Sulphuric Acid Manufacture - Coursework Example

Sulphuric acid manufacture PART Research report Sulphuric acid is regarded as an acid of the mineral type that is very corrosive. It made up of three major chemical atoms. It has hydrogen, oxygen and sulphur. Hence the chemical bond of one molecule of the acid has the chemical formulae of H2SO4. Expanding this chemical formula means that the molecule is made up of 1 sulphur atom, 2 hydrogen atoms and 4 oxygen atoms. The mineral acid, apart from being corrosive, it is colorless like water and it is oily in nature. It has the following definite properties-: I. It has a melting point of 10.3 degrees II. The boiling point is at 338 degrees III. The weight in the formula is 98.08 IV. It has a density of 1.94 V. Contains a flash point of none. The acid is formulated when there has been a dissolving of water and sulphur trioxide. It assumes the following chemical formulae SO3 + H2O = H2SO4 Sulphuric acid is regarded as a very vigorous corrosive; hence it qualifies as a strong acid. It chemical nature the determinant of strong or weakness of an acid is determined by ionization degree in an aqueous solution. In the case of H2SO4 the hydrogen ion when taken through the test it is ionized to 100%, in contrast other acids regarded as weak tend to be ionized to different percentages such as 5%, 30% and so on. Like all other acids, sulphuric acid has certain acids which are inherent in its chemical structure and this include-: I. It is an averagely strong oxidizing agent II. It is an even stronger dehydrating agent. This means that it is normally used to displace any molecule of water in organic compounds III. it is a mighty protonating agent IV. In terms of salts, the acid when in dilute solution forms two salt series making it a powerful dibasic. This means that the acid has an incorporation of two atoms of hydrogen which can be ionized; hence it qualifies as a mighty dibasic. In the laboratory or a safe place, an individual can easily make the acid in tiny droplets when they have understood the chemical formulas involved. A sulphur fragment produces a blue flame when burnt. If the burning fragment is introduced to a chamber with oxygen the following happens-: S + O2 = SO2 Then 2S + 3O2 = 2SO3 In the first formulae the fragment reacts with oxygen producing sulphur dioxide, then momentarily some sulphur trioxide is formed, this is different from the sulphur dioxide because it is cloudy. From here in order to get closer to sulphuric acid environment the byproducts during the burning are shaken in some water, resulting to-: SO2 + H2O = H2SO3 Then SO2 + H20 =H2SO4 When the dissolving in water occurs the resulting product is a sulphurous acid then momentarily there is some aspect of sulphuric acid. An individual can confirm the presence of the acid by an aid of a litmus paper. The paper evolves to red on sulphuric acid detection. The world uses sulphuric acid in large quantities. Countries have hence invested in the manufacture and sale of the acid in huge quantities. The world has moved from a system of acid production known as lead-chamber and into contact process. The new process is better and more efficient than the latter in numerous ways. Contact process involves the oxidation of sulphur dioxide in a catalytic manner. Contact process involves the making of the following elements-: a) Sulphur dioxide b) Conversion of sulphur dioxide into sulphur trioxide c) Then the conversion of sulphur trioxide into sulphuric acid. In the process, sulphur dioxide is made through the following processes, either, Sulphur is burnt in excess air S + O2 = SO2 Or the burning of ores of sulphide occurs. This one is also done in excess air For example with burning of pyrite we get 4FeS2 + 11O2 = 2Fe2O3 + 8SO2 In both processes the end result is achieved, and the end result is getting mixing of sulphur dioxide with air to be used in the next process. In the stage that follows the step is to turn sulphur dioxide into sulphur trioxide. The process is known as reversible meaning that, if the manufacturer so wanted they can turn the trioxide into a dioxide. 2SO2 + O2 < ------- > 2SO3 The so far is a pure reaction between the air and sulphur and some mix of catalyst to hasten the process. The above process is illustrated in a flow chart as follows-; The above ratios of mixture have a reason, and according to the law of Avogadro when two or more gases are subjected to similar pressure and heat and they are equal in proportions, they normally contain equal molecules too. Hence when measured against the above equation for making a trioxide it means that the process uses excess oxygen. But since according to the principle of chatelier equilibrium of the equation will move towards higher trioxide formation, the ratio is hence favored. This does not mean that there can be usage of huge amounts of oxygen though, since it will tire the catalyst. Hence the above ratio produced the best results and yield. In the second box, the operation temperature is put as 400 to 450 degrees. In order for chatelier principle to make sense, the equilibrium needs to go towards trioxide production. This only happens when there is lowering of temperature. When temperatures are low, the equilibrium moves to the right, but then again, this lowering of heat will reduce the production rate. Laws of business and economies of scale demand that, production goes up, or else the cost of production will be higher. Hence the ultimate purpose of a company is to produce in huge amounts at a shorter time. Therefore a temperature of 400 to 450 is higher but it is the best temperature for optimal production, therefore daily production of trioxide reaches a quantity that is good for business. In terms of pressure, yields are better with higher pressure, but this makes there to be more reaction which triggers the production of more molecules which lower it again. Therefore pressure is normally