MD919Z - Process for regeneration of electrolyte - Google Patents

Process for regeneration of electrolyte Download PDF

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Publication number
MD919Z
MD919Z MDS20150001A MDS20150001A MD919Z MD 919 Z MD919 Z MD 919Z MD S20150001 A MDS20150001 A MD S20150001A MD S20150001 A MDS20150001 A MD S20150001A MD 919 Z MD919 Z MD 919Z
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Moldova
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electrolyte
regeneration
direct current
ions
density
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MDS20150001A
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Romanian (ro)
Russian (ru)
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Руслан ТИФОЙ
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Сп Завод Топаз Ао
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Publication of MD919Z publication Critical patent/MD919Z/en

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Abstract

The invention relates to a process for regeneration of electrolyte based on aqueous solutions of sodium chloride and nitrate with a content of hexavalent chromium, and can be used in the process of electrochemical machining of gas-turbine engine blades.The process for regeneration of electrolyte based on aqueous solutions of sodium chloride and nitrate with a content of Cr+6 includes applying a direct current of normal polarity with a density of 0.4…0.5 A dm2 for 5…10 min and subsequently applying the direct current of reverse polarity with the same density and duration, after which by centrifugation is removed the sludge from the electrolyte.

Description

Invenţia se referă la un procedeu de regenerare a electrolitului bazat pe soluţii apoase de clorură şi nitrat de sodiu cu conţinut de crom hexavalent, şi poate fi utilizată în procesul de prelucrare electrochimică a paletelor de turbomotoare cu gaze. The invention relates to an electrolyte regeneration process based on aqueous solutions of sodium chloride and nitrate containing hexavalent chromium, and can be used in the electrochemical processing of gas turbine engine blades.

Una dintre cele mai importante cerinţe moderne de protecţie a mediului de emisii nocive în prelucrarea electrochimică este asigurarea purităţii ecologice a electrolitului, care necesită aplicarea măsurilor de regenerare a electrolitului, şi anume, neutralizarea elementelor toxice, precum şi eliminarea depunerilor acumulate. One of the most important modern requirements for environmental protection from harmful emissions in electrochemical processing is ensuring the ecological purity of the electrolyte, which requires the application of electrolyte regeneration measures, namely, the neutralization of toxic elements, as well as the elimination of accumulated deposits.

În procesul prelucrării electrochimice a paletelor de turbomotoare cu gaze fabricate din oţel aliat, metalele de aliere trec în electrolit în formă ionică, de exemplu, ioni de crom dizolvaţi hexavalent, cu formarea ionilor de cromat ce nu formează un precipitat. In the process of electrochemical processing of gas turbine engine blades made of alloy steel, alloying metals pass into the electrolyte in ionic form, for example, dissolved hexavalent chromium ions, with the formation of chromate ions that do not form a precipitate.

Toxicitatea ionilor de cromat se referă la clasa 1 de pericol. Pe măsura desfăşurării prelucrării electrochimice, ionii de cromat se acumulează în electrolit şi depăşesc normele sanitare admise. Mai mult ca atât, în electrolit se acumulează depuneri, care înrăutăţesc calitatea suprafeţei aliajului prelucrat. Prin urmare, este necesară transferarea ionilor de crom hexavalent toxic în formă trivalentă cu eliminarea continuă a depunerilor. The toxicity of chromate ions refers to hazard class 1. As electrochemical processing proceeds, chromate ions accumulate in the electrolyte and exceed the permissible sanitary standards. Moreover, deposits accumulate in the electrolyte, which worsen the quality of the surface of the processed alloy. Therefore, it is necessary to transfer toxic hexavalent chromium ions to trivalent form with continuous removal of deposits.

