Disclosed is a novel process for cleaning and restoring the operating efficiency of organic liquid chemical exchangers in a safe and effective manner and in a very short period of time, without a need to disassemble the equipment and without the need to rinse contaminate from the equipment after cleaning. Used is a formulation of monocyclic saturated terpene mixed with a non-ionic surfactant package specifically suited to oil rinsing. The terpene-based chemical is injected into organically contaminated exchangers using a novel process involving high-pressure steam to form a very effective cleaning vapor.
1. A method of cleaning a contaminated vessel, comprising the steps of:
providing a steam source;
providing a surfactant source;
providing a organic solvent source comprising a terpene;
delivering steam from said steam source to said vessel;
removing vaporized hydrocarbon contaminants out of said vessel while steam is delivered to the vessel;
introducing said terpene from said organic solvent source into the steam delivered to said vessel during said removing step; and
introducing a surfactant from said surfactant source into the steam delivered to the vessel during said removing step.
2. The method of claim 1 including the additional step of preheating the vessel with said steam prior to the introduction of said terpene and said surfactant.
FIG. 7 is a schematic diagram showing the administration of the cleaning process of the present invention in cleaning two exchangers at once.
DETAILED DESCRIPTION OF THE INVENTION
The present invention solves the problems present in the prior art methods.
First, by enabling the exchangers to be cleaned more regularly, the resulting unfouled exchangers operate more efficiently, with less heat input. Thus, operating expense is reduced. FIG. 2 shows how operating expense is reduced when a regular maintenance program using the disclosed process is established-the area below a curve computed using a regular cleaning regimen and above the curve without a cleaning regimen. A basic net present value calculation can be used to determine a most optimal cleaning cycle. A curve that identifies a 6 month period as the optimal cleaning interval when comparing cost to clean versus loss in efficiency is shown in FIG. 4. This interval is much shorter than before possible with the prior art methods in which delays of 24 months are typical.
Regular cleaning is possible because the present invention enables the exchangers to be cleaned much more quickly than with the prior art methods. Because the exchangers are cleaned much more quickly, the refinery is able to boost efficiency by defouling while minimizing downtime. The invention does not require equipment disassembly, so equipment requiring cleaning can be cleaned without having to remove the equipment from a feed stream. The invention does not utilize corrosive chemicals or abrasive techniques to work effectively so that equipment will not suffer unpredictable damage during the cleaning process. Using the disclosed invention, the aforementioned crude preheat exchangers can be cleaned without disconnection from the feed train in 2 to 4 hours. During the cleaning process the tube bundles are not removed and the temperature of the exchangers remains elevated. In fact, the elevated temperature of the equipment serves to aid the cleaning process.
The efficiency and effectiveness of the disclosed invention enables completely new operating paradigms. Individual pieces of equipment in a feed stream foul at different rates. Therefore, chemical producers achieve the greatest efficiency gain for the least cleaning expense when targeted equipment is cleaned. With the prior art methods, cleaning required entire plants of equipment to be completely shut down for cleaning and maintenance. After shut down, it is found that some equipment is quite fouled and other equipment is relatively clean. Nevertheless, because the plant is shut down anyway, all the equipment is cleaned-including equipment that is relatively clean. The disclosed invention, however, allows the most fouled (or capacity constraining) equipment to be cleaned on a more frequent basis without necessarily cleaning other less-fouled equipment. Preheat crude exchangers are installed serially in the distillation crude system. There may be as many as 60 exchangers aligned in series so that each exchanger feeds the next. The exchangers foul at different rates, so that at any point one or two exchangers affect the performance of the entire feed train. The invention of the present invention allows one of these most-fouled exchangers to be cleaned while the other exchangers remain in service during the 2 to 4 hour cleaning process. Thus, cleaning time and resources are not wasted on the relatively-clean exchangers. Because the plant does not have to be shut down, operating efficiency of the facility is dramatically increased.
These technologies also enable two different exchangers to be cleaned in series, as can be seen in FIG.
7. As shown in the figure, both sides of two heat exchangers may be cleaned at the same time. Like the selective cleaning of a single exchanger as discussed above, selectively cleaning the two most-fouled exchangers in a series reduces resources wasted in cleaning the other relatively clean exchangers, thus increasing the operating efficiency of the facility.
The process of the present invention also allows for cleaning one side of an exchanger at a time. Exchangers each have two operating sides, with one side often fouling at a faster rate than the other. The process of the present invention allows the user to clean only the most-fouled side of an exchanger. The other side of the exchanger is able to remain in service.
