uniform infiltration of the cooking liquor into the interior of the fiber material, thereby enabling time-efficient and efficient production of high-quality pulp.
1.3 VPI Cooking Influencing Factors In the VPI cooking process, the rate at which the cooking liquor enters the fiber raw material and the degree of impregnation that can be achieved are affected by many factors, such as the concentration of the impregnating liquid, the immersion time, the impregnation temperature, the degree of vacuum, the pressure, and the raw materials. The state of the organization and how to add the impregnated raw materials. Passed by this article, the main components are: vertical cooking pot, liquid circulation system, liquid supply system, vacuum system, air compression system, working steam system, etc.: 10. 3.2 Features of the device 3.2.1 three-stage steam jet pump The VPI cooking apparatus uses a three-stage steam jet pump as a vacuum obtaining device, and its structure is as shown. It is generally believed that the role of the nozzle is a rapid pressure drop, the role of the pressure reducer pressure. After a certain pressure of working steam is accelerated by the nozzle and flows to the pressure vessel, due to the transition of pressure energy (potential energy) to velocity energy (kinetic energy), a low pressure zone (mixing chamber) is formed around it, and the pumped gas is mixed with high pressure steam in the mixing chamber. It is carried into the pressure vessel. In the pressure vessel, the opposite process occurs in the nozzle, and the mixed fluid is discharged after being compressed and pressurized. Water VPI Equipment Structure Diagram The steam injection pump has the characteristics of stronger pumping capability than other vacuum obtaining devices at a vacuum degree of 40000 ~13Pa, and the working medium is easily supplied, there is no relative moving parts, the performance is stable, and the maintenance cost is low.
The specific design process of the vacuum system can be
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