WO2012068650A1

WO2012068650A1 - Fluidodynamic elbow used in horizontal-circuit bioreactors with bubble impulsion

Info

Publication number: WO2012068650A1
Application number: PCT/BR2010/000389
Authority: WO
Inventors: Marcelo Rocha Martinelli; Daniel Fonseca De Carvalho E Silva; Leonardo Brantes Bacellar Mendes
Original assignee: Petróleo Brasileiro S.A. - Petrobras
Priority date: 2010-11-25
Filing date: 2010-11-25
Publication date: 2012-05-31

Abstract

The present invention relates to an agitation/impulsion device and more specifically to a fluidodynamic elbow used in horizontal-circuit bioreactors with bubble impulsion, which comprises a basic structure capable of minimizing dispersions of energy in the course of the passage of the fluid through the impulsion elbow. The impulsion elbow is used in bioreactor tanks, especially tanks for producing microalgae on an industrial scale, and it is capable of drastically reducing the consumption of energy necessary in each production cycle.

Description

FLUIDODYMIN PATH APPLIED IN HORIZONTAL CIRCUIT BIORACTORS WITH BULB IMPULSION

FIELD OF INVENTION

The present invention relates to an impulse pit applied to bioreactor tanks, specifically of industrial scale microalgae production, which causes the culture medium to circulate in horizontal tanks, but capable of drastically reducing the energy consumption required at each time. productive cycle. The system minimizes energy dispersion during the passage of fluid in the impulse pit.

BACKGROUND OF THE INVENTION

Currently the need for renewable energy matrices has led the oil industry to invest in constant research in search of green fuel alternatives. One of the lines of research of greatest interest is biodiesel.

Biodiesel is a natural fuel used in diesel cycle engines, produced from renewable oil sources, that meets the specifications of the National Petroleum Agency (ANP). It can be produced based on vegetable oils or animal fat.

Obtaining it can be briefly described as the result of mixing one of these types of oil with alcohol or methanol, which is then stimulated by a catalyst to cause a chemical reaction between the oil and alcohol to give a mixture of esters and glycerin.

One of these typical chemical processes for making biodiesel is called transesterification. The process generates two main products: biodiesel (ester mixture) and glycerin (valued product in the soap market).

The amount of biodiesel needed for the market, given the growing demand for fuels to maintain the modern lifestyle, would be impossible to obtain in the face of population growth. global food needs, and the growing reduction in areas available for agricultural production.

However biodiesel can also be added to petroleum derived fuel, forming a technically and economically viable blend. Mixing is possible and commercially permitted in any proportion with ultra-low sulfur diesel oil, giving it better lubricity characteristics.

The possibility of increasing the use of seed oil as a biodiesel feedstock, even though the oil being used alternatively as a complementary fraction in the current energy matrix, has also raised the concern of governments and a worldwide controversy.

Biodiesel requires large volumes of oilseeds for its production. With current seed processing techniques it is possible to extract on average 80% flour and only 20% oil. Thus, interest in the search for another plant source with promising oilseed characteristics increased: microalgae.

Microalgae have similar physicochemical and chemical characteristics to oilseed plants such as castor beans and soybeans, but unlike these have the advantage that they are not currently considered as the focus of human food. Other advantages reinforce the interest in microalgae: they, similar to oilseeds, require a very small space for cultivation, harvesting and transport costs are relatively low and there is a possibility of extracting more oil than oilseeds in general.

Despite this potential, there are not many studies on the subject, especially research focusing on microalgae cultivation media and their equipment for the industrial production of biofuels.

Thus a new strand of biodiesel research is currently underway. focused on the goal of producing microalgae on an industrial scale, so that it can replace raw materials like soybeans in biofuel production.

Microalgae cultivation has undeniable advantages: the multiplication rate of the crop is extraordinary, as it has a very short residence time per cycle of cultivated area. Yield is 200 to 300 times higher than known oilseeds. Its production area is 100 times smaller than traditional crops, requiring only 2,500 hectares to supply a refinery with a capacity of 250,000 tons, against 500,000 hectares of soybeans and 250,000 hectares of sunflower.

The micro-algae have the further advantage of "sequestering" carbon dioxide (C0 ₂₎ in its development process, thus contributing to the reduction of emissions of greenhouse gases to the atmosphere. For each ton produced micro-algae are consumed two tons of C0 _2, that is, equivalent to up to twenty times more than the other oilseeds such as soya, sunflower and palm.