It is also possible to simultaneously clean single sides of two different exchangers in series using the present invention. For example, the shell side of one heat exchanger may be cleaned at the same time as the shell side of another heat exchanger in the series while the tube sides of these exchangers are not cleaned. It is also possible to clean two tube sides of two different exchangers in series and not the shell sides. FIG. 3 charts the effects of these cleaning methods on a bank of 8 exchangers, where only the tube sides of two exchangers were cleaned. As can be seen from the figure, cleaning the tube sides of two different exchangers in series greatly improves overall operating efficiency.
In addition to improving overall efficiency, the present invention is also more environmentally friendly. Again, before the present invention, refineries would continue to operate heavily-fouled equipment in order to avoid the expense of a complete shut-down. The selective cleaning methods of the present invention avoid this dilemma-by enabling more frequent cleanings. Because the equipment is cleaned more often, it operates more efficiently. This reduces the amount of heat/energy required to operate the refinery. The generation of heat/energy required to operate the refinery creates the emissions of toxins such as carbon dioxide, sulfur dioxide, nitrogen oxide and other gases. A reduction in energy consumption of 30% could reduce the total emissions of these toxic gases by 6%. Furthermore, the process of the present invention does not require circulation or rinsing. Instead, by-products of the present invention may be processed as regular chemical feed by the refiner since they contain a preponderance of feed material. Therefore, because no water circulation procedures are necessary, no hazardous waste is produced that must be specially treated.
In addition to protecting the environment, the disclosed process also protects refinery workers from hazardous working conditions. Prior to this invention, workers were required to disassemble heavy equipment and then clean it by hydro-blasting. Workers would sometimes be crushed or otherwise harmed by the heavy equipment involved. Additionally, these workers would potentially be exposed to the dangerous chemicals used.
An additional benefit of the process of the present invention is its ability to clean large equipment using a volume of cleaning agent equivalent to only 1-5% of the volume of the vessel. Also, the time needed to perform the cleaning process is dramatically less than current cleaning processes in the industry. By cleaning with less chemical, more thoroughly, and in a shorter period of time, the disclosed process significantly improves cleaning efficiency while eliminating the need for dangerous disassembly of equipment.
The present invention accomplishes the above described benefits using a naturally occuring organic solvent as the cleaning agent. The cleaning agent is injected directly into high-pressure steam lines already present in the refinery's system. Once injected, the cleaning agent is vaporized, and allowed to clean all surfaces inside the vessel in a very short period of time. The cleaning agent is also unique because it utilizes a surfactant package that improves the detergency (solvency strength) of the product allowing it to be more oil-soluble. This enables the users of the process to "rinse" using the refinery's hydrocarbon process stream rather than the water rinse process used in prior art methods.
This is accomplished using a cleaning agent having two ingredients. The first is a terpene. The term "terpenes" traditionally applied to cyclic hydrocarbons having structures with empirical formula C
10H
16 which occur in the essential oils of plants. Knowledge of the chemistry of the terpene field has developed and compounds related both chemically and biogenetically to the C
10H
16 carbons have been identified. Some natural products have been synthesized and other synthetic compounds resemble known terpene structures. Consequently, the term "terpenes" may now be understood to include not only the numerous C
10H
16 hydrocarbons, but also their hydrogenated derivatives and other hydrocarbons possessing similar fundamental chemical structures. These hydrocarbons may be acyclic or cyclic, simple or complex, and of natural or synthetic origin. The cyclic terpene hydrocarbons may be classified as monocyclic, bicyclic, or tricyclic. Many of their carbon skeletons have been shown to consist of multiples of the isoprene nucleus, C
5H
8.
