Moisture and Plasma Gasification

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It has been discussed previously within this forum that plasma-arc, plasma gasification systems, such as PEAT’s plasma thermal destruction and recovery (PTDR) systems, have the ability to process a wider range of feedstocks that other thermal treatment technologies largely because the heat source is independent of the waste being processed. This means that plasma-arc plasma gasification systems can process industrial hazardous waste feedstocks with very low calorific values (i.e. high moisture and inorganics). Further, plasma systems can co-process a variety of waste streams simultaneously.

With this said when a feedstock has a higher moisture and/or inorganic material content, the required plasma heating power from the plasma arc increases. Simply put, waste streams with 30% moisture content vs. ones with 10% moisture require more plasma-arc power (i.e. more electricity) to ensure a complete destruction of the waste feedstock.

For example, here is a representative composition for medical waste treatment (infectious red bag) in Asia, reflecting a moisture content of 18%.

Medical Waste Treatment Composition
% by wt
CARBON 36.780%
HYDROGEN 7.300%
CHLORINE 1.600%
OXYGEN 25.880%
NITROGEN 0.570%
SULFUR 0.190%
WATER 18.000%
METALS 1.835%
INORGANICS PLUS FLUXING AGENTS 7.845%
TOTAL 100.000%

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Based on modeling exercises and experience, the plasma-arc power required in a PTDR-100 system is 80 kWe (based on 75% electrical-to-thermal efficiency). This plasma-arc power is required to vaporize the moisture required for medical waste treatment.

Now, here is a representative composition for medical waste treatment from the United States, reflecting a moisture content of 8.4% (we have been told the differences between US and Asia are related to how the medical waste is ultimately sorted).

Medical Waste Treatment Composition
% by wt
CARBON 46.390%
HYDROGEN 7.300%
CHLORINE 1.600%
OXYGEN 25.880%
NITROGEN 0.568%
SULFUR 0.191%
WATER 8.400%
METALS 1.835%
INORGANICS PLUS FLUXING AGENTS 7.836%
TOTAL 100.000%

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Based on modeling exercises and experience, the required plasma-arc power required in a PTDR-100 system is under 5 kWe (based on 75% electrical-to-thermal efficiency).

The medical waste treatment streams are largely the same except for the moisture content; however the required plasma-arc plasma gasification power is reduced by over 93%!

An important reminder, plasma gasification is a thermal chemical conversion process designed to optimize the conversion of waste into the syngas. The chemical reactions take place under oxygen starved conditions. The ratio of oxygen molecules to carbon molecules can be less than one in a plasma gasification reactor (sometimes a stoichiometric amount of oxygen to achieve pyrolysis).

The following simplified chemical conversion formulas describe some of the thermo-chemical processes that are typically occurring in gasification.

Equation 1 C (fuel) + O2 →CO2 + heat (exothermic)
Equation 2 C + H2O (steam) → CO + H2 (exothermic)
Equation 3 C + CO2 → 2CO (exothermic)
Equation 4 C + 2H2 → CH4 (exothermic)
Equation 5 CO + H2O → CO2 + H2 (exothermic)
Equation 6 CO + 3H2 → CH4 + H2O (exothermic)

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Some of the waste undergoes partial oxidation by precisely controlling the amount of oxygen fed into the plasma-arc reactor (see first reaction above). The heat released in the above exothermic reactions provides additional thermal energy for the primary gasification reaction (endothermic formulas above) to proceed very rapidly.

At higher temperatures (around 3,600°F) the endothermic reactions are typically favored as such in a PTDR reactor only equations 1-3 are seen.

Vitrified Matrix Testing From Initial Run At China Refinery

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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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PTDR-100 Refinery Waste Treatment Plant in China

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PEAT recently finalized the installation of a PTDR-100 Refinery Waste Treatment plasma gasification system for a client in China. This plasma-arc, plasma gasification system, is being sought to treat refinery sludge and petrochemical waste.

Here are some pictures of the plasma-arc system:

PTDR-100 Waste Treatment Plant in China

Plasma-Arc PTDR-100 Plasma Gasification Reactor

PTDR-100 Waste Treatment Plant in China

Side view of both skids on the PTDR-100 Plasma Gasification System

The refinery waste product contains primarily water, and smaller amounts of non-aqueous liquids and solids, both organic and inorganic, are by-products of the refining and petrochemical industries. For example, a typical industrial waste stream from an oil refinery operation will contain about 80 percent-by-weight water, about 15 percent-by-weight oil, e.g., hydrocarbons and other non-aqueous liquids, and about 5 percent-by-weight solids. Due to environmental regulations, this industrial waste stream poses significant disposal problems for the oil refineries.

The PTDR plasma-arc waste-to-energy system will convert via plasma gasification approximately 50 kilograms/hr (110 lbs) of this refinery waste into syngas estimated to be almost 600,000 BTU/hr (150,000 kCal/hr).

