GB2567340B - Belt-conveyor three-phase reactor - Google Patents

Description

belt-conveyor three-phase reactor

This invention is related to industrial three phase reactor used for massive production.

Biomass production and other Bio-base products are facing a major problem during industrial production through high construction and operating costs compared to the sales price.

Previous designs of Gas-Liquid or three phase bioreactors had solved a lot of engineering challenges through reliable designs, they successfully moved the production of lab scale reactors to the world of industry, but unfortunately a lot of them were not preferable choice in the industrial sector due to high construction, operating, and/or maintenance costs.

The key problem is either or both of agitation quality or/and Gas-Liquid mass transfer, as in most of the previous designs, when solving a problem, it causes another one.

For Example, when placing a baffles in a flat plate bioreactor to increase the mass transfer, that will cause a static area around the edges or corners of the baffles which reduces the agitation quality, or when removing the baffles or utilize motor for agitation purpose, this as well, will decrease the mass transfer rate and increase operating cost respectively.

Also, some of the designs encountered the problem of difficult maintenance or accessing smoothly to all parts of the system, and the other faced the lack of possibility to Scale-Up the system and the lack of lighted surfaces in the photo bio-reaction applications .

To overcome these withdraws, a three phase reactor that has a developed feature which can overcome economic failures during industrial operation is designed to overcome the high capital and operating costs.

It's important to stand on the above withdraws in detail, and it's Proposed to identify points of overlap of each problem with the other problems, thus the design is based on solving each problem independently without causing a defect or problem on another factor.

In the plan of integrated design solution, the interacting factors are linked in packages so that each package can be resolved through a single design add-on (to reduce cost), thus solving all problems through a final design (that integrates all solution packages) that requires minimal improvements to solve all problems. A Proposed "Z" shape three phase reactor, supported by a metal stiffening structure, which gives the mechanical force against the hydrostatic pressure, and that reduces the thickness required to build the reactor wall and cost of construction, and included development of a core in the center of the reactor, consists of a conveyor belt rotates between two conveyor pulleys that rotate on two parallel axes on one vertical plane, and the sieve trays are fixed to the belt. The "Z" shape as well will form a smooth path during the rotation of trays.

The gas is pumped from the rear-bottom part of the reactor to follow a "zigzag" path as it penetrates its way through the rear sieve trays (which move upwards), causing an increase in both of the gas hold-up and gas-liquid surface area for the mass transfer and thus increasing production rate.

From the front of the reactor, the trays mounted on the belt move downwards. Both of the upward and downwards moving trays generate agitation with high turbulent currents under and beside each tray to make the reactor in continuous homogeneity state during the continuous operation in the dense operating conditions, and thus obtained a high agitation by investing the potential energy of the water above the gas bubbles (the buoyancy force), which totally eliminates the operational cost of agitation.

The designing problems are linked and the proposed design is performed in the following sequenced packages stages in detail where :

Figure 1 shows the final structure of the reactor,

Figure 2 shows a sieve tray imbedded with gas reservoir,

Figure 3 shows a side view of the reactor which illustrates the path of moving trays,

Figure 4 shows a front view of the reactor which illustrates the "zigzag" gas-path through the sieve trays,

Figure 5 shows a cross-sectional view of the structure used to attach the conveyor pulleys axes to the reactor walls.

Figure 6 shows a cross-sectional view of a rising sieve tray, illustrating the Gas-Liquid mass transfer.

Figure 7 shows a cross-sectional view of the conveyor pulley, illustrating the rotation of a tray at the rotating end of the conveyor belt.

Package one includes: a) The problem of short gas path, and b) The problem of agitation quality. The design in Figure 2 propose a movable sieve tray used as a Gas-baffle as well as an agitation Paddle .

Package Two includes: a) The problem of Pumped-Gas ratio (gas flow rate with respect to reactor volume), b) The problem of the power needed for agitation (to move the trays), and c) The problem of low "Gas hold-up" inside the reactor. Figure 2 shows the design of air reservoirs 19 within the trays 5, 12 its Proposed to reduce the inlet gas flow rate, move the trays 5 upwards and increase the amount of gas held.

