Limestone Sludge Research Articles

A Study on the Desulfurization Efficiency of Limestone Sludge with Various Admixtures

The flue gas desulfurization (FGD) process is one of the most effective methods to reduce the amount of SO₂ gas (up to 90%) generated by the use of fossil fuel. Limestone is usually used as a desulfurizing agent in the wet-type FGD process; however, the limestone reserves of domestic mines have become exhausted. In this study, limestone sludge produced from the steel works process is used as a desulfurizing agent. Seven different types of additives are also used to improve the efficiency of the desulfurization process. As a result, alkaline additive is identified as the least effective additive, while certain types of organic acids show higher efficiency. It is also observed that the amount of FGD gypsum, which is a by-product of the FGD process, increases with the used of some of those additives.

Hydration characteristics of cement for co‐sintered from washed‐fly ash and waste sludge

The purpose of this study is to co‐sinter washed‐fly ash, limestone sludge, stone sludge, and iron‐oxide sludge to fabricate 4 types of eco‐cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form the eco‐cement clinkers, all of which met the toxicity characteristic leaching procedure requirements. The results show that the major components of ordinary Portland cement (OPC), C3S, C2S, C3A, and C4AF, were present in the eco‐cement clinkers. The compressive strength development indicated that the EcoA pastes were similar to those of commercial OPC products. The compressive strength in the EcoG pastes decreased because of the amount the α‐C2S increased. The mercury intrusion porosimetry results showed that the pore volume in the pastes gradually decreased when the curing time increased. Additionally, from the X‐ray diffraction results, all the eco‐cements produced Ca(OH)2 during hydration, which also increased with curing age. The scanning electron microscopy images of OPC and EcoA pastes showed that the pore volume decreased and the denser structural increased with the curing time increased. In addition, adding higher amounts of 1% washed‐fly ash caused to increase the content of α‐C2S. The result show that this co‐sintered process from 1% washed‐fly ash and 99% waste sludge (77% limestone sludge, 19.51% stone sludge and 2.49% iron‐oxide sludge) to produce eco‐cement with excellent mechanical characteristics. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 964–972, 2015

제철 산업부산물인 석회석 슬러지의 배연탈황 공정 적용에 관한 연구

The flue gas desulfurization (FGD) process is currently the most effective process utilized to remove sulfur dioxide from stack gases of coal-fired plants. However, FGD systems use a lot of limestone as desulfurizing agent. In this study, we use limestone sludge, which is a by-product of the steel industry, to replace the desulfurizing agent of the FGD system. The limestone particle size is found to be unrelated to the desulfurizing rate; the gypsum purity, however, is related. Limestone sludge mixes with limestone slurry delivered at a constant rate in a desulfurizing agent with organic acid are expected to lead to a high desulfurization efficiency and high quality byproduct (gypsum).

Limestone Sludge in the Brick Body

Influence of limestone sludge (generated during the washing process of limestone crushed aggregates) with high content of CaO in the form of calcite on the properties of brick body made from non-calcareous sludge (from the washing process of quartz sand) as a basic plastic brick clay was determined. Presence of calcite very distinctly influenced the firing process and properties of fired body. Limestone sludge decreases firing shrinkage, bulk density and coefficient of thermal conductivity of the brick body after the firing in the range of 850 – 950 °C. Higher modulus of rupture and water absorption is typical for fired bodies with limestone sludge addition. Most of these improvement are caused by the formation of anorthite only in the bodies based on the limestone sludge.

Fornecimento de cálcio para plantas de eucalyptus saligna por meio de aplicação de resíduo industrial lama de cal

O resíduo industrial lama de cal, originado da produção de papel kraft branqueada de eucalipto, apresenta em sua composição quantidade considerável de cálcio (Ca), o que pode contribuir para reduzir o consumo de fertilizantes em plantios florestais. Com o objetivo de avaliar o efeito da lama de cal como fonte de Ca e seus efeitos sobre a disponibilidade de nutrientes e produção de matéria seca da parte aérea de plantas de eucalipto, foram conduzidos dois ensaios em vasos, em casa de vegetação, na área de pesquisa da Klabin Florestal do Paraná. Os solos utilizados foram um Neossolo Quartzarênico órtico (RQo) e um Nitossolo Vermelho eutroférrico (NV). Os tratamentos constituíram-se de duas fontes de Ca, calcário dolomítico e lama de cal, e de uma testemunha, sendo identificados como: RQo testemunha, RQo calcário e RQo lama de cal; e NV testemunha, NV calcário e NV lama de cal. O delineamento experimental utilizado foi inteiramente casualizado, com quatro repetições. Para tanto, plantas de Eucalyptus saligna foram mantidas por 126 dias em vasos. Quantificou-se a produção de matéria seca e realizaram-se as análises de folhas e dos solos, por ocasião da coleta das plantas. Os dados revelaram que tanto a adição de calcário dolomítico quanto a lama de cal promoveram o fornecimento de Ca para as plantas de eucalipto, proporcionando aumentos na produção de matéria seca. Os teores de Ca e Na nas folhas de eucalipto foram acrescidos com a adição do resíduo ao solo, em comparação com o tratamento com calcário dolomítico, enquanto os teores de N, P, K e S foram semelhantes. As plantas cultivadas nos tratamentos RQo testemunha e RQo lama de cal apresentaram teores foliares de Mg abaixo da faixa considerada adequada. A adição de lama no solo elevou o pH e as concentrações de Ca e de Na, reduziu o Al trocável e não influenciou na disponibilidade de Mg, fato que pode proporcionar deficiência de Mg às plantas, em solos com baixos níveis desse nutriente, conforme observado neste estudo.