PEAT International designs advanced plasma-arc, plasma gasification systems. PEAT’s industrial waste treatment plants converts refinery waste into energy and other useful end products.

Pharmaceutical Waste and PTDR

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It has been estimated that hospitals and long-term care (LTC) facilities in the US waste at least 125 million pounds of pharmaceuticals annually – a staggering figure. Kevin Bain in third quarter edition of Medical Waste Management looked at the inventories of drugs maintained by coroner offices to assess the scope and magnitude of household pharmaceutical waste. Data from a pilot study conducted by the Clark County Coroner’s Office in Nevada illustrated a death rate of 0.008 (same as the US in 2005). The total number of cases accepted by the coroner’s office was 3,393; of those, 46.4% included drug inventories. 325,000 doses of wide array of drugs – not including liquids, powders or delivery systems (i.e. Patches or syringes) were collected representing greater than 102 kilograms of active pharmaceutical ingredients. Bain then extrapolated that data to the entire US deceased population, the coroner’s office estimated that almost 18 metric tons of APIs are disposed of just by coroner’s office alone.

How is all this pharmaceutical waste disposed of currently?

Flushing them down the toilet is the most common method used by coroners to dispose of Pharmaceutical Waste remaining in the household following a person’s death. The issue is that the wastewater treatment plants or domestic septic systems are not designed to remove pharmaceutical waste from the effluent – this results in small concentrations of pharmaceutical waste can end up in drinking water. The FDA recommends that most pharmaceutical waste be disposed of by basically mixing them with coffee grounds or kitty litter and putting them into sealable bag or empty coffee can and tossing them out in the trash.

Pharmaceutical waste is an ideal feedstock for a plasma-arc, plasma gasification waste to energy system in that it is typically low in moisture/water content and high in oxygen and carbon. This combination minimizes the energy and heat required from the plasma arc, plasma gasification heating system (i.e. plasma torches). When the required from the plasma torches is low in the PTDR plasma-arc system, generating waste to energy becomes much more favorable.

For example, in a recent PTDR-100 a plasma-arc, plasma gasification waste to energy system proposal advanced where the feedstock proposed is 90% pharmaceutical waste (balance was inorganic alkaline batteries), the heat required from the plasma arc system was minimized to where the estimated power consumption for the entire system was less than 50 kW. Assuming an efficiency of 17,000 BTU/kW-hr on the generation side, it was estimated that this PTDR-100 a plasma-arc, plasma gasification waste to energy system would generate over 60 kW of electricity.

PTDR-100
Waste Treatment Plant

Cheap PTDR Technology Exists in India for Disposal of Bhopal Union Carbide’s Toxic Waste

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Cheap PTDR Technology Exists in India for Disposal of Bhopal Union Carbide’s Toxic Waste at Plant’s Site. No collateral damage to environment or people living nearby, claims PEAT International Co.

Cheer up. There is some good news for the survivors of Bhopal gas tragedy, the worlds worst industrial disaster, including the NGOs working for them and the Madhya Pradesh Government as far as disposing off the toxic waste lying in the erstwhile killer Union Carbide pesticide plant, which has become an enigma for one and all, is concerned.

The good news is that a technology known as Plasma Thermal Destruction Recovery (PTDR), of a company christened as PEAT International, is available in India to clean up the Bhopal Union Carbide plants toxic waste effectively and cleanly at site itself without having to transport the hazardous material to any far off place for its disposal. It can be disposed off at the site within the premises of the Union Carbide factory at Bhopal without creating any collateral damage to the environment and / or the people living in the surrounding areas of the facility, claims Peat International.

According to Pradeep Mathur, CEO India for PEAT International India, if the said technology is adopted for the treatment of this waste, then the problem will be completely resolved, requiring no further treatment and without any requirement of land filling, the company claims. The facility once constructed will be available for treating other wastes even after the treatment of the waste is completed.

Talking to this correspondent Mr. Mathur said the cost of the treatment is also very nominal. For about 350 metric tonnes (MT) toxic waste, PTDR-100 unit would suffice and the cost may come around to Rs. 50 to 60 million only. It is interesting to note here that the Union Government has earmarked Rs. 3000 millions for the 350 MT toxic waste kept in the factory godown. Thus, this cost amount of Rs. 50 to 60 million would be just 1.5 per cent of the sanctioned amount Rs. 3000 millions which is dam cheap.

It would be better in the interests of the survivors and the Madhya Pradesh Government itself if it contacts the Peat International India officials as soon as possible and discuss the whole issue of toxic waste disposal immediately without any delay. After taking overall view of the matter the state Government must weigh the options available to it so far with the huge cost involved. It should initiate steps for it on priority basis at the first go looking at the very cheap cost involved to solve the issue which has been hanging on fire for over last 25 years.

PEAT International (“PEAT”), which is headquartered in Northbrook, Illinois, its chairman being Mr. Joseph Rosin, is a waste-to-resources company specializing in the deployment of its proprietary PTDR technology for the treatment and recycling of a wide range of waste feed-stocks, including: industrial waste, universal waste and medical waste.

