Feedstock Definitions Black Liquor is defined as a solution of 65% solids and 35% water, by mass. Of the total solid mass, 45% is defined to be lignin, the primary chemical feedstock of this process. Of the mass of lignin, 12.5% is defined to be methoxy groups, the reactive portion of the lignin polymer. The spent black liquor, after reacting, will be sent back to the Kraft mill this process will be co-located with, in order for the Kraft mill to burn it in their recovery boilers. All other portions not previously defined are assumed to be inert for the purposes of this process. For clarity’s sake, this includes: all non-methoxy portions of the lignin polymer, all non-lignin solid mass in black liquor, along with any and all water contained in the black liquor. Sulfur is defined as pure, elemental sulfur, in the liquid phase. Plant utilities will be used to maintain sulfur in this state prior to any reactive steps in the process. All sulfur supplied will be utilized in a reactive step, leaving no waste sulfur. Any impurities contained in the sulfur are assumed to be inert for the purposes of this process. Tall Oil is defined as a useful by-product of the Kraft process that is added to our molten sulfur (in a 1% by mass ratio) to inhibit polymerization. It is obtained from the paper mill this plant will be co-located with. It will be returned to the Kraft mill in the spent Black Liquor stream. The tall oil and any impurities present in the tall oil are assumed to be inert for the purposes of this process. Sodium Hydroxide is defined as a saturated (50%) solution of sodium hydroxide in water. It is used to control the pH of the Black Liquor, important for a reactive step in the process. The sodium hydroxide added will be returned to the Kraft mill in the spent Black Liquor stream. The mixed in sodium hydroxide, as well as any impurities present within it, are assumed to be inert for the purposes of this process. Ammonia is defined as pure ammonia, obtained from a working pipeline dedicated to its transport. It will be obtained from the pipeline as a pressurized liquid and then vaporized as needed. Any unreacted ammonia will be disposed of by dissolution in a water solution, with the water being obtained from a reaction of ammonia with oxygen. Any impurities present in the ammonia are assumed to be inert for the purposes of this process. Conversion Technology Description Lignin->DMS Reactor: This agitated reactor, constructed out of stainless steel, converts the methoxy groups in lignin into dimethyl sulfide, via the action of elemental sulfur. The elemental sulfur anion displaces methyl groups in series from a methoxy group of the polymer in an Sn2-like reaction. When two groups have been displaced, DMS is formed and bubbles out of the solution fed to the reactor, in a 50% yield with respect to the lignin supplied. This reaction occurs at a temperature exceeding the normal boiling point of water (343F), and in the aqueous solution. Therefore, some method must be employed to keep the water in black liquor from vaporizing. Our method used is to supply steam to the reactor at such a rate that the overall pressure in the reactor is maintained at 116psia. The supplied steam mixes with the DMS produced in the reaction and this vapor continues on for further processing. This reaction is exothermic, and this reactor has a cooling jacket with cooling water used to maintain its temperature. DMS->DMSO Reactor: This reactor, constructed out of stainless steel, converts vaporized dry DMS to DMSO via the action of NO2. The reaction occurs in the vapor phase, and at relatively mild conditions (atmospheric pressure and 132F). This reaction is exothermic, and this reactor has a cooling jacket with cooling water used to maintain its temperature. An optional condensation plate can be added to this reactor for two reasons. First, this condensation plate gives a place for the produced DMSO to condense onto, and secondly, the colder this condensation plate is maintained at, the less by-products the reactor will form. NH3 -> NO Reactor: This reactor, constructed out of Inconel 600, converts vaporized ammonia, mixed with air containing enough oxygen sufficient to convert all ammonia to nitrogen dioxide (as well as monoxide), is heated to 1472F via a fired heater, and passed over a catalyst of platinum with up to 10% rhodium. The catalyst, along with the extreme temperatures, converts ammonia and oxygen to nitrogen monoxide and water in a 9598% yield. This reaction is exothermic, and the reactor has a cooling jacket of hot oil used to maintain its temperature. The hot oil can be further cooled in a steam generator, generating useful steam for this process. NO -> NO2 Reactor: This reactor, constructed out of stainless steel, converts the nitrogen monoxide produced in the previous step to nitrogen dioxide, using the remaining oxygen in the fed air stream. This reactor also doubles as a regeneration point for recycled nitrogen monoxide after it has reacted with DMS. The reaction occurs in the vapor phase, at mild conditions (203F, atmospheric pressure), but care must be taken to keep the temperature of this reaction low, as the reaction will reverse itself at higher temperatures, leading to the breakdown of nitrogen dioxide. This reaction is exothermic, and the reactor has a cooling jacket of cooling water used to maintain its temperature. Separation Technology Description It is assumed the reader is familiar with the general working concept of flash drums and distillation columns. Flash drums are used throughout this process to separate more