1. Field of the Invention
The present invention relates to “solar powered Chlorine producing module” known as “SCPM” and, more specifically, to design a chlorine producing plant at the site of the municipalities' water and sewer treatment plants or any other chlorine consumer industry.
2. Description of the Related Art
This invention utilizes the solar energy, a permanent, non-delectable and free source of energy. This invention is specifically designed to eliminate the dependence of new chlorine producing plant on power utility network. Chlorine and caustic soda (jointly) are among top ten chemical produced by chemical industries. Chlorine producing facilities, known as “chloric-alkali process plants” are one of the very high-energy consuming industry. Even partial elimination of conventional plants from power network lowers the stress of already overloaded power utility system.
3. The present invention “SCPM”, unlike the conventional plant, does not run by power from the grid and does not need all the related power installation of high voltage service, step down transformer, converter of A/C power to DC power, and heavy conductor to carry very high electric current to electrolysis cells. DC Power generated by solar panel directly feed to chlorine producing cells.
Any invention that eliminates or reduces the use of carbon base energy is advantageous to everyone. Reduction of dependence on oil imports and effects on the environment from burning fossil fuels are among the top benefits. More importantly though, and less discussed, is the fact that oil is a limited and deplete-able resource, one that is very valuable in the production of plastics, pharmaceutical, nylons, polyesters, pesticides and fertilizers, to name a few.
Chlorine production in the site of municipalities' water and sewer plants with this invention eliminates the handling, transportation and large storage facilities that are for chlorine, which is considered hazardous material.
The saving from this invention is large enough to pay off initial capital investment of plant within five to ten years.
Furthermore, the chlorine producing plant design with use of solar powered chlorine producing module, unlike the conventional plant, is environmental friendly. In this design, 2500 kWh of solar power will be used to produce one ton of chlorine. In conventional plant using utility power for each ton of chlorine, produced 5450 pounds of carbon dioxide will be released into the atmosphere by power plant, while CO2 released by this invention is zero. The use of oil product to transport is eliminated.
Finally, this invention utilizes the membrane technology that is superior among the three popular electrolysis process of chlorine production due to its lowest energy need per ton of chlorine produced (very high quality products and friendliest process to environment).
In an effort to improve the deficiencies of conventional chlorine producing plants, first objective of this invention is to provide a design that utilizes the solar energy to power the chlorine producing cells.
The second objective of the present invention is to eliminate expensive electrical installation that receive high voltage A/C power from utility network, lower the voltage, and convert it from A/C to 3-volt DC current to power electrolysis cells.
The third objective of the present invention is to eliminate the power loss in electrical installations and conversion.
The fourth objective of this invention is to decrease stress on the electric network by eliminating high-energy users.
The fifth objective of this invention is to eliminate rigidity in production and high initial capital cost of traditional plants by use of solar powered chlorine producing module “SCPM”.
The sixth objective of the present invention is to eliminate transportation and storage of hazardous material on our roads and in the cities.
It is a seventh objective of the present invention to use the membrane technology that has the lowest consumed energy the highest quality products. It is also most friendly process to the environment.
It is a further objective of the present invention to use solar power and eliminate at least 2500 kWh from utility network for each ton of chlorine production that is equal to 5.9 barrel of crude oil not burned in power plants and less dependency to foreign oil.
Finally, it is an objective of the present design to reduce the pollutants, which result from burning of fossil fuel in power generating plant and transportation. Traditional method for each ton of chlorine produced, power plant releases 5450 pound of carbon dioxide while the emission of CO2 from this invention is zero.
The following legend is provided at the opening of this section for easy reference when abbreviations are found throughout the detailed description section. Any abbreviation or symbols not in the legend are deemed to be known to those skilled in the art:
To describe this invention, it is important that the solar technology and chemistry science on topic of electrolysis process be explained, and Prior to a detailed description of the invention, the following subjects need to be covered.
A—Chemical science behind the electrolysis process, and popular methods in the chemical industry.
B—Science and technology of solar power.
Thereafter, the detailed description of invention becomes simpler and better understandable.