Este cunoscut procedeul de regenerare pentru reutilizarea multiplă a electrolitului la prelucrarea electrochimică a pieselor fabricate din nichel, fier şi crom, în care soluţia neapoasă, care constă din acid oxalic şi un acid tare, dizolvat într-un amestec de alcool benzilic şi tri-n-butil fosfat reprezintă un purtător, în care reducerea conţinutului soluţiei apoase de cromat utilizat în prelucrarea electrochimică se accelerează până la valori similare cu cazul reducătorilor anorganici. Separarea ulterioară a fazelor duce la extracţia produselor de oxidare, în timp ce produsele de reducere, dizolvate în faza apoasă, se elimină prin condiţionare alcalină, care permite de a elimina ionii de crom hexavalent, pentru a obţine un electrolit reutilizabil [1]. The regeneration process for multiple reuse of the electrolyte in the electrochemical processing of parts made of nickel, iron and chromium is known, in which the non-aqueous solution, which consists of oxalic acid and a strong acid, dissolved in a mixture of benzyl alcohol and tri-n-butyl phosphate represents a carrier, in which the reduction of the aqueous chromate solution content used in the electrochemical processing is accelerated to values similar to the case of inorganic reductants. Subsequent phase separation leads to the extraction of the oxidation products, while the reduction products, dissolved in the aqueous phase, are eliminated by alkaline conditioning, which allows to eliminate the hexavalent chromium ions, to obtain a reusable electrolyte [1].

Dezavantajul acestui procedeu constă în complexitatea implementării cu echipament a tehnologiei de regenerare a electrolitului, precum şi necesitatea utilizării mai multor reactivi organici şi a acizilor tari. The disadvantage of this process lies in the complexity of implementing the electrolyte regeneration technology with equipment, as well as the need to use several organic reagents and strong acids.

Mai este cunoscut procedeul, realizat în sistemul de pregătire şi regenerare a electrolitului strungului electrochimic. Procedeul constă în succesiunea operaţiilor de dizolvare a electrolitului solid, eliminare a impurităţilor, pregătire a electrolitului de concentraţia necesară, stocare a electrolitului, purificare ulterioară a electrolitului ca urmare a prelucrării electrochimice, precum şi de stabilizare a parametrilor fizico-chimici ai electrolitului [2]. The process is also known, carried out in the system of preparation and regeneration of the electrolyte of the electrochemical lathe. The process consists of the sequence of operations of dissolving the solid electrolyte, removing impurities, preparing the electrolyte of the required concentration, storing the electrolyte, subsequent purification of the electrolyte as a result of electrochemical processing, as well as stabilizing the physicochemical parameters of the electrolyte [2].

Dezavantajele acestui procedeu constau în eliminarea incompletă din soluţia de electrolit a ionilor toxici de crom bine solubili în apă, fapt care nu asigură securitatea muncii operatorului la strung, complicarea semnificativă a procesului de prelucrare a deşeurilor - depunerilor şi electrolitului, precum şi creşterea costului de utilizare a lor. The disadvantages of this process consist in the incomplete elimination of toxic chromium ions that are highly soluble in water from the electrolyte solution, which does not ensure the safety of the lathe operator, the significant complication of the waste processing process - deposits and electrolyte, as well as the increase in the cost of their use.

Cea mai apropiată soluţie este procedeul de dirijare automată a sistemului de pregătire şi regenerare a electrolitului, conform căruia se neutralizează compuşii toxici de crom, totodată la prima fază a procesului, pH-ul electrolitului se reduce până la valoarea pH1, ce corespunde mediului acid al electrolitului, care este optimal pentru reacţie. În timpul primei faze a procesului se injectează acidul până la atingerea unui nivel predeterminat de pH1 şi se efectuează agitarea electrolitului. La faza a doua a procesului, pH-ul electrolitului se menţine egal cu pH1 şi apoi se injectează o doză specifică a reactivului de neutralizare a compusului toxic de crom, după care se controlează modificarea potenţialului redox. Dacă potenţialul redox începe să crească, se injectează reactivul de neutralizare a compusului toxic de crom, ulterior procesul se repetă până când după o altă injectare a reactivului de neutralizare a compusului toxic de crom potenţialul redox va scădea sau va rămâne neschimbat pentru un interval de timp îndelungat, după expirarea căruia se determină finalizarea reacţiei. La a treia fază a procesului se efectuează creşterea valorii pH a electrolitului până la atingerea unui nivel predeterminat pH2 prin adăugare de alcaliu în electrolit [3]. The closest solution is the process of automatically controlling the electrolyte preparation and regeneration system, according to which the toxic chromium compounds are neutralized, while in the first phase of the process, the pH of the electrolyte is reduced to the value of pH1, which corresponds to the acidic environment of the electrolyte, which is optimal for the reaction. During the first phase of the process, the acid is injected until a predetermined level of pH1 is reached and the electrolyte is stirred. In the second phase of the process, the pH of the electrolyte is maintained equal to pH1 and then a specific dose of the reagent for neutralizing the toxic chromium compound is injected, after which the change in the redox potential is controlled. If the redox potential begins to increase, the reagent for neutralizing the toxic chromium compound is injected, then the process is repeated until after another injection of the reagent for neutralizing the toxic chromium compound the redox potential decreases or remains unchanged for a long time, after which the reaction is determined to be complete. In the third phase of the process, the pH value of the electrolyte is increased until a predetermined pH2 level is reached by adding alkali to the electrolyte [3].