RELATED TECHNIQUE

The large scale production of microalgae whatever the final application requires water, C0 _2, nutrients (N, P) and sunlight. Sun and heat are fundamental in the cultivation of microalgae that are cultivated in their own structures, called photobioreactors, equipment that facilitate the capture of this light.

Today's photobioreactors feature varied construction techniques and configurations for optimal use of sunlight exposure as well as agitation of the culture fluid. Among the most adopted methods for cultivation of microalgae on an industrial scale, focused on energy sources, culture in large open or closed tanks is predominant.

They are generally shaped like a masonry structure in shallow, divided oval shape to form at least two parallel channels, at least one of which is provided with at least one stirrer for moving the suspended biomass.

Agitation is generally promoted by submerged pumping, air injection or alternatively by rotating blades.

In this cultivation concept, the pond volume is estimated according to the following parameters: hydraulic retention time (minimum re 30 days); applied organic load (Color, maximum 2000 mg / L) and movement speed, standardized around 0.15 m / s for the optimization of algae production.

This last parameter, the movement, however, is directly related to the operant mode of the current photobioreactors, which besides revolving also force the suspended biomass to circulate inside the generally oval tanks of the photobioreactors.

The circulation and agitation of the culture fluid inside the tank are important to the good performance of the photosynthetic system, as it moves the suspended biomass, allowing a homogenization of microalgae to sunlight exposure and nutrients.

It is easy to understand that only in the process of circulating the cultivation fluid in the circuit to be traveled inside a tank is there a loss of energy. However, there is a greater loss of energy in the culture fluid agitation and thrusting process.

Masonry tanks and industrial dimensions have a configuration that privileges the area of exposure of sunlight, thus having little height and much width in each circulation channel. Consequently, a large peripheral area of the culture fluid flow is in direct contact with the tank bed surface, causing a constant drag vector, which propagates through successive flow blades to the surface of the fluid mass. This one The problem of pressure drop in tank beds has been countered by adopting on these surfaces materials that give a smoother finish.

However, a snippet of current industrial scale bioreactors has not received the attention of researchers. In systems where the culture fluid is agitated and moved by bubbling, there is a large loss of energy concentrated in the push pits, mainly due to the successive and abrupt changes of direction imposed on the fluid during the push process within a standard impeller gap.

The configuration of a standard impulse pit, currently used to promote circulation in microalgae growing tanks, consists of a parallelepiped shaped pit provided below the bottom of one of the growing tank channels. The gap has the same width as said channel; It is divided by a vertical wall, transversely to the direction of flow of the fluid, resulting in two adjacent columns and also in the form of parallelepiped. Each of these two columns connects at the top with the tank channel and at the bottom with each other, as the dividing wall does not reach the bottom of the pit. In the lower portion of the downstream column a quantity of gas (which may be air or other gas of interest) is injected by bubblers. This gas, when rising through the fluid causes circulation in the system. The fluid from the tank enters the pit downward in the upstream part of the tank channel, passes under the dividing wall of the pit and rises with the gas downstream of the channel. Each edge of the pit inlet and outlet columns, as well as the lower edges at the intersection of the columns, also represent pressure drop zones.

It is easy to see that this constructive configuration commonly adopted in large bioreactor thrust pits causes a dramatic break in the boundary layers of production culture due to sudden changes in the direction of circulation during the passage of fluid inside.

As an impeller pit always provided with a linear width equivalent to the width of the tank circulation channel, it will therefore have four times the same linear extension as a zone capable of generating pressure loss, since each of the four edges represents a zone of sudden change of direction. and layer breakage boundaries of the flow.

It should be noted that in the bioreactor impeller gap there is the gas bubbling action, which also generates pressure drop due to the various vortices generated in the fluid, and the larger the volume of gas required to achieve the necessary fluid circulation, system power consumption.

The pressure drop to promote the circulation of the entire culture fluid volume along the length of the culture tank channels represents 10% to 20% of the total system absorbed relative to the remaining energy expenditure that occurs only within of the impeller gap.

Thus, the present invention aims to offer a new stirring and thrusting option for industrial scale bioreactors of simple technical application which allows for greater economic viability per cultivation cycle.

As a result of research in this regard, the fluid-dynamical ditch applied in the now proposed bubbling horizontal loop bioreactors has been invented.

The concern in the development of this new agitation and thrust system is to cheapen the operational stage of revolving and boosting suspended biomass, offering a very low energy consumption option, making the cultivation of large volumes of microalgae for biofuel production competitive.

