Join us on a high tech adventure that will recycle an abundant waste product to produce electricity and heat for sale while reducing greenhouse gas emissions and improving the world in which we live! Leading this project is Dr. Igor Matveev, PhD, a former Soviet Union defense scientist. Dr. Matveev now lives and works in America pushing the envelope in the new field of Plasma Assisted Combustion (PAC). PAC has the ability to inject any energy-containing feedstock, including waste products, into a high-energy plasma where they are chemically dissembled at extremely high temperatures and energies into syngas (mostly a blend of CO and H2). The syngas can then be burned for heat, or piped into internal combustion engines, turbine engines, and solid oxide fuel cells to produce electricity and heat. Due to high thermal efficiency of the process, significant amount of excess energy could be released to generate extra power to be exported and make the project economically sound. A successful prototype unit has already been delivered to Venezuela and is being used to destroy toxic chemicals. Dr. Matveev now proposes to adapt the same PAC technology to convert biosolids into syngas.
There are over 18,000 waste treatment plants in the United States. Each of them processes human and other waste in a series of steps that, in the end, result in a byproduct known as biosolids (sludge). See video of conventional sewage treatment technology in Fairfax County, Virginia http://www.fairfaxcounty.gov/cable/channel16/asx/wastewater_management.asx. 10 million tons are produced each year, and there are currently few options for responsible disposal. Biosolids can be dried in a kiln and used as fertilizer, but more often, they are incinerated and the ash is transported to a landfill. We have an environmentally sound alternative. PAC technology can be used to convert the biosolids into syngas. The syngas can then be used onsite to produce electricity and heat – two forms of energy that can be used immediately by the waste treatment facility. About 18,000 GW*h of clean energy can be produced. That will cover about 0.5% of the national electricity consumption and provide electricity to over 1.5 million of population.
The same technology could be applied for processing manure from cows, pigs and chickens, following anaerobic digestion. These two processes combined in one fuel, power and heat production module could significantly improve economics of food production and make animal farm look like a surgery.
More over, sewage sludge can be blended with other waste liquids or solids with some heating value, as used motor and transformer oil, hydraulic liquids, oil from the bars and restaurants, grinded coal, glycerol to name a few. This will just help to increase the process efficiency, generate more power, and make your project more profitable.
The flow diagram configuration shown in Figure1 will provide efficiencies that are not possible through any other technology, and will significantly offset purchases of electricity and natural gas by the treatment plants. Ash removal requirements will be minimized and a net reduction in greenhouse gas emissions will be achieved. We have validated our process using a series of computer models, but no one in the waste water industry wants to go first – we need to build, test, and perfect the prototype so that we can show the industry a working unit.
Fig.1. Sewage sludge power plant: 1 – control system; 2 – plate power module of the RF power source; 3 – RF module; 4 – RF plasma torch; 5 – multi-stage sludge gasifier; 6 – sludge blender and feeder; 7 – air compressor for sludge atomizing; 8 – synthesis gas storage tank; 9 (1), 9 (2), 9 (3) – synthesis gas cooler; 10 – fuel synthesis gas compressor; 11 – gas turbine engine (GTE); 12 (1,2) – power generators; 13 – steam turbine (ST); 14 – steam condenser; 15 – hot well; 16 – water treatment system; 17 (1,2) – heat-recovery steam generators (HRSG); 18 – synthesis gas treatment module; 19 – synthesis gas compressor; 20 – oxygen production module. Working mediums: A – cooling water, B – plasma gas; C – sewage sludge; D – air for gasification; E – water steam for gasification; F – atmospheric air; G – fuel synthesis gas; H – GTE exhaust; J – overheated water steam; L – feed water HRSG; O – purging oxygen; P – fresh water; S – synthesis gas after the gasifier.
The key element of such a plant is a plasma assisted gasifier, using next generation radio-frequency (RF) plasma torches with virtually unlimited lifetime. General operation principles of the plasma gasifier are illustrated in Fig.2, where plasma module 1 works as the process initiator and sustainer for downstream gasification modules 2, 3, and 4. All these modules also operate as the power and flow multipliers with feedstock and oxidizer injection into each of them. This approach dramatically reduces torch power requirements and overall plasma system costs while increasing residence time for particle processing. A controllable specific fuel-to-oxidizer ratio helps to optimize calorific value of the output syngas by keeping H2 yield as high as possible. Each of these modules utilize a reverse vortex gas dynamics, which provides excellent mixing of the reagents, longer residence time for reacting components, and shielding walls from hot temperature reaction zone enabling so named cold wall operation. We employ this patented technique in almost all of our products from reactors and combustors to plasma torches with 12,000 ◦C internal plasma temperature.
