Chromite ore with the composition shown in Table 5 was roasted with different potassium and sodium based alkali salts. Due to the low yields reported in the literature, 44–46 an alkali/mineral ratio of 1.11 …Web

In the present investigation, the oxidizing roasting process of chromite with sodium carbonate to prepare potassium dichromate crystals was studied in the microwave field with air, by heating the chromite and sodium carbonate. The chromite and sodium carbonate heated separately at 1000 °C in the microwave oven (frequency: 2.45 GHz; …Web

The development of alkali roasting process has undergone three steps: the high lime roasting, the low lime roasting and the lime-free roasting. Thereinto, lime-free technology, which can prevent CaCrO 4 generation and remarkably reduce the discharged residue yield, is the most advanced chromite ore roasting technology (Weber et al., …Web

Chromite ore processing tailing, a solid waste generated during the processing of chromite ore, is difficult to recover due to its ultra-fine size. ... Reduction roasting of manganese ores is a ...Web

Chromium chemicals are produced through alkaline roasting of chromite ore with alkali salts (such as NaOH, Na 2 CO 3, NaNO 3 or NaFeO 2 ) with or without lime addition at temperatures of 650-1200 ...Web

Chromite Ore Processing Residue (COPR) is a solid waste generated during the high temperature (∼1200 °C) roasting process that is used to extract chromium from chromite ore (Antony et al., 2006). Lime-based roasting has been the prevalent method to complex other metals in ore (Fe, Mg, Al) and isolate Cr.Web

The mineral coulsonite (FeV 2 O 4) is often associated with magnetite (Radtke, 1962) and forms a series with magnetite and chromite, FeCr 2 O 4 (Reznitsky et al., 2005). Ilmenite is also known to host vanadium ... The ore is roasted under reducing conditions to selectively reduce iron. The iron is then removed by magnetic separation, …Web

Several researchers have used sodium carbonate with chromite ore in the soda-ash roasting reaction. Temperatures used are above 1073 K in air. The decomposition of sodium carbonate has resulted sodium oxide to react with chromium ion (Cr 3+) under an oxidizing atmosphere. This results into the sodium chromate formation [8, 10, 11]. The ...Web

Chromite ore can be separated in a high-strength field, despite the presence of iron impurities. The choice of method depends on several factors, primarily the type of the gangue. ... During roasting, sulfur is removed from the pellets by 70% to 80% (due to oxidation of sulfides like pyrite). The remaining sulfur is of the sulfate type ...Web

Introduction. Chromite ore processing residue (COPR) is a byproduct produced in chromite processing at high temperature (1000–1200 °C). 2.5–3 tons of lime-based COPR were generated per ton of chromium salt (calculated by Na 2 CrO 4) (Fu et al., 2021).Although soda roasting (less than 0.8 tons of COPR per ton of sodium …Web

The old landfill sites, used for the dis- to use the South African chromite ores for a lime-free roast- posal of chromite ore processing residue (COPR) contain- ing process. The conversion efficiency of South African ing carcinogenic and mutagenic Cr6 ions, have now become chromite ore for the soda-ash roasting process is about 85 pct. a major ...Web

A new green metallurgical process for chromite ore has been proposed and developed to solve the serious environmental problem in the traditional production process of chromate. In the new process, the oxidation of chromite ore is carried out in sub-molten potassium hydroxide at 300 °C. Compared with the traditional roasting process in a …Web

Its chromite ore processing residue (COPR) includes carcinogenic and mutagenic calcium chromate ... (1200 °C) of the calcium-free roasting process of chromite ore (Antony et al., 2013b), the liquid-phase oxidation pressure leaching method achieved a high Cr leaching rate at lower reaction temperature (260 °C). It greatly reduced energy ...Web

Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste ...Web

Chromite ore processing residue (COPR) is a waste byproduct of chromate production that contains high levels of hexavalent chromium (Cr[VI]). ... with lime preventing dissolutio n when the roast ...Web

Chromite ore is usually a combination of spinels with associated minerals such as calcite, magnetite, talc, serpentines and uvarovite. Chromites crystals exhibit an octahedral …Web

Introduction. Chromite ore is the most important mineral for chromate production (Ding and Ji, 2003). Traditionally, chromite ore is processed by roasting with sodium carbonate at 1200. °C in a rotary kiln with the addition of limestone and dolomite, yielding only 75% of Cr in the ore.. Furthermore, the residue discharged (2.5–3.0 ton per …Web

Chromium chemicals are produced through alkaline roasting of chromite ore with alkali salts (such as NaOH, Na 2 CO 3, NaNO 3 or NaFeO 2 ) with or without lime addition at temperatures of 650-1200 ...Web

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800 °C to 900°C. The …Web

In the present investigation, the oxidizing roasting process of chromite with sodium carbonate to prepare potassium dichromate crystals was studied in the microwave field with air, by heating the ...Web

Chromium ore processing residue (COPR) is a hazardous waste generated during the production of chromate. Currently, approximately 10% of Cr 2 O 3 cannot be extracted after chromite sodium roasting and remains in COPR, wasting valuable Cr resources. In this study, Mg was selectively removed by using (NH 4) 2 SO 4 roasting in …Web

The traditional recovery of Cr from chromite ore dominantly involves roasting with Na 2 CO 3 above 1100°C (Ladd and Vanderpool, 1987;Habashi, 1997; Antony et al., 2001; Dhal et al., 2013;Li et al ...Web

Carbothermic reduction roasting for processing of ferruginous chromite ore using conventional and microwave heating 1. Introduction. The chromite ore occurs as a …Web

Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate during the soda-ash roasting reaction depends on the oxygen partial pressure and availability of oxygen at the reaction front. The effects of temperature, oxygen partial pressure, charge …Web

1. Introduction. The soda ash roasting process produces Chromite Ore Processing Residue (COPR) containing 1130–8500 mg/kg carcinogenic hexavalent chromium (Cr(VI)) due to the industrial incomplete leaching (Du and Chrysochoou, 2018, Chrysochoou et al., 2009)pared with the lime-based roasting process, soda ash as …Web

Chromium has a wide range of applications, including as an alloy addition in various steels and also as a corrosion resistance coating. Carbothermal reduction of chromite ore (FeCr 2 O 4) in a submerged arc furnace is an important industrial process for extracting chromium, but the energy consumption is excessive.It is suggested that one …Web

Chromite ore and sodium carbonate are roasted at temperatures ranging between 900 °C and 1200 °C in oxidative atmosphere (Antony et al., 2001). Under these …Web

Antony et al. [26] and Zhang et al. [27] have been processed chromite ore by roasting with sodium carbonate, limestone and dolomite at 1000-1200 °C [27]. In the current study, the traditional ...Web

To explicate the thermodynamics of the chromite ore lime-free roasting process, the thermodynamics of reactions involved in this process was calculated and …Web