What is chlorine?
Chlorine is a substance that does not exist in nature but is abundant in compound form of metal chloride like table salt everywhere.
Chemical Property:
In chemistry science, chlorine is known as a member of one of the five elements of the Halogen group in periodic table. Its abbreviated symbol is “Cl”. Its atomic number is 17, and its atomic weight is 35.453 grams, and molecular weight of 70.906 gram. Chlorine usually forms compounds with a valence of (−1), but it can compound with a valence of (+1), (+2), (+3), (+4), (+5) and (+7).
Physical Property:
Chlorine is a greenish-yellow gas at room temperature and atmospheric pressure. It has the following physical properties:
Chlorine, along with its byproduct, caustic soda, is among the top ten products in the chemical industry. The world's chlorine production in 2014 was 56 million tons. Europe and North America's share were 16 and 11 million tons respectively. Presently, most chlorine is produced off site of the user industry. By this invention, the cost to liquefy the chlorine, bottling and shipment is eliminated. However, for chlorine to be used in water and sewer plants, it needs to be dried by passing it through concentrated sulfuric acid, then compressed and liquefied into cylinders for transportation.
In chemistry lab, chlorine can be produced in many ways but in the chemical industry, chlorine is produced by a breakdown of the chlorine compound (most commonly known as table salt, (Na Cl) by electrolysis of brine
A solution of acid or alkaline or salts in water is called electrolyte. Electrolyte is conductive due to ions from ionization of one of the above substance in water. Ions Cl−1, So4−2 and O−2 have negative charge and are known as “Anions”. Ions like H+1, Na+1, and Fe+2 have positive charge and are labeled as “Cations”. In electrolyte, anions and cations are mixed together randomly and uniformly. When electrolyte solution is placed in electrostatic field, separation and orientation of ions will happen and anions go to anode while cations head toward cathode.
The process of separating the positive and negative ions in electrostatic field is called electrolysis.
2ClNa→2Cl−1+2Na+1 in electrolyte
2Cl−1→Cl2+2e−1 in anode(Chlorine Gas)
2H2O2H+1+2(OH)−1 in cathode
2H+1+2e−1→H2 in cathode(Hydrogen Gas)
2Na+1+2(OH)−1→2NaoH in cathode(Caustic Soda)
In order to obtain chlorine, it is necessary to break the chemical bond of sodium and chlorine in salt solution by electric power input through the electrolysis process. One ion of chlorine (Cl−1) has a negative charge equal to the charge of one electron. When one ion of chlorine (Cl−1) is pulled toward anode, it will give up one electron to become one atom of chlorine gas.
The electrical energy to produce one atom gram of chlorine is given in “Coulomb” by the following equations:
[C] Energy (In Coulomb)=[Electric charge of one electron]×[Number of atoms in one atom gram of chlorine].
(C)=1.6022×10−19×6.022×1023=96,485 coulomb.
1.6022×10−19 is negative charge of one electron
6.022×1023 is Avogadro's No.=Number of atoms in one atom gram
1 Farad is 96,485 Coulomb
The theoretical input energy is calculated by the following equations,
C/1 ton Cl2=(96,485)×(106 gr/35.5 gr)=2.718×109Coulomb/one ton Cl2
C
coulomb
=I
amps
×t
sec (Current×Time) or(Ampere×Second).
P
watt
=V×I
A
=V×C/t
sec
P
watt/ton=3.3v×(2.718×109Coulomb/ton Cl2)
P
KWH
=P
watt/(1000 watt/1 kw)×(3600 second/hour)
P
KWH
=P
watt/3.6×106 watt×second
P
KWH/ton=3.3v×(2.718×109 Coulomb/ton)/3.6×106
P
KWH/ton=2492 KWH/one ton Cl2
P
KWH/ton=2492 KWH/one ton Cl2
In new membrane cells, the input energy per one ton of chlorine production is 2500 KWH.
