Process for cleaning fouled heat exchangers

Heat exchangers which become fouled during cooling of CuAlCl.sub.4 .multidot.solvent (such as toluene) solutions employed in extracting carbon monoxide from acetylene is cleaned by circulating through the fouled exchanger a solvent solution of CuAlCl.sub.4 .multidot.solvent containing aluminum trichloride.

SUMMARY OF THE INVENTION 
The present invention is directed to a process for cleaning heat exchangers 
which become fouled during the extraction of carbon monoxide or 
hydrocarbons from mixed gaseous streams containing same with a solvent 
solution of CuAlX.sub.4. solvent. 
BACKGROUND OF THE INVENTION 
The use of cuprous aluminum halide (CuAlX.sub.4) as a complexing agent in 
recovering carbon monoxide, aliphatic or aromatic hydrocarbons from 
gaseous streams containing same have been described in U.S. Pat. Nos. 
3,592,865; 3,647,843; 3,651,159; 3,754,047 and 3,755,487. 
In processes which employ cuprous aluminum halide.solvent sorbent solutions 
to extract carbon monoxide or aliphatic or aromatic hydrocarbons from 
streams containing same there is a tendency, particularly when the 
solution of complexing agent becomes contaminated with water, for a black 
"gunky" scale to form on the walls of the heat exchanger. This ultimately 
causes a loss in efficiency of the heat exchanger, i.e. a drop or decrease 
in the temperature differential, .DELTA.T, between the outlet and inlet of 
the exchanger. Heretofore, this scale or "gunky" material (a mixture of 
tars and cuprous halide) has been removed by hydroblasting, e.g., 
contacting with water or steam under high pressure. Such is undesirable 
because care must be exercised to remove the residual water before placing 
the exchanger back in service. The process of the present invention 
represents an improvement over the hydroblasting method for the following 
reasons: (1) maintenance costs are reduced, (2) less exposure of 
maintenance personnel to the sorption agent, (3) less down time since this 
method is faster than hydroblasting and (4) there is no solvent 
degradation due to residual water which could result from hydroblasting. 
Some of the above noted disadvantages to the hydroblasting can be solved by 
the present invention.

DETAILED DESCRIPTION OF THE INVENTION 
In the process of the present invention heat exchangers which become fouled 
as a result of passing therethrough a sorption fluid containing a solvent 
solution of cuprous aluminum tetrahalide (cuAlX.sub.4).solvent are cleaned 
by circulating through the heat exchanger a solvent solution of 
CuAlX.sub.4.solvent containing AlX.sub.3 wherein X is chlorine, bromine, 
fluorine or iodine such that the fouled portion thereof is contacted with 
the solution. 
While it is not known the exact mechanism by which the fouling is removed, 
it is believed to be due to a chemical reaction between the aluminum 
trihalide and the cuprous halide to form cuprous aluminum 
tetrahalide.solvent according to the reaction 
EQU CuCl + AlX.sub.3 .sup.solvent CuAlX.sub.4.solvent 
which tends to loosen the "gunky" material and permit it to be carried away 
and which can subsequently be removed from the solvent containing the 
complexing agent CuAlX.sub.4. solvent by filtration, centrifugation, 
decantation or other known methods. 
In the drawing, a gaseous stream containing CO, N.sub.2, H.sub.2, CO.sub.2 
and C.sub.2 H.sub.2 is fed via line 10 into an absorber 11 wherein said 
stream is counter currently contacted with a toluene solution of 
CuAlCl.sub.4.toluene as a sorbent or complexing agent. A stream containing 
CO rich solvent is removed from the absorber 11 via line 13 wherein it 
passes through a crossexchanger 14 into stripper 15 wherein the CO is 
removed via line 16. The lean toluene solution containing the complexing 
or sorption agent, CuAlCl.sub.4.toluene, is removed from stripper 15 via 
line 17 through crossexchanger 14 into an air cooler 18 containing a 
plurality of finned tubes and from there via line 19 into absorber 11 thus 
completing the cycle. Pumps, flow controllers, and other equipment are 
obviously not shown. 
The sorbent solvent solution to which the aluminum halide is added can 
contain from about 20% to about 80%, preferably from about 40% to about 
70% of CuAlX.sub.4.solvent complex by weight. 
The amount of aluminum halide which can be added to the sorbent solvent 
solution can be from about 1% to about 15% preferably from about 8% to 
about 10% by weight based upon the combined weight of aluminum halide plus 
sorbent solvent solution. 
In practicing the present invention, the sorbent solution containing the 
AlX.sub.3 can be circulated through the fouled heat exchanger at 
temperatures of from about 0.degree. C to about 50.degree. C preferably 
from about 20.degree. C to about 40.degree. C for a time sufficient to 
reduce the amount of fouling to the extent possible, i.e., further 
treatment would no longer remove any additional quantities of fouling, or 
the fouling is removed to the extent desired. 
The higher the temperature the less time is required to remove a like 
quantity of fouling from the exchanger or more fouling can be removed for 
a like period of time of treatment. 
The following examples are illustrative of the invention but are not to be 
construed as to limiting the scope thereof in any manner. 
EXAMPLE 1 
One of the finned tubes from the air cooler 18 shown in the drawing 
measuring approximately 1-inch by 12-inches which had become fouled during 
operation of the CO extraction process was cleaned by circulating through 
the tube at a rate of about 1 gallon per minute of a toluene solution of 
CuAlCl.sub.4.toluene containing 10% AlCl.sub.3 by weight, said toluene 
solution containing 10% CuAlCl.sub.4. toluene by weight of solution. After 
20 hours, visual inspection of the tube indicated the removal of 
essentially all of the fouling from the tube. 
EXAMPLE 2 
During one operation of the process shown in the drawing, after cleaning 
the air cooler 18 by hydroblasting, the inlet and outlet temperatures were 
90.degree. C and 40.degree. C respectively. When the outlet temperature 
had reached 74.degree. C, a solution containing 600 lbs of AlCl.sub.3 in 
10,037.65 lbs of a toluene solution of CuAlCl.sub.4.toluene (containing 
0.65 lb of CuAlCl.sub.4.toluene per lb of solution) was circulated through 
the air cooler at ambient temperature (about 23.degree. C) for 96 hours. 
When the air cooler was placed back into operation, the inlet and outlet 
temperatures were 90.degree. C and 51.degree. C respectively. 
The above example indicates that approximately 67% of the fouling had been 
removed calculated on the temperature differential as follows: 
outlet temperature of cooler before fouling: 40.degree. C 
outlet temperature of fouled cooler: 74.degree. C 
outlet temperature of cooler after cleaning by method of this invention: 
51.degree. C