Fig.2. Plasma gasifier (US Patents 7,452,513 B2 and 7,955,567 B2): 1 – plasma generation module, 2,3,4 – stages of the gasification module, 5 – starting torch, 6 – starting torch plume, 7 – starting gas, 8 - starting gas vortex, 9 – inductor, 10 – plasmoid, 11 – main plasma gas (air, oxygen, blends), 12 – main gas reverse vortex, 13 – feedstock 1 fraction 1, 14 - feedstock 1 flow,15 - feedstock 2 (optionally water steam), 16 – feedstock 2 vortex, 17 – feedstock 1 fraction 2, 18 – feedstock 1 flow, 19 – feedstock 2 fraction 2, 20 – feedstock 1 fraction 3, 22 – feedstock 1 fraction 3 flow, 23 - reaction products – syngas.
In this project we plan to use a 50 kW RF plasma torch. Why RF? Because this is the only available high power plasma source with virtually unlimited lifetime due to its electrodeless design. No electrodes – no erosion. We recently completed the development of a line of these torches with power output ranging from 20 kW to 500 kW exclusively for applications requiring long periods of non-stop operation. To our knowledge, we are the sole manufacturer of this product, and our target is 20,000 running hours non-stop.Based on a typical 30% biosolids water content, we calculate that a 50 kW plasma power level will supply sufficient power to initiate the process in the first stage. In future larger scale projects, we will increase power up to 1 MW per torch.
The ideal gas for this feedstock gasification is oxygen. We plan to apply a membrane technology for air separation to produce oxygen on-site, and we may be able to market compressed N2 as a by-product. This membrane technology will provide oxygen with 94-97% purity at an affordable price – about 0.4 kW*h per kg of O2. Pressure requirements depend mainly upon the power generation equipment. In case of gas turbine application, we will pressurize the syngas to about 12 bar (174 psig). This means that the gasifier and torch should work at similar or above pressures. At present, all known RF torches are limited to the range of vacuum to 1 bar. Our torch, with a homemade power supply, has demonstrated stable operation with pressure at the exit nozzle of 7 bar (105 psi). We need only one more step to reach the necessary pressure. To do this, we will replace the gas control system and develop a high pressure, water cooled vessel for the torch tests.
Cooled down and cleaned up syngas will power a gas turbine, modified to operate on low-Btu gas. According to preliminary modeled results, we expect net calorific value (CV) or lower heating value (LHV) of syngas from 8 MJ/kg to 10 MJ/kg, which is much lower than that for natural gas (37 MJ/m3 or 47.14 MJ/kg) and LPG (46.6 MJ/kg) [http://cta.ornl.gov/bedb/appendix_a/Lower_and_Higher_Heating_Values_of_Gas_Liquid_and_Solid_Fuels.pdf], but good for such exotic low-Btu and wet fuel, and still enough to be efficiently burned in the heat engines. Engine modification will be mainly focused on the fuel nozzles replacement to feed more gas, turbine cross section expansion to allow higher gas flow, control system adjustments, fuel pipelines replacements, gear box modifications, and so forth. A retired military helicopter gas turbines will be used and coupled with a power generator. The gas turbine will be also equipped by a double stage heat exchanger. One stage will produce overheated steam for steam turbine and further power generation, another one will heat up the sewage sludge prior to its injection into the gasifier.
The main objectives of current project is to develop a demonstration plant with treatment capacity of 10 tons a day of sewage sludge with about 30% water content, subsequent 6-month field operation with further experimental data collection, technology improvement, and scaling it up for wide industrial application.This plant could generate up to 500 kW of electricity or total 20 MW*h of thermal energy, at least 100 kg per hour of fertilizer, and become the first of a kind highly efficient and clean sewage processing technology utilizing the most recent developments in the field of plasmas. The US will benefit not only from greener power production, but also from new jobs and higher export potential.
The project will be based on earlier performed prototypes, including plasma system for hazardous liquid waste combustion shown in Fig.3. Here one can see a 50 kW RF torch on the left coupled with a staged combustor for 100 liters per hour waste treatment. Combustor’s OD is 13” or about 300 mm. The torch, coupled with four nozzle fuel injection section and the air swirlers are shown in Fig.4. A two-module power supply, including high voltage DC module and RF module is shown in Fig.5.
Its complete performance will take up to 12 months and additional $1,200,000, but syngas production will begin in 7-8 months. Our tangible contribution is a fabricated torch and a 70% completed power supply.
To see a RF torch is operation visit www.plasmacombustion.com
Risks and challenges
For the project success we have highly skilled team under Dr. Matveev’s supervision (has 35 years in the field of plasma assisted technologies with over 1,200 plasma systems in operation worldwide); 3,500 square feet laboratory with 600 kW power input; machine shop; unique patented plasma torches; own power supplies; modeled results of the process optimization; international research team, including plasma and combustion specialists, computation fluid dynamics and chemical kinetics researchers, electronics and automation engineers; clear understanding of what and how to do, and real customers waiting for the operating demonstration plant.Learn about accountability on Kickstarter
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