Feed Water Heater – Types , Open and Closed Feed Water Heater

FEED WATER HEATER

低压进料热水器用于冷凝水泵放电和锅炉饲料泵之间的冷凝水系统中，并利用低压涡轮提取或辅助涡轮排气蒸汽加热冷凝水。
High pressure feed water heaters are used in the feed water system between the boiler feed pump discharge and the boiler, and utilize high pressure turbine extraction steam for heating the feed water. The condensate or feed water temperature increase for each feed water heater will be in the range of 28 to 56 degrees C with the actual value determined by turbine manufacturer‟s stage location of steam extraction nozzles. Depending on turbine size, some turbines offer alternate number of extraction nozzles with usually a choice of using the highest pressure extraction nozzle. The selection, in this case, of the total number of feed water heaters to use should be based on economic evaluation.

低压加热器
使用一个或多个低压馈电加热器，将冷凝水温度从冷凝水泵放电温度提高到脱水剂入口温度。将加热器排水管从较高的压力加热器级联到下一个较低压力加热器，最低压力加热器排入冷凝器。

高压加热器
Use one or more high pressure feed water heaters to raise the temperature of feed water from de-aerator outlet temperature to the required boiler economizer inlet temperature. The heater drains are cascaded from heater to heater, back to the de-aerator in a fashion similar to the heater drain system for the low pressure heaters.

优点
(a) Fuel economy.
（b）锅炉的寿命更长。
(c) Increase in steaming capacity.

A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduced back into the steam cycle.

Working Of Feed Water Heater :

It should be noted that the energy used to heat the feedwater is usually derived from steam extracted between the stages of the steam turbine. Therefore, the steam that would be used to perform expansion work in the turbine is not utilized for that purpose. The percentage of the total cycle steam mass flow used for the feedwater heater must be carefully optimized for maximum power plant thermal efficiency since increasing this causes a decrease in turbine power output.

进食加热器也可以是开放和封闭的热交换器。一个开放式水加热器is merely a direct-contact heat exchanger in which extracted steam is allowed to mix with the feedwater. This kind of heater will normally require a feed pump at both the feed inlet and outlet since the pressure in the heater is between the boiler pressure and the condenser pressure. A deaerator is a special case of the open feedwater heater which is specifically designed to remove non-condensable gases from the feedwater.

封闭的饲料加热器通常是外壳和管热交换器，在整个管中供气通过，并通过涡轮提取蒸汽加热。这些在加热器之前和之后不需要单独的泵即可将馈电蒸汽的压力增加，因为蒸汽的压力与开放的加热器一样。但是，然后必须将提取的蒸汽推向冷凝器压力。
许多发电厂都融合了许多供水加热器，并可能使用开放和封闭的组件。

给水加热器用于化石和nuclear-fueled power plants. Smaller versions have also been installed on steam locomotives, portable engines and stationary engines. An economiser serves a similar purpose to a feedwater heater, but is technically different. Instead of using actual cycle steam for heating, it uses the lowest-temperature flue gas from the furnace to heat the water before it enters the boiler proper. This allows for the heat transfer between the furnace and the feedwater occurring across a smaller average temperature gradient. System efficiency is therefore further increased when viewed with respect to actual energy content of the fuel

Open Feed Water Heater (Deaerator)

一个开放式水加热器, also called direct-contact and deaerating (DA) heater, is one that heats the feedwater by directly mixing it with bled steam from the turbine. Usually only one DA is used at Power Plant.

由于这样的加热器中的压力不能超过提取点的涡轮压力，因此必须跟随加热器泵（主锅炉供水泵）。蒸汽和水流的汇合使得有效去除非连接物以及进料水的加热。

DA出口给水处于或接近饱和度。由于压降低于饱和压力，泵送饱和水会导致空气水，从而导致泵叶片的背面闪烁。因此，DA加热器通常位于高度高于其泵上方的动力植物蒸汽发电机屋中，可能是60英尺。这提供了足够的泵入口压力，可以使饱和的水压缩（或子冷却）并防止空洞。

There are three types of DA heaters for industrial and utility use.

1) Spray-Type deaerators .

在这种类型的情况下，馈线通过喷嘴进入加热器，将其喷入提取步骤的加热器空间。将水加热并擦洗以释放非降解气体。内部阻碍系统提供了另一种蒸汽流对现在加热的饲料的第二次搅动。

2）托盘式拔出器。

在这里，馈电水定向到一系列级联的水平托盘上。它落在纸盘或托盘的床单或管中，并与托盘系统底部接收的提取蒸汽接触。随着擦洗的发生和不可渗透气体的气体和一些蒸汽的升高，它们与较冷的水接触，从而减少了高浓度的非凝结物，从而进入大气中。

3）组合喷雾式卸载器

在这种类型的情况下，首先将馈送水喷入充满蒸汽的空间中，然后将其制成以降落的托盘。该组合类型具有水平不锈钢托盘，目前是公用事业的首选。