Qiangqiang Ren

NOx and N2O Precursors from Biomass Pyrolysis: Nitrogen Transformation from Amino Acid

Large quantities of NO(x) and N(2)O emissions can be produced from biomass burning. Understanding nitrogen behavior during biomass pyrolysis is crucial. Nitrogen in biomass is mainly in forms of proteins (amino acids). Phenylalanine, aspartic acid, and glutamic acid were used as the model compounds for the nitrogen in biomass. Release behavior tests of nitrogen species from the three amino acids during pyrolysis in argon and gasification with O(2) and CO(2) were performed using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer. The results indicate that although the influence of oxygen and CO(2) in the atmosphere on nitrogen behavior is different for the amino acids, it is interesting to find some phenomenon in common. The presence of oxygen promotes NO and HNCO formation for all the three amino acids; HCN and HNCO formation are suppressed by introduced CO(2) for all the three amino acids. This can reveal the N-conversion mechanism from biomass in depth under the same conditions.

TG-FTIR study on co-pyrolysis of municipal solid waste with biomass.

Co-pyrolysis of cotton stalk, a representative agricultural biomass in China, mixed with municipal solid waste (MSW) with high ash content and low calorific value was carried out using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer in Ar atmosphere. Pyrolysis characteristic and pollutant emission performance from MSW and stalk blends at different mass proportions were studied. The results show that as the mass proportion of stalk added increases, the total weight loss of the blend during pyrolysis increases. The addition of stalk has substantial effects on the N-selectivity to HCN, NH(3) and HNCO. In the presence of stalk, lower concentrations of HCl are detected.

Feasibility of CO2/SO2 uptake enhancement of calcined limestone modified with rice husk ash during pressurized carbonation

The calcination/carbonation cycle using calcium-based sorbents appears to be a viable method for carbon dioxide (CO₂) capture from combustion gases. Recent attempts to improve the CO₂/SO₂ uptake of a calcium-based sorbent modified by using rice husk ash (RHA) in the hydration process have succeeded in enhancing its effectiveness. The optimal mole ratio of RHA to calcined limestone (M(Si/Ca)) was adjusted to 0.2. The cyclic CO₂ capture characteristics and the SO₂ uptake activity of the modified sorbent were evaluated in a calcination/pressurized carbonation reactor system. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) spectrum of the sorbent were also taken to supplement the study. The results showed that the carbonation conversion was greatly increased for the sorbent with M(Si/Ca) ratio of 0.2. For this sorbent formulation the optimal operating conditions were 700-750 °C and 0.5-0.7 MPa. CO₂ absorption was not proportional to CO₂ concentration in the carbonation atmosphere, but was directly related to reaction time. The CO₂ uptake decreased in the presence of SO₂. SO₂ uptake increased, and the total calcium utilization was maintained over multiple cycles. Analysis has shown that the silicate component is evenly or well distributed, and this serves as a framework to prevent sintering, thus preserving the available microstructure for reaction. The sorbent also displayed high activity to SO₂ absorption and could be used to capture CO₂ and SO₂ simultaneously.

NOx and N2O Precursors from Co-pyrolysis of biomass and sludge

Biomass is an effective substitute for fossil fuels and has a substantial impact on CO2 reduction. Meanwhile, alkali metal-related problem is a major barrier in biomass combustion. Sludge is a waste with low heating value, high water, sulfur, and nitrogen contents, as well as high phosphorus content, which makes the sludge a potential choice to inhibit the alkali metal-related problems during biomass combustion. The nitrogen behavior and the emissions of NOx and N2O are one of the key problems when sewage sludge is co-fired with biomass. Thus, nitrogen transformation during co-pyrolysis of cotton stalk and sludge at different heating rates were studied. The results show that HCN and HNCO are the major nitrogen-containing species for petrochemical sludge. The addition of petrochemical sludge changes the path of the conversion of fuel nitrogen and the presence of cotton stalk in the mixture promotes NH3 and HCN formation.

