Pelletizer for the production of Iced Carbon Dioxide pellets (CD – ICE) with 100% transformation rate from liquid to solid 2 nd International Conference on Dry Ice Blasting 1 Berlin, 2010
Abstract The present state of the art in the construction of dry ice pelletizer allows the realization of mechanic producer of dry ice pellets with standard density and the realisation of hydraulic pelletizer for the production of pellets with high density. The transformation rate from Liquid CO 2 into the solid phase is about 38-40% whereas the remaining part (60-62%) turns into CO 2 gas. The P1/1 Pelletizer can realise a 100% transformation of the Liquid CO 2 into a solid phase with the under cooling of the Liquid CO 2 into iced CO 2 using Liquid Nitrogen. The advantages compared with traditional pelletizer are: - 100% transformation of Liquid CO 2 into Iced Carbon Dioxide pellets (CD – ICE), erasing completely the discharge of the CO 2 gas which is usually released in the atmosphere with a perceptible benefit on the greenhouse effect. - Transformation of Liquid CO 2 into Iced carbon dioxide (CD – ICE) and not in dry ice with the following advantages: - The CD-ICE is harder than Dry Ice - Slow – going sublimation compared with dry ice - Sharp – edges break line These advantages lead to a longer shelf life of the CD - ICE during the storage and better performance when used for blasting. - Transformation of 1kg of Liquid CO 2 into 1kg of iced CO 2 pellets (CD-ICE) with a cost reduction of about 52/54% compared with the dry ice one. 2nd International Conference on Dry Ice Blasting 2 Berlin 2010
INTRODUCTION What are the emissions responsible for Global Warming? The CO 2 is the gas which contribuites mostly to the Greenhouse effect 24% CO2 Methane Nitrous oxide Others 10% 63% 3% Contribution to the increase of the Greenhouse effect from the most Important greenhouse gas. Before the beginning of the Industrial Revolution, for 800 years (and maybe more), the concentration of Carbon Dioxide in the atmosphere remained almost constant at 280 parts per million (ppm). Today is almost 380 ppm and growsalmost 1 ppm per year 2nd International Conference on Dry Ice Blasting 3 Berlin 2010
What the Greenhouse effect is? 2nd International Conference on Dry Ice Blasting 4 Berlin 2010
Carbon Dioxide The Carbon Dioxide is an acid oxide composed by one atom of Carbon linked to two atoms of oxigen . It is a Fundamental substance in the vital process of plants and animals. The carbon Dioxide is considered one of the greenhouse gas present In the earth ’s atmosphere. At ambient temperature and pressure the Carbon Dioxide is colourless and odourless . Its Chemical formula is CO 2 . At a solid phase is called “Dry Ice”. It sublimates at – 78°C. The molecule of the Carbon Dioxide is linear. The Carbon has a number of oxidation 4+ , so it is at its maximum phase of oxidation possible. Conseguently, the Carbon Dioxide is not flammable and from the chimical point of view is relatively inert. The Carbon Dioxide is colourless and odourless; it is not toxic but it is not breathable so it can cause the death of Asphyxiation. Breathing an atmosphere particularly full of CO 2 produces an acidulous flavour in your mouth and irritation in your nose and in your throat ; this is due to its reaction with water for the formation of Carbonic Acid. The density of Carbon Dioxide, at ambient temperature and pressure is about one time and half the density of the air; so it tends to stratify at the bottom of closed and airless environments. At the solid phase , at temperature up to – 78°C and at ambient pressure, the Carbon Dioxide doesn ’t melt but sublimates. The Carbon dioxide is known also as dry ice. The dry ice ( solid carbon dioxide) is used for the Dry Ice Blasting. The dry ice is made with the compression of the Carbon Dioxide till its liquefaction , so cooling it and leaving it to expand quicky. 2nd International Conference on Dry Ice Blasting 5 Berlin 2010