Ninety-five percent (95%) of industrial chlorine production is by electrolysis of saturated salt solution. Now, three types of electrolysis cells, diaphragm cell, mercury cell, and membrane cell have been used extensively. The breakdown of brine is the same in all three, and their main difference is the manner by which their products are separated from the mixed and quality of the products.
The diaphragm cell per
The saturated Brine 100 enters to anode Chamber 109 from the top. Brine elevation in anode Chamber 109 is higher than cathode Chamber 110 and create pressure drop across the permeable Diaphragm 107 to facilitate the movement of Brine 100 through Diaphragm 107 toward the Cathode 102. In anode Chamber 109, ion of Cl−1 goes to Anode 101, and give up its electron and leaves anode as Chlorine gas 104 per
2Cl−1→Cl2+2e−1
In cathode Chamber 110, water will be ionized to H+1 and OH−1. Ion of H+1 receives one electron and as H2 gas 105 leaves the Cathode 102, and ion of OH−1 combines with ion of Na+1 to produce Na OH 106.
In addition, in cathode Chamber 110, the ion of Na+1 reaches the cathode, 102 receive the missing electron to become metallic sodium. Metallic sodium reacts with water and produce caustic soda 106 and hydrogen gas 105 according to the following equations.
In the diaphragm, process chlorine gas 104 is collected at the top of anode Chamber 109, and hydrogen gas 105 is collected at the top of Cathode Chamber 110.
The leaving solution 106 from cathode Chamber 110 contains about 10 to 12% Na OH (caustic soda) and 15% of Na Cl. By evaporation of diluted caustic soda 106 with steam and reduced its volume to 20% of original volume, when sodium chloride (Na Cl) crystallized and separates. The remaining solution containing 50% caustic soda and less than 1% Na Cl becomes marketable. However, the non-purified caustic solution 106 is suitable for 80% of market demand.
Anode Chamber 109 includes anode 101 that is connected to positive pole of power source 103. Saturated brine 100 enters in the lower part of the chamber. As it moves upward, it gives up its ions and anion Cl−1 attracts to anode 101, gives one electron to anode and as chlorine gas 104 is collected at the top of Chamber 109, depleted brine 116 leaves at the top of Chamber 109 to Brine concentrator 115.
Cathode chamber 110 has cathode 102 connected to negative power source 103. Cathode Chamber 110 receives cation Na+1 from membrane 107. Diluted caustic soda 106 by pure water 112 enters at the lower part of the chamber 110 moves up and gains additional “Na OH” becomes concentrated 33% caustic ˜113 when it leaves the cathode chamber 110.
In cathode chamber 110, hydrogen gas H2 105 and sodium hydroxide (Na OH) 113 will be produced per the following reactions.
2H2O2H+1+2OH−1
2H+1+2e−1→H2(Hydrogen gas)
2OH−1+2Na—Hg→2NaOH+2Hg(Caustic Soda & Metallic Mercury)
In decomposer unit 117, hydrogen gas 105 will be collected at top of decomposer 117, regenerated mercury 119 recycles back to mercury cell 108, and caustic soda solution 113 goes to further purification if it is needed. Mercury cell caustic has the higher quality than the products of the other two Cells that was previously mentioned. However, there is 0.2 to 3 grams of mercury pollutant per each ton of chlorine.
The following table is the summary of the cell's specifications. It helps in better understanding and proper cell selection.
2650 (2)
(1) Current density of 5 KA/m2 uses more energy but increase production. High density creates more heat. Warmer caustic and less steam is required.
(2) New membrane for first two years uses 2575 KWH/ton of chlorine.
After study of science behind the electrolysis and three popular chlorine-producing cells, the membrane technology has been selected with the following considerations.
Solar cell is a diode of semi-conductors that generate electric energy when irradiated by the sun's rays. Solar cells are often electrically connected and encapsulated as a panel that have a sheet of glass on the sun's side allowing the light to pass while protecting the semi-conductors from rain, hail and other elements. In solar panel, cells are connected in series for voltage increase and in parallel for current increase. An array is a group of cells that are electrically connected in parallel and series with desire DC voltage and current. The power output of solar array is measured in watts or kilowatts. To calculate the energy needed for an application, a measurement of KHW per day is often used. A common rule of thumb is that the average power over 24 hours is equal to 20% of pick power, so the solar panel energy production in 24 hours is equal to production of same panel with peak power in five (5) hours. The solar generated energy most often is fed into power utility network by using inverters. In stand-alone systems, batteries are used to store the energy that is not needed immediately.
