Waste Gypsum Board and Ash-Related Problems during Combustion of Biomass. 1. Fluidized Bed

Abstract

This paper is the first in a series of two describing the use of waste gypsum boards as an additive during combustion of biomass. This paper focuses on experiments performed in a bench-scale bubbling fluidized-bed reactor (5 kW). Three biomass fuels were used, i.e., wheat straw (WS), reed canary grass (RC), and spruce bark (SB), with and without addition of shredded waste gypsum board (SWGB). The objective of this work was to determine the effect of SWGB addition on biomass ash transformation reactions during fluidized bed combustion. The combustion was carried out in a bed of quartz sand at 800 or 700°C for 8 h. After the combustion stage, a controlled fluidized−bed agglomeration test was carried out to determine the defluidization temperature. During combustion experiments, outlet gas composition was continuously measured by means of Fourier transform infrared spectroscopy. At the same place in the flue gas channel, particulate matter was collected with a 13-stage Dekati low-pressure impactor. Bottom and cyclone fly ash samples were collected after the combustion tests. In addition, during the combustion tests a 6-h deposit sample was collected with an air-cooled (430°C) probe. All ash samples were analyzed by means of scanning electron microscopy combined with energy dispersive X-ray spectrometry for elemental composition and with X-ray powder diffraction for the detection of crystalline phases. Decomposition of CaSO 4 originating from SWGB was mainly observed during combustion of reed canary grass at 800°C. The decomposition was observed as doubled SO 2 emissions. No significant increase of SO 2 during combustion of SB and WS was observed. However, the interaction of SWGB particles with WS and SB ash forming matter, mainly potassium containing compounds, led to the formation of K 2 Ca 2 (SO 4 ) 3 .

Waste Gypsum Board and Ash-Related Problems during Combustion of Biomass. 2. Fixed Bed

“…In the previous paper in this series, interactions between SWGB and the formed ash was seen, and it was furthermore concluded that SWGB can be used as an additive against operational problems during combustion of phosphorus-poor biomass in a fluidized bed . The conditions in the fluidized bed used in that study were mainly oxidizing, and the temperature is very stable which may impair the decomposition of SWGB.…”

“…The fixed bed combustion experiments in small and large scale both show a statistically significant increase in SO 2 of 100% or more with addition of SWGB. In the previous study using a bubbling fluidized bed (BFB), SWGB addition to RG showed a statistically uncertain increase in SO 2 whereas little or no effect on SO 2 could be observed for WS and SB. The fuel blends used in the BFB experiments contained more SWGB for RG (2 wt %) and WS (2 and 3 wt %); and a similar level for SB (1 wt %) than the fuel blends used in the fixed bed experiments.…”

“…The slag formation on grates and in burners has been shown to be related to the composition of the ingoing fuel ash and explained as the result of alkali-silicate melt formation. − , Therefore, silicon rich fuels with formation of alkali-silicates dominating the ash transformation reactions, like RG or WS, show high slagging tendencies . The levels of Ca and S added as SWGB to the reed canary grass (RG), wheat straw (WS), and spruce bark (SB) are based on thermodynamic equilibrium calculations performed for the first paper in this series and are presented in Table . The SWGB was sieved to a particle size of ∼0.85–1.4 mm and distributed onto the grate using a separate feeder (see section below) during combustion.…”

“…This is the second paper of two that investigates the use of shredded waste gypsum board (SWGB) as a fuel additive to prevent high temperature corrosion and slag formation during combustion of biomass. The first part studied the use of SWGB as an additive during combustion of phosphorus-poor biomass fuels in a bubbling fluidized bed . In this follow-up paper, the properties and behavior of SWGB will be discussed when used as an additive in two different kinds of fixed bed combustion appliances; a residential pellet burner and a large scale grate fired boiler.…”

Synthesis of Activated Carbon from Citric Acid Residue by Phosphoric Acid Activation for the Removal of Chemical Oxygen Demand from Sugar-Containing Wastewater

“…Phone: +86-10-68984448; Fax: +86-10-68984448; E-mail: yaoxiaolong@btbu.edu.cn Citric acid residue (CAR) is a typical by-product in the process of citric acid production. Over 2 million tons of CAR are produced in China each year (Ma et al, 2017) and mainly treated through preparation of building materials as the additives or production of feed (Mironiuk et al, 2012;Piotrowska et al, 2015;Juliastuti et al, 2017). Nevertheless, AC has seldom been fabricated based on CAR (CAR-AC).…”