Full-Scale Removal of Arsenate and Chromate from Water Using a Limestone and Ochreous Sludge Mixture as a Low-Cost Sorbent Material

The oxyanions arsenate (AsO4(3-)) and chromate (CrO4(2-)) are major freshwater contaminants. Arsenate is a problematic contaminant in drinking water reservoirs, and chromate limits the use of urban stormwater runoff. High-capacity, low-cost, energy-efficient treatment technologies are required for the removal of these toxic anions from freshwater sources. Using a 50-m-long dual porosity filter, with limestone as filtering grains, treating stormwater runoff from Copenhagen, Denmark, we tested if addition of the waste product ochreous sludge can improve the removal of arsenate (As) and chromate (Cr) without compromising the calcite's removal affinity fowards metallic cations. Upon on-site embedding of the ochreous sludge, removal of arsenic and chromium was improved greatly, and copper (Cu) removal remained high. Steady-state effluent concentrations were reduced from 31 to 2 microg As/L, 127 to 1.5 microg Cr/L, and 18 to 9.6 microg Cu/L upon mixing with the ochreous sludge. Limestone-ochreous sludge represents a promising low-cost oxyanion and cation sorbent operating at neutral pH without pH control.

EVALUATION OF SLUDGE PRODUCED BY LIMESTONE NEUTRALIZATION OF AMD AT THE FRIENDSHIP HILL NATIONAL HISTORIC SITE

A pulsed limestone bed (PLB) treatment plant for remediation of acid mine drainage (AMD) has been tested at the Friendship Hill National Historic site in southwestern Pennsylvania. The plant performed well, neutralizing over 50 metric tons of acidity over a 14-month period, but the cost of disposal of the 450 metric tons of sludge generated was high, because the sludge was hauled from the site and disposed of in a commercial landfill to minimize the impact on park property. Although the sludge was found to be non-hazardous based on the Toxicity Characteristics Leaching Protocol (TCLP), hauling and disposal costs were still elevated, at $40 per m 3 . Since sludge handling and disposal was a significant fraction of the operating cost of the facility, a study of the sludge characteristics and possible alternate handling methods was undertaken. Samples of AMD influent, treated water and settled sludge were used in a series of small- scale treatment studies. These tests showed that the sludge volume produced by limestone neutralization was less than half of that for lime, sodium hydroxide or ammonia. The settling rate was also greater for the limestone-based sludge. Vacuum filtration tests demonstrated that the limestone sludge was more readily filtered than sludges generated with sodium hydroxide or lime and that solids contents of up to 28% could be achieved. Because of lower maintenance costs, pressure filtration using a plate and frame filter is recommended for future plant operations. In this case, solids contents of as high as 31% were realized. As an alternative to the operating costs of mechanical filtration, a settling/percolation process was tested. Percolation tests showed that solids content of the settled sludge could be increased from 8% to 25%. These results show that sludge disposal costs for the treatment plant could be decreased through installation of a settling or filtration process. Moreover, the PLB process offers saving not only in reagent costs, but also in sludge disposal costs, through decreased sludge volume generated, rapid settling rates and ready filterability.

Systematic Investigation of the Compositional Variations in Solid Waste Products from Coal Combustion: ABSTRACT

A systematic study of the chemical and physical characteristics of feed coal, fly ash, bottom ash, feed limestone, and flue gas desulfurization sludge has been initiated at a Kentucky power plant. Two units at the power plant are sampled monthly for a two-year period. One unit bums a high-sulfur coal (3 wt % total S); the other unit burns a low-sulfur coal (<1 wt % total S). One focus of the study is to evaluate the variability in feed coal compositions and resulting variability in the composition of combustion solids. Major, minor, and trace element composition and mineralogy are determined on most samples. In addition, modes of occurrence, magnetic properties, stable and radiogenic isotopic composition, organic chemistry, and leachability under different conditions are determined on selected samples. Mass balance calculations show that most elements (data for Hg are not available) are retained in the solid waste products except for Se. The ratios of trace elements in the fly ash to bottom ash for both units are very similar to the order of element volatility reported in the literature. Ni, Cr, and Co show substantial enrichment in the magnetic fraction of the fly ash from the low-sulfur unit. Laboratory leaching ofmore » the fly ash and bottom ash shows that the magnetic particles are very rapidly dissolved by mild acids. Fission track results indicate that U is uniformly distributed within some fly ash cenospheres. Dark, iron-rich glass may have higher concentrations of U than does clear glass. The distribution of As appears to be uniform at low levels in most fly ash particles.« less

Numbers of iron‐oxidizing bacteria and oxidation potential of sulfur and iron components in coal refuse amended with limestone and sewage sludge

Abstract Counts of acidophilic iron‐oxidizing bacteria, ratios of S2O3=—S/SO4=—S and Fe+3/Fe+2, and S2O3=—S oxidation potentials were examined over a two‐year period in coal refuse (acid gob) treated with limestone and/or sewage sludge. A non‐amended treatment was used as a control. No significant difference in population counts of acidophilic iron‐oxidizing bacteria were observed between treatments in either year of the study. S2O3=—S/SO4=—S and Fe+3/Fe+2 ratios indicated active sulfur and iron oxidation suggesting that limestone and/or sewage sludge may be ineffective in suppressing pyrite oxidation. Under optimal conditions, S2O3=—S oxidation potentials (in vitro) showed a logarithmic increase in SO4=—S formation for all four treatments over time. The final pH of the treatments following twenty days of perfusion ranged from 3.06 to 3.59.