A module for thermal processing of solid domestic waste with a productivity of 2 t / y of garbage with deep thermal treatment of combustion products on the basis of a rotary kiln

The solid domestic waste of only the urban population of Ukraine is 40 million m 3 per year (or 10 million tons). To the total amount of waste in each city should add another 20-30% of industrial waste, which can also be disposed of by burning.
A number of schemes adopted in the USA, Germany and France for the burning of domestic solid waste are not suitable due to the following circumstances: garbage in Ukraine has a significantly lower net calorific value than in developed countries – 900-1300 kcal / kg compared to 2200 – 2600 kcal / kg (for example, in the USA).

This is explained by:

  • a smaller share of packaging (cardboard, etc.);
  • a bigger share of food waste (up to 30-40% compared with 10-20 in developed countries, where part of the food waste is ground and goes into the sewage;

For the burning of such substances as soot, with benzopyrene adsorbed on it, dioxins, etc. Required temperatures above 1200 C and time of stay in the zone of such temperatures for at least 2 seconds.
Since such parameters are practically impossible to do when combustion of low-calorie garbage without combustion of large amounts of additional fuel, it is supposed to develop and apply as a module a rotary kiln based on a standard rotary kiln produced by the Progress plant (Berdichev, Ukraine).
The oven has a diameter of 2.2 m and lined with a chamotte brick thickness of 230 mm. The length of the furnace is assumed to be 10 m (in the presence of pre-cleaning in boilers), and 18 m in its absence, the speed of the furnace to 1 rpm, the angle of the furnace – 3?.
From the end of the furnace there is a gas-fired burner, which operates only during the period of fire of the furnace and automatically unlocks when the temperature in the furnace is higher than 1200 oC.
The project provides an original system of thermal after-treatment of gases. According to the project, the incineration complex is being built on the territory of existing district boiler houses. In this case, there is no need in the construction of a heat recovery system, the construction of a chimney and a number of other nodes.

The advantages of a rotary kiln are:

  • at higher temperatures than in chamber furnaces of incinerator boilers. If the last temperatures are within 800-980 oC, then the rotary kiln has 4 zones – low-temperature input (at a length of 2-2.5 m), a melting zone (900 oC, 2-2.5 m), a combustion zone (1100-1200 oC , 4-5 m) and the outlet zone (1500-1600 oC, 7-8 m);
  • availability of the system of thermal after-treatment of gases;
  • no need for high buildings to accommodate the furnace itself;
  • the ability to quickly replace the lining and elements of the furnace during repairs.

Under this scheme, combustion products of the incinerator are mixed in the amount of 10-20% to the boiling air supplied to the combustion boiler of an existing boiler and are involved in the combustion process as part of the oxidant of fuel.
In this case, sufficient time for the combustion products in the high temperature zone 1500-1600 ° C and the complete decomposition and oxidation of dioxins, furans, carcinogenic substances to CO2 and H2O is provided. Such a scheme gives grounds for using the heat from the exhaust gases of the furnace for heating the combustion air, and an increase in the ballast in the oxidant reduces the formation of nitrogen oxides by 40-50% in the furnaces of the boilers, and thus reduces the toxicity of the exhaust gases of the boiler-house.
This scheme is experimentally tested on a waste incinerator, some of its units have been tested for long-term use.
The system of gas purification of inorganic compounds consists of three stages. At the first stage – the initial zone of the furnace. At the second stage (scrubbing), catching most of the solids and organic acids, nitrogen dioxide, hydrochloric acid and sulfur compounds through the irrigation of alkaline water by cooling the slag is carried out. At the third stage, an electrofilter with a degree of purification of 99.9% is used, which purifies emissions from ash particles and other solid particles, including finely divided The total expected slag output will be about 600 kg / h.
The solid residue – slag and ash are used in road construction and only a small amount in case of deterioration of quality, enters the oven gasket.
Advantages of this scheme:

  • Opportunities for reducing especially low-calorific, tall-like waste, characteristic of developing countries.
  • Ability to reduce the cost of building the system due to the fact that virtually all units are manufactured in Ukraine, where due to low wages, the cost is reduced by 1.5-2 times.