Other purposes than the fluid dynamic ditch applied in Bubble-boosted horizontal circuit photobioreactors, object of the present invention, are intended to be achieved as follows: a) Lower operating costs.

b) Provide a high energy efficient stirring / thrusting option for multipurpose reactors and bioreactors.

c) Easily adaptable to reactor structures already in operation, enabling them to operate with this new stirring / thrust concept.

d) Drastically reduce energy consumption in crop agitation, reaching up to 90% energy savings from currently available impulse ditches.

e) Ensure maximum efficiency of biomass revolving between the bottom of the tank and the ideal lighting zone, with the lowest cost and easy implementation.

f) Guarantee the reduction of the energy cost in several chemical processes that make use of impulse ditch reactors.

g) Allow the use of air compression (gas) equipment with lower volumetric flow capacity, therefore more economical and even simpler.

SUMMARY OF THE INVENTION

The present invention relates to an agitator and impeller device, more specifically a fluid dynamic ditch, applied to bubbling horizontal circuit bioreactors, which comprises a basic structure composed of a predominantly parallelepiped shaped configuration tank having a curvilinear finish; arranged from edge to edge of at least one of the channels of a tank.

The pit is provided with a vertical partition wall, transversely to the direction of flow of the fluid but not reaching the bottom of said fossa.

The wall divides the pit so that two contiguous columns result, and also predominantly cobblestone. Each of these two columns connects at the top with the tank channel and at the bottom end with each other.

The intersection of the inlet and outlet of the pit with the channel bed as well as the lower end of the vertical partition wall are provided by a curvilinear finish with a configuration in which the following variables can be identified:

D1 - corresponding to the distance between the inner walls of the pit; D3 - corresponding to the distance between the tank bed and the lower end of the vertical partition wall;

D2 - corresponding to the distance between the lower end of the vertical partition wall and the bottom of the pit;

R1 - corresponding to the radius of curvature between the tank bed and the internal inlet and outlet walls of the pit; R2 corresponds to the radius of curvature between the base of the pit and the inner walls of the inlet and outlet of the pit;

R3 - corresponding to the radius of curvature between the vertical partition wall and the fluid surface;

R4 - corresponding to the radius of curvature of the vertical partition wall.

Each of these variables that characterize the configuration of the pit follows equational parameters pre-calculated by computational modeling, capable of shaping the flow of culture fluid within the proposed fluid dynamic ditch, in order to minimize the breakdown of the boundary layers, making the flow the same. closer to a laminar regimen. BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in more detail below in together with the following drawings, which, by way of example, accompany this report, of which it is an integral part, and in which:

Figure 1 depicts a schematic view of a microalgae culture tank provided with a fluid dynamic ditch as proposed.

Figure 2 presents an isometric perspective view of the preferred constructive configuration of said fluid dynamic ditch, applied to bubbling horizontal loop photobioreactors.

Figure 3 depicts a cross-sectional view of said fluid-dynamic moat applied to bubbling horizontal loop bioreactors, indicating the relevant parameters. DETAILED DESCRIPTION OF THE INVENTION

The fluid dynamic ditch applied to bubbling horizontal loop bioreactors, object of the present invention, is intended to reduce the energy consumption expended during biomass revolving and cultivation fluid thrust within a photobioreactor. Considering that the purpose of microalgae cultivation is for energy production, it is essential to detect and eliminate any waste of energy related to the process, so that the final energy balance is as profitable as possible.

Figure 1 shows a schematic view of a tank (1) where the thrust is made from a vertical bubbling moat. The image already depicts the fluid dynamic ditch 100 proposed by the present invention.

Figure 2 shows in detail a schematic cross-sectional view of the fluid dynamic ditch (100) applied to bubbling horizontal loop bioreactors, which minimizes the problems highlighted above.

It can be seen that the invention basically comprises a predominantly parallelepiped configuration (110) disposed from one side to the other of one of the channels (2) of a microalgae cultivation tank (1), so that the upper end of the fluid dynamic ditch (100) is provided at the same level as the bed of said channel. Alternatively, in the same tank (1) and / or channel (2), as many fluid-dynamic pits (100) as the design requirements may require to maintain optimal flow may be provided.

The fluid dynamic dome 100 has a vertical dividing wall 120 transverse to the direction of flow of the fluid. Said wall divides the pit 110 so that two adjacent columns result, a first column 121 and a second column 122, also predominantly parallelepiped in shape.

