CN1776950A - Air cathode biological fuel cell for electric generation from organic waste water - Google Patents

Abstract

The biological fuel cell includes anode and cathode, which are setup at two ends of cylindrical reactor. Sample point is at middle of upper part of the reactor. Water inlet and water outlet are setup at two ends of the reactor. Anode material is carbon paper, and cathode material is carbon fabric containing catalyst of metal Pt. anode area : cathode area = 3 : 1. Anode and cathode are connected to each other through copper conductor. Making important improvement for traditional biological fuel cell, besides advantages of general biological fuel cells, the invention possesses particular strongpoints: (1) taking out proton exchange membrane so as to lower investment; (2) obtaining higher power output since lower internal resistance; (3) recovering electrons from organic substance in high efficiency so that system runs more stably.

Description

Air cathode biological fuel cell for electric generation from organic wastewater

(1) technical field

What the present invention relates to is a kind of Blast Furnace Top Gas Recovery Turbine Unit (TRT), and the utility model also relates to a kind of processing unit of sewage, specifically a kind of biological fuel cell that utilizes organic wastewater.

(2) background technology

The quantity of the disposable energy such as tellurian natural gas, oil, coal is limited.Between in the future 10～20 years, the oil production rate in the whole world will no longer can satisfy the demand of people to the energy, the worldwide energy crisis second time of this after date morning seventies in 20th century that causes possibly continuing.In addition, it is serious day by day that current environment pollutes, and that the whole world is used to handle the energy of waste water consumption every year is very huge, brings white elephant for the development of society.Therefore, need seek new clean energy resource replaces the disposable energy on the one hand, needs to develop new technology on the other hand and reclaims the energy to reduce the disposal cost of waste water from waste water.

The energy that can reclaim from organic wastewater mainly contains methane, hydrogen and electric energy.

Organic substance can under anaerobic be converted to methane gas, reclaims as the energy.But the subject matter of this method has two.On the one hand, because methane-producing bacteria is very responsive to environmental condition, make system for anaerobic treatment reach stable so be difficult to the control appropriate condition; On the other hand, methane belongs to greenhouse gas, and a large amount of the use can be quickened global warming, is not the environmental friendliness energy therefore.Therefore, this method has been subjected to certain restriction.

Hydrogen is considered to one of clean energy resource of tool potentiality to be exploited, and utilizing fermentative microorganism to extract hydrogen from waste water is the effective way that obtains cheap hydrogen.But pointed as Benemann, this method only makes the conversion ratio of hydrogen bring up to 60%-80% just economic worth ^[1]Regrettably, to realize that at present this target need overcome very big technology barrier.In theory,, extract hydrogen as substrate with glucose if use hydrogen-producing bacteria as catalyst, the glucose of every degraded 1mol, the output of hydrogen is 12mol.But in fact, known bacterial classification can only make the output maximum of hydrogen reach 4mol at present, and gross efficiency is 33%, and the numerical value in actual moving process also will be far below this.Utilize Unareobic fermentation to extract hydrogen from organic wastewater 15% form with hydrogen in the organic wastewater energy is existed, in other words, all the other energy of 85% still have been wasted.Therefore, need seek new approach and reclaim the energy in the organic wastewater.

Also having a kind of method is directly to generate electricity from organic substance.The device that can generate electricity from organic substance is called biological fuel cell.In biological fuel cell, the oxidized process of organic substance will produce electronics and proton (NADH), and electronics is transferred to anode under the catalytic action of microbe, and proton is stayed in the liquid phase.If with lead anode and negative electrode are coupled together, electronics will arrive negative electrode.At negative electrode, electronics and electron acceptor and remaining proton can react, and follow the reaction of anode organic matter degradation and negative electrode, can obtain continuous electric current at external circuit.In fact, the organic pollution process of decomposing under microbial action is exactly the process of electron transfer.If the migration of electronics is to finish in liquid phase inside, corresponding process is exactly the activated sludge process in the sewage disposal; If the electronics that produces can be derived, electronics is moved at external circuit, corresponding process is exactly a biological fuel cell.

Biological fuel cell is under the effect of microbial catalyst, and chemical energy is changed into the device of electric energy, is divided into anode region and cathodic region, and these two districts are separated by proton exchange membrane (PEM).In the anode region, microbe with organic substance as electron donor, with electrode as electron acceptor with oxidation operation, this process can produce proton and electronics, electronics is enrichment on anode, transfers on the negative electrode by external circuit; Proton enters the cathodic region by proton exchange membrane.In the cathodic region, electronics, proton and combination with oxygen generate water, if Fig. 1 provide be the principle of biological fuel cell with glucose as the generating substrate, oxygen is as electron acceptor, then the half-reaction on two electrodes is respectively:

The anode half-reaction: E ⁰＝0.014V (1)

The negative electrode half-reaction: E ⁰＝1.23V (2)

In theory, the glucose of every oxidation 1mol can produce the voltage of 1.216V.

