ES2788722T3 - Pulp press propellers with double spiral pitch - Google Patents

Abstract

Double helix volumetric press, comprising two horizontal sub-helixes in parallel, each sub-helix (3) having a second pitch or edge of turns (2) complete and identical to a first pass or edge of turns in the same sub-helix, both sub-helixes ( 3) inserted in a longitudinal sleeve or casing (4) and located so that there is no collision during the free travel of the turns in the area where the two sub-propellers are closest, therefore each sub-helix (3) is shaped according to two steps or edges of turns that have the same distance to the filter jacket, this distance being constant and between one and two millimeters to the filter jacket or envelope (4) that contains the pulp, characterized by the fact that the edge of both first and second pass coils (1, 2), presents an extension of the coil or scraper-cleaner (5) as a hard coating provided by welding, and with a knife effect as it passes through the inside the filter jacket (4), and with the ability to scrape or wipe that makes up the leading edge of all the turns of each of the two sub-propellers (3), based on their termination forming an obtuse angle with the own filter jacket (4) on the face that carries out the compression on the pulp, maintaining a constant distance to the filter jacket around its outer perimeter between one to two millimeters.

Description

DESCRIPTION

Pulp press propellers with double spiral pitch

OBJECT OF THE INVENTION

The present invention, as expressed in the wording of this specification, relates to a double helix volumetric press, as defined in claim 1, having two horizontal sub-helixes in parallel with double pitch of turns.

The field of application of the present invention is the manufacture of pressing machines commonly used in the sugar industry, which increase the performance of the aforementioned presses, based on the optimization of the cleaning of the accumulated pulp that obstructs the filtering surface, preventing the outflow of water, its mixing and squeezing, as well as a greater labyrinth effect of the pulp path as it passes through the press. That is, a geometric closure that prevents the backward movement of the product when compressed.

BACKGROUND OF THE TECHNIQUE

By way of introduction, horizontal volumetric presses with two parallel propellers were invented by the Norwegian company Stord for pressing fish remains for the subsequent production of fish meal. With the passage of time, it has been given new applications, among the main ones is its use to this day, for pressing depleted beet pulp in sugar mills.

Thus, in the 1970s, the companies STORD, BABBINI & C SAS FLLI and MERCIER itself linked to the present invention, have supplied these machines to sugar factories all over the world, without incorporating great innovations in the passage of time. his design; use of conical propellers instead of bicylindrical ones, use of drilled / filter cores in the propellers and installation of small turns in the pressure zone, mainly.

At present, the performance of the pressing of the exhausted beet pulp in the referred presses conditions the subsequent final thermal drying processes, with the consequent fuel savings. Usually, this thermal drying is carried out in rotary kilns / dryers where the product is dried until it reaches around 90% dry matter, then undergoes a final pressing into pellets, before being sold as livestock feed. .

Likewise, it is also important to highlight the fact that the aforementioned horizontal volumetric presses with two parallel propellers are also used for other waste generated in sugar mills such as beet leaves and stalks, chicory pulp, fish waste, waste meat products, agricultural by-products such as soybeans, starch, citrus fruits, alfalfa, potatoes, etc., waste treatment and, in general, all kinds of products on which the pressing process adds value.

According to the state of the art, only the invention patent identified by its publication number and title, respectively; EP0773100B1 “Screw press for dehydrating fibrous materials”, under the ownership of BABBINI & C SAS FLLI, provides a parallel double helix press, with double pitch of turns, where the height of one of the turns is significantly less than that of the other. In other words, they are double-pitch propellers in which use is made of a second turn with a height between 50 and 60 mm, substantially less than the height of the first turn. Additionally, it is not a question of turns of constant total height either. Another prior art document WO 2005/025846 A1 describes a double pass volumetric press according to the preamble of claim 1.