at atmospheric standard and the conversion rates are good. The catalyst in this process does nothing for equilibrium. It performs well for speed purposes, hastening the process of production. The main purpose of catalyst is to increase the production rates of trioxide, it should be noted that without the catalyst nothing can happen in real time. Hence in its incorporation the reactor builds up enough gases. After the formulation of sulphur trioxide, the next step is ending the process by making the acid itself. When the gas is added directly to water, the preceding reaction creates a foggy acid. Therefore the process needs a clever approach-; H2SO4 + SO3 =H2S2O7 Then H2S2O7 + H2O =2H2SO4 In the first equation the sulphur trioxide is mixed with a sulphuric acid which is concentrated to form something known as oleum. This is a product of sulphuric acid which is fuming. In the second formula the oleum is then mixed with water which leads to the formation of sulphuric acid. Contact process hence derives its name from the contact of oxygen, sulphur, water and expediency medium of a catalyst. Hence in a typical sulphuric acid manufacturing plant, there can be a number of by products other than the sulphuric acid. This includes-: Hence in a plant that is well capable, it produces four by products. It produces sulphuric acid, oleum, liquid sulphurous dioxide and liquid sulphurous trioxide. But in the process sulphur acid production there are some emissions that do not favor the environment at all. During the production, there is a release of sulphur dioxide into the atmosphere. Sulphur manifests itself better during winter when it triggers the formation of fogs. On an individual level, sulphur dioxide makes the lining inside a nose or a throat to experience some form of irritation. Asthmatic people especially are very sensitive to the gas. Fortunately, the industry producing sulphuric acid is not the main polluter of the environment (Louie, 2005, pg. 67). Elements of this polluter can be found in the transport industry in big quantities in fact it accounts for the biggest percentage of this emission. Also the manufacturing industry releases carbon to the environment and some elements of sulphuric trioxide. The above diagram shows the routes in a map through which sulphuric acid is produced when we narrow to production in the factory. To start with the plant is fed with water and the other raw materials necessary for the production of the acid. The route shows that, there is a production of steam which I had not mentioned earlier in the production process. This one can be condensed down and the water is recyclable. The world countries use sulphuric acid a lot. In recent history there has been a huge sulphuric acid production in majority of countries. Consequently, it lowered the prices of sulphuric acid in the world market. The future of sulphuric acid is bright though, catalyzed by the development of countries that had earlier stagnated in development. The major and the most common uses of sulphuric acid include-; a) Oil refining- during the refining of oil. The process normally requires the use of a catalyst hence sulphuric acid comes through as a good agent for this purpose. The acid gets applied in a unit known as unit of sulphuric acid alkylation. b) Metal refining- in the removal of impurities the sulphuric acid is used. The process is identified as pickling. The acids use these days is minimal because it causes the loss of base metal during the process. But it was widely used a while back. c) Manufacturing of chemicals- the acid is a chemical compound of great importance when it involves the making of other acids. It assists in the making of-: nitric acid, hydrochloric acid, phosphoric acid etc. d) Making of lead acid type batteries- the acid is used as diluted in order to act as a medium of flow of electrons. In another name, the acid in the battery is known battery acid, with a strength capacity of 28 to 32%. e) Making of medicines- some special types of medicines are made using Sulphuric acid, such as the medicines used in chemotherapy. Other products made using some aspects of sulphuric acid include paints, plastics and perfumes etc. f) Potato harvesting- farmer’s spray their potato crops with the acid so that they can make the crops to dry fast making the harvesting machines to harvest crops. g) The making of rayon- this is a material made of cellulose fibers originating from wood. Then the fibers are dissolved in amine copper 11. The product is then dissolved in the acid to form rayon. The chart below shows the percentages of main uses of the acid, in most countries. Fertilizer creates the biggest market for sulphuric acid. Hence most countries import or make it. This report focus will go into designing of a manufacturing plant with the purpose of handling a production of 660 tonnes of sulphuric acid every single day. In a production of such magnitude, it is hence necessary to keep up with the safeguarding of the environment through adopting technologies that will favor the environment. To reduce the release of gases into the air, the best recommended plant design is to use two absorption columns. Such a process would look as illustrated below-: This design is able to achieve a percentage of 99.5% of sulphuric acid conversion rate. This is so because at the first converter there are some elements of sulphur dioxide which remain unconverted, this are then driven to the second converter and then a conversion occurs in this section. Due to full push of equilibrium towards sulphur production, the yields are normally very high. The result is that at the tail end of the process, a very small percentage of a byproduct gas is released into the environment. Most of the sulphur dioxide is normally converted for production in the above process hence lower release. This makes sure that the plant it cautious of the UK set limits for pollution. The UK has engaged on