Generally, the terpene selected could be acyclic, bicyclic, or tricyclic. Examples of acyclic terpenes that might be used are geraniolene, myrcene, dihydromycene, ocimene, and allo-ocimene. Examples of monocyclic terpenes that might be used are ρ-menthane; carvomethene, methene, dihydroterpinolene; dihydrodipentene; α-terpinene; γ-terpinene; α-phellandrene; pseudolimonene; limonene; d-limonene; 1-limonene; d,1-limonene; isolimonene; terpinolene; isoterpinolene; β-phellandrene; β-terpinene; cyclogeraniolane; pyronane; α-cyclogeraniolene; β-cyclogeraniolene; γ-cyclogeraniolene; methyl-γ-pyronene; 1-ethyl-5 5-dimethyl-1,3-cyclohexadiene; 2-ethyl-6,6-dimethyl-1,3-cyclohexadiene; 2-ρ-menthene 1(7)-ρ-methadiene; 3,8-ρ-menthene; 2,4-ρ-menthadiene; 2,5-ρ-menthadiene; 1(7),4(8)-ρ-methadiene; 3,8-ρ-menthadiene; 1,2,3,5-tetramethyl-1-3-cyclohexadiene; 1,2,4,6-tetramethyl-1,3-cyclohexadiene; 1,6,6-trimethylcyclohexene and 1,1-dimethylcyclohexane. Examples bicyclic terpenes that might be used are norsabinane; northujene; 5-isopropylbicyclohex-2-ene; thujane; β-thujene; α-thujene; sabinene; 3,7-thujadiene; norcarane; 2-norcarene; 3-norcarene; 2-4-norcaradiene; carane; 2-carene; 3-carene; β-carene; nonpinane; 2-norpinene; apopinane; apopinene; orthodene; norpadiene; homopinene; pinane; 2-pinene; 3-pinene; β-pinene; verbenene; homoverbanene; 4-methylene-2-pinene; norcamphane; apocamphane; campane; α-fenchane; α-fenchene; sartenane; santane; norcamphene; camphenilane; fenchane; isocamphane; β-fenchane; camphene; β-fenchane; 2-norbornene; apobornylene; bornylene; 2,7,7-trimethyl-2-norbornene; santene; 1,2,3,-trimethyl-2-norbornene; isocamphodiene; camphenilene; isofenchene and 2,5,-trimethyl-2-norbornene.
The terpene normally used, and most preferred as the first ingredient in the cleaning agent of the present invention is a monocyclic saturated terpene that is rich in para-menthane (C
10H
20). Para-menthane has a molecular weight of 140.268. This active ingredient includes both the cis- and trans-isomers. Common and approved synonyms for para-menthane include: 1-methyl-4-(1-methylethyl)-cyclohexane and 1-isopropyl-4-methylcyclohexane. Para-menthane is all natural, readily biodegradable by EPA methods, and non-toxic by OSHA standards. Monocyclic saturated terpenes, however, are not the only compounds that may be used as the active ingredient of the cleaning agent. Other naturally occuring terpenes, such as (i) monocyclic unsaturated isoprenoids such as d-limonene (C
10H
16), (ii) bi-cyclic pine terpenes such as -pinene & -pinene, or (iii) any combination of monocyclic and bi-cyclic terpenes could also be used.
A second ingredient in the cleaning agent is an additive. The additive of the present invention is a non-ionic surfactant package which enhances detergency, wetting, oil solubility, and oil rinsing. The first major constituent of the surfactant package includes a linear alcohol ethoxylate (C
12-C
15) with an ethoxylated propoxylated end cap. This linear alcohol ethoxylate greatly enhances the detergency or cleaning power of the cleaning agent formulation. Linear alcohol ethoxylates are also more environmentally friendly than more traditional surfactants. They exhibit good biodegradation, and aquatic toxicity properties. Another major constituent of the cleaning agent surfactant package is a fatty alkanolamide primarily consisting of amides and tall oil fatty N,N-bis(hydroxyethyl) This fatty alkanolamide primarily aids in oil rinsing, oil solubility, and wetting. The combination in the proper ratios of these two classes of surfactants achieves the desired enhancements of the cleaning agent formulation. The following non-ionic surfactants with an HLB range of 6.0-10.5 are also acceptable as an additive package but not limited to (i) nonylphenol polyethoxylates, (ii) straight Chain linear alcohol ethoxylates, (iii) linear alcohol ethoxylates with block copolymers of ethylene and propylene oxide, (iv) oleamide DEA, or (v) diethanolamine. Of course, one skilled in the art would recognize that other additives could be used which would still fall within the scope of the invention.
