US1961351A - Art of manufacturing pulp - Google Patents

Description

`lune 5, 1934. A GUS-rm v1,961,351

ART OF MANUFACTURING PULP Filed May 25, 1929 2 Sheets-Sheet l /J TTORNEVS June 5,-1934."' A. GUSTIN ART oF MANUFACTURING PULP Filed May 2:5, 1929 2 Sheets-Sheet 2 ILVE.

m m m F /Nl/ENTUR /7//70/1/ 6//57//1/ BY A TTOR/VE YS W J TNESS ff Patented June 5, 1934 PATENT OFFICE ART OF MANUFACTURING PULP Anton Gustin, Oconto Falls, Wis., assignor to Continental Paper & Bag Corporation, New York, N. Y., a corporation of Delaware Application May 23, 1929, Serial No. 365,280

2 Claims.

This invention relates to the art of manufacturing pulp, and more particularly to the pulp washing and the liquor recovery system of such art.

In the manufacture of paper by the sulphate process, for instance, it has been the common practice to discharge cooked pulp from a digester to a diffuser where the pulp was freed from cooking liquor and was washed with large volumes of hot water. The cooking liquor separated from the pulp in the diffuser was recovered in a recovery system for economical and commercial operation of the pulp-making process.

In the recovery system the cooking liquor was first pumped to the so-called black liquor storage tank which acted as a reservoir for feeding the rest of the system. The black lliquor was fed from the storage tank to an indirect evaporator which removed some of the water from the liquor.

A29 The concentrated liquor then flowed to a second black liquor storage tank which fed a disc type of evaporator wherein further concentration of the black liquor occurred. After treatment in the disc evaporator the black liquor was pumped 25 into a rotary incinerator which was heated by hot flue gases coming from a smelt furnace and which evaporated'the black liquor to a powdered form containing a large percentage of combustible material.

The powdered material, commonly called black ash, was fired into a smelt furnace in admixture with salt cake which acted as the make-up of sodium sulphate. AIn case supplementary fuel was needed it was fed in with the aforesaid mixture. In the smelt furnace, as is well known, the combustible material burned and caused in the mixture a chemical reaction, which involved the formation of sodium sulphide and sodium carbonate. These materials melted and fell to the bottom of the smelt furnace where they were drawn off through a smelt spout.

The smelt containing sodium sulphide and sodium carbonate was spouted into a dissolving tank which was partially lled with water. After sufncient sodium sulphide and sodium carbonate were dissolved in the water to form a liquor of a certain density, the liquor thus formed was pumped to a causticizing system.

The heat generated by the smelt furnace was in excess of that which was actually required therein. This excess heat was, therefore, utilized in the rotary incinerator for producing black ash and in the disc evaporator for concentrating the black liquor to a density suitable for use in the incinerator. In order to conduct the hot waste (c1. zs-is) gases from the smelt furnace to the rotary incinerator an arch made of soapstone was provided at the top of the furnace. As is well known, this soapstone arch was very unsatisfactory in practice and was continually failing due to the high temperatures and deteriorating influences to which it was subjected. Many attempts have been made to remedy this objectionable soapstone arch and to avoid the necessity and difficulty of maintaining in working order but none, as far as I am aware, has proven to be satisfactory and successful in commercial operation.

I have discovered aV structure which overcomes the disadvantages noted hereinabove and which provides a simple, economical and practical structure in which cooking or digesting liquor can be recovered.

It is also within the contemplation of the present invention to provide an improved process and apparatus wherein the washing of paper pulp and the recovery of liquor can Vbe conducted in an erlicient, economic and practical manner.

A further object of the present invention is to provide a washing and recovery system which is reliable, which is relatively free from shutdowns due to breaking or furnace arches and -the like, and which economizes heat while at the' same time preventing critical parts of the recovery furnace from becoming overheated.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, in which:-

Fig. 1 represents a diagrammatic illustration of a pulp washing and liquor recovery system embodying my invention;

Fig. 2 is an elevation, partly in section, of my improved smelt furnace depicted in Fig. l;

Fig. 3 illustrates an end elevational view of Fig. 2; and

Fig. 4 is a top plan view of the furnace shown in Fig. 2.

