Search Results (5)

The structure of large biomass circulating fluidized bed (BCFB) boilers is complex, and control schemes for coal-fired boilers cannot be simply applied to biomass boilers. Multivariable coupling and operational disturbances are also common issues. In this study, a state space model of a 130 t/h BCFB boiler was established under different operating conditions. Using the 100% operating point as an example, a model predictive controller was designed and tested under output disturbance and input disturbance conditions. The results show that the predictive control system designed in this study has a fast response speed and good stability. Full article

Soil contamination with heavy metals is one of the most important threats to the environment because they are easily incorporated into the food chain, threatening the health of plants, animals, and humans. In this study, the effectiveness of the introduced substances (compost and fly ash) was assessed in terms of its influence on the content of Cu and Zn in the soil, potential accumulation of these metals in the cultivated plants (camelina and oat), and thus in food products prepared from these plants. Therefore, the following indicators were used: bioconcentration factors calculated for the total amount (BCF_T) and bioavailable amount of metals (BCF_B) as well as gender-estimated daily intake (EDI) and health risk index (HRI). Regardless of gender, the EDI values ranged from 0.31 µg·kg⁻¹ to 0.49 µg·kg⁻¹ for Cu and from 0.9 µg·kg⁻¹ to 1.8 µg·kg⁻¹ for Zn in oat. For camelina, the calculated values were as follows: 4.1–8.5 µg·kg⁻¹ for Cu and 7.1–12.1 µg·kg⁻¹ for Zn. The HRI values were very low (in general 0.03–0.2), indicating no health risk connected with potential consumption of oat or camelina food products. The amounts of Cu and Zn in the crops grown on the soil amended with compost or fly ash were significantly lower (by 21–37% for oat and 14–34% for camelina) compared to the content of these metals in the control plants. Moreover, the levels of bioavailable metals decreased in soil as a result of the applied immobilizing agents. The study showed that the immobilization efficiency of compost and fly ash was comparable, and therefore the choice of either of these substances for the chemical remediation of soil contaminated with heavy metals is justified. Full article

A four-year research study was conducted on aquatic plants (reed canary grass) growing in the beds of three rivers and their tributaries in Lower Silesia, Poland. Metal contents (Cu, Cd, Ni, Pb, Zn, Fe, Mn) were determined in plant samples, metal accumulation in water (BCF_w) and sediment (BCF_B), Metal Pollution Index (MPI) and Enrichment Factor (EF) were calculated. The highest contents of copper, lead, nickel and cadmium were found in reed canary grass sampled from the Nysa Szalona River. The highest values were recorded for zinc in the Bystrzyca River, and for iron and manganese in the Strzegomka River. The series of metals were as follows: Nysa Szalona and Strzegomka: Cd < Ni < Pb < Cu < Zn < Mn < Fe, Bystrzyca: Cd < Ni < Cu < Pb < Zn < Mn < Fe. Throughout the study period, the lowest values of metals in plants were recorded in 2015 and 2018, and the highest in 2017. The general picture of MPI in aquatic plants is arranged in the series Bystrzyca < Strzegomka < Nysa Szalona. These values classify the studied material at a high level of pollution in all rivers. In the comparison of the two extreme sites, i.e., source–mouth, higher values were found at the mouth of the reservoir, which suggests that metals move with the water current and accumulate more with the direction of the river flow, which is most likely a consequence of the influence of the catchment area as the source of metals. The series of EF enrichment factor values were as follows: Bystrzyca—Ni < Cd < Fe < Cu < Zn < Mn < Pb, Nysa Szalona—Ni < Fe < Zn < Cd < Mn < Cu < Pb, Strzegomka—Ni < Cd < Fe < Zn < Cu < Pb < Mn. For all the samples studied, the values found in spring were much higher than in autumn, which indicates the great importance for research in that area. The levels of copper and iron were within the range of moderate values, lead and manganese reached very high and exceptionally high values, and the remaining metals were within the values described as significant. Bioaccumulation of metals determined relative to bottom sediments was highest in 2017 and lowest in 2018, while bioaccumulation relative to water was highest in 2018 and lowest in 2016. The four-year study found that the metal content in reed canary grass was mostly within the range of mean values presented in the literature from moderately polluted areas. Also, no significant deviation was found from levels that have been recorded for the same rivers for more than two decades. Full article

This study aimed to determine aluminum levels in reed canary grass Phalaris arundinacea L.) in rivers in southwestern Poland—Bystrzyca, Strzegomka, and Nysa Szalona, together with their tributaries. The samples were collected in spring and autumn 2015–2018. The highest amounts of aluminum were recorded in the Nysa Szalona, and the lowest in the Bystrzyca. During the four-year cycle of studies, the highest values were recorded in the last year, and the lowest in the first year. The highest amounts of aluminum were found in all three rivers in the lowland tributaries. In the main rivers, higher amounts of aluminum were found at the mouth of the Nysa Szalona and Strzegomka reservoirs, while the opposite situation was found for the Bystrzyca. Higher aluminum contents were recorded in autumn than in spring, and the values of BCF_W (aluminum bioaccumulation factor in relation to water) and BCF_B (aluminum bioaccumulation factor in relation to bottom sediments) coefficients were also higher. The MPI (metal pollution index) was arranged in a series: Bystrzyca < Strzegomka < Nysa Szalona, while the degree of pollution was high for Bystrzyca and very high for the other two rivers. The variability in Al levels may be attributed to pollution level in the catchments, but also to successive modernization works carried out in the beds of the main rivers and their tributaries. All these works were carried out in a variable way and often covered only a fragment of the riverbed; therefore, the consequences of activity may have been visible in the catchment but not necessarily in the same vegetation cycles. Full article

In general, the biomass raw materials burned by biomass power plants generally have the characteristics of variable fuel types, high moisture content, and high volatile content. In this paper, a 130 t/h biomass circulating fluidized bed (BCFB) model was established on the MWorks platform with Modelica language. The influence of biomass type changes on operation parameters, the corresponding steady-state characteristics, and the dynamic characteristics of the BCFB were carried out. The temperature corresponding to the combustion of pine was overall higher than that of the other fuels, and the flue gas from the combustion of pine had the highest concentration of SO₂, up to 520.49 mg/Nm³. The flue gas from the combustion of pure cotton sticks had the highest concentration of NO, up to 254.34 mg/Nm³. The changes of fuel type and moisture content all have a great influence on the operation of BCFBs. The emission of pollutants was not only related to the element content of fuel, but also closely related to the furnace temperature. The fuel moisture content also indirectly affects the pollutant emission concentration and the steam-water system. Full article