Carbon Dioxide The expansion causes a sinking of the temperature that makes the carbon dioxide freezing into crystals similar to the snow , which are then compressed. In an atmosphere of carbon Dioxide, the fire goes out. Between the food additive the Carbon Dioxide is identified by E 290. The limits imposed by the OSHA – Occupational Safety & Health Administration ( The US agency for job safety an Health) for the concentration of Carbon Dioxide at work are 0,5% (5000ppm) for a continous exposition and the 3% for a short exposition (15 minutes). In 2007, about 0,038% ( ≈ 381 ppm )in volume of carbon dioxide was measured in the eart ’s athmosphere. Despite of its small concentration, the CO 2 is a fundamental component in the earth ’s atmosphere because, together with the water vapour and the methane, it trappes the infrared radiation of the sunlight riflecting it again towards the earth ’s surface ( the so called Greenhouse effect ), preventing the Earth to cool down. It is estimated that the atmospherical concentration of Carbon dioxide before the Industrial Revolution was 280 ppm, then it increased by 35% since the Industrial Revolution and 20% from 1958. The theroy of the global warming appeared for the first time in the scientific litterature at the end of XIX Century. The increase of Carbon Dioxide in the atmosphere augments the Greenhouse effect and it contributes then at the raise of the average temperature of the planet, to which ecosystems have no time to adapt. 2nd International Conference on Dry Ice Blasting 6 Berlin2010
Carbon Dioxide : Temperature – Pressure Diagram 2nd International Conference on Dry Ice Blasting 7 Berlin 2010
Dry Ice 2nd International Conference on Dry Ice Blasting 8 Berlin 2010
CD – ICE Carbon Dioxide Ice 2nd International Conference on Dry Ice Blasting 9 Berlin 2010
Balance report pressure/temperature of the CO 2 Balance report pressure/temperature of the CO 2 Temperature Relative Pressure Density °C Bar Solid /gas -78,5 - -75 0,328 -70 0,964 -65 1,852 -60 3,078 Triple Point -56,57 4,172 1,177 -55 4,53 -50 5,816 -45 7,311 -40 9,037 -35 11,02 1,095 -30 13,27 1,074 -25 15,82 1,052 -20 18,69 1,03 Liquid/gas -15 21,9 1,006 -10 25,48 -5 29,45 0 33,84 5 38,67 10 43,99 15 49,83 20 56,25 25 63,3 30 71,06 Critical Point 31,06 72,81 0,464 2nd International Conference on Dry Ice Blasting 10 Berlin 2010
Balance report pressure/temperature of the CO 2 Triple Point Absolute Pressure Temperature °C Latent Heat bar Boiling vaporization - Kcal/kg Temperature Pressure Specific Volume 20 -20 68 °C bar -56,6 4,1 1,178 - Liquid + gas 15 -29 72 -56,6 4,1 1,513 - Solid + gas 8 -46 79 ATTITUDE OF THE SOLID CO 2 At T = - 78,5°C and P = 1 absolute bar for sublimation it absorbs 136,4 Kgcal / kg 1dm 3 develops 835Lt of gas 1dm 3 weights 1,562kg 2nd International Conference on Dry Ice Blasting 11 Berlin 2010
P 1/ 1/1 New production process for the realization of CD - ICE At present, the known process used for the production of dry ice pellets, contemplate the use of liquid carbon dioxide (CO 2 ) , what is expanded in order to produce snow carbon dioxide; the snow carbon dioxide is then pressed and is passed though a die for the production of cylinders (pellets) of dry ice. The Liquid CO 2 is available in the market in cylinder at the ambient temperature, that is at 20°C and 57 bar pressure (MPT – Middle Pressure Tank), or then it is stored in thermal insulated tank at – 20°C and at 20 bar pressure (LPT – Low Pressure Tank). The field of use of the CO 2 at the liquid phase goes from the critical point (31°C /74 bar) to the Triple point ( -56,6°C / 5,18 bar). According to the known process, the Liquid CO 2 tapped from tanks like MPT or LPT is expanded in a room where pressure can vary from 0 and 2,5 bar or below the triple point pressure by 5,18 bar in order to produce dry ice. The transformation percentage of the liquid CO 2 in snow carbon dioxide is variable and it depends to the initial temperature and pressure conditions; indicatively, the transformation percentage can vary from about 20% for high pressure and temperature ( cylinders MPT) to about 40% for Low pressure and temperatures (tanks LPT). The fraction not transformed in dry ice is composed by CO 2 Vapour which is generally recovered in order to be used once again in the process: this allows a certain saving of the raw materials but it implies inevitably further costs for the process and for the plant. 2nd International Conference on Dry Ice Blasting 12 Berlin 2010
Recommend
More recommend
