carbon regeneration kiln

carbon regeneration kiln

OurCustom Rotary Kilns are based around process first and foremost. Designed to ensure correct residence time at hold temperature of 20 minutes -not 10 minutes, they ensure stable progressive feed of your carbon with reliable three zone heating with independent controls, robust thermal lifter designs, co-current movement of reaction products and correct thermal conduction area and bed thickness defining retort size.

Comprises an agitated conical bottom vessel with transfer eductor, fresh carbon feed chute and electric monorail for supply of the carbon to your elution system. Gentle agitation reduces the carbon fines introduced into your CIL/CIP system

Used in conjunction with the Transfer Water System, this system recovers carbon fines with high gold bearing loads from the transfer water assisting to reduce the high (up to 50g/t loss) carbon losses experienced in the CIL plant.

This system recovers hydraulic transfer used for carbon movement around the circuit. Hydraulic transfer rather than impeller pumps reduces attrition of the carbon extending your carbon life and lowering solids to tails. The transfer water recovery system incorporates a large transfer water vessel with a transfer water pump system providing water for carbon transfer around the plant.

This sludge recovery equipment aides in the recovery of gold sludges when stainless steel mesh cathode wire is used in the electrowinning cells rather than the traditional mild steel wool where gold is plated to the wool. Sludges and gold fines are collected and dried to a cake suitable for post thermal drying prior to being smelted in the barring furnace.

carbon regeneration

carbon regeneration

In normal process streams activated carbon is exposed to a variety of chemicals. Organic compounds tend to adsorb readily on the hydrophobic activated carbon, which reduces site availability for gold cyanide. Other compounds such as calcium and magnesium carbonate commonly precipitate on the carbon surface and restrict gold adsorption access. Consequently, the performance of the activated carbon decreases unless it is regenerated. Regeneration generally consists primarily of thermal activation in a rotary kiln at around 650 C in steam to remove organic debris. Thennal activation is preceded or followed by exposure to hydrochloric acid to remove inorganic precipitates such as carbonates.

The carbon reactivation circuit is series of unit processes designed to restore the activated carbons ability to recover precious metals from cyanidation circuit solutions. Since each circuit will be treating a unique solution, which will result in unique carbon fouling problems, the reactivation circuit design must consider several variables, which includes the preference of the plant operator.

The main unit operations within the reactivation circuit are acid washing, elution and thermal reactivation. This paper will focus on the design considerations in the acid wash and thermal reactivation circuits, although it should be noted that all three operations must be operated efficiently to ensure proper carbon reactivation and the resultant low soluble gold losses from the cyanidation circuit.

As noted previously, carbon kinetic activity is an important factor in the efficient operation of a CIP circuit. Lower carbon activity will result in higher carbon inventories in the circuit, lower gold loadings on the carbon, and higher soluble gold losses from the circuit. The average carbon activity in a circuit is mainly a function of the efficiency of the carbon regeneration process (i.e.. not the activity of the new carbon).

The importance of returning barren carbon to good kinetic activity has long been known. Despite this knowledge, gold processing operations have generally not been particularly good at regenerating barren carbon. Experience over the past 30 years suggests that on average regenerated carbon has a kinetic activity no better than 50% of new carbon and often only 20-40%. A minority of operations to achieve good regeneration (>70% of new carbon), demonstrating that a satisfactory outcome is possible with proper equipment and procedures.

In general, process operations manage the acid washing and elution stages well; however, the thermal regeneration process is often problematic. Lack of focus in this atva often leads to underinvestment in good equipment, poor operating practices (insufficient temperature/residence time/steam), and poor maintenance. Often operations will cease thermal regeneration for an extended period due to equipment failure. While there is often no observed immediate impact, over time a significant degradation in CIL performance will occur.

