Nitric Acid Revamp and Upgrading of the Alarm & Protection Safety System at Petrokemija, Croatia

Every industrial production, particularly chemical processing, demands special attention in conducting the technological process with regard to the security requirements. For this reason, production processes should be continuously monitored by means of control and alarm safety instrumented systems. In the production of nitric acid at Petrokemija d. d., the original alarm safety system was designed as a combination of an electrical relay safety system and transistorized alarm module system. In order to increase safety requirements and modernize the technological process of nitric acid production, revamping and upgrading of the existing alarm safety system was initiated with a new microprocessor system. The newly derived alarm safety system, Simatic PCS 7, links the function of "classically" distributed control (DCS) and logical systems in a common hardware and software platform with integrated engineering tools and operator interface to meet the minimum safety standards with safety integrity level 2 (SIL2) up to level 3 (SIL3), according to IEC 61508 and IEC 61511. This professional paper demonstrates the methodology of upgrading the logic of the alarm safety system in the production of nitric acid in the form of a logical diagram, which was the basis for a further step in its design and construction. Based on the mentioned logical diagram and defined security requirements, the project was implemented in three phases: analysis and testing, installation of the safety equipment and system, and commissioning. Developed also was a verification system of all safety conditions, which could be applied to other facilities for production of nitric acid. With the revamped and upgraded interlock alarm safety system, a new and improved safety boundary in the production of nitric acid was set, which created the foundation for further improvement of the production process in terms of improved analysis

Poboljšanje i nadogradnja uzbunjujuće-sigurnosno-blokirajućeg sustava u proizvodnji dušične kiseline Petrokemije d. d.

Every industrial production, particularly chemical processing, demands special attention in conducting the technological process with regard to the security requirements. For this reason, production processes should be continuously monitored by means of control and alarm safety instrumented systems. In the production of nitric acid at Petrokemija d. d., the original alarm safety system was designed as a combination of an electrical relay safety system and transistorized alarm module system. In order to increase safety requirements and modernize the technological process of nitric acid production, revamping and upgrading of the existing alarm safety system was initiated with a new microprocessor system. The newly derived alarm safety system, Simatic PCS 7, links the function of “classically” distributed control (DCS) and logical systems in a common hardware and software platform with integrated engineering tools and operator interface to meet the minimum safety standards with safety integrity level 2 (SIL2) up to level 3 (SIL3), according to IEC 61508 and IEC 61511. This professional paper demonstrates the methodology of upgrading the logic of the alarm safety system in the production of nitric acid in the form of a logical diagram, which was the basis for a further step in its design and construction. Based on the mentioned logical diagram and defined security requirements, the project was implemented in three phases: analysis and testing, installation of the safety equipment and system, and commissioning. Developed also was a verification system of all safety conditions, which could be applied to other facilities for production of nitric acid. With the revamped and upgraded interlock alarm safety system, a new and improved safety boundary in the production of nitric acid was set, which created the foundation for further improvement of the production process in terms of improved analysis.Svakom industrijskom procesu, osobito kemijskom, potrebno je posvetiti posebnu pažnju s obzirom na sigurnosne zahtjeve. Zbog toga se proizvodni procesi trebaju kontinuirano pratiti kontrolnim i uzbunjujuće-sigurnosno-blokirajućim sustavima. U proizvodnji dušične kiseline Petrokemije d. d. izvorni uzbunjujuće-sigurnosno-blokirajući sustav bio je izveden u obliku električno-relejnog sigurnosno-blokirajućeg sustava i tranzistorskog uzbunjujućeg sustava. Radi povećanja sigurnosnih zahtjeva i poboljšanja postojećeg uzbunjujuće-sigurnosno-blokirajućeg sustava provedena je nadogradnja postojećeg s novim mikroprocesorskim sustavom. Novi uzbunjujuće-sigurnosno- blokirajući sustav, Simatic PCS 7, povezuje funkcije klasičnih logičkih kontrolnih sustava s uzbunjujuće-sigurnosno-blokirajućim funkcijama u zajedničku bazu kako bi se zadovoljili minimalne sigurnosne norme do razina sigurnosnih integriteta 2 i 3 s obzirom na standarde IEC 61508 i IEC 61511. Prikazan je pristup nadogradnje logike uzbunjujuće-sigurnosno-blokirajućeg sustava u proizvodnji dušične kiseline u obliku logičkog dijagrama koji je bio osnova za daljnje izvođenje radova. Na temelju izrađenog logičkog dijagrama i definiranih sigurnosnih zahtjeva, projekt je proveden u tri faze koje su bile faza analize i testiranja, ugradnje nove opreme te puštanje u pogon cijelog izvedenog sustava. Razvijen je sustav provjere svih sigurnosno-blokirajućih uvjeta, koji se može primijeniti i na druga postrojenja za proizvodnju dušične kiseline. S obnovljenim i nadograđenim uzbunjujuće-sigurnosno-blokirajućim sustavom postavljene su nove poboljšane sigurnosne granice te je osigurana osnova za daljnje unaprjeđenje proizvodnog procesa

