Steam injection and mixing apparatus

A device for the injection and mixing of steam into a fluid stream. A conduit which is cylindrically-shaped is provided for carrying a fluid such as water. A tubular conduit is then provided for discharging steam in the vicinity of a material mixing apparatus which possesses a plug for intermittently blocking steam discharge within the cylindrically-shaped conduit. A material mixing apparatus is positioned with the cylindrically-shaped conduit for mixing steam with the fluid stream, the material mixing apparatus being in the shape of the conduit and having openings containing mixing elements each of which induce a rotational angular velocity of the same sign to the fluid.

TECHNICAL FIELD OF THE INVENTION 
The present invention deals with a device for the injection and mixing of 
steam into a fluid stream of, for example, water. 
BACKGROUND OF THE INVENTION 
It has long been recognized that an exceedingly efficient technique for 
heating liquids is to directly inject steam within the liquid to be 
heated. When steam is injected directly into a liquid, one can realize 
almost one hundred percent of the BTU's in the steam which are absorbed 
directly into the liquid. Unlike indirect heating by means of, for 
example, a heat exchanger, there is no condensate retaining unused 
sensible heat. Because of this high heat-transferability, direct steam 
injection can save a great deal in energy costs. 
Direct steam injection systems offer other benefits as well when compared 
to heat exchangers and comparable indirect heating systems. A direct steam 
injection system can provide very accurate temperature control within 
several degrees fahrenheit and are efficient in that scale buildup does 
not become an issue. Systems of this nature also tend to be more compact 
than comparable heat exchange devices. 
There are four basic types of direct steam injection systems, namely, the 
sparger, the mixing tee, the Venturi and the modulating injection system. 
The sparger is the simplest system in that it generally consists of 
nothing more than a perforated pipe discharging steam in a vented storage 
tank. However, these systems are not without their disadvantages. For 
example, they must be operated at a set and constant flow rate to prevent 
the hammering effect observed in steam/water systems. This is the result 
of operating at steam and water pressures which are at or near 
equilibrium. 
Mixing tees comprise nothing more than steam and water lines which join a 
common conduit. Because separate lines are used for each fluid, capital 
equipment tends to be expensive and inconvenient to install. 
Venturi systems are generally more acceptable than those previously 
discussed, but should be operated under conditions of constant steam 
pressure, inlet water pressure and outflow demand. If they do not, a 
hammering effect can again be observed as the steam and inlet water 
pressures approach an equilibrium condition. In addition, changes in these 
variables can result in varying outlet temperatures which may not be 
desired. 
Prior attempts have even been made to employ static mixers for direct steam 
injection into a liquid stream. However, as in the other prior art 
approaches, the results have proven spotty with instability and lack of 
control problems being manifest. 
FIG. 1, labeled "prior art" was reproduced from an article appearing in 
Chemical Engineering in its June 28, 1982, issue. The article, entitled 
"Considered Direct Steam Injection for Heating Liquids" by Pick 
illustrates a variable-orifice injector system with modulating steam 
control. More specifically, cylindrical tube 10 is shown as possessing 
steam inlet 1 which injects the steam into an injector tube 2 and piston 
5. The piston is biased by spring 3 which acts to block or free holes 
contained in injector tube 2 depending upon steam pressure emanating from 
inlet 1. Bias is maintained by spring 3, the overall effect being to heat 
water entering from cold water inlet 6 as it emanates from cylindrical 
tube 10 at outlet 4. In light of the fact that this product has tiny 
holes, depending upon the quality of the water or liquid being used, the 
system can become plugged. 
It is thus an object of the present invention to provide a modulating 
injection system for the introduction of steam to a fluid without the 
drawbacks as experienced in prior devices such as those shown in FIG. 1.