Dezavantajul acestui procedeu constă în complexitatea procesului tehnologic, utilizarea reactivilor chimici suplimentari, precum şi necesitatea de a adăuga alcaliu în electrolit. The disadvantage of this process lies in the complexity of the technological process, the use of additional chemical reagents, as well as the need to add alkali to the electrolyte.

Problema tehnică pe care o rezolvă invenţia constă în accelerarea şi simplificarea procesului de regenerare a electrolitului, neutralizarea ionilor toxici de crom hexavalent, precum şi evitarea utilizării reactivilor chimici suplimentari. The technical problem solved by the invention consists in accelerating and simplifying the electrolyte regeneration process, neutralizing toxic hexavalent chromium ions, and avoiding the use of additional chemical reagents.

Procedeul, conform invenţiei, înlătură dezavantajele menţionate mai sus prin aceea că include aplicarea unui curent continuu de polaritate directă cu o densitate de 0,4…0,5 A/dm2 timp de 5…10 min şi aplicarea ulterioară a curentului continuu de polaritate inversă cu aceeaşi densitate şi durată de timp, după care prin centrifugare se înlătură depunerile din electrolit. The process, according to the invention, eliminates the disadvantages mentioned above by including the application of a direct polarity direct current with a density of 0.4…0.5 A/dm2 for 5…10 min and the subsequent application of a reverse polarity direct current with the same density and duration, after which the deposits from the electrolyte are removed by centrifugation.

Rezultatul tehnic al invenţiei constă în reducerea semnificativă a concentraţiei de ioni cu toxicitate ridicată Cr+6 în electrolit. The technical result of the invention consists in significantly reducing the concentration of highly toxic Cr+6 ions in the electrolyte.

Invenţia se explică prin desenul din figură, care reprezintă o schemă tehnologică de regenerare a electrolitului conform procedeului revendicat. The invention is explained by the drawing in the figure, which represents a technological scheme for electrolyte regeneration according to the claimed process.

Instalaţia pentru aplicarea procedeului revendicat de regenerare a electrolitului conţine rezervorul pentru electrolit uzat 1, electrocoagulatorul 2, pompa 3, redresorul 4 pentru convertizarea tensiunii de curent alternativ de 380 V în tensiune de curent continuu, centrifuga 5 de acţiune continuă pentru eliminarea depunerilor din electrolit. The installation for applying the claimed electrolyte regeneration process contains the spent electrolyte tank 1, the electrocoagulator 2, the pump 3, the rectifier 4 for converting the 380 V alternating current voltage into direct current voltage, the continuous action centrifuge 5 for removing deposits from the electrolyte.