Optimization of the Clarification System for Raw Water from the Pakra Reservoir Lake

Prvi korak u obradi sirove vode akumulacijskog jezera Pakra za potrebe proizvodnje gnojiva u Petrokemiji d. d. započinje oksidacijom organskih tvari u sirovoj vodi plinovitim klorom, Cl2. Nakon toga slijede tehnološki postupci bistrenja i filtriranja pomoau flokulatora, odnosno pješčanih filtara. Izvedba flokulatora i pješčanih filtara omogućava samo uklanjanje suspendiranih tvari iz sirove vode, bez utjecaja na njezinu ukupnu tvrdoću. Kontrola rada flokulatora te uklanjanje suspendiranih tvari iz sirove vode postiže se dodavanjem vodenih otopina aluminijeva sulfata, Al2(SO2)3⋅ 18 H2O i organskog polielektrolita odgovarajućih koncentracija. Učinkovitost tehnološkog procesa flokulacije kontrolira se laboratorijskim određivanjem razlike m-alkaliteta na ulazu odnosno izlazu sirove vode iz flokulatora. Optimalna iskustvena vrijednost razlike m-alkaliteta za najučinkovitije bistrenje iznosi 0,65 mmol L-1 za pH sirove vode između 7,0 i 8,0. Prije obrade izbistrene vode sustavom ionske dekarbonatizacije i demineralizacije, radi zaštite ionskih masa od suviška slobodnog Cl2, dodatno se provodi dodavanje vodene otopine natrijeva bisulfita, NaHSO3 odgovarajuće koncentracije. Kako bi se postiglo optimalno doziranje plinovitog Cl2u sirovu vodu, poboljšao tehnološki proces bistrenja u flokulatoru te optimalno doziranje vodene otopine NaHSO3, predložen je poboljšan sustav kontinuirana mjerenja koncentracija slobodnog Cl2 u sirovoj i izbistrenoj vodi te razlike pH na ulazu odnosno izlazu iz flokulatora. Laboratorijskim ispitivanjem pokazano je da prosječna razlika pH od 0,65 do 0,75 na ulazu odnosno izlazu iz flokulatora uz pH sirove vode od 7,0 do 8,0 jednako učinkovito zamjenjuje laboratorijsko određivanje m-alkaliteta. Isto tako pokazana je povratno-uzroena veza između mase doziranog plinovitog Cl2 u sirovu vodu, razlike u pH na ulazu i izlazu iz flokulatora te mase doziranog NaHSO3. Predloženim kontinuiranim mjerenjem koncentracije slobodnog Cl2 i pH u sirovoj i izbistrenoj vodi postiže se poboljšan i siguran sustav bistrenja sirove vode uz istodobnu godišnju uštedu na plinovitom Cl2 od 15 % te na NaHSO3od 50 %.The first step in processing raw water from the Pakra lake for use in fertilizer production at Petrokemija is oxidation of total organic carbon matter with gaseous chlorine, Cl2. Thereupon it is clarified and filtered with the help of a clarification reactor and sand filters. Construction of the clarification reactor and process sand filters enables only the removal of the suspended matter from the raw water, without affecting its overall hardness. Process control of the clarification reactor and removal of the suspended matter from the raw water is achieved by adding corresponding mass concentration water solutions of aluminum sulphate, Al2(SO4)3 · 18 H2O and organic polyelectrolyte. The effectiveness of flocculation is carried out by laboratory determination of the m-alkalinity difference between inlet and outlet of raw water from the clarification reactor. For the most effective clarification of raw water, the optimal empirical value of the m-alkalinity difference is 0.65 mmol L-1 in the pH range of raw water from 7.0 to 8.0. Prior to processing clarified water by ionic decarbonatisation and demineralisation for protection of the ionic exchange resin from excess free Cl2, a corresponding mass concentration of a sodium bisulfite water solution, NaHSO3, is added. An improved system is proposed for continuous measurement of mass concentrations of free Cl2 in raw and clarified water, and pH difference value at the inlet and outlet of the clarification reactor. The proposed system can achieve optimal dosage of gaseous Cl2 in the raw water, improving the clarification process in the reactor as well as optimal dosage of water solution of NaHSO3. It is shown that the average pH difference from 0.65 to 0.75 at the inlet and outlet of the clarification reactor in the pH range of the raw water from 7.0 to 8.0 is an equally effective replacement for the laboratory determination of m-alkalinity. Also shown is the connection between dosage mass of the gaseous Cl2 in the raw water, pH difference value at the inlet and outlet of the clarification reactor and dosage mass of the NaHSO3. The proposed system for the continuous measurement of mass concentration of free Cl2 and pH values in the raw and clarified water achieved a better and safer system of processing raw water with annual savings of gaseous Cl2 of 15 % and NaHSO3 of 50 %

