Device and method of recovering heat energy in waste water anaerobic treatment process

Abstract

The invention discloses a device and a method of recovering heat energy in a waste water anaerobic treatment process. Biogas is generated in waste water anaerobic treatment. Heat energy generated by combustion of biogas is transferred to a heat conducting fluid by means of a thin-walled tubular heat exchanger, and the heated heat conducting fluid heats a target according to a process demand, so that heat energy is recovered and utilized. According to the method, a combustion-supporting air/gas ratio and an air distributing pressure are set according to compositions of biogas, so that biogas iscombusted fully, and the emission amount of combusted tail gas is reduced. A thin-walled heat exchange tube system which is good in heat conducting property transfers heat to the heat conducting fluid efficiently, so that the comprehensive recycling ratio of heat energy of the waste water anaerobic fermentation product biogas reaches 80-90% which is far higher than 30% of biogas power generation.The method is suitable for recycling combustion heat energy of various organic waste water anaerobic fermentation products, has the advantages of being high in recycling ratio of heat energy, safe and easy to operate and small in tail gas pollutant emission, and has an application prospect in the field of recycling organic pollutant energy sources in waste water.

Description

technical field [0001] The invention belongs to the technical field of environmental protection and energy, and in particular relates to a device and method for recovering heat energy from wastewater anaerobic treatment process. Background technique [0002] With the rapid economic development and the country's increasing requirements for environmental governance, my country's wastewater treatment volume has increased year by year. In 2017, my country's wastewater treatment volume reached 46.549 billion cubic meters. Wastewater contains high concentrations of organic pollutants, and anaerobic biological treatment before conventional aerobic biochemical treatment has become a necessary part of the combined wastewater treatment process. After anaerobic fermentation of wastewater containing organic pollutants, a large amount of energy substances such as biogas whose main component is methane can be produced. Combustion and utilization of biogas generated during anaerobic treatm...

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Problems solved by technology

[0003] The existing energy recovery and utilization equipment from the anaerobic treatment process of wastewater is mainly biogas generators, but there are the following problems: (1) The operation stability is poor, and the existing biogas generators are mainly high-speed diesel generators with a power of more than 500kw The biogas flow and pressure generated by the common anaerobic tower are not enough to meet the operation requirements of the biogas generator. Once the biogas generated by the anaerobic treatment of wastewater is restricted by factors such as the influent flow, the concentration of organic pollutants, and the treatment effect, the biogas Fluctuations in production and pressure can easily lead to unstable operation or even shutdown of biogas generators

(2) The energy utilization rate is low. The chemical energy-electric energy conversion rate of the existing biogas generator does not exceed 30%. The biogas generator will release high-temperature exhaust gas, but the heat in the exhaust gas is difficult to recycle, resulting in a large amount of energy waste

(3) The equipment is severely corroded. Since the biogas contains impurities such as ammonia, hydrogen sulfide and phosphorus elements, when the biogas is burned in the cylinder of the generator, oxides of nitrogen, sulfur and phosphorus will be produced, and during the combustion of the biogas will produce A large number of water molecules, nitrogen, sulfur, phosphorus oxides combined with water molecules are strongly acidic, which will seriously corrode the cylinder wall and piston, causing them to rust, destroy the smoothness of the cylinder inner wall and piston surface, and easily cause piston lock to generate electricity machine parking

(4) Due to the poor combustion stability, it is easy to cause incomplete combustion of some components in the biogas, and it is easy to produce VOCs, nitrogen, phosphorus oxides and other pollutants, causing secondary pollution

(5) The structure of the generator is precise, the operation and maintenance management is difficult, and the failure rate is high, so it is not suitable for use in wastewater treatment stations or wastewater treatment plants with relatively harsh environments

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