Google analytics tag

Friday, December 18, 2015

Decarbonizing Planet Earth with Carbon


“The method adopted in Vedanta to impart the knowledge of Brahman is known as the method of superimposition (adhyaaropa) and subsequent negation (apavaada). In the Bhashya, Bhagavatpada says, “The transmigrating self is indeed Brahman. He who knows the self as Brahman which is beyond fear becomes Brahman. This is the purport of the whole Upanishad put in a nutshell. It is to bring out this purport that the ideas of creation, maintenance and dissolution of the universe, as well as the ideas of action, its factors and results were superimposed on the Self. Then, by the negation of the superimposed attributes the true nature of Brahman as free from all attributes has been brought out. This is the method of adhyaaropa and apavaada, superimposition and negation, which is adopted by Vedanta.” (Ref: What are Upanishads? : An over view by S.N. Sastri on Luthur.com) The analogy that is often used to describe the process of superimposition and negation is that of ‘using a thorn to remove a thorn’. Finally, when the last thorn is removed, the thorn used to remove it is thrown away as well. Similarly, Carbon can be used to reduce carbon emission while power is generated! Let us consider the issues of Carbon emission and global warming resulting in climate change in the above context. Recent conference in Climate change held in Paris is acclaimed to be a success to the planet earth collectively adopted by 195 countries both developed and developing. In a nutshell they all have agreed to reduce their carbon emissions to limit the global warming to less than 2C or even 1.5 between 2030 and 2050. Is it really practical to achieve the above target given the nature of reduction and the complexity of imposing such a reduction within the time frame? It is a big question mark. The only practical method to reduce CO2 is by using Hydrogen CO2 + H2----> CO + H2O and then convert CO into a useful product such as Urea NH2CONH2 a fertilizer. Production of Urea requires additional Hydrogen which is again obtained by combustion of fossil fuel resulting in CO2 emission. Moreover, CO2 will eventually be released at the point of usage of urea later. While trying to reduce Carbon emission one will end up with more Carbon emission in the atmosphere.
The carbon emission from power plants can be substituted with renewable energy sources such as wind and solar at a very high cost but how the emissions from chemical plants such as urea or from automobile emissions, steel plants and cement plants be contained? We should also remember that silicon wafer to produce solar panels consume large amount of power which now comes invariably from fossil fuels. There is a long list of such plants emitting Carbon every day from all over the world. But there is a possibility to reduce emissions substantially by converting CO2 emissions from power plants into a synthetic fuel which can then substitute fossil fuel to continue power generation. The CO2 resulting from combustion of synthetic fuel will be recycled in the same manner mentioned above thus completing a cycle. To convert CO2 into a synthetic fuel we will require Hydrogen either by renewable sources or non-renewable sources. The non-renewable sources for Hydrogen cannot be a long term solution but renewable Hydrogen is very expensive at this stage. Therefore, Hydrogen is the only source which will not only help reduce Carbon emissions but also help eliminate Carbon completely from planet earth. Renewable Hydrogen is the key to decarbonize the planet earth. However, it may be possible to decarbonize the planet temporarily by using Hydrogen derived from fossil fuel without emitting CO2! It is not just a theory but practical because the technology has already been tested! In this process the Carbon will remain in the loop where it will neither be buried nor emitted into the atmosphere but constantly recycled.

Tuesday, August 25, 2015

Production of Caustic soda by desalination of sea water with fresh water as by-product