Each of these two columns (121 and 122) connects at the top with the channel (2) of the tank (1), and at the bottom end with each other, as the vertical dividing wall (120) does not reach the bottom of the pit (110).

At the lower end of the second column (122) gas is injected by means of bubbles (not shown in the figure). This gas, when rising through the fluid towards the surface, causes circulation in the system. The fluid from the tank (1) enters the sump (110) downwards through the upper end of the first column (121) upstream of the channel (2 ') of the tank (1), it passes under the vertical partition wall (120) of the sump (110) and rises with the gas thrust through the second column (122) to the downstream portion of the channel (2 ").

In order to avoid loss of pressure generated by the intersecting edges of the inlet and outlet of the pit 110 with the channel bed 2, the fluid dynamic pit 100 provides the entry of the first column 121 upstream of the channel. (2 '), the second column outlet (122) to the downstream portion of the channel (2 ") and also the lower end of the vertical partition wall (120), with a curvilinear finish. obeys pre-computed equational parameters by computational modeling that result in a constructive configuration capable of shaping the flow of culture fluid to minimize the breakdown of boundary layers, bringing the flow closer to a laminar regime during its passage through the interior. of the fluid dynamic ditch (100).

Accordingly, in obtaining a laminar regime, the fluid-dynamic moat 100, applied to bubbling horizontal loop bioreactors, may employ a much smaller flow gas disperser than those currently used.

Figure 3 shows a cross-sectional image of the constructive configuration of the fluid dynamic ditch 100, in which the following key variables can be identified in order for the invention to actually achieve the desired economy. Thus we have:

D1 = distance between the inner walls of the pit (110);

D3 = distance between the tank bed (1) and the lower end of the vertical partition wall (120);

D2 = distance between the lower end of the vertical partition wall (120) and the bottom of the pit (110);

R1 = radius of curvature between the tank bed (1) and the internal inlet and outlet walls of the pit (110);

R2 = radius of curvature between the base of the pit (110) and the inner walls of the inlet and outlet of the pit (110);

R3 = radius of curvature between the vertical partition wall (120) and the fluid surface;

R4 = radius of curvature of the vertical partition wall (120).

In order for the thrust effect of a reactor to continue to reach the optimum velocity within the channels (2) of the tank (1), and to conform to the circulation pattern required by the chemical or biochemical process, but in such a way that they are reduced to the maximum the effects of vortices generated by the impulse gas bubbling, as well as the losses of Due to sudden changes in the direction of flow within the thrust gap, the configuration variables disclosed above should preferably be restricted to a range of values that meet specific criteria.

With such a designed and shaped gap, energy savings of up to 80% are achieved compared to the energy currently consumed by industry and laboratories in the sector.

The following criteria reflect specific equational parameters, pre-calculated by computer modeling, and should be applied to the value of the pond area, expressed in square meters. Thus, from a generated table and the area actually occupied by the culture fluid, one can quickly specify the best values for the fluid dynamic ditch configuration variables (100) applied to bubbling horizontal loop bioreactors. As a result, lower power air dispersers may be specified and therefore more economical.

The table presented below by way of example reveals minimum and maximum values of factors that can be applied to obtain each configuration variable of the fluid dynamic ditch (100). Thus, the following application procedure is adopted:

A factor value, corresponding to one of the variables, must be chosen within the range of maximum and minimum possible values for that parameter, and multiplied by the square root of the intended floor area value (Au), expressed in square meters. . The result of the operation will be the dimensional value to be used for the chosen configuration variable, expressed in decimeters:

(Au ^A 2) in m ² x factorDI = D1 in dm

From there, the dimensional value of the other variables is obtained by the same methodology, applying the chosen factors in the formula. directly in the same factor table, in the other maximum and minimum value ranges of the remaining variables.

These factors can and should be selected according to the type of fluid to be driven, and can be applied in reactors or bioreactors, both in algae cultures and in organic waste processing.

Thus, a random factor value within the factor range of each variable can be chosen that will achieve significant savings in the load losses generated by the bubbling drive system.

A preferred embodiment for microalgae culture is given below in Table 1.