Package three includes: a) The problem of linking the trays with one frame or axis (oval or circular), b) The problem of transferring the energy in the gas-filled trays to the other trays to form homogenous agitation, and c) The problem of the engineering limitations regarding the scaling-up of the agitation element. Figure 3 shows The conveyor belt 4 Proposed to form the moving structure supporting the trays 5 which move upwards and trays 12 which moves downwards and drive them, as well as to transfer the energy from trays 5 to trays 12 while rotating. The whole structure could be scaled-up in a flexible manner and could be implemented without hitting any engineering boundary.

Package Four includes: a) The problem of the reactor wall thickness (structural cost), b) The problem of moving trays path, and c) The problem of low external lighted surface area (for the photo bio-reaction applications). Figure 3 shows the flat-walled reactor with "Z" shape Proposed to provide a large lighted surface area, creating a mechanical extra force at the two "Z" corners 33 that reduces the thickness required for construction, and to form a tight and precise path for the movement of the trays 5, 12 during rotation at the belts 4 upper and lower rotating ends.

It has been found that solving the problem of each package does not negatively affect the remaining packages, and therefore the integration of these packages solutions led to a design shown in Figure 1 characterized by accuracy and efficiency in solving all the problems mentioned.

In the mentioned solution Package one, the idea consists of a column of sieve trays 5,12 (shown in Figure 2) to draw a zigzagging path for the gas, and also to be used after being installed on a particular axis as agitation Paddles.

Each sieve tray 5, 12 consists of parallel holes 13 arranged in triangles to increase the mass transfer coefficient.

The trays 5, 12 are designed and installed as shown in Figure 4 so that the holes 13 of each tray 5,12 are placed to the opposite side of the holes in the previous tray, thus, the zigzag path is formed, which increases the length of the gas bubbles 23 path as it passes through the reactor and increases the total amount of gas retained in the reactor (Gas hold-up).

In the mentioned solution Package two, the idea of the solution is to develop the sieve tray to hold some of the gas rising through it, in the proposed gaseous reservoir, the gas will accumulate during the continuous operating, the accumulated gas will generate the energy to move the tray. The idea of semistatic gas storage reservoirs 19 in each tray will solve the problem of moving the trays as well as increase the amount of gas trapped inside the reactor and decrease the required Gas flowrate for continuous operating.

The difference in densities between the fluids inside and outside the gaseous reservoir 19 leads to the generation of a buoyancy force 31 that moves the trays 5 upwards.

Figure 2 shows the design of the gaseous reservoir in detail. Each tray contains a gaseous reservoir 19 that holds a fixed gas amount at each vertical height, where the gaseous reservoirs 19 are at highest gas storage continuously during operation while it's at the lowest rear point above the gas sparger 7, and it's at the lowest gas storage while it's at the highest vertical point. And it's also shows the addition of small slipping edges 20 to reduce the friction between the trays 5, 12 and the walls of the reactor 29 during the movement.

In the mentioned solution Package three, the idea of solving this package is the most important element in the final reactor design. The idea solved obstacles that are completely not connected to each other. The idea proposes to create a conveyor belt 4 on which all the trays 5,12 will be installed. This will solve all previous problems as shown in Figure 3. the idea proposed that the belt 4 will be able to hold the trays 5,12 upright vertical, and provides the optimal path for the rising gas without escaping out of the assigned path in front of or beside the trays 5 during operation, while at the same time to reverse the lost energy of rising gas (buoyancy force 31) which is directed upward and return it back to the reactor to be invested in agitating the liquid medium and overcome the resistance of the liquid particles during the agitation. Each tray 5, 12 is fitted to the belt 4 using a conveyor belt-tape 17 cemented to the top horizontal line of the tray 5, 12 and then sewed to the belt 4 using conveyor belt thread 18 so that it can rotate smoothly as shown in Figure 3 and Figure 7.

The belt 4 rotates around two parallel pulleys 21 located on a single vertical plane. They are fixed by two shafts 22, two discs 2 are added at the ends of the pulleys 21 to determine the movement of the belt 4 and prevent it from going out of its path as shown in Figure 4.