Selective Oxidation of Soft Grade Carbon Blacks with Ammonium Nitrate

Obrada površine "mekih" tipova čađa kao što su N660 i N772 koji se proizvode uljno-pećnim postupkom zahtijeva poseban naknadni tretman, budući da se adekvatna kvaliteta iste ne može postići konvencionalnim putem. Radi toga je razvijena metoda eliminiranja zaostalog neizreagiranog ulja s površine "mekih" tipova čađa uz pomoć njezine selektivne oksidacije. "Meki" tipovi čađa sa niskim vrijednostima obojenja otapala miješani su s vodenim otopinama masene koncentracije 1,25 do 10,00 g L-1 amonijevog nitrata p. a., u odnosu na masu čađe. Nakon homogeniziranja smjesa je sušena na temperaturi od 180 do 210 °C u vremenskom razmaku od 30 do 120 min kako bi došlo do selektivne oksidacije neizreagiranog ulja na površini čađe. Navedenim laboratorijskim postupkom improvizirani su industrijski uvjeti granuliranja "mekih" tipova čađe, koji je uspješno proveden, te se primjenjuje u konvencionalnom industrijskom postupku proizvodnje "mekih" tipova uljno-pećnih čađa na postrojenju proizvodnje čađe u Kutini.Oil-furnace carbon black is produced by pyrolysis of gaseous or liquid hydrocarbons or their mixtures. The oil feedstock for the production of oil-furnace carbon black is mainly composed of high-boiling aromatic hydrocarbons, which are residues of petroleum cracking, while the gaseous raw material is commonly natural gas. Most of the oil-furnace carbon black production (> 99 %) is used as a reinforcing agent in rubber compounds. Occasionally, oil-furnace carbon blacks are used in contact with other rubber compounds and fillers that have different pigments, particularly with the color white. It has been observed that frequently a migrating rubber soluble colorant would enter the white or light colored rubber composition from the adjacent carbon black filled rubber, resulting in a highly undesirable staining effect. Methods for determining non-oxidized residue on the surface of the oil-furnace carbon black include extraction of carbon black with the appropriate organic solvent, and measuring the color of the organic solvent by means of a colorimeter on 425 nm (ASTM D 1618-99). Transmittance values of 85 % or more are indicative of a practically non-staining carbon black, while transmittance values below 50 % generally lead to a carbon black with pronounced staining characteristics. Many oil-furnace carbon blacks, particularly those with a larger particle size (dp > 50 nm) which are produced by pyrolysis, have strongly adsorbed non-reacted oil on their surfaces. Upon incorporation in a rubber compound, the colored materials are gradually dissolved by the rubber matrix and migrate freely into adjacent light colored rubber compounds, causing a highly objectionable staining effect. Adjusting furnace parameters in the industrial process of producing specific soft grades of carbon black cannot obtain minimal values of toluene discoloration. The minimal value of toluene discoloration is very important in special applications. Therefore, after-treatment of the surface area is essential. Mutual oxidizing agents are ozone, air, mixture of nitric oxide and air, and nitric acid. However, treatment with highly oxidizing agents in a gaseous phase or aqueous medium may highly increase the concentration of acid oxides on the surface area of the carbon black. Acid oxides on the surface area of carbon black decrease the pH value, which is closely connected to the vulcanization of rubber compounds. Furthermore, the afore-mentioned method has other disadvantages. In the case of nitrate acid, the major disadvantage is corrosion of plant equipment. The mixture of nitrite oxide and air demands a very complicated plant, and the same procedure is very time consuming. Ozone increases the oxygen content on the surface area of the carbon black by as much as 15 %, which creates carbon dioxide and reduces utilization. Air creates thermally unstable surface area oxides, since the process demands a temperature range between 450 and 700 °C. Due to all these reasons, an oxidation method was developed of eliminating non-reacted oil from the surface area of oil-furnace carbon black, which cannot be produced with the conventional production method. An aqueous solution of salt ammonium nitrate p.a. proved to be a very good oxidizing agent. Conventional soft grades of oil-furnace carbon blacks with very high contents of non-reacted oil on their surface area, were mixed with the appropriate mass weight of ammonium nitrate p. a. (1.25 to 10.00 g L-1 NH4NO3 p. a.). The obtained homogeneous mixture was dried at temperatures from 180 to 210 °C for a period of 30 to 120 min. Namely, oil-furnace carbon blacks are first produced in a "fluffy" form with exceptionally small mass density, which is why they are very unpractical for manipulation. The "fluffy" oil-furnace carbon black must be transformed to a greater weight density and have a smaller quantity of fines as possible. However, there are many industrial processes of transforming "fluffy" carbon black into granules, and the most famous are the wet, semi-wet, and the dry process. In the oil-furnace process, the wet process of granulation is the most acceptable, in which the "fluffy" carbon black is mixed with water in an approximate ratio. After granulation, the carbon black is dried in a rotary drum at temperatures ranging between 180 to 210 °C. The period of drying is various, and depends on the production capacity and moisture fraction. The described laboratory procedure improvised successfully industrial conditions of granulating soft grade carbon black, and it is applicable to the conventional industrial method of producing soft grade oil-furnace carbon black at the Kutina plant, which is shown in Tables 1-7, and Figures 1-2