a journey to reduce emissions to the environment, as mentioned earlier, gases like sulphur dioxide are affecting asthmatic people, and also its effect is noticeable especially during winter, when there is the presence of heavy fog in the country. Hence the country has set certain projections that should be met by all the players who are responsible for any kind of release into the environment. Pollutant 2010 2015 2 020 2.5 percentile 97.5 percentile 2.5 percentile 97.5 percentile 2.5 percentile 97.5 percentile NH3 244 342 241 342 240 340 NOx 1054 1384 903 1128 688 872 SO2 383 433 330 377 309 357 NMVOC 750 911 686 842 666 823 The table above shows the projections and the goals of the UK environment agency to reduce the percentage of gas release. In specific, sulphuric dioxide gas is projected to reduce from a high of 383 kilo tonnes to 309 kilo tonnes by 2020. Double absorption technology hence plays a big role in stepping up on scaling down on sulphur dioxide environment release. PART 2: Project Design. In the manufacture of sulphuric acid, there are or there is depending on the number, columns known as absorption columns. They are normally found at the end of the sulphuric acid manufacturing process, to assist with the final conversion of the acid, the diagram below illustrates the location-: The towers are found at the end of the manufacture cycle. In this research paper, I am interested in reviewing the absorption column in detail, in order to understand how it works and the chemical engineering design that has gone into its formulation. The columns are responsible for the withdrawal of sulphur trioxide gas, by mixing this with water to finally produce the acid. Like explained earlier, the double absorption towers increase efficiency while lowering the rate of gas released into the environment as a pollutant. The heat range in these columns is between 70 degrees and 90 degrees for optimal performance. Below the columns there are acid coolers present to drop the heat in the acid ready for storage or packaging. The diagram above shows, a computer application that shows the job of an absorber correctly. It can be seen well that, it is from this chamber that we are able to get sulphuric acid. It can produce oleum and also it can produce sulphuric dioxide. The chamber has a very high volume of water for the dilution. Below is a real example of an absorption column in a plant. The tower has a stack which releases gases which are low in pollutants. Figure 1.1 Figure 1.1 above shows the tiny components of an absorption tower in sulphuric acid manufacture. The unit has the following components-: a) Shell- it is the outer structure of the device b) Lower absorption zone- it is a zone packed with sulphur trioxide, it is on the lower part of the device. c) Upper absorption zone- also a zone packed with sulphur trioxide that is found on a location on top of the lower zone. d) Medium for injecting a stream of sulphuric acid into the lower absorption zone. e) Medium for injecting a stream of hot sulphur trioxide. The gas also goes into the lower combustion f) A way to take the refined sulphuric acid from the lower zone to the upper zone of the device. g) A way to take the sulphuric acid on the lower part to the upper part of the device and also a way to take the acid from the upper part to the lower part. h) A medium to collect the concentrated and ready sulphuric acid on the lower part of the device. i) A technology a fixed to the apparatus that assist in cooling down of the hot and processed sulphuric acid j) A way to collect the already cooled sulphuric acid, in order to get it ready for pumping or packaging (Sinnot, 2005, pg.98). Second absorption column in a sulphuric acid manufacturing mechanism, performs the important duty of absorbing the gaseous form of sulphur trioxide which is then used to formulate the production of the liquid sulphuric acid. The absorption needs to take place so that the plant can achieve environment regulations. If the gas is not well absorbed this situation can lead to the release of harmful SO3 in to the environment. When the gas is released into the environment it takes the characteristic of reacting with air leading to the creation of particles known as sub-micron mist which is a health hazard. The design of a sulphuric acid chemical plant should be a replica of what should be constructed on the ground. The size of the absorption column is hence very much visible because it is one of the tallest columns in a sulphuric acid manufacturing plant. The figure below is a sketch and a photograph of the real factory. The above diagram shows the two absorption columns on a chart. The absorption columns are visible in the next real picture. The column in white is the converter, while the two grey towers are the absorption chambers. Absorption columns do not work alone, it is a process of engineered structural system that relies on small machines and pumps for its smooth operation. In a system of absorption, the structure harbors the following sub units-: a) The tower of absorption- this is the column that I described above. For its manufacture, engineers use copper steel as its lining or the engineers can use brick. The column has a distributor of acid, mist eliminator, and support for packing. b) Tank for acid pump- the tank harbors acid that is then systematically circulated to the absorption column. The acid held in this chamber is enough to keep the whole system in operation mode and also acts as a medium of storage when the machines and the system are not in working order. c) Acid pumps- the pump acts as a medium through which acid is moved from the holding tank to the medium of distribution inside the main absorption chamber. The pumps can be affixed on any viable option; it can be horizontally or vertically depending on the structure of the chamber. d) Acid cooler- since the process of mixing of water and SO3 is a heat affair, meaning it