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PROCESSING OF MEDICAL, BIOLOGICAL AND VETERINARY WASTE IN AUTHOTHERMAL PLANT IMA2006f WITH POWER 0.4 MW
JSC CIS-Natural Resources developed, manufactured and within 2008 tested an experimental-industrial prototype of the complex for thermal waste-processing IMA2006F. This complex belongs to utility equipment and is designed for authothermal neutralization (burning) of solid waste with the system of purification of output gases from hazardous substances up to maximum permissible concentrations. The complex is designed for processing of veterinary, biological and medical waste of hazard types B and C (in Sanitary Regulations and Standards 2.1.7.728-99) – hereinafter referred to as “the fuel”. JSC CIS-Natural Resources followed the following objectives at development of this complex: - the plant is to have simple controls and be reliable in operation, free warranty period – 6 months; - the complex should be highly efficient – with capacity at least 100 kg\hour at minimum density of “the fuel” and should be repaid at estimated operational costs within the period not exceeding 1.5 year; - to ensure complete after-burning of output gases in the afterburner chamber; - achievement of thermal and physical characteristics, aero-dynamical parameters and pollutant discharge concentrations with or without operating gas purification system, quantitatively exceeding Russian and foreign analogs and having all indications of world novelty.
Complex IMA2006F operates in an open air at air temperature from -45 to + 40°С in conditionally clean and industrial atmosphere.
The complex includes a two-chamber vertical furnace with air-supply system, evaporation cooling plant, output gas purification system and output gas discharge plant, system of automatic lifting and unloading of 120-liter containers with “the fuel” into the plant for grinding and continuous-discrete feeding to the lower chamber. The plant for grinding and feeding “the fuel” operates under permanent negative pressure; air from it goes to the reactor through the fan. The complex’s furnace is encased into a metal case and is fettled inside with fireproof material with operating temperature 1300°С. In the lower chamber there is a stationary steel fire grate which, through the door, may be taken out for examination or replacement. Under the grate there is a metal ash box which can also be taken from the furnace easily for emptying. On the upper chamber there is a gas duct with a safety valve in case of dramatic increase of pressure in the furnace. Autothermal burning processes in the furnace take place with excess of oxygen and negative pressure. Air from the pressure fan through the air duct system is fed to under the fire grate, to the operating space of the combustion chamber, to the narrow spot between the chambers and to the operating space of the afterburner chamber. The chambers are rated and designed in such a way that at burning the time of presence of gases inside each chamber complies with the time of ideal displacement of gases from the zones: from 2 seconds and more. The distinguishing characteristic of the furnace is absence of accompanying (exterior) fuel for maintaining the burning process. Waste itself is the fuel and supply of excess oxygen (air) in a particular proportion to the above four levels of the furnace ensures stable burning temperature: in the combustion chamber it is 1200°С, in the afterburner chamber – 1250°С. Air feeding is controlled using six throttles: two – for preliminary adjustment, four – to control operational mode. The furnace as well as the whole complex is under permanent rarefaction performed with the smoke exhauster mounted in the smoke gas discharge plant. Temperature in the chambers is controlled visually using instruments receiving signals from thermocouples installed in the lower and upper chambers. The completed tests confirmed the preliminary estimates: from 100 to 120 kilograms of medical waste are incinerated in the furnace an hour. But it is not recommended to use medical waste for furnace firing due to their high calorie content and possibility to damage the fettling at sharp temperature increase. For furnace firing it is reasonable to use industrial wood residue: shavings, wood chips, saw timber cuttings are a gas cylinder with a portable sprayer. The completed tests demonstrated that with such firing the furnace achieves the operating mode in 2.5-3 hours at the first launch and in 1.5 hours maximum after a scheduled maintenance stop. The gas evaporation cooling plant in connected with the furnace with a fettled gas duct and cools hot gases using dispersed water from 1250°С to 250-280°С within 0.6 second. In the upper part of the plant there is a sprayer for feeding water with pressure 5.5-6 bars with consumption of about 280 liters/hour. Water is supplied from a tank with a pump with corresponding characteristics. Vapor generating at cooling together with gases goes into the purification system. Temperature of cooled gases after the gas evaporation cooling plant is also controlled visually using an instrument connected to a thermocouple. The gas purification system is located behind the evaporation cooling plant and includes a three-stage filter with replaceable cartridges made of special heat-resistance fabrics. The cartridges are round. Testing of industrial designs demonstrated that cyclone may be excluded from the complex due to absence of dust as such. The smoke gas discharge plant includes a fan functioning as a smoke exhauster and a smoke pipe 8 meters high. The fan should be operated with the temperature of incoming gases not exceeding 80°С. The temperature of outgoing gases at this point is measured with a thermocouple.
The estimated operation period of the complex is estimated as 3 years in case of continuous 24-hour operation.
In accordance with the tests a new modification of the complex was developed with new elements, namely: the gas evaporation cooling plant combined with a reserve water tank and feeding pump, the automated control system including automatic control of temperatures and percentage of oxygen in the afterburner chamber, and the system of two-branch outgoing gas purification ensuring continuous operation of the complex. The technology of industrial operation of the complex was determined: a specialized truck of Gazelle type with all metal universal cargo body delivers waste for burning in plastic 120-liter returnable containers to the production site. Waste in containers is in plastic bags. Maximum weight of a container with waste is 50 kg (maximum weight of waste – 40 kg). Containers are unloaded manually by two workers to a temporary storage area. A worker moves a container from the temporary storage area to the mechanism of lifting and unloading into the loading unit. Periodicity of loading is each 10-20 minutes (depending on calorific value of waste). The empty container is moved by a worker to a preliminary disinfection point where it is disinfected using the method of dispersed irrigation (100 grams of work solution per 1 m). At the preliminary disinfection point there is space for the technological equipment and a particular number of containers. After drying containers are moved and placed in an area for temporary storage of empty containers, from where they are loaded into an empty truck. This operation technology belongs to group of production processes 1c.
1 – two-chamber furnace, 2 – loading unit, 3 – evaporation cooling system, 4 – air supply system, 5 – outgoing gas temperature regulating fan, 6 – cartridge filter, 7 – smoke exhauster, 8 – smoke pipe.
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