US2655436A - Tank reactor - Google Patents

Description

Oct. 13, 1953 c BISHOP ETAL 2,655,436

TANK REACTOR Filed July 26, 1949 IIIIIIIIIII II Patented Oct. 13, 1953 2,655,436 TANK REACTOR Charles A; Bishop and Thomas-F. Reed; Mount Lebanon}. Pm; assignors td United States Steel G'orp'ora'tiomai corporation of New J el'sey Appliatitii .fiiiy 2t, 1949, seriarN't'. 106,946

dzGlaimfi:

This invention teie tes t apparatus fortrating ifnsaltisolutioris" and more partieu rly teapp'aratiis'fi for treating" wa te pickle ut er toolitain a black granular ir'bn oxide; airsan" ammeiiiun'i.saitsubstaiitieuy free from net. The em 'r qisp os ng or waste pickle liquor has ex d for many ars andunany prbpo'sedsoluti he have been varie'ed'; However, none of l" iorrnerprdc'esses have proved to be" come1 successful; In some instances; the cost of equipment is exaeseiyeor the operation isso slowthat th space requirements for the equipexcessive. In other instances the end pro et of the process is such that it" cannotbe re dily disposed; of. Theidealprocess wouldbe one in which tll cost" Ofljhe equipment is not excessive and in which the value of the end products is such that they can be disposed of at aprofit. Such a process is described in the pending application to Robert G. Thompson, sriarNo. 83,227, filed March 24,1949; The apparatus of'this' invention issuitable for carryihg out the Thompson process and is described in the Thompson application. Such apparatus can" also bens ed in carrying out theprocess describecl' in Wilson, Patent No. 2,419,24U; dated .ipr'iliZZg lQ'l. H U i t is" therefore an. obJ"ector ou jityntiofi to provide apparatus particularly adapted for efficiently treating ironsalt solutions p This and other objects-will be ndreapparent after referring to the followingd'esei'iption and attached drawings, in which:

Figure 1 is a perspective view of apparatusfor eel- 17m out our invention with parts thereof broken away; H

Figure 2'i's a plan view of a cehtricone impeller; Figure Bis a sectional view taken on the-line IlI III'of Figure 2 H figure 4 is a plan View of a turbineimpeller; dl v figure 5'is asideelevationof Figure 4. v

Referring more particularly to the drawings,

the reirence numeral 2 indicates'a vertical tank,

having a shaft 4 having its bottom and resting in 8; bearing sun the bottom of the ta'nk and its top end; ext nding through anti-friction thrust bearing 8 in-the top of the tank. The

shaft H's rotated fromamoto'r ll) through a gear reducer l2 and a set of bevelled gears l4. Two opposed centricone impellers l6 are fasedflto thelower butt of the shaft}; A turbine iznpelle'r l8 mounted on the shaft 4 a short distaste abovefthe to impeller I6 prevents th forniation or a vertex at the toper the tank.

A plurality o'f fvertical bafiies l9 are provided on the" tank wallsto aid agitation. A plurality of ammonia inlets are provided near the bottom of the tank and are distributed around the. peripheryof the tank so as to avoidhigh local concentrations of the ammonia. A piureutyer pickle liquor inlets 22' and a steam inlet- 24- are also provided at the bottom of the tank adjacent the ammonia inlets 20. Located between the two centricones l6 are e plurality of. air inlets 26 arranged around the periphery the tank. An outlet 28; for the treated: iiquia is provided a short distance below the top of the tank. Located adjacent; the top of'thetanK is an ammonia absorb'erto'wer 3tliwlii'chtis Dajcked with eeramie Raschig rings. The bott'tmerjtue tower to is eonne eted to the top or tank; iiby means of a pipe 32. Waste pickl liquor is fed to the towerfilrthroiigh a pipe at. A this. leads from the bottom or tower 3o; tdttie acid inlets 22: err exhaust 3a is prttidea the top of the tower. 30. Cooling coils 40 are provided to aid in maintaining the proper reaction temperature.