volatile components from less volatile components. An 8-tray distillation column is used at the end of the process as the final purification step in producing DMSO. The feed is fed at stage three, numbering stages from the top down. All flash drums as well as the distillation column are constructed out of stainless steel. This process uses two packed desiccation columns, to produce dry DMS from a “wet” DMS feed obtained by decantation. The columns should be packed with a desiccant – such as silica gel - sufficient to remove enough water to reach an industrial specification for dryness of DMS. Two columns are used, because as one column is actively desiccating a DMS stream, another column can be regenerating. In order to regenerate the column, an electric heater contained in the column can be turned on. This process also uses pressure swing adsorption (PSA) to separate various components of a vapor mixture from each other. Four PSA columns will be used, two pairs of two. The first pair of columns will be used to separate NO2 from the other components in the vapor stream, and the second pair of columns will be used to separate nitrogen and argon from the remaining components in the vapor stream. If this PSA separation was not present, nitrogen and argon would accumulate in the system, ultimately requiring periodic venting of hazardous gases, or overuse of relief valves. The columns themselves will be packed with a zeolite or membrane sufficient to perform the stated seperation. In each pair of columns, one column will be venting the effluent, while the other column will be venting the retained gas of interest. Valves and vacuum pumps will ensure the gases will move in the correct fashion. The nitrogen and argon will be vented to the atmosphere. Product Description Dimethyl Sulfoxide (DMSO) is the product of this overall process. It will be produced at a rate of approximately 2200 lb/hr for 8000 hr/yr. We believe we can sell this product at a price of $1.75/lb. The DMSO produced will meet at least technical grade requirements (99.7% purity), ranging upwards to reagent and medical grade. More information about the various grades of DMSO can be found in Appendix 13. Location Sensitivity Analysis Repeating the statements made about our process location and explaining the reasoning behind each one: Our process will be co-located with a Kraft paper mill, in the state of Louisiana. Co-location with Kraft paper mill: The vast majority of the operating costs of this process derive from the cost of black liquor, and the lignin contained therein. Due to the large mass of black liquor required (on the order of 50,000 lb/hour) for the desired throughput of DMSO, economic feasibility demands that the price of black liquor be no more than perhaps 10 cents per pound. Calculations derived from bond energies put the total energy loss of black liquor as the result of our process at approximately 15% of the energy content of the incoming black liquor. Based off the higher heating value of black liquor, and a standard cost of energy, this energy loss is given a value of approximately 2.2 cents per pound. Co-location with the paper mill allows us to completely eliminate transportation costs associated with black liquor. Furthermore, since black liquor is already burned for energy by the paper mill, we can return our spent liquor back to them for processing in their plant. They likely have the facilities to handle its combustion, recovery of salts used in the production of paper, and sequestration of components deemed unhealthy for the environment. The paper mill also receives a large tax credit for burning black liquor instead of disposing it in other fashions. If this process were to be truly stand-alone, we would have to pay transportation costs for black liquor, along with the full energy costs of black liquor plus the inert gases the Kraft mill covets, along with facilities for the proper disposal of waste components in black liquor. All of these costs added together would likely push the price of black liquor into the dollars per pound range, and render the process economically suicidal. Less important reasons for co-location include the free obtainment of Tall Oil for use as a polymerization inhibitor, along with large reserves of water available for our process. State of Louisiana: Several reasons point towards Louisiana being a prime location. First, certain states do not allow the manufacture of hazardous gases (in our case, DMS) by industry. Louisiana is not one of these states. Secondly, due to the large amount of preexisting petrochemical refineries in Louisiana, and the required desulfurization of diesel fuel, sulfur prices in Louisiana should be very low compared to the rest of the country. Lastly, in Louisiana there are ammonia pipelines we can tap into, giving an opportunity for elimination of transportation costs relating to that feedstock. Turndown Ratio A study of the minimum throughput this process can obtain is outside the scope of this design document. That said, this process is designed for nominal start-up operation (without recycle streams), which operate at approximately 25-35% greater flow rates than their corresponding values at steady-state. Compliance All efforts have been maintained to abide by the currently understood state of the science behind chemical engineering. An engineering safety hazards assay was not performed as part of the production of this process. If this process were to proceed further, this design would be improved or modified to ensure compliance with these accepted standards and laws.