Y \CEI01\3310 WO\spec and claιms\Spec & Claims FINAL 061026 wpd

FORMULATION FOR HYDROGEN SULPHIDE SCAVENGING FROM HYDROCARBON STREAMS AND USE THEREOF

FIELD

The present invention relates to a formulation comprising triethylene glycol for the reduction of hydrogen sulphide levels in hydrocarbon streams. Additionally, the present invention relates to a method for reducing hydrogen sulphide levels in hydrocarbon streams while alleviating solid dithiazine deposit buildup.

BACKGROUND

It is well known in the industry that hydrogen sulphide is a toxic gas that poses a threat to public health and safety. In addition there are serious environmental concerns about the combustion of fuels that contain hydrogen sulphide since sulfur dioxide is formed upon combustion of said fuels which if released into the atmosphere produce acid rain. Currently, many regulations exist regarding the upper limits of hydrogen sulphide in various gas and liquid hydrocarbon streams such as pipeline gas. Considerable expense and efforts are made annually to reduce or eliminate the levels of hydrogen sulphide in gas and liquid hydrocarbon streams for both safety and environmental reasons.

A large number of non-regenerative chemical formulations exist in the market place for removal of hydrogen sulphide. One important group of these chemical scavengers is based on aldehyde and amine reaction products, particularly triazines. Formulations can consist of low molecular weight aldehydes such as formaldehyde but can also consist of ketones and various adducts thereof. Amines used to produce triazines in prior formulations include alkylamines as disclosed in U.S. Pat. No. 5,674,377, alkanolamines as disclosed in U.S. Pat. No. 4,978,512 and in some cases a combination of amines can be used as disclosed in U.S. Pat. No. 5,347,004 and U.S. Pat. No. 5,554,349.

Scavengers based on aldehyde and amine reaction products such as that disclosed in U.S.

Patent No. 4,978,512 have been shown to be effective at removing hydrogen sulphide from hydrocarbon streams in in-line injection systems, hydrogen sulphide scrubber systems or chemical solvent systems. If glycol is added to the formulation, water can additionally be

removed. Depending upon the amount of water present, the glycol content can be as high as 90%

Despite the fact that US Patent No. 4,978,512 states that contacting a gas stream with the reaction products of formaldehyde and monoethanolamine provides a selective and almost instantaneous reaction with the sulphides present in the gas stream, producing no precipitate solids or deleterious environmental effects, it was found that under field conditions, serious problems arose with regard to formation of crystals. This is because the product of the reaction between the reaction product and hydrogen sulphide produces diathiazine. Under optimal conditions, such as those found in the laboratory, a two phase system is produced, with the dithiazine, methanol and reaction byproducts forming one liquid layer and water and various other components forming a second liquid layer. In temperatures of about 2O ⁰ C or lower, under field conditions, solid dithiazine crystals can form in the dithiazine layer. These precipitate out of the layer, thus causing plugging problems in processing equipment, storage vessels, truck tanks or disposal wells. As was stated in US Patent 6,582,624, "It is believed that the presence of contaminants in field applications offers numerous nucleation sites to initiate and promote crystallization."

The problems associated with crystalline dithiazine could be avoided by substituting a minor amount of monoethanolamine with diglycolamine as disclosed in Canadian Patent No.

02333794. Again, a two phase system was produced after the reaction with sufficient quantities of hydrogen sulphide. The top layer consisted of an aqueous liquid phase containing water and other reaction components and impurities, while the bottom layer which primarily consisted of dithiazine, was in the form of a liquid at operating temperatures between about -5 ⁰ C and 2O ⁰ C. At temperatures below about -5 ⁰ C, the layer became an amorphous solid.

More recently, methods for removal of hydrogen sulphide have been undertaken at higher temperatures. It was found that at temperatures above about 2O ⁰ C and more typically in the range of 3O ⁰ C and above, a new problem arose. The dithiazine layer, which had remained liquid at normal operating temperatures that were below about 2O ⁰ C, became a brownish, amorphous solid at the higher temperatures. The amorphous solid formed after exposure to high temperatures leads to solid deposit buildup and equipment blockages.

The amorphous dithiazine solids are characterized by an amorphous and "mushy" consistency. It is believed that a number of factors can contribute to the formation of dithiazine solids in the field including conditions that lower the solubility of dithiazine in the dithiazine/methanol layer, conditions that strip methanol from the dithiazine layer and overspending the scavenger solution.