is exothermic, this makes the sulphuric acid produced to be hot and high in temperatures, therefore the system needs a device to do away with the heat. Therefore a cooler comes in handy to reduce the heat through heat exchanger plates. e) Piping- a plant cannot be operational without the presence of piping. This is the only highway through which the acid transports itself from one location to the next, through gravitational science or through the aid of a machine. Piping tubes are built on a variety of material depending on acidity, heat and concentration as the factors. f) Controls and relevant instrumentation- these are the control options available to technicians to be able to monitor the flow of every single aspect within the manufacturing plant. Some of the monitored and control factors include. Heat, rate in the flow, concentration of acidity and sound levels (Sinnot, 2005, pg. 185). When the above basics are in place, the absorption column plus the support systems are able to operate seamlessly without complications. The process of absorption has steps and a basic standard process in its operation. For the absorption system to be able to operate correctly, it must be able to fully sort out SO3 to the lowest levels possible. The process depends on equilibrium to function and it is affected by a number of factors so that the gas can be absorbed fully. The following factors affect the rate of absorption in the system-: a) The pressure- this is the pressure of the trioxide vapor. The tower operates in a small range of mix between heat and concentration. When there is a good equilibrium between the two, the pressure will go into a minimum, which will lead into maximum absorption of the gas. When pressure is down, that is when absorption is at its best. b) Density and viscosity. When temperature is low, other factors come through to affect the absorption process. Hence in order to avoid negative effects from these factors, most companies use a heat degree of 65 to 85 degrees at acid inlet. The factors though vary according to how the tower has been built and designed, some of the characteristics that affect the factors include, packing, design of distribution channel, efficiency in mist elimination. A technician can be able to understand the factors by observing the stack eliminates. Hence the right balance and combination needs to be observed so that there can be a process in the absorption sector. For a sulphuric acid plant to operate well without incurring corrosion costs engineers had to find a way of reducing the rate of corrosiveness. The acid is highly corrosive, then in any form whether gas in form of SO3 or the acid itself, it will have the effect of corroding the chambers and units. Hence the construction of the absorption chamber is lined with copper material and the piping system also harbors the same qualities. The plant that is to be built in this chemical design paper, will aim to eliminate as much pollution as possible hence, the preferred absorption format like earlier mentioned will be double absorption. And the process involved in this manufacture will be contact process. In double absorption process, the piping is wide and the structure is a bit large. In the process, the absorption unit is characterized by three towers. There is the tower of drying, tower of intermediate absorbing and tower of final absorption. All the three have of none corrosive material such as membranes of brick, and carbon steel material. In the construction of this towers all the laws of chemical engineering must be observed. The laws of chemical engineering should not only be used to construct the absorption tower but they should be used to make the whole sulphuric acid manufacturing plant. By using the laws and designs of chemical engineering, a plant benefits in the functioning of the plant. The following benefits occur due to the use of chemical engineering and designs, also known as the chemetics design-: a) The acid is always well irrigated throughout the top of the tower; this is through special piping and proprietary piping and distributors. b) The corrosion in the piping is reduced through materials of chemetics that reduce the level of corrosion. This is through the use of superior material of acceptable standards. c) The incorporation of a supporting brick dome in support of the tower ensures that the weight of packing is transferred to the shell and not to the base. d) Dished bottoms are found in the towers, this once prevent the bricks from heaving if , there is a formation of sulphate substance between the main shell and the brick layer. e) Elevation of the towers, is not coincidental, it helps to assist in maintenance. Such that personnel can access the towers. f) Mechanical designs of the piping, makes sure that inlet and outlet pressures of the pipes are controlled to avoid stress. g) High quality supervision added with linings of acid resistant material makes sure that there is scarce maintenance of the tower (Louie, 2005, pg 165). Fig 2.1 With all those fundamentals taken in place, the construction of this sulphuric acid plant will be smooth. The environment will be taken care of and the plant will have the right efficiency and effectiveness to ensure that 600 tonnes of sulphuric acid will be produced without inducing stress to the system and the plant. When the absorption column is complete it should have an outer look of excellent linings on the outside and inside. The figure above shows the final look of the plant once the construction is finalized and ready to operate. References LOUIE, D. K. (2005). Handbook of sulphuric acid manufacturing. Thornhill, Ont, DKL Engineering. SINNOTT, R. K., COULSON, J. M., & RICHARDSON, J. F. (2005). Coulson &Richardsons chemical engineering. Vol. 6, Vol. 6. Amsterdam, Elsevier Butterworth-Heinemann. MCGLAUGHLIN, M. D. (1991). Sulfuric acid process plant systems design. Regina, University of Regina. Read More