Automatic Method for Controlling the Iodine Adsorption Number in Carbon Black Oil Furnaces

Uvjeti rada industrijske peći za proizvodnju uljno-pećne čađe pod utjecajem su raznih ulaznih procesnih varijabli, koje je potrebno kontinuirano i automatski podešavati radi osiguravanja stabilnosti kvalitete krajnjeg proizvoda. Maseni protok ugljikovodične sirovine jedan je od bitnijih ulaznih procesnih veličina kojima se prilagođava adsorpcijska aktivnost uljno-pećne čađe. Adsorpcijska moć uljno-pećnih čađa u industrijskom postupku proizvodnje određuje se laboratorijskom analizom jodnog adsorpcijskog broja. Da bi se postigla što učinkovitija kontrola nad adsorpcijskom kvalitetom čađe, prikazana je kontinuirano-automatska metoda kontrole jodnog adsorpcijskog broja u industrijskim pećima za proizvodnju uljno-pećne čađe. Metoda se temelji na ovisnosti kvalitativno-kvantitativnog sastava otpadnih procesnih plinova nastalih u procesu proizvodnje uljno-pećne čađe o odnosu obujma zraka za gorenje i mase ugljikovodične sirovine (Vzrak : mCH). Pokazano je da je relacija između količine sagorijevanja zraka za gorenje i ugljikovodične sirovine presudna za adsorpcijsku aktivnost izraženu pomoću jodnog adsorbcijskog broja, s obzirom na BMCI-indeks ugljikovodične sirovine, pri čemu BMCI-indeks opisuje aromatski karakter ugljikovodične sirovine. Od ukupnog sastava otpadnih procesnih plinova najbolju ovisnost za kontinuiranu i automatsku kontrolu jodnog adsorpcijskog broja pokazuje obujmni udjel metana. Obujmni udjel metana ((φCH4 ) u otpadnim procesnim plinovima linearno se povećava sa smanjenjem vrijednosti jodnog adsorpcijskog broja uljno-pećnih čađa. Linearna ovisnost može se primijeniti u kontinuirano-automatskoj metodi kontrole proizvodnje uljno-pećne čađe s vrijednostima jodnog adsorpcijskog broja u području od 30 do 140 mg kg-1. Obujmni udjel metana u otpadnim procesnim plinovima kontinuirano i automatski se mjeri odgovarajućim analizatorom. Izmjereni obujmni udjel metana povezan je izravno-povratnom spregom s regulacijskim ventilom i masenim mjerilom ugljikovodične sirovine, čime se ostvaruje postizanje željene vrijednosti obujmnog udjela metana, odnosno jodnog adsorpcijskog broja.There are numerous of different inlet process factors in carbon black oil furnaces which must be continuously and automatically adjusted, due to stable quality of final product. The most important six inlet process factors in carbon black oil-furnaces are: 1. volume flow of process air for combustion 2. temperature of process air for combustion 3. volume flow of natural gas for insurance the necessary heat for thermal reaction of conversion the hydrocarbon oil feedstock in oil-furnace carbon black 4. mass flow rate of hydrocarbon oil feedstock 5. type and quantity of additive for adjustment the structure of oil-furnace carbon black 6. quantity and position of the quench water for cooling the reaction of oil-furnace carbon black. The control of oil-furnace carbon black adsorption capacity is made with mass flow rate of hydrocarbon feedstock, which is the most important inlet process factor. Oil-furnace carbon black adsorption capacity in industrial process is determined with laboratory analyze of iodine adsorption number. It is shown continuously and automatically method for controlling iodine adsorption number in carbon black oil-furnaces to get as much as possible efficient control of adsorption capacity. In the proposed method it can be seen the correlation between qualitatively-quantitatively composition of the process tail gasses in the production of oil-furnace carbon black and relationship between air for combustion and hydrocarbon feedstock. It is shown that the ratio between air for combustion and hydrocarbon oil feedstock is depended of adsorption capacity summarized by iodine adsorption number, regarding to BMCI index of hydrocarbon oil feedstock. The mentioned correlation can be seen through the figures from 1. to 4. From the whole composition of the process tail gasses the best correlation for continuously and automatically control of iodine adsorption number is show the volume fraction of methane. The volume fraction of methane in the process tail gasses is increased with the decreasing values of iodine adsorption number of the oil-furnace carbon black which can be seen through the Figs. 5. and 6. These linear correlation can be applied in continuously and automatically method of control during the production of carbon black oil-furnace process with the range of the iodine adsorption number between q = 30 and 140 mg kg-1. The volume fraction of methane in the process tail gasses are measuring continuously and automatically with adequate analyzer. The measured values of volume fractions of methane are connected through direct-reverse connection with regulation valve and mass micro motion of hydrocarbon feedstock thereby this conjunction is served for adjusting the set point of volume fraction of methane and iodine adsorption number. The proposed control loop is shown on the Fig. 7