The formation of amorphous dithiazine is extremely problematic since substantial deposits can form blockages in chemical storage tanks, bulk truck tanks, gas processing equipment and in produced water disposal wells. Clean up procedures are often time consuming and requires equipment to be taken off-line or shut down. This makes cleaning up solid dithiazine deposits an expensive venture.

As an alternative approach, US Patent Application Serial No. 250436 discloses a process for the reduction or elimination of hydrogen sulphide that does not use triazine, and in fact, teaches away from the use of amines that result in triazines in the reaction products. The hydrogen sulphide scavenging formulation is derived by the reaction of a carbonyl group- containing compound with an alcohol, thiol, amide, thioamide, urea or thiourea. The carbonyl group-containing compound is preferably formaldehyde, and preferably the product is derivable by reaction of formaldehyde with an amine-free alcohol or urea selected from ethylene glycol, propylene glycol, glycerol, diethylene glycol, triethylene glycol, ethyl alcohol, n-butanol, a sugar, a low molecular weight polyvinyl alcohol, castor oil fatty acid and urea. More especially, the scavenger product is used with an amine, especially monoethanolamine.

There remains a need for a formulation that is effective at removing hydrogen sulphide from gas and liquid hydrocarbon streams that avoids the problem of amorphous and crystalline dithiazine solid deposit buildup. It is an object of the present invention to overcome the deficiencies in the prior art.

SUMMARY

The current invention provides a solution to the problem of dithiazine solid deposit buildup observed with triazine-based scavengers used for the removal of hydrogen sulphide from hydrocarbon streams. In an attempt to reduce the formation of the amorphous solids that build up at the higher operating temperatures (approximately 3O ⁰ C), triethylene glycol was

added initially to the reaction products of monoethanolamine, diglycolamine and formaldehyde. After contacting the hydrocarbon stream, a spent product was produced that consisted substantially of a single phase. Any amorphous dithiazine solids that formed where suspended in the single phase, and the remainder of the dithiazine was in solution. Further testing showed, surprisingly, that a scavenging formulation comprising triethylene glycol and the reaction products of monoethanolamine and formaldehyde produced a spent product that formed a substantially single phase, with the dithiazine either in solution or suspended in the phase and minimal crystalline dithiazine. Thus in accordance with the present invention, there is provided chemical formulation comprising triethylene glycol and the reaction products of monoethanolamine and formaldehyde, for the removal of hydrogen sulphide from hydrocarbon streams.

In one embodiment of the invention, a hydrogen sulphide and mercaptan scavenging formulation for reducing dithiazine solids is provided. The formulation comprises triethylene glycol and the reaction products of reacting a first amine and an aldehyde.

In one aspect of the invention, the first amine is monoethanolamine and the aldehyde is formaldehyde.

In another aspect of the invention, the weight of triethylene glycol is about 15% to about

95%.

In another aspect of the invention the weight of triethylene glycol is about 15% to about 50%.

In another aspect of the invention the weight of triethylene glycol is about 15% to about 25%.

In another aspect of the invention the reaction products comprises 2-[3,5-bis-(2-hydroxy- ethyl)-[1 ,3,5]triazinan-1 -yl]-ethanol.

In another aspect of the invention, the formulation further comprises a second amine.

In another aspect of the invention the second amine is diglycolamine.

In another embodiment of the invention, a scavenging formulation is provided comprising a mixture of triethylene glycol, and at least one triazine.

In another embodiment of the invention, a method for reducing the levels of hydrogen sulphide and mercaptans in hydrocarbon streams comprising contacting said streams with a formulation comprising triethylene glycol and the reaction products of reacting a first amine and an aldehyde, and reacting said reaction products with hydrogen sulphide is provided, thereby reducing the levels of hydrogen sulphide, mercaptans and solid dithiazine deposits.

In one aspect of the method the first amine is monoethanolamine and the aldehyde is formaldehyde.

In another aspect of the method , the weight of triethylene glycol is about 15% to about 95% .

In another aspect of the method, the weight of triethylene glycol is about 15% to about 50%.

In another aspect of the method, the weight of triethylene glycol is about 15% to about 25%.

In another aspect of the invention, the method further comprises reacting a second amine with the first amine and the aldehyde to produce the reaction product.

In another aspect of the method, the second amine is diglycolamine.

In another aspect of the method, the hydrocarbon stream is a gaseous or liquid stream.

In another aspect of the method, the hydrocarbon stream is a sour natural gas stream.