Solar cell's “energy conversion efficiency” is the ratio of power converted to electricity divided by solar energy irradiated to solar cell's surface. The efficiency is calculated by the ratio of the maximum power point, (Pmwatt) of panel with area of Ac, (meter squared, M2) divided by the total panel sunlight power. The total panel sunlight power, Psunlight, is the sunlight power irradiance E, (EWATT/M2) on panel area of Ac under standard test conditions (STC), per equation (1.)
Standard test condition is temperature of 25° C., irradiance of E=1000 w/M2, and air mass of “A M 1.5” spectrum.
The Air mass number varies, it dependent on geographic location, altitude, sun location and elevation. It varies with time of the day and with seasons of the year, it could have any value and because of that, it called AM spectrum.
For a path length “L” through the atmosphere for solar radiation incident at angle “Z” relative to the normal to the earth's surface, the air mass coefficient is;
AM=L/L
0=1/Cos Z°
“L0” is the Zenith path length (Atmosphere vertical length at the sea level).
“Z” is the Zenith Angle in degree.
For sun at angle “Z=48.19°.”
A solar cell may operate over a wide range of voltage (V) and current (I) depending on the resistance of connected circuit. Circuit with zero resistance (short circuit condition) voltage is zero. Current is max called “Isc” when circuit resistance increases to infinity (open-circuit), voltage has the highest value called “Voc” and current is zero. At those two ends of resistance spectrum, solar power generated is zero, and will have value when both voltage and current have no-zero values. With certain circuit resistance, the power generated is max. This is known as power point (Pm).
A high quality mono-crystalline solar silicon cell may produce 0.6 volts (V0) at cell temperature of 25° C. In ambient temperature of 25° C. and full sum, the temperature of irradiated cell will be about 45° C. This higher temperature reduces the voltage Voc to 0.55 volts per each cell.
At an ambient of 25° C. and silicon cell working temperature of 45° C., the maximum power is produced with voltage of 75% to 80% Voc (say 0.43 volts) and the current is 90% of Isc (short-circuit). Therefore, the maximum power point (Pm) is about 70% of “Voc×Isc”.
Low quality cells have more rapid voltage drop with current increase and its power point voltage is 50% of Voc. Its current is 50% Isc, and the power point could drop from 70% of Voc×Isc to 50% or even 25%.
Use of power point (Voc×Isc) in solar cell alone as a guide in solar cell selection is misleading and insufficient. However, full spectrum of power generation curve with current increase should be considered.
The ratio of summation of power spectrum correspond to current from zero (Io) to (Isc), that is the area under power curve (in plot of power versus current), to power point of Voc×Isc is called Fill Factor. Fill Factor is useful in cell selection.
From equation 1, substitute, (Pm=m×E×Ac) in to equation (2)
The short circuit current (Isc) is nearly proportional to illumination intensity. Open-circuit voltage (Voc) is less sensitive to illumination. By 80% drop of illumination there is only 10% drop in open-circuit voltage (Voc).
Solar cell efficiencies vary from 6% (amorphous silicon base) to 40.2% and 42.8% (multiple junctions in research laboratories).
Commercially available multi-crystalline silicon cells have efficiency of 14% to 19%.
The highest efficiency cells are not the most economical. Multi-junction cell with efficiency of 30% based on exotic materials such as “Gallium Arsenide” or “Indium Selenide” will cost 100 times of silicon cell with 8% efficiency and only produce four times the power.
The price of delivered KWH is the way to justify the economic cost of power generated by solar cell. In cost analysis, the following dominating parameters should be considered:
1. Efficiency conversion of solar panel
2. Intensity of sun irradiation
3. The useful life of solar panel
4. Fill Factor (FF); the larger the number the better the cell
5. Curve of power versus current
The above parameters will lead to overall system selection between the choices.
