WO2009065220A1

WO2009065220A1 - Chemical injection system

Info

Publication number: WO2009065220A1
Application number: PCT/CA2008/002041
Authority: WO
Inventors: Jim Fraser; Michael Sasges; Steven Bakker
Original assignee: Trojan Technologies
Priority date: 2007-11-23
Filing date: 2008-11-24
Publication date: 2009-05-28

Abstract

There is described a chemical injection system. Preferably, the system comprises a number of tubular members. The distal end of each tubular member is configured to be immersed in a flow of fluid and the proximal end of each tubular member is connected to a chemical supply. The system further includes a guide member for receiving at least one tubular member. The guide member is configured to orient the at least one tubular in a predetermined region of the flow of fluid. The chemical injection system may be regarded as a trailing array of flexible injection lines. By balancing the flexibility, length, weight, diameter, buoyancy, hydrodynamic characteristics and/or the angle at which each flexible injection line is positioned relative the flow of fluid, it is possible to dispose the distal end of each flexible injection line in a pre-determined region in the flow of fluid.

Description

CHEMICAL INJECTION SYSTEM

FIELD OF THE INVENTION

In one of its aspects, the present invention relates to a chemical injection system. In another of its aspects, the present invention relates to a process for injecting a chemical into a flow of fluid, particularly a flow of water.

DESCRIPTION OF THE PRIOR ART

Over the last 20 years, treatment of water has become more important due to increasing population in metropolitan areas and decreasing supply of fresh water sources.

Thus, the operation of municipal drinking water and wastewater treatment plants has become more prevalent. In these plants, water is treated by various means and thereafter discharged into a water reservoir (e.g., a lake, river, etc.) in the case of wastewater or into a water distribution network for delivery to users in the case of municipal drinking water treatment plants.

In the course of treating municipal water and wastewater, it is commonly desired to inject one or more chemicals into the water. This can be done upstream of the treatment plant, downstream of the treatment plant, within the treatment plant or any combination of these.

By way of a first example, the inlet streams for these plants, particularly wastewater treatment plants, often contains solubilized iron (typically in the form of a ferrous compound). It is desirable to remove this solubilized iron as part of the treatment operation. Conventionally, this has been done by adding an oxidant such as hydrogen peroxide (H₂O₂) to convert the solubilized iron to insoluble iron (typically in the form of a ferric compound). The insolubilized iron is then useful as a flocculant during downstream treatment of the water.

Conventionally, hydrogen peroxide has been added by spraying on to the surface of water just upstream of the treatment plant. Unfortunately, this approach is inefficient and does not result in complete conversion of the solubilized iron to insoluble iron due to insufficient and timely mixing of the hydrogen peroxide in the flow of water. This results in the development of localized areas of overdosing of the hydrogen peroxide which leads to the wasteful decomposition of the hydrogen peroxide into dissolved oxygen.

By way of a second example, it is known to add bleach to (e.g., in the form of sodium hypochlorite) to the water to react with ammonia to produce monochloramine. In this approach, when localized areas of overdosing occur (due to insufficient and timely mixing of the bleach in the flow of water), this leads to "over-oxidation" resulting in the production of trichloramine which is believed to be a prescursor to the byproduct n-nitrosodimethylamine (NDMA), a suspect carcinogen.

By way of a third example, it is known to add an oxidant to water to selectively oxidize ferrous sulphide to produce solubized ferrous ion in the water, free of sulfide ions. Again, when localized areas of overdosing occur (due to insufficient and timely mixing of the oxidant in the flow of water), this leads to "over-oxidation" resulting in production of the ferric form of iron, which then binds irreversibly to phosphates present in the water, thereby rendering the iron unavailable for subsequent sulfide control (ref: US Peroxide US 6,773,604).

In some cases, in addition to the problems referred to above, increasing the dosing of the chemical being added leads to a further problem with unwanted chemicals (e.g., the chemical being added, a by-product of overdosing and the like) which do not get removed in the treatment plant (or in a particular process unit within the treatment plant). Thus, there is a significant risk that the discharge from the wastewater treatment plant (or a particular process unit) will contain the unwanted chemicals which can have deleterious effects on the environment (e.g., marine life, vegetation, etc.) or subsequent process units within the treatment plant.