In another aspect of the method, the level of hydrogen sulphide is reduced to a level of about 16 ppm or less.

In another aspect of the method, the hydrogen sulphide level is reduced to zero.

In another aspect of the method, the step of contacting reacts the formulation with hydrogen sulphide to form a spent formulation comprising a single phase.

In another aspect of the method, the step of contacting reacts the formulation with hydrogen sulphide to form a spent formulation comprising dithiazine.

In another aspect of the method, the step of contacting reacts the formulation with hydrogen sulphide to form a spent formulation comprising dithiazine wherein the dithiazine may be either a suspended amorphous solid or dissolved in the single phase.

In another aspect of the method, the step of contacting reacts the formulation with hydrogen sulphide to form a spent formulation comprising dithiazine, wherein the dithiazine deposits are minimized or eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graphical representation of the hydrogen sulphide scavenging performance of a triazine based scavenging formulation of the prior art.

Figure 2 is a graphical representation of the hydrogen sulphide scavenging performance of a scavenging formulation of the present invention which contains a 1 :1 molar ratio of total amine to formaldehyde and 24% by weight of triethylene glycol.

Figure 3 is a graphical representation of the hydrogen sulphide scavenging performance of a scavenging formulation of the present invention which contains a 1 : 1.5 molar ratio of total amine to formaldehyde and 20% by weight of triethylene glycol.

DESCRIPTION Definitions

Mercaptans: Mercaptans are a group of sulphur containing organic compounds in which the sulphur has replaced an oxygen of a hydroxyl group in the corresponding oxygenated compound. For example, but not limited to, methyl mercaptan, in which the oxygen in methanol has been replaced, mercaptanol, in which one oxygen in ethanol has been replaced, and cyclohexyl mercaptan, in which the oxygen in cyclohexanol is replaced.

Sulphides: Sulphides include HS ₁ which is variously called hydrogen sulphide ion, hydrosulphide ion, sulfhydryl ion, or bisulphide ion, and H ₂ S, hydrogen sulphide

Dithiazine solids. Dithiazine solids include amorphous solids and crystalline dithiazine.

Detailed Description

The formulation of the present invention can be used to scavenge hydrogen sulphide and mercaptans from a variety of hydrocarbon streams, including liquid hydrocarbon streams and sour natural gas. The formulation can be contacted to hydrocarbon streams by various methods including but not limited to simple mixing, inline injection and with a contact scrubber tower. The scavenger formulation of the present invention can be used to reduce the levels of hydrogen sulphide to levels below 16 ppm and as low as 0 ppm.

The reaction of hydrogen sulphide with the scavenging formulation of the present invention produces a spent formulation characterized by a single liquid phase that does not contain crystalline dithiazine solids. Any dithiazine that results from the scavenging solution reacting with hydrogen sulphide will be suspended or dissolved in solution and solid dithiazine deposit buildup will be minimized or eliminated. Examples of the embodiment of the invention are outline by Examples 2 to 9.

Example 1

As a reference sample, a solution was prepared from 56.2 wt% Formalin (37.5% formaldehyde; 25% methanol), 41.6 wt% monoethanolamine, and 2.2 wt% diglycolamine was formulated. The molar ratio of total amines to formaldehyde was approximately 1 :1.

The scavenger solution was subjected to a hydrogen sulphide scavenging capacity test which was performed by passing a feed gas with a known hydrogen sulphide concentration at a known rate through a specified volume or mass of scavenger while the outlet hydrogen sulphide level was measured as a function of time. The test used 57.14 grams of the scavenger formulation maintained at 50°C during the duration of the test and an inlet gas comprised of approximately 18.4% hydrogen sulphide balanced with carbon dioxide. These conditions were used to strip methanol from the spent solution.

The results of this capacity test are presented in Figure #1 and shows that breakthrough occurred at 95 minutes. The breakthrough point was determined as the time required for the detection of H ₂ S in the outlet stream. The capacity test was continued beyond breakthrough until the molar concentration of hydrogen sulphide in the outlet gas reached 15.5% which is approximately 84% of the hydrogen sulphide content of the inlet feed gas.

The spent solution at 2O ⁰ C produced from the reaction of hydrogen sulphide with the scavenger solution had two distinct phases: a clear yellow liquid and an amorphous dithiazine solid deposited on the bottom of the reaction vessel. The dithiazine solid was characterized by a sticky and mushy consistency and it took considerable effort to remove the deposit from the reaction vessel.

