The present invention relates to an apparatus and process for the granulation of liquified substances, and in particular to forming generally spherical sulphur granules from molten sulphur.
Sulphur is a by-product of sour petroleum production, usually oil and natural gas. Previously, extracted sulphur was typically dried and solidified (i.e. “frozen”) into large blocks for on-site storage, and then broken down for transportation elsewhere. Such blocks were inconvenient to handle, created much unwanted dust and did not compact efficiently for transport, as too many voids resulted. Hence, processes were developed as early as the 1970s to create spherical granules of sulphur, as such granules resulted in easier handling, including less dust during handling, and better storage and more efficient transportation due to improved bulk density when both poured and packed (i.e. fewer unnecessary voids).
However, these earlier granulation processes, and the apparatuses for carrying out these process, suffered from many disadvantages. Some required several passes through a device to form the product, or the drums needed to be seeded from other sources, while others could not adequately control the quality of produced product as seed or granule formation was not adequately controlled. Granule production plants were also constructed to produce very large volumes (e.g. 55-60 tonnes/hr), had relatively large footprints and were rather expensive to manufacture and operate. This either limits or eliminates their desirability in smaller production and refinery facilities. The reality in today's market is that there are greater numbers of smaller-scale sulphur production operations, and that sulphur producers require granulation equipment that is smaller in scale and more portable.
What is therefore desired is a novel sulphur granulation apparatus of more compact and cost effective design that overcomes the above disadvantages and provides a more efficient process to achieve granules of desired quality. It should be a completely self-contained granulation process where in essence the only emission is scrubbed process air. It should preferably be transportable.
According to the present invention, there is provided in one aspect an apparatus for producing granular particles comprising:
a support frame;
an elongate hollow drum rotatably mounted on the support frame having a first end and an opposed second end lying along a longitudinal axis of rotation;
means on the support frame for rotating the drum about the axis;
a plurality of flights circumferentially spaced inside the drum for creating a curtain of falling particles during rotation;
a processing fluid conduit extending in the drum and having a plurality of processing fluid nozzles spaced therealong for spraying the processing fluid in a predetermined spray pattern;
a cooling fluid conduit extending in the drum providing a plurality of cooling fluid nozzles for spraying cooling fluid, a first segment of the cooling fluid nozzles defining a seed generation zone by providing an intense cooling fluid spray pattern for a first portion of the processing fluid nozzles to create solid seed particles, and a second segment of the cooling fluid nozzles defining a product growth zone by providing a moderate cooling fluid spray pattern for a second portion of the processing fluid nozzles to grow the seed particles to granular particles;
a drying means for introducing a drying gas into the drum along the axis to flush unwanted moisture and dust in an exhaust air stream; and,
an outlet at the second end for the exhaust air stream and for removing the granular particles from the drum.
In another aspect the invention provides a cyclone separator for filtering the exhaust air stream.
In yet another aspect the invention provides a granular air filter for filtering the exhaust air stream, whether in place of or in conjunction with the cyclone separator.
In yet another aspect a split ring collar is provided for drum maintenance and operation.
In another aspect the invention provides a granulation process for producing granular particles comprising:
a) rotating an elongate hollow drum having a first end and an opposed second end lying along a longitudinal axis of rotation;
b) spraying a processing fluid in a processing fluid spray pattern having first and second portions inside the drum;
c) spraying a cooling fluid inside the drum in a first segment defining a seed generation zone by providing an intense cooling fluid spray pattern for the first portion of the processing fluid spray to create solid seed particles, and in a second segment defining a product growth zone by providing a moderate cooling fluid spray pattern for the second portion of the processing fluid spray to grow the seed particles to granular particles;
d) creating a curtain of falling particles inside the drum during rotation;
e) introducing a drying gas into the drum along the axis to flush unwanted moisture and dust in an exhaust air stream; and,
f) removing the granular particles and exhaust air stream through an outlet at the second end of the drum.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:
a is an isometric view of the granulation apparatus according to a preferred embodiment of the present invention;
b is a front elevation view of the apparatus of
c is a plan view of the apparatus of
d is an end elevation view of the apparatus viewed from the right of
a is an isometric view of a top portion of the apparatus of
b is a front elevation view of
c is a plan view of
d is a sectional view along line 3d-3d in
e is a cross-sectional view along line 3e-3e in
f is a cross-sectional view along line 3f-3f in
g is a cross-sectional view along line 3g-3g in
h is a detailed view of the circled area in
a is a more detailed elevational view of the spray bar arrangement seen in
b is a cross-sectional view along line 4b-4b in
c is a cross-sectional view along line 4c-4c in
a is an isometric view of the drum shown in
b is an isolated isometric view of a circumferential collar from the drum of
c is a more detailed plan view of the circled portion in
a is an isometric view of a cyclone separator of
b is an isometric view of the cyclone separator of
c is an elevational view from the left side of
d is a cross-sectional view along line 6d-6d of
e to 6g are views of
The present invention is an apparatus (generally indicated in the figures by reference numeral 10) and process for producing granular particles from processing fluids in a single pass through the apparatus. The particles may also be referred to herein as granular solids, granules or “product”, and the processing fluids may encompass a known range of suitable liquified substances, such as urea and bentonite fertilizers. For illustrative purposes, the preferred processing fluid is a molten sulphur for forming sulphur granules. It is also noted that terms such as “front”, “rear”, “upper”, “lower” and the like may also be used for identifying certain features of the apparatus. The use of these terms is not necessarily intended to limit its use or orientation. Further, when describing the invention, all terms not defined herein have their common art-recognized meaning.