In the mentioned solution Package four, the reactor wall is designed to form a "Z" shape as shown in Figure 3. The ribs 33 formed by the "Z" shape are mechanical Support points for the reactor which is further supported by the addition of a metal stiffening structure 10, 14, 15, 16. The metal stiffeners 10, 14, 15, 16 along with the extended reactor walls 6 distribute the hydrostatic pressure to twenty-two planes, at which the force transfers to the perimeter (frame) of each plane to be loaded on the metal stiffening structure 10, 14, 15, 16 as shown in Figure 1.

The wall design also provides a smooth path for the movement of trays 5, 12 while rotating on the conveyor pulleys 21 in a streamlined manner that provides perfect agitation throughout the reactor as shown in Figure 3.

Figure 1 shows the final design of the reactor, the final design idea proposes linking the four solution Packages integrally to produce a final design that has all the specifications mentioned in each package.

In a preferred embodiment for the photo bio-reaction applications, the walls of the reactor 29 as well as the trays 5, 12 may be manufactured using Acrylic sheets, due to its unique chemical and physical properties, the high transparency compared to glass, and its high UV resistance compared to polycarbonates, it is preferred to work in both internal and external operating conditions .

In a preferred embodiment for the invention regarding the photo bio-reaction applications, and as soon the following assumptions exist: l)a metal stiffening structure 10, 14, 15, 16 exists, 2)a reactor is formed with "z" shape, 3)the spacing between metal stiffeners is less than 25cm, 4) a spacing between the metal stiffeners and the reactor wall exists and filled with a damping material, 5)a proper cementing of acrylic sheets, 6)the bottom of the tank is at one level and fully supported, 7) the hydrostatic height 11 in sell then 5m and 8) operation temperature is less than 45 degree Celsius, the walls of the reactor 29 thickness (t) could be calculated using the following proposed equation for Acrylic sheets: t[mm]=0.19*(reactor height[cm])Λ0.8, and if the width of the trays 5, 12 is 40cm or less, the trays 5, 12 could be built using 3mm thickness Acrylic sheet and if its larger, its Proposed to install a triangular bracer inside the tray gaseous reservoir 19 each 40cm spacing.

In a preferred embodiment for the invention, the metal stiffening structure 10, 14, 15, 16 could be built using Aluminum, as it could resist the wet environment as well as its low fabrication and raw material cost.

In a preferred embodiment, the metal stiffening structure 10, 14, 15, 16 is designed to withstand all the hydrostatic pressure, when the hydrostatic height 11 is 100cm or less, its preferred to use Aluminum hollow bar for the Primary Stiffener 14 with the dimensions of 2.0 * 4.0 cm (thickness 1.0 mm), and for the Secondary Stiffener 15 a "T" shaped Aluminum bar with dimensions of 3.0 * 1.5 cm (thickness 2.0 mm) .

Additionally, it is preferred to use Aluminum corner with a thickness of 2mm for the top and bottom supporting structure 10, 16.

In another aspect, its preferred to use steel Mechanical structure for the large scale reactors with a hydrostatic height 11 greater than 200cm.

It is proposed to leave a gap between the metal stiffeners 10, 14, 15, 16 and the reactor wall 29, and fill that gap with a damping material such as Silicon or rubber.

According to one embodiment of the invention, its preferred for the conveyor belt 4 material, to use a flat reinforced belt that has the ability to operate submerged while driving the trays 5, 12. The proposed material is a polyvinyl chloride belt coated by a UV-resistant material and reinforced by a fiber mesh.

In another embodiment of the present invention, another Proposed option regarding the material of the conveyor belt 4 is to use the same belt but with holes between trays 5, 12 to allow light (for photo bio-reactions) to pass through the belt 4 to the reactor core, but in this proposal, some of the gas bubbles 23 may escape from its path through the belt holes.

In another aspect, the use of Mesh Conveyor Belt is not preferable because of the very high edges that provide a dark dead areas suitable for contaminant growth.

Since the limiting reagent for the reaction inside the gas-liquid-solid reactor is mostly the concentrations of gases (regarding the biomass production at external operating conditions) which is controlled by the mass transfer between gas and liquid, the flat belt 4 as shown in Figure 4 is highly recommended and preferred to the other options.