With commercial silicon panel and efficiency of 8% to 19%, the cost of solar power in 2005 ranged from $0.6/kwh (Europe) down to $0.3/kwh (in regions with high sun irradiation). The large portion of above cost is due to cost of large conductors, low voltage DC power (direct current) to AC (alternative current) convertors, step up transformer, and synchronizing and metering equipment. Also in process of converting 30-volt DC power to AC, power with 20 kv volt (utility distribution voltage) over 30% of energy generated convert to heat as loss. Worldwide, the cost of conventional power plants in year 2005 was between $0-04/kwh to $0.25/kwh depending on plant size and fuel.
Based on above argument, it can be concluded that use of solar panel to feed power utilities network is not feasible.
Solar Power in this Invention:
Chlorine producing cells use low voltage DC power (3 volts). To provide such power from high voltage utility network requires installation of expensive electrical equipment to lower the voltage and convert it from AC to DC power. This process associates with power loss of 30% and more, but solar panels generate exact power that is consumed by chlorine producing cells.
In this case, the cost of delivering KWH to chlorine cell drops to less than $0.1/kwh that makes the use of solar power economically feasible.
Solar Cell Selection for this invention:
The solar cell technology is relatively spread in regards to:
1. Costs, solar cells have price from low to very high
2. Efficiency: the efficiency of solar cells ranges from 6% to 40%
3. Durability: resistance against severe elements and ultra violet
4. Life: useful life span
Considering the above parameters, crystalline silicon “C—Si” is a good choice. Crystalline silicon also known as “solar grade silicon” is the most prevalent bulk material for solar panels with an average efficiency of 15%. A commercial solar panel of crystalline silicon “C—Si” model “LG265 Si—C 265G3” product line of “Monox”, with dimension of 65″×40″×1.4″, and efficiency of 16.4% with the following specification has been selected.
For construction purposes, it is feasible to select a “solar frame” as a unit power generator to power the electrolysis cells. This frame should have a dimension easy to build, transport, installed, and have enough irradiant capture area. The frame is made from four (4) panels of “LG 265 Si C” and has dimension of 3.3 m×2.0 m with area of 6.6 m2.
The frame energy production when installed in California or Florida (with annual average of 1000 w/m2) and with efficiency of 16.4% will be:
Pm=16/4%×1000 w/m2×6.6 m2=1082 w (frame power point)
Annual Frame's production is:
KWH/year=(365 days)×(five hrs./day)×1.082 kW=1975 KWH/yr.
Frame's Life production is:
KWH/yr.×25 yrs.=49,366 KWH/lifetime
The cost of each frame made of four (4) panels LG 265 Si C will be:
4 panel×$310/panel+$260.holding frame=$1500/frame
All four (4) panels each with power voltage of 31.2 v and current of 8.46 amps electrically connected in parallel. Therefore, the frame voltage is 31.2 volts and frame current is near 35 amps.
Frame energy production in Column C is dependent on operating voltage of chlorine producing cells.
In membrane cell (selected for this invention), the operating voltage is 3 to 3.6 volts with average of 3.3 volts.
Frame's energy in column for one (1) year and lifetime is given per the following equations:
I=W
watts
/V
volts
=A
amps
I=1082 w/3.3 v=327.9 Amps
C
column
=I
Amps
×t
second
C/Frame annual=(327.9 Amps)×(365 day/yr.)×(5 hrs./day)×(3600 sec/hr.)
C/Frame annual=2.154×109 column/year
C/Frame 25 year=5.386×1010 column/25 yeas.
F/Frame year=2.23/104 Farad/year
F/Frame 25 years=5.582×105 Farad/25 year
In theory, one farad of electric energy in electrolysis of one molecule gram of table salt solution will produce the following elements:
The Invention is Solar Powered Chlorine Producing Module for 50 tons of chlorine per year, called “SCPM”.