Incarrying out the process described in the above identified Thompson application, the tank his first filled with water slightly abovethe top of upper; impeller 16', after which the meter. HI is started so as to rotate shaft 4' and the inipellers thereon. Steaih is introduced through pipe 24 until the, temperature or the water is betwee 1 and 160 F. are the iiiakiiiium amount of an s introduceiti thrbliglitlie nlets 251 Arhmoriiais fed into the tank until the water therein contains atlast one era-m t monia per liter, after which the flow of'p'ibl'rle liquor at the operating rate is started. The flow of ammonia iscontinued at a rate in excess of the stoichiometric amount correspohdin'gtdthe analyses andifee'd rate of the pic le lidu'o, The ebeve deseribe'd steps are continued. until; the tank 2 is filled. t0. the outlet pibe At this tiine the tegiiterature off the liquid, will. b Betweeii P' and F., theratib betweer'i 'f erific and ferrous iron will be at least 2.2, the pH. value will beat least 8.4. Continuous etera tionof the process istl'ien star-ted.

While it. is preferred to operate the; process ata temperature between 150? and 160 F. iiperience has shown that the process can operate satisfactorily m a temperature range between 140 and. Heat is developed by the reaction in the tank 2, and therefore it :fiiay be necessary to use the cooling coils 40 to pretest the temperature from rising too high. The air delivered into the tank aids the impellers l6 and I8 in agitating the bath, thus providing for more eincient reaction; and also oxidizes part of the iron originally present in the ferrous state to the ferric state. This is necessary in order to have at least 50% of the total volume of oxide produced settle within 2 /2 minutes. Any slower settling rate will not be commercially acceptable. In order to have a commercially salable product, the total iron content in the filtrate should not exceed .05 gram per liter. To determine the iron content, speciments of the filtrate are sampled and a few drops of hydrogen peroxide are added thereto. If an orange precipitate forms, the product will be unsatisfactory. The effect of the ferric to ferrous iron ratio. on the efliciency of the method can be seen in the following table:

TABLE NO. I

Time for Ferric :ferrous ratio 50% setfi i tling, min. m 9

Present.

Do. Do. None.

Do. Do.

TABLE NO. II

Fe content PH 111 filtrate Present.

None.

Do. Do.

.It has been found that an ammonia content of at least 1.5 grams per liter and a pH value of at least 8.4, other conditions being constant, lowers the iron content of the filtrate below the permissible maximum.

In brief, the operation of the continuous process is as follows:

Into a solution of waste pickle liquor and ammonia having a pH value of at least 8.4 is continuously delivered ammonia and waste pickle liquor with the ammonia being admitted in an excess over the stoichiometric amount necessary to react with the waste pickle liquor being admitted. The solution is agitated by means of the impellers l6 and 18 as well as by the air being introduced into the system. The air also oxidizes the iron in order to obtain the desired ferric to ferrous iron ratio of between 2 /2 to 1 and 6 to l in the precipitate. The temperature of the solution is maintained between 140.and 170 F. The treated liquid is continuously removed from the tank 2 through the opening 28 and the iron oxide is allowed to settle out therefrom. The operation is controlled by testing 4 the resulting efliuent to determine if the amount of excess ammonia is at least 1.5 grams per liter and preferably between 1.5 and 5 grams per liter and the precipitate is tested to determine whether the ratio of ferric to ferrous iron therein is at least 2.2 and is preferably between 2.2 to 1 and 6 to 1. Under these conditions the operation of the process will be such that the settling rate and the purity of the eflluent is that desired. Even though the conditions are slightly outside of these ranges the process will still operate successfully. However, any test result outside these ranges indicates that the conditions in the tank 2 are progressively becoming worse and that soon an unsatisfactory product will be obtained. Therefore, if the tests show that the desired conditions are not present, the feed rate of the pickle liquor and/or the ammonia is changed so that the control conditions will be met. Thus, by this method of control, departure from the desired product is anticipated and the conditions controlled to prevent unsatisfactory products from being produced. The efiluent and precipitate are then treated in a conventional manner to obtain crystalline ammonium sulphate and dry magnetic iron oxide. Air leaves the tank 2 through the tower 30 and is stripped of ammonia therein by the raw pickle liquor entering the tower 30 through pipe 34. The air escapes to the atmosphere through the outlet 38 and the pickle liquor partly neutralized by the ammonia is introduced through pipe 36 into the tank 2.