Improvement of the Rotary Dryers of Wet Pelletized Oil-Furnace Carbon Blacks

Radi potreba povećanja proizvodnog kapaciteta te uštede prirodnog plina u operaciji sušenja mokro granuliranih uljno-pećnih čađa provedeno je poboljšanje rada rotirajućih sušionika. Instalirani rotirajući sušionici u svojoj originalnoj izvedbi bili su predviđeni za sušenje polumokro granuliranih uljno-pećnih čađa. Zbog tog razloga nisu u potpunosti bili zadovoljeni optimalni uvjeti sušenja mokro granuliranih uljno-pećnih čađa. Energija potrebna za sušenje mokro granuliranih uljno-pećnih čađa osigurana je sagorijevanjem prirodnog plina na sustavu otvorenog ložišta uz nekontrolirani pristup zraka za sagorijevanje. Poboljšanje rada rotirajućih sušionika sastojalo se u podešavanju suviška kisika u sagorjevnim izlaznim otpadnim plinovima putem "leptir" zaklopke na dimnjaku sušionika. Reguliranjem takve zaklopke na dimnjaku sušionika te primjenom predviđene tehnologije sušenja mokro granulirane uljno-pećne čađe, suvišak kisika u sagorjevnim izlaznim otpadnim plinovima tijekom operacije sušenja podešavan je u području od φ = 3,0 % do 5,0 % ovisno o tipu uljno-pećne čađe. Isto tako predložena je ugradnja automatske "leptir" zaklopke koja bi radila u povratno-uzročnoj sprezi s automatskim određivanjem obujamskog udjela kisika u sagorjevnim izlaznim otpadnim plinovima, odnosno regulacijom obujamskog protoka prirodnog plina za sagorijevanje. Osim toga, predložen je postupak predgrijavanja procesne vode na temperaturu od 70 °C do 80 °C upotrebom otpadne topline iz procesa proizvodnje uljno-pećne čađe u postupku mokre granulacije. Navedenim postupcima optimalizacije dobivena je ušteda na prosječnom energetskom normativu prirodnog plina u operaciji sušenja od 25 % do 35 % ovisno o tipu uljno-pećne čađe te posljedično tome smanjenje emisije ugljikova(IV) oksida do 40 %.Due to the demand for higher production capacity and natural-gas energy savings, improvements were made to the rotary dryers in the drying process of wet pelletized oil-furnace carbon blacks. Since the rotary dryers were originally designed for drying semi-wet pelletized oil-furnace carbon blacks, they did not entirely satisfy optimal conditions for drying wet pelletized oil-furnace carbon blacks. Figure 1 shows the drying principle with key dimensions. The energy for drying the wet pelletized oil-furnace carbon blacks was provided by natural gas combustion in an open-furnace system with an uncontrolled feed of combustion air. Improvements on the rotary dryers were carried out by adjusting the excess oxygen in the gases passing through the butterfly valve on the dryer exhaust stack. By regulating the butterfly valve on the dryer exhaust stack, and applying the prescribed operations for drying wet pelletized oil furnace carbon blacks, the excess oxygen in the tail gases was adjusted in the range of φ = 3.0 % and 5.0 %, depending on the type of oil-furnace carbon blacks. Suggested also is installation of a direct-reverse automatic butterfly valve on the dryer exhaust stack to automatically determine the volume fraction of oxygen in the tail gas, and the volume flow rate of natural gas for combustion. The results the improvements carried out are shown in Tables 3 to 5. Table 2 shows the thermal calculations for the hood of the rotary dryer. Preheating of the process water in the temperature range of 70 °C and 80 °C is also recommended using the net heat from the oil-furnace process for wet pelletization. The results of preheating the process water are shown in Table 1. Depending on the type of oil-furnace carbon black, the aforementioned improvements resulted in natural gas energy savings ranging from 25 % to 35 % in relation to the average natural gas requirement in the drying process, and thus a reduction in carbon emissions of up to 40 %, which is shown in Table 6. A schematic of the next proposed situation for complete automatization of the process for drying wet pelletized oil-furnace carbon blacks is shown in Figure 2