In a preferred embodiment for the invention, its preferred to use Polyvinyl chloride conveyor pulleys 21, due to the strong brittle property, light weight and good chemical resistance, as well, it provides a sufficient friction strength on the inner surface of the belt.

In another aspect, the use of grooved Conveyor pulleys is not preferable, the groove areas may facilitate the growth of contaminants inside. And its recommended to totally seal the ends of the pulleys 27 for the same purpose.

According to one embodiment of the invention, its preferred to use fine polished stainless steel shaft 22 to hold the Conveyor pulleys 21, it has the ability to withstand continuous rotation friction, as well as bearing the weight of the Conveyor pulleys 21, belt 4 and trays 5, 12.

Figure 5 shows the proposed structure to attach the conveyor pulleys 21 axes to the reactor walls 29, where the ends of the conveyor pulleys where sealed by an Acrylic disks 27 cemented to the inner diameter. The two other large disks 2 then cemented to the sealing disks 27, then a final small bearing disks 26 is cemented to the large disks 2. The shaft 22 inters a sliding contact bearing hole through the bearing disk 26 and the large disk 2, where the length of the bearing will be the summation of the thicknesses of the two disks 26, 2, and utilizing the liquid media to lubricate the bearing area during the operation. The shaft 22 fixed to a white Teflon cylinder 23 to be cemented to a Male Thread Plug 3 (shaft holder). The shaft holder 3 is plugged into a standard threaded bulkhead.24, 25 where the female 25 of the Bulkhead is located on the inner side of the reactor wall 29 and the male 24 is on the external side. The hole 28 in the reactor wall is made little bit larger than the Bulkhead male thread 24, the extra area of the hole 28 is made for calibrating the conveyor pulleys.

Figure 6 shows the unsteady state gas inside the gaseous reservoir 19, where the gaseous reservoir 19 in trays 5 is at continues state of gaining gas from the bottom of the tray 5 and losing gas through the upper holes 13 of the tray 5. each accumulated gas in the gaseous reservoirs 19 will generate a buoyancy force 31 on trays 5 and moves the conveyor belt 4 upwards. While the gas bubbles 23 is accumulating from the bottom of the tray it forms a small turbulent layer of foam 30 which increases the mass transfer area between the gas and the liquid.

According to one embodiment of the invention, its preferred to fix the trays to the conveyor belt using a conveyor belt-tape 17 made from the same material used for the conveyor belt 4 cemented to the top horizontal line of the tray 5, 12 and sewed to the conveyor belt 4 using a fine and strong conveyor belt thread 18 as shown in Figure 6.

According to one embodiment of the invention, the small slipping edges 20 play an important role in the rotation procedure, as they reduce the area of friction between the trays and the reactor wall by 98%, thus, the rotation will be totally inefficient without them as shown in Figure 4 and Figure 6.

Figure 7 shows the ribs 33 formed by the "Z" shape that form the expanded volume of the reactor, these expansions play an important role in the rotation procedure, as the trays 5, 12 reach the rotating end of the conveyor belt 4, they will start to rotate and extend their long diagonal wall towards the wall of the reactor 29, thus, without the expanded volume of the reactor formed by the "Z" shape, the trays 5, 12 will stuck and never rotate at the two rotating pulleys 21 of the belt conveyor system.

According to one embodiment of the invention, the buoyancy force 31 will Overcomes the friction forces 32 of bearing (at disks 2 and 26), slipping (at edges 20), Solid-liquid, and liquid-liquid during the continues operation as shown in Figure 7.

In a preferred embodiment for the invention regarding the photo bio-reaction and some other applications, its preferred to build the proposed reactor with a height: width: depth ratio of 4.74: 2.63: 1 and the two expanded walls expand with a factor of 0.158 of the reactor depth.

In a preferred embodiment for the invention, its proposed to build the sieve trays diagonal wall with an angle of 38 degree from the vertical wall of trays 5, with a reactor depth: tray height ratio of 2.714: 1 and a reactor width: tray width ratio of 5: 4. It is Proposed to calculate the diameter of conveyor pulley (D) , conveyor belt length, and total number of trays (n) from the following equations respectively: D= reactor depth*0.263, L=2*(height of reactor*(2/3)-D)+(n*D), and n=(4/45)*height of reactor[cm].

