Waste to Energy and Recycling

Medical Waste Treatment, PTDR Systems, Plasma Arcs, Plasma Gasification, TVRC Technology, Waste To Energy, Waste Treatment, medical waste No Comments »

Many contest that the primary goals for waste management; to reduce, reuse and recycle, and increasing waste conversion (i.e. waste-to-energy) rates are not compatible. However, in the United States, the states making the most use of waste-to-energy facilities are also those that recycle the most.

In addition, according to a recent study conducted by the EPA, increasing recycling wastes actually improves the efficiency of waste conversion (i.e. waste-to-energy).

Consumers are increasingly recycling more biogenic waste (paper and food) and throwing away more non-biogenic waste (rubber and plastics).

The higher energy content of non-biogenic waste makes it a more productive feedstock for generating electricity through a waste-to-energy technology such as the TVRC. Conversely to previously held views then, recycling is not just compatible with waste conversion, it actually improves the energy content of the leftover waste, boosting the potential of key waste-to-energy technologies, including plasma-arc plasma gasification.

Plasma-Arc and Plasma-Arc Electrodes

PTDR Systems, Plasma Arcs, Plasma Gasification, Waste To Energy, Waste Treatment 2 Comments »

PEAT’s plasma-arc plasma gasification system consists of DC-powered plasma-arc graphite electrodes rather than plasma torches, typically marketed by other companies. There are a number of benefits associated with using DC-powered plasma-arc electrodes.

Minimization of capital costs as plasma-arc graphite electrodes generate plasma-arcs directly with exposed anodes and cathodes without requiring an independent torch. Plasma torches are expensive and increase the capital costs associated with overall systems.

Minimization of operational costs as plasma-arc graphite electrodes require no water cooling or any externally-supplied carrier gas (i.e. argon or nitrogen). This increases the electrical to thermal conversion rates (typically seen around 85-90% in PTDR plasma-arc plasma gasification systems).

Plasma torches require water cooling, carrier gases and have lower efficiencies as their power output can be as low as 50% of the power input for small torches. This means that one half of the electricity of the plasma torch is dissipated to the cooling water or efficiency of the plasma-arc power supply.

More on Plasma Gasification

PTDR Systems, Plasma Arcs, Plasma Gasification, Uncategorized, Waste To Energy No Comments »

Plasma pyrolysis and plasma-arc plasma gasification, like incineration, are options for recovering value from waste by thermal treatment. Both pyrolysis and plasma-arc plasma gasification convert feedstocks/wastes into energy by heating the waste under controlled conditions. Whereas incineration converts the input waste into a combusted flue-gas that can then be used to recover thermal energy (usually in the form of steam) and ash, pyrolysis and plasma-arc plasma gasification deliberately limits the conversion so that combustion does not take place directly. Instead, they convert the waste into potentially valuable intermediates that can be further processed for materials recycling or energy recovery. Pyrolysis and plasma-arc plasma gasification offer more scope for recovering products from waste than incineration.

One of the benefits associated with plasma-arc plasma gasification is that plasma-arc plasma gasification reactors do not require moving grates and the smaller volume of gases generated means that the plasma-arc plasma gasification reactors can accommodate the required minimum residence times in a smaller volume. Further, the smaller gas production and reducing environment within plasma-arc plasma gasification reactors does facilitate smaller sized air pollution control systems.

Vitrified Matrix Testing From Initial Run At China Refinery

Waste To Energy, Waste Treatment No Comments »

As discussed earlier in this blog, a vitrified matrix or slag is the primary solid byproduct of plasma arc waste-to-energy processing. The vitrified matrix from plasma arc processing contains the mineral matter associated with the feed materials in a vitrified form – a hard, glassy-like substance. The amount of matrix produced is a function of how much non-combustible mineral matter is present in the feedstock.

This matrix is the result of operating temperatures within the plasma arc reactor above the melting temperature of the mineral matter. Under these conditions in the plasma arc reactor, non-volatile metals and metal oxides bind together in molten form until it is cooled via natural heat loss or via a pool of water, where it would fracture and granulate.

The compressive strength of a slag sample generated from fly ash from coal-fired power plant as well as some sodium carbonate (fluxing agent) was 480 kg/cm2, while its average mortar strength was tested at 169 kg/cm.

The vitrified matrix or slag generated by plasma arc treatment is primarily made up of silicon dioxide (SiO2), aluminum oxide (Al2O3) and calcium oxide (CaO). Toxicity Characteristic Leaching Procedure (TCLP) tests are designed to determine the mobility of both organic and inorganic analytes present in the slag. The most recent TCLP results on the vitrified matrix from the plasma arc waste-to-energy system located at a China refinery is presented in the below table.

Contaminant
USA – EPA
(40 CFR 261.24)
Regulatory Level
(mg/L)
China EPA
Regulatory Level
(mg/L)
China Refinery
Vitrified Matrix
(mg/L)
Arsenic 5 5 ND < 0.050
Barium 100 100 0.371
Cadmium 1 1 ND < 0.008
Chromium 5 5 ND < 0.017
Copper 15 8.7
Hexavalent Chromium 2.5 ND < 0.25
Lead 5 5 ND < 0.018
Mercury 0.2 0.2 ND < 0.0005
Nickle 0.441
Selenium 1 1 ND < 0.041
Silver 5 5 ND < 0.013
Zinc 1.22
ND = Not Detectable (detectable limit follows)
NR = Not reported

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Plasma Arc Gasification and Its Environmental Footprint

Waste To Energy, Waste Treatment 1 Comment »

There are a number of perceptions within the marketplace regarding plasma arc treatment and plasma arc gasification processes. Last week, this blog addressed the idea/claim regarding the plasma arc technology’s ability to generate significant useable recyclable end-products and energy with no residual waste.

This week we address some aspects of the environmental footprint associated with plasma arc gasification processes

The high temperatures within plasma arc gasification reactors do facilitate higher thermal destruction with regards to volatizing organic material in the feedstock and breaking them down to simple molecules, however some plasma arc gasification systems require a secondary reactor or cracking stage to accomplish this breakdown indicating that not all reactions occur within the “blackbox.”

With regards to lower emissions claims, specifically dioxins for example, the high temperature within the plasma arc gasification reactors, while important, alone does not ensure little to no dioxin formation, the rapid cooling of the syngas as it leaves the plasma arc gasification reactor is equally important to ensure these complex compounds do not reform.

As discussed in this blog entry:

Plasma Arc Gasification and Wastewater Other Residuals

http://www.peat.com/blog/plasma-arc-gasification-and-wastewater-other-residuals/

other by-products generated during the gas cleaning and conditioning require proper handling. In some plasma arc gasification process configurations, it is feasible to re-inject the by-products collected/generated during this stage into the plasma arc gasification reactor to be vitrified, however this requires planning during the early design stages. If these by-products cannot be re-fed, then secondary treatment would be mandatory.

 
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