The formulation of the cleaning agent of the present invention is effective at any of the following composition ranges by using a combination of the acceptable chemistries from above:
| | |
| | Component | Range (by weight) |
| | |
| | Terpene | 50%-95% |
| | Additive Package | 5%-50% |
| | |
The formulation of the cleaning agent of the present invention has been found to be most effective when in the following ranges:
| | |
| | Component | Range (by weight) |
| | |
| | Terpene | 85%-88% |
| | Additive Package | 12%-15% |
| | |
Calculating a ratio based the percentages immediately above, we see that the ratio by weight of the additive surfactants to organic solvents (Terpene) of said cleaning agent should be between 0.136 and 0.176 in order to obtain the best results. It is, however, still within the scope of the invention to use ratios outside the 0.136-0.176 range. The combination of the unique cleaning agent formulation is used according to the following procedures. First, the side or sides of the exchanger desired to be cleaned must be blocked in and evacuated. The exchanger is blocked in by closing off incoming and outgoing fluid valves or by inserting a solid plate (also called "blinding") between the flange faces at interconnecting flanges. FIG. 6 shows how the exchanger may be blocked in using feed valves. Referring to the figure, a typical heat exchanger
10 has a tube side
12 and a shell side
14. Tube side
12 has a feed in
16 and a feed out
18. The flow of fluids in the tube side is in the opposite direction of the flow of fluids in the shell side. Thus, the feed in
20 and feed out
22 on the shell side
14 are reversed in orientation to feeds
16 and
18 on the tube side
12. A tube-side ingoing fluid valve
24 allows the flow of processing fluids into the exchanger when open and a tube-side outgoing valve
26 allows flow out. Similarly, a shell side feed in valve
28 and feed out valve
30 allow flow through the shell side when open. In order to block in the exchanger, valves
24,
26,
28, and
30 are closed. This stops the flow of any processing fluids, blocking the exchanger in. The fluids remaining in the now-blocked-in exchanger are then removed from the exchanger by simple draining.
Once tube and shell sides of the exchanger have been drained and blocked in, the source of stream and venting systems are tapped into the exchanger. Referring again to FIG. 6, each of feeds
16,
18,
20, and
22 have bleeder connections at
32,
34,
36, and
38, respectively. Bleeder connections
32,
34,
36, and
38 enable the user to gain fluid access to exchanger
10 after it is blocked in so that steam may be introduced and then vented.
Steam is tapped into the exchanger using bleeder connections
32 (associated with the tube side in-feed
16) and
36 (associated with the shell side out-feed
22). A first source of steam
40 may usually be tapped into in-feed
16 by simply removing a cap (not pictured) that exists on most bleeder connections. This same procedure is also used to attach a second source of steam
42 to the shell side out-feed
22 through bleeder connection
36. First and second sources of steam,
40 and
42 respectively, are normally obtained from preexisting steam lines in the plant. The lines selected should have steam temperatures of at least 330 degrees Fahrenheit, and are attached to bleeders
32 and
36 in a manner well known to those skilled in the art. Ideally, the line temperatures should be between about 350 to 450 degrees Fahrenheit. The typical 150 psi refinery steam line will work effectively, however, super-heated 40 psi steam lines, which deliver steam at temperatures in excess of 400 degrees Fahrenheit, may be used as well. The injected steam increases internal temperatures within the exchanger.
A first source of cleaning agent
44, which is to be used later on in the process, Is tapped into steam line
40 upstream of the bleeder connection
32. The introduction of cleaning agent is made possible by joining source of steam
40 with cleaner source
44.
The administration of both steam and cleaner are accomplished using an administrator
11. The details regarding administrator
11 of the present invention are shown in FIG.
5. FIG. 5 discloses that steam
40 and cleaner
44 sources joined at a T-junction
35. Such T-junctions are standard plumbing, and acceptable embodiments are readily available to one skilled in the art. The refinery steam hose (not shown) selected as steam source
40 for use in the cleaning process is attached to steam conduit using a standard connector
51. Conduit
37 transmits the steam under pressure to a first side of junction
35. Between steam source
40 and junction
35 on conduit
37, a gate valve
43 serves to either open or shut off the source of steam
40 after the hose is attached. Immediately downstream, a check valve
47 allows flow in the downstream direction only. This prevents back flow of cleaning chemical or effluent into steam source. Interposed on conduit
39 between cleaner source
44 and junction
35 are gate valve
45 and check valve
49. Gate valve
45 is used to either allow or shut off the flow of cleaner from source
44. Check valve
49 allows flow in the downstream only to prevent the back flow of steam into the cleaner container. A standard elbow
55 is used to converge conduit
37 and
39 into junction
35. After steam and cleaner conduits,
37 and
39 respectively, meet up at junction
35, their collective flows are converged into a common line
57, shown in FIG.
5. Common line
57 is tapped into bleeder connection
32, shown in FIG.
6. This valved-T-junction arrangement enables the user to optionally: (i) introduce neither steam, nor cleaner; (ii) introduce only steam; or (iii) introduce steam and vaporized cleaner through bleeder connection
32 into in-feed
16, into the tube side
12 of exchanger
10. Cleaner is administered using a pneumatic barrel pump (not pictured) which is attached to a connector
53 on cleaner conduit
39. The cleaner is initially in liquid form, however, when it reaches T-fitting
35, it is immediately vaporized and is administered to the exchanger in vaporous form.