Traditional two chambers biological fuel cell generally is made up of an anode reaction chamber and a cathode reaction chambers, and is middle with the proton exchange membrane separation, as shown in Figure 2.But the reaction unit of this form is because (1) equipment is too complicated, and difficulty is all compared in operation and management; (2) intermittent duty is difficult to uninterruptable power generation in the reality; (3) employed PEM cost is very expensive; (4) increased operating cost to the negative electrode aeration; (5) generated output output is low.These weak points have limited its application.

In order to overcome the shortcoming of traditional double chamber fuel cell, people have researched and developed air cathode biological fuel cell.The fuel cell of this form is single pond form, and as negative electrode, its design feature is with air: (1) anode and negative electrode are in the same reative cell; (2) negative electrode has saved expensive proton exchange membrane.Compare with traditional two chambers fuel cell, it has fairly obvious advantage: (1) design is extremely simple; (2) because negative electrode has replaced aeration with air diffuser, reduced the operating cost that aeration consumes, because the oxidation-reduction potential of air is higher than the liquid phase aeration, cathode potential be can improve in addition, and then the electromotive force and the power output of battery increased; (3) removed the capital expenditure that proton exchange membrane can reduce system greatly.But, the biological fuel cell of this form of having reported in the world at present has identical anode and cathode area, its maximum shortcoming is owing to saved proton exchange membrane, increased the diffusion rate of negative electrode oxygen greatly, destroy anaerobic condition after the oxygen that sees through from negative electrode enters into reactor, reduced the electronics rate of recovery of system greatly.

(3) summary of the invention

The object of the present invention is to provide a kind of can the increase to improve the air cathode biological fuel cell for electric generation from organic wastewater that electronics reclaims when the power of battery is exported.

The object of the present invention is achieved like this: it comprises anode and negative electrode, anode and negative electrode place the two ends of cylindrical reactor respectively, the middle part of the upper end of reactor is provided with sample tap, two ends are respectively equipped with water inlet and delivery port, anode material is a carbon paper, cathode material is the carbon cloth that contains metal Pt catalyst, and annode area is greater than cathode area, is connected with copper conductor between anode and the negative electrode.

In traditional waste water aerobic is handled, if according to handling 1m ³Sanitary sewage consume the 0.5kWh electric energy and calculate a medium scale sewage treatment plant (treating capacity 3.0 * 10 ⁵m ³) electric energy that consumes of disposing of sewage every day is 1.5 * 10 ⁵KWh, if 1 degree is electric according to 0.6 yuan of calculating, the sewage treatment plant of scale will consume nearly 3,500 ten thousand yuan electricity charge every year like this.Along with the increasing to the environmental protection dynamics, the quantity of sewage treatment plant will constantly increase, and treatment scale will continue to strengthen, and this is a serious burden to government and society.Biological fuel cell can be converted into the chemical energy in the carbohydrate in the waste water energy-electric energy that cleans most as catalyst with microbe.Compare with traditional method, it has fairly obvious advantage.The first, it can move under middle temperature even cryogenic conditions; The second, can not produce the gas that air is had pollution, as hydrogen sulfide; The 3rd, sludge yield is few, has reduced the expense of Treatment of Sludge; The 4th, can dispose of sewage in the time of generating.Therefore utilize biological fuel cell from organic wastewater, to generate electricity and to realize the sustainable development of sewage and waste water treatment to greatest extent, in case realize to produce immeasurable society, environment and economic benefit.

The air cathode biological fuel cell that anode cathode area of the present invention does not wait, be the significant improvement to the traditional biological fuel cell, except the advantage that possesses general biological fuel cell, it also has some unique advantages: first, remove proton exchange and touched, greatly reduced capital expenditure; The second, have lower interior resistance, therefore can obtain higher power output; The 3rd, the electronics that has improved system effectively reclaims.Therefore can be when improving power output, the electronics in the high efficiency recovery organic substance moves more stable.

(4) description of drawings

Fig. 1 biological fuel cell operation principle;

Fig. 2 is the structural representation of traditional double chamber biological fuel cell;

Fig. 3 is a structural representation of the present invention;

Fig. 4 is starting period voltage output;

Fig. 5 is the variation of volumetric power density with current density;

Fig. 6 is the linear regression curve of voltage and current intensity

Fig. 7 is that (glucose is as substrate, 650mg/L) for voltage output and electronics recovery.