According to Mr. Mathur the novel and patented PTDR technology uses heat generated by plasma torches in an oxygen starved (pyrolysis) environment to first pull apart (dissociate) the molecules that make-up the organic portions of the waste, then, depending on the composition of the waste stream, a controlled (stoichiometric) amount of oxygen is added to reform the dissociated elements of the waste into a synthesis gas (“Syngas”), consisting mainly of Carbon Monoxide (CO) and Hydrogen (H2). The Syngas can then be used in a variety of ways: as a fuel for thermal or electricity production or as a feedstock for the production of liquid fuels (i.e. ethanol).

PEAT’s PTDR 100, a 60 kilograms-an-hour system, would be ideal for the 350 MT toxic waste. The PTDR 100 is an ideal, turn-key solution for treating this kind of waste on-site without undertaking the danger of moving this dangerous and volatile waste to a treatment facility. A PTDR 100 unit costs approx. Rs. 40 millions as initial Capital Cost. The treatment Cost would be about Rs. 20 per kg. The PTDR 100 unit takes only about 100 sq. metre of space and can be stalled in 6 months time. Operating at 60 kg / hr PTDR-100 can finish the 350 MT in about 10 months time from the start of the toxic waste treatment, Mathur revealed.

He claimed that the PTDR technology has received numerous regulatory approvals throughout the globe, including: Taiwan Environment Protection Agency; Taiwan Ministry of Education; Kaohsiung Department of Environment Protection; Virginia Department of Environment Quality; Alabama Department of Environmental Management; City of Huntsville Natural Resources Division; San Diego Air Pollution Control District; Sacramento Air Pollution Control District; Indiana Department of Environment Management; Michigan Department of Environment Quality; California Department of Public Health and Ministry of Environment and Forests, Government of India.

It may be mentioned here that the ghost of disposing off the toxic waste is haunting the Madhya Pradesh Government, the survivors of the gas tragedy and the NGOs working for them alike. The Government is concerned only about the 350 MT stocked in the godown of the factory. While the survivors and the NGOs are very much perturbed over the enormous quantity of the waste amounting to 18,000 to 25,000 MT or may be even more spread in the campus of the factory and in the solar evaporation ponds which has leeched into the soil and contaminated drinking water reserves of the people living in the vicinity of the factory. There is an urgent need to detoxify the soil in order to stop contamination of water.

The point of contention is how to dispose off this toxic waste without harming the environment and the populace together with carrying it this highly poisonous material safely to any far off disposal site ruling out possibility of any mishap. The huge cost involved to carry out this operation is another overriding factor. If the enormous quantity of the waste amounting to 18,000 to 25,000 MT spread in the campus of the factory and in the solar evaporation ponds is taken up then the cost would be mind boggling.

If the survivors and the NGOs stand is taken about the enormous amount of toxic waste being 18,000 to 25,000 MT or more then PTDR 100 plant would not be suitable. At PEAT International there are two larger plants – the PTDR 500 / which can treat 9 tons per day, and the PTDR 1000 / which can treat 30 tons per day. A PTDR 500 would require 2,000 working days – whereas the PTDR 1000 would require 600 days. The type of waste is not an issue – because all PTDR units can handle all types of poisonous materials. A PTDR 500 – the Capital Cost is approx. Rs. 250 millions and it requires about 750 sq. metre of space. The PTDR 1000 – the Capital Cost is approx. Rs. 800 millions and it requires about 2,850 sq. metre of space. Depending upon the type of waste – the above units would also generate surplus Electricity for supply to the grid.

Meanwhile, it may be pointed out here that the judiciary is also seized of the matter of toxic waste disposal. The Madhya Pradesh High Court adopted a strict view of the toxic waste lying at the defunct Union Carbide factory, on August 17 again directed Dow Chemicals to present all the documents pertaining to the merger of the two companies. The court set September 30 as the deadline for submitting the documents and posted the next hearing for October 26.

An NGO Gas Kand Trasdi Morcha had filed a PIL before the Jabalpur High Court, seeking the fixing of responsibility for the disposal of the toxic waste. The double bench of the High Court comprising Justice Arun Mishra and Sushma Srivastava repeated the direction issued at the last hearing, ordering Dow Chemicals to present the merger agreement and documents pertaining to properties before the court by September 30. Though, the Union Carbide owned the factory at the time of the Gas Tragedy, Dow Chemical later took over the pesticide manufacturing giant.

It may be recalled here that on the intervening night of December 2-3, 1984, 40 MT of poisonous Methyl Iso-cyanate spewed out from Union Carbide pesticide plant in Bhopal killing thousands of people and maiming nearly half a million others. The fall out of the disaster has been that people who inhaled the gas have been dying and death over the years has crossed 25,000 mark and is still counting.

 
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