A cleaning-agent administrator identical to the one discussed in detail above is used to introduce steam from source
42 and cleaner from source
46 through bleeder connection
36 into out-feed line
22 into the shell side
14 of exchanger
10. Though not pictured in order to avoid being duplicitous, it should be understood that the arrangement and operation of such an administrator would be identical to the one disclosed in FIG.
5.
After being delivered by the administrator, the steam (or steam plus cleaner) introduced into tube side
12 and shell side
14 of the exchanger is then vented from the exchanger through bleeder connections
34 (associated with tube side out-feed
18) and
38 (associated with shell side in-feed
20). Bleeders
34 and
38 are fluidly connected to the ventilation system of the refinery using techniques and equipment known to those skilled in the art. This connection should be consistent with a predetermined plan devised for dealing with the vented effluent. It is important that this particular plan complies with all state and local regulations. This can be done by any number of methods. Some examples of methods that have been used successfully are: (i) allowing the vapor to condense through the overhead circuit and tie into the flare so that it may be burned, or (ii) opening an overhead vent to the atmosphere. Of course, one skilled in the art will realize that other methods of managing the effluent are possible and are to be considered within the scope of the present invention. It is also important to note that the invention is not limited in scope to the use of bleeders (such as
32,
34,
36, and
38) in order to gain fluid access to the exchanger. In fact, any potential opening to the exchanger may be used. For example, in some exchangers process gauge connections are used instead of bleeders. Sometimes a combination of bleeders and process gauges might be used. Other kinds of exchanger openings giving access to the exchanger may be used as well. Thus, though the embodiments disclosed in this application show the use of bleeder connections to tap into the exchanger, the particular device used to gain vaporous access to the exchanger is not to be considered an essential or limiting feature of the present invention.
Once the steam and venting systems have been tapped in, the exchanger is then pre-heated by injecting only steam into both sides of the exchanger. Both sides of the exchanger are continually vented throughout the preheating process. Again, the steam delivered should have temperatures of at least about 330 degrees Fahrenheit. The injected steam increases internal temperatures within the exchanger. These internal temperatures should be increased until they exceed about 225 degrees Fahrenheit. Since this steam preheating and the subsequent injection process are both carried out at atmospheric pressure (substantially) while venting the exchanger, it is important for the production facility to have a plan in effect for managing the vaporous, vented effluent as mentioned earlier. The preheating process will cause the development of some condensed water mixed with contaminants at the bottom of the exchanger. Therefore, in order to remove this mixture after the exchanger has reached the 225 degree target, the steam is temporarily turned off so that the mixture may be drained from both sides of the exchanger. Because draining the exchanger may cause it to cool slightly, the steam should then be reactivated until the exchanger reaches 225 degrees.
Once the exchanger has been preheated as so, it is time to inject the cleaner into the already running steam. The amount of cleaner necessary is dependent on the total enclosed volume of each side of the exchanger, and the nature and volume of contaminate. Satisfactory results have been obtained using 55 gallons of cleaner per 100 to 1000 cubic feet of exchanger volume (from 0.055 to 0.55 gallons per cubic foot of exchanger volume). Ideally in terms of performance, no less than 55 gallons should be used per 200 cubic feet of exchanger volume (no less than 0.275 gallons per cubic foot of exchanger volume). Most commonly, a 0.275 ratio has been used to minimize cost, while at the same time maintaining sufficient cleaning power. However, if the amount of contamination is greater than typical, this ratio should be increased to higher levels to accommodate. The volume of the exchanger can be calculated by multiplying the cross sectional area of the exchanger by the length. Typically, the shell side of an exchanger accounts for 60% of the total exchanger volume, whereas the tube side accounts for only 40%. Thus, about 60% of the cleaning chemical is injected into the shell side of the exchanger using cleaner source
44, and 40% injected into the tube side using cleaner source
46.
Cleaner from each of sources
44 and
46 is delivered using administrators like the one shown in FIG.
5. The pneumatic pumps (not shown) used for the procedure require approximately 9 minutes per 55-gallon drum to inject the cleaning agent. The steam will vaporize the cleaning agent and carry it into the equipment.
Once the vaporized cleaning chemical enters into the exchanger, two distinct cleaning actions take place simultaneously. First, the vaporous cleaning agent solublizes the light end hydrocarbons (benzene, H
2S, LEL, etc.) that are present in the inside of the exchanger. Once solubized by the vaporous cleaning agent, these light end materials are carried out of the exchanger in vaporous form through the vent. The vapors coming out of the vent should be handled in accord with the plan set forth in advance. As already discussed, possible plans include, but are not limited to, (i) allowing the vapor to condense through the overhead circuit and then tie into the flare to be burned, or (ii) opening an overhead vent to the atmosphere.