Although the conditions used in the capacity test represent a worse case scenario in terms of "overspending" the scavenger solution since continuing to use a scavenging solution until well after breakthrough is not typical in the field, it clearly illustrates the problem that can arise from the deposition of amorphous dithiazine solids.

Example 2

A scavenger solution was formulated from 41.9 wt% Formalin (37.5% formaldehyde; 25% methanol), 32.4 wt% monoethanolamine (MEA), 1.7 wt% diglycolamine (DGA) and 24 wt% triethylene glycol (about 25 wt% triethylene glycol). The solution was blended by adding the formalin and triethylene glycol to the MEA/DGA mixture. The molar ratio of total amines to formaldehyde was approximately 1 :1.

The scavenger solution was subjected to a hydrogen sulphide scavenging capacity test.

70.53 grams of scavenger formulation was used with an inlet gas consisting of approximately 18.6% hydrogen sulphide and 81.4% carbon dioxide. The temperature was maintained at 50 ⁰ C throughout the duration of the test. The results of this capacity test are presented in Figure #2 and shows that breakthrough occurred at 95 minutes. The breakthrough point was determined as the time required for the detection of H ₂ S in the outlet stream. The capacity test was continued beyond breakthrough until the molar concentration of hydrogen sulphide in the outlet gas reached approximately 14.7% which is approximately 80% of the hydrogen sulphide content of the inlet feed gas.

The heavily overspent solution which resulted from the scavenging capacity test was an opaque yellow single phase liquid at 20 ⁰ C. The solution was thought to be opaque due to an over saturation of dithiazine in the spent solution.

The physical stability of the solution was first tested by allowing the solution to sit for an extended period of time (over a week) at approximately 20 ⁰ C to observe whether dithiazine

would settle out of the solution and form deposits on the bottom of the sample container. Interestingly, dithiazine did not settle out of the solution and no deposits were formed, in fact, the solution was so stable that it could be centrifuged at 3500 rpm for 30 minutes without observing the formation of a dithiazine layer or deposit. The stability of the solution was also tested at low temperatures, a condition which is known to bring about the formation of dithiazine solids. A portion of the sample was placed in a scintillation vial and cooled in a fridge to a temperature of approximately 2 ⁰ C. Visually, the solution appeared the same as that at 20 ⁰ C but was slightly more viscous. The temperature of the solution was then lowered to approximately -30 ⁰ C by placing the sample in the freezer for 72 hours. Although the solution was noticeably more viscous at this temperature, the solution did not freeze and was considered "pump-able". Most importantly, even at these low temperatures, a condition which can cause the formation of amorphous deposits, dithiazine did not settle out of solution and did not form solid deposits. These results were a stark contrast from those described in Example 1 wherein solids were formed at a much higher temperature (2O ⁰ C). Clearly, the results demonstrate the potential of the formulation disclosed in the present invention to alleviate solid amorphous dithiazine buildup.

Example 3

A scavenger solution was formulated from 51.4 wt% Formalin (37.5% formaldehyde; 25% methanol), 27.2 wt% monoethanolamine (MEA), 1.4 wt% diglycolamine (DGA) and 20 wt% triethylene glycol. The molar ratio of total amines to formaldehyde was approximately 1 :1.5.

The scavenger formulation was subjected to a hydrogen sulphide scavenging test. The test used 57.14 grams of the scavenger formulation and an inlet gas comprised of approximately 18.7% hydrogen sulphide balanced with carbon dioxide. The temperature was maintained at 50 ⁰ C throughout the duration of the test. The results of this capacity test are presented in Figure #3 and shows that breakthrough occurred at 106 minutes. The capacity test was continued beyond breakthrough until the molar concentration of hydrogen sulphide in the outlet gas reached approximately 14.8%. The resulting spent solution can be considered heavily overspent similar to that outlined in Example 2.

The spent solution was an opaque, yellow, single layered liquid similar to that observed in

Example 2. No solid dithiazine settled out of the solution upon allowing the spent solution to sit for 24 hours at 2O ⁰ C. Nitrogen gas was then bubbled through the spent solution at a rate of 250 mL/minute for 24 hours in order to simulate a high gas velocity which strips

methanol out of spent solution. A small quantity of dithiazine began to settle out of the solution; however, unlike other forms of dithiazine such as that described in Example 1 or that observed in the field, this dithiazine was dispersed back into the spent solution by gentle agitation. The dithiazine in the present spent solution was not sticky or thick and was considered to still be "pump-able" which represents a marked improvement over the reference sample.