Accordingly, there is a need in the art for a system that is capable of introducing a chemical compound such as an oxidant in a flow of fluid to achieve, on the one hand correct dosing for a desired chemical conversion while, on the other hand, minimizing the occurrence of overdosing to achieve that chemical conversion to a prescribed level. It would be highly desirable if such dosing could be achieved in a relatively fast manner. SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a novel chemical injection system.

Accordingly, in one of its aspects, the present invention provides a chemical injection system comprising: a plurality of tubular members, a distal end of each tubular member configured to be immersed in a flow of fluid and a proximal end of each tubular member connected to a chemical supply; and a guide member for receiving at least one tubular member, the guide member configured to orient the at least one tubular in a predetermined region of the flow of fluid.

A number of advantages accrue from the present chemical injection system.

These include but are not limited to one or more of the following:

• the system significantly improves the mixing efficiency of the chemical in the flow of fluid - e.g., the H₂O₂ conversion of iron described above - while concurrently reducing the occurrence of overdosing the fluid with the chemical;

• the system does not foul with debris that is contained in the flow of fluid - e.g., a rag or other debris that contacts a tubular member would slide down the line and off of the end as there are no protrusions and/or the force of the fluid against this line would assist debris removal.;

• the system is capable of accomodating varying fluid flow levels in the conduit;

• the system is reliable and relatively easy to maintain; • the system is readily adapttable to various fluid conduit configurations;

• the system is readily removable without the need for ingress into the piping or manhole structures;

• the injectors are always in the flow: even if the fluid flow level rises or falls, the position of the injector lines is relatively self- adjusting;

• the system is modular and the tubular members could be used in many different situations - e.g., variable manhole sizes, variable pipe sizes and variable types of these, etc. (a small pulley system may be desirable for very deep manholes);

• the system accommodates varying manhole depths;

• the system can be maintained externally, no breathing apparatus required;

• the system can be readily removed if required for piping service; and

• the system is readily adaptable specific needs - e.g., flow velocities, new larger pipe diameter and the like.

In one sense, the present chemical injection system may be regarded as a trailing array of flexible injection lines. By balancing the flexibility, length, weight, diameter, buoyancy, hydrodynamic characteristics and/or the angle at which each flexible injection line is positioned relative the flow of fluid, it is possible to dispose the distal end of each flexible injection line in a pre-determined region in the flow of fluid.

A series of factors can influence the vertical position of the distal end (usually comprising the injection port for the chemical) of the flexible injection line: • the relative velocity of the fluid to trailing array of flexible injection lines;

• the weight of the end of the each trailing flexible injection line - i.e., a relatively heavy end will cause the trailing flexible injection line to sink further;

• the hydrodynamics of the trailing flexible injection line - e.g., a relatively girthy line has more drag and would lift the distal end of the flexible injector line (all other factors being constant), a wing, foil or fin could be affixed to the distal end of the flexible injector line to position that end;

• the stiffness of the flexible injector line could be changed to modify the position of the distal end of the line (e.g., an extremely flexible line would allow the line to sink as deep as the other parameters allow); if on the other hand, a spring steel wire of the same diameter (and weight) were used, the distal end of the line would actually sink deeper as the line would tend to try to stay straight due the stiffness of the line; and

• the stiffness of the flexible injector line can be varied from line to line and/or along the length of a given flexible injector line.

Of these parameters, varying the stiffness of the line by use of a spring member (or other stiffening) incorporated with the flexible injector line and the weight of the flexible injector line are believed to be the parameters more readily varied by the user to adapt the sytem to a particular conduit and flow conditions.

