Mathematical Tool Based on Breakthrough Curves to Evaluate the Economic Advantages of Chemical Regeneration of Activated Carbon in Power Plants: A Comparative Study

Abstract

A mathematical tool has been developed to evaluate the economic advantages of in-situ chemical regeneration of fixed-bed industrial adsorbers of granular activated carbon for cooling water treatment systems in Cuban power plants. Two scenarios of activated carbon (AC) management in a power plant were compared by applying the proposed model. The economic profit by implementing the regeneration strategy as a function of the number of regeneration cycles was determined and optimized. Breakthrough curves were obtained to assess the adsorption performance of the AC after progressive saturation–chemical regeneration cycles using synthetic water and hydrochloric acid, respectively. For the first saturation cycle, the breakthrough time was 272 min and after 10 cycles, it was reduced to 58 min, indicating a decrease of the adsorption capacity of 21%. The AC adsorption performance in terms of saturation time as a function of the number of regeneration cycles was considered one of the tool parameters. The proposed tool allows to determine the optimal number of regeneration cycles for a maximum economic profit in the regeneration strategy. It was demonstrated, using the proposed tool, that after an optimum of seven regeneration cycles, the power plant expends only 26% of the total investment. The simplicity of the tool permits a rapid way to find the most profitable number of regeneration cycles by combining economic, technical and adsorption efficiency parameters in one function, thus improving the AC management strategy at an industrial scale with corresponding environmental and economic advantages, including sustainability.

Chemical Regeneration of Activated Carbon Used in A Water Treatment System for Medical Services

“…In addition to the batch desorption regeneration tests, column tests for free chlorine(removal) and hardness(adsorption) were carried out using a glass column (2.5 cm diameter, 5 cm height) filled with approximately 10 g powder AC (0.063 mm). The scaling down of the GAC adsorber for column laboratory experiments was done following the scaling down rules for commercial GAC adsorbers according to [2]. Briefly, the ratio between the diameter and the length of the industrial and the lab scale adsorber was kept constant.…”

“…Because of its special pore structure and surface characteristics, activated carbon (AC) adsorption has been widely used to remove organic and inorganic pollutants from waters and wastewaters. These properties promoted the use of AC in all kinds of industries such as: food, chemical processes, metallurgy, energy, water treatment and medical services [1,2]. In Cuba, granular activated carbon (GAC) is commonly used in hospitals for HClO, ClO -(forming free chlorine) and/or chloramines removal after the addition of chlorinated compounds to the water city supply for water disinfection [3,4].…”

“…In this regard GAC regeneration has an important role in its correct management for the hospitals. Correct management of GAC constitutes four main steps: (1) Characterization, (2) Exploitation, (3) Regeneration and (4) Reuse [2,3]. Therefore, the regeneration of the GAC cannot only preserve the natural resources and reduce secondary pollution, but can also bring economic profit [2].…”

“…The most common regeneration technique for removing volatile organics is thermal regeneration. This technique has the disadvantage that the spent GAC commonly needs to be transported to an off-site specialized facility and the increased costs due to the frequency of regeneration cycles [2]. In this regard chemical regeneration arises as a suitable method for in situ regeneration of GAC adsorbers used in hospitals for dialysis water production.…”

“…The rapid small-scale column test (RSSCT) has been used to study its breakthrough behavior. Additionally, acid-leached sample tests prove that much of the calcium is removed via acid washing, resulting in a lower calcium and ash content [2,7,[12][13][14].…”