Exemplu Example

Se umple rezervorul 1 cu volumul de 300 l cu o soluţie apoasă de electrolit, care conţine 5…10% NaNO3 şi 5…10% NaCl cu următorii parametri: pH-ul electrolitului - 7,4, concentraţia de Cr+6 - 0,2 g/l (10…3 mol/l), căderea de potenţial - 0,263 mV (măsurată de ionometrul ”Anion 4110”). Apoi se conectează pompa 3 a electrocoagulatorului 2 de tip МУИ TOCA 306128.010, care se umple cu electrolit uzat. După deconectarea pompei 3, se conectează redresorul de tip TERI- 800/24T-01. La prima fază a prelucrării electrolitului uzat se aplică un curent continuu de polaritate directă cu o densitate de curent de 0,4…0,5 A/dm2 timp de 5…10 min, după care se aplică un curent continuu de polaritate inversă cu aceeaşi densitate de curent şi durată de timp. Ulterior prin centrifugare se înlătură depunerile din electrolit, utilizând centrifuga 5 de acţiune continuă. Fill the tank 1 with a volume of 300 l with an aqueous electrolyte solution containing 5…10% NaNO3 and 5…10% NaCl with the following parameters: electrolyte pH - 7.4, Cr+6 concentration - 0.2 g/l (10…3 mol/l), potential drop - 0.263 mV (measured by the ionometer "Anion 4110"). Then connect the pump 3 of the electrocoagulator 2 of the type МУИ TOCA 306128.010, which is filled with used electrolyte. After disconnecting the pump 3, connect the rectifier of the type TERI-800/24T-01. In the first phase of the spent electrolyte processing, a direct current of direct polarity is applied with a current density of 0.4…0.5 A/dm2 for 5…10 min, after which a reverse polarity direct current is applied with the same current density and time duration. Subsequently, deposits are removed from the electrolyte by centrifugation, using a continuous action centrifuge 5.

Parametrii specifici ai prelucrării electrolitului uzat sunt indicaţi în tabel. The specific parameters of the processing of spent electrolyte are indicated in the table.

Tabel Table

Curent, А Durata de prelucrare, min pH-ul electrolitului Concentraţia ionilor de Cr+6 Concentraţia ionilor de Cr+6 măsurată de ionometru, mol/l Căderea de potenţial, mV Datele iniţiale ale electrolitului uzat - - 7,4 0,2 10-3 +0,263 Proba nr.1 (regimul direct al redresorului) 500 10 8,7 0,17 10-3 +0,240 Proba nr.2 (regimul direct al redresorului) 750 10 9,6 0,02 10-5 +0,205 Proba nr. 3 (regimul revers al redresorului) 750 10 pe anod, 10 pe catod 10,6 0 10-8…10-9 +0,040Current, А Processing time, min Electrolyte pH Cr+6 ion concentration Cr+6 ion concentration measured by ionometer, mol/l Potential drop, mV Initial data of spent electrolyte - - 7.4 0.2 10-3 +0.263 Sample no. 1 (direct rectifier mode) 500 10 8.7 0.17 10-3 +0.240 Sample no. 2 (direct rectifier mode) 750 10 9.6 0.02 10-5 +0.205 Sample no. 3 (reverse rectifier mode) 750 10 on anode, 10 on cathode 10.6 0 10-8…10-9 +0.040

După cum rezultă din tabel: As can be seen from the table:

- cu creşterea intensităţii curentului electric creşte şi pH-ul electrolitului; - as the intensity of the electric current increases, the pH of the electrolyte also increases;

- cu creşterea pH-ului electrolitului, concentraţia de Cr+ 6 şi căderea de potenţial se reduc; - with increasing electrolyte pH, the Cr+ 6 concentration and the potential drop are reduced;

- proba a treia este optimă pentru neutralizarea ionilor de Cr+6, adică concentraţia lor, măsurată printr-o metodă titrometrică, este 0, iar resturile de ioni de Cr+6, măsurate de ionometrul „Anion 4110” constituie 10-8…10-9 mol/l. Astfel neutralizarea ionilor de Cr+6 în electrolit trebuie să fie efectuată în regimul de polaritate inversă de funcţionare a redresorului, adică cu aplicarea curentului electric de polaritate directă şi inversă. În procesul prelucrării electrolitului uzat, ionii toxici de Cr+6 se transferă în ioni netoxici de Cr+3 în conţinutul depunerilor, care sunt eliminate prin centrifugare continuă. - the third sample is optimal for neutralizing Cr+6 ions, i.e. their concentration, measured by a titrometric method, is 0, and the remains of Cr+6 ions, measured by the ionometer "Anion 4110" are 10-8…10-9 mol/l. Thus, the neutralization of Cr+6 ions in the electrolyte must be carried out in the reverse polarity mode of operation of the rectifier, i.e. with the application of electric current of direct and reverse polarity. In the process of processing the spent electrolyte, toxic Cr+6 ions are transferred to non-toxic Cr+3 ions in the content of the deposits, which are eliminated by continuous centrifugation.