To accurately place the lines and the injectors in the flow of fluid, various parameters of the flexible injector lines and the required chemical (e.g., an oxidant such as H₂O₂, bleach and the like) distribution should be addressed and optimized, including one or more of the following:

• flow rate per injector line and per injector (tip); • material selection for the inner liner of the tubular member that carries the chemical to be injected (e.g., H₂O₂ mixture);

• material used as the stiffener spring (if present) incorporated with the tubular member;

• material used for an outer sheath of tubular member (e.g.,

Teflon™) that will be the least likely to foul and the diameter of this sheath which affects the impact of the pressure of the flow on the tubular members;

• length of each tubular member;

• weight of each tubular member;

• weight of the distal end of each tubular member;

• in some applications, use of an adjustable guide member;

• in some applications use of a non-adjustable guide member; and

• the angle at which the tubular member is presented to the flow relative to the direction of fluid flow through the conduite seen from a side view (above or below the horizontal), and the angle the line is presented to the flow when seen from above the system (towards the wall or in line with the direction of fluid flow in the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference to the accompanying drawings, wherein like reference numerals denote like parts, and in which:

Figure 1 illustrates an isometric schematic view of the present chemical injection system used in a relatively high fluid flow application;

Figure 2 illustrates a downstream view of the embodiment show in Figure 1 ; Figure 3 illustrates a side elevation of the embodiment shown in Figure 1;

Figure 4 illustrates a top view of the embodiment illustrates in Figure 1 ;

Figure 5 illustrates an isometric schematic view of the present chemical injection system used in a relatively low fluid flow application;

Figure 6 illustrates a downstream view of the embodiment show in Figure 5;

Figure 7 illustrates a side elevation of the embodiment shown in Figure 5;

Figure 8 illustrates an enlarged view of a portion of the chemical injection system illustrated in Figures 1-7;

Figure 9 illustrates a preferred embodiment of a tubular member used in the present chemical injection system;

Figure 10 illustrates an enlarged isometric view of the distal end of the tubular member illustrated in Figure 9;

Figure 11 illustrates a sectional view of a distal end of a preferred tubular member of the present chemical injection system; and

Figure 12 illustrates an alternate embodiment of the present chemical injection system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the preferred embodiments of the invention will be described with reference to injection of hydrogen peroxide in a flow of wastewater, it will be understood that the invention is not restricted to this particular application.

For wastewater entering or being conveyed to a conventional treatment plant, the following constraints and paramaters are typically encountered:

• the piping can be from 3 feet to 10 feet in diameter;

• the piping can be round or rectilinear (e.g., square-shaped cross- section); • the piping can be opened or closed in cross-section (e.g., the piping can be a pressured or non-pressurized conduit or it can be an open channel);

• the flow velocity typically is 2-3 feet/second;

• the fluid level in the piping (conduit) can change from ¹A full to ²A full (typical) - occasionally, the piping (conduit) can be 100% full;

• the manhole access can be a 2 ft. to 3 ft. diameter hole up to 30-40 feet deep or an open rectangular structure the width of the pipe

• the potential for hydrogen sulphide in the manholes and piping requires that a full breathing apparatus be worn if a worker were to have to go into these areas.

With reference to Figures 1-4, there is illustrated a portion of a conduit system 10 comprising a man-hole 12. As shown, fluid 14 is flowing in conduit system 10 in the direction of arrow 16 and the level of fluid 14 is indicated at FLl. Disposed in man-hole 12 is a preferred embodiment of the present chemical injection system 20.

Chemical injection system 20 comprises a carriage 22 which will be described in more detail below. As shown, a handle 24 is connected to carriage 22. Handle 24 can be used to engage a cam (not shown) to secure carriage 22 to man-hole 12.

A series of tubular members 26 are disposed in fluid 14 and are connected at their proximal end to carriage 22. This will be described in more detail below with reference to Figure 8.

Figures 5-7 illustrate an alternate embodiment wherein the fluid level is relatively low compared in Figures 1-3. In Figures 5-7, the fluid level is indicated at FL2. Thus, chemical injection system 20 may be used in a given conduit system 10 in which the fluid level fluctuates from very low to FLl to FL2 to completely full.

With reference to Figure 8, there is illustrated an enlarged view of carriage 22. As shown, each tubular member 26 is secured to carriage 22 by a swivel device 30. Swivel device 30 is a double action device that is capable of independently rotating in the direction of arrow 32 and in the direction of arrow 34. When swivel device 30 is rotated in the arrow 32, this allows for lateral or horizontal adjustment of the tubular members 26. When swivel device 30 is rotated in the direction of arrow 34, this allows for adjustment of the vertical position of tubular members 26. This type of adjustment is particularly advantageous when transitioning between high fluid level use (Figures 1-3) and low fluid level use (Figures 5-7). Tubular members 26 are connected to a manifold 36 which, in turn, is connected to a supply of chemical (not shown; e.g., H₂O₂).