In a preferred embodiment for the invention, its proposed to calculate the thickness (w) required for the proposed flat reinforced belt conveyor using the following equation: w [m] = 0.19 *(liquid viscosity [kg/m.s])Λ1.5 *(liquid density [kg/m3]) Λ0.666 *( conveyor belt length [m])A0.5.

In a preferred embodiment, the top led of the reactor could be fixed to the reactor using flanging connection, or it could be fixed using industrial stainless steel spring loaded toggle clamps .

In a preferred embodiment for the invention, and if the length of the conveyor belt is 2m or less, it is proposed to use stainless steel shaft 22 with 6mm diameter, with length subjected to bearing of 8mm.

In a preferred embodiment for the invention, it is proposed that the holes 13 of the trays 5, 12 is made with micro-drilling, and for a 2m conveyor belt length, it is proposed to drill a five horizontal rows of holes, as the hydrostatic pressure is unequal on each row of holes it is proposed to use different micro drilling Bits of 1mm, 0.95mm, 0.9mm, 0.85mm, 0.8mm, and 0.75mm for the first lower row to the fifth highest row respectively.

In another aspect, the use of constant hole diameter is not preferable, as the gas bubbles will only escape from the lowest pressure point at the highest row of holes only.

In a preferred embodiment for the invention, it is proposed that the slipping edges 20 is made of a small half cylindrical shape of high density polyethylene having the radius of 2.1mm and a length of 6mm with a highly polished surface.

The number of slipping edges 20 on each tray is proposed to be two for 40cm tray width, and it is needed to add extra slipping edge for each extra 20cm width. A red color slipping edges is proposed to be installed for the first tray only to be recognized during the rotation and a white color slipping edges for the remaining trays.

It is preferred to calibrate the axis of the two conveyor pulleys as well as the tension of the conveyor belt by adjusting the position of the threaded bulkhead.24, 25 which is tighten between the hole 28, and its preferred to adjust the two lower threaded bulkheads first and then adjusting the upper two.

It is proposed that the reactor will be operated using a full controlled system where input and output streams, Temperature, pH, and other controlled variables are fully controlled using different instrumentations and piping through the reactor inlets and outlets 1, 8 .

The proposed invention has seven inlets and outlets, the outlet 8 is designed to be for the -liquid- outlet product stream where the product control-valve is located, while the other six reactor inlets and outlets 1 are designed as follows: one for the sensors signal wires, two for the gas input streams, one for the gas outlet stream, one for liquid inlet stream where the liquid inlet control-valve is located, and one for the inlet of pH liquid control buffers where two dosing pumps are utilized.

In a preferred embodiment for the invention regarding the photo bio-reaction application, and if the inlet gas is a fresh air, it is proposed to connect the suction of the gas compressor to the upper part of the main control panel board, to invest the gas flow in the aeration of the controllers and electronic modules .

Its preferred that the Maintenance of the current invention is to be done easily by opining the lid of reactor 9 and maintain the trays 5, 12 and the belt 4 while rotating them, and maintain the inner wall 29 of the reactor periodically by unplugging the shaft holders 3 and taking off the core of the reactor 21, 4, 5, 12 .

While operating the current invention under the above criteria, it's supposed to achieve a lighting rate of 17.073 m2 of lighted area / m3 of actual liquid volume.

It is also supposed for the conveyor belt 4 according to the above criteria to achieve a linear velocity of 3.225 m/min if the liquid viscosity and density is at the range of 0.001 to 0.00123 kg/m.s and 999.58 to 1001 kg/m3 respectively.

Furthermore, it is also supposed regarding the agitation, that the liquid particles linear speed will reach more than 2.5 of the belt 4 (trays 5, 12) speed at the maximum points that are located beside each tray (at the two farthest ends of the tray)

In a preferred embodiment for the invention, it is proposed that the reactor is operated as a photo bio-reactor in a full controlled industrial outdoor closed system to produce the biomass from microalgae.

In a preferred embodiment for the invention, it is proposed that the reactor may be operated as a gas-liquid absorption unit.

In a preferred embodiment for the invention, it is proposed that the reactor may be operated as a gas-liquid Continuous stirred-tank reactor.

