Method for introducing a first fluid into a second fluid, preferably introduction of steam into flowing cellulose pulp

#The invention concerns an apparatus for introducing a first fluid into a second fluid which is flowing in a pipe, which apparatus consists of a pipe-shaped body with a through-flow channel for the said second fluid of essentially constant cross-sectional area, one or more chambers which extend round at least the majority of the circumference of the through-flow channel along at least a part of its longitudinal extent, a connection for supplying the first fluid to the said chambers from a pressure source, in which a series of through-holes is arranged in the said pipe-shaped body in the region of the said one or more chambers, through which holes the first fluid can be directed into the second fluid which is flowing through the said through-flow channel under the influence of the difference in pressure between the said chambers and the said through-flow channel.

#The invention is advantageously applied to the admixing of steam into a flow of cellulose pulp.

#Apparatuses of the type mentioned above are known, see for example SE 468 341 and SE 502 393. The apparatus described in SE 502 393 is used primarily as a mixer in the bleaching departments in the cellulose factories for the admixing of steam into a pulp suspension in order to raise its temperature to a level which is required to ensure that a specific reaction takes place with the desired speed in a subsequent bleaching step. The apparatus can give good admixing of steam into the suspension, but it is difficult to control the quantity of steam needed for temperature control without reducing the effectiveness of the admixing at the same time. The steam admixing is regulated conventionally by means of a valve in the steam pipe to the said chamber. However, as the steam supply is throttled to reduce the steam introduction, the pressure in the chamber also falls and hence also the pressure difference between the inside of the chamber and the pulp suspension in the pipe. This implies, in turn, a reduction in the speed of the steam, as it enters the pulp through-flow pipe, and thereby also the penetration of the steam into the pulp suspension.

#In the following description of a preferred embodiment reference is made to the appended drawings, in which:

#FIG. 1 is a side view of the apparatus according to the invention mounted in a pipe, and

#FIG. 2. shows selected parts of a side view of the apparatus, partly in cross section and with certain parts omitted.

#The apparatus, which shall be described in the following, is developed and designed to be used for the admixing of steam into a suspension of cellulose fibres (pulp) in a pipe conveying the pulp into a cellulose factory bleaching department in order to preheat the pulp to a specified temperature suitable for a subsequent bleaching stage. However, the principle of the invention can be used also for equipment for the admixing of fluids other than steam into a second fluid, e.g. admixing of gases, such as oxygen, chlorine gas and possibly also ozone, or for admixing of a liquid, such as e.g. a pH adjusting liquid, chlorine dioxide or other treatment liquid or diluting liquid into the said second fluid, which need not necessarily be a pulp suspension.

#Referring firstly to FIG. 1, an apparatus according to the invention is labelled generally with the number 1. This is arranged in a pipe 2 for a pulp suspension, which, in the example as shall be described here, has a fibre content of medium consistency, MC i.e. a dry substance content of 5-20%, preferably 8-16%. The conveying pipe 2 extends from an MC pump (not shown) to a treatment vessel (not shown) in a bleaching department. The example shows a peroxide step. The task to be carried out by means of the apparatus 1 is to preheat the pulp suspension by means of steam in the conveying pipe 2 to a temperature suitable for the bleaching process, for example about 100° C. The flow rate of the pulp in the pipe 2 is about 5-15 m/s. A steam injection pipe labelled 4 brings steam under pressure from a pressure source (not shown) into the apparatus 1. There is a throttle valve 5 in pipe 4.

#A central, first element in the apparatus is labelled 10. This first element 10 consists of a circular cylindrical, pipe-shaped part referred to as pipe body in the following. The pipe body has the same internal diameter as the upstream pipe 2A to which the pipe body is joined. The inside of the pipe body, defined by the inner walls, forms a through-flow channel for the pulp which is being conveyed in the pipe 2. For installing the apparatus 1 in pipe 2 a first flange 11, and a second flange 12 are provided respectively. The first flange butts against a downstream wall 13 of a chamber 14 for the steam, which chamber is described in more detail in the following. The other flange 12 butts against flange 16 which is located in the upstream end of the pipe body 10. Flange 11 and wall 13, as well as flange 12 and flange 16 respectively are joined to each other with bolts in the conventional way.