“SCPM” has two main parts:
A—Solar panel assembly that provides power called “solar power producer”
B— Chlorine Producing Unit called “Cl2 Unit”
The power source of this module is the assembly 215 that is made of 64 solar frames 208, and arranged in eight columns. Each column has eight (8) solar frames 208. The solar frame 208 are made from four (4) commercially silicon solar panels of 209. The solar panel is model “LG265 Si.C 265G3” product line of “Monox” that its specification is already given in the solar section. All sixty-four (64) solar frame are electrically connected in parallel according to wiring 210, and the final power feeder 211 to “Cl2 unit 212” will have voltage of 31 volts and the current of 2233 amps.
Feeder 211 of
“Cl2 Unit 212” Electrical Connection 211:
Up to 1970 electrolytic cell, anodes were graphite. New anodes are Titanium (Ti) metal electro-coated with an Oxide of Platinum group family (Ruthenium, Titanium, Tin and zirconium). Titanium anode Electro-Coated with Ruthenium Oxide (RUO2) and Titanium oxide (TiO2) are high current density in low voltage. The use of RUO2 and TiO2 coated Titanium Anodes reduces energy consumption by about 10% and higher life expectancy. Competitive design of anode geometry is today's industry challenge, all with the aim of improving gas release, to reduce Ohmic resistance losses and increase the anode life by improving the homogeneity of the brine.
Metal Anode lives are 12, 8 and 4 years for diaphragm, membrane, and mercury, respectively. In mercury cell, short circuit between anode and cathode cause the wear of anode coating.
Is nickel often coated to reduce energy consumption? Reducing the distance between Anode 101 and Cathode 102 will reduce the ohmic resistance and Will reduces the operating voltage and energy. This is the reason behind the new slim cylinder cells.
Recently, a new oxygen depolarized cathode (ODC) has been used. Oxygen is pumped into the cell to react with liberated hydrogen in Cathode to form water, results in lower cell resistance, and lower the voltage needed for the electrolysis process. This voltage reduction could be as low as 50%. A disadvantage of this process is that the hydrogen is no longer available as an important and valuable product.
Membrane 107 with thickness 0.15 to 0.3 mm is co-polymer of tetra-fluoroethylene (C2.F4) Groups, and is non-permeable, but ion exchanger membrane.
To reduce the maintenance cost of cell operation, the following precautions should be considered:
Chlorine produced by all cells has some water vapor. Concentrated sulfuric acid (92% to 98% of So4H2) is used to dry chlorine. If re-concentration takes place at site, also a small amount of the sulfuric acid per ton of chlorine will be used for elimination of (Cl—O—Na) and PH control.
Caustic soda produced by cells has some Cl Na, by boiling the product; excess salt will be crystallized and separate from caustic soda.
Indirect heating with steam will do caustic soda concentration, and sulfuric acid concentration.
This invention was applied in design of chlorine producing plant for a municipality with a population of 170,000.
In this design, the production capacity could be increased throughout the life of the plant if chlorine demand increases. In the 25-year life of the plant, there will be four times capacity expansion at the start of the 2nd, 3rd, 4th and 5th period of five years period with addition of 3, 3, 4, and 3 “SCPM, 50 ton/yr.” to the plant. Due to this expansion, the increase of Cl2 production takes place in four (4) steps, while the city demand is exponential; that results in excess Cl2 production.
The excess chlorine will be sold to other cities at 80% of the buying price of offsite Chlorine by city, as an income to the city.
The city's caustic soda consumption is about 33% of the plant production. The 67% excess product of the plant will be sold to other cities at 75% of the buying price of offsite caustic soda by city, as an income to the city.
The plant hydrogen by-product may be sold at the price of 75% of the market price as income to the city.
If, instead of selling the hydrogen, it is converted to ammonia (NH3), it will provide 56.5% of City's consumption, and the city needs to buy only 43.5% of its consumption.
The summary of this case study has been given in the following graphs.
To explain and better understanding of drawings, assigned numbers has identified the products, elements of solar power producing unit, chlorine producing cell assembly, and related accessories. The assigned numbers used in figures are given in the following table.