In a preferred embodiment for the invention, it is proposed that the reactor may be operated as a three phase chemical reactor.

In a preferred embodiment for the invention, it is proposed that the reactor may be operated as a three phase catalytic reactor, where the solid catalyst may be fixed to the outer and/or inner walls of the trays 5, 12. in a further aspect for the earlier proposal, the catalyst on the moving trays 5, 12 will break the liquid boundary layer at their walls while moving which increases the mass transfer coefficient.

In a preferred embodiment for the invention, it is proposed to build the trays 5, 12 with less or no holes 13 for the very-low gas flowrate three phase operating conditions.

Claims (19)

Claims

1. A three-phase reactor for at least gas and liquid phases, the reactor comprises an inner belt conveyor and moving sieve trays, each moving sieve tray is fixed horizontally to the belt conveyor where it rotates with a vertical displacement, each moving sieve tray comprises a number of holes and gaseous reservoir, the gas phase is fed to the reactor from a location below the moving sieve tray to enter its gaseous reservoir then passes out through the holes to the next upper gaseous reservoir which allows mass transfer to occur during agitation.

2. A three-phase reactor according to claim 1, in which the holes in each moving sieve tray are made with different diameters with respect to hydrostatic pressure on each hole.

3. A three-phase reactor according to claim 1, in which the moving sieve trays contain gaseous chambers opened from the bottom side which act as unsteady gaseous reservoirs during operation.

4. A three-phase reactor according to claim 1, in which the belt conveyor utilizes a polyvinyl chloride belt coated with a UV-resistant material and reinforced by a fiber mesh.

5. A three-phase reactor according to claim 1, in which the conveyor pulleys are rotating on a sliding contact bearing and utilizing the liquid media inside the reactor to lubricate the bearing area.

6. A three-phase reactor according to claim 1, in which the reactor is in the shape of "Z" and supported by metal stiffeners and extended reactor walls.

7. A three-phase reactor according to claim 1, in which the reactor is in the shape of "Z" which forms two horizontally expanded volumes from the top and bottom of the reactor.

8. A three-phase reactor according to claim 1, in which the moving sieve trays have slipping edges which reduces friction area between the moving sieve trays and the reactor wall.

9. A three-phase reactor according to claim 1, in which the holes of each moving sieve tray are made to the opposite side of the holes in the previous moving sieve tray.

10. A three-phase reactor according to claim 1, in which the moving sieve trays have gaseous reservoirs with a right-angled triangular cross-section fixd to the belt conveyor so that its diagonal wall is close to the reactor wall and the right-angle is at the bottom of the upward moving sieve tray.

11. A three-phase reactor according to claim 1, in which the conveyor pulleys holders are adjustable so that the conveyor pulleys axes and the tension of the conveyor belt can be calibrated.

12. A three-phase reactor according to claim 1, in which the reactor operates as a photobioreactor and fed with fresh air, and reactor control panel is aerated by connecting the section of the air compressor unit that supplies the reactor to the upper part of the control panel.

13. A three-phase reactor according to claim 8, in which the color of the slipping edges of one moving sieve tray are red and the slipping edges of the remaining moving sieve trays are white.

14. A three-phase reactor according to claim 6, in which the gap between the metal stiffeners and the reactor wall is filled with a damping material.

15. A three-phase reactor according to claim 4, in which conveyor pulleys are sealed cylinders with two discs at the ends of each cylinder which determine the movement of the conveyor belt.

16. A three-phase reactor according to claims 4 and 10, in which the moving sieve trays are fixed to the conveyor belt using a conveyor belt-tape cemented to the top horizontal line of each moving sieve tray and sewed to the conveyor belt.

17. A three-phase reactor according to claim 1, in which the reactor operates as a three-phase catalytic reactor, where the solid catalyst is fixed to the outer and/or inner walls of the moving sieve trays.

18. A three-phase reactor according to claim 1, in which the reactor is used as a gas-liquid absorption unit, a gas-liquid continuous stirred-tank reactor, or a three-phase chemical reactor .

19. A three-phase reactor according to any of the preceding claims, in which the number of holes in each moving sieve tray could be adjusted.