' Referring more particularly to Fig. l, the numeral l designates a diffuser which receives pulp that is blown in through pipe line 2 from well known digesters (not shown). The pulp collects in the diffuser 1 on a false bottom 3 located in the lower portion of the diffuser so that it is possible to remove the cooking liquor from the pulp. The liquor is displaced from the diffuser by pumping hot water under pressure from hot water tank 4 by means of pump 5 into the top 6 of the diffuser through pipe line "I. The pumping of hot water into the diffuser is continued until 'the pulp is freed vfrom cooking lil() liquor. This operation of displacing cooking liquor from the diffuser and of washing the pulp free of cooking liquor requires, as is well known, relatively large volumes of hot water.

Connected to the bottom of the diffuser is a discharge line 8 which conducts the cooking liquor displaced from the diffuser and washed from the pulp to a so-called black liquor storage tank 9 which acts as a supply reservoir for feeding an indirect evaporator 10 via pump 11 and pipe lines 12 and 13. The indirect evaporator is supplied with steam from a suitable source and is effective for evaporating water from the black liquor so as to concentrate the liquor to a desired density. Although only one evaporator is illustrated a series of two or more evaporators may be used.

After the black liquor has been concentrated to desired or pre-determined density in the evaporator 10, the concentrated black liquor is discharged through pipe 14 into a second black liquor storage tank 15 which supplies a disc evaporator 16. This disc evaporator as is well known, consists essentially of a series of sheet discs rotating in a body or pool of concentrated black liquor to a certain depth. Each of the rotating discs carries a lm of liquor on the surface thereof where a portion of the water content of the liquor is evaporated by the action of hot flue gases which ow in contact therewith in passing through the disc evaporator. These gases enter through an inlet channel 17 and leave via an outlet ilue 13 which leads to a stack (not shown).

The concentration of liquor in the disc evaporator is controlled by a valve 19 located in pipe line 20 on the discharge side of pump 2l. The black liquor removed from disc evaporator via outlet line 22 is either returned thereto if the density of the liquor is not heavy enough or pumped to a rotary incinerator 23 if the liquor has the desired density.

In rotary incinerator 23 the black liquor is heated to such an extent that the liquid present in the liquor is evaporated and a black powder is produced. This powder known as black ash, contains a large percentage of combustible material and is discharged from Vthe incinerator via outlet 24 to a suitable receiver 25. The heat used to produce the black ash may be supplied in any suitable way but I prefer to utilize the heat of the hot flue gases generated in smelt furnace 26.

Make-up sodium sulphate, commonly known as salt cake, and carbonaceous fuel, if required, are red with the black ash from receiver 25 into smelt furnace 26 through a firing port 27. The mixture falls through furnace 26 as a burning mass wherein a chemical reaction occurs. The mass of material falls to the bottom 28 of the furnace in a molten condition. The molten material, usually called the smelt, consisting principally of sodium sulphide and sodium carbonate is Withdrawn from the furnace via spout 29.

The hot gases generated in the smelt furnace rise to the top of the furnace from whence they are conducted to the interior of the incinerator. Heretofore, a soapstone arch and lue were used to close the upper part of the furnace and to make a connection with the incinerator. Due to the deteriorating eifect of the hot gases the soapstone arch and flue were breaking down and failing. Great diflculty has been experienced in attempting to maintain the soapstone arch and flue in an operating condition. I have found that the effective cause of the aforesaid deterioration was an accentuated thermal condition in the hot gases.

To overcome this condition I have devised a new structure which is a remedy to the situation and which is effective in overcoming prior defects without detrimentally affecting the heating value of the hot ilue gases or their power to perform their intended function in the rotary incinerator and in the disc evaporator. The new structure as will be explained in more detail hereinafter consists essentially of a metal arch and flue 30 and a hood 31 enveloping said arch and iiue so as to provide a chamber 32 through which a tempering fluid is passed. In my preferred embodiment I utilize clean water as the tempering fluid and introduce the water in the lower part of chamber 32 via pipe line 33. The water in passing through the chamber tempers the hot ilue gases by reducing their temperature to a restricted degree and in turn acquires heat which raises its temperature. The rate at which the water is passed through the chamber is controlled and regulated so that the water becomes hot enough for use as the water to displace the liquor from the diffuser and to wash the pulp therein'whereas the hot flue gases are tempered to such a degree that they have no deV teriorating influences on the structures with which they contact, but nevertheless the hot gases still possess suflicient heating value to effect the conversion of black liquor into black ash by treating the liquor in the disc evaporator and rotary incinerator. The heated water leaves chamber 32 through an outlet 34 at the upper part of the chamber and iiows to the hot water tank 4. By this procedure it is possible not only to temper the gases and to strip them of their deteriorating activities, but also to provide hot water for use in displacing the liquor from the diffuserand in washing the pulp therein.

