Process Questions and Answers

Q1. What does a typical EPR gasification plant look like and how does it work?

A1. Our gasification plants produce a clean burning fuel gas from renewable solid or liquid waste fuels. This gas is used to fire a boiler, which produces steam to drive a quiet and efficient steam turbine generator. Electricity generated is sold to the grid. Solid waste from the process is an inert non-leachable sintered material that constitutes about 8% of the weight of the original fuel material. It can be safely landfilled or sold for aggregate. Flue gas from the boiler is inherently clean compared to incineration and is further scrubbed prior to release.

Q2. What is the energy balance for the plant?

A2. Our standard 32 MW plant processes some 850 TPD of MSW, approximately 680 tons of which actually enters the gasifier. The feed is selected and sorted so as to have an average BTU value of approximately 7,200 BTU/lb. The overall thermal efficiency of the plant is between 21% and 24%, depending on factors such as plant capacity, feed type, composition and moisture content. Ancillary fuels are sometimes required to bring the feed calorific value to the required minimum average of 7,200 BTU/lb. The gasifiers are manufactured and deployed in nominal 16 to 24 MW / 400 to 650 TPD modules, with two or three such modules comprising the basic power plant. Parasitic power is relatively low, in part because these systems do not use plasma torches. In addition to power, the plants are capable of providing steam for nearby industrial processes. The sale of thermal energy in the form of steam can enhance revenues.

Q3. What does the receiving facility look like? 

A.3 The receiving facility has many of the same characteristics of a standard transfer station, it is installed inside a building or enclosure and features specialized manual sorting lines, supported by standard bag openers, shredders, conveyors, and magnetic belts for removal of ferrous materials, as needed. Recyclable materials such as metals and glass are recovered and sold. Components used for preparation of refuse derived waste from MSW. 

Q4. What are the characteristics of the feed stocks that can be handled by the technology? 

A4. The core gasification technology has been proven on a number of feed stocks over a period of more than 20 years. These include refuse derived fuel (derived from sorted MSW), coal, construction and demolition waste light fraction, rice hulls, chicken litter with both wood and rice hull bedding, waste carpet, used tires, wood dust, sewage sludge, several types of green waste, switch grass, etc. EPR has also developed a cogeneration system that system that produces a clean, low Btu gas that can be used as ancillary fuel by other thermal power plants. Heat recovered from clloing this gas is used to generate electricity. The EPR plants operate very efficiently on mixed gas and solid phase renewable fuels.

Q5. What is the level of tipping fees needed to balance the pro forma?

Q5. Our gasification facilities produce electrical power. The required tipping fee is, in part, a function of the price for which electrical power can be sold. For a typical 30 MW facility, the numbers work with a price of approximately 8.5 cents per k-h for electricity and a tipping fee of approximately $20.00 per ton. Recyclable materials recovered from the sorting line including ferrous metals, aluminum, copper, glass and the like can also be sold to help offset the labor costs of the sorting line. 

Q6. What is the mass balance of the typical size gasification plant? 

A6. A 48 MW facility operating on MSW with a sorting facility would be best situated on a 20 - 30 acre plot to provide sufficient staging area for trucks and storage of onsite ancillary fuels as required. In terms of mass balance in the case of a 16 MW module, for example, approximately 220 tons of sorted and chipped C&D waste per day are required to generate an average of approximately 13 MW net to the bar. From the 220 tons entering the gasifier, approximately 16 tones of sintered solid material is produced. The remaining material is converted to a fuel gas which is reformed and combusted to produce steam in a boiler. EPR plants incorporate flue gas recycle to greatly reduce inherent NOx emissions.

Q7. How much, and what kind of residuals are created by this process?

A7. When sorting is properly done, the facility normally generates approximately 180 lbs of an inert material (sintered ash) for every ton of waste processed through the gasifier. This material is completely inert and non-leachable and can be used as an aggregate, or embankment fill, or safely landfilled.

Q8. What kind of air pollution controls will be used? 

Fuel gas produced in the gasifier is sent through a refractory-lined cyclone before being reformed and used to fire a boiler that produces steam which drives one or more multi-stage steam turbines. Boiler flue gas clean-up process units include a standard flue gas desulphurization unit electrostatic precipitator (ESP), and a bag house with carbon and lime injection. The specifications for these units can be modified to fit specific requirements based on fuels and local conditions.

Q9. What is the gasification temperatures expected?

 Depending on the fuel and mode of operation, temperatures in the first chamber will reach approximately 750 to 850 oC. The second rotary kiln gasifier will reach temperatures of up to approximately 1,300 oC. Temperatures in the reformer may reach 1,100oC. Before entering the boiler, gas temperatures are reduced to no more than 750oC to avoid tube fouling and extend the life of the boiler tubes.

Q10. Is this a batch process?

A10. All EPR gasifiers operate on a continuous process basis.