The Use of Demulsifiers for Separating Water from Anthracene Oil

U radu je pokazana uporaba deemulgatora za odvajanje homogene smjese antracenskog ulja i vode. Emulzija antracenskog ulja i vode sadržavala je oko w = 10•10 -2 vode. Voda je stvarala vrlo velike poteškoće u manipulaciji navedenog ulja prilikom proizvodnje uljno-pećne čađe. Budući da se radilo o količini od oko 800 tona ulja te da je plamište antracenskog ulja od 100 do 105 °C, nemoguća je bila uporaba klasičnih metoda otparavanja i destilacije navedene emulzije. Kao potencijalna mogućnost, pokazala se primjena različitih deemulgatora za odvajanje emulzije vode i antracenskog ulja. Uzorna količina dodanog deemulgatora je bila u rasponu od 0,5 do 1,0 g po kg antracenskog ulja. Nakon odvajanja vodene faze od antracenskog ulja maseni udjel vode u uljnoj fazi kretao se od w = 1,0 do 2,9•10-2. Navedenim načinom uspješno je odvojeno oko 720 tona antracenskog ulja s prosječnim masenim udjelom vode od w = 1,73•10-2. U preostalih 80 tona ostala je emulzija vode i antracenskog ulja s prosječnim masenim udjelom vode od oko w = 80•10-2.The main feedstocks for the production of oil-furnace carbon black are different kinds of liquid hydrocarbons. The quality and utilization of oil-furnace carbon black mainly depends on the type of liquid hydrocarbons contained in the oil feedstocks. In practice, both carbochemical and petrochemical oils are used as feedstock sources. Carbochemical oils are fractions obtained during coal tar distillation. Anthracene oil is one of these oils. Depending on the conditions of distillation, coal tars contain up to w = 18·10–2 highly aromatic fractions, which can be used as carbon black feedstock. The sulphur fraction of these oils can vary between w = 0.5 and 0.7·10–2, depending on the origin of the coal. The availability of carbochemical oils obtained from coal tar is largely dependent on the production of coke used in the manufacture of steel. The quantities available today are insufficient to satisfy the demand for carbon black feedstock. In addition, in highly industrialized countries, production of carbochemical oils is declining. Although, carbochemical oils are preferred in terms of efficiency, petrochemical oils are more important in terms of quantities available, particularly in the production of furnace blacks. These are residual oils resulting either from catalytic cracking processes or from the production of olefins in steam crackers using naphtha or gas oil as raw material. Nevertheless, the choice of carbon black feedstock is not determined merely by price and efficiency, but also by specific quality criteria. However, due to their origin, the feedstocks are mixtures of a large number of individual substances and are, therefore, not easy to characterize. More than 200 different components have been recorded in the range detectable by gas chromatography. Some important components of carbon black feedstock are listed in table 1.1 An important parameter for the evaluation of carbon black feedstock is density, since it increases with increasing aromaticity. It is also used for determination of the Bureau of Mines Correlation Index (BMCI),2 which is obtained either from density and midboiling point, or from density and viscosity for those feedstocks which cannot be distilled completely. This index is used by the carbon black industry as an important criteria for feedstock evaluation. The sulphur fraction in feedstocks should not exceed w = 2.5 ·10–2, because a higher content greatly affects the quality of carbon black, pollutes the atmosphere, and accelerates corrosion of the facility. The maximum sulphur content in the typical hydrocarbon feedstock is w = 1.2 · 10–2.3 A very important factor of hydrocarbon feedstock is the fraction of alkaline earth metals, especially sodium and potassium. The maximum sodium fraction may be w = 20·10–6, while the maximum potassium fraction is w = 2·10–6. The maximum fraction of asphalthenes is w = 15 ·10–2. Asphalthenes, determined as pentane-insoluble matter, provide indications concerning the possibility of grit formation. Another very important factor is the temperature range of distillation, which should be low enough, because the hydrocarbon feedstock must evaporize before entering the hot region of the reactor. The viscosity, the pour point, and for safety reasons, the flash point determines the handling properties and storage conditions of the feedstock. In addition, the water fraction in the hydrocarbon feedstock is one of the most important factors. The water fraction in hydrocarbon feedstock influences the handling properties of the same. The maximum water fraction in hydrocarbon feedstock may be w = 2.0·10–2, and desirably below w = 1.0·10–2. A higher water fraction represent a considerable impact on the financial construction. Also, it is very difficult to manipulate such feedstock, especially unloading, and in the production of oil-furnace carbon black. Namely, every water fraction higher than w = 2.0·10–2 in the hydrocarbon feedstock, causes the phenomenon of cavitations. In the oil-furnace carbon black plant of Petrokemija d. d. Kutina, the storage tank TK48003, was filled with 800 tons of anthracene oil. The average water fraction in the tank was w = 10·10–2. It was impossible to manipulate in the process of production, because the mentioned water fraction caused the cavitations effect. Therefore, it was necessary to decrease the water fraction to below w = 2.0·10–2, which will be satisfactory for production. As the water and anthracene oil formed a homogeneous emulsion (similar density at all temperatures), it was impossible to manage decanting the water from the anthracene oil. Additionally, it was impossible to manage evaporation of the water from the oil by heating the whole emulsion, because the flash point of anthracene oil is in the temperature range of T = 100 to 105 °C. Distillation of the whole emulsion of 800 tons was also impossible, because there was no distillation column adequate for separating the water from the anthracene oil. Thus, the use of different demulsifiers proved as a potential solution for separating the homogeneous mixture of anthracene oil and water. Namely, demulsifiers are a special type of high molecular tensides and organic solvents, which serve for separation the water from different hydrocarbons. The most common use is in emulsions with “lighter” hydrocarbons, especially when the density is not above r=0.850 g cm–3. Since the density of anthracene oil ranges from r=1.05 to 1.09 g cm–3, it was necessary to customise the conditions of application, and to choose the most adequate demulsifier for the separation of water from anthracene oil. Therefore, we experimented with different kinds of demulsifiers in cooperation with the companies TEH PROJEKT KEMO d. o. o. and KEM PROJEKT d. o. o. In laboratory conditions, we tested five different demulsifiers with different concentrations, and their efficiency in separating the water from anthracene oil. We then chose the most adequate demulsifier, which was applied on an industrial level