With reference first to
The various components of this process will now be described in more detail. Reference is now made to
One of the key components of the apparatus is the granulator 40 shown in isolation and greater detail in
The drum's interior is defined by a substantially smooth, non-perforated, cylindrical inner wall 68 having a plurality of particle lifting flights 70 pointing radially inwardly which are uniformly and circumferentially spaced and substantially extend the length of the drum 50. It will be appreciated that rotation of the drum in a clockwise direction, as viewed in
Referring now as well to
A means for contacting the hot sulphur spray with a cooling fluid, preferably water, is likewise provided in the form of a water conduit 82 located longitudinally in the drum and closely spaced to the sulphur conduit 78, and has a plurality of longitudinally spaced water nozzles 84 therealong for spraying water. A first segment 82a of these water nozzles is located in the seed generation zone 74 for wetting and rapidly cooling the sprayed sulphur to a temperature range below sulphur's melting point to solidify the sprayed sulphur into the desired seed particles. A second segment 82b of the water nozzles is located in the product growth zone 76 to promote growth of the sulphur granules by keeping the granules cool (i.e. below the melting point of sulphur) to ensure solidification as they are coated with additional layers of sprayed sulphur thereon.
In the preferred embodiment the seed generation zone is defined by certain features of the water spray system which provide an intense water spray pattern. Firstly, the first segment 82a of water nozzles in the seed generation zone has a first portion of water nozzles, identified by 84a, that are located opposite a second portion of the water nozzles, identified by 84b, so that the sulphur nozzles 80 are framed intermediate these water nozzles 84a and 84b. Specifically, the upper and lower water nozzles 84a, 84b are located above and below, respectively, of respective sulphur nozzles 80, and are vertically aligned with these sulphur nozzles (i.e. all are in the same vertical plane). Secondly, each of the upper water nozzles 84a are directed downwardly toward the sprayed sulphur exiting a respective sulphur nozzle 80, and likewise each of the lower nozzles 80b are directed upwardly toward a respective sulphur nozzle, as best seen in
The water spray pattern in the downstream product growth zone 76 is substantially different and more moderate since the goal is to merely provide enough water to continue to keep the granules cool in the falling sulphur curtain as the cascading granules are coated with more layers of molten sulphur from the sulphur nozzles 80 in that zone. Although the water nozzles 84 are vertically aligned with the sulphur nozzles as in the seed generation zone, they are aimed away from the sulphur nozzles 80 and toward the granule curtain 72, as best seen in
As water is introduced into the drum to cool the sprayed molted sulphur, steam or moisture is generated which must be removed. A drying means in the form of the exhaust fan 21 draws drying gas, preferably ambient air, from the drum's inlet to discharge ends 60, 64 and creates a negative pressure inside relative to the ambient. Openings 18c in the inlet plenum 62 allow atmospheric air to be drawn into the granulation process. As the air passes lengthwise through the drum it also picks up residual sulphur dust. The resulting “dirty air” forms an exhaust air stream that passes through the drum's discharge end and the discharge plenum 66, into the cyclone separator 100 and then out the vent 22.
