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Development of Deformable Calcium Carbonate for High Filler Paper.

ABSTRACT: Controlling the size and rigidity of calcium carbonate became possible. HCCs were developed and manufactured by the in situ reaction of carbon dioxide and calcium oxide, which were already preflocculated together with GCC using ionic polymers before the reaction. HCC is deformable under pressure during the papermaking process, and its degree of rigidity can be controlled by adjusting the fraction of calcium oxide. The size of HCC can be further controlled by adjusting shearing force. The more the fraction of calcium oxide, the more rigid the HCC and the smaller the diameter of the HCC. When used in papermaking, HCC increased the tensile strength and bulk of paper simultaneously without lowering other essential paper properties, and its deformable nature under pressure improved paper smoothness. Saving chemical pulp by 10% by replacing it with HCC, which is 3–4 times less expensive than the chemical pulp, was demonstrated successfully without lowering the essential properties of paper. Implementation of HCC in the paper mill may result in saving chemical pulp, drying energy, and production cost. The paper mill may utilize the carbon dioxide from the mill stack after purification for HCC preparation.

SUBMITTER: Kang DS

PROVIDER: S-EPMC7331051 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Project description:Simple plugging of the high-permeability "thief zones" of oil reservoirs is the most plausible and also the most straightforwardly achievable approach to enhance sweep efficiency and oil recovery. Sporosarcina pasteurii is a representative microorganism with the ability to precipitate calcium carbonate (CaCO3) via enzymatic hydrolysis of urea in the presence of calcium ions. Microbially induced calcium carbonate precipitation (MICP) can cement and seal the granular and fractured media and thus can be used as a potential microbial plugging agent for the high-permeability zones of oil reservoirs. The following investigated the microscopic characteristics of MICP plugging and its efficacy in permeability reduction. The columns of near-spherical silica sand and angular silica sand with three separate granularities (40/60, 60/80, and 80/120 mesh) were used as artificial rock cores representing distinct pore sizes and pore characteristics to investigate the efficacy and microprocess of MICP plugging with different biotreatment periods. The results indicated that permeability is reduced significantly after only short periods of biotreatment. After eight cycles of MICP treatments, the permeability for each type of cores dropped by 54-90% of individual initial permeabilities. The measured CaCO3 content indicated that the decreasing rate in permeability with the increasing CaCO3 content experiences three contrasting stages, namely, slow decline, speedy decline, and plateauing. X-ray diffraction indicated that most of the generated CaCO3 crystals occur as vaterite with only a small amount of calcite. Imaging by scanning electron microscopy further revealed the microprocess of MICP plugging. Microorganisms first concentrate on the pore wall to secrete CaCO3, forming a thin and large uniform layer of CaCO3. Then, some nucleation sites of CaCO3 crystals will experience further preferential growth, resulting in large, dominant crystals that act as a plugging agent within the pore space. Compared to extracellular polymeric substances, which are currently the primary microbial plugging agent used to enhance sweep efficiency of oil reservoirs, bio-CaCO3 appears more effective in plugging in terms of its morphology, size, and growth characteristics.

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Development of Deformable Calcium Carbonate for High Filler Paper.

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