The smelt containing sodium sulphide and sodium rcarbonate runs from the spout 29 of the furnace 26 into a dissolving tank 35 which contains a pool of water. The solution formed by the dissolution of sodium sulphide and sodium carbonate in the water is then pumped to the causticizing system and is Ytreated in a well-known manner.

lustrated more particularly in Figs. 2 to 4. The reference character 50 designates the body of smelt furnace 26 which is constructed in the customary manner upon foundations 51. The top of furnace is covered with an arch 52 which is built of refractory material. This arch is provided `with an outlet port 53, which communicates with metallic flue 30. The terminal end of Iiue 30 projects into the rotary incinerator 23 so that an efficient passage of the hot gases from the smelt furnace to the rotary incinerator is secured. I

Enveloping ilue 30 is a hood 31 which forms therewith a sealed chamber 32. This chamberV is preferably extended to the terminal end of flue 30 so as to provide protection for the latter. Communicating with the lower portion of chamber 32 is a water inlet 33 and with the upper portion a water outlet 34. By passing water into inlet 33, chamber 32 is practically filled and the entire ilue including its terminal end is surrounded with a protective body of water. As the water takes up heat it rises and then leaves the chamber via outlet 34. As explained heretofore the action of my improved procedure is to protect the ue from deterioration and destruction while' at the same time providing hot water from the diffuser Without detrimentally affecting the hot furnace gases or interfering with their intended Asmelt furnace embodying my invention is ilfunction in the rotary incinerator and disc evaporator.

It will be observed that my invention provides an improved process in the art of manufacturing pulp which involves separating and washing cooking liquor from digested pulp and recovering the said cooking liquor. This liquor is recovered in a system which includes disc evaporating and incinerating the liquor to black ash by heat, converting the black ash with salt cake into a smelt containing sodium sulphide and sodium carbonate in a smelting operation involving the production of hot flue gases at an aocentuatedly high temperature, passing the said hot flue gases from the smelting step to the disc evaporating and incinerating steps and utilizing the heat of said hot flue gases to effect the conversion of cooking liquor into black ash in said disc evaporating and incinerating steps. Between the smelting and the incinerating operations subjecting the hot ue gases at an accentuatedly high temperature to tempering treatment With Water via a heat transfer Wall and regulating said tempering treatment to reduce the accentuatedly high temperature of said hot iiue gases to such a degree that the said gases will not possess destructive and deteriorating qualities but will retain sufficient heating value to effect their intended function in the disc evaporating and incinerating steps.

I claimt- 1. In the process of recovering values from pulp cooking liquor, the steps comprising firing black ash in a furnace having an internal Water chamber positioned above the bed of the furnace, introducing Water into said chamber in regulated amount determined by the heat developed in said furnace, heating Water with the hot gases developed from the firing of the black ash and simultaneously Water-cooling the furnace Walls surrounding saidrchamber, conveying the hot Water away from said furnace, subjecting the liquor to the action of said hot Water, conveying the resultant black liquor to an evaporator and exposing it to the indirect action of steam, moving the liquor towards said furnace and simultaneously giving said liquor a rotary motion, exposing the black liquor to the action of said gases While the gases are passing in the direction opposite to the direction of travel of the liquor and heating the black liquor With said gases to reduce it to black ash, introducing the black ash into the furnace and firing said black ash.

2. In the process of recovering values from pulp cooking liquor, the steps comprising firing black ash in a furnace having an internal Water chamber positioned above the bed of the furnace, producing hot gases in the furnace, continuously subjecting fresh Water in said chamber to the heating action of said gases to cool the chamber Walls and heat the fresh Water, continuously drawing hot water from said chamber, subjecting the liquor to the action of the said hot Water, subjecting the resultant black liquor to indirect heat, leading said hot gases through a predetermined path tovvard an exhaust outlet, exposing said black liquor, in the form of a film, in proximity to said exhaust outlet to said gases to concentrate said liquor While said gases are moving in the direction opposite to the direction of movement of said liquor and incinerating said concentrated liquor to reduce it to black ash, introducing said black ash into the furnace and forthwith firing the same.

ANTON GUSTIN.

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