Example 4

A scavenger solution was formulated from 51.4 wt% Formalin (37.5% formaldehyde; 25% methanol), 27.2 wt% monoethanolamine (MEA), 1.4 wt% diglycolamine (DGA) and 15% wt% triethylene glycol. It was determined that this concentration of TEG was approximately the minimum concentration needed to maintain the reacted chemical in a uniform solution.

Example 5

The scavenger formulation disclosed in Example 3 was subjected to a scavenging capacity test using an inlet gas containing approximately 18% hydrogen sulphide and 82% carbon dioxide. The test was stopped after the level of hydrogen sulphide in the outlet gas reached approximately 1%. The spent solution produced by this test is more representative of field conditions relative to those outlined in Examples 2 and 3 since using a scavenging solution until well after breakthrough is not typically experienced in the field.

The capacity test produced a clear yellow single-phased spent solution. The stability of said solution was first tested by bubbling nitrogen through it at a rate of 250 mL/minute for 72 hours. The spent solution turned slightly turbid over the course of the experiment but no solid dithiazine formed. This solution was then cooled to approximately -25 ⁰ C for an extended period of time and although the solution did not freeze, the viscosity increased slightly and turned milky white. The change in appearance is thought to be due to dithiazine solids beginning to form in the solution; however, no dithiazine settled out of solution and no solid deposits were formed. This process was found to be completely reversible since the milky white characteristic appearance disappeared after the temperature was increased to 20 ⁰ C.

Example 6

A scavenger solution was formulated from 51.4 wt% Formalin (37.5% formaldehyde; 25% methanol), 27.2 wt% monoethanolamine (MEA), 1.4 wt% diglycolamine (DGA) and 15% wt% triethylene glycol. The scavenger formulation was field tested and shown to be effective in inhibiting formation of solid deposits.

Example 7

A scavenger solution was formulated from 51.4 wt% Formalin (37.5% formaldehyde; 25% methanol), 27.2 wt% monoethanolamine (MEA), 1.4 wt% diglycolamine (DGA) and 20wt% triethylene glycol. The scavenger formulation was field tested and shown to be effective in inhibiting formation of solid deposits.

Example 8 Field Test Results

In a specific application in southern Alberta, the operating conditions were consistent with a hydrogen sulphide concentration of 1100 ppm, pressure of 620 kPag, operating temperature of 45 to 50 ⁰ C and a carbon dioxide rich stream with a flowrate of 4 to 5

MMscfd. The previous process involved partially filling a contact vessel with a formulation comprising of formalin (37.5 wt% formaldehyde) and amine (monoethanolamine and 2-(2- aminoethoxy) ethanol blend). After 18 days of operation, the outlet hydrogen sulphide content exceeded the allowable limit and arrangements were made to change out the reacted liquid scavenger. In the process of trying to remove the reacted product from the vessel, it was observed that there was a significant amount of solid material that was orange and yellow in colour with the consistency of wet mud. Samples of the solid material were collected and identified through laboratory analysis as being predominantly dithiazine; a reaction by-product of triazine and hydrogen sulphide.

An upper manway on the contactor was opened after the vessel was drained of all pumpable liquid. The contactor was observed to contain a 2 to 4 inch layer of solid dithiazine on the walls of the vessel. In addition, a significant amount of solid dithiazine was observed to remain in the bottom section and on the inlet gas dispersion bars.

Arrangements were made to wash the contactor out with hot caustic, drain and ventilate the vessel, and then visually inspect the internals. Once this 24 hour process was completed, some solid dithiazine material remained in the vessel; particularly in the bottom and on the gas distributor. The remainder of the solid dithiazine was manually removed from the contactor.

Efforts were successfully made in the laboratory to duplicate the formation of the analyzed solid dithiazine by completing capacity tests under similar operating conditions as the processing plant. Initial tests were completed with products that were formulated with reduced formalin to amine ratios. Although a slight reduction in solids formation was observed with smaller formalin to amine ratios, a significant amount of a "pasty" solid

(identified as dithiazine) continued to be formed. The second phase of the evaluation was to assess the effects of modifying the formulation with various additives to improve the solubility of the generated dithiazine. It was through these tests with various additives that the benefits of triethylene glycol were realized.