(5) embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

In conjunction with Fig. 3, the composition of air cathode biological fuel cell for electric generation comprises anode 1 and negative electrode 2 from organic wastewater, anode and negative electrode place the two ends of cylindrical reactor 3 respectively, two ends are respectively equipped with water inlet 4 and delivery port 5, and anode material is a carbon paper, and cathode material is the carbon cloth that contains metal Pt catalyst, annode area is greater than cathode area, general annode area: cathode area=(3-6): 1, the best is an annode area: be connected with copper conductor 6 between the cathode area=3: 1, anode and negative electrode.Be connected with resistance 7 between anode and the negative electrode, voltage is measured with universal instrument 8.

For the power generation performance of fuel cell more of the present invention, design two air cathode biological fuel cells and be respectively ACMFC1 and ACMFC2.With cylindrical reactor (dischargeable capacity 60mL) two ends that anode and the negative electrode of ACMFC1 places polymethyl methacrylate to make respectively, the middle part of upper end is provided with sample tap, and two ends are respectively equipped with into water and delivery port.Anode uses carbon paper (effective area 13cm ², E-TEK) to make, negative electrode is made by the carbon cloth that contains metal Pt catalyst.ACMFC2 is the fuel cell that we design voluntarily, and dischargeable capacity is 80mL, and anode is carbon paper (effective area 40cm ², E-TEK), negative electrode is carbon cloth electrode material (the effective area 12.56cm that scribbles the Pt catalyst ²), the anode of two fuel cells all is connected with copper conductor with negative electrode.

Result of the test is as follows:

1, voltage output

With sanitary sewage (COD=314.67～327.75mg/L, pH=7.0～7.5) and sodium acetate (1.0mM) nutrient solution ^[3]Mixture and cultured anaerobic sludge (MLSS=4000mg/L) be added in the reactor intermittent duty.Change sanitary sewage and activated sludge through 5 times, ACMFC1 has produced the voltage of 0.301V; ACMFC2 has produced the voltage (external resistance 1000 Ω) of 0.364V, as shown in Figure 4.

2, power output

As shown in Figure 5, when using glucose (650mg/L) to generate electricity as substrate, the maximum power of ACMFC1 is output as 3070mW/m ³(current density is 13mA/dm ³); The maximum power density of ACMFC2 has reached 9800mW/m ³(current density is 35mA/dm ³), be about 3 times of ACMFC1.

3, internal resistance and electromotive force

As can be seen from Figure 6, the internal resistance of ACMFC1 is 307.72 Ω, and the internal resistance of ACMFC2 is littler, is 107.79 Ω.This is to cause the immediate cause of the power density of ACMFC2 greater than ACMFC1.Therefore, can reduce battery two distance between electrodes by design, the cross-sectional area of augmenting response device reduces internal resistance simultaneously.Reason is,

$r=\mathrm{\ρ}\frac{l}{A}---\left(5\right)$

Wherein, r (Ω) is the internal resistance of cell, and ρ (Ω m) is a resistivity, and l (cm) is the two poles of the earth distance; A (cm ²) be cross-sectional area.The l/A value of ACMFC2 is 0.37m ^-1, less than ACMFC (0.05m ^-1), therefore have littler internal resistance.

In addition, the electromotive force of ACMFC1 is 0.4665V, and the ACMFC2 electromotive force is 0.5894V.This mainly be because the annode area of ACMFC2 greater than the annode area of ACMFC1, thereby for the metastatic electron microbial growth provides sufficient area, the bacterium of more metastatic electron can be finished the rising of voltage.

4, electronics reclaims

The running time of ACMFC1, electronics was recovered as 9.78% only less than 50h; And ACMFC2 can move more than the 220h continuously, and the electronics rate of recovery is 30.1%; (all exporting less than 0.05V as reaction end) with voltage, as shown in Figure 7.This result exceeds 10%～20% than people's results reported such as Liu.

Claims (3)

1, a kind of from organic wastewater air cathode biological fuel cell for electric generation, it comprises anode and negative electrode, it is characterized in that: anode and negative electrode place the two ends of cylindrical reactor respectively, the middle part of the upper end of reactor is provided with sample tap, two ends are respectively equipped with water inlet and delivery port, and anode material is a carbon paper, and cathode material is the carbon cloth that contains metal Pt catalyst, annode area is greater than cathode area, is connected with copper conductor between anode and the negative electrode.

2, according to claim 1 from organic wastewater air cathode biological fuel cell for electric generation, it is characterized in that: annode area: cathode area=(3-6): 1.

3, according to claim 1 from organic wastewater air cathode biological fuel cell for electric generation, it is characterized in that: annode area: cathode area=3: 1.

Images