With reference to Figures 9-11, there is illustrated tubular member 26 described above. Tubular member 26 comprises a flexible conduit 40 interposed between a pipe connection member 42 and a nozzle 44. Nozzle 44 comprises a number of annular ports 46.

Flexible conduit 40 is made of a resilient material that is resistant to the chemical being conveyed there through. For example, if the chemical to be injected is hydrogen peroxide, it is preferred that flexible conduit 40 be constructed of a material such as Teflon™ tubing, soft polyvinylchlorine (PVC) tubing or a combination thereof (e.g., PVC tubing with a coating of Teflon™). The material should possess durable mechanical properties having regard to the nature of the chemical being injected and the nature of the fluid with which the injection system is being used. Disposed within flexible conduit 40 is a spring stiffener element 50 (Figure 11) which serves to provide an appropriate stiffness to tubular member 26 and to keep nozzle 44 correctly oriented with respect to the flow of fluid.

It will be understood that the guide member of the present chemical injector may be carriage 22 which incorporates swivel device 30. In an alternate embodiment, carriage 22 may be omitted and swivel device 30 (as shown or modified to be a single action swivel device) my be the guide member. In the further alternate embodiment, both carriage 22 and swivel device 30 may be omitted and replaced by a structure that servies to orient and maintain nozzle 44 in the correct region in fluid 14.

With reference to Figure 12, there is illustrated an alternate embodiment of the chemical injection system described above. In Figure 12, circles A have been used to denote distal injection ports that are disposed on tubular members 26 - this is similar to the embodiment described above. In the variation in Figure 12, there are additional injection ports shown at circles B disposed proximally with respect to the injection ports shown at circles A. The use of the additional injection ports can be beneficial when large dosing of the chemical is required and/or the throughput volume of the fluid is high.

While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments.

All publications, patents and patent applications referred to herein are incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.

Claims

What is claimed is:

1. A chemical injection system comprising: a plurality of tubular members, a distal end of each tubular member configured to be immersed in a flow of fluid and a proximal end of each tubular member connected to a chemical supply; and a guide member for receiving at least one tubular member, the guide member configured to orient the at least one tubular in a predetermined region of the flow of fluid.

2. The chemical injection system defined in Claim 1, further comprising a carriage secured with respect to a conduit for receiving the flow of fluid, the carriage configure to receive the plurality of tubular members.

3. The chemical injection system defined in Claim 2, wherein the carriage comprises a first adjustment member for adjusting the tubular members with respect to a first plane containing a direction of fluid flow through the conduit.

4. The chemical injection system defined in Claim 2, wherein each tubular member is connected to a first adjustment member for adjusting the orientation of the tubular member with respect to a first plane containing a direction of fluid flow through the conduit.

5. The chemical injection system defined in Claim 2, wherein the carriage comprises a first adjustment member for adjusting the tubular members with respect to a first plane containing a direction of fluid flow through the conduit.

6. The chemical injection system defined in any one of Claims 4-5, wherein the first plane comprises a substantially horizontal plane.

7. The chemical injection system defined in any one of Claims 4-6, wherein each tubular member is connected to a second adjustment member for adjusting the orientation of the tubular member with respect to a second plane different from the first plane and containing a direction of fluid flow through the conduit.

8. The chemical injection system defined in any one of Claims 4-6, wherein the carriage comprises a second adjustment member for adjusting the tubular members with respect to a second plane different than the first plane and containing a direction of fluid flow through the conduit.

9. The chemical injection system defined in Claim 7-8, wherein the second plane is orthogonal with respect to the first plane.

10. The chemical injection system defined in any one of Claims 7-8, wherein the second plane comprises a substantially vertical plane.

11. The chemical injection system defined in any one of Claims 2-10, further comprises a locking member to reversibly secure the carriage to the opening of the conduit.

