RU2266481C2 - Gas-water heat exchanger with protection from low-temperature corrosion on gas side - Google Patents

Abstract

FIELD: water heating equipment engineering, can be used in steam-gas energy plants, water heating cauldrons, industrial utilization plants.

SUBSTANCE: device has heat-exchange surface, pipeline for feeding cold water to its input and means for increasing temperature of cold water at input until value is reached, exceeding water steam condensation point in heating gases. Heat exchange surface is separated on at least two sections, serially engaged water-wise. Heat exchanger is provided with bypass pipeline for mixing cold water in accordance to cascade circuit scheme except first one to all sections. Means for temperature increase of cold water is made in form of water heater of cold water, connected via heating substance to output of hot water from last section of heat exchange surface.

EFFECT: protection of gas-water heat exchangers from low-temperature corrosion on gas side.

1 dwg

Description

The invention relates to heat exchange technology and can be used in hot water boilers, industrial hot water recovery boilers, gas condensate heaters, network and make-up water of recovery boilers installed behind gas turbines and diesel engines, etc. to protect gas-water heat exchangers from low-temperature corrosion on the gas side, resulting from condensation of water vapor contained in flue gases at a cold heat exchange surface, at rated power, and also to provide a given law for changing the temperature of the water leaving the heat exchanger with a decrease in its thermal power.

Known gas-water heat exchanger containing a heat exchange surface, a supply pipe to the cold water heat exchanger and a means of increasing the temperature of cold water at the inlet of the heat exchanger to a value exceeding the dew point of water vapor in the heating gases ([1] - analog). The means for raising the temperature of cold water at the inlet to the heat exchanger according to [1] is made in the form of a recirculation pipe equipped with a pump connecting the hot water outlet of the heat exchanger with a cold water pipe. The heat exchanger is a water boiler equipped with an economizer included in the recirculation loop, the recirculation pipe of the water heated in the boiler being connected to the input of the water economizer.

The disadvantages of the known heat exchanger [1] are the necessity of using a recirculation pump of greater productivity, significant energy costs for creating the recirculation flow necessary to heat the water entering the boiler to a temperature safe under conditions of low-temperature corrosion.

Known for the intended purpose and the achieved effect is a gas-water heat exchanger containing a heat exchange surface divided into at least two sections connected in series by water, a cold water supply pipe to the first section, a bypass pipe for mixing cold water in a cascade circuit to all other sections and a means of increasing temperature of cold water at the inlet to the first of the mentioned sections to a value exceeding the dew point of water vapor in heating gases ([2] - prototype). The means for raising the temperature of cold water according to [2], as in [1], is a recirculation pipe equipped with a pump. By reducing the amount of recirculated water as a result of mixing cold water into all sections of the heat exchange surface, the technical solution [2] allows to reduce the energy consumption for recirculation, but cannot completely eliminate the need for a recirculation pump.

The achieved result of the invention is the complete elimination of the need for a circulation pump with the corresponding complete elimination of capital costs for its acquisition and operational energy costs for pump drive.

Obtaining this result is ensured by the fact that in a gas-water heat exchanger containing a heat exchange surface divided into at least two sections connected in series by water, a cold water supply pipe to the first section, a bypass pipe for mixing cold water in a cascade circuit to all other sections and an increase means temperature of cold water at the inlet to the first of the said sections to a value exceeding the dew point of water vapor in the heating gases, according to the invention, said medium TVO is in the form of water-water preheater cold water connected by a heating medium to the outlet of hot water from the last section of the heat exchange surface.

The drawing shows, by way of example, a circuit for switching on a gas-water heat exchanger (gas condensate heater) according to the invention on the heated side (water) and the heating side (flue gas).

The heat exchanger in a particular case contains four pipe sections 1.1, 1.2, 1.3, 1.4 of the heat exchange surface, connected in series via water with lines 2 of the main condensate stream and washed in parallel with a flue gas stream 3, a cold water supply pipe 4 to the first section 1.1, a bypass pipe 5 for mixing cold water in a cascade scheme to all other sections 1.2-1.4 and a means of increasing the temperature of cold water at the entrance to the first section 1.1 to a value exceeding the dew point of water vapor in the heating gases (in this example, 60 ° C), moreover, the said means is made in the form of a cold-water pre-heater 6, connected via a heating medium by line 7 to the outlet of hot water from the last section 1.4 of the heat exchange surface, and through the heated medium to cut the cold water supply pipe 4 to the first section 1.1. Lines 4 and 5 are connected to a common supply pipe 8 of cold water, equipped with a pump 9.

The operation of the gas-water heat exchanger according to the invention is as follows. With pump 9, cold water (condensate) is pumped through line 4 to preheater 6, after which, heated to a temperature safe by corrosion (in this example, to 60 ° C), it enters the inlet of the first section 1.1 of the heat exchange surface of the gas condensate heater. After passing successively sections 1.1-1.4 of the heat exchange surface of the heater, hot condensate as a heating medium is supplied to the preheater 6, after cooling in which it reaches the consumer at a temperature of 160 ° C. Part of the cold condensate in pipeline 5 is cascaded into the inlet of each section 1.2-1.4.

Thus, according to the invention, over the entire condensate heating path, its temperature exceeds by a predetermined value the temperature of the dew point of water vapor in flue (heating) gases, which protects the heat exchange surface from low temperature corrosion on the gas side without the need for a recirculation pump. This reduces energy consumption and increases the reliability of the heat exchanger.

Information sources:

1. USSR copyright certificate No. 1390489, 4 F 24 H 1/00, 1986.

2. Application No. 2003111636 of 04.25.2003 for the grant of a patent of the Russian Federation for a utility model.

Claims (1)

A gas-water heat exchanger comprising a heat exchange surface, a cold water supply conduit at its inlet, and means for raising cold water inlet temperature to a value higher than the dew point of water vapor in the heating gases, characterized in that the heat exchange surface is divided into at least two in series sections included in water, the heat exchanger is equipped with a bypass pipe for mixing cold water in a cascade scheme, except for the first, in all sections, and the said tool is made in the form of water o-water pre-heater of cold water connected via a heating medium to the outlet of hot water from the last section of the heat exchange surface.