Procedure of Destructive Chemical Recovery of Precious Metals in Nitric Acid Production

Svi selektivni heterogeni katalizatori platinske grupe plemenitih metala koji se upotrebljavaju za oksidaciju plinovitog amonijaka do dušikovih oksida u proizvodnji dušične kiseline troše se tijekom svojeg radnog vijeka. Što je veći tlak oksidacije plinovitog amonijaka, to je veći maseni gubitak plemenitih metala platinske grupe s površine primijenjenog selektivnog heterogenog katalizatora. Ukupni gubici tijekom jedne šarže upotrebe selektivnog heterogenog katalizatora mogu iznositi od 20 do 40 % od ukupno ugrađene mase plemenitih metala. Jedan dio izgubljene mase plemenitih metala može se oporabiti ugradnjom odgovarajućih sustava "hvatača" u obliku mreža smještenih ispod katalizatora ili postavljenjem različitih filtara u procesni tok, gdje dolazi do izdvajanja čvrstih čestica plemenitih metala iz plinovite ili tekuće faze. Iako je učinkovitost njihove oporabe relativno velika, oveća količina plemenitih metala zadržava se i na površini operativne opreme zadužene za proizvodnju i predgrijavanje pare u proizvodnji dušične kiseline. Iz navedene operativne opreme zadržana masa plemenitih metala može se ponovno oporabiti postupcima nedestruktivne i destruktivne kemijske ekstrakcije čvrsto-tekuće. U radu je prikazan postupak destruktivne kemijske oporabe predgrijača i kotla za proizvodnju pare primjenom vodene otopine sumporne kiseline masenog udjela od 20 % te naknadni postupak prerade dobivenog taloga do konačne oporabe plemenitih metala. Metodom destruktivne kemijske oporabe ukupno je ekstrahirano 212,64 kg taloga u kojem je nakon postupka prerade određen kvalitativno-kvantitativan sastav s obzirom na Pt, Pd i Rh čiji su maseni udjeli iznosili w(Pt) = 18,119 %, w(Pd) = 1,749 % i w(Rh) = 0,419 %. Opisanim postupkom uspješno je oporabljeno u procesu proizvodnje dušične kiseline 38 528,2 g Pt, 3719,5 g Pd i 891,1 g Rh minimalne čistoće 99,90 %.The heart of the nitric acid production process is the chemical reactor containing a platinum-based catalyst pack and an associated catchment system, which allows the ammonia oxidation reaction to take place efficiently. Under the severe operating conditions imposed by the high-pressure ammonia oxidation process, the catalyst gauzes experience progressive deterioration, as shown by the restricted surface of the catalyst wires, the loss of catalytic activity and the loss of catalytic materials. The higher the pressure of gaseous ammonia oxidation, the greater the loss of platinum group metals from the surface of the applied selective heterogeneous catalysts. Total losses for one batch over the whole period of using selective heterogeneous catalysts may account in the range from 20 to 40 % of the total installed quantity of precious metals. An important part of the platinum removed from the platinum-rhodium alloy wires can be recovered at the outlet of the reactor by means of palladium catchment gauzes. However, this catchment process, which is based on the great ability of palladium to alloy with platinum, is not 100 % effective and a fraction of the platinum and practically all of the rhodium lost by the catalyst wires, evades the catchment package and is then deposited in other parts of the plant, especially heat exchangers. From the above mentioned operating equipment, the retained mass of precious metals can be recovered by the technical procedure of non-destructive and destructive chemical solid-liquid extraction. Shown is the technical procedure of destructive chemical recovery of preheater and boiler for preheating and production of steam by applying sulfuric acid (w = 20 %) and subsequent procedure of raffination of derived sludge, to the final recovery of precious metals. The technical procedure of destructive chemical recovery of precious metals from preheater and boiler for preheating and production of steam in nitric acid production is shown in Fig. 1. The technical and technological characteristics of the preheater and boiler for preheating and production of steam in nitric acid production at Petrokemija d. d. is shown in Table 1. The overall results of the destructive chemical cleaning of the preheater and boiler by H 2 SO 4 (w = 20 %) is shown in Table 3. By the method of destructive chemical recovery, 212.64 kg of dry sludge were extracted, which following the refining procedure of determined qualitative and quantitative composition of Pt, Pd and Rh amounted to: w(Pt) = 18.118 %, w(Pd) = 1.749 % and w(Rh) = 0.419 %. With the applied technical procedure, the mass of the precious metals successfully recovered in the process of nitric acid production was as follows: 38528.2 g of Pt, 3719.5 g of Pd and 891.1 g of Rh with minimum purity of 99.90 %. The entire quantity of recovered precious metals is used for preparation of new catalytic gauzes, which will serve in the nitric acid production for ammonia oxidation