The second cleaning action is more gradual. Due to the partial pressures of cleaning agent, some of its vapors will re-condense into liquid upon contacting the cooler metal surfaces inside the exchanger. These metal surfaces are usually heavily coated with petroleum residues and processing fluids. The kinetic energy generated when portions of the cleaning agent's vapors condense onto these metal surfaces (the transformation from a vapor phase to a liquid phase releases energy), along with the tremendous solvency strength of the formulation, allow the petroleum contaminants to be dissolved away from the metal surfaces inside the exchanger. Once removed, these contaminants become detached from the metal and drip to the drain at the bottom of the exchanger. Some contaminants, however, remain bound to the metal surfaces inside the exchanger. These more stubborn contaminants, though still clinging to metal, are saturated by and subjected to the strong detergency, wetting, oil solubility, and oil rinsing properties of the surfactant. This causes them to be loosened and easily soluble into oil. Thus, they are easily rinsed away by the flow of ordinary processing fluids after the exchanger is returned to service.
After about one hour, the injection of cleaner into the exchanger is stopped. Steam, however, continues to be injected.
Following the injection phase, the equipment is allowed to dwell for about one more hour at elevated temperature while steam is continually injected into the equipment. This dwell cycle allows the contaminants to further dissolve via continuous revaporization of the condensed cleaner.
After the dwell cycle, the steam injection is stopped, and the drain is opened to a post-processing or containment system. When the exchanger is drained, liquid effluent comprising contaminate and residual cleaning agent is removed. The liquid effluent may be removed by carrying it out of the exchanger directly to slop tanks. Once in the slop tanks, the effluent is easily post processed. The post processing is made easy because the cleaning agent is all natural, and thus, biodegradable. The effluent might also be passed directly through the post processing equipment in the refinery, where it will be refined in the normal course of production. Because the cleaning agent included in the drained effluent is a naturally occurring hydrocarbon which does not contain any chelating agents, phosphates, silicates, or any chemicals that would cause problems with treatment facilities, it may be easily re-refined without harming the facility's equipment.
Following the drain process the equipment is resealed, blinds are removed, and valves are opened. After the exchanger has been repacked (filled with processing fluids), the exchanger is then returned to service. At this time, the contaminants still clinging to metal within the exchanger have been made loose and more oil soluble by the additives/surfactants. Thus, they are rinsed away by the flow of ordinary processing fluids in the ordinary course of operation after the exchanger has been returned to service. The cleaned exchanger, its contaminants removed, will now operate at maximum efficiency.
These same general principles may be employed in the simultaneous cleaning of two heat exchangers as well. FIG. 7 shows a first exchanger
52 and a second exchanger
54 connected in series, as would be common with a train of exchangers in a refinery. In such an arrangement, tube out-feed
72 of tube side
56 of first exchanger
52 is fluidly connected to the in-feed
68 of the tube side
60 of second exchanger
54. Likewise, in-feed
74 of shell side
58 of first exchanger
52 is fluidly connected to out-feed
70 of second exchanger
54. It is common for the shell sides and tube sides of a pair of exchangers to be linked together as shown in FIG. 7 during ordinary course of operation. Thus, it is usually not necessary to connect the feeds
72 and
74 to feeds
68 and
70 because they will already be hooked up.
The process of cleaning two exchangers at once is accomplished in much the same manner as describe for the one-exchanger process. First, the side or sides of the exchanger desired to be cleaned must be blocked in and evacuated. The two exchangers
52, and
54 are blocked in by closing the tube side ingoing fluid valve
84 and shell side outgoing fluid valve
86 of first exchanger
52, and then closing off the outgoing tube side fluid valve
88 and ingoing shell side fluid valves on second exchanger
54. Thus, tube sides
56 and
60, being fluidly connected, are completely blocked in as well as fluidly connected shell sides
58 and
62. The fluids remaining in both exchangers are then drained.
Once both exchangers have been blocked in and drained, access to the exchanger is gained by tapping in at bleeder connections
92,
94,
96,
98,
108, and
110. Connections
92,
94,
108 and
110 are used to tap in steam and cleaner in the exact same way as disclosed for the single-exchanger method represented in FIG.