12. The chemical injection system defined in Claim 11, wherein the locking mechanism comprises a cam member movable with respect to the carriage between a locked first position and an unlocked second position.

13. The chemical injection system defined in Claim 12, wherein the carriage further comprises at least one biasing member for biasing against a surface of the opening to the conduit in the cam member is in the locked first position.

14. The chemical injection system defined in any one of Claims 2-12, further comprising a deployment member for modifying the position of the carriage with respect to the opening in the conduit.

15. The chemical injection system defined in any one of Claims 1-13, wherein the plurality of tubular members are of the same length.

16. The chemical injection system defined in any one of Claims 1-13, wherein the plurality of tubular members are of different length.

17. The chemical injection system defined in any one of Claims 1-15, wherein each tubular member comprises an injector portion and a flexible conduit portion.

18. The chemical injection system defined in Claim 17, wherein the injector portion comprises a single injection port.

19. The chemical injection system defined in Claim 17, wherein the injector portion comprises a plurality of injection ports.

20. The chemical injection system defined in Claim 17, wherein the injector portion comprises a plurality of annularly disposed injection ports.

21. The chemical injection system defined in any one of Claims 17-20, wherein each tubular member comprises a first injector portion near the distal end thereof.

22. The chemical injection system defined in any one of Claims 17-20, wherein each tubular member comprises a first injector portion at the distal end thereof.

23. The chemical injection system defined in any one of Claims 21-22, wherein each tubular member comprises a second injector portion disposed proximally of the first injector portion.

24. The chemical injection system defined in any one of Claims 1-23, wherein at least one tubular member comprises a weight member.

25. The chemical injection system defined in any one of Claims 1-23, wherein at least two tubular members each comprise a weight member.

26. The chemical injection system defined in any one of Claims 1-23, wherein each tubular member comprises a weight member.

27. The chemical injection system defined in any one of Claims 24-26, wherein the weight member is disposed at the distal end of the tubular member.

28. The chemical injection system defined in any one of Claims 24-26, wherein the weight member is disposed proximally of the distal end of the tubular member.

29. The chemical injection system defined in Claim 28, wherein the weight member is integral with a conduit portion of the tubular member

30. The chemical injection system defined in any one of Claims 1-29, wherein at least one tubular member comprises a stiffening member.

31. The chemical injection system defined in any one of Claims 1-29, wherein at least two tubular members each comprise a stiffening member.

32. The chemical injection system defined in any one of Claims 1-29, wherein each tubular member comprises a stiffening member.

33. The chemical injection system defined in any one of Claims 30-32, wherein the stiffening member is disposed at the distal end of the tubular member.

34. The chemical injection system defined in any one of Claims 23-25, wherein the stiffening member disposed proximally of the distal end of the tubular member.

35. The chemical injection system defined in Claim 34, wherein the weight member is integral with a conduit portion of the tubular member.

36. The chemical injection system defined in any one of Claims 1-35, wherein each tubular member has substantially the same weight.

37. The chemical injection system defined in any one of Claims 1-35, wherein at least two tubular members different weights.

38. The chemical injection system defined in any one of Claims 1-37, wherein the proximal end of each tubular member is connected to a manifold member, the manifold member connected to the chemical supply.

39. A method of injecting a chemical into a flow of fluid comprising the steps of: securing the the carriage of the chemical injection system defined in any one of Claims 1-38 to the opening of the conduit; immersing the distal end of each tubular member in the flow fluid; and injecting the chemical into the flow fluid.

40. The method defined in Claim 39, wherein the chemical comprises an oxidant.

41. The method defined in Claim 39, wherein the chemical comprises a peroxide compound.

42. The method defined in Claim 39, wherein the chemical comprises hydrogen peroxide.

43. The method defined in any one of Claims 39-42, comprising the further step of: adjusting the position of at least one tubular member in response to a change in fluid level in the conduit.

44. The method defined in any one of Claims 39-42, comprising the further step of: adjusting the position of at least two tubular members in response to a change in fluid level in the conduit.

45. The method defined in any one of Claims 39-42, comprising the further step of: adjusting the position of each tubular member in response to a change in fluid level in the conduit.

46. The method defined in any one of Claims 39-45, wherein the fluid comprises water.