A theoretical study on the mass input and output and energy of the biomedical waste incinerator

. Medical waste production has increased with many government and private hospitals and health centres due to the increase in the population, especially in the spread of Coronavirus Covid-19. This increase in medical waste is treating in medical incinerators. One of the advantages of incineration is the reduction of volume, weight and energy recovery. This paper examines the medical waste incinerator of one of the Medical City hospitals in Baghdad, as this incinerator internally divided into primary and secondary chambers. The medical waste for yellow bags placed in the primary chamber is burned with the help of air and a burner of 178-356 kW, resulting in waste burned. Then the combustion products pass through the secondary chamber, wherewith air and another burner of 178-356 kW, the combustion of gases and volatile materials from the waste completed. Air is then supplied to the flue gases to dilute the emission concentrations and reduce the flue gas temperature. This paper presents a study on the inputs and outputs of waste, air, fuel and the advantage of the heat quantity generated from the combustion of biomedical waste. As a result of this theoretical work, this incinerator provides an acceptable and durable solution to waste disposal problems and the risks of spreading viruses today.


Introduction
Medical waste has increased due to the increase in the population [1] [2], especially in the spread of Coronavirus Covid-19 as the quantities of waste increased due to the frequent use of protective clothing and for all people. In the incineration process, waste treated to reduce the volume of waste by about 90%, weight by about 70%, disinfection, energy recapture, detoxification, and resource recapture [3] [4][5] [6]. Incineration is a practically reliable method of waste treatment. It is currently the best treatment method at present, especially from the third month of 2020. Incinerators have proven the efficiency of their work and the rapid disposal of medical waste [7]. The advantages of incineration treating become clearer. Medical waste completely burned at high temperatures of 1200°C, and high temperatures must be under controlled to ensure complete combustion to reduce env health pollution. The results of waste incineration are

Medical waste incineration
There are three types of incinerators for treating biomedical waste: Controlled air, Rotary kiln [9], and Mobil incinerator [10].

Specifications of the medical waste incinerator
The incinerator used in this study is the airof yellow bags of medical waste with a capacity of 100 kg per hour, shown in fig  There are no air pollution control devices and no filter bags in the chimney.

Thermal processes inside a medical waste incinerator
The Medical Waste (MW) incineration process divided into: Drying. When the heat vaporizes, superficial water and inherent water in the combustion chamber, the drying stage divide to: conduction drying, convection drying and radiation drying achieved by heat transfer. Whereas the higher the water content of the MW, accompanied by longer the drying phase will be consumed more thermal energy, and the temperature will be reduced and subsequently affecting the burning process.
Decomposition and thermal volatilization of combustible materials in MW generates many volatile hydrocarbons and carbon capture products. The pyrolysis reaction consists of endothermic and exothermic reactions. The thermal decomposition speed is related to the combustible components' composition, heat and mass transfer rate, and the organic solids' particle size.
Combustion. Gaseous and solid combustible substances resulting from drying and thermal decomposition, insufficient contact with air in the incinerator become a flame and start combustion at high temperatures. Therefore, MW burning is a mixed gas-phase combustion process and heterogeneous combustion, which is more complex than gaseous fuels and liquid fuels [12].

Heat and Material Balance
Heat and material balance calculation is an integral part of designing and evaluating incinerators. This technique involves a detailed estimation of the input and output conditions of the incinerator and to determine the combustion air and auxiliary fuel requirements for incinerating a given medical waste and determining an existing incinerator's limitations when charged with a known waste [12] [13]. The characterization of biomedical waste is described extensively in [13]. The figure below (Fig 2) shows the different types of waste and the properties of hospitals biomedical waste in yellow bags. The steps to calculate the heat and material balance sample are presented below.

Heating values of input material
The material flow per hour into the incinerator is 100 kg/h. Based on an input waste, yellow bags waste is assumed to have the composition, according to the Table 1 and as shown in Figure 2 as well to consist of dry tissue, polyethylene, polyvinylchloride, cellulose, water, and ash represents 10, 45, 3, 30, 2, 10 kg/h respectively.

Determination of stoichiometric oxygen for combustible medical wastes and combustion air rates
The total theoretical amount of oxygen required to burn the waste determined by the chemical equilibrium equations of the biomedical waste's components from laboratory analysis, the theoretical oxygen to burn the medical waste's combustible component (100 kg/h). We can calculate the total requirements for the theoretical amount of oxygen required to burn (oxidize) the waste [3].

The shape of incinerator and biomedical waste
Higher heating values and total heat of the combustible medical waste total theoretical amount of oxygen required to burn the waste determined by the chemical equilibrium equations of the biomedical waste's components from laboratory analysis, the theoretical oxygen to burn the medical waste's combustible component (100 ). We can calculate the total requirements for the theoretical amount of oxygen a) Radiation losses = 5% (of the heat produced from the yellow waste bag burning +heat produce from 2 burners) [13]. Radiation Q ��� = 0.05 * 4278320 = 213916 b) Ash heat rate: here: ṁ� �� − mass of ash = 10 kg / h Cp − for ash = 0.831 kJ / kg º C ∆T − Temperature difference = (1200 Q̇� �� = 10 * 0.831 * 1180 = 9805.

Conclusion
The experiment calculates the heat, mass and energy from the incineration of medical waste using a double-stage diesel furnace and the effect of recovering the positive thermal energy generated from the incineration of the waste component. Could use the heat generated from waste burning to heating water that supplies the hospital; this system is more valuable with a large waste quantity. The theoretical calculations for an incinerator located in one of Baghdad hospitals, in the Medical City, and the temperatures were constant in the burning: 800°C-1200°C for the primary and secondary chamber. Our reading was depending on actual waste which daily collected from the hospital and diesel consumption.
The inputs and outputs of waste, air, and fuel studied were close to the standard range. The heat generated is compared to the energy produced by the burners in the combustion chambers the energy of medical waste. The result was a very small difference due to the amount of diesel fuel consumed for the burners or heat loss in the insolation area.
As per the experiment, medical waste incinerators are appropriate for treating waste, reducing its volume and weight, purifying it, and recovering useful energy.