In conclusion, the "pulp press propellers with double spiral pitch" contribute with respect to the state of the art in general and, particularly, with respect to the aforementioned invention of BABBINI & C SAS FLLI, a horizontal double helix press, where the propellers They have a double pitch of coils of the same height, housed in such a way that there is no collision between them and whose use contributes, in combination with the incorporation of a scraper / cleaning edge on the outer end of the coils that make up the propellers of the press , the following benefits or effects that lead to an overall performance improvement of the press.

A. Cleaning effect: This effect is improved by the use of a cutting edge with appropriate geometry and that gives it a great capacity for scraping and cleaning. In addition, the length of the effective edge of the turns on the filter jacket is doubled. This implies doubling the cleaning of the perforation of the filter jacket that can be blocked by the pulp during the pressing operation and that is cleaned or uncovered when the propeller passes by scratching the pulp accumulated on the surface.

B. Mixing Effect: The capacity of the machine to mix the pulp that reaches the intersection zone between the propellers is doubled, where the turns of both propellers break the "packages" or volumes of pulp that are intercepted in this area when treating to share the same space. In this area the turns of both helices attack the pulp "packages" breaking them and thus mixing the pulp. This mixing and reordering of pulp prevents the particles from advancing in blocks from start to finish of the machine without being exposed, the particles inside the filter jacket, thus dislodging the water they contain through it.

C. Squeezing Effect: The squeezing and twisting capacity of pulp fibers is considerably increased as there are more turns and closer to each other. This effect takes place in the central area between the two propellers. In this area, between the flanks of turns of different helices when rotating in the opposite direction very close to each other and the product being trapped between said turns, there is a squeezing, twisting and crushing of the pulp fibers, which is very beneficial for the extraction of water inside.

D. Labyrinth effect: The closure of paths through which the product can go back due to pressure differences during the compression of the product is significantly increased. Thus, in the area between the two helices, the coils are so close together that any pulp movement between the passages or coil compartments is limited.

These effects are achieved with a double pass volumetric press according to claim 1.

EXPLANATION OF THE INVENTION

By way of explanation of the invention of the “pulp press with double helixes”, it consists of a system of sub-helixes with double pitch of turns with two horizontal sub-helixes in parallel, where each sub-helix incorporates the following specifications:

As already mentioned, a second pass or edge of turns identical to a first pass or edge of turns, where both pass of turns are inserted in a longitudinal sleeve or envelope, and located so that they do not collide in the free path of the turns in the area where the two sub-propellers are closest. Therefore, each sub-helix is shaped according to two steps or edges of turns of the same distance to the filter jacket, this being constant and remaining once assembled in the volumetric press, said distance between one and two millimeters to the filter jacket or envelope containing the pulp.

Additionally, the edge of both first and second pass coils presents an extension of the coil or scraper-cleaner as a hard coating provided by abrasion resistant welding and with a knife effect as it passes through the interior of the filter jacket, based on its termination forming an obtuse angle with the filter jacket itself, with the ability to have a scraper-cleaning effect that forms the leading edge of all the turns of each of the two sub-propellers, on the face that carries out compression on the pulp, maintaining a constant distance around its outer perimeter. Therefore, in such a way that along the path of each loop inside the filter jacket, there is a minimum distance to the filter jacket itself between one and two millimeters, optimizing the scraping-cleaning and unplugging effect, It is essential for the water to be evacuated through the filter jacket itself, usually limited by the obstruction of its holes when retaining the pressed pulp itself.

DESCRIPTION OF THE FIGURES

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to some preferred practical example embodiments, a set of figures is attached as an integral part of this description. , for illustrative and non-limiting purposes, the following has been represented:

Figure 1.- Shows a main section of "pulp press propellers with double spiral passage".

Figure 2.- Shows a main section of “pulp press propellers with double spiral passage” inside a horizontal volumetric press with two horizontal sub-propellers in parallel.

Figure 3.- shows a detail of the scraper-cleaning edge of "pulp press propellers with double spiral passage" along the route of the spiral inside the filter jacket.