During adsorption, many organic and inorganic adsorbates can accumulate within the porous structure of activated carbon. Micropores (up to 3 nm) constitute the primary adsorption sites, and therefore tend to become congested to a greater degree than do mesopores (3 to 60 nm) and macropores (60 to 10000 nm). However, mesopores and macropores also capture adsorbates of relatively high molecular mass and, as a result, there is a progressive decline in adsorption efficiency. Activated carbon that is used to purify water upstream of a carbon-in-pulp (CIP) processby capturing organic compounds that are likely to foul the carbon in the CIP reactors needs periodic thermal treatment to selectively remove the organic adsorbates and thus restore its activity. In a CIP arrangement that does not include adsorptive pretreatment, organic adsorbates can be partially desorbed during the elution of the precious metals from the carbon (including pretreatment with hot acid), but a substantial fraction of these adsorbates will remain and will have to be dealt with at regular intervals by thermal treatment.

The objectives during regeneration are the selective removal of the adsorbates that have accumulated on the carbon during adsorption operations, and the restoration of the original porous structure and activity of the carbon with as little damage as possible to the carbon itself.

The first three steps, viz drying, vaporization, and pyrolysis, normally proceed with few complications. However, pyrolysis should not be conducted at temperatures higher than 850 C in a non-oxidizing atmosphere, since graphitization of the pyrolysed residue can occur, resulting in a structure similar to that of activated carbon and equally refractive. Hence, during subsequent selective oxidation, it would be difficult to remove the residue without extensively damaging the structure of the activated carbon. Pyrolysed residues obtained at lower temperatures are reported to be more reactive, and therefore more readily oxidizable, than activated carbon.

The proper reactivation of carbon does not involve direct oxidation of the pyrolysed residue with oxygen. On the contrary, the atmosphere within that zone of the furnace is deliberately depleted in oxygen so that the following reactions will be minimized.

All thermal regenerations were conducted using a two-inch externally heated rotary Cube furnace. In order to simulate an expected plant condition of 50 percent moisture in the carbon prior to regeneration, 100 g of oven dried material was placed in a 250 ml jar and 50 g of D.I. water was added. The jar was then tightly capped and Che carbon allowed to equilibrate. Additional water, when required, was added by pumping the required volume of water through a steam superheater prior to entering Che rotary furnace. The pump race was adjusted to give the additional water required over the course of the regeneration retention time. The 100 g charge of wetted carbon was placed in a nichrome 60 mesh basket assembly which was then quickly introduced into the tube furnace and the end cap securely fastened. After the required time, the carbon and basket assembly was removed, then cooled in a sealed cooling chamber.

a look at activated carbon thermal regeneration

a look at activated carbon thermal regeneration

One of the major benefits to activated carbon is that it is capable of being restored, meaning that spent carbon, or carbon saturated with the adsorbed components, can be desorbed of the components to yield an activated carbon that is again ready for use.

Albeit large, activated carbon does have a finite adsorption capacity. Throughout the course of its use, this capacity becomes diminished as the activated carbon adsorbs more components onto its surface. Once the activated carbon has reached capacity, it can no longer be effectively used. The now spent carbon can either be sent to a landfill or incinerator for disposal, or recycled through regeneration. Typically powdered activated carbon (PAC) is not regenerated, but rather, disposed of, while granular activated carbon (GAC) is regenerated.

Regeneration, often referred to as reactivation, is a method of thermally processing the activated carbon to destroy the adsorbed components contained on its surface. In regeneration, the adsorbed components are almost completely removed, yielding a regenerated carbon that can again function as an adsorbent.

Its important to note that regeneration and reactivation actually refer to two technically different processes. However, these terms are frequently used interchangeably across many industries, and as such, are used so in this article.

Regeneration is most commonly carried out using a thermal approach in which high temperatures are used to destroy the adsorbed components. While this process can differ based on the source material and the adsorbed components, in general, it happens in three stages.

The material is first dried. Once the material has been dried to the desired moisture content, volatilization can occur. The material is heated up to around 1000 F, which volatilizes 75 90% of the adsorbed materials. At this point, steam is injected into the system to remove the remaining volatiles and reactivate the carbon.