Application of Primary Abatement Technology for Reduction of N2O Emmision in Petrokemija Nitric Acid Production

U industrijskoj proizvodnji dušične kiseline oksidacijom plinovitog amonijaka Ostwaldovim postupkom kao neželjeni proizvod nastaje bezbojni dušikov(I) oksid, N2O. Budući da je emisija N2O ozbiljan problem zbog njegova velikog doprinosa globalnom zatopljenju, potrebno je poduzeti određene mjere s ciljem njegova smanjenja. Smanjenje emisije N2O u proizvodnji dušične kiseline može se postići u različitim dijelovima procesa, ovisno o primijenjenim dostupnim tehnologijama. Od raspoloživih dostupnih tehnologija smanjenja emisije N2O u proizvodnji dušične kiseline za proizvodne procese Petrokemije posebno su zanimljive primarne i sekundarne tehnologije. Navedene tehnologije omogućuju smanjenje emisije N2O primjenom poboljšanih selektivnih heterogenih katalizatora u fazi oksidacije plinovitog amonijaka. Kao selektivni heterogeni katalizatori u primarnim tehnologijama upotrebljavaju se plemeniti metali u obliku mreža, dok je u slučaju sekundarnih tehnologija kao katalizator odabran Fe2O3 na Al2O3-nosaču u obliku granula. U radu je prikazana primjena primarnih tehnologija smanjenja emisija N2O na oba postrojenja za proizvodnju dušične kiseline u odnosu na konvencionalne selektivne heterogene katalizatore te priprema za ugradnju sekundarnih selektivnih katalizatora. Emisija N2O primjenom primarnih tehnologija na oba postrojenja smanjena je s 12 kg N2O na 7 kg N2O po toni čiste dušične kiseline. Primarnim smanjenjem emisije N2O omogućeno je daljnje smanjenje sekundarnom tehnologijom na vrijednost od 0,7 kg N2O po toni čiste dušične kiseline, odnosno ispod 200 mg m-3 (pri n. u.). Primijenjenim tehnologijama smanjenja emisije N2O iz postrojenja za proizvodnju dušične kiseline Petrokemije zadovoljit će se buduće granične vrijednosti emisija.Industrial nitric acid production by oxidation of gaseous ammonia with Ostwald procedure produces an unwanted by-product – colorless nitrous oxide, N2O. As emission of N2O represents a very serious problem due of its huge contribution to global warming, certain measures focused on its maximum reduction should be undertaken. Minimization of N2O emission in nitric acid production can be achieved in different parts of the process flow, depending on the applied available technologies. For the abatement of N2O emissions in Petrokemija\u27s nitric acid production processes from the list of the best available technologies chosen were primary and secondary abatement technologies. The mentioned ensures reduction of N2O by use of improved selective heterogeneous catalysts in the step of gaseous ammonia oxidation. Precious metals in the shape of gauzes are used as selective heterogeneous catalyst in primary technology, while in the case of secondary technology the Fe2O3 catalyst on Al2O3 support in the shape of spherical pellets is chosen. Shown is the application of primary technology for the abatement of N2O in both nitric acid production facilities and their comparison with classical heterogeneous catalyst and preparation for the installation of secondary selective catalyst. N2O emissions with the application of primary technology in both production facilities were reduced from 12 kg of N2O to 7 kg of N2O per ton of pure HNO3. With the primary reduction in N2O emissions the foundation was established for further reduction with the secondary technology to the final value of 0.7 kg of N2O per ton of pure HNO3, which represents mass concentration in the tail gas below 200 mg m-3 (at n. c.). With the applied technologies for the abatement of N2O emissions in Petrokemija\u27s nitric acid production the future prescribed emission limit value will be satisfie