Chun Deng

Optimization of water network integrated with process models

In this paper, a novel approach for the synthesis of water network incorporated with process models is introduced. The process models are utilized to relate the variables (i.e., flow rate and concentration) of process output (typically defined as internal water source) with those of process input (i.e., water sink). A generalized water network superstructure is developed to embed all possible process units and all the connections among resources, interceptors, process units, and wastes. The problem is formulated as four optimization problems (minimum freshwater flow rate, intercepted flow rate, intercepted mass load, and number of connections), and the four models are solved in sequence to locate the targets. A literature case is used to validate the proposed approach. Moreover, a sour water network of a practical refinery plant is presented to illustrate the applicability and effectiveness of the proposed approach.

Pinch Location of the Hydrogen Network with Purification Reuse

In the hydrogen network with the minimum hydrogen utility flow rate, the pinch appears at the point with zero hydrogen surplus, while the hydrogen surpluses of all the other points are positive. In the hydrogen purity profiles, the pinch can only lie at the sink-tie-line intersecting the source purity profile. According to the alternative distribution of the negative and positive regions, the effect of the purification to the hydrogen surplus is analyzed. The results show that when the purification is applied, the pinch point will appear neither above the purification feed nor between the initial pinch point and the purification feed, no matter the purification feed lies above or below the initial pinch point. This is validated by two case studies.

Optimal design of hydrogen network with intermediate header and minimum compressor work

Refinery hydrogen consumers (i.e. hydrocracker, hydro-treater) are operated in high pressure. The makeup hydrogen and recycle hydrogen compressors are placed to increase the pressure of hydrogen streams. It leads to a large contribution on compression work and operating cost. Therefore, except for the minimizing the flowrate of hydrogen utility, it is extremely important to reduce the compression work when optimizing hydrogen network. The improved problem table is applied to locate the flowrate targets of hydrogen network with intermediate header in the first step. Next, a novel nearest neighbors algorithm as well as pressure-impurity diagram are proposed to design the optimal hydrogen network with intermediate header and minimum compression work. The proposed approach is illustrated via a case study. The results show that the optimal targets (11.89 MJ, 8 compressors) are much better than those reported (15.09 MJ, 11 compressors) in the literature. It indicates that intermediate hydrogen header can be installed to reduce the number of compressors as well as the compression work.

Preparation of feed grade calcium formate from calcium carbide residue

Calcium carbide residue is generated from the reaction of CaC2 (calcium carbide) and water in the production of acetylene in the chlor-alkali industry. The main component contained in calcium carbide residue is Ca(OH)2 (calcium hydroxide). At present, great amounts of calcium carbide residue in China are disposed by land stockpiling or landfilling. These disposal practices cause serious environmental pollution and lead to resource wastage. Effective disposal methods by recycling and reusing the calcium carbide residue are urgently needed. In this paper, a novel method for producing feed grade calcium formate from calcium carbide residue is introduced. The calcium carbide residue and CO (carbon monoxide) are utilized as raw materials to prepare Ca(HCOO)2 (calcium formate) through thexa0carbonylationxa0synthesis route. The optimalxa0reaction conditions (reaction temperaturexa0=xa0200xa0°C, reaction pressurexa0=xa06xa0MPa, reaction timexa0=xa022.5xa0min, and slurry concentrationxa0=xa00.125xa0g/mL) have been obtained through pilot-scale experimental studies with the aim of producing high-quality feed grade calcium formate product. Data from the continuous pilot plant are used to evaluate the economic feasibility of the production method. In addition, CO, which is acquired from industrial exhausts, is innovatively used as a reactant to produce calcium formate instead of being treated as a waste material, reducing carbon dioxide emissions significantly. Therefore, the proposed method is a very promising clean and green chemical technology that turns calcium carbide residue and industrial exhaust gas into a useful product, promoting the development of industrial waste recycling in China.

Synthesis of Refinery Hydrogen Networks with Parametric Uncertainties

Abstract This work presents a fuzzy optimisation model for the synthesis of refinery hydrogen networks under uncertainty. Based on a generic superstructure that incorporates all the possible connections between the hydrogen system elements (sources, sinks, compressors etc.), the mathematical formulation consists mainly of flowrate and impurity load balances, where fuzzy intervals are introduced to account for parametric uncertainties. Pressure constraints and the optimal placement of compressors are also taken into account. A case study is presented to illustrate the proposed approach.

Optimal Design of Refinery Hydrogen Network with Mixed Pattern Configuration

Abstract Based on the combination of conventional hydrogen network and that with pure intermediate hydrogen headers, a novel configuration of hydrogen network with mixed pattern is proposed where the hydrogen sources and sinks can be connected directly or indirectly via intermediate hydrogen headers. The corresponding superstructure for the synthesis of hydrogen networks with mixed pattern is firstly presented and its mathematical model is proposed accordingly. One literature case is solved and analysed. The optimal results are compared with those for the conventional hydrogen network and the network with pure intermediate hydrogen headers. It indicates that, the network with mixed pattern can reach the minimum hydrogen utility. The total number of connections between units is less than that of the conventional hydrogen network and the network flexibility is enhanced. Compared with the hydrogen network with pure intermediate hydrogen headers, the number of intermediate hydrogen header is reduced from two to one and it will effectively reduce the investment and retrofit costs.