NOx and N2O Precursors from Biomass Pyrolysis: Role of Cellulose, Hemicellulose and Lignin

Cellulose, hemicellulose, and lignin play important roles in biomass. Nitrogen in biomass is mainly in forms of proteins (amino acids). Two amino acids, proline and glutamic acid, with different structures were selected as the nitrogen-containing model compound in biomass. Interaction between the two amino acids with cellulose, hemicelluloses, or lignin at different weight ratios was investigated to understand nitrogen chemistry. Considering the composition of wood and agricultural straw, proline and the mixture of cellulose, hemicellulose, and lignin were pyrolyzed under the same condition. Nitrogen transformation during copyrolysis of amino acid with the component at different ratios was identified to determine the role of cellulose, hemicellulose, and lignin. The emissions of HCN and NH3 were detected with a Fourier transform infrared (FTIR) spectrometer. The results indicate that although the structure of the amino acid has a significant effect on the nitrogen transformation during pyrolysis, it is interesting to find some characteristics in common for the aliphatic amino acid and heterocyclic amino acid. The effects of hemicellulose on NH3 formation from the two amino acids are similar, hemicellulose inhibits N-NH3 conversion and lignin promotes NH3 formation for the two amino acids.

NO formation during agricultural straw combustion

NO formation during combustion of four typical kinds of straw (wheat straw, rice straw, cotton stalk and corn stalk) which belong to soft straw and hard straw was studied in a tubular quartz fixed bed reactor under conditions relevant to grate boiler combustion. Regarding the real situation in biomass fired power plants in China, NO formation from blended straw combustion was also investigated. Nitrogen transfer during blended straw pyrolysis was performed using a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer. The results show that NO conversion for the four straws during combustion is distinctive. Over 70% fuel-N converts into NO for cotton stalk, while only 37% for wheat straw under the same condition. When wheat straw and cotton stalk were mixed, N-NO conversion increases. The limestone addition promotes NO emission during cotton stalk combustion. The presence of SO(2) in atmosphere suppresses NO formation from straw combustion.

NOx and N2O precursors from biomass pyrolysis

Chlorine content in agricultural straw is high, and HCl formation during straw combustion is a challenging problem. The relationship between HCl and the formation of NOx and N2O is important and unclear. Effect of HCl in atmosphere on nitrogen transfer during wheat straw and cotton stalk pyrolysis was performed using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Pyrolysis of polyvinyl chloride supplies HCl. The pathway of nitrogen transfer in the presence of HCl was studied. The results show that in the presence of HCl, the temperature corresponding to NH3 starting release during wheat straw pyrolysis increases, and those of HCN and HNCO reduce. HCl inhibits the conversion of straw–N into NH3, however, favors the transformation of straw nitrogen into HCN and HNCO.

NOx and N2O precursors from biomass pyrolysis Effect of chlorine

Chlorine content in agricultural straw is high, and HCl formation during straw combustion is a challenging problem. The relationship between HCl and the formation of NOx and N2O is important and unclear. Effect of HCl in atmosphere on nitrogen transfer during wheat straw and cotton stalk pyrolysis was performed using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Pyrolysis of polyvinyl chloride supplies HCl. The pathway of nitrogen transfer in the presence of HCl was studied. The results show that in the presence of HCl, the temperature corresponding to NH3 starting release during wheat straw pyrolysis increases, and those of HCN and HNCO reduce. HCl inhibits the conversion of straw–N into NH3, however, favors the transformation of straw nitrogen into HCN and HNCO.

Pollutant Emission and Ash Characteristics during Co-combustion of Municipal Solid Waste and Corn Stalk

Abstract Co-combustion performance of blends of municipal solid waste with high ash content and low calorific value and corn stalk was investigated using a thermogravimetric analyzer coupled with a Fourier transform infrared spectroscopy. Ignition temperature, emissions of major gaseous pollutants, and the ash characterization were studied. The ashes of the blends were characterized with Fourier transform infrared, X-ray diffraction, and a nitrogen adsorption analyzer. The results show that SO2 and NO emission from the blends are a little higher than that from municipal solid waste. X-ray diffraction results indicate that the reaction between calcium in corn stalk and chlorine to form CaCl2 results in an HCl reduction from co-combustion. The higher surface area and pore volume of ash shows that the blends undergo complete combustion.

NO x and N 2 O precursors from biomass pyrolysis

Chlorine content in agricultural straw is high, and HCl formation during straw combustion is a challenging problem. The relationship between HCl and the formation of NOx and N2O is important and unclear. Effect of HCl in atmosphere on nitrogen transfer during wheat straw and cotton stalk pyrolysis was performed using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Pyrolysis of polyvinyl chloride supplies HCl. The pathway of nitrogen transfer in the presence of HCl was studied. The results show that in the presence of HCl, the temperature corresponding to NH3 starting release during wheat straw pyrolysis increases, and those of HCN and HNCO reduce. HCl inhibits the conversion of straw–N into NH3, however, favors the transformation of straw nitrogen into HCN and HNCO.