CA1101257A

CA1101257A - Method and apparatus in pulping

Info

Publication number: CA1101257A
Application number: CA325,836A
Authority: CA
Inventors: Agne T. Mattsson
Original assignee: Bahco Ventilation AB
Current assignee: Bahco Ventilation AB
Priority date: 1978-04-21
Filing date: 1979-04-19
Publication date: 1981-05-19
Also published as: SE411133B; FI67102B; SE7804602L; FI791267A; FI67102C

Abstract

ABSTRACT OF THE DISCLOSURE

The specification describes a method of defibrating wood chips in steam where the pulp produced is conveyed from a pulper to a separator for separating pulp and steam. The invention also relates to apparatus for carrying out the method.

Description

A METHOD ANL) APPARATUS IN PUI.PING
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The invention relates to a method in defibrating wood chips in steam where the pulp produced is conveyed from a pulper to a separator for separating pulp and steam. The invention also relates to apparatus for carrying out the method.
It is usual to utilize the rather high pressure of steam in the pulper, often 0.5 - 1 MPa over atmospheric pressure, for conveying the pulp therefrom to the separator, the steam being allowed to expand to atmospheric pressure and quite often allowed to flow out into the atmosphere after completing conveying work, which means a considerable loss of energy. Even if steam is sometimes recovered after the separator, it is a source of energy of lower value than the steam in the pulper, due to its reduced pressure and temperature.
The object of the in~ention is to provide a method and apparatus for conveying the pulp between the pulper and separator, the method and apparatus allowing recovery of all excess steam at high pressure and temperature.
The desired results are achieved, in accordance with the present invention, by the provision of a method in defibrating wood chips in steam, where the pulp produced is conveyed from a pulper to a separator for separatin~ pulp and steam, characterized in that a flow of steam which has been separated from the pulp is taken from the separator, is given an increased pxessure and supplied as a driving flow to an ejector, the ejector being used for removing a flow

2~ oE pulp and steam from the p~lper, both the flows merged in n ~7 . .

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the ejector being supplied to the separator, which is kept pressurized by the steam by separating it from the atmosphere, while a limited amount of excess steam is taken off and refluxed to a chips preheater connected to the pulper and/
or is used as a source of energy for other purposes.
In accordance with a further aspect of the present invention, there is provided an apparatus for carrying out the method, comprising a pipe connection between a pulper and a separator, which is arranged for separating pulp and steam received from the pulper, characterized by a pressure increasing conveying means for steam, e.g. a fan, the pressure increasing means having its suction side connected to the steam outlet of the separator, and an ejector, the pressure ; increasing means having its pressure side connected to the ejector inlet for a driving medium, while the ejector inlet for a conveyed medium is connected to the pulper outlet for pulp and steam, and the ejector out:Let is connected to the separator inlet, the circuit formed by the pressure-increasing means, ejector, separat~r and intermediate connecting pipes constituting a closed system, in which the separator is also kept pressurized by the steam by adjusted bleeding-off of excess steam, which is refluxed to a chips preheater connected to the pulper and/or is used as a source of energy for other purposes.
The invention is described in detail in the following, while referring to the accompanying schematic drawing showing the plant.

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- la -~ LZS7 Uncoolsed chips, possibl~ somewhat preheated, are supplied to the screw conveyor 1, which presses the chips in-to the preheat-ing chamber 3 of the pulper 2. ,' supply pipe 4 for fresh steam is connected to -the preheater 3, to heat the chips at least during the starting phase of the defibration process. The chips heated to defibration tempèrature are fed b~ a further screw conveyor 5 into the pulper 2. The pulp produced in the pulper is taken o~f together with steam both supplied to, and generated in the pulper by means of an ejector 6, the suction side 7 of which is connected to the outle-t ~ of the pulper.
The driving ~low of the ejector consists of steam, and the merging flo~s departing from the ejector outlet 9 thus consist of pulp and steum, ~hich are conveyed by the ejector to a separa-tor lO~ to the inle-t 11 of which the ejector outlet 9 is connected by means of a pipe. The separator consists of two serie~-coupled cyclone collectors 12. ~;
The pulp separ~ted from steam in the collectors 12 i9 talcen off by discharging equipment for use in a conventional manner~ this equipment being of a kind such that the disch ~-ge ends 13 of the collectors are kept pressure-tight, so that the latter can be pressurized~
The steam liberated from pulp is taken from the gas outlet 14 of the last collector 12 via a pipe to the suction side of a fan 15, the pressure side of which is connected by a further pipe to the inlet 16 of t~e ejector 6 for the driving flow.
The ejector 6~ separator 10 and fan 15 thus participate in a ciculation circuit in a closed system in which the separa-tor is also pressurized to the same order of magnitude as the pulper. The driving flow of the ejector consists of steam separated from the pulp~ talcen from the separator 10 and given the required pressure - : ':..

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~ 3 ~ ~ S7 boost by the fan 15. The supply of fresh steam via the pipe 4 can be varied~ usually reduced, after a starting phase~ steam for heating in the preheater 3 being taken instead from the circula-tion circuit via the pipe 17. The grinding energy in the pulper generates an excess of steam from the ~ioisture in the chips ~hich, due to the whole system being put under pressure, can be taken off a-t high pressure and -temperature via a further pipe 18~ the apparatus in accordance with the inven-tion thus bcing able to serve as a source of energy for many different purposes.

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Claims

1. A method in defibrating wood chips in steam, where the pulp produced is conveyed from a pulper (2) to a separator (10) for separating pulp and steam, characterized in that a flow of steam which has been separated from the pulp is taken from the separator (10), is given an increased pressure and supplied as a driving flow to an ejector (6), the ejector being used for removing a flow of pulp and steam from the pulper, both said flows merged in the ejector being supplied to the separator (10), which is kept pressurized by the steam by separating it from the atmosphere, while a limited amount of excess steam is taken off and refluxed to a chips preheater (3) connected to the pulper (2) and/or is used as a source of energy for other purposes.

2. Apparatus arranged for carrying out the method according to claim 1, and comprising a pipe connection between a pulper (2) and a separator (10), which is arranged for separating pulp and steam received from the pulper, characterized by a pressure -increasing conveying means (15) for steam, e.g. a fan, said pressure increasing means having its suction side connected to the steam outlet (14) of the separator (10), and an ejector (6), the pressure increasing means (15) having its pressure side connected to the ejector inlet (16) for a driving medium, while the ejector inlet (7) for a conveyed medium is connected to the pulper outlet (8) for pulp and steam, and the ejector outlet (9) is connected to the separator inlet (11), the circuit formed by the pressure-increasing means (15), ejector (6), separator (10) and intermediate connecting pipes constituting a closed system, in which the separator (10) is also kept pressurized by the steam by adjusted bleeding-off of excess steam, which is refluxed to a chips preheater (3) connected to the pulper (2) and/or is used as a source of energy for other purposes.