A formulation comprising of an 80 wt% triazine blend (the reaction products of 95% MEA and 5% DGA) and 20 by wt% triethylene glycol was manufactured and loaded into the contact vessel. The processing system operated for 3 weeks with the triethylene glycol enhanced product with no detection of newly formed dithiazine solids. The processing facility continues to operate with no formation of dithiazine solids; recovered reaction product is a low viscosity, pumpable liquid solution. With the triethylene glycol enhanced liquid scavenger formulation, this particular facility has attained a record number of operating days with no unscheduled down time. As would be known to one skilled in the art, the gas stream contained hydrogen sulphide. Accordingly, the formulation and method is effective in removing hydrogen sulphide from the gas stream and inhibiting the formation of dithiazine solids.

Example 9

To determine whether other glycols could act as a suitable co-solvent two additional scavenger formulations were subjected to a capacity test using an inlet gas containing approximately 18% hydrogen sulphide and 82% carbon dioxide. The capacity tests were stopped after the level of hydrogen sulphide in the outlet gas reached approximately 4%. The two formulations each consisted of a 1 :1.5 molar ratio of amines to formaldehyde, with one formulation containing 15% ethylene glycol, and the second formulation containing 20% diethylene glycol (DEG). The spent solutions of both formulations produced large quantities of sticky dithiazine solids that were deposited on the walls of the vessel. These results indicate that amorphous dithiazine deposits cannot be controlled or prevented by the addition of ethylene glycol or diethylene glycol, suggesting that the effect is specific to the addition of triethylene glycol in approximately the quantities disclosed.

Example 10

A scavenger composition was formulated from 56.6% wt% Formalin (37.5%formaldehyde; 10-15% methanol), 28.4% monoethanolamine (MEA) and 15% triethylene glycol. The scavenger composition was subjected to a scavenging capacity test at 2O ⁰ C using an inlet gas containing approximately 18.5% hydrogen sulfide and 81.5% carbon dioxide. The test was stopped after the level of hydrogen sulfide in the outlet gas reached approximately 3%.

The spent solution consisted of a single phase and more importantly, neither crystalline nor amorphous dithiazine solids formed at 2O ⁰ C. The spent solution was further tested by cooling the solution to -10 ⁰ C and then -25 ⁰ C for extended periods of time. Although these are conditions that are known to promote the formation of dithiazine solids, neither crystalline nor amorphous dithiazine solids formed at these sub-zero temperatures. These results demonstrate that the alleviation of problems associated with dithiazine solid deposit buildup do not require the presence of a second amine but instead can be attributed to the presence of triethylene glycol in the triazine formulation. Accordingly, the results indicate that the range of triethylene glycol used in the presence of the reaction products of monoethanolamine, diglycolamine and formaldehyde would be equally as applicable to the formulation made without diglycolamine (about 15% to 25%).

In summary, it has been found that formulations containing monoethanolamine, formaldehyde and triethylene glycol produce a spent product which consists of a single liquid phase. Any amorphous dithiazine solids which may or may not form will be suspended in solution and solid deposits on equipment which could lead to blockages are minimized or eliminated.

Without being bound to one particular theory, it is believed that spent solutions of the present invention consist of a single liquid phase for the reason that triethylene glycol acts as a co-solvent for water, methanol, dithiazine and the other reaction byproducts. The spent solution retains a single phase even after high temperature conditions since the co-solvent is nonvolatile and is not stripped out of the formulation. In situations when the scavenger solution is normally spent as in Example 4, the dithiazine remains dissolved in the spent formulation. However, as the temperature decreases the solubility of dithiazine in the spent formulation also decreases and amorphous dithiazine solids begin to form; this is observed as an increase in the turbidity of the solution. Alternately, in situations where the scavenger solution is heavily overspent, excess amorphous solids are formed from the insoluble

dithiazine. It has been found that depending on the ratio of triethylene glycol to total amines and formaldehyde, the amorphous dithiazine solids can be kept as a suspension which subsequently eliminates solid dithiazine deposit buildup. In fact, the ratio of triethylene glycol to total amines and formaldehyde can be altered to produce different desired effects depending on the application.

The foregoing is a description of an embodiment of the invention. As would be known to one skilled in the art, variations are contemplated that do not alter the scope of the invention. For example, the percentage of triethylene glycol could be greater than 24%, for example, 30%, or 35%. The limiting factor is the cost of triethylene glycol and at the present time, a percentage above about 24% is considered to be uneconomical. Further, it should be understood that the amount of triethylene glycol will vary depending on the application, field conditions and desired effect, however, as would be known to one skilled in the art, as the triethylene glycol content is increased above a threshold the scavenging capacity of the formulation decreases thus less dithiazine is produced.