But, for an experiment performed, the factors that presented the best results, reaching savings of up to 90% in microalgae cultures, can be represented by:

(Au ^A 2) in m ² x 1, 5 = D1 in dm

(Au ^A 2) in m ² x 0.2 = D2 in dm

(Au ^A 2) in m ² x 0.8 = D3 in dm

(Au ^A 2) in m ² x 0.4 = R1 in dm

(Au ^A 2) in m ² x 0.35 = R2 in dm

(Au ^A 2) in m ² x 0.4 = R3 in dm

(Au ^A 2) in m ² x 0.25 = R4 in dm

It is important to note that it is not enough to provide the finishing of a Round-shaped bubbling pit for energy gains and economic results, as such practice may, in some combinations of fluid type, volume and velocity involved, result in an energy loss equivalent to that of the currently employed live corners.

The biofuels industry really needs relevant and substantive results to achieve a recognized commercial economic scale that meets other established cultures.

Regarding the use of existing tanks, there are no technical impediments to converting horizontal bioreactors, so that they can operate with the fluid dynamic ditch (100) applied to the proposed bubbling horizontal loop bioreactors by simply providing the existing tank with a fluid-dynamical ditch of masonry or prefabricated.

The adoption of the proposed fluid dynamic ditch (100), which is able to establish low resistance to fluid displacement within the ditch and reduce by up to 90% the energy commonly used for agitation and thrusting of crops, a critical energy stage of the production process. in industrial scale photobioreactors, it will also open the possibility of searching for less expensive air diffusers.

The invention has been described herein with reference to its preferred embodiments. It should, however, be clear that the invention is not limited to such embodiments, and those skilled in the art will immediately realize that changes and substitutions may be made within this inventive concept described herein.

Claims

FLUIDODYNAMIC PATH APPLIED TO HORIZONTAL CIRCUIT BULLETOR BIORACTORS, comprising a basic structure composed of a predominantly parallelepiped configuration (110), disposed from one side to the other of one of the channels (2) of a tank (1 ); the sump (110) being provided with a vertical partition wall (120) transversely to the direction of fluid flow and not reaching the bottom of said sump (110); said vertical partition wall (120) divides the pit (110) so that two contiguous columns result: a first column (121) and a second column (122), also predominantly parallelepiped in shape; each of these two columns connects at the top with the channel (2) of the tank (1) and at the bottom end with each other; It is further characterized in that the intersection of the inlet and outlet of the sump (110) with the channel bed (2), and also the lower end of the vertical partition wall (120), are provided with a curvilinear finish that obeys pre-equational parameters. computed by computational modeling and resulting in a constructive configuration capable of shaping the flow of the culture fluid to minimize the breakdown of boundary layers, bringing the flow closer to a laminar regime as it passes through the fluid dynamic ditch ( 100), said parameters being:

D1 - corresponding to the distance between the inner walls of the pit (110);

D3 - corresponding to the distance between the tank bed (1) and the lower end of the vertical partition wall (120);

D2 - corresponding to the distance between the lower end of the vertical partition wall (120) and the bottom of the pit (110); R1 - corresponding to the radius of curvature between the tank bed (1) and the internal inlet and outlet walls of the pit (110);

R2 corresponds to the radius of curvature between the bottom of the pit (110) and the inner walls of the inlet and outlet of the pit (110);

R3 - corresponding to the radius of curvature between the vertical partition wall (120) and the fluid surface;

R4 - corresponding to the radius of curvature of the vertical partition wall (120).

Fluidodynamic moat applied to HORIZONTAL CURRENT BULLET CIRCUIT BIORACTORS according to claim 1, characterized in that the dimensional values for the configuration parameters D1, D2, R1, R2, R3 and R4 of said fluid dynamic ditch (100 ) are the result of the square root product of the desired floor area (Au) value, expressed in square meters, by the value of a factor chosen within the range of maximum and minimum possible values for the respective parameter; the result of the operation being the dimensional value to be used for the chosen parameter, expressed in decimeters, namely:

D1 - between 0.5 and 4.5;

D2 - between 0.05 and 0.8;

D3 - between 0.4 and 1.6;

R1 - between 0.1 and 1.6;

R 2 - between 0.1 and 1,225;

R3 - between 0.1 and 1.6; and

R4 - between 0.06 and 1.0.

3- FLUIDODYNAMIC PIT APPLIED IN HORIZONTAL CIRCUIT BIORRECTORS WITH BULLETING IMPULSION, according to claim 1, characterized in that alternatively in the same tank (1) or channel (2), as many fluid-dynamic pits (100) can be provided as the design requirements for maintaining an optimal flow may be required.