The negative air pressure is maintained in the drum and adjacent portions of the granulator to avoid unwanted egress of sulphur particles or other deleterious matter to the ambient during operation. As such, an effective seal 86 is also provided between the outer edge of the rotating drum and the stationary inlet and outlet plenums 62, 66 at each end of the drum to prevent air flow, either into or out of the drum. Shown in greater detail in
Such deviations in the drum's rotation are reduced by proper maintenance of the earlier-noted collars 58 on the drum's outer surface. With reference to
Another key component and important aspect of the apparatus is the filtering system for the granulator's exhaust air stream, namely the cyclone separator 100 for removing residual sulphur particles and moisture trapped in the exhaust air stream. Referring in greater detail to
In another embodiment of the apparatus, the separator 100 is replaced by a granular air filter 130 shown in
Although such replenishment of granules may be performed periodically based on certain parameters, in the preferred embodiment the bed 134 is continuously replenished with new sulphur granules from the granulator by diverting or directing some or all of the produced granules from the granulator into the inlet 136 to establish a desired continuous stream of granules into the top of the bed. Concurrently, the granule outlet 142 operates as an air lock to block air escape therethrough and a flow restrictor to control the outflow of granules from the bottom of the bed. The outflow control maintains the continuously replenishing bed at a predetermined level for a desired air flow and scrubbing quality through the filter.
In another embodiment the granular air filter 130 is used in conjunction with the separator 100, such as being in series with the separator 100 upstream thereof to clean the drum's exhaust air prior to its entry into the separator's inlet 106.
A control system is provided to monitor and control all aspects of the process and apparatus operation. For instance, the system adjusts water flow to the nozzles to maintain granule temperatures within a desired range when leaving the drum.
The operation of the granulation apparatus and the resulting granulation process, and some of the many advantages of the present invention, should now be better understood. Molten sulphur is sprayed into the rotating drum 50 though a number of longitudinally spaced sulphur nozzles 80 into two distinct zones, namely the seed generation zone 74 to form sulphur seeds and the downstream product growth zone 76 to further coat and grow those seeds into desired sulphur granules. The seed generation zone is characterized by an intense water spray pattern for each sulphur nozzle in that the sulphur spray exiting a nozzle is immediately impacted by a direct, intersecting water spray from respective upper and lower water nozzles 84a, 84b to create the desired sulphur seeds. The flights 70 of the rotating drum then begin forming a particle curtain 72 to carry these seeds into the product growth zone 76 where the sulphur spray coats the curtain of falling sulphur particles to grow the forming granules to a desired size and quality, namely a generally spherical granule, entirely dry and free of voids. The product growth zone is further characterized by a much less intense water spray pattern than in the seed generation zone, namely there is only a 1:1 ratio of water to sulphur nozzles, and the water nozzles provide a non-intersecting type of spray pattern that largely impacts the granule curtain to merely keep it cool (i.e. below sulphur's melting point). Air is passed along the drum to carry any dust and moisture to the drum's discharge end 64. In the preferred embodiment the granules are formed in a single pass through the granulator and thus exit at the drum's discharge end and fall through granule exit 20 into an appropriate hopper or other conveyance. In contrast, the drum's discharged air is filtered through the cyclone separator 100 where residual sulphur particles are captured, re-melted by the cyclone's heated interior walls and returned to the sulphur reservoir, whereas the cleaned air is vented to the ambient. A tangential inlet 106 and an arcuate smoothing plate 108 promote a generally laminar flow with reduced turbulence to enhance particle contact with the separator's heated surfaces, and vortex finders 112a, 112b enhance the pressure drop in the separator which helps impart high velocities to the incoming discharge air to drive more particles toward the separator's heated body 102. In an alternate embodiment a granular air filter is employed either in conjunction with, or in place of, the cyclone separator to use the generated sulphur granules to filter the discharge air stream from the drum. The granules in the filter are preferably continuously replenished by fresh granules from the drum. Further, desired maintenance of the drum is facilitated by the improved collars 58 whose 45 degree cut ends and clamping arrangement 96 provide for more convenient replacement of worn collars.
The above description is intended in an illustrative rather than a restrictive sense, and variations to the specific configurations described may be apparent to skilled persons in adapting the present invention to other specific applications. Such variations are intended to form part of the present invention insofar as they are within the spirit and scope of the claims below.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CA2008/001207 | 6/27/2008 | WO | 00 | 2/28/2011 |