SUMMARY OF THE INVENTION 
The present invention deals with a device for the injection and mixing of 
steam into a fluid stream of, for example, water. The device comprises of 
substantially cylindrically-shaped conduit having a longitudinal axis and 
substantially circular cross-section for carrying the fluid stream. The 
conduit is also provided with an inlet for accepting the fluid stream and 
an outlet for discharging the fluid stream along the longitudinal axis. 
Means are provided for discharging steam substantially proximate the 
longitudinal axis of the cylindrically-shaped conduit. Material mixing 
apparatus for mixing the steam with the fluid stream is provided in the 
shape of the conduit. The material mixing apparatus comprises a plurality 
of openings having mixing elements which induce a rotational angular 
velocity to the fluid stream passing therethrough. The material mixing 
apparatus further is characterized as possessing plug means for 
substantially blocking the steam discharge means when the plug means in is 
a first position but not blocking the steam discharge means when plug 
means is in a second position. Means are also provided for urging the plug 
means to the first position and resisting movement of the plug means from 
assuming the second position. 
DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 has been previously discussed as being representative of the state 
of the art of modulating injector systems, in this case, employing piston 
control. This design provides certain advantages over disparger, mixing 
tees and Venturi-type systems. The piston 5 maintains a differential 
pressure between steam and water pressures preventing pressure 
equalization and eliminating steam-water hammer. Because it compensates 
automatically for changes in steam pressure, inlet-water pressure and 
hot-water demand, the system, when properly instrumented, provides a wide 
range of turndown capabilities and accurate temperature control under 
varying load conditions. However, as noted in the article cited previously 
from Chemical Engineering in its June 28, 1982, issue, the author 
recognized that a piston controlled modulating system has moving parts and 
very small holes that can sometimes, depending upon the quality of the 
water or liquid being used, get stuck or plugged. The device of the 
present invention is intended to provide the advantages of such a system 
without any significant disadvantages. 
The present invention is illustrated in FIGS. 2, 3 and 4. Turning first to 
FIG. 2, the device of the present invention shown as device 20 in partial 
cross-section is depicted by substantially cylindrically-shaped conduit 21 
having inlet 22 and outlet 26. Inlet 22 is intended to receive a fluid 
such as water in the direction of arrow 23 along the longitudinal axis 37 
of device 20. 
The means for discharging steam comprises tubular conduit 24 passing 
through a wall of cylindrically-shaped conduit 21. The tubular conduit 24 
is configured substantially in the shape of an L with section 27 of the L 
passing through a wall of cylindrically-shaped conduit 21 and a second 
section 28 of the L being substantially within the cylindrically-shaped 
conduit 21 having a longitudinal axis which substantially coincides with 
longitudinal axis 37 of cylindrically-shaped conduit 21. As such, steam 
enters tubular conduit 24 at inlet 25 and is discharged at outlet 29 
proximate material mixing apparatus 32. 
Material mixing apparatus 32 is in the shape of conduit 21 and comprises a 
plurality of openings 35 (FIG. 4) housing mixing elements 36 which induce 
a rotational angular velocity to the fluid stream passing therethrough. 
The material mixing apparatus is further characterized a possessing plug 
means 30. Plug means 30 is configured to substantially block steam 
discharge means 24 at its outlet 29 when in a first position but not block 
the steam discharge means when plug means 30 is in a second position. This 
is accomplished by employing means for urging the plug means to this first 
position. Plug means 30 as well as downstream cap 31 are shown to be 
generally in the shape of a cone. Plug means 30 is shown to possess a 
pointed end facing upstream and a base portion facing downstream, the base 
portion being sized to slidably move within the material mixing apparatus 
along its inner wall 34 in response to steam pressure in the tubular 
conduit which is resisted by urging means shown in FIG. 3 as preferably 
being a stainless steel spring 33. When the steam pressure is below a 
threshold value, plug means 30 at least partially enters the tubular 
conduit at its exit 29 and is not pushed away from that location until 
steam pressure within tubular conduit 24 provides a force stronger than 
that exerted by urging means 33. Once this has been accomplished, steam 
exits at 29 and passes over and around plug means 30 to pass within mixing 
means 32 through orifices 35. 
Orifices 35 are generally of the type disclosed in Applicant's prior U.S. 
Pat. Nos. 3,923,288 and 4,614,440, the disclosures of which are hereby 
incorporated by reference. The mixing elements contemplated for use herein 
are intended to induce a rotational velocity to the fluid passing 
therethrough. In practice, it is intended that each of the mixing elements 
induce or impart the same rotational sign to the fluid passing through the 
openings 35. 
The benefits derived from using the static mixing device shown in FIGS. 3 
and 4 and in U.S. Pat. Nos. 3,923,288 and 4,614,440 cannot be overly 
emphasized. The mixing elements 36, being all of the same sign produce 
sets of rotational vortexes that impinge on each other greatly enhancing 
mixture of the steam into the liquid stream. Not only do the vortex pairs 
37A/37B, 37B/37C, 37C/37D, 37D/37E, 37E/37F and 37F/37A impinge upon each 
other, non-adjacent pairs such as 37A/37D, 37B/37E and 37C/37F among 
others also establish impingement points. 
The interaction at these impingement points makes the vortexes mutually 
destroy themselves resulting in zero net rotational forces at the exit. 
This avoids the problem of centrifugal separation of gas (steam) and 
liquid (water) while providing superior mixing. 
In viewing the above discussion and appended claims, it becomes readily 
apparent that in practicing the present invention, one is able, for the 
first time, to provide a modulating system which eliminates prior art 
injector tube 2 and thus eliminates the plugging problems of prior 
devices. The present mixing means fully integrates steam injection with a 
moving fluid stream which efficiently transfers those BTU's contained 
within the steam to the fluid. 
In view of the foregoing, modification to the disclosed embodiments can be 
made while remaining within the spirit of the invention by those of 
ordinary skill in the art. As such, the scope of the invention is to be 
limited only by the appended claims.