6. The steam sources are all drawn from existing stream lines in the refinery having steam temperatures of at least about 330 degrees Fahrenheit-ideally between about 350 to 450 degrees Fahrenheit-just like with the one-exchanger method. It will be observed that the FIG. 7 process requires two additional sources of steam,
112 and
114, and two additional sources of cleaner,
116 and
118. Steam source
112 is tapped into bleeder
108. The steam introduced mixes with vaporous effluent coming out of the out-feed
72 of the tube side
56 of first exchanger
52 before passing into the in-feed
68 of the tube side
60 of the second exchanger
54. Similarly, steam source
114 is tapped into bleeder
110. This steam mixes with the effluent coming out of shell side in-feed
74. Then it passes into out-feed
70 of shell side
62 of second exchanger
54.
The administration of both steam and cleaner in this two-exchanger cleaning method is accomplished using administrators with T-junctions (not shown, but all just like the one shown in FIG. 5) to mix cleaner from sources
104,
106,
116, and
118 with steam from sources
100,
102,
112, and
114 respectively. The administrators are tapped in to bleeder connections
92,
94,
108, and
110. As with the one-exchanger process, these administrators enable the user to optionally: (i) introduce neither steam, nor cleaner; (ii) introduce only steam; or (iii) introduce steam and vaporized cleaner into feed lines
64 and
66 and connecting lines
80 and
82.
There are two reasons that the fresh steam and cleaner are injected into connecting lines
80 and
82. This is because (i) the temperature of the vaporous effluent coming out of the first exchanger will have dropped to below ideal temperatures, and (ii) the amount of cleaner present in the second exchanger will have dissipated from the time in which it was introduced into the first exchanger. The fresh steam and cleaner injected into lines
80 and
82 will raise temperatures and cleaner concentrations to the point that the second exchanger may be effectively cleaned.
As with the one-exchanger method shown in FIG. 6, the FIG. 7 two-exchanger method vents the vaporous effluent. With the two-exchanger method, effluent is vented through bleeder connections
96 and
98 into the ventilation system of the refinery which has been prepared in advance. Again, there must be a predetermined plan in place for dealing with the vented effluent. As with the earlier method, this can be done by (i) allowing the vapor to condense through the overhead circuit and tie into the flare so that it may be burned, (ii) opening an overhead vent to the atmosphere, or managing the effluent in any other way known to those skilled in the art. Though bleeder connections are used in this embodiment, certainly process gauge openings or any other acceptable opening on the exchanger may be used.
Once the steam and venting systems have been tapped in, the exchanger is pre-heated by injecting only steam at about 330 degrees Fahrenheit minimum into bleeder connections
92,
94,
108 and
110. This will preheat tube sides
56 and
60 and shell sides
58 and
62. The steam is continually vented through bleeders
96 and
98 throughout the preheating process. This preheating should continue until the internal temperatures of both exchangers reaches exceed about 225 degrees Fahrenheit. Once this temperature is reached, all the steam sources (
100,
102,
112, and
114) are temporarily turned off so that any water (due to condensation) and contaminants at the floor of exchangers
54 and
58 may be drained. Because all the steam sources are shut off during draining, the exchangers will cool. In order to bring them back above the minimum temperature (225 degrees) the steam sources should be reactivated.
Once the reactivated steam brings the internal temperatures of both exchangers to above at least 225 degrees, cleaner from sources
104,
106,
116, and
118 is injected into already running steam sources
100,
102,
112, and
114. In terms of its chemical make-up, the cleaner used here is the same as described for use in the one-exchanger cleaning method depicted in FIG.
6. The amount of cleaner necessary, like with the one-exchanger method, is calculated based on the total enclosed volume of each side of each exchanger. Again, the ratio of gallons of cleaner per cubic foot of exchanger may range from 0.055 to 0.55, however, for best results a ratio of no less than 0.275 gallons per cubic foot should be used for typical contamination. This ratio should be slightly increased for greater than average contamination. Because the shell side of an exchanger accounts for 60% of the total exchanger volume, whereas the tube side accounts for only 40%, about 60% of the cleaning chemical should be injected into the shell sides
56 and
60, and only 40% injected into tube sides
58 and
62. Of the 60% of total cleaner designated to shell sides
56 and
60, half of this total is injected from source
104 through bleeder
92 and the other half is injected from source
116 through bleeder
108. Likewise, of the 60% total cleaner designated for the shell sides, half is injected from source
106 through bleeder
94 and the other half is injected from source
118 through bleeder
110.
Cleaner from each of sources
104,
106,
116, and
118 is delivered into administrators like the one shown in FIG. 5 into bleeder connections
92,
94,
108, and
110. The steam and vaporized cleaner injected into bleeder
92 enters into tube side
56 of first exchanger
52 at in-feed
64 to begin the cleaning actions therein. The light end hydrocarbons (benzene, H
2S, LEL, etc.) are solubized, and exit (along with steam and cleaner) through out-feed
72. This effluent from out-feed
72 mixes with the fresh steam and cleaner from sources
112 and
116 introduced at bleeder
108. This mix is then passed into tube side
60 of second exchanger
60 where it solubizes the light end hydrocarbons and then vents through bleeder
96 according to the predetermined plan for handling the vaporous effluent for that particular facility.