The result is near-completely restored activated carbon ready for reuse. During this process, it is common to have carbon losses between 5 10%. For this reason, each time spent carbon is regenerated, that amount of new activated carbon will need to be added to make up for the losses.

Depending on various factors, these stages may be carried out all in one piece of equipment, or multiple pieces. Upon regeneration, the activated carbon is commonly cooled in a rotary cooler before it moves on to shipping, storage, or reuse.

Both multiple hearth furnaces and rotary kilns have proven effective in the regeneration of activated carbon. In comparing the two reactivation methods, a study from the EPA found several advantages and disadvantages to be apparent.

In addition to these factors, capacity is often a determining consideration between the two types of equipment; multiple hearth furnaces offer significantly greater capacities. However, rotary kilns are more favorable for smaller applications.

Often times, the same company that produces the activated carbon will offer a regeneration service as well. This allows companies to send their spent carbon back to the manufacturer for regeneration, and then get it back, ready for reuse.

Many activated carbon producers will also offer their customers a carbon pool or sharing option. Here, customers that do not require getting their specific carbon back can submit their spent carbon along with other companies in order to keep costs low.

activated carbon thermal regeneration activated carbon

activated carbon thermal regeneration activated carbon

One of the major benefits to activated carbon is that it is capable of being restored, meaning that spent carbon, or carbon saturated with the adsorbed components, can be desorbed of the components to yield an activated carbon that is again ready for use.

Albeit large, activated carbon does have a finite adsorption capacity. Throughout the course of its use, this capacity becomes diminished as the activated carbon adsorbs more components onto its surface. Once the activated carbon has reached capacity, it can no longer be effectively used. The now spent carbon can either be sent to a landfill or incinerator for disposal, or recycled through regeneration. Typically powdered activated carbon (PAC) is not regenerated, but rather, disposed of, while granular activated carbon (GAC) is regenerated.

Regeneration, often referred to as reactivation, is a method of thermally processing the activated carbon to destroy the adsorbed components contained on its surface. In regeneration, the adsorbed components are almost completely removed, yielding a regenerated carbon that can again function as an adsorbent.

Its important to note that regeneration and reactivation actually refer to two technically different processes. However, these terms are frequently used interchangeably across many industries, and as such, are used so in this article.

Regeneration is most commonly carried out using a thermal approach in which high temperatures are used to destroy the adsorbed components. While this process can differ based on the source material and the adsorbed components, in general, it happens in three stages.

The material is first dried. Once the material has been dried to the desired moisture content, volatilization can occur. The material is heated up to around 1000 F, which volatilizes 75 90% of the adsorbed materials. At this point, steam is injected into the system to remove the remaining volatiles and reactivate the carbon.

The result is near-completely restored activated carbon ready for reuse. During this process, it is common to have carbon losses between 5 10%. For this reason, each time spent carbon is regenerated, that amount of new activated carbon will need to be added to make up for the losses.

Depending on various factors, these stages may be carried out all in one piece of equipment, or multiple pieces. Upon regeneration, the activated carbon is commonly cooled in a rotary cooler before it moves on to shipping, storage, or reuse.

Both multiple hearth furnaces and rotary kilns have proven effective in the regeneration of activated carbon. In comparing the two reactivation methods, a study from the EPA found several advantages and disadvantages to be apparent.

In addition to these factors, capacity is often a determining consideration between the two types of equipment; multiple hearth furnaces offer significantly greater capacities. However, rotary kilns are more favorable for smaller applications.

Often times, the same company that produces the activated carbon will offer a regeneration service as well. This allows companies to send their spent carbon back to the manufacturer for regeneration, and then get it back, ready for reuse.

Many activated carbon producers will also offer their customers a carbon pool or sharing option. Here, customers that do not require getting their specific carbon back can submit their spent carbon along with other companies in order to keep costs low.

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