1. EP 2386377 A1 2011.11.16 1. EP 2386377 A1 2011.11.16

2. Седыкин Ф.В., Дмитриев Л.Б., Иванов Н.И. и др. Оборудование для размерной электрохимической обработки деталей машин. Москва, Машиностроение, 1980, p. 161-162 2. Sedykin F.V., Dmitriev L.B., Ivanov N.I. and others Equipment for large-scale electrochemical processing of machine parts. Moscow, Машиностроение, 1980, p. 161-162

3. RU 2471594 C1 2013.01.10 3. RU 2471594 C1 2013.01.10

Claims (1)

Procedeu de regenerare a electrolitului bazat pe soluţii apoase de clorură şi nitrat de sodiu cu conţinut de Cr+6, care include aplicarea unui curent continuu de polaritate directă cu o densitate de 0,4…0,5 A/dm2 timp de 5…10 min şi aplicarea ulterioară a curentului continuu de polaritate inversă cu aceeaşi densitate şi durată de timp, după care prin centrifugare se înlătură depunerile din electrolit.Electrolyte regeneration process based on aqueous solutions of sodium chloride and nitrate containing Cr+6, which includes the application of a direct polarity direct current with a density of 0.4…0.5 A/dm2 for 5…10 min and the subsequent application of reverse polarity direct current with the same density and duration, after which the deposits from the electrolyte are removed by centrifugation.
MDS20150001A 2015-01-13 2015-01-13 Process for regeneration of electrolyte MD919Z (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
MD2504G2 (en) * 2002-11-26 2005-01-31 Государственный Университет Молд0 Process for chromed electrolyte generation by automatic control
RU2422374C2 (en) * 2005-11-30 2011-06-27 Индустрие Де Нора С.П.А. Electrochemical treatment of solutions containing hexavalent chromium
EP2386377A1 (en) * 2010-05-12 2011-11-16 Industria de Turbo Propulsores S.A. Method of getting reusable electrolyte from electrochemical machining of parts made up of nickel, iron and chromium.
RU2471594C1 (en) * 2011-07-07 2013-01-10 Общество С Ограниченной Ответственностью "Есм" Method of automatic control over system of preparation and recovery of electrolyte and device to this end
  • 2015

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
MD2504G2 (en) * 2002-11-26 2005-01-31 Государственный Университет Молд0 Process for chromed electrolyte generation by automatic control
RU2422374C2 (en) * 2005-11-30 2011-06-27 Индустрие Де Нора С.П.А. Electrochemical treatment of solutions containing hexavalent chromium
EP2386377A1 (en) * 2010-05-12 2011-11-16 Industria de Turbo Propulsores S.A. Method of getting reusable electrolyte from electrochemical machining of parts made up of nickel, iron and chromium.
RU2471594C1 (en) * 2011-07-07 2013-01-10 Общество С Ограниченной Ответственностью "Есм" Method of automatic control over system of preparation and recovery of electrolyte and device to this end

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Еланёва С.И. Физикохимические методы снижения агрессивности отработанных электролитов путем перевода Cr (VI) в Cr (III). Известия Пензенского государственного педагогического университета им. В.Г. Белинского, nr. 10/2008 *
Седыкин Ф.В., Дмитриев Л.Б., Иванов Н.И. и др. Оборудование для размерной электрохимической обработки деталей машин. Москва, Машиностроение, 1980, p. 161-162 *
Урецкий Е.А. Ресурсосберегающие технологии в водном хозяйстве промышленных предприятий. Брест, 2007 *

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