Meanwhile, some of the vaporous cleaning agent will re-condense into liquid upon contacting the cooler metal surfaces inside of tube sides
56 and
60. The terpenes will dissolve much of the contaminant away from the metal. The remaining contaminant will be made more oil soluble by the surfactant package so as to be loosened and easily soluble into oil. This will cause these remaining contaminants to be easily rinsed away by the flow of ordinary processing fluids after the exchanger is returned to service.
The shell sides
58 and
62 are cleaned simultaneously with tube sides
56 and
60-and in exactly the same way. The steam and vaporized cleaner injected into bleeder
94 enters into shell side
58 of first exchanger
58 at in-feed
66. The effluent steam, remaining cleaner, and solubized light end hydrocarbons exit through out-feed
74 and mixes with the fresh steam and cleaner from sources
114 and
118 introduced at bleeder
110. The vaporous mixture is then passed into shell side
62 of second exchanger
60 where it removes the light end hydrocarbons and then vents through bleeder
98. Just like with the tube side procedure, terpenes in the cleaner that condenses on the metal surfaces will dissolve some of the contaminants, and the remaining contaminants will be made more oil-soluble by the surfactants in order to be washed away when the exchanger is returned to service.
After about one hour of running steam and vaporous cleaner through both exchangers, the injection of cleaner into the exchanger is stopped at all four locations (
104,
106,
116,
118). Steam, however, continues to be injected-allowing the two exchangers dwell for about one more hour at elevated temperature.
After the one-hour dwell cycle, steam sources
100,
102,
112, and
114 are turned off, and the drains of exchangers
54 and
58 are opened to a post-processing or containment systems. When the exchangers are drained, liquid effluent comprising contaminate and residual cleaning agent is removed to slop tanks for post-processing (or directly through the post-processing equipment in the refinery to be refined in the normal course of production).
Following the drain process, exchangers
52 and
54 are resealed, blinds are removed, and valves are opened to repack the exchanger with processing fluids. After the exchanger has been repacked, the exchanger is then returned to service and the remaining contaminants, now oil soluble are rinsed away by the flow of ordinary processing fluids in the ordinary course of operation. Exchangers
52 and
54, now decontaminated, should operate at maximum efficiency.
These same processes may be used in other ways than the one-exchanger and two-exchanger methods already discussed. The same process may also be used to clean only one side of one exchanger (shell or tube) at a time. This is sometimes advantageous when one side of the exchanger (e.g., tube side) is more contaminated than the other (e.g., shell side). Referring to FIG. 6, this is accomplished in the same way described for the one-exchanger method-except that only half of the exchanger would be cleaned. To do this, one of the tube side
12 or shell side
14 could be cleaned without cleaning the other side. This would be done by closing valves
24 and
26 to block in tube side
12, draining, preheating and cleaning the same as described for the one-exchanger process described above, while shell side remained in service, still transmitting processing fluids. The reverse is true as well. Shell side
14 could be blocked off and cleaned while tube side
12 remained in service.
This same approach may also be applied to clean only one side of two exchangers at once. Referring to FIG. 7, tube sides
56 and
60 may be blocked in (by closing valves
84 and
88) and then cleaned while valves
86 and
90 are left open so that shell sides
58 and
62 remain in service. The reverse is also true. Shell sides
58 and
62 could be blocked in and cleaned while tube sides
56 and
60 remained in service.
It is important to note, that although the examples above suggest the use of multiples sources of steam, and multiple sources of cleaner, that single sources of steam or cleaner could be used. For example, multiple hoses could be drawn from one common source of steam. Cleaner sources could all be drawn from the same source.
The methods of the present invention, as described above enable an exchanger to be cleaned in 2 to 4 hours-an accomplishment that before would have taken 3 to 5 days. Additionally, these methods allow for cleaning without the dangerous disassembly of equipment, and in a more environmentally friendly manner, than was known before.
Thus, there has been shown and described a method for cleaning a vessel in a refinery which fulfills all of the object and advantages sought therefore. Many changes, modifications, variations, and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification together with the accompanying figures and claims. The same process, together with ensuing benefits are also applicable to similar equipment in unrelated industries (such as sugar, pulp and paper) where organic contaminants must be removed from heat exchangers or process equipment so as to improve operating efficiencies. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.