In the aforementioned figures, the following constituent elements can be highlighted:

1. First pass turns.

2. Second pass turns.

3. Horizontal axes in parallel.

4. Filter jacket.

5. Spiral edge with scraper-cleaning effect.

6. Pulp

7. Area of the filter jacket with reduced water extraction.

8. High water extraction filter jacket area.

EXAMPLE OF A PREFERRED EMBODIMENT

As an example of a preferred embodiment of the "double helix volumetric press" in view of Figures 1 and 2, it can be seen how use has been made of a system of sub-propellers with double pitch of turns, with two horizontal sub-propellers in parallel ( 3), where, additionally, each sub-helix contains a second pitch or edge of turns (2) identical to the first pitch or edge of turns (1). In other words, each sub-helix is shaped according to two steps of turns (1, 2) introduced in a sleeve (4) or longitudinal envelope, of the same constant distance in relation to the interior of the longitudinal sleeve (4) itself, to position itself in its swept inside the filter jacket (4). Said minimum distance is between one and two millimeters.

Likewise, Figure 3 shows the turn edge (1) with an abrasion-resistant scraper-cleaner (5) with identical configuration for the second pass turns (2).

In their natural forward movement, the passages or spiral edges (1, 2) move the pulp (6) with the scraper cleaner (5), consequently cleaning the pulp layer (6) that obstructs the perforated surface of the filter jacket (4) and making a differentiation between a previous area of the filter jacket (4) along its passage where the extraction of water is low (7) which is followed by a later area where the extraction of water is high (8 ). To evaluate the results, the yields obtained in the same horizontal volumetric press with two horizontal propellers in parallel, making use of two single-pass propellers, are compared, through certified tests in a sugar factory, in relation to the use of the propellers object of the present invention, showing an increase in dry matter comprised between 2% and 2.5%.

For a complete analysis of the results obtained, it should be taken into account that a pulp press working below its performance obtains between 20 and 24% of dry matter, while at optimum performance it would be between 30 and 34% in dry matter, showing an increase in the obtained dry matter of between 2% and 2.5% of dry matter. This is a very relevant increase, + 18% in the pressing performance, taking into account that the performance range of the press is between 20% and 34%.

Therefore, by way of conclusion, an important increase in the performance of the pressing and mechanical drying process of the spent pulp of beet has been observed, which implies for the industrialist a high saving in the subsequent demand of fuel necessary to carry out the final thermal drying of the pressed pulp. In an alternative embodiment, it is also possible to design the double coil pitch (2) only in one section of each of the two sub-helixes, being, at the same time, identical to the first coil pitch (1) to position itself in its sweep through the inside the filter jacket (4) at a minimum distance from it between one and two millimeters.

Likewise, in another alternative embodiment, use could be made of the improvement described in the present invention, incorporating them into horizontal volumetric presses with three or, in general, more than two sub-propellers in parallel. It is not considered necessary to make this description more extensive for any person skilled in the art to understand the scope of the invention and the advantages derived from it. The elements that compose it, their dimensions, forms or implementation techniques, will be susceptible to variation as long as this does not imply an alteration in the essentiality of the invention.

Claims (1)

1. Double helix volumetric press, comprising two horizontal sub-helixes in parallel, each sub-helix (3) having a second pitch or edge of turns (2) complete and identical to a first pass or edge of turns in the same sub-helix, both being sub-propellers (3) inserted in a longitudinal jacket or casing (4) and located in such a way that there is no collision during the free travel of the turns in the area where the two sub-propellers are closest, therefore each sub-propeller (3) It is shaped according to two steps or spiral edges that have the same distance to the filter jacket, this distance being constant and between one and two millimeters to the filter jacket or envelope (4) that contains the pulp, characterized by the fact that the edge of both first and second pass coils (1, 2), presents an extension of the coil or scraper-cleaner (5) as a hard coating provided by welding, and with a knife effect as it passes through the inside of the filter jacket (4), and with the ability to scrape or clean the effect that forms the leading edge of all the turns of each of the two sub-propellers (3), based on their termination forming an obtuse angle with the filter jacket itself (4) on the face that carries out the compression on the pulp, maintaining a constant distance to the filter jacket around its outer perimeter between one to two millimeters.