While one embodiment of our invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

1. Apparatus for treating iron salt solutions comprising a tank, a shaft extending vertically through said tank, means for rotating said shaft, a pair of opposed centricone impellers fastened to the lower part of said shaft, the small diameter ends of said centricone impellers being adjacent each other with a space therebetween, a turbine impeller fastened to said shaft above said centricone impellers, a plurality of ammonia inlets near the bottom of the tank around the periphery thereof, a plurality of iron salt inlets adjacent the ammonia inlets, a plurality of air inlets around the periphery of the tank at a level between the centricone impellers, and an outlet from said tank a short distance below the top thereof. 7

2. Apparatus for treating iron salt solutions comprising a tank, a shaft extending vertically through said tank, means for rotating said shaft, a pair of opposed centricone impellers fastened to the lower part of said shaft, the small diameter endsof said centricone impellers being adjacent each other with a space therebetween, a turbine impeller fastened to said shaft above said centricone impellers, a plurality of air inlets around the periphery of the tank at a level between the centricone impellers, 'anoutlet from said tank a short distancebelow the top-of the tank, an ammonia absorber tower adjacent the tank, a connection between the top of the tank and the tower, and means for separately introducing iron salt solutions and ammonia into the bottom of said tank. 7

3. Apparatus for treating iron salt solutions comprising a tank, a shaft extending vertically through said tank, means for rotating said shaft, a pair of opposed centricone impellers fastened to the lower part of said shaft, the small diameter ends of said centricone impellers being adjacent each other with a space therebetween, a turbine impeller fastened to said shaft above said centricone impellers, a plurality of ammonia inlets near the bottom of the tank around the periphery thereof, a plurality of iron salt inlets adjacent the ammonia inlets, a plurality of air inlets around the periphery of the tank at a level between the centricone impellers, an outlet from said tank a short distance below the top of the tank, an ammonia absorber tower adjacent the tank, a connection between the top of the tank and the tower, and a conduit leading through said tower to said iron salt inlets.

4. Apparatus for treating iron salt solutions comprising a tank, a shaft extending vertically through said tank, means for rotating said shaft, a pair of opposed centricone impellers fastened to the lower part of said shaft, the small diameter ends of said centricone impellers being adjacent each other with a space therebetween, a turbine impeller fastened to said shaft above said centricone impellers, a plurality of vertical bafiies fastened to the walls of said tank, a plurality of ammonia inlets near the bottom of the tank around the periphery thereof, a plurality of iron salt inlets adjacent the ammonia inlets, a plurality of air inlets around the periphery of the tank at a level between the centricone impellers, an outlet from said tank a short distance below the top thereof, an ammonia absorber tower adjacent the tank, a connection between the top of the tank and the tower, and a conduit leading through said tower to said iron salt inlets.

CHARLES A. BISHOP. THOMAS F. REED.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 612,317 Dundon Oct, 11, 1898 1,097,785 Wolf May 26, 1914 1,949,696 Schoneborn Mar. 6, 1934 2,019,325 Stone et al. Oct. 29, 1935 2,063,789 Burk Dec. 8, 1936 2,133,267 Ayers Oct. 18, 1939 2,182,078 Fleming et al. Dec. 5, 1939 2,254,127 Underwood Aug. 26, 1941 2,361,503 Schutte et a1 Oct. 31, 1944 2,450,174 Weinrich et al. Sept. 28, 1948 2,542,031 Humfeld Feb. 20, 1951

Claims (1)

1. APPARATUS FOR TREATING IRON SALT SOLUTIONS COMPRISING A TANK, A SHAFT EXTENDING VERTICALLY THROUGH SAID TANK, MEANS FOR ROTATING SAID SHAFT, A PAIR OF OPPOSED CENTRICONE IMPELLERS FASTENED TO THE LOWER PART OF SAID SHAFT, THE SMALL DIAMETER ENDS OF SAID CENTRICONE IMPELLERS BEING ADJACENT EACH OTHER WITH A SPACE THEREBETWEEN, A TURBINE IMPELLER FASTENED TO SAID SHAFT ABOVE SAID CENTRICONE IMPELLERS A PLURALITY OF AMMONIA INLETS NEAR THE BOTTOM OF THE TANK AROUND THE PERIPHERY THEREOF, A PLURALITY OF IRON SALT INLETS ADJACENT THE AMMONIA INLETS, A PLURALITY OF AIR INLETS AROUND THE PERIPHERY OF THE TANK AT A LEVEL BETWEEN THE CENTRICONE IMPELLERS, AND AN OUTLET

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