There is a great deal of misconception about desalination of seawater and the word ‘desalination’ is taken literally as a method of separating fresh water from seawater but not the separation of salt from seawater. The main focus here is only about recovery of fresh water from seawater or from any saline water sources but not salt. In fact separation of salt from seawater is also known as desalination or desalting. The reason for this misconception is because fresh drinking water is in demand and people are concerned only with fresh water and not the salt. There is a huge demand for fresh drinking water all over the world. Increasing population, large scale usage of fresh water by industries, pollution of fresh water by domestic and industrial effluents, failure of monsoon or seasonal rains due to climate change are some of the factors that contributes to water shortage. There is also a demand for water by agriculture industry both in terms of quality and quantity. Bulk of the ground water is used as a main source of fresh water by agriculture industries in many countries. But sea water also contains number of minerals or salts which have greater economic and commercial value. In terms of quantity their presence is small, only 3.5% and the rest 96.5% is fresh water. For example Chemical industries such as Caustic soda and Soda ash plants use salt as their raw material. But they also use demineralized water to dissolve salt to produce brine which is their feed stock. Therefore Chemical plants are the largest users of seawater in terms of salt as well as fresh water. Power plants mainly located on seashore also use large quantity of demineralized or desalinated water for boilers and for cooling towers. Sea is now becoming a great source of fresh water as the inland water supply is becoming scarcer due to dwindling water table by drought or flooding by too much rains, pollution by industries etc. In earlier days seawater was the only source of common salt known as Sodium chloride produced by solar evaporation. Bulk of the salt is till used by this method. Therefore it is logical to locate a chemical plant and a power plant side by side so that seawater can be utilized efficiently. CEWT (Australian company) has developed a new desalination technology called ‘CAPZ desalination technology’ that can generate fresh water as well as Sodium chloride brine simultaneously which is suitable for Caustic soda/Soda ash production. They can integrate such a facility with a skid mounted Chlorine plant of smaller capacities. This plant can generate large volume of drinking water (WHO standard) as a by-product that can be supplied to municipalities and agriculture industries. Locating large scale solar salt pans near such a facility will be a problem because it requires a huge area of arid land with good wind velocity and it takes nearly a year to harvest the salt. Using CAPZ desalination technology one can generate saturated Sodium chloride brine of 315 gpl concentration as well as fresh drinking water directly from seawater. The brine is purified to meet the specifications required by membrane Electrolysis for the production of Caustic Soda. The same brine can also be used for the production of Soda ash using Solvay process. It is no longer necessary to produce brine from solar salt. Solar salt requires vast area of arid land with good wind velocity and least rain fall and large manual labour force to work under harsh conditions; it is a very slow process and takes almost a year to harvest the salt, which is full of impurities and requires elaborate purification process during the production of Caustic Soda. Such purification process generates huge volume of solid waste for disposal. Chlor-alkali industry is one of the most polluting industries in the world. In fact these impurities can be converted into more value added products such as recovery of Magnesium metal or recover of Potassium salts. CAPZ technology is developing a ZLD (zero liquid discharge) desalination process where the effluent containing the above impurities such as Calcium, Magnesium and Sulphates are converted into value added products. By recovering more such salts from seawater one can recover additional fresh water. Therefore desalination of sea water is now emerging as an integral part of Chlor-alkali industry. By such integration Chlor-alkali can become a major player is meeting fresh drinking water of a nation. By careful integration and co-location of a desalination plant, Caustic soda plant, Food and pharmaceutical grade salt plant and a power plant on a sea shore will be a win situation for everybody involved. Let us take a specific case study of setting up a Caustic soda plant, a captive power plant and a desalination facility. A typical skid mounted Chlorine plant will have the following configuration: Capacity of Caustic Soda: 50.7 Mt/day (100% basis) Capacity of Chlorine : 45.00 Mt/day (100% basis) Hydrogen production : 14,800m3/day (100% basis) A typical usage of Vacuum salt for such skid mounted Chlorine plant will be about 76.50 Mt/day with a power consumption of 2.29 Mwhr/Mt of NaOH (100%). A captive power plant of capacity 200Mw will be able to supply necessary power for both Desalination facility as well as Caustic soda plant. The CAPZ desalination facility can supply a saturated sodium chloride brine (315gpl concentration) 245 Mt/day and 9122 m3/day of fresh drinking water from the desalination plant. This water can be used for boiler feed in the power plant. Surplus water can be supplied as drinking water meeting WHO specifications.
The Hydrogen gas the by-product from caustic soda plant with capacity of 14,800 m3/day can be used to generate clean power using a Fuel cell. The power generated from Fuel cell will be about 20 Mwhr/day that can be supplemented for the Caustic soda production thereby reducing the power consumption from 2.29Mwhr to 1.46 Mwhr/Mt of NaOH (100%) By careful integration of a large (ZLD) desalination facility with caustic soda plant and power plant it will be possible in future to generate a clean energy using Hydrogen, a by-product of Caustic soda plant and solar thermal plant to produce chemicals in a clean and environmentally sustainable manner. For further information on CAPZ technology, please contact ahilan@clean-energy-water-tech.com.